fair.c 219.0 KB
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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
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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 */

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#include <linux/latencytop.h>
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#include <linux/sched.h>
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#include <linux/cpumask.h>
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#include <linux/cpuidle.h>
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#include <linux/slab.h>
#include <linux/profile.h>
#include <linux/interrupt.h>
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#include <linux/mempolicy.h>
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#include <linux/migrate.h>
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#include <linux/task_work.h>
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#include <trace/events/sched.h>

#include "sched.h"
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/*
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 * Targeted preemption latency for CPU-bound tasks:
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 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
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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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 */
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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
 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
 *
 * Options are:
 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
 */
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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 * (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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 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
 */
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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.
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 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
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 *
 * 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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unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
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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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/*
 * The exponential sliding  window over which load is averaged for shares
 * distribution.
 * (default: 10msec)
 */
unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;

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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.
 *
 * default: 5 msec, units: microseconds
  */
unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
#endif

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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
 *
 * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case
 * 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)
{
#ifdef CONFIG_SCHED_DEBUG
	WARN_ON_ONCE(!entity_is_task(se));
#endif
	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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		/*
		 * Ensure we either appear before our parent (if already
		 * enqueued) or force our parent to appear after us when it is
		 * enqueued.  The fact that we always enqueue bottom-up
		 * reduces this to two cases.
		 */
		if (cfs_rq->tg->parent &&
		    cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
			list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
				&rq_of(cfs_rq)->leaf_cfs_rq_list);
		} else {
			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
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				&rq_of(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 */
#define for_each_leaf_cfs_rq(rq, cfs_rq) \
	list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)

/* 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(rq, cfs_rq) \
		for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)

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)
{
	u64 vruntime = cfs_rq->min_vruntime;

	if (cfs_rq->curr)
		vruntime = cfs_rq->curr->vruntime;

	if (cfs_rq->rb_leftmost) {
		struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
						   struct sched_entity,
						   run_node);

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		if (!cfs_rq->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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{
	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
	struct rb_node *parent = NULL;
	struct sched_entity *entry;
	int leftmost = 1;

	/*
	 * 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;
			leftmost = 0;
		}
	}

	/*
	 * Maintain a cache of leftmost tree entries (it is frequently
	 * used):
	 */
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	if (leftmost)
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		cfs_rq->rb_leftmost = &se->run_node;
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	rb_link_node(&se->run_node, parent, link);
	rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
}

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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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	if (cfs_rq->rb_leftmost == &se->run_node) {
		struct rb_node *next_node;

		next_node = rb_next(&se->run_node);
		cfs_rq->rb_leftmost = next_node;
	}
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	rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
}

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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 = cfs_rq->rb_leftmost;

	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);
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	if (!last)
		return NULL;
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	return rb_entry(last, struct sched_entity, run_node);
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}

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

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

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

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

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

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

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/*
 * We calculate the wall-time slice from the period by taking a part
 * proportional to the weight.
 *
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 * s = p*P[w/rw]
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 */
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static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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	u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq);
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	for_each_sched_entity(se) {
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		struct load_weight *load;
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		struct load_weight lw;
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		cfs_rq = cfs_rq_of(se);
		load = &cfs_rq->load;
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		if (unlikely(!se->on_rq)) {
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			lw = cfs_rq->load;
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			update_load_add(&lw, se->load.weight);
			load = &lw;
		}
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		slice = __calc_delta(slice, se->load.weight, load);
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	}
	return slice;
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}

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/*
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 * We calculate the vruntime slice of a to-be-inserted task.
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 *
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 * vs = s/w
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 */
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static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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	return calc_delta_fair(sched_slice(cfs_rq, se), se);
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}

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#ifdef CONFIG_SMP
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static int select_idle_sibling(struct task_struct *p, int cpu);
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static unsigned long task_h_load(struct task_struct *p);

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/*
 * We choose a half-life close to 1 scheduling period.
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 * Note: The tables runnable_avg_yN_inv and runnable_avg_yN_sum are
 * dependent on this value.
666 667 668
 */
#define LOAD_AVG_PERIOD 32
#define LOAD_AVG_MAX 47742 /* maximum possible load avg */
669
#define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */
670

671 672
/* Give new sched_entity start runnable values to heavy its load in infant time */
void init_entity_runnable_average(struct sched_entity *se)
673
{
674
	struct sched_avg *sa = &se->avg;
675

676 677 678 679 680 681 682
	sa->last_update_time = 0;
	/*
	 * sched_avg's period_contrib should be strictly less then 1024, so
	 * we give it 1023 to make sure it is almost a period (1024us), and
	 * will definitely be update (after enqueue).
	 */
	sa->period_contrib = 1023;
683
	sa->load_avg = scale_load_down(se->load.weight);
684 685
	sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
	sa->util_avg = scale_load_down(SCHED_LOAD_SCALE);
686
	sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
687
	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
688
}
689 690 691

static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq);
static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq);
692
#else
693
void init_entity_runnable_average(struct sched_entity *se)
694 695 696 697
{
}
#endif

698
/*
699
 * Update the current task's runtime statistics.
700
 */
701
static void update_curr(struct cfs_rq *cfs_rq)
702
{
703
	struct sched_entity *curr = cfs_rq->curr;
704
	u64 now = rq_clock_task(rq_of(cfs_rq));
705
	u64 delta_exec;
706 707 708 709

	if (unlikely(!curr))
		return;

710 711
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
712
		return;
713

I
Ingo Molnar 已提交
714
	curr->exec_start = now;
715

716 717 718 719 720 721 722 723 724
	schedstat_set(curr->statistics.exec_max,
		      max(delta_exec, curr->statistics.exec_max));

	curr->sum_exec_runtime += delta_exec;
	schedstat_add(cfs_rq, exec_clock, delta_exec);

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

725 726 727
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

728
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
729
		cpuacct_charge(curtask, delta_exec);
730
		account_group_exec_runtime(curtask, delta_exec);
731
	}
732 733

	account_cfs_rq_runtime(cfs_rq, delta_exec);
734 735
}

736 737 738 739 740
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

741
#ifdef CONFIG_SCHEDSTATS
742
static inline void
743
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
744
{
745 746 747 748 749 750 751
	u64 wait_start = rq_clock(rq_of(cfs_rq));

	if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
	    likely(wait_start > se->statistics.wait_start))
		wait_start -= se->statistics.wait_start;

	se->statistics.wait_start = wait_start;
752 753
}

754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790
static void
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *p;
	u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start;

	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.
			 */
			se->statistics.wait_start = delta;
			return;
		}
		trace_sched_stat_wait(p, delta);
	}

	se->statistics.wait_max = max(se->statistics.wait_max, delta);
	se->statistics.wait_count++;
	se->statistics.wait_sum += delta;
	se->statistics.wait_start = 0;
}
#else
static inline void
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
}

static inline void
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
}
#endif

791 792 793
/*
 * Task is being enqueued - update stats:
 */
794
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
795 796 797 798 799
{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
800
	if (se != cfs_rq->curr)
801
		update_stats_wait_start(cfs_rq, se);
802 803 804
}

static inline void
805
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
806 807 808 809 810
{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
811
	if (se != cfs_rq->curr)
812
		update_stats_wait_end(cfs_rq, se);
813 814 815 816 817 818
}

/*
 * We are picking a new current task - update its stats:
 */
static inline void
819
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
820 821 822 823
{
	/*
	 * We are starting a new run period:
	 */
824
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
825 826 827 828 829 830
}

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

831 832
#ifdef CONFIG_NUMA_BALANCING
/*
833 834 835
 * 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.
836
 */
837 838
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
839 840 841

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
842

843 844 845
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869
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)
{
870
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
871 872 873
	unsigned int scan, floor;
	unsigned int windows = 1;

874 875
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891
	floor = 1000 / windows;

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

static unsigned int task_scan_max(struct task_struct *p)
{
	unsigned int smin = task_scan_min(p);
	unsigned int smax;

	/* Watch for min being lower than max due to floor calculations */
	smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
	return max(smin, smax);
}

892 893 894 895 896 897 898 899 900 901 902 903
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));
}

904 905 906 907 908
struct numa_group {
	atomic_t refcount;

	spinlock_t lock; /* nr_tasks, tasks */
	int nr_tasks;
909
	pid_t gid;
910 911

	struct rcu_head rcu;
912
	nodemask_t active_nodes;
913
	unsigned long total_faults;
914 915 916 917 918
	/*
	 * 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.
	 */
919
	unsigned long *faults_cpu;
920
	unsigned long faults[0];
921 922
};

923 924 925 926 927 928 929 930 931
/* 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)

932 933 934 935 936
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

937 938 939 940 941 942 943
/*
 * The averaged statistics, shared & private, memory & cpu,
 * 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)
944
{
945
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
946 947 948 949
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
950
	if (!p->numa_faults)
951 952
		return 0;

953 954
	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
955 956
}

957 958 959 960 961
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

962 963
	return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
964 965
}

966 967
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
968 969
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
970 971
}

972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036
/* 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;
}

1037 1038 1039 1040 1041 1042
/*
 * 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.
 */
1043 1044
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1045
{
1046
	unsigned long faults, total_faults;
1047

1048
	if (!p->numa_faults)
1049 1050 1051 1052 1053 1054 1055
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1056
	faults = task_faults(p, nid);
1057 1058
	faults += score_nearby_nodes(p, nid, dist, true);

1059
	return 1000 * faults / total_faults;
1060 1061
}

1062 1063
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1064
{
1065 1066 1067 1068 1069 1070 1071 1072
	unsigned long faults, total_faults;

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1073 1074
		return 0;

1075
	faults = group_faults(p, nid);
1076 1077
	faults += score_nearby_nodes(p, nid, dist, false);

1078
	return 1000 * faults / total_faults;
1079 1080
}

1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143
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;

	/*
	 * Do not migrate if the destination is not a node that
	 * is actively used by this numa group.
	 */
	if (!node_isset(dst_nid, ng->active_nodes))
		return false;

	/*
	 * Source is a node that is not actively used by this
	 * numa group, while the destination is. Migrate.
	 */
	if (!node_isset(src_nid, ng->active_nodes))
		return true;

	/*
	 * Both source and destination are nodes in active
	 * use by this numa group. Maximize memory bandwidth
	 * by migrating from more heavily used groups, to less
	 * heavily used ones, spreading the load around.
	 * Use a 1/4 hysteresis to avoid spurious page movement.
	 */
	return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4);
}

1144
static unsigned long weighted_cpuload(const int cpu);
1145 1146
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1147
static unsigned long capacity_of(int cpu);
1148 1149
static long effective_load(struct task_group *tg, int cpu, long wl, long wg);

1150
/* Cached statistics for all CPUs within a node */
1151
struct numa_stats {
1152
	unsigned long nr_running;
1153
	unsigned long load;
1154 1155

	/* Total compute capacity of CPUs on a node */
1156
	unsigned long compute_capacity;
1157 1158

	/* Approximate capacity in terms of runnable tasks on a node */
1159
	unsigned long task_capacity;
1160
	int has_free_capacity;
1161
};
1162

1163 1164 1165 1166 1167
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1168 1169
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1170 1171 1172 1173 1174 1175 1176

	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;
		ns->load += weighted_cpuload(cpu);
1177
		ns->compute_capacity += capacity_of(cpu);
1178 1179

		cpus++;
1180 1181
	}

1182 1183 1184 1185 1186
	/*
	 * 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.
	 *
1187 1188
	 * We'll either bail at !has_free_capacity, or we'll detect a huge
	 * imbalance and bail there.
1189 1190 1191 1192
	 */
	if (!cpus)
		return;

1193 1194 1195 1196 1197 1198
	/* 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));
1199
	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1200 1201
}

1202 1203
struct task_numa_env {
	struct task_struct *p;
1204

1205 1206
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1207

1208
	struct numa_stats src_stats, dst_stats;
1209

1210
	int imbalance_pct;
1211
	int dist;
1212 1213 1214

	struct task_struct *best_task;
	long best_imp;
1215 1216 1217
	int best_cpu;
};

1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230
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);
	if (p)
		get_task_struct(p);

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

1231
static bool load_too_imbalanced(long src_load, long dst_load,
1232 1233
				struct task_numa_env *env)
{
1234 1235
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246
	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;
1247 1248

	/* We care about the slope of the imbalance, not the direction. */
1249 1250
	if (dst_load < src_load)
		swap(dst_load, src_load);
1251 1252

	/* Is the difference below the threshold? */
1253 1254
	imb = dst_load * src_capacity * 100 -
	      src_load * dst_capacity * env->imbalance_pct;
1255 1256 1257 1258 1259
	if (imb <= 0)
		return false;

	/*
	 * The imbalance is above the allowed threshold.
1260
	 * Compare it with the old imbalance.
1261
	 */
1262
	orig_src_load = env->src_stats.load;
1263
	orig_dst_load = env->dst_stats.load;
1264

1265 1266
	if (orig_dst_load < orig_src_load)
		swap(orig_dst_load, orig_src_load);
1267

1268 1269 1270 1271 1272
	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);
1273 1274
}

1275 1276 1277 1278 1279 1280
/*
 * 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
 */
1281 1282
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1283 1284 1285 1286
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1287
	long src_load, dst_load;
1288
	long load;
1289
	long imp = env->p->numa_group ? groupimp : taskimp;
1290
	long moveimp = imp;
1291
	int dist = env->dist;
1292 1293

	rcu_read_lock();
1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304

	raw_spin_lock_irq(&dst_rq->lock);
	cur = dst_rq->curr;
	/*
	 * No need to move the exiting task, and this ensures that ->curr
	 * wasn't reaped and thus get_task_struct() in task_numa_assign()
	 * is safe under RCU read lock.
	 * Note that rcu_read_lock() itself can't protect from the final
	 * put_task_struct() after the last schedule().
	 */
	if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1305
		cur = NULL;
1306
	raw_spin_unlock_irq(&dst_rq->lock);
1307

1308 1309 1310 1311 1312 1313 1314
	/*
	 * 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;

1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326
	/*
	 * "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) {
		/* Skip this swap candidate if cannot move to the source cpu */
		if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
			goto unlock;

1327 1328
		/*
		 * If dst and source tasks are in the same NUMA group, or not
1329
		 * in any group then look only at task weights.
1330
		 */
1331
		if (cur->numa_group == env->p->numa_group) {
1332 1333
			imp = taskimp + task_weight(cur, env->src_nid, dist) -
			      task_weight(cur, env->dst_nid, dist);
1334 1335 1336 1337 1338 1339
			/*
			 * Add some hysteresis to prevent swapping the
			 * tasks within a group over tiny differences.
			 */
			if (cur->numa_group)
				imp -= imp/16;
1340
		} else {
1341 1342 1343 1344 1345 1346
			/*
			 * 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)
1347 1348
				imp += group_weight(cur, env->src_nid, dist) -
				       group_weight(cur, env->dst_nid, dist);
1349
			else
1350 1351
				imp += task_weight(cur, env->src_nid, dist) -
				       task_weight(cur, env->dst_nid, dist);
1352
		}
1353 1354
	}

1355
	if (imp <= env->best_imp && moveimp <= env->best_imp)
1356 1357 1358 1359
		goto unlock;

	if (!cur) {
		/* Is there capacity at our destination? */
1360
		if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1361
		    !env->dst_stats.has_free_capacity)
1362 1363 1364 1365 1366 1367
			goto unlock;

		goto balance;
	}

	/* Balance doesn't matter much if we're running a task per cpu */
1368 1369
	if (imp > env->best_imp && src_rq->nr_running == 1 &&
			dst_rq->nr_running == 1)
1370 1371 1372 1373 1374 1375
		goto assign;

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
balance:
1376 1377 1378
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1379

1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396
	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;

1397
	if (cur) {
1398 1399 1400
		load = task_h_load(cur);
		dst_load -= load;
		src_load += load;
1401 1402
	}

1403
	if (load_too_imbalanced(src_load, dst_load, env))
1404 1405
		goto unlock;

1406 1407 1408 1409 1410 1411 1412
	/*
	 * One idle CPU per node is evaluated for a task numa move.
	 * Call select_idle_sibling to maybe find a better one.
	 */
	if (!cur)
		env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);

1413 1414 1415 1416 1417 1418
assign:
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1419 1420
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1421 1422 1423 1424 1425 1426 1427 1428 1429
{
	int cpu;

	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
		/* Skip this CPU if the source task cannot migrate */
		if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
			continue;

		env->dst_cpu = cpu;
1430
		task_numa_compare(env, taskimp, groupimp);
1431 1432 1433
	}
}

1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450
/* 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
	 */
1451 1452 1453
	if (src->load * dst->compute_capacity * env->imbalance_pct >

	    dst->load * src->compute_capacity * 100)
1454 1455 1456 1457 1458
		return true;

	return false;
}

1459 1460 1461 1462
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1463

1464
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1465
		.src_nid = task_node(p),
1466 1467 1468 1469 1470 1471

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
		.best_cpu = -1
1472 1473
	};
	struct sched_domain *sd;
1474
	unsigned long taskweight, groupweight;
1475
	int nid, ret, dist;
1476
	long taskimp, groupimp;
1477

1478
	/*
1479 1480 1481 1482 1483 1484
	 * 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.
1485 1486
	 */
	rcu_read_lock();
1487
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1488 1489
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1490 1491
	rcu_read_unlock();

1492 1493 1494 1495 1496 1497 1498
	/*
	 * 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)) {
1499
		p->numa_preferred_nid = task_node(p);
1500 1501 1502
		return -EINVAL;
	}

1503
	env.dst_nid = p->numa_preferred_nid;
1504 1505 1506 1507 1508 1509
	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;
1510
	update_numa_stats(&env.dst_stats, env.dst_nid);
1511

1512
	/* Try to find a spot on the preferred nid. */
1513 1514
	if (numa_has_capacity(&env))
		task_numa_find_cpu(&env, taskimp, groupimp);
1515

1516 1517 1518 1519 1520 1521 1522 1523 1524
	/*
	 * 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.
	 */
	if (env.best_cpu == -1 || (p->numa_group &&
			nodes_weight(p->numa_group->active_nodes) > 1)) {
1525 1526 1527
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1528

1529
			dist = node_distance(env.src_nid, env.dst_nid);
1530 1531 1532 1533 1534
			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);
			}
1535

1536
			/* Only consider nodes where both task and groups benefit */
1537 1538
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1539
			if (taskimp < 0 && groupimp < 0)
1540 1541
				continue;

1542
			env.dist = dist;
1543 1544
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1545 1546
			if (numa_has_capacity(&env))
				task_numa_find_cpu(&env, taskimp, groupimp);
1547 1548 1549
		}
	}

1550 1551 1552 1553 1554 1555 1556 1557
	/*
	 * 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.
	 */
1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570
	if (p->numa_group) {
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
			nid = env.dst_nid;

		if (node_isset(nid, p->numa_group->active_nodes))
			sched_setnuma(p, env.dst_nid);
	}

