fair.c 267.3 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

799 800 801 802 803 804 805 806 807
static inline void
update_exec_raw(struct cfs_rq *cfs_rq, struct sched_entity *curr)
{
	u64 now = rq_clock(rq_of(cfs_rq));

	curr->sum_exec_raw += now - curr->exec_start_raw;
	curr->exec_start_raw = now;
}

808
/*
809
 * Update the current task's runtime statistics.
810
 */
811
static void update_curr(struct cfs_rq *cfs_rq)
812
{
813
	struct sched_entity *curr = cfs_rq->curr;
814
	u64 now = rq_clock_task(rq_of(cfs_rq));
815
	u64 delta_exec;
816 817 818 819

	if (unlikely(!curr))
		return;

820 821
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
822
		return;
823

I
Ingo Molnar 已提交
824
	curr->exec_start = now;
825

826 827 828 829
	schedstat_set(curr->statistics.exec_max,
		      max(delta_exec, curr->statistics.exec_max));

	curr->sum_exec_runtime += delta_exec;
830
	schedstat_add(cfs_rq->exec_clock, delta_exec);
831 832 833 834

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

835 836 837
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

838
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
839
		cgroup_account_cputime(curtask, delta_exec);
840
		account_group_exec_runtime(curtask, delta_exec);
841
	}
842 843

	account_cfs_rq_runtime(cfs_rq, delta_exec);
844
	update_exec_raw(cfs_rq, curr);
845 846
}

847 848 849 850 851
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

852
static inline void
853
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
854
{
855 856 857 858 859 860 861
	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);
862 863

	if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
864 865
	    likely(wait_start > prev_wait_start))
		wait_start -= prev_wait_start;
866

867
	__schedstat_set(se->statistics.wait_start, wait_start);
868 869
}

870
static inline void
871 872 873
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *p;
874 875
	u64 delta;

876 877 878 879
	if (!schedstat_enabled())
		return;

	delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
880 881 882 883 884 885 886 887 888

	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.
			 */
889
			__schedstat_set(se->statistics.wait_start, delta);
890 891 892 893
			return;
		}
		trace_sched_stat_wait(p, delta);
	}
894
	cpuacct_update_latency(se, delta);
895

896
	__schedstat_set(se->statistics.wait_max,
897
		      max(schedstat_val(se->statistics.wait_max), delta));
898 899 900
	__schedstat_inc(se->statistics.wait_count);
	__schedstat_add(se->statistics.wait_sum, delta);
	__schedstat_set(se->statistics.wait_start, 0);
901 902
}

903
static inline void
904 905 906
update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *tsk = NULL;
907 908 909 910 911 912 913
	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);
914 915 916 917

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

918 919
	if (sleep_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
920 921 922 923

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

924
		if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
925
			__schedstat_set(se->statistics.sleep_max, delta);
926

927 928
		__schedstat_set(se->statistics.sleep_start, 0);
		__schedstat_add(se->statistics.sum_sleep_runtime, delta);
929 930 931 932 933 934

		if (tsk) {
			account_scheduler_latency(tsk, delta >> 10, 1);
			trace_sched_stat_sleep(tsk, delta);
		}
	}
935 936
	if (block_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
937 938 939 940

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

941
		if (unlikely(delta > schedstat_val(se->statistics.block_max)))
942
			__schedstat_set(se->statistics.block_max, delta);
943

944 945
		__schedstat_set(se->statistics.block_start, 0);
		__schedstat_add(se->statistics.sum_sleep_runtime, delta);
946 947

		if (tsk) {
948
			task_ca_update_block(tsk, delta);
949
			if (tsk->in_iowait) {
950 951
				__schedstat_add(se->statistics.iowait_sum, delta);
				__schedstat_inc(se->statistics.iowait_count);
952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969
				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);
		}
	}
970 971
}

972 973 974
/*
 * Task is being enqueued - update stats:
 */
975
static inline void
976
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
977
{
978 979 980
	if (!schedstat_enabled())
		return;

981 982 983 984
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
985
	if (se != cfs_rq->curr)
986
		update_stats_wait_start(cfs_rq, se);
987 988 989

	if (flags & ENQUEUE_WAKEUP)
		update_stats_enqueue_sleeper(cfs_rq, se);
990 991 992
}

static inline void
993
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
994
{
995 996 997 998

	if (!schedstat_enabled())
		return;

999 1000 1001 1002
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
1003
	if (se != cfs_rq->curr)
1004
		update_stats_wait_end(cfs_rq, se);
1005

1006 1007
	if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
		struct task_struct *tsk = task_of(se);
1008

1009
		if (tsk->state & TASK_INTERRUPTIBLE)
1010
			__schedstat_set(se->statistics.sleep_start,
1011 1012
				      rq_clock(rq_of(cfs_rq)));
		if (tsk->state & TASK_UNINTERRUPTIBLE)
1013
			__schedstat_set(se->statistics.block_start,
1014
				      rq_clock(rq_of(cfs_rq)));
1015 1016 1017
	}
}

1018 1019 1020 1021
/*
 * We are picking a new current task - update its stats:
 */
static inline void
1022
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
1023 1024 1025 1026
{
	/*
	 * We are starting a new run period:
	 */
1027
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
1028
	se->exec_start_raw = rq_clock(rq_of(cfs_rq));
1029 1030 1031 1032 1033 1034
}

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

1035 1036
#ifdef CONFIG_NUMA_BALANCING
/*
1037 1038 1039
 * 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.
1040
 */
1041 1042
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1043 1044 1045

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
1046

1047 1048 1049
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069
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];
};

1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084
/*
 * 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);
}

1085 1086 1087
static inline unsigned long group_faults_priv(struct numa_group *ng);
static inline unsigned long group_faults_shared(struct numa_group *ng);

1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111
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)
{
1112
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1113 1114 1115
	unsigned int scan, floor;
	unsigned int windows = 1;

1116 1117
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
1118 1119 1120 1121 1122 1123
	floor = 1000 / windows;

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

1124 1125 1126 1127
static unsigned int task_scan_start(struct task_struct *p)
{
	unsigned long smin = task_scan_min(p);
	unsigned long period = smin;
1128
	struct numa_group *ng;
1129 1130

	/* Scale the maximum scan period with the amount of shared memory. */
1131 1132 1133
	rcu_read_lock();
	ng = rcu_dereference(p->numa_group);
	if (ng) {
1134 1135 1136 1137 1138 1139 1140
		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;
	}
1141
	rcu_read_unlock();
1142 1143 1144 1145

	return max(smin, period);
}

1146 1147
static unsigned int task_scan_max(struct task_struct *p)
{
1148 1149
	unsigned long smin = task_scan_min(p);
	unsigned long smax;
1150
	struct numa_group *ng;
1151 1152 1153

	/* Watch for min being lower than max due to floor calculations */
	smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
1154 1155

	/* Scale the maximum scan period with the amount of shared memory. */
1156 1157
	ng = deref_curr_numa_group(p);
	if (ng) {
1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168
		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);
	}

1169 1170 1171
	return max(smin, smax);
}

1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188
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;
1189
	RCU_INIT_POINTER(p->numa_group, NULL);
1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212
	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;
	}
}

1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224
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));
}

1225 1226 1227 1228 1229 1230 1231 1232 1233
/* 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)

1234 1235
pid_t task_numa_group_id(struct task_struct *p)
{
1236 1237 1238 1239 1240 1241 1242 1243 1244 1245
	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;
1246 1247
}

1248
/*
1249
 * The averaged statistics, shared & private, memory & CPU,
1250 1251 1252 1253 1254
 * 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)
1255
{
1256
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1257 1258 1259 1260
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
1261
	if (!p->numa_faults)
1262 1263
		return 0;

1264 1265
	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1266 1267
}

1268 1269
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
1270 1271 1272
	struct numa_group *ng = deref_task_numa_group(p);

	if (!ng)
1273 1274
		return 0;

1275 1276
	return ng->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		ng->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1277 1278
}

1279 1280
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
1281 1282
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1283 1284
}

1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308
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;
}

1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320
/*
 * 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;
}

1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357
/* 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 &&
1358
					dist >= maxdist)
1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385
			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;
}

1386 1387 1388 1389 1390 1391
/*
 * 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.
 */
1392 1393
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1394
{
1395
	unsigned long faults, total_faults;
1396

1397
	if (!p->numa_faults)
1398 1399 1400 1401 1402 1403 1404
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1405
	faults = task_faults(p, nid);
1406 1407
	faults += score_nearby_nodes(p, nid, dist, true);

1408
	return 1000 * faults / total_faults;
1409 1410
}

1411 1412
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1413
{
1414
	struct numa_group *ng = deref_task_numa_group(p);
1415 1416
	unsigned long faults, total_faults;

1417
	if (!ng)
1418 1419
		return 0;

1420
	total_faults = ng->total_faults;
1421 1422

	if (!total_faults)
1423 1424
		return 0;

1425
	faults = group_faults(p, nid);
1426 1427
	faults += score_nearby_nodes(p, nid, dist, false);

1428
	return 1000 * faults / total_faults;
1429 1430
}

1431 1432 1433
bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
				int src_nid, int dst_cpu)
{
1434
	struct numa_group *ng = deref_curr_numa_group(p);
1435 1436 1437 1438
	int dst_nid = cpu_to_node(dst_cpu);
	int last_cpupid, this_cpupid;

	this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);
1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449
	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;
1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480

	/*
	 * 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;

	/*
1481 1482
	 * Destination node is much more heavily used than the source
	 * node? Allow migration.
1483
	 */
1484 1485
	if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
					ACTIVE_NODE_FRACTION)
1486 1487 1488
		return true;

	/*
1489 1490 1491 1492 1493 1494
	 * 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)
1495
	 */
1496 1497
	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;
1498 1499
}

1500
static unsigned long weighted_cpuload(struct rq *rq);
1501 1502
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1503
static unsigned long capacity_of(int cpu);
1504

1505
/* Cached statistics for all CPUs within a node */
1506 1507
struct numa_stats {
	unsigned long load;
1508 1509

	/* Total compute capacity of CPUs on a node */
1510
	unsigned long compute_capacity;
1511

1512
	unsigned int nr_running;
1513
};
1514

1515 1516 1517 1518 1519
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1520 1521
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1522 1523 1524 1525 1526 1527

	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;
1528
		ns->load += weighted_cpuload(rq);
1529
		ns->compute_capacity += capacity_of(cpu);
1530 1531

		cpus++;
1532 1533
	}

1534 1535 1536 1537 1538
	/*
	 * 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.
	 *
1539
	 * We'll detect a huge imbalance and bail there.
1540 1541 1542 1543
	 */
	if (!cpus)
		return;

1544 1545 1546 1547
	/* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
	smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
	capacity = cpus / smt; /* cores */

1548
	capacity = min_t(unsigned, capacity,
1549
		DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1550 1551
}

1552 1553
struct task_numa_env {
	struct task_struct *p;
1554

1555 1556
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1557

1558
	struct numa_stats src_stats, dst_stats;
1559

1560
	int imbalance_pct;
1561
	int dist;
1562 1563 1564

	struct task_struct *best_task;
	long best_imp;
1565 1566 1567
	int best_cpu;
};

1568 1569 1570
static void task_numa_assign(struct task_numa_env *env,
			     struct task_struct *p, long imp)
{
1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585
	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);
	}

1586 1587
	if (env->best_task)
		put_task_struct(env->best_task);
1588 1589
	if (p)
		get_task_struct(p);
1590 1591 1592 1593 1594 1595

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

1596
static bool load_too_imbalanced(long src_load, long dst_load,
1597 1598
				struct task_numa_env *env)
{
1599 1600
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611
	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;
1612

1613
	imb = abs(dst_load * src_capacity - src_load * dst_capacity);
1614

1615
	orig_src_load = env->src_stats.load;
1616
	orig_dst_load = env->dst_stats.load;
1617

1618
	old_imb = abs(orig_dst_load * src_capacity - orig_src_load * dst_capacity);
1619 1620 1621

	/* Would this change make things worse? */
	return (imb > old_imb);
1622 1623
}

1624 1625 1626 1627 1628 1629 1630
/*
 * Maximum NUMA importance can be 1998 (2*999);
 * SMALLIMP @ 30 would be close to 1998/64.
 * Used to deter task migration.
 */
#define SMALLIMP	30

1631 1632 1633 1634 1635 1636
/*
 * 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
 */
1637
static void task_numa_compare(struct task_numa_env *env,
1638
			      long taskimp, long groupimp, bool maymove)
1639
{
1640
	struct numa_group *cur_ng, *p_ng = deref_curr_numa_group(env->p);
1641
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
1642
	long imp = p_ng ? groupimp : taskimp;
1643
	struct task_struct *cur;
1644
	long src_load, dst_load;
1645
	int dist = env->dist;
1646 1647
	long moveimp = imp;
	long load;
1648

1649 1650 1651
	if (READ_ONCE(dst_rq->numa_migrate_on))
		return;

1652
	rcu_read_lock();
1653 1654
	cur = task_rcu_dereference(&dst_rq->curr);
	if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1655 1656
		cur = NULL;

1657 1658 1659 1660 1661 1662 1663
	/*
	 * 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;

1664
	if (!cur) {
1665
		if (maymove && moveimp >= env->best_imp)
1666 1667 1668 1669 1670
			goto assign;
		else
			goto unlock;
	}

1671 1672 1673 1674
	/*
	 * "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
1675
	 * the value is, the more remote accesses that would be expected to
1676 1677
	 * be incurred if the tasks were swapped.
	 */
1678 1679 1680
	/* Skip this swap candidate if cannot move to the source cpu */
	if (!cpumask_test_cpu(env->src_cpu, &cur->cpus_allowed))
		goto unlock;
1681

1682 1683 1684 1685
	/*
	 * If dst and source tasks are in the same NUMA group, or not
	 * in any group then look only at task weights.
	 */
1686 1687
	cur_ng = rcu_dereference(cur->numa_group);
	if (cur_ng == p_ng) {
1688 1689
		imp = taskimp + task_weight(cur, env->src_nid, dist) -
		      task_weight(cur, env->dst_nid, dist);
1690
		/*
1691 1692
		 * Add some hysteresis to prevent swapping the
		 * tasks within a group over tiny differences.
1693
		 */
1694
		if (cur_ng)
1695 1696 1697 1698 1699 1700
			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.
		 */
1701
		if (cur_ng && p_ng)
1702 1703 1704 1705 1706
			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);
1707 1708
	}

1709
	if (maymove && moveimp > imp && moveimp > env->best_imp) {
1710
		imp = moveimp;
1711
		cur = NULL;
1712
		goto assign;
1713
	}
1714

1715 1716 1717 1718 1719 1720 1721 1722 1723
	/*
	 * 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;

1724 1725 1726
	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
1727 1728 1729 1730
	load = task_h_load(env->p) - task_h_load(cur);
	if (!load)
		goto assign;

1731 1732
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1733

1734
	if (load_too_imbalanced(src_load, dst_load, env))
1735 1736
		goto unlock;

1737
assign:
1738 1739 1740 1741
	/*
	 * One idle CPU per node is evaluated for a task numa move.
	 * Call select_idle_sibling to maybe find a better one.
	 */
1742 1743
	if (!cur) {
		/*
1744
		 * select_idle_siblings() uses an per-CPU cpumask that
1745 1746 1747
		 * can be used from IRQ context.
		 */
		local_irq_disable();
1748 1749
		env->dst_cpu = select_idle_sibling(env->p, env->src_cpu,
						   env->dst_cpu);
1750 1751
		local_irq_enable();
	}
1752

1753 1754 1755 1756 1757
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1758 1759
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1760
{
1761 1762
	long src_load, dst_load, load;
	bool maymove = false;
1763 1764
	int cpu;

1765 1766 1767 1768 1769 1770 1771 1772 1773 1774
	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);

1775 1776
	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
		/* Skip this CPU if the source task cannot migrate */
1777
		if (!cpumask_test_cpu(cpu, &env->p->cpus_allowed))
1778 1779 1780
			continue;

		env->dst_cpu = cpu;
1781
		task_numa_compare(env, taskimp, groupimp, maymove);
1782 1783 1784
	}
}

1785 1786 1787 1788
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1789

1790
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1791
		.src_nid = task_node(p),
1792 1793 1794 1795 1796

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
1797
		.best_cpu = -1,
1798
	};
1799
	unsigned long taskweight, groupweight;
1800
	struct sched_domain *sd;
1801 1802
	long taskimp, groupimp;
	struct numa_group *ng;
1803
	struct rq *best_rq;
1804
	int nid, ret, dist;
1805

1806
	/*
1807 1808 1809 1810 1811 1812
	 * 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.
1813 1814
	 */
	rcu_read_lock();
1815
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1816 1817
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1818 1819
	rcu_read_unlock();

1820 1821 1822 1823 1824 1825 1826
	/*
	 * 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)) {
1827
		sched_setnuma(p, task_node(p));
1828 1829 1830
		return -EINVAL;
	}

1831
	env.dst_nid = p->numa_preferred_nid;
1832 1833 1834 1835 1836 1837
	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;
1838
	update_numa_stats(&env.dst_stats, env.dst_nid);
1839

1840
	/* Try to find a spot on the preferred nid. */
1841
	task_numa_find_cpu(&env, taskimp, groupimp);
1842

1843 1844 1845 1846 1847 1848 1849
	/*
	 * 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.
	 */
1850 1851
	ng = deref_curr_numa_group(p);
	if (env.best_cpu == -1 || (ng && ng->active_nodes > 1)) {
1852 1853 1854
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1855

1856
			dist = node_distance(env.src_nid, env.dst_nid);
1857 1858 1859 1860 1861
			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);
			}
1862

1863
			/* Only consider nodes where both task and groups benefit */
1864 1865
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1866
			if (taskimp < 0 && groupimp < 0)
1867 1868
				continue;

1869
			env.dist = dist;
1870 1871
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1872
			task_numa_find_cpu(&env, taskimp, groupimp);
1873 1874 1875
		}
	}

1876 1877 1878 1879 1880 1881 1882 1883
	/*
	 * 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.
	 */
1884
	if (ng) {
1885 1886 1887
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
1888
			nid = cpu_to_node(env.best_cpu);
1889

1890 1891
		if (nid != p->numa_preferred_nid)
			sched_setnuma(p, nid);
1892 1893 1894 1895 1896
	}

	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;
1897

1898
	best_rq = cpu_rq(env.best_cpu);
1899
	if (env.best_task == NULL) {
1900
		ret = migrate_task_to(p, env.best_cpu);
1901
		WRITE_ONCE(best_rq->numa_migrate_on, 0);
1902 1903
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1904 1905 1906
		return ret;
	}

1907
	ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu);
1908
	WRITE_ONCE(best_rq->numa_migrate_on, 0);
1909

1910 1911
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1912 1913
	put_task_struct(env.best_task);
	return ret;
1914 1915
}

1916 1917 1918
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1919 1920
	unsigned long interval = HZ;

1921
	/* This task has no NUMA fault statistics yet */
1922
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1923 1924
		return;

1925
	/* Periodically retry migrating the task to the preferred node */
1926
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1927
	p->numa_migrate_retry = jiffies + interval;
1928 1929

	/* Success if task is already running on preferred CPU */
1930
	if (task_node(p) == p->numa_preferred_nid)
1931 1932 1933
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1934
	task_numa_migrate(p);
1935 1936
}

1937
/*
1938
 * Find out how many nodes on the workload is actively running on. Do this by
1939 1940 1941 1942
 * 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.
 */
1943
static void numa_group_count_active_nodes(struct numa_group *numa_group)
1944 1945
{
	unsigned long faults, max_faults = 0;
1946
	int nid, active_nodes = 0;
1947 1948 1949 1950 1951 1952 1953 1954 1955

	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);
1956 1957
		if (faults * ACTIVE_NODE_FRACTION > max_faults)
			active_nodes++;
1958
	}
1959 1960 1961

	numa_group->max_faults_cpu = max_faults;
	numa_group->active_nodes = active_nodes;
1962 1963
}

1964 1965 1966
/*
 * 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
1967 1968 1969
 * 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.
1970 1971
 */
#define NUMA_PERIOD_SLOTS 10
1972
#define NUMA_PERIOD_THRESHOLD 7
1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983

/*
 * 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;
1984
	int lr_ratio, ps_ratio;
1985 1986 1987 1988 1989 1990 1991 1992
	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
1993 1994 1995
	 * 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
1996
	 */
1997
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
		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);
2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032
	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;
2033 2034 2035 2036 2037
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else {
		/*
2038 2039 2040
		 * 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.
2041
		 */
2042 2043
		int ratio = max(lr_ratio, ps_ratio);
		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
2044 2045 2046 2047 2048 2049 2050
	}

	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));
}

2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067
/*
 * 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;
2068 2069 2070 2071

		/* Avoid time going backwards, prevent potential divide error: */
		if (unlikely((s64)*period < 0))
			*period = 0;
2072
	} else {
2073
		delta = p->se.avg.load_sum;
2074
		*period = LOAD_AVG_MAX;
2075 2076 2077 2078 2079 2080 2081 2082
	}

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

	return delta;
}

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 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129
/*
 * 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;
2130
		nodemask_t max_group = NODE_MASK_NONE;
2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163
		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. */
2164 2165
		if (!max_faults)
			break;
2166 2167 2168 2169 2170
		nodes = max_group;
	}
	return nid;
}

2171 2172
static void task_numa_placement(struct task_struct *p)
{
2173 2174
	int seq, nid, max_nid = -1;
	unsigned long max_faults = 0;
2175
	unsigned long fault_types[2] = { 0, 0 };
2176 2177
	unsigned long total_faults;
	u64 runtime, period;
2178
	spinlock_t *group_lock = NULL;
2179
	struct numa_group *ng;
2180

2181 2182 2183 2184 2185
	/*
	 * 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:
	 */
2186
	seq = READ_ONCE(p->mm->numa_scan_seq);
2187 2188 2189
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
2190
	p->numa_scan_period_max = task_scan_max(p);
2191

2192 2193 2194 2195
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

2196
	/* If the task is part of a group prevent parallel updates to group stats */
2197 2198 2199
	ng = deref_curr_numa_group(p);
	if (ng) {
		group_lock = &ng->lock;
2200
		spin_lock_irq(group_lock);
2201 2202
	}

