fair.c 271.5 KB
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// SPDX-License-Identifier: GPL-2.0
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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
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 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
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 */
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#include "sched.h"
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#include <trace/events/sched.h>

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/*
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 * Targeted preemption latency for CPU-bound tasks:
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 *
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 * NOTE: this latency value is not the same as the concept of
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 * 'timeslice length' - timeslices in CFS are of variable length
 * and have no persistent notion like in traditional, time-slice
 * based scheduling concepts.
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 *
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 * (to see the precise effective timeslice length of your workload,
 *  run vmstat and monitor the context-switches (cs) field)
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 *
 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
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 */
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unsigned int sysctl_sched_latency			= 6000000ULL;
unsigned int normalized_sysctl_sched_latency		= 6000000ULL;
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/*
 * The initial- and re-scaling of tunables is configurable
 *
 * Options are:
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 *
 *   SCHED_TUNABLESCALING_NONE - unscaled, always *1
 *   SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
 *   SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
 *
 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
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 */
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enum sched_tunable_scaling sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
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/*
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 * Minimal preemption granularity for CPU-bound tasks:
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 *
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 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
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 */
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unsigned int sysctl_sched_min_granularity		= 750000ULL;
unsigned int normalized_sysctl_sched_min_granularity	= 750000ULL;
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/*
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 * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity
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 */
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static unsigned int sched_nr_latency = 8;
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/*
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 * After fork, child runs first. If set to 0 (default) then
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 * parent will (try to) run first.
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 */
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unsigned int sysctl_sched_child_runs_first __read_mostly;
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/*
 * SCHED_OTHER wake-up granularity.
 *
 * This option delays the preemption effects of decoupled workloads
 * and reduces their over-scheduling. Synchronous workloads will still
 * have immediate wakeup/sleep latencies.
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 *
 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
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 */
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unsigned int sysctl_sched_wakeup_granularity		= 1000000UL;
unsigned int normalized_sysctl_sched_wakeup_granularity	= 1000000UL;
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const_debug unsigned int sysctl_sched_migration_cost	= 500000UL;
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#ifdef CONFIG_SMP
/*
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 * For asym packing, by default the lower numbered CPU has higher priority.
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 */
int __weak arch_asym_cpu_priority(int cpu)
{
	return -cpu;
}
#endif

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#ifdef CONFIG_CFS_BANDWIDTH
/*
 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
 * each time a cfs_rq requests quota.
 *
 * Note: in the case that the slice exceeds the runtime remaining (either due
 * to consumption or the quota being specified to be smaller than the slice)
 * we will always only issue the remaining available time.
 *
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 * (default: 5 msec, units: microseconds)
 */
unsigned int sysctl_sched_cfs_bandwidth_slice		= 5000UL;
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#endif

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/*
 * The margin used when comparing utilization with CPU capacity:
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 * util * margin < capacity * 1024
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 *
 * (default: ~20%)
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 */
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unsigned int capacity_margin				= 1280;
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static inline void update_load_add(struct load_weight *lw, unsigned long inc)
{
	lw->weight += inc;
	lw->inv_weight = 0;
}

static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
{
	lw->weight -= dec;
	lw->inv_weight = 0;
}

static inline void update_load_set(struct load_weight *lw, unsigned long w)
{
	lw->weight = w;
	lw->inv_weight = 0;
}

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/*
 * Increase the granularity value when there are more CPUs,
 * because with more CPUs the 'effective latency' as visible
 * to users decreases. But the relationship is not linear,
 * so pick a second-best guess by going with the log2 of the
 * number of CPUs.
 *
 * This idea comes from the SD scheduler of Con Kolivas:
 */
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static unsigned int get_update_sysctl_factor(void)
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{
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	unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
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	unsigned int factor;

	switch (sysctl_sched_tunable_scaling) {
	case SCHED_TUNABLESCALING_NONE:
		factor = 1;
		break;
	case SCHED_TUNABLESCALING_LINEAR:
		factor = cpus;
		break;
	case SCHED_TUNABLESCALING_LOG:
	default:
		factor = 1 + ilog2(cpus);
		break;
	}

	return factor;
}

static void update_sysctl(void)
{
	unsigned int factor = get_update_sysctl_factor();

#define SET_SYSCTL(name) \
	(sysctl_##name = (factor) * normalized_sysctl_##name)
	SET_SYSCTL(sched_min_granularity);
	SET_SYSCTL(sched_latency);
	SET_SYSCTL(sched_wakeup_granularity);
#undef SET_SYSCTL
}

void sched_init_granularity(void)
{
	update_sysctl();
}

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#define WMULT_CONST	(~0U)
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#define WMULT_SHIFT	32

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static void __update_inv_weight(struct load_weight *lw)
{
	unsigned long w;

	if (likely(lw->inv_weight))
		return;

	w = scale_load_down(lw->weight);

	if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
		lw->inv_weight = 1;
	else if (unlikely(!w))
		lw->inv_weight = WMULT_CONST;
	else
		lw->inv_weight = WMULT_CONST / w;
}
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/*
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 * delta_exec * weight / lw.weight
 *   OR
 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
 *
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 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
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 * we're guaranteed shift stays positive because inv_weight is guaranteed to
 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
 *
 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
 * weight/lw.weight <= 1, and therefore our shift will also be positive.
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 */
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static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
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{
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	u64 fact = scale_load_down(weight);
	int shift = WMULT_SHIFT;
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	__update_inv_weight(lw);
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	if (unlikely(fact >> 32)) {
		while (fact >> 32) {
			fact >>= 1;
			shift--;
		}
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	}

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	/* hint to use a 32x32->64 mul */
	fact = (u64)(u32)fact * lw->inv_weight;
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	while (fact >> 32) {
		fact >>= 1;
		shift--;
	}
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	return mul_u64_u32_shr(delta_exec, fact, shift);
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}


const struct sched_class fair_sched_class;
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/**************************************************************
 * CFS operations on generic schedulable entities:
 */

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#ifdef CONFIG_FAIR_GROUP_SCHED
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/* cpu runqueue to which this cfs_rq is attached */
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
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	return cfs_rq->rq;
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}

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static inline struct task_struct *task_of(struct sched_entity *se)
{
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	SCHED_WARN_ON(!entity_is_task(se));
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	return container_of(se, struct task_struct, se);
}

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/* Walk up scheduling entities hierarchy */
#define for_each_sched_entity(se) \
		for (; se; se = se->parent)

static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
{
	return p->se.cfs_rq;
}

/* runqueue on which this entity is (to be) queued */
static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
{
	return se->cfs_rq;
}

/* runqueue "owned" by this group */
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
{
	return grp->my_q;
}

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static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (!cfs_rq->on_list) {
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		struct rq *rq = rq_of(cfs_rq);
		int cpu = cpu_of(rq);
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		/*
		 * Ensure we either appear before our parent (if already
		 * enqueued) or force our parent to appear after us when it is
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		 * enqueued. The fact that we always enqueue bottom-up
		 * reduces this to two cases and a special case for the root
		 * cfs_rq. Furthermore, it also means that we will always reset
		 * tmp_alone_branch either when the branch is connected
		 * to a tree or when we reach the beg of the tree
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		 */
		if (cfs_rq->tg->parent &&
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		    cfs_rq->tg->parent->cfs_rq[cpu]->on_list) {
			/*
			 * If parent is already on the list, we add the child
			 * just before. Thanks to circular linked property of
			 * the list, this means to put the child at the tail
			 * of the list that starts by parent.
			 */
			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
				&(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list));
			/*
			 * The branch is now connected to its tree so we can
			 * reset tmp_alone_branch to the beginning of the
			 * list.
			 */
			rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
		} else if (!cfs_rq->tg->parent) {
			/*
			 * cfs rq without parent should be put
			 * at the tail of the list.
			 */
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			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
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				&rq->leaf_cfs_rq_list);
			/*
			 * We have reach the beg of a tree so we can reset
			 * tmp_alone_branch to the beginning of the list.
			 */
			rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
		} else {
			/*
			 * The parent has not already been added so we want to
			 * make sure that it will be put after us.
			 * tmp_alone_branch points to the beg of the branch
			 * where we will add parent.
			 */
			list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
				rq->tmp_alone_branch);
			/*
			 * update tmp_alone_branch to points to the new beg
			 * of the branch
			 */
			rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list;
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		}
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		cfs_rq->on_list = 1;
	}
}

static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (cfs_rq->on_list) {
		list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
		cfs_rq->on_list = 0;
	}
}

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/* Iterate through all leaf cfs_rq's on a runqueue: */
#define for_each_leaf_cfs_rq(rq, cfs_rq) \
	list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
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/* Do the two (enqueued) entities belong to the same group ? */
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static inline struct cfs_rq *
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is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
	if (se->cfs_rq == pse->cfs_rq)
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		return se->cfs_rq;
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	return NULL;
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}

static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
	return se->parent;
}

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static void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
	int se_depth, pse_depth;

	/*
	 * preemption test can be made between sibling entities who are in the
	 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
	 * both tasks until we find their ancestors who are siblings of common
	 * parent.
	 */

	/* First walk up until both entities are at same depth */
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	se_depth = (*se)->depth;
	pse_depth = (*pse)->depth;
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	while (se_depth > pse_depth) {
		se_depth--;
		*se = parent_entity(*se);
	}

	while (pse_depth > se_depth) {
		pse_depth--;
		*pse = parent_entity(*pse);
	}

	while (!is_same_group(*se, *pse)) {
		*se = parent_entity(*se);
		*pse = parent_entity(*pse);
	}
}

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#else	/* !CONFIG_FAIR_GROUP_SCHED */

static inline struct task_struct *task_of(struct sched_entity *se)
{
	return container_of(se, struct task_struct, se);
}
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
	return container_of(cfs_rq, struct rq, cfs);
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}


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#define for_each_sched_entity(se) \
		for (; se; se = NULL)
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static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
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{
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	return &task_rq(p)->cfs;
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}

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static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
{
	struct task_struct *p = task_of(se);
	struct rq *rq = task_rq(p);

	return &rq->cfs;
}

/* runqueue "owned" by this group */
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
{
	return NULL;
}

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static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
}

static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
}

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#define for_each_leaf_cfs_rq(rq, cfs_rq)	\
		for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
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static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
	return NULL;
}

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static inline void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
}

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#endif	/* CONFIG_FAIR_GROUP_SCHED */

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static __always_inline
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void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
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/**************************************************************
 * Scheduling class tree data structure manipulation methods:
 */

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static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
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{
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	s64 delta = (s64)(vruntime - max_vruntime);
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	if (delta > 0)
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		max_vruntime = vruntime;
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	return max_vruntime;
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}

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static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
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{
	s64 delta = (s64)(vruntime - min_vruntime);
	if (delta < 0)
		min_vruntime = vruntime;

	return min_vruntime;
}

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static inline int entity_before(struct sched_entity *a,
				struct sched_entity *b)
{
	return (s64)(a->vruntime - b->vruntime) < 0;
}

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static void update_min_vruntime(struct cfs_rq *cfs_rq)
{
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	struct sched_entity *curr = cfs_rq->curr;
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	struct rb_node *leftmost = rb_first_cached(&cfs_rq->tasks_timeline);
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	u64 vruntime = cfs_rq->min_vruntime;

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	if (curr) {
		if (curr->on_rq)
			vruntime = curr->vruntime;
		else
			curr = NULL;
	}
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	if (leftmost) { /* non-empty tree */
		struct sched_entity *se;
		se = rb_entry(leftmost, struct sched_entity, run_node);
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		if (!curr)
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			vruntime = se->vruntime;
		else
			vruntime = min_vruntime(vruntime, se->vruntime);
	}

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	/* ensure we never gain time by being placed backwards. */
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	cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
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#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
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}

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/*
 * Enqueue an entity into the rb-tree:
 */
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static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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	struct rb_node **link = &cfs_rq->tasks_timeline.rb_root.rb_node;
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	struct rb_node *parent = NULL;
	struct sched_entity *entry;
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	bool leftmost = true;
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	/*
	 * Find the right place in the rbtree:
	 */
	while (*link) {
		parent = *link;
		entry = rb_entry(parent, struct sched_entity, run_node);
		/*
		 * We dont care about collisions. Nodes with
		 * the same key stay together.
		 */
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		if (entity_before(se, entry)) {
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			link = &parent->rb_left;
		} else {
			link = &parent->rb_right;
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			leftmost = false;
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		}
	}

	rb_link_node(&se->run_node, parent, link);
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	rb_insert_color_cached(&se->run_node,
			       &cfs_rq->tasks_timeline, leftmost);
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}

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static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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	rb_erase_cached(&se->run_node, &cfs_rq->tasks_timeline);
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}

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struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
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{
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	struct rb_node *left = rb_first_cached(&cfs_rq->tasks_timeline);
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	if (!left)
		return NULL;

	return rb_entry(left, struct sched_entity, run_node);
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}

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static struct sched_entity *__pick_next_entity(struct sched_entity *se)
{
	struct rb_node *next = rb_next(&se->run_node);

	if (!next)
		return NULL;

	return rb_entry(next, struct sched_entity, run_node);
}

#ifdef CONFIG_SCHED_DEBUG
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struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
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{
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	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline.rb_root);
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	if (!last)
		return NULL;
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	return rb_entry(last, struct sched_entity, run_node);
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}

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/**************************************************************
 * Scheduling class statistics methods:
 */

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int sched_proc_update_handler(struct ctl_table *table, int write,
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		void __user *buffer, size_t *lenp,
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		loff_t *ppos)
{
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	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
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	unsigned int factor = get_update_sysctl_factor();
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	if (ret || !write)
		return ret;

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

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#define WRT_SYSCTL(name) \
	(normalized_sysctl_##name = sysctl_##name / (factor))
	WRT_SYSCTL(sched_min_granularity);
	WRT_SYSCTL(sched_latency);
	WRT_SYSCTL(sched_wakeup_granularity);
#undef WRT_SYSCTL

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	return 0;
}
#endif
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/*
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 * delta /= w
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 */
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static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se)
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{
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	if (unlikely(se->load.weight != NICE_0_LOAD))
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		delta = __calc_delta(delta, NICE_0_LOAD, &se->load);
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	return delta;
}

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/*
 * The idea is to set a period in which each task runs once.
 *
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 * When there are too many tasks (sched_nr_latency) we have to stretch
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 * this period because otherwise the slices get too small.
 *
 * p = (nr <= nl) ? l : l*nr/nl
 */
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static u64 __sched_period(unsigned long nr_running)
{
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	if (unlikely(nr_running > sched_nr_latency))
		return nr_running * sysctl_sched_min_granularity;
	else
		return sysctl_sched_latency;
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}

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/*
 * We calculate the wall-time slice from the period by taking a part
 * proportional to the weight.
 *
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 * s = p*P[w/rw]
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 */
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static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
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	for_each_sched_entity(se) {
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		struct load_weight *load;
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		struct load_weight lw;
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		cfs_rq = cfs_rq_of(se);
		load = &cfs_rq->load;
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		if (unlikely(!se->on_rq)) {
669
			lw = cfs_rq->load;
M
Mike Galbraith 已提交
670 671 672 673

			update_load_add(&lw, se->load.weight);
			load = &lw;
		}
674
		slice = __calc_delta(slice, se->load.weight, load);
M
Mike Galbraith 已提交
675 676
	}
	return slice;
677 678
}

679
/*
A
Andrei Epure 已提交
680
 * We calculate the vruntime slice of a to-be-inserted task.
681
 *
682
 * vs = s/w
683
 */
684
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
P
Peter Zijlstra 已提交
685
{
686
	return calc_delta_fair(sched_slice(cfs_rq, se), se);
687 688
}

689
#ifdef CONFIG_SMP
690
#include "pelt.h"
691 692
#include "sched-pelt.h"

693
static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
694
static unsigned long task_h_load(struct task_struct *p);
695
static unsigned long task_h_load_static(struct task_struct *p);
696

697 698
/* Give new sched_entity start runnable values to heavy its load in infant time */
void init_entity_runnable_average(struct sched_entity *se)
699
{
700
	struct sched_avg *sa = &se->avg;
701

702 703
	memset(sa, 0, sizeof(*sa));

704 705 706 707 708 709 710
	/*
	 * Tasks are intialized with full load to be seen as heavy tasks until
	 * they get a chance to stabilize to their real load level.
	 * Group entities are intialized with zero load to reflect the fact that
	 * nothing has been attached to the task group yet.
	 */
	if (entity_is_task(se))
711 712
		sa->runnable_load_avg = sa->load_avg = scale_load_down(se->load.weight);

713 714
	se->runnable_weight = se->load.weight;

715
	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
716
}
717

718
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
719
static void attach_entity_cfs_rq(struct sched_entity *se);
720

721 722 723 724 725 726 727 728 729 730 731 732 733
/*
 * With new tasks being created, their initial util_avgs are extrapolated
 * based on the cfs_rq's current util_avg:
 *
 *   util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
 *
 * However, in many cases, the above util_avg does not give a desired
 * value. Moreover, the sum of the util_avgs may be divergent, such
 * as when the series is a harmonic series.
 *
 * To solve this problem, we also cap the util_avg of successive tasks to
 * only 1/2 of the left utilization budget:
 *
734
 *   util_avg_cap = (cpu_scale - cfs_rq->avg.util_avg) / 2^n
735
 *
736
 * where n denotes the nth task and cpu_scale the CPU capacity.
737
 *
738 739
 * For example, for a CPU with 1024 of capacity, a simplest series from
 * the beginning would be like:
740 741 742 743 744 745 746 747 748 749 750
 *
 *  task  util_avg: 512, 256, 128,  64,  32,   16,    8, ...
 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
 *
 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
 * if util_avg > util_avg_cap.
 */
void post_init_entity_util_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	struct sched_avg *sa = &se->avg;
751 752
	long cpu_scale = arch_scale_cpu_capacity(NULL, cpu_of(rq_of(cfs_rq)));
	long cap = (long)(cpu_scale - cfs_rq->avg.util_avg) / 2;
753 754 755 756 757 758 759 760 761 762 763 764

	if (cap > 0) {
		if (cfs_rq->avg.util_avg != 0) {
			sa->util_avg  = cfs_rq->avg.util_avg * se->load.weight;
			sa->util_avg /= (cfs_rq->avg.load_avg + 1);

			if (sa->util_avg > cap)
				sa->util_avg = cap;
		} else {
			sa->util_avg = cap;
		}
	}
765 766 767 768 769 770 771

	if (entity_is_task(se)) {
		struct task_struct *p = task_of(se);
		if (p->sched_class != &fair_sched_class) {
			/*
			 * For !fair tasks do:
			 *
772
			update_cfs_rq_load_avg(now, cfs_rq);
773
			attach_entity_load_avg(cfs_rq, se, 0);
774 775 776 777 778
			switched_from_fair(rq, p);
			 *
			 * such that the next switched_to_fair() has the
			 * expected state.
			 */
779
			se->avg.last_update_time = cfs_rq_clock_task(cfs_rq);
780 781 782 783
			return;
		}
	}

784
	attach_entity_cfs_rq(se);
785 786
}

787
#else /* !CONFIG_SMP */
788
void init_entity_runnable_average(struct sched_entity *se)
789 790
{
}
791 792 793
void post_init_entity_util_avg(struct sched_entity *se)
{
}
794 795 796
static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
{
}
797
#endif /* CONFIG_SMP */
798

799
/*
800
 * Update the current task's runtime statistics.
801
 */
802
static void update_curr(struct cfs_rq *cfs_rq)
803
{
804
	struct sched_entity *curr = cfs_rq->curr;
805
	u64 now = rq_clock_task(rq_of(cfs_rq));
806
	u64 delta_exec;
807 808 809 810

	if (unlikely(!curr))
		return;

811 812
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
813
		return;
814

I
Ingo Molnar 已提交
815
	curr->exec_start = now;
816

817 818 819 820
	schedstat_set(curr->statistics.exec_max,
		      max(delta_exec, curr->statistics.exec_max));

	curr->sum_exec_runtime += delta_exec;
821
	schedstat_add(cfs_rq->exec_clock, delta_exec);
822 823 824 825

	curr->vruntime += calc_delta_fair(delta_exec, curr);
	update_min_vruntime(cfs_rq);

826 827 828
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

829
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
830
		cgroup_account_cputime(curtask, delta_exec);
831
		account_group_exec_runtime(curtask, delta_exec);
832
	}
833 834

	account_cfs_rq_runtime(cfs_rq, delta_exec);
835 836
}

837 838 839 840 841
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

842
static inline void
843
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
844
{
845 846 847 848 849 850 851
	u64 wait_start, prev_wait_start;

	if (!schedstat_enabled())
		return;

	wait_start = rq_clock(rq_of(cfs_rq));
	prev_wait_start = schedstat_val(se->statistics.wait_start);
852 853

	if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
854 855
	    likely(wait_start > prev_wait_start))
		wait_start -= prev_wait_start;
856

857
	__schedstat_set(se->statistics.wait_start, wait_start);
858 859
}

860
static inline void
861 862 863
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *p;
864 865
	u64 delta;

866 867 868 869
	if (!schedstat_enabled())
		return;

	delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
870 871 872 873 874 875 876 877 878

	if (entity_is_task(se)) {
		p = task_of(se);
		if (task_on_rq_migrating(p)) {
			/*
			 * Preserve migrating task's wait time so wait_start
			 * time stamp can be adjusted to accumulate wait time
			 * prior to migration.
			 */
879
			__schedstat_set(se->statistics.wait_start, delta);
880 881 882 883 884
			return;
		}
		trace_sched_stat_wait(p, delta);
	}

885
	__schedstat_set(se->statistics.wait_max,
886
		      max(schedstat_val(se->statistics.wait_max), delta));
887 888 889
	__schedstat_inc(se->statistics.wait_count);
	__schedstat_add(se->statistics.wait_sum, delta);
	__schedstat_set(se->statistics.wait_start, 0);
890 891
}

892
static inline void
893 894 895
update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *tsk = NULL;
896 897 898 899 900 901 902
	u64 sleep_start, block_start;

	if (!schedstat_enabled())
		return;

	sleep_start = schedstat_val(se->statistics.sleep_start);
	block_start = schedstat_val(se->statistics.block_start);
903 904 905 906

	if (entity_is_task(se))
		tsk = task_of(se);

907 908
	if (sleep_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
909 910 911 912

		if ((s64)delta < 0)
			delta = 0;

913
		if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
914
			__schedstat_set(se->statistics.sleep_max, delta);
915

916 917
		__schedstat_set(se->statistics.sleep_start, 0);
		__schedstat_add(se->statistics.sum_sleep_runtime, delta);
918 919 920 921 922 923

		if (tsk) {
			account_scheduler_latency(tsk, delta >> 10, 1);
			trace_sched_stat_sleep(tsk, delta);
		}
	}
924 925
	if (block_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
926 927 928 929

		if ((s64)delta < 0)
			delta = 0;

930
		if (unlikely(delta > schedstat_val(se->statistics.block_max)))
931
			__schedstat_set(se->statistics.block_max, delta);
932

933 934
		__schedstat_set(se->statistics.block_start, 0);
		__schedstat_add(se->statistics.sum_sleep_runtime, delta);
935 936 937

		if (tsk) {
			if (tsk->in_iowait) {
938 939
				__schedstat_add(se->statistics.iowait_sum, delta);
				__schedstat_inc(se->statistics.iowait_count);
940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957
				trace_sched_stat_iowait(tsk, delta);
			}

			trace_sched_stat_blocked(tsk, delta);

			/*
			 * Blocking time is in units of nanosecs, so shift by
			 * 20 to get a milliseconds-range estimation of the
			 * amount of time that the task spent sleeping:
			 */
			if (unlikely(prof_on == SLEEP_PROFILING)) {
				profile_hits(SLEEP_PROFILING,
						(void *)get_wchan(tsk),
						delta >> 20);
			}
			account_scheduler_latency(tsk, delta >> 10, 0);
		}
	}
958 959
}

960 961 962
/*
 * Task is being enqueued - update stats:
 */
963
static inline void
964
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
965
{
966 967 968
	if (!schedstat_enabled())
		return;

969 970 971 972
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
973
	if (se != cfs_rq->curr)
974
		update_stats_wait_start(cfs_rq, se);
975 976 977

	if (flags & ENQUEUE_WAKEUP)
		update_stats_enqueue_sleeper(cfs_rq, se);
978 979 980
}

static inline void
981
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
982
{
983 984 985 986

	if (!schedstat_enabled())
		return;

987 988 989 990
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
991
	if (se != cfs_rq->curr)
992
		update_stats_wait_end(cfs_rq, se);
993

994 995
	if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
		struct task_struct *tsk = task_of(se);
996

997
		if (tsk->state & TASK_INTERRUPTIBLE)
998
			__schedstat_set(se->statistics.sleep_start,
999 1000
				      rq_clock(rq_of(cfs_rq)));
		if (tsk->state & TASK_UNINTERRUPTIBLE)
1001
			__schedstat_set(se->statistics.block_start,
1002
				      rq_clock(rq_of(cfs_rq)));
1003 1004 1005
	}
}

1006 1007 1008 1009
/*
 * We are picking a new current task - update its stats:
 */
static inline void
1010
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
1011 1012 1013 1014
{
	/*
	 * We are starting a new run period:
	 */
1015
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
1016 1017 1018 1019 1020 1021
}

/**************************************************
 * Scheduling class queueing methods:
 */

1022 1023
#ifdef CONFIG_NUMA_BALANCING
/*
1024 1025 1026
 * Approximate time to scan a full NUMA task in ms. The task scan period is
 * calculated based on the tasks virtual memory size and
 * numa_balancing_scan_size.
1027
 */
1028 1029
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1030 1031 1032

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
1033

1034 1035 1036
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056
struct numa_group {
	atomic_t refcount;

	spinlock_t lock; /* nr_tasks, tasks */
	int nr_tasks;
	pid_t gid;
	int active_nodes;

	struct rcu_head rcu;
	unsigned long total_faults;
	unsigned long max_faults_cpu;
	/*
	 * Faults_cpu is used to decide whether memory should move
	 * towards the CPU. As a consequence, these stats are weighted
	 * more by CPU use than by memory faults.
	 */
	unsigned long *faults_cpu;
	unsigned long faults[0];
};

1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071
/*
 * For functions that can be called in multiple contexts that permit reading
 * ->numa_group (see struct task_struct for locking rules).
 */
static struct numa_group *deref_task_numa_group(struct task_struct *p)
{
	return rcu_dereference_check(p->numa_group, p == current ||
		(lockdep_is_held(&task_rq(p)->lock) && !READ_ONCE(p->on_cpu)));
}

static struct numa_group *deref_curr_numa_group(struct task_struct *p)
{
	return rcu_dereference_protected(p->numa_group, p == current);
}

1072 1073 1074
static inline unsigned long group_faults_priv(struct numa_group *ng);
static inline unsigned long group_faults_shared(struct numa_group *ng);

1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098
static unsigned int task_nr_scan_windows(struct task_struct *p)
{
	unsigned long rss = 0;
	unsigned long nr_scan_pages;

	/*
	 * Calculations based on RSS as non-present and empty pages are skipped
	 * by the PTE scanner and NUMA hinting faults should be trapped based
	 * on resident pages
	 */
	nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
	rss = get_mm_rss(p->mm);
	if (!rss)
		rss = nr_scan_pages;

	rss = round_up(rss, nr_scan_pages);
	return rss / nr_scan_pages;
}

/* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
#define MAX_SCAN_WINDOW 2560

static unsigned int task_scan_min(struct task_struct *p)
{
1099
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1100 1101 1102
	unsigned int scan, floor;
	unsigned int windows = 1;

1103 1104
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
1105 1106 1107 1108 1109 1110
	floor = 1000 / windows;

	scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
	return max_t(unsigned int, floor, scan);
}

1111 1112 1113 1114
static unsigned int task_scan_start(struct task_struct *p)
{
	unsigned long smin = task_scan_min(p);
	unsigned long period = smin;
1115
	struct numa_group *ng;
1116 1117

	/* Scale the maximum scan period with the amount of shared memory. */
1118 1119 1120
	rcu_read_lock();
	ng = rcu_dereference(p->numa_group);
	if (ng) {
1121 1122 1123 1124 1125 1126 1127
		unsigned long shared = group_faults_shared(ng);
		unsigned long private = group_faults_priv(ng);

		period *= atomic_read(&ng->refcount);
		period *= shared + 1;
		period /= private + shared + 1;
	}
1128
	rcu_read_unlock();
1129 1130 1131 1132

	return max(smin, period);
}

1133 1134
static unsigned int task_scan_max(struct task_struct *p)
{
1135 1136
	unsigned long smin = task_scan_min(p);
	unsigned long smax;
1137
	struct numa_group *ng;
1138 1139 1140

	/* Watch for min being lower than max due to floor calculations */
	smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
1141 1142

	/* Scale the maximum scan period with the amount of shared memory. */
1143 1144
	ng = deref_curr_numa_group(p);
	if (ng) {
1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155
		unsigned long shared = group_faults_shared(ng);
		unsigned long private = group_faults_priv(ng);
		unsigned long period = smax;

		period *= atomic_read(&ng->refcount);
		period *= shared + 1;
		period /= private + shared + 1;

		smax = max(smax, period);
	}

1156 1157 1158
	return max(smin, smax);
}

1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175
void init_numa_balancing(unsigned long clone_flags, struct task_struct *p)
{
	int mm_users = 0;
	struct mm_struct *mm = p->mm;

	if (mm) {
		mm_users = atomic_read(&mm->mm_users);
		if (mm_users == 1) {
			mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
			mm->numa_scan_seq = 0;
		}
	}
	p->node_stamp			= 0;
	p->numa_scan_seq		= mm ? mm->numa_scan_seq : 0;
	p->numa_scan_period		= sysctl_numa_balancing_scan_delay;
	p->numa_work.next		= &p->numa_work;
	p->numa_faults			= NULL;
1176
	RCU_INIT_POINTER(p->numa_group, NULL);
1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199
	p->last_task_numa_placement	= 0;
	p->last_sum_exec_runtime	= 0;

	/* New address space, reset the preferred nid */
	if (!(clone_flags & CLONE_VM)) {
		p->numa_preferred_nid = -1;
		return;
	}

	/*
	 * New thread, keep existing numa_preferred_nid which should be copied
	 * already by arch_dup_task_struct but stagger when scans start.
	 */
	if (mm) {
		unsigned int delay;

		delay = min_t(unsigned int, task_scan_max(current),
			current->numa_scan_period * mm_users * NSEC_PER_MSEC);
		delay += 2 * TICK_NSEC;
		p->node_stamp = delay;
	}
}

1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211
static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
{
	rq->nr_numa_running += (p->numa_preferred_nid != -1);
	rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
}

static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
{
	rq->nr_numa_running -= (p->numa_preferred_nid != -1);
	rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
}

1212 1213 1214 1215 1216 1217 1218 1219 1220
/* Shared or private faults. */
#define NR_NUMA_HINT_FAULT_TYPES 2

/* Memory and CPU locality */
#define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)

/* Averaged statistics, and temporary buffers. */
#define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)

1221 1222
pid_t task_numa_group_id(struct task_struct *p)
{
1223 1224 1225 1226 1227 1228 1229 1230 1231 1232
	struct numa_group *ng;
	pid_t gid = 0;

	rcu_read_lock();
	ng = rcu_dereference(p->numa_group);
	if (ng)
		gid = ng->gid;
	rcu_read_unlock();

	return gid;
1233 1234
}

1235
/*
1236
 * The averaged statistics, shared & private, memory & CPU,
1237 1238 1239 1240 1241
 * occupy the first half of the array. The second half of the
 * array is for current counters, which are averaged into the
 * first set by task_numa_placement.
 */
static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
1242
{
1243
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1244 1245 1246 1247
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
1248
	if (!p->numa_faults)
1249 1250
		return 0;

1251 1252
	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1253 1254
}

1255 1256
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
1257 1258 1259
	struct numa_group *ng = deref_task_numa_group(p);

	if (!ng)
1260 1261
		return 0;

1262 1263
	return ng->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		ng->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1264 1265
}

1266 1267
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
1268 1269
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1270 1271
}

1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295
static inline unsigned long group_faults_priv(struct numa_group *ng)
{
	unsigned long faults = 0;
	int node;

	for_each_online_node(node) {
		faults += ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
	}

	return faults;
}

static inline unsigned long group_faults_shared(struct numa_group *ng)
{
	unsigned long faults = 0;
	int node;

	for_each_online_node(node) {
		faults += ng->faults[task_faults_idx(NUMA_MEM, node, 0)];
	}

	return faults;
}

1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307
/*
 * A node triggering more than 1/3 as many NUMA faults as the maximum is
 * considered part of a numa group's pseudo-interleaving set. Migrations
 * between these nodes are slowed down, to allow things to settle down.
 */
#define ACTIVE_NODE_FRACTION 3

static bool numa_is_active_node(int nid, struct numa_group *ng)
{
	return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
}

1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344
/* Handle placement on systems where not all nodes are directly connected. */
static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
					int maxdist, bool task)
{
	unsigned long score = 0;
	int node;

	/*
	 * All nodes are directly connected, and the same distance
	 * from each other. No need for fancy placement algorithms.
	 */
	if (sched_numa_topology_type == NUMA_DIRECT)
		return 0;

	/*
	 * This code is called for each node, introducing N^2 complexity,
	 * which should be ok given the number of nodes rarely exceeds 8.
	 */
	for_each_online_node(node) {
		unsigned long faults;
		int dist = node_distance(nid, node);

		/*
		 * The furthest away nodes in the system are not interesting
		 * for placement; nid was already counted.
		 */
		if (dist == sched_max_numa_distance || node == nid)
			continue;

		/*
		 * On systems with a backplane NUMA topology, compare groups
		 * of nodes, and move tasks towards the group with the most
		 * memory accesses. When comparing two nodes at distance
		 * "hoplimit", only nodes closer by than "hoplimit" are part
		 * of each group. Skip other nodes.
		 */
		if (sched_numa_topology_type == NUMA_BACKPLANE &&
1345
					dist >= maxdist)
1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372
			continue;

		/* Add up the faults from nearby nodes. */
		if (task)
			faults = task_faults(p, node);
		else
			faults = group_faults(p, node);

		/*
		 * On systems with a glueless mesh NUMA topology, there are
		 * no fixed "groups of nodes". Instead, nodes that are not
		 * directly connected bounce traffic through intermediate
		 * nodes; a numa_group can occupy any set of nodes.
		 * The further away a node is, the less the faults count.
		 * This seems to result in good task placement.
		 */
		if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
			faults *= (sched_max_numa_distance - dist);
			faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
		}

		score += faults;
	}

	return score;
}

1373 1374 1375 1376 1377 1378
/*
 * These return the fraction of accesses done by a particular task, or
 * task group, on a particular numa node.  The group weight is given a
 * larger multiplier, in order to group tasks together that are almost
 * evenly spread out between numa nodes.
 */
1379 1380
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1381
{
1382
	unsigned long faults, total_faults;
1383

1384
	if (!p->numa_faults)
1385 1386 1387 1388 1389 1390 1391
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1392
	faults = task_faults(p, nid);
1393 1394
	faults += score_nearby_nodes(p, nid, dist, true);

1395
	return 1000 * faults / total_faults;
1396 1397
}

1398 1399
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1400
{
1401
	struct numa_group *ng = deref_task_numa_group(p);
1402 1403
	unsigned long faults, total_faults;

1404
	if (!ng)
1405 1406
		return 0;

1407
	total_faults = ng->total_faults;
1408 1409

	if (!total_faults)
1410 1411
		return 0;

1412
	faults = group_faults(p, nid);
1413 1414
	faults += score_nearby_nodes(p, nid, dist, false);

1415
	return 1000 * faults / total_faults;
1416 1417
}

1418 1419 1420
bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
				int src_nid, int dst_cpu)
{
1421
	struct numa_group *ng = deref_curr_numa_group(p);
1422 1423 1424 1425
	int dst_nid = cpu_to_node(dst_cpu);
	int last_cpupid, this_cpupid;

	this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436
	last_cpupid = page_cpupid_xchg_last(page, this_cpupid);

	/*
	 * Allow first faults or private faults to migrate immediately early in
	 * the lifetime of a task. The magic number 4 is based on waiting for
	 * two full passes of the "multi-stage node selection" test that is
	 * executed below.
	 */
	if ((p->numa_preferred_nid == -1 || p->numa_scan_seq <= 4) &&
	    (cpupid_pid_unset(last_cpupid) || cpupid_match_pid(p, last_cpupid)))
		return true;
1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467

	/*
	 * Multi-stage node selection is used in conjunction with a periodic
	 * migration fault to build a temporal task<->page relation. By using
	 * a two-stage filter we remove short/unlikely relations.
	 *
	 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
	 * a task's usage of a particular page (n_p) per total usage of this
	 * page (n_t) (in a given time-span) to a probability.
	 *
	 * Our periodic faults will sample this probability and getting the
	 * same result twice in a row, given these samples are fully
	 * independent, is then given by P(n)^2, provided our sample period
	 * is sufficiently short compared to the usage pattern.
	 *
	 * This quadric squishes small probabilities, making it less likely we
	 * act on an unlikely task<->page relation.
	 */
	if (!cpupid_pid_unset(last_cpupid) &&
				cpupid_to_nid(last_cpupid) != dst_nid)
		return false;

	/* Always allow migrate on private faults */
	if (cpupid_match_pid(p, last_cpupid))
		return true;

	/* A shared fault, but p->numa_group has not been set up yet. */
	if (!ng)
		return true;

	/*
1468 1469
	 * Destination node is much more heavily used than the source
	 * node? Allow migration.
1470
	 */
1471 1472
	if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
					ACTIVE_NODE_FRACTION)
1473 1474 1475
		return true;

	/*
1476 1477 1478 1479 1480 1481
	 * Distribute memory according to CPU & memory use on each node,
	 * with 3/4 hysteresis to avoid unnecessary memory migrations:
	 *
	 * faults_cpu(dst)   3   faults_cpu(src)
	 * --------------- * - > ---------------
	 * faults_mem(dst)   4   faults_mem(src)
1482
	 */
1483 1484
	return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
	       group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1485 1486
}

1487
static unsigned long weighted_cpuload(struct rq *rq);
1488 1489
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1490
static unsigned long capacity_of(int cpu);
1491

1492
/* Cached statistics for all CPUs within a node */
1493 1494
struct numa_stats {
	unsigned long load;
1495 1496

	/* Total compute capacity of CPUs on a node */
1497
	unsigned long compute_capacity;
1498