	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;
1571

1572 1573 1574 1575 1576 1577
	/*
	 * Reset the scan period if the task is being rescheduled on an
	 * alternative node to recheck if the tasks is now properly placed.
	 */
	p->numa_scan_period = task_scan_min(p);

1578
	if (env.best_task == NULL) {
1579 1580 1581
		ret = migrate_task_to(p, env.best_cpu);
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1582 1583 1584 1585
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
1586 1587
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1588 1589
	put_task_struct(env.best_task);
	return ret;
1590 1591
}

1592 1593 1594
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1595 1596
	unsigned long interval = HZ;

1597
	/* This task has no NUMA fault statistics yet */
1598
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1599 1600
		return;

1601
	/* Periodically retry migrating the task to the preferred node */
1602 1603
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
	p->numa_migrate_retry = jiffies + interval;
1604 1605

	/* Success if task is already running on preferred CPU */
1606
	if (task_node(p) == p->numa_preferred_nid)
1607 1608 1609
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1610
	task_numa_migrate(p);
1611 1612
}

1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644
/*
 * Find the nodes on which the workload is actively running. We do this by
 * 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.
 *
 * The bitmask is used to make smarter decisions on when to do NUMA page
 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
 * are added when they cause over 6/16 of the maximum number of faults, but
 * only removed when they drop below 3/16.
 */
static void update_numa_active_node_mask(struct numa_group *numa_group)
{
	unsigned long faults, max_faults = 0;
	int nid;

	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);
		if (!node_isset(nid, numa_group->active_nodes)) {
			if (faults > max_faults * 6 / 16)
				node_set(nid, numa_group->active_nodes);
		} else if (faults < max_faults * 3 / 16)
			node_clear(nid, numa_group->active_nodes);
	}
}

1645 1646 1647
/*
 * 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
1648 1649 1650
 * 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.
1651 1652
 */
#define NUMA_PERIOD_SLOTS 10
1653
#define NUMA_PERIOD_THRESHOLD 7
1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673

/*
 * 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;
	int ratio;
	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
1674 1675 1676
	 * 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
1677
	 */
1678
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711
		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);
	ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
	if (ratio >= NUMA_PERIOD_THRESHOLD) {
		int slot = ratio - NUMA_PERIOD_THRESHOLD;
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else {
		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;

		/*
		 * Scale scan rate increases based on sharing. There is an
		 * inverse relationship between the degree of sharing and
		 * the adjustment made to the scanning period. Broadly
		 * speaking the intent is that there is little point
		 * scanning faster if shared accesses dominate as it may
		 * simply bounce migrations uselessly
		 */
1712
		ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1713 1714 1715 1716 1717 1718 1719 1720
		diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
	}

	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));
}

1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738
/*
 * 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 {
1739 1740
		delta = p->se.avg.load_sum / p->se.load.weight;
		*period = LOAD_AVG_MAX;
1741 1742 1743 1744 1745 1746 1747 1748
	}

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

	return delta;
}

1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795
/*
 * 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;
1796
		nodemask_t max_group = NODE_MASK_NONE;
1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829
		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. */
1830 1831
		if (!max_faults)
			break;
1832 1833 1834 1835 1836
		nodes = max_group;
	}
	return nid;
}

1837 1838
static void task_numa_placement(struct task_struct *p)
{
1839 1840
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
1841
	unsigned long fault_types[2] = { 0, 0 };
1842 1843
	unsigned long total_faults;
	u64 runtime, period;
1844
	spinlock_t *group_lock = NULL;
1845

1846 1847 1848 1849 1850
	/*
	 * 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:
	 */
1851
	seq = READ_ONCE(p->mm->numa_scan_seq);
1852 1853 1854
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
1855
	p->numa_scan_period_max = task_scan_max(p);
1856

1857 1858 1859 1860
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

1861 1862 1863
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
1864
		spin_lock_irq(group_lock);
1865 1866
	}

1867 1868
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
1869 1870
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1871
		unsigned long faults = 0, group_faults = 0;
1872
		int priv;
1873

1874
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1875
			long diff, f_diff, f_weight;
1876

1877 1878 1879 1880
			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);
1881

1882
			/* Decay existing window, copy faults since last scan */
1883 1884 1885
			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;
1886

1887 1888 1889 1890 1891 1892 1893 1894
			/*
			 * 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);
1895
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1896
				   (total_faults + 1);
1897 1898
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
1899

1900 1901 1902
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
1903
			p->total_numa_faults += diff;
1904
			if (p->numa_group) {
1905 1906 1907 1908 1909 1910 1911 1912 1913
				/*
				 * 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;
1914
				p->numa_group->total_faults += diff;
1915
				group_faults += p->numa_group->faults[mem_idx];
1916
			}
1917 1918
		}

1919 1920 1921 1922
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
1923 1924 1925 1926 1927 1928 1929

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

1930 1931
	update_task_scan_period(p, fault_types[0], fault_types[1]);

1932
	if (p->numa_group) {
1933
		update_numa_active_node_mask(p->numa_group);
1934
		spin_unlock_irq(group_lock);
1935
		max_nid = preferred_group_nid(p, max_group_nid);
1936 1937
	}

1938 1939 1940 1941 1942 1943 1944
	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);
1945
	}
1946 1947
}

1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958
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);
}

1959 1960
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
1961 1962 1963 1964 1965 1966 1967 1968 1969
{
	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) +
1970
				    4*nr_node_ids*sizeof(unsigned long);
1971 1972 1973 1974 1975 1976 1977

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

		atomic_set(&grp->refcount, 1);
		spin_lock_init(&grp->lock);
1978
		grp->gid = p->pid;
1979
		/* Second half of the array tracks nids where faults happen */
1980 1981
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
1982

1983 1984
		node_set(task_node(current), grp->active_nodes);

1985
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1986
			grp->faults[i] = p->numa_faults[i];
1987

1988
		grp->total_faults = p->total_numa_faults;
1989

1990 1991 1992 1993 1994
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
1995
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
1996 1997

	if (!cpupid_match_pid(tsk, cpupid))
1998
		goto no_join;
1999 2000 2001

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
2002
		goto no_join;
2003 2004 2005

	my_grp = p->numa_group;
	if (grp == my_grp)
2006
		goto no_join;
2007 2008 2009 2010 2011 2012

	/*
	 * 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)
2013
		goto no_join;
2014 2015 2016 2017 2018

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2019
		goto no_join;
2020

2021 2022 2023 2024 2025 2026 2027
	/* 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;
2028

2029 2030 2031
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2032
	if (join && !get_numa_group(grp))
2033
		goto no_join;
2034 2035 2036 2037 2038 2039

	rcu_read_unlock();

	if (!join)
		return;

2040 2041
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2042

2043
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2044 2045
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2046
	}
2047 2048
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2049 2050 2051 2052 2053

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

	spin_unlock(&my_grp->lock);
2054
	spin_unlock_irq(&grp->lock);
2055 2056 2057 2058

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2059 2060 2061 2062 2063
	return;

no_join:
	rcu_read_unlock();
	return;
2064 2065 2066 2067 2068
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
2069
	void *numa_faults = p->numa_faults;
2070 2071
	unsigned long flags;
	int i;
2072 2073

	if (grp) {
2074
		spin_lock_irqsave(&grp->lock, flags);
2075
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2076
			grp->faults[i] -= p->numa_faults[i];
2077
		grp->total_faults -= p->total_numa_faults;
2078

2079
		grp->nr_tasks--;
2080
		spin_unlock_irqrestore(&grp->lock, flags);
2081
		RCU_INIT_POINTER(p->numa_group, NULL);
2082 2083 2084
		put_numa_group(grp);
	}

2085
	p->numa_faults = NULL;
2086
	kfree(numa_faults);
2087 2088
}

2089 2090 2091
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2092
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2093 2094
{
	struct task_struct *p = current;
2095
	bool migrated = flags & TNF_MIGRATED;
2096
	int cpu_node = task_node(current);
2097
	int local = !!(flags & TNF_FAULT_LOCAL);
2098
	int priv;
2099

2100
	if (!static_branch_likely(&sched_numa_balancing))
2101 2102
		return;

2103 2104 2105 2106
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2107
	/* Allocate buffer to track faults on a per-node basis */
2108 2109
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2110
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2111

2112 2113
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2114
			return;
2115

2116
		p->total_numa_faults = 0;
2117
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2118
	}
2119

2120 2121 2122 2123 2124 2125 2126 2127
	/*
	 * 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);
2128
		if (!priv && !(flags & TNF_NO_GROUP))
2129
			task_numa_group(p, last_cpupid, flags, &priv);
2130 2131
	}

2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142
	/*
	 * 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.
	 */
	if (!priv && !local && p->numa_group &&
			node_isset(cpu_node, p->numa_group->active_nodes) &&
			node_isset(mem_node, p->numa_group->active_nodes))
		local = 1;

2143
	task_numa_placement(p);
2144

2145 2146 2147 2148 2149
	/*
	 * 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))
2150 2151
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
2152 2153
	if (migrated)
		p->numa_pages_migrated += pages;
2154 2155
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2156

2157 2158
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2159
	p->numa_faults_locality[local] += pages;
2160 2161
}

2162 2163
static void reset_ptenuma_scan(struct task_struct *p)
{
2164 2165 2166 2167 2168 2169 2170 2171
	/*
	 * 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:
	 */
2172
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2173 2174 2175
	p->mm->numa_scan_offset = 0;
}

2176 2177 2178 2179 2180 2181 2182 2183 2184
/*
 * 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;
2185
	u64 runtime = p->se.sum_exec_runtime;
2186
	struct vm_area_struct *vma;
2187
	unsigned long start, end;
2188
	unsigned long nr_pte_updates = 0;
2189
	long pages, virtpages;
2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204

	WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));

	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;

2205
	if (!mm->numa_next_scan) {
2206 2207
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2208 2209
	}

2210 2211 2212 2213 2214 2215 2216
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2217 2218 2219 2220
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
		p->numa_scan_period = task_scan_min(p);
	}
2221

2222
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2223 2224 2225
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2226 2227 2228 2229 2230 2231
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2232 2233 2234
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2235
	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2236 2237
	if (!pages)
		return;
2238

2239

2240
	down_read(&mm->mmap_sem);
2241
	vma = find_vma(mm, start);
2242 2243
	if (!vma) {
		reset_ptenuma_scan(p);
2244
		start = 0;
2245 2246
		vma = mm->mmap;
	}
2247
	for (; vma; vma = vma->vm_next) {
2248
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2249
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2250
			continue;
2251
		}
2252

2253 2254 2255 2256 2257 2258 2259 2260 2261 2262
		/*
		 * 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
2263 2264 2265 2266 2267 2268
		/*
		 * 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;
2269

2270 2271 2272 2273
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2274
			nr_pte_updates = change_prot_numa(vma, start, end);
2275 2276

			/*
2277 2278 2279 2280 2281 2282
			 * 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.
2283 2284 2285
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2286
			virtpages -= (end - start) >> PAGE_SHIFT;
2287

2288
			start = end;
2289
			if (pages <= 0 || virtpages <= 0)
2290
				goto out;
2291 2292

			cond_resched();
2293
		} while (end != vma->vm_end);
2294
	}
2295

2296
out:
2297
	/*
P
Peter Zijlstra 已提交
2298 2299 2300 2301
	 * 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.
2302 2303
	 */
	if (vma)
2304
		mm->numa_scan_offset = start;
2305 2306 2307
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318

	/*
	 * 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;
	}
2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343
}

/*
 * 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;

2344
	if (now > curr->node_stamp + period) {
2345
		if (!curr->node_stamp)
2346
			curr->numa_scan_period = task_scan_min(curr);
2347
		curr->node_stamp += period;
2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358

		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);
		}
	}
}
#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
}
2359 2360 2361 2362 2363 2364 2365 2366

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)
{
}
2367 2368
#endif /* CONFIG_NUMA_BALANCING */

2369 2370 2371 2372
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2373
	if (!parent_entity(se))
2374
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2375
#ifdef CONFIG_SMP
2376 2377 2378 2379 2380 2381
	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);
	}
2382
#endif
2383 2384 2385 2386 2387 2388 2389
	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);
2390
	if (!parent_entity(se))
2391
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2392 2393
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2394
		list_del_init(&se->group_node);
2395
	}
2396 2397 2398
	cfs_rq->nr_running--;
}

2399 2400
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
2401 2402 2403 2404 2405
static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
{
	long tg_weight;

	/*
2406 2407 2408
	 * Use this CPU's real-time load instead of the last load contribution
	 * as the updating of the contribution is delayed, and we will use the
	 * the real-time load to calc the share. See update_tg_load_avg().
2409
	 */
2410
	tg_weight = atomic_long_read(&tg->load_avg);
2411
	tg_weight -= cfs_rq->tg_load_avg_contrib;
2412
	tg_weight += cfs_rq->load.weight;
2413 2414 2415 2416

	return tg_weight;
}

2417
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2418
{
2419
	long tg_weight, load, shares;
2420

2421
	tg_weight = calc_tg_weight(tg, cfs_rq);
2422
	load = cfs_rq->load.weight;
2423 2424

	shares = (tg->shares * load);
2425 2426
	if (tg_weight)
		shares /= tg_weight;
2427 2428 2429 2430 2431 2432 2433 2434 2435

	if (shares < MIN_SHARES)
		shares = MIN_SHARES;
	if (shares > tg->shares)
		shares = tg->shares;

	return shares;
}
# else /* CONFIG_SMP */
2436
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2437 2438 2439 2440
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
2441 2442 2443
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
2444 2445 2446 2447
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
2448
		account_entity_dequeue(cfs_rq, se);
2449
	}
P
Peter Zijlstra 已提交
2450 2451 2452 2453 2454 2455 2456

	update_load_set(&se->load, weight);

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

2457 2458
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2459
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2460 2461 2462
{
	struct task_group *tg;
	struct sched_entity *se;
2463
	long shares;
P
Peter Zijlstra 已提交
2464 2465 2466

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
2467
	if (!se || throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
2468
		return;
2469 2470 2471 2472
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
2473
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
2474 2475 2476 2477

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
2478
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2479 2480 2481 2482
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

2483
#ifdef CONFIG_SMP
2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503
/* Precomputed fixed inverse multiplies for multiplication by y^n */
static const u32 runnable_avg_yN_inv[] = {
	0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
	0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
	0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
	0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
	0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
	0x85aac367, 0x82cd8698,
};

/*
 * Precomputed \Sum y^k { 1<=k<=n }.  These are floor(true_value) to prevent
 * over-estimates when re-combining.
 */
static const u32 runnable_avg_yN_sum[] = {
	    0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103,
	 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082,
	17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371,
};

2504 2505 2506 2507 2508 2509
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521
	unsigned int local_n;

	if (!n)
		return val;
	else if (unlikely(n > LOAD_AVG_PERIOD * 63))
		return 0;

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

	/*
	 * As y^PERIOD = 1/2, we can combine
2522 2523
	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
	 * With a look-up table which covers y^n (n<PERIOD)
2524 2525 2526 2527 2528 2529
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
2530 2531
	}

2532 2533
	val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
	return val;
2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561
}

/*
 * For updates fully spanning n periods, the contribution to runnable
 * average will be: \Sum 1024*y^n
 *
 * We can compute this reasonably efficiently by combining:
 *   y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for  n <PERIOD}
 */
static u32 __compute_runnable_contrib(u64 n)
{
	u32 contrib = 0;

	if (likely(n <= LOAD_AVG_PERIOD))
		return runnable_avg_yN_sum[n];
	else if (unlikely(n >= LOAD_AVG_MAX_N))
		return LOAD_AVG_MAX;

	/* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */
	do {
		contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */
		contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD];

		n -= LOAD_AVG_PERIOD;
	} while (n > LOAD_AVG_PERIOD);

	contrib = decay_load(contrib, n);
	return contrib + runnable_avg_yN_sum[n];
2562 2563
}

2564 2565 2566 2567
#if (SCHED_LOAD_SHIFT - SCHED_LOAD_RESOLUTION) != 10 || SCHED_CAPACITY_SHIFT != 10
#error "load tracking assumes 2^10 as unit"
#endif

2568
#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2569

2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597
/*
 * 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}]
 */
2598 2599
static __always_inline int
__update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2600
		  unsigned long weight, int running, struct cfs_rq *cfs_rq)
2601
{
2602
	u64 delta, scaled_delta, periods;
2603
	u32 contrib;
2604
	unsigned int delta_w, scaled_delta_w, decayed = 0;
2605
	unsigned long scale_freq, scale_cpu;
2606

2607
	delta = now - sa->last_update_time;
2608 2609 2610 2611 2612
	/*
	 * 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) {
2613
		sa->last_update_time = now;
2614 2615 2616 2617 2618 2619 2620 2621 2622 2623
		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;
2624
	sa->last_update_time = now;
2625

2626 2627 2628
	scale_freq = arch_scale_freq_capacity(NULL, cpu);
	scale_cpu = arch_scale_cpu_capacity(NULL, cpu);

2629
	/* delta_w is the amount already accumulated against our next period */
2630
	delta_w = sa->period_contrib;
2631 2632 2633
	if (delta + delta_w >= 1024) {
		decayed = 1;

2634 2635 2636
		/* how much left for next period will start over, we don't know yet */
		sa->period_contrib = 0;

2637 2638 2639 2640 2641 2642
		/*
		 * Now that we know we're crossing a period boundary, figure
		 * out how much from delta we need to complete the current
		 * period and accrue it.
		 */
		delta_w = 1024 - delta_w;
2643
		scaled_delta_w = cap_scale(delta_w, scale_freq);
2644
		if (weight) {
2645 2646 2647 2648 2649
			sa->load_sum += weight * scaled_delta_w;
			if (cfs_rq) {
				cfs_rq->runnable_load_sum +=
						weight * scaled_delta_w;
			}
2650
		}
2651
		if (running)
2652
			sa->util_sum += scaled_delta_w * scale_cpu;
2653 2654 2655 2656 2657 2658 2659

		delta -= delta_w;

		/* Figure out how many additional periods this update spans */
		periods = delta / 1024;
		delta %= 1024;

2660
		sa->load_sum = decay_load(sa->load_sum, periods + 1);
2661 2662 2663 2664
		if (cfs_rq) {
			cfs_rq->runnable_load_sum =
				decay_load(cfs_rq->runnable_load_sum, periods + 1);
		}
2665
		sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2666 2667

		/* Efficiently calculate \sum (1..n_period) 1024*y^i */
2668
		contrib = __compute_runnable_contrib(periods);
2669
		contrib = cap_scale(contrib, scale_freq);
2670
		if (weight) {
2671
			sa->load_sum += weight * contrib;
2672 2673 2674
			if (cfs_rq)
				cfs_rq->runnable_load_sum += weight * contrib;
		}
2675
		if (running)
2676
			sa->util_sum += contrib * scale_cpu;
2677 2678 2679
	}