2203 2204
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
2205 2206
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2207
		unsigned long faults = 0, group_faults = 0;
2208
		int priv;
2209

2210
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2211
			long diff, f_diff, f_weight;
2212

2213 2214 2215 2216
			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);
2217

2218
			/* Decay existing window, copy faults since last scan */
2219 2220 2221
			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;
2222

2223 2224 2225 2226 2227 2228 2229 2230
			/*
			 * 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);
2231
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2232
				   (total_faults + 1);
2233 2234
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
2235

2236 2237 2238
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
2239
			p->total_numa_faults += diff;
2240
			if (ng) {
2241 2242 2243 2244 2245 2246 2247
				/*
				 * 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.
				 */
2248 2249 2250 2251
				ng->faults[mem_idx] += diff;
				ng->faults_cpu[mem_idx] += f_diff;
				ng->total_faults += diff;
				group_faults += ng->faults[mem_idx];
2252
			}
2253 2254
		}

2255
		if (!ng) {
2256 2257 2258 2259 2260 2261
			if (faults > max_faults) {
				max_faults = faults;
				max_nid = nid;
			}
		} else if (group_faults > max_faults) {
			max_faults = group_faults;
2262 2263
			max_nid = nid;
		}
2264 2265
	}

2266 2267
	if (ng) {
		numa_group_count_active_nodes(ng);
2268
		spin_unlock_irq(group_lock);
2269
		max_nid = preferred_group_nid(p, max_nid);
2270 2271
	}

2272 2273 2274 2275
	if (max_faults) {
		/* Set the new preferred node */
		if (max_nid != p->numa_preferred_nid)
			sched_setnuma(p, max_nid);
2276
	}
2277 2278

	update_task_scan_period(p, fault_types[0], fault_types[1]);
2279 2280
}

2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291
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);
}

2292 2293
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
2294 2295 2296 2297 2298 2299 2300
{
	struct numa_group *grp, *my_grp;
	struct task_struct *tsk;
	bool join = false;
	int cpu = cpupid_to_cpu(cpupid);
	int i;

2301
	if (unlikely(!deref_curr_numa_group(p))) {
2302
		unsigned int size = sizeof(struct numa_group) +
2303
				    4*nr_node_ids*sizeof(unsigned long);
2304 2305 2306 2307 2308 2309

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

		atomic_set(&grp->refcount, 1);
2310 2311
		grp->active_nodes = 1;
		grp->max_faults_cpu = 0;
2312
		spin_lock_init(&grp->lock);
2313
		grp->gid = p->pid;
2314
		/* Second half of the array tracks nids where faults happen */
2315 2316
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
2317

2318
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2319
			grp->faults[i] = p->numa_faults[i];
2320

2321
		grp->total_faults = p->total_numa_faults;
2322

2323 2324 2325 2326 2327
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
2328
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
2329 2330

	if (!cpupid_match_pid(tsk, cpupid))
2331
		goto no_join;
2332 2333 2334

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
2335
		goto no_join;
2336

2337
	my_grp = deref_curr_numa_group(p);
2338
	if (grp == my_grp)
2339
		goto no_join;
2340 2341 2342 2343 2344 2345

	/*
	 * 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)
2346
		goto no_join;
2347 2348 2349 2350 2351

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2352
		goto no_join;
2353

2354 2355 2356 2357 2358 2359 2360
	/* 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;
2361

2362 2363 2364
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2365
	if (join && !get_numa_group(grp))
2366
		goto no_join;
2367 2368 2369 2370 2371 2372

	rcu_read_unlock();

	if (!join)
		return;

2373 2374
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2375

2376
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2377 2378
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2379
	}
2380 2381
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2382 2383 2384 2385 2386

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

	spin_unlock(&my_grp->lock);
2387
	spin_unlock_irq(&grp->lock);
2388 2389 2390 2391

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2392 2393 2394 2395 2396
	return;

no_join:
	rcu_read_unlock();
	return;
2397 2398
}

2399 2400 2401 2402 2403 2404 2405 2406
/*
 * 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)
2407
{
2408 2409
	/* safe: p either is current or is being freed by current */
	struct numa_group *grp = rcu_dereference_raw(p->numa_group);
2410
	unsigned long *numa_faults = p->numa_faults;
2411 2412
	unsigned long flags;
	int i;
2413

2414 2415 2416
	if (!numa_faults)
		return;

2417
	if (grp) {
2418
		spin_lock_irqsave(&grp->lock, flags);
2419
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2420
			grp->faults[i] -= p->numa_faults[i];
2421
		grp->total_faults -= p->total_numa_faults;
2422

2423
		grp->nr_tasks--;
2424
		spin_unlock_irqrestore(&grp->lock, flags);
2425
		RCU_INIT_POINTER(p->numa_group, NULL);
2426 2427 2428
		put_numa_group(grp);
	}

2429 2430 2431 2432 2433 2434 2435 2436
	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;
	}
2437 2438
}

2439 2440 2441
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2442
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2443 2444
{
	struct task_struct *p = current;
2445
	bool migrated = flags & TNF_MIGRATED;
2446
	int cpu_node = task_node(current);
2447
	int local = !!(flags & TNF_FAULT_LOCAL);
2448
	struct numa_group *ng;
2449
	int priv;
2450

2451
	if (!static_branch_likely(&sched_numa_balancing))
2452 2453
		return;

2454 2455 2456 2457
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2458
	/* Allocate buffer to track faults on a per-node basis */
2459 2460
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2461
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2462

2463 2464
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2465
			return;
2466

2467
		p->total_numa_faults = 0;
2468
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2469
	}
2470

2471 2472 2473 2474 2475 2476 2477 2478
	/*
	 * 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);
2479
		if (!priv && !(flags & TNF_NO_GROUP))
2480
			task_numa_group(p, last_cpupid, flags, &priv);
2481 2482
	}

2483 2484 2485 2486 2487 2488
	/*
	 * 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.
	 */
2489
	ng = deref_curr_numa_group(p);
2490 2491 2492
	if (!priv && !local && ng && ng->active_nodes > 1 &&
				numa_is_active_node(cpu_node, ng) &&
				numa_is_active_node(mem_node, ng))
2493 2494
		local = 1;

2495 2496 2497 2498
	/*
	 * Retry task to preferred node migration periodically, in case it
	 * case it previously failed, or the scheduler moved us.
	 */
2499 2500
	if (time_after(jiffies, p->numa_migrate_retry)) {
		task_numa_placement(p);
2501
		numa_migrate_preferred(p);
2502
	}
2503

I
Ingo Molnar 已提交
2504 2505
	if (migrated)
		p->numa_pages_migrated += pages;
2506 2507
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2508

2509 2510
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2511
	p->numa_faults_locality[local] += pages;
2512 2513
}

2514 2515
static void reset_ptenuma_scan(struct task_struct *p)
{
2516 2517 2518 2519 2520 2521 2522 2523
	/*
	 * 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:
	 */
2524
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2525 2526 2527
	p->mm->numa_scan_offset = 0;
}

2528 2529 2530 2531 2532 2533 2534 2535 2536
/*
 * 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;
2537
	u64 runtime = p->se.sum_exec_runtime;
2538
	struct vm_area_struct *vma;
2539
	unsigned long start, end;
2540
	unsigned long nr_pte_updates = 0;
2541
	long pages, virtpages;
2542

2543
	SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556

	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;

2557
	if (!mm->numa_next_scan) {
2558 2559
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2560 2561
	}

2562 2563 2564 2565 2566 2567 2568
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2569 2570
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
2571
		p->numa_scan_period = task_scan_start(p);
2572
	}
2573

2574
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2575 2576 2577
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2578 2579 2580 2581 2582 2583
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2584 2585 2586
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2587
	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2588 2589
	if (!pages)
		return;
2590

2591

2592 2593
	if (!down_read_trylock(&mm->mmap_sem))
		return;
2594
	vma = find_vma(mm, start);
2595 2596
	if (!vma) {
		reset_ptenuma_scan(p);
2597
		start = 0;
2598 2599
		vma = mm->mmap;
	}
2600
	for (; vma; vma = vma->vm_next) {
2601
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2602
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2603
			continue;
2604
		}
2605

2606 2607 2608 2609 2610 2611 2612 2613 2614 2615
		/*
		 * 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
2616 2617 2618 2619 2620 2621
		/*
		 * 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;
2622

2623 2624 2625 2626
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2627
			nr_pte_updates = change_prot_numa(vma, start, end);
2628 2629

			/*
2630 2631 2632 2633 2634 2635
			 * 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.
2636 2637 2638
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2639
			virtpages -= (end - start) >> PAGE_SHIFT;
2640

2641
			start = end;
2642
			if (pages <= 0 || virtpages <= 0)
2643
				goto out;
2644 2645

			cond_resched();
2646
		} while (end != vma->vm_end);
2647
	}
2648

2649
out:
2650
	/*
P
Peter Zijlstra 已提交
2651 2652 2653 2654
	 * 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.
2655 2656
	 */
	if (vma)
2657
		mm->numa_scan_offset = start;
2658 2659 2660
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671

	/*
	 * 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;
	}
2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684
}

/*
 * 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.
	 */
2685
	if ((curr->flags & (PF_EXITING | PF_KTHREAD)) || work->next != work)
2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696
		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;

2697
	if (now > curr->node_stamp + period) {
2698
		if (!curr->node_stamp)
2699
			curr->numa_scan_period = task_scan_start(curr);
2700
		curr->node_stamp += period;
2701 2702 2703 2704 2705 2706 2707

		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);
		}
	}
}
2708

2709 2710 2711 2712 2713
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);

2714 2715 2716
	if (!static_branch_likely(&sched_numa_balancing))
		return;

2717 2718 2719
	if (!p->mm || !p->numa_faults || (p->flags & PF_EXITING))
		return;

2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739
	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);
2740 2741
}

2742 2743 2744 2745
#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
}
2746 2747 2748 2749 2750 2751 2752 2753

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)
{
}
2754

2755 2756 2757 2758
static inline void update_scan_period(struct task_struct *p, int new_cpu)
{
}

2759 2760
#endif /* CONFIG_NUMA_BALANCING */

2761 2762 2763 2764
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2765
#ifdef CONFIG_SMP
2766 2767 2768 2769 2770 2771
	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);
	}
2772
#endif
2773 2774 2775 2776 2777 2778 2779
	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);
2780
#ifdef CONFIG_SMP
2781 2782
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2783
		list_del_init(&se->group_node);
2784
	}
2785
#endif
2786 2787 2788
	cfs_rq->nr_running--;
}

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 2821 2822 2823 2824 2825 2826 2827 2828 2829
/*
 * 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)
{
2830 2831 2832 2833
	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;
2834 2835 2836 2837 2838
}

static inline void
dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2839 2840 2841 2842 2843
	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);
2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869
}

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

2870
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2871
			    unsigned long weight, unsigned long runnable)
2872 2873 2874 2875 2876 2877 2878 2879 2880 2881
{
	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);

2882
	se->runnable_weight = runnable;
2883 2884 2885
	update_load_set(&se->load, weight);

#ifdef CONFIG_SMP
2886 2887 2888 2889 2890 2891 2892
	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);
2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908
#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]);

2909
	reweight_entity(cfs_rq, se, weight, weight);
2910 2911 2912
	load->inv_weight = sched_prio_to_wmult[prio];
}

2913
#ifdef CONFIG_FAIR_GROUP_SCHED
2914
#ifdef CONFIG_SMP
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 2944 2945 2946 2947 2948 2949 2950 2951 2952
/*
 * 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
2953
 *   ge->load.weight = ----------------------------- = tg->weight   (4)
2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966
 *			    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
 *
2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978
 * 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)
2979 2980 2981 2982 2983 2984 2985 2986 2987
 *
 * 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!
 */
2988
static long calc_group_shares(struct cfs_rq *cfs_rq)
2989
{
2990 2991 2992 2993
	long tg_weight, tg_shares, load, shares;
	struct task_group *tg = cfs_rq->tg;

	tg_shares = READ_ONCE(tg->shares);
2994

2995
	load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
2996

2997
	tg_weight = atomic_long_read(&tg->load_avg);
2998

2999 3000 3001
	/* Ensure tg_weight >= load */
	tg_weight -= cfs_rq->tg_load_avg_contrib;
	tg_weight += load;
3002

3003
	shares = (tg_shares * load);
3004 3005
	if (tg_weight)
		shares /= tg_weight;
3006

3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018
	/*
	 * 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.
	 */
3019
	return clamp_t(long, shares, MIN_SHARES, tg_shares);
3020
}
3021 3022

/*
3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047
 * 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).
3048 3049 3050
 */
static long calc_group_runnable(struct cfs_rq *cfs_rq, long shares)
{
3051 3052 3053 3054 3055 3056 3057
	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));
3058 3059 3060 3061

	runnable *= shares;
	if (load_avg)
		runnable /= load_avg;
3062

3063 3064
	return clamp_t(long, runnable, MIN_SHARES, shares);
}
3065
#endif /* CONFIG_SMP */
3066

3067 3068
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

3069 3070 3071 3072 3073
/*
 * 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
3074
{
3075 3076
	struct cfs_rq *gcfs_rq = group_cfs_rq(se);
	long shares, runnable;
P
Peter Zijlstra 已提交
3077

3078
	if (!gcfs_rq)
3079 3080
		return;

3081
	if (throttled_hierarchy(gcfs_rq))
P
Peter Zijlstra 已提交
3082
		return;
3083

3084
#ifndef CONFIG_SMP
3085
	runnable = shares = READ_ONCE(gcfs_rq->tg->shares);
3086 3087

	if (likely(se->load.weight == shares))
3088
		return;
3089
#else
3090 3091
	shares   = calc_group_shares(gcfs_rq);
	runnable = calc_group_runnable(gcfs_rq, shares);
3092
#endif
P
Peter Zijlstra 已提交
3093

3094
	reweight_entity(cfs_rq_of(se), se, shares, runnable);
P
Peter Zijlstra 已提交
3095
}
3096

P
Peter Zijlstra 已提交
3097
#else /* CONFIG_FAIR_GROUP_SCHED */
3098
static inline void update_cfs_group(struct sched_entity *se)
P
Peter Zijlstra 已提交
3099 3100 3101 3102
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

3103
static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
3104
{
3105 3106
	struct rq *rq = rq_of(cfs_rq);

3107
	if (&rq->cfs == cfs_rq || (flags & SCHED_CPUFREQ_MIGRATION)) {
3108 3109 3110
		/*
		 * There are a few boundary cases this might miss but it should
		 * get called often enough that that should (hopefully) not be
3111
		 * a real problem.
3112 3113 3114 3115 3116 3117 3118 3119 3120 3121
		 *
		 * 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().
		 */
3122
		cpufreq_update_util(rq, flags);
3123 3124 3125
	}
}

3126
#ifdef CONFIG_SMP
3127
#ifdef CONFIG_FAIR_GROUP_SCHED
3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140
/**
 * 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'.
 *
3141
 * Updating tg's load_avg is necessary before update_cfs_share().
3142
 */
3143
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
3144
{
3145
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
3146

3147 3148 3149 3150 3151 3152
	/*
	 * No need to update load_avg for root_task_group as it is not used.
	 */
	if (cfs_rq->tg == &root_task_group)
		return;

3153 3154 3155
	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;
3156
	}
3157
}
3158

3159
/*
3160
 * Called within set_task_rq() right before setting a task's CPU. The
3161 3162 3163 3164 3165 3166
 * 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)
{
3167 3168 3169
	u64 p_last_update_time;
	u64 n_last_update_time;

3170 3171 3172 3173 3174 3175 3176 3177 3178 3179
	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.
	 */
3180 3181
	if (!(se->avg.last_update_time && prev))
		return;
3182 3183

#ifndef CONFIG_64BIT
3184
	{
3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198
		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);
3199
	}
3200
#else
3201 3202
	p_last_update_time = prev->avg.last_update_time;
	n_last_update_time = next->avg.last_update_time;
3203
#endif
3204 3205
	__update_load_avg_blocked_se(p_last_update_time, cpu_of(rq_of(prev)), se);
	se->avg.last_update_time = n_last_update_time;
3206
}
3207

3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218

/*
 * 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.
 *
3219 3220 3221
 * 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).
3222 3223 3224 3225 3226 3227 3228 3229
 *
 * 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:
 *
3230
 *   grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg	(3)
3231 3232 3233
 *
 * And per (1) we have:
 *
3234
 *   ge->avg.runnable_avg == grq->avg.runnable_avg
3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252
 *
 * 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).
 *
3253 3254 3255 3256 3257 3258
 * 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.
3259
 *
3260
 * So we'll have to approximate.. :/
3261
 *
3262
 * Given the constraint:
3263
 *
3264
 *   ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
3265
 *
3266 3267
 * We can construct a rule that adds runnable to a rq by assuming minimal
 * overlap.
3268
 *
3269
 * On removal, we'll assume each task is equally runnable; which yields:
3270
 *
3271
 *   grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
3272
 *
3273
 * XXX: only do this for the part of runnable > running ?
3274 3275 3276
 *
 */

3277
static inline void
3278
update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3279 3280 3281 3282 3283 3284 3285
{
	long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;

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

3286 3287 3288 3289 3290 3291 3292 3293
	/*
	 * 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.
	 */

3294 3295 3296 3297 3298 3299 3300 3301 3302 3303
	/* 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
3304
update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3305
{
3306 3307 3308 3309
	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;
3310

3311 3312
	if (!runnable_sum)
		return;
3313

3314
	gcfs_rq->prop_runnable_sum = 0;
3315

3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338
	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
3339
	 * As running sum is scale with CPU capacity wehreas the runnable sum
3340 3341 3342 3343 3344 3345
	 * 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);

3346 3347
	load_sum = (s64)se_weight(se) * runnable_sum;
	load_avg = div_s64(load_sum, LOAD_AVG_MAX);
3348

3349 3350
	delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
	delta_avg = load_avg - se->avg.load_avg;
3351

3352 3353 3354 3355
	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);
3356

3357 3358
	runnable_load_sum = (s64)se_runnable(se) * runnable_sum;
	runnable_load_avg = div_s64(runnable_load_sum, LOAD_AVG_MAX);
3359 3360
	delta_sum = runnable_load_sum - se_weight(se) * se->avg.runnable_load_sum;
	delta_avg = runnable_load_avg - se->avg.runnable_load_avg;
3361

3362 3363
	se->avg.runnable_load_sum = runnable_sum;
	se->avg.runnable_load_avg = runnable_load_avg;
3364

3365
	if (se->on_rq) {
3366 3367
		add_positive(&cfs_rq->avg.runnable_load_avg, delta_avg);
		add_positive(&cfs_rq->avg.runnable_load_sum, delta_sum);
3368 3369 3370
	}
}

3371
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
3372
{
3373 3374
	cfs_rq->propagate = 1;
	cfs_rq->prop_runnable_sum += runnable_sum;
3375 3376 3377 3378 3379
}

/* Update task and its cfs_rq load average */
static inline int propagate_entity_load_avg(struct sched_entity *se)
{
3380
	struct cfs_rq *cfs_rq, *gcfs_rq;
3381 3382 3383 3384

	if (entity_is_task(se))
		return 0;

3385 3386
	gcfs_rq = group_cfs_rq(se);
	if (!gcfs_rq->propagate)
3387 3388
		return 0;

3389 3390
	gcfs_rq->propagate = 0;

3391 3392
	cfs_rq = cfs_rq_of(se);

3393
	add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
3394

3395 3396
	update_tg_cfs_util(cfs_rq, se, gcfs_rq);
	update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
3397 3398 3399 3400

	return 1;
}

3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419
/*
 * 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:
	 */
3420
	if (gcfs_rq->propagate)
3421 3422 3423 3424 3425 3426 3427 3428 3429 3430
		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;
}

3431
#else /* CONFIG_FAIR_GROUP_SCHED */
3432

3433
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
3434 3435 3436 3437 3438 3439

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

3440
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
3441

3442
#endif /* CONFIG_FAIR_GROUP_SCHED */
3443

3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454
/**
 * 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.
 *
3455 3456 3457 3458
 * 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.
3459
 */
3460
static inline int
3461
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3462
{
3463
	unsigned long removed_load = 0, removed_util = 0, removed_runnable_sum = 0;
3464
	struct sched_avg *sa = &cfs_rq->avg;
3465
	int decayed = 0;
3466

3467 3468
	if (cfs_rq->removed.nr) {
		unsigned long r;
3469
		u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
3470 3471 3472 3473

		raw_spin_lock(&cfs_rq->removed.lock);
		swap(cfs_rq->removed.util_avg, removed_util);
		swap(cfs_rq->removed.load_avg, removed_load);
3474
		swap(cfs_rq->removed.runnable_sum, removed_runnable_sum);
3475 3476 3477 3478
		cfs_rq->removed.nr = 0;
		raw_spin_unlock(&cfs_rq->removed.lock);

		r = removed_load;
3479
		sub_positive(&sa->load_avg, r);
3480
		sub_positive(&sa->load_sum, r * divider);
3481

3482
		r = removed_util;
3483
		sub_positive(&sa->util_avg, r);
3484
		sub_positive(&sa->util_sum, r * divider);
3485

3486
		add_tg_cfs_propagate(cfs_rq, -(long)removed_runnable_sum);
3487 3488

		decayed = 1;
3489
	}
3490

3491
	decayed |= __update_load_avg_cfs_rq(now, cpu_of(rq_of(cfs_rq)), cfs_rq);
3492

3493 3494 3495 3496
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
3497

3498
	if (decayed)
3499
		cfs_rq_util_change(cfs_rq, 0);
3500

3501
	return decayed;
3502 3503
}

3504 3505 3506 3507
/**
 * 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
3508
 * @flags: migration hints
3509 3510 3511 3512
 *
 * Must call update_cfs_rq_load_avg() before this, since we rely on
 * cfs_rq->avg.last_update_time being current.
 */
3513
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3514
{
3515 3516 3517 3518 3519 3520 3521 3522 3523
	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
	 */
3524
	se->avg.last_update_time = cfs_rq->avg.last_update_time;
3525 3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542
	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;