1499
	unsigned int nr_running;
1500
};
1501

1502 1503 1504 1505 1506
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1507 1508
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1509 1510 1511 1512 1513 1514

	memset(ns, 0, sizeof(*ns));
	for_each_cpu(cpu, cpumask_of_node(nid)) {
		struct rq *rq = cpu_rq(cpu);

		ns->nr_running += rq->nr_running;
1515
		ns->load += weighted_cpuload(rq);
1516
		ns->compute_capacity += capacity_of(cpu);
1517 1518

		cpus++;
1519 1520
	}

1521 1522 1523 1524 1525
	/*
	 * If we raced with hotplug and there are no CPUs left in our mask
	 * the @ns structure is NULL'ed and task_numa_compare() will
	 * not find this node attractive.
	 *
1526
	 * We'll detect a huge imbalance and bail there.
1527 1528 1529 1530
	 */
	if (!cpus)
		return;

1531 1532 1533 1534
	/* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
	smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
	capacity = cpus / smt; /* cores */

1535
	capacity = min_t(unsigned, capacity,
1536
		DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1537 1538
}

1539 1540
struct task_numa_env {
	struct task_struct *p;
1541

1542 1543
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1544

1545
	struct numa_stats src_stats, dst_stats;
1546

1547
	int imbalance_pct;
1548
	int dist;
1549 1550 1551

	struct task_struct *best_task;
	long best_imp;
1552 1553 1554
	int best_cpu;
};

1555 1556 1557
static void task_numa_assign(struct task_numa_env *env,
			     struct task_struct *p, long imp)
{
1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572
	struct rq *rq = cpu_rq(env->dst_cpu);

	/* Bail out if run-queue part of active NUMA balance. */
	if (xchg(&rq->numa_migrate_on, 1))
		return;

	/*
	 * Clear previous best_cpu/rq numa-migrate flag, since task now
	 * found a better CPU to move/swap.
	 */
	if (env->best_cpu != -1) {
		rq = cpu_rq(env->best_cpu);
		WRITE_ONCE(rq->numa_migrate_on, 0);
	}

1573 1574
	if (env->best_task)
		put_task_struct(env->best_task);
1575 1576
	if (p)
		get_task_struct(p);
1577 1578 1579 1580 1581 1582

	env->best_task = p;
	env->best_imp = imp;
	env->best_cpu = env->dst_cpu;
}

1583
static bool load_too_imbalanced(long src_load, long dst_load,
1584 1585
				struct task_numa_env *env)
{
1586 1587
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598
	long src_capacity, dst_capacity;

	/*
	 * The load is corrected for the CPU capacity available on each node.
	 *
	 * src_load        dst_load
	 * ------------ vs ---------
	 * src_capacity    dst_capacity
	 */
	src_capacity = env->src_stats.compute_capacity;
	dst_capacity = env->dst_stats.compute_capacity;
1599

1600
	imb = abs(dst_load * src_capacity - src_load * dst_capacity);
1601

1602
	orig_src_load = env->src_stats.load;
1603
	orig_dst_load = env->dst_stats.load;
1604

1605
	old_imb = abs(orig_dst_load * src_capacity - orig_src_load * dst_capacity);
1606 1607 1608

	/* Would this change make things worse? */
	return (imb > old_imb);
1609 1610
}

1611 1612 1613 1614 1615 1616 1617
/*
 * Maximum NUMA importance can be 1998 (2*999);
 * SMALLIMP @ 30 would be close to 1998/64.
 * Used to deter task migration.
 */
#define SMALLIMP	30

1618 1619 1620 1621 1622 1623
/*
 * This checks if the overall compute and NUMA accesses of the system would
 * be improved if the source tasks was migrated to the target dst_cpu taking
 * into account that it might be best if task running on the dst_cpu should
 * be exchanged with the source task
 */
1624
static void task_numa_compare(struct task_numa_env *env,
1625
			      long taskimp, long groupimp, bool maymove)
1626
{
1627
	struct numa_group *cur_ng, *p_ng = deref_curr_numa_group(env->p);
1628
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
1629
	long imp = p_ng ? groupimp : taskimp;
1630
	struct task_struct *cur;
1631
	long src_load, dst_load;
1632
	int dist = env->dist;
1633 1634
	long moveimp = imp;
	long load;
1635

1636 1637 1638
	if (READ_ONCE(dst_rq->numa_migrate_on))
		return;

1639
	rcu_read_lock();
1640 1641
	cur = task_rcu_dereference(&dst_rq->curr);
	if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1642 1643
		cur = NULL;

1644 1645 1646 1647 1648 1649 1650
	/*
	 * Because we have preemption enabled we can get migrated around and
	 * end try selecting ourselves (current == env->p) as a swap candidate.
	 */
	if (cur == env->p)
		goto unlock;

1651
	if (!cur) {
1652
		if (maymove && moveimp >= env->best_imp)
1653 1654 1655 1656 1657
			goto assign;
		else
			goto unlock;
	}

1658 1659 1660 1661
	/*
	 * "imp" is the fault differential for the source task between the
	 * source and destination node. Calculate the total differential for
	 * the source task and potential destination task. The more negative
1662
	 * the value is, the more remote accesses that would be expected to
1663 1664
	 * be incurred if the tasks were swapped.
	 */
1665 1666 1667
	/* Skip this swap candidate if cannot move to the source cpu */
	if (!cpumask_test_cpu(env->src_cpu, &cur->cpus_allowed))
		goto unlock;
1668

1669 1670 1671 1672
	/*
	 * If dst and source tasks are in the same NUMA group, or not
	 * in any group then look only at task weights.
	 */
1673 1674
	cur_ng = rcu_dereference(cur->numa_group);
	if (cur_ng == p_ng) {
1675 1676
		imp = taskimp + task_weight(cur, env->src_nid, dist) -
		      task_weight(cur, env->dst_nid, dist);
1677
		/*
1678 1679
		 * Add some hysteresis to prevent swapping the
		 * tasks within a group over tiny differences.
1680
		 */
1681
		if (cur_ng)
1682 1683 1684 1685 1686 1687
			imp -= imp / 16;
	} else {
		/*
		 * Compare the group weights. If a task is all by itself
		 * (not part of a group), use the task weight instead.
		 */
1688
		if (cur_ng && p_ng)
1689 1690 1691 1692 1693
			imp += group_weight(cur, env->src_nid, dist) -
			       group_weight(cur, env->dst_nid, dist);
		else
			imp += task_weight(cur, env->src_nid, dist) -
			       task_weight(cur, env->dst_nid, dist);
1694 1695
	}

1696
	if (maymove && moveimp > imp && moveimp > env->best_imp) {
1697
		imp = moveimp;
1698
		cur = NULL;
1699
		goto assign;
1700
	}
1701

1702 1703 1704 1705 1706 1707 1708 1709 1710
	/*
	 * If the NUMA importance is less than SMALLIMP,
	 * task migration might only result in ping pong
	 * of tasks and also hurt performance due to cache
	 * misses.
	 */
	if (imp < SMALLIMP || imp <= env->best_imp + SMALLIMP / 2)
		goto unlock;

1711 1712 1713
	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
1714 1715 1716 1717
	load = task_h_load(env->p) - task_h_load(cur);
	if (!load)
		goto assign;

1718 1719
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1720

1721
	if (load_too_imbalanced(src_load, dst_load, env))
1722 1723
		goto unlock;

1724
assign:
1725 1726 1727 1728
	/*
	 * One idle CPU per node is evaluated for a task numa move.
	 * Call select_idle_sibling to maybe find a better one.
	 */
1729 1730
	if (!cur) {
		/*
1731
		 * select_idle_siblings() uses an per-CPU cpumask that
1732 1733 1734
		 * can be used from IRQ context.
		 */
		local_irq_disable();
1735 1736
		env->dst_cpu = select_idle_sibling(env->p, env->src_cpu,
						   env->dst_cpu);
1737 1738
		local_irq_enable();
	}
1739

1740 1741 1742 1743 1744
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1745 1746
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1747
{
1748 1749
	long src_load, dst_load, load;
	bool maymove = false;
1750 1751
	int cpu;

1752 1753 1754 1755 1756 1757 1758 1759 1760 1761
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;

	/*
	 * If the improvement from just moving env->p direction is better
	 * than swapping tasks around, check if a move is possible.
	 */
	maymove = !load_too_imbalanced(src_load, dst_load, env);

1762 1763
	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
		/* Skip this CPU if the source task cannot migrate */
1764
		if (!cpumask_test_cpu(cpu, &env->p->cpus_allowed))
1765 1766 1767
			continue;

		env->dst_cpu = cpu;
1768
		task_numa_compare(env, taskimp, groupimp, maymove);
1769 1770 1771
	}
}

1772 1773 1774 1775
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1776

1777
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1778
		.src_nid = task_node(p),
1779 1780 1781 1782 1783

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
1784
		.best_cpu = -1,
1785
	};
1786
	unsigned long taskweight, groupweight;
1787
	struct sched_domain *sd;
1788 1789
	long taskimp, groupimp;
	struct numa_group *ng;
1790
	struct rq *best_rq;
1791
	int nid, ret, dist;
1792

1793
	/*
1794 1795 1796 1797 1798 1799
	 * Pick the lowest SD_NUMA domain, as that would have the smallest
	 * imbalance and would be the first to start moving tasks about.
	 *
	 * And we want to avoid any moving of tasks about, as that would create
	 * random movement of tasks -- counter the numa conditions we're trying
	 * to satisfy here.
1800 1801
	 */
	rcu_read_lock();
1802
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1803 1804
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1805 1806
	rcu_read_unlock();

1807 1808 1809 1810 1811 1812 1813
	/*
	 * Cpusets can break the scheduler domain tree into smaller
	 * balance domains, some of which do not cross NUMA boundaries.
	 * Tasks that are "trapped" in such domains cannot be migrated
	 * elsewhere, so there is no point in (re)trying.
	 */
	if (unlikely(!sd)) {
1814
		sched_setnuma(p, task_node(p));
1815 1816 1817
		return -EINVAL;
	}

1818
	env.dst_nid = p->numa_preferred_nid;
1819 1820 1821 1822 1823 1824
	dist = env.dist = node_distance(env.src_nid, env.dst_nid);
	taskweight = task_weight(p, env.src_nid, dist);
	groupweight = group_weight(p, env.src_nid, dist);
	update_numa_stats(&env.src_stats, env.src_nid);
	taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
	groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1825
	update_numa_stats(&env.dst_stats, env.dst_nid);
1826

1827
	/* Try to find a spot on the preferred nid. */
1828
	task_numa_find_cpu(&env, taskimp, groupimp);
1829

1830 1831 1832 1833 1834 1835 1836
	/*
	 * Look at other nodes in these cases:
	 * - there is no space available on the preferred_nid
	 * - the task is part of a numa_group that is interleaved across
	 *   multiple NUMA nodes; in order to better consolidate the group,
	 *   we need to check other locations.
	 */
1837 1838
	ng = deref_curr_numa_group(p);
	if (env.best_cpu == -1 || (ng && ng->active_nodes > 1)) {
1839 1840 1841
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1842

1843
			dist = node_distance(env.src_nid, env.dst_nid);
1844 1845 1846 1847 1848
			if (sched_numa_topology_type == NUMA_BACKPLANE &&
						dist != env.dist) {
				taskweight = task_weight(p, env.src_nid, dist);
				groupweight = group_weight(p, env.src_nid, dist);
			}
1849

1850
			/* Only consider nodes where both task and groups benefit */
1851 1852
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1853
			if (taskimp < 0 && groupimp < 0)
1854 1855
				continue;

1856
			env.dist = dist;
1857 1858
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1859
			task_numa_find_cpu(&env, taskimp, groupimp);
1860 1861 1862
		}
	}

1863 1864 1865 1866 1867 1868 1869 1870
	/*
	 * If the task is part of a workload that spans multiple NUMA nodes,
	 * and is migrating into one of the workload's active nodes, remember
	 * this node as the task's preferred numa node, so the workload can
	 * settle down.
	 * A task that migrated to a second choice node will be better off
	 * trying for a better one later. Do not set the preferred node here.
	 */
1871
	if (ng) {
1872 1873 1874
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
1875
			nid = cpu_to_node(env.best_cpu);
1876

1877 1878
		if (nid != p->numa_preferred_nid)
			sched_setnuma(p, nid);
1879 1880 1881 1882 1883
	}

	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;
1884

1885
	best_rq = cpu_rq(env.best_cpu);
1886
	if (env.best_task == NULL) {
1887
		ret = migrate_task_to(p, env.best_cpu);
1888
		WRITE_ONCE(best_rq->numa_migrate_on, 0);
1889 1890
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1891 1892 1893
		return ret;
	}

1894
	ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu);
1895
	WRITE_ONCE(best_rq->numa_migrate_on, 0);
1896

1897 1898
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1899 1900
	put_task_struct(env.best_task);
	return ret;
1901 1902
}

1903 1904 1905
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1906 1907
	unsigned long interval = HZ;

1908
	/* This task has no NUMA fault statistics yet */
1909
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1910 1911
		return;

1912
	/* Periodically retry migrating the task to the preferred node */
1913
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1914
	p->numa_migrate_retry = jiffies + interval;
1915 1916

	/* Success if task is already running on preferred CPU */
1917
	if (task_node(p) == p->numa_preferred_nid)
1918 1919 1920
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1921
	task_numa_migrate(p);
1922 1923
}

1924
/*
1925
 * Find out how many nodes on the workload is actively running on. Do this by
1926 1927 1928 1929
 * tracking the nodes from which NUMA hinting faults are triggered. This can
 * be different from the set of nodes where the workload's memory is currently
 * located.
 */
1930
static void numa_group_count_active_nodes(struct numa_group *numa_group)
1931 1932
{
	unsigned long faults, max_faults = 0;
1933
	int nid, active_nodes = 0;
1934 1935 1936 1937 1938 1939 1940 1941 1942

	for_each_online_node(nid) {
		faults = group_faults_cpu(numa_group, nid);
		if (faults > max_faults)
			max_faults = faults;
	}

	for_each_online_node(nid) {
		faults = group_faults_cpu(numa_group, nid);
1943 1944
		if (faults * ACTIVE_NODE_FRACTION > max_faults)
			active_nodes++;
1945
	}
1946 1947 1948

	numa_group->max_faults_cpu = max_faults;
	numa_group->active_nodes = active_nodes;
1949 1950
}

1951 1952 1953
/*
 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
 * increments. The more local the fault statistics are, the higher the scan
1954 1955 1956
 * period will be for the next scan window. If local/(local+remote) ratio is
 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
 * the scan period will decrease. Aim for 70% local accesses.
1957 1958
 */
#define NUMA_PERIOD_SLOTS 10
1959
#define NUMA_PERIOD_THRESHOLD 7
1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970

/*
 * Increase the scan period (slow down scanning) if the majority of
 * our memory is already on our local node, or if the majority of
 * the page accesses are shared with other processes.
 * Otherwise, decrease the scan period.
 */
static void update_task_scan_period(struct task_struct *p,
			unsigned long shared, unsigned long private)
{
	unsigned int period_slot;
1971
	int lr_ratio, ps_ratio;
1972 1973 1974 1975 1976 1977 1978 1979
	int diff;

	unsigned long remote = p->numa_faults_locality[0];
	unsigned long local = p->numa_faults_locality[1];

	/*
	 * If there were no record hinting faults then either the task is
	 * completely idle or all activity is areas that are not of interest
1980 1981 1982
	 * to automatic numa balancing. Related to that, if there were failed
	 * migration then it implies we are migrating too quickly or the local
	 * node is overloaded. In either case, scan slower
1983
	 */
1984
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000
		p->numa_scan_period = min(p->numa_scan_period_max,
			p->numa_scan_period << 1);

		p->mm->numa_next_scan = jiffies +
			msecs_to_jiffies(p->numa_scan_period);

		return;
	}

	/*
	 * Prepare to scale scan period relative to the current period.
	 *	 == NUMA_PERIOD_THRESHOLD scan period stays the same
	 *       <  NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
	 *	 >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
	 */
	period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
	lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
	ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);

	if (ps_ratio >= NUMA_PERIOD_THRESHOLD) {
		/*
		 * Most memory accesses are local. There is no need to
		 * do fast NUMA scanning, since memory is already local.
		 */
		int slot = ps_ratio - NUMA_PERIOD_THRESHOLD;
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else if (lr_ratio >= NUMA_PERIOD_THRESHOLD) {
		/*
		 * Most memory accesses are shared with other tasks.
		 * There is no point in continuing fast NUMA scanning,
		 * since other tasks may just move the memory elsewhere.
		 */
		int slot = lr_ratio - NUMA_PERIOD_THRESHOLD;
2020 2021 2022 2023 2024
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else {
		/*
2025 2026 2027
		 * Private memory faults exceed (SLOTS-THRESHOLD)/SLOTS,
		 * yet they are not on the local NUMA node. Speed up
		 * NUMA scanning to get the memory moved over.
2028
		 */
2029 2030
		int ratio = max(lr_ratio, ps_ratio);
		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
2031 2032 2033 2034 2035 2036 2037
	}

	p->numa_scan_period = clamp(p->numa_scan_period + diff,
			task_scan_min(p), task_scan_max(p));
	memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
}

2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054
/*
 * Get the fraction of time the task has been running since the last
 * NUMA placement cycle. The scheduler keeps similar statistics, but
 * decays those on a 32ms period, which is orders of magnitude off
 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
 * stats only if the task is so new there are no NUMA statistics yet.
 */
static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
{
	u64 runtime, delta, now;
	/* Use the start of this time slice to avoid calculations. */
	now = p->se.exec_start;
	runtime = p->se.sum_exec_runtime;

	if (p->last_task_numa_placement) {
		delta = runtime - p->last_sum_exec_runtime;
		*period = now - p->last_task_numa_placement;
2055 2056 2057 2058

		/* Avoid time going backwards, prevent potential divide error: */
		if (unlikely((s64)*period < 0))
			*period = 0;
2059
	} else {
2060
		delta = p->se.avg.load_sum;
2061
		*period = LOAD_AVG_MAX;
2062 2063 2064 2065 2066 2067 2068 2069
	}

	p->last_sum_exec_runtime = runtime;
	p->last_task_numa_placement = now;

	return delta;
}

2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116
/*
 * Determine the preferred nid for a task in a numa_group. This needs to
 * be done in a way that produces consistent results with group_weight,
 * otherwise workloads might not converge.
 */
static int preferred_group_nid(struct task_struct *p, int nid)
{
	nodemask_t nodes;
	int dist;

	/* Direct connections between all NUMA nodes. */
	if (sched_numa_topology_type == NUMA_DIRECT)
		return nid;

	/*
	 * On a system with glueless mesh NUMA topology, group_weight
	 * scores nodes according to the number of NUMA hinting faults on
	 * both the node itself, and on nearby nodes.
	 */
	if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
		unsigned long score, max_score = 0;
		int node, max_node = nid;

		dist = sched_max_numa_distance;

		for_each_online_node(node) {
			score = group_weight(p, node, dist);
			if (score > max_score) {
				max_score = score;
				max_node = node;
			}
		}
		return max_node;
	}

	/*
	 * Finding the preferred nid in a system with NUMA backplane
	 * interconnect topology is more involved. The goal is to locate
	 * tasks from numa_groups near each other in the system, and
	 * untangle workloads from different sides of the system. This requires
	 * searching down the hierarchy of node groups, recursively searching
	 * inside the highest scoring group of nodes. The nodemask tricks
	 * keep the complexity of the search down.
	 */
	nodes = node_online_map;
	for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
		unsigned long max_faults = 0;
2117
		nodemask_t max_group = NODE_MASK_NONE;
2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150
		int a, b;

		/* Are there nodes at this distance from each other? */
		if (!find_numa_distance(dist))
			continue;

		for_each_node_mask(a, nodes) {
			unsigned long faults = 0;
			nodemask_t this_group;
			nodes_clear(this_group);

			/* Sum group's NUMA faults; includes a==b case. */
			for_each_node_mask(b, nodes) {
				if (node_distance(a, b) < dist) {
					faults += group_faults(p, b);
					node_set(b, this_group);
					node_clear(b, nodes);
				}
			}

			/* Remember the top group. */
			if (faults > max_faults) {
				max_faults = faults;
				max_group = this_group;
				/*
				 * subtle: at the smallest distance there is
				 * just one node left in each "group", the
				 * winner is the preferred nid.
				 */
				nid = a;
			}
		}
		/* Next round, evaluate the nodes within max_group. */
2151 2152
		if (!max_faults)
			break;
2153 2154 2155 2156 2157
		nodes = max_group;
	}
	return nid;
}

2158 2159
static void task_numa_placement(struct task_struct *p)
{
2160 2161
	int seq, nid, max_nid = -1;
	unsigned long max_faults = 0;
2162
	unsigned long fault_types[2] = { 0, 0 };
2163 2164
	unsigned long total_faults;
	u64 runtime, period;
2165
	spinlock_t *group_lock = NULL;
2166
	struct numa_group *ng;
2167

2168 2169 2170 2171 2172
	/*
	 * The p->mm->numa_scan_seq field gets updated without
	 * exclusive access. Use READ_ONCE() here to ensure
	 * that the field is read in a single access:
	 */
2173
	seq = READ_ONCE(p->mm->numa_scan_seq);
2174 2175 2176
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
2177
	p->numa_scan_period_max = task_scan_max(p);
2178

2179 2180 2181 2182
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

2183
	/* If the task is part of a group prevent parallel updates to group stats */
2184 2185 2186
	ng = deref_curr_numa_group(p);
	if (ng) {
		group_lock = &ng->lock;
2187
		spin_lock_irq(group_lock);
2188 2189
	}

2190 2191
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
2192 2193
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2194
		unsigned long faults = 0, group_faults = 0;
2195
		int priv;
2196

2197
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2198
			long diff, f_diff, f_weight;
2199

2200 2201 2202 2203
			mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
			membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
			cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
			cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
2204

2205
			/* Decay existing window, copy faults since last scan */
2206 2207 2208
			diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
			fault_types[priv] += p->numa_faults[membuf_idx];
			p->numa_faults[membuf_idx] = 0;
2209

2210 2211 2212 2213 2214 2215 2216 2217
			/*
			 * Normalize the faults_from, so all tasks in a group
			 * count according to CPU use, instead of by the raw
			 * number of faults. Tasks with little runtime have
			 * little over-all impact on throughput, and thus their
			 * faults are less important.
			 */
			f_weight = div64_u64(runtime << 16, period + 1);
2218
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2219
				   (total_faults + 1);
2220 2221
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
2222

2223 2224 2225
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
2226
			p->total_numa_faults += diff;
2227
			if (ng) {
2228 2229 2230 2231 2232 2233 2234
				/*
				 * safe because we can only change our own group
				 *
				 * mem_idx represents the offset for a given
				 * nid and priv in a specific region because it
				 * is at the beginning of the numa_faults array.
				 */
2235 2236 2237 2238
				ng->faults[mem_idx] += diff;
				ng->faults_cpu[mem_idx] += f_diff;
				ng->total_faults += diff;
				group_faults += ng->faults[mem_idx];
2239
			}
2240 2241
		}

2242
		if (!ng) {
2243 2244 2245 2246 2247 2248
			if (faults > max_faults) {
				max_faults = faults;
				max_nid = nid;
			}
		} else if (group_faults > max_faults) {
			max_faults = group_faults;
2249 2250
			max_nid = nid;
		}
2251 2252
	}

2253 2254
	if (ng) {
		numa_group_count_active_nodes(ng);
2255
		spin_unlock_irq(group_lock);
2256
		max_nid = preferred_group_nid(p, max_nid);
2257 2258
	}

2259 2260 2261 2262
	if (max_faults) {
		/* Set the new preferred node */
		if (max_nid != p->numa_preferred_nid)
			sched_setnuma(p, max_nid);
2263
	}
2264 2265

	update_task_scan_period(p, fault_types[0], fault_types[1]);
2266 2267
}

2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278
static inline int get_numa_group(struct numa_group *grp)
{
	return atomic_inc_not_zero(&grp->refcount);
}

static inline void put_numa_group(struct numa_group *grp)
{
	if (atomic_dec_and_test(&grp->refcount))
		kfree_rcu(grp, rcu);
}

2279 2280
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
2281 2282 2283 2284 2285 2286 2287
{
	struct numa_group *grp, *my_grp;
	struct task_struct *tsk;
	bool join = false;
	int cpu = cpupid_to_cpu(cpupid);
	int i;

2288
	if (unlikely(!deref_curr_numa_group(p))) {
2289
		unsigned int size = sizeof(struct numa_group) +
2290
				    4*nr_node_ids*sizeof(unsigned long);
2291 2292 2293 2294 2295 2296

		grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
		if (!grp)
			return;

		atomic_set(&grp->refcount, 1);
2297 2298
		grp->active_nodes = 1;
		grp->max_faults_cpu = 0;
2299
		spin_lock_init(&grp->lock);
2300
		grp->gid = p->pid;
2301
		/* Second half of the array tracks nids where faults happen */
2302 2303
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
2304

2305
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2306
			grp->faults[i] = p->numa_faults[i];
2307

2308
		grp->total_faults = p->total_numa_faults;
2309

2310 2311 2312 2313 2314
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
2315
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
2316 2317

	if (!cpupid_match_pid(tsk, cpupid))
2318
		goto no_join;
2319 2320 2321

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
2322
		goto no_join;
2323

2324
	my_grp = deref_curr_numa_group(p);
2325
	if (grp == my_grp)
2326
		goto no_join;
2327 2328 2329 2330 2331 2332

	/*
	 * Only join the other group if its bigger; if we're the bigger group,
	 * the other task will join us.
	 */
	if (my_grp->nr_tasks > grp->nr_tasks)
2333
		goto no_join;
2334 2335 2336 2337 2338

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2339
		goto no_join;
2340

2341 2342 2343 2344 2345 2346 2347
	/* Always join threads in the same process. */
	if (tsk->mm == current->mm)
		join = true;

	/* Simple filter to avoid false positives due to PID collisions */
	if (flags & TNF_SHARED)
		join = true;
2348

2349 2350 2351
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2352
	if (join && !get_numa_group(grp))
2353
		goto no_join;
2354 2355 2356 2357 2358 2359

	rcu_read_unlock();

	if (!join)
		return;

2360 2361
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2362

2363
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2364 2365
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2366
	}
2367 2368
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2369 2370 2371 2372 2373

	my_grp->nr_tasks--;
	grp->nr_tasks++;

	spin_unlock(&my_grp->lock);
2374
	spin_unlock_irq(&grp->lock);
2375 2376 2377 2378

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2379 2380 2381 2382 2383
	return;

no_join:
	rcu_read_unlock();
	return;
2384 2385
}

2386 2387 2388 2389 2390 2391 2392 2393
/*
 * Get rid of NUMA staticstics associated with a task (either current or dead).
 * If @final is set, the task is dead and has reached refcount zero, so we can
 * safely free all relevant data structures. Otherwise, there might be
 * concurrent reads from places like load balancing and procfs, and we should
 * reset the data back to default state without freeing ->numa_faults.
 */
void task_numa_free(struct task_struct *p, bool final)
2394
{
2395 2396
	/* safe: p either is current or is being freed by current */
	struct numa_group *grp = rcu_dereference_raw(p->numa_group);
2397
	unsigned long *numa_faults = p->numa_faults;
2398 2399
	unsigned long flags;
	int i;
2400

2401 2402 2403
	if (!numa_faults)
		return;

2404
	if (grp) {
2405
		spin_lock_irqsave(&grp->lock, flags);
2406
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2407
			grp->faults[i] -= p->numa_faults[i];
2408
		grp->total_faults -= p->total_numa_faults;
2409

2410
		grp->nr_tasks--;
2411
		spin_unlock_irqrestore(&grp->lock, flags);
2412
		RCU_INIT_POINTER(p->numa_group, NULL);
2413 2414 2415
		put_numa_group(grp);
	}

2416 2417 2418 2419 2420 2421 2422 2423
	if (final) {
		p->numa_faults = NULL;
		kfree(numa_faults);
	} else {
		p->total_numa_faults = 0;
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
			numa_faults[i] = 0;
	}
2424 2425
}

2426 2427 2428
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2429
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2430 2431
{
	struct task_struct *p = current;
2432
	bool migrated = flags & TNF_MIGRATED;
2433
	int cpu_node = task_node(current);
2434
	int local = !!(flags & TNF_FAULT_LOCAL);
2435
	struct numa_group *ng;
2436
	int priv;
2437

2438
	if (!static_branch_likely(&sched_numa_balancing))
2439 2440
		return;

2441 2442 2443 2444
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2445
	/* Allocate buffer to track faults on a per-node basis */
2446 2447
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2448
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2449

2450 2451
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2452
			return;
2453

2454
		p->total_numa_faults = 0;
2455
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2456
	}
2457

2458 2459 2460 2461 2462 2463 2464 2465
	/*
	 * First accesses are treated as private, otherwise consider accesses
	 * to be private if the accessing pid has not changed
	 */
	if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
		priv = 1;
	} else {
		priv = cpupid_match_pid(p, last_cpupid);
2466
		if (!priv && !(flags & TNF_NO_GROUP))
2467
			task_numa_group(p, last_cpupid, flags, &priv);
2468 2469
	}

2470 2471 2472 2473 2474 2475
	/*
	 * If a workload spans multiple NUMA nodes, a shared fault that
	 * occurs wholly within the set of nodes that the workload is
	 * actively using should be counted as local. This allows the
	 * scan rate to slow down when a workload has settled down.
	 */
2476
	ng = deref_curr_numa_group(p);
2477 2478 2479
	if (!priv && !local && ng && ng->active_nodes > 1 &&
				numa_is_active_node(cpu_node, ng) &&
				numa_is_active_node(mem_node, ng))
2480 2481
		local = 1;

2482 2483 2484 2485
	/*
	 * Retry task to preferred node migration periodically, in case it
	 * case it previously failed, or the scheduler moved us.
	 */
2486 2487
	if (time_after(jiffies, p->numa_migrate_retry)) {
		task_numa_placement(p);
2488
		numa_migrate_preferred(p);
2489
	}
2490

I
Ingo Molnar 已提交
2491 2492
	if (migrated)
		p->numa_pages_migrated += pages;
2493 2494
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2495

2496 2497
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2498
	p->numa_faults_locality[local] += pages;
2499 2500
}

2501 2502
static void reset_ptenuma_scan(struct task_struct *p)
{
2503 2504 2505 2506 2507 2508 2509 2510
	/*
	 * We only did a read acquisition of the mmap sem, so
	 * p->mm->numa_scan_seq is written to without exclusive access
	 * and the update is not guaranteed to be atomic. That's not
	 * much of an issue though, since this is just used for
	 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
	 * expensive, to avoid any form of compiler optimizations:
	 */
2511
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2512 2513 2514
	p->mm->numa_scan_offset = 0;
}

2515 2516 2517 2518 2519 2520 2521 2522 2523
/*
 * The expensive part of numa migration is done from task_work context.
 * Triggered from task_tick_numa().
 */
void task_numa_work(struct callback_head *work)
{
	unsigned long migrate, next_scan, now = jiffies;
	struct task_struct *p = current;
	struct mm_struct *mm = p->mm;
2524
	u64 runtime = p->se.sum_exec_runtime;
2525
	struct vm_area_struct *vma;
2526
	unsigned long start, end;
2527
	unsigned long nr_pte_updates = 0;
2528
	long pages, virtpages;
2529

2530
	SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543

	work->next = work; /* protect against double add */
	/*
	 * Who cares about NUMA placement when they're dying.
	 *
	 * NOTE: make sure not to dereference p->mm before this check,
	 * exit_task_work() happens _after_ exit_mm() so we could be called
	 * without p->mm even though we still had it when we enqueued this
	 * work.
	 */
	if (p->flags & PF_EXITING)
		return;

2544
	if (!mm->numa_next_scan) {
2545 2546
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2547 2548
	}

2549 2550 2551 2552 2553 2554 2555
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2556 2557
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
2558
		p->numa_scan_period = task_scan_start(p);
2559
	}
2560

2561
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2562 2563 2564
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2565 2566 2567 2568 2569 2570
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2571 2572 2573
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2574
	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2575 2576
	if (!pages)
		return;
2577

2578

2579 2580
	if (!down_read_trylock(&mm->mmap_sem))
		return;
2581
	vma = find_vma(mm, start);
2582 2583
	if (!vma) {
		reset_ptenuma_scan(p);
2584
		start = 0;
2585 2586
		vma = mm->mmap;
	}
2587
	for (; vma; vma = vma->vm_next) {
2588
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2589
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2590
			continue;
2591
		}
2592

2593 2594 2595 2596 2597 2598 2599 2600 2601 2602
		/*
		 * Shared library pages mapped by multiple processes are not
		 * migrated as it is expected they are cache replicated. Avoid
		 * hinting faults in read-only file-backed mappings or the vdso
		 * as migrating the pages will be of marginal benefit.
		 */
		if (!vma->vm_mm ||
		    (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ)))
			continue;

M
Mel Gorman 已提交
2603 2604 2605 2606 2607 2608
		/*
		 * Skip inaccessible VMAs to avoid any confusion between
		 * PROT_NONE and NUMA hinting ptes
		 */
		if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
			continue;
2609

2610 2611 2612 2613
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2614
			nr_pte_updates = change_prot_numa(vma, start, end);
2615 2616

			/*
2617 2618 2619 2620 2621 2622
			 * Try to scan sysctl_numa_balancing_size worth of
			 * hpages that have at least one present PTE that
			 * is not already pte-numa. If the VMA contains
			 * areas that are unused or already full of prot_numa
			 * PTEs, scan up to virtpages, to skip through those
			 * areas faster.
2623 2624 2625
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2626
			virtpages -= (end - start) >> PAGE_SHIFT;
2627

2628
			start = end;
2629
			if (pages <= 0 || virtpages <= 0)
2630
				goto out;
2631 2632

			cond_resched();
2633
		} while (end != vma->vm_end);
2634
	}
2635

2636
out:
2637
	/*
P
Peter Zijlstra 已提交
2638 2639 2640 2641
	 * It is possible to reach the end of the VMA list but the last few
	 * VMAs are not guaranteed to the vma_migratable. If they are not, we
	 * would find the !migratable VMA on the next scan but not reset the
	 * scanner to the start so check it now.
2642 2643
	 */
	if (vma)
2644
		mm->numa_scan_offset = start;
2645 2646 2647
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658

	/*
	 * Make sure tasks use at least 32x as much time to run other code
	 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
	 * Usually update_task_scan_period slows down scanning enough; on an
	 * overloaded system we need to limit overhead on a per task basis.
	 */
	if (unlikely(p->se.sum_exec_runtime != runtime)) {
		u64 diff = p->se.sum_exec_runtime - runtime;
		p->node_stamp += 32 * diff;
	}
2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683
}

/*
 * Drive the periodic memory faults..
 */
void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
	struct callback_head *work = &curr->numa_work;
	u64 period, now;

	/*
	 * We don't care about NUMA placement if we don't have memory.
	 */
	if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
		return;

	/*
	 * Using runtime rather than walltime has the dual advantage that
	 * we (mostly) drive the selection from busy threads and that the
	 * task needs to have done some actual work before we bother with
	 * NUMA placement.
	 */
	now = curr->se.sum_exec_runtime;
	period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;

2684
	if (now > curr->node_stamp + period) {
2685
		if (!curr->node_stamp)
2686
			curr->numa_scan_period = task_scan_start(curr);
2687
		curr->node_stamp += period;
2688 2689 2690 2691 2692 2693 2694

		if (!time_before(jiffies, curr->mm->numa_next_scan)) {
			init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
			task_work_add(curr, work, true);
		}
	}
}
2695

2696 2697 2698 2699 2700
static void update_scan_period(struct task_struct *p, int new_cpu)
{
	int src_nid = cpu_to_node(task_cpu(p));
	int dst_nid = cpu_to_node(new_cpu);

2701 2702 2703
	if (!static_branch_likely(&sched_numa_balancing))
		return;

2704 2705 2706
	if (!p->mm || !p->numa_faults || (p->flags & PF_EXITING))
		return;

2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726
	if (src_nid == dst_nid)
		return;

	/*
	 * Allow resets if faults have been trapped before one scan
	 * has completed. This is most likely due to a new task that
	 * is pulled cross-node due to wakeups or load balancing.
	 */
	if (p->numa_scan_seq) {
		/*
		 * Avoid scan adjustments if moving to the preferred
		 * node or if the task was not previously running on
		 * the preferred node.
		 */
		if (dst_nid == p->numa_preferred_nid ||
		    (p->numa_preferred_nid != -1 && src_nid != p->numa_preferred_nid))
			return;
	}

	p->numa_scan_period = task_scan_start(p);
2727 2728
}

2729 2730 2731 2732
#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
}
2733 2734 2735 2736 2737 2738 2739 2740

static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
{
}

static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
{
}
2741

2742 2743 2744 2745
static inline void update_scan_period(struct task_struct *p, int new_cpu)
{
}

2746 2747
#endif /* CONFIG_NUMA_BALANCING */

2748 2749 2750 2751
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2752
	if (!parent_entity(se))
2753
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2754
#ifdef CONFIG_SMP
2755 2756 2757 2758 2759 2760
	if (entity_is_task(se)) {
		struct rq *rq = rq_of(cfs_rq);

		account_numa_enqueue(rq, task_of(se));
		list_add(&se->group_node, &rq->cfs_tasks);
	}
2761
#endif
2762 2763 2764 2765 2766 2767 2768
	cfs_rq->nr_running++;
}

static void
account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_sub(&cfs_rq->load, se->load.weight);
2769
	if (!parent_entity(se))
2770
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2771
#ifdef CONFIG_SMP
2772 2773
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2774
		list_del_init(&se->group_node);
2775
	}
2776
#endif
2777 2778 2779
	cfs_rq->nr_running--;
}

2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820
/*
 * Signed add and clamp on underflow.
 *
 * Explicitly do a load-store to ensure the intermediate value never hits
 * memory. This allows lockless observations without ever seeing the negative
 * values.
 */
#define add_positive(_ptr, _val) do {                           \
	typeof(_ptr) ptr = (_ptr);                              \
	typeof(_val) val = (_val);                              \
	typeof(*ptr) res, var = READ_ONCE(*ptr);                \
								\
	res = var + val;                                        \
								\
	if (val < 0 && res > var)                               \
		res = 0;                                        \
								\
	WRITE_ONCE(*ptr, res);                                  \
} while (0)

/*
 * Unsigned subtract and clamp on underflow.
 *
 * Explicitly do a load-store to ensure the intermediate value never hits
 * memory. This allows lockless observations without ever seeing the negative
 * values.
 */
#define sub_positive(_ptr, _val) do {				\
	typeof(_ptr) ptr = (_ptr);				\
	typeof(*ptr) val = (_val);				\
	typeof(*ptr) res, var = READ_ONCE(*ptr);		\
	res = var - val;					\
	if (res > var)						\
		res = 0;					\
	WRITE_ONCE(*ptr, res);					\
} while (0)