	/* Remainder of delta accrued against u_0` */
2680
	scaled_delta = cap_scale(delta, scale_freq);
2681
	if (weight) {
2682
		sa->load_sum += weight * scaled_delta;
2683
		if (cfs_rq)
2684
			cfs_rq->runnable_load_sum += weight * scaled_delta;
2685
	}
2686
	if (running)
2687
		sa->util_sum += scaled_delta * scale_cpu;
2688

2689
	sa->period_contrib += delta;
2690

2691 2692
	if (decayed) {
		sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2693 2694 2695 2696
		if (cfs_rq) {
			cfs_rq->runnable_load_avg =
				div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
		}
2697
		sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2698
	}
2699

2700
	return decayed;
2701 2702
}

2703
#ifdef CONFIG_FAIR_GROUP_SCHED
2704
/*
2705 2706
 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
 * and effective_load (which is not done because it is too costly).
2707
 */
2708
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2709
{
2710
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2711

2712 2713 2714
	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;
2715
	}
2716
}
2717

2718
#else /* CONFIG_FAIR_GROUP_SCHED */
2719
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2720
#endif /* CONFIG_FAIR_GROUP_SCHED */
2721

2722
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2723

2724 2725
/* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2726
{
2727
	struct sched_avg *sa = &cfs_rq->avg;
2728
	int decayed, removed = 0;
2729

2730 2731 2732 2733
	if (atomic_long_read(&cfs_rq->removed_load_avg)) {
		long r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
		sa->load_avg = max_t(long, sa->load_avg - r, 0);
		sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
2734
		removed = 1;
2735
	}
2736

2737 2738 2739
	if (atomic_long_read(&cfs_rq->removed_util_avg)) {
		long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
		sa->util_avg = max_t(long, sa->util_avg - r, 0);
2740
		sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
2741
	}
2742

2743
	decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2744
		scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2745

2746 2747 2748 2749
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
2750

2751
	return decayed || removed;
2752 2753
}

2754 2755
/* Update task and its cfs_rq load average */
static inline void update_load_avg(struct sched_entity *se, int update_tg)
2756
{
2757
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
2758
	u64 now = cfs_rq_clock_task(cfs_rq);
2759
	int cpu = cpu_of(rq_of(cfs_rq));
2760

2761
	/*
2762 2763
	 * 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
2764
	 */
2765
	__update_load_avg(now, cpu, &se->avg,
2766 2767
			  se->on_rq * scale_load_down(se->load.weight),
			  cfs_rq->curr == se, NULL);
2768

2769 2770
	if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
		update_tg_load_avg(cfs_rq, 0);
2771 2772
}

2773 2774
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2775 2776 2777
	if (!sched_feat(ATTACH_AGE_LOAD))
		goto skip_aging;

2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791
	/*
	 * If we got migrated (either between CPUs or between cgroups) we'll
	 * have aged the average right before clearing @last_update_time.
	 */
	if (se->avg.last_update_time) {
		__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
				  &se->avg, 0, 0, NULL);

		/*
		 * XXX: we could have just aged the entire load away if we've been
		 * absent from the fair class for too long.
		 */
	}

2792
skip_aging:
2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811
	se->avg.last_update_time = cfs_rq->avg.last_update_time;
	cfs_rq->avg.load_avg += se->avg.load_avg;
	cfs_rq->avg.load_sum += se->avg.load_sum;
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
}

static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
			  &se->avg, se->on_rq * scale_load_down(se->load.weight),
			  cfs_rq->curr == se, NULL);

	cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
	cfs_rq->avg.load_sum = max_t(s64,  cfs_rq->avg.load_sum - se->avg.load_sum, 0);
	cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
	cfs_rq->avg.util_sum = max_t(s32,  cfs_rq->avg.util_sum - se->avg.util_sum, 0);
}

2812 2813 2814
/* Add the load generated by se into cfs_rq's load average */
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
2815
{
2816 2817
	struct sched_avg *sa = &se->avg;
	u64 now = cfs_rq_clock_task(cfs_rq);
2818
	int migrated, decayed;
2819

2820 2821
	migrated = !sa->last_update_time;
	if (!migrated) {
2822
		__update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2823 2824
			se->on_rq * scale_load_down(se->load.weight),
			cfs_rq->curr == se, NULL);
2825
	}
2826

2827
	decayed = update_cfs_rq_load_avg(now, cfs_rq);
2828

2829 2830 2831
	cfs_rq->runnable_load_avg += sa->load_avg;
	cfs_rq->runnable_load_sum += sa->load_sum;

2832 2833
	if (migrated)
		attach_entity_load_avg(cfs_rq, se);
2834

2835 2836
	if (decayed || migrated)
		update_tg_load_avg(cfs_rq, 0);
2837 2838
}

2839 2840 2841 2842 2843 2844 2845 2846 2847
/* Remove the runnable load generated by se from cfs_rq's runnable load average */
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_avg(se, 1);

	cfs_rq->runnable_load_avg =
		max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
	cfs_rq->runnable_load_sum =
2848
		max_t(s64,  cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2849 2850
}

2851
/*
2852 2853
 * Task first catches up with cfs_rq, and then subtract
 * itself from the cfs_rq (task must be off the queue now).
2854
 */
2855
void remove_entity_load_avg(struct sched_entity *se)
2856
{
2857 2858 2859 2860 2861
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 last_update_time;

#ifndef CONFIG_64BIT
	u64 last_update_time_copy;
2862

2863 2864 2865 2866 2867 2868 2869 2870 2871
	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);
#else
	last_update_time = cfs_rq->avg.last_update_time;
#endif

2872
	__update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2873 2874
	atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
	atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2875
}
2876

2877 2878 2879 2880 2881 2882 2883 2884 2885 2886
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
{
	return cfs_rq->runnable_load_avg;
}

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

2887 2888
static int idle_balance(struct rq *this_rq);

2889 2890
#else /* CONFIG_SMP */

2891 2892 2893
static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2894 2895
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2896
static inline void remove_entity_load_avg(struct sched_entity *se) {}
2897

2898 2899 2900 2901 2902
static inline void
attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
static inline void
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}

2903 2904 2905 2906 2907
static inline int idle_balance(struct rq *rq)
{
	return 0;
}

2908
#endif /* CONFIG_SMP */
2909

2910
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2911 2912
{
#ifdef CONFIG_SCHEDSTATS
2913 2914 2915 2916 2917
	struct task_struct *tsk = NULL;

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

2918
	if (se->statistics.sleep_start) {
2919
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2920 2921 2922 2923

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

2924 2925
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
2926

2927
		se->statistics.sleep_start = 0;
2928
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
2929

2930
		if (tsk) {
2931
			account_scheduler_latency(tsk, delta >> 10, 1);
2932 2933
			trace_sched_stat_sleep(tsk, delta);
		}
2934
	}
2935
	if (se->statistics.block_start) {
2936
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2937 2938 2939 2940

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

2941 2942
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
2943

2944
		se->statistics.block_start = 0;
2945
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
2946

2947
		if (tsk) {
2948
			if (tsk->in_iowait) {
2949 2950
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
2951
				trace_sched_stat_iowait(tsk, delta);
2952 2953
			}

2954 2955
			trace_sched_stat_blocked(tsk, delta);

2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966
			/*
			 * 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);
I
Ingo Molnar 已提交
2967
		}
2968 2969 2970 2971
	}
#endif
}

P
Peter Zijlstra 已提交
2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984
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)
		schedstat_inc(cfs_rq, nr_spread_over);
#endif
}

2985 2986 2987
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
2988
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
2989

2990 2991 2992 2993 2994 2995
	/*
	 * 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
2996
	if (initial && sched_feat(START_DEBIT))
2997
		vruntime += sched_vslice(cfs_rq, se);
2998

2999
	/* sleeps up to a single latency don't count. */
3000
	if (!initial) {
3001
		unsigned long thresh = sysctl_sched_latency;
3002

3003 3004 3005 3006 3007 3008
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3009

3010
		vruntime -= thresh;
3011 3012
	}

3013
	/* ensure we never gain time by being placed backwards. */
3014
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3015 3016
}

3017 3018
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3019
static void
3020
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3021
{
3022 3023
	/*
	 * Update the normalized vruntime before updating min_vruntime
3024
	 * through calling update_curr().
3025
	 */
3026
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
3027 3028
		se->vruntime += cfs_rq->min_vruntime;

3029
	/*
3030
	 * Update run-time statistics of the 'current'.
3031
	 */
3032
	update_curr(cfs_rq);
3033
	enqueue_entity_load_avg(cfs_rq, se);
3034 3035
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
3036

3037
	if (flags & ENQUEUE_WAKEUP) {
3038
		place_entity(cfs_rq, se, 0);
3039
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
3040
	}
3041

3042
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
3043
	check_spread(cfs_rq, se);
3044 3045
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3046
	se->on_rq = 1;
3047

3048
	if (cfs_rq->nr_running == 1) {
3049
		list_add_leaf_cfs_rq(cfs_rq);
3050 3051
		check_enqueue_throttle(cfs_rq);
	}
3052 3053
}

3054
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3055
{
3056 3057
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3058
		if (cfs_rq->last != se)
3059
			break;
3060 3061

		cfs_rq->last = NULL;
3062 3063
	}
}
P
Peter Zijlstra 已提交
3064

3065 3066 3067 3068
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3069
		if (cfs_rq->next != se)
3070
			break;
3071 3072

		cfs_rq->next = NULL;
3073
	}
P
Peter Zijlstra 已提交
3074 3075
}

3076 3077 3078 3079
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3080
		if (cfs_rq->skip != se)
3081
			break;
3082 3083

		cfs_rq->skip = NULL;
3084 3085 3086
	}
}

P
Peter Zijlstra 已提交
3087 3088
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3089 3090 3091 3092 3093
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
3094 3095 3096

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
3097 3098
}

3099
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3100

3101
static void
3102
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3103
{
3104 3105 3106 3107
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
3108
	dequeue_entity_load_avg(cfs_rq, se);
3109

3110
	update_stats_dequeue(cfs_rq, se);
3111
	if (flags & DEQUEUE_SLEEP) {
P
Peter Zijlstra 已提交
3112
#ifdef CONFIG_SCHEDSTATS
3113 3114 3115 3116
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
3117
				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3118
			if (tsk->state & TASK_UNINTERRUPTIBLE)
3119
				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3120
		}
3121
#endif
P
Peter Zijlstra 已提交
3122 3123
	}

P
Peter Zijlstra 已提交
3124
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3125

3126
	if (se != cfs_rq->curr)
3127
		__dequeue_entity(cfs_rq, se);
3128
	se->on_rq = 0;
3129
	account_entity_dequeue(cfs_rq, se);
3130 3131 3132 3133 3134 3135

	/*
	 * Normalize the entity after updating the min_vruntime because the
	 * update can refer to the ->curr item and we need to reflect this
	 * movement in our normalized position.
	 */
3136
	if (!(flags & DEQUEUE_SLEEP))
3137
		se->vruntime -= cfs_rq->min_vruntime;
3138

3139 3140 3141
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3142
	update_min_vruntime(cfs_rq);
3143
	update_cfs_shares(cfs_rq);
3144 3145 3146 3147 3148
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
3149
static void
I
Ingo Molnar 已提交
3150
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3151
{
3152
	unsigned long ideal_runtime, delta_exec;
3153 3154
	struct sched_entity *se;
	s64 delta;
3155

P
Peter Zijlstra 已提交
3156
	ideal_runtime = sched_slice(cfs_rq, curr);
3157
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3158
	if (delta_exec > ideal_runtime) {
3159
		resched_curr(rq_of(cfs_rq));
3160 3161 3162 3163 3164
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175
		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;

3176 3177
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
3178

3179 3180
	if (delta < 0)
		return;
3181

3182
	if (delta > ideal_runtime)
3183
		resched_curr(rq_of(cfs_rq));
3184 3185
}

3186
static void
3187
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3188
{
3189 3190 3191 3192 3193 3194 3195 3196 3197
	/* '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.
		 */
		update_stats_wait_end(cfs_rq, se);
		__dequeue_entity(cfs_rq, se);
3198
		update_load_avg(se, 1);
3199 3200
	}

3201
	update_stats_curr_start(cfs_rq, se);
3202
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
3203 3204 3205 3206 3207 3208
#ifdef CONFIG_SCHEDSTATS
	/*
	 * 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):
	 */
3209
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3210
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
3211 3212 3213
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
3214
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
3215 3216
}

3217 3218 3219
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

3220 3221 3222 3223 3224 3225 3226
/*
 * 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
 */
3227 3228
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3229
{
3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240
	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 */
3241

3242 3243 3244 3245 3246
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
3247 3248 3249 3250 3251 3252 3253 3254 3255 3256
		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;
		}

3257 3258 3259
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
3260

3261 3262 3263 3264 3265 3266
	/*
	 * 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;

3267 3268 3269 3270 3271 3272
	/*
	 * 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;

3273
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3274 3275

	return se;
3276 3277
}

3278
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3279

3280
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3281 3282 3283 3284 3285 3286
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
3287
		update_curr(cfs_rq);
3288

3289 3290 3291
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

P
Peter Zijlstra 已提交
3292
	check_spread(cfs_rq, prev);
3293
	if (prev->on_rq) {
3294
		update_stats_wait_start(cfs_rq, prev);
3295 3296
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
3297
		/* in !on_rq case, update occurred at dequeue */
3298
		update_load_avg(prev, 0);
3299
	}
3300
	cfs_rq->curr = NULL;
3301 3302
}

P
Peter Zijlstra 已提交
3303 3304
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3305 3306
{
	/*
3307
	 * Update run-time statistics of the 'current'.
3308
	 */
3309
	update_curr(cfs_rq);
3310

3311 3312 3313
	/*
	 * Ensure that runnable average is periodically updated.
	 */
3314
	update_load_avg(curr, 1);
3315
	update_cfs_shares(cfs_rq);
3316

P
Peter Zijlstra 已提交
3317 3318 3319 3320 3321
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
3322
	if (queued) {
3323
		resched_curr(rq_of(cfs_rq));
3324 3325
		return;
	}
P
Peter Zijlstra 已提交
3326 3327 3328 3329 3330 3331 3332 3333
	/*
	 * 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
3334
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
3335
		check_preempt_tick(cfs_rq, curr);
3336 3337
}

3338 3339 3340 3341 3342 3343

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

#ifdef CONFIG_CFS_BANDWIDTH
3344 3345

#ifdef HAVE_JUMP_LABEL
3346
static struct static_key __cfs_bandwidth_used;
3347 3348 3349

static inline bool cfs_bandwidth_used(void)
{
3350
	return static_key_false(&__cfs_bandwidth_used);
3351 3352
}

3353
void cfs_bandwidth_usage_inc(void)
3354
{
3355 3356 3357 3358 3359 3360
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
3361 3362 3363 3364 3365 3366 3367
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

3368 3369
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
3370 3371
#endif /* HAVE_JUMP_LABEL */

3372 3373 3374 3375 3376 3377 3378 3379
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
3380 3381 3382 3383 3384 3385

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

P
Paul Turner 已提交
3386 3387 3388 3389 3390 3391 3392
/*
 * 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
 */
3393
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404
{
	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);
}

3405 3406 3407 3408 3409
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

3410 3411 3412 3413 3414 3415
/* 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))
		return cfs_rq->throttled_clock_task;

3416
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3417 3418
}

3419 3420
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3421 3422 3423
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
3424
	u64 amount = 0, min_amount, expires;
3425 3426 3427 3428 3429 3430 3431

	/* 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;
3432
	else {
P
Peter Zijlstra 已提交
3433
		start_cfs_bandwidth(cfs_b);
3434 3435 3436 3437 3438 3439

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
3440
	}
P
Paul Turner 已提交
3441
	expires = cfs_b->runtime_expires;
3442 3443 3444
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
3445 3446 3447 3448 3449 3450 3451
	/*
	 * 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;
3452 3453

	return cfs_rq->runtime_remaining > 0;
3454 3455
}

P
Paul Turner 已提交
3456 3457 3458 3459 3460
/*
 * 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)
3461
{
P
Paul Turner 已提交
3462 3463 3464
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
3465
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3466 3467
		return;

P
Paul Turner 已提交
3468 3469 3470 3471 3472 3473 3474 3475 3476
	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
3477 3478 3479
	 * 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
3480 3481
	 */

3482
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
3483 3484 3485 3486 3487 3488 3489 3490
		/* 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;
	}
}

3491
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
3492 3493
{
	/* dock delta_exec before expiring quota (as it could span periods) */
3494
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
3495 3496 3497
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
3498 3499
		return;

3500 3501 3502 3503 3504
	/*
	 * 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))
3505
		resched_curr(rq_of(cfs_rq));
3506 3507
}

3508
static __always_inline
3509
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3510
{
3511
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3512 3513 3514 3515 3516
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

3517 3518
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
3519
	return cfs_bandwidth_used() && cfs_rq->throttled;
3520 3521
}

3522 3523 3524
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
3525
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546 3547 3548 3549 3550 3551 3552 3553
}

/*
 * 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--;
#ifdef CONFIG_SMP
	if (!cfs_rq->throttle_count) {
3554
		/* adjust cfs_rq_clock_task() */
3555
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3556
					     cfs_rq->throttled_clock_task;
3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567
	}
#endif

	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)];

3568 3569
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
3570
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
3571 3572 3573 3574 3575
	cfs_rq->throttle_count++;

	return 0;
}

3576
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3577 3578 3579 3580 3581
{
	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
3582
	bool empty;
3583 3584 3585

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

3586
	/* freeze hierarchy runnable averages while throttled */
3587 3588 3589
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606

	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)
3607
		sub_nr_running(rq, task_delta);
3608 3609

	cfs_rq->throttled = 1;
3610
	cfs_rq->throttled_clock = rq_clock(rq);
3611
	raw_spin_lock(&cfs_b->lock);
3612
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
3613

3614 3615 3616 3617 3618
	/*
	 * 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
3619 3620 3621 3622 3623 3624 3625 3626

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

3627 3628 3629
	raw_spin_unlock(&cfs_b->lock);
}

3630
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3631 3632 3633 3634 3635 3636 3637
{
	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;

3638
	se = cfs_rq->tg->se[cpu_of(rq)];
3639 3640

	cfs_rq->throttled = 0;
3641 3642 3643

	update_rq_clock(rq);

3644
	raw_spin_lock(&cfs_b->lock);
3645
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3646 3647 3648
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

3649 3650 3651
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

3652 3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669
	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)
3670
		add_nr_running(rq, task_delta);
3671 3672 3673

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
3674
		resched_curr(rq);
3675 3676 3677 3678 3679 3680
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
3681 3682
	u64 runtime;
	u64 starting_runtime = remaining;
3683 3684 3685 3686 3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712

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

		raw_spin_lock(&rq->lock);
		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:
		raw_spin_unlock(&rq->lock);

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

3713
	return starting_runtime - remaining;
3714 3715
}

3716 3717 3718 3719 3720 3721 3722 3723
/*
 * 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)
{
3724
	u64 runtime, runtime_expires;
3725
	int throttled;
3726 3727 3728