3543
	enqueue_load_avg(cfs_rq, se);
3544 3545
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
3546 3547

	add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
3548

3549
	cfs_rq_util_change(cfs_rq, flags);
3550 3551
}

3552 3553 3554 3555 3556 3557 3558 3559
/**
 * 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.
 */
3560 3561
static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3562
	dequeue_load_avg(cfs_rq, se);
3563 3564
	sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
	sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3565 3566

	add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
3567

3568
	cfs_rq_util_change(cfs_rq, 0);
3569 3570
}

3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597
/*
 * 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)) {

3598 3599 3600 3601 3602 3603 3604 3605
		/*
		 * 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);
3606 3607 3608 3609 3610 3611
		update_tg_load_avg(cfs_rq, 0);

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

3612
#ifndef CONFIG_64BIT
3613 3614
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
3615
	u64 last_update_time_copy;
3616
	u64 last_update_time;
3617

3618 3619 3620 3621 3622
	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);
3623 3624 3625

	return last_update_time;
}
3626
#else
3627 3628 3629 3630
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.last_update_time;
}
3631 3632
#endif

3633 3634 3635 3636 3637 3638 3639 3640 3641 3642
/*
 * 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);
3643
	__update_load_avg_blocked_se(last_update_time, cpu_of(rq_of(cfs_rq)), se);
3644 3645
}

3646 3647 3648 3649 3650 3651 3652
/*
 * 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);
3653
	unsigned long flags;
3654 3655

	/*
3656 3657 3658 3659 3660 3661 3662
	 * 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.
3663 3664
	 */

3665
	sync_entity_load_avg(se);
3666 3667 3668 3669 3670

	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;
3671
	cfs_rq->removed.runnable_sum	+= se->avg.load_sum; /* == runnable_sum */
3672
	raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
3673
}
3674

3675 3676
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
{
3677
	return cfs_rq->avg.runnable_load_avg;
3678 3679 3680 3681 3682 3683 3684
}

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

3685
static int idle_balance(struct rq *this_rq, struct rq_flags *rf);
3686

3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713
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;
3714
	enqueued += (_task_util_est(p) | UTIL_AVG_UNCHANGED);
3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739
	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;

3740 3741 3742 3743
	/* 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));
3744 3745 3746 3747 3748 3749 3750 3751 3752
	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;

3753 3754 3755 3756 3757 3758 3759 3760
	/*
	 * 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;

3761 3762 3763 3764
	/*
	 * Skip update of task's estimated utilization when its EWMA is
	 * already ~1% close to its last activation value.
	 */
3765
	ue.enqueued = (task_util(p) | UTIL_AVG_UNCHANGED);
3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792
	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);
}

3793 3794
#else /* CONFIG_SMP */

3795 3796
#define UPDATE_TG	0x0
#define SKIP_AGE_LOAD	0x0
3797
#define DO_ATTACH	0x0
3798

3799
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
3800
{
3801
	cfs_rq_util_change(cfs_rq, 0);
3802 3803
}

3804
static inline void remove_entity_load_avg(struct sched_entity *se) {}
3805

3806
static inline void
3807
attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) {}
3808 3809 3810
static inline void
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}

3811
static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
3812 3813 3814 3815
{
	return 0;
}

3816 3817 3818 3819 3820 3821 3822
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) {}

3823
#endif /* CONFIG_SMP */
3824

P
Peter Zijlstra 已提交
3825 3826 3827 3828 3829 3830 3831 3832 3833
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)
3834
		schedstat_inc(cfs_rq->nr_spread_over);
P
Peter Zijlstra 已提交
3835 3836 3837
#endif
}

3838 3839 3840
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3841
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3842

3843 3844 3845 3846 3847 3848
	/*
	 * 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
3849
	if (initial && sched_feat(START_DEBIT))
3850
		vruntime += sched_vslice(cfs_rq, se);
3851

3852
	/* sleeps up to a single latency don't count. */
3853
	if (!initial) {
3854
		unsigned long thresh = sysctl_sched_latency;
3855

3856 3857 3858 3859 3860 3861
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3862

3863
		vruntime -= thresh;
3864 3865
	}

3866
	/* ensure we never gain time by being placed backwards. */
3867
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3868 3869
}

3870 3871
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883
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())  {
3884
		printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3885
			     "stat_blocked and stat_runtime require the "
3886
			     "kernel parameter schedstats=enable or "
3887 3888 3889 3890 3891
			     "kernel.sched_schedstats=1\n");
	}
#endif
}

3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909 3910

/*
 * 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)
 *
3911
 *	->migrate_task_rq_fair() (p->state == TASK_WAKING)
3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922
 *	  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.
 */

3923
static void
3924
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3925
{
3926 3927 3928
	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
	bool curr = cfs_rq->curr == se;

3929
	/*
3930 3931
	 * If we're the current task, we must renormalise before calling
	 * update_curr().
3932
	 */
3933
	if (renorm && curr)
3934 3935
		se->vruntime += cfs_rq->min_vruntime;

3936 3937
	update_curr(cfs_rq);

3938
	/*
3939 3940 3941 3942
	 * 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.
3943
	 */
3944 3945 3946
	if (renorm && !curr)
		se->vruntime += cfs_rq->min_vruntime;

3947 3948 3949 3950 3951 3952 3953 3954
	/*
	 * 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
	 */
3955
	update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
3956
	update_cfs_group(se);
3957
	enqueue_runnable_load_avg(cfs_rq, se);
3958
	account_entity_enqueue(cfs_rq, se);
3959

3960
	if (flags & ENQUEUE_WAKEUP)
3961
		place_entity(cfs_rq, se, 0);
3962

3963
	check_schedstat_required();
3964 3965
	update_stats_enqueue(cfs_rq, se, flags);
	check_spread(cfs_rq, se);
3966
	if (!curr)
3967
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3968
	se->on_rq = 1;
3969

3970
	if (cfs_rq->nr_running == 1) {
3971
		list_add_leaf_cfs_rq(cfs_rq);
3972 3973
		check_enqueue_throttle(cfs_rq);
	}
3974 3975
}

3976
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3977
{
3978 3979
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3980
		if (cfs_rq->last != se)
3981
			break;
3982 3983

		cfs_rq->last = NULL;
3984 3985
	}
}
P
Peter Zijlstra 已提交
3986

3987 3988 3989 3990
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3991
		if (cfs_rq->next != se)
3992
			break;
3993 3994

		cfs_rq->next = NULL;
3995
	}
P
Peter Zijlstra 已提交
3996 3997
}

3998 3999 4000 4001
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
4002
		if (cfs_rq->skip != se)
4003
			break;
4004 4005

		cfs_rq->skip = NULL;
4006 4007 4008
	}
}

P
Peter Zijlstra 已提交
4009 4010
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
4011 4012 4013 4014 4015
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
4016 4017 4018

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
4019 4020
}

4021
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4022

4023
static void
4024
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4025
{
4026 4027 4028 4029
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
4030 4031 4032 4033 4034 4035 4036 4037 4038

	/*
	 * 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.
	 */
4039
	update_load_avg(cfs_rq, se, UPDATE_TG);
4040
	dequeue_runnable_load_avg(cfs_rq, se);
4041

4042
	update_stats_dequeue(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
4043

P
Peter Zijlstra 已提交
4044
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
4045

4046
	if (se != cfs_rq->curr)
4047
		__dequeue_entity(cfs_rq, se);
4048
	se->on_rq = 0;
4049
	account_entity_dequeue(cfs_rq, se);
4050 4051

	/*
4052 4053 4054 4055
	 * 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.
4056
	 */
4057
	if (!(flags & DEQUEUE_SLEEP))
4058
		se->vruntime -= cfs_rq->min_vruntime;
4059

4060 4061 4062
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

4063
	update_cfs_group(se);
4064 4065 4066 4067 4068 4069 4070

	/*
	 * 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.
	 */
4071
	if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) != DEQUEUE_SAVE)
4072
		update_min_vruntime(cfs_rq);
4073 4074 4075 4076 4077
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
4078
static void
I
Ingo Molnar 已提交
4079
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4080
{
4081
	unsigned long ideal_runtime, delta_exec;
4082 4083
	struct sched_entity *se;
	s64 delta;
4084

P
Peter Zijlstra 已提交
4085
	ideal_runtime = sched_slice(cfs_rq, curr);
4086
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
4087
	if (delta_exec > ideal_runtime) {
4088
		resched_curr(rq_of(cfs_rq));
4089 4090 4091 4092 4093
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
4094 4095 4096 4097 4098 4099 4100 4101 4102 4103 4104
		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;

4105 4106
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
4107

4108 4109
	if (delta < 0)
		return;
4110

4111
	if (delta > ideal_runtime)
4112
		resched_curr(rq_of(cfs_rq));
4113 4114
}

4115
static void
4116
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
4117
{
4118 4119 4120 4121 4122 4123 4124
	/* '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.
		 */
4125
		update_stats_wait_end(cfs_rq, se);
4126
		__dequeue_entity(cfs_rq, se);
4127
		update_load_avg(cfs_rq, se, UPDATE_TG);
4128 4129
	}

4130
	update_stats_curr_start(cfs_rq, se);
4131
	cfs_rq->curr = se;
4132

I
Ingo Molnar 已提交
4133 4134 4135 4136 4137
	/*
	 * 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):
	 */
D
Dietmar Eggemann 已提交
4138 4139
	if (schedstat_enabled() &&
	    rq_of(cfs_rq)->cfs.load.weight >= 2*se->load.weight) {
4140 4141 4142
		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
4143
	}
4144

4145
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
4146 4147
}

4148 4149 4150
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

4151 4152 4153 4154 4155 4156 4157
/*
 * 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
 */
4158 4159
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4160
{
4161 4162 4163 4164 4165 4166 4167 4168 4169 4170 4171
	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 */
4172

4173 4174 4175 4176 4177
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
4178 4179 4180 4181 4182 4183 4184 4185 4186 4187
		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;
		}

4188 4189 4190
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
4191

4192 4193 4194 4195 4196 4197
	/*
	 * 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;

4198 4199 4200 4201 4202 4203
	/*
	 * 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;

4204
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
4205 4206

	return se;
4207 4208
}

4209
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4210

4211
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
4212 4213 4214 4215 4216 4217
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
4218
		update_curr(cfs_rq);
4219

4220 4221 4222
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

4223
	check_spread(cfs_rq, prev);
4224

4225
	if (prev->on_rq) {
4226
		update_stats_wait_start(cfs_rq, prev);
4227 4228
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
4229
		/* in !on_rq case, update occurred at dequeue */
4230
		update_load_avg(cfs_rq, prev, 0);
4231
	}
4232
	cfs_rq->curr = NULL;
4233 4234
}

4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 4256 4257 4258 4259 4260 4261 4262 4263 4264
DEFINE_STATIC_KEY_TRUE(sched_tick_update_load);

static void set_tick_update_load(bool enabled)
{
	if (enabled)
		static_branch_enable(&sched_tick_update_load);
	else
		static_branch_disable(&sched_tick_update_load);
}

int sysctl_tick_update_load(struct ctl_table *table, int write,
				void __user *buffer, size_t *lenp, loff_t *ppos)
{
	struct ctl_table t;
	int err;
	int state = static_branch_likely(&sched_tick_update_load);

	if (write && !capable(CAP_SYS_ADMIN))
		return -EPERM;

	t = *table;
	t.data = &state;
	err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
	if (err < 0)
		return err;
	if (write)
		set_tick_update_load(state);
	return err;
}

P
Peter Zijlstra 已提交
4265 4266
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
4267 4268
{
	/*
4269
	 * Update run-time statistics of the 'current'.
4270
	 */
4271
	update_curr(cfs_rq);
4272

4273 4274 4275 4276 4277 4278 4279
	if (static_branch_likely(&sched_tick_update_load)) {
		/*
		 * Ensure that runnable average is periodically updated.
		 */
		update_load_avg(cfs_rq, curr, UPDATE_TG);
		update_cfs_group(curr);
	}
4280

P
Peter Zijlstra 已提交
4281 4282 4283 4284 4285
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
4286
	if (queued) {
4287
		resched_curr(rq_of(cfs_rq));
4288 4289
		return;
	}
P
Peter Zijlstra 已提交
4290 4291 4292 4293 4294 4295 4296 4297
	/*
	 * 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
4298
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
4299
		check_preempt_tick(cfs_rq, curr);
4300 4301
}

4302 4303 4304 4305 4306 4307

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

#ifdef CONFIG_CFS_BANDWIDTH
4308

4309
#ifdef CONFIG_JUMP_LABEL
4310
static struct static_key __cfs_bandwidth_used;
4311 4312 4313

static inline bool cfs_bandwidth_used(void)
{
4314
	return static_key_false(&__cfs_bandwidth_used);
4315 4316
}

4317
void cfs_bandwidth_usage_inc(void)
4318
{
4319
	static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
4320 4321 4322 4323
}

void cfs_bandwidth_usage_dec(void)
{
4324
	static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
4325
}
4326
#else /* CONFIG_JUMP_LABEL */
4327 4328 4329 4330 4331
static bool cfs_bandwidth_used(void)
{
	return true;
}

4332 4333
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
4334
#endif /* CONFIG_JUMP_LABEL */
4335

4336 4337 4338 4339 4340 4341 4342 4343
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
4344 4345 4346 4347 4348 4349

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

P
Paul Turner 已提交
4350
/*
4351 4352 4353
 * 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
4354 4355 4356
 *
 * requires cfs_b->lock
 */
4357
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
4358
{
4359 4360
	if (cfs_b->quota != RUNTIME_INF)
		cfs_b->runtime = cfs_b->quota;
P
Paul Turner 已提交
4361 4362
}

4363 4364 4365 4366 4367
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

4368 4369 4370 4371
/* 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))
4372
		return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
4373

4374
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
4375 4376
}

4377 4378
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4379 4380 4381
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
4382
	u64 amount = 0, min_amount;
4383 4384 4385 4386 4387 4388 4389

	/* 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;
4390
	else {
P
Peter Zijlstra 已提交
4391
		start_cfs_bandwidth(cfs_b);
4392 4393 4394 4395 4396 4397

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
4398 4399 4400 4401
	}
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
4402 4403

	return cfs_rq->runtime_remaining > 0;
4404 4405
}

4406
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
4407 4408
{
	/* dock delta_exec before expiring quota (as it could span periods) */
4409
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
4410 4411

	if (likely(cfs_rq->runtime_remaining > 0))
4412 4413
		return;

4414 4415
	if (cfs_rq->throttled)
		return;
4416 4417 4418 4419 4420
	/*
	 * 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))
4421
		resched_curr(rq_of(cfs_rq));
4422 4423
}

4424
static __always_inline
4425
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4426
{
4427
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4428 4429 4430 4431 4432
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

4433 4434
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
4435
	return cfs_bandwidth_used() && cfs_rq->throttled;
4436 4437
}

4438 4439 4440
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
4441
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
4442 4443 4444 4445 4446 4447 4448 4449 4450 4451 4452 4453 4454 4455 4456 4457 4458 4459 4460 4461 4462 4463 4464 4465 4466 4467
}

/*
 * 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) {
4468
		/* adjust cfs_rq_clock_task() */
4469
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4470
					     cfs_rq->throttled_clock_task;
4471 4472 4473 4474 4475 4476 4477 4478 4479 4480
	}

	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)];

4481 4482
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
4483
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
4484 4485 4486 4487 4488
	cfs_rq->throttle_count++;

	return 0;
}

4489
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
4490 4491 4492 4493 4494
{
	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
4495
	bool empty;
4496 4497 4498

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

4499
	/* freeze hierarchy runnable averages while throttled */
4500 4501 4502
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
4503 4504 4505 4506 4507 4508 4509

	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;
4510 4511 4512
		if (dequeue) {
			if (se->my_q != cfs_rq)
				cgroup_idle_start(se);
4513
			dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);
4514
		}
4515 4516 4517 4518 4519 4520 4521
		qcfs_rq->h_nr_running -= task_delta;

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

	if (!se)
4522
		sub_nr_running(rq, task_delta);
4523 4524

	cfs_rq->throttled = 1;
4525
	cfs_rq->throttled_clock = rq_clock(rq);
4526
	raw_spin_lock(&cfs_b->lock);
4527
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4528

4529 4530
	/*
	 * Add to the _head_ of the list, so that an already-started
4531 4532
	 * 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.
4533
	 */
4534 4535 4536 4537
	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
4538 4539 4540 4541 4542 4543 4544 4545

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

4546 4547 4548
	raw_spin_unlock(&cfs_b->lock);
}

4549
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4550
{
4551
	struct cfs_rq *bottom_cfs_rq = cfs_rq;
4552 4553 4554 4555 4556 4557
	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;

4558
	se = cfs_rq->tg->se[cpu_of(rq)];
4559 4560

	cfs_rq->throttled = 0;
4561 4562 4563

	update_rq_clock(rq);

4564
	raw_spin_lock(&cfs_b->lock);
4565
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4566 4567 4568
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

4569 4570 4571
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

4572 4573 4574 4575 4576 4577 4578 4579 4580
	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);
4581 4582 4583
		if (enqueue) {
			if (se->my_q != bottom_cfs_rq)
				cgroup_idle_end(se);
4584
			enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP);
4585
		}
4586 4587 4588 4589 4590 4591 4592
		cfs_rq->h_nr_running += task_delta;

		if (cfs_rq_throttled(cfs_rq))
			break;
	}

	if (!se)
4593
		add_nr_running(rq, task_delta);
4594

4595
	/* Determine whether we need to wake up potentially idle CPU: */
4596
	if (rq->curr == rq->idle && rq->cfs.nr_running)
4597
		resched_curr(rq);
4598 4599
}

4600
static void distribute_cfs_runtime(struct cfs_bandwidth *cfs_b)
4601 4602
{
	struct cfs_rq *cfs_rq;
4603
	u64 runtime, remaining = 1;
4604 4605 4606 4607 4608

	rcu_read_lock();
	list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
				throttled_list) {
		struct rq *rq = rq_of(cfs_rq);
4609
		struct rq_flags rf;
4610

4611
		rq_lock(rq, &rf);
4612 4613 4614
		if (!cfs_rq_throttled(cfs_rq))
			goto next;

4615 4616 4617
		/* By the above check, this should never be true */
		SCHED_WARN_ON(cfs_rq->runtime_remaining > 0);

4618
		raw_spin_lock(&cfs_b->lock);
4619
		runtime = -cfs_rq->runtime_remaining + 1;
4620 4621 4622 4623 4624
		if (runtime > cfs_b->runtime)
			runtime = cfs_b->runtime;
		cfs_b->runtime -= runtime;
		remaining = cfs_b->runtime;
		raw_spin_unlock(&cfs_b->lock);
4625 4626 4627 4628 4629 4630 4631 4632

		cfs_rq->runtime_remaining += runtime;

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

next:
4633
		rq_unlock(rq, &rf);
4634 4635 4636 4637 4638 4639 4640

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

4641 4642 4643 4644 4645 4646 4647 4648
/*
 * 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)
{
4649
	int throttled;
4650 4651 4652

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
4653
		goto out_deactivate;
4654

4655
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4656
	cfs_b->nr_periods += overrun;
4657

4658 4659 4660 4661 4662 4663
	/*
	 * 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
4664 4665 4666

	__refill_cfs_bandwidth_runtime(cfs_b);

4667 4668 4669
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
4670
		return 0;
4671 4672
	}

4673 4674 4675
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

4676
	/*
4677
	 * This check is repeated as we release cfs_b->lock while we unthrottle.
4678
	 */
4679 4680
	while (throttled && cfs_b->runtime > 0 && !cfs_b->distribute_running) {
		cfs_b->distribute_running = 1;
4681 4682
		raw_spin_unlock(&cfs_b->lock);
		/* we can't nest cfs_b->lock while distributing bandwidth */
4683
		distribute_cfs_runtime(cfs_b);
4684 4685
		raw_spin_lock(&cfs_b->lock);

4686
		cfs_b->distribute_running = 0;
4687 4688
		throttled = !list_empty(&cfs_b->throttled_cfs_rq);
	}
4689

4690 4691 4692 4693 4694 4695 4696
	/*
	 * 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;
4697

4698 4699 4700 4701
	return 0;

out_deactivate:
	return 1;
4702
}
4703

4704 4705 4706 4707 4708 4709 4710
/* 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;

4711 4712 4713 4714
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4715
 * hrtimer base being cleared by hrtimer_start. In the case of
4716 4717
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
4718 4719 4720 4721 4722 4723 4724 4725 4726 4727 4728 4729 4730 4731 4732 4733 4734 4735 4736 4737 4738 4739 4740 4741 4742
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;

4743 4744 4745 4746 4747
	/* don't push forwards an existing deferred unthrottle */
	if (cfs_b->slack_started)
		return;
	cfs_b->slack_started = true;

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Peter Zijlstra 已提交
4748 4749 4750
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
4751 4752 4753 4754 4755 4756 4757 4758 4759 4760 4761 4762
}

/* 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);
4763
	if (cfs_b->quota != RUNTIME_INF) {
4764 4765 4766 4767 4768 4769 4770 4771 4772 4773 4774 4775 4776 4777 4778
		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)
{
4779 4780 4781
	if (!cfs_bandwidth_used())
		return;

4782
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4783 4784 4785 4786 4787 4788 4789 4790 4791 4792 4793 4794 4795 4796
		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 */
4797
	raw_spin_lock(&cfs_b->lock);
4798
	cfs_b->slack_started = false;
4799 4800 4801 4802 4803
	if (cfs_b->distribute_running) {
		raw_spin_unlock(&cfs_b->lock);
		return;
	}

4804 4805
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
4806
		return;
4807
	}
4808

4809
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4810
		runtime = cfs_b->runtime;
4811

4812 4813 4814
	if (runtime)
		cfs_b->distribute_running = 1;

4815 4816 4817 4818 4819
	raw_spin_unlock(&cfs_b->lock);

	if (!runtime)
		return;

4820
	distribute_cfs_runtime(cfs_b);
4821 4822

	raw_spin_lock(&cfs_b->lock);
4823
	cfs_b->distribute_running = 0;
4824 4825 4826
	raw_spin_unlock(&cfs_b->lock);
}

4827 4828 4829 4830 4831 4832 4833
/*
 * 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)
{
4834 4835 4836
	if (!cfs_bandwidth_used())
		return;

4837 4838 4839 4840 4841 4842 4843 4844 4845 4846 4847 4848 4849 4850
	/* 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);
}

