fair.c 220.5 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 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763
/*
 * Called within set_task_rq() right before setting a task's cpu. The
 * caller only guarantees p->pi_lock is held; no other assumptions,
 * including the state of rq->lock, should be made.
 */
void set_task_rq_fair(struct sched_entity *se,
		      struct cfs_rq *prev, struct cfs_rq *next)
{
	if (!sched_feat(ATTACH_AGE_LOAD))
		return;

	/*
	 * We are supposed to update the task to "current" time, then its up to
	 * date and ready to go to new CPU/cfs_rq. But we have difficulty in
	 * getting what current time is, so simply throw away the out-of-date
	 * time. This will result in the wakee task is less decayed, but giving
	 * the wakee more load sounds not bad.
	 */
	if (se->avg.last_update_time && prev) {
		u64 p_last_update_time;
		u64 n_last_update_time;

#ifndef CONFIG_64BIT
		u64 p_last_update_time_copy;
		u64 n_last_update_time_copy;

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

			smp_rmb();

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

		} while (p_last_update_time != p_last_update_time_copy ||
			 n_last_update_time != n_last_update_time_copy);
#else
		p_last_update_time = prev->avg.last_update_time;
		n_last_update_time = next->avg.last_update_time;
#endif
		__update_load_avg(p_last_update_time, cpu_of(rq_of(prev)),
				  &se->avg, 0, 0, NULL);
		se->avg.last_update_time = n_last_update_time;
	}
}
2764
#else /* CONFIG_FAIR_GROUP_SCHED */
2765
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2766
#endif /* CONFIG_FAIR_GROUP_SCHED */
2767

2768
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2769

2770 2771
/* 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)
2772
{
2773
	struct sched_avg *sa = &cfs_rq->avg;
2774
	int decayed, removed = 0;
2775

2776 2777 2778 2779
	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);
2780
		removed = 1;
2781
	}
2782

2783 2784 2785
	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);
2786
		sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
2787
	}
2788

2789
	decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2790
		scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2791

2792 2793 2794 2795
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
2796

2797
	return decayed || removed;
2798 2799
}

2800 2801
/* Update task and its cfs_rq load average */
static inline void update_load_avg(struct sched_entity *se, int update_tg)
2802
{
2803
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
2804
	u64 now = cfs_rq_clock_task(cfs_rq);
2805
	int cpu = cpu_of(rq_of(cfs_rq));
2806

2807
	/*
2808 2809
	 * 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
2810
	 */
2811
	__update_load_avg(now, cpu, &se->avg,
2812 2813
			  se->on_rq * scale_load_down(se->load.weight),
			  cfs_rq->curr == se, NULL);
2814

2815 2816
	if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
		update_tg_load_avg(cfs_rq, 0);
2817 2818
}

2819 2820
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2821 2822 2823
	if (!sched_feat(ATTACH_AGE_LOAD))
		goto skip_aging;

2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837
	/*
	 * 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.
		 */
	}

2838
skip_aging:
2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857
	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);
}

2858 2859 2860
/* 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)
2861
{
2862 2863
	struct sched_avg *sa = &se->avg;
	u64 now = cfs_rq_clock_task(cfs_rq);
2864
	int migrated, decayed;
2865

2866 2867
	migrated = !sa->last_update_time;
	if (!migrated) {
2868
		__update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2869 2870
			se->on_rq * scale_load_down(se->load.weight),
			cfs_rq->curr == se, NULL);
2871
	}
2872

2873
	decayed = update_cfs_rq_load_avg(now, cfs_rq);
2874

2875 2876 2877
	cfs_rq->runnable_load_avg += sa->load_avg;
	cfs_rq->runnable_load_sum += sa->load_sum;

2878 2879
	if (migrated)
		attach_entity_load_avg(cfs_rq, se);
2880

2881 2882
	if (decayed || migrated)
		update_tg_load_avg(cfs_rq, 0);
2883 2884
}

2885 2886 2887 2888 2889 2890 2891 2892 2893
/* 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 =
2894
		max_t(s64,  cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2895 2896
}

2897
/*
2898 2899
 * Task first catches up with cfs_rq, and then subtract
 * itself from the cfs_rq (task must be off the queue now).
2900
 */
2901
void remove_entity_load_avg(struct sched_entity *se)
2902
{
2903 2904 2905 2906 2907
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 last_update_time;

#ifndef CONFIG_64BIT
	u64 last_update_time_copy;
2908

2909 2910 2911 2912 2913 2914 2915 2916 2917
	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

2918
	__update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2919 2920
	atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
	atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2921
}
2922

2923 2924 2925 2926 2927 2928 2929 2930 2931 2932
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;
}

2933 2934
static int idle_balance(struct rq *this_rq);

2935 2936
#else /* CONFIG_SMP */

2937 2938 2939
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) {}
2940 2941
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2942
static inline void remove_entity_load_avg(struct sched_entity *se) {}
2943

2944 2945 2946 2947 2948
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) {}

2949 2950 2951 2952 2953
static inline int idle_balance(struct rq *rq)
{
	return 0;
}

2954
#endif /* CONFIG_SMP */
2955

2956
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2957 2958
{
#ifdef CONFIG_SCHEDSTATS
2959 2960 2961 2962 2963
	struct task_struct *tsk = NULL;

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

2964
	if (se->statistics.sleep_start) {
2965
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2966 2967 2968 2969

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

2970 2971
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
2972

2973
		se->statistics.sleep_start = 0;
2974
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
2975

2976
		if (tsk) {
2977
			account_scheduler_latency(tsk, delta >> 10, 1);
2978 2979
			trace_sched_stat_sleep(tsk, delta);
		}
2980
	}
2981
	if (se->statistics.block_start) {
2982
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2983 2984 2985 2986

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

2987 2988
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
2989

2990
		se->statistics.block_start = 0;
2991
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
2992

2993
		if (tsk) {
2994
			if (tsk->in_iowait) {
2995 2996
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
2997
				trace_sched_stat_iowait(tsk, delta);
2998 2999
			}

3000 3001
			trace_sched_stat_blocked(tsk, delta);

3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012
			/*
			 * 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
3013
		}
3014 3015 3016 3017
	}
#endif
}

P
Peter Zijlstra 已提交
3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030
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
}

3031 3032 3033
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3034
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3035

3036 3037 3038 3039 3040 3041
	/*
	 * 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
3042
	if (initial && sched_feat(START_DEBIT))
3043
		vruntime += sched_vslice(cfs_rq, se);
3044

3045
	/* sleeps up to a single latency don't count. */
3046
	if (!initial) {
3047
		unsigned long thresh = sysctl_sched_latency;
3048

3049 3050 3051 3052 3053 3054
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3055

3056
		vruntime -= thresh;
3057 3058
	}

3059
	/* ensure we never gain time by being placed backwards. */
3060
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3061 3062
}

3063 3064
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3065
static void
3066
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3067
{
3068 3069
	/*
	 * Update the normalized vruntime before updating min_vruntime
3070
	 * through calling update_curr().
3071
	 */
3072
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
3073 3074
		se->vruntime += cfs_rq->min_vruntime;

3075
	/*
3076
	 * Update run-time statistics of the 'current'.
3077
	 */
3078
	update_curr(cfs_rq);
3079
	enqueue_entity_load_avg(cfs_rq, se);
3080 3081
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
3082

3083
	if (flags & ENQUEUE_WAKEUP) {
3084
		place_entity(cfs_rq, se, 0);
3085
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
3086
	}
3087

3088
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
3089
	check_spread(cfs_rq, se);
3090 3091
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3092
	se->on_rq = 1;
3093

3094
	if (cfs_rq->nr_running == 1) {
3095
		list_add_leaf_cfs_rq(cfs_rq);
3096 3097
		check_enqueue_throttle(cfs_rq);
	}
3098 3099
}

3100
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3101
{
3102 3103
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3104
		if (cfs_rq->last != se)
3105
			break;
3106 3107

		cfs_rq->last = NULL;
3108 3109
	}
}
P
Peter Zijlstra 已提交
3110

3111 3112 3113 3114
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3115
		if (cfs_rq->next != se)
3116
			break;
3117 3118

		cfs_rq->next = NULL;
3119
	}
P
Peter Zijlstra 已提交
3120 3121
}

3122 3123 3124 3125
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3126
		if (cfs_rq->skip != se)
3127
			break;
3128 3129

		cfs_rq->skip = NULL;
3130 3131 3132
	}
}

P
Peter Zijlstra 已提交
3133 3134
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3135 3136 3137 3138 3139
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
3140 3141 3142

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
3143 3144
}

3145
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3146

3147
static void
3148
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3149
{
3150 3151 3152 3153
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
3154
	dequeue_entity_load_avg(cfs_rq, se);
3155

3156
	update_stats_dequeue(cfs_rq, se);
3157
	if (flags & DEQUEUE_SLEEP) {
P
Peter Zijlstra 已提交
3158
#ifdef CONFIG_SCHEDSTATS
3159 3160 3161 3162
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
3163
				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3164
			if (tsk->state & TASK_UNINTERRUPTIBLE)
3165
				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3166
		}
3167
#endif
P
Peter Zijlstra 已提交
3168 3169
	}

P
Peter Zijlstra 已提交
3170
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3171

3172
	if (se != cfs_rq->curr)
3173
		__dequeue_entity(cfs_rq, se);
3174
	se->on_rq = 0;
3175
	account_entity_dequeue(cfs_rq, se);
3176 3177 3178 3179 3180 3181

	/*
	 * 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.
	 */
3182
	if (!(flags & DEQUEUE_SLEEP))
3183
		se->vruntime -= cfs_rq->min_vruntime;
3184

3185 3186 3187
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3188
	update_min_vruntime(cfs_rq);
3189
	update_cfs_shares(cfs_rq);
3190 3191 3192 3193 3194
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
3195
static void
I
Ingo Molnar 已提交
3196
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3197
{
3198
	unsigned long ideal_runtime, delta_exec;
3199 3200
	struct sched_entity *se;
	s64 delta;
3201

P
Peter Zijlstra 已提交
3202
	ideal_runtime = sched_slice(cfs_rq, curr);
3203
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3204
	if (delta_exec > ideal_runtime) {
3205
		resched_curr(rq_of(cfs_rq));
3206 3207 3208 3209 3210
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221
		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;