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
3729
		goto out_deactivate;
3730

3731
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3732
	cfs_b->nr_periods += overrun;
3733

3734 3735 3736 3737 3738 3739
	/*
	 * 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
3740 3741 3742

	__refill_cfs_bandwidth_runtime(cfs_b);

3743 3744 3745
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
3746
		return 0;
3747 3748
	}

3749 3750 3751
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

3752 3753 3754
	runtime_expires = cfs_b->runtime_expires;

	/*
3755 3756 3757 3758 3759
	 * 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.
3760
	 */
3761 3762
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
3763 3764 3765 3766 3767 3768 3769
		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);
3770 3771

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
3772
	}
3773

3774 3775 3776 3777 3778 3779 3780
	/*
	 * 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;
3781

3782 3783 3784 3785
	return 0;

out_deactivate:
	return 1;
3786
}
3787

3788 3789 3790 3791 3792 3793 3794
/* 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;

3795 3796 3797 3798
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3799
 * hrtimer base being cleared by hrtimer_start. In the case of
3800 3801
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826
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
3827 3828 3829
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
3830 3831 3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858
}

/* 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)
{
3859 3860 3861
	if (!cfs_bandwidth_used())
		return;

3862
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873 3874 3875 3876 3877
		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 */
3878 3879 3880
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
3881
		return;
3882
	}
3883

3884
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3885
		runtime = cfs_b->runtime;
3886

3887 3888 3889 3890 3891 3892 3893 3894 3895 3896
	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)
3897
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
3898 3899 3900
	raw_spin_unlock(&cfs_b->lock);
}

3901 3902 3903 3904 3905 3906 3907
/*
 * 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)
{
3908 3909 3910
	if (!cfs_bandwidth_used())
		return;

3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925
	/* 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);
}

/* conditionally throttle active cfs_rq's from put_prev_entity() */
3926
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3927
{
3928
	if (!cfs_bandwidth_used())
3929
		return false;
3930

3931
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3932
		return false;
3933 3934 3935 3936 3937 3938

	/*
	 * 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))
3939
		return true;
3940 3941

	throttle_cfs_rq(cfs_rq);
3942
	return true;
3943
}
3944 3945 3946 3947 3948

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
3949

3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961
	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;

3962
	raw_spin_lock(&cfs_b->lock);
3963
	for (;;) {
P
Peter Zijlstra 已提交
3964
		overrun = hrtimer_forward_now(timer, cfs_b->period);
3965 3966 3967 3968 3969
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
P
Peter Zijlstra 已提交
3970 3971
	if (idle)
		cfs_b->period_active = 0;
3972
	raw_spin_unlock(&cfs_b->lock);
3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984

	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
3985
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996
	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
3997
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3998
{
P
Peter Zijlstra 已提交
3999
	lockdep_assert_held(&cfs_b->lock);
4000

P
Peter Zijlstra 已提交
4001 4002 4003 4004 4005
	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);
	}
4006 4007 4008 4009
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4010 4011 4012 4013
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4014 4015 4016 4017
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

4018 4019 4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030
static void __maybe_unused update_runtime_enabled(struct rq *rq)
{
	struct cfs_rq *cfs_rq;

	for_each_leaf_cfs_rq(rq, cfs_rq) {
		struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth;

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

4031
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042
{
	struct cfs_rq *cfs_rq;

	for_each_leaf_cfs_rq(rq, cfs_rq) {
		if (!cfs_rq->runtime_enabled)
			continue;

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
4043
		cfs_rq->runtime_remaining = 1;
4044 4045 4046 4047 4048 4049
		/*
		 * Offline rq is schedulable till cpu is completely disabled
		 * in take_cpu_down(), so we prevent new cfs throttling here.
		 */
		cfs_rq->runtime_enabled = 0;

4050 4051 4052 4053 4054 4055
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
}

#else /* CONFIG_CFS_BANDWIDTH */
4056 4057
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
4058
	return rq_clock_task(rq_of(cfs_rq));
4059 4060
}

4061
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4062
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4063
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4064
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4065 4066 4067 4068 4069

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080

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;
}
4081 4082 4083 4084 4085

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) {}
4086 4087
#endif

4088 4089 4090 4091 4092
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) {}
4093
static inline void update_runtime_enabled(struct rq *rq) {}
4094
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4095 4096 4097

#endif /* CONFIG_CFS_BANDWIDTH */

4098 4099 4100 4101
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
4102 4103 4104 4105 4106 4107 4108 4109
#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);

	WARN_ON(task_rq(p) != rq);

4110
	if (cfs_rq->nr_running > 1) {
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Peter Zijlstra 已提交
4111 4112 4113 4114 4115 4116
		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)
4117
				resched_curr(rq);
P
Peter Zijlstra 已提交
4118 4119
			return;
		}
4120
		hrtick_start(rq, delta);
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Peter Zijlstra 已提交
4121 4122
	}
}
4123 4124 4125 4126 4127 4128 4129 4130 4131 4132

/*
 * 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;

4133
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4134 4135 4136 4137 4138
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
4139
#else /* !CONFIG_SCHED_HRTICK */
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4140 4141 4142 4143
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
4144 4145 4146 4147

static inline void hrtick_update(struct rq *rq)
{
}
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Peter Zijlstra 已提交
4148 4149
#endif

4150 4151 4152 4153 4154
/*
 * 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:
 */
4155
static void
4156
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4157 4158
{
	struct cfs_rq *cfs_rq;
4159
	struct sched_entity *se = &p->se;
4160 4161

	for_each_sched_entity(se) {
4162
		if (se->on_rq)
4163 4164
			break;
		cfs_rq = cfs_rq_of(se);
4165
		enqueue_entity(cfs_rq, se, flags);
4166 4167 4168 4169 4170 4171 4172 4173 4174

		/*
		 * 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.
		*/
		if (cfs_rq_throttled(cfs_rq))
			break;
4175
		cfs_rq->h_nr_running++;
4176

4177
		flags = ENQUEUE_WAKEUP;
4178
	}
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Peter Zijlstra 已提交
4179

P
Peter Zijlstra 已提交
4180
	for_each_sched_entity(se) {
4181
		cfs_rq = cfs_rq_of(se);
4182
		cfs_rq->h_nr_running++;
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Peter Zijlstra 已提交
4183

4184 4185 4186
		if (cfs_rq_throttled(cfs_rq))
			break;

4187
		update_load_avg(se, 1);
4188
		update_cfs_shares(cfs_rq);
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Peter Zijlstra 已提交
4189 4190
	}

Y
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4191
	if (!se)
4192
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
4193

4194
	hrtick_update(rq);
4195 4196
}

4197 4198
static void set_next_buddy(struct sched_entity *se);

4199 4200 4201 4202 4203
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
4204
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4205 4206
{
	struct cfs_rq *cfs_rq;
4207
	struct sched_entity *se = &p->se;
4208
	int task_sleep = flags & DEQUEUE_SLEEP;
4209 4210 4211

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
4212
		dequeue_entity(cfs_rq, se, flags);
4213 4214 4215 4216 4217 4218 4219 4220 4221

		/*
		 * 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;
4222
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4223

4224
		/* Don't dequeue parent if it has other entities besides us */
4225 4226 4227 4228 4229 4230 4231
		if (cfs_rq->load.weight) {
			/*
			 * Bias pick_next to pick a task from this cfs_rq, as
			 * p is sleeping when it is within its sched_slice.
			 */
			if (task_sleep && parent_entity(se))
				set_next_buddy(parent_entity(se));
4232 4233 4234

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
4235
			break;
4236
		}
4237
		flags |= DEQUEUE_SLEEP;
4238
	}
P
Peter Zijlstra 已提交
4239

P
Peter Zijlstra 已提交
4240
	for_each_sched_entity(se) {
4241
		cfs_rq = cfs_rq_of(se);
4242
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4243

4244 4245 4246
		if (cfs_rq_throttled(cfs_rq))
			break;

4247
		update_load_avg(se, 1);
4248
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4249 4250
	}

Y
Yuyang Du 已提交
4251
	if (!se)
4252
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
4253

4254
	hrtick_update(rq);
4255 4256
}

4257
#ifdef CONFIG_SMP
4258 4259 4260 4261 4262 4263

/*
 * per rq 'load' arrray crap; XXX kill this.
 */

/*
4264
 * The exact cpuload calculated at every tick would be:
4265
 *
4266 4267 4268 4269 4270 4271 4272
 *   load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
 *
 * 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:
 *
 *   load_n   = (1 - 1/2^i)^n * load_0
 *   load_n+1 = (1 - 1/2^i)   * load_n + (1/2^i) * cur_load
4273 4274 4275
 *
 * decay_load_missed() below does efficient calculation of
 *
4276 4277 4278 4279 4280 4281
 *   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())
4282
 *
4283
 * The calculation is approximated on a 128 point scale.
4284 4285
 */
#define DEGRADE_SHIFT		7
4286 4287 4288 4289 4290 4291 4292 4293 4294

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 }
};
4295 4296 4297 4298 4299 4300 4301 4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 4315 4316 4317 4318 4319 4320 4321 4322 4323 4324

/*
 * 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;
}

4325 4326 4327 4328 4329 4330 4331
/**
 * __update_cpu_load - update the rq->cpu_load[] statistics
 * @this_rq: The rq to update statistics for
 * @this_load: The current load
 * @pending_updates: The number of missed updates
 * @active: !0 for NOHZ_FULL
 *
4332
 * Update rq->cpu_load[] statistics. This function is usually called every
4333 4334 4335 4336 4337 4338 4339 4340 4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359
 * 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
 * term. See the @active paramter.
4360 4361
 */
static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4362
			      unsigned long pending_updates, int active)
4363
{
4364
	unsigned long tickless_load = active ? this_rq->cpu_load[0] : 0;
4365 4366 4367 4368 4369 4370 4371 4372 4373 4374 4375
	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 */

4376
		old_load = this_rq->cpu_load[i] - tickless_load;
4377
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
4378
		old_load += tickless_load;
4379 4380 4381 4382 4383 4384 4385 4386 4387 4388 4389 4390 4391 4392 4393
		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);
}

4394 4395 4396 4397 4398 4399
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
	return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
}

4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415 4416 4417 4418 4419
#ifdef CONFIG_NO_HZ_COMMON
/*
 * There is no sane way to deal with nohz on smp when using jiffies because the
 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
 *
 * Therefore we cannot use the delta approach from the regular tick since that
 * would seriously skew the load calculation. However we'll make do for those
 * updates happening while idle (nohz_idle_balance) or coming out of idle
 * (tick_nohz_idle_exit).
 *
 * This means we might still be one tick off for nohz periods.
 */

/*
 * Called from nohz_idle_balance() to update the load ratings before doing the
 * idle balance.
 */
static void update_idle_cpu_load(struct rq *this_rq)
{
4420
	unsigned long curr_jiffies = READ_ONCE(jiffies);
4421
	unsigned long load = weighted_cpuload(cpu_of(this_rq));
4422 4423 4424 4425 4426 4427 4428 4429 4430 4431 4432
	unsigned long pending_updates;

	/*
	 * bail if there's load or we're actually up-to-date.
	 */
	if (load || curr_jiffies == this_rq->last_load_update_tick)
		return;

	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
	this_rq->last_load_update_tick = curr_jiffies;

4433
	__update_cpu_load(this_rq, load, pending_updates, 0);
4434 4435 4436 4437 4438
}

/*
 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
 */
4439
void update_cpu_load_nohz(int active)
4440 4441
{
	struct rq *this_rq = this_rq();
4442
	unsigned long curr_jiffies = READ_ONCE(jiffies);
4443
	unsigned long load = active ? weighted_cpuload(cpu_of(this_rq)) : 0;
4444 4445 4446 4447 4448 4449 4450 4451 4452 4453
	unsigned long pending_updates;

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

	raw_spin_lock(&this_rq->lock);
	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
	if (pending_updates) {
		this_rq->last_load_update_tick = curr_jiffies;
		/*
4454 4455 4456
		 * 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.
4457
		 */
4458
		__update_cpu_load(this_rq, load, pending_updates, active);
4459 4460 4461 4462 4463 4464 4465 4466 4467 4468
	}
	raw_spin_unlock(&this_rq->lock);
}
#endif /* CONFIG_NO_HZ */

/*
 * Called from scheduler_tick()
 */
void update_cpu_load_active(struct rq *this_rq)
{
4469
	unsigned long load = weighted_cpuload(cpu_of(this_rq));
4470 4471 4472 4473
	/*
	 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
	 */
	this_rq->last_load_update_tick = jiffies;
4474
	__update_cpu_load(this_rq, load, 1, 1);
4475 4476
}

4477 4478 4479 4480 4481 4482 4483 4484 4485 4486 4487 4488 4489 4490 4491 4492 4493 4494 4495 4496 4497 4498 4499 4500 4501 4502 4503 4504 4505 4506 4507 4508 4509
/*
 * Return a low guess at the load of a migration-source cpu weighted
 * 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);
	unsigned long total = weighted_cpuload(cpu);

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

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

/*
 * Return a high guess at the load of a migration-target cpu weighted
 * according to the scheduling class and "nice" value.
 */
static unsigned long target_load(int cpu, int type)
{
	struct rq *rq = cpu_rq(cpu);
	unsigned long total = weighted_cpuload(cpu);

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

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

4510
static unsigned long capacity_of(int cpu)
4511
{
4512
	return cpu_rq(cpu)->cpu_capacity;
4513 4514
}

4515 4516 4517 4518 4519
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

4520 4521 4522
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
4523
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4524
	unsigned long load_avg = weighted_cpuload(cpu);
4525 4526

	if (nr_running)
4527
		return load_avg / nr_running;
4528 4529 4530 4531

	return 0;
}

4532 4533 4534 4535 4536 4537 4538
static void record_wakee(struct task_struct *p)
{
	/*
	 * Rough decay (wiping) for cost saving, don't worry
	 * about the boundary, really active task won't care
	 * about the loss.
	 */
4539
	if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4540
		current->wakee_flips >>= 1;
4541 4542 4543 4544 4545 4546 4547 4548
		current->wakee_flip_decay_ts = jiffies;
	}

	if (current->last_wakee != p) {
		current->last_wakee = p;
		current->wakee_flips++;
	}
}
4549

4550
static void task_waking_fair(struct task_struct *p)
4551 4552 4553
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
4554 4555 4556 4557
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
4558

4559 4560 4561 4562 4563 4564 4565 4566
	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
4567

4568
	se->vruntime -= min_vruntime;
4569
	record_wakee(p);
4570 4571
}

4572
#ifdef CONFIG_FAIR_GROUP_SCHED
4573 4574 4575 4576 4577 4578
/*
 * effective_load() calculates the load change as seen from the root_task_group
 *
 * Adding load to a group doesn't make a group heavier, but can cause movement
 * of group shares between cpus. Assuming the shares were perfectly aligned one
 * can calculate the shift in shares.
4579 4580 4581 4582 4583 4584 4585 4586 4587 4588 4589 4590 4591 4592 4593 4594 4595 4596 4597 4598 4599 4600 4601 4602 4603 4604 4605 4606 4607 4608 4609 4610 4611 4612 4613 4614 4615 4616 4617 4618 4619 4620 4621
 *
 * Calculate the effective load difference if @wl is added (subtracted) to @tg
 * on this @cpu and results in a total addition (subtraction) of @wg to the
 * total group weight.
 *
 * Given a runqueue weight distribution (rw_i) we can compute a shares
 * distribution (s_i) using:
 *
 *   s_i = rw_i / \Sum rw_j						(1)
 *
 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and
 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting
 * shares distribution (s_i):
 *
 *   rw_i = {   2,   4,   1,   0 }
 *   s_i  = { 2/7, 4/7, 1/7,   0 }
 *
 * As per wake_affine() we're interested in the load of two CPUs (the CPU the
 * task used to run on and the CPU the waker is running on), we need to
 * compute the effect of waking a task on either CPU and, in case of a sync
 * wakeup, compute the effect of the current task going to sleep.
 *
 * So for a change of @wl to the local @cpu with an overall group weight change
 * of @wl we can compute the new shares distribution (s'_i) using:
 *
 *   s'_i = (rw_i + @wl) / (@wg + \Sum rw_j)				(2)
 *
 * Suppose we're interested in CPUs 0 and 1, and want to compute the load
 * differences in waking a task to CPU 0. The additional task changes the
 * weight and shares distributions like:
 *
 *   rw'_i = {   3,   4,   1,   0 }
 *   s'_i  = { 3/8, 4/8, 1/8,   0 }
 *
 * We can then compute the difference in effective weight by using:
 *
 *   dw_i = S * (s'_i - s_i)						(3)
 *
 * Where 'S' is the group weight as seen by its parent.
 *
 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7)
 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 -
 * 4/7) times the weight of the group.
4622
 */
P
Peter Zijlstra 已提交
4623
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4624
{
P
Peter Zijlstra 已提交
4625
	struct sched_entity *se = tg->se[cpu];
4626

4627
	if (!tg->parent)	/* the trivial, non-cgroup case */
4628 4629
		return wl;

P
Peter Zijlstra 已提交
4630
	for_each_sched_entity(se) {
4631
		long w, W;
P
Peter Zijlstra 已提交
4632

4633
		tg = se->my_q->tg;
4634

4635 4636 4637 4638
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
4639

4640 4641 4642
		/*
		 * w = rw_i + @wl
		 */
4643
		w = cfs_rq_load_avg(se->my_q) + wl;
4644

4645 4646 4647 4648
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
4649
			wl = (w * (long)tg->shares) / W;
4650 4651
		else
			wl = tg->shares;
4652

4653 4654 4655 4656 4657
		/*
		 * Per the above, wl is the new se->load.weight value; since
		 * those are clipped to [MIN_SHARES, ...) do so now. See
		 * calc_cfs_shares().
		 */
4658 4659
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
4660 4661 4662 4663

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
4664
		wl -= se->avg.load_avg;
4665 4666 4667 4668 4669 4670 4671 4672

		/*
		 * Recursively apply this logic to all parent groups to compute
		 * the final effective load change on the root group. Since
		 * only the @tg group gets extra weight, all parent groups can
		 * only redistribute existing shares. @wl is the shift in shares
		 * resulting from this level per the above.
		 */
P
Peter Zijlstra 已提交
4673 4674
		wg = 0;
	}
4675

P
Peter Zijlstra 已提交
4676
	return wl;
4677 4678
}
#else
P
Peter Zijlstra 已提交
4679

4680
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
P
Peter Zijlstra 已提交
4681
{
4682
	return wl;
4683
}
P
Peter Zijlstra 已提交
4684

4685 4686
#endif

M
Mike Galbraith 已提交
4687 4688 4689 4690 4691 4692 4693 4694 4695 4696 4697 4698
/*
 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
 * A waker of many should wake a different task than the one last awakened
 * at a frequency roughly N times higher than one of its wakees.  In order
 * to determine whether we should let the load spread vs consolodating 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.
 */
4699 4700
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
4701 4702
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
4703
	int factor = this_cpu_read(sd_llc_size);
4704