#ifdef CONFIG_SMP
static inline void
enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2821 2822 2823 2824
	cfs_rq->runnable_weight += se->runnable_weight;

	cfs_rq->avg.runnable_load_avg += se->avg.runnable_load_avg;
	cfs_rq->avg.runnable_load_sum += se_runnable(se) * se->avg.runnable_load_sum;
2825 2826 2827 2828 2829
}

static inline void
dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2830 2831 2832 2833 2834
	cfs_rq->runnable_weight -= se->runnable_weight;

	sub_positive(&cfs_rq->avg.runnable_load_avg, se->avg.runnable_load_avg);
	sub_positive(&cfs_rq->avg.runnable_load_sum,
		     se_runnable(se) * se->avg.runnable_load_sum);
2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860
}

static inline void
enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	cfs_rq->avg.load_avg += se->avg.load_avg;
	cfs_rq->avg.load_sum += se_weight(se) * se->avg.load_sum;
}

static inline void
dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
	sub_positive(&cfs_rq->avg.load_sum, se_weight(se) * se->avg.load_sum);
}
#else
static inline void
enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
static inline void
dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
static inline void
enqueue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
static inline void
dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
#endif

2861
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2862
			    unsigned long weight, unsigned long runnable)
2863 2864 2865 2866 2867 2868 2869 2870 2871 2872
{
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
		account_entity_dequeue(cfs_rq, se);
		dequeue_runnable_load_avg(cfs_rq, se);
	}
	dequeue_load_avg(cfs_rq, se);

2873
	se->runnable_weight = runnable;
2874 2875 2876
	update_load_set(&se->load, weight);

#ifdef CONFIG_SMP
2877 2878 2879 2880 2881 2882 2883
	do {
		u32 divider = LOAD_AVG_MAX - 1024 + se->avg.period_contrib;

		se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum, divider);
		se->avg.runnable_load_avg =
			div_u64(se_runnable(se) * se->avg.runnable_load_sum, divider);
	} while (0);
2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899
#endif

	enqueue_load_avg(cfs_rq, se);
	if (se->on_rq) {
		account_entity_enqueue(cfs_rq, se);
		enqueue_runnable_load_avg(cfs_rq, se);
	}
}

void reweight_task(struct task_struct *p, int prio)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	struct load_weight *load = &se->load;
	unsigned long weight = scale_load(sched_prio_to_weight[prio]);

2900
	reweight_entity(cfs_rq, se, weight, weight);
2901 2902 2903
	load->inv_weight = sched_prio_to_wmult[prio];
}

2904
#ifdef CONFIG_FAIR_GROUP_SCHED
2905
#ifdef CONFIG_SMP
2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943
/*
 * All this does is approximate the hierarchical proportion which includes that
 * global sum we all love to hate.
 *
 * That is, the weight of a group entity, is the proportional share of the
 * group weight based on the group runqueue weights. That is:
 *
 *                     tg->weight * grq->load.weight
 *   ge->load.weight = -----------------------------               (1)
 *			  \Sum grq->load.weight
 *
 * Now, because computing that sum is prohibitively expensive to compute (been
 * there, done that) we approximate it with this average stuff. The average
 * moves slower and therefore the approximation is cheaper and more stable.
 *
 * So instead of the above, we substitute:
 *
 *   grq->load.weight -> grq->avg.load_avg                         (2)
 *
 * which yields the following:
 *
 *                     tg->weight * grq->avg.load_avg
 *   ge->load.weight = ------------------------------              (3)
 *				tg->load_avg
 *
 * Where: tg->load_avg ~= \Sum grq->avg.load_avg
 *
 * That is shares_avg, and it is right (given the approximation (2)).
 *
 * The problem with it is that because the average is slow -- it was designed
 * to be exactly that of course -- this leads to transients in boundary
 * conditions. In specific, the case where the group was idle and we start the
 * one task. It takes time for our CPU's grq->avg.load_avg to build up,
 * yielding bad latency etc..
 *
 * Now, in that special case (1) reduces to:
 *
 *                     tg->weight * grq->load.weight
2944
 *   ge->load.weight = ----------------------------- = tg->weight   (4)
2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957
 *			    grp->load.weight
 *
 * That is, the sum collapses because all other CPUs are idle; the UP scenario.
 *
 * So what we do is modify our approximation (3) to approach (4) in the (near)
 * UP case, like:
 *
 *   ge->load.weight =
 *
 *              tg->weight * grq->load.weight
 *     ---------------------------------------------------         (5)
 *     tg->load_avg - grq->avg.load_avg + grq->load.weight
 *
2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969
 * But because grq->load.weight can drop to 0, resulting in a divide by zero,
 * we need to use grq->avg.load_avg as its lower bound, which then gives:
 *
 *
 *                     tg->weight * grq->load.weight
 *   ge->load.weight = -----------------------------		   (6)
 *				tg_load_avg'
 *
 * Where:
 *
 *   tg_load_avg' = tg->load_avg - grq->avg.load_avg +
 *                  max(grq->load.weight, grq->avg.load_avg)
2970 2971 2972 2973 2974 2975 2976 2977 2978
 *
 * And that is shares_weight and is icky. In the (near) UP case it approaches
 * (4) while in the normal case it approaches (3). It consistently
 * overestimates the ge->load.weight and therefore:
 *
 *   \Sum ge->load.weight >= tg->weight
 *
 * hence icky!
 */
2979
static long calc_group_shares(struct cfs_rq *cfs_rq)
2980
{
2981 2982 2983 2984
	long tg_weight, tg_shares, load, shares;
	struct task_group *tg = cfs_rq->tg;

	tg_shares = READ_ONCE(tg->shares);
2985

2986
	load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
2987

2988
	tg_weight = atomic_long_read(&tg->load_avg);
2989

2990 2991 2992
	/* Ensure tg_weight >= load */
	tg_weight -= cfs_rq->tg_load_avg_contrib;
	tg_weight += load;
2993

2994
	shares = (tg_shares * load);
2995 2996
	if (tg_weight)
		shares /= tg_weight;
2997

2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009
	/*
	 * MIN_SHARES has to be unscaled here to support per-CPU partitioning
	 * of a group with small tg->shares value. It is a floor value which is
	 * assigned as a minimum load.weight to the sched_entity representing
	 * the group on a CPU.
	 *
	 * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024
	 * on an 8-core system with 8 tasks each runnable on one CPU shares has
	 * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In
	 * case no task is runnable on a CPU MIN_SHARES=2 should be returned
	 * instead of 0.
	 */
3010
	return clamp_t(long, shares, MIN_SHARES, tg_shares);
3011
}
3012 3013

/*
3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038
 * This calculates the effective runnable weight for a group entity based on
 * the group entity weight calculated above.
 *
 * Because of the above approximation (2), our group entity weight is
 * an load_avg based ratio (3). This means that it includes blocked load and
 * does not represent the runnable weight.
 *
 * Approximate the group entity's runnable weight per ratio from the group
 * runqueue:
 *
 *					     grq->avg.runnable_load_avg
 *   ge->runnable_weight = ge->load.weight * -------------------------- (7)
 *						 grq->avg.load_avg
 *
 * However, analogous to above, since the avg numbers are slow, this leads to
 * transients in the from-idle case. Instead we use:
 *
 *   ge->runnable_weight = ge->load.weight *
 *
 *		max(grq->avg.runnable_load_avg, grq->runnable_weight)
 *		-----------------------------------------------------	(8)
 *		      max(grq->avg.load_avg, grq->load.weight)
 *
 * Where these max() serve both to use the 'instant' values to fix the slow
 * from-idle and avoid the /0 on to-idle, similar to (6).
3039 3040 3041
 */
static long calc_group_runnable(struct cfs_rq *cfs_rq, long shares)
{
3042 3043 3044 3045 3046 3047 3048
	long runnable, load_avg;

	load_avg = max(cfs_rq->avg.load_avg,
		       scale_load_down(cfs_rq->load.weight));

	runnable = max(cfs_rq->avg.runnable_load_avg,
		       scale_load_down(cfs_rq->runnable_weight));
3049 3050 3051 3052

	runnable *= shares;
	if (load_avg)
		runnable /= load_avg;
3053

3054 3055
	return clamp_t(long, runnable, MIN_SHARES, shares);
}
3056
#endif /* CONFIG_SMP */
3057

3058 3059
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

3060 3061 3062 3063 3064
/*
 * Recomputes the group entity based on the current state of its group
 * runqueue.
 */
static void update_cfs_group(struct sched_entity *se)
P
Peter Zijlstra 已提交
3065
{
3066 3067
	struct cfs_rq *gcfs_rq = group_cfs_rq(se);
	long shares, runnable;
P
Peter Zijlstra 已提交
3068

3069
	if (!gcfs_rq)
3070 3071
		return;

3072
	if (throttled_hierarchy(gcfs_rq))
P
Peter Zijlstra 已提交
3073
		return;
3074

3075
#ifndef CONFIG_SMP
3076
	runnable = shares = READ_ONCE(gcfs_rq->tg->shares);
3077 3078

	if (likely(se->load.weight == shares))
3079
		return;
3080
#else
3081 3082
	shares   = calc_group_shares(gcfs_rq);
	runnable = calc_group_runnable(gcfs_rq, shares);
3083
#endif
P
Peter Zijlstra 已提交
3084

3085
	reweight_entity(cfs_rq_of(se), se, shares, runnable);
P
Peter Zijlstra 已提交
3086
}
3087

P
Peter Zijlstra 已提交
3088
#else /* CONFIG_FAIR_GROUP_SCHED */
3089
static inline void update_cfs_group(struct sched_entity *se)
P
Peter Zijlstra 已提交
3090 3091 3092 3093
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

3094
static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
3095
{
3096 3097
	struct rq *rq = rq_of(cfs_rq);

3098
	if (&rq->cfs == cfs_rq || (flags & SCHED_CPUFREQ_MIGRATION)) {
3099 3100 3101
		/*
		 * There are a few boundary cases this might miss but it should
		 * get called often enough that that should (hopefully) not be
3102
		 * a real problem.
3103 3104 3105 3106 3107 3108 3109 3110 3111 3112
		 *
		 * It will not get called when we go idle, because the idle
		 * thread is a different class (!fair), nor will the utilization
		 * number include things like RT tasks.
		 *
		 * As is, the util number is not freq-invariant (we'd have to
		 * implement arch_scale_freq_capacity() for that).
		 *
		 * See cpu_util().
		 */
3113
		cpufreq_update_util(rq, flags);
3114 3115 3116
	}
}

3117
#ifdef CONFIG_SMP
3118
#ifdef CONFIG_FAIR_GROUP_SCHED
3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131
/**
 * update_tg_load_avg - update the tg's load avg
 * @cfs_rq: the cfs_rq whose avg changed
 * @force: update regardless of how small the difference
 *
 * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
 * However, because tg->load_avg is a global value there are performance
 * considerations.
 *
 * In order to avoid having to look at the other cfs_rq's, we use a
 * differential update where we store the last value we propagated. This in
 * turn allows skipping updates if the differential is 'small'.
 *
3132
 * Updating tg's load_avg is necessary before update_cfs_share().
3133
 */
3134
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
3135
{
3136
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
3137

3138 3139 3140 3141 3142 3143
	/*
	 * No need to update load_avg for root_task_group as it is not used.
	 */
	if (cfs_rq->tg == &root_task_group)
		return;

3144 3145 3146
	if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
		atomic_long_add(delta, &cfs_rq->tg->load_avg);
		cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
3147
	}
3148
}
3149

3150
/*
3151
 * Called within set_task_rq() right before setting a task's CPU. The
3152 3153 3154 3155 3156 3157
 * caller only guarantees p->pi_lock is held; no other assumptions,
 * including the state of rq->lock, should be made.
 */
void set_task_rq_fair(struct sched_entity *se,
		      struct cfs_rq *prev, struct cfs_rq *next)
{
3158 3159 3160
	u64 p_last_update_time;
	u64 n_last_update_time;

3161 3162 3163 3164 3165 3166 3167 3168 3169 3170
	if (!sched_feat(ATTACH_AGE_LOAD))
		return;

	/*
	 * We are supposed to update the task to "current" time, then its up to
	 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
	 * getting what current time is, so simply throw away the out-of-date
	 * time. This will result in the wakee task is less decayed, but giving
	 * the wakee more load sounds not bad.
	 */
3171 3172
	if (!(se->avg.last_update_time && prev))
		return;
3173 3174

#ifndef CONFIG_64BIT
3175
	{
3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189
		u64 p_last_update_time_copy;
		u64 n_last_update_time_copy;

		do {
			p_last_update_time_copy = prev->load_last_update_time_copy;
			n_last_update_time_copy = next->load_last_update_time_copy;

			smp_rmb();

			p_last_update_time = prev->avg.last_update_time;
			n_last_update_time = next->avg.last_update_time;

		} while (p_last_update_time != p_last_update_time_copy ||
			 n_last_update_time != n_last_update_time_copy);
3190
	}
3191
#else
3192 3193
	p_last_update_time = prev->avg.last_update_time;
	n_last_update_time = next->avg.last_update_time;
3194
#endif
3195 3196
	__update_load_avg_blocked_se(p_last_update_time, cpu_of(rq_of(prev)), se);
	se->avg.last_update_time = n_last_update_time;
3197
}
3198

3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209

/*
 * When on migration a sched_entity joins/leaves the PELT hierarchy, we need to
 * propagate its contribution. The key to this propagation is the invariant
 * that for each group:
 *
 *   ge->avg == grq->avg						(1)
 *
 * _IFF_ we look at the pure running and runnable sums. Because they
 * represent the very same entity, just at different points in the hierarchy.
 *
3210 3211 3212
 * Per the above update_tg_cfs_util() is trivial and simply copies the running
 * sum over (but still wrong, because the group entity and group rq do not have
 * their PELT windows aligned).
3213 3214 3215 3216 3217 3218 3219 3220
 *
 * However, update_tg_cfs_runnable() is more complex. So we have:
 *
 *   ge->avg.load_avg = ge->load.weight * ge->avg.runnable_avg		(2)
 *
 * And since, like util, the runnable part should be directly transferable,
 * the following would _appear_ to be the straight forward approach:
 *
3221
 *   grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg	(3)
3222 3223 3224
 *
 * And per (1) we have:
 *
3225
 *   ge->avg.runnable_avg == grq->avg.runnable_avg
3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243
 *
 * Which gives:
 *
 *                      ge->load.weight * grq->avg.load_avg
 *   ge->avg.load_avg = -----------------------------------		(4)
 *                               grq->load.weight
 *
 * Except that is wrong!
 *
 * Because while for entities historical weight is not important and we
 * really only care about our future and therefore can consider a pure
 * runnable sum, runqueues can NOT do this.
 *
 * We specifically want runqueues to have a load_avg that includes
 * historical weights. Those represent the blocked load, the load we expect
 * to (shortly) return to us. This only works by keeping the weights as
 * integral part of the sum. We therefore cannot decompose as per (3).
 *
3244 3245 3246 3247 3248 3249
 * Another reason this doesn't work is that runnable isn't a 0-sum entity.
 * Imagine a rq with 2 tasks that each are runnable 2/3 of the time. Then the
 * rq itself is runnable anywhere between 2/3 and 1 depending on how the
 * runnable section of these tasks overlap (or not). If they were to perfectly
 * align the rq as a whole would be runnable 2/3 of the time. If however we
 * always have at least 1 runnable task, the rq as a whole is always runnable.
3250
 *
3251
 * So we'll have to approximate.. :/
3252
 *
3253
 * Given the constraint:
3254
 *
3255
 *   ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
3256
 *
3257 3258
 * We can construct a rule that adds runnable to a rq by assuming minimal
 * overlap.
3259
 *
3260
 * On removal, we'll assume each task is equally runnable; which yields:
3261
 *
3262
 *   grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
3263
 *
3264
 * XXX: only do this for the part of runnable > running ?
3265 3266 3267
 *
 */

3268
static inline void
3269
update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3270 3271 3272 3273 3274 3275 3276
{
	long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;

	/* Nothing to update */
	if (!delta)
		return;

3277 3278 3279 3280 3281 3282 3283 3284
	/*
	 * The relation between sum and avg is:
	 *
	 *   LOAD_AVG_MAX - 1024 + sa->period_contrib
	 *
	 * however, the PELT windows are not aligned between grq and gse.
	 */

3285 3286 3287 3288 3289 3290 3291 3292 3293 3294
	/* Set new sched_entity's utilization */
	se->avg.util_avg = gcfs_rq->avg.util_avg;
	se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX;

	/* Update parent cfs_rq utilization */
	add_positive(&cfs_rq->avg.util_avg, delta);
	cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX;
}

static inline void
3295
update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3296
{
3297 3298 3299 3300
	long delta_avg, running_sum, runnable_sum = gcfs_rq->prop_runnable_sum;
	unsigned long runnable_load_avg, load_avg;
	u64 runnable_load_sum, load_sum = 0;
	s64 delta_sum;
3301

3302 3303
	if (!runnable_sum)
		return;
3304

3305
	gcfs_rq->prop_runnable_sum = 0;
3306

3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329
	if (runnable_sum >= 0) {
		/*
		 * Add runnable; clip at LOAD_AVG_MAX. Reflects that until
		 * the CPU is saturated running == runnable.
		 */
		runnable_sum += se->avg.load_sum;
		runnable_sum = min(runnable_sum, (long)LOAD_AVG_MAX);
	} else {
		/*
		 * Estimate the new unweighted runnable_sum of the gcfs_rq by
		 * assuming all tasks are equally runnable.
		 */
		if (scale_load_down(gcfs_rq->load.weight)) {
			load_sum = div_s64(gcfs_rq->avg.load_sum,
				scale_load_down(gcfs_rq->load.weight));
		}

		/* But make sure to not inflate se's runnable */
		runnable_sum = min(se->avg.load_sum, load_sum);
	}

	/*
	 * runnable_sum can't be lower than running_sum
3330
	 * As running sum is scale with CPU capacity wehreas the runnable sum
3331 3332 3333 3334 3335 3336
	 * is not we rescale running_sum 1st
	 */
	running_sum = se->avg.util_sum /
		arch_scale_cpu_capacity(NULL, cpu_of(rq_of(cfs_rq)));
	runnable_sum = max(runnable_sum, running_sum);

3337 3338
	load_sum = (s64)se_weight(se) * runnable_sum;
	load_avg = div_s64(load_sum, LOAD_AVG_MAX);
3339

3340 3341
	delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
	delta_avg = load_avg - se->avg.load_avg;
3342

3343 3344 3345 3346
	se->avg.load_sum = runnable_sum;
	se->avg.load_avg = load_avg;
	add_positive(&cfs_rq->avg.load_avg, delta_avg);
	add_positive(&cfs_rq->avg.load_sum, delta_sum);
3347

3348 3349
	runnable_load_sum = (s64)se_runnable(se) * runnable_sum;
	runnable_load_avg = div_s64(runnable_load_sum, LOAD_AVG_MAX);
3350 3351
	delta_sum = runnable_load_sum - se_weight(se) * se->avg.runnable_load_sum;
	delta_avg = runnable_load_avg - se->avg.runnable_load_avg;
3352

3353 3354
	se->avg.runnable_load_sum = runnable_sum;
	se->avg.runnable_load_avg = runnable_load_avg;
3355

3356
	if (se->on_rq) {
3357 3358
		add_positive(&cfs_rq->avg.runnable_load_avg, delta_avg);
		add_positive(&cfs_rq->avg.runnable_load_sum, delta_sum);
3359 3360 3361
	}
}

3362
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
3363
{
3364 3365
	cfs_rq->propagate = 1;
	cfs_rq->prop_runnable_sum += runnable_sum;
3366 3367 3368 3369 3370
}

/* Update task and its cfs_rq load average */
static inline int propagate_entity_load_avg(struct sched_entity *se)
{
3371
	struct cfs_rq *cfs_rq, *gcfs_rq;
3372 3373 3374 3375

	if (entity_is_task(se))
		return 0;

3376 3377
	gcfs_rq = group_cfs_rq(se);
	if (!gcfs_rq->propagate)
3378 3379
		return 0;

3380 3381
	gcfs_rq->propagate = 0;

3382 3383
	cfs_rq = cfs_rq_of(se);

3384
	add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
3385

3386 3387
	update_tg_cfs_util(cfs_rq, se, gcfs_rq);
	update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
3388 3389 3390 3391

	return 1;
}

3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410
/*
 * Check if we need to update the load and the utilization of a blocked
 * group_entity:
 */
static inline bool skip_blocked_update(struct sched_entity *se)
{
	struct cfs_rq *gcfs_rq = group_cfs_rq(se);

	/*
	 * If sched_entity still have not zero load or utilization, we have to
	 * decay it:
	 */
	if (se->avg.load_avg || se->avg.util_avg)
		return false;

	/*
	 * If there is a pending propagation, we have to update the load and
	 * the utilization of the sched_entity:
	 */
3411
	if (gcfs_rq->propagate)
3412 3413 3414 3415 3416 3417 3418 3419 3420 3421
		return false;

	/*
	 * Otherwise, the load and the utilization of the sched_entity is
	 * already zero and there is no pending propagation, so it will be a
	 * waste of time to try to decay it:
	 */
	return true;
}

3422
#else /* CONFIG_FAIR_GROUP_SCHED */
3423

3424
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
3425 3426 3427 3428 3429 3430

static inline int propagate_entity_load_avg(struct sched_entity *se)
{
	return 0;
}

3431
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
3432

3433
#endif /* CONFIG_FAIR_GROUP_SCHED */
3434

3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445
/**
 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
 * @now: current time, as per cfs_rq_clock_task()
 * @cfs_rq: cfs_rq to update
 *
 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
 * avg. The immediate corollary is that all (fair) tasks must be attached, see
 * post_init_entity_util_avg().
 *
 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
 *
3446 3447 3448 3449
 * Returns true if the load decayed or we removed load.
 *
 * Since both these conditions indicate a changed cfs_rq->avg.load we should
 * call update_tg_load_avg() when this function returns true.
3450
 */
3451
static inline int
3452
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3453
{
3454
	unsigned long removed_load = 0, removed_util = 0, removed_runnable_sum = 0;
3455
	struct sched_avg *sa = &cfs_rq->avg;
3456
	int decayed = 0;
3457

3458 3459
	if (cfs_rq->removed.nr) {
		unsigned long r;
3460
		u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
3461 3462 3463 3464

		raw_spin_lock(&cfs_rq->removed.lock);
		swap(cfs_rq->removed.util_avg, removed_util);
		swap(cfs_rq->removed.load_avg, removed_load);
3465
		swap(cfs_rq->removed.runnable_sum, removed_runnable_sum);
3466 3467 3468 3469
		cfs_rq->removed.nr = 0;
		raw_spin_unlock(&cfs_rq->removed.lock);

		r = removed_load;
3470
		sub_positive(&sa->load_avg, r);
3471
		sub_positive(&sa->load_sum, r * divider);
3472

3473
		r = removed_util;
3474
		sub_positive(&sa->util_avg, r);
3475
		sub_positive(&sa->util_sum, r * divider);
3476

3477
		add_tg_cfs_propagate(cfs_rq, -(long)removed_runnable_sum);
3478 3479

		decayed = 1;
3480
	}
3481

3482
	decayed |= __update_load_avg_cfs_rq(now, cpu_of(rq_of(cfs_rq)), cfs_rq);
3483

3484 3485 3486 3487
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
3488

3489
	if (decayed)
3490
		cfs_rq_util_change(cfs_rq, 0);
3491

3492
	return decayed;
3493 3494
}

3495 3496 3497 3498
/**
 * attach_entity_load_avg - attach this entity to its cfs_rq load avg
 * @cfs_rq: cfs_rq to attach to
 * @se: sched_entity to attach
3499
 * @flags: migration hints
3500 3501 3502 3503
 *
 * Must call update_cfs_rq_load_avg() before this, since we rely on
 * cfs_rq->avg.last_update_time being current.
 */
3504
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3505
{
3506 3507 3508 3509 3510 3511 3512 3513 3514
	u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib;

	/*
	 * When we attach the @se to the @cfs_rq, we must align the decay
	 * window because without that, really weird and wonderful things can
	 * happen.
	 *
	 * XXX illustrate
	 */
3515
	se->avg.last_update_time = cfs_rq->avg.last_update_time;
3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532 3533
	se->avg.period_contrib = cfs_rq->avg.period_contrib;

	/*
	 * Hell(o) Nasty stuff.. we need to recompute _sum based on the new
	 * period_contrib. This isn't strictly correct, but since we're
	 * entirely outside of the PELT hierarchy, nobody cares if we truncate
	 * _sum a little.
	 */
	se->avg.util_sum = se->avg.util_avg * divider;

	se->avg.load_sum = divider;
	if (se_weight(se)) {
		se->avg.load_sum =
			div_u64(se->avg.load_avg * se->avg.load_sum, se_weight(se));
	}

	se->avg.runnable_load_sum = se->avg.load_sum;

3534
	enqueue_load_avg(cfs_rq, se);
3535 3536
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
3537 3538

	add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
3539

3540
	cfs_rq_util_change(cfs_rq, flags);
3541 3542
}

3543 3544 3545 3546 3547 3548 3549 3550
/**
 * detach_entity_load_avg - detach this entity from its cfs_rq load avg
 * @cfs_rq: cfs_rq to detach from
 * @se: sched_entity to detach
 *
 * Must call update_cfs_rq_load_avg() before this, since we rely on
 * cfs_rq->avg.last_update_time being current.
 */
3551 3552
static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3553
	dequeue_load_avg(cfs_rq, se);
3554 3555
	sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
	sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3556 3557

	add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
3558

3559
	cfs_rq_util_change(cfs_rq, 0);
3560 3561
}

3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588
/*
 * Optional action to be done while updating the load average
 */
#define UPDATE_TG	0x1
#define SKIP_AGE_LOAD	0x2
#define DO_ATTACH	0x4

/* Update task and its cfs_rq load average */
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
	u64 now = cfs_rq_clock_task(cfs_rq);
	struct rq *rq = rq_of(cfs_rq);
	int cpu = cpu_of(rq);
	int decayed;

	/*
	 * Track task load average for carrying it to new CPU after migrated, and
	 * track group sched_entity load average for task_h_load calc in migration
	 */
	if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
		__update_load_avg_se(now, cpu, cfs_rq, se);

	decayed  = update_cfs_rq_load_avg(now, cfs_rq);
	decayed |= propagate_entity_load_avg(se);

	if (!se->avg.last_update_time && (flags & DO_ATTACH)) {

3589 3590 3591 3592 3593 3594 3595 3596
		/*
		 * DO_ATTACH means we're here from enqueue_entity().
		 * !last_update_time means we've passed through
		 * migrate_task_rq_fair() indicating we migrated.
		 *
		 * IOW we're enqueueing a task on a new CPU.
		 */
		attach_entity_load_avg(cfs_rq, se, SCHED_CPUFREQ_MIGRATION);
3597 3598 3599 3600 3601 3602
		update_tg_load_avg(cfs_rq, 0);

	} else if (decayed && (flags & UPDATE_TG))
		update_tg_load_avg(cfs_rq, 0);
}

3603
#ifndef CONFIG_64BIT
3604 3605
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
3606
	u64 last_update_time_copy;
3607
	u64 last_update_time;
3608

3609 3610 3611 3612 3613
	do {
		last_update_time_copy = cfs_rq->load_last_update_time_copy;
		smp_rmb();
		last_update_time = cfs_rq->avg.last_update_time;
	} while (last_update_time != last_update_time_copy);
3614 3615 3616

	return last_update_time;
}
3617
#else
3618 3619 3620 3621
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.last_update_time;
}
3622 3623
#endif

3624 3625 3626 3627 3628 3629 3630 3631 3632 3633
/*
 * Synchronize entity load avg of dequeued entity without locking
 * the previous rq.
 */
void sync_entity_load_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 last_update_time;

	last_update_time = cfs_rq_last_update_time(cfs_rq);
3634
	__update_load_avg_blocked_se(last_update_time, cpu_of(rq_of(cfs_rq)), se);
3635 3636
}

3637 3638 3639 3640 3641 3642 3643
/*
 * Task first catches up with cfs_rq, and then subtract
 * itself from the cfs_rq (task must be off the queue now).
 */
void remove_entity_load_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
3644
	unsigned long flags;
3645 3646

	/*
3647 3648 3649 3650 3651 3652 3653
	 * tasks cannot exit without having gone through wake_up_new_task() ->
	 * post_init_entity_util_avg() which will have added things to the
	 * cfs_rq, so we can remove unconditionally.
	 *
	 * Similarly for groups, they will have passed through
	 * post_init_entity_util_avg() before unregister_sched_fair_group()
	 * calls this.
3654 3655
	 */

3656
	sync_entity_load_avg(se);
3657 3658 3659 3660 3661

	raw_spin_lock_irqsave(&cfs_rq->removed.lock, flags);
	++cfs_rq->removed.nr;
	cfs_rq->removed.util_avg	+= se->avg.util_avg;
	cfs_rq->removed.load_avg	+= se->avg.load_avg;
3662
	cfs_rq->removed.runnable_sum	+= se->avg.load_sum; /* == runnable_sum */
3663
	raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
3664
}
3665

3666 3667
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
{
3668
	return cfs_rq->avg.runnable_load_avg;
3669 3670 3671 3672 3673 3674 3675
}

static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.load_avg;
}

3676
static int idle_balance(struct rq *this_rq, struct rq_flags *rf);
3677

3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704
static inline unsigned long task_util(struct task_struct *p)
{
	return READ_ONCE(p->se.avg.util_avg);
}

static inline unsigned long _task_util_est(struct task_struct *p)
{
	struct util_est ue = READ_ONCE(p->se.avg.util_est);

	return max(ue.ewma, ue.enqueued);
}

static inline unsigned long task_util_est(struct task_struct *p)
{
	return max(task_util(p), _task_util_est(p));
}

static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
				    struct task_struct *p)
{
	unsigned int enqueued;

	if (!sched_feat(UTIL_EST))
		return;

	/* Update root cfs_rq's estimated utilization */
	enqueued  = cfs_rq->avg.util_est.enqueued;
3705
	enqueued += (_task_util_est(p) | UTIL_AVG_UNCHANGED);
3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730
	WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
}

/*
 * Check if a (signed) value is within a specified (unsigned) margin,
 * based on the observation that:
 *
 *     abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
 *
 * NOTE: this only works when value + maring < INT_MAX.
 */
static inline bool within_margin(int value, int margin)
{
	return ((unsigned int)(value + margin - 1) < (2 * margin - 1));
}

static void
util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
{
	long last_ewma_diff;
	struct util_est ue;

	if (!sched_feat(UTIL_EST))
		return;

3731 3732 3733 3734
	/* Update root cfs_rq's estimated utilization */
	ue.enqueued  = cfs_rq->avg.util_est.enqueued;
	ue.enqueued -= min_t(unsigned int, ue.enqueued,
			     (_task_util_est(p) | UTIL_AVG_UNCHANGED));
3735 3736 3737 3738 3739 3740 3741 3742 3743
	WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued);

	/*
	 * Skip update of task's estimated utilization when the task has not
	 * yet completed an activation, e.g. being migrated.
	 */
	if (!task_sleep)
		return;

3744 3745 3746 3747 3748 3749 3750 3751
	/*
	 * If the PELT values haven't changed since enqueue time,
	 * skip the util_est update.
	 */
	ue = p->se.avg.util_est;
	if (ue.enqueued & UTIL_AVG_UNCHANGED)
		return;

3752 3753 3754 3755
	/*
	 * Skip update of task's estimated utilization when its EWMA is
	 * already ~1% close to its last activation value.
	 */
3756
	ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED);
3757 3758 3759 3760 3761 3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783
	last_ewma_diff = ue.enqueued - ue.ewma;
	if (within_margin(last_ewma_diff, (SCHED_CAPACITY_SCALE / 100)))
		return;

	/*
	 * Update Task's estimated utilization
	 *
	 * When *p completes an activation we can consolidate another sample
	 * of the task size. This is done by storing the current PELT value
	 * as ue.enqueued and by using this value to update the Exponential
	 * Weighted Moving Average (EWMA):
	 *
	 *  ewma(t) = w *  task_util(p) + (1-w) * ewma(t-1)
	 *          = w *  task_util(p) +         ewma(t-1)  - w * ewma(t-1)
	 *          = w * (task_util(p) -         ewma(t-1)) +     ewma(t-1)
	 *          = w * (      last_ewma_diff            ) +     ewma(t-1)
	 *          = w * (last_ewma_diff  +  ewma(t-1) / w)
	 *
	 * Where 'w' is the weight of new samples, which is configured to be
	 * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
	 */
	ue.ewma <<= UTIL_EST_WEIGHT_SHIFT;
	ue.ewma  += last_ewma_diff;
	ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
	WRITE_ONCE(p->se.avg.util_est, ue);
}

3784 3785
#else /* CONFIG_SMP */

3786 3787
#define UPDATE_TG	0x0
#define SKIP_AGE_LOAD	0x0
3788
#define DO_ATTACH	0x0
3789

3790
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
3791
{
3792
	cfs_rq_util_change(cfs_rq, 0);
3793 3794
}

3795
static inline void remove_entity_load_avg(struct sched_entity *se) {}
3796

3797
static inline void
3798
attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) {}
3799 3800 3801
static inline void
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}

3802
static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
3803 3804 3805 3806
{
	return 0;
}

3807 3808 3809 3810 3811 3812 3813
static inline void
util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}

static inline void
util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p,
		 bool task_sleep) {}

3814
#endif /* CONFIG_SMP */
3815

P
Peter Zijlstra 已提交
3816 3817 3818 3819 3820 3821 3822 3823 3824
static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
#ifdef CONFIG_SCHED_DEBUG
	s64 d = se->vruntime - cfs_rq->min_vruntime;

	if (d < 0)
		d = -d;

	if (d > 3*sysctl_sched_latency)
3825
		schedstat_inc(cfs_rq->nr_spread_over);
P
Peter Zijlstra 已提交
3826 3827 3828
#endif
}

3829 3830 3831
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3832
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3833

3834 3835 3836 3837 3838 3839
	/*
	 * The 'current' period is already promised to the current tasks,
	 * however the extra weight of the new task will slow them down a
	 * little, place the new task so that it fits in the slot that
	 * stays open at the end.
	 */
P
Peter Zijlstra 已提交
3840
	if (initial && sched_feat(START_DEBIT))
3841
		vruntime += sched_vslice(cfs_rq, se);
3842

3843
	/* sleeps up to a single latency don't count. */
3844
	if (!initial) {
3845
		unsigned long thresh = sysctl_sched_latency;
3846

3847 3848 3849 3850 3851 3852
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3853

3854
		vruntime -= thresh;
3855 3856
	}

3857
	/* ensure we never gain time by being placed backwards. */
3858
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3859 3860
}

3861 3862
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873 3874
static inline void check_schedstat_required(void)
{
#ifdef CONFIG_SCHEDSTATS
	if (schedstat_enabled())
		return;

	/* Force schedstat enabled if a dependent tracepoint is active */
	if (trace_sched_stat_wait_enabled()    ||
			trace_sched_stat_sleep_enabled()   ||
			trace_sched_stat_iowait_enabled()  ||
			trace_sched_stat_blocked_enabled() ||
			trace_sched_stat_runtime_enabled())  {
3875
		printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3876
			     "stat_blocked and stat_runtime require the "
3877
			     "kernel parameter schedstats=enable or "
3878 3879 3880 3881 3882
			     "kernel.sched_schedstats=1\n");
	}
#endif
}

3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901

/*
 * MIGRATION
 *
 *	dequeue
 *	  update_curr()
 *	    update_min_vruntime()
 *	  vruntime -= min_vruntime
 *
 *	enqueue
 *	  update_curr()
 *	    update_min_vruntime()
 *	  vruntime += min_vruntime
 *
 * this way the vruntime transition between RQs is done when both
 * min_vruntime are up-to-date.
 *
 * WAKEUP (remote)
 *
3902
 *	->migrate_task_rq_fair() (p->state == TASK_WAKING)
3903 3904 3905 3906 3907 3908 3909 3910 3911 3912 3913
 *	  vruntime -= min_vruntime
 *
 *	enqueue
 *	  update_curr()
 *	    update_min_vruntime()
 *	  vruntime += min_vruntime
 *
 * this way we don't have the most up-to-date min_vruntime on the originating
 * CPU and an up-to-date min_vruntime on the destination CPU.
 */

3914
static void
3915
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3916
{
3917 3918 3919
	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
	bool curr = cfs_rq->curr == se;

3920
	/*
3921 3922
	 * If we're the current task, we must renormalise before calling
	 * update_curr().
3923
	 */
3924
	if (renorm && curr)
3925 3926
		se->vruntime += cfs_rq->min_vruntime;

3927 3928
	update_curr(cfs_rq);

3929
	/*
3930 3931 3932 3933
	 * Otherwise, renormalise after, such that we're placed at the current
	 * moment in time, instead of some random moment in the past. Being
	 * placed in the past could significantly boost this task to the
	 * fairness detriment of existing tasks.
3934
	 */
3935 3936 3937
	if (renorm && !curr)
		se->vruntime += cfs_rq->min_vruntime;

3938 3939 3940 3941 3942 3943 3944 3945
	/*
	 * When enqueuing a sched_entity, we must:
	 *   - Update loads to have both entity and cfs_rq synced with now.
	 *   - Add its load to cfs_rq->runnable_avg
	 *   - For group_entity, update its weight to reflect the new share of
	 *     its group cfs_rq
	 *   - Add its new weight to cfs_rq->load.weight
	 */
3946
	update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
3947
	update_cfs_group(se);
3948
	enqueue_runnable_load_avg(cfs_rq, se);
3949
	account_entity_enqueue(cfs_rq, se);
3950

3951
	if (flags & ENQUEUE_WAKEUP)
3952
		place_entity(cfs_rq, se, 0);
3953

3954
	check_schedstat_required();
3955 3956
	update_stats_enqueue(cfs_rq, se, flags);
	check_spread(cfs_rq, se);
3957
	if (!curr)
3958
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3959
	se->on_rq = 1;
3960

3961
	if (cfs_rq->nr_running == 1) {
3962
		list_add_leaf_cfs_rq(cfs_rq);
3963 3964
		check_enqueue_throttle(cfs_rq);
	}
3965 3966
}

3967
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3968
{
3969 3970
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3971
		if (cfs_rq->last != se)
3972
			break;
3973 3974

		cfs_rq->last = NULL;
3975 3976
	}
}
P
Peter Zijlstra 已提交
3977

3978 3979 3980 3981
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3982
		if (cfs_rq->next != se)
3983
			break;
3984 3985

		cfs_rq->next = NULL;
3986
	}
P
Peter Zijlstra 已提交
3987 3988
}

3989 3990 3991 3992
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3993
		if (cfs_rq->skip != se)
3994
			break;
3995 3996

		cfs_rq->skip = NULL;
3997 3998 3999
	}
}

P
Peter Zijlstra 已提交
4000 4001
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
4002 4003 4004 4005 4006
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
4007 4008 4009