3222 3223
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
3224

3225 3226
	if (delta < 0)
		return;
3227

3228
	if (delta > ideal_runtime)
3229
		resched_curr(rq_of(cfs_rq));
3230 3231
}

3232
static void
3233
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3234
{
3235 3236 3237 3238 3239 3240 3241 3242 3243
	/* '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);
3244
		update_load_avg(se, 1);
3245 3246
	}

3247
	update_stats_curr_start(cfs_rq, se);
3248
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
3249 3250 3251 3252 3253 3254
#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):
	 */
3255
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3256
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
3257 3258 3259
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
3260
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
3261 3262
}

3263 3264 3265
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

3266 3267 3268 3269 3270 3271 3272
/*
 * 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
 */
3273 3274
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3275
{
3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286
	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 */
3287

3288 3289 3290 3291 3292
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
3293 3294 3295 3296 3297 3298 3299 3300 3301 3302
		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;
		}

3303 3304 3305
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
3306

3307 3308 3309 3310 3311 3312
	/*
	 * 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;

3313 3314 3315 3316 3317 3318
	/*
	 * 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;

3319
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3320 3321

	return se;
3322 3323
}

3324
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3325

3326
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3327 3328 3329 3330 3331 3332
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
3333
		update_curr(cfs_rq);
3334

3335 3336 3337
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

P
Peter Zijlstra 已提交
3338
	check_spread(cfs_rq, prev);
3339
	if (prev->on_rq) {
3340
		update_stats_wait_start(cfs_rq, prev);
3341 3342
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
3343
		/* in !on_rq case, update occurred at dequeue */
3344
		update_load_avg(prev, 0);
3345
	}
3346
	cfs_rq->curr = NULL;
3347 3348
}

P
Peter Zijlstra 已提交
3349 3350
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3351 3352
{
	/*
3353
	 * Update run-time statistics of the 'current'.
3354
	 */
3355
	update_curr(cfs_rq);
3356

3357 3358 3359
	/*
	 * Ensure that runnable average is periodically updated.
	 */
3360
	update_load_avg(curr, 1);
3361
	update_cfs_shares(cfs_rq);
3362

P
Peter Zijlstra 已提交
3363 3364 3365 3366 3367
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
3368
	if (queued) {
3369
		resched_curr(rq_of(cfs_rq));
3370 3371
		return;
	}
P
Peter Zijlstra 已提交
3372 3373 3374 3375 3376 3377 3378 3379
	/*
	 * 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
3380
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
3381
		check_preempt_tick(cfs_rq, curr);
3382 3383
}

3384 3385 3386 3387 3388 3389

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

#ifdef CONFIG_CFS_BANDWIDTH
3390 3391

#ifdef HAVE_JUMP_LABEL
3392
static struct static_key __cfs_bandwidth_used;
3393 3394 3395

static inline bool cfs_bandwidth_used(void)
{
3396
	return static_key_false(&__cfs_bandwidth_used);
3397 3398
}

3399
void cfs_bandwidth_usage_inc(void)
3400
{
3401 3402 3403 3404 3405 3406
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
3407 3408 3409 3410 3411 3412 3413
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

3414 3415
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
3416 3417
#endif /* HAVE_JUMP_LABEL */

3418 3419 3420 3421 3422 3423 3424 3425
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
3426 3427 3428 3429 3430 3431

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

P
Paul Turner 已提交
3432 3433 3434 3435 3436 3437 3438
/*
 * 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
 */
3439
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450
{
	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);
}

3451 3452 3453 3454 3455
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

3456 3457 3458 3459 3460 3461
/* 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;

3462
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3463 3464
}

3465 3466
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3467 3468 3469
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
3470
	u64 amount = 0, min_amount, expires;
3471 3472 3473 3474 3475 3476 3477

	/* 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;
3478
	else {
P
Peter Zijlstra 已提交
3479
		start_cfs_bandwidth(cfs_b);
3480 3481 3482 3483 3484 3485

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
3486
	}
P
Paul Turner 已提交
3487
	expires = cfs_b->runtime_expires;
3488 3489 3490
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
3491 3492 3493 3494 3495 3496 3497
	/*
	 * 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;
3498 3499

	return cfs_rq->runtime_remaining > 0;
3500 3501
}

P
Paul Turner 已提交
3502 3503 3504 3505 3506
/*
 * 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)
3507
{
P
Paul Turner 已提交
3508 3509 3510
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
3511
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3512 3513
		return;

P
Paul Turner 已提交
3514 3515 3516 3517 3518 3519 3520 3521 3522
	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
3523 3524 3525
	 * 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
3526 3527
	 */

3528
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
3529 3530 3531 3532 3533 3534 3535 3536
		/* 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;
	}
}

3537
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
3538 3539
{
	/* dock delta_exec before expiring quota (as it could span periods) */
3540
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
3541 3542 3543
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
3544 3545
		return;

3546 3547 3548 3549 3550
	/*
	 * 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))
3551
		resched_curr(rq_of(cfs_rq));
3552 3553
}

3554
static __always_inline
3555
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3556
{
3557
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3558 3559 3560 3561 3562
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

3563 3564
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
3565
	return cfs_bandwidth_used() && cfs_rq->throttled;
3566 3567
}

3568 3569 3570
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
3571
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 3599
}

/*
 * 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) {
3600
		/* adjust cfs_rq_clock_task() */
3601
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3602
					     cfs_rq->throttled_clock_task;
3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613
	}
#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)];

3614 3615
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
3616
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
3617 3618 3619 3620 3621
	cfs_rq->throttle_count++;

	return 0;
}

3622
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3623 3624 3625 3626 3627
{
	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
3628
	bool empty;
3629 3630 3631

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

3632
	/* freeze hierarchy runnable averages while throttled */
3633 3634 3635
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649 3650 3651 3652

	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)
3653
		sub_nr_running(rq, task_delta);
3654 3655

	cfs_rq->throttled = 1;
3656
	cfs_rq->throttled_clock = rq_clock(rq);
3657
	raw_spin_lock(&cfs_b->lock);
3658
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
3659

3660 3661 3662 3663 3664
	/*
	 * 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
3665 3666 3667 3668 3669 3670 3671 3672

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

3673 3674 3675
	raw_spin_unlock(&cfs_b->lock);
}

3676
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3677 3678 3679 3680 3681 3682 3683
{
	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;

3684
	se = cfs_rq->tg->se[cpu_of(rq)];
3685 3686

	cfs_rq->throttled = 0;
3687 3688 3689

	update_rq_clock(rq);

3690
	raw_spin_lock(&cfs_b->lock);
3691
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3692 3693 3694
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

3695 3696 3697
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715
	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)
3716
		add_nr_running(rq, task_delta);
3717 3718 3719

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
3720
		resched_curr(rq);
3721 3722 3723 3724 3725 3726
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
3727 3728
	u64 runtime;
	u64 starting_runtime = remaining;
3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754 3755 3756 3757 3758

	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();

3759
	return starting_runtime - remaining;
3760 3761
}

3762 3763 3764 3765 3766 3767 3768 3769
/*
 * 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)
{
3770
	u64 runtime, runtime_expires;
3771
	int throttled;
3772 3773 3774

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
3775
		goto out_deactivate;
3776

3777
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3778
	cfs_b->nr_periods += overrun;
3779

3780 3781 3782 3783 3784 3785
	/*
	 * 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
3786 3787 3788

	__refill_cfs_bandwidth_runtime(cfs_b);

3789 3790 3791
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
3792
		return 0;
3793 3794
	}

3795 3796 3797
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

3798 3799 3800
	runtime_expires = cfs_b->runtime_expires;

	/*
3801 3802 3803 3804 3805
	 * 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.
3806
	 */
3807 3808
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
3809 3810 3811 3812 3813 3814 3815
		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);
3816 3817

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
3818
	}
3819

3820 3821 3822 3823 3824 3825 3826
	/*
	 * 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;
3827

3828 3829 3830 3831
	return 0;

out_deactivate:
	return 1;
3832
}
3833

3834 3835 3836 3837 3838 3839 3840
/* 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;

3841 3842 3843 3844
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3845
 * hrtimer base being cleared by hrtimer_start. In the case of
3846 3847
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861 3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872
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
3873 3874 3875
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904
}

/* 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)
{
3905 3906 3907
	if (!cfs_bandwidth_used())
		return;

3908
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923
		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 */
3924 3925 3926
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
3927
		return;
3928
	}
3929

3930
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3931
		runtime = cfs_b->runtime;
3932

3933 3934 3935 3936 3937 3938 3939 3940 3941 3942
	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)
3943
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
3944 3945 3946
	raw_spin_unlock(&cfs_b->lock);
}

3947 3948 3949 3950 3951 3952 3953
/*
 * 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)
{
3954 3955 3956
	if (!cfs_bandwidth_used())
		return;

3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971
	/* 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() */
3972
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3973
{
3974
	if (!cfs_bandwidth_used())
3975
		return false;
3976

3977
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3978
		return false;
3979 3980 3981 3982 3983 3984

	/*
	 * 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))
3985
		return true;
3986 3987

	throttle_cfs_rq(cfs_rq);
3988
	return true;
3989
}
3990 3991 3992 3993 3994

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
3995

3996 3997 3998 3999 4000 4001 4002 4003 4004 4005 4006 4007
	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;

4008
	raw_spin_lock(&cfs_b->lock);
4009
	for (;;) {
P
Peter Zijlstra 已提交
4010
		overrun = hrtimer_forward_now(timer, cfs_b->period);
4011 4012 4013 4014 4015
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
P
Peter Zijlstra 已提交
4016 4017
	if (idle)
		cfs_b->period_active = 0;
4018
	raw_spin_unlock(&cfs_b->lock);
4019 4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030

	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
4031
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042
	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
4043
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4044
{
P
Peter Zijlstra 已提交
4045
	lockdep_assert_held(&cfs_b->lock);
4046

P
Peter Zijlstra 已提交
4047 4048 4049 4050 4051
	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);
	}
4052 4053 4054 4055
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4056 4057 4058 4059
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4060 4061 4062 4063
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076
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);
	}
}

4077
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4078 4079 4080 4081 4082 4083 4084 4085 4086 4087 4088
{
	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
		 */
4089
		cfs_rq->runtime_remaining = 1;
4090 4091 4092 4093 4094 4095
		/*
		 * 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;

4096 4097 4098 4099 4100 4101
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
}

#else /* CONFIG_CFS_BANDWIDTH */
4102 4103
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
4104
	return rq_clock_task(rq_of(cfs_rq));
4105 4106
}