4851 4852 4853 4854 4855 4856 4857 4858 4859 4860 4861 4862 4863 4864
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;
4865
	cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
4866 4867
}

4868
/* conditionally throttle active cfs_rq's from put_prev_entity() */
4869
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4870
{
4871
	if (!cfs_bandwidth_used())
4872
		return false;
4873

4874
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4875
		return false;
4876 4877 4878 4879 4880 4881

	/*
	 * 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))
4882
		return true;
4883 4884

	throttle_cfs_rq(cfs_rq);
4885
	return true;
4886
}
4887 4888 4889 4890 4891

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
4892

4893 4894 4895 4896 4897
	do_sched_cfs_slack_timer(cfs_b);

	return HRTIMER_NORESTART;
}

4898 4899
extern const u64 max_cfs_quota_period;

4900 4901 4902 4903 4904 4905
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;
4906
	int count = 0;
4907

4908
	raw_spin_lock(&cfs_b->lock);
4909
	for (;;) {
P
Peter Zijlstra 已提交
4910
		overrun = hrtimer_forward_now(timer, cfs_b->period);
4911 4912 4913
		if (!overrun)
			break;

4914 4915 4916
		if (++count > 3) {
			u64 new, old = ktime_to_ns(cfs_b->period);

4917 4918 4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935 4936 4937 4938
			/*
			 * 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));
			}
4939 4940 4941 4942 4943

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

4944 4945
		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
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Peter Zijlstra 已提交
4946 4947
	if (idle)
		cfs_b->period_active = 0;
4948
	raw_spin_unlock(&cfs_b->lock);
4949 4950 4951 4952 4953 4954 4955 4956 4957 4958 4959 4960

	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
4961
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4962 4963 4964
	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;
4965
	cfs_b->distribute_running = 0;
4966
	cfs_b->slack_started = false;
4967 4968 4969 4970 4971 4972 4973 4974
}

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
4975
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4976
{
P
Peter Zijlstra 已提交
4977
	lockdep_assert_held(&cfs_b->lock);
4978

4979 4980 4981 4982
	if (cfs_b->period_active)
		return;

	cfs_b->period_active = 1;
4983
	hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
4984
	hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
4985 4986 4987 4988
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4989 4990 4991 4992
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4993 4994 4995 4996
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

4997
/*
4998
 * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
4999 5000 5001 5002 5003 5004
 *
 * The race is harmless, since modifying bandwidth settings of unhooked group
 * bits doesn't do much.
 */

/* cpu online calback */
5005 5006
static void __maybe_unused update_runtime_enabled(struct rq *rq)
{
5007
	struct task_group *tg;
5008

5009 5010 5011 5012 5013 5014
	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)];
5015 5016 5017 5018 5019

		raw_spin_lock(&cfs_b->lock);
		cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
		raw_spin_unlock(&cfs_b->lock);
	}
5020
	rcu_read_unlock();
5021 5022
}

5023
/* cpu offline callback */
5024
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
5025
{
5026 5027 5028 5029 5030 5031 5032
	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)];
5033 5034 5035 5036 5037 5038 5039 5040

		if (!cfs_rq->runtime_enabled)
			continue;

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
5041
		cfs_rq->runtime_remaining = 1;
5042
		/*
5043
		 * Offline rq is schedulable till CPU is completely disabled
5044 5045 5046 5047
		 * in take_cpu_down(), so we prevent new cfs throttling here.
		 */
		cfs_rq->runtime_enabled = 0;

5048 5049 5050
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
5051
	rcu_read_unlock();
5052 5053 5054
}

#else /* CONFIG_CFS_BANDWIDTH */
5055 5056
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
5057
	return rq_clock_task(rq_of(cfs_rq));
5058 5059
}

5060
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
5061
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
5062
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
5063
static inline void sync_throttle(struct task_group *tg, int cpu) {}
5064
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5065 5066 5067 5068 5069

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
5070 5071 5072 5073 5074 5075 5076 5077 5078 5079 5080

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;
}
5081 5082 5083 5084 5085

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) {}
5086 5087
#endif

5088 5089 5090 5091 5092
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) {}
5093
static inline void update_runtime_enabled(struct rq *rq) {}
5094
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
5095 5096 5097

#endif /* CONFIG_CFS_BANDWIDTH */

5098 5099 5100 5101
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
5102 5103 5104 5105 5106 5107
#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);

5108
	SCHED_WARN_ON(task_rq(p) != rq);
P
Peter Zijlstra 已提交
5109

5110
	if (rq->cfs.h_nr_running > 1) {
P
Peter Zijlstra 已提交
5111 5112 5113 5114 5115 5116
		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)
5117
				resched_curr(rq);
P
Peter Zijlstra 已提交
5118 5119
			return;
		}
5120
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
5121 5122
	}
}
5123 5124 5125 5126 5127 5128 5129 5130 5131 5132

/*
 * 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;

5133
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
5134 5135 5136 5137 5138
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
5139
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
5140 5141 5142 5143
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
5144 5145 5146 5147

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
5148 5149
#endif

5150 5151 5152 5153 5154
/*
 * 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:
 */
5155
static void
5156
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5157 5158
{
	struct cfs_rq *cfs_rq;
5159
	struct sched_entity *se = &p->se;
5160

5161 5162 5163 5164 5165 5166 5167 5168
	/*
	 * 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);

5169 5170 5171 5172 5173 5174
	/*
	 * 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)
5175
		cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
5176

5177
	for_each_sched_entity(se) {
5178
		if (se->on_rq)
5179 5180
			break;
		cfs_rq = cfs_rq_of(se);
5181
		enqueue_entity(cfs_rq, se, flags);
5182

5183 5184 5185
		if (!entity_is_task(se))
			cgroup_idle_end(se);

5186 5187 5188 5189 5190
		/*
		 * 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.
5191
		 */
5192 5193 5194 5195 5196
		if (cfs_rq_throttled(cfs_rq)) {
#ifdef CONFIG_FAIR_GROUP_SCHED
			if (cfs_rq->nr_running == 1)
				cgroup_idle_end(se->parent);
#endif
5197
			break;
5198
		}
5199
		cfs_rq->h_nr_running++;
5200

5201
		flags = ENQUEUE_WAKEUP;
5202
	}
P
Peter Zijlstra 已提交
5203

P
Peter Zijlstra 已提交
5204
	for_each_sched_entity(se) {
5205
		cfs_rq = cfs_rq_of(se);
5206
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
5207

5208 5209 5210
		if (cfs_rq_throttled(cfs_rq))
			break;

5211
		update_load_avg(cfs_rq, se, UPDATE_TG);
5212
		update_cfs_group(se);
P
Peter Zijlstra 已提交
5213 5214
	}

Y
Yuyang Du 已提交
5215
	if (!se)
5216
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
5217

5218
	hrtick_update(rq);
5219 5220
}

5221 5222
static void set_next_buddy(struct sched_entity *se);

5223 5224 5225 5226 5227
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
5228
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5229 5230
{
	struct cfs_rq *cfs_rq;
5231
	struct sched_entity *se = &p->se;
5232
	int task_sleep = flags & DEQUEUE_SLEEP;
5233 5234 5235

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5236
		dequeue_entity(cfs_rq, se, flags);
5237

5238 5239 5240
		if (!entity_is_task(se))
			cgroup_idle_start(se);

5241 5242 5243 5244 5245 5246
		/*
		 * 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.
		*/
5247 5248 5249 5250 5251
		if (cfs_rq_throttled(cfs_rq)) {
#ifdef CONFIG_FAIR_GROUP_SCHED
			if (!cfs_rq->nr_running)
				cgroup_idle_start(se->parent);
#endif
5252
			break;
5253
		}
5254
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
5255

5256
		/* Don't dequeue parent if it has other entities besides us */
5257
		if (cfs_rq->load.weight) {
5258 5259
			/* Avoid re-evaluating load for this entity: */
			se = parent_entity(se);
5260 5261 5262 5263
			/*
			 * Bias pick_next to pick a task from this cfs_rq, as
			 * p is sleeping when it is within its sched_slice.
			 */
5264 5265
			if (task_sleep && se && !throttled_hierarchy(cfs_rq))
				set_next_buddy(se);
5266
			break;
5267
		}
5268
		flags |= DEQUEUE_SLEEP;
5269
	}
P
Peter Zijlstra 已提交
5270

P
Peter Zijlstra 已提交
5271
	for_each_sched_entity(se) {
5272
		cfs_rq = cfs_rq_of(se);
5273
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
5274

5275 5276 5277
		if (cfs_rq_throttled(cfs_rq))
			break;

5278
		update_load_avg(cfs_rq, se, UPDATE_TG);
5279
		update_cfs_group(se);
P
Peter Zijlstra 已提交
5280 5281
	}

Y
Yuyang Du 已提交
5282
	if (!se)
5283
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
5284

5285
	util_est_dequeue(&rq->cfs, p, task_sleep);
5286
	hrtick_update(rq);
5287 5288
}

5289
#ifdef CONFIG_SMP
5290 5291 5292 5293 5294

/* 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);

5295
#ifdef CONFIG_NO_HZ_COMMON
5296 5297 5298 5299

static struct {
	cpumask_var_t idle_cpus_mask;
	atomic_t nr_cpus;
5300
	int has_blocked;		/* Idle CPUS has blocked load */
5301
	unsigned long next_balance;     /* in jiffy units */
5302
	unsigned long next_blocked;	/* Next update of blocked load in jiffies */
5303 5304
} nohz ____cacheline_aligned;

5305
#endif /* CONFIG_NO_HZ_COMMON */
5306

5307
/* Used instead of source_load when we know the type == 0 */
5308
static unsigned long weighted_cpuload(struct rq *rq)
5309
{
5310
	return cfs_rq_runnable_load_avg(&rq->cfs);
5311 5312
}

5313
/*
5314
 * Return a low guess at the load of a migration-source CPU weighted
5315 5316 5317 5318 5319 5320 5321 5322
 * 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);
5323
	unsigned long total = weighted_cpuload(rq);
5324 5325 5326 5327 5328 5329 5330 5331

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

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

/*
5332
 * Return a high guess at the load of a migration-target CPU weighted
5333 5334 5335 5336 5337
 * according to the scheduling class and "nice" value.
 */
static unsigned long target_load(int cpu, int type)
{
	struct rq *rq = cpu_rq(cpu);
5338
	unsigned long total = weighted_cpuload(rq);
5339 5340 5341 5342 5343 5344 5345

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

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

5346
static unsigned long capacity_of(int cpu)
5347
{
5348
	return cpu_rq(cpu)->cpu_capacity;
5349 5350
}

5351 5352 5353 5354 5355
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

5356 5357 5358
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
5359
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
5360
	unsigned long load_avg = weighted_cpuload(rq);
5361 5362

	if (nr_running)
5363
		return load_avg / nr_running;
5364 5365 5366 5367

	return 0;
}

P
Peter Zijlstra 已提交
5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379 5380 5381 5382 5383 5384
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
5385 5386
/*
 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
P
Peter Zijlstra 已提交
5387
 *
M
Mike Galbraith 已提交
5388
 * A waker of many should wake a different task than the one last awakened
P
Peter Zijlstra 已提交
5389 5390 5391 5392 5393 5394 5395 5396 5397 5398 5399 5400
 * 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
5401
 */
5402 5403
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
5404 5405
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
5406
	int factor = this_cpu_read(sd_llc_size);
5407

M
Mike Galbraith 已提交
5408 5409 5410 5411 5412
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
5413 5414
}

5415
/*
5416 5417 5418
 * 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.
5419
 *
5420 5421
 * wake_affine_idle() - only considers 'now', it check if the waking CPU is
 *			cache-affine and is (or	will be) idle.
5422 5423 5424 5425
 *
 * wake_affine_weight() - considers the weight to reflect the average
 *			  scheduling latency of the CPUs. This seems to work
 *			  for the overloaded case.
5426
 */
5427
static int
5428
wake_affine_idle(int this_cpu, int prev_cpu, int sync)
5429
{
5430 5431 5432 5433 5434
	/*
	 * 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.
5435 5436 5437 5438 5439 5440
	 *
	 * 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.
5441
	 */
5442 5443
	if (available_idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
		return available_idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
5444

5445
	if (sync && cpu_rq(this_cpu)->nr_running == 1)
5446
		return this_cpu;
5447

5448
	return nr_cpumask_bits;
5449 5450
}

5451
static int
5452 5453
wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
		   int this_cpu, int prev_cpu, int sync)
5454 5455 5456 5457
{
	s64 this_eff_load, prev_eff_load;
	unsigned long task_load;

5458 5459 5460 5461 5462
	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);
5463 5464

	if (sync) {
5465 5466 5467 5468 5469 5470
		unsigned long current_load;

		if (sched_feat(WA_STATIC_WEIGHT))
			current_load = task_h_load_static(current);
		else
			current_load = task_h_load(current);
5471

5472
		if (current_load > this_eff_load)
5473
			return this_cpu;
5474

5475
		this_eff_load -= current_load;
5476 5477
	}

5478 5479 5480 5481
	if (sched_feat(WA_STATIC_WEIGHT))
		task_load = task_h_load_static(p);
	else
		task_load = task_h_load(p);
5482

5483 5484 5485 5486
	this_eff_load += task_load;
	if (sched_feat(WA_BIAS))
		this_eff_load *= 100;
	this_eff_load *= capacity_of(prev_cpu);
5487

5488 5489 5490 5491 5492
	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);
5493 5494 5495 5496
	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);
5497

5498 5499 5500 5501 5502 5503 5504 5505 5506 5507
	/*
	 * 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;
5508 5509
}

5510
static int wake_affine(struct sched_domain *sd, struct task_struct *p,
5511
		       int this_cpu, int prev_cpu, int sync)
5512
{
5513
	int target = nr_cpumask_bits;
5514

5515
	if (sched_feat(WA_IDLE))
5516
		target = wake_affine_idle(this_cpu, prev_cpu, sync);
5517

5518 5519
	if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
		target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
5520

5521
	schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5522 5523
	if (target == nr_cpumask_bits)
		return prev_cpu;
5524

5525 5526 5527
	schedstat_inc(sd->ttwu_move_affine);
	schedstat_inc(p->se.statistics.nr_wakeups_affine);
	return target;
5528 5529
}

5530
static unsigned long cpu_util_without(int cpu, struct task_struct *p);
5531

5532
static unsigned long capacity_spare_without(int cpu, struct task_struct *p)
5533
{
5534
	return max_t(long, capacity_of(cpu) - cpu_util_without(cpu, p), 0);
5535 5536
}

5537 5538 5539
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
5540 5541
 *
 * Assumes p is allowed on at least one CPU in sd.
5542 5543
 */
static struct sched_group *
P
Peter Zijlstra 已提交
5544
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5545
		  int this_cpu, int sd_flag)
5546
{
5547
	struct sched_group *idlest = NULL, *group = sd->groups;
5548
	struct sched_group *most_spare_sg = NULL;
5549 5550 5551
	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;
5552
	unsigned long most_spare = 0, this_spare = 0;
5553
	int load_idx = sd->forkexec_idx;
5554 5555 5556
	int imbalance_scale = 100 + (sd->imbalance_pct-100)/2;
	unsigned long imbalance = scale_load_down(NICE_0_LOAD) *
				(sd->imbalance_pct-100) / 100;
5557

5558 5559 5560
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

5561
	do {
5562 5563
		unsigned long load, avg_load, runnable_load;
		unsigned long spare_cap, max_spare_cap;
5564 5565
		int local_group;
		int i;
5566

5567
		/* Skip over this group if it has no CPUs allowed */
5568
		if (!cpumask_intersects(sched_group_span(group),
5569
					&p->cpus_allowed))
5570 5571 5572
			continue;

		local_group = cpumask_test_cpu(this_cpu,
5573
					       sched_group_span(group));
5574

5575 5576 5577 5578
		/*
		 * Tally up the load of all CPUs in the group and find
		 * the group containing the CPU with most spare capacity.
		 */
5579
		avg_load = 0;
5580
		runnable_load = 0;
5581
		max_spare_cap = 0;
5582

5583
		for_each_cpu(i, sched_group_span(group)) {
5584
			/* Bias balancing toward CPUs of our domain */
5585 5586 5587 5588 5589
			if (local_group)
				load = source_load(i, load_idx);
			else
				load = target_load(i, load_idx);

5590 5591 5592
			runnable_load += load;

			avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs);
5593

5594
			spare_cap = capacity_spare_without(i, p);
5595 5596 5597

			if (spare_cap > max_spare_cap)
				max_spare_cap = spare_cap;
5598 5599
		}

5600
		/* Adjust by relative CPU capacity of the group */
5601 5602 5603 5604
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
		runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
5605 5606

		if (local_group) {
5607 5608
			this_runnable_load = runnable_load;
			this_avg_load = avg_load;
5609 5610
			this_spare = max_spare_cap;
		} else {
5611 5612 5613
			if (min_runnable_load > (runnable_load + imbalance)) {
				/*
				 * The runnable load is significantly smaller
5614
				 * so we can pick this new CPU:
5615 5616 5617 5618 5619 5620 5621 5622
				 */
				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
5623
				 * blocked load into account through avg_load:
5624 5625
				 */
				min_avg_load = avg_load;
5626 5627 5628 5629 5630 5631 5632
				idlest = group;
			}

			if (most_spare < max_spare_cap) {
				most_spare = max_spare_cap;
				most_spare_sg = group;
			}
5633 5634 5635
		}
	} while (group = group->next, group != sd->groups);

5636 5637 5638 5639 5640 5641
	/*
	 * 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.
5642 5643 5644 5645
	 *
	 * 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.
5646
	 */
5647 5648 5649
	if (sd_flag & SD_BALANCE_FORK)
		goto skip_spare;

5650
	if (this_spare > task_util(p) / 2 &&
5651
	    imbalance_scale*this_spare > 100*most_spare)
5652
		return NULL;
5653 5654

	if (most_spare > task_util(p) / 2)
5655 5656
		return most_spare_sg;

5657
skip_spare:
5658 5659 5660
	if (!idlest)
		return NULL;

5661 5662 5663 5664 5665 5666 5667 5668 5669 5670 5671 5672
	/*
	 * 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;

5673
	if (min_runnable_load > (this_runnable_load + imbalance))
5674
		return NULL;
5675 5676 5677 5678 5679

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

5680 5681 5682 5683
	return idlest;
}

/*
5684
 * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
5685 5686
 */
static int
5687
find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5688 5689
{
	unsigned long load, min_load = ULONG_MAX;
5690 5691 5692 5693
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
5694 5695
	int i;

5696 5697
	/* Check if we have any choice: */
	if (group->group_weight == 1)
5698
		return cpumask_first(sched_group_span(group));
5699

5700
	/* Traverse only the allowed CPUs */
5701
	for_each_cpu_and(i, sched_group_span(group), &p->cpus_allowed) {
5702
		if (available_idle_cpu(i)) {
5703 5704 5705 5706 5707 5708 5709 5710 5711 5712 5713 5714 5715 5716 5717 5718 5719 5720 5721 5722 5723
			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;
			}
5724
		} else if (shallowest_idle_cpu == -1) {
5725
			load = weighted_cpuload(cpu_rq(i));
5726
			if (load < min_load) {
5727 5728 5729
				min_load = load;
				least_loaded_cpu = i;
			}
5730 5731 5732
		}
	}

5733
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5734
}
5735

5736 5737 5738
static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
				  int cpu, int prev_cpu, int sd_flag)
{
5739
	int new_cpu = cpu;
5740

5741 5742 5743
	if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed))
		return prev_cpu;

5744
	/*
5745 5746
	 * We need task's util for capacity_spare_without, sync it up to
	 * prev_cpu's last_update_time.
5747 5748 5749 5750
	 */
	if (!(sd_flag & SD_BALANCE_FORK))
		sync_entity_load_avg(&p->se);

5751 5752 5753 5754 5755 5756 5757 5758 5759 5760 5761 5762 5763 5764 5765 5766 5767
	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);
5768
		if (new_cpu == cpu) {
5769
			/* Now try balancing at a lower domain level of 'cpu': */
5770 5771 5772 5773
			sd = sd->child;
			continue;
		}

5774
		/* Now try balancing at a lower domain level of 'new_cpu': */
5775 5776 5777 5778 5779 5780 5781 5782 5783 5784 5785 5786 5787 5788
		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;
}

5789
#ifdef CONFIG_SCHED_SMT
5790
DEFINE_STATIC_KEY_FALSE(sched_smt_present);
5791
EXPORT_SYMBOL_GPL(sched_smt_present);
5792 5793 5794 5795 5796 5797 5798 5799 5800 5801 5802 5803 5804 5805 5806 5807 5808 5809 5810 5811 5812 5813 5814 5815 5816 5817 5818 5819

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
5820
void __update_idle_core(struct rq *rq)
5821 5822 5823 5824 5825 5826 5827 5828 5829 5830 5831 5832
{
	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;

5833
		if (!available_idle_cpu(cpu))
5834 5835 5836 5837 5838 5839 5840 5841 5842 5843 5844 5845 5846 5847 5848 5849
			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);
5850
	int core, cpu;
5851

P
Peter Zijlstra 已提交
5852 5853 5854
	if (!static_branch_likely(&sched_smt_present))
		return -1;

5855 5856 5857
	if (!test_idle_cores(target, false))
		return -1;

5858
	cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed);
5859

5860
	for_each_cpu_wrap(core, cpus, target) {
5861 5862 5863 5864
		bool idle = true;

		for_each_cpu(cpu, cpu_smt_mask(core)) {
			cpumask_clear_cpu(cpu, cpus);
5865
			if (!available_idle_cpu(cpu))
5866 5867 5868 5869 5870 5871 5872 5873 5874 5875 5876 5877 5878 5879 5880 5881 5882 5883 5884 5885 5886 5887
				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
5888 5889 5890
	if (!static_branch_likely(&sched_smt_present))
		return -1;

5891
	for_each_cpu(cpu, cpu_smt_mask(target)) {
5892
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
5893
			continue;
5894
		if (available_idle_cpu(cpu))
5895 5896 5897 5898 5899 5900 5901 5902 5903 5904 5905 5906 5907 5908 5909 5910 5911 5912 5913 5914 5915 5916 5917 5918
			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).
5919
 */
5920 5921
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
{
5922
	struct sched_domain *this_sd;
5923
	u64 avg_cost, avg_idle;
5924 5925
	u64 time, cost;
	s64 delta;
5926
	int cpu, nr = INT_MAX;
5927