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
4010 4011
}

4012
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4013

4014
static void
4015
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4016
{
4017 4018 4019 4020
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
4021 4022 4023 4024 4025 4026 4027 4028 4029

	/*
	 * When dequeuing a sched_entity, we must:
	 *   - Update loads to have both entity and cfs_rq synced with now.
	 *   - Substract its load from the cfs_rq->runnable_avg.
	 *   - Substract its previous weight from cfs_rq->load.weight.
	 *   - For group entity, update its weight to reflect the new share
	 *     of its group cfs_rq.
	 */
4030
	update_load_avg(cfs_rq, se, UPDATE_TG);
4031
	dequeue_runnable_load_avg(cfs_rq, se);
4032

4033
	update_stats_dequeue(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
4034

P
Peter Zijlstra 已提交
4035
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
4036

4037
	if (se != cfs_rq->curr)
4038
		__dequeue_entity(cfs_rq, se);
4039
	se->on_rq = 0;
4040
	account_entity_dequeue(cfs_rq, se);
4041 4042

	/*
4043 4044 4045 4046
	 * Normalize after update_curr(); which will also have moved
	 * min_vruntime if @se is the one holding it back. But before doing
	 * update_min_vruntime() again, which will discount @se's position and
	 * can move min_vruntime forward still more.
4047
	 */
4048
	if (!(flags & DEQUEUE_SLEEP))
4049
		se->vruntime -= cfs_rq->min_vruntime;
4050

4051 4052 4053
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

4054
	update_cfs_group(se);
4055 4056 4057 4058 4059 4060 4061

	/*
	 * Now advance min_vruntime if @se was the entity holding it back,
	 * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be
	 * put back on, and if we advance min_vruntime, we'll be placed back
	 * further than we started -- ie. we'll be penalized.
	 */
4062
	if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
4063
		update_min_vruntime(cfs_rq);
4064 4065 4066 4067 4068
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
4069
static void
I
Ingo Molnar 已提交
4070
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4071
{
4072
	unsigned long ideal_runtime, delta_exec;
4073 4074
	struct sched_entity *se;
	s64 delta;
4075

P
Peter Zijlstra 已提交
4076
	ideal_runtime = sched_slice(cfs_rq, curr);
4077
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
4078
	if (delta_exec > ideal_runtime) {
4079
		resched_curr(rq_of(cfs_rq));
4080 4081 4082 4083 4084
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
4085 4086 4087 4088 4089 4090 4091 4092 4093 4094 4095
		return;
	}

	/*
	 * Ensure that a task that missed wakeup preemption by a
	 * narrow margin doesn't have to wait for a full slice.
	 * This also mitigates buddy induced latencies under load.
	 */
	if (delta_exec < sysctl_sched_min_granularity)
		return;

4096 4097
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
4098

4099 4100
	if (delta < 0)
		return;
4101

4102
	if (delta > ideal_runtime)
4103
		resched_curr(rq_of(cfs_rq));
4104 4105
}

4106
static void
4107
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
4108
{
4109 4110 4111 4112 4113 4114 4115
	/* 'current' is not kept within the tree. */
	if (se->on_rq) {
		/*
		 * Any task has to be enqueued before it get to execute on
		 * a CPU. So account for the time it spent waiting on the
		 * runqueue.
		 */
4116
		update_stats_wait_end(cfs_rq, se);
4117
		__dequeue_entity(cfs_rq, se);
4118
		update_load_avg(cfs_rq, se, UPDATE_TG);
4119 4120
	}

4121
	update_stats_curr_start(cfs_rq, se);
4122
	cfs_rq->curr = se;
4123

I
Ingo Molnar 已提交
4124 4125 4126 4127 4128
	/*
	 * Track our maximum slice length, if the CPU's load is at
	 * least twice that of our own weight (i.e. dont track it
	 * when there are only lesser-weight tasks around):
	 */
4129
	if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
4130 4131 4132
		schedstat_set(se->statistics.slice_max,
			max((u64)schedstat_val(se->statistics.slice_max),
			    se->sum_exec_runtime - se->prev_sum_exec_runtime));
I
Ingo Molnar 已提交
4133
	}
4134

4135
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
4136 4137
}

4138 4139 4140
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

4141 4142 4143 4144 4145 4146 4147
/*
 * Pick the next process, keeping these things in mind, in this order:
 * 1) keep things fair between processes/task groups
 * 2) pick the "next" process, since someone really wants that to run
 * 3) pick the "last" process, for cache locality
 * 4) do not run the "skip" process, if something else is available
 */
4148 4149
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4150
{
4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161
	struct sched_entity *left = __pick_first_entity(cfs_rq);
	struct sched_entity *se;

	/*
	 * If curr is set we have to see if its left of the leftmost entity
	 * still in the tree, provided there was anything in the tree at all.
	 */
	if (!left || (curr && entity_before(curr, left)))
		left = curr;

	se = left; /* ideally we run the leftmost entity */
4162

4163 4164 4165 4166 4167
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
4168 4169 4170 4171 4172 4173 4174 4175 4176 4177
		struct sched_entity *second;

		if (se == curr) {
			second = __pick_first_entity(cfs_rq);
		} else {
			second = __pick_next_entity(se);
			if (!second || (curr && entity_before(curr, second)))
				second = curr;
		}

4178 4179 4180
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
4181

4182 4183 4184 4185 4186 4187
	/*
	 * Prefer last buddy, try to return the CPU to a preempted task.
	 */
	if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
		se = cfs_rq->last;

4188 4189 4190 4191 4192 4193
	/*
	 * Someone really wants this to run. If it's not unfair, run it.
	 */
	if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
		se = cfs_rq->next;

4194
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
4195 4196

	return se;
4197 4198
}

4199
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4200

4201
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
4202 4203 4204 4205 4206 4207
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
4208
		update_curr(cfs_rq);
4209

4210 4211 4212
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

4213
	check_spread(cfs_rq, prev);
4214

4215
	if (prev->on_rq) {
4216
		update_stats_wait_start(cfs_rq, prev);
4217 4218
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
4219
		/* in !on_rq case, update occurred at dequeue */
4220
		update_load_avg(cfs_rq, prev, 0);
4221
	}
4222
	cfs_rq->curr = NULL;
4223 4224
}

P
Peter Zijlstra 已提交
4225 4226
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
4227 4228
{
	/*
4229
	 * Update run-time statistics of the 'current'.
4230
	 */
4231
	update_curr(cfs_rq);
4232

4233 4234 4235
	/*
	 * Ensure that runnable average is periodically updated.
	 */
4236
	update_load_avg(cfs_rq, curr, UPDATE_TG);
4237
	update_cfs_group(curr);
4238

P
Peter Zijlstra 已提交
4239 4240 4241 4242 4243
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
4244
	if (queued) {
4245
		resched_curr(rq_of(cfs_rq));
4246 4247
		return;
	}
P
Peter Zijlstra 已提交
4248 4249 4250 4251 4252 4253 4254 4255
	/*
	 * don't let the period tick interfere with the hrtick preemption
	 */
	if (!sched_feat(DOUBLE_TICK) &&
			hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
		return;
#endif

Y
Yong Zhang 已提交
4256
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
4257
		check_preempt_tick(cfs_rq, curr);
4258 4259
}

4260 4261 4262 4263 4264 4265

/**************************************************
 * CFS bandwidth control machinery
 */

#ifdef CONFIG_CFS_BANDWIDTH
4266

4267
#ifdef CONFIG_JUMP_LABEL
4268
static struct static_key __cfs_bandwidth_used;
4269 4270 4271

static inline bool cfs_bandwidth_used(void)
{
4272
	return static_key_false(&__cfs_bandwidth_used);
4273 4274
}

4275
void cfs_bandwidth_usage_inc(void)
4276
{
4277
	static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
4278 4279 4280 4281
}

void cfs_bandwidth_usage_dec(void)
{
4282
	static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
4283
}
4284
#else /* CONFIG_JUMP_LABEL */
4285 4286 4287 4288 4289
static bool cfs_bandwidth_used(void)
{
	return true;
}

4290 4291
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
4292
#endif /* CONFIG_JUMP_LABEL */
4293

4294 4295 4296 4297 4298 4299 4300 4301
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
4302 4303 4304 4305 4306 4307

static inline u64 sched_cfs_bandwidth_slice(void)
{
	return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC;
}

P
Paul Turner 已提交
4308
/*
4309 4310 4311
 * Replenish runtime according to assigned quota. We use sched_clock_cpu
 * directly instead of rq->clock to avoid adding additional synchronization
 * around rq->lock.
P
Paul Turner 已提交
4312 4313 4314
 *
 * requires cfs_b->lock
 */
4315
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
4316
{
4317 4318
	if (cfs_b->quota != RUNTIME_INF)
		cfs_b->runtime = cfs_b->quota;
P
Paul Turner 已提交
4319 4320
}

4321 4322 4323 4324 4325
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

4326 4327 4328 4329
/* rq->task_clock normalized against any time this cfs_rq has spent throttled */
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
	if (unlikely(cfs_rq->throttle_count))
4330
		return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
4331

4332
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
4333 4334
}

4335 4336
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4337 4338 4339
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
4340
	u64 amount = 0, min_amount;
4341 4342 4343 4344 4345 4346 4347

	/* note: this is a positive sum as runtime_remaining <= 0 */
	min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining;

	raw_spin_lock(&cfs_b->lock);
	if (cfs_b->quota == RUNTIME_INF)
		amount = min_amount;
4348
	else {
P
Peter Zijlstra 已提交
4349
		start_cfs_bandwidth(cfs_b);
4350 4351 4352 4353 4354 4355

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
4356 4357 4358 4359
	}
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
4360 4361

	return cfs_rq->runtime_remaining > 0;
4362 4363
}

4364
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
4365 4366
{
	/* dock delta_exec before expiring quota (as it could span periods) */
4367
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
4368 4369

	if (likely(cfs_rq->runtime_remaining > 0))
4370 4371
		return;

4372 4373
	if (cfs_rq->throttled)
		return;
4374 4375 4376 4377 4378
	/*
	 * if we're unable to extend our runtime we resched so that the active
	 * hierarchy can be throttled
	 */
	if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))
4379
		resched_curr(rq_of(cfs_rq));
4380 4381
}

4382
static __always_inline
4383
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4384
{
4385
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4386 4387 4388 4389 4390
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

4391 4392
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
4393
	return cfs_bandwidth_used() && cfs_rq->throttled;
4394 4395
}

4396 4397 4398
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
4399
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415 4416 4417 4418 4419 4420 4421 4422 4423 4424 4425
}

/*
 * Ensure that neither of the group entities corresponding to src_cpu or
 * dest_cpu are members of a throttled hierarchy when performing group
 * load-balance operations.
 */
static inline int throttled_lb_pair(struct task_group *tg,
				    int src_cpu, int dest_cpu)
{
	struct cfs_rq *src_cfs_rq, *dest_cfs_rq;

	src_cfs_rq = tg->cfs_rq[src_cpu];
	dest_cfs_rq = tg->cfs_rq[dest_cpu];

	return throttled_hierarchy(src_cfs_rq) ||
	       throttled_hierarchy(dest_cfs_rq);
}

static int tg_unthrottle_up(struct task_group *tg, void *data)
{
	struct rq *rq = data;
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

	cfs_rq->throttle_count--;
	if (!cfs_rq->throttle_count) {
4426
		/* adjust cfs_rq_clock_task() */
4427
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4428
					     cfs_rq->throttled_clock_task;
4429 4430 4431 4432 4433 4434 4435 4436 4437 4438
	}

	return 0;
}

static int tg_throttle_down(struct task_group *tg, void *data)
{
	struct rq *rq = data;
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

4439 4440
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
4441
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
4442 4443 4444 4445 4446
	cfs_rq->throttle_count++;

	return 0;
}

4447
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
4448 4449 4450 4451 4452
{
	struct rq *rq = rq_of(cfs_rq);
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
	struct sched_entity *se;
	long task_delta, dequeue = 1;
P
Peter Zijlstra 已提交
4453
	bool empty;
4454 4455 4456

	se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];

4457
	/* freeze hierarchy runnable averages while throttled */
4458 4459 4460
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
4461 4462 4463 4464 4465 4466 4467 4468 4469 4470 4471 4472 4473 4474 4475 4476 4477

	task_delta = cfs_rq->h_nr_running;
	for_each_sched_entity(se) {
		struct cfs_rq *qcfs_rq = cfs_rq_of(se);
		/* throttled entity or throttle-on-deactivate */
		if (!se->on_rq)
			break;

		if (dequeue)
			dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
		qcfs_rq->h_nr_running -= task_delta;

		if (qcfs_rq->load.weight)
			dequeue = 0;
	}

	if (!se)
4478
		sub_nr_running(rq, task_delta);
4479 4480

	cfs_rq->throttled = 1;
4481
	cfs_rq->throttled_clock = rq_clock(rq);
4482
	raw_spin_lock(&cfs_b->lock);
4483
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4484

4485 4486
	/*
	 * Add to the _head_ of the list, so that an already-started
4487 4488
	 * distribute_cfs_runtime will not see us. If disribute_cfs_runtime is
	 * not running add to the tail so that later runqueues don't get starved.
4489
	 */
4490 4491 4492 4493
	if (cfs_b->distribute_running)
		list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
	else
		list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4494 4495 4496 4497 4498 4499 4500 4501

	/*
	 * If we're the first throttled task, make sure the bandwidth
	 * timer is running.
	 */
	if (empty)
		start_cfs_bandwidth(cfs_b);

4502 4503 4504
	raw_spin_unlock(&cfs_b->lock);
}

4505
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4506 4507 4508 4509 4510 4511 4512
{
	struct rq *rq = rq_of(cfs_rq);
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
	struct sched_entity *se;
	int enqueue = 1;
	long task_delta;

4513
	se = cfs_rq->tg->se[cpu_of(rq)];
4514 4515

	cfs_rq->throttled = 0;
4516 4517 4518

	update_rq_clock(rq);

4519
	raw_spin_lock(&cfs_b->lock);
4520
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4521 4522 4523
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

4524 4525 4526
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544
	if (!cfs_rq->load.weight)
		return;

	task_delta = cfs_rq->h_nr_running;
	for_each_sched_entity(se) {
		if (se->on_rq)
			enqueue = 0;

		cfs_rq = cfs_rq_of(se);
		if (enqueue)
			enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
		cfs_rq->h_nr_running += task_delta;

		if (cfs_rq_throttled(cfs_rq))
			break;
	}

	if (!se)
4545
		add_nr_running(rq, task_delta);
4546

4547
	/* Determine whether we need to wake up potentially idle CPU: */
4548
	if (rq->curr == rq->idle && rq->cfs.nr_running)
4549
		resched_curr(rq);
4550 4551
}

4552
static void distribute_cfs_runtime(struct cfs_bandwidth *cfs_b)
4553 4554
{
	struct cfs_rq *cfs_rq;
4555
	u64 runtime, remaining = 1;
4556 4557 4558 4559 4560

	rcu_read_lock();
	list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
				throttled_list) {
		struct rq *rq = rq_of(cfs_rq);
4561
		struct rq_flags rf;
4562

4563
		rq_lock(rq, &rf);
4564 4565 4566
		if (!cfs_rq_throttled(cfs_rq))
			goto next;

4567 4568 4569
		/* By the above check, this should never be true */
		SCHED_WARN_ON(cfs_rq->runtime_remaining > 0);

4570
		raw_spin_lock(&cfs_b->lock);
4571
		runtime = -cfs_rq->runtime_remaining + 1;
4572 4573 4574 4575 4576
		if (runtime > cfs_b->runtime)
			runtime = cfs_b->runtime;
		cfs_b->runtime -= runtime;
		remaining = cfs_b->runtime;
		raw_spin_unlock(&cfs_b->lock);
4577 4578 4579 4580 4581 4582 4583 4584

		cfs_rq->runtime_remaining += runtime;

		/* we check whether we're throttled above */
		if (cfs_rq->runtime_remaining > 0)
			unthrottle_cfs_rq(cfs_rq);

next:
4585
		rq_unlock(rq, &rf);
4586 4587 4588 4589 4590 4591 4592

		if (!remaining)
			break;
	}
	rcu_read_unlock();
}

4593 4594 4595 4596 4597 4598 4599 4600
/*
 * Responsible for refilling a task_group's bandwidth and unthrottling its
 * cfs_rqs as appropriate. If there has been no activity within the last
 * period the timer is deactivated until scheduling resumes; cfs_b->idle is
 * used to track this state.
 */
static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
{
4601
	int throttled;
4602 4603 4604

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
4605
		goto out_deactivate;
4606

4607
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4608
	cfs_b->nr_periods += overrun;
4609

4610 4611 4612 4613 4614 4615
	/*
	 * idle depends on !throttled (for the case of a large deficit), and if
	 * we're going inactive then everything else can be deferred
	 */
	if (cfs_b->idle && !throttled)
		goto out_deactivate;
P
Paul Turner 已提交
4616 4617 4618

	__refill_cfs_bandwidth_runtime(cfs_b);

4619 4620 4621
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
4622
		return 0;
4623 4624
	}

4625 4626 4627
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

4628
	/*
4629
	 * This check is repeated as we release cfs_b->lock while we unthrottle.
4630
	 */
4631 4632
	while (throttled && cfs_b->runtime > 0 && !cfs_b->distribute_running) {
		cfs_b->distribute_running = 1;
4633 4634
		raw_spin_unlock(&cfs_b->lock);
		/* we can't nest cfs_b->lock while distributing bandwidth */
4635
		distribute_cfs_runtime(cfs_b);
4636 4637
		raw_spin_lock(&cfs_b->lock);

4638
		cfs_b->distribute_running = 0;
4639 4640
		throttled = !list_empty(&cfs_b->throttled_cfs_rq);
	}
4641

4642 4643 4644 4645 4646 4647 4648
	/*
	 * While we are ensured activity in the period following an
	 * unthrottle, this also covers the case in which the new bandwidth is
	 * insufficient to cover the existing bandwidth deficit.  (Forcing the
	 * timer to remain active while there are any throttled entities.)
	 */
	cfs_b->idle = 0;
4649

4650 4651 4652 4653
	return 0;

out_deactivate:
	return 1;
4654
}
4655

4656 4657 4658 4659 4660 4661 4662
/* a cfs_rq won't donate quota below this amount */
static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC;
/* minimum remaining period time to redistribute slack quota */
static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
/* how long we wait to gather additional slack before distributing */
static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;

4663 4664 4665 4666
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4667
 * hrtimer base being cleared by hrtimer_start. In the case of
4668 4669
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680 4681 4682 4683 4684 4685 4686 4687 4688 4689 4690 4691 4692 4693 4694
static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
{
	struct hrtimer *refresh_timer = &cfs_b->period_timer;
	u64 remaining;

	/* if the call-back is running a quota refresh is already occurring */
	if (hrtimer_callback_running(refresh_timer))
		return 1;

	/* is a quota refresh about to occur? */
	remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
	if (remaining < min_expire)
		return 1;

	return 0;
}

static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
{
	u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;

	/* if there's a quota refresh soon don't bother with slack */
	if (runtime_refresh_within(cfs_b, min_left))
		return;

4695 4696 4697 4698 4699
	/* don't push forwards an existing deferred unthrottle */
	if (cfs_b->slack_started)
		return;
	cfs_b->slack_started = true;

P
Peter Zijlstra 已提交
4700 4701 4702
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
4703 4704 4705 4706 4707 4708 4709 4710 4711 4712 4713 4714
}

/* we know any runtime found here is valid as update_curr() precedes return */
static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
	s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;

	if (slack_runtime <= 0)
		return;

	raw_spin_lock(&cfs_b->lock);
4715
	if (cfs_b->quota != RUNTIME_INF) {
4716 4717 4718 4719 4720 4721 4722 4723 4724 4725 4726 4727 4728 4729 4730
		cfs_b->runtime += slack_runtime;

		/* we are under rq->lock, defer unthrottling using a timer */
		if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
		    !list_empty(&cfs_b->throttled_cfs_rq))
			start_cfs_slack_bandwidth(cfs_b);
	}
	raw_spin_unlock(&cfs_b->lock);

	/* even if it's not valid for return we don't want to try again */
	cfs_rq->runtime_remaining -= slack_runtime;
}

static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
4731 4732 4733
	if (!cfs_bandwidth_used())
		return;

4734
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4735 4736 4737 4738 4739 4740 4741 4742 4743 4744 4745 4746 4747 4748
		return;

	__return_cfs_rq_runtime(cfs_rq);
}

/*
 * This is done with a timer (instead of inline with bandwidth return) since
 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs.
 */
static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
{
	u64 runtime = 0, slice = sched_cfs_bandwidth_slice();

	/* confirm we're still not at a refresh boundary */
4749
	raw_spin_lock(&cfs_b->lock);
4750
	cfs_b->slack_started = false;
4751 4752 4753 4754 4755
	if (cfs_b->distribute_running) {
		raw_spin_unlock(&cfs_b->lock);
		return;
	}

4756 4757
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
4758
		return;
4759
	}
4760

4761
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4762
		runtime = cfs_b->runtime;
4763

4764 4765 4766
	if (runtime)
		cfs_b->distribute_running = 1;

4767 4768 4769 4770 4771
	raw_spin_unlock(&cfs_b->lock);

	if (!runtime)
		return;

4772
	distribute_cfs_runtime(cfs_b);
4773 4774

	raw_spin_lock(&cfs_b->lock);
4775
	cfs_b->distribute_running = 0;
4776 4777 4778
	raw_spin_unlock(&cfs_b->lock);
}

4779 4780 4781 4782 4783 4784 4785
/*
 * When a group wakes up we want to make sure that its quota is not already
 * expired/exceeded, otherwise it may be allowed to steal additional ticks of
 * runtime as update_curr() throttling can not not trigger until it's on-rq.
 */
static void check_enqueue_throttle(struct cfs_rq *cfs_rq)
{
4786 4787 4788
	if (!cfs_bandwidth_used())
		return;

4789 4790 4791 4792 4793 4794 4795 4796 4797 4798 4799 4800 4801 4802
	/* an active group must be handled by the update_curr()->put() path */
	if (!cfs_rq->runtime_enabled || cfs_rq->curr)
		return;

	/* ensure the group is not already throttled */
	if (cfs_rq_throttled(cfs_rq))
		return;

	/* update runtime allocation */
	account_cfs_rq_runtime(cfs_rq, 0);
	if (cfs_rq->runtime_remaining <= 0)
		throttle_cfs_rq(cfs_rq);
}

4803 4804 4805 4806 4807 4808 4809 4810 4811 4812 4813 4814 4815 4816
static void sync_throttle(struct task_group *tg, int cpu)
{
	struct cfs_rq *pcfs_rq, *cfs_rq;

	if (!cfs_bandwidth_used())
		return;

	if (!tg->parent)
		return;

	cfs_rq = tg->cfs_rq[cpu];
	pcfs_rq = tg->parent->cfs_rq[cpu];

	cfs_rq->throttle_count = pcfs_rq->throttle_count;
4817
	cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
4818 4819
}

4820
/* conditionally throttle active cfs_rq's from put_prev_entity() */
4821
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4822
{
4823
	if (!cfs_bandwidth_used())
4824
		return false;
4825

4826
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4827
		return false;
4828 4829 4830 4831 4832 4833

	/*
	 * it's possible for a throttled entity to be forced into a running
	 * state (e.g. set_curr_task), in this case we're finished.
	 */
	if (cfs_rq_throttled(cfs_rq))
4834
		return true;
4835 4836

	throttle_cfs_rq(cfs_rq);
4837
	return true;
4838
}
4839 4840 4841 4842 4843

static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, slack_timer);
P
Peter Zijlstra 已提交
4844

4845 4846 4847 4848 4849
	do_sched_cfs_slack_timer(cfs_b);

	return HRTIMER_NORESTART;
}

4850 4851
extern const u64 max_cfs_quota_period;

4852 4853 4854 4855 4856 4857
static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, period_timer);
	int overrun;
	int idle = 0;
4858
	int count = 0;
4859

4860
	raw_spin_lock(&cfs_b->lock);
4861
	for (;;) {
P
Peter Zijlstra 已提交
4862
		overrun = hrtimer_forward_now(timer, cfs_b->period);
4863 4864 4865
		if (!overrun)
			break;

4866 4867 4868
		if (++count > 3) {
			u64 new, old = ktime_to_ns(cfs_b->period);

4869 4870 4871 4872 4873 4874 4875 4876 4877 4878 4879 4880 4881 4882 4883 4884 4885 4886 4887 4888 4889 4890
			/*
			 * Grow period by a factor of 2 to avoid losing precision.
			 * Precision loss in the quota/period ratio can cause __cfs_schedulable
			 * to fail.
			 */
			new = old * 2;
			if (new < max_cfs_quota_period) {
				cfs_b->period = ns_to_ktime(new);
				cfs_b->quota *= 2;

				pr_warn_ratelimited(
	"cfs_period_timer[cpu%d]: period too short, scaling up (new cfs_period_us = %lld, cfs_quota_us = %lld)\n",
					smp_processor_id(),
					div_u64(new, NSEC_PER_USEC),
					div_u64(cfs_b->quota, NSEC_PER_USEC));
			} else {
				pr_warn_ratelimited(
	"cfs_period_timer[cpu%d]: period too short, but cannot scale up without losing precision (cfs_period_us = %lld, cfs_quota_us = %lld)\n",
					smp_processor_id(),
					div_u64(old, NSEC_PER_USEC),
					div_u64(cfs_b->quota, NSEC_PER_USEC));
			}
4891 4892 4893 4894 4895

			/* reset count so we don't come right back in here */
			count = 0;
		}

4896 4897
		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
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Peter Zijlstra 已提交
4898 4899
	if (idle)
		cfs_b->period_active = 0;
4900
	raw_spin_unlock(&cfs_b->lock);
4901 4902 4903 4904 4905 4906 4907 4908 4909 4910 4911 4912

	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
}

void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
	raw_spin_lock_init(&cfs_b->lock);
	cfs_b->runtime = 0;
	cfs_b->quota = RUNTIME_INF;
	cfs_b->period = ns_to_ktime(default_cfs_period());

	INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4913
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4914 4915 4916
	cfs_b->period_timer.function = sched_cfs_period_timer;
	hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	cfs_b->slack_timer.function = sched_cfs_slack_timer;
4917
	cfs_b->distribute_running = 0;
4918
	cfs_b->slack_started = false;
4919 4920 4921 4922 4923 4924 4925 4926
}

static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
	cfs_rq->runtime_enabled = 0;
	INIT_LIST_HEAD(&cfs_rq->throttled_list);
}

P
Peter Zijlstra 已提交
4927
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4928
{
P
Peter Zijlstra 已提交
4929
	lockdep_assert_held(&cfs_b->lock);
4930

4931 4932 4933 4934
	if (cfs_b->period_active)
		return;

	cfs_b->period_active = 1;
4935
	hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4936
	hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4937 4938 4939 4940
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4941 4942 4943 4944
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4945 4946 4947 4948
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

4949
/*
4950
 * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
4951 4952 4953 4954 4955 4956
 *
 * The race is harmless, since modifying bandwidth settings of unhooked group
 * bits doesn't do much.
 */

/* cpu online calback */
4957 4958
static void __maybe_unused update_runtime_enabled(struct rq *rq)
{
4959
	struct task_group *tg;
4960

4961 4962 4963 4964 4965 4966
	lockdep_assert_held(&rq->lock);

	rcu_read_lock();
	list_for_each_entry_rcu(tg, &task_groups, list) {
		struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
		struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4967 4968 4969 4970 4971

		raw_spin_lock(&cfs_b->lock);
		cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
		raw_spin_unlock(&cfs_b->lock);
	}
4972
	rcu_read_unlock();
4973 4974
}

4975
/* cpu offline callback */
4976
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4977
{
4978 4979 4980 4981 4982 4983 4984
	struct task_group *tg;

	lockdep_assert_held(&rq->lock);

	rcu_read_lock();
	list_for_each_entry_rcu(tg, &task_groups, list) {
		struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
4985 4986 4987 4988 4989 4990 4991 4992

		if (!cfs_rq->runtime_enabled)
			continue;

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
4993
		cfs_rq->runtime_remaining = 1;
4994
		/*
4995
		 * Offline rq is schedulable till CPU is completely disabled
4996 4997 4998 4999
		 * in take_cpu_down(), so we prevent new cfs throttling here.
		 */
		cfs_rq->runtime_enabled = 0;

5000 5001 5002
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
5003
	rcu_read_unlock();
5004 5005 5006
}

#else /* CONFIG_CFS_BANDWIDTH */
5007 5008
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
5009
	return rq_clock_task(rq_of(cfs_rq));
5010 5011
}

5012
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
5013
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
5014
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
5015
static inline void sync_throttle(struct task_group *tg, int cpu) {}
5016
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5017 5018 5019 5020 5021

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
5022 5023 5024 5025 5026 5027 5028 5029 5030 5031 5032

static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
	return 0;
}

static inline int throttled_lb_pair(struct task_group *tg,
				    int src_cpu, int dest_cpu)
{
	return 0;
}
5033 5034 5035 5036 5037

void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}

#ifdef CONFIG_FAIR_GROUP_SCHED
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5038 5039
#endif

5040 5041 5042 5043 5044
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return NULL;
}
static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {}
5045
static inline void update_runtime_enabled(struct rq *rq) {}
5046
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
5047 5048 5049

#endif /* CONFIG_CFS_BANDWIDTH */

5050 5051 5052 5053
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
5054 5055 5056 5057 5058 5059
#ifdef CONFIG_SCHED_HRTICK
static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

5060
	SCHED_WARN_ON(task_rq(p) != rq);
P
Peter Zijlstra 已提交
5061

5062
	if (rq->cfs.h_nr_running > 1) {
P
Peter Zijlstra 已提交
5063 5064 5065 5066 5067 5068
		u64 slice = sched_slice(cfs_rq, se);
		u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
		s64 delta = slice - ran;

		if (delta < 0) {
			if (rq->curr == p)
5069
				resched_curr(rq);
P
Peter Zijlstra 已提交
5070 5071
			return;
		}
5072
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
5073 5074
	}
}
5075 5076 5077 5078 5079 5080 5081 5082 5083 5084

/*
 * called from enqueue/dequeue and updates the hrtick when the
 * current task is from our class and nr_running is low enough
 * to matter.
 */
static void hrtick_update(struct rq *rq)
{
	struct task_struct *curr = rq->curr;

5085
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
5086 5087 5088 5089 5090
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
5091
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
5092 5093 5094 5095
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
5096 5097 5098 5099

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
5100 5101
#endif

5102 5103 5104 5105 5106
/*
 * The enqueue_task method is called before nr_running is
 * increased. Here we update the fair scheduling stats and
 * then put the task into the rbtree:
 */
5107
static void
5108
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5109 5110
{
	struct cfs_rq *cfs_rq;
5111
	struct sched_entity *se = &p->se;
5112

5113 5114 5115 5116 5117 5118 5119 5120
	/*
	 * The code below (indirectly) updates schedutil which looks at
	 * the cfs_rq utilization to select a frequency.
	 * Let's add the task's estimated utilization to the cfs_rq's
	 * estimated utilization, before we update schedutil.
	 */
	util_est_enqueue(&rq->cfs, p);

5121 5122 5123 5124 5125 5126
	/*
	 * If in_iowait is set, the code below may not trigger any cpufreq
	 * utilization updates, so do it here explicitly with the IOWAIT flag
	 * passed.
	 */
	if (p->in_iowait)
5127
		cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
5128

5129
	for_each_sched_entity(se) {
5130
		if (se->on_rq)
5131 5132
			break;
		cfs_rq = cfs_rq_of(se);
5133
		enqueue_entity(cfs_rq, se, flags);
5134 5135 5136 5137 5138 5139

		/*
		 * end evaluation on encountering a throttled cfs_rq
		 *
		 * note: in the case of encountering a throttled cfs_rq we will
		 * post the final h_nr_running increment below.
5140
		 */
5141 5142
		if (cfs_rq_throttled(cfs_rq))
			break;
5143
		cfs_rq->h_nr_running++;
5144

5145
		flags = ENQUEUE_WAKEUP;
5146
	}
P
Peter Zijlstra 已提交
5147

P
Peter Zijlstra 已提交
5148
	for_each_sched_entity(se) {
5149
		cfs_rq = cfs_rq_of(se);
5150
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
5151

5152 5153 5154
		if (cfs_rq_throttled(cfs_rq))
			break;

5155
		update_load_avg(cfs_rq, se, UPDATE_TG);
5156
		update_cfs_group(se);
P
Peter Zijlstra 已提交
5157 5158
	}

Y
Yuyang Du 已提交
5159
	if (!se)
5160
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
5161

5162
	hrtick_update(rq);
5163 5164
}

5165 5166
static void set_next_buddy(struct sched_entity *se);

5167 5168 5169 5170 5171
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
5172
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5173 5174
{
	struct cfs_rq *cfs_rq;
5175
	struct sched_entity *se = &p->se;
5176
	int task_sleep = flags & DEQUEUE_SLEEP;
5177 5178 5179

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5180
		dequeue_entity(cfs_rq, se, flags);
5181 5182 5183 5184 5185 5186 5187 5188 5189

		/*
		 * end evaluation on encountering a throttled cfs_rq
		 *
		 * note: in the case of encountering a throttled cfs_rq we will
		 * post the final h_nr_running decrement below.
		*/
		if (cfs_rq_throttled(cfs_rq))
			break;
5190
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
5191

5192
		/* Don't dequeue parent if it has other entities besides us */
5193
		if (cfs_rq->load.weight) {
5194 5195
			/* Avoid re-evaluating load for this entity: */
			se = parent_entity(se);
5196 5197 5198 5199
			/*
			 * Bias pick_next to pick a task from this cfs_rq, as
			 * p is sleeping when it is within its sched_slice.
			 */
5200 5201
			if (task_sleep && se && !throttled_hierarchy(cfs_rq))
				set_next_buddy(se);
5202
			break;
5203
		}
5204
		flags |= DEQUEUE_SLEEP;
5205
	}
P
Peter Zijlstra 已提交
5206

P
Peter Zijlstra 已提交
5207
	for_each_sched_entity(se) {
5208
		cfs_rq = cfs_rq_of(se);
5209
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
5210

5211 5212 5213
		if (cfs_rq_throttled(cfs_rq))
			break;

5214
		update_load_avg(cfs_rq, se, UPDATE_TG);
5215
		update_cfs_group(se);
P
Peter Zijlstra 已提交
5216 5217
	}

Y
Yuyang Du 已提交
5218
	if (!se)
5219
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
5220

5221
	util_est_dequeue(&rq->cfs, p, task_sleep);
5222
	hrtick_update(rq);
5223 5224
}

5225
#ifdef CONFIG_SMP
5226 5227 5228 5229 5230

/* Working cpumask for: load_balance, load_balance_newidle. */
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);

5231
#ifdef CONFIG_NO_HZ_COMMON
5232 5233 5234 5235 5236
/*
 * per rq 'load' arrray crap; XXX kill this.
 */

/*
5237
 * The exact cpuload calculated at every tick would be:
5238
 *
5239 5240
 *   load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
 *
5241 5242
 * If a CPU misses updates for n ticks (as it was idle) and update gets
 * called on the n+1-th tick when CPU may be busy, then we have:
5243 5244 5245
 *
 *   load_n   = (1 - 1/2^i)^n * load_0
 *   load_n+1 = (1 - 1/2^i)   * load_n + (1/2^i) * cur_load
5246 5247 5248
 *
 * decay_load_missed() below does efficient calculation of
 *
5249 5250 5251 5252 5253 5254
 *   load' = (1 - 1/2^i)^n * load
 *
 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
 * This allows us to precompute the above in said factors, thereby allowing the
 * reduction of an arbitrary n in O(log_2 n) steps. (See also
 * fixed_power_int())
5255
 *
5256
 * The calculation is approximated on a 128 point scale.
5257 5258
 */
#define DEGRADE_SHIFT		7
5259 5260 5261 5262 5263 5264 5265 5266 5267

static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
	{   0,   0,  0,  0,  0,  0, 0, 0 },
	{  64,  32,  8,  0,  0,  0, 0, 0 },
	{  96,  72, 40, 12,  1,  0, 0, 0 },
	{ 112,  98, 75, 43, 15,  1, 0, 0 },
	{ 120, 112, 98, 76, 45, 16, 2, 0 }
};
5268 5269 5270 5271 5272 5273 5274 5275 5276 5277 5278 5279 5280 5281 5282 5283 5284 5285 5286 5287 5288 5289 5290 5291 5292 5293 5294 5295 5296

/*
 * Update cpu_load for any missed ticks, due to tickless idle. The backlog
 * would be when CPU is idle and so we just decay the old load without
 * adding any new load.
 */
static unsigned long
decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
{
	int j = 0;

	if (!missed_updates)
		return load;

	if (missed_updates >= degrade_zero_ticks[idx])
		return 0;

	if (idx == 1)
		return load >> missed_updates;

	while (missed_updates) {
		if (missed_updates % 2)
			load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;

		missed_updates >>= 1;
		j++;
	}
	return load;
}
5297 5298 5299 5300

static struct {
	cpumask_var_t idle_cpus_mask;
	atomic_t nr_cpus;
5301
	int has_blocked;		/* Idle CPUS has blocked load */
5302
	unsigned long next_balance;     /* in jiffy units */
5303
	unsigned long next_blocked;	/* Next update of blocked load in jiffies */
5304 5305
} nohz ____cacheline_aligned;

5306
#endif /* CONFIG_NO_HZ_COMMON */
5307

5308
/**
5309
 * __cpu_load_update - update the rq->cpu_load[] statistics
5310 5311 5312 5313
 * @this_rq: The rq to update statistics for
 * @this_load: The current load
 * @pending_updates: The number of missed updates
 *
5314
 * Update rq->cpu_load[] statistics. This function is usually called every
5315 5316 5317 5318 5319 5320 5321 5322 5323 5324 5325 5326 5327 5328 5329 5330 5331 5332 5333 5334 5335 5336 5337 5338 5339 5340
 * scheduler tick (TICK_NSEC).
 *
 * This function computes a decaying average:
 *
 *   load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
 *
 * Because of NOHZ it might not get called on every tick which gives need for
 * the @pending_updates argument.
 *
 *   load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
 *             = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
 *             = A * (A * load[i]_n-2 + B) + B
 *             = A * (A * (A * load[i]_n-3 + B) + B) + B
 *             = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
 *             = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
 *             = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
 *             = (1 - 1/2^i)^n * (load[i]_0 - load) + load
 *
 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
 * any change in load would have resulted in the tick being turned back on.
 *
 * For regular NOHZ, this reduces to:
 *
 *   load[i]_n = (1 - 1/2^i)^n * load[i]_0
 *
 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
5341
 * term.
5342
 */
5343 5344
static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
			    unsigned long pending_updates)
5345
{
5346
	unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
5347 5348 5349 5350 5351 5352 5353 5354 5355 5356 5357
	int i, scale;

	this_rq->nr_load_updates++;