4107
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4108
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4109
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4110
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4111 4112 4113 4114 4115

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
4116 4117 4118 4119 4120 4121 4122 4123 4124 4125 4126

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;
}
4127 4128 4129 4130 4131

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) {}
4132 4133
#endif

4134 4135 4136 4137 4138
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) {}
4139
static inline void update_runtime_enabled(struct rq *rq) {}
4140
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4141 4142 4143

#endif /* CONFIG_CFS_BANDWIDTH */

4144 4145 4146 4147
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
4148 4149 4150 4151 4152 4153 4154 4155
#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);

4156
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
4157 4158 4159 4160 4161 4162
		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)
4163
				resched_curr(rq);
P
Peter Zijlstra 已提交
4164 4165
			return;
		}
4166
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
4167 4168
	}
}
4169 4170 4171 4172 4173 4174 4175 4176 4177 4178

/*
 * 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;

4179
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4180 4181 4182 4183 4184
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
4185
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
4186 4187 4188 4189
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
4190 4191 4192 4193

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
4194 4195
#endif

4196 4197 4198 4199 4200
/*
 * 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:
 */
4201
static void
4202
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4203 4204
{
	struct cfs_rq *cfs_rq;
4205
	struct sched_entity *se = &p->se;
4206 4207

	for_each_sched_entity(se) {
4208
		if (se->on_rq)
4209 4210
			break;
		cfs_rq = cfs_rq_of(se);
4211
		enqueue_entity(cfs_rq, se, flags);
4212 4213 4214 4215 4216 4217 4218 4219 4220

		/*
		 * 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;
4221
		cfs_rq->h_nr_running++;
4222

4223
		flags = ENQUEUE_WAKEUP;
4224
	}
P
Peter Zijlstra 已提交
4225

P
Peter Zijlstra 已提交
4226
	for_each_sched_entity(se) {
4227
		cfs_rq = cfs_rq_of(se);
4228
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
4229

4230 4231 4232
		if (cfs_rq_throttled(cfs_rq))
			break;

4233
		update_load_avg(se, 1);
4234
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4235 4236
	}

Y
Yuyang Du 已提交
4237
	if (!se)
4238
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
4239

4240
	hrtick_update(rq);
4241 4242
}

4243 4244
static void set_next_buddy(struct sched_entity *se);

4245 4246 4247 4248 4249
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
4250
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4251 4252
{
	struct cfs_rq *cfs_rq;
4253
	struct sched_entity *se = &p->se;
4254
	int task_sleep = flags & DEQUEUE_SLEEP;
4255 4256 4257

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
4258
		dequeue_entity(cfs_rq, se, flags);
4259 4260 4261 4262 4263 4264 4265 4266 4267

		/*
		 * 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;
4268
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4269

4270
		/* Don't dequeue parent if it has other entities besides us */
4271 4272 4273 4274 4275 4276 4277
		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));
4278 4279 4280

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
4281
			break;
4282
		}
4283
		flags |= DEQUEUE_SLEEP;
4284
	}
P
Peter Zijlstra 已提交
4285

P
Peter Zijlstra 已提交
4286
	for_each_sched_entity(se) {
4287
		cfs_rq = cfs_rq_of(se);
4288
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4289

4290 4291 4292
		if (cfs_rq_throttled(cfs_rq))
			break;

4293
		update_load_avg(se, 1);
4294
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4295 4296
	}

Y
Yuyang Du 已提交
4297
	if (!se)
4298
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
4299

4300
	hrtick_update(rq);
4301 4302
}

4303
#ifdef CONFIG_SMP
4304 4305 4306 4307 4308 4309

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

/*
4310
 * The exact cpuload calculated at every tick would be:
4311
 *
4312 4313 4314 4315 4316 4317 4318
 *   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
4319 4320 4321
 *
 * decay_load_missed() below does efficient calculation of
 *
4322 4323 4324 4325 4326 4327
 *   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())
4328
 *
4329
 * The calculation is approximated on a 128 point scale.
4330 4331
 */
#define DEGRADE_SHIFT		7
4332 4333 4334 4335 4336 4337 4338 4339 4340

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 }
};
4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370

/*
 * 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;
}

4371 4372 4373 4374 4375 4376 4377
/**
 * __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
 *
4378
 * Update rq->cpu_load[] statistics. This function is usually called every
4379 4380 4381 4382 4383 4384 4385 4386 4387 4388 4389 4390 4391 4392 4393 4394 4395 4396 4397 4398 4399 4400 4401 4402 4403 4404 4405
 * 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.
4406 4407
 */
static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4408
			      unsigned long pending_updates, int active)
4409
{
4410
	unsigned long tickless_load = active ? this_rq->cpu_load[0] : 0;
4411 4412 4413 4414 4415 4416 4417 4418 4419 4420 4421
	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 */

4422
		old_load = this_rq->cpu_load[i] - tickless_load;
4423
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
4424
		old_load += tickless_load;
4425 4426 4427 4428 4429 4430 4431 4432 4433 4434 4435 4436 4437 4438 4439
		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);
}

4440 4441 4442 4443 4444 4445
/* 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);
}

4446 4447 4448 4449 4450 4451 4452 4453 4454 4455 4456 4457 4458 4459 4460 4461 4462 4463 4464 4465
#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)
{
4466
	unsigned long curr_jiffies = READ_ONCE(jiffies);
4467
	unsigned long load = weighted_cpuload(cpu_of(this_rq));
4468 4469 4470 4471 4472 4473 4474 4475 4476 4477 4478
	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;

4479
	__update_cpu_load(this_rq, load, pending_updates, 0);
4480 4481 4482 4483 4484
}

/*
 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
 */
4485
void update_cpu_load_nohz(int active)
4486 4487
{
	struct rq *this_rq = this_rq();
4488
	unsigned long curr_jiffies = READ_ONCE(jiffies);
4489
	unsigned long load = active ? weighted_cpuload(cpu_of(this_rq)) : 0;
4490 4491 4492 4493 4494 4495 4496 4497 4498 4499
	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;
		/*
4500 4501 4502
		 * 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.
4503
		 */
4504
		__update_cpu_load(this_rq, load, pending_updates, active);
4505 4506 4507 4508 4509 4510 4511 4512 4513 4514
	}
	raw_spin_unlock(&this_rq->lock);
}
#endif /* CONFIG_NO_HZ */

/*
 * Called from scheduler_tick()
 */
void update_cpu_load_active(struct rq *this_rq)
{
4515
	unsigned long load = weighted_cpuload(cpu_of(this_rq));
4516 4517 4518 4519
	/*
	 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
	 */
	this_rq->last_load_update_tick = jiffies;
4520
	__update_cpu_load(this_rq, load, 1, 1);
4521 4522
}

4523 4524 4525 4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550 4551 4552 4553 4554 4555
/*
 * 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);
}

4556
static unsigned long capacity_of(int cpu)
4557
{
4558
	return cpu_rq(cpu)->cpu_capacity;
4559 4560
}

4561 4562 4563 4564 4565
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

4566 4567 4568
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
4569
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4570
	unsigned long load_avg = weighted_cpuload(cpu);
4571 4572

	if (nr_running)
4573
		return load_avg / nr_running;
4574 4575 4576 4577

	return 0;
}

4578 4579 4580 4581 4582 4583 4584
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.
	 */
4585
	if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4586
		current->wakee_flips >>= 1;
4587 4588 4589 4590 4591 4592 4593 4594
		current->wakee_flip_decay_ts = jiffies;
	}

	if (current->last_wakee != p) {
		current->last_wakee = p;
		current->wakee_flips++;
	}
}
4595

4596
static void task_waking_fair(struct task_struct *p)
4597 4598 4599
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
4600 4601 4602 4603
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
4604

4605 4606 4607 4608 4609 4610 4611 4612
	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
4613

4614
	se->vruntime -= min_vruntime;
4615
	record_wakee(p);
4616 4617
}

4618
#ifdef CONFIG_FAIR_GROUP_SCHED
4619 4620 4621 4622 4623 4624
/*
 * 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.
4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636 4637 4638 4639 4640 4641 4642 4643 4644 4645 4646 4647 4648 4649 4650 4651 4652 4653 4654 4655 4656 4657 4658 4659 4660 4661 4662 4663 4664 4665 4666 4667
 *
 * 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.
4668
 */
P
Peter Zijlstra 已提交
4669
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4670
{
P
Peter Zijlstra 已提交
4671
	struct sched_entity *se = tg->se[cpu];
4672

4673
	if (!tg->parent)	/* the trivial, non-cgroup case */
4674 4675
		return wl;

P
Peter Zijlstra 已提交
4676
	for_each_sched_entity(se) {
4677
		long w, W;
P
Peter Zijlstra 已提交
4678

4679
		tg = se->my_q->tg;
4680

4681 4682 4683 4684
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
4685

4686 4687 4688
		/*
		 * w = rw_i + @wl
		 */
4689
		w = cfs_rq_load_avg(se->my_q) + wl;
4690

4691 4692 4693 4694
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
4695
			wl = (w * (long)tg->shares) / W;
4696 4697
		else
			wl = tg->shares;
4698

4699 4700 4701 4702 4703
		/*
		 * 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().
		 */
4704 4705
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
4706 4707 4708 4709

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
4710
		wl -= se->avg.load_avg;
4711 4712 4713 4714 4715 4716 4717 4718

		/*
		 * 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
4719 4720
		wg = 0;
	}
4721

P
Peter Zijlstra 已提交
4722
	return wl;
4723 4724
}
#else
P
Peter Zijlstra 已提交
4725

4726
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
P
Peter Zijlstra 已提交
4727
{
4728
	return wl;
4729
}
P
Peter Zijlstra 已提交
4730

4731 4732
#endif

M
Mike Galbraith 已提交
4733 4734 4735 4736 4737 4738 4739 4740 4741 4742 4743 4744
/*
 * 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.
 */
4745 4746
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
4747 4748
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
4749
	int factor = this_cpu_read(sd_llc_size);
4750

M
Mike Galbraith 已提交
4751 4752 4753 4754 4755
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
4756 4757
}

4758
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4759
{
4760
	s64 this_load, load;
4761
	s64 this_eff_load, prev_eff_load;
4762 4763
	int idx, this_cpu, prev_cpu;
	struct task_group *tg;
4764
	unsigned long weight;
4765
	int balanced;
4766

4767 4768 4769 4770 4771
	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);
4772

