fair.c 267.4 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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/* An entity is a task if it doesn't "own" a runqueue */
#define entity_is_task(se)	(!se->my_q)
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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 thr' all leaf cfs_rq's on a runqueue */
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#define for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos)			\
	list_for_each_entry_safe(cfs_rq, pos, &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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}

#define entity_is_task(se)	1

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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_safe(rq, cfs_rq, pos)	\
		for (cfs_rq = &rq->cfs, pos = NULL; cfs_rq; cfs_rq = pos)
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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;
668
		struct load_weight lw;
L
Lin Ming 已提交
669 670 671

		cfs_rq = cfs_rq_of(se);
		load = &cfs_rq->load;
672

M
Mike Galbraith 已提交
673
		if (unlikely(!se->on_rq)) {
674
			lw = cfs_rq->load;
M
Mike Galbraith 已提交
675 676 677 678

			update_load_add(&lw, se->load.weight);
			load = &lw;
		}
679
		slice = __calc_delta(slice, se->load.weight, load);
M
Mike Galbraith 已提交
680 681
	}
	return slice;
682 683
}

684
/*
A
Andrei Epure 已提交
685
 * We calculate the vruntime slice of a to-be-inserted task.
686
 *
687
 * vs = s/w
688
 */
689
static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
P
Peter Zijlstra 已提交
690
{
691
	return calc_delta_fair(sched_slice(cfs_rq, se), se);
692 693
}

694
#ifdef CONFIG_SMP
695 696 697

#include "sched-pelt.h"

698
static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu);
699 700
static unsigned long task_h_load(struct task_struct *p);

701 702
/* Give new sched_entity start runnable values to heavy its load in infant time */
void init_entity_runnable_average(struct sched_entity *se)
703
{
704
	struct sched_avg *sa = &se->avg;
705

706 707
	memset(sa, 0, sizeof(*sa));

708 709 710 711 712 713 714
	/*
	 * 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))
715 716
		sa->runnable_load_avg = sa->load_avg = scale_load_down(se->load.weight);

717 718
	se->runnable_weight = se->load.weight;

719
	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
720
}
721

722
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
723
static void attach_entity_cfs_rq(struct sched_entity *se);
724

725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753
/*
 * 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:
 *
 *   util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
 *
 * where n denotes the nth task.
 *
 * For example, a simplest series from the beginning would be like:
 *
 *  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;
754
	long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
755 756 757 758 759 760 761 762 763 764 765 766

	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;
		}
	}
767 768 769 770 771 772 773

	if (entity_is_task(se)) {
		struct task_struct *p = task_of(se);
		if (p->sched_class != &fair_sched_class) {
			/*
			 * For !fair tasks do:
			 *
774
			update_cfs_rq_load_avg(now, cfs_rq);
775
			attach_entity_load_avg(cfs_rq, se, 0);
776 777 778 779 780
			switched_from_fair(rq, p);
			 *
			 * such that the next switched_to_fair() has the
			 * expected state.
			 */
781
			se->avg.last_update_time = cfs_rq_clock_task(cfs_rq);
782 783 784 785
			return;
		}
	}

786
	attach_entity_cfs_rq(se);
787 788
}

789
#else /* !CONFIG_SMP */
790
void init_entity_runnable_average(struct sched_entity *se)
791 792
{
}
793 794 795
void post_init_entity_util_avg(struct sched_entity *se)
{
}
796 797 798
static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
{
}
799
#endif /* CONFIG_SMP */
800

801
/*
802
 * Update the current task's runtime statistics.
803
 */
804
static void update_curr(struct cfs_rq *cfs_rq)
805
{
806
	struct sched_entity *curr = cfs_rq->curr;
807
	u64 now = rq_clock_task(rq_of(cfs_rq));
808
	u64 delta_exec;
809 810 811 812

	if (unlikely(!curr))
		return;

813 814
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
815
		return;
816

I
Ingo Molnar 已提交
817
	curr->exec_start = now;
818

819 820 821 822
	schedstat_set(curr->statistics.exec_max,
		      max(delta_exec, curr->statistics.exec_max));

	curr->sum_exec_runtime += delta_exec;
823
	schedstat_add(cfs_rq->exec_clock, delta_exec);
824 825 826 827

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

828 829 830
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

831
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
832
		cgroup_account_cputime(curtask, delta_exec);
833
		account_group_exec_runtime(curtask, delta_exec);
834
	}
835 836

	account_cfs_rq_runtime(cfs_rq, delta_exec);
837 838
}

839 840 841 842 843
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

844
static inline void
845
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
846
{
847 848 849 850 851 852 853
	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);
854 855

	if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
856 857
	    likely(wait_start > prev_wait_start))
		wait_start -= prev_wait_start;
858

859
	__schedstat_set(se->statistics.wait_start, wait_start);
860 861
}

862
static inline void
863 864 865
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *p;
866 867
	u64 delta;

868 869 870 871
	if (!schedstat_enabled())
		return;

	delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start);
872 873 874 875 876 877 878 879 880

	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.
			 */
881
			__schedstat_set(se->statistics.wait_start, delta);
882 883 884 885 886
			return;
		}
		trace_sched_stat_wait(p, delta);
	}

887
	__schedstat_set(se->statistics.wait_max,
888
		      max(schedstat_val(se->statistics.wait_max), delta));
889 890 891
	__schedstat_inc(se->statistics.wait_count);
	__schedstat_add(se->statistics.wait_sum, delta);
	__schedstat_set(se->statistics.wait_start, 0);
892 893
}

894
static inline void
895 896 897
update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *tsk = NULL;
898 899 900 901 902 903 904
	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);
905 906 907 908

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

909 910
	if (sleep_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start;
911 912 913 914

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

915
		if (unlikely(delta > schedstat_val(se->statistics.sleep_max)))
916
			__schedstat_set(se->statistics.sleep_max, delta);
917

918 919
		__schedstat_set(se->statistics.sleep_start, 0);
		__schedstat_add(se->statistics.sum_sleep_runtime, delta);
920 921 922 923 924 925

		if (tsk) {
			account_scheduler_latency(tsk, delta >> 10, 1);
			trace_sched_stat_sleep(tsk, delta);
		}
	}
926 927
	if (block_start) {
		u64 delta = rq_clock(rq_of(cfs_rq)) - block_start;
928 929 930 931

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

932
		if (unlikely(delta > schedstat_val(se->statistics.block_max)))
933
			__schedstat_set(se->statistics.block_max, delta);
934

935 936
		__schedstat_set(se->statistics.block_start, 0);
		__schedstat_add(se->statistics.sum_sleep_runtime, delta);
937 938 939

		if (tsk) {
			if (tsk->in_iowait) {
940 941
				__schedstat_add(se->statistics.iowait_sum, delta);
				__schedstat_inc(se->statistics.iowait_count);
942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959
				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);
		}
	}
960 961
}

962 963 964
/*
 * Task is being enqueued - update stats:
 */
965
static inline void
966
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
967
{
968 969 970
	if (!schedstat_enabled())
		return;

971 972 973 974
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
975
	if (se != cfs_rq->curr)
976
		update_stats_wait_start(cfs_rq, se);
977 978 979

	if (flags & ENQUEUE_WAKEUP)
		update_stats_enqueue_sleeper(cfs_rq, se);
980 981 982
}

static inline void
983
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
984
{
985 986 987 988

	if (!schedstat_enabled())
		return;

989 990 991 992
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
993
	if (se != cfs_rq->curr)
994
		update_stats_wait_end(cfs_rq, se);
995

996 997
	if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) {
		struct task_struct *tsk = task_of(se);
998

999
		if (tsk->state & TASK_INTERRUPTIBLE)
1000
			__schedstat_set(se->statistics.sleep_start,
1001 1002
				      rq_clock(rq_of(cfs_rq)));
		if (tsk->state & TASK_UNINTERRUPTIBLE)
1003
			__schedstat_set(se->statistics.block_start,
1004
				      rq_clock(rq_of(cfs_rq)));
1005 1006 1007
	}
}

1008 1009 1010 1011
/*
 * We are picking a new current task - update its stats:
 */
static inline void
1012
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
1013 1014 1015 1016
{
	/*
	 * We are starting a new run period:
	 */
1017
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
1018 1019 1020 1021 1022 1023
}

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

1024 1025
#ifdef CONFIG_NUMA_BALANCING
/*
1026 1027 1028
 * 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.
1029
 */
1030 1031
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
1032 1033 1034

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
1035

1036 1037 1038
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061
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];
};

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

1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085
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)
{
1086
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
1087 1088 1089
	unsigned int scan, floor;
	unsigned int windows = 1;

1090 1091
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
1092 1093 1094 1095 1096 1097
	floor = 1000 / windows;

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

1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116
static unsigned int task_scan_start(struct task_struct *p)
{
	unsigned long smin = task_scan_min(p);
	unsigned long period = smin;

	/* Scale the maximum scan period with the amount of shared memory. */
	if (p->numa_group) {
		struct numa_group *ng = p->numa_group;
		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;
	}

	return max(smin, period);
}

1117 1118
static unsigned int task_scan_max(struct task_struct *p)
{
1119 1120
	unsigned long smin = task_scan_min(p);
	unsigned long smax;
1121 1122 1123

	/* Watch for min being lower than max due to floor calculations */
	smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138

	/* Scale the maximum scan period with the amount of shared memory. */
	if (p->numa_group) {
		struct numa_group *ng = p->numa_group;
		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);
	}

1139 1140 1141
	return max(smin, smax);
}

1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153
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));
}

1154 1155 1156 1157 1158 1159 1160 1161 1162
/* 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)

1163 1164 1165 1166 1167
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

1168
/*
1169
 * The averaged statistics, shared & private, memory & CPU,
1170 1171 1172 1173 1174
 * 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)
1175
{
1176
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1177 1178 1179 1180
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
1181
	if (!p->numa_faults)
1182 1183
		return 0;

1184 1185
	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1186 1187
}

1188 1189 1190 1191 1192
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

1193 1194
	return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1195 1196
}

1197 1198
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
1199 1200
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1201 1202
}

1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226
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;
}

1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238
/*
 * 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;
}

1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303
/* 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 &&
					dist > maxdist)
			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;
}

1304 1305 1306 1307 1308 1309
/*
 * 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.
 */
1310 1311
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1312
{
1313
	unsigned long faults, total_faults;
1314

1315
	if (!p->numa_faults)
1316 1317 1318 1319 1320 1321 1322
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1323
	faults = task_faults(p, nid);
1324 1325
	faults += score_nearby_nodes(p, nid, dist, true);

1326
	return 1000 * faults / total_faults;
1327 1328
}

1329 1330
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1331
{
1332 1333 1334 1335 1336 1337 1338 1339
	unsigned long faults, total_faults;

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1340 1341
		return 0;

1342
	faults = group_faults(p, nid);
1343 1344
	faults += score_nearby_nodes(p, nid, dist, false);

1345
	return 1000 * faults / total_faults;
1346 1347
}

1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387
bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
				int src_nid, int dst_cpu)
{
	struct numa_group *ng = p->numa_group;
	int dst_nid = cpu_to_node(dst_cpu);
	int last_cpupid, this_cpupid;

	this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid);

	/*
	 * 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.
	 */
	last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
	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;

	/*
1388 1389
	 * Destination node is much more heavily used than the source
	 * node? Allow migration.
1390
	 */
1391 1392
	if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
					ACTIVE_NODE_FRACTION)
1393 1394 1395
		return true;

	/*
1396 1397 1398 1399 1400 1401
	 * 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)
1402
	 */
1403 1404
	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;
1405 1406
}

1407
static unsigned long weighted_cpuload(struct rq *rq);
1408 1409
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1410
static unsigned long capacity_of(int cpu);
1411

1412
/* Cached statistics for all CPUs within a node */
1413
struct numa_stats {
1414
	unsigned long nr_running;
1415
	unsigned long load;
1416 1417

	/* Total compute capacity of CPUs on a node */
1418
	unsigned long compute_capacity;
1419 1420

	/* Approximate capacity in terms of runnable tasks on a node */
1421
	unsigned long task_capacity;
1422
	int has_free_capacity;
1423
};
1424

1425 1426 1427 1428 1429
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1430 1431
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1432 1433 1434 1435 1436 1437

	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;
1438
		ns->load += weighted_cpuload(rq);
1439
		ns->compute_capacity += capacity_of(cpu);
1440 1441

		cpus++;
1442 1443
	}

1444 1445 1446 1447 1448
	/*
	 * 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.
	 *
1449 1450
	 * We'll either bail at !has_free_capacity, or we'll detect a huge
	 * imbalance and bail there.
1451 1452 1453 1454
	 */
	if (!cpus)
		return;

1455 1456 1457 1458 1459 1460
	/* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
	smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
	capacity = cpus / smt; /* cores */

	ns->task_capacity = min_t(unsigned, capacity,
		DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1461
	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1462 1463
}

1464 1465
struct task_numa_env {
	struct task_struct *p;
1466

1467 1468
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1469

1470
	struct numa_stats src_stats, dst_stats;
1471

1472
	int imbalance_pct;
1473
	int dist;
1474 1475 1476

	struct task_struct *best_task;
	long best_imp;
1477 1478 1479
	int best_cpu;
};

1480 1481 1482 1483 1484
static void task_numa_assign(struct task_numa_env *env,
			     struct task_struct *p, long imp)
{
	if (env->best_task)
		put_task_struct(env->best_task);
1485 1486
	if (p)
		get_task_struct(p);
1487 1488 1489 1490 1491 1492

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

1493
static bool load_too_imbalanced(long src_load, long dst_load,
1494 1495
				struct task_numa_env *env)
{
1496 1497
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508
	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;
1509 1510

	/* We care about the slope of the imbalance, not the direction. */
1511 1512
	if (dst_load < src_load)
		swap(dst_load, src_load);
1513 1514

	/* Is the difference below the threshold? */
1515 1516
	imb = dst_load * src_capacity * 100 -
	      src_load * dst_capacity * env->imbalance_pct;
1517 1518 1519 1520 1521
	if (imb <= 0)
		return false;

	/*
	 * The imbalance is above the allowed threshold.
1522
	 * Compare it with the old imbalance.
1523
	 */
1524
	orig_src_load = env->src_stats.load;
1525
	orig_dst_load = env->dst_stats.load;
1526

1527 1528
	if (orig_dst_load < orig_src_load)
		swap(orig_dst_load, orig_src_load);
1529

1530 1531 1532 1533 1534
	old_imb = orig_dst_load * src_capacity * 100 -
		  orig_src_load * dst_capacity * env->imbalance_pct;

	/* Would this change make things worse? */
	return (imb > old_imb);
1535 1536
}

1537 1538 1539 1540 1541 1542
/*
 * 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
 */
1543 1544
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1545 1546 1547 1548
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1549
	long src_load, dst_load;
1550
	long load;
1551
	long imp = env->p->numa_group ? groupimp : taskimp;
1552
	long moveimp = imp;
1553
	int dist = env->dist;
1554 1555

	rcu_read_lock();
1556 1557
	cur = task_rcu_dereference(&dst_rq->curr);
	if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1558 1559
		cur = NULL;

1560 1561 1562 1563 1564 1565 1566
	/*
	 * 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;

1567 1568 1569 1570 1571 1572 1573 1574
	/*
	 * "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
	 * the value is, the more rmeote accesses that would be expected to
	 * be incurred if the tasks were swapped.
	 */
	if (cur) {
1575
		/* Skip this swap candidate if cannot move to the source CPU: */
1576
		if (!cpumask_test_cpu(env->src_cpu, &cur->cpus_allowed))
1577 1578
			goto unlock;

1579 1580
		/*
		 * If dst and source tasks are in the same NUMA group, or not
1581
		 * in any group then look only at task weights.
1582
		 */
1583
		if (cur->numa_group == env->p->numa_group) {
1584 1585
			imp = taskimp + task_weight(cur, env->src_nid, dist) -
			      task_weight(cur, env->dst_nid, dist);
1586 1587 1588 1589 1590 1591
			/*
			 * Add some hysteresis to prevent swapping the
			 * tasks within a group over tiny differences.
			 */
			if (cur->numa_group)
				imp -= imp/16;
1592
		} else {
1593 1594 1595 1596 1597 1598
			/*
			 * Compare the group weights. If a task is all by
			 * itself (not part of a group), use the task weight
			 * instead.
			 */
			if (cur->numa_group)
1599 1600
				imp += group_weight(cur, env->src_nid, dist) -
				       group_weight(cur, env->dst_nid, dist);
1601
			else
1602 1603
				imp += task_weight(cur, env->src_nid, dist) -
				       task_weight(cur, env->dst_nid, dist);
1604
		}
1605 1606
	}

1607
	if (imp <= env->best_imp && moveimp <= env->best_imp)
1608 1609 1610 1611
		goto unlock;

	if (!cur) {
		/* Is there capacity at our destination? */
1612
		if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1613
		    !env->dst_stats.has_free_capacity)
1614 1615 1616 1617 1618
			goto unlock;

		goto balance;
	}

1619
	/* Balance doesn't matter much if we're running a task per CPU: */
1620 1621
	if (imp > env->best_imp && src_rq->nr_running == 1 &&
			dst_rq->nr_running == 1)
1622 1623 1624 1625 1626 1627
		goto assign;

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
balance:
1628 1629 1630
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1631

1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648
	if (moveimp > imp && moveimp > env->best_imp) {
		/*
		 * If the improvement from just moving env->p direction is
		 * better than swapping tasks around, check if a move is
		 * possible. Store a slightly smaller score than moveimp,
		 * so an actually idle CPU will win.
		 */
		if (!load_too_imbalanced(src_load, dst_load, env)) {
			imp = moveimp - 1;
			cur = NULL;
			goto assign;
		}
	}

	if (imp <= env->best_imp)
		goto unlock;

1649
	if (cur) {
1650 1651 1652
		load = task_h_load(cur);
		dst_load -= load;
		src_load += load;
1653 1654
	}

1655
	if (load_too_imbalanced(src_load, dst_load, env))
1656 1657
		goto unlock;

1658 1659 1660 1661
	/*
	 * One idle CPU per node is evaluated for a task numa move.
	 * Call select_idle_sibling to maybe find a better one.
	 */
1662 1663
	if (!cur) {
		/*
1664
		 * select_idle_siblings() uses an per-CPU cpumask that
1665 1666 1667
		 * can be used from IRQ context.
		 */
		local_irq_disable();
1668 1669
		env->dst_cpu = select_idle_sibling(env->p, env->src_cpu,
						   env->dst_cpu);
1670 1671
		local_irq_enable();
	}
1672

1673 1674 1675 1676 1677 1678
assign:
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1679 1680
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1681 1682 1683 1684 1685
{
	int cpu;

	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
		/* Skip this CPU if the source task cannot migrate */
1686
		if (!cpumask_test_cpu(cpu, &env->p->cpus_allowed))
1687 1688 1689
			continue;

		env->dst_cpu = cpu;
1690
		task_numa_compare(env, taskimp, groupimp);
1691 1692 1693
	}
}

1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710
/* Only move tasks to a NUMA node less busy than the current node. */
static bool numa_has_capacity(struct task_numa_env *env)
{
	struct numa_stats *src = &env->src_stats;
	struct numa_stats *dst = &env->dst_stats;

	if (src->has_free_capacity && !dst->has_free_capacity)
		return false;

	/*
	 * Only consider a task move if the source has a higher load
	 * than the destination, corrected for CPU capacity on each node.
	 *
	 *      src->load                dst->load
	 * --------------------- vs ---------------------
	 * src->compute_capacity    dst->compute_capacity
	 */
1711 1712 1713
	if (src->load * dst->compute_capacity * env->imbalance_pct >

	    dst->load * src->compute_capacity * 100)
1714 1715 1716 1717 1718
		return true;

	return false;
}

1719 1720 1721 1722
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1723

1724
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1725
		.src_nid = task_node(p),
1726 1727 1728 1729 1730

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
1731
		.best_cpu = -1,
1732 1733
	};
	struct sched_domain *sd;
1734
	unsigned long taskweight, groupweight;
1735
	int nid, ret, dist;
1736
	long taskimp, groupimp;
1737

1738
	/*
1739 1740 1741 1742 1743 1744
	 * 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.
1745 1746
	 */
	rcu_read_lock();
1747
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1748 1749
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1750 1751
	rcu_read_unlock();

1752 1753 1754 1755 1756 1757 1758
	/*
	 * 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)) {
1759
		p->numa_preferred_nid = task_node(p);
1760 1761 1762
		return -EINVAL;
	}

1763
	env.dst_nid = p->numa_preferred_nid;
1764 1765 1766 1767 1768 1769
	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;
1770
	update_numa_stats(&env.dst_stats, env.dst_nid);
1771

1772
	/* Try to find a spot on the preferred nid. */
1773 1774
	if (numa_has_capacity(&env))
		task_numa_find_cpu(&env, taskimp, groupimp);
1775

1776 1777 1778 1779 1780 1781 1782
	/*
	 * 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.
	 */
1783
	if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
1784 1785 1786
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1787

1788
			dist = node_distance(env.src_nid, env.dst_nid);
1789 1790 1791 1792 1793
			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);
			}
1794

1795
			/* Only consider nodes where both task and groups benefit */
1796 1797
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1798
			if (taskimp < 0 && groupimp < 0)
1799 1800
				continue;

1801
			env.dist = dist;
1802 1803
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1804 1805
			if (numa_has_capacity(&env))
				task_numa_find_cpu(&env, taskimp, groupimp);
1806 1807 1808
		}
	}

1809 1810 1811 1812 1813 1814 1815 1816
	/*
	 * 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.
	 */
1817
	if (p->numa_group) {
1818 1819
		struct numa_group *ng = p->numa_group;

1820 1821 1822 1823 1824
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
			nid = env.dst_nid;

1825
		if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
1826 1827 1828 1829 1830 1831
			sched_setnuma(p, env.dst_nid);
	}

	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;
1832

1833 1834 1835 1836
	/*
	 * Reset the scan period if the task is being rescheduled on an
	 * alternative node to recheck if the tasks is now properly placed.
	 */
1837
	p->numa_scan_period = task_scan_start(p);
1838

1839
	if (env.best_task == NULL) {
1840 1841 1842
		ret = migrate_task_to(p, env.best_cpu);
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1843 1844 1845 1846
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
1847 1848
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1849 1850
	put_task_struct(env.best_task);
	return ret;
1851 1852
}

1853 1854 1855
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1856
	unsigned long interval = HZ;
1857
	unsigned long numa_migrate_retry;
1858

1859
	/* This task has no NUMA fault statistics yet */
1860
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1861 1862
		return;

1863
	/* Periodically retry migrating the task to the preferred node */
1864
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876
	numa_migrate_retry = jiffies + interval;

	/*
	 * Check that the new retry threshold is after the current one. If
	 * the retry is in the future, it implies that wake_affine has
	 * temporarily asked NUMA balancing to backoff from placement.
	 */
	if (numa_migrate_retry > p->numa_migrate_retry)
		return;

	/* Safe to try placing the task on the preferred node */
	p->numa_migrate_retry = numa_migrate_retry;
1877 1878

	/* Success if task is already running on preferred CPU */
1879
	if (task_node(p) == p->numa_preferred_nid)
1880 1881 1882
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1883
	task_numa_migrate(p);
1884 1885
}

1886
/*
1887
 * Find out how many nodes on the workload is actively running on. Do this by
1888 1889 1890 1891
 * 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.
 */
1892
static void numa_group_count_active_nodes(struct numa_group *numa_group)
1893 1894
{
	unsigned long faults, max_faults = 0;
1895
	int nid, active_nodes = 0;
1896 1897 1898 1899 1900 1901 1902 1903 1904

	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);
1905 1906
		if (faults * ACTIVE_NODE_FRACTION > max_faults)
			active_nodes++;
1907
	}
1908 1909 1910

	numa_group->max_faults_cpu = max_faults;
	numa_group->active_nodes = active_nodes;
1911 1912
}

1913 1914 1915
/*
 * 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
1916 1917 1918
 * 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.
1919 1920
 */
#define NUMA_PERIOD_SLOTS 10
1921
#define NUMA_PERIOD_THRESHOLD 7
1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932

/*
 * 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;
1933
	int lr_ratio, ps_ratio;
1934 1935 1936 1937 1938 1939 1940 1941
	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
1942 1943 1944
	 * 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
1945
	 */
1946
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962
		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);
1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981
	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;
1982 1983 1984 1985 1986
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else {
		/*
1987 1988 1989
		 * 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.
1990
		 */
1991 1992
		int ratio = max(lr_ratio, ps_ratio);
		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;
1993 1994 1995 1996 1997 1998 1999
	}