5928 5929 5930 5931
	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
	if (!this_sd)
		return -1;

5932 5933 5934 5935
	/*
	 * Due to large variance we need a large fuzz factor; hackbench in
	 * particularly is sensitive here.
	 */
5936 5937 5938 5939
	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)
5940 5941
		return -1;

5942 5943 5944 5945 5946 5947 5948 5949
	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;
	}

5950 5951
	time = local_clock();

5952
	for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
5953 5954
		if (!--nr)
			return -1;
5955
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
5956
			continue;
5957
		if (available_idle_cpu(cpu))
5958 5959 5960 5961 5962 5963 5964 5965 5966 5967 5968 5969 5970
			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.
5971
 */
5972
static int select_idle_sibling(struct task_struct *p, int prev, int target)
5973
{
5974
	struct sched_domain *sd;
5975
	int i, recent_used_cpu;
5976

5977
	if (available_idle_cpu(target))
5978
		return target;
5979 5980

	/*
5981
	 * If the previous CPU is cache affine and idle, don't be stupid:
5982
	 */
5983
	if (prev != target && cpus_share_cache(prev, target) && available_idle_cpu(prev))
5984
		return prev;
5985

5986
	/* Check a recently used CPU as a potential idle candidate: */
5987 5988 5989 5990
	recent_used_cpu = p->recent_used_cpu;
	if (recent_used_cpu != prev &&
	    recent_used_cpu != target &&
	    cpus_share_cache(recent_used_cpu, target) &&
5991
	    available_idle_cpu(recent_used_cpu) &&
5992 5993 5994
	    cpumask_test_cpu(p->recent_used_cpu, &p->cpus_allowed)) {
		/*
		 * Replace recent_used_cpu with prev as it is a potential
5995
		 * candidate for the next wake:
5996 5997 5998 5999 6000
		 */
		p->recent_used_cpu = prev;
		return recent_used_cpu;
	}

6001
	sd = rcu_dereference(per_cpu(sd_llc, target));
6002 6003
	if (!sd)
		return target;
6004

6005 6006 6007
	i = select_idle_core(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;
6008

6009 6010 6011 6012 6013 6014 6015
	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;
6016

6017 6018
	return target;
}
6019

6020 6021 6022 6023 6024 6025 6026
/**
 * 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).
6027 6028 6029 6030 6031 6032 6033 6034 6035 6036
 *
 * 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.
 *
6037 6038 6039 6040 6041 6042 6043 6044
 * 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.
 *
6045 6046 6047 6048 6049 6050 6051 6052 6053 6054
 * 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).
6055 6056
 *
 * Return: the (estimated) utilization for the specified CPU
6057
 */
6058
static inline unsigned long cpu_util(int cpu)
6059
{
6060 6061 6062 6063 6064 6065 6066 6067
	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));
6068

6069
	return min_t(unsigned long, util, capacity_orig_of(cpu));
6070
}
6071

6072
/*
6073 6074 6075 6076 6077 6078 6079 6080 6081 6082 6083
 * 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.
6084
 */
6085
static unsigned long cpu_util_without(int cpu, struct task_struct *p)
6086
{
6087 6088
	struct cfs_rq *cfs_rq;
	unsigned int util;
6089 6090

	/* Task has no contribution or is new */
6091
	if (cpu != task_cpu(p) || !READ_ONCE(p->se.avg.last_update_time))
6092 6093
		return cpu_util(cpu);

6094 6095 6096
	cfs_rq = &cpu_rq(cpu)->cfs;
	util = READ_ONCE(cfs_rq->avg.util_avg);

6097
	/* Discount task's util from CPU's util */
6098
	util -= min_t(unsigned int, util, task_util(p));
6099

6100 6101 6102 6103 6104 6105
	/*
	 * 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:
6106
	 *      cpu_util_without = (cpu_util - task_util) = 0
6107 6108 6109 6110 6111 6112
	 *
	 * 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:
6113
	 *      cpu_util_without = (cpu_util - task_util) >= 0
6114 6115 6116 6117 6118 6119 6120 6121 6122 6123 6124 6125
	 *
	 * 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.
	 */
6126 6127 6128 6129 6130 6131 6132 6133 6134 6135 6136 6137 6138 6139 6140 6141 6142 6143 6144 6145 6146 6147 6148 6149 6150 6151 6152
	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);
	}
6153 6154 6155 6156 6157 6158 6159

	/*
	 * 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));
6160 6161
}

6162 6163 6164 6165 6166 6167 6168 6169 6170 6171 6172 6173 6174 6175 6176 6177 6178 6179
/*
 * 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;

6180 6181 6182
	/* Bring task utilization in sync with prev_cpu */
	sync_entity_load_avg(&p->se);

6183 6184 6185
	return min_cap * 1024 < task_util(p) * capacity_margin;
}

6186
/*
6187 6188 6189
 * 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.
6190
 *
6191 6192
 * 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.
6193
 *
6194
 * Returns the target CPU number.
6195 6196 6197
 *
 * preempt must be disabled.
 */
6198
static int
6199
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
6200
{
6201
	struct sched_domain *tmp, *sd = NULL;
6202
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
6203
	int new_cpu = prev_cpu;
6204
	int want_affine = 0;
6205
	int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
6206

P
Peter Zijlstra 已提交
6207 6208
	if (sd_flag & SD_BALANCE_WAKE) {
		record_wakee(p);
6209
		want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu)
6210
			      && cpumask_test_cpu(cpu, &p->cpus_allowed);
P
Peter Zijlstra 已提交
6211
	}
6212

6213
	rcu_read_lock();
6214
	for_each_domain(cpu, tmp) {
6215
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
6216
			break;
6217

6218
		/*
6219
		 * If both 'cpu' and 'prev_cpu' are part of this domain,
6220
		 * cpu is a valid SD_WAKE_AFFINE target.
6221
		 */
6222 6223
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
6224 6225 6226 6227
			if (cpu != prev_cpu)
				new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);

			sd = NULL; /* Prefer wake_affine over balance flags */
6228
			break;
6229
		}
6230

6231
		if (tmp->flags & sd_flag)
6232
			sd = tmp;
M
Mike Galbraith 已提交
6233 6234
		else if (!want_affine)
			break;
6235 6236
	}

6237 6238
	if (unlikely(sd)) {
		/* Slow path */
6239
		new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
6240 6241 6242 6243 6244 6245 6246
	} 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;
6247
	}
6248
	rcu_read_unlock();
6249

6250
	return new_cpu;
6251
}
6252

6253 6254
static void detach_entity_cfs_rq(struct sched_entity *se);

6255
/*
6256
 * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
6257
 * cfs_rq_of(p) references at time of call are still valid and identify the
6258
 * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6259
 */
6260
static void migrate_task_rq_fair(struct task_struct *p, int new_cpu)
6261
{
6262 6263 6264 6265 6266 6267 6268 6269 6270 6271 6272 6273 6274 6275 6276 6277 6278 6279 6280 6281 6282 6283 6284 6285 6286 6287
	/*
	 * 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;
	}

6288 6289 6290 6291 6292 6293 6294 6295 6296 6297 6298 6299 6300 6301 6302 6303 6304 6305 6306
	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);
	}
6307 6308 6309

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
6310 6311

	/* We have migrated, no longer consider this task hot */
6312
	p->se.exec_start = 0;
6313 6314

	update_scan_period(p, new_cpu);
6315
}
6316 6317 6318 6319 6320

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
6321 6322
#endif /* CONFIG_SMP */

6323
static unsigned long wakeup_gran(struct sched_entity *se)
6324 6325 6326 6327
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
6328 6329
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
6330 6331 6332 6333 6334 6335 6336 6337 6338
	 *
	 * 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.
6339
	 */
6340
	return calc_delta_fair(gran, se);
6341 6342
}

6343 6344 6345 6346 6347 6348 6349 6350 6351 6352 6353 6354 6355 6356 6357 6358 6359 6360 6361 6362 6363 6364
/*
 * 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;

6365
	gran = wakeup_gran(se);
6366 6367 6368 6369 6370 6371
	if (vdiff > gran)
		return 1;

	return 0;
}

6372 6373
static void set_last_buddy(struct sched_entity *se)
{
6374 6375 6376
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6377 6378 6379
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6380
		cfs_rq_of(se)->last = se;
6381
	}
6382 6383 6384 6385
}

static void set_next_buddy(struct sched_entity *se)
{
6386 6387 6388
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6389 6390 6391
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6392
		cfs_rq_of(se)->next = se;
6393
	}
6394 6395
}

6396 6397
static void set_skip_buddy(struct sched_entity *se)
{
6398 6399
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
6400 6401
}

6402 6403 6404
/*
 * Preempt the current task with a newly woken task if needed:
 */
6405
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
6406 6407
{
	struct task_struct *curr = rq->curr;
6408
	struct sched_entity *se = &curr->se, *pse = &p->se;
6409
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6410
	int scale = cfs_rq->nr_running >= sched_nr_latency;
6411
	int next_buddy_marked = 0;
6412

I
Ingo Molnar 已提交
6413 6414 6415
	if (unlikely(se == pse))
		return;

6416
	/*
6417
	 * This is possible from callers such as attach_tasks(), in which we
6418 6419 6420 6421 6422 6423 6424
	 * 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;

6425
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
6426
		set_next_buddy(pse);
6427 6428
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
6429

6430 6431 6432
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
6433 6434 6435 6436 6437 6438
	 *
	 * 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.
6439 6440 6441 6442
	 */
	if (test_tsk_need_resched(curr))
		return;

6443 6444 6445 6446 6447
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

6448
	/*
6449 6450
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
6451
	 */
6452
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
6453
		return;
6454

6455
	find_matching_se(&se, &pse);
6456
	update_curr(cfs_rq_of(se));
6457
	BUG_ON(!pse);
6458 6459 6460 6461 6462 6463 6464
	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);
6465
		goto preempt;
6466
	}
6467

6468
	return;
6469

6470
preempt:
6471
	resched_curr(rq);
6472 6473 6474 6475 6476 6477 6478 6479 6480 6481 6482 6483 6484 6485
	/*
	 * 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);
6486 6487
}

6488
static struct task_struct *
6489
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6490 6491 6492
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
6493
	struct task_struct *p;
6494
	int new_tasks;
6495

6496
again:
6497
	if (!cfs_rq->nr_running)
6498
		goto idle;
6499

6500
#ifdef CONFIG_FAIR_GROUP_SCHED
6501
	if (prev->sched_class != &fair_sched_class)
6502 6503 6504 6505 6506 6507 6508 6509 6510 6511 6512 6513 6514 6515 6516 6517 6518 6519 6520
		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.
		 */
6521 6522 6523 6524 6525
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
6526

6527 6528 6529
			/*
			 * This call to check_cfs_rq_runtime() will do the
			 * throttle and dequeue its entity in the parent(s).
6530
			 * Therefore the nr_running test will indeed
6531 6532
			 * be correct.
			 */
6533 6534 6535 6536 6537 6538
			if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
				cfs_rq = &rq->cfs;

				if (!cfs_rq->nr_running)
					goto idle;

6539
				goto simple;
6540
			}
6541
		}
6542 6543 6544 6545 6546 6547 6548 6549 6550 6551 6552 6553 6554 6555 6556 6557 6558 6559 6560 6561 6562 6563 6564 6565 6566 6567 6568 6569 6570 6571 6572 6573 6574

		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);
	}

6575
	goto done;
6576 6577
simple:
#endif
6578

6579
	put_prev_task(rq, prev);
6580

6581
	do {
6582
		se = pick_next_entity(cfs_rq, NULL);
6583
		set_next_entity(cfs_rq, se);
6584 6585 6586
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
6587
	p = task_of(se);
6588

6589
done: __maybe_unused;
6590 6591 6592 6593 6594 6595 6596 6597 6598
#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

6599 6600
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
6601 6602

	return p;
6603 6604

idle:
6605 6606
	new_tasks = idle_balance(rq, rf);

6607 6608 6609 6610 6611
	/*
	 * 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.
	 */
6612
	if (new_tasks < 0)
6613 6614
		return RETRY_TASK;

6615
	if (new_tasks > 0)
6616 6617 6618
		goto again;

	return NULL;
6619 6620 6621 6622 6623
}

/*
 * Account for a descheduled task:
 */
6624
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
6625 6626 6627 6628 6629 6630
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
6631
		put_prev_entity(cfs_rq, se);
6632 6633 6634
	}
}

6635 6636 6637 6638 6639 6640 6641 6642 6643 6644 6645 6646 6647 6648 6649 6650 6651 6652 6653 6654 6655 6656 6657 6658 6659
/*
 * 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);
6660 6661 6662 6663 6664
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
6665
		rq_clock_skip_update(rq);
6666 6667 6668 6669 6670
	}

	set_skip_buddy(se);
}

6671 6672 6673 6674
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

6675 6676
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
6677 6678 6679 6680 6681 6682 6683 6684 6685 6686
		return false;

	/* Tell the scheduler that we'd really like pse to run next. */
	set_next_buddy(se);

	yield_task_fair(rq);

	return true;
}

6687
#ifdef CONFIG_SMP
6688
/**************************************************
P
Peter Zijlstra 已提交
6689 6690 6691 6692 6693
 * Fair scheduling class load-balancing methods.
 *
 * BASICS
 *
 * The purpose of load-balancing is to achieve the same basic fairness the
6694
 * per-CPU scheduler provides, namely provide a proportional amount of compute
P
Peter Zijlstra 已提交
6695 6696 6697 6698
 * 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)
 *
6699
 * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
P
Peter Zijlstra 已提交
6700 6701 6702 6703
 * W_i,0 is defined as:
 *
 *   W_i,0 = \Sum_j w_i,j                                             (2)
 *
6704
 * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
6705
 * is derived from the nice value as per sched_prio_to_weight[].
P
Peter Zijlstra 已提交
6706 6707 6708 6709 6710 6711
 *
 * 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)
 *
6712
 * C_i is the compute capacity of CPU i, typically it is the
P
Peter Zijlstra 已提交
6713 6714 6715 6716 6717 6718
 * 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):
 *
6719
 *   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
6720 6721 6722 6723 6724 6725 6726 6727 6728 6729 6730 6731 6732
 *
 * 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)
6733
 * for all i,j solution, we create a tree of CPUs that follows the hardware
P
Peter Zijlstra 已提交
6734
 * topology where each level pairs two lower groups (or better). This results
6735
 * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
P
Peter Zijlstra 已提交
6736
 * tree to only the first of the previous level and we decrease the frequency
6737
 * of load-balance at each level inv. proportional to the number of CPUs in
P
Peter Zijlstra 已提交
6738 6739 6740 6741 6742 6743 6744 6745
 * 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
6746
 *         |         |     `- number of CPUs doing load-balance
P
Peter Zijlstra 已提交
6747 6748 6749 6750 6751 6752 6753
 *         |         `- 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
6754
 * to every other CPU in at most O(log n) steps:
P
Peter Zijlstra 已提交
6755 6756 6757
 *
 * The adjacency matrix of the resulting graph is given by:
 *
6758
 *             log_2 n
P
Peter Zijlstra 已提交
6759 6760 6761 6762 6763 6764 6765
 *   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)
 *
6766
 * Showing there's indeed a path between every CPU in at most O(log n) steps.
P
Peter Zijlstra 已提交
6767 6768 6769 6770 6771 6772 6773 6774 6775
 * 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
6776
 * balancing is more aggressive and has the newly idle CPU iterate up the domain
P
Peter Zijlstra 已提交
6777 6778 6779 6780 6781 6782 6783 6784 6785 6786 6787 6788 6789 6790 6791 6792 6793 6794 6795 6796
 * 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)
 *
6797
 * 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
6798 6799 6800 6801 6802 6803
 *
 * 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.]
6804
 */
6805

6806 6807
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

6808 6809
enum fbq_type { regular, remote, all };

6810
#define LBF_ALL_PINNED	0x01
6811
#define LBF_NEED_BREAK	0x02
6812 6813
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
6814
#define LBF_NOHZ_STATS	0x10
6815
#define LBF_NOHZ_AGAIN	0x20
6816 6817 6818 6819 6820

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
6821
	int			src_cpu;
6822 6823 6824 6825

	int			dst_cpu;
	struct rq		*dst_rq;

6826 6827
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
6828
	enum cpu_idle_type	idle;
6829
	long			imbalance;
6830 6831 6832
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

6833
	unsigned int		flags;
6834 6835 6836 6837

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
6838 6839

	enum fbq_type		fbq_type;
6840
	struct list_head	tasks;
6841 6842
};

6843 6844 6845
/*
 * Is this task likely cache-hot:
 */
6846
static int task_hot(struct task_struct *p, struct lb_env *env)
6847 6848 6849
{
	s64 delta;

6850 6851
	lockdep_assert_held(&env->src_rq->lock);

6852 6853 6854 6855 6856 6857 6858 6859 6860
	if (p->sched_class != &fair_sched_class)
		return 0;

	if (unlikely(p->policy == SCHED_IDLE))
		return 0;

	/*
	 * Buddy candidates are cache hot:
	 */
6861
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6862 6863 6864 6865 6866 6867 6868 6869 6870
			(&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;

6871
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6872 6873 6874 6875

	return delta < (s64)sysctl_sched_migration_cost;
}

6876
#ifdef CONFIG_NUMA_BALANCING
6877
/*
6878 6879 6880
 * 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.
6881
 */
6882
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6883
{
6884
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
6885 6886
	unsigned long src_weight, dst_weight;
	int src_nid, dst_nid, dist;
6887

6888
	if (!static_branch_likely(&sched_numa_balancing))
6889 6890
		return -1;

6891
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6892
		return -1;
6893 6894 6895 6896

	src_nid = cpu_to_node(env->src_cpu);
	dst_nid = cpu_to_node(env->dst_cpu);

6897
	if (src_nid == dst_nid)
6898
		return -1;
6899

6900 6901 6902 6903 6904 6905 6906
	/* 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;
	}
6907

6908 6909
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
6910
		return 0;
6911

6912
	/* Leaving a core idle is often worse than degrading locality. */
6913
	if (env->idle == CPU_IDLE)
6914 6915
		return -1;

6916
	dist = node_distance(src_nid, dst_nid);
6917
	if (numa_group) {
6918 6919
		src_weight = group_weight(p, src_nid, dist);
		dst_weight = group_weight(p, dst_nid, dist);
6920
	} else {
6921 6922
		src_weight = task_weight(p, src_nid, dist);
		dst_weight = task_weight(p, dst_nid, dist);
6923 6924
	}

6925
	return dst_weight < src_weight;
6926 6927
}

6928
#else
6929
static inline int migrate_degrades_locality(struct task_struct *p,
6930 6931
					     struct lb_env *env)
{
6932
	return -1;
6933
}
6934 6935
#endif

6936 6937 6938 6939
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
6940
int can_migrate_task(struct task_struct *p, struct lb_env *env)
6941
{
6942
	int tsk_cache_hot;
6943 6944 6945

	lockdep_assert_held(&env->src_rq->lock);

6946 6947
	/*
	 * We do not migrate tasks that are:
6948
	 * 1) throttled_lb_pair, or
6949
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6950 6951
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
6952
	 */
6953 6954 6955
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

6956
	if (!cpumask_test_cpu(env->dst_cpu, &p->cpus_allowed)) {
6957
		int cpu;
6958

6959
		schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
6960

6961 6962
		env->flags |= LBF_SOME_PINNED;

6963
		/*
6964
		 * Remember if this task can be migrated to any other CPU in
6965 6966 6967
		 * our sched_group. We may want to revisit it if we couldn't
		 * meet load balance goals by pulling other tasks on src_cpu.
		 *
6968 6969
		 * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
		 * already computed one in current iteration.
6970
		 */
6971
		if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED))
6972 6973
			return 0;

6974
		/* Prevent to re-select dst_cpu via env's CPUs: */
6975
		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
6976
			if (cpumask_test_cpu(cpu, &p->cpus_allowed)) {
6977
				env->flags |= LBF_DST_PINNED;
6978 6979 6980
				env->new_dst_cpu = cpu;
				break;
			}
6981
		}
6982

6983 6984
		return 0;
	}
6985 6986

	/* Record that we found atleast one task that could run on dst_cpu */
6987
	env->flags &= ~LBF_ALL_PINNED;
6988

6989
	if (task_running(env->src_rq, p)) {
6990
		schedstat_inc(p->se.statistics.nr_failed_migrations_running);
6991 6992 6993 6994 6995
		return 0;
	}

	/*
	 * Aggressive migration if:
6996 6997 6998
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
6999
	 */
7000 7001 7002
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
7003

7004
	if (tsk_cache_hot <= 0 ||
7005
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
7006
		if (tsk_cache_hot == 1) {
7007 7008
			schedstat_inc(env->sd->lb_hot_gained[env->idle]);
			schedstat_inc(p->se.statistics.nr_forced_migrations);
7009
		}
7010 7011 7012
		return 1;
	}

7013
	schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
Z
Zhang Hang 已提交
7014
	return 0;
7015 7016
}

7017
/*
7018 7019 7020 7021 7022 7023 7024
 * 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;
7025
	deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
7026 7027 7028
	set_task_cpu(p, env->dst_cpu);
}

7029
/*
7030
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
7031 7032
 * part of active balancing operations within "domain".
 *
7033
 * Returns a task if successful and NULL otherwise.
7034
 */
7035
static struct task_struct *detach_one_task(struct lb_env *env)
7036
{
7037
	struct task_struct *p;
7038

7039 7040
	lockdep_assert_held(&env->src_rq->lock);

7041 7042
	list_for_each_entry_reverse(p,
			&env->src_rq->cfs_tasks, se.group_node) {
7043 7044
		if (!can_migrate_task(p, env))
			continue;
7045

7046
		detach_task(p, env);
7047

7048
		/*
7049
		 * Right now, this is only the second place where
7050
		 * lb_gained[env->idle] is updated (other is detach_tasks)
7051
		 * so we can safely collect stats here rather than
7052
		 * inside detach_tasks().
7053
		 */
7054
		schedstat_inc(env->sd->lb_gained[env->idle]);
7055
		return p;
7056
	}
7057
	return NULL;
7058 7059
}