4773 4774 4775 4776 4777
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
4778 4779
	if (sync) {
		tg = task_group(current);
4780
		weight = current->se.avg.load_avg;
4781

4782
		this_load += effective_load(tg, this_cpu, -weight, -weight);
4783 4784
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
4785

4786
	tg = task_group(p);
4787
	weight = p->se.avg.load_avg;
4788

4789 4790
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4791 4792 4793
	 * 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.
4794 4795 4796 4797
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
4798 4799
	this_eff_load = 100;
	this_eff_load *= capacity_of(prev_cpu);
4800

4801 4802
	prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= capacity_of(this_cpu);
4803

4804
	if (this_load > 0) {
4805 4806 4807 4808
		this_eff_load *= this_load +
			effective_load(tg, this_cpu, weight, weight);

		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4809
	}
4810

4811
	balanced = this_eff_load <= prev_eff_load;
4812

4813
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4814

4815 4816
	if (!balanced)
		return 0;
4817

4818 4819 4820 4821
	schedstat_inc(sd, ttwu_move_affine);
	schedstat_inc(p, se.statistics.nr_wakeups_affine);

	return 1;
4822 4823
}

4824 4825 4826 4827 4828
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
4829
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4830
		  int this_cpu, int sd_flag)
4831
{
4832
	struct sched_group *idlest = NULL, *group = sd->groups;
4833
	unsigned long min_load = ULONG_MAX, this_load = 0;
4834
	int load_idx = sd->forkexec_idx;
4835
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
4836

4837 4838 4839
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

4840 4841 4842 4843
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
4844

4845 4846
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
4847
					tsk_cpus_allowed(p)))
4848 4849 4850 4851 4852 4853 4854 4855 4856 4857 4858 4859 4860 4861 4862 4863 4864 4865
			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;
		}

4866
		/* Adjust by relative CPU capacity of the group */
4867
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4868 4869 4870 4871 4872 4873 4874 4875 4876 4877 4878 4879 4880 4881 4882 4883 4884 4885 4886 4887 4888

		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;
4889 4890 4891 4892
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
4893 4894 4895
	int i;

	/* Traverse only the allowed CPUs */
4896
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4897 4898 4899 4900 4901 4902 4903 4904 4905 4906 4907 4908 4909 4910 4911 4912 4913 4914 4915 4916 4917 4918
		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;
			}
4919
		} else if (shallowest_idle_cpu == -1) {
4920 4921 4922 4923 4924
			load = weighted_cpuload(i);
			if (load < min_load || (load == min_load && i == this_cpu)) {
				min_load = load;
				least_loaded_cpu = i;
			}
4925 4926 4927
		}
	}

4928
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
4929
}
4930

4931 4932 4933
/*
 * Try and locate an idle CPU in the sched_domain.
 */
4934
static int select_idle_sibling(struct task_struct *p, int target)
4935
{
4936
	struct sched_domain *sd;
4937
	struct sched_group *sg;
4938
	int i = task_cpu(p);
4939

4940 4941
	if (idle_cpu(target))
		return target;
4942 4943

	/*
4944
	 * If the prevous cpu is cache affine and idle, don't be stupid.
4945
	 */
4946 4947
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
4948 4949

	/*
4950
	 * Otherwise, iterate the domains and find an elegible idle cpu.
4951
	 */
4952
	sd = rcu_dereference(per_cpu(sd_llc, target));
4953
	for_each_lower_domain(sd) {
4954 4955 4956 4957 4958 4959 4960
		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)) {
4961
				if (i == target || !idle_cpu(i))
4962 4963
					goto next;
			}
4964

4965 4966 4967 4968 4969 4970 4971 4972
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
4973 4974
	return target;
}
4975

4976
/*
4977
 * cpu_util returns the amount of capacity of a CPU that is used by CFS
4978
 * tasks. The unit of the return value must be the one of capacity so we can
4979 4980
 * compare the utilization with the capacity of the CPU that is available for
 * CFS task (ie cpu_capacity).
4981 4982 4983 4984 4985 4986 4987 4988 4989 4990 4991 4992 4993 4994 4995 4996 4997 4998 4999 5000
 *
 * 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).
5001
 */
5002
static int cpu_util(int cpu)
5003
{
5004
	unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
5005 5006
	unsigned long capacity = capacity_orig_of(cpu);

5007
	return (util >= capacity) ? capacity : util;
5008
}
5009

5010
/*
5011 5012 5013
 * 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.
5014
 *
5015 5016
 * 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.
5017
 *
5018
 * Returns the target cpu number.
5019 5020 5021
 *
 * preempt must be disabled.
 */
5022
static int
5023
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5024
{
5025
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5026
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
5027
	int new_cpu = prev_cpu;
5028
	int want_affine = 0;
5029
	int sync = wake_flags & WF_SYNC;
5030

5031
	if (sd_flag & SD_BALANCE_WAKE)
M
Mike Galbraith 已提交
5032
		want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
5033

5034
	rcu_read_lock();
5035
	for_each_domain(cpu, tmp) {
5036
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
5037
			break;
5038

5039
		/*
5040 5041
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
5042
		 */
5043 5044 5045
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
5046
			break;
5047
		}
5048

5049
		if (tmp->flags & sd_flag)
5050
			sd = tmp;
M
Mike Galbraith 已提交
5051 5052
		else if (!want_affine)
			break;
5053 5054
	}

M
Mike Galbraith 已提交
5055 5056 5057 5058
	if (affine_sd) {
		sd = NULL; /* Prefer wake_affine over balance flags */
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
			new_cpu = cpu;
5059
	}
5060

M
Mike Galbraith 已提交
5061 5062 5063 5064 5065
	if (!sd) {
		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
			new_cpu = select_idle_sibling(p, new_cpu);

	} else while (sd) {
5066
		struct sched_group *group;
5067
		int weight;
5068

5069
		if (!(sd->flags & sd_flag)) {
5070 5071 5072
			sd = sd->child;
			continue;
		}
5073

5074
		group = find_idlest_group(sd, p, cpu, sd_flag);
5075 5076 5077 5078
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
5079

5080
		new_cpu = find_idlest_cpu(group, p, cpu);
5081 5082 5083 5084
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
5085
		}
5086 5087 5088

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
5089
		weight = sd->span_weight;
5090 5091
		sd = NULL;
		for_each_domain(cpu, tmp) {
5092
			if (weight <= tmp->span_weight)
5093
				break;
5094
			if (tmp->flags & sd_flag)
5095 5096 5097
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
5098
	}
5099
	rcu_read_unlock();
5100

5101
	return new_cpu;
5102
}
5103 5104 5105 5106

/*
 * 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
5107
 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5108
 */
5109
static void migrate_task_rq_fair(struct task_struct *p)
5110
{
5111
	/*
5112 5113 5114 5115 5116
	 * 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.
5117
	 */
5118 5119 5120 5121
	remove_entity_load_avg(&p->se);

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
5122 5123

	/* We have migrated, no longer consider this task hot */
5124
	p->se.exec_start = 0;
5125
}
5126 5127 5128 5129 5130

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
5131 5132
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
5133 5134
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5135 5136 5137 5138
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
5139 5140
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
5141 5142 5143 5144 5145 5146 5147 5148 5149
	 *
	 * 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.
5150
	 */
5151
	return calc_delta_fair(gran, se);
5152 5153
}

5154 5155 5156 5157 5158 5159 5160 5161 5162 5163 5164 5165 5166 5167 5168 5169 5170 5171 5172 5173 5174 5175
/*
 * 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
5176
	gran = wakeup_gran(curr, se);
5177 5178 5179 5180 5181 5182
	if (vdiff > gran)
		return 1;

	return 0;
}

5183 5184
static void set_last_buddy(struct sched_entity *se)
{
5185 5186 5187 5188 5189
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
5190 5191 5192 5193
}

static void set_next_buddy(struct sched_entity *se)
{
5194 5195 5196 5197 5198
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
5199 5200
}

5201 5202
static void set_skip_buddy(struct sched_entity *se)
{
5203 5204
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
5205 5206
}

5207 5208 5209
/*
 * Preempt the current task with a newly woken task if needed:
 */
5210
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5211 5212
{
	struct task_struct *curr = rq->curr;
5213
	struct sched_entity *se = &curr->se, *pse = &p->se;
5214
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5215
	int scale = cfs_rq->nr_running >= sched_nr_latency;
5216
	int next_buddy_marked = 0;
5217

I
Ingo Molnar 已提交
5218 5219 5220
	if (unlikely(se == pse))
		return;

5221
	/*
5222
	 * This is possible from callers such as attach_tasks(), in which we
5223 5224 5225 5226 5227 5228 5229
	 * 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;

5230
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
5231
		set_next_buddy(pse);
5232 5233
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
5234

5235 5236 5237
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
5238 5239 5240 5241 5242 5243
	 *
	 * 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.
5244 5245 5246 5247
	 */
	if (test_tsk_need_resched(curr))
		return;

5248 5249 5250 5251 5252
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

5253
	/*
5254 5255
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
5256
	 */
5257
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5258
		return;
5259

5260
	find_matching_se(&se, &pse);
5261
	update_curr(cfs_rq_of(se));
5262
	BUG_ON(!pse);
5263 5264 5265 5266 5267 5268 5269
	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);
5270
		goto preempt;
5271
	}
5272

5273
	return;
5274

5275
preempt:
5276
	resched_curr(rq);
5277 5278 5279 5280 5281 5282 5283 5284 5285 5286 5287 5288 5289 5290
	/*
	 * 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);
5291 5292
}

5293 5294
static struct task_struct *
pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5295 5296 5297
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
5298
	struct task_struct *p;
5299
	int new_tasks;
5300

5301
again:
5302 5303
#ifdef CONFIG_FAIR_GROUP_SCHED
	if (!cfs_rq->nr_running)
5304
		goto idle;
5305

5306
	if (prev->sched_class != &fair_sched_class)
5307 5308 5309 5310 5311 5312 5313 5314 5315 5316 5317 5318 5319 5320 5321 5322 5323 5324 5325
		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.
		 */
5326 5327 5328 5329 5330
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
5331

5332 5333 5334 5335 5336 5337 5338 5339 5340
			/*
			 * 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;
		}
5341 5342 5343 5344 5345 5346 5347 5348 5349 5350 5351 5352 5353 5354 5355 5356 5357 5358 5359 5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379 5380