	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));
}

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
/*
 * 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;
	} else {
2018
		delta = p->se.avg.load_sum;
2019
		*period = LOAD_AVG_MAX;
2020 2021 2022 2023 2024 2025 2026 2027
	}

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

	return delta;
}

2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074
/*
 * 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;
2075
		nodemask_t max_group = NODE_MASK_NONE;
2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108
		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. */
2109 2110
		if (!max_faults)
			break;
2111 2112 2113 2114 2115
		nodes = max_group;
	}
	return nid;
}

2116 2117
static void task_numa_placement(struct task_struct *p)
{
2118 2119
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
2120
	unsigned long fault_types[2] = { 0, 0 };
2121 2122
	unsigned long total_faults;
	u64 runtime, period;
2123
	spinlock_t *group_lock = NULL;
2124

2125 2126 2127 2128 2129
	/*
	 * 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:
	 */
2130
	seq = READ_ONCE(p->mm->numa_scan_seq);
2131 2132 2133
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
2134
	p->numa_scan_period_max = task_scan_max(p);
2135

2136 2137 2138 2139
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

2140 2141 2142
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
2143
		spin_lock_irq(group_lock);
2144 2145
	}

2146 2147
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
2148 2149
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
2150
		unsigned long faults = 0, group_faults = 0;
2151
		int priv;
2152

2153
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
2154
			long diff, f_diff, f_weight;
2155

2156 2157 2158 2159
			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);
2160

2161
			/* Decay existing window, copy faults since last scan */
2162 2163 2164
			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;
2165

2166 2167 2168 2169 2170 2171 2172 2173
			/*
			 * 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);
2174
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
2175
				   (total_faults + 1);
2176 2177
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
2178

2179 2180 2181
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
2182
			p->total_numa_faults += diff;
2183
			if (p->numa_group) {
2184 2185 2186 2187 2188 2189 2190 2191 2192
				/*
				 * 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.
				 */
				p->numa_group->faults[mem_idx] += diff;
				p->numa_group->faults_cpu[mem_idx] += f_diff;
2193
				p->numa_group->total_faults += diff;
2194
				group_faults += p->numa_group->faults[mem_idx];
2195
			}
2196 2197
		}

2198 2199 2200 2201
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
2202 2203 2204 2205 2206 2207 2208

		if (group_faults > max_group_faults) {
			max_group_faults = group_faults;
			max_group_nid = nid;
		}
	}

2209 2210
	update_task_scan_period(p, fault_types[0], fault_types[1]);

2211
	if (p->numa_group) {
2212
		numa_group_count_active_nodes(p->numa_group);
2213
		spin_unlock_irq(group_lock);
2214
		max_nid = preferred_group_nid(p, max_group_nid);
2215 2216
	}

2217 2218 2219 2220 2221 2222 2223
	if (max_faults) {
		/* Set the new preferred node */
		if (max_nid != p->numa_preferred_nid)
			sched_setnuma(p, max_nid);

		if (task_node(p) != p->numa_preferred_nid)
			numa_migrate_preferred(p);
2224
	}
2225 2226
}

2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237
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);
}

2238 2239
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
2240 2241 2242 2243 2244 2245 2246 2247 2248
{
	struct numa_group *grp, *my_grp;
	struct task_struct *tsk;
	bool join = false;
	int cpu = cpupid_to_cpu(cpupid);
	int i;

	if (unlikely(!p->numa_group)) {
		unsigned int size = sizeof(struct numa_group) +
2249
				    4*nr_node_ids*sizeof(unsigned long);
2250 2251 2252 2253 2254 2255

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

		atomic_set(&grp->refcount, 1);
2256 2257
		grp->active_nodes = 1;
		grp->max_faults_cpu = 0;
2258
		spin_lock_init(&grp->lock);
2259
		grp->gid = p->pid;
2260
		/* Second half of the array tracks nids where faults happen */
2261 2262
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
2263

2264
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2265
			grp->faults[i] = p->numa_faults[i];
2266

2267
		grp->total_faults = p->total_numa_faults;
2268

2269 2270 2271 2272 2273
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
2274
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
2275 2276

	if (!cpupid_match_pid(tsk, cpupid))
2277
		goto no_join;
2278 2279 2280

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
2281
		goto no_join;
2282 2283 2284

	my_grp = p->numa_group;
	if (grp == my_grp)
2285
		goto no_join;
2286 2287 2288 2289 2290 2291

	/*
	 * 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)
2292
		goto no_join;
2293 2294 2295 2296 2297

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2298
		goto no_join;
2299

2300 2301 2302 2303 2304 2305 2306
	/* 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;
2307

2308 2309 2310
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2311
	if (join && !get_numa_group(grp))
2312
		goto no_join;
2313 2314 2315 2316 2317 2318

	rcu_read_unlock();

	if (!join)
		return;

2319 2320
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2321

2322
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2323 2324
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2325
	}
2326 2327
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2328 2329 2330 2331 2332

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

	spin_unlock(&my_grp->lock);
2333
	spin_unlock_irq(&grp->lock);
2334 2335 2336 2337

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2338 2339 2340 2341 2342
	return;

no_join:
	rcu_read_unlock();
	return;
2343 2344 2345 2346 2347
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
2348
	void *numa_faults = p->numa_faults;
2349 2350
	unsigned long flags;
	int i;
2351 2352

	if (grp) {
2353
		spin_lock_irqsave(&grp->lock, flags);
2354
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2355
			grp->faults[i] -= p->numa_faults[i];
2356
		grp->total_faults -= p->total_numa_faults;
2357

2358
		grp->nr_tasks--;
2359
		spin_unlock_irqrestore(&grp->lock, flags);
2360
		RCU_INIT_POINTER(p->numa_group, NULL);
2361 2362 2363
		put_numa_group(grp);
	}

2364
	p->numa_faults = NULL;
2365
	kfree(numa_faults);
2366 2367
}

2368 2369 2370
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2371
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2372 2373
{
	struct task_struct *p = current;
2374
	bool migrated = flags & TNF_MIGRATED;
2375
	int cpu_node = task_node(current);
2376
	int local = !!(flags & TNF_FAULT_LOCAL);
2377
	struct numa_group *ng;
2378
	int priv;
2379

2380
	if (!static_branch_likely(&sched_numa_balancing))
2381 2382
		return;

2383 2384 2385 2386
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2387
	/* Allocate buffer to track faults on a per-node basis */
2388 2389
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2390
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2391

2392 2393
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2394
			return;
2395

2396
		p->total_numa_faults = 0;
2397
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2398
	}
2399

2400 2401 2402 2403 2404 2405 2406 2407
	/*
	 * 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);
2408
		if (!priv && !(flags & TNF_NO_GROUP))
2409
			task_numa_group(p, last_cpupid, flags, &priv);
2410 2411
	}

2412 2413 2414 2415 2416 2417
	/*
	 * 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.
	 */
2418 2419 2420 2421
	ng = p->numa_group;
	if (!priv && !local && ng && ng->active_nodes > 1 &&
				numa_is_active_node(cpu_node, ng) &&
				numa_is_active_node(mem_node, ng))
2422 2423
		local = 1;

2424
	task_numa_placement(p);
2425

2426 2427 2428 2429 2430
	/*
	 * Retry task to preferred node migration periodically, in case it
	 * case it previously failed, or the scheduler moved us.
	 */
	if (time_after(jiffies, p->numa_migrate_retry))
2431 2432
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
2433 2434
	if (migrated)
		p->numa_pages_migrated += pages;
2435 2436
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2437

2438 2439
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2440
	p->numa_faults_locality[local] += pages;
2441 2442
}

2443 2444
static void reset_ptenuma_scan(struct task_struct *p)
{
2445 2446 2447 2448 2449 2450 2451 2452
	/*
	 * 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:
	 */
2453
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2454 2455 2456
	p->mm->numa_scan_offset = 0;
}

2457 2458 2459 2460 2461 2462 2463 2464 2465
/*
 * 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;
2466
	u64 runtime = p->se.sum_exec_runtime;
2467
	struct vm_area_struct *vma;
2468
	unsigned long start, end;
2469
	unsigned long nr_pte_updates = 0;
2470
	long pages, virtpages;
2471

2472
	SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work));
2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485

	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;

2486
	if (!mm->numa_next_scan) {
2487 2488
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2489 2490
	}

2491 2492 2493 2494 2495 2496 2497
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2498 2499
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
2500
		p->numa_scan_period = task_scan_start(p);
2501
	}
2502

2503
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2504 2505 2506
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2507 2508 2509 2510 2511 2512
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2513 2514 2515
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2516
	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2517 2518
	if (!pages)
		return;
2519

2520

2521 2522
	if (!down_read_trylock(&mm->mmap_sem))
		return;
2523
	vma = find_vma(mm, start);
2524 2525
	if (!vma) {
		reset_ptenuma_scan(p);
2526
		start = 0;
2527 2528
		vma = mm->mmap;
	}
2529
	for (; vma; vma = vma->vm_next) {
2530
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2531
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2532
			continue;
2533
		}
2534

2535 2536 2537 2538 2539 2540 2541 2542 2543 2544
		/*
		 * 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
2545 2546 2547 2548 2549 2550
		/*
		 * 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;
2551

2552 2553 2554 2555
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2556
			nr_pte_updates = change_prot_numa(vma, start, end);
2557 2558

			/*
2559 2560 2561 2562 2563 2564
			 * 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.
2565 2566 2567
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2568
			virtpages -= (end - start) >> PAGE_SHIFT;
2569

2570
			start = end;
2571
			if (pages <= 0 || virtpages <= 0)
2572
				goto out;
2573 2574

			cond_resched();
2575
		} while (end != vma->vm_end);
2576
	}
2577

2578
out:
2579
	/*
P
Peter Zijlstra 已提交
2580 2581 2582 2583
	 * 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.
2584 2585
	 */
	if (vma)
2586
		mm->numa_scan_offset = start;
2587 2588 2589
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600

	/*
	 * 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;
	}
2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625
}

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

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

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

2626
	if (now > curr->node_stamp + period) {
2627
		if (!curr->node_stamp)
2628
			curr->numa_scan_period = task_scan_start(curr);
2629
		curr->node_stamp += period;
2630 2631 2632 2633 2634 2635 2636

		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);
		}
	}
}
2637

2638 2639 2640 2641
#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
}
2642 2643 2644 2645 2646 2647 2648 2649

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)
{
}
2650

2651 2652
#endif /* CONFIG_NUMA_BALANCING */

2653 2654 2655 2656
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2657
	if (!parent_entity(se))
2658
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2659
#ifdef CONFIG_SMP
2660 2661 2662 2663 2664 2665
	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);
	}
2666
#endif
2667 2668 2669 2670 2671 2672 2673
	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);
2674
	if (!parent_entity(se))
2675
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2676
#ifdef CONFIG_SMP
2677 2678
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2679
		list_del_init(&se->group_node);
2680
	}
2681
#endif
2682 2683 2684
	cfs_rq->nr_running--;
}

2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723
/*
 * 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
/*
2724
 * XXX we want to get rid of these helpers and use the full load resolution.
2725 2726 2727 2728 2729 2730
 */
static inline long se_weight(struct sched_entity *se)
{
	return scale_load_down(se->load.weight);
}

2731 2732 2733 2734 2735
static inline long se_runnable(struct sched_entity *se)
{
	return scale_load_down(se->runnable_weight);
}

2736 2737 2738
static inline void
enqueue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2739 2740 2741 2742
	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;
2743 2744 2745 2746 2747
}

static inline void
dequeue_runnable_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2748 2749 2750 2751 2752
	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);
2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778
}

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

2779
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
2780
			    unsigned long weight, unsigned long runnable)
2781 2782 2783 2784 2785 2786 2787 2788 2789 2790
{
	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);

2791
	se->runnable_weight = runnable;
2792 2793 2794
	update_load_set(&se->load, weight);

#ifdef CONFIG_SMP
2795 2796 2797 2798 2799 2800 2801
	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);
2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817
#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]);

2818
	reweight_entity(cfs_rq, se, weight, weight);
2819 2820 2821
	load->inv_weight = sched_prio_to_wmult[prio];
}

2822
#ifdef CONFIG_FAIR_GROUP_SCHED
2823
#ifdef CONFIG_SMP
2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861
/*
 * 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
2862
 *   ge->load.weight = ----------------------------- = tg->weight   (4)
2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875
 *			    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
 *
2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887
 * 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)
2888 2889 2890 2891 2892 2893 2894 2895 2896
 *
 * 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!
 */
2897
static long calc_group_shares(struct cfs_rq *cfs_rq)
2898
{
2899 2900 2901 2902
	long tg_weight, tg_shares, load, shares;
	struct task_group *tg = cfs_rq->tg;

	tg_shares = READ_ONCE(tg->shares);
2903

2904
	load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
2905

2906
	tg_weight = atomic_long_read(&tg->load_avg);
2907

2908 2909 2910
	/* Ensure tg_weight >= load */
	tg_weight -= cfs_rq->tg_load_avg_contrib;
	tg_weight += load;
2911

2912
	shares = (tg_shares * load);
2913 2914
	if (tg_weight)
		shares /= tg_weight;
2915

2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927
	/*
	 * 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.
	 */
2928
	return clamp_t(long, shares, MIN_SHARES, tg_shares);
2929
}
2930 2931

/*
2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956
 * 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).
2957 2958 2959
 */
static long calc_group_runnable(struct cfs_rq *cfs_rq, long shares)
{
2960 2961 2962 2963 2964 2965 2966
	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));
2967 2968 2969 2970

	runnable *= shares;
	if (load_avg)
		runnable /= load_avg;
2971

2972 2973
	return clamp_t(long, runnable, MIN_SHARES, shares);
}
2974
#endif /* CONFIG_SMP */
2975

2976 2977
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2978 2979 2980 2981 2982
/*
 * 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
2983
{
2984 2985
	struct cfs_rq *gcfs_rq = group_cfs_rq(se);
	long shares, runnable;
P
Peter Zijlstra 已提交
2986

2987
	if (!gcfs_rq)
2988 2989
		return;

2990
	if (throttled_hierarchy(gcfs_rq))
P
Peter Zijlstra 已提交
2991
		return;
2992

2993
#ifndef CONFIG_SMP
2994
	runnable = shares = READ_ONCE(gcfs_rq->tg->shares);
2995 2996

	if (likely(se->load.weight == shares))
2997
		return;
2998
#else
2999 3000
	shares   = calc_group_shares(gcfs_rq);
	runnable = calc_group_runnable(gcfs_rq, shares);
3001
#endif
P
Peter Zijlstra 已提交
3002

3003
	reweight_entity(cfs_rq_of(se), se, shares, runnable);
P
Peter Zijlstra 已提交
3004
}
3005

P
Peter Zijlstra 已提交
3006
#else /* CONFIG_FAIR_GROUP_SCHED */
3007
static inline void update_cfs_group(struct sched_entity *se)
P
Peter Zijlstra 已提交
3008 3009 3010 3011
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

3012
static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags)
3013
{
3014 3015
	struct rq *rq = rq_of(cfs_rq);

3016
	if (&rq->cfs == cfs_rq || (flags & SCHED_CPUFREQ_MIGRATION)) {
3017 3018 3019
		/*
		 * There are a few boundary cases this might miss but it should
		 * get called often enough that that should (hopefully) not be
3020
		 * a real problem.
3021 3022 3023 3024 3025 3026 3027 3028 3029 3030
		 *
		 * 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().
		 */
3031
		cpufreq_update_util(rq, flags);
3032 3033 3034
	}
}

3035
#ifdef CONFIG_SMP
3036 3037 3038 3039
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
3040
static u64 decay_load(u64 val, u64 n)
3041
{
3042 3043
	unsigned int local_n;

3044
	if (unlikely(n > LOAD_AVG_PERIOD * 63))
3045 3046 3047 3048 3049 3050 3051
		return 0;

	/* after bounds checking we can collapse to 32-bit */
	local_n = n;

	/*
	 * As y^PERIOD = 1/2, we can combine
3052 3053
	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
	 * With a look-up table which covers y^n (n<PERIOD)
3054 3055 3056 3057 3058 3059
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
3060 3061
	}

3062 3063
	val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
	return val;
3064 3065
}

3066
static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3)
3067
{
3068
	u32 c1, c2, c3 = d3; /* y^0 == 1 */
3069

3070
	/*
P
Peter Zijlstra 已提交
3071
	 * c1 = d1 y^p
3072
	 */
3073
	c1 = decay_load((u64)d1, periods);
3074 3075

	/*
P
Peter Zijlstra 已提交
3076
	 *            p-1
3077 3078
	 * c2 = 1024 \Sum y^n
	 *            n=1
3079
	 *
3080 3081
	 *              inf        inf
	 *    = 1024 ( \Sum y^n - \Sum y^n - y^0 )
P
Peter Zijlstra 已提交
3082
	 *              n=0        n=p
3083
	 */
3084
	c2 = LOAD_AVG_MAX - decay_load(LOAD_AVG_MAX, periods) - 1024;
3085 3086

	return c1 + c2 + c3;
3087 3088
}

3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099
/*
 * Accumulate the three separate parts of the sum; d1 the remainder
 * of the last (incomplete) period, d2 the span of full periods and d3
 * the remainder of the (incomplete) current period.
 *
 *           d1          d2           d3
 *           ^           ^            ^
 *           |           |            |
 *         |<->|<----------------->|<--->|
 * ... |---x---|------| ... |------|-----x (now)
 *
P
Peter Zijlstra 已提交
3100 3101 3102
 *                           p-1
 * u' = (u + d1) y^p + 1024 \Sum y^n + d3 y^0
 *                           n=1
3103
 *
P
Peter Zijlstra 已提交
3104
 *    = u y^p +					(Step 1)
3105
 *
P
Peter Zijlstra 已提交
3106 3107 3108
 *                     p-1
 *      d1 y^p + 1024 \Sum y^n + d3 y^0		(Step 2)
 *                     n=1
3109 3110 3111
 */
static __always_inline u32
accumulate_sum(u64 delta, int cpu, struct sched_avg *sa,
3112
	       unsigned long load, unsigned long runnable, int running)
3113 3114
{
	unsigned long scale_freq, scale_cpu;
3115
	u32 contrib = (u32)delta; /* p == 0 -> delta < 1024 */
3116 3117
	u64 periods;

3118
	scale_freq = arch_scale_freq_capacity(cpu);
3119 3120 3121 3122 3123 3124 3125 3126 3127 3128
	scale_cpu = arch_scale_cpu_capacity(NULL, cpu);

	delta += sa->period_contrib;
	periods = delta / 1024; /* A period is 1024us (~1ms) */

	/*
	 * Step 1: decay old *_sum if we crossed period boundaries.
	 */
	if (periods) {
		sa->load_sum = decay_load(sa->load_sum, periods);
3129 3130
		sa->runnable_load_sum =
			decay_load(sa->runnable_load_sum, periods);
3131 3132
		sa->util_sum = decay_load((u64)(sa->util_sum), periods);

3133 3134 3135 3136 3137 3138 3139
		/*
		 * Step 2
		 */
		delta %= 1024;
		contrib = __accumulate_pelt_segments(periods,
				1024 - sa->period_contrib, delta);
	}
3140 3141 3142
	sa->period_contrib = delta;

	contrib = cap_scale(contrib, scale_freq);
3143 3144 3145 3146
	if (load)
		sa->load_sum += load * contrib;
	if (runnable)
		sa->runnable_load_sum += runnable * contrib;
3147 3148 3149 3150 3151 3152
	if (running)
		sa->util_sum += contrib * scale_cpu;

	return periods;
}

3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180
/*
 * We can represent the historical contribution to runnable average as the
 * coefficients of a geometric series.  To do this we sub-divide our runnable
 * history into segments of approximately 1ms (1024us); label the segment that
 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
 *
 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
 *      p0            p1           p2
 *     (now)       (~1ms ago)  (~2ms ago)
 *
 * Let u_i denote the fraction of p_i that the entity was runnable.
 *
 * We then designate the fractions u_i as our co-efficients, yielding the
 * following representation of historical load:
 *   u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
 *
 * We choose y based on the with of a reasonably scheduling period, fixing:
 *   y^32 = 0.5
 *
 * This means that the contribution to load ~32ms ago (u_32) will be weighted
 * approximately half as much as the contribution to load within the last ms
 * (u_0).
 *
 * When a period "rolls over" and we have new u_0`, multiplying the previous
 * sum again by y is sufficient to update:
 *   load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
 *            = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
 */
3181
static __always_inline int
3182
___update_load_sum(u64 now, int cpu, struct sched_avg *sa,
3183
		  unsigned long load, unsigned long runnable, int running)
3184
{
3185
	u64 delta;
3186

3187
	delta = now - sa->last_update_time;
3188 3189 3190 3191 3192
	/*
	 * This should only happen when time goes backwards, which it
	 * unfortunately does during sched clock init when we swap over to TSC.
	 */
	if ((s64)delta < 0) {
3193
		sa->last_update_time = now;
3194 3195 3196 3197 3198 3199 3200 3201 3202 3203
		return 0;
	}

	/*
	 * Use 1024ns as the unit of measurement since it's a reasonable
	 * approximation of 1us and fast to compute.
	 */
	delta >>= 10;
	if (!delta)
		return 0;
3204 3205

	sa->last_update_time += delta << 10;
3206

3207 3208 3209 3210 3211 3212 3213 3214 3215
	/*
	 * running is a subset of runnable (weight) so running can't be set if
	 * runnable is clear. But there are some corner cases where the current
	 * se has been already dequeued but cfs_rq->curr still points to it.
	 * This means that weight will be 0 but not running for a sched_entity
	 * but also for a cfs_rq if the latter becomes idle. As an example,
	 * this happens during idle_balance() which calls
	 * update_blocked_averages()
	 */
3216 3217
	if (!load)
		runnable = running = 0;
3218

3219 3220 3221 3222 3223 3224 3225
	/*
	 * Now we know we crossed measurement unit boundaries. The *_avg
	 * accrues by two steps:
	 *
	 * Step 1: accumulate *_sum since last_update_time. If we haven't
	 * crossed period boundaries, finish.
	 */
3226
	if (!accumulate_sum(delta, cpu, sa, load, runnable, running))
3227
		return 0;
3228

3229 3230 3231 3232
	return 1;
}

static __always_inline void
3233
___update_load_avg(struct sched_avg *sa, unsigned long load, unsigned long runnable)
3234 3235 3236
{
	u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;

3237 3238 3239
	/*
	 * Step 2: update *_avg.
	 */
3240 3241
	sa->load_avg = div_u64(load * sa->load_sum, divider);
	sa->runnable_load_avg =	div_u64(runnable * sa->runnable_load_sum, divider);
3242 3243
	sa->util_avg = sa->util_sum / divider;
}
3244

3245 3246 3247
/*
 * sched_entity:
 *
3248 3249 3250 3251 3252 3253 3254
 *   task:
 *     se_runnable() == se_weight()
 *
 *   group: [ see update_cfs_group() ]
 *     se_weight()   = tg->weight * grq->load_avg / tg->load_avg
 *     se_runnable() = se_weight(se) * grq->runnable_load_avg / grq->load_avg
 *
3255 3256 3257
 *   load_sum := runnable_sum
 *   load_avg = se_weight(se) * runnable_avg
 *
3258 3259 3260 3261 3262
 *   runnable_load_sum := runnable_sum
 *   runnable_load_avg = se_runnable(se) * runnable_avg
 *
 * XXX collapse load_sum and runnable_load_sum
 *
3263 3264 3265 3266
 * cfq_rs:
 *
 *   load_sum = \Sum se_weight(se) * se->avg.load_sum
 *   load_avg = \Sum se->avg.load_avg
3267 3268 3269
 *
 *   runnable_load_sum = \Sum se_runnable(se) * se->avg.runnable_load_sum
 *   runnable_load_avg = \Sum se->avg.runable_load_avg
3270 3271
 */

3272 3273 3274
static int
__update_load_avg_blocked_se(u64 now, int cpu, struct sched_entity *se)
{
3275 3276 3277 3278 3279
	if (entity_is_task(se))
		se->runnable_weight = se->load.weight;

	if (___update_load_sum(now, cpu, &se->avg, 0, 0, 0)) {
		___update_load_avg(&se->avg, se_weight(se), se_runnable(se));
3280 3281 3282 3283
		return 1;
	}

	return 0;
3284 3285 3286 3287 3288
}

static int
__update_load_avg_se(u64 now, int cpu, struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3289 3290 3291 3292 3293
	if (entity_is_task(se))
		se->runnable_weight = se->load.weight;

	if (___update_load_sum(now, cpu, &se->avg, !!se->on_rq, !!se->on_rq,
				cfs_rq->curr == se)) {
3294