M
Mike Galbraith 已提交
4705 4706 4707 4708 4709
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
4710 4711
}

4712
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4713
{
4714
	s64 this_load, load;
4715
	s64 this_eff_load, prev_eff_load;
4716 4717
	int idx, this_cpu, prev_cpu;
	struct task_group *tg;
4718
	unsigned long weight;
4719
	int balanced;
4720

4721 4722 4723 4724 4725
	idx	  = sd->wake_idx;
	this_cpu  = smp_processor_id();
	prev_cpu  = task_cpu(p);
	load	  = source_load(prev_cpu, idx);
	this_load = target_load(this_cpu, idx);
4726

4727 4728 4729 4730 4731
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
4732 4733
	if (sync) {
		tg = task_group(current);
4734
		weight = current->se.avg.load_avg;
4735

4736
		this_load += effective_load(tg, this_cpu, -weight, -weight);
4737 4738
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
4739

4740
	tg = task_group(p);
4741
	weight = p->se.avg.load_avg;
4742

4743 4744
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4745 4746 4747
	 * due to the sync cause above having dropped this_load to 0, we'll
	 * always have an imbalance, but there's really nothing you can do
	 * about that, so that's good too.
4748 4749 4750 4751
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
4752 4753
	this_eff_load = 100;
	this_eff_load *= capacity_of(prev_cpu);
4754

4755 4756
	prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= capacity_of(this_cpu);
4757

4758
	if (this_load > 0) {
4759 4760 4761 4762
		this_eff_load *= this_load +
			effective_load(tg, this_cpu, weight, weight);

		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4763
	}
4764

4765
	balanced = this_eff_load <= prev_eff_load;
4766

4767
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4768

4769 4770
	if (!balanced)
		return 0;
4771

4772 4773 4774 4775
	schedstat_inc(sd, ttwu_move_affine);
	schedstat_inc(p, se.statistics.nr_wakeups_affine);

	return 1;
4776 4777
}

4778 4779 4780 4781 4782
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
4783
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4784
		  int this_cpu, int sd_flag)
4785
{
4786
	struct sched_group *idlest = NULL, *group = sd->groups;
4787
	unsigned long min_load = ULONG_MAX, this_load = 0;
4788
	int load_idx = sd->forkexec_idx;
4789
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
4790

4791 4792 4793
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

4794 4795 4796 4797
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
4798

4799 4800
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
4801
					tsk_cpus_allowed(p)))
4802 4803 4804 4805 4806 4807 4808 4809 4810 4811 4812 4813 4814 4815 4816 4817 4818 4819
			continue;

		local_group = cpumask_test_cpu(this_cpu,
					       sched_group_cpus(group));

		/* Tally up the load of all CPUs in the group */
		avg_load = 0;

		for_each_cpu(i, sched_group_cpus(group)) {
			/* Bias balancing toward cpus of our domain */
			if (local_group)
				load = source_load(i, load_idx);
			else
				load = target_load(i, load_idx);

			avg_load += load;
		}

4820
		/* Adjust by relative CPU capacity of the group */
4821
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4822 4823 4824 4825 4826 4827 4828 4829 4830 4831 4832 4833 4834 4835 4836 4837 4838 4839 4840 4841 4842

		if (local_group) {
			this_load = avg_load;
		} else if (avg_load < min_load) {
			min_load = avg_load;
			idlest = group;
		}
	} while (group = group->next, group != sd->groups);

	if (!idlest || 100*this_load < imbalance*min_load)
		return NULL;
	return idlest;
}

/*
 * find_idlest_cpu - find the idlest cpu among the cpus in group.
 */
static int
find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
{
	unsigned long load, min_load = ULONG_MAX;
4843 4844 4845 4846
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
4847 4848 4849
	int i;

	/* Traverse only the allowed CPUs */
4850
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4851 4852 4853 4854 4855 4856 4857 4858 4859 4860 4861 4862 4863 4864 4865 4866 4867 4868 4869 4870 4871 4872
		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;
			}
4873
		} else if (shallowest_idle_cpu == -1) {
4874 4875 4876 4877 4878
			load = weighted_cpuload(i);
			if (load < min_load || (load == min_load && i == this_cpu)) {
				min_load = load;
				least_loaded_cpu = i;
			}
4879 4880 4881
		}
	}

4882
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
4883
}
4884

4885 4886 4887
/*
 * Try and locate an idle CPU in the sched_domain.
 */
4888
static int select_idle_sibling(struct task_struct *p, int target)
4889
{
4890
	struct sched_domain *sd;
4891
	struct sched_group *sg;
4892
	int i = task_cpu(p);
4893

4894 4895
	if (idle_cpu(target))
		return target;
4896 4897

	/*
4898
	 * If the prevous cpu is cache affine and idle, don't be stupid.
4899
	 */
4900 4901
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
4902 4903

	/*
4904
	 * Otherwise, iterate the domains and find an elegible idle cpu.
4905
	 */
4906
	sd = rcu_dereference(per_cpu(sd_llc, target));
4907
	for_each_lower_domain(sd) {
4908 4909 4910 4911 4912 4913 4914
		sg = sd->groups;
		do {
			if (!cpumask_intersects(sched_group_cpus(sg),
						tsk_cpus_allowed(p)))
				goto next;

			for_each_cpu(i, sched_group_cpus(sg)) {
4915
				if (i == target || !idle_cpu(i))
4916 4917
					goto next;
			}
4918

4919 4920 4921 4922 4923 4924 4925 4926
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
4927 4928
	return target;
}
4929

4930
/*
4931
 * cpu_util returns the amount of capacity of a CPU that is used by CFS
4932
 * tasks. The unit of the return value must be the one of capacity so we can
4933 4934
 * compare the utilization with the capacity of the CPU that is available for
 * CFS task (ie cpu_capacity).
4935 4936 4937 4938 4939 4940 4941 4942 4943 4944 4945 4946 4947 4948 4949 4950 4951 4952 4953 4954
 *
 * 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).
4955
 */
4956
static int cpu_util(int cpu)
4957
{
4958
	unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
4959 4960
	unsigned long capacity = capacity_orig_of(cpu);

4961
	return (util >= capacity) ? capacity : util;
4962
}
4963

4964
/*
4965 4966 4967
 * 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.
4968
 *
4969 4970
 * 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.
4971
 *
4972
 * Returns the target cpu number.
4973 4974 4975
 *
 * preempt must be disabled.
 */
4976
static int
4977
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
4978
{
4979
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
4980
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
4981
	int new_cpu = prev_cpu;
4982
	int want_affine = 0;
4983
	int sync = wake_flags & WF_SYNC;
4984

4985
	if (sd_flag & SD_BALANCE_WAKE)
M
Mike Galbraith 已提交
4986
		want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
4987

4988
	rcu_read_lock();
4989
	for_each_domain(cpu, tmp) {
4990
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
4991
			break;
4992

4993
		/*
4994 4995
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
4996
		 */
4997 4998 4999
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
5000
			break;
5001
		}
5002

5003
		if (tmp->flags & sd_flag)
5004
			sd = tmp;
M
Mike Galbraith 已提交
5005 5006
		else if (!want_affine)
			break;
5007 5008
	}

M
Mike Galbraith 已提交
5009 5010 5011 5012
	if (affine_sd) {
		sd = NULL; /* Prefer wake_affine over balance flags */
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
			new_cpu = cpu;
5013
	}
5014

M
Mike Galbraith 已提交
5015 5016 5017 5018 5019
	if (!sd) {
		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
			new_cpu = select_idle_sibling(p, new_cpu);

	} else while (sd) {
5020
		struct sched_group *group;
5021
		int weight;
5022

5023
		if (!(sd->flags & sd_flag)) {
5024 5025 5026
			sd = sd->child;
			continue;
		}
5027

5028
		group = find_idlest_group(sd, p, cpu, sd_flag);
5029 5030 5031 5032
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
5033

5034
		new_cpu = find_idlest_cpu(group, p, cpu);
5035 5036 5037 5038
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
5039
		}
5040 5041 5042

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
5043
		weight = sd->span_weight;
5044 5045
		sd = NULL;
		for_each_domain(cpu, tmp) {
5046
			if (weight <= tmp->span_weight)
5047
				break;
5048
			if (tmp->flags & sd_flag)
5049 5050 5051
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
5052
	}
5053
	rcu_read_unlock();
5054

5055
	return new_cpu;
5056
}
5057 5058 5059 5060

/*
 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
 * cfs_rq_of(p) references at time of call are still valid and identify the
5061
 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5062
 */
5063
static void migrate_task_rq_fair(struct task_struct *p)
5064
{
5065
	/*
5066 5067 5068 5069 5070
	 * 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.
5071
	 */
5072 5073 5074 5075
	remove_entity_load_avg(&p->se);

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
5076 5077

	/* We have migrated, no longer consider this task hot */
5078
	p->se.exec_start = 0;
5079
}
5080 5081 5082 5083 5084

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
5085 5086
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
5087 5088
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5089 5090 5091 5092
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
5093 5094
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
5095 5096 5097 5098 5099 5100 5101 5102 5103
	 *
	 * 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.
5104
	 */
5105
	return calc_delta_fair(gran, se);
5106 5107
}

5108 5109 5110 5111 5112 5113 5114 5115 5116 5117 5118 5119 5120 5121 5122 5123 5124 5125 5126 5127 5128 5129
/*
 * 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;

P
Peter Zijlstra 已提交
5130
	gran = wakeup_gran(curr, se);
5131 5132 5133 5134 5135 5136
	if (vdiff > gran)
		return 1;

	return 0;
}

5137 5138
static void set_last_buddy(struct sched_entity *se)
{
5139 5140 5141 5142 5143
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
5144 5145 5146 5147
}

static void set_next_buddy(struct sched_entity *se)
{
5148 5149 5150 5151 5152
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
5153 5154
}

5155 5156
static void set_skip_buddy(struct sched_entity *se)
{
5157 5158
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
5159 5160
}

5161 5162 5163
/*
 * Preempt the current task with a newly woken task if needed:
 */
5164
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5165 5166
{
	struct task_struct *curr = rq->curr;
5167
	struct sched_entity *se = &curr->se, *pse = &p->se;
5168
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5169
	int scale = cfs_rq->nr_running >= sched_nr_latency;
5170
	int next_buddy_marked = 0;
5171

I
Ingo Molnar 已提交
5172 5173 5174
	if (unlikely(se == pse))
		return;

5175
	/*
5176
	 * This is possible from callers such as attach_tasks(), in which we
5177 5178 5179 5180 5181 5182 5183
	 * 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;

5184
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
5185
		set_next_buddy(pse);
5186 5187
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
5188

5189 5190 5191
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
5192 5193 5194 5195 5196 5197
	 *
	 * 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.
5198 5199 5200 5201
	 */
	if (test_tsk_need_resched(curr))
		return;

5202 5203 5204 5205 5206
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

5207
	/*
5208 5209
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
5210
	 */
5211
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5212
		return;
5213

5214
	find_matching_se(&se, &pse);
5215
	update_curr(cfs_rq_of(se));
5216
	BUG_ON(!pse);
5217 5218 5219 5220 5221 5222 5223
	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);
5224
		goto preempt;
5225
	}
5226

5227
	return;
5228

5229
preempt:
5230
	resched_curr(rq);
5231 5232 5233 5234 5235 5236 5237 5238 5239 5240 5241 5242 5243 5244
	/*
	 * 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);
5245 5246
}

5247 5248
static struct task_struct *
pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5249 5250 5251
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
5252
	struct task_struct *p;
5253
	int new_tasks;
5254

5255
again:
5256 5257
#ifdef CONFIG_FAIR_GROUP_SCHED
	if (!cfs_rq->nr_running)
5258
		goto idle;
5259

5260
	if (prev->sched_class != &fair_sched_class)
5261 5262 5263 5264 5265 5266 5267 5268 5269 5270 5271 5272 5273 5274 5275 5276 5277 5278 5279
		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.
		 */
5280 5281 5282 5283 5284
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
5285

5286 5287 5288 5289 5290 5291 5292 5293 5294
			/*
			 * This call to check_cfs_rq_runtime() will do the
			 * throttle and dequeue its entity in the parent(s).
			 * Therefore the 'simple' nr_running test will indeed
			 * be correct.
			 */
			if (unlikely(check_cfs_rq_runtime(cfs_rq)))
				goto simple;
		}
5295 5296 5297 5298 5299 5300 5301 5302 5303 5304 5305 5306 5307 5308 5309 5310 5311 5312 5313 5314 5315 5316 5317 5318 5319 5320 5321 5322 5323 5324 5325 5326 5327 5328 5329 5330 5331 5332 5333 5334

		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);
	}

	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);

	return p;
simple:
	cfs_rq = &rq->cfs;
#endif
5335

5336
	if (!cfs_rq->nr_running)
5337
		goto idle;
5338

5339
	put_prev_task(rq, prev);
5340

5341
	do {
5342
		se = pick_next_entity(cfs_rq, NULL);
5343
		set_next_entity(cfs_rq, se);
5344 5345 5346
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
5347
	p = task_of(se);
5348

5349 5350
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
5351 5352

	return p;
5353 5354

idle:
5355 5356 5357 5358 5359 5360 5361
	/*
	 * 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.
	 */
	lockdep_unpin_lock(&rq->lock);
5362
	new_tasks = idle_balance(rq);
5363
	lockdep_pin_lock(&rq->lock);
5364 5365 5366 5367 5368
	/*
	 * 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.
	 */
5369
	if (new_tasks < 0)
5370 5371
		return RETRY_TASK;

5372
	if (new_tasks > 0)
5373 5374 5375
		goto again;

	return NULL;
5376 5377 5378 5379 5380
}

/*
 * Account for a descheduled task:
 */
5381
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5382 5383 5384 5385 5386 5387
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5388
		put_prev_entity(cfs_rq, se);
5389 5390 5391
	}
}

5392 5393 5394 5395 5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416
/*
 * 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);
5417 5418 5419 5420 5421
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
5422
		rq_clock_skip_update(rq, true);
5423 5424 5425 5426 5427
	}

	set_skip_buddy(se);
}

5428 5429 5430 5431
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

5432 5433
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5434 5435 5436 5437 5438 5439 5440 5441 5442 5443
		return false;

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

	yield_task_fair(rq);

	return true;
}

5444
#ifdef CONFIG_SMP
5445
/**************************************************
P
Peter Zijlstra 已提交
5446 5447 5448 5449 5450 5451 5452 5453 5454 5455 5456 5457 5458 5459 5460 5461 5462 5463 5464 5465 5466 5467 5468
 * Fair scheduling class load-balancing methods.
 *
 * BASICS
 *
 * The purpose of load-balancing is to achieve the same basic fairness the
 * per-cpu scheduler provides, namely provide a proportional amount of compute
 * 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)
 *
 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
 * W_i,0 is defined as:
 *
 *   W_i,0 = \Sum_j w_i,j                                             (2)
 *
 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
 * is derived from the nice value as per prio_to_weight[].
 *
 * 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)
 *
5469
 * C_i is the compute capacity of cpu i, typically it is the
P
Peter Zijlstra 已提交
5470 5471 5472 5473 5474 5475
 * 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):
 *
5476
 *   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
5477 5478 5479 5480 5481 5482 5483 5484 5485 5486 5487 5488 5489 5490 5491 5492 5493 5494 5495 5496 5497 5498 5499 5500 5501 5502 5503 5504 5505 5506 5507 5508 5509 5510 5511 5512 5513 5514 5515 5516 5517 5518 5519 5520 5521 5522 5523 5524 5525 5526 5527 5528 5529 5530 5531 5532 5533 5534 5535 5536 5537 5538 5539 5540 5541 5542 5543 5544 5545 5546 5547 5548 5549 5550 5551 5552 5553 5554 5555 5556 5557 5558 5559 5560 5561
 *
 * 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)
 * for all i,j solution, we create a tree of cpus that follows the hardware
 * topology where each level pairs two lower groups (or better). This results
 * in O(log n) layers. Furthermore we reduce the number of cpus going up the
 * tree to only the first of the previous level and we decrease the frequency
 * of load-balance at each level inv. proportional to the number of cpus in
 * 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
 *         |         |     `- number of cpus doing load-balance
 *         |         `- 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
 * to every other cpu in at most O(log n) steps:
 *
 * The adjacency matrix of the resulting graph is given by:
 *
 *             log_2 n     
 *   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)
 *
 * Showing there's indeed a path between every cpu in at most O(log n) steps.
 * 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
 * balancing is more aggressive and has the newly idle cpu iterate up the domain
 * 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)
 *
 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i.
 *
 * 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.]
 */ 
5562

5563 5564
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

5565 5566
enum fbq_type { regular, remote, all };

5567
#define LBF_ALL_PINNED	0x01
5568
#define LBF_NEED_BREAK	0x02
5569 5570
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
5571 5572 5573 5574 5575

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
5576
	int			src_cpu;
5577 5578 5579 5580

	int			dst_cpu;
	struct rq		*dst_rq;

5581 5582
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
5583
	enum cpu_idle_type	idle;
5584
	long			imbalance;
5585 5586 5587
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

5588
	unsigned int		flags;
5589 5590 5591 5592

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
5593 5594

	enum fbq_type		fbq_type;
5595
	struct list_head	tasks;
5596 5597
};

5598 5599 5600
/*
 * Is this task likely cache-hot:
 */
5601
static int task_hot(struct task_struct *p, struct lb_env *env)
5602 5603 5604
{
	s64 delta;

5605 5606
	lockdep_assert_held(&env->src_rq->lock);

5607 5608 5609 5610 5611 5612 5613 5614 5615
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
5616
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5617 5618 5619 5620 5621 5622 5623 5624 5625
			(&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;

5626
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5627 5628 5629 5630

	return delta < (s64)sysctl_sched_migration_cost;
}

5631
#ifdef CONFIG_NUMA_BALANCING
5632
/*
5633 5634 5635
 * 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.
5636
 */
5637
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5638
{
5639
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
5640
	unsigned long src_faults, dst_faults;
5641 5642
	int src_nid, dst_nid;

5643
	if (!static_branch_likely(&sched_numa_balancing))
5644 5645
		return -1;

5646
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5647
		return -1;
5648 5649 5650 5651

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

5652
	if (src_nid == dst_nid)
5653
		return -1;
5654

5655 5656 5657 5658 5659 5660 5661
	/* 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;
	}
5662

5663 5664
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
5665
		return 0;
5666

5667 5668 5669 5670 5671 5672
	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);
5673 5674
	}

5675
	return dst_faults < src_faults;
5676 5677
}

5678
#else
5679
static inline int migrate_degrades_locality(struct task_struct *p,
5680 5681
					     struct lb_env *env)
{
5682
	return -1;
5683
}
5684 5685
#endif

5686 5687 5688 5689
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
5690
int can_migrate_task(struct task_struct *p, struct lb_env *env)
5691
{
5692
	int tsk_cache_hot;
5693 5694 5695