		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
5381

5382
	if (!cfs_rq->nr_running)
5383
		goto idle;
5384

5385
	put_prev_task(rq, prev);
5386

5387
	do {
5388
		se = pick_next_entity(cfs_rq, NULL);
5389
		set_next_entity(cfs_rq, se);
5390 5391 5392
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
5393
	p = task_of(se);
5394

5395 5396
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
5397 5398

	return p;
5399 5400

idle:
5401 5402 5403 5404 5405 5406 5407
	/*
	 * 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);
5408
	new_tasks = idle_balance(rq);
5409
	lockdep_pin_lock(&rq->lock);
5410 5411 5412 5413 5414
	/*
	 * 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.
	 */
5415
	if (new_tasks < 0)
5416 5417
		return RETRY_TASK;

5418
	if (new_tasks > 0)
5419 5420 5421
		goto again;

	return NULL;
5422 5423 5424 5425 5426
}

/*
 * Account for a descheduled task:
 */
5427
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5428 5429 5430 5431 5432 5433
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5434
		put_prev_entity(cfs_rq, se);
5435 5436 5437
	}
}

5438 5439 5440 5441 5442 5443 5444 5445 5446 5447 5448 5449 5450 5451 5452 5453 5454 5455 5456 5457 5458 5459 5460 5461 5462
/*
 * 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);
5463 5464 5465 5466 5467
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
5468
		rq_clock_skip_update(rq, true);
5469 5470 5471 5472 5473
	}

	set_skip_buddy(se);
}

5474 5475 5476 5477
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

5478 5479
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5480 5481 5482 5483 5484 5485 5486 5487 5488 5489
		return false;

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

	yield_task_fair(rq);

	return true;
}

5490
#ifdef CONFIG_SMP
5491
/**************************************************
P
Peter Zijlstra 已提交
5492 5493 5494 5495 5496 5497 5498 5499 5500 5501 5502 5503 5504 5505 5506 5507 5508 5509 5510 5511 5512 5513 5514
 * 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)
 *
5515
 * C_i is the compute capacity of cpu i, typically it is the
P
Peter Zijlstra 已提交
5516 5517 5518 5519 5520 5521
 * 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):
 *
5522
 *   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
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 5562 5563 5564 5565 5566 5567 5568 5569 5570 5571 5572 5573 5574 5575 5576 5577 5578 5579 5580 5581 5582 5583 5584 5585 5586 5587 5588 5589 5590 5591 5592 5593 5594 5595 5596 5597 5598 5599 5600 5601 5602 5603 5604 5605 5606 5607
 *
 * 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.]
 */ 
5608

5609 5610
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

5611 5612
enum fbq_type { regular, remote, all };

5613
#define LBF_ALL_PINNED	0x01
5614
#define LBF_NEED_BREAK	0x02
5615 5616
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
5617 5618 5619 5620 5621

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
5622
	int			src_cpu;
5623 5624 5625 5626

	int			dst_cpu;
	struct rq		*dst_rq;

5627 5628
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
5629
	enum cpu_idle_type	idle;
5630
	long			imbalance;
5631 5632 5633
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

5634
	unsigned int		flags;
5635 5636 5637 5638

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
5639 5640

	enum fbq_type		fbq_type;
5641
	struct list_head	tasks;
5642 5643
};

5644 5645 5646
/*
 * Is this task likely cache-hot:
 */
5647
static int task_hot(struct task_struct *p, struct lb_env *env)
5648 5649 5650
{
	s64 delta;

5651 5652
	lockdep_assert_held(&env->src_rq->lock);

5653 5654 5655 5656 5657 5658 5659 5660 5661
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
5662
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5663 5664 5665 5666 5667 5668 5669 5670 5671
			(&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;

5672
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5673 5674 5675 5676

	return delta < (s64)sysctl_sched_migration_cost;
}

5677
#ifdef CONFIG_NUMA_BALANCING
5678
/*
5679 5680 5681
 * 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.
5682
 */
5683
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5684
{
5685
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
5686
	unsigned long src_faults, dst_faults;
5687 5688
	int src_nid, dst_nid;

5689
	if (!static_branch_likely(&sched_numa_balancing))
5690 5691
		return -1;

5692
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5693
		return -1;
5694 5695 5696 5697

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

5698
	if (src_nid == dst_nid)
5699
		return -1;
5700

5701 5702 5703 5704 5705 5706 5707
	/* 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;
	}
5708

5709 5710
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
5711
		return 0;
5712

5713 5714 5715 5716 5717 5718
	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);
5719 5720
	}

5721
	return dst_faults < src_faults;
5722 5723
}

5724
#else
5725
static inline int migrate_degrades_locality(struct task_struct *p,
5726 5727
					     struct lb_env *env)
{
5728
	return -1;
5729
}
5730 5731
#endif

5732 5733 5734 5735
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
5736
int can_migrate_task(struct task_struct *p, struct lb_env *env)
5737
{
5738
	int tsk_cache_hot;
5739 5740 5741

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

5742 5743
	/*
	 * We do not migrate tasks that are:
5744
	 * 1) throttled_lb_pair, or
5745
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5746 5747
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
5748
	 */
5749 5750 5751
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

5752
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5753
		int cpu;
5754

5755
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5756

5757 5758
		env->flags |= LBF_SOME_PINNED;

5759 5760 5761 5762 5763 5764 5765 5766
		/*
		 * 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.
		 */
5767
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5768 5769
			return 0;

5770 5771 5772
		/* 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))) {
5773
				env->flags |= LBF_DST_PINNED;
5774 5775 5776
				env->new_dst_cpu = cpu;
				break;
			}
5777
		}
5778

5779 5780
		return 0;
	}
5781 5782

	/* Record that we found atleast one task that could run on dst_cpu */
5783
	env->flags &= ~LBF_ALL_PINNED;
5784

5785
	if (task_running(env->src_rq, p)) {
5786
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5787 5788 5789 5790 5791
		return 0;
	}

	/*
	 * Aggressive migration if:
5792 5793 5794
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
5795
	 */
5796 5797 5798
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
5799

5800
	if (tsk_cache_hot <= 0 ||
5801
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5802
		if (tsk_cache_hot == 1) {
5803 5804 5805
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
			schedstat_inc(p, se.statistics.nr_forced_migrations);
		}
5806 5807 5808
		return 1;
	}

Z
Zhang Hang 已提交
5809 5810
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
5811 5812
}

5813
/*
5814 5815 5816 5817 5818 5819 5820
 * 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;
5821
	deactivate_task(env->src_rq, p, 0);
5822 5823 5824
	set_task_cpu(p, env->dst_cpu);
}

5825
/*
5826
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5827 5828
 * part of active balancing operations within "domain".
 *
5829
 * Returns a task if successful and NULL otherwise.
5830
 */
5831
static struct task_struct *detach_one_task(struct lb_env *env)
5832 5833 5834
{
	struct task_struct *p, *n;

5835 5836
	lockdep_assert_held(&env->src_rq->lock);

5837 5838 5839
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
5840

5841
		detach_task(p, env);
5842

5843
		/*
5844
		 * Right now, this is only the second place where
5845
		 * lb_gained[env->idle] is updated (other is detach_tasks)
5846
		 * so we can safely collect stats here rather than
5847
		 * inside detach_tasks().
5848 5849
		 */
		schedstat_inc(env->sd, lb_gained[env->idle]);
5850
		return p;
5851
	}
5852
	return NULL;
5853 5854
}

5855 5856
static const unsigned int sched_nr_migrate_break = 32;

5857
/*
5858 5859
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
5860
 *
5861
 * Returns number of detached tasks if successful and 0 otherwise.
5862
 */
5863
static int detach_tasks(struct lb_env *env)
5864
{
5865 5866
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
5867
	unsigned long load;
5868 5869 5870
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
5871

5872
	if (env->imbalance <= 0)
5873
		return 0;
5874

5875
	while (!list_empty(tasks)) {
5876 5877 5878 5879 5880 5881 5882
		/*
		 * 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;

5883
		p = list_first_entry(tasks, struct task_struct, se.group_node);
5884

5885 5886
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
5887
		if (env->loop > env->loop_max)
5888
			break;
5889 5890

		/* take a breather every nr_migrate tasks */
5891
		if (env->loop > env->loop_break) {
5892
			env->loop_break += sched_nr_migrate_break;
5893
			env->flags |= LBF_NEED_BREAK;
5894
			break;
5895
		}
5896

5897
		if (!can_migrate_task(p, env))
5898 5899 5900
			goto next;

		load = task_h_load(p);
5901

5902
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5903 5904
			goto next;

5905
		if ((load / 2) > env->imbalance)
5906
			goto next;
5907

5908 5909 5910 5911
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
5912
		env->imbalance -= load;
5913 5914

#ifdef CONFIG_PREEMPT
5915 5916
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
5917
		 * kernels will stop after the first task is detached to minimize
5918 5919
		 * the critical section.
		 */
5920
		if (env->idle == CPU_NEWLY_IDLE)
5921
			break;
5922 5923
#endif

5924 5925 5926 5927
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
5928
		if (env->imbalance <= 0)
5929
			break;
5930 5931 5932

		continue;
next:
5933
		list_move_tail(&p->se.group_node, tasks);
5934
	}
5935

5936
	/*
5937 5938 5939
	 * 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().
5940
	 */
5941
	schedstat_add(env->sd, lb_gained[env->idle], detached);
5942

5943 5944 5945 5946 5947 5948 5949 5950 5951 5952 5953 5954
	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);
5955
	p->on_rq = TASK_ON_RQ_QUEUED;
5956 5957 5958 5959 5960 5961 5962 5963 5964 5965 5966 5967 5968 5969 5970 5971 5972 5973 5974 5975 5976 5977 5978 5979 5980 5981 5982 5983
	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);
5984

5985 5986 5987 5988
		attach_task(env->dst_rq, p);
	}

	raw_spin_unlock(&env->dst_rq->lock);
5989 5990
}

P
Peter Zijlstra 已提交
5991
#ifdef CONFIG_FAIR_GROUP_SCHED
5992
static void update_blocked_averages(int cpu)
5993 5994
{
	struct rq *rq = cpu_rq(cpu);
5995 5996
	struct cfs_rq *cfs_rq;
	unsigned long flags;
5997

5998 5999
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
6000

6001 6002 6003 6004
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
6005
	for_each_leaf_cfs_rq(rq, cfs_rq) {
6006 6007 6008
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
6009

6010 6011 6012
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
			update_tg_load_avg(cfs_rq, 0);
	}
6013
	raw_spin_unlock_irqrestore(&rq->lock, flags);
6014 6015
}