3295
		___update_load_avg(&se->avg, se_weight(se), se_runnable(se));
3296 3297 3298 3299
		return 1;
	}

	return 0;
3300 3301 3302 3303 3304
}

static int
__update_load_avg_cfs_rq(u64 now, int cpu, struct cfs_rq *cfs_rq)
{
3305 3306
	if (___update_load_sum(now, cpu, &cfs_rq->avg,
				scale_load_down(cfs_rq->load.weight),
3307 3308 3309 3310
				scale_load_down(cfs_rq->runnable_weight),
				cfs_rq->curr != NULL)) {

		___update_load_avg(&cfs_rq->avg, 1, 1);
3311 3312 3313 3314
		return 1;
	}

	return 0;
3315 3316
}

3317
#ifdef CONFIG_FAIR_GROUP_SCHED
3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330
/**
 * 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'.
 *
3331
 * Updating tg's load_avg is necessary before update_cfs_share().
3332
 */
3333
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
3334
{
3335
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
3336

3337 3338 3339 3340 3341 3342
	/*
	 * No need to update load_avg for root_task_group as it is not used.
	 */
	if (cfs_rq->tg == &root_task_group)
		return;

3343 3344 3345
	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;
3346
	}
3347
}
3348

3349
/*
3350
 * Called within set_task_rq() right before setting a task's CPU. The
3351 3352 3353 3354 3355 3356
 * 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)
{
3357 3358 3359
	u64 p_last_update_time;
	u64 n_last_update_time;

3360 3361 3362 3363 3364 3365 3366 3367 3368 3369
	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.
	 */
3370 3371
	if (!(se->avg.last_update_time && prev))
		return;
3372 3373

#ifndef CONFIG_64BIT
3374
	{
3375 3376 3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387 3388
		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);
3389
	}
3390
#else
3391 3392
	p_last_update_time = prev->avg.last_update_time;
	n_last_update_time = next->avg.last_update_time;
3393
#endif
3394 3395
	__update_load_avg_blocked_se(p_last_update_time, cpu_of(rq_of(prev)), se);
	se->avg.last_update_time = n_last_update_time;
3396
}
3397

3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408

/*
 * 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.
 *
3409 3410 3411
 * 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).
3412 3413 3414 3415 3416 3417 3418 3419
 *
 * 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:
 *
3420
 *   grq->avg.load_avg = grq->load.weight * grq->avg.runnable_avg	(3)
3421 3422 3423
 *
 * And per (1) we have:
 *
3424
 *   ge->avg.runnable_avg == grq->avg.runnable_avg
3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442
 *
 * 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).
 *
3443 3444 3445 3446 3447 3448
 * 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.
3449
 *
3450
 * So we'll have to approximate.. :/
3451
 *
3452
 * Given the constraint:
3453
 *
3454
 *   ge->avg.running_sum <= ge->avg.runnable_sum <= LOAD_AVG_MAX
3455
 *
3456 3457
 * We can construct a rule that adds runnable to a rq by assuming minimal
 * overlap.
3458
 *
3459
 * On removal, we'll assume each task is equally runnable; which yields:
3460
 *
3461
 *   grq->avg.runnable_sum = grq->avg.load_sum / grq->load.weight
3462
 *
3463
 * XXX: only do this for the part of runnable > running ?
3464 3465 3466
 *
 */

3467
static inline void
3468
update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3469 3470 3471 3472 3473 3474 3475
{
	long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;

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

3476 3477 3478 3479 3480 3481 3482 3483
	/*
	 * 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.
	 */

3484 3485 3486 3487 3488 3489 3490 3491 3492 3493
	/* 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
3494
update_tg_cfs_runnable(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
3495
{
3496 3497 3498 3499
	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;
3500

3501 3502
	if (!runnable_sum)
		return;
3503

3504
	gcfs_rq->prop_runnable_sum = 0;
3505

3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528
	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
3529
	 * As running sum is scale with CPU capacity wehreas the runnable sum
3530 3531 3532 3533 3534 3535
	 * 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);

3536 3537
	load_sum = (s64)se_weight(se) * runnable_sum;
	load_avg = div_s64(load_sum, LOAD_AVG_MAX);
3538

3539 3540
	delta_sum = load_sum - (s64)se_weight(se) * se->avg.load_sum;
	delta_avg = load_avg - se->avg.load_avg;
3541

3542 3543 3544 3545
	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);
3546

3547 3548
	runnable_load_sum = (s64)se_runnable(se) * runnable_sum;
	runnable_load_avg = div_s64(runnable_load_sum, LOAD_AVG_MAX);
3549 3550
	delta_sum = runnable_load_sum - se_weight(se) * se->avg.runnable_load_sum;
	delta_avg = runnable_load_avg - se->avg.runnable_load_avg;
3551

3552 3553
	se->avg.runnable_load_sum = runnable_sum;
	se->avg.runnable_load_avg = runnable_load_avg;
3554

3555
	if (se->on_rq) {
3556 3557
		add_positive(&cfs_rq->avg.runnable_load_avg, delta_avg);
		add_positive(&cfs_rq->avg.runnable_load_sum, delta_sum);
3558 3559 3560
	}
}

3561
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum)
3562
{
3563 3564
	cfs_rq->propagate = 1;
	cfs_rq->prop_runnable_sum += runnable_sum;
3565 3566 3567 3568 3569
}

/* Update task and its cfs_rq load average */
static inline int propagate_entity_load_avg(struct sched_entity *se)
{
3570
	struct cfs_rq *cfs_rq, *gcfs_rq;
3571 3572 3573 3574

	if (entity_is_task(se))
		return 0;

3575 3576
	gcfs_rq = group_cfs_rq(se);
	if (!gcfs_rq->propagate)
3577 3578
		return 0;

3579 3580
	gcfs_rq->propagate = 0;

3581 3582
	cfs_rq = cfs_rq_of(se);

3583
	add_tg_cfs_propagate(cfs_rq, gcfs_rq->prop_runnable_sum);
3584

3585 3586
	update_tg_cfs_util(cfs_rq, se, gcfs_rq);
	update_tg_cfs_runnable(cfs_rq, se, gcfs_rq);
3587 3588 3589 3590

	return 1;
}

3591 3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609
/*
 * 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:
	 */
3610
	if (gcfs_rq->propagate)
3611 3612 3613 3614 3615 3616 3617 3618 3619 3620
		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;
}

3621
#else /* CONFIG_FAIR_GROUP_SCHED */
3622

3623
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
3624 3625 3626 3627 3628 3629

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

3630
static inline void add_tg_cfs_propagate(struct cfs_rq *cfs_rq, long runnable_sum) {}
3631

3632
#endif /* CONFIG_FAIR_GROUP_SCHED */
3633

3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644
/**
 * 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.
 *
3645 3646 3647 3648
 * 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.
3649
 */
3650
static inline int
3651
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3652
{
3653
	unsigned long removed_load = 0, removed_util = 0, removed_runnable_sum = 0;
3654
	struct sched_avg *sa = &cfs_rq->avg;
3655
	int decayed = 0;
3656

3657 3658
	if (cfs_rq->removed.nr) {
		unsigned long r;
3659
		u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
3660 3661 3662 3663

		raw_spin_lock(&cfs_rq->removed.lock);
		swap(cfs_rq->removed.util_avg, removed_util);
		swap(cfs_rq->removed.load_avg, removed_load);
3664
		swap(cfs_rq->removed.runnable_sum, removed_runnable_sum);
3665 3666 3667 3668
		cfs_rq->removed.nr = 0;
		raw_spin_unlock(&cfs_rq->removed.lock);

		r = removed_load;
3669
		sub_positive(&sa->load_avg, r);
3670
		sub_positive(&sa->load_sum, r * divider);
3671

3672
		r = removed_util;
3673
		sub_positive(&sa->util_avg, r);
3674
		sub_positive(&sa->util_sum, r * divider);
3675

3676
		add_tg_cfs_propagate(cfs_rq, -(long)removed_runnable_sum);
3677 3678

		decayed = 1;
3679
	}
3680

3681
	decayed |= __update_load_avg_cfs_rq(now, cpu_of(rq_of(cfs_rq)), cfs_rq);
3682

3683 3684 3685 3686
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
3687

3688
	if (decayed)
3689
		cfs_rq_util_change(cfs_rq, 0);
3690

3691
	return decayed;
3692 3693
}

3694 3695 3696 3697 3698 3699 3700 3701
/**
 * 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
 *
 * Must call update_cfs_rq_load_avg() before this, since we rely on
 * cfs_rq->avg.last_update_time being current.
 */
3702
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3703
{
3704 3705 3706 3707 3708 3709 3710 3711 3712
	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
	 */
3713
	se->avg.last_update_time = cfs_rq->avg.last_update_time;
3714 3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731
	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;

3732
	enqueue_load_avg(cfs_rq, se);
3733 3734
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
3735 3736

	add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);
3737

3738
	cfs_rq_util_change(cfs_rq, flags);
3739 3740
}

3741 3742 3743 3744 3745 3746 3747 3748
/**
 * 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.
 */
3749 3750
static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3751
	dequeue_load_avg(cfs_rq, se);
3752 3753
	sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
	sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3754 3755

	add_tg_cfs_propagate(cfs_rq, -se->avg.load_sum);
3756

3757
	cfs_rq_util_change(cfs_rq, 0);
3758 3759
}

3760 3761 3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786
/*
 * 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)) {

3787 3788 3789 3790 3791 3792 3793 3794
		/*
		 * 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);
3795 3796 3797 3798 3799 3800
		update_tg_load_avg(cfs_rq, 0);

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

3801
#ifndef CONFIG_64BIT
3802 3803
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
3804
	u64 last_update_time_copy;
3805
	u64 last_update_time;
3806

3807 3808 3809 3810 3811
	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);
3812 3813 3814

	return last_update_time;
}
3815
#else
3816 3817 3818 3819
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.last_update_time;
}
3820 3821
#endif

3822 3823 3824 3825 3826 3827 3828 3829 3830 3831
/*
 * 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);
3832
	__update_load_avg_blocked_se(last_update_time, cpu_of(rq_of(cfs_rq)), se);
3833 3834
}

3835 3836 3837 3838 3839 3840 3841
/*
 * 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);
3842
	unsigned long flags;
3843 3844

	/*
3845 3846 3847 3848 3849 3850 3851
	 * 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.
3852 3853
	 */

3854
	sync_entity_load_avg(se);
3855 3856 3857 3858 3859

	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;
3860
	cfs_rq->removed.runnable_sum	+= se->avg.load_sum; /* == runnable_sum */
3861
	raw_spin_unlock_irqrestore(&cfs_rq->removed.lock, flags);
3862
}
3863

3864 3865
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
{
3866
	return cfs_rq->avg.runnable_load_avg;
3867 3868 3869 3870 3871 3872 3873
}

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

3874
static int idle_balance(struct rq *this_rq, struct rq_flags *rf);
3875

3876 3877
#else /* CONFIG_SMP */

3878
static inline int
3879
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
3880 3881 3882 3883
{
	return 0;
}

3884 3885
#define UPDATE_TG	0x0
#define SKIP_AGE_LOAD	0x0
3886
#define DO_ATTACH	0x0
3887

3888
static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int not_used1)
3889
{
3890
	cfs_rq_util_change(cfs_rq, 0);
3891 3892
}

3893
static inline void remove_entity_load_avg(struct sched_entity *se) {}
3894

3895
static inline void
3896
attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) {}
3897 3898 3899
static inline void
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}

3900
static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
3901 3902 3903 3904
{
	return 0;
}

3905
#endif /* CONFIG_SMP */
3906

P
Peter Zijlstra 已提交
3907 3908 3909 3910 3911 3912 3913 3914 3915
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)
3916
		schedstat_inc(cfs_rq->nr_spread_over);
P
Peter Zijlstra 已提交
3917 3918 3919
#endif
}

3920 3921 3922
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3923
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3924

3925 3926 3927 3928 3929 3930
	/*
	 * 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
3931
	if (initial && sched_feat(START_DEBIT))
3932
		vruntime += sched_vslice(cfs_rq, se);
3933

3934
	/* sleeps up to a single latency don't count. */
3935
	if (!initial) {
3936
		unsigned long thresh = sysctl_sched_latency;
3937

3938 3939 3940 3941 3942 3943
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3944

3945
		vruntime -= thresh;
3946 3947
	}

3948
	/* ensure we never gain time by being placed backwards. */
3949
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3950 3951
}

3952 3953
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965
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())  {
3966
		printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3967
			     "stat_blocked and stat_runtime require the "
3968
			     "kernel parameter schedstats=enable or "
3969 3970 3971 3972 3973
			     "kernel.sched_schedstats=1\n");
	}
#endif
}

3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989 3990 3991 3992

/*
 * 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)
 *
3993
 *	->migrate_task_rq_fair() (p->state == TASK_WAKING)
3994 3995 3996 3997 3998 3999 4000 4001 4002 4003 4004
 *	  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.
 */

4005
static void
4006
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4007
{
4008 4009 4010
	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
	bool curr = cfs_rq->curr == se;

4011
	/*
4012 4013
	 * If we're the current task, we must renormalise before calling
	 * update_curr().
4014
	 */
4015
	if (renorm && curr)
4016 4017
		se->vruntime += cfs_rq->min_vruntime;

4018 4019
	update_curr(cfs_rq);

4020
	/*
4021 4022 4023 4024
	 * 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.
4025
	 */
4026 4027 4028
	if (renorm && !curr)
		se->vruntime += cfs_rq->min_vruntime;

4029 4030 4031 4032 4033 4034 4035 4036
	/*
	 * 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
	 */
4037
	update_load_avg(cfs_rq, se, UPDATE_TG | DO_ATTACH);
4038
	update_cfs_group(se);
4039
	enqueue_runnable_load_avg(cfs_rq, se);
4040
	account_entity_enqueue(cfs_rq, se);
4041

4042
	if (flags & ENQUEUE_WAKEUP)
4043
		place_entity(cfs_rq, se, 0);
4044

4045
	check_schedstat_required();
4046 4047
	update_stats_enqueue(cfs_rq, se, flags);
	check_spread(cfs_rq, se);
4048
	if (!curr)
4049
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
4050
	se->on_rq = 1;
4051

4052
	if (cfs_rq->nr_running == 1) {
4053
		list_add_leaf_cfs_rq(cfs_rq);
4054 4055
		check_enqueue_throttle(cfs_rq);
	}
4056 4057
}

4058
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
4059
{
4060 4061
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
4062
		if (cfs_rq->last != se)
4063
			break;
4064 4065

		cfs_rq->last = NULL;
4066 4067
	}
}
P
Peter Zijlstra 已提交
4068

4069 4070 4071 4072
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
4073
		if (cfs_rq->next != se)
4074
			break;
4075 4076

		cfs_rq->next = NULL;
4077
	}
P
Peter Zijlstra 已提交
4078 4079
}

4080 4081 4082 4083
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
4084
		if (cfs_rq->skip != se)
4085
			break;
4086 4087

		cfs_rq->skip = NULL;
4088 4089 4090
	}
}

P
Peter Zijlstra 已提交
4091 4092
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
4093 4094 4095 4096 4097
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
4098 4099 4100

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
4101 4102
}

4103
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4104

4105
static void
4106
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
4107
{
4108 4109 4110 4111
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
4112 4113 4114 4115 4116 4117 4118 4119 4120

	/*
	 * 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.
	 */
4121
	update_load_avg(cfs_rq, se, UPDATE_TG);
4122
	dequeue_runnable_load_avg(cfs_rq, se);
4123

4124
	update_stats_dequeue(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
4125

P
Peter Zijlstra 已提交
4126
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
4127

4128
	if (se != cfs_rq->curr)
4129
		__dequeue_entity(cfs_rq, se);
4130
	se->on_rq = 0;
4131
	account_entity_dequeue(cfs_rq, se);
4132 4133

	/*
4134 4135 4136 4137
	 * 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.
4138
	 */
4139
	if (!(flags & DEQUEUE_SLEEP))
4140
		se->vruntime -= cfs_rq->min_vruntime;
4141

4142 4143 4144
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

4145
	update_cfs_group(se);
4146 4147 4148 4149 4150 4151 4152 4153 4154

	/*
	 * 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.
	 */
	if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE)
		update_min_vruntime(cfs_rq);
4155 4156 4157 4158 4159
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
4160
static void
I
Ingo Molnar 已提交
4161
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4162
{
4163
	unsigned long ideal_runtime, delta_exec;
4164 4165
	struct sched_entity *se;
	s64 delta;
4166

P
Peter Zijlstra 已提交
4167
	ideal_runtime = sched_slice(cfs_rq, curr);
4168
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
4169
	if (delta_exec > ideal_runtime) {
4170
		resched_curr(rq_of(cfs_rq));
4171 4172 4173 4174 4175
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
4176 4177 4178 4179 4180 4181 4182 4183 4184 4185 4186
		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;

4187 4188
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
4189

4190 4191
	if (delta < 0)
		return;
4192

4193
	if (delta > ideal_runtime)
4194
		resched_curr(rq_of(cfs_rq));
4195 4196
}

4197
static void
4198
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
4199
{
4200 4201 4202 4203 4204 4205 4206
	/* '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.
		 */
4207
		update_stats_wait_end(cfs_rq, se);
4208
		__dequeue_entity(cfs_rq, se);
4209
		update_load_avg(cfs_rq, se, UPDATE_TG);
4210 4211
	}

4212
	update_stats_curr_start(cfs_rq, se);
4213
	cfs_rq->curr = se;
4214

I
Ingo Molnar 已提交
4215 4216 4217 4218 4219
	/*
	 * 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):
	 */
4220
	if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
4221 4222 4223
		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
4224
	}
4225

4226
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
4227 4228
}

4229 4230 4231
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

4232 4233 4234 4235 4236 4237 4238
/*
 * 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
 */
4239 4240
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
4241
{
4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252
	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 */
4253

4254 4255 4256 4257 4258
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
4259 4260 4261 4262 4263 4264 4265 4266 4267 4268
		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;
		}

4269 4270 4271
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
4272

4273 4274 4275 4276 4277 4278
	/*
	 * 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;

4279 4280 4281 4282 4283 4284
	/*
	 * 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;

4285
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
4286 4287

	return se;
4288 4289
}

4290
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
4291

4292
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
4293 4294 4295 4296 4297 4298
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
4299
		update_curr(cfs_rq);
4300

4301 4302 4303
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

4304
	check_spread(cfs_rq, prev);
4305

4306
	if (prev->on_rq) {
4307
		update_stats_wait_start(cfs_rq, prev);
4308 4309
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
4310
		/* in !on_rq case, update occurred at dequeue */
4311
		update_load_avg(cfs_rq, prev, 0);
4312
	}
4313
	cfs_rq->curr = NULL;
4314 4315
}

P
Peter Zijlstra 已提交
4316 4317
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
4318 4319
{
	/*
4320
	 * Update run-time statistics of the 'current'.
4321
	 */
4322
	update_curr(cfs_rq);
4323

4324 4325 4326
	/*
	 * Ensure that runnable average is periodically updated.
	 */
4327
	update_load_avg(cfs_rq, curr, UPDATE_TG);
4328
	update_cfs_group(curr);
4329

P
Peter Zijlstra 已提交
4330 4331 4332 4333 4334
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
4335
	if (queued) {
4336
		resched_curr(rq_of(cfs_rq));
4337 4338
		return;
	}
P
Peter Zijlstra 已提交
4339 4340 4341 4342 4343 4344 4345 4346
	/*
	 * 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
4347
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
4348
		check_preempt_tick(cfs_rq, curr);
4349 4350
}

4351 4352 4353 4354 4355 4356

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

#ifdef CONFIG_CFS_BANDWIDTH
4357 4358

#ifdef HAVE_JUMP_LABEL
4359
static struct static_key __cfs_bandwidth_used;
4360 4361 4362

static inline bool cfs_bandwidth_used(void)
{
4363
	return static_key_false(&__cfs_bandwidth_used);
4364 4365
}

4366
void cfs_bandwidth_usage_inc(void)
4367
{
4368
	static_key_slow_inc_cpuslocked(&__cfs_bandwidth_used);
4369 4370 4371 4372
}

void cfs_bandwidth_usage_dec(void)
{
4373
	static_key_slow_dec_cpuslocked(&__cfs_bandwidth_used);
4374 4375 4376 4377 4378 4379 4380
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

4381 4382
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
4383 4384
#endif /* HAVE_JUMP_LABEL */

4385 4386 4387 4388 4389 4390 4391 4392
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
4393 4394 4395 4396 4397 4398

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

P
Paul Turner 已提交
4399 4400 4401 4402 4403 4404 4405
/*
 * Replenish runtime according to assigned quota and update expiration time.
 * We use sched_clock_cpu directly instead of rq->clock to avoid adding
 * additional synchronization around rq->lock.
 *
 * requires cfs_b->lock
 */
4406
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
4407 4408 4409 4410 4411 4412 4413 4414 4415 4416 4417
{
	u64 now;

	if (cfs_b->quota == RUNTIME_INF)
		return;

	now = sched_clock_cpu(smp_processor_id());
	cfs_b->runtime = cfs_b->quota;
	cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);
}

4418 4419 4420 4421 4422
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

4423 4424 4425 4426
/* 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))
4427
		return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
4428

4429
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
4430 4431
}

4432 4433
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4434 4435 4436
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
4437
	u64 amount = 0, min_amount, expires;
4438 4439 4440 4441 4442 4443 4444

	/* 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;
4445
	else {
P
Peter Zijlstra 已提交
4446
		start_cfs_bandwidth(cfs_b);
4447 4448 4449 4450 4451 4452

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
4453
	}
P
Paul Turner 已提交
4454
	expires = cfs_b->runtime_expires;
4455 4456 4457
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
4458 4459 4460 4461 4462 4463 4464
	/*
	 * we may have advanced our local expiration to account for allowed
	 * spread between our sched_clock and the one on which runtime was
	 * issued.
	 */
	if ((s64)(expires - cfs_rq->runtime_expires) > 0)
		cfs_rq->runtime_expires = expires;
4465 4466

	return cfs_rq->runtime_remaining > 0;
4467 4468
}

P
Paul Turner 已提交
4469 4470 4471 4472 4473
/*
 * Note: This depends on the synchronization provided by sched_clock and the
 * fact that rq->clock snapshots this value.
 */
static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4474
{
P
Paul Turner 已提交
4475 4476 4477
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
4478
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
4479 4480
		return;

P
Paul Turner 已提交
4481 4482 4483 4484 4485 4486 4487 4488 4489
	if (cfs_rq->runtime_remaining < 0)
		return;

	/*
	 * If the local deadline has passed we have to consider the
	 * possibility that our sched_clock is 'fast' and the global deadline
	 * has not truly expired.
	 *
	 * Fortunately we can check determine whether this the case by checking
4490 4491 4492
	 * whether the global deadline has advanced. It is valid to compare
	 * cfs_b->runtime_expires without any locks since we only care about
	 * exact equality, so a partial write will still work.
P
Paul Turner 已提交
4493 4494
	 */

4495
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
4496 4497 4498 4499 4500 4501 4502 4503
		/* extend local deadline, drift is bounded above by 2 ticks */
		cfs_rq->runtime_expires += TICK_NSEC;
	} else {
		/* global deadline is ahead, expiration has passed */
		cfs_rq->runtime_remaining = 0;
	}
}

4504
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
4505 4506
{
	/* dock delta_exec before expiring quota (as it could span periods) */
4507
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
4508 4509 4510
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
4511 4512
		return;

4513 4514 4515 4516 4517
	/*
	 * 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))
4518
		resched_curr(rq_of(cfs_rq));
4519 4520
}

4521
static __always_inline
4522
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
4523
{
4524
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
4525 4526 4527 4528 4529
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

4530 4531
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
4532
	return cfs_bandwidth_used() && cfs_rq->throttled;
4533 4534
}

4535 4536 4537
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
4538
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550 4551 4552 4553 4554 4555 4556 4557 4558 4559 4560 4561 4562 4563 4564 4565
}

/*
 * 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);
}

/* updated child weight may affect parent so we have to do this bottom up */
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) {
4566
		/* adjust cfs_rq_clock_task() */
4567
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
4568
					     cfs_rq->throttled_clock_task;
4569 4570 4571 4572 4573 4574 4575 4576 4577 4578
	}

	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)];

4579 4580
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
4581
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
4582 4583 4584 4585 4586
	cfs_rq->throttle_count++;

	return 0;
}

4587
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
4588 4589 4590 4591 4592
{
	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
4593
	bool empty;
4594 4595 4596

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

4597
	/* freeze hierarchy runnable averages while throttled */
4598 4599 4600
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
4601 4602 4603 4604 4605 4606 4607 4608 4609 4610 4611 4612 4613 4614 4615 4616 4617