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

5696 5697
	/*
	 * We do not migrate tasks that are:
5698
	 * 1) throttled_lb_pair, or
5699
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5700 5701
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
5702
	 */
5703 5704 5705
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

5706
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5707
		int cpu;
5708

5709
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5710

5711 5712
		env->flags |= LBF_SOME_PINNED;

5713 5714 5715 5716 5717 5718 5719 5720
		/*
		 * Remember if this task can be migrated to any other cpu in
		 * our sched_group. We may want to revisit it if we couldn't
		 * meet load balance goals by pulling other tasks on src_cpu.
		 *
		 * Also avoid computing new_dst_cpu if we have already computed
		 * one in current iteration.
		 */
5721
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5722 5723
			return 0;

5724 5725 5726
		/* Prevent to re-select dst_cpu via env's cpus */
		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
			if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
5727
				env->flags |= LBF_DST_PINNED;
5728 5729 5730
				env->new_dst_cpu = cpu;
				break;
			}
5731
		}
5732

5733 5734
		return 0;
	}
5735 5736

	/* Record that we found atleast one task that could run on dst_cpu */
5737
	env->flags &= ~LBF_ALL_PINNED;
5738

5739
	if (task_running(env->src_rq, p)) {
5740
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5741 5742 5743 5744 5745
		return 0;
	}

	/*
	 * Aggressive migration if:
5746 5747 5748
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
5749
	 */
5750 5751 5752
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
5753

5754
	if (tsk_cache_hot <= 0 ||
5755
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5756
		if (tsk_cache_hot == 1) {
5757 5758 5759
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
			schedstat_inc(p, se.statistics.nr_forced_migrations);
		}
5760 5761 5762
		return 1;
	}

Z
Zhang Hang 已提交
5763 5764
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
5765 5766
}

5767
/*
5768 5769 5770 5771 5772 5773 5774
 * 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;
5775
	deactivate_task(env->src_rq, p, 0);
5776 5777 5778
	set_task_cpu(p, env->dst_cpu);
}

5779
/*
5780
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5781 5782
 * part of active balancing operations within "domain".
 *
5783
 * Returns a task if successful and NULL otherwise.
5784
 */
5785
static struct task_struct *detach_one_task(struct lb_env *env)
5786 5787 5788
{
	struct task_struct *p, *n;

5789 5790
	lockdep_assert_held(&env->src_rq->lock);

5791 5792 5793
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
5794

5795
		detach_task(p, env);
5796

5797
		/*
5798
		 * Right now, this is only the second place where
5799
		 * lb_gained[env->idle] is updated (other is detach_tasks)
5800
		 * so we can safely collect stats here rather than
5801
		 * inside detach_tasks().
5802 5803
		 */
		schedstat_inc(env->sd, lb_gained[env->idle]);
5804
		return p;
5805
	}
5806
	return NULL;
5807 5808
}

5809 5810
static const unsigned int sched_nr_migrate_break = 32;

5811
/*
5812 5813
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
5814
 *
5815
 * Returns number of detached tasks if successful and 0 otherwise.
5816
 */
5817
static int detach_tasks(struct lb_env *env)
5818
{
5819 5820
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
5821
	unsigned long load;
5822 5823 5824
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
5825

5826
	if (env->imbalance <= 0)
5827
		return 0;
5828

5829
	while (!list_empty(tasks)) {
5830 5831 5832 5833 5834 5835 5836
		/*
		 * 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;

5837
		p = list_first_entry(tasks, struct task_struct, se.group_node);
5838

5839 5840
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
5841
		if (env->loop > env->loop_max)
5842
			break;
5843 5844

		/* take a breather every nr_migrate tasks */
5845
		if (env->loop > env->loop_break) {
5846
			env->loop_break += sched_nr_migrate_break;
5847
			env->flags |= LBF_NEED_BREAK;
5848
			break;
5849
		}
5850

5851
		if (!can_migrate_task(p, env))
5852 5853 5854
			goto next;

		load = task_h_load(p);
5855

5856
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5857 5858
			goto next;

5859
		if ((load / 2) > env->imbalance)
5860
			goto next;
5861

5862 5863 5864 5865
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
5866
		env->imbalance -= load;
5867 5868

#ifdef CONFIG_PREEMPT
5869 5870
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
5871
		 * kernels will stop after the first task is detached to minimize
5872 5873
		 * the critical section.
		 */
5874
		if (env->idle == CPU_NEWLY_IDLE)
5875
			break;
5876 5877
#endif

5878 5879 5880 5881
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
5882
		if (env->imbalance <= 0)
5883
			break;
5884 5885 5886

		continue;
next:
5887
		list_move_tail(&p->se.group_node, tasks);
5888
	}
5889

5890
	/*
5891 5892 5893
	 * 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().
5894
	 */
5895
	schedstat_add(env->sd, lb_gained[env->idle], detached);
5896

5897 5898 5899 5900 5901 5902 5903 5904 5905 5906 5907 5908
	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);
	activate_task(rq, p, 0);
5909
	p->on_rq = TASK_ON_RQ_QUEUED;
5910 5911 5912 5913 5914 5915 5916 5917 5918 5919 5920 5921 5922 5923 5924 5925 5926 5927 5928 5929 5930 5931 5932 5933 5934 5935 5936 5937
	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)
{
	raw_spin_lock(&rq->lock);
	attach_task(rq, p);
	raw_spin_unlock(&rq->lock);
}

/*
 * 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;

	raw_spin_lock(&env->dst_rq->lock);

	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
		list_del_init(&p->se.group_node);
5938

5939 5940 5941 5942
		attach_task(env->dst_rq, p);
	}

	raw_spin_unlock(&env->dst_rq->lock);
5943 5944
}

P
Peter Zijlstra 已提交
5945
#ifdef CONFIG_FAIR_GROUP_SCHED
5946
static void update_blocked_averages(int cpu)
5947 5948
{
	struct rq *rq = cpu_rq(cpu);
5949 5950
	struct cfs_rq *cfs_rq;
	unsigned long flags;
5951

5952 5953
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
5954

5955 5956 5957 5958
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
5959
	for_each_leaf_cfs_rq(rq, cfs_rq) {
5960 5961 5962
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
5963

5964 5965 5966
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
			update_tg_load_avg(cfs_rq, 0);
	}
5967
	raw_spin_unlock_irqrestore(&rq->lock, flags);
5968 5969
}

5970
/*
5971
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5972 5973 5974
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
5975
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
5976
{
5977 5978
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
5979
	unsigned long now = jiffies;
5980
	unsigned long load;
5981

5982
	if (cfs_rq->last_h_load_update == now)
5983 5984
		return;

5985 5986 5987 5988 5989 5990 5991
	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;
	}
5992

5993
	if (!se) {
5994
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
5995 5996 5997 5998 5999
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
6000 6001
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
6002 6003 6004 6005
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
6006 6007
}

6008
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
6009
{
6010
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
6011

6012
	update_cfs_rq_h_load(cfs_rq);
6013
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6014
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
6015 6016
}
#else
6017
static inline void update_blocked_averages(int cpu)
6018
{
6019 6020 6021 6022 6023 6024 6025 6026
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
	unsigned long flags;

	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
	raw_spin_unlock_irqrestore(&rq->lock, flags);
6027 6028
}

6029
static unsigned long task_h_load(struct task_struct *p)
6030
{
6031
	return p->se.avg.load_avg;
6032
}
P
Peter Zijlstra 已提交
6033
#endif
6034 6035

/********** Helpers for find_busiest_group ************************/
6036 6037 6038 6039 6040 6041 6042

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

6043 6044 6045 6046 6047 6048 6049
/*
 * 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
6050
	unsigned long load_per_task;
6051
	unsigned long group_capacity;
6052
	unsigned long group_util; /* Total utilization of the group */
6053 6054 6055
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
6056
	enum group_type group_type;
6057
	int group_no_capacity;
6058 6059 6060 6061
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
6062 6063
};

J
Joonsoo Kim 已提交
6064 6065 6066 6067 6068 6069 6070 6071
/*
 * 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 */
	unsigned long total_load;	/* Total load of all groups in sd */
6072
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
6073 6074 6075
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6076
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
6077 6078
};

6079 6080 6081 6082 6083 6084 6085 6086 6087 6088 6089 6090
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,
		.total_load = 0UL,
6091
		.total_capacity = 0UL,
6092 6093
		.busiest_stat = {
			.avg_load = 0UL,
6094 6095
			.sum_nr_running = 0,
			.group_type = group_other,
6096 6097 6098 6099
		},
	};
}

6100 6101 6102
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
6103
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6104 6105
 *
 * Return: The load index.
6106 6107 6108 6109 6110 6111 6112 6113 6114 6115 6116 6117 6118 6119 6120 6121 6122 6123 6124 6125 6126 6127
 */
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;
}

6128
static unsigned long scale_rt_capacity(int cpu)
6129 6130
{
	struct rq *rq = cpu_rq(cpu);
6131
	u64 total, used, age_stamp, avg;
6132
	s64 delta;
6133

6134 6135 6136 6137
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
6138 6139
	age_stamp = READ_ONCE(rq->age_stamp);
	avg = READ_ONCE(rq->rt_avg);
6140
	delta = __rq_clock_broken(rq) - age_stamp;
6141

6142 6143 6144 6145
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
6146

6147
	used = div_u64(avg, total);
6148

6149 6150
	if (likely(used < SCHED_CAPACITY_SCALE))
		return SCHED_CAPACITY_SCALE - used;
6151

6152
	return 1;
6153 6154
}

6155
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6156
{
6157
	unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6158 6159
	struct sched_group *sdg = sd->groups;

6160
	cpu_rq(cpu)->cpu_capacity_orig = capacity;
6161

6162
	capacity *= scale_rt_capacity(cpu);
6163
	capacity >>= SCHED_CAPACITY_SHIFT;
6164

6165 6166
	if (!capacity)
		capacity = 1;
6167

6168 6169
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
6170 6171
}

6172
void update_group_capacity(struct sched_domain *sd, int cpu)
6173 6174 6175
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
6176
	unsigned long capacity;
6177 6178 6179 6180
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
6181
	sdg->sgc->next_update = jiffies + interval;
6182 6183

	if (!child) {
6184
		update_cpu_capacity(sd, cpu);
6185 6186 6187
		return;
	}

6188
	capacity = 0;
6189

P
Peter Zijlstra 已提交
6190 6191 6192 6193 6194 6195
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

6196
		for_each_cpu(cpu, sched_group_cpus(sdg)) {
6197
			struct sched_group_capacity *sgc;
6198
			struct rq *rq = cpu_rq(cpu);
6199

6200
			/*
6201
			 * build_sched_domains() -> init_sched_groups_capacity()
6202 6203 6204
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
6205 6206
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
6207
			 *
6208
			 * This avoids capacity from being 0 and
6209 6210 6211
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
6212
				capacity += capacity_of(cpu);
6213 6214
				continue;
			}
6215

6216 6217
			sgc = rq->sd->groups->sgc;
			capacity += sgc->capacity;
6218
		}
P
Peter Zijlstra 已提交
6219 6220 6221 6222 6223 6224 6225 6226
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
6227
			capacity += group->sgc->capacity;
P
Peter Zijlstra 已提交
6228 6229 6230
			group = group->next;
		} while (group != child->groups);
	}
6231

6232
	sdg->sgc->capacity = capacity;
6233 6234
}

6235
/*
6236 6237 6238
 * 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
6239 6240
 */
static inline int
6241
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6242
{
6243 6244
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
6245 6246
}

6247 6248 6249 6250 6251 6252 6253 6254 6255 6256 6257 6258 6259 6260 6261 6262
/*
 * Group imbalance indicates (and tries to solve) the problem where balancing
 * groups is inadequate due to tsk_cpus_allowed() constraints.
 *
 * 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.
 * Something like:
 *
 * 	{ 0 1 2 3 } { 4 5 6 7 }
 * 	        *     * * *
 *
 * 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
 * cpu 3 and leave one of the cpus in the second group unused.
 *
 * The current solution to this issue is detecting the skew in the first group
6263 6264
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
6265 6266
 *
 * When this is so detected; this group becomes a candidate for busiest; see
6267
 * update_sd_pick_busiest(). And calculate_imbalance() and
6268
 * find_busiest_group() avoid some of the usual balance conditions to allow it
6269 6270 6271 6272 6273 6274 6275
 * 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.
 */

6276
static inline int sg_imbalanced(struct sched_group *group)
6277
{
6278
	return group->sgc->imbalance;
6279 6280
}

6281
/*
6282 6283 6284
 * 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
6285 6286
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
6287 6288 6289 6290 6291
 * 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.
6292
 */
6293 6294
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6295
{
6296 6297
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
6298

6299
	if ((sgs->group_capacity * 100) >
6300
			(sgs->group_util * env->sd->imbalance_pct))
6301
		return true;
6302

6303 6304 6305 6306 6307 6308 6309 6310 6311 6312 6313 6314 6315 6316 6317 6318
	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;
6319

6320
	if ((sgs->group_capacity * 100) <
6321
			(sgs->group_util * env->sd->imbalance_pct))
6322
		return true;
6323

6324
	return false;
6325 6326
}

6327 6328 6329
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
6330
{
6331
	if (sgs->group_no_capacity)
6332 6333 6334 6335 6336 6337 6338 6339
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

6340 6341
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6342
 * @env: The load balancing environment.
6343 6344 6345 6346
 * @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.
6347
 * @overload: Indicate more than one runnable task for any CPU.
6348
 */
6349 6350
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
6351 6352
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
6353
{
6354
	unsigned long load;
6355
	int i;
6356

6357 6358
	memset(sgs, 0, sizeof(*sgs));

6359
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6360 6361 6362
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
6363
		if (local_group)
6364
			load = target_load(i, load_idx);
6365
		else
6366 6367 6368
			load = source_load(i, load_idx);

		sgs->group_load += load;
6369
		sgs->group_util += cpu_util(i);
6370
		sgs->sum_nr_running += rq->cfs.h_nr_running;
6371 6372 6373 6374

		if (rq->nr_running > 1)
			*overload = true;

6375 6376 6377 6378
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
6379
		sgs->sum_weighted_load += weighted_cpuload(i);
6380 6381
		if (idle_cpu(i))
			sgs->idle_cpus++;
6382 6383
	}

6384 6385
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
6386
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6387

6388
	if (sgs->sum_nr_running)
6389
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6390

6391
	sgs->group_weight = group->group_weight;
6392

6393
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
6394
	sgs->group_type = group_classify(group, sgs);
6395 6396
}

6397 6398
/**
 * update_sd_pick_busiest - return 1 on busiest group
6399
 * @env: The load balancing environment.
6400 6401
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
6402
 * @sgs: sched_group statistics
6403 6404 6405
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
6406 6407 6408
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
6409
 */
6410
static bool update_sd_pick_busiest(struct lb_env *env,
6411 6412
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
6413
				   struct sg_lb_stats *sgs)
6414
{
6415
	struct sg_lb_stats *busiest = &sds->busiest_stat;
6416

6417
	if (sgs->group_type > busiest->group_type)
6418 6419
		return true;

6420 6421 6422 6423 6424 6425 6426 6427
	if (sgs->group_type < busiest->group_type)
		return false;

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

	/* This is the busiest node in its class. */
	if (!(env->sd->flags & SD_ASYM_PACKING))
6428 6429 6430 6431 6432 6433 6434
		return true;

	/*
	 * ASYM_PACKING needs to move all the work to the lowest
	 * numbered CPUs in the group, therefore mark all groups
	 * higher than ourself as busy.
	 */
6435
	if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6436 6437 6438 6439 6440 6441 6442 6443 6444 6445
		if (!sds->busiest)
			return true;

		if (group_first_cpu(sds->busiest) > group_first_cpu(sg))
			return true;
	}

	return false;
}

6446 6447 6448 6449 6450 6451 6452 6453 6454 6455 6456 6457 6458 6459 6460 6461 6462 6463 6464 6465 6466 6467 6468 6469 6470 6471 6472 6473 6474 6475
#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 */

6476
/**
6477
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6478
 * @env: The load balancing environment.
6479 6480
 * @sds: variable to hold the statistics for this sched_domain.
 */
6481
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6482
{
6483 6484
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
6485
	struct sg_lb_stats tmp_sgs;
6486
	int load_idx, prefer_sibling = 0;
6487
	bool overload = false;
6488 6489 6490 6491

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

6492
	load_idx = get_sd_load_idx(env->sd, env->idle);
6493 6494

	do {
J
Joonsoo Kim 已提交
6495
		struct sg_lb_stats *sgs = &tmp_sgs;
6496 6497
		int local_group;

6498
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
6499 6500 6501
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
6502 6503

			if (env->idle != CPU_NEWLY_IDLE ||
6504 6505
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
6506
		}
6507

6508 6509
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
6510

6511 6512 6513
		if (local_group)
			goto next_group;

6514 6515
		/*
		 * In case the child domain prefers tasks go to siblings
6516
		 * first, lower the sg capacity so that we'll try
6517 6518
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
6519 6520 6521 6522
		 * 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).
6523
		 */
6524
		if (prefer_sibling && sds->local &&
6525 6526 6527
		    group_has_capacity(env, &sds->local_stat) &&
		    (sgs->sum_nr_running > 1)) {
			sgs->group_no_capacity = 1;
6528
			sgs->group_type = group_classify(sg, sgs);
6529
		}
6530

6531
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6532
			sds->busiest = sg;
J
Joonsoo Kim 已提交
6533
			sds->busiest_stat = *sgs;
6534 6535
		}

6536 6537 6538
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
6539
		sds->total_capacity += sgs->group_capacity;
6540

6541
		sg = sg->next;
6542
	} while (sg != env->sd->groups);
6543 6544 6545

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6546 6547 6548 6549 6550 6551 6552

	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;
	}

6553 6554 6555 6556 6557 6558 6559 6560 6561 6562 6563 6564 6565 6566 6567 6568 6569 6570 6571
}

/**
 * check_asym_packing - Check to see if the group is packed into the
 *			sched doman.
 *
 * 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.
 *
6572
 * Return: 1 when packing is required and a task should be moved to
6573 6574
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
6575
 * @env: The load balancing environment.
6576 6577
 * @sds: Statistics of the sched_domain which is to be packed
 */
6578
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6579 6580 6581
{
	int busiest_cpu;

6582
	if (!(env->sd->flags & SD_ASYM_PACKING))
6583 6584 6585 6586 6587 6588
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
6589
	if (env->dst_cpu > busiest_cpu)
6590 6591
		return 0;

6592
	env->imbalance = DIV_ROUND_CLOSEST(
6593
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6594
		SCHED_CAPACITY_SCALE);
6595

6596
	return 1;
6597 6598 6599 6600 6601 6602
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
6603
 * @env: The load balancing environment.
6604 6605
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
6606 6607
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6608
{
6609
	unsigned long tmp, capa_now = 0, capa_move = 0;
6610
	unsigned int imbn = 2;
6611
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
6612
	struct sg_lb_stats *local, *busiest;
6613