6016
/*
6017
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6018 6019 6020
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
6021
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6022
{
6023 6024
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6025
	unsigned long now = jiffies;
6026
	unsigned long load;
6027

6028
	if (cfs_rq->last_h_load_update == now)
6029 6030
		return;

6031 6032 6033 6034 6035 6036 6037
	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;
	}
6038

6039
	if (!se) {
6040
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6041 6042 6043 6044 6045
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
6046 6047
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
6048 6049 6050 6051
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
6052 6053
}

6054
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
6055
{
6056
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
6057

6058
	update_cfs_rq_h_load(cfs_rq);
6059
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6060
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
6061 6062
}
#else
6063
static inline void update_blocked_averages(int cpu)
6064
{
6065 6066 6067 6068 6069 6070 6071 6072
	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);
6073 6074
}

6075
static unsigned long task_h_load(struct task_struct *p)
6076
{
6077
	return p->se.avg.load_avg;
6078
}
P
Peter Zijlstra 已提交
6079
#endif
6080 6081

/********** Helpers for find_busiest_group ************************/
6082 6083 6084 6085 6086 6087 6088

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

6089 6090 6091 6092 6093 6094 6095
/*
 * 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
6096
	unsigned long load_per_task;
6097
	unsigned long group_capacity;
6098
	unsigned long group_util; /* Total utilization of the group */
6099 6100 6101
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
6102
	enum group_type group_type;
6103
	int group_no_capacity;
6104 6105 6106 6107
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
6108 6109
};

J
Joonsoo Kim 已提交
6110 6111 6112 6113 6114 6115 6116 6117
/*
 * 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 */
6118
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
6119 6120 6121
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6122
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
6123 6124
};

6125 6126 6127 6128 6129 6130 6131 6132 6133 6134 6135 6136
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,
6137
		.total_capacity = 0UL,
6138 6139
		.busiest_stat = {
			.avg_load = 0UL,
6140 6141
			.sum_nr_running = 0,
			.group_type = group_other,
6142 6143 6144 6145
		},
	};
}

6146 6147 6148
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
6149
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6150 6151
 *
 * Return: The load index.
6152 6153 6154 6155 6156 6157 6158 6159 6160 6161 6162 6163 6164 6165 6166 6167 6168 6169 6170 6171 6172 6173
 */
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;
}

6174
static unsigned long scale_rt_capacity(int cpu)
6175 6176
{
	struct rq *rq = cpu_rq(cpu);
6177
	u64 total, used, age_stamp, avg;
6178
	s64 delta;
6179

6180 6181 6182 6183
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
6184 6185
	age_stamp = READ_ONCE(rq->age_stamp);
	avg = READ_ONCE(rq->rt_avg);
6186
	delta = __rq_clock_broken(rq) - age_stamp;
6187

6188 6189 6190 6191
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
6192

6193
	used = div_u64(avg, total);
6194

6195 6196
	if (likely(used < SCHED_CAPACITY_SCALE))
		return SCHED_CAPACITY_SCALE - used;
6197

6198
	return 1;
6199 6200
}

6201
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6202
{
6203
	unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6204 6205
	struct sched_group *sdg = sd->groups;

6206
	cpu_rq(cpu)->cpu_capacity_orig = capacity;
6207

6208
	capacity *= scale_rt_capacity(cpu);
6209
	capacity >>= SCHED_CAPACITY_SHIFT;
6210

6211 6212
	if (!capacity)
		capacity = 1;
6213

6214 6215
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
6216 6217
}

6218
void update_group_capacity(struct sched_domain *sd, int cpu)
6219 6220 6221
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
6222
	unsigned long capacity;
6223 6224 6225 6226
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
6227
	sdg->sgc->next_update = jiffies + interval;
6228 6229

	if (!child) {
6230
		update_cpu_capacity(sd, cpu);
6231 6232 6233
		return;
	}

6234
	capacity = 0;
6235

P
Peter Zijlstra 已提交
6236 6237 6238 6239 6240 6241
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

6242
		for_each_cpu(cpu, sched_group_cpus(sdg)) {
6243
			struct sched_group_capacity *sgc;
6244
			struct rq *rq = cpu_rq(cpu);
6245

6246
			/*
6247
			 * build_sched_domains() -> init_sched_groups_capacity()
6248 6249 6250
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
6251 6252
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
6253
			 *
6254
			 * This avoids capacity from being 0 and
6255 6256 6257
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
6258
				capacity += capacity_of(cpu);
6259 6260
				continue;
			}
6261

6262 6263
			sgc = rq->sd->groups->sgc;
			capacity += sgc->capacity;
6264
		}
P
Peter Zijlstra 已提交
6265 6266 6267 6268 6269 6270 6271 6272
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
6273
			capacity += group->sgc->capacity;
P
Peter Zijlstra 已提交
6274 6275 6276
			group = group->next;
		} while (group != child->groups);
	}
6277

6278
	sdg->sgc->capacity = capacity;
6279 6280
}

6281
/*
6282 6283 6284
 * 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
6285 6286
 */
static inline int
6287
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6288
{
6289 6290
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
6291 6292
}

6293 6294 6295 6296 6297 6298 6299 6300 6301 6302 6303 6304 6305 6306 6307 6308
/*
 * 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
6309 6310
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
6311 6312
 *
 * When this is so detected; this group becomes a candidate for busiest; see
6313
 * update_sd_pick_busiest(). And calculate_imbalance() and
6314
 * find_busiest_group() avoid some of the usual balance conditions to allow it
6315 6316 6317 6318 6319 6320 6321
 * 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.
 */

6322
static inline int sg_imbalanced(struct sched_group *group)
6323
{
6324
	return group->sgc->imbalance;
6325 6326
}

6327
/*
6328 6329 6330
 * 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
6331 6332
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
6333 6334 6335 6336 6337
 * 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.
6338
 */
6339 6340
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6341
{
6342 6343
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
6344

6345
	if ((sgs->group_capacity * 100) >
6346
			(sgs->group_util * env->sd->imbalance_pct))
6347
		return true;
6348

6349 6350 6351 6352 6353 6354 6355 6356 6357 6358 6359 6360 6361 6362 6363 6364
	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;
6365

6366
	if ((sgs->group_capacity * 100) <
6367
			(sgs->group_util * env->sd->imbalance_pct))
6368
		return true;
6369

6370
	return false;
6371 6372
}

6373 6374 6375
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
6376
{
6377
	if (sgs->group_no_capacity)
6378 6379 6380 6381 6382 6383 6384 6385
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

6386 6387
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6388
 * @env: The load balancing environment.
6389 6390 6391 6392
 * @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.
6393
 * @overload: Indicate more than one runnable task for any CPU.
6394
 */
6395 6396
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
6397 6398
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
6399
{
6400
	unsigned long load;
6401
	int i;
6402

6403 6404
	memset(sgs, 0, sizeof(*sgs));

6405
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6406 6407 6408
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
6409
		if (local_group)
6410
			load = target_load(i, load_idx);
6411
		else
6412 6413 6414
			load = source_load(i, load_idx);

		sgs->group_load += load;
6415
		sgs->group_util += cpu_util(i);
6416
		sgs->sum_nr_running += rq->cfs.h_nr_running;
6417 6418 6419 6420

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

6421 6422 6423 6424
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
6425
		sgs->sum_weighted_load += weighted_cpuload(i);
6426 6427
		if (idle_cpu(i))
			sgs->idle_cpus++;
6428 6429
	}

6430 6431
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
6432
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6433

6434
	if (sgs->sum_nr_running)
6435
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6436

6437
	sgs->group_weight = group->group_weight;
6438

6439
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
6440
	sgs->group_type = group_classify(group, sgs);
6441 6442
}

6443 6444
/**
 * update_sd_pick_busiest - return 1 on busiest group
6445
 * @env: The load balancing environment.
6446 6447
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
6448
 * @sgs: sched_group statistics
6449 6450 6451
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
6452 6453 6454
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
6455
 */
6456
static bool update_sd_pick_busiest(struct lb_env *env,
6457 6458
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
6459
				   struct sg_lb_stats *sgs)
6460
{
6461
	struct sg_lb_stats *busiest = &sds->busiest_stat;
6462

6463
	if (sgs->group_type > busiest->group_type)
6464 6465
		return true;

6466 6467 6468 6469 6470 6471 6472 6473
	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))
6474 6475 6476 6477 6478 6479 6480
		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.
	 */
6481
	if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6482 6483 6484 6485 6486 6487 6488 6489 6490 6491
		if (!sds->busiest)
			return true;

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

	return false;
}

6492 6493 6494 6495 6496 6497 6498 6499 6500 6501 6502 6503 6504 6505 6506 6507 6508 6509 6510 6511 6512 6513 6514 6515 6516 6517 6518 6519 6520 6521
#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 */

6522
/**
6523
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6524
 * @env: The load balancing environment.
6525 6526
 * @sds: variable to hold the statistics for this sched_domain.
 */
6527
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6528
{
6529 6530
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
6531
	struct sg_lb_stats tmp_sgs;
6532
	int load_idx, prefer_sibling = 0;
6533
	bool overload = false;
6534 6535 6536 6537

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

6538
	load_idx = get_sd_load_idx(env->sd, env->idle);
6539 6540

	do {
J
Joonsoo Kim 已提交
6541
		struct sg_lb_stats *sgs = &tmp_sgs;
6542 6543
		int local_group;

6544
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
6545 6546 6547
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
6548 6549

			if (env->idle != CPU_NEWLY_IDLE ||
6550 6551
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
6552
		}
6553

6554 6555
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
6556

6557 6558 6559
		if (local_group)
			goto next_group;

6560 6561
		/*
		 * In case the child domain prefers tasks go to siblings
6562
		 * first, lower the sg capacity so that we'll try
6563 6564
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
6565 6566 6567 6568
		 * 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).
6569
		 */
6570
		if (prefer_sibling && sds->local &&
6571 6572 6573
		    group_has_capacity(env, &sds->local_stat) &&
		    (sgs->sum_nr_running > 1)) {
			sgs->group_no_capacity = 1;
6574
			sgs->group_type = group_classify(sg, sgs);
6575
		}
6576

6577
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6578
			sds->busiest = sg;
J
Joonsoo Kim 已提交
6579
			sds->busiest_stat = *sgs;
6580 6581
		}

6582 6583 6584
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
6585
		sds->total_capacity += sgs->group_capacity;
6586