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

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

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

	if (!se)
4618
		sub_nr_running(rq, task_delta);
4619 4620

	cfs_rq->throttled = 1;
4621
	cfs_rq->throttled_clock = rq_clock(rq);
4622
	raw_spin_lock(&cfs_b->lock);
4623
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4624

4625 4626 4627 4628 4629
	/*
	 * Add to the _head_ of the list, so that an already-started
	 * distribute_cfs_runtime will not see us
	 */
	list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4630 4631 4632 4633 4634 4635 4636 4637

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

4638 4639 4640
	raw_spin_unlock(&cfs_b->lock);
}

4641
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
4642 4643 4644 4645 4646 4647 4648
{
	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;

4649
	se = cfs_rq->tg->se[cpu_of(rq)];
4650 4651

	cfs_rq->throttled = 0;
4652 4653 4654

	update_rq_clock(rq);

4655
	raw_spin_lock(&cfs_b->lock);
4656
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
4657 4658 4659
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

4660 4661 4662
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

4663 4664 4665 4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680
	if (!cfs_rq->load.weight)
		return;

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

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

		if (cfs_rq_throttled(cfs_rq))
			break;
	}

	if (!se)
4681
		add_nr_running(rq, task_delta);
4682

4683
	/* Determine whether we need to wake up potentially idle CPU: */
4684
	if (rq->curr == rq->idle && rq->cfs.nr_running)
4685
		resched_curr(rq);
4686 4687 4688 4689 4690 4691
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
4692 4693
	u64 runtime;
	u64 starting_runtime = remaining;
4694 4695 4696 4697 4698

	rcu_read_lock();
	list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq,
				throttled_list) {
		struct rq *rq = rq_of(cfs_rq);
4699
		struct rq_flags rf;
4700

4701
		rq_lock(rq, &rf);
4702 4703 4704 4705 4706 4707 4708 4709 4710 4711 4712 4713 4714 4715 4716 4717
		if (!cfs_rq_throttled(cfs_rq))
			goto next;

		runtime = -cfs_rq->runtime_remaining + 1;
		if (runtime > remaining)
			runtime = remaining;
		remaining -= runtime;

		cfs_rq->runtime_remaining += runtime;
		cfs_rq->runtime_expires = expires;

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

next:
4718
		rq_unlock(rq, &rf);
4719 4720 4721 4722 4723 4724

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

4725
	return starting_runtime - remaining;
4726 4727
}

4728 4729 4730 4731 4732 4733 4734 4735
/*
 * 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)
{
4736
	u64 runtime, runtime_expires;
4737
	int throttled;
4738 4739 4740

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
4741
		goto out_deactivate;
4742

4743
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4744
	cfs_b->nr_periods += overrun;
4745

4746 4747 4748 4749 4750 4751
	/*
	 * 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
4752 4753 4754

	__refill_cfs_bandwidth_runtime(cfs_b);

4755 4756 4757
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
4758
		return 0;
4759 4760
	}

4761 4762 4763
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

4764 4765 4766
	runtime_expires = cfs_b->runtime_expires;

	/*
4767 4768 4769 4770 4771
	 * This check is repeated as we are holding onto the new bandwidth while
	 * we unthrottle. This can potentially race with an unthrottled group
	 * trying to acquire new bandwidth from the global pool. This can result
	 * in us over-using our runtime if it is all used during this loop, but
	 * only by limited amounts in that extreme case.
4772
	 */
4773 4774
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
4775 4776 4777 4778 4779 4780 4781
		raw_spin_unlock(&cfs_b->lock);
		/* we can't nest cfs_b->lock while distributing bandwidth */
		runtime = distribute_cfs_runtime(cfs_b, runtime,
						 runtime_expires);
		raw_spin_lock(&cfs_b->lock);

		throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4782 4783

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4784
	}
4785

4786 4787 4788 4789 4790 4791 4792
	/*
	 * 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;
4793

4794 4795 4796 4797
	return 0;

out_deactivate:
	return 1;
4798
}
4799

4800 4801 4802 4803 4804 4805 4806
/* 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;

4807 4808 4809 4810
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4811
 * hrtimer base being cleared by hrtimer_start. In the case of
4812 4813
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
4814 4815 4816 4817 4818 4819 4820 4821 4822 4823 4824 4825 4826 4827 4828 4829 4830 4831 4832 4833 4834 4835 4836 4837 4838
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;

P
Peter Zijlstra 已提交
4839 4840 4841
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
4842 4843 4844 4845 4846 4847 4848 4849 4850 4851 4852 4853 4854 4855 4856 4857 4858 4859 4860 4861 4862 4863 4864 4865 4866 4867 4868 4869 4870
}

/* 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);
	if (cfs_b->quota != RUNTIME_INF &&
	    cfs_rq->runtime_expires == cfs_b->runtime_expires) {
		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)
{
4871 4872 4873
	if (!cfs_bandwidth_used())
		return;

4874
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4875 4876 4877 4878 4879 4880 4881 4882 4883 4884 4885 4886 4887 4888 4889
		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();
	u64 expires;

	/* confirm we're still not at a refresh boundary */
4890 4891 4892
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
4893
		return;
4894
	}
4895

4896
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4897
		runtime = cfs_b->runtime;
4898

4899 4900 4901 4902 4903 4904 4905 4906 4907 4908
	expires = cfs_b->runtime_expires;
	raw_spin_unlock(&cfs_b->lock);

	if (!runtime)
		return;

	runtime = distribute_cfs_runtime(cfs_b, runtime, expires);

	raw_spin_lock(&cfs_b->lock);
	if (expires == cfs_b->runtime_expires)
4909
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4910 4911 4912
	raw_spin_unlock(&cfs_b->lock);
}

4913 4914 4915 4916 4917 4918 4919
/*
 * 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)
{
4920 4921 4922
	if (!cfs_bandwidth_used())
		return;

4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935 4936
	/* 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);
}

4937 4938 4939 4940 4941 4942 4943 4944 4945 4946 4947 4948 4949 4950
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;
4951
	cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
4952 4953
}

4954
/* conditionally throttle active cfs_rq's from put_prev_entity() */
4955
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4956
{
4957
	if (!cfs_bandwidth_used())
4958
		return false;
4959

4960
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4961
		return false;
4962 4963 4964 4965 4966 4967

	/*
	 * 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))
4968
		return true;
4969 4970

	throttle_cfs_rq(cfs_rq);
4971
	return true;
4972
}
4973 4974 4975 4976 4977

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
4978

4979 4980 4981 4982 4983 4984 4985 4986 4987 4988 4989 4990
	do_sched_cfs_slack_timer(cfs_b);

	return HRTIMER_NORESTART;
}

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;

4991
	raw_spin_lock(&cfs_b->lock);
4992
	for (;;) {
P
Peter Zijlstra 已提交
4993
		overrun = hrtimer_forward_now(timer, cfs_b->period);
4994 4995 4996 4997 4998
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
P
Peter Zijlstra 已提交
4999 5000
	if (idle)
		cfs_b->period_active = 0;
5001
	raw_spin_unlock(&cfs_b->lock);
5002 5003 5004 5005 5006 5007 5008 5009 5010 5011 5012 5013

	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
5014
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
5015 5016 5017 5018 5019 5020 5021 5022 5023 5024 5025
	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;
}

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
5026
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
5027
{
P
Peter Zijlstra 已提交
5028
	lockdep_assert_held(&cfs_b->lock);
5029

P
Peter Zijlstra 已提交
5030 5031 5032 5033 5034
	if (!cfs_b->period_active) {
		cfs_b->period_active = 1;
		hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
		hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
	}
5035 5036 5037 5038
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
5039 5040 5041 5042
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

5043 5044 5045 5046
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

5047
/*
5048
 * Both these CPU hotplug callbacks race against unregister_fair_sched_group()
5049 5050 5051 5052 5053 5054
 *
 * The race is harmless, since modifying bandwidth settings of unhooked group
 * bits doesn't do much.
 */

/* cpu online calback */
5055 5056
static void __maybe_unused update_runtime_enabled(struct rq *rq)
{
5057
	struct task_group *tg;
5058

5059 5060 5061 5062 5063 5064
	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)];
5065 5066 5067 5068 5069

		raw_spin_lock(&cfs_b->lock);
		cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF;
		raw_spin_unlock(&cfs_b->lock);
	}
5070
	rcu_read_unlock();
5071 5072
}

5073
/* cpu offline callback */
5074
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
5075
{
5076 5077 5078 5079 5080 5081 5082
	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)];
5083 5084 5085 5086 5087 5088 5089 5090

		if (!cfs_rq->runtime_enabled)
			continue;

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
5091
		cfs_rq->runtime_remaining = 1;
5092
		/*
5093
		 * Offline rq is schedulable till CPU is completely disabled
5094 5095 5096 5097
		 * in take_cpu_down(), so we prevent new cfs throttling here.
		 */
		cfs_rq->runtime_enabled = 0;

5098 5099 5100
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
5101
	rcu_read_unlock();
5102 5103 5104
}

#else /* CONFIG_CFS_BANDWIDTH */
5105 5106
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
5107
	return rq_clock_task(rq_of(cfs_rq));
5108 5109
}

5110
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
5111
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
5112
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
5113
static inline void sync_throttle(struct task_group *tg, int cpu) {}
5114
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
5115 5116 5117 5118 5119

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
5120 5121 5122 5123 5124 5125 5126 5127 5128 5129 5130

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;
}
5131 5132 5133 5134 5135

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) {}
5136 5137
#endif

5138 5139 5140 5141 5142
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) {}
5143
static inline void update_runtime_enabled(struct rq *rq) {}
5144
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
5145 5146 5147

#endif /* CONFIG_CFS_BANDWIDTH */

5148 5149 5150 5151
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
5152 5153 5154 5155 5156 5157
#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);

5158
	SCHED_WARN_ON(task_rq(p) != rq);
P
Peter Zijlstra 已提交
5159

5160
	if (rq->cfs.h_nr_running > 1) {
P
Peter Zijlstra 已提交
5161 5162 5163 5164 5165 5166
		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)
5167
				resched_curr(rq);
P
Peter Zijlstra 已提交
5168 5169
			return;
		}
5170
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
5171 5172
	}
}
5173 5174 5175 5176 5177 5178 5179 5180 5181 5182

/*
 * 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;

5183
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
5184 5185 5186 5187 5188
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
5189
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
5190 5191 5192 5193
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
5194 5195 5196 5197

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
5198 5199
#endif

5200 5201 5202 5203 5204
/*
 * 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:
 */
5205
static void
5206
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5207 5208
{
	struct cfs_rq *cfs_rq;
5209
	struct sched_entity *se = &p->se;
5210

5211 5212 5213 5214 5215 5216
	/*
	 * 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)
5217
		cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
5218

5219
	for_each_sched_entity(se) {
5220
		if (se->on_rq)
5221 5222
			break;
		cfs_rq = cfs_rq_of(se);
5223
		enqueue_entity(cfs_rq, se, flags);
5224 5225 5226 5227 5228 5229

		/*
		 * 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.
5230
		 */
5231 5232
		if (cfs_rq_throttled(cfs_rq))
			break;
5233
		cfs_rq->h_nr_running++;
5234

5235
		flags = ENQUEUE_WAKEUP;
5236
	}
P
Peter Zijlstra 已提交
5237

P
Peter Zijlstra 已提交
5238
	for_each_sched_entity(se) {
5239
		cfs_rq = cfs_rq_of(se);
5240
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
5241

5242 5243 5244
		if (cfs_rq_throttled(cfs_rq))
			break;

5245
		update_load_avg(cfs_rq, se, UPDATE_TG);
5246
		update_cfs_group(se);
P
Peter Zijlstra 已提交
5247 5248
	}

Y
Yuyang Du 已提交
5249
	if (!se)
5250
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
5251

5252
	hrtick_update(rq);
5253 5254
}

5255 5256
static void set_next_buddy(struct sched_entity *se);

5257 5258 5259 5260 5261
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
5262
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
5263 5264
{
	struct cfs_rq *cfs_rq;
5265
	struct sched_entity *se = &p->se;
5266
	int task_sleep = flags & DEQUEUE_SLEEP;
5267 5268 5269

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5270
		dequeue_entity(cfs_rq, se, flags);
5271 5272 5273 5274 5275 5276 5277 5278 5279

		/*
		 * end evaluation on encountering a throttled cfs_rq
		 *
		 * note: in the case of encountering a throttled cfs_rq we will
		 * post the final h_nr_running decrement below.
		*/
		if (cfs_rq_throttled(cfs_rq))
			break;
5280
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
5281

5282
		/* Don't dequeue parent if it has other entities besides us */
5283
		if (cfs_rq->load.weight) {
5284 5285
			/* Avoid re-evaluating load for this entity: */
			se = parent_entity(se);
5286 5287 5288 5289
			/*
			 * Bias pick_next to pick a task from this cfs_rq, as
			 * p is sleeping when it is within its sched_slice.
			 */
5290 5291
			if (task_sleep && se && !throttled_hierarchy(cfs_rq))
				set_next_buddy(se);
5292
			break;
5293
		}
5294
		flags |= DEQUEUE_SLEEP;
5295
	}
P
Peter Zijlstra 已提交
5296

P
Peter Zijlstra 已提交
5297
	for_each_sched_entity(se) {
5298
		cfs_rq = cfs_rq_of(se);
5299
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
5300

5301 5302 5303
		if (cfs_rq_throttled(cfs_rq))
			break;

5304
		update_load_avg(cfs_rq, se, UPDATE_TG);
5305
		update_cfs_group(se);
P
Peter Zijlstra 已提交
5306 5307
	}

Y
Yuyang Du 已提交
5308
	if (!se)
5309
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
5310

5311
	hrtick_update(rq);
5312 5313
}

5314
#ifdef CONFIG_SMP
5315 5316 5317 5318 5319

/* 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);

5320
#ifdef CONFIG_NO_HZ_COMMON
5321 5322 5323 5324 5325
/*
 * per rq 'load' arrray crap; XXX kill this.
 */

/*
5326
 * The exact cpuload calculated at every tick would be:
5327
 *
5328 5329
 *   load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
 *
5330 5331
 * If a CPU misses updates for n ticks (as it was idle) and update gets
 * called on the n+1-th tick when CPU may be busy, then we have:
5332 5333 5334
 *
 *   load_n   = (1 - 1/2^i)^n * load_0
 *   load_n+1 = (1 - 1/2^i)   * load_n + (1/2^i) * cur_load
5335 5336 5337
 *
 * decay_load_missed() below does efficient calculation of
 *
5338 5339 5340 5341 5342 5343
 *   load' = (1 - 1/2^i)^n * load
 *
 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
 * This allows us to precompute the above in said factors, thereby allowing the
 * reduction of an arbitrary n in O(log_2 n) steps. (See also
 * fixed_power_int())
5344
 *
5345
 * The calculation is approximated on a 128 point scale.
5346 5347
 */
#define DEGRADE_SHIFT		7
5348 5349 5350 5351 5352 5353 5354 5355 5356

static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
	{   0,   0,  0,  0,  0,  0, 0, 0 },
	{  64,  32,  8,  0,  0,  0, 0, 0 },
	{  96,  72, 40, 12,  1,  0, 0, 0 },
	{ 112,  98, 75, 43, 15,  1, 0, 0 },
	{ 120, 112, 98, 76, 45, 16, 2, 0 }
};
5357 5358 5359 5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379 5380 5381 5382 5383 5384 5385

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

	if (!missed_updates)
		return load;

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

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

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

		missed_updates >>= 1;
		j++;
	}
	return load;
}
5386 5387 5388 5389

static struct {
	cpumask_var_t idle_cpus_mask;
	atomic_t nr_cpus;
5390
	int has_blocked;		/* Idle CPUS has blocked load */
5391
	unsigned long next_balance;     /* in jiffy units */
5392
	unsigned long next_blocked;	/* Next update of blocked load in jiffies */
5393 5394
} nohz ____cacheline_aligned;

5395
#endif /* CONFIG_NO_HZ_COMMON */
5396

5397
/**
5398
 * __cpu_load_update - update the rq->cpu_load[] statistics
5399 5400 5401 5402
 * @this_rq: The rq to update statistics for
 * @this_load: The current load
 * @pending_updates: The number of missed updates
 *
5403
 * Update rq->cpu_load[] statistics. This function is usually called every
5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418 5419 5420 5421 5422 5423 5424 5425 5426 5427 5428 5429
 * scheduler tick (TICK_NSEC).
 *
 * This function computes a decaying average:
 *
 *   load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
 *
 * Because of NOHZ it might not get called on every tick which gives need for
 * the @pending_updates argument.
 *
 *   load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
 *             = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
 *             = A * (A * load[i]_n-2 + B) + B
 *             = A * (A * (A * load[i]_n-3 + B) + B) + B
 *             = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
 *             = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
 *             = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
 *             = (1 - 1/2^i)^n * (load[i]_0 - load) + load
 *
 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
 * any change in load would have resulted in the tick being turned back on.
 *
 * For regular NOHZ, this reduces to:
 *
 *   load[i]_n = (1 - 1/2^i)^n * load[i]_0
 *
 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
5430
 * term.
5431
 */
5432 5433
static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
			    unsigned long pending_updates)
5434
{
5435
	unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
5436 5437 5438 5439 5440 5441 5442 5443 5444 5445 5446
	int i, scale;

	this_rq->nr_load_updates++;

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

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

5447
		old_load = this_rq->cpu_load[i];
5448
#ifdef CONFIG_NO_HZ_COMMON
5449
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
5450 5451 5452 5453 5454 5455 5456 5457 5458
		if (tickless_load) {
			old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
			/*
			 * old_load can never be a negative value because a
			 * decayed tickless_load cannot be greater than the
			 * original tickless_load.
			 */
			old_load += tickless_load;
		}
5459
#endif
5460 5461 5462 5463 5464 5465 5466 5467 5468 5469 5470 5471 5472 5473 5474
		new_load = this_load;
		/*
		 * Round up the averaging division if load is increasing. This
		 * prevents us from getting stuck on 9 if the load is 10, for
		 * example.
		 */
		if (new_load > old_load)
			new_load += scale - 1;

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

	sched_avg_update(this_rq);
}

5475
/* Used instead of source_load when we know the type == 0 */
5476
static unsigned long weighted_cpuload(struct rq *rq)
5477
{
5478
	return cfs_rq_runnable_load_avg(&rq->cfs);
5479 5480
}

5481
#ifdef CONFIG_NO_HZ_COMMON
5482 5483
/*
 * There is no sane way to deal with nohz on smp when using jiffies because the
5484
 * CPU doing the jiffies update might drift wrt the CPU doing the jiffy reading
5485 5486 5487 5488 5489 5490 5491 5492 5493 5494 5495 5496 5497 5498
 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
 *
 * Therefore we need to avoid the delta approach from the regular tick when
 * possible since that would seriously skew the load calculation. This is why we
 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
 * loop exit, nohz_idle_balance, nohz full exit...)
 *
 * This means we might still be one tick off for nohz periods.
 */

static void cpu_load_update_nohz(struct rq *this_rq,
				 unsigned long curr_jiffies,
				 unsigned long load)
5499 5500 5501 5502 5503 5504 5505 5506 5507 5508 5509
{
	unsigned long pending_updates;

	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
	if (pending_updates) {
		this_rq->last_load_update_tick = curr_jiffies;
		/*
		 * In the regular NOHZ case, we were idle, this means load 0.
		 * In the NOHZ_FULL case, we were non-idle, we should consider
		 * its weighted load.
		 */
5510
		cpu_load_update(this_rq, load, pending_updates);
5511 5512 5513
	}
}

5514 5515 5516 5517
/*
 * Called from nohz_idle_balance() to update the load ratings before doing the
 * idle balance.
 */
5518
static void cpu_load_update_idle(struct rq *this_rq)
5519 5520 5521 5522
{
	/*
	 * bail if there's load or we're actually up-to-date.
	 */
5523
	if (weighted_cpuload(this_rq))
5524 5525
		return;

5526
	cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
5527 5528 5529
}

/*
5530 5531 5532 5533
 * Record CPU load on nohz entry so we know the tickless load to account
 * on nohz exit. cpu_load[0] happens then to be updated more frequently
 * than other cpu_load[idx] but it should be fine as cpu_load readers
 * shouldn't rely into synchronized cpu_load[*] updates.
5534
 */
5535
void cpu_load_update_nohz_start(void)
5536 5537
{
	struct rq *this_rq = this_rq();
5538 5539 5540 5541 5542 5543

	/*
	 * This is all lockless but should be fine. If weighted_cpuload changes
	 * concurrently we'll exit nohz. And cpu_load write can race with
	 * cpu_load_update_idle() but both updater would be writing the same.
	 */
5544
	this_rq->cpu_load[0] = weighted_cpuload(this_rq);
5545 5546 5547 5548 5549 5550 5551
}

/*
 * Account the tickless load in the end of a nohz frame.
 */
void cpu_load_update_nohz_stop(void)
{
5552
	unsigned long curr_jiffies = READ_ONCE(jiffies);
5553 5554
	struct rq *this_rq = this_rq();
	unsigned long load;
5555
	struct rq_flags rf;
5556 5557 5558 5559

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

5560
	load = weighted_cpuload(this_rq);
5561
	rq_lock(this_rq, &rf);
5562
	update_rq_clock(this_rq);
5563
	cpu_load_update_nohz(this_rq, curr_jiffies, load);
5564
	rq_unlock(this_rq, &rf);
5565
}
5566 5567 5568 5569 5570 5571 5572 5573
#else /* !CONFIG_NO_HZ_COMMON */
static inline void cpu_load_update_nohz(struct rq *this_rq,
					unsigned long curr_jiffies,
					unsigned long load) { }
#endif /* CONFIG_NO_HZ_COMMON */

static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load)
{
5574
#ifdef CONFIG_NO_HZ_COMMON
5575 5576
	/* See the mess around cpu_load_update_nohz(). */
	this_rq->last_load_update_tick = READ_ONCE(jiffies);
5577
#endif
5578 5579
	cpu_load_update(this_rq, load, 1);
}
5580 5581 5582 5583

/*
 * Called from scheduler_tick()
 */
5584
void cpu_load_update_active(struct rq *this_rq)
5585
{
5586
	unsigned long load = weighted_cpuload(this_rq);
5587 5588 5589 5590 5591

	if (tick_nohz_tick_stopped())
		cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
	else
		cpu_load_update_periodic(this_rq, load);
5592 5593
}

5594
/*
5595
 * Return a low guess at the load of a migration-source CPU weighted
5596 5597 5598 5599 5600 5601 5602 5603
 * 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);
5604
	unsigned long total = weighted_cpuload(rq);
5605 5606 5607 5608 5609 5610 5611 5612

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

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

/*
5613
 * Return a high guess at the load of a migration-target CPU weighted
5614 5615 5616 5617 5618
 * according to the scheduling class and "nice" value.
 */
static unsigned long target_load(int cpu, int type)
{
	struct rq *rq = cpu_rq(cpu);
5619
	unsigned long total = weighted_cpuload(rq);
5620 5621 5622 5623 5624 5625 5626

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

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

5627
static unsigned long capacity_of(int cpu)
5628
{
5629
	return cpu_rq(cpu)->cpu_capacity;
5630 5631
}

5632 5633 5634 5635 5636
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

5637 5638 5639
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
5640
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
5641
	unsigned long load_avg = weighted_cpuload(rq);
5642 5643

	if (nr_running)
5644
		return load_avg / nr_running;
5645 5646 5647 5648

	return 0;
}

P
Peter Zijlstra 已提交
5649 5650 5651 5652 5653 5654 5655 5656 5657 5658 5659 5660 5661 5662 5663 5664 5665
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
5666 5667
/*
 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
P
Peter Zijlstra 已提交
5668
 *
M
Mike Galbraith 已提交
5669
 * A waker of many should wake a different task than the one last awakened
P
Peter Zijlstra 已提交
5670 5671 5672 5673 5674 5675 5676 5677 5678 5679 5680 5681
 * 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
5682
 */
5683 5684
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
5685 5686
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
5687
	int factor = this_cpu_read(sd_llc_size);
5688

M
Mike Galbraith 已提交
5689 5690 5691 5692 5693
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
5694 5695
}

5696
/*
5697 5698 5699
 * 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.
5700
 *
5701 5702
 * wake_affine_idle() - only considers 'now', it check if the waking CPU is
 *			cache-affine and is (or	will be) idle.
5703 5704 5705 5706
 *
 * wake_affine_weight() - considers the weight to reflect the average
 *			  scheduling latency of the CPUs. This seems to work
 *			  for the overloaded case.
5707
 */
5708
static int
5709
wake_affine_idle(int this_cpu, int prev_cpu, int sync)
5710
{
5711 5712 5713 5714 5715
	/*
	 * 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.
5716 5717 5718 5719 5720 5721
	 *
	 * 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.
5722 5723
	 */
	if (idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu))
5724
		return idle_cpu(prev_cpu) ? prev_cpu : this_cpu;
5725