7060 7061
static const unsigned int sched_nr_migrate_break = 32;

7062
/*
7063 7064
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
7065
 *
7066
 * Returns number of detached tasks if successful and 0 otherwise.
7067
 */
7068
static int detach_tasks(struct lb_env *env)
7069
{
7070 7071
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
7072
	unsigned long load;
7073 7074 7075
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
7076

7077
	if (env->imbalance <= 0)
7078
		return 0;
7079

7080
	while (!list_empty(tasks)) {
7081 7082 7083 7084 7085 7086 7087
		/*
		 * 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;

7088
		p = list_last_entry(tasks, struct task_struct, se.group_node);
7089

7090 7091
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
7092
		if (env->loop > env->loop_max)
7093
			break;
7094 7095

		/* take a breather every nr_migrate tasks */
7096
		if (env->loop > env->loop_break) {
7097
			env->loop_break += sched_nr_migrate_break;
7098
			env->flags |= LBF_NEED_BREAK;
7099
			break;
7100
		}
7101

7102
		if (!can_migrate_task(p, env))
7103 7104 7105
			goto next;

		load = task_h_load(p);
7106

7107
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
7108 7109
			goto next;

7110
		if ((load / 2) > env->imbalance)
7111
			goto next;
7112

7113 7114 7115 7116
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
7117
		env->imbalance -= load;
7118 7119

#ifdef CONFIG_PREEMPT
7120 7121
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
7122
		 * kernels will stop after the first task is detached to minimize
7123 7124
		 * the critical section.
		 */
7125
		if (env->idle == CPU_NEWLY_IDLE)
7126
			break;
7127 7128
#endif

7129 7130 7131 7132
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
7133
		if (env->imbalance <= 0)
7134
			break;
7135 7136 7137

		continue;
next:
7138
		list_move(&p->se.group_node, tasks);
7139
	}
7140

7141
	/*
7142 7143 7144
	 * 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().
7145
	 */
7146
	schedstat_add(env->sd->lb_gained[env->idle], detached);
7147

7148 7149 7150 7151 7152 7153 7154 7155 7156 7157 7158
	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);
7159
	activate_task(rq, p, ENQUEUE_NOCLOCK);
7160
	p->on_rq = TASK_ON_RQ_QUEUED;
7161 7162 7163 7164 7165 7166 7167 7168 7169
	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)
{
7170 7171 7172
	struct rq_flags rf;

	rq_lock(rq, &rf);
7173
	update_rq_clock(rq);
7174
	attach_task(rq, p);
7175
	rq_unlock(rq, &rf);
7176 7177 7178 7179 7180 7181 7182 7183 7184 7185
}

/*
 * 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;
7186
	struct rq_flags rf;
7187

7188
	rq_lock(env->dst_rq, &rf);
7189
	update_rq_clock(env->dst_rq);
7190 7191 7192 7193

	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
		list_del_init(&p->se.group_node);
7194

7195 7196 7197
		attach_task(env->dst_rq, p);
	}

7198
	rq_unlock(env->dst_rq, &rf);
7199 7200
}

7201 7202 7203 7204 7205 7206 7207 7208 7209 7210 7211
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;
}

7212
static inline bool others_have_blocked(struct rq *rq)
7213 7214 7215 7216
{
	if (READ_ONCE(rq->avg_rt.util_avg))
		return true;

7217 7218 7219
	if (READ_ONCE(rq->avg_dl.util_avg))
		return true;

7220
#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
7221 7222 7223 7224
	if (READ_ONCE(rq->avg_irq.util_avg))
		return true;
#endif

7225 7226 7227
	return false;
}

7228
#ifdef CONFIG_FAIR_GROUP_SCHED
7229 7230 7231 7232 7233 7234 7235 7236 7237 7238 7239 7240 7241 7242 7243 7244 7245 7246 7247 7248 7249 7250 7251 7252 7253 7254 7255 7256 7257
DEFINE_STATIC_KEY_TRUE(sched_blocked_averages);

static void set_blocked_averages(bool enabled)
{
	if (enabled)
		static_branch_enable(&sched_blocked_averages);
	else
		static_branch_disable(&sched_blocked_averages);
}

int sysctl_blocked_averages(struct ctl_table *table, int write,
				void __user *buffer, size_t *lenp, loff_t *ppos)
{
	struct ctl_table t;
	int err;
	int state = static_branch_likely(&sched_blocked_averages);

	if (write && !capable(CAP_SYS_ADMIN))
		return -EPERM;

	t = *table;
	t.data = &state;
	err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
	if (err < 0)
		return err;
	if (write)
		set_blocked_averages(state);
	return err;
}
7258

7259
static void update_blocked_averages(int cpu)
7260 7261
{
	struct rq *rq = cpu_rq(cpu);
7262
	struct cfs_rq *cfs_rq;
7263
	const struct sched_class *curr_class;
7264
	struct rq_flags rf;
7265
	bool done = true;
7266

7267 7268 7269
	if (!static_branch_unlikely(&sched_blocked_averages))
		return;

7270
	rq_lock_irqsave(rq, &rf);
7271
	update_rq_clock(rq);
7272

7273 7274 7275 7276
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
7277
	for_each_leaf_cfs_rq(rq, cfs_rq) {
7278 7279
		struct sched_entity *se;

7280 7281 7282
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
7283

7284
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
7285
			update_tg_load_avg(cfs_rq, 0);
7286

7287 7288 7289
		/* Propagate pending load changes to the parent, if any: */
		se = cfs_rq->tg->se[cpu];
		if (se && !skip_blocked_update(se))
7290
			update_load_avg(cfs_rq_of(se), se, 0);
7291

7292 7293
		/* Don't need periodic decay once load/util_avg are null */
		if (cfs_rq_has_blocked(cfs_rq))
7294
			done = false;
7295
	}
7296 7297 7298 7299

	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);
7300
	update_irq_load_avg(rq, 0);
7301
	/* Don't need periodic decay once load/util_avg are null */
7302
	if (others_have_blocked(rq))
7303
		done = false;
7304 7305 7306

#ifdef CONFIG_NO_HZ_COMMON
	rq->last_blocked_load_update_tick = jiffies;
7307 7308
	if (done)
		rq->has_blocked_load = 0;
7309
#endif
7310
	rq_unlock_irqrestore(rq, &rf);
7311 7312
}

7313
/*
7314
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
7315 7316 7317
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
7318
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
7319
{
7320 7321
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
7322
	unsigned long now = jiffies;
7323
	unsigned long load;
7324

7325
	if (cfs_rq->last_h_load_update == now)
7326 7327
		return;

7328
	WRITE_ONCE(cfs_rq->h_load_next, NULL);
7329 7330
	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
7331
		WRITE_ONCE(cfs_rq->h_load_next, se);
7332 7333 7334
		if (cfs_rq->last_h_load_update == now)
			break;
	}
7335

7336
	if (!se) {
7337
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
7338 7339 7340
		cfs_rq->last_h_load_update = now;
	}

7341
	while ((se = READ_ONCE(cfs_rq->h_load_next)) != NULL) {
7342
		load = cfs_rq->h_load;
7343 7344
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
7345 7346 7347 7348
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
7349 7350
}

7351
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
7352
{
7353
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
7354

7355
	update_cfs_rq_h_load(cfs_rq);
7356
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
7357
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
7358
}
7359 7360 7361 7362 7363 7364 7365 7366 7367 7368 7369 7370 7371 7372 7373 7374 7375 7376 7377 7378 7379 7380 7381 7382 7383 7384 7385 7386 7387 7388 7389 7390 7391 7392 7393 7394 7395 7396 7397 7398 7399 7400

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
7401
#else
7402
static inline void update_blocked_averages(int cpu)
7403
{
7404 7405 7406
	if (!static_key_true(&sched_blocked_averages))
		return;

7407 7408
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
7409
	const struct sched_class *curr_class;
7410
	struct rq_flags rf;
7411

7412
	rq_lock_irqsave(rq, &rf);
7413
	update_rq_clock(rq);
7414
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
7415 7416 7417 7418

	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);
7419
	update_irq_load_avg(rq, 0);
7420 7421
#ifdef CONFIG_NO_HZ_COMMON
	rq->last_blocked_load_update_tick = jiffies;
7422
	if (!cfs_rq_has_blocked(cfs_rq) && !others_have_blocked(rq))
7423
		rq->has_blocked_load = 0;
7424
#endif
7425
	rq_unlock_irqrestore(rq, &rf);
7426 7427
}

7428
static unsigned long task_h_load(struct task_struct *p)
7429
{
7430
	return p->se.avg.load_avg;
7431
}
7432 7433 7434 7435 7436

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
7437
#endif
7438 7439

/********** Helpers for find_busiest_group ************************/
7440 7441 7442 7443 7444 7445 7446

enum group_type {
	group_other = 0,
	group_imbalanced,
	group_overloaded,
};

7447 7448 7449 7450 7451 7452 7453
/*
 * 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
7454
	unsigned long load_per_task;
7455
	unsigned long group_capacity;
7456
	unsigned long group_util; /* Total utilization of the group */
7457 7458 7459
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
7460
	enum group_type group_type;
7461
	int group_no_capacity;
7462 7463 7464 7465
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
7466 7467
};

J
Joonsoo Kim 已提交
7468 7469 7470 7471 7472 7473 7474
/*
 * 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 */
7475
	unsigned long total_running;
J
Joonsoo Kim 已提交
7476
	unsigned long total_load;	/* Total load of all groups in sd */
7477
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
7478 7479 7480
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
7481
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
7482 7483
};

7484 7485 7486 7487 7488 7489 7490 7491 7492 7493 7494
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,
7495
		.total_running = 0UL,
7496
		.total_load = 0UL,
7497
		.total_capacity = 0UL,
7498 7499
		.busiest_stat = {
			.avg_load = 0UL,
7500 7501
			.sum_nr_running = 0,
			.group_type = group_other,
7502 7503 7504 7505
		},
	};
}

7506 7507 7508
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
7509
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
7510 7511
 *
 * Return: The load index.
7512 7513 7514 7515 7516 7517 7518 7519 7520 7521 7522 7523 7524 7525 7526 7527 7528 7529 7530 7531 7532 7533
 */
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;
}

7534
static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu)
7535 7536
{
	struct rq *rq = cpu_rq(cpu);
7537
	unsigned long max = arch_scale_cpu_capacity(sd, cpu);
7538 7539
	unsigned long used, free;
	unsigned long irq;
7540

7541
	irq = cpu_util_irq(rq);
7542

7543 7544
	if (unlikely(irq >= max))
		return 1;
7545

7546 7547
	used = READ_ONCE(rq->avg_rt.util_avg);
	used += READ_ONCE(rq->avg_dl.util_avg);
7548

7549 7550
	if (unlikely(used >= max))
		return 1;
7551

7552
	free = max - used;
7553 7554

	return scale_irq_capacity(free, irq, max);
7555 7556
}

7557
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
7558
{
7559
	unsigned long capacity = scale_rt_capacity(sd, cpu);
7560 7561
	struct sched_group *sdg = sd->groups;

7562
	cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(sd, cpu);
7563

7564 7565
	if (!capacity)
		capacity = 1;
7566

7567 7568
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
7569
	sdg->sgc->min_capacity = capacity;
7570 7571
}

7572
void update_group_capacity(struct sched_domain *sd, int cpu)
7573 7574 7575
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
7576
	unsigned long capacity, min_capacity;
7577 7578 7579 7580
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
7581
	sdg->sgc->next_update = jiffies + interval;
7582 7583

	if (!child) {
7584
		update_cpu_capacity(sd, cpu);
7585 7586 7587
		return;
	}

7588
	capacity = 0;
7589
	min_capacity = ULONG_MAX;
7590

P
Peter Zijlstra 已提交
7591 7592 7593 7594 7595 7596
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

7597
		for_each_cpu(cpu, sched_group_span(sdg)) {
7598
			struct sched_group_capacity *sgc;
7599
			struct rq *rq = cpu_rq(cpu);
7600

7601
			/*
7602
			 * build_sched_domains() -> init_sched_groups_capacity()
7603 7604 7605
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
7606 7607
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
7608
			 *
7609
			 * This avoids capacity from being 0 and
7610 7611 7612
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
7613
				capacity += capacity_of(cpu);
7614 7615 7616
			} else {
				sgc = rq->sd->groups->sgc;
				capacity += sgc->capacity;
7617
			}
7618

7619
			min_capacity = min(capacity, min_capacity);
7620
		}
P
Peter Zijlstra 已提交
7621 7622 7623 7624
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
7625
		 */
P
Peter Zijlstra 已提交
7626 7627 7628

		group = child->groups;
		do {
7629 7630 7631 7632
			struct sched_group_capacity *sgc = group->sgc;

			capacity += sgc->capacity;
			min_capacity = min(sgc->min_capacity, min_capacity);
P
Peter Zijlstra 已提交
7633 7634 7635
			group = group->next;
		} while (group != child->groups);
	}
7636

7637
	sdg->sgc->capacity = capacity;
7638
	sdg->sgc->min_capacity = min_capacity;
7639 7640
}

7641
/*
7642 7643 7644
 * 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
7645 7646
 */
static inline int
7647
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
7648
{
7649 7650
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
7651 7652
}

7653 7654
/*
 * Group imbalance indicates (and tries to solve) the problem where balancing
7655
 * groups is inadequate due to ->cpus_allowed constraints.
7656
 *
7657 7658
 * 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.
7659 7660
 * Something like:
 *
7661 7662
 *	{ 0 1 2 3 } { 4 5 6 7 }
 *	        *     * * *
7663 7664 7665
 *
 * 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
7666
 * cpu 3 and leave one of the CPUs in the second group unused.
7667 7668
 *
 * The current solution to this issue is detecting the skew in the first group
7669 7670
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
7671 7672
 *
 * When this is so detected; this group becomes a candidate for busiest; see
7673
 * update_sd_pick_busiest(). And calculate_imbalance() and
7674
 * find_busiest_group() avoid some of the usual balance conditions to allow it
7675 7676 7677 7678 7679 7680 7681
 * 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.
 */

7682
static inline int sg_imbalanced(struct sched_group *group)
7683
{
7684
	return group->sgc->imbalance;
7685 7686
}

7687
/*
7688 7689 7690
 * 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
7691 7692
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
7693 7694 7695 7696 7697
 * 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.
7698
 */
7699 7700
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
7701
{
7702 7703
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
7704

7705
	if ((sgs->group_capacity * 100) >
7706
			(sgs->group_util * env->sd->imbalance_pct))
7707
		return true;
7708

7709 7710 7711 7712 7713 7714 7715 7716 7717 7718 7719 7720 7721 7722 7723 7724
	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;
7725

7726
	if ((sgs->group_capacity * 100) <
7727
			(sgs->group_util * env->sd->imbalance_pct))
7728
		return true;
7729

7730
	return false;
7731 7732
}

7733 7734 7735 7736 7737 7738 7739 7740 7741 7742 7743
/*
 * 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;
}

7744 7745 7746
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
7747
{
7748
	if (sgs->group_no_capacity)
7749 7750 7751 7752 7753 7754 7755 7756
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

7757
static bool update_nohz_stats(struct rq *rq, bool force)
7758 7759 7760 7761
{
#ifdef CONFIG_NO_HZ_COMMON
	unsigned int cpu = rq->cpu;

7762 7763 7764
	if (!rq->has_blocked_load)
		return false;

7765
	if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
7766
		return false;
7767

7768
	if (!force && !time_after(jiffies, rq->last_blocked_load_update_tick))
7769
		return true;
7770 7771

	update_blocked_averages(cpu);
7772 7773 7774 7775

	return rq->has_blocked_load;
#else
	return false;
7776 7777 7778
#endif
}

7779 7780
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7781
 * @env: The load balancing environment.
7782 7783 7784 7785
 * @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.
7786
 * @overload: Indicate more than one runnable task for any CPU.
7787
 */
7788 7789
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
7790 7791
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
7792
{
7793
	unsigned long load;
7794
	int i, nr_running;
7795

7796 7797
	memset(sgs, 0, sizeof(*sgs));

7798
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
7799 7800
		struct rq *rq = cpu_rq(i);

7801
		if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq, false))
7802
			env->flags |= LBF_NOHZ_AGAIN;
7803

7804
		/* Bias balancing toward CPUs of our domain: */
7805
		if (local_group)
7806
			load = target_load(i, load_idx);
7807
		else
7808 7809 7810
			load = source_load(i, load_idx);

		sgs->group_load += load;
7811
		sgs->group_util += cpu_util(i);
7812
		sgs->sum_nr_running += rq->cfs.h_nr_running;
7813

7814 7815
		nr_running = rq->nr_running;
		if (nr_running > 1)
7816 7817
			*overload = true;

7818 7819 7820 7821
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
7822
		sgs->sum_weighted_load += weighted_cpuload(rq);
7823 7824 7825 7826
		/*
		 * No need to call idle_cpu() if nr_running is not 0
		 */
		if (!nr_running && idle_cpu(i))
7827
			sgs->idle_cpus++;
7828 7829
	}

7830 7831
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
7832
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
7833

7834
	if (sgs->sum_nr_running)
7835
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
7836

7837
	sgs->group_weight = group->group_weight;
7838

7839
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
7840
	sgs->group_type = group_classify(group, sgs);
7841 7842
}

7843 7844
/**
 * update_sd_pick_busiest - return 1 on busiest group
7845
 * @env: The load balancing environment.
7846 7847
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
7848
 * @sgs: sched_group statistics
7849 7850 7851
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
7852 7853 7854
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
7855
 */
7856
static bool update_sd_pick_busiest(struct lb_env *env,
7857 7858
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
7859
				   struct sg_lb_stats *sgs)
7860
{
7861
	struct sg_lb_stats *busiest = &sds->busiest_stat;
7862

7863
	if (sgs->group_type > busiest->group_type)
7864 7865
		return true;

7866 7867 7868 7869 7870 7871
	if (sgs->group_type < busiest->group_type)
		return false;

	if (sgs->avg_load <= busiest->avg_load)
		return false;

7872 7873 7874 7875 7876 7877 7878 7879 7880 7881 7882 7883 7884 7885
	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:
7886 7887
	/* This is the busiest node in its class. */
	if (!(env->sd->flags & SD_ASYM_PACKING))
7888 7889
		return true;

7890
	/* No ASYM_PACKING if target CPU is already busy */
7891 7892
	if (env->idle == CPU_NOT_IDLE)
		return true;
7893
	/*
T
Tim Chen 已提交
7894 7895 7896
	 * 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.
7897
	 */
T
Tim Chen 已提交
7898 7899
	if (sgs->sum_nr_running &&
	    sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) {
7900 7901 7902
		if (!sds->busiest)
			return true;

7903
		/* Prefer to move from lowest priority CPU's work */
T
Tim Chen 已提交
7904 7905
		if (sched_asym_prefer(sds->busiest->asym_prefer_cpu,
				      sg->asym_prefer_cpu))
7906 7907 7908 7909 7910 7911
			return true;
	}

	return false;
}

7912 7913 7914 7915 7916 7917 7918 7919 7920 7921 7922 7923 7924 7925 7926 7927 7928 7929 7930 7931 7932 7933 7934 7935 7936 7937 7938 7939 7940 7941
#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 */

7942
/**
7943
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
7944
 * @env: The load balancing environment.
7945 7946
 * @sds: variable to hold the statistics for this sched_domain.
 */
7947
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
7948
{
7949 7950
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
7951
	struct sg_lb_stats *local = &sds->local_stat;
J
Joonsoo Kim 已提交
7952
	struct sg_lb_stats tmp_sgs;
7953
	int load_idx, prefer_sibling = 0;
7954
	bool overload = false;
7955 7956 7957 7958

	if (child && child->flags & SD_PREFER_SIBLING)
		prefer_sibling = 1;

7959
#ifdef CONFIG_NO_HZ_COMMON
7960
	if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked))
7961 7962 7963
		env->flags |= LBF_NOHZ_STATS;
#endif

7964
	load_idx = get_sd_load_idx(env->sd, env->idle);
7965 7966

	do {
J
Joonsoo Kim 已提交
7967
		struct sg_lb_stats *sgs = &tmp_sgs;
7968 7969
		int local_group;

7970
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
J
Joonsoo Kim 已提交
7971 7972
		if (local_group) {
			sds->local = sg;
7973
			sgs = local;
7974 7975

			if (env->idle != CPU_NEWLY_IDLE ||
7976 7977
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
7978
		}
7979

7980 7981
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
7982

7983 7984 7985
		if (local_group)
			goto next_group;

7986 7987
		/*
		 * In case the child domain prefers tasks go to siblings
7988
		 * first, lower the sg capacity so that we'll try
7989 7990
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
7991 7992 7993 7994
		 * 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).
7995
		 */
7996
		if (prefer_sibling && sds->local &&
7997 7998
		    group_has_capacity(env, local) &&
		    (sgs->sum_nr_running > local->sum_nr_running + 1)) {
7999
			sgs->group_no_capacity = 1;
8000
			sgs->group_type = group_classify(sg, sgs);
8001
		}
8002

8003
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
8004
			sds->busiest = sg;
J
Joonsoo Kim 已提交
8005
			sds->busiest_stat = *sgs;
8006 8007
		}

8008 8009
next_group:
		/* Now, start updating sd_lb_stats */
8010
		sds->total_running += sgs->sum_nr_running;
8011
		sds->total_load += sgs->group_load;
8012
		sds->total_capacity += sgs->group_capacity;
8013

8014
		sg = sg->next;
8015
	} while (sg != env->sd->groups);
8016

8017 8018 8019 8020 8021 8022 8023 8024 8025
#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

8026 8027
	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
8028 8029 8030 8031 8032 8033

	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;
	}
8034 8035 8036 8037
}

/**
 * check_asym_packing - Check to see if the group is packed into the
8038
 *			sched domain.
8039 8040 8041 8042 8043 8044 8045 8046 8047 8048 8049 8050 8051 8052
 *
 * 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.
 *
8053
 * Return: 1 when packing is required and a task should be moved to
8054
 * this CPU.  The amount of the imbalance is returned in env->imbalance.
8055
 *
8056
 * @env: The load balancing environment.
8057 8058
 * @sds: Statistics of the sched_domain which is to be packed
 */
8059
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
8060 8061 8062
{
	int busiest_cpu;