6587
		sg = sg->next;
6588
	} while (sg != env->sd->groups);
6589 6590 6591

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6592 6593 6594 6595 6596 6597 6598

	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;
	}

6599 6600 6601 6602 6603 6604 6605 6606 6607 6608 6609 6610 6611 6612 6613 6614 6615 6616 6617
}

/**
 * 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.
 *
6618
 * Return: 1 when packing is required and a task should be moved to
6619 6620
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
6621
 * @env: The load balancing environment.
6622 6623
 * @sds: Statistics of the sched_domain which is to be packed
 */
6624
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6625 6626 6627
{
	int busiest_cpu;

6628
	if (!(env->sd->flags & SD_ASYM_PACKING))
6629 6630 6631 6632 6633 6634
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
6635
	if (env->dst_cpu > busiest_cpu)
6636 6637
		return 0;

6638
	env->imbalance = DIV_ROUND_CLOSEST(
6639
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6640
		SCHED_CAPACITY_SCALE);
6641

6642
	return 1;
6643 6644 6645 6646 6647 6648
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
6649
 * @env: The load balancing environment.
6650 6651
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
6652 6653
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6654
{
6655
	unsigned long tmp, capa_now = 0, capa_move = 0;
6656
	unsigned int imbn = 2;
6657
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
6658
	struct sg_lb_stats *local, *busiest;
6659

J
Joonsoo Kim 已提交
6660 6661
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6662

J
Joonsoo Kim 已提交
6663 6664 6665 6666
	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;
6667

J
Joonsoo Kim 已提交
6668
	scaled_busy_load_per_task =
6669
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6670
		busiest->group_capacity;
J
Joonsoo Kim 已提交
6671

6672 6673
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
6674
		env->imbalance = busiest->load_per_task;
6675 6676 6677 6678 6679
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
6680
	 * however we may be able to increase total CPU capacity used by
6681 6682 6683
	 * moving them.
	 */

6684
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
6685
			min(busiest->load_per_task, busiest->avg_load);
6686
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
6687
			min(local->load_per_task, local->avg_load);
6688
	capa_now /= SCHED_CAPACITY_SCALE;
6689 6690

	/* Amount of load we'd subtract */
6691
	if (busiest->avg_load > scaled_busy_load_per_task) {
6692
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
6693
			    min(busiest->load_per_task,
6694
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
6695
	}
6696 6697

	/* Amount of load we'd add */
6698
	if (busiest->avg_load * busiest->group_capacity <
6699
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6700 6701
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
6702
	} else {
6703
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6704
		      local->group_capacity;
J
Joonsoo Kim 已提交
6705
	}
6706
	capa_move += local->group_capacity *
6707
		    min(local->load_per_task, local->avg_load + tmp);
6708
	capa_move /= SCHED_CAPACITY_SCALE;
6709 6710

	/* Move if we gain throughput */
6711
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
6712
		env->imbalance = busiest->load_per_task;
6713 6714 6715 6716 6717
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
6718
 * @env: load balance environment
6719 6720
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
6721
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6722
{
6723
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
6724 6725 6726 6727
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6728

6729
	if (busiest->group_type == group_imbalanced) {
6730 6731 6732 6733
		/*
		 * 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
6734 6735
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
6736 6737
	}

6738 6739 6740
	/*
	 * 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
6741
	 * its cpu_capacity, while calculating max_load..)
6742
	 */
6743 6744
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
6745 6746
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
6747 6748
	}

6749 6750 6751 6752 6753
	/*
	 * If there aren't any idle cpus, avoid creating some.
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
6754 6755 6756 6757 6758 6759
		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;
6760 6761 6762 6763 6764 6765 6766 6767 6768 6769
	}

	/*
	 * 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.
	 */
6770
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6771 6772

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
6773
	env->imbalance = min(
6774 6775
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
6776
	) / SCHED_CAPACITY_SCALE;
6777 6778 6779

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
6780
	 * there is no guarantee that any tasks will be moved so we'll have
6781 6782 6783
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
6784
	if (env->imbalance < busiest->load_per_task)
6785
		return fix_small_imbalance(env, sds);
6786
}
6787

6788 6789 6790 6791 6792 6793 6794 6795 6796 6797 6798 6799
/******* 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.
 *
6800
 * @env: The load balancing environment.
6801
 *
6802
 * Return:	- The busiest group if imbalance exists.
6803 6804 6805 6806
 *		- 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
6807
static struct sched_group *find_busiest_group(struct lb_env *env)
6808
{
J
Joonsoo Kim 已提交
6809
	struct sg_lb_stats *local, *busiest;
6810 6811
	struct sd_lb_stats sds;

6812
	init_sd_lb_stats(&sds);
6813 6814 6815 6816 6817

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
6818
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
6819 6820
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
6821

6822
	/* ASYM feature bypasses nice load balance check */
6823 6824
	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(env, &sds))
6825 6826
		return sds.busiest;

6827
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
6828
	if (!sds.busiest || busiest->sum_nr_running == 0)
6829 6830
		goto out_balanced;

6831 6832
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
6833

P
Peter Zijlstra 已提交
6834 6835
	/*
	 * If the busiest group is imbalanced the below checks don't
6836
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
6837 6838
	 * isn't true due to cpus_allowed constraints and the like.
	 */
6839
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
6840 6841
		goto force_balance;

6842
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6843 6844
	if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
	    busiest->group_no_capacity)
6845 6846
		goto force_balance;

6847
	/*
6848
	 * If the local group is busier than the selected busiest group
6849 6850
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
6851
	if (local->avg_load >= busiest->avg_load)
6852 6853
		goto out_balanced;

6854 6855 6856 6857
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
6858
	if (local->avg_load >= sds.avg_load)
6859 6860
		goto out_balanced;

6861
	if (env->idle == CPU_IDLE) {
6862
		/*
6863 6864 6865 6866 6867
		 * 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
6868
		 */
6869 6870
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
6871
			goto out_balanced;
6872 6873 6874 6875 6876
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
6877 6878
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
6879
			goto out_balanced;
6880
	}
6881

6882
force_balance:
6883
	/* Looks like there is an imbalance. Compute it */
6884
	calculate_imbalance(env, &sds);
6885 6886 6887
	return sds.busiest;

out_balanced:
6888
	env->imbalance = 0;
6889 6890 6891 6892 6893 6894
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
6895
static struct rq *find_busiest_queue(struct lb_env *env,
6896
				     struct sched_group *group)
6897 6898
{
	struct rq *busiest = NULL, *rq;
6899
	unsigned long busiest_load = 0, busiest_capacity = 1;
6900 6901
	int i;

6902
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6903
		unsigned long capacity, wl;
6904 6905 6906 6907
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
6908

6909 6910 6911 6912 6913 6914 6915 6916 6917 6918 6919 6920 6921 6922 6923 6924 6925 6926 6927 6928 6929 6930
		/*
		 * 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;

6931
		capacity = capacity_of(i);
6932

6933
		wl = weighted_cpuload(i);
6934

6935 6936
		/*
		 * When comparing with imbalance, use weighted_cpuload()
6937
		 * which is not scaled with the cpu capacity.
6938
		 */
6939 6940 6941

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
6942 6943
			continue;

6944 6945
		/*
		 * For the load comparisons with the other cpu's, consider
6946 6947 6948
		 * 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.
6949
		 *
6950
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
6951
		 * multiplication to rid ourselves of the division works out
6952 6953
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
6954
		 */
6955
		if (wl * busiest_capacity > busiest_load * capacity) {
6956
			busiest_load = wl;
6957
			busiest_capacity = capacity;
6958 6959 6960 6961 6962 6963 6964 6965 6966 6967 6968 6969 6970 6971
			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. */
6972
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6973

6974
static int need_active_balance(struct lb_env *env)
6975
{
6976 6977 6978
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
6979 6980 6981 6982 6983 6984

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
6985
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6986
			return 1;
6987 6988
	}

6989 6990 6991 6992 6993 6994 6995 6996 6997 6998 6999 7000 7001
	/*
	 * 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;
	}

7002 7003 7004
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

7005 7006
static int active_load_balance_cpu_stop(void *data);

7007 7008 7009 7010 7011 7012 7013 7014 7015 7016 7017 7018 7019 7020 7021 7022 7023 7024 7025 7026 7027 7028 7029 7030 7031 7032 7033 7034 7035 7036 7037
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.
	 */
7038
	return balance_cpu == env->dst_cpu;
7039 7040
}

7041 7042 7043 7044 7045 7046
/*
 * 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,
7047
			int *continue_balancing)
7048
{
7049
	int ld_moved, cur_ld_moved, active_balance = 0;
7050
	struct sched_domain *sd_parent = sd->parent;
7051 7052 7053
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
7054
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7055

7056 7057
	struct lb_env env = {
		.sd		= sd,
7058 7059
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
7060
		.dst_grpmask    = sched_group_cpus(sd->groups),
7061
		.idle		= idle,
7062
		.loop_break	= sched_nr_migrate_break,
7063
		.cpus		= cpus,
7064
		.fbq_type	= all,
7065
		.tasks		= LIST_HEAD_INIT(env.tasks),
7066 7067
	};

7068 7069 7070 7071
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
7072
	if (idle == CPU_NEWLY_IDLE)
7073 7074
		env.dst_grpmask = NULL;

7075 7076 7077 7078 7079
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
7080 7081
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
7082
		goto out_balanced;
7083
	}
7084

7085
	group = find_busiest_group(&env);
7086 7087 7088 7089 7090
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

7091
	busiest = find_busiest_queue(&env, group);
7092 7093 7094 7095 7096
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

7097
	BUG_ON(busiest == env.dst_rq);
7098

7099
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7100

7101 7102 7103
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

7104 7105 7106 7107 7108 7109 7110 7111
	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.
		 */
7112
		env.flags |= LBF_ALL_PINNED;
7113
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
7114

7115
more_balance:
7116
		raw_spin_lock_irqsave(&busiest->lock, flags);
7117 7118 7119 7120 7121

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
7122
		cur_ld_moved = detach_tasks(&env);
7123 7124

		/*
7125 7126 7127 7128 7129
		 * 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.
7130
		 */
7131 7132 7133 7134 7135 7136 7137 7138

		raw_spin_unlock(&busiest->lock);

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

7139
		local_irq_restore(flags);
7140

7141 7142 7143 7144 7145
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

7146 7147 7148 7149 7150 7151 7152 7153 7154 7155 7156 7157 7158 7159 7160 7161 7162 7163 7164
		/*
		 * 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.
		 */
7165
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7166