5726
	if (sync && cpu_rq(this_cpu)->nr_running == 1)
5727
		return this_cpu;
5728

5729
	return nr_cpumask_bits;
5730 5731
}

5732
static int
5733 5734
wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
		   int this_cpu, int prev_cpu, int sync)
5735 5736 5737 5738
{
	s64 this_eff_load, prev_eff_load;
	unsigned long task_load;

5739
	this_eff_load = target_load(this_cpu, sd->wake_idx);
5740 5741 5742 5743

	if (sync) {
		unsigned long current_load = task_h_load(current);

5744
		if (current_load > this_eff_load)
5745
			return this_cpu;
5746

5747
		this_eff_load -= current_load;
5748 5749 5750 5751
	}

	task_load = task_h_load(p);

5752 5753 5754 5755
	this_eff_load += task_load;
	if (sched_feat(WA_BIAS))
		this_eff_load *= 100;
	this_eff_load *= capacity_of(prev_cpu);
5756

5757
	prev_eff_load = source_load(prev_cpu, sd->wake_idx);
5758 5759 5760 5761
	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);
5762

5763 5764 5765 5766 5767 5768 5769 5770 5771 5772
	/*
	 * 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;
5773 5774
}

5775 5776 5777 5778 5779 5780 5781 5782 5783 5784 5785 5786 5787 5788 5789 5790 5791 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
#ifdef CONFIG_NUMA_BALANCING
static void
update_wa_numa_placement(struct task_struct *p, int prev_cpu, int target)
{
	unsigned long interval;

	if (!static_branch_likely(&sched_numa_balancing))
		return;

	/* If balancing has no preference then continue gathering data */
	if (p->numa_preferred_nid == -1)
		return;

	/*
	 * If the wakeup is not affecting locality then it is neutral from
	 * the perspective of NUMA balacing so continue gathering data.
	 */
	if (cpu_to_node(prev_cpu) == cpu_to_node(target))
		return;

	/*
	 * Temporarily prevent NUMA balancing trying to place waker/wakee after
	 * wakee has been moved by wake_affine. This will potentially allow
	 * related tasks to converge and update their data placement. The
	 * 4 * numa_scan_period is to allow the two-pass filter to migrate
	 * hot data to the wakers node.
	 */
	interval = max(sysctl_numa_balancing_scan_delay,
			 p->numa_scan_period << 2);
	p->numa_migrate_retry = jiffies + msecs_to_jiffies(interval);

	interval = max(sysctl_numa_balancing_scan_delay,
			 current->numa_scan_period << 2);
	current->numa_migrate_retry = jiffies + msecs_to_jiffies(interval);
}
#else
static void
update_wa_numa_placement(struct task_struct *p, int prev_cpu, int target)
{
}
#endif

5817
static int wake_affine(struct sched_domain *sd, struct task_struct *p,
5818
		       int this_cpu, int prev_cpu, int sync)
5819
{
5820
	int target = nr_cpumask_bits;
5821

5822
	if (sched_feat(WA_IDLE))
5823
		target = wake_affine_idle(this_cpu, prev_cpu, sync);
5824

5825 5826
	if (sched_feat(WA_WEIGHT) && target == nr_cpumask_bits)
		target = wake_affine_weight(sd, p, this_cpu, prev_cpu, sync);
5827

5828
	schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
5829 5830
	if (target == nr_cpumask_bits)
		return prev_cpu;
5831

5832
	update_wa_numa_placement(p, prev_cpu, target);
5833 5834 5835
	schedstat_inc(sd->ttwu_move_affine);
	schedstat_inc(p->se.statistics.nr_wakeups_affine);
	return target;
5836 5837
}

5838 5839
static inline unsigned long task_util(struct task_struct *p);
static unsigned long cpu_util_wake(int cpu, struct task_struct *p);
5840 5841 5842

static unsigned long capacity_spare_wake(int cpu, struct task_struct *p)
{
5843
	return max_t(long, capacity_of(cpu) - cpu_util_wake(cpu, p), 0);
5844 5845
}

5846 5847 5848
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
5849 5850
 *
 * Assumes p is allowed on at least one CPU in sd.
5851 5852
 */
static struct sched_group *
P
Peter Zijlstra 已提交
5853
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5854
		  int this_cpu, int sd_flag)
5855
{
5856
	struct sched_group *idlest = NULL, *group = sd->groups;
5857
	struct sched_group *most_spare_sg = NULL;
5858 5859 5860
	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;
5861
	unsigned long most_spare = 0, this_spare = 0;
5862
	int load_idx = sd->forkexec_idx;
5863 5864 5865
	int imbalance_scale = 100 + (sd->imbalance_pct-100)/2;
	unsigned long imbalance = scale_load_down(NICE_0_LOAD) *
				(sd->imbalance_pct-100) / 100;
5866

5867 5868 5869
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

5870
	do {
5871 5872
		unsigned long load, avg_load, runnable_load;
		unsigned long spare_cap, max_spare_cap;
5873 5874
		int local_group;
		int i;
5875

5876
		/* Skip over this group if it has no CPUs allowed */
5877
		if (!cpumask_intersects(sched_group_span(group),
5878
					&p->cpus_allowed))
5879 5880 5881
			continue;

		local_group = cpumask_test_cpu(this_cpu,
5882
					       sched_group_span(group));
5883

5884 5885 5886 5887
		/*
		 * Tally up the load of all CPUs in the group and find
		 * the group containing the CPU with most spare capacity.
		 */
5888
		avg_load = 0;
5889
		runnable_load = 0;
5890
		max_spare_cap = 0;
5891

5892
		for_each_cpu(i, sched_group_span(group)) {
5893
			/* Bias balancing toward CPUs of our domain */
5894 5895 5896 5897 5898
			if (local_group)
				load = source_load(i, load_idx);
			else
				load = target_load(i, load_idx);

5899 5900 5901
			runnable_load += load;

			avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs);
5902 5903 5904 5905 5906

			spare_cap = capacity_spare_wake(i, p);

			if (spare_cap > max_spare_cap)
				max_spare_cap = spare_cap;
5907 5908
		}

5909
		/* Adjust by relative CPU capacity of the group */
5910 5911 5912 5913
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
		runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) /
					group->sgc->capacity;
5914 5915

		if (local_group) {
5916 5917
			this_runnable_load = runnable_load;
			this_avg_load = avg_load;
5918 5919
			this_spare = max_spare_cap;
		} else {
5920 5921 5922
			if (min_runnable_load > (runnable_load + imbalance)) {
				/*
				 * The runnable load is significantly smaller
5923
				 * so we can pick this new CPU:
5924 5925 5926 5927 5928 5929 5930 5931
				 */
				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
5932
				 * blocked load into account through avg_load:
5933 5934
				 */
				min_avg_load = avg_load;
5935 5936 5937 5938 5939 5940 5941
				idlest = group;
			}

			if (most_spare < max_spare_cap) {
				most_spare = max_spare_cap;
				most_spare_sg = group;
			}
5942 5943 5944
		}
	} while (group = group->next, group != sd->groups);

5945 5946 5947 5948 5949 5950
	/*
	 * 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.
5951 5952 5953 5954
	 *
	 * 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.
5955
	 */
5956 5957 5958
	if (sd_flag & SD_BALANCE_FORK)
		goto skip_spare;

5959
	if (this_spare > task_util(p) / 2 &&
5960
	    imbalance_scale*this_spare > 100*most_spare)
5961
		return NULL;
5962 5963

	if (most_spare > task_util(p) / 2)
5964 5965
		return most_spare_sg;

5966
skip_spare:
5967 5968 5969
	if (!idlest)
		return NULL;

5970 5971 5972 5973 5974 5975 5976 5977 5978 5979 5980 5981
	/*
	 * 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;

5982
	if (min_runnable_load > (this_runnable_load + imbalance))
5983
		return NULL;
5984 5985 5986 5987 5988

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

5989 5990 5991 5992
	return idlest;
}

/*
5993
 * find_idlest_group_cpu - find the idlest CPU among the CPUs in the group.
5994 5995
 */
static int
5996
find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
5997 5998
{
	unsigned long load, min_load = ULONG_MAX;
5999 6000 6001 6002
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
6003 6004
	int i;

6005 6006
	/* Check if we have any choice: */
	if (group->group_weight == 1)
6007
		return cpumask_first(sched_group_span(group));
6008

6009
	/* Traverse only the allowed CPUs */
6010
	for_each_cpu_and(i, sched_group_span(group), &p->cpus_allowed) {
6011 6012 6013 6014 6015 6016 6017 6018 6019 6020 6021 6022 6023 6024 6025 6026 6027 6028 6029 6030 6031 6032
		if (idle_cpu(i)) {
			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;
			}
6033
		} else if (shallowest_idle_cpu == -1) {
6034
			load = weighted_cpuload(cpu_rq(i));
6035
			if (load < min_load) {
6036 6037 6038
				min_load = load;
				least_loaded_cpu = i;
			}
6039 6040 6041
		}
	}

6042
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
6043
}
6044

6045 6046 6047
static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,
				  int cpu, int prev_cpu, int sd_flag)
{
6048
	int new_cpu = cpu;
6049

6050 6051 6052
	if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed))
		return prev_cpu;

6053 6054 6055 6056 6057 6058 6059 6060 6061 6062 6063 6064 6065 6066 6067 6068 6069
	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);
6070
		if (new_cpu == cpu) {
6071
			/* Now try balancing at a lower domain level of 'cpu': */
6072 6073 6074 6075
			sd = sd->child;
			continue;
		}

6076
		/* Now try balancing at a lower domain level of 'new_cpu': */
6077 6078 6079 6080 6081 6082 6083 6084 6085 6086 6087 6088 6089 6090
		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;
}

6091 6092 6093 6094 6095 6096 6097 6098 6099 6100 6101 6102 6103 6104 6105 6106 6107 6108 6109 6110 6111 6112 6113 6114 6115 6116 6117 6118 6119
#ifdef CONFIG_SCHED_SMT

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
6120
void __update_idle_core(struct rq *rq)
6121 6122 6123 6124 6125 6126 6127 6128 6129 6130 6131 6132 6133 6134 6135 6136 6137 6138 6139 6140 6141 6142 6143 6144 6145 6146 6147 6148 6149
{
	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;

		if (!idle_cpu(cpu))
			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);
6150
	int core, cpu;
6151

P
Peter Zijlstra 已提交
6152 6153 6154
	if (!static_branch_likely(&sched_smt_present))
		return -1;

6155 6156 6157
	if (!test_idle_cores(target, false))
		return -1;

6158
	cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed);
6159

6160
	for_each_cpu_wrap(core, cpus, target) {
6161 6162 6163 6164 6165 6166 6167 6168 6169 6170 6171 6172 6173 6174 6175 6176 6177 6178 6179 6180 6181 6182 6183 6184 6185 6186 6187
		bool idle = true;

		for_each_cpu(cpu, cpu_smt_mask(core)) {
			cpumask_clear_cpu(cpu, cpus);
			if (!idle_cpu(cpu))
				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
6188 6189 6190
	if (!static_branch_likely(&sched_smt_present))
		return -1;

6191
	for_each_cpu(cpu, cpu_smt_mask(target)) {
6192
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
6193 6194 6195 6196 6197 6198 6199 6200 6201 6202 6203 6204 6205 6206 6207 6208 6209 6210 6211 6212 6213 6214 6215 6216 6217 6218
			continue;
		if (idle_cpu(cpu))
			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).
6219
 */
6220 6221
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target)
{
6222
	struct sched_domain *this_sd;
6223
	u64 avg_cost, avg_idle;
6224 6225
	u64 time, cost;
	s64 delta;
6226
	int cpu, nr = INT_MAX;
6227

6228 6229 6230 6231
	this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
	if (!this_sd)
		return -1;

6232 6233 6234 6235
	/*
	 * Due to large variance we need a large fuzz factor; hackbench in
	 * particularly is sensitive here.
	 */
6236 6237 6238 6239
	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)
6240 6241
		return -1;

6242 6243 6244 6245 6246 6247 6248 6249
	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;
	}

6250 6251
	time = local_clock();

6252
	for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
6253 6254
		if (!--nr)
			return -1;
6255
		if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
6256 6257 6258 6259 6260 6261 6262 6263 6264 6265 6266 6267 6268 6269 6270
			continue;
		if (idle_cpu(cpu))
			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.
6271
 */
6272
static int select_idle_sibling(struct task_struct *p, int prev, int target)
6273
{
6274
	struct sched_domain *sd;
6275
	int i, recent_used_cpu;
6276

6277 6278
	if (idle_cpu(target))
		return target;
6279 6280

	/*
6281
	 * If the previous CPU is cache affine and idle, don't be stupid:
6282
	 */
6283 6284
	if (prev != target && cpus_share_cache(prev, target) && idle_cpu(prev))
		return prev;
6285

6286
	/* Check a recently used CPU as a potential idle candidate: */
6287 6288 6289 6290 6291 6292 6293 6294
	recent_used_cpu = p->recent_used_cpu;
	if (recent_used_cpu != prev &&
	    recent_used_cpu != target &&
	    cpus_share_cache(recent_used_cpu, target) &&
	    idle_cpu(recent_used_cpu) &&
	    cpumask_test_cpu(p->recent_used_cpu, &p->cpus_allowed)) {
		/*
		 * Replace recent_used_cpu with prev as it is a potential
6295
		 * candidate for the next wake:
6296 6297 6298 6299 6300
		 */
		p->recent_used_cpu = prev;
		return recent_used_cpu;
	}

6301
	sd = rcu_dereference(per_cpu(sd_llc, target));
6302 6303
	if (!sd)
		return target;
6304

6305 6306 6307
	i = select_idle_core(p, sd, target);
	if ((unsigned)i < nr_cpumask_bits)
		return i;
6308

6309 6310 6311 6312 6313 6314 6315
	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;
6316

6317 6318
	return target;
}
6319

6320
/*
6321
 * cpu_util returns the amount of capacity of a CPU that is used by CFS
6322
 * tasks. The unit of the return value must be the one of capacity so we can
6323 6324
 * compare the utilization with the capacity of the CPU that is available for
 * CFS task (ie cpu_capacity).
6325 6326 6327 6328 6329 6330 6331 6332 6333 6334 6335 6336 6337 6338 6339 6340 6341 6342 6343 6344
 *
 * 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.
 *
 * 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).
6345
 */
6346
static unsigned long cpu_util(int cpu)
6347
{
6348
	unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
6349 6350
	unsigned long capacity = capacity_orig_of(cpu);

6351
	return (util >= capacity) ? capacity : util;
6352
}
6353

6354
static inline unsigned long task_util(struct task_struct *p)
6355 6356 6357 6358
{
	return p->se.avg.util_avg;
}

6359
/*
6360
 * cpu_util_wake: Compute CPU utilization with any contributions from
6361 6362
 * the waking task p removed.
 */
6363
static unsigned long cpu_util_wake(int cpu, struct task_struct *p)
6364 6365 6366 6367 6368 6369 6370 6371 6372 6373 6374 6375 6376
{
	unsigned long util, capacity;

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

	capacity = capacity_orig_of(cpu);
	util = max_t(long, cpu_rq(cpu)->cfs.avg.util_avg - task_util(p), 0);

	return (util >= capacity) ? capacity : util;
}

6377 6378 6379 6380 6381 6382 6383 6384 6385 6386 6387 6388 6389 6390 6391 6392 6393 6394
/*
 * 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;

6395 6396 6397
	/* Bring task utilization in sync with prev_cpu */
	sync_entity_load_avg(&p->se);

6398 6399 6400
	return min_cap * 1024 < task_util(p) * capacity_margin;
}

6401
/*
6402 6403 6404
 * 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.
6405
 *
6406 6407
 * 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.
6408
 *
6409
 * Returns the target CPU number.
6410 6411 6412
 *
 * preempt must be disabled.
 */
6413
static int
6414
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
6415
{
6416
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
6417
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
6418
	int new_cpu = prev_cpu;
6419
	int want_affine = 0;
6420
	int sync = (wake_flags & WF_SYNC) && !(current->flags & PF_EXITING);
6421

P
Peter Zijlstra 已提交
6422 6423
	if (sd_flag & SD_BALANCE_WAKE) {
		record_wakee(p);
6424
		want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu)
6425
			      && cpumask_test_cpu(cpu, &p->cpus_allowed);
P
Peter Zijlstra 已提交
6426
	}
6427

6428
	rcu_read_lock();
6429
	for_each_domain(cpu, tmp) {
6430
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
6431
			break;
6432

6433
		/*
6434
		 * If both 'cpu' and 'prev_cpu' are part of this domain,
6435
		 * cpu is a valid SD_WAKE_AFFINE target.
6436
		 */
6437 6438 6439
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
6440
			break;
6441
		}
6442

6443
		if (tmp->flags & sd_flag)
6444
			sd = tmp;
M
Mike Galbraith 已提交
6445 6446
		else if (!want_affine)
			break;
6447 6448
	}

M
Mike Galbraith 已提交
6449 6450
	if (affine_sd) {
		sd = NULL; /* Prefer wake_affine over balance flags */
6451 6452 6453
		if (cpu == prev_cpu)
			goto pick_cpu;

6454
		new_cpu = wake_affine(affine_sd, p, cpu, prev_cpu, sync);
6455
	}
6456

6457 6458 6459 6460 6461 6462 6463 6464 6465
	if (sd && !(sd_flag & SD_BALANCE_FORK)) {
		/*
		 * We're going to need the task's util for capacity_spare_wake
		 * in find_idlest_group. Sync it up to prev_cpu's
		 * last_update_time.
		 */
		sync_entity_load_avg(&p->se);
	}

M
Mike Galbraith 已提交
6466
	if (!sd) {
6467
pick_cpu:
6468
		if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
6469
			new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
M
Mike Galbraith 已提交
6470

6471 6472 6473
			if (want_affine)
				current->recent_used_cpu = cpu;
		}
6474 6475
	} else {
		new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
6476
	}
6477
	rcu_read_unlock();
6478

6479
	return new_cpu;
6480
}
6481

6482 6483
static void detach_entity_cfs_rq(struct sched_entity *se);

6484
/*
6485
 * Called immediately before a task is migrated to a new CPU; task_cpu(p) and
6486
 * cfs_rq_of(p) references at time of call are still valid and identify the
6487
 * previous CPU. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
6488
 */
6489
static void migrate_task_rq_fair(struct task_struct *p)
6490
{
6491 6492 6493 6494 6495 6496 6497 6498 6499 6500 6501 6502 6503 6504 6505 6506 6507 6508 6509 6510 6511 6512 6513 6514 6515 6516
	/*
	 * 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;
	}

6517 6518 6519 6520 6521 6522 6523 6524 6525 6526 6527 6528 6529 6530 6531 6532 6533 6534 6535
	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);
	}
6536 6537 6538

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
6539 6540

	/* We have migrated, no longer consider this task hot */
6541
	p->se.exec_start = 0;
6542
}
6543 6544 6545 6546 6547

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
6548 6549
#endif /* CONFIG_SMP */

6550
static unsigned long wakeup_gran(struct sched_entity *se)
6551 6552 6553 6554
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
6555 6556
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
6557 6558 6559 6560 6561 6562 6563 6564 6565
	 *
	 * 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.
6566
	 */
6567
	return calc_delta_fair(gran, se);
6568 6569
}

6570 6571 6572 6573 6574 6575 6576 6577 6578 6579 6580 6581 6582 6583 6584 6585 6586 6587 6588 6589 6590 6591
/*
 * 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;

6592
	gran = wakeup_gran(se);
6593 6594 6595 6596 6597 6598
	if (vdiff > gran)
		return 1;

	return 0;
}

6599 6600
static void set_last_buddy(struct sched_entity *se)
{
6601 6602 6603
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6604 6605 6606
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6607
		cfs_rq_of(se)->last = se;
6608
	}
6609 6610 6611 6612
}

static void set_next_buddy(struct sched_entity *se)
{
6613 6614 6615
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

6616 6617 6618
	for_each_sched_entity(se) {
		if (SCHED_WARN_ON(!se->on_rq))
			return;
6619
		cfs_rq_of(se)->next = se;
6620
	}
6621 6622
}

6623 6624
static void set_skip_buddy(struct sched_entity *se)
{
6625 6626
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
6627 6628
}

6629 6630 6631
/*
 * Preempt the current task with a newly woken task if needed:
 */
6632
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
6633 6634
{
	struct task_struct *curr = rq->curr;
6635
	struct sched_entity *se = &curr->se, *pse = &p->se;
6636
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
6637
	int scale = cfs_rq->nr_running >= sched_nr_latency;
6638
	int next_buddy_marked = 0;
6639

I
Ingo Molnar 已提交
6640 6641 6642
	if (unlikely(se == pse))
		return;

6643
	/*
6644
	 * This is possible from callers such as attach_tasks(), in which we
6645 6646 6647 6648 6649 6650 6651
	 * 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;

6652
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
6653
		set_next_buddy(pse);
6654 6655
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
6656

6657 6658 6659
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
6660 6661 6662 6663 6664 6665
	 *
	 * 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.
6666 6667 6668 6669
	 */
	if (test_tsk_need_resched(curr))
		return;

6670 6671 6672 6673 6674
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

6675
	/*
6676 6677
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
6678
	 */
6679
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
6680
		return;
6681

6682
	find_matching_se(&se, &pse);
6683
	update_curr(cfs_rq_of(se));
6684
	BUG_ON(!pse);
6685 6686 6687 6688 6689 6690 6691
	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);
6692
		goto preempt;
6693
	}
6694

6695
	return;
6696

6697
preempt:
6698
	resched_curr(rq);
6699 6700 6701 6702 6703 6704 6705 6706 6707 6708 6709 6710 6711 6712
	/*
	 * 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);
6713 6714
}

6715
static struct task_struct *
6716
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6717 6718 6719
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
6720
	struct task_struct *p;
6721
	int new_tasks;
6722

6723
again:
6724
	if (!cfs_rq->nr_running)
6725
		goto idle;
6726

6727
#ifdef CONFIG_FAIR_GROUP_SCHED
6728
	if (prev->sched_class != &fair_sched_class)
6729 6730 6731 6732 6733 6734 6735 6736 6737 6738 6739 6740 6741 6742 6743 6744 6745 6746 6747
		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.
		 */
6748 6749 6750 6751 6752
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
6753

6754 6755 6756
			/*
			 * This call to check_cfs_rq_runtime() will do the
			 * throttle and dequeue its entity in the parent(s).
6757
			 * Therefore the nr_running test will indeed
6758 6759
			 * be correct.
			 */
6760 6761 6762 6763 6764 6765
			if (unlikely(check_cfs_rq_runtime(cfs_rq))) {
				cfs_rq = &rq->cfs;

				if (!cfs_rq->nr_running)
					goto idle;

6766
				goto simple;
6767
			}
6768
		}
6769 6770 6771 6772 6773 6774 6775 6776 6777 6778 6779 6780 6781 6782 6783 6784 6785 6786 6787 6788 6789 6790 6791 6792 6793 6794 6795 6796 6797 6798 6799 6800 6801

		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);
	}

6802
	goto done;
6803 6804
simple:
#endif
6805

6806
	put_prev_task(rq, prev);
6807

6808
	do {
6809
		se = pick_next_entity(cfs_rq, NULL);
6810
		set_next_entity(cfs_rq, se);
6811 6812 6813
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
6814
	p = task_of(se);
6815

6816
done: __maybe_unused;
6817 6818 6819 6820 6821 6822 6823 6824 6825
#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

6826 6827
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
6828 6829

	return p;
6830 6831

idle:
6832 6833
	new_tasks = idle_balance(rq, rf);

6834 6835 6836 6837 6838
	/*
	 * 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.
	 */
6839
	if (new_tasks < 0)
6840 6841
		return RETRY_TASK;

6842
	if (new_tasks > 0)
6843 6844 6845
		goto again;

	return NULL;
6846 6847 6848 6849 6850
}

/*
 * Account for a descheduled task:
 */
6851
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
6852 6853 6854 6855 6856 6857
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
6858
		put_prev_entity(cfs_rq, se);
6859 6860 6861
	}
}