8063
	if (!(env->sd->flags & SD_ASYM_PACKING))
8064 8065
		return 0;

8066 8067 8068
	if (env->idle == CPU_NOT_IDLE)
		return 0;

8069 8070 8071
	if (!sds->busiest)
		return 0;

T
Tim Chen 已提交
8072 8073
	busiest_cpu = sds->busiest->asym_prefer_cpu;
	if (sched_asym_prefer(busiest_cpu, env->dst_cpu))
8074 8075
		return 0;

8076
	env->imbalance = DIV_ROUND_CLOSEST(
8077
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
8078
		SCHED_CAPACITY_SCALE);
8079

8080
	return 1;
8081 8082 8083 8084 8085 8086
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
8087
 * @env: The load balancing environment.
8088 8089
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
8090 8091
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8092
{
8093
	unsigned long tmp, capa_now = 0, capa_move = 0;
8094
	unsigned int imbn = 2;
8095
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
8096
	struct sg_lb_stats *local, *busiest;
8097

J
Joonsoo Kim 已提交
8098 8099
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
8100

J
Joonsoo Kim 已提交
8101 8102 8103 8104
	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;
8105

J
Joonsoo Kim 已提交
8106
	scaled_busy_load_per_task =
8107
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
8108
		busiest->group_capacity;
J
Joonsoo Kim 已提交
8109

8110 8111
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
8112
		env->imbalance = busiest->load_per_task;
8113 8114 8115 8116 8117
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
8118
	 * however we may be able to increase total CPU capacity used by
8119 8120 8121
	 * moving them.
	 */

8122
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
8123
			min(busiest->load_per_task, busiest->avg_load);
8124
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
8125
			min(local->load_per_task, local->avg_load);
8126
	capa_now /= SCHED_CAPACITY_SCALE;
8127 8128

	/* Amount of load we'd subtract */
8129
	if (busiest->avg_load > scaled_busy_load_per_task) {
8130
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
8131
			    min(busiest->load_per_task,
8132
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
8133
	}
8134 8135

	/* Amount of load we'd add */
8136
	if (busiest->avg_load * busiest->group_capacity <
8137
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
8138 8139
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
8140
	} else {
8141
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
8142
		      local->group_capacity;
J
Joonsoo Kim 已提交
8143
	}
8144
	capa_move += local->group_capacity *
8145
		    min(local->load_per_task, local->avg_load + tmp);
8146
	capa_move /= SCHED_CAPACITY_SCALE;
8147 8148

	/* Move if we gain throughput */
8149
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
8150
		env->imbalance = busiest->load_per_task;
8151 8152 8153 8154 8155
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
8156
 * @env: load balance environment
8157 8158
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
8159
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8160
{
8161
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
8162 8163 8164 8165
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
8166

8167
	if (busiest->group_type == group_imbalanced) {
8168 8169
		/*
		 * In the group_imb case we cannot rely on group-wide averages
8170
		 * to ensure CPU-load equilibrium, look at wider averages. XXX
8171
		 */
J
Joonsoo Kim 已提交
8172 8173
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
8174 8175
	}

8176
	/*
8177 8178 8179 8180
	 * 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:
8181
	 */
8182 8183
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
8184 8185
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
8186 8187
	}

8188
	/*
8189
	 * If there aren't any idle CPUs, avoid creating some.
8190 8191 8192
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
8193
		load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
8194
		if (load_above_capacity > busiest->group_capacity) {
8195
			load_above_capacity -= busiest->group_capacity;
8196
			load_above_capacity *= scale_load_down(NICE_0_LOAD);
8197 8198
			load_above_capacity /= busiest->group_capacity;
		} else
8199
			load_above_capacity = ~0UL;
8200 8201 8202
	}

	/*
8203
	 * We're trying to get all the CPUs to the average_load, so we don't
8204
	 * want to push ourselves above the average load, nor do we wish to
8205
	 * reduce the max loaded CPU below the average load. At the same time,
8206 8207
	 * we also don't want to reduce the group load below the group
	 * capacity. Thus we look for the minimum possible imbalance.
8208
	 */
8209
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
8210 8211

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
8212
	env->imbalance = min(
8213 8214
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
8215
	) / SCHED_CAPACITY_SCALE;
8216 8217 8218

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
8219
	 * there is no guarantee that any tasks will be moved so we'll have
8220 8221 8222
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
8223
	if (env->imbalance < busiest->load_per_task)
8224
		return fix_small_imbalance(env, sds);
8225
}
8226

8227 8228 8229 8230
/******* find_busiest_group() helpers end here *********************/

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
8231
 * if there is an imbalance.
8232 8233 8234 8235
 *
 * Also calculates the amount of weighted load which should be moved
 * to restore balance.
 *
8236
 * @env: The load balancing environment.
8237
 *
8238
 * Return:	- The busiest group if imbalance exists.
8239
 */
J
Joonsoo Kim 已提交
8240
static struct sched_group *find_busiest_group(struct lb_env *env)
8241
{
J
Joonsoo Kim 已提交
8242
	struct sg_lb_stats *local, *busiest;
8243 8244
	struct sd_lb_stats sds;

8245
	init_sd_lb_stats(&sds);
8246 8247 8248 8249 8250

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
8251
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
8252 8253
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
8254

8255
	/* ASYM feature bypasses nice load balance check */
8256
	if (check_asym_packing(env, &sds))
8257 8258
		return sds.busiest;

8259
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
8260
	if (!sds.busiest || busiest->sum_nr_running == 0)
8261 8262
		goto out_balanced;

8263
	/* XXX broken for overlapping NUMA groups */
8264 8265
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
8266

P
Peter Zijlstra 已提交
8267 8268
	/*
	 * If the busiest group is imbalanced the below checks don't
8269
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
8270 8271
	 * isn't true due to cpus_allowed constraints and the like.
	 */
8272
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
8273 8274
		goto force_balance;

8275 8276 8277 8278 8279
	/*
	 * 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) &&
8280
	    busiest->group_no_capacity)
8281 8282
		goto force_balance;

8283
	/*
8284
	 * If the local group is busier than the selected busiest group
8285 8286
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
8287
	if (local->avg_load >= busiest->avg_load)
8288 8289
		goto out_balanced;

8290 8291 8292 8293
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
8294
	if (local->avg_load >= sds.avg_load)
8295 8296
		goto out_balanced;

8297
	if (env->idle == CPU_IDLE) {
8298
		/*
8299
		 * This CPU is idle. If the busiest group is not overloaded
8300
		 * and there is no imbalance between this and busiest group
8301
		 * wrt idle CPUs, it is balanced. The imbalance becomes
8302 8303
		 * significant if the diff is greater than 1 otherwise we
		 * might end up to just move the imbalance on another group
8304
		 */
8305 8306
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
8307
			goto out_balanced;
8308 8309 8310 8311 8312
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
8313 8314
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
8315
			goto out_balanced;
8316
	}
8317

8318
force_balance:
8319
	/* Looks like there is an imbalance. Compute it */
8320
	calculate_imbalance(env, &sds);
8321
	return env->imbalance ? sds.busiest : NULL;
8322 8323

out_balanced:
8324
	env->imbalance = 0;
8325 8326 8327 8328
	return NULL;
}

/*
8329
 * find_busiest_queue - find the busiest runqueue among the CPUs in the group.
8330
 */
8331
static struct rq *find_busiest_queue(struct lb_env *env,
8332
				     struct sched_group *group)
8333 8334
{
	struct rq *busiest = NULL, *rq;
8335
	unsigned long busiest_load = 0, busiest_capacity = 1;
8336 8337
	int i;

8338
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
8339
		unsigned long capacity, wl;
8340 8341 8342 8343
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
8344

8345 8346 8347 8348 8349 8350 8351 8352 8353 8354 8355 8356 8357 8358 8359 8360 8361 8362 8363 8364 8365 8366
		/*
		 * 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;

8367
		capacity = capacity_of(i);
8368

8369
		wl = weighted_cpuload(rq);
8370

8371 8372
		/*
		 * When comparing with imbalance, use weighted_cpuload()
8373
		 * which is not scaled with the CPU capacity.
8374
		 */
8375 8376 8377

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
8378 8379
			continue;

8380
		/*
8381 8382 8383
		 * 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
8384
		 * potentially running at a lower capacity.
8385
		 *
8386
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
8387
		 * multiplication to rid ourselves of the division works out
8388 8389
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
8390
		 */
8391
		if (wl * busiest_capacity > busiest_load * capacity) {
8392
			busiest_load = wl;
8393
			busiest_capacity = capacity;
8394 8395 8396 8397 8398 8399 8400 8401 8402 8403 8404 8405 8406
			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

8407
static int need_active_balance(struct lb_env *env)
8408
{
8409 8410 8411
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
8412 8413 8414

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
T
Tim Chen 已提交
8415 8416
		 * lower priority CPUs in order to pack all tasks in the
		 * highest priority CPUs.
8417
		 */
T
Tim Chen 已提交
8418 8419
		if ((sd->flags & SD_ASYM_PACKING) &&
		    sched_asym_prefer(env->dst_cpu, env->src_cpu))
8420
			return 1;
8421 8422
	}

8423 8424 8425 8426 8427 8428 8429 8430 8431 8432 8433 8434 8435
	/*
	 * 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;
	}

8436 8437 8438
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

8439 8440
static int active_load_balance_cpu_stop(void *data);

8441 8442 8443 8444 8445
static int should_we_balance(struct lb_env *env)
{
	struct sched_group *sg = env->sd->groups;
	int cpu, balance_cpu = -1;

8446 8447 8448 8449 8450 8451 8452
	/*
	 * 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;

8453
	/*
8454
	 * In the newly idle case, we will allow all the CPUs
8455 8456 8457 8458 8459
	 * to do the newly idle load balance.
	 */
	if (env->idle == CPU_NEWLY_IDLE)
		return 1;

8460
	/* Try to find first idle CPU */
8461
	for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
8462
		if (!idle_cpu(cpu))
8463 8464 8465 8466 8467 8468 8469 8470 8471 8472
			continue;

		balance_cpu = cpu;
		break;
	}

	if (balance_cpu == -1)
		balance_cpu = group_balance_cpu(sg);

	/*
8473
	 * First idle CPU or the first CPU(busiest) in this sched group
8474 8475
	 * is eligible for doing load balancing at this and above domains.
	 */
8476
	return balance_cpu == env->dst_cpu;
8477 8478
}

8479 8480 8481 8482 8483 8484
/*
 * 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,
8485
			int *continue_balancing)
8486
{
8487
	int ld_moved, cur_ld_moved, active_balance = 0;
8488
	struct sched_domain *sd_parent = sd->parent;
8489 8490
	struct sched_group *group;
	struct rq *busiest;
8491
	struct rq_flags rf;
8492
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
8493

8494 8495
	struct lb_env env = {
		.sd		= sd,
8496 8497
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
8498
		.dst_grpmask    = sched_group_span(sd->groups),
8499
		.idle		= idle,
8500
		.loop_break	= sched_nr_migrate_break,
8501
		.cpus		= cpus,
8502
		.fbq_type	= all,
8503
		.tasks		= LIST_HEAD_INIT(env.tasks),
8504 8505
	};

8506
	cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
8507

8508
	schedstat_inc(sd->lb_count[idle]);
8509 8510

redo:
8511 8512
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
8513
		goto out_balanced;
8514
	}
8515

8516
	group = find_busiest_group(&env);
8517
	if (!group) {
8518
		schedstat_inc(sd->lb_nobusyg[idle]);
8519 8520 8521
		goto out_balanced;
	}

8522
	busiest = find_busiest_queue(&env, group);
8523
	if (!busiest) {
8524
		schedstat_inc(sd->lb_nobusyq[idle]);
8525 8526 8527
		goto out_balanced;
	}

8528
	BUG_ON(busiest == env.dst_rq);
8529

8530
	schedstat_add(sd->lb_imbalance[idle], env.imbalance);
8531

8532 8533 8534
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

8535 8536 8537 8538 8539 8540 8541 8542
	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.
		 */
8543
		env.flags |= LBF_ALL_PINNED;
8544
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
8545

8546
more_balance:
8547
		rq_lock_irqsave(busiest, &rf);
8548
		update_rq_clock(busiest);
8549 8550 8551 8552 8553

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
8554
		cur_ld_moved = detach_tasks(&env);
8555 8556

		/*
8557 8558 8559 8560 8561
		 * 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.
8562
		 */
8563

8564
		rq_unlock(busiest, &rf);
8565 8566 8567 8568 8569 8570

		if (cur_ld_moved) {
			attach_tasks(&env);
			ld_moved += cur_ld_moved;
		}

8571
		local_irq_restore(rf.flags);
8572

8573 8574 8575 8576 8577
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

8578 8579 8580 8581
		/*
		 * 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
8582
		 * iterate on same src_cpu is dependent on number of CPUs in our
8583 8584 8585 8586 8587 8588 8589 8590 8591 8592 8593 8594 8595 8596
		 * 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.
		 */
8597
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
8598

8599
			/* Prevent to re-select dst_cpu via env's CPUs */
8600 8601
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

8602
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
8603
			env.dst_cpu	 = env.new_dst_cpu;
8604
			env.flags	&= ~LBF_DST_PINNED;
8605 8606
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
8607

8608 8609 8610 8611 8612 8613
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
8614

8615 8616 8617 8618
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
8619
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8620

8621
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
8622 8623 8624
				*group_imbalance = 1;
		}

8625
		/* All tasks on this runqueue were pinned by CPU affinity */
8626
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
8627
			cpumask_clear_cpu(cpu_of(busiest), cpus);
8628 8629 8630 8631 8632 8633 8634 8635 8636
			/*
			 * 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)) {
8637 8638
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
8639
				goto redo;
8640
			}
8641
			goto out_all_pinned;
8642 8643 8644 8645
		}
	}

	if (!ld_moved) {
8646
		schedstat_inc(sd->lb_failed[idle]);
8647 8648 8649 8650 8651 8652 8653 8654
		/*
		 * 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++;
8655

8656
		if (need_active_balance(&env)) {
8657 8658
			unsigned long flags;

8659 8660
			raw_spin_lock_irqsave(&busiest->lock, flags);

8661 8662 8663 8664
			/*
			 * Don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest CPU can't be
			 * moved to this_cpu:
8665
			 */
8666
			if (!cpumask_test_cpu(this_cpu, &busiest->curr->cpus_allowed)) {
8667 8668
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
8669
				env.flags |= LBF_ALL_PINNED;
8670 8671 8672
				goto out_one_pinned;
			}

8673 8674 8675 8676 8677
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
8678 8679 8680 8681 8682 8683
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
8684

8685
			if (active_balance) {
8686 8687 8688
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
8689
			}
8690

8691
			/* We've kicked active balancing, force task migration. */
8692 8693 8694 8695 8696 8697 8698 8699 8700 8701 8702 8703 8704
			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
8705
		 * detach_tasks).
8706 8707 8708 8709 8710 8711 8712 8713
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
8714 8715
	/*
	 * We reach balance although we may have faced some affinity
8716 8717
	 * constraints. Clear the imbalance flag only if other tasks got
	 * a chance to move and fix the imbalance.
8718
	 */
8719
	if (sd_parent && !(env.flags & LBF_ALL_PINNED)) {
8720 8721 8722 8723 8724 8725 8726 8727 8728 8729 8730 8731
		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.
	 */
8732
	schedstat_inc(sd->lb_balanced[idle]);
8733 8734 8735 8736

	sd->nr_balance_failed = 0;

out_one_pinned:
8737 8738 8739 8740 8741 8742 8743 8744 8745 8746 8747
	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;

8748
	/* tune up the balancing interval */
8749
	if (((env.flags & LBF_ALL_PINNED) &&
8750
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
8751 8752 8753 8754 8755 8756
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;
out:
	return ld_moved;
}

8757 8758 8759 8760 8761 8762 8763 8764 8765 8766 8767 8768 8769 8770 8771 8772
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
8773
update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
8774 8775 8776
{
	unsigned long interval, next;

8777 8778
	/* used by idle balance, so cpu_busy = 0 */
	interval = get_sd_balance_interval(sd, 0);
8779 8780 8781 8782 8783 8784
	next = sd->last_balance + interval;

	if (time_after(*next_balance, next))
		*next_balance = next;
}

8785
/*
8786
 * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
8787 8788 8789
 * 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.
8790
 */
8791
static int active_load_balance_cpu_stop(void *data)
8792
{
8793 8794
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
8795
	int target_cpu = busiest_rq->push_cpu;
8796
	struct rq *target_rq = cpu_rq(target_cpu);
8797
	struct sched_domain *sd;
8798
	struct task_struct *p = NULL;
8799
	struct rq_flags rf;
8800

8801
	rq_lock_irq(busiest_rq, &rf);
8802 8803 8804 8805 8806 8807 8808
	/*
	 * 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;
8809

8810
	/* Make sure the requested CPU hasn't gone down in the meantime: */
8811 8812 8813
	if (unlikely(busiest_cpu != smp_processor_id() ||
		     !busiest_rq->active_balance))
		goto out_unlock;
8814 8815 8816

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
8817
		goto out_unlock;
8818 8819 8820 8821

	/*
	 * This condition is "impossible", if it occurs
	 * we need to fix it. Originally reported by
8822
	 * Bjorn Helgaas on a 128-CPU setup.
8823 8824 8825 8826
	 */
	BUG_ON(busiest_rq == target_rq);

	/* Search for an sd spanning us and the target CPU. */
8827
	rcu_read_lock();
8828 8829 8830 8831 8832 8833 8834
	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)) {
8835 8836
		struct lb_env env = {
			.sd		= sd,
8837 8838 8839 8840
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
8841
			.idle		= CPU_IDLE,
8842 8843 8844 8845 8846 8847 8848
			/*
			 * 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,
8849 8850
		};

8851
		schedstat_inc(sd->alb_count);
8852
		update_rq_clock(busiest_rq);
8853

8854
		p = detach_one_task(&env);
8855
		if (p) {
8856
			schedstat_inc(sd->alb_pushed);
8857 8858 8859
			/* Active balancing done, reset the failure counter. */
			sd->nr_balance_failed = 0;
		} else {
8860
			schedstat_inc(sd->alb_failed);
8861
		}
8862
	}
8863
	rcu_read_unlock();
8864 8865
out_unlock:
	busiest_rq->active_balance = 0;
8866
	rq_unlock(busiest_rq, &rf);
8867 8868 8869 8870 8871 8872

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

8873
	return 0;
8874 8875
}

8876 8877 8878 8879 8880 8881 8882 8883 8884 8885 8886 8887 8888 8889 8890 8891 8892 8893 8894 8895 8896 8897 8898 8899 8900 8901 8902 8903 8904 8905 8906 8907 8908 8909 8910 8911 8912 8913 8914 8915 8916 8917 8918 8919 8920 8921 8922 8923 8924 8925 8926 8927 8928 8929 8930 8931 8932 8933 8934 8935 8936 8937 8938 8939 8940 8941 8942 8943 8944 8945 8946 8947 8948 8949 8950 8951 8952 8953 8954 8955 8956 8957 8958 8959 8960 8961 8962 8963 8964 8965 8966 8967 8968 8969 8970 8971 8972 8973 8974 8975 8976 8977 8978 8979 8980 8981 8982 8983 8984 8985 8986 8987 8988 8989 8990 8991 8992 8993
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
	}
}

8994 8995 8996 8997 8998
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

8999
#ifdef CONFIG_NO_HZ_COMMON
9000 9001 9002 9003 9004
/*
 * 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.
9005 9006
 * - HK_FLAG_MISC CPUs are used for this task, because HK_FLAG_SCHED not set
 *   anywhere yet.
9007
 */
9008

9009
static inline int find_new_ilb(void)
9010
{
9011
	int ilb;
9012

9013 9014 9015 9016 9017
	for_each_cpu_and(ilb, nohz.idle_cpus_mask,
			      housekeeping_cpumask(HK_FLAG_MISC)) {
		if (idle_cpu(ilb))
			return ilb;
	}
9018 9019

	return nr_cpu_ids;
9020 9021
}

9022
/*
9023 9024
 * 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).
9025
 */
9026
static void kick_ilb(unsigned int flags)
9027 9028 9029 9030 9031
{
	int ilb_cpu;

	nohz.next_balance++;

9032
	ilb_cpu = find_new_ilb();
9033

9034 9035
	if (ilb_cpu >= nr_cpu_ids)
		return;
9036

9037
	flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
P
Peter Zijlstra 已提交
9038
	if (flags & NOHZ_KICK_MASK)
9039
		return;
9040

9041 9042
	/*
	 * Use smp_send_reschedule() instead of resched_cpu().
9043
	 * This way we generate a sched IPI on the target CPU which
9044 9045 9046 9047
	 * is idle. And the softirq performing nohz idle load balance
	 * will be run before returning from the IPI.
	 */
	smp_send_reschedule(ilb_cpu);
9048 9049 9050 9051 9052 9053 9054 9055 9056 9057 9058 9059 9060 9061 9062 9063 9064 9065 9066
}

/*
 * 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;
9067
	unsigned int flags = 0;
9068 9069 9070 9071 9072 9073 9074 9075

	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.
	 */
9076
	nohz_balance_exit_idle(rq);
9077 9078 9079 9080 9081 9082 9083 9084

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
		return;

9085 9086
	if (READ_ONCE(nohz.has_blocked) &&
	    time_after(now, READ_ONCE(nohz.next_blocked)))
9087 9088
		flags = NOHZ_STATS_KICK;

9089
	if (time_before(now, nohz.next_balance))
9090
		goto out;
9091 9092

	if (rq->nr_running >= 2) {
9093
		flags = NOHZ_KICK_MASK;
9094 9095 9096 9097 9098 9099 9100 9101 9102 9103 9104 9105
		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) {
9106
			flags = NOHZ_KICK_MASK;
9107 9108 9109 9110 9111 9112 9113 9114 9115
			goto unlock;
		}

	}

	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
9116
			flags = NOHZ_KICK_MASK;
9117 9118 9119 9120 9121 9122 9123 9124 9125 9126 9127 9128
			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)) {
9129
				flags = NOHZ_KICK_MASK;
9130 9131 9132 9133 9134 9135 9136
				goto unlock;
			}
		}
	}
unlock:
	rcu_read_unlock();
out:
9137 9138
	if (flags)
		kick_ilb(flags);
9139 9140
}