J
Joonsoo Kim 已提交
6614 6615
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6616

J
Joonsoo Kim 已提交
6617 6618 6619 6620
	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;
6621

J
Joonsoo Kim 已提交
6622
	scaled_busy_load_per_task =
6623
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6624
		busiest->group_capacity;
J
Joonsoo Kim 已提交
6625

6626 6627
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
6628
		env->imbalance = busiest->load_per_task;
6629 6630 6631 6632 6633
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
6634
	 * however we may be able to increase total CPU capacity used by
6635 6636 6637
	 * moving them.
	 */

6638
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
6639
			min(busiest->load_per_task, busiest->avg_load);
6640
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
6641
			min(local->load_per_task, local->avg_load);
6642
	capa_now /= SCHED_CAPACITY_SCALE;
6643 6644

	/* Amount of load we'd subtract */
6645
	if (busiest->avg_load > scaled_busy_load_per_task) {
6646
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
6647
			    min(busiest->load_per_task,
6648
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
6649
	}
6650 6651

	/* Amount of load we'd add */
6652
	if (busiest->avg_load * busiest->group_capacity <
6653
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6654 6655
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
6656
	} else {
6657
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6658
		      local->group_capacity;
J
Joonsoo Kim 已提交
6659
	}
6660
	capa_move += local->group_capacity *
6661
		    min(local->load_per_task, local->avg_load + tmp);
6662
	capa_move /= SCHED_CAPACITY_SCALE;
6663 6664

	/* Move if we gain throughput */
6665
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
6666
		env->imbalance = busiest->load_per_task;
6667 6668 6669 6670 6671
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
6672
 * @env: load balance environment
6673 6674
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
6675
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6676
{
6677
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
6678 6679 6680 6681
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6682

6683
	if (busiest->group_type == group_imbalanced) {
6684 6685 6686 6687
		/*
		 * In the group_imb case we cannot rely on group-wide averages
		 * to ensure cpu-load equilibrium, look at wider averages. XXX
		 */
J
Joonsoo Kim 已提交
6688 6689
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
6690 6691
	}

6692 6693 6694
	/*
	 * In the presence of smp nice balancing, certain scenarios can have
	 * max load less than avg load(as we skip the groups at or below
6695
	 * its cpu_capacity, while calculating max_load..)
6696
	 */
6697 6698
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
6699 6700
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
6701 6702
	}

6703 6704 6705 6706 6707
	/*
	 * If there aren't any idle cpus, avoid creating some.
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
6708 6709 6710 6711 6712 6713
		load_above_capacity = busiest->sum_nr_running *
					SCHED_LOAD_SCALE;
		if (load_above_capacity > busiest->group_capacity)
			load_above_capacity -= busiest->group_capacity;
		else
			load_above_capacity = ~0UL;
6714 6715 6716 6717 6718 6719 6720 6721 6722 6723
	}

	/*
	 * We're trying to get all the cpus to the average_load, so we don't
	 * want to push ourselves above the average load, nor do we wish to
	 * reduce the max loaded cpu below the average load. At the same time,
	 * we also don't want to reduce the group load below the group capacity
	 * (so that we can implement power-savings policies etc). Thus we look
	 * for the minimum possible imbalance.
	 */
6724
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6725 6726

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
6727
	env->imbalance = min(
6728 6729
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
6730
	) / SCHED_CAPACITY_SCALE;
6731 6732 6733

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
6734
	 * there is no guarantee that any tasks will be moved so we'll have
6735 6736 6737
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
6738
	if (env->imbalance < busiest->load_per_task)
6739
		return fix_small_imbalance(env, sds);
6740
}
6741

6742 6743 6744 6745 6746 6747 6748 6749 6750 6751 6752 6753
/******* find_busiest_group() helpers end here *********************/

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
 * if there is an imbalance. If there isn't an imbalance, and
 * the user has opted for power-savings, it returns a group whose
 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
 * such a group exists.
 *
 * Also calculates the amount of weighted load which should be moved
 * to restore balance.
 *
6754
 * @env: The load balancing environment.
6755
 *
6756
 * Return:	- The busiest group if imbalance exists.
6757 6758 6759 6760
 *		- If no imbalance and user has opted for power-savings balance,
 *		   return the least loaded group whose CPUs can be
 *		   put to idle by rebalancing its tasks onto our group.
 */
J
Joonsoo Kim 已提交
6761
static struct sched_group *find_busiest_group(struct lb_env *env)
6762
{
J
Joonsoo Kim 已提交
6763
	struct sg_lb_stats *local, *busiest;
6764 6765
	struct sd_lb_stats sds;

6766
	init_sd_lb_stats(&sds);
6767 6768 6769 6770 6771

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
6772
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
6773 6774
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
6775

6776
	/* ASYM feature bypasses nice load balance check */
6777 6778
	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(env, &sds))
6779 6780
		return sds.busiest;

6781
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
6782
	if (!sds.busiest || busiest->sum_nr_running == 0)
6783 6784
		goto out_balanced;

6785 6786
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
6787

P
Peter Zijlstra 已提交
6788 6789
	/*
	 * If the busiest group is imbalanced the below checks don't
6790
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
6791 6792
	 * isn't true due to cpus_allowed constraints and the like.
	 */
6793
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
6794 6795
		goto force_balance;

6796
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6797 6798
	if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
	    busiest->group_no_capacity)
6799 6800
		goto force_balance;

6801
	/*
6802
	 * If the local group is busier than the selected busiest group
6803 6804
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
6805
	if (local->avg_load >= busiest->avg_load)
6806 6807
		goto out_balanced;

6808 6809 6810 6811
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
6812
	if (local->avg_load >= sds.avg_load)
6813 6814
		goto out_balanced;

6815
	if (env->idle == CPU_IDLE) {
6816
		/*
6817 6818 6819 6820 6821
		 * This cpu is idle. If the busiest group is not overloaded
		 * and there is no imbalance between this and busiest group
		 * wrt idle cpus, it is balanced. The imbalance becomes
		 * significant if the diff is greater than 1 otherwise we
		 * might end up to just move the imbalance on another group
6822
		 */
6823 6824
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
6825
			goto out_balanced;
6826 6827 6828 6829 6830
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
6831 6832
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
6833
			goto out_balanced;
6834
	}
6835

6836
force_balance:
6837
	/* Looks like there is an imbalance. Compute it */
6838
	calculate_imbalance(env, &sds);
6839 6840 6841
	return sds.busiest;

out_balanced:
6842
	env->imbalance = 0;
6843 6844 6845 6846 6847 6848
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
6849
static struct rq *find_busiest_queue(struct lb_env *env,
6850
				     struct sched_group *group)
6851 6852
{
	struct rq *busiest = NULL, *rq;
6853
	unsigned long busiest_load = 0, busiest_capacity = 1;
6854 6855
	int i;

6856
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6857
		unsigned long capacity, wl;
6858 6859 6860 6861
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
6862

6863 6864 6865 6866 6867 6868 6869 6870 6871 6872 6873 6874 6875 6876 6877 6878 6879 6880 6881 6882 6883 6884
		/*
		 * 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;

6885
		capacity = capacity_of(i);
6886

6887
		wl = weighted_cpuload(i);
6888

6889 6890
		/*
		 * When comparing with imbalance, use weighted_cpuload()
6891
		 * which is not scaled with the cpu capacity.
6892
		 */
6893 6894 6895

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
6896 6897
			continue;

6898 6899
		/*
		 * For the load comparisons with the other cpu's, consider
6900 6901 6902
		 * the weighted_cpuload() scaled with the cpu capacity, so
		 * that the load can be moved away from the cpu that is
		 * potentially running at a lower capacity.
6903
		 *
6904
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
6905
		 * multiplication to rid ourselves of the division works out
6906 6907
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
6908
		 */
6909
		if (wl * busiest_capacity > busiest_load * capacity) {
6910
			busiest_load = wl;
6911
			busiest_capacity = capacity;
6912 6913 6914 6915 6916 6917 6918 6919 6920 6921 6922 6923 6924 6925
			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

/* Working cpumask for load_balance and load_balance_newidle. */
6926
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6927

6928
static int need_active_balance(struct lb_env *env)
6929
{
6930 6931 6932
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
6933 6934 6935 6936 6937 6938

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
6939
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6940
			return 1;
6941 6942
	}

6943 6944 6945 6946 6947 6948 6949 6950 6951 6952 6953 6954 6955
	/*
	 * 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;
	}

6956 6957 6958
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

6959 6960
static int active_load_balance_cpu_stop(void *data);

6961 6962 6963 6964 6965 6966 6967 6968 6969 6970 6971 6972 6973 6974 6975 6976 6977 6978 6979 6980 6981 6982 6983 6984 6985 6986 6987 6988 6989 6990 6991
static int should_we_balance(struct lb_env *env)
{
	struct sched_group *sg = env->sd->groups;
	struct cpumask *sg_cpus, *sg_mask;
	int cpu, balance_cpu = -1;

	/*
	 * In the newly idle case, we will allow all the cpu's
	 * to do the newly idle load balance.
	 */
	if (env->idle == CPU_NEWLY_IDLE)
		return 1;

	sg_cpus = sched_group_cpus(sg);
	sg_mask = sched_group_mask(sg);
	/* Try to find first idle cpu */
	for_each_cpu_and(cpu, sg_cpus, env->cpus) {
		if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
			continue;

		balance_cpu = cpu;
		break;
	}

	if (balance_cpu == -1)
		balance_cpu = group_balance_cpu(sg);

	/*
	 * First idle cpu or the first cpu(busiest) in this sched group
	 * is eligible for doing load balancing at this and above domains.
	 */
6992
	return balance_cpu == env->dst_cpu;
6993 6994
}

6995 6996 6997 6998 6999 7000
/*
 * 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,
7001
			int *continue_balancing)
7002
{
7003
	int ld_moved, cur_ld_moved, active_balance = 0;
7004
	struct sched_domain *sd_parent = sd->parent;
7005 7006 7007
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
7008
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7009

7010 7011
	struct lb_env env = {
		.sd		= sd,
7012 7013
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
7014
		.dst_grpmask    = sched_group_cpus(sd->groups),
7015
		.idle		= idle,
7016
		.loop_break	= sched_nr_migrate_break,
7017
		.cpus		= cpus,
7018
		.fbq_type	= all,
7019
		.tasks		= LIST_HEAD_INIT(env.tasks),
7020 7021
	};

7022 7023 7024 7025
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
7026
	if (idle == CPU_NEWLY_IDLE)
7027 7028
		env.dst_grpmask = NULL;

7029 7030 7031 7032 7033
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
7034 7035
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
7036
		goto out_balanced;
7037
	}
7038

7039
	group = find_busiest_group(&env);
7040 7041 7042 7043 7044
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

7045
	busiest = find_busiest_queue(&env, group);
7046 7047 7048 7049 7050
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

7051
	BUG_ON(busiest == env.dst_rq);
7052

7053
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7054

7055 7056 7057
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

7058 7059 7060 7061 7062 7063 7064 7065
	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.
		 */
7066
		env.flags |= LBF_ALL_PINNED;
7067
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
7068

7069
more_balance:
7070
		raw_spin_lock_irqsave(&busiest->lock, flags);
7071 7072 7073 7074 7075

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
7076
		cur_ld_moved = detach_tasks(&env);
7077 7078

		/*
7079 7080 7081 7082 7083
		 * 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.
7084
		 */
7085 7086 7087 7088 7089 7090 7091 7092

		raw_spin_unlock(&busiest->lock);

		if (cur_ld_moved) {
			attach_tasks(&env);
			ld_moved += cur_ld_moved;
		}

7093
		local_irq_restore(flags);
7094

7095 7096 7097 7098 7099
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

7100 7101 7102 7103 7104 7105 7106 7107 7108 7109 7110 7111 7112 7113 7114 7115 7116 7117 7118
		/*
		 * 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
		 * iterate on same src_cpu is dependent on number of cpus in our
		 * 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.
		 */
7119
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7120

7121 7122 7123
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

7124
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
7125
			env.dst_cpu	 = env.new_dst_cpu;
7126
			env.flags	&= ~LBF_DST_PINNED;
7127 7128
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
7129

7130 7131 7132 7133 7134 7135
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
7136

7137 7138 7139 7140
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
7141
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7142

7143
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7144 7145 7146
				*group_imbalance = 1;
		}

7147
		/* All tasks on this runqueue were pinned by CPU affinity */
7148
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
7149
			cpumask_clear_cpu(cpu_of(busiest), cpus);
7150 7151 7152
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
7153
				goto redo;
7154
			}
7155
			goto out_all_pinned;
7156 7157 7158 7159 7160
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
7161 7162 7163 7164 7165 7166 7167 7168
		/*
		 * 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++;
7169

7170
		if (need_active_balance(&env)) {
7171 7172
			raw_spin_lock_irqsave(&busiest->lock, flags);

7173 7174 7175
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
7176 7177
			 */
			if (!cpumask_test_cpu(this_cpu,
7178
					tsk_cpus_allowed(busiest->curr))) {
7179 7180
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
7181
				env.flags |= LBF_ALL_PINNED;
7182 7183 7184
				goto out_one_pinned;
			}

7185 7186 7187 7188 7189
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
7190 7191 7192 7193 7194 7195
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
7196

7197
			if (active_balance) {
7198 7199 7200
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
7201
			}
7202 7203 7204 7205 7206 7207 7208 7209 7210 7211 7212 7213 7214 7215 7216 7217 7218 7219

			/*
			 * We've kicked active balancing, reset the failure
			 * counter.
			 */
			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
7220
		 * detach_tasks).
7221 7222 7223 7224 7225 7226 7227 7228
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
7229 7230 7231 7232 7233 7234 7235 7236 7237 7238 7239 7240 7241 7242 7243 7244 7245
	/*
	 * 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.
	 */
7246 7247 7248 7249 7250 7251
	schedstat_inc(sd, lb_balanced[idle]);

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
7252
	if (((env.flags & LBF_ALL_PINNED) &&
7253
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
7254 7255 7256
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

7257
	ld_moved = 0;
7258 7259 7260 7261
out:
	return ld_moved;
}

7262 7263 7264 7265 7266 7267 7268 7269 7270 7271 7272 7273 7274 7275 7276 7277 7278 7279 7280 7281 7282 7283 7284 7285 7286 7287 7288
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
update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
{
	unsigned long interval, next;

	interval = get_sd_balance_interval(sd, cpu_busy);
	next = sd->last_balance + interval;

	if (time_after(*next_balance, next))
		*next_balance = next;
}

7289 7290 7291 7292
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
7293
static int idle_balance(struct rq *this_rq)
7294
{
7295 7296
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
7297 7298
	struct sched_domain *sd;
	int pulled_task = 0;
7299
	u64 curr_cost = 0;
7300

7301 7302 7303 7304 7305 7306
	/*
	 * 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);

7307 7308
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
7309 7310 7311 7312 7313 7314
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
			update_next_balance(sd, 0, &next_balance);
		rcu_read_unlock();

7315
		goto out;
7316
	}
7317

7318 7319
	raw_spin_unlock(&this_rq->lock);

7320
	update_blocked_averages(this_cpu);
7321
	rcu_read_lock();
7322
	for_each_domain(this_cpu, sd) {
7323
		int continue_balancing = 1;
7324
		u64 t0, domain_cost;
7325 7326 7327 7328

		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

7329 7330
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
			update_next_balance(sd, 0, &next_balance);
7331
			break;
7332
		}
7333

7334
		if (sd->flags & SD_BALANCE_NEWIDLE) {
7335 7336
			t0 = sched_clock_cpu(this_cpu);

7337
			pulled_task = load_balance(this_cpu, this_rq,
7338 7339
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
7340 7341 7342 7343 7344 7345

			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;
7346
		}
7347

7348
		update_next_balance(sd, 0, &next_balance);
7349 7350 7351 7352 7353 7354

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
7355 7356
			break;
	}
7357
	rcu_read_unlock();
7358 7359 7360

	raw_spin_lock(&this_rq->lock);

7361 7362 7363
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

7364
	/*
7365 7366 7367
	 * 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.
7368
	 */
7369
	if (this_rq->cfs.h_nr_running && !pulled_task)
7370
		pulled_task = 1;
7371

7372 7373 7374
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
7375
		this_rq->next_balance = next_balance;
7376

7377
	/* Is there a task of a high priority class? */
7378
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7379 7380
		pulled_task = -1;

7381
	if (pulled_task)
7382 7383
		this_rq->idle_stamp = 0;

7384
	return pulled_task;
7385 7386 7387
}

/*
7388 7389 7390 7391
 * active_load_balance_cpu_stop is run by cpu stopper. It pushes
 * 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.
7392
 */
7393
static int active_load_balance_cpu_stop(void *data)
7394
{
7395 7396
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
7397
	int target_cpu = busiest_rq->push_cpu;
7398
	struct rq *target_rq = cpu_rq(target_cpu);
7399
	struct sched_domain *sd;
7400
	struct task_struct *p = NULL;
7401 7402 7403 7404 7405 7406 7407

	raw_spin_lock_irq(&busiest_rq->lock);

	/* make sure the requested cpu hasn't gone down in the meantime */
	if (unlikely(busiest_cpu != smp_processor_id() ||
		     !busiest_rq->active_balance))
		goto out_unlock;
7408 7409 7410

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
7411
		goto out_unlock;
7412 7413 7414 7415 7416 7417 7418 7419 7420

	/*
	 * This condition is "impossible", if it occurs
	 * we need to fix it. Originally reported by
	 * Bjorn Helgaas on a 128-cpu setup.
	 */
	BUG_ON(busiest_rq == target_rq);

	/* Search for an sd spanning us and the target CPU. */
7421
	rcu_read_lock();
7422 7423 7424 7425 7426 7427 7428
	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)) {
7429 7430
		struct lb_env env = {
			.sd		= sd,
7431 7432 7433 7434
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
7435 7436 7437
			.idle		= CPU_IDLE,
		};

7438 7439
		schedstat_inc(sd, alb_count);

7440 7441
		p = detach_one_task(&env);
		if (p)
7442 7443 7444 7445
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
7446
	rcu_read_unlock();
7447 7448
out_unlock:
	busiest_rq->active_balance = 0;
7449 7450 7451 7452 7453 7454 7455
	raw_spin_unlock(&busiest_rq->lock);

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

7456
	return 0;
7457 7458
}

7459 7460 7461 7462 7463
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

7464
#ifdef CONFIG_NO_HZ_COMMON
7465 7466 7467 7468 7469 7470
/*
 * 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.
 */
7471
static struct {
7472
	cpumask_var_t idle_cpus_mask;
7473
	atomic_t nr_cpus;
7474 7475
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
7476

7477
static inline int find_new_ilb(void)
7478
{
7479
	int ilb = cpumask_first(nohz.idle_cpus_mask);
7480

7481 7482 7483 7484
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
7485 7486
}