6862 6863 6864 6865 6866 6867 6868 6869 6870 6871 6872 6873 6874 6875 6876 6877 6878 6879 6880 6881 6882 6883 6884 6885 6886
/*
 * 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);
6887 6888 6889 6890 6891
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
6892
		rq_clock_skip_update(rq, true);
6893 6894 6895 6896 6897
	}

	set_skip_buddy(se);
}

6898 6899 6900 6901
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

6902 6903
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
6904 6905 6906 6907 6908 6909 6910 6911 6912 6913
		return false;

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

	yield_task_fair(rq);

	return true;
}

6914
#ifdef CONFIG_SMP
6915
/**************************************************
P
Peter Zijlstra 已提交
6916 6917 6918 6919 6920
 * Fair scheduling class load-balancing methods.
 *
 * BASICS
 *
 * The purpose of load-balancing is to achieve the same basic fairness the
6921
 * per-CPU scheduler provides, namely provide a proportional amount of compute
P
Peter Zijlstra 已提交
6922 6923 6924 6925
 * 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)
 *
6926
 * Where W_i,n is the n-th weight average for CPU i. The instantaneous weight
P
Peter Zijlstra 已提交
6927 6928 6929 6930
 * W_i,0 is defined as:
 *
 *   W_i,0 = \Sum_j w_i,j                                             (2)
 *
6931
 * Where w_i,j is the weight of the j-th runnable task on CPU i. This weight
6932
 * is derived from the nice value as per sched_prio_to_weight[].
P
Peter Zijlstra 已提交
6933 6934 6935 6936 6937 6938
 *
 * 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)
 *
6939
 * C_i is the compute capacity of CPU i, typically it is the
P
Peter Zijlstra 已提交
6940 6941 6942 6943 6944 6945
 * 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):
 *
6946
 *   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
6947 6948 6949 6950 6951 6952 6953 6954 6955 6956 6957 6958 6959
 *
 * 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)
6960
 * for all i,j solution, we create a tree of CPUs that follows the hardware
P
Peter Zijlstra 已提交
6961
 * topology where each level pairs two lower groups (or better). This results
6962
 * in O(log n) layers. Furthermore we reduce the number of CPUs going up the
P
Peter Zijlstra 已提交
6963
 * tree to only the first of the previous level and we decrease the frequency
6964
 * of load-balance at each level inv. proportional to the number of CPUs in
P
Peter Zijlstra 已提交
6965 6966 6967 6968 6969 6970 6971 6972
 * 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
6973
 *         |         |     `- number of CPUs doing load-balance
P
Peter Zijlstra 已提交
6974 6975 6976 6977 6978 6979 6980
 *         |         `- 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
6981
 * to every other CPU in at most O(log n) steps:
P
Peter Zijlstra 已提交
6982 6983 6984
 *
 * The adjacency matrix of the resulting graph is given by:
 *
6985
 *             log_2 n
P
Peter Zijlstra 已提交
6986 6987 6988 6989 6990 6991 6992
 *   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)
 *
6993
 * Showing there's indeed a path between every CPU in at most O(log n) steps.
P
Peter Zijlstra 已提交
6994 6995 6996 6997 6998 6999 7000 7001 7002
 * 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
7003
 * balancing is more aggressive and has the newly idle CPU iterate up the domain
P
Peter Zijlstra 已提交
7004 7005 7006 7007 7008 7009 7010 7011 7012 7013 7014 7015 7016 7017 7018 7019 7020 7021 7022 7023
 * 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)
 *
7024
 * 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
7025 7026 7027 7028 7029 7030
 *
 * 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.]
7031
 */
7032

7033 7034
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

7035 7036
enum fbq_type { regular, remote, all };

7037
#define LBF_ALL_PINNED	0x01
7038
#define LBF_NEED_BREAK	0x02
7039 7040
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
7041
#define LBF_NOHZ_STATS	0x10
7042
#define LBF_NOHZ_AGAIN	0x20
7043 7044 7045 7046 7047

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
7048
	int			src_cpu;
7049 7050 7051 7052

	int			dst_cpu;
	struct rq		*dst_rq;

7053 7054
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
7055
	enum cpu_idle_type	idle;
7056
	long			imbalance;
7057 7058 7059
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

7060
	unsigned int		flags;
7061 7062 7063 7064

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
7065 7066

	enum fbq_type		fbq_type;
7067
	struct list_head	tasks;
7068 7069
};

7070 7071 7072
/*
 * Is this task likely cache-hot:
 */
7073
static int task_hot(struct task_struct *p, struct lb_env *env)
7074 7075 7076
{
	s64 delta;

7077 7078
	lockdep_assert_held(&env->src_rq->lock);

7079 7080 7081 7082 7083 7084 7085 7086 7087
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
7088
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
7089 7090 7091 7092 7093 7094 7095 7096 7097
			(&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;

7098
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
7099 7100 7101 7102

	return delta < (s64)sysctl_sched_migration_cost;
}

7103
#ifdef CONFIG_NUMA_BALANCING
7104
/*
7105 7106 7107
 * 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.
7108
 */
7109
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
7110
{
7111
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
7112
	unsigned long src_faults, dst_faults;
7113 7114
	int src_nid, dst_nid;

7115
	if (!static_branch_likely(&sched_numa_balancing))
7116 7117
		return -1;

7118
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
7119
		return -1;
7120 7121 7122 7123

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

7124
	if (src_nid == dst_nid)
7125
		return -1;
7126

7127 7128 7129 7130 7131 7132 7133
	/* 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;
	}
7134

7135 7136
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
7137
		return 0;
7138

7139 7140 7141 7142
	/* Leaving a core idle is often worse than degrading locality. */
	if (env->idle != CPU_NOT_IDLE)
		return -1;

7143 7144 7145 7146 7147 7148
	if (numa_group) {
		src_faults = group_faults(p, src_nid);
		dst_faults = group_faults(p, dst_nid);
	} else {
		src_faults = task_faults(p, src_nid);
		dst_faults = task_faults(p, dst_nid);
7149 7150
	}

7151
	return dst_faults < src_faults;
7152 7153
}

7154
#else
7155
static inline int migrate_degrades_locality(struct task_struct *p,
7156 7157
					     struct lb_env *env)
{
7158
	return -1;
7159
}
7160 7161
#endif

7162 7163 7164 7165
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
7166
int can_migrate_task(struct task_struct *p, struct lb_env *env)
7167
{
7168
	int tsk_cache_hot;
7169 7170 7171

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

7172 7173
	/*
	 * We do not migrate tasks that are:
7174
	 * 1) throttled_lb_pair, or
7175
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
7176 7177
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
7178
	 */
7179 7180 7181
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

7182
	if (!cpumask_test_cpu(env->dst_cpu, &p->cpus_allowed)) {
7183
		int cpu;
7184

7185
		schedstat_inc(p->se.statistics.nr_failed_migrations_affine);
7186

7187 7188
		env->flags |= LBF_SOME_PINNED;

7189
		/*
7190
		 * Remember if this task can be migrated to any other CPU in
7191 7192 7193
		 * our sched_group. We may want to revisit it if we couldn't
		 * meet load balance goals by pulling other tasks on src_cpu.
		 *
7194 7195
		 * Avoid computing new_dst_cpu for NEWLY_IDLE or if we have
		 * already computed one in current iteration.
7196
		 */
7197
		if (env->idle == CPU_NEWLY_IDLE || (env->flags & LBF_DST_PINNED))
7198 7199
			return 0;

7200
		/* Prevent to re-select dst_cpu via env's CPUs: */
7201
		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
7202
			if (cpumask_test_cpu(cpu, &p->cpus_allowed)) {
7203
				env->flags |= LBF_DST_PINNED;
7204 7205 7206
				env->new_dst_cpu = cpu;
				break;
			}
7207
		}
7208

7209 7210
		return 0;
	}
7211 7212

	/* Record that we found atleast one task that could run on dst_cpu */
7213
	env->flags &= ~LBF_ALL_PINNED;
7214

7215
	if (task_running(env->src_rq, p)) {
7216
		schedstat_inc(p->se.statistics.nr_failed_migrations_running);
7217 7218 7219 7220 7221
		return 0;
	}

	/*
	 * Aggressive migration if:
7222 7223 7224
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
7225
	 */
7226 7227 7228
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
7229

7230
	if (tsk_cache_hot <= 0 ||
7231
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
7232
		if (tsk_cache_hot == 1) {
7233 7234
			schedstat_inc(env->sd->lb_hot_gained[env->idle]);
			schedstat_inc(p->se.statistics.nr_forced_migrations);
7235
		}
7236 7237 7238
		return 1;
	}

7239
	schedstat_inc(p->se.statistics.nr_failed_migrations_hot);
Z
Zhang Hang 已提交
7240
	return 0;
7241 7242
}

7243
/*
7244 7245 7246 7247 7248 7249 7250
 * 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;
7251
	deactivate_task(env->src_rq, p, DEQUEUE_NOCLOCK);
7252 7253 7254
	set_task_cpu(p, env->dst_cpu);
}

7255
/*
7256
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
7257 7258
 * part of active balancing operations within "domain".
 *
7259
 * Returns a task if successful and NULL otherwise.
7260
 */
7261
static struct task_struct *detach_one_task(struct lb_env *env)
7262
{
7263
	struct task_struct *p;
7264

7265 7266
	lockdep_assert_held(&env->src_rq->lock);

7267 7268
	list_for_each_entry_reverse(p,
			&env->src_rq->cfs_tasks, se.group_node) {
7269 7270
		if (!can_migrate_task(p, env))
			continue;
7271

7272
		detach_task(p, env);
7273

7274
		/*
7275
		 * Right now, this is only the second place where
7276
		 * lb_gained[env->idle] is updated (other is detach_tasks)
7277
		 * so we can safely collect stats here rather than
7278
		 * inside detach_tasks().
7279
		 */
7280
		schedstat_inc(env->sd->lb_gained[env->idle]);
7281
		return p;
7282
	}
7283
	return NULL;
7284 7285
}

7286 7287
static const unsigned int sched_nr_migrate_break = 32;

7288
/*
7289 7290
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
7291
 *
7292
 * Returns number of detached tasks if successful and 0 otherwise.
7293
 */
7294
static int detach_tasks(struct lb_env *env)
7295
{
7296 7297
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
7298
	unsigned long load;
7299 7300 7301
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
7302

7303
	if (env->imbalance <= 0)
7304
		return 0;
7305

7306
	while (!list_empty(tasks)) {
7307 7308 7309 7310 7311 7312 7313
		/*
		 * 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;

7314
		p = list_last_entry(tasks, struct task_struct, se.group_node);
7315

7316 7317
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
7318
		if (env->loop > env->loop_max)
7319
			break;
7320 7321

		/* take a breather every nr_migrate tasks */
7322
		if (env->loop > env->loop_break) {
7323
			env->loop_break += sched_nr_migrate_break;
7324
			env->flags |= LBF_NEED_BREAK;
7325
			break;
7326
		}
7327

7328
		if (!can_migrate_task(p, env))
7329 7330 7331
			goto next;

		load = task_h_load(p);
7332

7333
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
7334 7335
			goto next;

7336
		if ((load / 2) > env->imbalance)
7337
			goto next;
7338

7339 7340 7341 7342
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
7343
		env->imbalance -= load;
7344 7345

#ifdef CONFIG_PREEMPT
7346 7347
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
7348
		 * kernels will stop after the first task is detached to minimize
7349 7350
		 * the critical section.
		 */
7351
		if (env->idle == CPU_NEWLY_IDLE)
7352
			break;
7353 7354
#endif

7355 7356 7357 7358
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
7359
		if (env->imbalance <= 0)
7360
			break;
7361 7362 7363

		continue;
next:
7364
		list_move(&p->se.group_node, tasks);
7365
	}
7366

7367
	/*
7368 7369 7370
	 * 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().
7371
	 */
7372
	schedstat_add(env->sd->lb_gained[env->idle], detached);
7373

7374 7375 7376 7377 7378 7379 7380 7381 7382 7383 7384
	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);
7385
	activate_task(rq, p, ENQUEUE_NOCLOCK);
7386
	p->on_rq = TASK_ON_RQ_QUEUED;
7387 7388 7389 7390 7391 7392 7393 7394 7395
	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)
{
7396 7397 7398
	struct rq_flags rf;

	rq_lock(rq, &rf);
7399
	update_rq_clock(rq);
7400
	attach_task(rq, p);
7401
	rq_unlock(rq, &rf);
7402 7403 7404 7405 7406 7407 7408 7409 7410 7411
}

/*
 * 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;
7412
	struct rq_flags rf;
7413

7414
	rq_lock(env->dst_rq, &rf);
7415
	update_rq_clock(env->dst_rq);
7416 7417 7418 7419

	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
		list_del_init(&p->se.group_node);
7420

7421 7422 7423
		attach_task(env->dst_rq, p);
	}

7424
	rq_unlock(env->dst_rq, &rf);
7425 7426
}

7427 7428 7429 7430 7431 7432 7433 7434 7435 7436 7437 7438 7439
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;
}

#ifdef CONFIG_FAIR_GROUP_SCHED

7440 7441 7442 7443 7444 7445 7446 7447 7448 7449 7450
static inline bool cfs_rq_is_decayed(struct cfs_rq *cfs_rq)
{
	if (cfs_rq->load.weight)
		return false;

	if (cfs_rq->avg.load_sum)
		return false;

	if (cfs_rq->avg.util_sum)
		return false;

7451
	if (cfs_rq->avg.runnable_load_sum)
7452 7453 7454 7455 7456
		return false;

	return true;
}

7457
static void update_blocked_averages(int cpu)
7458 7459
{
	struct rq *rq = cpu_rq(cpu);
7460
	struct cfs_rq *cfs_rq, *pos;
7461
	struct rq_flags rf;
7462
	bool done = true;
7463

7464
	rq_lock_irqsave(rq, &rf);
7465
	update_rq_clock(rq);
7466

7467 7468 7469 7470
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
7471
	for_each_leaf_cfs_rq_safe(rq, cfs_rq, pos) {
7472 7473
		struct sched_entity *se;

7474 7475 7476
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
7477

7478
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
7479
			update_tg_load_avg(cfs_rq, 0);
7480

7481 7482 7483
		/* Propagate pending load changes to the parent, if any: */
		se = cfs_rq->tg->se[cpu];
		if (se && !skip_blocked_update(se))
7484
			update_load_avg(cfs_rq_of(se), se, 0);
7485 7486 7487 7488 7489 7490 7491

		/*
		 * There can be a lot of idle CPU cgroups.  Don't let fully
		 * decayed cfs_rqs linger on the list.
		 */
		if (cfs_rq_is_decayed(cfs_rq))
			list_del_leaf_cfs_rq(cfs_rq);
7492 7493 7494

		/* Don't need periodic decay once load/util_avg are null */
		if (cfs_rq_has_blocked(cfs_rq))
7495
			done = false;
7496
	}
7497 7498 7499

#ifdef CONFIG_NO_HZ_COMMON
	rq->last_blocked_load_update_tick = jiffies;
7500 7501
	if (done)
		rq->has_blocked_load = 0;
7502
#endif
7503
	rq_unlock_irqrestore(rq, &rf);
7504 7505
}

7506
/*
7507
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
7508 7509 7510
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
7511
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
7512
{
7513 7514
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
7515
	unsigned long now = jiffies;
7516
	unsigned long load;
7517

7518
	if (cfs_rq->last_h_load_update == now)
7519 7520
		return;

7521 7522 7523 7524 7525 7526 7527
	cfs_rq->h_load_next = NULL;
	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
		cfs_rq->h_load_next = se;
		if (cfs_rq->last_h_load_update == now)
			break;
	}
7528

7529
	if (!se) {
7530
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
7531 7532 7533 7534 7535
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
7536 7537
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
7538 7539 7540 7541
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
7542 7543
}

7544
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
7545
{
7546
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
7547

7548
	update_cfs_rq_h_load(cfs_rq);
7549
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
7550
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
7551 7552
}
#else
7553
static inline void update_blocked_averages(int cpu)
7554
{
7555 7556
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
7557
	struct rq_flags rf;
7558

7559
	rq_lock_irqsave(rq, &rf);
7560
	update_rq_clock(rq);
7561
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
7562 7563
#ifdef CONFIG_NO_HZ_COMMON
	rq->last_blocked_load_update_tick = jiffies;
7564
	if (!cfs_rq_has_blocked(cfs_rq))
7565
		rq->has_blocked_load = 0;
7566
#endif
7567
	rq_unlock_irqrestore(rq, &rf);
7568 7569
}

7570
static unsigned long task_h_load(struct task_struct *p)
7571
{
7572
	return p->se.avg.load_avg;
7573
}
P
Peter Zijlstra 已提交
7574
#endif
7575 7576

/********** Helpers for find_busiest_group ************************/
7577 7578 7579 7580 7581 7582 7583

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

7584 7585 7586 7587 7588 7589 7590
/*
 * 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
7591
	unsigned long load_per_task;
7592
	unsigned long group_capacity;
7593
	unsigned long group_util; /* Total utilization of the group */
7594 7595 7596
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
7597
	enum group_type group_type;
7598
	int group_no_capacity;
7599 7600 7601 7602
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
7603 7604
};

J
Joonsoo Kim 已提交
7605 7606 7607 7608 7609 7610 7611
/*
 * 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 */
7612
	unsigned long total_running;
J
Joonsoo Kim 已提交
7613
	unsigned long total_load;	/* Total load of all groups in sd */
7614
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
7615 7616 7617
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
7618
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
7619 7620
};

7621 7622 7623 7624 7625 7626 7627 7628 7629 7630 7631
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,
7632
		.total_running = 0UL,
7633
		.total_load = 0UL,
7634
		.total_capacity = 0UL,
7635 7636
		.busiest_stat = {
			.avg_load = 0UL,
7637 7638
			.sum_nr_running = 0,
			.group_type = group_other,
7639 7640 7641 7642
		},
	};
}

7643 7644 7645
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
7646
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
7647 7648
 *
 * Return: The load index.
7649 7650 7651 7652 7653 7654 7655 7656 7657 7658 7659 7660 7661 7662 7663 7664 7665 7666 7667 7668 7669 7670
 */
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;
}

7671
static unsigned long scale_rt_capacity(int cpu)
7672 7673
{
	struct rq *rq = cpu_rq(cpu);
7674
	u64 total, used, age_stamp, avg;
7675
	s64 delta;
7676

7677 7678 7679 7680
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
7681 7682
	age_stamp = READ_ONCE(rq->age_stamp);
	avg = READ_ONCE(rq->rt_avg);
7683
	delta = __rq_clock_broken(rq) - age_stamp;
7684

7685 7686 7687 7688
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
7689

7690
	used = div_u64(avg, total);
7691

7692 7693
	if (likely(used < SCHED_CAPACITY_SCALE))
		return SCHED_CAPACITY_SCALE - used;
7694

7695
	return 1;
7696 7697
}

7698
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
7699
{
7700
	unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
7701 7702
	struct sched_group *sdg = sd->groups;

7703
	cpu_rq(cpu)->cpu_capacity_orig = capacity;
7704

7705
	capacity *= scale_rt_capacity(cpu);
7706
	capacity >>= SCHED_CAPACITY_SHIFT;
7707

7708 7709
	if (!capacity)
		capacity = 1;
7710

7711 7712
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
7713
	sdg->sgc->min_capacity = capacity;
7714 7715
}

7716
void update_group_capacity(struct sched_domain *sd, int cpu)
7717 7718 7719
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
7720
	unsigned long capacity, min_capacity;
7721 7722 7723 7724
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
7725
	sdg->sgc->next_update = jiffies + interval;
7726 7727

	if (!child) {
7728
		update_cpu_capacity(sd, cpu);
7729 7730 7731
		return;
	}

7732
	capacity = 0;
7733
	min_capacity = ULONG_MAX;
7734

P
Peter Zijlstra 已提交
7735 7736 7737 7738 7739 7740
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

7741
		for_each_cpu(cpu, sched_group_span(sdg)) {
7742
			struct sched_group_capacity *sgc;
7743
			struct rq *rq = cpu_rq(cpu);
7744

7745
			/*
7746
			 * build_sched_domains() -> init_sched_groups_capacity()
7747 7748 7749
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
7750 7751
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
7752
			 *
7753
			 * This avoids capacity from being 0 and
7754 7755 7756
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
7757
				capacity += capacity_of(cpu);
7758 7759 7760
			} else {
				sgc = rq->sd->groups->sgc;
				capacity += sgc->capacity;
7761
			}
7762

7763
			min_capacity = min(capacity, min_capacity);
7764
		}
P
Peter Zijlstra 已提交
7765 7766 7767 7768
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
7769
		 */
P
Peter Zijlstra 已提交
7770 7771 7772

		group = child->groups;
		do {
7773 7774 7775 7776
			struct sched_group_capacity *sgc = group->sgc;

			capacity += sgc->capacity;
			min_capacity = min(sgc->min_capacity, min_capacity);
P
Peter Zijlstra 已提交
7777 7778 7779
			group = group->next;
		} while (group != child->groups);
	}
7780

7781
	sdg->sgc->capacity = capacity;
7782
	sdg->sgc->min_capacity = min_capacity;
7783 7784
}

7785
/*
7786 7787 7788
 * 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
7789 7790
 */
static inline int
7791
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
7792
{
7793 7794
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
7795 7796
}

7797 7798
/*
 * Group imbalance indicates (and tries to solve) the problem where balancing
7799
 * groups is inadequate due to ->cpus_allowed constraints.
7800
 *
7801 7802
 * 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.
7803 7804
 * Something like:
 *
7805 7806
 *	{ 0 1 2 3 } { 4 5 6 7 }
 *	        *     * * *
7807 7808 7809
 *
 * 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
7810
 * cpu 3 and leave one of the CPUs in the second group unused.
7811 7812
 *
 * The current solution to this issue is detecting the skew in the first group
7813 7814
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
7815 7816
 *
 * When this is so detected; this group becomes a candidate for busiest; see
7817
 * update_sd_pick_busiest(). And calculate_imbalance() and
7818
 * find_busiest_group() avoid some of the usual balance conditions to allow it
7819 7820 7821 7822 7823 7824 7825
 * 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.
 */

7826
static inline int sg_imbalanced(struct sched_group *group)
7827
{
7828
	return group->sgc->imbalance;
7829 7830
}

7831
/*
7832 7833 7834
 * 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
7835 7836
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
7837 7838 7839 7840 7841
 * 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.
7842
 */
7843 7844
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
7845
{
7846 7847
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
7848

7849
	if ((sgs->group_capacity * 100) >
7850
			(sgs->group_util * env->sd->imbalance_pct))
7851
		return true;
7852

7853 7854 7855 7856 7857 7858 7859 7860 7861 7862 7863 7864 7865 7866 7867 7868
	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;
7869

7870
	if ((sgs->group_capacity * 100) <
7871
			(sgs->group_util * env->sd->imbalance_pct))
7872
		return true;
7873

7874
	return false;
7875 7876
}

7877 7878 7879 7880 7881 7882 7883 7884 7885 7886 7887
/*
 * 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;
}

7888 7889 7890
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
7891
{
7892
	if (sgs->group_no_capacity)
7893 7894 7895 7896 7897 7898 7899 7900
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

7901
static bool update_nohz_stats(struct rq *rq, bool force)
7902 7903 7904 7905
{
#ifdef CONFIG_NO_HZ_COMMON
	unsigned int cpu = rq->cpu;

7906 7907 7908
	if (!rq->has_blocked_load)
		return false;

7909
	if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
7910
		return false;
7911

7912
	if (!force && !time_after(jiffies, rq->last_blocked_load_update_tick))
7913
		return true;
7914 7915

	update_blocked_averages(cpu);
7916 7917 7918 7919

	return rq->has_blocked_load;
#else
	return false;
7920 7921 7922
#endif
}

7923 7924
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
7925
 * @env: The load balancing environment.
7926 7927 7928 7929
 * @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.
7930
 * @overload: Indicate more than one runnable task for any CPU.
7931
 */
7932 7933
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
7934 7935
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
7936
{
7937
	unsigned long load;
7938
	int i, nr_running;
7939

7940 7941
	memset(sgs, 0, sizeof(*sgs));

7942
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
7943 7944
		struct rq *rq = cpu_rq(i);

7945
		if ((env->flags & LBF_NOHZ_STATS) && update_nohz_stats(rq, false))
7946
			env->flags |= LBF_NOHZ_AGAIN;
7947

7948
		/* Bias balancing toward CPUs of our domain: */
7949
		if (local_group)
7950
			load = target_load(i, load_idx);
7951
		else
7952 7953 7954
			load = source_load(i, load_idx);

		sgs->group_load += load;
7955
		sgs->group_util += cpu_util(i);
7956
		sgs->sum_nr_running += rq->cfs.h_nr_running;
7957

7958 7959
		nr_running = rq->nr_running;
		if (nr_running > 1)
7960 7961
			*overload = true;