	/* Update our load: */
	this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
	for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
		unsigned long old_load, new_load;

		/* scale is effectively 1 << i now, and >> i divides by scale */

5358
		old_load = this_rq->cpu_load[i];
5359
#ifdef CONFIG_NO_HZ_COMMON
5360
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
5361 5362 5363 5364 5365 5366 5367 5368 5369
		if (tickless_load) {
			old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
			/*
			 * old_load can never be a negative value because a
			 * decayed tickless_load cannot be greater than the
			 * original tickless_load.
			 */
			old_load += tickless_load;
		}
5370
#endif
5371 5372 5373 5374 5375 5376 5377 5378 5379 5380 5381 5382 5383
		new_load = this_load;
		/*
		 * Round up the averaging division if load is increasing. This
		 * prevents us from getting stuck on 9 if the load is 10, for
		 * example.
		 */
		if (new_load > old_load)
			new_load += scale - 1;

		this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
	}
}

5384
/* Used instead of source_load when we know the type == 0 */
5385
static unsigned long weighted_cpuload(struct rq *rq)
5386
{
5387
	return cfs_rq_runnable_load_avg(&rq->cfs);
5388 5389
}

5390
#ifdef CONFIG_NO_HZ_COMMON
5391 5392
/*
 * There is no sane way to deal with nohz on smp when using jiffies because the
5393
 * CPU doing the jiffies update might drift wrt the CPU doing the jiffy reading
5394 5395 5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406 5407
 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
 *
 * Therefore we need to avoid the delta approach from the regular tick when
 * possible since that would seriously skew the load calculation. This is why we
 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
 * loop exit, nohz_idle_balance, nohz full exit...)
 *
 * This means we might still be one tick off for nohz periods.
 */

static void cpu_load_update_nohz(struct rq *this_rq,
				 unsigned long curr_jiffies,
				 unsigned long load)
5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418
{
	unsigned long pending_updates;

	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
	if (pending_updates) {
		this_rq->last_load_update_tick = curr_jiffies;
		/*
		 * In the regular NOHZ case, we were idle, this means load 0.
		 * In the NOHZ_FULL case, we were non-idle, we should consider
		 * its weighted load.
		 */
5419
		cpu_load_update(this_rq, load, pending_updates);
5420 5421 5422
	}
}

5423 5424 5425 5426
/*
 * Called from nohz_idle_balance() to update the load ratings before doing the
 * idle balance.
 */
5427
static void cpu_load_update_idle(struct rq *this_rq)
5428 5429 5430 5431
{
	/*
	 * bail if there's load or we're actually up-to-date.
	 */
5432
	if (weighted_cpuload(this_rq))
5433 5434
		return;

5435
	cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
5436 5437 5438
}

/*
5439 5440 5441 5442
 * Record CPU load on nohz entry so we know the tickless load to account
 * on nohz exit. cpu_load[0] happens then to be updated more frequently
 * than other cpu_load[idx] but it should be fine as cpu_load readers
 * shouldn't rely into synchronized cpu_load[*] updates.
5443
 */
5444
void cpu_load_update_nohz_start(void)
5445 5446
{
	struct rq *this_rq = this_rq();
5447 5448 5449 5450 5451 5452

	/*
	 * This is all lockless but should be fine. If weighted_cpuload changes
	 * concurrently we'll exit nohz. And cpu_load write can race with
	 * cpu_load_update_idle() but both updater would be writing the same.
	 */
5453
	this_rq->cpu_load[0] = weighted_cpuload(this_rq);
5454 5455 5456 5457 5458 5459 5460
}

/*
 * Account the tickless load in the end of a nohz frame.
 */
void cpu_load_update_nohz_stop(void)
{
5461
	unsigned long curr_jiffies = READ_ONCE(jiffies);
5462 5463
	struct rq *this_rq = this_rq();
	unsigned long load;
5464
	struct rq_flags rf;
5465 5466 5467 5468

	if (curr_jiffies == this_rq->last_load_update_tick)
		return;

5469
	load = weighted_cpuload(this_rq);
5470
	rq_lock(this_rq, &rf);
5471
	update_rq_clock(this_rq);
5472
	cpu_load_update_nohz(this_rq, curr_jiffies, load);
5473
	rq_unlock(this_rq, &rf);
5474
}
5475 5476 5477 5478 5479 5480 5481 5482
#else /* !CONFIG_NO_HZ_COMMON */
static inline void cpu_load_update_nohz(struct rq *this_rq,
					unsigned long curr_jiffies,
					unsigned long load) { }
#endif /* CONFIG_NO_HZ_COMMON */

static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load)
{
5483
#ifdef CONFIG_NO_HZ_COMMON
5484 5485
	/* See the mess around cpu_load_update_nohz(). */
	this_rq->last_load_update_tick = READ_ONCE(jiffies);
5486
#endif
5487 5488
	cpu_load_update(this_rq, load, 1);
}
5489 5490 5491 5492

/*
 * Called from scheduler_tick()
 */
5493
void cpu_load_update_active(struct rq *this_rq)
5494
{
5495
	unsigned long load = weighted_cpuload(this_rq);
5496 5497 5498 5499 5500

	if (tick_nohz_tick_stopped())
		cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
	else
		cpu_load_update_periodic(this_rq, load);
5501 5502
}

5503
/*
5504
 * Return a low guess at the load of a migration-source CPU weighted
5505 5506 5507 5508 5509 5510 5511 5512
 * according to the scheduling class and "nice" value.
 *
 * We want to under-estimate the load of migration sources, to
 * balance conservatively.
 */
static unsigned long source_load(int cpu, int type)
{
	struct rq *rq = cpu_rq(cpu);
5513
	unsigned long total = weighted_cpuload(rq);
5514 5515 5516 5517 5518 5519 5520 5521

	if (type == 0 || !sched_feat(LB_BIAS))
		return total;

	return min(rq->cpu_load[type-1], total);
}

/*
5522
 * Return a high guess at the load of a migration-target CPU weighted
5523 5524 5525 5526 5527
 * according to the scheduling class and "nice" value.
 */
static unsigned long target_load(int cpu, int type)
{
	struct rq *rq = cpu_rq(cpu);
5528
	unsigned long total = weighted_cpuload(rq);
5529 5530 5531 5532 5533 5534 5535

	if (type == 0 || !sched_feat(LB_BIAS))
		return total;

	return max(rq->cpu_load[type-1], total);
}

5536
static unsigned long capacity_of(int cpu)
5537
{
5538
	return cpu_rq(cpu)->cpu_capacity;
5539 5540
}

5541 5542 5543 5544 5545
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

5546 5547 5548
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
5549
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
5550
	unsigned long load_avg = weighted_cpuload(rq);
5551 5552

	if (nr_running)
5553
		return load_avg / nr_running;
5554 5555 5556 5557

	return 0;
}

P
Peter Zijlstra 已提交
5558 5559 5560 5561 5562 5563 5564 5565 5566 5567 5568 5569 5570 5571 5572 5573 5574
static void record_wakee(struct task_struct *p)
{
	/*
	 * Only decay a single time; tasks that have less then 1 wakeup per
	 * jiffy will not have built up many flips.
	 */
	if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
		current->wakee_flips >>= 1;
		current->wakee_flip_decay_ts = jiffies;
	}

	if (current->last_wakee != p) {
		current->last_wakee = p;
		current->wakee_flips++;
	}
}

M
Mike Galbraith 已提交
5575 5576
/*
 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
P
Peter Zijlstra 已提交
5577
 *
M
Mike Galbraith 已提交
5578
 * A waker of many should wake a different task than the one last awakened
P
Peter Zijlstra 已提交
5579 5580 5581 5582 5583 5584 5585 5586 5587 5588 5589 5590
 * at a frequency roughly N times higher than one of its wakees.
 *
 * In order to determine whether we should let the load spread vs consolidating
 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
 * partner, and a factor of lls_size higher frequency in the other.
 *
 * With both conditions met, we can be relatively sure that the relationship is
 * non-monogamous, with partner count exceeding socket size.
 *
 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
 * whatever is irrelevant, spread criteria is apparent partner count exceeds
 * socket size.
M
Mike Galbraith 已提交
5591
 */
5592 5593
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
5594 5595
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
5596
	int factor = this_cpu_read(sd_llc_size);
5597

M
Mike Galbraith 已提交
5598 5599 5600 5601 5602
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
5603 5604
}

5605
/*
5606 5607 5608
 * The purpose of wake_affine() is to quickly determine on which CPU we can run
 * soonest. For the purpose of speed we only consider the waking and previous
 * CPU.
5609
 *
5610 5611
 * wake_affine_idle() - only considers 'now', it check if the waking CPU is
 *			cache-affine and is (or	will be) idle.
5612 5613 5614 5615
 *
 * wake_affine_weight() - considers the weight to reflect the average
 *			  scheduling latency of the CPUs. This seems to work
 *			  for the overloaded case.
5616
 */
5617
static int
5618
wake_affine_idle(int this_cpu, int prev_cpu, int sync)
5619
{
5620 5621 5622 5623 5624
	/*
	 * If this_cpu is idle, it implies the wakeup is from interrupt
	 * context. Only allow the move if cache is shared. Otherwise an
	 * interrupt intensive workload could force all tasks onto one
	 * node depending on the IO topology or IRQ affinity settings.
5625 5626 5627 5628 5629 5630
	 *
	 * If the prev_cpu is idle and cache affine then avoid a migration.
	 * There is no guarantee that the cache hot data from an interrupt
	 * is more important than cache hot data on the prev_cpu and from
	 * a cpufreq perspective, it's better to have higher utilisation
	 * on one CPU.
5631
	 */
5632 5633
	if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
		return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
5634

5635
	if (sync && cpu_rq(this_cpu)->nr_running == 1)
5636
		return this_cpu;
5637

5638
	return nr_cpumask_bits;
5639 5640
}

5641
static int
5642 5643
wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
		   int this_cpu, int prev_cpu, int sync)
5644 5645 5646 5647
{
	s64 this_eff_load, prev_eff_load;
	unsigned long task_load;

5648 5649 5650 5651 5652
	if (sched_feat(WA_STATIC_WEIGHT))
		this_eff_load =
			scale_load_down(cpu_rq(this_cpu)->cfs.load.weight);
	else
		this_eff_load = target_load(this_cpu, sd->wake_idx);
5653 5654

	if (sync) {
5655 5656 5657 5658 5659 5660
		unsigned long current_load;

		if (sched_feat(WA_STATIC_WEIGHT))
			current_load = task_h_load_static(current);
		else
			current_load = task_h_load(current);
5661

5662
		if (current_load > this_eff_load)
5663
			return this_cpu;
5664

5665
		this_eff_load -= current_load;
5666 5667
	}

5668 5669 5670 5671
	if (sched_feat(WA_STATIC_WEIGHT))
		task_load = task_h_load_static(p);
	else
		task_load = task_h_load(p);
5672

5673 5674 5675 5676
	this_eff_load += task_load;
	if (sched_feat(WA_BIAS))
		this_eff_load *= 100;
	this_eff_load *= capacity_of(prev_cpu);
5677

5678 5679 5680 5681 5682
	if (sched_feat(WA_STATIC_WEIGHT))
		prev_eff_load =
			scale_load_down(cpu_rq(prev_cpu)->cfs.load.weight);
	else
		prev_eff_load = source_load(prev_cpu, sd->wake_idx);
5683 5684 5685 5686
	prev_eff_load -= task_load;
	if (sched_feat(WA_BIAS))
		prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= capacity_of(this_cpu);
5687

5688 5689 5690 5691 5692 5693 5694 5695 5696 5697
	/*
	 * If sync, adjust the weight of prev_eff_load such that if
	 * prev_eff == this_eff that select_idle_sibling() will consider
	 * stacking the wakee on top of the waker if no other CPU is
	 * idle.
	 */
	if (sync)
		prev_eff_load += 1;

	return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
5698 5699
}

5700
static int wake_affine(struct sched_domain *sd, struct task_struct *p,
5701
		       int this_cpu, int prev_cpu, int sync)
5702
{
5703
	int target = nr_cpumask_bits;
5704

5705
	if (sched_feat(WA_IDLE))
5706
		target = wake_affine_idle(this_cpu, prev_cpu, sync);
5707

5708 5709
	if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
		target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
5710

5711
	schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5712 5713
	if (target == nr_cpumask_bits)
		return prev_cpu;
5714

5715 5716 5717
	schedstat_inc(sd->ttwu_move_affine);
	schedstat_inc(p->se.statistics.nr_wakeups_affine);
	return target;
5718 5719
}

5720
static unsigned long cpu_util_without(int cpu, struct task_struct *p);
5721

5722
static unsigned long capacity_spare_without(int cpu, struct task_struct *p)
5723
{
5724
	return max_t(long, capacity_of(cpu) - cpu_util_without(cpu, p), 0);
5725 5726
}

5727 5728 5729
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
5730 5731
 *
 * Assumes p is allowed on at least one CPU in sd.
5732 5733
 */
static struct sched_group *
P
Peter Zijlstra 已提交
5734
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5735
		  int this_cpu, int sd_flag)
5736
{
5737
	struct sched_group *idlest = NULL, *group = sd->groups;
5738
	struct sched_group *most_spare_sg = NULL;
5739 5740 5741
	unsigned long min_runnable_load = ULONG_MAX;
	unsigned long this_runnable_load = ULONG_MAX;
	unsigned long min_avg_load = ULONG_MAX, this_avg_load = ULONG_MAX;
5742
	unsigned long most_spare = 0, this_spare = 0;
5743
	int load_idx = sd->forkexec_idx;
5744 5745 5746
	int imbalance_scale = 100 + (sd->imbalance_pct-100)/2;
	unsigned long imbalance = scale_load_down(NICE_0_LOAD) *
				(sd->imbalance_pct-100) / 100;
5747

5748 5749 5750
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

5751
	do {
5752 5753
		unsigned long load, avg_load, runnable_load;
		unsigned long spare_cap, max_spare_cap;
5754 5755
		int local_group;
		int i;
5756

5757
		/* Skip over this group if it has no CPUs allowed */
5758
		if (!cpumask_intersects(sched_group_span(group),
5759
					&p->cpus_allowed))
5760 5761 5762
			continue;

		local_group = cpumask_test_cpu(this_cpu,
5763
					       sched_group_span(group));
5764

5765 5766 5767 5768
		/*
		 * Tally up the load of all CPUs in the group and find
		 * the group containing the CPU with most spare capacity.
		 */
5769
		avg_load = 0;
5770
		runnable_load = 0;
5771
		max_spare_cap = 0;
5772

5773
		for_each_cpu(i, sched_group_span(group)) {
5774
			/* Bias balancing toward CPUs of our domain */
5775 5776 5777 5778 5779
			if (local_group)
				load = source_load(i, load_idx);
			else
				load = target_load(i, load_idx);

5780 5781 5782
			runnable_load += load;

			avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs);
5783

5784
			spare_cap = capacity_spare_without(i, p);
5785 5786 5787

			if (spare_cap > max_spare_cap)
				max_spare_cap = spare_cap;
5788 5789
		}

5790
		/* Adjust by relative CPU capacity of the group */
5791 5792 5793 5794
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
		runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
5795 5796

		if (local_group) {
5797 5798
			this_runnable_load = runnable_load;
			this_avg_load = avg_load;
5799 5800
			this_spare = max_spare_cap;
		} else {
5801 5802 5803
			if (min_runnable_load > (runnable_load + imbalance)) {
				/*
				 * The runnable load is significantly smaller
5804
				 * so we can pick this new CPU:
5805 5806 5807 5808 5809 5810 5811 5812
				 */
				min_runnable_load = runnable_load;
				min_avg_load = avg_load;
				idlest = group;
			} else if ((runnable_load < (min_runnable_load + imbalance)) &&
				   (100*min_avg_load > imbalance_scale*avg_load)) {
				/*
				 * The runnable loads are close so take the
5813
				 * blocked load into account through avg_load:
5814 5815
				 */
				min_avg_load = avg_load;
5816 5817 5818 5819 5820 5821 5822
				idlest = group;
			}

			if (most_spare < max_spare_cap) {
				most_spare = max_spare_cap;
				most_spare_sg = group;
			}
5823 5824 5825
		}
	} while (group = group->next, group != sd->groups);

5826 5827 5828 5829 5830 5831
	/*
	 * The cross-over point between using spare capacity or least load
	 * is too conservative for high utilization tasks on partially
	 * utilized systems if we require spare_capacity > task_util(p),
	 * so we allow for some task stuffing by using
	 * spare_capacity > task_util(p)/2.
5832 5833 5834 5835
	 *
	 * Spare capacity can't be used for fork because the utilization has
	 * not been set yet, we must first select a rq to compute the initial
	 * utilization.
5836
	 */
5837 5838 5839
	if (sd_flag & SD_BALANCE_FORK)
		goto skip_spare;

5840
	if (this_spare > task_util(p) / 2 &&
5841
	    imbalance_scale*this_spare > 100*most_spare)
5842
		return NULL;
5843 5844

	if (most_spare > task_util(p) / 2)
5845 5846
		return most_spare_sg;

5847
skip_spare:
5848 5849 5850
	if (!idlest)
		return NULL;

5851 5852 5853 5854 5855 5856 5857 5858 5859 5860 5861 5862
	/*
	 * When comparing groups across NUMA domains, it's possible for the
	 * local domain to be very lightly loaded relative to the remote
	 * domains but "imbalance" skews the comparison making remote CPUs
	 * look much more favourable. When considering cross-domain, add
	 * imbalance to the runnable load on the remote node and consider
	 * staying local.
	 */
	if ((sd->flags & SD_NUMA) &&
	    min_runnable_load + imbalance >= this_runnable_load)
		return NULL;

5863
	if (min_runnable_load > (this_runnable_load + imbalance))
5864
		return NULL;
5865 5866 5867 5868 5869

	if ((this_runnable_load < (min_runnable_load + imbalance)) &&
	     (100*this_avg_load < imbalance_scale*min_avg_load))
		return NULL;

5870 5871 5872 5873
	return idlest;
}

/*
5874
 * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
5875 5876
 */
static int
5877
find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5878 5879
{
	unsigned long load, min_load = ULONG_MAX;
5880 5881 5882 5883
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
5884 5885
	int i;

5886 5887
	/* Check if we have any choice: */
	if (group->group_weight == 1)
5888
		return cpumask_first(sched_group_span(group));
5889

5890
	/* Traverse only the allowed CPUs */
5891
	for_each_cpu_and(i, sched_group_span(group), &p->cpus_allowed) {
5892
		if (available_idle_cpu(i)) {
5893 5894 5895 5896 5897 5898 5899 5900 5901 5902 5903 5904 5905 5906 5907 5908 5909 5910 5911 5912 5913
			struct rq *rq = cpu_rq(i);
			struct cpuidle_state *idle = idle_get_state(rq);
			if (idle && idle->exit_latency < min_exit_latency) {
				/*
				 * We give priority to a CPU whose idle state
				 * has the smallest exit latency irrespective
				 * of any idle timestamp.
				 */
				min_exit_latency = idle->exit_latency;
				latest_idle_timestamp = rq->idle_stamp;
				shallowest_idle_cpu = i;
			} else if ((!idle || idle->exit_latency == min_exit_latency) &&
				   rq->idle_stamp > latest_idle_timestamp) {
				/*
				 * If equal or no active idle state, then
				 * the most recently idled CPU might have
				 * a warmer cache.
				 */
				latest_idle_timestamp = rq->idle_stamp;
				shallowest_idle_cpu = i;
			}
5914
		} else if (shallowest_idle_cpu == -1) {
5915
			load = weighted_cpuload(cpu_rq(i));
5916
			if (load < min_load) {
5917 5918 5919
				min_load = load;
				least_loaded_cpu = i;
			}
5920 5921 5922
		}
	}

5923
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5924
}
5925

5926 5927 5928
static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
				  int cpu, int prev_cpu, int sd_flag)
{
5929
	int new_cpu = cpu;
5930

5931 5932 5933
	if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed))
		return prev_cpu;

5934
	/*
5935 5936
	 * We need task's util for capacity_spare_without, sync it up to
	 * prev_cpu's last_update_time.
5937 5938 5939 5940
	 */
	if (!(sd_flag & SD_BALANCE_FORK))
		sync_entity_load_avg(&p->se);

5941 5942 5943 5944 5945 5946 5947 5948 5949 5950 5951 5952 5953 5954 5955 5956 5957
	while (sd) {
		struct sched_group *group;
		struct sched_domain *tmp;
		int weight;

		if (!(sd->flags & sd_flag)) {
			sd = sd->child;
			continue;
		}

		group = find_idlest_group(sd, p, cpu, sd_flag);
		if (!group) {
			sd = sd->child;
			continue;
		}

		new_cpu = find_idlest_group_cpu(group, p, cpu);
5958
		if (new_cpu == cpu) {
5959
			/* Now try balancing at a lower domain level of 'cpu': */
5960 5961 5962 5963
			sd = sd->child;
			continue;
		}

5964
		/* Now try balancing at a lower domain level of 'new_cpu': */
5965 5966 5967 5968 5969 5970 5971 5972 5973 5974 5975 5976 5977 5978
		cpu = new_cpu;
		weight = sd->span_weight;
		sd = NULL;
		for_each_domain(cpu, tmp) {
			if (weight <= tmp->span_weight)
				break;
			if (tmp->flags & sd_flag)
				sd = tmp;
		}
	}

	return new_cpu;
}

5979
#ifdef CONFIG_SCHED_SMT
5980
DEFINE_STATIC_KEY_FALSE(sched_smt_present);
5981
EXPORT_SYMBOL_GPL(sched_smt_present);
5982 5983 5984 5985 5986 5987 5988 5989 5990 5991 5992 5993 5994 5995 5996 5997 5998 5999 6000 6001 6002 6003 6004 6005 6006 6007 6008 6009

static inline void set_idle_cores(int cpu, int val)
{
	struct sched_domain_shared *sds;

	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
	if (sds)
		WRITE_ONCE(sds->has_idle_cores, val);
}

static inline bool test_idle_cores(int cpu, bool def)
{
	struct sched_domain_shared *sds;

	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
	if (sds)
		return READ_ONCE(sds->has_idle_cores);

	return def;
}

/*
 * Scans the local SMT mask to see if the entire core is idle, and records this
 * information in sd_llc_shared->has_idle_cores.
 *
 * Since SMT siblings share all cache levels, inspecting this limited remote
 * state should be fairly cheap.
 */
P
Peter Zijlstra 已提交
6010
void __update_idle_core(struct rq *rq)
6011 6012 6013 6014 6015 6016 6017 6018 6019 6020 6021 6022
{
	int core = cpu_of(rq);
	int cpu;

	rcu_read_lock();
	if (test_idle_cores(core, true))
		goto unlock;

	for_each_cpu(cpu, cpu_smt_mask(core)) {
		if (cpu == core)
			continue;

6023
		if (!available_idle_cpu(cpu))
6024 6025 6026 6027 6028 6029 6030 6031 6032 6033 6034 6035 6036 6037 6038 6039
			goto unlock;
	}

	set_idle_cores(core, 1);
unlock:
	rcu_read_unlock();
}

/*
 * Scan the entire LLC domain for idle cores; this dynamically switches off if
 * there are no idle cores left in the system; tracked through
 * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above.
 */
static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
{
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
6040
	int core, cpu;
6041

P
Peter Zijlstra 已提交
6042 6043 6044
	if (!static_branch_likely(&sched_smt_present))
		return -1;

6045 6046 6047
	if (!test_idle_cores(target, false))
		return -1;

6048
	cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed);
6049

6050
	for_each_cpu_wrap(core, cpus, target) {
6051 6052 6053 6054
		bool idle = true;

		for_each_cpu(cpu, cpu_smt_mask(core)) {
			cpumask_clear_cpu(cpu, cpus);
6055
			if (!available_idle_cpu(cpu))
6056 6057 6058 6059 6060 6061 6062 6063 6064 6065 6066 6067 6068 6069 6070 6071 6072 6073 6074 6075 6076 6077
				idle = false;
		}

		if (idle)
			return core;
	}

	/*
	 * Failed to find an idle core; stop looking for one.
	 */
	set_idle_cores(target, 0);

	return -1;
}

/*
 * Scan the local SMT mask for idle CPUs.
 */
static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
{
	int cpu;

P
Peter Zijlstra 已提交
6078 6079 6080
	if (!static_branch_likely(&sched_smt_present))
		return -1;

6081
	for_each_cpu(cpu, cpu_smt_mask(target)) {
6082
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
6083
			continue;
6084
		if (available_idle_cpu(cpu))
6085 6086 6087 6088 6089 6090 6091 6092 6093 6094 6095 6096 6097 6098 6099 6100 6101 6102 6103 6104 6105 6106 6107 6108
			return cpu;
	}

	return -1;
}

#else /* CONFIG_SCHED_SMT */

static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
{
	return -1;
}

static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
{
	return -1;
}

#endif /* CONFIG_SCHED_SMT */

/*
 * Scan the LLC domain for idle CPUs; this is dynamically regulated by
 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the
 * average idle time for this rq (as found in rq->avg_idle).
6109
 */
6110 6111
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
{
6112
	struct sched_domain *this_sd;
6113
	u64 avg_cost, avg_idle;
6114 6115
	u64 time, cost;
	s64 delta;
6116
	int cpu, nr = INT_MAX;
6117

6118 6119 6120 6121
	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
	if (!this_sd)
		return -1;

6122 6123 6124 6125
	/*
	 * Due to large variance we need a large fuzz factor; hackbench in
	 * particularly is sensitive here.
	 */
6126 6127 6128 6129
	avg_idle = this_rq()->avg_idle / 512;
	avg_cost = this_sd->avg_scan_cost + 1;

	if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost)
6130 6131
		return -1;

6132 6133 6134 6135 6136 6137 6138 6139
	if (sched_feat(SIS_PROP)) {
		u64 span_avg = sd->span_weight * avg_idle;
		if (span_avg > 4*avg_cost)
			nr = div_u64(span_avg, avg_cost);
		else
			nr = 4;
	}

6140 6141
	time = local_clock();

6142
	for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
6143 6144
		if (!--nr)
			return -1;
6145
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
6146
			continue;
6147
		if (available_idle_cpu(cpu))
6148 6149 6150 6151 6152 6153 6154 6155 6156 6157 6158 6159 6160
			break;
	}

	time = local_clock() - time;
	cost = this_sd->avg_scan_cost;
	delta = (s64)(time - cost) / 8;
	this_sd->avg_scan_cost += delta;

	return cpu;
}

/*
 * Try and locate an idle core/thread in the LLC cache domain.
6161
 */
6162
static int select_idle_sibling(struct task_struct *p, int prev, int target)
6163
{
6164
	struct sched_domain *sd;
6165
	int i, recent_used_cpu;
6166

6167
	if (available_idle_cpu(target))
6168
		return target;
6169 6170

	/*
6171
	 * If the previous CPU is cache affine and idle, don't be stupid:
6172
	 */
6173
	if (prev != target && cpus_share_cache(prev, target) && available_idle_cpu(prev))
6174
		return prev;
6175

6176
	/* Check a recently used CPU as a potential idle candidate: */
6177 6178 6179 6180
	recent_used_cpu = p->recent_used_cpu;
	if (recent_used_cpu != prev &&
	    recent_used_cpu != target &&
	    cpus_share_cache(recent_used_cpu, target) &&
6181
	    available_idle_cpu(recent_used_cpu) &&
6182 6183 6184
	    cpumask_test_cpu(p->recent_used_cpu, &p->cpus_allowed)) {
		/*
		 * Replace recent_used_cpu with prev as it is a potential
6185
		 * candidate for the next wake:
6186 6187 6188 6189 6190
		 */
		p->recent_used_cpu = prev;
		return recent_used_cpu;
	}

6191
	sd = rcu_dereference(per_cpu(sd_llc, target));
6192 6193
	if (!sd)
		return target;
6194

6195 6196 6197
	i = select_idle_core(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;
6198

6199 6200 6201 6202 6203 6204 6205
	i = select_idle_cpu(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;

	i = select_idle_smt(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;
6206

6207 6208
	return target;
}
6209

6210 6211 6212 6213 6214 6215 6216
/**
 * Amount of capacity of a CPU that is (estimated to be) used by CFS tasks
 * @cpu: the CPU to get the utilization of
 *
 * The unit of the return value must be the one of capacity so we can compare
 * the utilization with the capacity of the CPU that is available for CFS task
 * (ie cpu_capacity).
6217 6218 6219 6220 6221 6222 6223 6224 6225 6226
 *
 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
 * recent utilization of currently non-runnable tasks on a CPU. It represents
 * the amount of utilization of a CPU in the range [0..capacity_orig] where
 * capacity_orig is the cpu_capacity available at the highest frequency
 * (arch_scale_freq_capacity()).
 * The utilization of a CPU converges towards a sum equal to or less than the
 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
 * the running time on this CPU scaled by capacity_curr.
 *
6227 6228 6229 6230 6231 6232 6233 6234
 * The estimated utilization of a CPU is defined to be the maximum between its
 * cfs_rq.avg.util_avg and the sum of the estimated utilization of the tasks
 * currently RUNNABLE on that CPU.
 * This allows to properly represent the expected utilization of a CPU which
 * has just got a big task running since a long sleep period. At the same time
 * however it preserves the benefits of the "blocked utilization" in
 * describing the potential for other tasks waking up on the same CPU.
 *
6235 6236 6237 6238 6239 6240 6241 6242 6243 6244
 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
 * higher than capacity_orig because of unfortunate rounding in
 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
 * the average stabilizes with the new running time. We need to check that the
 * utilization stays within the range of [0..capacity_orig] and cap it if
 * necessary. Without utilization capping, a group could be seen as overloaded
 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
 * available capacity. We allow utilization to overshoot capacity_curr (but not
 * capacity_orig) as it useful for predicting the capacity required after task
 * migrations (scheduler-driven DVFS).
6245 6246
 *
 * Return: the (estimated) utilization for the specified CPU
6247
 */
6248
static inline unsigned long cpu_util(int cpu)
6249
{
6250 6251 6252 6253 6254 6255 6256 6257
	struct cfs_rq *cfs_rq;
	unsigned int util;

	cfs_rq = &cpu_rq(cpu)->cfs;
	util = READ_ONCE(cfs_rq->avg.util_avg);

	if (sched_feat(UTIL_EST))
		util = max(util, READ_ONCE(cfs_rq->avg.util_est.enqueued));
6258

6259
	return min_t(unsigned long, util, capacity_orig_of(cpu));
6260
}
6261

6262
/*
6263 6264 6265 6266 6267 6268 6269 6270 6271 6272 6273
 * cpu_util_without: compute cpu utilization without any contributions from *p
 * @cpu: the CPU which utilization is requested
 * @p: the task which utilization should be discounted
 *
 * The utilization of a CPU is defined by the utilization of tasks currently
 * enqueued on that CPU as well as tasks which are currently sleeping after an
 * execution on that CPU.
 *
 * This method returns the utilization of the specified CPU by discounting the
 * utilization of the specified task, whenever the task is currently
 * contributing to the CPU utilization.
6274
 */
6275
static unsigned long cpu_util_without(int cpu, struct task_struct *p)
6276
{
6277 6278
	struct cfs_rq *cfs_rq;
	unsigned int util;
6279 6280

	/* Task has no contribution or is new */
6281
	if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
6282 6283
		return cpu_util(cpu);

6284 6285 6286
	cfs_rq = &cpu_rq(cpu)->cfs;
	util = READ_ONCE(cfs_rq->avg.util_avg);

6287
	/* Discount task's util from CPU's util */
6288
	util -= min_t(unsigned int, util, task_util(p));
6289

6290 6291 6292 6293 6294 6295
	/*
	 * Covered cases:
	 *
	 * a) if *p is the only task sleeping on this CPU, then:
	 *      cpu_util (== task_util) > util_est (== 0)
	 *    and thus we return:
6296
	 *      cpu_util_without = (cpu_util - task_util) = 0
6297 6298 6299 6300 6301 6302
	 *
	 * b) if other tasks are SLEEPING on this CPU, which is now exiting
	 *    IDLE, then:
	 *      cpu_util >= task_util
	 *      cpu_util > util_est (== 0)
	 *    and thus we discount *p's blocked utilization to return:
6303
	 *      cpu_util_without = (cpu_util - task_util) >= 0
6304 6305 6306 6307 6308 6309 6310 6311 6312 6313 6314 6315
	 *
	 * c) if other tasks are RUNNABLE on that CPU and
	 *      util_est > cpu_util
	 *    then we use util_est since it returns a more restrictive
	 *    estimation of the spare capacity on that CPU, by just
	 *    considering the expected utilization of tasks already
	 *    runnable on that CPU.
	 *
	 * Cases a) and b) are covered by the above code, while case c) is
	 * covered by the following code when estimated utilization is
	 * enabled.
	 */
6316 6317 6318 6319 6320 6321 6322 6323 6324 6325 6326 6327 6328 6329 6330 6331 6332 6333 6334 6335 6336 6337 6338 6339 6340 6341 6342
	if (sched_feat(UTIL_EST)) {
		unsigned int estimated =
			READ_ONCE(cfs_rq->avg.util_est.enqueued);

		/*
		 * Despite the following checks we still have a small window
		 * for a possible race, when an execl's select_task_rq_fair()
		 * races with LB's detach_task():
		 *
		 *   detach_task()
		 *     p->on_rq = TASK_ON_RQ_MIGRATING;
		 *     ---------------------------------- A
		 *     deactivate_task()                   \
		 *       dequeue_task()                     + RaceTime
		 *         util_est_dequeue()              /
		 *     ---------------------------------- B
		 *
		 * The additional check on "current == p" it's required to
		 * properly fix the execl regression and it helps in further
		 * reducing the chances for the above race.
		 */
		if (unlikely(task_on_rq_queued(p) || current == p)) {
			estimated -= min_t(unsigned int, estimated,
					   (_task_util_est(p) | UTIL_AVG_UNCHANGED));
		}
		util = max(util, estimated);
	}
6343 6344 6345 6346 6347 6348 6349

	/*
	 * Utilization (estimated) can exceed the CPU capacity, thus let's
	 * clamp to the maximum CPU capacity to ensure consistency with
	 * the cpu_util call.
	 */
	return min_t(unsigned long, util, capacity_orig_of(cpu));
6350 6351
}

6352 6353 6354 6355 6356 6357 6358 6359 6360 6361 6362 6363 6364 6365 6366 6367 6368 6369
/*
 * Disable WAKE_AFFINE in the case where task @p doesn't fit in the
 * capacity of either the waking CPU @cpu or the previous CPU @prev_cpu.
 *
 * In that case WAKE_AFFINE doesn't make sense and we'll let
 * BALANCE_WAKE sort things out.
 */
static int wake_cap(struct task_struct *p, int cpu, int prev_cpu)
{
	long min_cap, max_cap;

	min_cap = min(capacity_orig_of(prev_cpu), capacity_orig_of(cpu));
	max_cap = cpu_rq(cpu)->rd->max_cpu_capacity;

	/* Minimum capacity is close to max, no need to abort wake_affine */
	if (max_cap - min_cap < max_cap >> 3)
		return 0;

6370 6371 6372
	/* Bring task utilization in sync with prev_cpu */
	sync_entity_load_avg(&p->se);

6373 6374 6375
	return min_cap * 1024 < task_util(p) * capacity_margin;
}

6376
/*
6377 6378 6379
 * select_task_rq_fair: Select target runqueue for the waking task in domains
 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
 * SD_BALANCE_FORK, or SD_BALANCE_EXEC.
6380
 *
6381 6382
 * Balances load by selecting the idlest CPU in the idlest group, or under
 * certain conditions an idle sibling CPU if the domain has SD_WAKE_AFFINE set.
6383
 *
6384
 * Returns the target CPU number.
6385 6386 6387
 *
 * preempt must be disabled.
 */
6388
static int
6389
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
6390
{
6391
	struct sched_domain *tmp, *sd = NULL;
6392
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
6393
	int new_cpu = prev_cpu;
6394
	int want_affine = 0;
6395
	int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
6396

P
Peter Zijlstra 已提交
6397 6398
	if (sd_flag & SD_BALANCE_WAKE) {
		record_wakee(p);
6399
		want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu)
6400
			      && cpumask_test_cpu(cpu, &p->cpus_allowed);
P
Peter Zijlstra 已提交
6401
	}
6402

6403
	rcu_read_lock();
6404
	for_each_domain(cpu, tmp) {
6405
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
6406
			break;
6407

6408
		/*
6409
		 * If both 'cpu' and 'prev_cpu' are part of this domain,
6410
		 * cpu is a valid SD_WAKE_AFFINE target.
6411
		 */
6412 6413
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
6414 6415 6416 6417
			if (cpu != prev_cpu)
				new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);

			sd = NULL; /* Prefer wake_affine over balance flags */
6418
			break;
6419
		}
6420

6421
		if (tmp->flags & sd_flag)
6422
			sd = tmp;
M
Mike Galbraith 已提交
6423 6424
		else if (!want_affine)
			break;
6425 6426
	}

6427 6428
	if (unlikely(sd)) {
		/* Slow path */
6429
		new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
6430 6431 6432 6433 6434 6435 6436
	} else if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
		/* Fast path */

		new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);

		if (want_affine)
			current->recent_used_cpu = cpu;
6437
	}
6438
	rcu_read_unlock();
6439

6440
	return new_cpu;
6441
}
6442

6443 6444
static void detach_entity_cfs_rq(struct sched_entity *se);

6445
/*
6446
 * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
6447
 * cfs_rq_of(p) references at time of call are still valid and identify the
6448
 * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6449
 */
6450
static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
6451
{
6452 6453 6454 6455 6456 6457 6458 6459 6460 6461 6462 6463 6464 6465 6466 6467 6468 6469 6470 6471 6472 6473 6474 6475 6476 6477
	/*
	 * As blocked tasks retain absolute vruntime the migration needs to
	 * deal with this by subtracting the old and adding the new
	 * min_vruntime -- the latter is done by enqueue_entity() when placing
	 * the task on the new runqueue.
	 */
	if (p->state == TASK_WAKING) {
		struct sched_entity *se = &p->se;
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
		u64 min_vruntime;

#ifndef CONFIG_64BIT
		u64 min_vruntime_copy;

		do {
			min_vruntime_copy = cfs_rq->min_vruntime_copy;
			smp_rmb();
			min_vruntime = cfs_rq->min_vruntime;
		} while (min_vruntime != min_vruntime_copy);
#else
		min_vruntime = cfs_rq->min_vruntime;
#endif

		se->vruntime -= min_vruntime;
	}

6478 6479 6480 6481 6482 6483 6484 6485 6486 6487 6488 6489 6490 6491 6492 6493 6494 6495 6496
	if (p->on_rq == TASK_ON_RQ_MIGRATING) {
		/*
		 * In case of TASK_ON_RQ_MIGRATING we in fact hold the 'old'
		 * rq->lock and can modify state directly.
		 */
		lockdep_assert_held(&task_rq(p)->lock);
		detach_entity_cfs_rq(&p->se);