9141
static void set_cpu_sd_state_busy(int cpu)
9142
{
9143
	struct sched_domain *sd;
9144

9145 9146
	rcu_read_lock();
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
9147

9148 9149 9150 9151 9152 9153 9154
	if (!sd || !sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 0;

	atomic_inc(&sd->shared->nr_busy_cpus);
unlock:
	rcu_read_unlock();
9155 9156
}

9157 9158 9159 9160 9161 9162 9163 9164 9165 9166 9167 9168 9169 9170 9171
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)
9172 9173 9174 9175
{
	struct sched_domain *sd;

	rcu_read_lock();
9176
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
V
Vincent Guittot 已提交
9177 9178 9179 9180 9181

	if (!sd || sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 1;

9182
	atomic_dec(&sd->shared->nr_busy_cpus);
V
Vincent Guittot 已提交
9183
unlock:
9184 9185 9186
	rcu_read_unlock();
}

9187
/*
9188
 * This routine will record that the CPU is going idle with tick stopped.
9189
 * This info will be used in performing idle load balancing in the future.
9190
 */
9191
void nohz_balance_enter_idle(int cpu)
9192
{
9193 9194 9195 9196
	struct rq *rq = cpu_rq(cpu);

	SCHED_WARN_ON(cpu != smp_processor_id());

9197
	/* If this CPU is going down, then nothing needs to be done: */
9198 9199 9200
	if (!cpu_active(cpu))
		return;

9201
	/* Spare idle load balancing on CPUs that don't want to be disturbed: */
9202
	if (!housekeeping_cpu(cpu, HK_FLAG_SCHED))
9203 9204
		return;

9205 9206 9207 9208 9209 9210 9211 9212 9213 9214 9215 9216 9217
	/*
	 * 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
	 */
9218
	if (rq->nohz_tick_stopped)
9219
		goto out;
9220

9221
	/* If we're a completely isolated CPU, we don't play: */
9222
	if (on_null_domain(rq))
9223 9224
		return;

9225 9226
	rq->nohz_tick_stopped = 1;

9227 9228
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
9229

9230 9231 9232 9233 9234 9235 9236
	/*
	 * 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();

9237
	set_cpu_sd_state_idle(cpu);
9238 9239 9240 9241 9242 9243 9244

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);
9245 9246 9247
}

/*
9248 9249 9250 9251 9252
 * 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.
9253
 */
9254 9255
static bool _nohz_idle_balance(struct rq *this_rq, unsigned int flags,
			       enum cpu_idle_type idle)
9256
{
9257
	/* Earliest time when we have to do rebalance again */
9258 9259
	unsigned long now = jiffies;
	unsigned long next_balance = now + 60*HZ;
9260
	bool has_blocked_load = false;
9261
	int update_next_balance = 0;
P
Peter Zijlstra 已提交
9262 9263
	int this_cpu = this_rq->cpu;
	int balance_cpu;
9264
	int ret = false;
P
Peter Zijlstra 已提交
9265
	struct rq *rq;
9266

P
Peter Zijlstra 已提交
9267
	SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
9268

9269 9270 9271 9272 9273 9274 9275 9276 9277 9278 9279 9280 9281 9282 9283 9284
	/*
	 * 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();

9285
	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
9286
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
9287 9288 9289
			continue;

		/*
9290 9291
		 * If this CPU gets work to do, stop the load balancing
		 * work being done for other CPUs. Next load
9292 9293
		 * balancing owner will pick it up.
		 */
9294 9295 9296 9297
		if (need_resched()) {
			has_blocked_load = true;
			goto abort;
		}
9298

V
Vincent Guittot 已提交
9299 9300
		rq = cpu_rq(balance_cpu);

9301
		has_blocked_load |= update_nohz_stats(rq, true);
9302

9303 9304 9305 9306 9307
		/*
		 * If time for next balance is due,
		 * do the balance.
		 */
		if (time_after_eq(jiffies, rq->next_balance)) {
9308 9309
			struct rq_flags rf;

9310
			rq_lock_irqsave(rq, &rf);
9311
			update_rq_clock(rq);
9312
			rq_unlock_irqrestore(rq, &rf);
9313

P
Peter Zijlstra 已提交
9314 9315
			if (flags & NOHZ_BALANCE_KICK)
				rebalance_domains(rq, CPU_IDLE);
9316
		}
9317

9318 9319 9320 9321
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
9322
	}
9323

9324 9325 9326 9327 9328 9329
	/* 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
9330 9331 9332
	if (flags & NOHZ_BALANCE_KICK)
		rebalance_domains(this_rq, CPU_IDLE);

9333 9334 9335
	WRITE_ONCE(nohz.next_blocked,
		now + msecs_to_jiffies(LOAD_AVG_PERIOD));

9336 9337 9338
	/* The full idle balance loop has been done */
	ret = true;

9339 9340 9341 9342
abort:
	/* There is still blocked load, enable periodic update */
	if (has_blocked_load)
		WRITE_ONCE(nohz.has_blocked, 1);
9343

9344 9345 9346 9347 9348 9349 9350
	/*
	 * 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
9351

9352 9353 9354 9355 9356 9357 9358 9359 9360 9361 9362 9363 9364 9365 9366 9367 9368 9369 9370 9371 9372 9373 9374 9375 9376 9377 9378 9379 9380
	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
9381
	return true;
9382
}
9383 9384 9385 9386 9387 9388 9389 9390 9391 9392 9393 9394 9395 9396 9397 9398 9399 9400 9401 9402 9403 9404 9405 9406 9407 9408 9409 9410 9411 9412 9413 9414 9415

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);
}

9416 9417 9418
#else /* !CONFIG_NO_HZ_COMMON */
static inline void nohz_balancer_kick(struct rq *rq) { }

9419
static inline bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
P
Peter Zijlstra 已提交
9420 9421 9422
{
	return false;
}
9423 9424

static inline void nohz_newidle_balance(struct rq *this_rq) { }
9425
#endif /* CONFIG_NO_HZ_COMMON */
9426

P
Peter Zijlstra 已提交
9427 9428 9429 9430 9431 9432 9433 9434 9435 9436 9437 9438 9439 9440 9441 9442 9443 9444 9445 9446 9447 9448 9449 9450 9451 9452 9453 9454 9455 9456 9457 9458 9459 9460
/*
 * 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) {
9461

P
Peter Zijlstra 已提交
9462 9463 9464 9465 9466 9467
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
			update_next_balance(sd, &next_balance);
		rcu_read_unlock();

9468 9469
		nohz_newidle_balance(this_rq);

P
Peter Zijlstra 已提交
9470 9471 9472 9473 9474 9475 9476 9477 9478 9479 9480 9481 9482 9483 9484 9485 9486 9487 9488 9489 9490 9491 9492 9493 9494 9495 9496 9497 9498 9499 9500 9501 9502 9503 9504 9505 9506 9507 9508 9509 9510 9511 9512 9513 9514 9515 9516 9517 9518
		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;

9519
out:
P
Peter Zijlstra 已提交
9520 9521 9522 9523 9524 9525 9526 9527 9528 9529 9530 9531 9532 9533 9534 9535 9536 9537 9538 9539 9540 9541 9542 9543
	/*
	 * 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;
}

9544 9545 9546 9547
/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
9548
static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
9549
{
9550
	struct rq *this_rq = this_rq();
9551
	enum cpu_idle_type idle = this_rq->idle_balance ?
9552 9553 9554
						CPU_IDLE : CPU_NOT_IDLE;

	/*
9555 9556
	 * If this CPU has a pending nohz_balance_kick, then do the
	 * balancing on behalf of the other idle CPUs whose ticks are
9557
	 * stopped. Do nohz_idle_balance *before* rebalance_domains to
9558
	 * give the idle CPUs a chance to load balance. Else we may
9559 9560
	 * load balance only within the local sched_domain hierarchy
	 * and abort nohz_idle_balance altogether if we pull some load.
9561
	 */
P
Peter Zijlstra 已提交
9562 9563 9564 9565 9566
	if (nohz_idle_balance(this_rq, idle))
		return;

	/* normal load balance */
	update_blocked_averages(this_rq->cpu);
9567
	rebalance_domains(this_rq, idle);
9568 9569 9570 9571 9572
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
9573
void trigger_load_balance(struct rq *rq)
9574 9575
{
	/* Don't need to rebalance while attached to NULL domain */
9576 9577 9578 9579
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
9580
		raise_softirq(SCHED_SOFTIRQ);
9581 9582

	nohz_balancer_kick(rq);
9583 9584
}

9585 9586 9587
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
9588 9589

	update_runtime_enabled(rq);
9590 9591 9592 9593 9594
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
9595 9596 9597

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
9598 9599
}

9600
#endif /* CONFIG_SMP */
9601

9602
/*
9603 9604 9605 9606 9607 9608
 * 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.
9609
 */
P
Peter Zijlstra 已提交
9610
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
9611 9612 9613 9614 9615 9616
{
	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
9617
		entity_tick(cfs_rq, se, queued);
9618
	}
9619

9620
	if (static_branch_unlikely(&sched_numa_balancing))
9621
		task_tick_numa(rq, curr);
9622 9623 9624
}

/*
P
Peter Zijlstra 已提交
9625 9626 9627
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
9628
 */
P
Peter Zijlstra 已提交
9629
static void task_fork_fair(struct task_struct *p)
9630
{
9631 9632
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
P
Peter Zijlstra 已提交
9633
	struct rq *rq = this_rq();
9634
	struct rq_flags rf;
9635

9636
	rq_lock(rq, &rf);
9637 9638
	update_rq_clock(rq);

9639 9640
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;
9641 9642
	if (curr) {
		update_curr(cfs_rq);
9643
		se->vruntime = curr->vruntime;
9644
	}
9645
	place_entity(cfs_rq, se, 1);
9646

P
Peter Zijlstra 已提交
9647
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
9648
		/*
9649 9650 9651
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
9652
		swap(curr->vruntime, se->vruntime);
9653
		resched_curr(rq);
9654
	}
9655

9656
	se->vruntime -= cfs_rq->min_vruntime;
9657
	rq_unlock(rq, &rf);
9658 9659
}

9660 9661 9662 9663
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
9664 9665
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
9666
{
9667
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
9668 9669
		return;

9670 9671 9672 9673 9674
	/*
	 * 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
9675
	if (rq->curr == p) {
9676
		if (p->prio > oldprio)
9677
			resched_curr(rq);
9678
	} else
9679
		check_preempt_curr(rq, p, 0);
9680 9681
}

9682
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
9683 9684 9685 9686
{
	struct sched_entity *se = &p->se;

	/*
9687 9688 9689 9690 9691 9692 9693 9694 9695 9696
	 * 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
9697
	 *
9698 9699 9700 9701
	 * - 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
9702
	 */
9703 9704
	if (!se->sum_exec_runtime ||
	    (p->state == TASK_WAKING && p->sched_remote_wakeup))
9705 9706 9707 9708 9709
		return true;

	return false;
}

9710 9711 9712 9713 9714 9715 9716 9717 9718 9719 9720 9721 9722 9723 9724 9725 9726 9727
#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;

9728
		update_load_avg(cfs_rq, se, UPDATE_TG);
9729 9730 9731 9732 9733 9734
	}
}
#else
static void propagate_entity_cfs_rq(struct sched_entity *se) { }
#endif

9735
static void detach_entity_cfs_rq(struct sched_entity *se)
9736 9737 9738
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

9739
	/* Catch up with the cfs_rq and remove our load when we leave */
9740
	update_load_avg(cfs_rq, se, 0);
9741
	detach_entity_load_avg(cfs_rq, se);
9742
	update_tg_load_avg(cfs_rq, false);
9743
	propagate_entity_cfs_rq(se);
P
Peter Zijlstra 已提交
9744 9745
}

9746
static void attach_entity_cfs_rq(struct sched_entity *se)
9747
{
9748
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
9749 9750

#ifdef CONFIG_FAIR_GROUP_SCHED
9751 9752 9753 9754 9755 9756
	/*
	 * 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
9757

9758
	/* Synchronize entity with its cfs_rq */
9759
	update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
9760
	attach_entity_load_avg(cfs_rq, se, 0);
9761
	update_tg_load_avg(cfs_rq, false);
9762
	propagate_entity_cfs_rq(se);
9763 9764 9765 9766 9767 9768 9769 9770 9771 9772 9773 9774 9775 9776 9777 9778 9779 9780 9781 9782 9783 9784 9785 9786 9787
}

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);
9788 9789 9790 9791

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
9792

9793 9794 9795 9796 9797 9798 9799 9800
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);
9801

9802
	if (task_on_rq_queued(p)) {
9803
		/*
9804 9805 9806
		 * 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.
9807
		 */
9808 9809 9810 9811
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
9812
	}
9813 9814
}

9815 9816 9817 9818 9819 9820 9821 9822 9823
/* 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;

9824 9825 9826 9827 9828 9829 9830
	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);
	}
9831 9832
}

9833 9834
void init_cfs_rq(struct cfs_rq *cfs_rq)
{
9835
	cfs_rq->tasks_timeline = RB_ROOT_CACHED;
9836 9837 9838 9839
	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
#ifndef CONFIG_64BIT
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
9840
#ifdef CONFIG_SMP
9841
	raw_spin_lock_init(&cfs_rq->removed.lock);
9842
#endif
9843 9844
}

P
Peter Zijlstra 已提交
9845
#ifdef CONFIG_FAIR_GROUP_SCHED
9846 9847 9848 9849 9850 9851 9852 9853 9854 9855
#ifdef CONFIG_SCHED_SLI
static void update_nr_iowait_fair(struct task_struct *p, long inc)
{
	unsigned long flags;
	struct sched_entity *se = p->se.parent;
	u64 clock;

	if (!schedstat_enabled())
		return;

9856
	clock = __rq_clock_broken(cpu_rq(task_cpu(p)));
9857 9858 9859 9860 9861 9862 9863 9864 9865 9866 9867 9868 9869 9870 9871 9872 9873 9874 9875 9876 9877 9878 9879 9880 9881 9882 9883

	for_each_sched_entity(se) {
		/*
		 * Avoid locking rq->lock from try_to_wakeup hot path, in
		 * the price of poor consistency among cgroup hierarchy,
		 * which we can tolerate.
		 * While accessing se->on_rq does need to hold rq->lock. We
		 * already do, because when inc==1, the caller is __schedule
		 * and task_move_group_fair
		 */
		spin_lock_irqsave(&se->iowait_lock, flags);
		if (!se->on_rq && !schedstat_val(se->cg_nr_iowait) && inc > 0)
			__schedstat_set(se->cg_iowait_start, clock);
		if (schedstat_val(se->cg_iowait_start) > 0 &&
			schedstat_val(se->cg_nr_iowait) + inc == 0) {
			__schedstat_add(se->cg_iowait_sum, clock -
				schedstat_val(se->cg_iowait_start));
			__schedstat_set(se->cg_iowait_start, 0);
		}
		__schedstat_add(se->cg_nr_iowait, inc);
		spin_unlock_irqrestore(&se->iowait_lock, flags);
	}
}
#else
static void update_nr_iowait_fair(struct task_struct *p, long inc) {}
#endif

9884 9885 9886 9887 9888 9889 9890 9891
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;
}

9892
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
9893
{
9894 9895
	if (p->in_iowait)
		update_nr_iowait_fair(p, -1);
9896
	detach_task_cfs_rq(p);
9897
	set_task_rq(p, task_cpu(p));
9898 9899 9900 9901 9902

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
9903
	attach_task_cfs_rq(p);
9904 9905
	if (p->in_iowait)
		update_nr_iowait_fair(p, 1);
P
Peter Zijlstra 已提交
9906
}
9907

9908 9909 9910 9911 9912 9913 9914 9915 9916 9917 9918 9919 9920
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;
	}
}

9921 9922 9923 9924 9925 9926 9927 9928 9929
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]);
9930
		if (tg->se)
9931 9932 9933 9934 9935 9936 9937 9938 9939 9940
			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;
9941
	struct cfs_rq *cfs_rq;
9942 9943
	int i;

K
Kees Cook 已提交
9944
	tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL);
9945 9946
	if (!tg->cfs_rq)
		goto err;
K
Kees Cook 已提交
9947
	tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL);
9948 9949 9950 9951 9952 9953 9954 9955 9956 9957 9958 9959 9960 9961 9962 9963 9964 9965 9966 9967
	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]);
9968
		init_entity_runnable_average(se);
9969 9970 9971 9972 9973 9974 9975 9976 9977 9978
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

9979 9980 9981
void online_fair_sched_group(struct task_group *tg)
{
	struct sched_entity *se;
9982
	struct rq_flags rf;
9983 9984 9985 9986 9987 9988
	struct rq *rq;
	int i;

	for_each_possible_cpu(i) {
		rq = cpu_rq(i);
		se = tg->se[i];
9989
		rq_lock_irq(rq, &rf);
9990
		update_rq_clock(rq);
9991
		attach_entity_cfs_rq(se);
9992
		sync_throttle(tg, i);
9993
		rq_unlock_irq(rq, &rf);
9994 9995 9996
	}
}

9997
void unregister_fair_sched_group(struct task_group *tg)
9998 9999
{
	unsigned long flags;
10000 10001
	struct rq *rq;
	int cpu;
10002

10003 10004 10005
	for_each_possible_cpu(cpu) {
		if (tg->se[cpu])
			remove_entity_load_avg(tg->se[cpu]);
10006

10007 10008 10009 10010 10011 10012 10013 10014 10015 10016 10017 10018 10019
		/*
		 * 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);
	}
10020 10021 10022 10023 10024 10025 10026 10027 10028 10029 10030 10031 10032 10033 10034 10035 10036 10037 10038
}

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;

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Peter Zijlstra 已提交
10039
	if (!parent) {
10040
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
10041 10042
		se->depth = 0;
	} else {
10043
		se->cfs_rq = parent->my_q;
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Peter Zijlstra 已提交
10044 10045
		se->depth = parent->depth + 1;
	}
10046 10047

	se->my_q = cfs_rq;
10048 10049
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
10050
	se->parent = parent;
10051
	seqcount_init(&se->idle_seqcount);
10052
	spin_lock_init(&se->iowait_lock);
10053
	se->cg_idle_start = se->cg_init_time = cpu_clock(cpu);
10054 10055 10056 10057 10058 10059 10060 10061 10062 10063 10064 10065 10066 10067 10068 10069 10070 10071 10072 10073 10074 10075 10076
}

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);
10077 10078
		struct sched_entity *se = tg->se[i];
		struct rq_flags rf;
10079 10080

		/* Propagate contribution to hierarchy */
10081
		rq_lock_irqsave(rq, &rf);
10082
		update_rq_clock(rq);
10083
		for_each_sched_entity(se) {
10084
			update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
10085
			update_cfs_group(se);
10086
		}
10087
		rq_unlock_irqrestore(rq, &rf);
10088 10089 10090 10091 10092 10093 10094 10095 10096 10097 10098 10099 10100 10101 10102
	}

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;
}

10103 10104
void online_fair_sched_group(struct task_group *tg) { }

10105
void unregister_fair_sched_group(struct task_group *tg) { }
10106 10107 10108

#endif /* CONFIG_FAIR_GROUP_SCHED */

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10110
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
10111 10112 10113 10114 10115 10116 10117 10118 10119
{
	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)
10120
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
10121 10122 10123 10124

	return rr_interval;
}

10125 10126 10127
/*
 * All the scheduling class methods:
 */
10128
const struct sched_class fair_sched_class = {
10129
	.next			= &idle_sched_class,
10130 10131 10132
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
10133
	.yield_to_task		= yield_to_task_fair,
10134

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Ingo Molnar 已提交
10135
	.check_preempt_curr	= check_preempt_wakeup,
10136 10137 10138 10139

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

10140
#ifdef CONFIG_SMP
L
Li Zefan 已提交
10141
	.select_task_rq		= select_task_rq_fair,
10142
	.migrate_task_rq	= migrate_task_rq_fair,
10143

10144 10145
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
10146

10147
	.task_dead		= task_dead_fair,
10148
	.set_cpus_allowed	= set_cpus_allowed_common,
10149
#endif
10150

10151
	.set_curr_task          = set_curr_task_fair,
10152
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
10153
	.task_fork		= task_fork_fair,
10154 10155

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
10156
	.switched_from		= switched_from_fair,
10157
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
10158

10159 10160
	.get_rr_interval	= get_rr_interval_fair,

10161 10162
	.update_curr		= update_curr_fair,

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10163
#ifdef CONFIG_FAIR_GROUP_SCHED
10164
	.task_change_group	= task_change_group_fair,
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Peter Zijlstra 已提交
10165
#endif
10166 10167

#ifdef CONFIG_SCHED_SLI
10168
	.update_nr_iowait	= update_nr_iowait_fair,
10169
#endif
10170 10171 10172
};

#ifdef CONFIG_SCHED_DEBUG
10173
void print_cfs_stats(struct seq_file *m, int cpu)
10174
{
10175
	struct cfs_rq *cfs_rq;
10176

10177
	rcu_read_lock();
10178
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
10179
		print_cfs_rq(m, cpu, cfs_rq);
10180
	rcu_read_unlock();
10181
}
10182 10183 10184 10185 10186 10187

#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;
10188
	struct numa_group *ng;
10189

10190 10191
	rcu_read_lock();
	ng = rcu_dereference(p->numa_group);
10192 10193 10194 10195 10196
	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)];
		}
10197 10198 10199
		if (ng) {
			gsf = ng->faults[task_faults_idx(NUMA_MEM, node, 0)],
			gpf = ng->faults[task_faults_idx(NUMA_MEM, node, 1)];
10200 10201 10202
		}
		print_numa_stats(m, node, tsf, tpf, gsf, gpf);
	}
10203
	rcu_read_unlock();
10204 10205 10206
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_SCHED_DEBUG */
10207 10208 10209 10210 10211 10212

__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

10213
#ifdef CONFIG_NO_HZ_COMMON
10214
	nohz.next_balance = jiffies;
10215
	nohz.next_blocked = jiffies;
10216 10217 10218 10219 10220
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
#endif
#endif /* SMP */

}