7962 7963 7964 7965
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
7966
		sgs->sum_weighted_load += weighted_cpuload(rq);
7967 7968 7969 7970
		/*
		 * No need to call idle_cpu() if nr_running is not 0
		 */
		if (!nr_running && idle_cpu(i))
7971
			sgs->idle_cpus++;
7972 7973
	}

7974 7975
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
7976
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
7977

7978
	if (sgs->sum_nr_running)
7979
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
7980

7981
	sgs->group_weight = group->group_weight;
7982

7983
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
7984
	sgs->group_type = group_classify(group, sgs);
7985 7986
}

7987 7988
/**
 * update_sd_pick_busiest - return 1 on busiest group
7989
 * @env: The load balancing environment.
7990 7991
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
7992
 * @sgs: sched_group statistics
7993 7994 7995
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
7996 7997 7998
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
7999
 */
8000
static bool update_sd_pick_busiest(struct lb_env *env,
8001 8002
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
8003
				   struct sg_lb_stats *sgs)
8004
{
8005
	struct sg_lb_stats *busiest = &sds->busiest_stat;
8006

8007
	if (sgs->group_type > busiest->group_type)
8008 8009
		return true;

8010 8011 8012 8013 8014 8015
	if (sgs->group_type < busiest->group_type)
		return false;

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

8016 8017 8018 8019 8020 8021 8022 8023 8024 8025 8026 8027 8028 8029
	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:
8030 8031
	/* This is the busiest node in its class. */
	if (!(env->sd->flags & SD_ASYM_PACKING))
8032 8033
		return true;

8034
	/* No ASYM_PACKING if target CPU is already busy */
8035 8036
	if (env->idle == CPU_NOT_IDLE)
		return true;
8037
	/*
T
Tim Chen 已提交
8038 8039 8040
	 * 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.
8041
	 */
T
Tim Chen 已提交
8042 8043
	if (sgs->sum_nr_running &&
	    sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) {
8044 8045 8046
		if (!sds->busiest)
			return true;

8047
		/* Prefer to move from lowest priority CPU's work */
T
Tim Chen 已提交
8048 8049
		if (sched_asym_prefer(sds->busiest->asym_prefer_cpu,
				      sg->asym_prefer_cpu))
8050 8051 8052 8053 8054 8055
			return true;
	}

	return false;
}

8056 8057 8058 8059 8060 8061 8062 8063 8064 8065 8066 8067 8068 8069 8070 8071 8072 8073 8074 8075 8076 8077 8078 8079 8080 8081 8082 8083 8084 8085
#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 */

8086
/**
8087
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
8088
 * @env: The load balancing environment.
8089 8090
 * @sds: variable to hold the statistics for this sched_domain.
 */
8091
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
8092
{
8093 8094
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
8095
	struct sg_lb_stats *local = &sds->local_stat;
J
Joonsoo Kim 已提交
8096
	struct sg_lb_stats tmp_sgs;
8097
	int load_idx, prefer_sibling = 0;
8098
	bool overload = false;
8099 8100 8101 8102

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

8103
#ifdef CONFIG_NO_HZ_COMMON
8104
	if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked))
8105 8106 8107
		env->flags |= LBF_NOHZ_STATS;
#endif

8108
	load_idx = get_sd_load_idx(env->sd, env->idle);
8109 8110

	do {
J
Joonsoo Kim 已提交
8111
		struct sg_lb_stats *sgs = &tmp_sgs;
8112 8113
		int local_group;

8114
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(sg));
J
Joonsoo Kim 已提交
8115 8116
		if (local_group) {
			sds->local = sg;
8117
			sgs = local;
8118 8119

			if (env->idle != CPU_NEWLY_IDLE ||
8120 8121
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
8122
		}
8123

8124 8125
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
8126

8127 8128 8129
		if (local_group)
			goto next_group;

8130 8131
		/*
		 * In case the child domain prefers tasks go to siblings
8132
		 * first, lower the sg capacity so that we'll try
8133 8134
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
8135 8136 8137 8138
		 * 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).
8139
		 */
8140
		if (prefer_sibling && sds->local &&
8141 8142
		    group_has_capacity(env, local) &&
		    (sgs->sum_nr_running > local->sum_nr_running + 1)) {
8143
			sgs->group_no_capacity = 1;
8144
			sgs->group_type = group_classify(sg, sgs);
8145
		}
8146

8147
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
8148
			sds->busiest = sg;
J
Joonsoo Kim 已提交
8149
			sds->busiest_stat = *sgs;
8150 8151
		}

8152 8153
next_group:
		/* Now, start updating sd_lb_stats */
8154
		sds->total_running += sgs->sum_nr_running;
8155
		sds->total_load += sgs->group_load;
8156
		sds->total_capacity += sgs->group_capacity;
8157

8158
		sg = sg->next;
8159
	} while (sg != env->sd->groups);
8160

8161 8162 8163 8164 8165 8166 8167 8168 8169
#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

8170 8171
	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
8172 8173 8174 8175 8176 8177

	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;
	}
8178 8179 8180 8181
}

/**
 * check_asym_packing - Check to see if the group is packed into the
8182
 *			sched domain.
8183 8184 8185 8186 8187 8188 8189 8190 8191 8192 8193 8194 8195 8196
 *
 * 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.
 *
8197
 * Return: 1 when packing is required and a task should be moved to
8198
 * this CPU.  The amount of the imbalance is returned in env->imbalance.
8199
 *
8200
 * @env: The load balancing environment.
8201 8202
 * @sds: Statistics of the sched_domain which is to be packed
 */
8203
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
8204 8205 8206
{
	int busiest_cpu;

8207
	if (!(env->sd->flags & SD_ASYM_PACKING))
8208 8209
		return 0;

8210 8211 8212
	if (env->idle == CPU_NOT_IDLE)
		return 0;

8213 8214 8215
	if (!sds->busiest)
		return 0;

T
Tim Chen 已提交
8216 8217
	busiest_cpu = sds->busiest->asym_prefer_cpu;
	if (sched_asym_prefer(busiest_cpu, env->dst_cpu))
8218 8219
		return 0;

8220
	env->imbalance = DIV_ROUND_CLOSEST(
8221
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
8222
		SCHED_CAPACITY_SCALE);
8223

8224
	return 1;
8225 8226 8227 8228 8229 8230
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
8231
 * @env: The load balancing environment.
8232 8233
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
8234 8235
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8236
{
8237
	unsigned long tmp, capa_now = 0, capa_move = 0;
8238
	unsigned int imbn = 2;
8239
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
8240
	struct sg_lb_stats *local, *busiest;
8241

J
Joonsoo Kim 已提交
8242 8243
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
8244

J
Joonsoo Kim 已提交
8245 8246 8247 8248
	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;
8249

J
Joonsoo Kim 已提交
8250
	scaled_busy_load_per_task =
8251
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
8252
		busiest->group_capacity;
J
Joonsoo Kim 已提交
8253

8254 8255
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
8256
		env->imbalance = busiest->load_per_task;
8257 8258 8259 8260 8261
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
8262
	 * however we may be able to increase total CPU capacity used by
8263 8264 8265
	 * moving them.
	 */

8266
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
8267
			min(busiest->load_per_task, busiest->avg_load);
8268
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
8269
			min(local->load_per_task, local->avg_load);
8270
	capa_now /= SCHED_CAPACITY_SCALE;
8271 8272

	/* Amount of load we'd subtract */
8273
	if (busiest->avg_load > scaled_busy_load_per_task) {
8274
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
8275
			    min(busiest->load_per_task,
8276
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
8277
	}
8278 8279

	/* Amount of load we'd add */
8280
	if (busiest->avg_load * busiest->group_capacity <
8281
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
8282 8283
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
8284
	} else {
8285
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
8286
		      local->group_capacity;
J
Joonsoo Kim 已提交
8287
	}
8288
	capa_move += local->group_capacity *
8289
		    min(local->load_per_task, local->avg_load + tmp);
8290
	capa_move /= SCHED_CAPACITY_SCALE;
8291 8292

	/* Move if we gain throughput */
8293
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
8294
		env->imbalance = busiest->load_per_task;
8295 8296 8297 8298 8299
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
8300
 * @env: load balance environment
8301 8302
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
8303
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
8304
{
8305
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
8306 8307 8308 8309
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
8310

8311
	if (busiest->group_type == group_imbalanced) {
8312 8313
		/*
		 * In the group_imb case we cannot rely on group-wide averages
8314
		 * to ensure CPU-load equilibrium, look at wider averages. XXX
8315
		 */
J
Joonsoo Kim 已提交
8316 8317
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
8318 8319
	}

8320
	/*
8321 8322 8323 8324
	 * 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:
8325
	 */
8326 8327
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
8328 8329
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
8330 8331
	}

8332
	/*
8333
	 * If there aren't any idle CPUs, avoid creating some.
8334 8335 8336
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
8337
		load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
8338
		if (load_above_capacity > busiest->group_capacity) {
8339
			load_above_capacity -= busiest->group_capacity;
8340
			load_above_capacity *= scale_load_down(NICE_0_LOAD);
8341 8342
			load_above_capacity /= busiest->group_capacity;
		} else
8343
			load_above_capacity = ~0UL;
8344 8345 8346
	}

	/*
8347
	 * We're trying to get all the CPUs to the average_load, so we don't
8348
	 * want to push ourselves above the average load, nor do we wish to
8349
	 * reduce the max loaded CPU below the average load. At the same time,
8350 8351
	 * we also don't want to reduce the group load below the group
	 * capacity. Thus we look for the minimum possible imbalance.
8352
	 */
8353
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
8354 8355

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
8356
	env->imbalance = min(
8357 8358
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
8359
	) / SCHED_CAPACITY_SCALE;
8360 8361 8362

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
8363
	 * there is no guarantee that any tasks will be moved so we'll have
8364 8365 8366
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
8367
	if (env->imbalance < busiest->load_per_task)
8368
		return fix_small_imbalance(env, sds);
8369
}
8370

8371 8372 8373 8374
/******* find_busiest_group() helpers end here *********************/

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
8375
 * if there is an imbalance.
8376 8377 8378 8379
 *
 * Also calculates the amount of weighted load which should be moved
 * to restore balance.
 *
8380
 * @env: The load balancing environment.
8381
 *
8382
 * Return:	- The busiest group if imbalance exists.
8383
 */
J
Joonsoo Kim 已提交
8384
static struct sched_group *find_busiest_group(struct lb_env *env)
8385
{
J
Joonsoo Kim 已提交
8386
	struct sg_lb_stats *local, *busiest;
8387 8388
	struct sd_lb_stats sds;

8389
	init_sd_lb_stats(&sds);
8390 8391 8392 8393 8394

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
8395
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
8396 8397
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
8398

8399
	/* ASYM feature bypasses nice load balance check */
8400
	if (check_asym_packing(env, &sds))
8401 8402
		return sds.busiest;

8403
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
8404
	if (!sds.busiest || busiest->sum_nr_running == 0)
8405 8406
		goto out_balanced;

8407
	/* XXX broken for overlapping NUMA groups */
8408 8409
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
8410

P
Peter Zijlstra 已提交
8411 8412
	/*
	 * If the busiest group is imbalanced the below checks don't
8413
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
8414 8415
	 * isn't true due to cpus_allowed constraints and the like.
	 */
8416
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
8417 8418
		goto force_balance;

8419 8420 8421 8422 8423
	/*
	 * 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) &&
8424
	    busiest->group_no_capacity)
8425 8426
		goto force_balance;

8427
	/*
8428
	 * If the local group is busier than the selected busiest group
8429 8430
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
8431
	if (local->avg_load >= busiest->avg_load)
8432 8433
		goto out_balanced;

8434 8435 8436 8437
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
8438
	if (local->avg_load >= sds.avg_load)
8439 8440
		goto out_balanced;

8441
	if (env->idle == CPU_IDLE) {
8442
		/*
8443
		 * This CPU is idle. If the busiest group is not overloaded
8444
		 * and there is no imbalance between this and busiest group
8445
		 * wrt idle CPUs, it is balanced. The imbalance becomes
8446 8447
		 * significant if the diff is greater than 1 otherwise we
		 * might end up to just move the imbalance on another group
8448
		 */
8449 8450
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
8451
			goto out_balanced;
8452 8453 8454 8455 8456
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
8457 8458
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
8459
			goto out_balanced;
8460
	}
8461

8462
force_balance:
8463
	/* Looks like there is an imbalance. Compute it */
8464
	calculate_imbalance(env, &sds);
8465 8466 8467
	return sds.busiest;

out_balanced:
8468
	env->imbalance = 0;
8469 8470 8471 8472
	return NULL;
}

/*
8473
 * find_busiest_queue - find the busiest runqueue among the CPUs in the group.
8474
 */
8475
static struct rq *find_busiest_queue(struct lb_env *env,
8476
				     struct sched_group *group)
8477 8478
{
	struct rq *busiest = NULL, *rq;
8479
	unsigned long busiest_load = 0, busiest_capacity = 1;
8480 8481
	int i;

8482
	for_each_cpu_and(i, sched_group_span(group), env->cpus) {
8483
		unsigned long capacity, wl;
8484 8485 8486 8487
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
8488

8489 8490 8491 8492 8493 8494 8495 8496 8497 8498 8499 8500 8501 8502 8503 8504 8505 8506 8507 8508 8509 8510
		/*
		 * 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;

8511
		capacity = capacity_of(i);
8512

8513
		wl = weighted_cpuload(rq);
8514

8515 8516
		/*
		 * When comparing with imbalance, use weighted_cpuload()
8517
		 * which is not scaled with the CPU capacity.
8518
		 */
8519 8520 8521

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
8522 8523
			continue;

8524
		/*
8525 8526 8527
		 * 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
8528
		 * potentially running at a lower capacity.
8529
		 *
8530
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
8531
		 * multiplication to rid ourselves of the division works out
8532 8533
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
8534
		 */
8535
		if (wl * busiest_capacity > busiest_load * capacity) {
8536
			busiest_load = wl;
8537
			busiest_capacity = capacity;
8538 8539 8540 8541 8542 8543 8544 8545 8546 8547 8548 8549 8550
			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

8551
static int need_active_balance(struct lb_env *env)
8552
{
8553 8554 8555
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
8556 8557 8558

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
T
Tim Chen 已提交
8559 8560
		 * lower priority CPUs in order to pack all tasks in the
		 * highest priority CPUs.
8561
		 */
T
Tim Chen 已提交
8562 8563
		if ((sd->flags & SD_ASYM_PACKING) &&
		    sched_asym_prefer(env->dst_cpu, env->src_cpu))
8564
			return 1;
8565 8566
	}

8567 8568 8569 8570 8571 8572 8573 8574 8575 8576 8577 8578 8579
	/*
	 * 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;
	}

8580 8581 8582
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

8583 8584
static int active_load_balance_cpu_stop(void *data);

8585 8586 8587 8588 8589
static int should_we_balance(struct lb_env *env)
{
	struct sched_group *sg = env->sd->groups;
	int cpu, balance_cpu = -1;

8590 8591 8592 8593 8594 8595 8596
	/*
	 * 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;

8597
	/*
8598
	 * In the newly idle case, we will allow all the CPUs
8599 8600 8601 8602 8603
	 * to do the newly idle load balance.
	 */
	if (env->idle == CPU_NEWLY_IDLE)
		return 1;

8604
	/* Try to find first idle CPU */
8605
	for_each_cpu_and(cpu, group_balance_mask(sg), env->cpus) {
8606
		if (!idle_cpu(cpu))
8607 8608 8609 8610 8611 8612 8613 8614 8615 8616
			continue;

		balance_cpu = cpu;
		break;
	}

	if (balance_cpu == -1)
		balance_cpu = group_balance_cpu(sg);

	/*
8617
	 * First idle CPU or the first CPU(busiest) in this sched group
8618 8619
	 * is eligible for doing load balancing at this and above domains.
	 */
8620
	return balance_cpu == env->dst_cpu;
8621 8622
}

8623 8624 8625 8626 8627 8628
/*
 * 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,
8629
			int *continue_balancing)
8630
{
8631
	int ld_moved, cur_ld_moved, active_balance = 0;
8632
	struct sched_domain *sd_parent = sd->parent;
8633 8634
	struct sched_group *group;
	struct rq *busiest;
8635
	struct rq_flags rf;
8636
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
8637

8638 8639
	struct lb_env env = {
		.sd		= sd,
8640 8641
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
8642
		.dst_grpmask    = sched_group_span(sd->groups),
8643
		.idle		= idle,
8644
		.loop_break	= sched_nr_migrate_break,
8645
		.cpus		= cpus,
8646
		.fbq_type	= all,
8647
		.tasks		= LIST_HEAD_INIT(env.tasks),
8648 8649
	};

8650
	cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
8651

8652
	schedstat_inc(sd->lb_count[idle]);
8653 8654

redo:
8655 8656
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
8657
		goto out_balanced;
8658
	}
8659

8660
	group = find_busiest_group(&env);
8661
	if (!group) {
8662
		schedstat_inc(sd->lb_nobusyg[idle]);
8663 8664 8665
		goto out_balanced;
	}

8666
	busiest = find_busiest_queue(&env, group);
8667
	if (!busiest) {
8668
		schedstat_inc(sd->lb_nobusyq[idle]);
8669 8670 8671
		goto out_balanced;
	}

8672
	BUG_ON(busiest == env.dst_rq);
8673

8674
	schedstat_add(sd->lb_imbalance[idle], env.imbalance);
8675

8676 8677 8678
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

8679 8680 8681 8682 8683 8684 8685 8686
	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.
		 */
8687
		env.flags |= LBF_ALL_PINNED;
8688
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
8689

8690
more_balance:
8691
		rq_lock_irqsave(busiest, &rf);
8692
		update_rq_clock(busiest);
8693 8694 8695 8696 8697

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
8698
		cur_ld_moved = detach_tasks(&env);
8699 8700

		/*
8701 8702 8703 8704 8705
		 * 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.
8706
		 */
8707

8708
		rq_unlock(busiest, &rf);
8709 8710 8711 8712 8713 8714

		if (cur_ld_moved) {
			attach_tasks(&env);
			ld_moved += cur_ld_moved;
		}

8715
		local_irq_restore(rf.flags);
8716

8717 8718 8719 8720 8721
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

8722 8723 8724 8725
		/*
		 * 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
8726
		 * iterate on same src_cpu is dependent on number of CPUs in our
8727 8728 8729 8730 8731 8732 8733 8734 8735 8736 8737 8738 8739 8740
		 * 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.
		 */
8741
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
8742

8743
			/* Prevent to re-select dst_cpu via env's CPUs */
8744 8745
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

8746
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
8747
			env.dst_cpu	 = env.new_dst_cpu;
8748
			env.flags	&= ~LBF_DST_PINNED;
8749 8750
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
8751

8752 8753 8754 8755 8756 8757
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
8758

8759 8760 8761 8762
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
8763
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
8764

8765
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
8766 8767 8768
				*group_imbalance = 1;
		}

8769
		/* All tasks on this runqueue were pinned by CPU affinity */
8770
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
8771
			cpumask_clear_cpu(cpu_of(busiest), cpus);
8772 8773 8774 8775 8776 8777 8778 8779 8780
			/*
			 * 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)) {
8781 8782
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
8783
				goto redo;
8784
			}
8785
			goto out_all_pinned;
8786 8787 8788 8789
		}
	}

	if (!ld_moved) {
8790
		schedstat_inc(sd->lb_failed[idle]);
8791 8792 8793 8794 8795 8796 8797 8798
		/*
		 * 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++;
8799

8800
		if (need_active_balance(&env)) {
8801 8802
			unsigned long flags;

8803 8804
			raw_spin_lock_irqsave(&busiest->lock, flags);

8805 8806 8807 8808
			/*
			 * Don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest CPU can't be
			 * moved to this_cpu:
8809
			 */
8810
			if (!cpumask_test_cpu(this_cpu, &busiest->curr->cpus_allowed)) {
8811 8812
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
8813
				env.flags |= LBF_ALL_PINNED;
8814 8815 8816
				goto out_one_pinned;
			}

8817 8818 8819 8820 8821
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
8822 8823 8824 8825 8826 8827
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
8828

8829
			if (active_balance) {
8830 8831 8832
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
8833
			}
8834

8835
			/* We've kicked active balancing, force task migration. */
8836 8837 8838 8839 8840 8841 8842 8843 8844 8845 8846 8847 8848
			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
8849
		 * detach_tasks).
8850 8851 8852 8853 8854 8855 8856 8857
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
8858 8859 8860 8861 8862 8863 8864 8865 8866 8867 8868 8869 8870 8871 8872 8873 8874
	/*
	 * We reach balance although we may have faced some affinity
	 * constraints. Clear the imbalance flag if it was set.
	 */
	if (sd_parent) {
		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.
	 */
8875
	schedstat_inc(sd->lb_balanced[idle]);
8876 8877 8878 8879 8880

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
8881
	if (((env.flags & LBF_ALL_PINNED) &&
8882
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
8883 8884 8885
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

8886
	ld_moved = 0;
8887 8888 8889 8890
out:
	return ld_moved;
}

8891 8892 8893 8894 8895 8896 8897 8898 8899 8900 8901 8902 8903 8904 8905 8906
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
8907
update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
8908 8909 8910
{
	unsigned long interval, next;

8911 8912
	/* used by idle balance, so cpu_busy = 0 */
	interval = get_sd_balance_interval(sd, 0);
8913 8914 8915 8916 8917 8918
	next = sd->last_balance + interval;

	if (time_after(*next_balance, next))
		*next_balance = next;
}

8919 8920 8921 8922
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
8923
static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
8924
{
8925 8926
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
8927 8928
	struct sched_domain *sd;
	int pulled_task = 0;
8929
	u64 curr_cost = 0;
8930

8931 8932 8933 8934 8935 8936
	/*
	 * 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);

8937 8938 8939 8940 8941 8942
	/*
	 * Do not pull tasks towards !active CPUs...
	 */
	if (!cpu_active(this_cpu))
		return 0;

8943 8944 8945 8946 8947 8948 8949 8950
	/*
	 * 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);

8951 8952
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
8953 8954 8955
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
8956
			update_next_balance(sd, &next_balance);
8957 8958
		rcu_read_unlock();

8959
		goto out;
8960
	}
8961

8962 8963
	raw_spin_unlock(&this_rq->lock);

8964
	update_blocked_averages(this_cpu);
8965
	rcu_read_lock();
8966
	for_each_domain(this_cpu, sd) {
8967
		int continue_balancing = 1;
8968
		u64 t0, domain_cost;
8969 8970 8971 8972

		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

8973
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
8974
			update_next_balance(sd, &next_balance);
8975
			break;
8976
		}
8977

8978
		if (sd->flags & SD_BALANCE_NEWIDLE) {
8979 8980
			t0 = sched_clock_cpu(this_cpu);

8981
			pulled_task = load_balance(this_cpu, this_rq,
8982 8983
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
8984 8985 8986 8987 8988 8989

			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;
8990
		}
8991

8992
		update_next_balance(sd, &next_balance);
8993 8994 8995 8996 8997 8998

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
8999 9000
			break;
	}
9001
	rcu_read_unlock();
9002 9003 9004

	raw_spin_lock(&this_rq->lock);

9005 9006 9007
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

9008
	/*
9009 9010 9011
	 * 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.
9012
	 */
9013
	if (this_rq->cfs.h_nr_running && !pulled_task)
9014
		pulled_task = 1;
9015

9016 9017 9018
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
9019
		this_rq->next_balance = next_balance;
9020

9021
	/* Is there a task of a high priority class? */
9022
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
9023 9024
		pulled_task = -1;

9025
	if (pulled_task)
9026 9027
		this_rq->idle_stamp = 0;

9028 9029
	rq_repin_lock(this_rq, rf);

9030
	return pulled_task;
9031 9032 9033
}

/*
9034
 * active_load_balance_cpu_stop is run by the CPU stopper. It pushes
9035 9036 9037
 * 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.
9038
 */
9039
static int active_load_balance_cpu_stop(void *data)
9040
{
9041 9042
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
9043
	int target_cpu = busiest_rq->push_cpu;
9044
	struct rq *target_rq = cpu_rq(target_cpu);
9045
	struct sched_domain *sd;
9046
	struct task_struct *p = NULL;
9047
	struct rq_flags rf;
9048

9049
	rq_lock_irq(busiest_rq, &rf);
9050 9051 9052 9053 9054 9055 9056
	/*
	 * 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;
9057

9058
	/* Make sure the requested CPU hasn't gone down in the meantime: */
9059 9060 9061
	if (unlikely(busiest_cpu != smp_processor_id() ||
		     !busiest_rq->active_balance))
		goto out_unlock;
9062 9063 9064