	} else {
		/*
		 * We are supposed to update the task to "current" time, then
		 * its up to date and ready to go to new CPU/cfs_rq. But we
		 * have difficulty in getting what current time is, so simply
		 * throw away the out-of-date time. This will result in the
		 * wakee task is less decayed, but giving the wakee more load
		 * sounds not bad.
		 */
		remove_entity_load_avg(&p->se);
	}
6497 6498 6499

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
6500 6501

	/* We have migrated, no longer consider this task hot */
6502
	p->se.exec_start = 0;
6503 6504

	update_scan_period(p, new_cpu);
6505
}
6506 6507 6508 6509 6510

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
6511 6512
#endif /* CONFIG_SMP */

6513
static unsigned long wakeup_gran(struct sched_entity *se)
6514 6515 6516 6517
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
6518 6519
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
6520 6521 6522 6523 6524 6525 6526 6527 6528
	 *
	 * By using 'se' instead of 'curr' we penalize light tasks, so
	 * they get preempted easier. That is, if 'se' < 'curr' then
	 * the resulting gran will be larger, therefore penalizing the
	 * lighter, if otoh 'se' > 'curr' then the resulting gran will
	 * be smaller, again penalizing the lighter task.
	 *
	 * This is especially important for buddies when the leftmost
	 * task is higher priority than the buddy.
6529
	 */
6530
	return calc_delta_fair(gran, se);
6531 6532
}

6533 6534 6535 6536 6537 6538 6539 6540 6541 6542 6543 6544 6545 6546 6547 6548 6549 6550 6551 6552 6553 6554
/*
 * Should 'se' preempt 'curr'.
 *
 *             |s1
 *        |s2
 *   |s3
 *         g
 *      |<--->|c
 *
 *  w(c, s1) = -1
 *  w(c, s2) =  0
 *  w(c, s3) =  1
 *
 */
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
{
	s64 gran, vdiff = curr->vruntime - se->vruntime;

	if (vdiff <= 0)
		return -1;

6555
	gran = wakeup_gran(se);
6556 6557 6558 6559 6560 6561
	if (vdiff > gran)
		return 1;

	return 0;
}

6562 6563
static void set_last_buddy(struct sched_entity *se)
{
6564 6565 6566
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6567 6568 6569
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6570
		cfs_rq_of(se)->last = se;
6571
	}
6572 6573 6574 6575
}

static void set_next_buddy(struct sched_entity *se)
{
6576 6577 6578
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6579 6580 6581
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6582
		cfs_rq_of(se)->next = se;
6583
	}
6584 6585
}

6586 6587
static void set_skip_buddy(struct sched_entity *se)
{
6588 6589
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
6590 6591
}

6592 6593 6594
/*
 * Preempt the current task with a newly woken task if needed:
 */
6595
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
6596 6597
{
	struct task_struct *curr = rq->curr;
6598
	struct sched_entity *se = &curr->se, *pse = &p->se;
6599
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6600
	int scale = cfs_rq->nr_running >= sched_nr_latency;
6601
	int next_buddy_marked = 0;
6602

I
Ingo Molnar 已提交
6603 6604 6605
	if (unlikely(se == pse))
		return;

6606
	/*
6607
	 * This is possible from callers such as attach_tasks(), in which we
6608 6609 6610 6611 6612 6613 6614
	 * unconditionally check_prempt_curr() after an enqueue (which may have
	 * lead to a throttle).  This both saves work and prevents false
	 * next-buddy nomination below.
	 */
	if (unlikely(throttled_hierarchy(cfs_rq_of(pse))))
		return;

6615
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
6616
		set_next_buddy(pse);
6617 6618
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
6619

6620 6621 6622
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
6623 6624 6625 6626 6627 6628
	 *
	 * Note: this also catches the edge-case of curr being in a throttled
	 * group (e.g. via set_curr_task), since update_curr() (in the
	 * enqueue of curr) will have resulted in resched being set.  This
	 * prevents us from potentially nominating it as a false LAST_BUDDY
	 * below.
6629 6630 6631 6632
	 */
	if (test_tsk_need_resched(curr))
		return;

6633 6634 6635 6636 6637
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

6638
	/*
6639 6640
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
6641
	 */
6642
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
6643
		return;
6644

6645
	find_matching_se(&se, &pse);
6646
	update_curr(cfs_rq_of(se));
6647
	BUG_ON(!pse);
6648 6649 6650 6651 6652 6653 6654
	if (wakeup_preempt_entity(se, pse) == 1) {
		/*
		 * Bias pick_next to pick the sched entity that is
		 * triggering this preemption.
		 */
		if (!next_buddy_marked)
			set_next_buddy(pse);
6655
		goto preempt;
6656
	}
6657

6658
	return;
6659

6660
preempt:
6661
	resched_curr(rq);
6662 6663 6664 6665 6666 6667 6668 6669 6670 6671 6672 6673 6674 6675
	/*
	 * Only set the backward buddy when the current task is still
	 * on the rq. This can happen when a wakeup gets interleaved
	 * with schedule on the ->pre_schedule() or idle_balance()
	 * point, either of which can * drop the rq lock.
	 *
	 * Also, during early boot the idle thread is in the fair class,
	 * for obvious reasons its a bad idea to schedule back to it.
	 */
	if (unlikely(!se->on_rq || curr == rq->idle))
		return;

	if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
		set_last_buddy(se);
6676 6677
}

6678
static struct task_struct *
6679
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6680 6681 6682
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
6683
	struct task_struct *p;
6684
	int new_tasks;
6685

6686
again:
6687
	if (!cfs_rq->nr_running)
6688
		goto idle;
6689

6690
#ifdef CONFIG_FAIR_GROUP_SCHED
6691
	if (prev->sched_class != &fair_sched_class)
6692 6693 6694 6695 6696 6697 6698 6699 6700 6701 6702 6703 6704 6705 6706 6707 6708 6709 6710
		goto simple;

	/*
	 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
	 * likely that a next task is from the same cgroup as the current.
	 *
	 * Therefore attempt to avoid putting and setting the entire cgroup
	 * hierarchy, only change the part that actually changes.
	 */

	do {
		struct sched_entity *curr = cfs_rq->curr;

		/*
		 * Since we got here without doing put_prev_entity() we also
		 * have to consider cfs_rq->curr. If it is still a runnable
		 * entity, update_curr() will update its vruntime, otherwise
		 * forget we've ever seen it.
		 */
6711 6712 6713 6714 6715
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
6716

6717 6718 6719
			/*
			 * This call to check_cfs_rq_runtime() will do the
			 * throttle and dequeue its entity in the parent(s).
6720
			 * Therefore the nr_running test will indeed
6721 6722
			 * be correct.
			 */
6723 6724 6725 6726 6727 6728
			if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
				cfs_rq = &rq->cfs;

				if (!cfs_rq->nr_running)
					goto idle;

6729
				goto simple;
6730
			}
6731
		}
6732 6733 6734 6735 6736 6737 6738 6739 6740 6741 6742 6743 6744 6745 6746 6747 6748 6749 6750 6751 6752 6753 6754 6755 6756 6757 6758 6759 6760 6761 6762 6763 6764

		se = pick_next_entity(cfs_rq, curr);
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

	p = task_of(se);

	/*
	 * Since we haven't yet done put_prev_entity and if the selected task
	 * is a different task than we started out with, try and touch the
	 * least amount of cfs_rqs.
	 */
	if (prev != p) {
		struct sched_entity *pse = &prev->se;

		while (!(cfs_rq = is_same_group(se, pse))) {
			int se_depth = se->depth;
			int pse_depth = pse->depth;

			if (se_depth <= pse_depth) {
				put_prev_entity(cfs_rq_of(pse), pse);
				pse = parent_entity(pse);
			}
			if (se_depth >= pse_depth) {
				set_next_entity(cfs_rq_of(se), se);
				se = parent_entity(se);
			}
		}

		put_prev_entity(cfs_rq, pse);
		set_next_entity(cfs_rq, se);
	}

6765
	goto done;
6766 6767
simple:
#endif
6768

6769
	put_prev_task(rq, prev);
6770

6771
	do {
6772
		se = pick_next_entity(cfs_rq, NULL);
6773
		set_next_entity(cfs_rq, se);
6774 6775 6776
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
6777
	p = task_of(se);
6778

6779
done: __maybe_unused;
6780 6781 6782 6783 6784 6785 6786 6787 6788
#ifdef CONFIG_SMP
	/*
	 * Move the next running task to the front of
	 * the list, so our cfs_tasks list becomes MRU
	 * one.
	 */
	list_move(&p->se.group_node, &rq->cfs_tasks);
#endif

6789 6790
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
6791 6792

	return p;
6793 6794

idle:
6795 6796
	new_tasks = idle_balance(rq, rf);

6797 6798 6799 6800 6801
	/*
	 * Because idle_balance() releases (and re-acquires) rq->lock, it is
	 * possible for any higher priority task to appear. In that case we
	 * must re-start the pick_next_entity() loop.
	 */
6802
	if (new_tasks < 0)
6803 6804
		return RETRY_TASK;

6805
	if (new_tasks > 0)
6806 6807 6808
		goto again;

	return NULL;
6809 6810 6811 6812 6813
}

/*
 * Account for a descheduled task:
 */
6814
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
6815 6816 6817 6818 6819 6820
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
6821
		put_prev_entity(cfs_rq, se);
6822 6823 6824
	}
}

6825 6826 6827 6828 6829 6830 6831 6832 6833 6834 6835 6836 6837 6838 6839 6840 6841 6842 6843 6844 6845 6846 6847 6848 6849
/*
 * sched_yield() is very simple
 *
 * The magic of dealing with the ->skip buddy is in pick_next_entity.
 */
static void yield_task_fair(struct rq *rq)
{
	struct task_struct *curr = rq->curr;
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
	struct sched_entity *se = &curr->se;

	/*
	 * Are we the only task in the tree?
	 */
	if (unlikely(rq->nr_running == 1))
		return;

	clear_buddies(cfs_rq, se);

	if (curr->policy != SCHED_BATCH) {
		update_rq_clock(rq);
		/*
		 * Update run-time statistics of the 'current'.
		 */
		update_curr(cfs_rq);
6850 6851 6852 6853 6854
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
6855
		rq_clock_skip_update(rq);
6856 6857 6858 6859 6860
	}

	set_skip_buddy(se);
}

6861 6862 6863 6864
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

6865 6866
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
6867 6868 6869 6870 6871 6872 6873 6874 6875 6876
		return false;

	/* Tell the scheduler that we'd really like pse to run next. */
	set_next_buddy(se);

	yield_task_fair(rq);

	return true;
}

6877
#ifdef CONFIG_SMP
6878
/**************************************************
P
Peter Zijlstra 已提交
6879 6880 6881 6882 6883
 * Fair scheduling class load-balancing methods.
 *
 * BASICS
 *
 * The purpose of load-balancing is to achieve the same basic fairness the
6884
 * per-CPU scheduler provides, namely provide a proportional amount of compute
P
Peter Zijlstra 已提交
6885 6886 6887 6888
 * time to each task. This is expressed in the following equation:
 *
 *   W_i,n/P_i == W_j,n/P_j for all i,j                               (1)
 *
6889
 * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
P
Peter Zijlstra 已提交
6890 6891 6892 6893
 * W_i,0 is defined as:
 *
 *   W_i,0 = \Sum_j w_i,j                                             (2)
 *
6894
 * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
6895
 * is derived from the nice value as per sched_prio_to_weight[].
P
Peter Zijlstra 已提交
6896 6897 6898 6899 6900 6901
 *
 * The weight average is an exponential decay average of the instantaneous
 * weight:
 *
 *   W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0               (3)
 *
6902
 * C_i is the compute capacity of CPU i, typically it is the
P
Peter Zijlstra 已提交
6903 6904 6905 6906 6907 6908
 * fraction of 'recent' time available for SCHED_OTHER task execution. But it
 * can also include other factors [XXX].
 *
 * To achieve this balance we define a measure of imbalance which follows
 * directly from (1):
 *
6909
 *   imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j }    (4)
P
Peter Zijlstra 已提交
6910 6911 6912 6913 6914 6915 6916 6917 6918 6919 6920 6921 6922
 *
 * We them move tasks around to minimize the imbalance. In the continuous
 * function space it is obvious this converges, in the discrete case we get
 * a few fun cases generally called infeasible weight scenarios.
 *
 * [XXX expand on:
 *     - infeasible weights;
 *     - local vs global optima in the discrete case. ]
 *
 *
 * SCHED DOMAINS
 *
 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2)
6923
 * for all i,j solution, we create a tree of CPUs that follows the hardware
P
Peter Zijlstra 已提交
6924
 * topology where each level pairs two lower groups (or better). This results
6925
 * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
P
Peter Zijlstra 已提交
6926
 * tree to only the first of the previous level and we decrease the frequency
6927
 * of load-balance at each level inv. proportional to the number of CPUs in
P
Peter Zijlstra 已提交
6928 6929 6930 6931 6932 6933 6934 6935
 * the groups.
 *
 * This yields:
 *
 *     log_2 n     1     n
 *   \Sum       { --- * --- * 2^i } = O(n)                            (5)
 *     i = 0      2^i   2^i
 *                               `- size of each group
6936
 *         |         |     `- number of CPUs doing load-balance
P
Peter Zijlstra 已提交
6937 6938 6939 6940 6941 6942 6943
 *         |         `- freq
 *         `- sum over all levels
 *
 * Coupled with a limit on how many tasks we can migrate every balance pass,
 * this makes (5) the runtime complexity of the balancer.
 *
 * An important property here is that each CPU is still (indirectly) connected
6944
 * to every other CPU in at most O(log n) steps:
P
Peter Zijlstra 已提交
6945 6946 6947
 *
 * The adjacency matrix of the resulting graph is given by:
 *
6948
 *             log_2 n
P
Peter Zijlstra 已提交
6949 6950 6951 6952 6953 6954 6955
 *   A_i,j = \Union     (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1)  (6)
 *             k = 0
 *
 * And you'll find that:
 *
 *   A^(log_2 n)_i,j != 0  for all i,j                                (7)
 *
6956
 * Showing there's indeed a path between every CPU in at most O(log n) steps.
P
Peter Zijlstra 已提交
6957 6958 6959 6960 6961 6962 6963 6964 6965
 * The task movement gives a factor of O(m), giving a convergence complexity
 * of:
 *
 *   O(nm log n),  n := nr_cpus, m := nr_tasks                        (8)
 *
 *
 * WORK CONSERVING
 *
 * In order to avoid CPUs going idle while there's still work to do, new idle
6966
 * balancing is more aggressive and has the newly idle CPU iterate up the domain
P
Peter Zijlstra 已提交
6967 6968 6969 6970 6971 6972 6973 6974 6975 6976 6977 6978 6979 6980 6981 6982 6983 6984 6985 6986
 * tree itself instead of relying on other CPUs to bring it work.
 *
 * This adds some complexity to both (5) and (8) but it reduces the total idle
 * time.
 *
 * [XXX more?]
 *
 *
 * CGROUPS
 *
 * Cgroups make a horror show out of (2), instead of a simple sum we get:
 *
 *                                s_k,i
 *   W_i,0 = \Sum_j \Prod_k w_k * -----                               (9)
 *                                 S_k
 *
 * Where
 *
 *   s_k,i = \Sum_j w_i,j,k  and  S_k = \Sum_i s_k,i                 (10)
 *
6987
 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on CPU i.
P
Peter Zijlstra 已提交
6988 6989 6990 6991 6992 6993
 *
 * The big problem is S_k, its a global sum needed to compute a local (W_i)
 * property.
 *
 * [XXX write more on how we solve this.. _after_ merging pjt's patches that
 *      rewrite all of this once again.]
6994
 */
6995

6996 6997
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

6998 6999
enum fbq_type { regular, remote, all };

7000
#define LBF_ALL_PINNED	0x01
7001
#define LBF_NEED_BREAK	0x02
7002 7003
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
7004
#define LBF_NOHZ_STATS	0x10
7005
#define LBF_NOHZ_AGAIN	0x20
7006 7007 7008 7009 7010

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
7011
	int			src_cpu;
7012 7013 7014 7015

	int			dst_cpu;
	struct rq		*dst_rq;

7016 7017
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
7018
	enum cpu_idle_type	idle;
7019
	long			imbalance;
7020 7021 7022
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

7023
	unsigned int		flags;
7024 7025 7026 7027

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
7028 7029

	enum fbq_type		fbq_type;
7030
	struct list_head	tasks;
7031 7032
};

7033 7034 7035
/*
 * Is this task likely cache-hot:
 */
7036
static int task_hot(struct task_struct *p, struct lb_env *env)
7037 7038 7039
{
	s64 delta;

7040 7041
	lockdep_assert_held(&env->src_rq->lock);

7042 7043 7044 7045 7046 7047 7048 7049 7050
	if (p->sched_class != &fair_sched_class)
		return 0;

	if (unlikely(p->policy == SCHED_IDLE))
		return 0;

	/*
	 * Buddy candidates are cache hot:
	 */
7051
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
7052 7053 7054 7055 7056 7057 7058 7059 7060
			(&p->se == cfs_rq_of(&p->se)->next ||
			 &p->se == cfs_rq_of(&p->se)->last))
		return 1;

	if (sysctl_sched_migration_cost == -1)
		return 1;
	if (sysctl_sched_migration_cost == 0)
		return 0;

7061
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
7062 7063 7064 7065

	return delta < (s64)sysctl_sched_migration_cost;
}

7066
#ifdef CONFIG_NUMA_BALANCING
7067
/*
7068 7069 7070
 * Returns 1, if task migration degrades locality
 * Returns 0, if task migration improves locality i.e migration preferred.
 * Returns -1, if task migration is not affected by locality.
7071
 */
7072
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
7073
{
7074
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
7075 7076
	unsigned long src_weight, dst_weight;
	int src_nid, dst_nid, dist;
7077

7078
	if (!static_branch_likely(&sched_numa_balancing))
7079 7080
		return -1;

7081
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
7082
		return -1;
7083 7084 7085 7086

	src_nid = cpu_to_node(env->src_cpu);
	dst_nid = cpu_to_node(env->dst_cpu);

7087
	if (src_nid == dst_nid)
7088
		return -1;
7089

7090 7091 7092 7093 7094 7095 7096
	/* Migrating away from the preferred node is always bad. */
	if (src_nid == p->numa_preferred_nid) {
		if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
			return 1;
		else
			return -1;
	}
7097

7098 7099
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
7100
		return 0;
7101

7102
	/* Leaving a core idle is often worse than degrading locality. */
7103
	if (env->idle == CPU_IDLE)
7104 7105
		return -1;

7106
	dist = node_distance(src_nid, dst_nid);
7107
	if (numa_group) {
7108 7109
		src_weight = group_weight(p, src_nid, dist);
		dst_weight = group_weight(p, dst_nid, dist);
7110
	} else {
7111 7112
		src_weight = task_weight(p, src_nid, dist);
		dst_weight = task_weight(p, dst_nid, dist);
7113 7114
	}

7115
	return dst_weight < src_weight;
7116 7117
}

7118
#else
7119
static inline int migrate_degrades_locality(struct task_struct *p,
7120 7121
					     struct lb_env *env)
{
7122
	return -1;
7123
}
7124 7125
#endif

7126 7127 7128 7129
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
7130
int can_migrate_task(struct task_struct *p, struct lb_env *env)
7131
{
7132
	int tsk_cache_hot;
7133 7134 7135

	lockdep_assert_held(&env->src_rq->lock);

7136 7137
	/*
	 * We do not migrate tasks that are:
7138
	 * 1) throttled_lb_pair, or
7139
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
7140 7141
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
7142
	 */
7143 7144 7145
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

7146
	if (!cpumask_test_cpu(env->dst_cpu, &p->cpus_allowed)) {
7147
		int cpu;
7148

7149
		schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
7150

7151 7152
		env->flags |= LBF_SOME_PINNED;

7153
		/*
7154
		 * Remember if this task can be migrated to any other CPU in
7155 7156 7157
		 * our sched_group. We may want to revisit it if we couldn't
		 * meet load balance goals by pulling other tasks on src_cpu.
		 *
7158 7159
		 * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
		 * already computed one in current iteration.
7160
		 */
7161
		if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED))
7162 7163
			return 0;

7164
		/* Prevent to re-select dst_cpu via env's CPUs: */
7165
		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
7166
			if (cpumask_test_cpu(cpu, &p->cpus_allowed)) {
7167
				env->flags |= LBF_DST_PINNED;
7168 7169 7170
				env->new_dst_cpu = cpu;
				break;
			}
7171
		}
7172

7173 7174
		return 0;
	}
7175 7176

	/* Record that we found atleast one task that could run on dst_cpu */
7177
	env->flags &= ~LBF_ALL_PINNED;
7178

7179
	if (task_running(env->src_rq, p)) {
7180
		schedstat_inc(p->se.statistics.nr_failed_migrations_running);
7181 7182 7183 7184 7185
		return 0;
	}

	/*
	 * Aggressive migration if:
7186 7187 7188
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
7189
	 */
7190 7191 7192
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
7193

7194
	if (tsk_cache_hot <= 0 ||
7195
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
7196
		if (tsk_cache_hot == 1) {
7197 7198
			schedstat_inc(env->sd->lb_hot_gained[env->idle]);
			schedstat_inc(p->se.statistics.nr_forced_migrations);
7199
		}
7200 7201 7202
		return 1;
	}

7203
	schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
Z
Zhang Hang 已提交
7204
	return 0;
7205 7206
}

7207
/*
7208 7209 7210 7211 7212 7213 7214
 * detach_task() -- detach the task for the migration specified in env
 */
static void detach_task(struct task_struct *p, struct lb_env *env)
{
	lockdep_assert_held(&env->src_rq->lock);

	p->on_rq = TASK_ON_RQ_MIGRATING;
7215
	deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
7216 7217 7218
	set_task_cpu(p, env->dst_cpu);
}

7219
/*
7220
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
7221 7222
 * part of active balancing operations within "domain".
 *
7223
 * Returns a task if successful and NULL otherwise.
7224
 */
7225
static struct task_struct *detach_one_task(struct lb_env *env)
7226
{
7227
	struct task_struct *p;
7228

7229 7230
	lockdep_assert_held(&env->src_rq->lock);

7231 7232
	list_for_each_entry_reverse(p,
			&env->src_rq->cfs_tasks, se.group_node) {
7233 7234
		if (!can_migrate_task(p, env))
			continue;
7235

7236
		detach_task(p, env);
7237

7238
		/*
7239
		 * Right now, this is only the second place where
7240
		 * lb_gained[env->idle] is updated (other is detach_tasks)
7241
		 * so we can safely collect stats here rather than
7242
		 * inside detach_tasks().
7243
		 */
7244
		schedstat_inc(env->sd->lb_gained[env->idle]);
7245
		return p;
7246
	}
7247
	return NULL;
7248 7249
}

7250 7251
static const unsigned int sched_nr_migrate_break = 32;

7252
/*
7253 7254
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
7255
 *
7256
 * Returns number of detached tasks if successful and 0 otherwise.
7257
 */
7258
static int detach_tasks(struct lb_env *env)
7259
{
7260 7261
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
7262
	unsigned long load;
7263 7264 7265
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
7266

7267
	if (env->imbalance <= 0)
7268
		return 0;
7269

7270
	while (!list_empty(tasks)) {
7271 7272 7273 7274 7275 7276 7277
		/*
		 * We don't want to steal all, otherwise we may be treated likewise,
		 * which could at worst lead to a livelock crash.
		 */
		if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
			break;

7278
		p = list_last_entry(tasks, struct task_struct, se.group_node);
7279

7280 7281
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
7282
		if (env->loop > env->loop_max)
7283
			break;
7284 7285

		/* take a breather every nr_migrate tasks */
7286
		if (env->loop > env->loop_break) {
7287
			env->loop_break += sched_nr_migrate_break;
7288
			env->flags |= LBF_NEED_BREAK;
7289
			break;
7290
		}
7291

7292
		if (!can_migrate_task(p, env))
7293 7294 7295
			goto next;

		load = task_h_load(p);
7296

7297
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
7298 7299
			goto next;

7300
		if ((load / 2) > env->imbalance)
7301
			goto next;
7302

7303 7304 7305 7306
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
7307
		env->imbalance -= load;
7308 7309

#ifdef CONFIG_PREEMPT
7310 7311
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
7312
		 * kernels will stop after the first task is detached to minimize
7313 7314
		 * the critical section.
		 */
7315
		if (env->idle == CPU_NEWLY_IDLE)
7316
			break;
7317 7318
#endif

7319 7320 7321 7322
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
7323
		if (env->imbalance <= 0)
7324
			break;
7325 7326 7327

		continue;
next:
7328
		list_move(&p->se.group_node, tasks);
7329
	}
7330

7331
	/*
7332 7333 7334
	 * Right now, this is one of only two places we collect this stat
	 * so we can safely collect detach_one_task() stats here rather
	 * than inside detach_one_task().
7335
	 */
7336
	schedstat_add(env->sd->lb_gained[env->idle], detached);
7337

7338 7339 7340 7341 7342 7343 7344 7345 7346 7347 7348
	return detached;
}

/*
 * attach_task() -- attach the task detached by detach_task() to its new rq.
 */
static void attach_task(struct rq *rq, struct task_struct *p)
{
	lockdep_assert_held(&rq->lock);

	BUG_ON(task_rq(p) != rq);
7349
	activate_task(rq, p, ENQUEUE_NOCLOCK);
7350
	p->on_rq = TASK_ON_RQ_QUEUED;
7351 7352 7353 7354 7355 7356 7357 7358 7359
	check_preempt_curr(rq, p, 0);
}

/*
 * attach_one_task() -- attaches the task returned from detach_one_task() to
 * its new rq.
 */
static void attach_one_task(struct rq *rq, struct task_struct *p)
{
7360 7361 7362
	struct rq_flags rf;

	rq_lock(rq, &rf);
7363
	update_rq_clock(rq);
7364
	attach_task(rq, p);
7365
	rq_unlock(rq, &rf);
7366 7367 7368 7369 7370 7371 7372 7373 7374 7375
}

/*
 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
 * new rq.
 */
static void attach_tasks(struct lb_env *env)
{
	struct list_head *tasks = &env->tasks;
	struct task_struct *p;
7376
	struct rq_flags rf;
7377

7378
	rq_lock(env->dst_rq, &rf);
7379
	update_rq_clock(env->dst_rq);
7380 7381 7382 7383

	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
		list_del_init(&p->se.group_node);
7384

7385 7386 7387
		attach_task(env->dst_rq, p);
	}

7388
	rq_unlock(env->dst_rq, &rf);
7389 7390
}

7391 7392 7393 7394 7395 7396 7397 7398 7399 7400 7401
static inline bool cfs_rq_has_blocked(struct cfs_rq *cfs_rq)
{
	if (cfs_rq->avg.load_avg)
		return true;

	if (cfs_rq->avg.util_avg)
		return true;

	return false;
}

7402
static inline bool others_have_blocked(struct rq *rq)
7403 7404 7405 7406
{
	if (READ_ONCE(rq->avg_rt.util_avg))
		return true;

7407 7408 7409
	if (READ_ONCE(rq->avg_dl.util_avg))
		return true;

7410
#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
7411 7412 7413 7414
	if (READ_ONCE(rq->avg_irq.util_avg))
		return true;
#endif

7415 7416 7417
	return false;
}

7418 7419
#ifdef CONFIG_FAIR_GROUP_SCHED

7420
static void update_blocked_averages(int cpu)
7421 7422
{
	struct rq *rq = cpu_rq(cpu);
7423
	struct cfs_rq *cfs_rq;
7424
	const struct sched_class *curr_class;
7425
	struct rq_flags rf;
7426
	bool done = true;
7427

7428
	rq_lock_irqsave(rq, &rf);
7429
	update_rq_clock(rq);
7430

7431 7432 7433 7434
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
7435
	for_each_leaf_cfs_rq(rq, cfs_rq) {
7436 7437
		struct sched_entity *se;

7438 7439 7440
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
7441

7442
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
7443
			update_tg_load_avg(cfs_rq, 0);
7444

7445 7446 7447
		/* Propagate pending load changes to the parent, if any: */
		se = cfs_rq->tg->se[cpu];
		if (se && !skip_blocked_update(se))
7448
			update_load_avg(cfs_rq_of(se), se, 0);
7449

7450 7451
		/* Don't need periodic decay once load/util_avg are null */
		if (cfs_rq_has_blocked(cfs_rq))
7452
			done = false;
7453
	}
7454 7455 7456 7457

	curr_class = rq->curr->sched_class;
	update_rt_rq_load_avg(rq_clock_task(rq), rq, curr_class == &rt_sched_class);
	update_dl_rq_load_avg(rq_clock_task(rq), rq, curr_class == &dl_sched_class);
7458
	update_irq_load_avg(rq, 0);
7459
	/* Don't need periodic decay once load/util_avg are null */
7460
	if (others_have_blocked(rq))
7461
		done = false;
7462 7463 7464

#ifdef CONFIG_NO_HZ_COMMON
	rq->last_blocked_load_update_tick = jiffies;
7465 7466
	if (done)
		rq->has_blocked_load = 0;
7467
#endif
7468
	rq_unlock_irqrestore(rq, &rf);
7469 7470
}

7471
/*
7472
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
7473 7474 7475
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
7476
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
7477
{
7478 7479
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
7480
	unsigned long now = jiffies;
7481
	unsigned long load;
7482

7483
	if (cfs_rq->last_h_load_update == now)
7484 7485
		return;

7486
	WRITE_ONCE(cfs_rq->h_load_next, NULL);
7487 7488
	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
7489
		WRITE_ONCE(cfs_rq->h_load_next, se);
7490 7491 7492
		if (cfs_rq->last_h_load_update == now)
			break;
	}
7493

7494
	if (!se) {
7495
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
7496 7497 7498
		cfs_rq->last_h_load_update = now;
	}

7499
	while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) {
7500
		load = cfs_rq->h_load;
7501 7502
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
7503 7504 7505 7506
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
7507 7508
}

7509
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
7510
{
7511
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
7512

7513
	update_cfs_rq_h_load(cfs_rq);
7514
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
7515
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
7516
}
7517 7518 7519 7520 7521 7522 7523 7524 7525 7526 7527 7528 7529 7530 7531 7532 7533 7534 7535 7536 7537 7538 7539 7540 7541 7542 7543 7544 7545 7546 7547 7548 7549 7550 7551 7552 7553 7554 7555 7556 7557 7558

static void update_cfs_rq_h_load_static(struct cfs_rq *cfs_rq)
{
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
	unsigned long now = jiffies;
	unsigned long load;

	if (cfs_rq->last_h_load_update == now)
		return;

	WRITE_ONCE(cfs_rq->h_load_next, NULL);
	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
		WRITE_ONCE(cfs_rq->h_load_next, se);
		if (cfs_rq->last_h_load_update == now)
			break;
	}

	if (!se) {
		cfs_rq->h_load = scale_load_down(cfs_rq->load.weight);
		cfs_rq->last_h_load_update = now;
	}

	while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) {
		load = cfs_rq->h_load;
		load = div64_ul(load * se->load.weight,
			cfs_rq->load.weight + 1);
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
}

static unsigned long task_h_load_static(struct task_struct *p)
{
	struct cfs_rq *cfs_rq = task_cfs_rq(p);

	update_cfs_rq_h_load_static(cfs_rq);
	return div64_ul(p->se.load.weight * cfs_rq->h_load,
			cfs_rq->load.weight + 1);
}
P
Peter Zijlstra 已提交
7559
#else
7560
static inline void update_blocked_averages(int cpu)
7561
{
7562 7563
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
7564
	const struct sched_class *curr_class;
7565
	struct rq_flags rf;
7566

7567
	rq_lock_irqsave(rq, &rf);
7568
	update_rq_clock(rq);
7569
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
7570 7571 7572 7573

	curr_class = rq->curr->sched_class;
	update_rt_rq_load_avg(rq_clock_task(rq), rq, curr_class == &rt_sched_class);
	update_dl_rq_load_avg(rq_clock_task(rq), rq, curr_class == &dl_sched_class);
7574
	update_irq_load_avg(rq, 0);
7575 7576
#ifdef CONFIG_NO_HZ_COMMON
	rq->last_blocked_load_update_tick = jiffies;
7577
	if (!cfs_rq_has_blocked(cfs_rq) && !others_have_blocked(rq))
7578
		rq->has_blocked_load = 0;
7579
#endif
7580
	rq_unlock_irqrestore(rq, &rf);
7581 7582
}

7583
static unsigned long task_h_load(struct task_struct *p)
7584
{
7585
	return p->se.avg.load_avg;
7586
}
7587 7588 7589 7590 7591

static unsigned long task_h_load_static(struct task_struct *p)
{
	return scale_load_down(p->se.load.weight);
}
P
Peter Zijlstra 已提交
7592
#endif
7593 7594

/********** Helpers for find_busiest_group ************************/
7595 7596 7597 7598 7599 7600 7601

enum group_type {
	group_other = 0,
	group_imbalanced,
	group_overloaded,
};

7602 7603 7604 7605 7606 7607 7608
/*
 * sg_lb_stats - stats of a sched_group required for load_balancing
 */
struct sg_lb_stats {
	unsigned long avg_load; /*Avg load across the CPUs of the group */
	unsigned long group_load; /* Total load over the CPUs of the group */
	unsigned long sum_weighted_load; /* Weighted load of group's tasks */
J
Joonsoo Kim 已提交
7609
	unsigned long load_per_task;
7610
	unsigned long group_capacity;
7611
	unsigned long group_util; /* Total utilization of the group */
7612 7613 7614
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
7615
	enum group_type group_type;
7616
	int group_no_capacity;
7617 7618 7619 7620
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
7621 7622
};

J
Joonsoo Kim 已提交
7623 7624 7625 7626 7627 7628 7629
/*
 * sd_lb_stats - Structure to store the statistics of a sched_domain
 *		 during load balancing.
 */
struct sd_lb_stats {
	struct sched_group *busiest;	/* Busiest group in this sd */
	struct sched_group *local;	/* Local group in this sd */
7630
	unsigned long total_running;
J
Joonsoo Kim 已提交
7631
	unsigned long total_load;	/* Total load of all groups in sd */
7632
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
7633 7634 7635
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
7636
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
7637 7638
};

7639 7640 7641 7642 7643 7644 7645 7646 7647 7648 7649
static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
{
	/*
	 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
	 * local_stat because update_sg_lb_stats() does a full clear/assignment.
	 * We must however clear busiest_stat::avg_load because
	 * update_sd_pick_busiest() reads this before assignment.
	 */
	*sds = (struct sd_lb_stats){
		.busiest = NULL,
		.local = NULL,
7650
		.total_running = 0UL,
7651
		.total_load = 0UL,
7652
		.total_capacity = 0UL,
7653 7654
		.busiest_stat = {
			.avg_load = 0UL,
7655 7656
			.sum_nr_running = 0,
			.group_type = group_other,
7657 7658 7659 7660
		},
	};
}

7661 7662 7663
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
7664
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
7665 7666
 *
 * Return: The load index.
7667 7668 7669 7670 7671 7672 7673 7674 7675 7676 7677 7678 7679 7680 7681 7682 7683 7684 7685 7686 7687 7688
 */
static inline int get_sd_load_idx(struct sched_domain *sd,
					enum cpu_idle_type idle)
{
	int load_idx;

	switch (idle) {
	case CPU_NOT_IDLE:
		load_idx = sd->busy_idx;
		break;

	case CPU_NEWLY_IDLE:
		load_idx = sd->newidle_idx;
		break;
	default:
		load_idx = sd->idle_idx;
		break;
	}

	return load_idx;
}

7689
static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu)
7690 7691
{
	struct rq *rq = cpu_rq(cpu);
7692
	unsigned long max = arch_scale_cpu_capacity(sd, cpu);
7693 7694
	unsigned long used, free;
	unsigned long irq;
7695

7696
	irq = cpu_util_irq(rq);
7697

7698 7699
	if (unlikely(irq >= max))
		return 1;
7700

7701 7702
	used = READ_ONCE(rq->avg_rt.util_avg);
	used += READ_ONCE(rq->avg_dl.util_avg);
7703

7704 7705
	if (unlikely(used >= max))
		return 1;
7706

7707
	free = max - used;
7708 7709

	return scale_irq_capacity(free, irq, max);
7710 7711
}

7712
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
7713
{
7714
	unsigned long capacity = scale_rt_capacity(sd, cpu);
7715 7716
	struct sched_group *sdg = sd->groups;

7717
	cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(sd, cpu);
7718

7719 7720
	if (!capacity)
		capacity = 1;
7721

7722 7723
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
7724
	sdg->sgc->min_capacity = capacity;
7725 7726
}

7727
void update_group_capacity(struct sched_domain *sd, int cpu)
7728 7729 7730
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
7731
	unsigned long capacity, min_capacity;
7732 7733 7734 7735
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
7736
	sdg->sgc->next_update = jiffies + interval;
7737 7738

	if (!child) {
7739
		update_cpu_capacity(sd, cpu);
7740 7741 7742
		return;
	}

7743
	capacity = 0;
7744
	min_capacity = ULONG_MAX;
7745

P
Peter Zijlstra 已提交
7746 7747 7748 7749 7750 7751
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

7752
		for_each_cpu(cpu, sched_group_span(sdg)) {
7753
			struct sched_group_capacity *sgc;
7754
			struct rq *rq = cpu_rq(cpu);
7755

7756
			/*
7757
			 * build_sched_domains() -> init_sched_groups_capacity()
7758 7759 7760
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
7761 7762
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
7763
			 *
7764
			 * This avoids capacity from being 0 and
7765 7766 7767
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
7768
				capacity += capacity_of(cpu);
7769 7770 7771
			} else {
				sgc = rq->sd->groups->sgc;
				capacity += sgc->capacity;
7772
			}
7773

7774
			min_capacity = min(capacity, min_capacity);
7775
		}
P
Peter Zijlstra 已提交
7776 7777 7778 7779
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
7780
		 */
P
Peter Zijlstra 已提交
7781 7782 7783

		group = child->groups;
		do {
7784 7785 7786 7787
			struct sched_group_capacity *sgc = group->sgc;

			capacity += sgc->capacity;
			min_capacity = min(sgc->min_capacity, min_capacity);
P
Peter Zijlstra 已提交
7788 7789 7790
			group = group->next;
		} while (group != child->groups);
	}
7791

7792
	sdg->sgc->capacity = capacity;
7793
	sdg->sgc->min_capacity = min_capacity;
7794 7795
}