7487 7488 7489 7490 7491
/*
 * 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).
 */
7492
static void nohz_balancer_kick(void)
7493 7494 7495 7496 7497
{
	int ilb_cpu;

	nohz.next_balance++;

7498
	ilb_cpu = find_new_ilb();
7499

7500 7501
	if (ilb_cpu >= nr_cpu_ids)
		return;
7502

7503
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7504 7505 7506 7507 7508 7509 7510 7511
		return;
	/*
	 * Use smp_send_reschedule() instead of resched_cpu().
	 * This way we generate a sched IPI on the target cpu which
	 * is idle. And the softirq performing nohz idle load balance
	 * will be run before returning from the IPI.
	 */
	smp_send_reschedule(ilb_cpu);
7512 7513 7514
	return;
}

7515
static inline void nohz_balance_exit_idle(int cpu)
7516 7517
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7518 7519 7520 7521 7522 7523 7524
		/*
		 * Completely isolated CPUs don't ever set, so we must test.
		 */
		if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
			cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
			atomic_dec(&nohz.nr_cpus);
		}
7525 7526 7527 7528
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

7529 7530 7531
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
7532
	int cpu = smp_processor_id();
7533 7534

	rcu_read_lock();
7535
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7536 7537 7538 7539 7540

	if (!sd || !sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 0;

7541
	atomic_inc(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7542
unlock:
7543 7544 7545 7546 7547 7548
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
7549
	int cpu = smp_processor_id();
7550 7551

	rcu_read_lock();
7552
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7553 7554 7555 7556 7557

	if (!sd || sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 1;

7558
	atomic_dec(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7559
unlock:
7560 7561 7562
	rcu_read_unlock();
}

7563
/*
7564
 * This routine will record that the cpu is going idle with tick stopped.
7565
 * This info will be used in performing idle load balancing in the future.
7566
 */
7567
void nohz_balance_enter_idle(int cpu)
7568
{
7569 7570 7571 7572 7573 7574
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

7575 7576
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
7577

7578 7579 7580 7581 7582 7583
	/*
	 * If we're a completely isolated CPU, we don't play.
	 */
	if (on_null_domain(cpu_rq(cpu)))
		return;

7584 7585 7586
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7587
}
7588

7589
static int sched_ilb_notifier(struct notifier_block *nfb,
7590 7591 7592 7593
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
7594
		nohz_balance_exit_idle(smp_processor_id());
7595 7596 7597 7598 7599
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
7600 7601 7602 7603
#endif

static DEFINE_SPINLOCK(balancing);

7604 7605 7606 7607
/*
 * 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.
 */
7608
void update_max_interval(void)
7609 7610 7611 7612
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

7613 7614 7615 7616
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
7617
 * Balancing parameters are set up in init_sched_domains.
7618
 */
7619
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7620
{
7621
	int continue_balancing = 1;
7622
	int cpu = rq->cpu;
7623
	unsigned long interval;
7624
	struct sched_domain *sd;
7625 7626 7627
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
7628 7629
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
7630

7631
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
7632

7633
	rcu_read_lock();
7634
	for_each_domain(cpu, sd) {
7635 7636 7637 7638 7639 7640 7641 7642 7643 7644 7645 7646
		/*
		 * 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;

7647 7648 7649
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

7650 7651 7652 7653 7654 7655 7656 7657 7658 7659 7660
		/*
		 * 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;
		}

7661
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7662 7663 7664 7665 7666 7667 7668 7669

		need_serialize = sd->flags & SD_SERIALIZE;
		if (need_serialize) {
			if (!spin_trylock(&balancing))
				goto out;
		}

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
7670
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7671
				/*
7672
				 * The LBF_DST_PINNED logic could have changed
7673 7674
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
7675
				 */
7676
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7677 7678
			}
			sd->last_balance = jiffies;
7679
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7680 7681 7682 7683 7684 7685 7686 7687
		}
		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;
		}
7688 7689
	}
	if (need_decay) {
7690
		/*
7691 7692
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
7693
		 */
7694 7695
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
7696
	}
7697
	rcu_read_unlock();
7698 7699 7700 7701 7702 7703

	/*
	 * 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.
	 */
7704
	if (likely(update_next_balance)) {
7705
		rq->next_balance = next_balance;
7706 7707 7708 7709 7710 7711 7712 7713 7714 7715 7716 7717 7718 7719

#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
	}
7720 7721
}

7722
#ifdef CONFIG_NO_HZ_COMMON
7723
/*
7724
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7725 7726
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
7727
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7728
{
7729
	int this_cpu = this_rq->cpu;
7730 7731
	struct rq *rq;
	int balance_cpu;
7732 7733 7734
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
7735

7736 7737 7738
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
7739 7740

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7741
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7742 7743 7744 7745 7746 7747 7748
			continue;

		/*
		 * If this cpu gets work to do, stop the load balancing
		 * work being done for other cpus. Next load
		 * balancing owner will pick it up.
		 */
7749
		if (need_resched())
7750 7751
			break;

V
Vincent Guittot 已提交
7752 7753
		rq = cpu_rq(balance_cpu);

7754 7755 7756 7757 7758 7759 7760 7761 7762 7763 7764
		/*
		 * If time for next balance is due,
		 * do the balance.
		 */
		if (time_after_eq(jiffies, rq->next_balance)) {
			raw_spin_lock_irq(&rq->lock);
			update_rq_clock(rq);
			update_idle_cpu_load(rq);
			raw_spin_unlock_irq(&rq->lock);
			rebalance_domains(rq, CPU_IDLE);
		}
7765

7766 7767 7768 7769
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
7770
	}
7771 7772 7773 7774 7775 7776 7777 7778

	/*
	 * 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;
7779 7780
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7781 7782 7783
}

/*
7784
 * Current heuristic for kicking the idle load balancer in the presence
7785
 * of an idle cpu in the system.
7786
 *   - This rq has more than one task.
7787 7788 7789 7790
 *   - 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.
7791 7792
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
7793
 */
7794
static inline bool nohz_kick_needed(struct rq *rq)
7795 7796
{
	unsigned long now = jiffies;
7797
	struct sched_domain *sd;
7798
	struct sched_group_capacity *sgc;
7799
	int nr_busy, cpu = rq->cpu;
7800
	bool kick = false;
7801

7802
	if (unlikely(rq->idle_balance))
7803
		return false;
7804

7805 7806 7807 7808
       /*
	* 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.
	*/
7809
	set_cpu_sd_state_busy();
7810
	nohz_balance_exit_idle(cpu);
7811 7812 7813 7814 7815 7816

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
7817
		return false;
7818 7819

	if (time_before(now, nohz.next_balance))
7820
		return false;
7821

7822
	if (rq->nr_running >= 2)
7823
		return true;
7824

7825
	rcu_read_lock();
7826 7827
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
	if (sd) {
7828 7829
		sgc = sd->groups->sgc;
		nr_busy = atomic_read(&sgc->nr_busy_cpus);
7830

7831 7832 7833 7834 7835
		if (nr_busy > 1) {
			kick = true;
			goto unlock;
		}

7836
	}
7837

7838 7839 7840 7841 7842 7843 7844 7845
	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
			kick = true;
			goto unlock;
		}
	}
7846

7847
	sd = rcu_dereference(per_cpu(sd_asym, cpu));
7848
	if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
7849 7850 7851 7852
				  sched_domain_span(sd)) < cpu)) {
		kick = true;
		goto unlock;
	}
7853

7854
unlock:
7855
	rcu_read_unlock();
7856
	return kick;
7857 7858
}
#else
7859
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7860 7861 7862 7863 7864 7865
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
7866 7867
static void run_rebalance_domains(struct softirq_action *h)
{
7868
	struct rq *this_rq = this_rq();
7869
	enum cpu_idle_type idle = this_rq->idle_balance ?
7870 7871 7872
						CPU_IDLE : CPU_NOT_IDLE;

	/*
7873
	 * If this cpu has a pending nohz_balance_kick, then do the
7874
	 * balancing on behalf of the other idle cpus whose ticks are
7875 7876 7877 7878
	 * stopped. Do nohz_idle_balance *before* rebalance_domains to
	 * give the idle cpus a chance to load balance. Else we may
	 * load balance only within the local sched_domain hierarchy
	 * and abort nohz_idle_balance altogether if we pull some load.
7879
	 */
7880
	nohz_idle_balance(this_rq, idle);
7881
	rebalance_domains(this_rq, idle);
7882 7883 7884 7885 7886
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
7887
void trigger_load_balance(struct rq *rq)
7888 7889
{
	/* Don't need to rebalance while attached to NULL domain */
7890 7891 7892 7893
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
7894
		raise_softirq(SCHED_SOFTIRQ);
7895
#ifdef CONFIG_NO_HZ_COMMON
7896
	if (nohz_kick_needed(rq))
7897
		nohz_balancer_kick();
7898
#endif
7899 7900
}

7901 7902 7903
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
7904 7905

	update_runtime_enabled(rq);
7906 7907 7908 7909 7910
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
7911 7912 7913

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
7914 7915
}

7916
#endif /* CONFIG_SMP */
7917

7918 7919 7920
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
7921
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
7922 7923 7924 7925 7926 7927
{
	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
7928
		entity_tick(cfs_rq, se, queued);
7929
	}
7930

7931
	if (static_branch_unlikely(&sched_numa_balancing))
7932
		task_tick_numa(rq, curr);
7933 7934 7935
}

/*
P
Peter Zijlstra 已提交
7936 7937 7938
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
7939
 */
P
Peter Zijlstra 已提交
7940
static void task_fork_fair(struct task_struct *p)
7941
{
7942 7943
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
7944
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
7945 7946 7947
	struct rq *rq = this_rq();
	unsigned long flags;

7948
	raw_spin_lock_irqsave(&rq->lock, flags);
7949

7950 7951
	update_rq_clock(rq);

7952 7953 7954
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

7955 7956 7957 7958 7959 7960 7961 7962 7963
	/*
	 * Not only the cpu but also the task_group of the parent might have
	 * been changed after parent->se.parent,cfs_rq were copied to
	 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
	 * of child point to valid ones.
	 */
	rcu_read_lock();
	__set_task_cpu(p, this_cpu);
	rcu_read_unlock();
7964

7965
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
7966

7967 7968
	if (curr)
		se->vruntime = curr->vruntime;
7969
	place_entity(cfs_rq, se, 1);
7970

P
Peter Zijlstra 已提交
7971
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
7972
		/*
7973 7974 7975
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
7976
		swap(curr->vruntime, se->vruntime);
7977
		resched_curr(rq);
7978
	}
7979

7980 7981
	se->vruntime -= cfs_rq->min_vruntime;

7982
	raw_spin_unlock_irqrestore(&rq->lock, flags);
7983 7984
}

7985 7986 7987 7988
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
7989 7990
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
7991
{
7992
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
7993 7994
		return;

7995 7996 7997 7998 7999
	/*
	 * 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
8000
	if (rq->curr == p) {
8001
		if (p->prio > oldprio)
8002
			resched_curr(rq);
8003
	} else
8004
		check_preempt_curr(rq, p, 0);
8005 8006
}

8007
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
8008 8009 8010 8011
{
	struct sched_entity *se = &p->se;

	/*
8012 8013 8014 8015 8016 8017 8018 8019 8020 8021
	 * 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
8022
	 *
8023 8024 8025 8026
	 * - 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
8027
	 */
8028 8029 8030 8031 8032 8033 8034 8035 8036 8037 8038 8039
	if (!se->sum_exec_runtime || p->state == TASK_WAKING)
		return true;

	return false;
}

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)) {
P
Peter Zijlstra 已提交
8040 8041 8042 8043 8044 8045 8046
		/*
		 * 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;
	}
8047

8048
	/* Catch up with the cfs_rq and remove our load when we leave */
8049
	detach_entity_load_avg(cfs_rq, se);
P
Peter Zijlstra 已提交
8050 8051
}

8052
static void attach_task_cfs_rq(struct task_struct *p)
8053
{
8054
	struct sched_entity *se = &p->se;
8055
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
8056 8057

#ifdef CONFIG_FAIR_GROUP_SCHED
8058 8059 8060 8061 8062 8063
	/*
	 * 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
8064

8065
	/* Synchronize task with its cfs_rq */
8066 8067 8068 8069 8070
	attach_entity_load_avg(cfs_rq, se);

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
8071

8072 8073 8074 8075 8076 8077 8078 8079
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);
8080

8081
	if (task_on_rq_queued(p)) {
8082
		/*
8083 8084 8085
		 * 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.
8086
		 */
8087 8088 8089 8090
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
8091
	}
8092 8093
}

8094 8095 8096 8097 8098 8099 8100 8101 8102
/* 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;

8103 8104 8105 8106 8107 8108 8109
	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);
	}
8110 8111
}

8112 8113 8114 8115 8116 8117 8118
void init_cfs_rq(struct cfs_rq *cfs_rq)
{
	cfs_rq->tasks_timeline = RB_ROOT;
	cfs_rq->min_vruntime = (u64)(-(1LL << 20));
#ifndef CONFIG_64BIT
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
8119
#ifdef CONFIG_SMP
8120 8121
	atomic_long_set(&cfs_rq->removed_load_avg, 0);
	atomic_long_set(&cfs_rq->removed_util_avg, 0);
8122
#endif
8123 8124
}

P
Peter Zijlstra 已提交
8125
#ifdef CONFIG_FAIR_GROUP_SCHED
8126
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
8127
{
8128
	detach_task_cfs_rq(p);
8129
	set_task_rq(p, task_cpu(p));
8130 8131 8132 8133 8134

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
8135
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
8136
}
8137 8138 8139 8140 8141 8142 8143 8144 8145 8146

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]);
8147 8148 8149
		if (tg->se) {
			if (tg->se[i])
				remove_entity_load_avg(tg->se[i]);
8150
			kfree(tg->se[i]);
8151
		}
8152 8153 8154 8155 8156 8157 8158 8159 8160 8161 8162 8163 8164 8165 8166 8167 8168 8169 8170 8171 8172 8173 8174 8175 8176 8177 8178 8179 8180 8181 8182 8183 8184 8185 8186 8187
	}

	kfree(tg->cfs_rq);
	kfree(tg->se);
}

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
	struct cfs_rq *cfs_rq;
	struct sched_entity *se;
	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]);
8188
		init_entity_runnable_average(se);
8189 8190 8191 8192 8193 8194 8195 8196 8197 8198 8199 8200 8201 8202 8203 8204 8205 8206 8207 8208 8209 8210 8211 8212 8213 8214 8215 8216 8217 8218 8219 8220 8221 8222 8223 8224 8225 8226 8227 8228 8229 8230 8231 8232
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

void unregister_fair_sched_group(struct task_group *tg, int cpu)
{
	struct rq *rq = cpu_rq(cpu);
	unsigned long flags;

	/*
	* 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)
		return;

	raw_spin_lock_irqsave(&rq->lock, flags);
	list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
	raw_spin_unlock_irqrestore(&rq->lock, flags);
}

void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
			struct sched_entity *se, int cpu,
			struct sched_entity *parent)
{
	struct rq *rq = cpu_rq(cpu);

	cfs_rq->tg = tg;
	cfs_rq->rq = rq;
	init_cfs_rq_runtime(cfs_rq);

	tg->cfs_rq[cpu] = cfs_rq;
	tg->se[cpu] = se;

	/* se could be NULL for root_task_group */
	if (!se)
		return;

P
Peter Zijlstra 已提交
8233
	if (!parent) {
8234
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
8235 8236
		se->depth = 0;
	} else {
8237
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
8238 8239
		se->depth = parent->depth + 1;
	}
8240 8241

	se->my_q = cfs_rq;
8242 8243
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
8244 8245 8246 8247 8248 8249 8250 8251 8252 8253 8254 8255 8256 8257 8258 8259 8260 8261 8262 8263 8264 8265 8266 8267 8268 8269 8270 8271 8272 8273
	se->parent = parent;
}

static DEFINE_MUTEX(shares_mutex);

int sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
	int i;
	unsigned long flags;

	/*
	 * 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);
		struct sched_entity *se;

		se = tg->se[i];
		/* Propagate contribution to hierarchy */
		raw_spin_lock_irqsave(&rq->lock, flags);
8274 8275 8276

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
8277
		for_each_sched_entity(se)
8278 8279 8280 8281 8282 8283 8284 8285 8286 8287 8288 8289 8290 8291 8292 8293 8294 8295 8296 8297 8298
			update_cfs_shares(group_cfs_rq(se));
		raw_spin_unlock_irqrestore(&rq->lock, flags);
	}

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;
}

void unregister_fair_sched_group(struct task_group *tg, int cpu) { }

#endif /* CONFIG_FAIR_GROUP_SCHED */

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Peter Zijlstra 已提交
8299

8300
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8301 8302 8303 8304 8305 8306 8307 8308 8309
{
	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)
8310
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8311 8312 8313 8314

	return rr_interval;
}

8315 8316 8317
/*
 * All the scheduling class methods:
 */
8318
const struct sched_class fair_sched_class = {
8319
	.next			= &idle_sched_class,
8320 8321 8322
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
8323
	.yield_to_task		= yield_to_task_fair,
8324

I
Ingo Molnar 已提交
8325
	.check_preempt_curr	= check_preempt_wakeup,
8326 8327 8328 8329

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

8330
#ifdef CONFIG_SMP
L
Li Zefan 已提交
8331
	.select_task_rq		= select_task_rq_fair,
8332
	.migrate_task_rq	= migrate_task_rq_fair,
8333

8334 8335
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
8336 8337

	.task_waking		= task_waking_fair,
8338
	.task_dead		= task_dead_fair,
8339
	.set_cpus_allowed	= set_cpus_allowed_common,
8340
#endif
8341

8342
	.set_curr_task          = set_curr_task_fair,
8343
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
8344
	.task_fork		= task_fork_fair,
8345 8346

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
8347
	.switched_from		= switched_from_fair,
8348
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
8349

8350 8351
	.get_rr_interval	= get_rr_interval_fair,

8352 8353
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
8354
#ifdef CONFIG_FAIR_GROUP_SCHED
8355
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
8356
#endif
8357 8358 8359
};

#ifdef CONFIG_SCHED_DEBUG
8360
void print_cfs_stats(struct seq_file *m, int cpu)
8361 8362 8363
{
	struct cfs_rq *cfs_rq;

8364
	rcu_read_lock();
8365
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8366
		print_cfs_rq(m, cpu, cfs_rq);
8367
	rcu_read_unlock();
8368
}
8369 8370 8371 8372 8373 8374 8375 8376 8377 8378 8379 8380 8381 8382 8383 8384 8385 8386 8387 8388 8389

#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 */
8390 8391 8392 8393 8394 8395

__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

8396
#ifdef CONFIG_NO_HZ_COMMON
8397
	nohz.next_balance = jiffies;
8398
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8399
	cpu_notifier(sched_ilb_notifier, 0);
8400 8401 8402 8403
#endif
#endif /* SMP */

}