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
9065
		goto out_unlock;
9066 9067 9068 9069

	/*
	 * This condition is "impossible", if it occurs
	 * we need to fix it. Originally reported by
9070
	 * Bjorn Helgaas on a 128-CPU setup.
9071 9072 9073 9074
	 */
	BUG_ON(busiest_rq == target_rq);

	/* Search for an sd spanning us and the target CPU. */
9075
	rcu_read_lock();
9076 9077 9078 9079 9080 9081 9082
	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)) {
9083 9084
		struct lb_env env = {
			.sd		= sd,
9085 9086 9087 9088
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
9089
			.idle		= CPU_IDLE,
9090 9091 9092 9093 9094 9095 9096
			/*
			 * 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,
9097 9098
		};

9099
		schedstat_inc(sd->alb_count);
9100
		update_rq_clock(busiest_rq);
9101

9102
		p = detach_one_task(&env);
9103
		if (p) {
9104
			schedstat_inc(sd->alb_pushed);
9105 9106 9107
			/* Active balancing done, reset the failure counter. */
			sd->nr_balance_failed = 0;
		} else {
9108
			schedstat_inc(sd->alb_failed);
9109
		}
9110
	}
9111
	rcu_read_unlock();
9112 9113
out_unlock:
	busiest_rq->active_balance = 0;
9114
	rq_unlock(busiest_rq, &rf);
9115 9116 9117 9118 9119 9120

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

9121
	return 0;
9122 9123
}

9124 9125 9126 9127 9128
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

9129
#ifdef CONFIG_NO_HZ_COMMON
9130 9131 9132 9133 9134 9135
/*
 * 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.
 */
9136

9137
static inline int find_new_ilb(void)
9138
{
9139
	int ilb = cpumask_first(nohz.idle_cpus_mask);
9140

9141 9142 9143 9144
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
9145 9146
}

9147 9148 9149 9150 9151
/*
 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
 * CPU (if there is one).
 */
9152
static void kick_ilb(unsigned int flags)
9153 9154 9155 9156 9157
{
	int ilb_cpu;

	nohz.next_balance++;

9158
	ilb_cpu = find_new_ilb();
9159

9160 9161
	if (ilb_cpu >= nr_cpu_ids)
		return;
9162

9163
	flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu));
P
Peter Zijlstra 已提交
9164
	if (flags & NOHZ_KICK_MASK)
9165
		return;
9166

9167 9168
	/*
	 * Use smp_send_reschedule() instead of resched_cpu().
9169
	 * This way we generate a sched IPI on the target CPU which
9170 9171 9172 9173
	 * is idle. And the softirq performing nohz idle load balance
	 * will be run before returning from the IPI.
	 */
	smp_send_reschedule(ilb_cpu);
9174 9175 9176 9177 9178 9179 9180 9181 9182 9183 9184 9185 9186 9187 9188 9189 9190 9191 9192
}

/*
 * 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;
9193
	unsigned int flags = 0;
9194 9195 9196 9197 9198 9199 9200 9201

	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.
	 */
9202
	nohz_balance_exit_idle(rq);
9203 9204 9205 9206 9207 9208 9209 9210

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
		return;

9211 9212
	if (READ_ONCE(nohz.has_blocked) &&
	    time_after(now, READ_ONCE(nohz.next_blocked)))
9213 9214
		flags = NOHZ_STATS_KICK;

9215
	if (time_before(now, nohz.next_balance))
9216
		goto out;
9217 9218

	if (rq->nr_running >= 2) {
9219
		flags = NOHZ_KICK_MASK;
9220 9221 9222 9223 9224 9225 9226 9227 9228 9229 9230 9231
		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) {
9232
			flags = NOHZ_KICK_MASK;
9233 9234 9235 9236 9237 9238 9239 9240 9241
			goto unlock;
		}

	}

	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
9242
			flags = NOHZ_KICK_MASK;
9243 9244 9245 9246 9247 9248 9249 9250 9251 9252 9253 9254
			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)) {
9255
				flags = NOHZ_KICK_MASK;
9256 9257 9258 9259 9260 9261 9262
				goto unlock;
			}
		}
	}
unlock:
	rcu_read_unlock();
out:
9263 9264
	if (flags)
		kick_ilb(flags);
9265 9266
}

9267
static void set_cpu_sd_state_busy(int cpu)
9268
{
9269
	struct sched_domain *sd;
9270

9271 9272
	rcu_read_lock();
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
9273

9274 9275 9276 9277 9278 9279 9280
	if (!sd || !sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 0;

	atomic_inc(&sd->shared->nr_busy_cpus);
unlock:
	rcu_read_unlock();
9281 9282
}

9283 9284 9285 9286 9287 9288 9289 9290 9291 9292 9293 9294 9295 9296 9297
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)
9298 9299 9300 9301
{
	struct sched_domain *sd;

	rcu_read_lock();
9302
	sd = rcu_dereference(per_cpu(sd_llc, cpu));
V
Vincent Guittot 已提交
9303 9304 9305 9306 9307

	if (!sd || sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 1;

9308
	atomic_dec(&sd->shared->nr_busy_cpus);
V
Vincent Guittot 已提交
9309
unlock:
9310 9311 9312
	rcu_read_unlock();
}

9313
/*
9314
 * This routine will record that the CPU is going idle with tick stopped.
9315
 * This info will be used in performing idle load balancing in the future.
9316
 */
9317
void nohz_balance_enter_idle(int cpu)
9318
{
9319 9320 9321 9322
	struct rq *rq = cpu_rq(cpu);

	SCHED_WARN_ON(cpu != smp_processor_id());

9323
	/* If this CPU is going down, then nothing needs to be done: */
9324 9325 9326
	if (!cpu_active(cpu))
		return;

9327
	/* Spare idle load balancing on CPUs that don't want to be disturbed: */
9328
	if (!housekeeping_cpu(cpu, HK_FLAG_SCHED))
9329 9330
		return;

9331 9332 9333 9334 9335 9336 9337 9338 9339 9340 9341 9342 9343
	/*
	 * 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
	 */
9344
	if (rq->nohz_tick_stopped)
9345
		goto out;
9346

9347
	/* If we're a completely isolated CPU, we don't play: */
9348
	if (on_null_domain(rq))
9349 9350
		return;

9351 9352
	rq->nohz_tick_stopped = 1;

9353 9354
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
9355

9356 9357 9358 9359 9360 9361 9362
	/*
	 * 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();

9363
	set_cpu_sd_state_idle(cpu);
9364 9365 9366 9367 9368 9369 9370

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);
9371
}
9372 9373
#else
static inline void nohz_balancer_kick(struct rq *rq) { }
9374 9375 9376 9377
#endif

static DEFINE_SPINLOCK(balancing);

9378 9379 9380 9381
/*
 * 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.
 */
9382
void update_max_interval(void)
9383 9384 9385 9386
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

9387 9388 9389 9390
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
9391
 * Balancing parameters are set up in init_sched_domains.
9392
 */
9393
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
9394
{
9395
	int continue_balancing = 1;
9396
	int cpu = rq->cpu;
9397
	unsigned long interval;
9398
	struct sched_domain *sd;
9399 9400 9401
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
9402 9403
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
9404

9405
	rcu_read_lock();
9406
	for_each_domain(cpu, sd) {
9407 9408 9409 9410 9411 9412 9413 9414 9415 9416 9417 9418
		/*
		 * 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;

9419 9420 9421
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

9422 9423 9424 9425 9426 9427 9428 9429 9430 9431 9432
		/*
		 * 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;
		}

9433
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
9434 9435 9436 9437 9438 9439 9440 9441

		need_serialize = sd->flags & SD_SERIALIZE;
		if (need_serialize) {
			if (!spin_trylock(&balancing))
				goto out;
		}

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
9442
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
9443
				/*
9444
				 * The LBF_DST_PINNED logic could have changed
9445 9446
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
9447
				 */
9448
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
9449 9450
			}
			sd->last_balance = jiffies;
9451
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
9452 9453 9454 9455 9456 9457 9458 9459
		}
		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;
		}
9460 9461
	}
	if (need_decay) {
9462
		/*
9463 9464
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
9465
		 */
9466 9467
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
9468
	}
9469
	rcu_read_unlock();
9470 9471 9472

	/*
	 * next_balance will be updated only when there is a need.
9473
	 * When the CPU is attached to null domain for ex, it will not be
9474 9475
	 * updated.
	 */
9476
	if (likely(update_next_balance)) {
9477
		rq->next_balance = next_balance;
9478 9479 9480 9481 9482 9483 9484 9485 9486 9487 9488 9489 9490 9491

#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
	}
9492 9493
}

9494
#ifdef CONFIG_NO_HZ_COMMON
9495
/*
9496
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
9497
 * rebalancing for all the CPUs for whom scheduler ticks are stopped.
9498
 */
P
Peter Zijlstra 已提交
9499
static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
9500
{
9501
	/* Earliest time when we have to do rebalance again */
9502 9503
	unsigned long now = jiffies;
	unsigned long next_balance = now + 60*HZ;
9504
	bool has_blocked_load = false;
9505
	int update_next_balance = 0;
P
Peter Zijlstra 已提交
9506 9507 9508 9509
	int this_cpu = this_rq->cpu;
	unsigned int flags;
	int balance_cpu;
	struct rq *rq;
9510

P
Peter Zijlstra 已提交
9511 9512
	if (!(atomic_read(nohz_flags(this_cpu)) & NOHZ_KICK_MASK))
		return false;
9513

P
Peter Zijlstra 已提交
9514 9515 9516 9517 9518 9519 9520 9521
	if (idle != CPU_IDLE) {
		atomic_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));
		return false;
	}

	flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(this_cpu));

	SCHED_WARN_ON((flags & NOHZ_KICK_MASK) == NOHZ_BALANCE_KICK);
9522

9523 9524 9525 9526 9527 9528 9529 9530 9531 9532 9533 9534 9535 9536 9537 9538
	/*
	 * 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();

9539
	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
9540
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
9541 9542 9543
			continue;

		/*
9544 9545
		 * If this CPU gets work to do, stop the load balancing
		 * work being done for other CPUs. Next load
9546 9547
		 * balancing owner will pick it up.
		 */
9548 9549 9550 9551
		if (need_resched()) {
			has_blocked_load = true;
			goto abort;
		}
9552

V
Vincent Guittot 已提交
9553 9554
		rq = cpu_rq(balance_cpu);

9555
		has_blocked_load |= update_nohz_stats(rq, true);
9556

9557 9558 9559 9560 9561
		/*
		 * If time for next balance is due,
		 * do the balance.
		 */
		if (time_after_eq(jiffies, rq->next_balance)) {
9562 9563 9564
			struct rq_flags rf;

			rq_lock_irq(rq, &rf);
9565
			update_rq_clock(rq);
9566
			cpu_load_update_idle(rq);
9567 9568
			rq_unlock_irq(rq, &rf);

P
Peter Zijlstra 已提交
9569 9570
			if (flags & NOHZ_BALANCE_KICK)
				rebalance_domains(rq, CPU_IDLE);
9571
		}
9572

9573 9574 9575 9576
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
9577
	}
9578

P
Peter Zijlstra 已提交
9579 9580 9581 9582
	update_blocked_averages(this_cpu);
	if (flags & NOHZ_BALANCE_KICK)
		rebalance_domains(this_rq, CPU_IDLE);

9583 9584 9585 9586 9587 9588 9589
	WRITE_ONCE(nohz.next_blocked,
		now + msecs_to_jiffies(LOAD_AVG_PERIOD));

abort:
	/* There is still blocked load, enable periodic update */
	if (has_blocked_load)
		WRITE_ONCE(nohz.has_blocked, 1);
9590

9591 9592 9593 9594 9595 9596 9597
	/*
	 * 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
9598 9599

	return true;
9600 9601
}
#else
P
Peter Zijlstra 已提交
9602 9603 9604 9605
static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
{
	return false;
}
9606 9607 9608 9609 9610 9611
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
9612
static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
9613
{
9614
	struct rq *this_rq = this_rq();
9615
	enum cpu_idle_type idle = this_rq->idle_balance ?
9616 9617 9618
						CPU_IDLE : CPU_NOT_IDLE;

	/*
9619 9620
	 * If this CPU has a pending nohz_balance_kick, then do the
	 * balancing on behalf of the other idle CPUs whose ticks are
9621
	 * stopped. Do nohz_idle_balance *before* rebalance_domains to
9622
	 * give the idle CPUs a chance to load balance. Else we may
9623 9624
	 * load balance only within the local sched_domain hierarchy
	 * and abort nohz_idle_balance altogether if we pull some load.
9625
	 */
P
Peter Zijlstra 已提交
9626 9627 9628 9629 9630
	if (nohz_idle_balance(this_rq, idle))
		return;

	/* normal load balance */
	update_blocked_averages(this_rq->cpu);
9631
	rebalance_domains(this_rq, idle);
9632 9633 9634 9635 9636
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
9637
void trigger_load_balance(struct rq *rq)
9638 9639
{
	/* Don't need to rebalance while attached to NULL domain */
9640 9641 9642 9643
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
9644
		raise_softirq(SCHED_SOFTIRQ);
9645 9646

	nohz_balancer_kick(rq);
9647 9648
}

9649 9650 9651
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
9652 9653

	update_runtime_enabled(rq);
9654 9655 9656 9657 9658
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
9659 9660 9661

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
9662 9663
}

9664
#endif /* CONFIG_SMP */
9665

9666
/*
9667 9668 9669 9670 9671 9672
 * 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.
9673
 */
P
Peter Zijlstra 已提交
9674
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
9675 9676 9677 9678 9679 9680
{
	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
9681
		entity_tick(cfs_rq, se, queued);
9682
	}
9683

9684
	if (static_branch_unlikely(&sched_numa_balancing))
9685
		task_tick_numa(rq, curr);
9686 9687 9688
}

/*
P
Peter Zijlstra 已提交
9689 9690 9691
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
9692
 */
P
Peter Zijlstra 已提交
9693
static void task_fork_fair(struct task_struct *p)
9694
{
9695 9696
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
P
Peter Zijlstra 已提交
9697
	struct rq *rq = this_rq();
9698
	struct rq_flags rf;
9699

9700
	rq_lock(rq, &rf);
9701 9702
	update_rq_clock(rq);

9703 9704
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;
9705 9706
	if (curr) {
		update_curr(cfs_rq);
9707
		se->vruntime = curr->vruntime;
9708
	}
9709
	place_entity(cfs_rq, se, 1);
9710

P
Peter Zijlstra 已提交
9711
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
9712
		/*
9713 9714 9715
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
9716
		swap(curr->vruntime, se->vruntime);
9717
		resched_curr(rq);
9718
	}
9719

9720
	se->vruntime -= cfs_rq->min_vruntime;
9721
	rq_unlock(rq, &rf);
9722 9723
}

9724 9725 9726 9727
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
9728 9729
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
9730
{
9731
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
9732 9733
		return;

9734 9735 9736 9737 9738
	/*
	 * 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
9739
	if (rq->curr == p) {
9740
		if (p->prio > oldprio)
9741
			resched_curr(rq);
9742
	} else
9743
		check_preempt_curr(rq, p, 0);
9744 9745
}

9746
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
9747 9748 9749 9750
{
	struct sched_entity *se = &p->se;

	/*
9751 9752 9753 9754 9755 9756 9757 9758 9759 9760
	 * 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
9761
	 *
9762 9763 9764 9765
	 * - 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
9766
	 */
9767 9768 9769 9770 9771 9772
	if (!se->sum_exec_runtime || p->state == TASK_WAKING)
		return true;

	return false;
}

9773 9774 9775 9776 9777 9778 9779 9780 9781 9782 9783 9784 9785 9786 9787 9788 9789 9790
#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;

9791
		update_load_avg(cfs_rq, se, UPDATE_TG);
9792 9793 9794 9795 9796 9797
	}
}
#else
static void propagate_entity_cfs_rq(struct sched_entity *se) { }
#endif

9798
static void detach_entity_cfs_rq(struct sched_entity *se)
9799 9800 9801
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

9802
	/* Catch up with the cfs_rq and remove our load when we leave */
9803
	update_load_avg(cfs_rq, se, 0);
9804
	detach_entity_load_avg(cfs_rq, se);
9805
	update_tg_load_avg(cfs_rq, false);
9806
	propagate_entity_cfs_rq(se);
P
Peter Zijlstra 已提交
9807 9808
}

9809
static void attach_entity_cfs_rq(struct sched_entity *se)
9810
{
9811
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
9812 9813

#ifdef CONFIG_FAIR_GROUP_SCHED
9814 9815 9816 9817 9818 9819
	/*
	 * 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
9820

9821
	/* Synchronize entity with its cfs_rq */
9822
	update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);
9823
	attach_entity_load_avg(cfs_rq, se, 0);
9824
	update_tg_load_avg(cfs_rq, false);
9825
	propagate_entity_cfs_rq(se);
9826 9827 9828 9829 9830 9831 9832 9833 9834 9835 9836 9837 9838 9839 9840 9841 9842 9843 9844 9845 9846 9847 9848 9849 9850
}

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);
9851 9852 9853 9854

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
9855

9856 9857 9858 9859 9860 9861 9862 9863
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);
9864

9865
	if (task_on_rq_queued(p)) {
9866
		/*
9867 9868 9869
		 * 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.
9870
		 */
9871 9872 9873 9874
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
9875
	}
9876 9877
}

9878 9879 9880 9881 9882 9883 9884 9885 9886
/* 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;

9887 9888 9889 9890 9891 9892 9893
	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);
	}
9894 9895
}

9896 9897
void init_cfs_rq(struct cfs_rq *cfs_rq)
{
9898
	cfs_rq->tasks_timeline = RB_ROOT_CACHED;
9899 9900 9901 9902
	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
#ifndef CONFIG_64BIT
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
9903
#ifdef CONFIG_SMP
9904
	raw_spin_lock_init(&cfs_rq->removed.lock);
9905
#endif
9906 9907
}

P
Peter Zijlstra 已提交
9908
#ifdef CONFIG_FAIR_GROUP_SCHED
9909 9910 9911 9912 9913 9914 9915 9916
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;
}

9917
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
9918
{
9919
	detach_task_cfs_rq(p);
9920
	set_task_rq(p, task_cpu(p));
9921 9922 9923 9924 9925

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
9926
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
9927
}
9928

9929 9930 9931 9932 9933 9934 9935 9936 9937 9938 9939 9940 9941
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;
	}
}

9942 9943 9944 9945 9946 9947 9948 9949 9950
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]);
9951
		if (tg->se)
9952 9953 9954 9955 9956 9957 9958 9959 9960 9961
			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;
9962
	struct cfs_rq *cfs_rq;
9963 9964 9965 9966 9967 9968 9969 9970 9971 9972 9973 9974 9975 9976 9977 9978 9979 9980 9981 9982 9983 9984 9985 9986 9987 9988
	int i;

	tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
	if (!tg->cfs_rq)
		goto err;
	tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
	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]);
9989
		init_entity_runnable_average(se);
9990 9991 9992 9993 9994 9995 9996 9997 9998 9999
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

10000 10001 10002 10003 10004 10005 10006 10007 10008 10009 10010
void online_fair_sched_group(struct task_group *tg)
{
	struct sched_entity *se;
	struct rq *rq;
	int i;

	for_each_possible_cpu(i) {
		rq = cpu_rq(i);
		se = tg->se[i];

		raw_spin_lock_irq(&rq->lock);
10011
		update_rq_clock(rq);
10012
		attach_entity_cfs_rq(se);
10013
		sync_throttle(tg, i);
10014 10015 10016 10017
		raw_spin_unlock_irq(&rq->lock);
	}
}

10018
void unregister_fair_sched_group(struct task_group *tg)
10019 10020
{
	unsigned long flags;
10021 10022
	struct rq *rq;
	int cpu;
10023

10024 10025 10026
	for_each_possible_cpu(cpu) {
		if (tg->se[cpu])
			remove_entity_load_avg(tg->se[cpu]);
10027

10028 10029 10030 10031 10032 10033 10034 10035 10036 10037 10038 10039 10040
		/*
		 * 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);
	}
10041 10042 10043 10044 10045 10046 10047 10048 10049 10050 10051 10052 10053 10054 10055 10056 10057 10058 10059
}

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
10060
	if (!parent) {
10061
		se->cfs_rq = &rq->cfs;
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10062 10063
		se->depth = 0;
	} else {
10064
		se->cfs_rq = parent->my_q;
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Peter Zijlstra 已提交
10065 10066
		se->depth = parent->depth + 1;
	}
10067 10068

	se->my_q = cfs_rq;
10069 10070
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
10071 10072 10073 10074 10075 10076 10077 10078 10079 10080 10081 10082 10083 10084 10085 10086 10087 10088 10089 10090 10091 10092 10093 10094
	se->parent = parent;
}

static DEFINE_MUTEX(shares_mutex);

int sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
	int i;

	/*
	 * We can't change the weight of the root cgroup.
	 */
	if (!tg->se[0])
		return -EINVAL;

	shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));

	mutex_lock(&shares_mutex);
	if (tg->shares == shares)
		goto done;

	tg->shares = shares;
	for_each_possible_cpu(i) {
		struct rq *rq = cpu_rq(i);
10095 10096
		struct sched_entity *se = tg->se[i];
		struct rq_flags rf;
10097 10098

		/* Propagate contribution to hierarchy */
10099
		rq_lock_irqsave(rq, &rf);
10100
		update_rq_clock(rq);
10101
		for_each_sched_entity(se) {
10102
			update_load_avg(cfs_rq_of(se), se, UPDATE_TG);
10103
			update_cfs_group(se);
10104
		}
10105
		rq_unlock_irqrestore(rq, &rf);
10106 10107 10108 10109 10110 10111 10112 10113 10114 10115 10116 10117 10118 10119 10120
	}

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;
}

10121 10122
void online_fair_sched_group(struct task_group *tg) { }

10123
void unregister_fair_sched_group(struct task_group *tg) { }
10124 10125 10126

#endif /* CONFIG_FAIR_GROUP_SCHED */

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10127

10128
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
10129 10130 10131 10132 10133 10134 10135 10136 10137
{
	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)
10138
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
10139 10140 10141 10142

	return rr_interval;
}

10143 10144 10145
/*
 * All the scheduling class methods:
 */
10146
const struct sched_class fair_sched_class = {
10147
	.next			= &idle_sched_class,
10148 10149 10150
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
10151
	.yield_to_task		= yield_to_task_fair,
10152

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Ingo Molnar 已提交
10153
	.check_preempt_curr	= check_preempt_wakeup,
10154 10155 10156 10157

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

10158
#ifdef CONFIG_SMP
L
Li Zefan 已提交
10159
	.select_task_rq		= select_task_rq_fair,
10160
	.migrate_task_rq	= migrate_task_rq_fair,
10161

10162 10163
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
10164

10165
	.task_dead		= task_dead_fair,
10166
	.set_cpus_allowed	= set_cpus_allowed_common,
10167
#endif
10168

10169
	.set_curr_task          = set_curr_task_fair,
10170
	.task_tick		= task_tick_fair,
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Peter Zijlstra 已提交
10171
	.task_fork		= task_fork_fair,
10172 10173

	.prio_changed		= prio_changed_fair,
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10174
	.switched_from		= switched_from_fair,
10175
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
10176

10177 10178
	.get_rr_interval	= get_rr_interval_fair,

10179 10180
	.update_curr		= update_curr_fair,

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10181
#ifdef CONFIG_FAIR_GROUP_SCHED
10182
	.task_change_group	= task_change_group_fair,
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10183
#endif
10184 10185 10186
};

#ifdef CONFIG_SCHED_DEBUG
10187
void print_cfs_stats(struct seq_file *m, int cpu)
10188
{
10189
	struct cfs_rq *cfs_rq, *pos;
10190

10191
	rcu_read_lock();
10192
	for_each_leaf_cfs_rq_safe(cpu_rq(cpu), cfs_rq, pos)
10193
		print_cfs_rq(m, cpu, cfs_rq);
10194
	rcu_read_unlock();
10195
}
10196 10197 10198 10199 10200 10201 10202 10203 10204 10205 10206 10207 10208 10209 10210 10211 10212 10213 10214 10215 10216

#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;

	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)];
		}
		if (p->numa_group) {
			gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
			gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
		}
		print_numa_stats(m, node, tsf, tpf, gsf, gpf);
	}
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_SCHED_DEBUG */
10217 10218 10219 10220 10221 10222

__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

10223
#ifdef CONFIG_NO_HZ_COMMON
10224
	nohz.next_balance = jiffies;
10225
	nohz.next_blocked = jiffies;
10226 10227 10228 10229 10230
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
#endif
#endif /* SMP */

}