7796
/*
7797 7798 7799
 * Check whether the capacity of the rq has been noticeably reduced by side
 * activity. The imbalance_pct is used for the threshold.
 * Return true is the capacity is reduced
7800 7801
 */
static inline int
7802
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
7803
{
7804 7805
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
7806 7807
}

7808 7809
/*
 * Group imbalance indicates (and tries to solve) the problem where balancing
7810
 * groups is inadequate due to ->cpus_allowed constraints.
7811
 *
7812 7813
 * Imagine a situation of two groups of 4 CPUs each and 4 tasks each with a
 * cpumask covering 1 CPU of the first group and 3 CPUs of the second group.
7814 7815
 * Something like:
 *
7816 7817
 *	{ 0 1 2 3 } { 4 5 6 7 }
 *	        *     * * *
7818 7819 7820
 *
 * If we were to balance group-wise we'd place two tasks in the first group and
 * two tasks in the second group. Clearly this is undesired as it will overload
7821
 * cpu 3 and leave one of the CPUs in the second group unused.
7822 7823
 *
 * The current solution to this issue is detecting the skew in the first group
7824 7825
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
7826 7827
 *
 * When this is so detected; this group becomes a candidate for busiest; see
7828
 * update_sd_pick_busiest(). And calculate_imbalance() and
7829
 * find_busiest_group() avoid some of the usual balance conditions to allow it
7830 7831 7832 7833 7834 7835 7836
 * to create an effective group imbalance.
 *
 * This is a somewhat tricky proposition since the next run might not find the
 * group imbalance and decide the groups need to be balanced again. A most
 * subtle and fragile situation.
 */

7837
static inline int sg_imbalanced(struct sched_group *group)
7838
{
7839
	return group->sgc->imbalance;
7840 7841
}

7842
/*
7843 7844 7845
 * group_has_capacity returns true if the group has spare capacity that could
 * be used by some tasks.
 * We consider that a group has spare capacity if the  * number of task is
7846 7847
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
7848 7849 7850 7851 7852
 * For the latter, we use a threshold to stabilize the state, to take into
 * account the variance of the tasks' load and to return true if the available
 * capacity in meaningful for the load balancer.
 * As an example, an available capacity of 1% can appear but it doesn't make
 * any benefit for the load balance.
7853
 */
7854 7855
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
7856
{
7857 7858
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
7859

7860
	if ((sgs->group_capacity * 100) >
7861
			(sgs->group_util * env->sd->imbalance_pct))
7862
		return true;
7863

7864 7865 7866 7867 7868 7869 7870 7871 7872 7873 7874 7875 7876 7877 7878 7879
	return false;
}

/*
 *  group_is_overloaded returns true if the group has more tasks than it can
 *  handle.
 *  group_is_overloaded is not equals to !group_has_capacity because a group
 *  with the exact right number of tasks, has no more spare capacity but is not
 *  overloaded so both group_has_capacity and group_is_overloaded return
 *  false.
 */
static inline bool
group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
{
	if (sgs->sum_nr_running <= sgs->group_weight)
		return false;
7880

7881
	if ((sgs->group_capacity * 100) <
7882
			(sgs->group_util * env->sd->imbalance_pct))
7883
		return true;
7884

7885
	return false;
7886 7887
}

7888 7889 7890 7891 7892 7893 7894 7895 7896 7897 7898
/*
 * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller
 * per-CPU capacity than sched_group ref.
 */
static inline bool
group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref)
{
	return sg->sgc->min_capacity * capacity_margin <
						ref->sgc->min_capacity * 1024;
}

7899 7900 7901
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
7902
{
7903
	if (sgs->group_no_capacity)
7904 7905 7906 7907 7908 7909 7910 7911
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

7912
static bool update_nohz_stats(struct rq *rq, bool force)
7913 7914 7915 7916
{
#ifdef CONFIG_NO_HZ_COMMON
	unsigned int cpu = rq->cpu;

7917 7918 7919
	if (!rq->has_blocked_load)
		return false;

7920
	if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
7921
		return false;
7922

7923
	if (!force && !time_after(jiffies, rq->last_blocked_load_update_tick))
7924
		return true;
7925 7926

	update_blocked_averages(cpu);
7927 7928 7929 7930

	return rq->has_blocked_load;
#else
	return false;
7931 7932 7933
#endif
}

7934 7935
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7936
 * @env: The load balancing environment.
7937 7938 7939 7940
 * @group: sched_group whose statistics are to be updated.
 * @load_idx: Load index of sched_domain of this_cpu for load calc.
 * @local_group: Does group contain this_cpu.
 * @sgs: variable to hold the statistics for this group.
7941
 * @overload: Indicate more than one runnable task for any CPU.
7942
 */
7943 7944
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
7945 7946
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
7947
{
7948
	unsigned long load;
7949
	int i, nr_running;
7950

7951 7952
	memset(sgs, 0, sizeof(*sgs));

7953
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
7954 7955
		struct rq *rq = cpu_rq(i);

7956
		if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq, false))
7957
			env->flags |= LBF_NOHZ_AGAIN;
7958

7959
		/* Bias balancing toward CPUs of our domain: */
7960
		if (local_group)
7961
			load = target_load(i, load_idx);
7962
		else
7963 7964 7965
			load = source_load(i, load_idx);

		sgs->group_load += load;
7966
		sgs->group_util += cpu_util(i);
7967
		sgs->sum_nr_running += rq->cfs.h_nr_running;
7968

7969 7970
		nr_running = rq->nr_running;
		if (nr_running > 1)
7971 7972
			*overload = true;

7973 7974 7975 7976
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
7977
		sgs->sum_weighted_load += weighted_cpuload(rq);
7978 7979 7980 7981
		/*
		 * No need to call idle_cpu() if nr_running is not 0
		 */
		if (!nr_running && idle_cpu(i))
7982
			sgs->idle_cpus++;
7983 7984
	}

7985 7986
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
7987
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
7988

7989
	if (sgs->sum_nr_running)
7990
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
7991

7992
	sgs->group_weight = group->group_weight;
7993

7994
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
7995
	sgs->group_type = group_classify(group, sgs);
7996 7997
}

7998 7999
/**
 * update_sd_pick_busiest - return 1 on busiest group
8000
 * @env: The load balancing environment.
8001 8002
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
8003
 * @sgs: sched_group statistics
8004 8005 8006
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
8007 8008 8009
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
8010
 */
8011
static bool update_sd_pick_busiest(struct lb_env *env,
8012 8013
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
8014
				   struct sg_lb_stats *sgs)
8015
{
8016
	struct sg_lb_stats *busiest = &sds->busiest_stat;
8017

8018
	if (sgs->group_type > busiest->group_type)
8019 8020
		return true;

8021 8022 8023 8024 8025 8026
	if (sgs->group_type < busiest->group_type)
		return false;

	if (sgs->avg_load <= busiest->avg_load)
		return false;

8027 8028 8029 8030 8031 8032 8033 8034 8035 8036 8037 8038 8039 8040
	if (!(env->sd->flags & SD_ASYM_CPUCAPACITY))
		goto asym_packing;

	/*
	 * Candidate sg has no more than one task per CPU and
	 * has higher per-CPU capacity. Migrating tasks to less
	 * capable CPUs may harm throughput. Maximize throughput,
	 * power/energy consequences are not considered.
	 */
	if (sgs->sum_nr_running <= sgs->group_weight &&
	    group_smaller_cpu_capacity(sds->local, sg))
		return false;

asym_packing:
8041 8042
	/* This is the busiest node in its class. */
	if (!(env->sd->flags & SD_ASYM_PACKING))
8043 8044
		return true;

8045
	/* No ASYM_PACKING if target CPU is already busy */
8046 8047
	if (env->idle == CPU_NOT_IDLE)
		return true;
8048
	/*
T
Tim Chen 已提交
8049 8050 8051
	 * ASYM_PACKING needs to move all the work to the highest
	 * prority CPUs in the group, therefore mark all groups
	 * of lower priority than ourself as busy.
8052
	 */
T
Tim Chen 已提交
8053 8054
	if (sgs->sum_nr_running &&
	    sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) {
8055 8056 8057
		if (!sds->busiest)
			return true;

8058
		/* Prefer to move from lowest priority CPU's work */
T
Tim Chen 已提交
8059 8060
		if (sched_asym_prefer(sds->busiest->asym_prefer_cpu,
				      sg->asym_prefer_cpu))
8061 8062 8063 8064 8065 8066
			return true;
	}

	return false;
}

8067 8068 8069 8070 8071 8072 8073 8074 8075 8076 8077 8078 8079 8080 8081 8082 8083 8084 8085 8086 8087 8088 8089 8090 8091 8092 8093 8094 8095 8096
#ifdef CONFIG_NUMA_BALANCING
static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
{
	if (sgs->sum_nr_running > sgs->nr_numa_running)
		return regular;
	if (sgs->sum_nr_running > sgs->nr_preferred_running)
		return remote;
	return all;
}

static inline enum fbq_type fbq_classify_rq(struct rq *rq)
{
	if (rq->nr_running > rq->nr_numa_running)
		return regular;
	if (rq->nr_running > rq->nr_preferred_running)
		return remote;
	return all;
}
#else
static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs)
{
	return all;
}

static inline enum fbq_type fbq_classify_rq(struct rq *rq)
{
	return regular;
}
#endif /* CONFIG_NUMA_BALANCING */

8097
/**
8098
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
8099
 * @env: The load balancing environment.
8100 8101
 * @sds: variable to hold the statistics for this sched_domain.
 */
8102
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
8103
{
8104 8105
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
8106
	struct sg_lb_stats *local = &sds->local_stat;
J
Joonsoo Kim 已提交
8107
	struct sg_lb_stats tmp_sgs;
8108
	int load_idx, prefer_sibling = 0;
8109
	bool overload = false;
8110 8111 8112 8113

	if (child && child->flags & SD_PREFER_SIBLING)
		prefer_sibling = 1;

8114
#ifdef CONFIG_NO_HZ_COMMON
8115
	if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked))
8116 8117 8118
		env->flags |= LBF_NOHZ_STATS;
#endif

8119
	load_idx = get_sd_load_idx(env->sd, env->idle);
8120 8121

	do {
J
Joonsoo Kim 已提交
8122
		struct sg_lb_stats *sgs = &tmp_sgs;
8123 8124
		int local_group;

8125
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
J
Joonsoo Kim 已提交
8126 8127
		if (local_group) {
			sds->local = sg;
8128
			sgs = local;
8129 8130

			if (env->idle != CPU_NEWLY_IDLE ||
8131 8132
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
8133
		}
8134

8135 8136
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
8137

8138 8139 8140
		if (local_group)
			goto next_group;

8141 8142
		/*
		 * In case the child domain prefers tasks go to siblings
8143
		 * first, lower the sg capacity so that we'll try
8144 8145
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
8146 8147 8148 8149
		 * these excess tasks. The extra check prevents the case where
		 * you always pull from the heaviest group when it is already
		 * under-utilized (possible with a large weight task outweighs
		 * the tasks on the system).
8150
		 */
8151
		if (prefer_sibling && sds->local &&
8152 8153
		    group_has_capacity(env, local) &&
		    (sgs->sum_nr_running > local->sum_nr_running + 1)) {
8154
			sgs->group_no_capacity = 1;
8155
			sgs->group_type = group_classify(sg, sgs);
8156
		}
8157

8158
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
8159
			sds->busiest = sg;
J
Joonsoo Kim 已提交
8160
			sds->busiest_stat = *sgs;
8161 8162
		}

8163 8164
next_group:
		/* Now, start updating sd_lb_stats */
8165
		sds->total_running += sgs->sum_nr_running;
8166
		sds->total_load += sgs->group_load;
8167
		sds->total_capacity += sgs->group_capacity;
8168

8169
		sg = sg->next;
8170
	} while (sg != env->sd->groups);
8171

8172 8173 8174 8175 8176 8177 8178 8179 8180
#ifdef CONFIG_NO_HZ_COMMON
	if ((env->flags & LBF_NOHZ_AGAIN) &&
	    cpumask_subset(nohz.idle_cpus_mask, sched_domain_span(env->sd))) {

		WRITE_ONCE(nohz.next_blocked,
			   jiffies + msecs_to_jiffies(LOAD_AVG_PERIOD));
	}
#endif

8181 8182
	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
8183 8184 8185 8186 8187 8188

	if (!env->sd->parent) {
		/* update overload indicator if we are at root domain */
		if (env->dst_rq->rd->overload != overload)
			env->dst_rq->rd->overload = overload;
	}
8189 8190 8191 8192
}

/**
 * check_asym_packing - Check to see if the group is packed into the
8193
 *			sched domain.
8194 8195 8196 8197 8198 8199 8200 8201 8202 8203 8204 8205 8206 8207
 *
 * This is primarily intended to used at the sibling level.  Some
 * cores like POWER7 prefer to use lower numbered SMT threads.  In the
 * case of POWER7, it can move to lower SMT modes only when higher
 * threads are idle.  When in lower SMT modes, the threads will
 * perform better since they share less core resources.  Hence when we
 * have idle threads, we want them to be the higher ones.
 *
 * This packing function is run on idle threads.  It checks to see if
 * the busiest CPU in this domain (core in the P7 case) has a higher
 * CPU number than the packing function is being run on.  Here we are
 * assuming lower CPU number will be equivalent to lower a SMT thread
 * number.
 *
8208
 * Return: 1 when packing is required and a task should be moved to
8209
 * this CPU.  The amount of the imbalance is returned in env->imbalance.
8210
 *
8211
 * @env: The load balancing environment.
8212 8213
 * @sds: Statistics of the sched_domain which is to be packed
 */
8214
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
8215 8216 8217
{
	int busiest_cpu;

8218
	if (!(env->sd->flags & SD_ASYM_PACKING))
8219 8220
		return 0;

8221 8222 8223
	if (env->idle == CPU_NOT_IDLE)
		return 0;

8224 8225 8226
	if (!sds->busiest)
		return 0;

T
Tim Chen 已提交
8227 8228
	busiest_cpu = sds->busiest->asym_prefer_cpu;
	if (sched_asym_prefer(busiest_cpu, env->dst_cpu))
8229 8230
		return 0;

8231
	env->imbalance = DIV_ROUND_CLOSEST(
8232
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
8233
		SCHED_CAPACITY_SCALE);
8234

8235
	return 1;
8236 8237 8238 8239 8240 8241
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
8242
 * @env: The load balancing environment.
8243 8244
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
8245 8246
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8247
{
8248
	unsigned long tmp, capa_now = 0, capa_move = 0;
8249
	unsigned int imbn = 2;
8250
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
8251
	struct sg_lb_stats *local, *busiest;
8252

J
Joonsoo Kim 已提交
8253 8254
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
8255

J
Joonsoo Kim 已提交
8256 8257 8258 8259
	if (!local->sum_nr_running)
		local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
	else if (busiest->load_per_task > local->load_per_task)
		imbn = 1;
8260

J
Joonsoo Kim 已提交
8261
	scaled_busy_load_per_task =
8262
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
8263
		busiest->group_capacity;
J
Joonsoo Kim 已提交
8264

8265 8266
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
8267
		env->imbalance = busiest->load_per_task;
8268 8269 8270 8271 8272
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
8273
	 * however we may be able to increase total CPU capacity used by
8274 8275 8276
	 * moving them.
	 */

8277
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
8278
			min(busiest->load_per_task, busiest->avg_load);
8279
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
8280
			min(local->load_per_task, local->avg_load);
8281
	capa_now /= SCHED_CAPACITY_SCALE;
8282 8283

	/* Amount of load we'd subtract */
8284
	if (busiest->avg_load > scaled_busy_load_per_task) {
8285
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
8286
			    min(busiest->load_per_task,
8287
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
8288
	}
8289 8290

	/* Amount of load we'd add */
8291
	if (busiest->avg_load * busiest->group_capacity <
8292
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
8293 8294
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
8295
	} else {
8296
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
8297
		      local->group_capacity;
J
Joonsoo Kim 已提交
8298
	}
8299
	capa_move += local->group_capacity *
8300
		    min(local->load_per_task, local->avg_load + tmp);
8301
	capa_move /= SCHED_CAPACITY_SCALE;
8302 8303

	/* Move if we gain throughput */
8304
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
8305
		env->imbalance = busiest->load_per_task;
8306 8307 8308 8309 8310
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
8311
 * @env: load balance environment
8312 8313
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
8314
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8315
{
8316
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
8317 8318 8319 8320
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
8321

8322
	if (busiest->group_type == group_imbalanced) {
8323 8324
		/*
		 * In the group_imb case we cannot rely on group-wide averages
8325
		 * to ensure CPU-load equilibrium, look at wider averages. XXX
8326
		 */
J
Joonsoo Kim 已提交
8327 8328
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
8329 8330
	}

8331
	/*
8332 8333 8334 8335
	 * Avg load of busiest sg can be less and avg load of local sg can
	 * be greater than avg load across all sgs of sd because avg load
	 * factors in sg capacity and sgs with smaller group_type are
	 * skipped when updating the busiest sg:
8336
	 */
8337 8338
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
8339 8340
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
8341 8342
	}

8343
	/*
8344
	 * If there aren't any idle CPUs, avoid creating some.
8345 8346 8347
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
8348
		load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
8349
		if (load_above_capacity > busiest->group_capacity) {
8350
			load_above_capacity -= busiest->group_capacity;
8351
			load_above_capacity *= scale_load_down(NICE_0_LOAD);
8352 8353
			load_above_capacity /= busiest->group_capacity;
		} else
8354
			load_above_capacity = ~0UL;
8355 8356 8357
	}

	/*
8358
	 * We're trying to get all the CPUs to the average_load, so we don't
8359
	 * want to push ourselves above the average load, nor do we wish to
8360
	 * reduce the max loaded CPU below the average load. At the same time,
8361 8362
	 * we also don't want to reduce the group load below the group
	 * capacity. Thus we look for the minimum possible imbalance.
8363
	 */
8364
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
8365 8366

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
8367
	env->imbalance = min(
8368 8369
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
8370
	) / SCHED_CAPACITY_SCALE;
8371 8372 8373

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
8374
	 * there is no guarantee that any tasks will be moved so we'll have
8375 8376 8377
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
8378
	if (env->imbalance < busiest->load_per_task)
8379
		return fix_small_imbalance(env, sds);
8380
}
8381

8382 8383 8384 8385
/******* find_busiest_group() helpers end here *********************/

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
8386
 * if there is an imbalance.
8387 8388 8389 8390
 *
 * Also calculates the amount of weighted load which should be moved
 * to restore balance.
 *
8391
 * @env: The load balancing environment.
8392
 *
8393
 * Return:	- The busiest group if imbalance exists.
8394
 */
J
Joonsoo Kim 已提交
8395
static struct sched_group *find_busiest_group(struct lb_env *env)
8396
{
J
Joonsoo Kim 已提交
8397
	struct sg_lb_stats *local, *busiest;
8398 8399
	struct sd_lb_stats sds;

8400
	init_sd_lb_stats(&sds);
8401 8402 8403 8404 8405

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
8406
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
8407 8408
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
8409

8410
	/* ASYM feature bypasses nice load balance check */
8411
	if (check_asym_packing(env, &sds))
8412 8413
		return sds.busiest;

8414
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
8415
	if (!sds.busiest || busiest->sum_nr_running == 0)
8416 8417
		goto out_balanced;

8418
	/* XXX broken for overlapping NUMA groups */
8419 8420
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
8421

P
Peter Zijlstra 已提交
8422 8423
	/*
	 * If the busiest group is imbalanced the below checks don't
8424
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
8425 8426
	 * isn't true due to cpus_allowed constraints and the like.
	 */
8427
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
8428 8429
		goto force_balance;

8430 8431 8432 8433 8434
	/*
	 * When dst_cpu is idle, prevent SMP nice and/or asymmetric group
	 * capacities from resulting in underutilization due to avg_load.
	 */
	if (env->idle != CPU_NOT_IDLE && group_has_capacity(env, local) &&
8435
	    busiest->group_no_capacity)
8436 8437
		goto force_balance;

8438
	/*
8439
	 * If the local group is busier than the selected busiest group
8440 8441
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
8442
	if (local->avg_load >= busiest->avg_load)
8443 8444
		goto out_balanced;

8445 8446 8447 8448
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
8449
	if (local->avg_load >= sds.avg_load)
8450 8451
		goto out_balanced;

8452
	if (env->idle == CPU_IDLE) {
8453
		/*
8454
		 * This CPU is idle. If the busiest group is not overloaded
8455
		 * and there is no imbalance between this and busiest group
8456
		 * wrt idle CPUs, it is balanced. The imbalance becomes
8457 8458
		 * significant if the diff is greater than 1 otherwise we
		 * might end up to just move the imbalance on another group
8459
		 */
8460 8461
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
8462
			goto out_balanced;
8463 8464 8465 8466 8467
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
8468 8469
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
8470
			goto out_balanced;
8471
	}
8472

8473
force_balance:
8474
	/* Looks like there is an imbalance. Compute it */
8475
	calculate_imbalance(env, &sds);
8476
	return env->imbalance ? sds.busiest : NULL;
8477 8478

out_balanced:
8479
	env->imbalance = 0;
8480 8481 8482 8483
	return NULL;
}

/*
8484
 * find_busiest_queue - find the busiest runqueue among the CPUs in the group.
8485
 */
8486
static struct rq *find_busiest_queue(struct lb_env *env,
8487
				     struct sched_group *group)
8488 8489
{
	struct rq *busiest = NULL, *rq;
8490
	unsigned long busiest_load = 0, busiest_capacity = 1;
8491 8492
	int i;

8493
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
8494
		unsigned long capacity, wl;
8495 8496 8497 8498
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
8499

8500 8501 8502 8503 8504 8505 8506 8507 8508 8509 8510 8511 8512 8513 8514 8515 8516 8517 8518 8519 8520 8521
		/*
		 * We classify groups/runqueues into three groups:
		 *  - regular: there are !numa tasks
		 *  - remote:  there are numa tasks that run on the 'wrong' node
		 *  - all:     there is no distinction
		 *
		 * In order to avoid migrating ideally placed numa tasks,
		 * ignore those when there's better options.
		 *
		 * If we ignore the actual busiest queue to migrate another
		 * task, the next balance pass can still reduce the busiest
		 * queue by moving tasks around inside the node.
		 *
		 * If we cannot move enough load due to this classification
		 * the next pass will adjust the group classification and
		 * allow migration of more tasks.
		 *
		 * Both cases only affect the total convergence complexity.
		 */
		if (rt > env->fbq_type)
			continue;

8522
		capacity = capacity_of(i);
8523

8524
		wl = weighted_cpuload(rq);
8525

8526 8527
		/*
		 * When comparing with imbalance, use weighted_cpuload()
8528
		 * which is not scaled with the CPU capacity.
8529
		 */
8530 8531 8532

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
8533 8534
			continue;

8535
		/*
8536 8537 8538
		 * For the load comparisons with the other CPU's, consider
		 * the weighted_cpuload() scaled with the CPU capacity, so
		 * that the load can be moved away from the CPU that is
8539
		 * potentially running at a lower capacity.
8540
		 *
8541
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
8542
		 * multiplication to rid ourselves of the division works out
8543 8544
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
8545
		 */
8546
		if (wl * busiest_capacity > busiest_load * capacity) {
8547
			busiest_load = wl;
8548
			busiest_capacity = capacity;
8549 8550 8551 8552 8553 8554 8555 8556 8557 8558 8559 8560 8561
			busiest = rq;
		}
	}

	return busiest;
}

/*
 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
 * so long as it is large enough.
 */
#define MAX_PINNED_INTERVAL	512

8562
static int need_active_balance(struct lb_env *env)
8563
{
8564 8565 8566
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
8567 8568 8569

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
T
Tim Chen 已提交
8570 8571
		 * lower priority CPUs in order to pack all tasks in the
		 * highest priority CPUs.
8572
		 */
T
Tim Chen 已提交
8573 8574
		if ((sd->flags & SD_ASYM_PACKING) &&
		    sched_asym_prefer(env->dst_cpu, env->src_cpu))
8575
			return 1;
8576 8577
	}

8578 8579 8580 8581 8582 8583 8584 8585 8586 8587 8588 8589 8590
	/*
	 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
	 * It's worth migrating the task if the src_cpu's capacity is reduced
	 * because of other sched_class or IRQs if more capacity stays
	 * available on dst_cpu.
	 */
	if ((env->idle != CPU_NOT_IDLE) &&
	    (env->src_rq->cfs.h_nr_running == 1)) {
		if ((check_cpu_capacity(env->src_rq, sd)) &&
		    (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
			return 1;
	}

8591 8592 8593
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

8594 8595
static int active_load_balance_cpu_stop(void *data);

8596 8597 8598 8599 8600
static int should_we_balance(struct lb_env *env)
{
	struct sched_group *sg = env->sd->groups;
	int cpu, balance_cpu = -1;

8601 8602 8603 8604 8605 8606 8607
	/*
	 * Ensure the balancing environment is consistent; can happen
	 * when the softirq triggers 'during' hotplug.
	 */
	if (!cpumask_test_cpu(env->dst_cpu, env->cpus))
		return 0;

8608
	/*
8609
	 * In the newly idle case, we will allow all the CPUs
8610 8611 8612 8613 8614
	 * to do the newly idle load balance.
	 */
	if (env->idle == CPU_NEWLY_IDLE)
		return 1;

8615
	/* Try to find first idle CPU */
8616
	for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
8617
		if (!idle_cpu(cpu))
8618 8619 8620 8621 8622 8623 8624 8625 8626 8627
			continue;

		balance_cpu = cpu;
		break;
	}

	if (balance_cpu == -1)
		balance_cpu = group_balance_cpu(sg);

	/*
8628
	 * First idle CPU or the first CPU(busiest) in this sched group
8629 8630
	 * is eligible for doing load balancing at this and above domains.
	 */
8631
	return balance_cpu == env->dst_cpu;
8632 8633
}

8634 8635 8636 8637 8638 8639
/*
 * Check this_cpu to ensure it is balanced within domain. Attempt to move
 * tasks if there is an imbalance.
 */
static int load_balance(int this_cpu, struct rq *this_rq,
			struct sched_domain *sd, enum cpu_idle_type idle,
8640
			int *continue_balancing)
8641
{
8642
	int ld_moved, cur_ld_moved, active_balance = 0;
8643
	struct sched_domain *sd_parent = sd->parent;
8644 8645
	struct sched_group *group;
	struct rq *busiest;
8646
	struct rq_flags rf;
8647
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
8648

8649 8650
	struct lb_env env = {
		.sd		= sd,
8651 8652
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
8653
		.dst_grpmask    = sched_group_span(sd->groups),
8654
		.idle		= idle,
8655
		.loop_break	= sched_nr_migrate_break,
8656
		.cpus		= cpus,
8657
		.fbq_type	= all,
8658
		.tasks		= LIST_HEAD_INIT(env.tasks),
8659 8660
	};

8661
	cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
8662

8663
	schedstat_inc(sd->lb_count[idle]);
8664 8665

redo:
8666 8667
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
8668
		goto out_balanced;
8669
	}
8670

8671
	group = find_busiest_group(&env);
8672
	if (!group) {
8673
		schedstat_inc(sd->lb_nobusyg[idle]);
8674 8675 8676
		goto out_balanced;
	}

8677
	busiest = find_busiest_queue(&env, group);
8678
	if (!busiest) {
8679
		schedstat_inc(sd->lb_nobusyq[idle]);
8680 8681 8682
		goto out_balanced;
	}

8683
	BUG_ON(busiest == env.dst_rq);
8684

8685
	schedstat_add(sd->lb_imbalance[idle], env.imbalance);
8686

8687 8688 8689
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

8690 8691 8692 8693 8694 8695 8696 8697
	ld_moved = 0;
	if (busiest->nr_running > 1) {
		/*
		 * Attempt to move tasks. If find_busiest_group has found
		 * an imbalance but busiest->nr_running <= 1, the group is
		 * still unbalanced. ld_moved simply stays zero, so it is
		 * correctly treated as an imbalance.
		 */
8698
		env.flags |= LBF_ALL_PINNED;
8699
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
8700

8701
more_balance:
8702
		rq_lock_irqsave(busiest, &rf);
8703
		update_rq_clock(busiest);
8704 8705 8706 8707 8708

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
8709
		cur_ld_moved = detach_tasks(&env);
8710 8711

		/*
8712 8713 8714 8715 8716
		 * We've detached some tasks from busiest_rq. Every
		 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
		 * unlock busiest->lock, and we are able to be sure
		 * that nobody can manipulate the tasks in parallel.
		 * See task_rq_lock() family for the details.
8717
		 */
8718

8719
		rq_unlock(busiest, &rf);
8720 8721 8722 8723 8724 8725

		if (cur_ld_moved) {
			attach_tasks(&env);
			ld_moved += cur_ld_moved;
		}

8726
		local_irq_restore(rf.flags);
8727

8728 8729 8730 8731 8732
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

8733 8734 8735 8736
		/*
		 * Revisit (affine) tasks on src_cpu that couldn't be moved to
		 * us and move them to an alternate dst_cpu in our sched_group
		 * where they can run. The upper limit on how many times we
8737
		 * iterate on same src_cpu is dependent on number of CPUs in our
8738 8739 8740 8741 8742 8743 8744 8745 8746 8747 8748 8749 8750 8751
		 * sched_group.
		 *
		 * This changes load balance semantics a bit on who can move
		 * load to a given_cpu. In addition to the given_cpu itself
		 * (or a ilb_cpu acting on its behalf where given_cpu is
		 * nohz-idle), we now have balance_cpu in a position to move
		 * load to given_cpu. In rare situations, this may cause
		 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
		 * _independently_ and at _same_ time to move some load to
		 * given_cpu) causing exceess load to be moved to given_cpu.
		 * This however should not happen so much in practice and
		 * moreover subsequent load balance cycles should correct the
		 * excess load moved.
		 */
8752
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
8753

8754
			/* Prevent to re-select dst_cpu via env's CPUs */
8755 8756
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

8757
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
8758
			env.dst_cpu	 = env.new_dst_cpu;
8759
			env.flags	&= ~LBF_DST_PINNED;
8760 8761
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
8762

8763 8764 8765 8766 8767 8768
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
8769

8770 8771 8772 8773
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
8774
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8775

8776
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
8777 8778 8779
				*group_imbalance = 1;
		}

8780
		/* All tasks on this runqueue were pinned by CPU affinity */
8781
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
8782
			cpumask_clear_cpu(cpu_of(busiest), cpus);
8783 8784 8785 8786 8787 8788 8789 8790 8791
			/*
			 * Attempting to continue load balancing at the current
			 * sched_domain level only makes sense if there are
			 * active CPUs remaining as possible busiest CPUs to
			 * pull load from which are not contained within the
			 * destination group that is receiving any migrated
			 * load.
			 */
			if (!cpumask_subset(cpus, env.dst_grpmask)) {
8792 8793
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
8794
				goto redo;
8795
			}
8796
			goto out_all_pinned;
8797 8798 8799 8800
		}
	}

	if (!ld_moved) {
8801
		schedstat_inc(sd->lb_failed[idle]);
8802 8803 8804 8805 8806 8807 8808 8809
		/*
		 * Increment the failure counter only on periodic balance.
		 * We do not want newidle balance, which can be very
		 * frequent, pollute the failure counter causing
		 * excessive cache_hot migrations and active balances.
		 */
		if (idle != CPU_NEWLY_IDLE)
			sd->nr_balance_failed++;
8810

8811
		if (need_active_balance(&env)) {
8812 8813
			unsigned long flags;

8814 8815
			raw_spin_lock_irqsave(&busiest->lock, flags);

8816 8817 8818 8819
			/*
			 * Don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest CPU can't be
			 * moved to this_cpu:
8820
			 */
8821
			if (!cpumask_test_cpu(this_cpu, &busiest->curr->cpus_allowed)) {
8822 8823
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
8824
				env.flags |= LBF_ALL_PINNED;
8825 8826 8827
				goto out_one_pinned;
			}

8828 8829 8830 8831 8832
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
8833 8834 8835 8836 8837 8838
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
8839

8840
			if (active_balance) {
8841 8842 8843
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
8844
			}
8845

8846
			/* We've kicked active balancing, force task migration. */
8847 8848 8849 8850 8851 8852 8853 8854 8855 8856 8857 8858 8859
			sd->nr_balance_failed = sd->cache_nice_tries+1;
		}
	} else
		sd->nr_balance_failed = 0;

	if (likely(!active_balance)) {
		/* We were unbalanced, so reset the balancing interval */
		sd->balance_interval = sd->min_interval;
	} else {
		/*
		 * If we've begun active balancing, start to back off. This
		 * case may not be covered by the all_pinned logic if there
		 * is only 1 task on the busy runqueue (because we don't call
8860
		 * detach_tasks).
8861 8862 8863 8864 8865 8866 8867 8868
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
8869 8870
	/*
	 * We reach balance although we may have faced some affinity
8871 8872
	 * constraints. Clear the imbalance flag only if other tasks got
	 * a chance to move and fix the imbalance.
8873
	 */
8874
	if (sd_parent && !(env.flags & LBF_ALL_PINNED)) {
8875 8876 8877 8878 8879 8880 8881 8882 8883 8884 8885 8886
		int *group_imbalance = &sd_parent->groups->sgc->imbalance;

		if (*group_imbalance)
			*group_imbalance = 0;
	}

out_all_pinned:
	/*
	 * We reach balance because all tasks are pinned at this level so
	 * we can't migrate them. Let the imbalance flag set so parent level
	 * can try to migrate them.
	 */
8887
	schedstat_inc(sd->lb_balanced[idle]);
8888 8889 8890 8891

	sd->nr_balance_failed = 0;

out_one_pinned:
8892 8893 8894 8895 8896 8897 8898 8899 8900 8901 8902
	ld_moved = 0;

	/*
	 * idle_balance() disregards balance intervals, so we could repeatedly
	 * reach this code, which would lead to balance_interval skyrocketting
	 * in a short amount of time. Skip the balance_interval increase logic
	 * to avoid that.
	 */
	if (env.idle == CPU_NEWLY_IDLE)
		goto out;

8903
	/* tune up the balancing interval */
8904
	if (((env.flags & LBF_ALL_PINNED) &&
8905
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
8906 8907 8908 8909 8910 8911
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;
out:
	return ld_moved;
}

8912 8913 8914 8915 8916 8917 8918 8919 8920 8921 8922 8923 8924 8925 8926 8927
static inline unsigned long
get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
{
	unsigned long interval = sd->balance_interval;

	if (cpu_busy)
		interval *= sd->busy_factor;

	/* scale ms to jiffies */
	interval = msecs_to_jiffies(interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);

	return interval;
}

static inline void
8928
update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
8929 8930 8931
{
	unsigned long interval, next;

8932 8933
	/* used by idle balance, so cpu_busy = 0 */
	interval = get_sd_balance_interval(sd, 0);
8934 8935 8936 8937 8938 8939
	next = sd->last_balance + interval;

	if (time_after(*next_balance, next))
		*next_balance = next;
}

8940
/*
8941
 * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
8942 8943 8944
 * running tasks off the busiest CPU onto idle CPUs. It requires at
 * least 1 task to be running on each physical CPU where possible, and
 * avoids physical / logical imbalances.
8945
 */
8946
static int active_load_balance_cpu_stop(void *data)
8947
{
8948 8949
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
8950
	int target_cpu = busiest_rq->push_cpu;
8951
	struct rq *target_rq = cpu_rq(target_cpu);
8952
	struct sched_domain *sd;
8953
	struct task_struct *p = NULL;
8954
	struct rq_flags rf;
8955

8956
	rq_lock_irq(busiest_rq, &rf);
8957 8958 8959 8960 8961 8962 8963
	/*
	 * Between queueing the stop-work and running it is a hole in which
	 * CPUs can become inactive. We should not move tasks from or to
	 * inactive CPUs.
	 */
	if (!cpu_active(busiest_cpu) || !cpu_active(target_cpu))
		goto out_unlock;
8964

8965
	/* Make sure the requested CPU hasn't gone down in the meantime: */
8966 8967 8968
	if (unlikely(busiest_cpu != smp_processor_id() ||
		     !busiest_rq->active_balance))
		goto out_unlock;
8969 8970 8971

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
8972
		goto out_unlock;
8973 8974 8975 8976

	/*
	 * This condition is "impossible", if it occurs
	 * we need to fix it. Originally reported by
8977
	 * Bjorn Helgaas on a 128-CPU setup.
8978 8979 8980 8981
	 */
	BUG_ON(busiest_rq == target_rq);

	/* Search for an sd spanning us and the target CPU. */
8982
	rcu_read_lock();
8983 8984 8985 8986 8987 8988 8989
	for_each_domain(target_cpu, sd) {
		if ((sd->flags & SD_LOAD_BALANCE) &&
		    cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
				break;
	}

	if (likely(sd)) {
8990 8991
		struct lb_env env = {
			.sd		= sd,
8992 8993 8994 8995
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
8996
			.idle		= CPU_IDLE,
8997 8998 8999 9000 9001 9002 9003
			/*
			 * can_migrate_task() doesn't need to compute new_dst_cpu
			 * for active balancing. Since we have CPU_IDLE, but no
			 * @dst_grpmask we need to make that test go away with lying
			 * about DST_PINNED.
			 */
			.flags		= LBF_DST_PINNED,
9004 9005
		};

9006
		schedstat_inc(sd->alb_count);
9007
		update_rq_clock(busiest_rq);
9008

9009
		p = detach_one_task(&env);
9010
		if (p) {
9011
			schedstat_inc(sd->alb_pushed);
9012 9013 9014
			/* Active balancing done, reset the failure counter. */
			sd->nr_balance_failed = 0;
		} else {
9015
			schedstat_inc(sd->alb_failed);
9016
		}
9017
	}
9018
	rcu_read_unlock();
9019 9020
out_unlock:
	busiest_rq->active_balance = 0;
9021
	rq_unlock(busiest_rq, &rf);
9022 9023 9024 9025 9026 9027

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

9028
	return 0;
9029 9030
}

9031 9032 9033 9034 9035 9036 9037 9038 9039 9040 9041 9042 9043 9044 9045 9046 9047 9048 9049 9050 9051 9052 9053 9054 9055 9056 9057 9058 9059 9060 9061 9062 9063 9064 9065 9066 9067 9068 9069 9070 9071 9072 9073 9074 9075 9076 9077 9078 9079 9080 9081 9082 9083 9084 9085 9086 9087 9088 9089 9090 9091 9092 9093 9094 9095 9096 9097 9098 9099 9100 9101 9102 9103 9104 9105 9106 9107 9108 9109 9110 9111 9112 9113 9114 9115 9116 9117 9118 9119 9120 9121 9122 9123 9124 9125 9126 9127 9128 9129 9130 9131 9132 9133 9134 9135 9136 9137 9138 9139 9140 9141 9142 9143 9144 9145 9146 9147 9148
static DEFINE_SPINLOCK(balancing);

/*
 * Scale the max load_balance interval with the number of CPUs in the system.
 * This trades load-balance latency on larger machines for less cross talk.
 */
void update_max_interval(void)
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
 * Balancing parameters are set up in init_sched_domains.
 */
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
{
	int continue_balancing = 1;
	int cpu = rq->cpu;
	unsigned long interval;
	struct sched_domain *sd;
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;

	rcu_read_lock();
	for_each_domain(cpu, sd) {
		/*
		 * Decay the newidle max times here because this is a regular
		 * visit to all the domains. Decay ~1% per second.
		 */
		if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
			sd->max_newidle_lb_cost =
				(sd->max_newidle_lb_cost * 253) / 256;
			sd->next_decay_max_lb_cost = jiffies + HZ;
			need_decay = 1;
		}
		max_cost += sd->max_newidle_lb_cost;

		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

		/*
		 * Stop the load balance at this level. There is another
		 * CPU in our sched group which is doing load balancing more
		 * actively.
		 */
		if (!continue_balancing) {
			if (need_decay)
				continue;
			break;
		}

		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);

		need_serialize = sd->flags & SD_SERIALIZE;
		if (need_serialize) {
			if (!spin_trylock(&balancing))
				goto out;
		}

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
				/*
				 * The LBF_DST_PINNED logic could have changed
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
				 */
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
			}
			sd->last_balance = jiffies;
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
		}
		if (need_serialize)
			spin_unlock(&balancing);
out:
		if (time_after(next_balance, sd->last_balance + interval)) {
			next_balance = sd->last_balance + interval;
			update_next_balance = 1;
		}
	}
	if (need_decay) {
		/*
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
		 */
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
	}
	rcu_read_unlock();

	/*
	 * next_balance will be updated only when there is a need.
	 * When the cpu is attached to null domain for ex, it will not be
	 * updated.
	 */
	if (likely(update_next_balance)) {
		rq->next_balance = next_balance;

#ifdef CONFIG_NO_HZ_COMMON
		/*
		 * If this CPU has been elected to perform the nohz idle
		 * balance. Other idle CPUs have already rebalanced with
		 * nohz_idle_balance() and nohz.next_balance has been
		 * updated accordingly. This CPU is now running the idle load
		 * balance for itself and we need to update the
		 * nohz.next_balance accordingly.
		 */
		if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
			nohz.next_balance = rq->next_balance;
#endif
	}
}

9149 9150 9151 9152 9153
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

9154
#ifdef CONFIG_NO_HZ_COMMON
9155 9156 9157 9158 9159
/*
 * idle load balancing details
 * - When one of the busy CPUs notice that there may be an idle rebalancing
 *   needed, they will kick the idle load balancer, which then does idle
 *   load balancing for all the idle CPUs.
9160 9161
 * - HK_FLAG_MISC CPUs are used for this task, because HK_FLAG_SCHED not set
 *   anywhere yet.
9162
 */
9163

9164
static inline int find_new_ilb(void)
9165
{
9166
	int ilb;
9167

9168 9169 9170 9171 9172
	for_each_cpu_and(ilb, nohz.idle_cpus_mask,
			      housekeeping_cpumask(HK_FLAG_MISC)) {
		if (idle_cpu(ilb))
			return ilb;
	}
9173 9174

	return nr_cpu_ids;
9175 9176
}

9177
/*
9178 9179
 * Kick a CPU to do the nohz balancing, if it is time for it. We pick any
 * idle CPU in the HK_FLAG_MISC housekeeping set (if there is one).
9180
 */
9181
static void kick_ilb(unsigned int flags)
9182 9183 9184 9185 9186
{
	int ilb_cpu;

	nohz.next_balance++;

9187
	ilb_cpu = find_new_ilb();
9188

9189 9190
	if (ilb_cpu >= nr_cpu_ids)
		return;
9191

9192
	flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
P
Peter Zijlstra 已提交
9193
	if (flags & NOHZ_KICK_MASK)
9194
		return;
9195

9196 9197
	/*
	 * Use smp_send_reschedule() instead of resched_cpu().
9198
	 * This way we generate a sched IPI on the target CPU which
9199 9200 9201 9202
	 * is idle. And the softirq performing nohz idle load balance
	 * will be run before returning from the IPI.
	 */
	smp_send_reschedule(ilb_cpu);
9203 9204 9205 9206 9207 9208 9209 9210 9211 9212 9213 9214 9215 9216 9217 9218 9219 9220 9221
}

/*
 * Current heuristic for kicking the idle load balancer in the presence
 * of an idle cpu in the system.
 *   - This rq has more than one task.
 *   - This rq has at least one CFS task and the capacity of the CPU is
 *     significantly reduced because of RT tasks or IRQs.
 *   - At parent of LLC scheduler domain level, this cpu's scheduler group has
 *     multiple busy cpu.
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
 */
static void nohz_balancer_kick(struct rq *rq)
{
	unsigned long now = jiffies;
	struct sched_domain_shared *sds;
	struct sched_domain *sd;
	int nr_busy, i, cpu = rq->cpu;
9222
	unsigned int flags = 0;
9223 9224 9225 9226 9227 9228 9229 9230

	if (unlikely(rq->idle_balance))
		return;

	/*
	 * We may be recently in ticked or tickless idle mode. At the first
	 * busy tick after returning from idle, we will update the busy stats.
	 */
9231
	nohz_balance_exit_idle(rq);
9232 9233 9234 9235 9236 9237 9238 9239

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
		return;

9240 9241
	if (READ_ONCE(nohz.has_blocked) &&
	    time_after(now, READ_ONCE(nohz.next_blocked)))
9242 9243
		flags = NOHZ_STATS_KICK;

9244
	if (time_before(now, nohz.next_balance))
9245
		goto out;
9246 9247

	if (rq->nr_running >= 2) {
9248
		flags = NOHZ_KICK_MASK;
9249 9250 9251 9252 9253 9254 9255 9256 9257 9258 9259 9260
		goto out;
	}

	rcu_read_lock();
	sds = rcu_dereference(per_cpu(sd_llc_shared, cpu));
	if (sds) {
		/*
		 * XXX: write a coherent comment on why we do this.
		 * See also: http://lkml.kernel.org/r/20111202010832.602203411@sbsiddha-desk.sc.intel.com
		 */
		nr_busy = atomic_read(&sds->nr_busy_cpus);
		if (nr_busy > 1) {
9261
			flags = NOHZ_KICK_MASK;
9262 9263 9264 9265 9266 9267 9268 9269 9270
			goto unlock;
		}

	}

	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
9271
			flags = NOHZ_KICK_MASK;
9272 9273 9274 9275 9276 9277 9278 9279 9280 9281 9282 9283
			goto unlock;
		}
	}

	sd = rcu_dereference(per_cpu(sd_asym, cpu));
	if (sd) {
		for_each_cpu(i, sched_domain_span(sd)) {
			if (i == cpu ||
			    !cpumask_test_cpu(i, nohz.idle_cpus_mask))
				continue;

			if (sched_asym_prefer(i, cpu)) {
9284
				flags = NOHZ_KICK_MASK;
9285 9286 9287 9288 9289 9290 9291
				goto unlock;
			}
		}
	}
unlock:
	rcu_read_unlock();
out:
9292 9293
	if (flags)
		kick_ilb(flags);
9294 9295
}

9296
static void set_cpu_sd_state_busy(int cpu)
9297
{
9298
	struct sched_domain *sd;
9299

9300 9301
	rcu_read_lock();
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
9302

9303 9304 9305 9306 9307 9308 9309
	if (!sd || !sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 0;

	atomic_inc(&sd->shared->nr_busy_cpus);
unlock:
	rcu_read_unlock();
9310 9311
}

9312 9313 9314 9315 9316 9317 9318 9319 9320 9321 9322 9323 9324 9325 9326
void nohz_balance_exit_idle(struct rq *rq)
{
	SCHED_WARN_ON(rq != this_rq());

	if (likely(!rq->nohz_tick_stopped))
		return;

	rq->nohz_tick_stopped = 0;
	cpumask_clear_cpu(rq->cpu, nohz.idle_cpus_mask);
	atomic_dec(&nohz.nr_cpus);

	set_cpu_sd_state_busy(rq->cpu);
}

static void set_cpu_sd_state_idle(int cpu)
9327 9328 9329 9330
{
	struct sched_domain *sd;

	rcu_read_lock();
9331
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
V
Vincent Guittot 已提交
9332 9333 9334 9335 9336

	if (!sd || sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 1;

9337
	atomic_dec(&sd->shared->nr_busy_cpus);
V
Vincent Guittot 已提交
9338
unlock:
9339 9340 9341
	rcu_read_unlock();
}

9342
/*
9343
 * This routine will record that the CPU is going idle with tick stopped.
9344
 * This info will be used in performing idle load balancing in the future.
9345
 */
9346
void nohz_balance_enter_idle(int cpu)
9347
{
9348 9349 9350 9351
	struct rq *rq = cpu_rq(cpu);

	SCHED_WARN_ON(cpu != smp_processor_id());

9352
	/* If this CPU is going down, then nothing needs to be done: */
9353 9354 9355
	if (!cpu_active(cpu))
		return;

9356
	/* Spare idle load balancing on CPUs that don't want to be disturbed: */
9357
	if (!housekeeping_cpu(cpu, HK_FLAG_SCHED))
9358 9359
		return;

9360 9361 9362 9363 9364 9365 9366 9367 9368 9369 9370 9371 9372
	/*
	 * Can be set safely without rq->lock held
	 * If a clear happens, it will have evaluated last additions because
	 * rq->lock is held during the check and the clear
	 */
	rq->has_blocked_load = 1;

	/*
	 * The tick is still stopped but load could have been added in the
	 * meantime. We set the nohz.has_blocked flag to trig a check of the
	 * *_avg. The CPU is already part of nohz.idle_cpus_mask so the clear
	 * of nohz.has_blocked can only happen after checking the new load
	 */
9373
	if (rq->nohz_tick_stopped)
9374
		goto out;
9375

9376
	/* If we're a completely isolated CPU, we don't play: */
9377
	if (on_null_domain(rq))
9378 9379
		return;

9380 9381
	rq->nohz_tick_stopped = 1;

9382 9383
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
9384

9385 9386 9387 9388 9389 9390 9391
	/*
	 * Ensures that if nohz_idle_balance() fails to observe our
	 * @idle_cpus_mask store, it must observe the @has_blocked
	 * store.
	 */
	smp_mb__after_atomic();

9392
	set_cpu_sd_state_idle(cpu);
9393 9394 9395 9396 9397 9398 9399

out:
	/*
	 * Each time a cpu enter idle, we assume that it has blocked load and
	 * enable the periodic update of the load of idle cpus
	 */
	WRITE_ONCE(nohz.has_blocked, 1);
9400 9401 9402
}

/*
9403 9404 9405 9406 9407
 * Internal function that runs load balance for all idle cpus. The load balance
 * can be a simple update of blocked load or a complete load balance with
 * tasks movement depending of flags.
 * The function returns false if the loop has stopped before running
 * through all idle CPUs.
9408
 */
9409 9410
static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
			       enum cpu_idle_type idle)
9411
{
9412
	/* Earliest time when we have to do rebalance again */
9413 9414
	unsigned long now = jiffies;
	unsigned long next_balance = now + 60*HZ;
9415
	bool has_blocked_load = false;
9416
	int update_next_balance = 0;
P
Peter Zijlstra 已提交
9417 9418
	int this_cpu = this_rq->cpu;
	int balance_cpu;
9419
	int ret = false;
P
Peter Zijlstra 已提交
9420
	struct rq *rq;
9421

P
Peter Zijlstra 已提交
9422
	SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
9423

9424 9425 9426 9427 9428 9429 9430 9431 9432 9433 9434 9435 9436 9437 9438 9439
	/*
	 * We assume there will be no idle load after this update and clear
	 * the has_blocked flag. If a cpu enters idle in the mean time, it will
	 * set the has_blocked flag and trig another update of idle load.
	 * Because a cpu that becomes idle, is added to idle_cpus_mask before
	 * setting the flag, we are sure to not clear the state and not
	 * check the load of an idle cpu.
	 */
	WRITE_ONCE(nohz.has_blocked, 0);

	/*
	 * Ensures that if we miss the CPU, we must see the has_blocked
	 * store from nohz_balance_enter_idle().
	 */
	smp_mb();

9440
	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
9441
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
9442 9443 9444
			continue;

		/*
9445 9446
		 * If this CPU gets work to do, stop the load balancing
		 * work being done for other CPUs. Next load
9447 9448
		 * balancing owner will pick it up.
		 */
9449 9450 9451 9452
		if (need_resched()) {
			has_blocked_load = true;
			goto abort;
		}
9453

V
Vincent Guittot 已提交
9454 9455
		rq = cpu_rq(balance_cpu);

9456
		has_blocked_load |= update_nohz_stats(rq, true);
9457

9458 9459 9460 9461 9462
		/*
		 * If time for next balance is due,
		 * do the balance.
		 */
		if (time_after_eq(jiffies, rq->next_balance)) {
9463 9464
			struct rq_flags rf;

9465
			rq_lock_irqsave(rq, &rf);
9466
			update_rq_clock(rq);
9467
			cpu_load_update_idle(rq);
9468
			rq_unlock_irqrestore(rq, &rf);
9469

P
Peter Zijlstra 已提交
9470 9471
			if (flags & NOHZ_BALANCE_KICK)
				rebalance_domains(rq, CPU_IDLE);
9472
		}
9473

9474 9475 9476 9477
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
9478
	}
9479

9480 9481 9482 9483 9484 9485
	/* Newly idle CPU doesn't need an update */
	if (idle != CPU_NEWLY_IDLE) {
		update_blocked_averages(this_cpu);
		has_blocked_load |= this_rq->has_blocked_load;
	}

P
Peter Zijlstra 已提交
9486 9487 9488
	if (flags & NOHZ_BALANCE_KICK)
		rebalance_domains(this_rq, CPU_IDLE);

9489 9490 9491
	WRITE_ONCE(nohz.next_blocked,
		now + msecs_to_jiffies(LOAD_AVG_PERIOD));

9492 9493 9494
	/* The full idle balance loop has been done */
	ret = true;

9495 9496 9497 9498
abort:
	/* There is still blocked load, enable periodic update */
	if (has_blocked_load)
		WRITE_ONCE(nohz.has_blocked, 1);
9499

9500 9501 9502 9503 9504 9505 9506
	/*
	 * next_balance will be updated only when there is a need.
	 * When the CPU is attached to null domain for ex, it will not be
	 * updated.
	 */
	if (likely(update_next_balance))
		nohz.next_balance = next_balance;
P
Peter Zijlstra 已提交
9507

9508 9509 9510 9511 9512 9513 9514 9515 9516 9517 9518 9519 9520 9521 9522 9523 9524 9525 9526 9527 9528 9529 9530 9531 9532 9533 9534 9535 9536
	return ret;
}

/*
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
{
	int this_cpu = this_rq->cpu;
	unsigned int flags;

	if (!(atomic_read(nohz_flags(this_cpu)) & NOHZ_KICK_MASK))
		return false;

	if (idle != CPU_IDLE) {
		atomic_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
		return false;
	}

	/*
	 * barrier, pairs with nohz_balance_enter_idle(), ensures ...
	 */
	flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
	if (!(flags & NOHZ_KICK_MASK))
		return false;

	_nohz_idle_balance(this_rq, flags, idle);

P
Peter Zijlstra 已提交
9537
	return true;
9538
}
9539 9540 9541 9542 9543 9544 9545 9546 9547 9548 9549 9550 9551 9552 9553 9554 9555 9556 9557 9558 9559 9560 9561 9562 9563 9564 9565 9566 9567 9568 9569 9570 9571

static void nohz_newidle_balance(struct rq *this_rq)
{
	int this_cpu = this_rq->cpu;

	/*
	 * This CPU doesn't want to be disturbed by scheduler
	 * housekeeping
	 */
	if (!housekeeping_cpu(this_cpu, HK_FLAG_SCHED))
		return;

	/* Will wake up very soon. No time for doing anything else*/
	if (this_rq->avg_idle < sysctl_sched_migration_cost)
		return;

	/* Don't need to update blocked load of idle CPUs*/
	if (!READ_ONCE(nohz.has_blocked) ||
	    time_before(jiffies, READ_ONCE(nohz.next_blocked)))
		return;

	raw_spin_unlock(&this_rq->lock);
	/*
	 * This CPU is going to be idle and blocked load of idle CPUs
	 * need to be updated. Run the ilb locally as it is a good
	 * candidate for ilb instead of waking up another idle CPU.
	 * Kick an normal ilb if we failed to do the update.
	 */
	if (!_nohz_idle_balance(this_rq, NOHZ_STATS_KICK, CPU_NEWLY_IDLE))
		kick_ilb(NOHZ_STATS_KICK);
	raw_spin_lock(&this_rq->lock);
}

9572 9573 9574
#else /* !CONFIG_NO_HZ_COMMON */
static inline void nohz_balancer_kick(struct rq *rq) { }

9575
static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
P
Peter Zijlstra 已提交
9576 9577 9578
{
	return false;
}
9579 9580

static inline void nohz_newidle_balance(struct rq *this_rq) { }
9581
#endif /* CONFIG_NO_HZ_COMMON */
9582

P
Peter Zijlstra 已提交
9583 9584 9585 9586 9587 9588 9589 9590 9591 9592 9593 9594 9595 9596 9597 9598 9599 9600 9601 9602 9603 9604 9605 9606 9607 9608 9609 9610 9611 9612 9613 9614 9615 9616
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
{
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
	struct sched_domain *sd;
	int pulled_task = 0;
	u64 curr_cost = 0;

	/*
	 * We must set idle_stamp _before_ calling idle_balance(), such that we
	 * measure the duration of idle_balance() as idle time.
	 */
	this_rq->idle_stamp = rq_clock(this_rq);

	/*
	 * Do not pull tasks towards !active CPUs...
	 */
	if (!cpu_active(this_cpu))
		return 0;

	/*
	 * This is OK, because current is on_cpu, which avoids it being picked
	 * for load-balance and preemption/IRQs are still disabled avoiding
	 * further scheduler activity on it and we're being very careful to
	 * re-start the picking loop.
	 */
	rq_unpin_lock(this_rq, rf);

	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
9617

P
Peter Zijlstra 已提交
9618 9619 9620 9621 9622 9623
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
			update_next_balance(sd, &next_balance);
		rcu_read_unlock();

9624 9625
		nohz_newidle_balance(this_rq);

P
Peter Zijlstra 已提交
9626 9627 9628 9629 9630 9631 9632 9633 9634 9635 9636 9637 9638 9639 9640 9641 9642 9643 9644 9645 9646 9647 9648 9649 9650 9651 9652 9653 9654 9655 9656 9657 9658 9659 9660 9661 9662 9663 9664 9665 9666 9667 9668 9669 9670 9671 9672 9673 9674
		goto out;
	}

	raw_spin_unlock(&this_rq->lock);

	update_blocked_averages(this_cpu);
	rcu_read_lock();
	for_each_domain(this_cpu, sd) {
		int continue_balancing = 1;
		u64 t0, domain_cost;

		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
			update_next_balance(sd, &next_balance);
			break;
		}

		if (sd->flags & SD_BALANCE_NEWIDLE) {
			t0 = sched_clock_cpu(this_cpu);

			pulled_task = load_balance(this_cpu, this_rq,
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);

			domain_cost = sched_clock_cpu(this_cpu) - t0;
			if (domain_cost > sd->max_newidle_lb_cost)
				sd->max_newidle_lb_cost = domain_cost;

			curr_cost += domain_cost;
		}

		update_next_balance(sd, &next_balance);

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
			break;
	}
	rcu_read_unlock();

	raw_spin_lock(&this_rq->lock);

	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

9675
out:
P
Peter Zijlstra 已提交
9676 9677 9678 9679 9680 9681 9682 9683 9684 9685 9686 9687 9688 9689 9690 9691 9692 9693 9694 9695 9696 9697 9698 9699
	/*
	 * While browsing the domains, we released the rq lock, a task could
	 * have been enqueued in the meantime. Since we're not going idle,
	 * pretend we pulled a task.
	 */
	if (this_rq->cfs.h_nr_running && !pulled_task)
		pulled_task = 1;

	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
		this_rq->next_balance = next_balance;

	/* Is there a task of a high priority class? */
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
		pulled_task = -1;

	if (pulled_task)
		this_rq->idle_stamp = 0;

	rq_repin_lock(this_rq, rf);

	return pulled_task;
}

9700 9701 9702 9703
/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
9704
static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
9705
{
9706
	struct rq *this_rq = this_rq();
9707
	enum cpu_idle_type idle = this_rq->idle_balance ?
9708 9709 9710
						CPU_IDLE : CPU_NOT_IDLE;

	/*
9711 9712
	 * If this CPU has a pending nohz_balance_kick, then do the
	 * balancing on behalf of the other idle CPUs whose ticks are
9713
	 * stopped. Do nohz_idle_balance *before* rebalance_domains to
9714
	 * give the idle CPUs a chance to load balance. Else we may
9715 9716
	 * load balance only within the local sched_domain hierarchy
	 * and abort nohz_idle_balance altogether if we pull some load.
9717
	 */
P
Peter Zijlstra 已提交
9718 9719 9720 9721 9722
	if (nohz_idle_balance(this_rq, idle))
		return;

	/* normal load balance */
	update_blocked_averages(this_rq->cpu);
9723
	rebalance_domains(this_rq, idle);
9724 9725 9726 9727 9728
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
9729
void trigger_load_balance(struct rq *rq)
9730 9731
{
	/* Don't need to rebalance while attached to NULL domain */
9732 9733 9734 9735
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
9736
		raise_softirq(SCHED_SOFTIRQ);
9737 9738

	nohz_balancer_kick(rq);
9739 9740
}

9741 9742 9743
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
9744 9745

	update_runtime_enabled(rq);
9746 9747 9748 9749 9750
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
9751 9752 9753

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
9754 9755
}

9756
#endif /* CONFIG_SMP */
9757

9758
/*
9759 9760 9761 9762 9763 9764
 * scheduler tick hitting a task of our scheduling class.
 *
 * NOTE: This function can be called remotely by the tick offload that
 * goes along full dynticks. Therefore no local assumption can be made
 * and everything must be accessed through the @rq and @curr passed in
 * parameters.
9765
 */
P
Peter Zijlstra 已提交
9766
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
9767 9768 9769 9770 9771 9772
{
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &curr->se;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
P
Peter Zijlstra 已提交
9773
		entity_tick(cfs_rq, se, queued);
9774
	}
9775

9776
	if (static_branch_unlikely(&sched_numa_balancing))
9777
		task_tick_numa(rq, curr);
9778 9779 9780
}

/*
P
Peter Zijlstra 已提交
9781 9782 9783
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
9784
 */
P
Peter Zijlstra 已提交
9785
static void task_fork_fair(struct task_struct *p)
9786
{
9787 9788
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
P
Peter Zijlstra 已提交
9789
	struct rq *rq = this_rq();
9790
	struct rq_flags rf;
9791

9792
	rq_lock(rq, &rf);
9793 9794
	update_rq_clock(rq);

9795 9796
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;
9797 9798
	if (curr) {
		update_curr(cfs_rq);
9799
		se->vruntime = curr->vruntime;
9800
	}
9801
	place_entity(cfs_rq, se, 1);
9802

P
Peter Zijlstra 已提交
9803
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
9804
		/*
9805 9806 9807
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
9808
		swap(curr->vruntime, se->vruntime);
9809
		resched_curr(rq);
9810
	}
9811

9812
	se->vruntime -= cfs_rq->min_vruntime;
9813
	rq_unlock(rq, &rf);
9814 9815
}

9816 9817 9818 9819
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
9820 9821
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
9822
{
9823
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
9824 9825
		return;

9826 9827 9828 9829 9830
	/*
	 * Reschedule if we are currently running on this runqueue and
	 * our priority decreased, or if we are not currently running on
	 * this runqueue and our priority is higher than the current's
	 */
P
Peter Zijlstra 已提交
9831
	if (rq->curr == p) {
9832
		if (p->prio > oldprio)
9833
			resched_curr(rq);
9834
	} else
9835
		check_preempt_curr(rq, p, 0);
9836 9837
}

9838
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
9839 9840 9841 9842
{
	struct sched_entity *se = &p->se;

	/*
9843 9844 9845 9846 9847 9848 9849 9850 9851 9852
	 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
	 * the dequeue_entity(.flags=0) will already have normalized the
	 * vruntime.
	 */
	if (p->on_rq)
		return true;

	/*
	 * When !on_rq, vruntime of the task has usually NOT been normalized.
	 * But there are some cases where it has already been normalized:
P
Peter Zijlstra 已提交
9853
	 *
9854 9855 9856 9857
	 * - A forked child which is waiting for being woken up by
	 *   wake_up_new_task().
	 * - A task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
P
Peter Zijlstra 已提交
9858
	 */
9859 9860
	if (!se->sum_exec_runtime ||
	    (p->state == TASK_WAKING && p->sched_remote_wakeup))
9861 9862 9863 9864 9865
		return true;

	return false;
}

9866 9867 9868 9869 9870 9871 9872 9873 9874 9875 9876 9877 9878 9879 9880 9881 9882 9883
#ifdef CONFIG_FAIR_GROUP_SCHED
/*
 * Propagate the changes of the sched_entity across the tg tree to make it
 * visible to the root
 */
static void propagate_entity_cfs_rq(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq;

	/* Start to propagate at parent */
	se = se->parent;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);

		if (cfs_rq_throttled(cfs_rq))
			break;

9884
		update_load_avg(cfs_rq, se, UPDATE_TG);
9885 9886 9887 9888 9889 9890
	}
}
#else
static void propagate_entity_cfs_rq(struct sched_entity *se) { }
#endif

9891
static void detach_entity_cfs_rq(struct sched_entity *se)
9892 9893 9894
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

9895
	/* Catch up with the cfs_rq and remove our load when we leave */
9896
	update_load_avg(cfs_rq, se, 0);
9897
	detach_entity_load_avg(cfs_rq, se);
9898
	update_tg_load_avg(cfs_rq, false);
9899
	propagate_entity_cfs_rq(se);
P
Peter Zijlstra 已提交
9900 9901
}

9902
static void attach_entity_cfs_rq(struct sched_entity *se)
9903
{
9904
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
9905 9906

#ifdef CONFIG_FAIR_GROUP_SCHED
9907 9908 9909 9910 9911 9912
	/*
	 * Since the real-depth could have been changed (only FAIR
	 * class maintain depth value), reset depth properly.
	 */
	se->depth = se->parent ? se->parent->depth + 1 : 0;
#endif
9913

9914
	/* Synchronize entity with its cfs_rq */
9915
	update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
9916
	attach_entity_load_avg(cfs_rq, se, 0);
9917
	update_tg_load_avg(cfs_rq, false);
9918
	propagate_entity_cfs_rq(se);
9919 9920 9921 9922 9923 9924 9925 9926 9927 9928 9929 9930 9931 9932 9933 9934 9935 9936 9937 9938 9939 9940 9941 9942 9943
}

static void detach_task_cfs_rq(struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	if (!vruntime_normalized(p)) {
		/*
		 * Fix up our vruntime so that the current sleep doesn't
		 * cause 'unlimited' sleep bonus.
		 */
		place_entity(cfs_rq, se, 0);
		se->vruntime -= cfs_rq->min_vruntime;
	}

	detach_entity_cfs_rq(se);
}

static void attach_task_cfs_rq(struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	attach_entity_cfs_rq(se);
9944 9945 9946 9947

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
9948

9949 9950 9951 9952 9953 9954 9955 9956
static void switched_from_fair(struct rq *rq, struct task_struct *p)
{
	detach_task_cfs_rq(p);
}

static void switched_to_fair(struct rq *rq, struct task_struct *p)
{
	attach_task_cfs_rq(p);
9957

9958
	if (task_on_rq_queued(p)) {
9959
		/*
9960 9961 9962
		 * We were most likely switched from sched_rt, so
		 * kick off the schedule if running, otherwise just see
		 * if we can still preempt the current task.
9963
		 */
9964 9965 9966 9967
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
9968
	}
9969 9970
}

9971 9972 9973 9974 9975 9976 9977 9978 9979
/* Account for a task changing its policy or group.
 *
 * This routine is mostly called to set cfs_rq->curr field when a task
 * migrates between groups/classes.
 */
static void set_curr_task_fair(struct rq *rq)
{
	struct sched_entity *se = &rq->curr->se;

9980 9981 9982 9983 9984 9985 9986
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

		set_next_entity(cfs_rq, se);
		/* ensure bandwidth has been allocated on our new cfs_rq */
		account_cfs_rq_runtime(cfs_rq, 0);
	}
9987 9988
}

9989 9990
void init_cfs_rq(struct cfs_rq *cfs_rq)
{
9991
	cfs_rq->tasks_timeline = RB_ROOT_CACHED;
9992 9993 9994 9995
	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
#ifndef CONFIG_64BIT
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
9996
#ifdef CONFIG_SMP
9997
	raw_spin_lock_init(&cfs_rq->removed.lock);
9998
#endif
9999 10000
}

P
Peter Zijlstra 已提交
10001
#ifdef CONFIG_FAIR_GROUP_SCHED
10002 10003 10004 10005 10006 10007 10008 10009
static void task_set_group_fair(struct task_struct *p)
{
	struct sched_entity *se = &p->se;

	set_task_rq(p, task_cpu(p));
	se->depth = se->parent ? se->parent->depth + 1 : 0;
}

10010
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
10011
{
10012
	detach_task_cfs_rq(p);
10013
	set_task_rq(p, task_cpu(p));
10014 10015 10016 10017 10018

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
10019
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
10020
}
10021

10022 10023 10024 10025 10026 10027 10028 10029 10030 10031 10032 10033 10034
static void task_change_group_fair(struct task_struct *p, int type)
{
	switch (type) {
	case TASK_SET_GROUP:
		task_set_group_fair(p);
		break;

	case TASK_MOVE_GROUP:
		task_move_group_fair(p);
		break;
	}
}

10035 10036 10037 10038 10039 10040 10041 10042 10043
void free_fair_sched_group(struct task_group *tg)
{
	int i;

	destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));

	for_each_possible_cpu(i) {
		if (tg->cfs_rq)
			kfree(tg->cfs_rq[i]);
10044
		if (tg->se)
10045 10046 10047 10048 10049 10050 10051 10052 10053 10054
			kfree(tg->se[i]);
	}

	kfree(tg->cfs_rq);
	kfree(tg->se);
}

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
	struct sched_entity *se;
10055
	struct cfs_rq *cfs_rq;
10056 10057
	int i;

K
Kees Cook 已提交
10058
	tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL);
10059 10060
	if (!tg->cfs_rq)
		goto err;
K
Kees Cook 已提交
10061
	tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL);
10062 10063 10064 10065 10066 10067 10068 10069 10070 10071 10072 10073 10074 10075 10076 10077 10078 10079 10080 10081
	if (!tg->se)
		goto err;

	tg->shares = NICE_0_LOAD;

	init_cfs_bandwidth(tg_cfs_bandwidth(tg));

	for_each_possible_cpu(i) {
		cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
				      GFP_KERNEL, cpu_to_node(i));
		if (!cfs_rq)
			goto err;

		se = kzalloc_node(sizeof(struct sched_entity),
				  GFP_KERNEL, cpu_to_node(i));
		if (!se)
			goto err_free_rq;

		init_cfs_rq(cfs_rq);
		init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
10082
		init_entity_runnable_average(se);
10083 10084 10085 10086 10087 10088 10089 10090 10091 10092
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

10093 10094 10095
void online_fair_sched_group(struct task_group *tg)
{
	struct sched_entity *se;
10096
	struct rq_flags rf;
10097 10098 10099 10100 10101 10102
	struct rq *rq;
	int i;

	for_each_possible_cpu(i) {
		rq = cpu_rq(i);
		se = tg->se[i];
10103
		rq_lock_irq(rq, &rf);
10104
		update_rq_clock(rq);
10105
		attach_entity_cfs_rq(se);
10106
		sync_throttle(tg, i);
10107
		rq_unlock_irq(rq, &rf);
10108 10109 10110
	}
}

10111
void unregister_fair_sched_group(struct task_group *tg)
10112 10113
{
	unsigned long flags;
10114 10115
	struct rq *rq;
	int cpu;
10116

10117 10118 10119
	for_each_possible_cpu(cpu) {
		if (tg->se[cpu])
			remove_entity_load_avg(tg->se[cpu]);
10120

10121 10122 10123 10124 10125 10126 10127 10128 10129 10130 10131 10132 10133
		/*
		 * Only empty task groups can be destroyed; so we can speculatively
		 * check on_list without danger of it being re-added.
		 */
		if (!tg->cfs_rq[cpu]->on_list)
			continue;

		rq = cpu_rq(cpu);

		raw_spin_lock_irqsave(&rq->lock, flags);
		list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
		raw_spin_unlock_irqrestore(&rq->lock, flags);
	}
10134 10135 10136 10137 10138 10139 10140 10141 10142 10143 10144 10145 10146 10147 10148 10149 10150 10151 10152
}

void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
			struct sched_entity *se, int cpu,
			struct sched_entity *parent)
{
	struct rq *rq = cpu_rq(cpu);

	cfs_rq->tg = tg;
	cfs_rq->rq = rq;
	init_cfs_rq_runtime(cfs_rq);

	tg->cfs_rq[cpu] = cfs_rq;
	tg->se[cpu] = se;

	/* se could be NULL for root_task_group */
	if (!se)
		return;

P
Peter Zijlstra 已提交
10153
	if (!parent) {
10154
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
10155 10156
		se->depth = 0;
	} else {
10157
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
10158 10159
		se->depth = parent->depth + 1;
	}
10160 10161

	se->my_q = cfs_rq;
10162 10163
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
10164 10165 10166 10167 10168 10169 10170 10171 10172 10173 10174 10175 10176 10177 10178 10179 10180 10181 10182 10183 10184 10185 10186 10187
	se->parent = parent;
}

static DEFINE_MUTEX(shares_mutex);

int sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
	int i;

	/*
	 * We can't change the weight of the root cgroup.
	 */
	if (!tg->se[0])
		return -EINVAL;

	shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));

	mutex_lock(&shares_mutex);
	if (tg->shares == shares)
		goto done;

	tg->shares = shares;
	for_each_possible_cpu(i) {
		struct rq *rq = cpu_rq(i);
10188 10189
		struct sched_entity *se = tg->se[i];
		struct rq_flags rf;
10190 10191

		/* Propagate contribution to hierarchy */
10192
		rq_lock_irqsave(rq, &rf);
10193
		update_rq_clock(rq);
10194
		for_each_sched_entity(se) {
10195
			update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
10196
			update_cfs_group(se);
10197
		}
10198
		rq_unlock_irqrestore(rq, &rf);
10199 10200 10201 10202 10203 10204 10205 10206 10207 10208 10209 10210 10211 10212 10213
	}

done:
	mutex_unlock(&shares_mutex);
	return 0;
}
#else /* CONFIG_FAIR_GROUP_SCHED */

void free_fair_sched_group(struct task_group *tg) { }

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
	return 1;
}

10214 10215
void online_fair_sched_group(struct task_group *tg) { }

10216
void unregister_fair_sched_group(struct task_group *tg) { }
10217 10218 10219

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
10220

10221
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
10222 10223 10224 10225 10226 10227 10228 10229 10230
{
	struct sched_entity *se = &task->se;
	unsigned int rr_interval = 0;

	/*
	 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
	 * idle runqueue:
	 */
	if (rq->cfs.load.weight)
10231
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
10232 10233 10234 10235

	return rr_interval;
}

10236 10237 10238 10239 10240 10241 10242 10243 10244 10245
#ifdef CONFIG_SCHED_SLI
static void update_nr_uninterruptible_fair(struct task_struct *p, long inc)
{
	struct sched_entity *se = &p->se;

	for_each_sched_entity(se)
		cfs_rq_of(se)->nr_uninterruptible += inc;
}
#endif

10246 10247 10248
/*
 * All the scheduling class methods:
 */
10249
const struct sched_class fair_sched_class = {
10250
	.next			= &idle_sched_class,
10251 10252 10253
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
10254
	.yield_to_task		= yield_to_task_fair,
10255

I
Ingo Molnar 已提交
10256
	.check_preempt_curr	= check_preempt_wakeup,
10257 10258 10259 10260

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

10261
#ifdef CONFIG_SMP
L
Li Zefan 已提交
10262
	.select_task_rq		= select_task_rq_fair,
10263
	.migrate_task_rq	= migrate_task_rq_fair,
10264

10265 10266
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
10267

10268
	.task_dead		= task_dead_fair,
10269
	.set_cpus_allowed	= set_cpus_allowed_common,
10270
#endif
10271

10272
	.set_curr_task          = set_curr_task_fair,
10273
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
10274
	.task_fork		= task_fork_fair,
10275 10276

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
10277
	.switched_from		= switched_from_fair,
10278
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
10279

10280 10281
	.get_rr_interval	= get_rr_interval_fair,

10282 10283
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
10284
#ifdef CONFIG_FAIR_GROUP_SCHED
10285
	.task_change_group	= task_change_group_fair,
P
Peter Zijlstra 已提交
10286
#endif
10287 10288 10289 10290

#ifdef CONFIG_SCHED_SLI
	.update_nr_uninterruptible = update_nr_uninterruptible_fair,
#endif
10291 10292 10293
};

#ifdef CONFIG_SCHED_DEBUG
10294
void print_cfs_stats(struct seq_file *m, int cpu)
10295
{
10296
	struct cfs_rq *cfs_rq;
10297

10298
	rcu_read_lock();
10299
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
10300
		print_cfs_rq(m, cpu, cfs_rq);
10301
	rcu_read_unlock();
10302
}
10303 10304 10305 10306 10307 10308

#ifdef CONFIG_NUMA_BALANCING
void show_numa_stats(struct task_struct *p, struct seq_file *m)
{
	int node;
	unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;
10309
	struct numa_group *ng;
10310

10311 10312
	rcu_read_lock();
	ng = rcu_dereference(p->numa_group);
10313 10314 10315 10316 10317
	for_each_online_node(node) {
		if (p->numa_faults) {
			tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
			tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
		}
10318 10319 10320
		if (ng) {
			gsf = ng->faults[task_faults_idx(NUMA_MEM, node, 0)],
			gpf = ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
10321 10322 10323
		}
		print_numa_stats(m, node, tsf, tpf, gsf, gpf);
	}
10324
	rcu_read_unlock();
10325 10326 10327
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_SCHED_DEBUG */
10328 10329 10330 10331 10332 10333

__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

10334
#ifdef CONFIG_NO_HZ_COMMON
10335
	nohz.next_balance = jiffies;
10336
	nohz.next_blocked = jiffies;
10337 10338 10339 10340 10341
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
#endif
#endif /* SMP */

}