7167 7168 7169
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

7170
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
7171
			env.dst_cpu	 = env.new_dst_cpu;
7172
			env.flags	&= ~LBF_DST_PINNED;
7173 7174
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
7175

7176 7177 7178 7179 7180 7181
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
7182

7183 7184 7185 7186
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
7187
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7188

7189
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7190 7191 7192
				*group_imbalance = 1;
		}

7193
		/* All tasks on this runqueue were pinned by CPU affinity */
7194
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
7195
			cpumask_clear_cpu(cpu_of(busiest), cpus);
7196 7197 7198
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
7199
				goto redo;
7200
			}
7201
			goto out_all_pinned;
7202 7203 7204 7205 7206
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
7207 7208 7209 7210 7211 7212 7213 7214
		/*
		 * 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++;
7215

7216
		if (need_active_balance(&env)) {
7217 7218
			raw_spin_lock_irqsave(&busiest->lock, flags);

7219 7220 7221
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
7222 7223
			 */
			if (!cpumask_test_cpu(this_cpu,
7224
					tsk_cpus_allowed(busiest->curr))) {
7225 7226
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
7227
				env.flags |= LBF_ALL_PINNED;
7228 7229 7230
				goto out_one_pinned;
			}

7231 7232 7233 7234 7235
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
7236 7237 7238 7239 7240 7241
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
7242

7243
			if (active_balance) {
7244 7245 7246
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
7247
			}
7248 7249 7250 7251 7252 7253 7254 7255 7256 7257 7258 7259 7260 7261 7262 7263 7264 7265

			/*
			 * 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
7266
		 * detach_tasks).
7267 7268 7269 7270 7271 7272 7273 7274
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
7275 7276 7277 7278 7279 7280 7281 7282 7283 7284 7285 7286 7287 7288 7289 7290 7291
	/*
	 * 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.
	 */
7292 7293 7294 7295 7296 7297
	schedstat_inc(sd, lb_balanced[idle]);

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
7298
	if (((env.flags & LBF_ALL_PINNED) &&
7299
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
7300 7301 7302
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

7303
	ld_moved = 0;
7304 7305 7306 7307
out:
	return ld_moved;
}

7308 7309 7310 7311 7312 7313 7314 7315 7316 7317 7318 7319 7320 7321 7322 7323 7324 7325 7326 7327 7328 7329 7330 7331 7332 7333 7334
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;
}

7335 7336 7337 7338
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
7339
static int idle_balance(struct rq *this_rq)
7340
{
7341 7342
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
7343 7344
	struct sched_domain *sd;
	int pulled_task = 0;
7345
	u64 curr_cost = 0;
7346

7347 7348 7349 7350 7351 7352
	/*
	 * 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);

7353 7354
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
7355 7356 7357 7358 7359 7360
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
			update_next_balance(sd, 0, &next_balance);
		rcu_read_unlock();

7361
		goto out;
7362
	}
7363

7364 7365
	raw_spin_unlock(&this_rq->lock);

7366
	update_blocked_averages(this_cpu);
7367
	rcu_read_lock();
7368
	for_each_domain(this_cpu, sd) {
7369
		int continue_balancing = 1;
7370
		u64 t0, domain_cost;
7371 7372 7373 7374

		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

7375 7376
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
			update_next_balance(sd, 0, &next_balance);
7377
			break;
7378
		}
7379

7380
		if (sd->flags & SD_BALANCE_NEWIDLE) {
7381 7382
			t0 = sched_clock_cpu(this_cpu);

7383
			pulled_task = load_balance(this_cpu, this_rq,
7384 7385
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
7386 7387 7388 7389 7390 7391

			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;
7392
		}
7393

7394
		update_next_balance(sd, 0, &next_balance);
7395 7396 7397 7398 7399 7400

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
7401 7402
			break;
	}
7403
	rcu_read_unlock();
7404 7405 7406

	raw_spin_lock(&this_rq->lock);

7407 7408 7409
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

7410
	/*
7411 7412 7413
	 * 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.
7414
	 */
7415
	if (this_rq->cfs.h_nr_running && !pulled_task)
7416
		pulled_task = 1;
7417

7418 7419 7420
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
7421
		this_rq->next_balance = next_balance;
7422

7423
	/* Is there a task of a high priority class? */
7424
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7425 7426
		pulled_task = -1;

7427
	if (pulled_task)
7428 7429
		this_rq->idle_stamp = 0;

7430
	return pulled_task;
7431 7432 7433
}

/*
7434 7435 7436 7437
 * 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.
7438
 */
7439
static int active_load_balance_cpu_stop(void *data)
7440
{
7441 7442
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
7443
	int target_cpu = busiest_rq->push_cpu;
7444
	struct rq *target_rq = cpu_rq(target_cpu);
7445
	struct sched_domain *sd;
7446
	struct task_struct *p = NULL;
7447 7448 7449 7450 7451 7452 7453

	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;
7454 7455 7456

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
7457
		goto out_unlock;
7458 7459 7460 7461 7462 7463 7464 7465 7466

	/*
	 * 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. */
7467
	rcu_read_lock();
7468 7469 7470 7471 7472 7473 7474
	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)) {
7475 7476
		struct lb_env env = {
			.sd		= sd,
7477 7478 7479 7480
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
7481 7482 7483
			.idle		= CPU_IDLE,
		};

7484 7485
		schedstat_inc(sd, alb_count);

7486 7487
		p = detach_one_task(&env);
		if (p)
7488 7489 7490 7491
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
7492
	rcu_read_unlock();
7493 7494
out_unlock:
	busiest_rq->active_balance = 0;
7495 7496 7497 7498 7499 7500 7501
	raw_spin_unlock(&busiest_rq->lock);

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

7502
	return 0;
7503 7504
}

7505 7506 7507 7508 7509
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

7510
#ifdef CONFIG_NO_HZ_COMMON
7511 7512 7513 7514 7515 7516
/*
 * 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.
 */
7517
static struct {
7518
	cpumask_var_t idle_cpus_mask;
7519
	atomic_t nr_cpus;
7520 7521
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
7522

7523
static inline int find_new_ilb(void)
7524
{
7525
	int ilb = cpumask_first(nohz.idle_cpus_mask);
7526

7527 7528 7529 7530
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
7531 7532
}

7533 7534 7535 7536 7537
/*
 * 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).
 */
7538
static void nohz_balancer_kick(void)
7539 7540 7541 7542 7543
{
	int ilb_cpu;

	nohz.next_balance++;

7544
	ilb_cpu = find_new_ilb();
7545

7546 7547
	if (ilb_cpu >= nr_cpu_ids)
		return;
7548

7549
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7550 7551 7552 7553 7554 7555 7556 7557
		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);
7558 7559 7560
	return;
}

7561
static inline void nohz_balance_exit_idle(int cpu)
7562 7563
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7564 7565 7566 7567 7568 7569 7570
		/*
		 * 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);
		}
7571 7572 7573 7574
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

7575 7576 7577
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
7578
	int cpu = smp_processor_id();
7579 7580

	rcu_read_lock();
7581
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7582 7583 7584 7585 7586

	if (!sd || !sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 0;

7587
	atomic_inc(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7588
unlock:
7589 7590 7591 7592 7593 7594
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
7595
	int cpu = smp_processor_id();
7596 7597

	rcu_read_lock();
7598
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7599 7600 7601 7602 7603

	if (!sd || sd->nohz_idle)
		goto unlock;
	sd->nohz_idle = 1;

7604
	atomic_dec(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7605
unlock:
7606 7607 7608
	rcu_read_unlock();
}

7609
/*
7610
 * This routine will record that the cpu is going idle with tick stopped.
7611
 * This info will be used in performing idle load balancing in the future.
7612
 */
7613
void nohz_balance_enter_idle(int cpu)
7614
{
7615 7616 7617 7618 7619 7620
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

7621 7622
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
7623

7624 7625 7626 7627 7628 7629
	/*
	 * If we're a completely isolated CPU, we don't play.
	 */
	if (on_null_domain(cpu_rq(cpu)))
		return;

7630 7631 7632
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7633
}
7634

7635
static int sched_ilb_notifier(struct notifier_block *nfb,
7636 7637 7638 7639
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
7640
		nohz_balance_exit_idle(smp_processor_id());
7641 7642 7643 7644 7645
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
7646 7647 7648 7649
#endif

static DEFINE_SPINLOCK(balancing);

7650 7651 7652 7653
/*
 * 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.
 */
7654
void update_max_interval(void)
7655 7656 7657 7658
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

7659 7660 7661 7662
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
7663
 * Balancing parameters are set up in init_sched_domains.
7664
 */
7665
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7666
{
7667
	int continue_balancing = 1;
7668
	int cpu = rq->cpu;
7669
	unsigned long interval;
7670
	struct sched_domain *sd;
7671 7672 7673
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
7674 7675
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
7676

7677
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
7678

7679
	rcu_read_lock();
7680
	for_each_domain(cpu, sd) {
7681 7682 7683 7684 7685 7686 7687 7688 7689 7690 7691 7692
		/*
		 * 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;

7693 7694 7695
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

7696 7697 7698 7699 7700 7701 7702 7703 7704 7705 7706
		/*
		 * 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;
		}

7707
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7708 7709 7710 7711 7712 7713 7714 7715

		need_serialize = sd->flags & SD_SERIALIZE;
		if (need_serialize) {
			if (!spin_trylock(&balancing))
				goto out;
		}

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
7716
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7717
				/*
7718
				 * The LBF_DST_PINNED logic could have changed
7719 7720
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
7721
				 */
7722
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7723 7724
			}
			sd->last_balance = jiffies;
7725
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7726 7727 7728 7729 7730 7731 7732 7733
		}
		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;
		}
7734 7735
	}
	if (need_decay) {
7736
		/*
7737 7738
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
7739
		 */
7740 7741
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
7742
	}
7743
	rcu_read_unlock();
7744 7745 7746 7747 7748 7749

	/*
	 * 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.
	 */
7750
	if (likely(update_next_balance)) {
7751
		rq->next_balance = next_balance;
7752 7753 7754 7755 7756 7757 7758 7759 7760 7761 7762 7763 7764 7765

#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
	}
7766 7767
}

7768
#ifdef CONFIG_NO_HZ_COMMON
7769
/*
7770
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7771 7772
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
7773
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7774
{
7775
	int this_cpu = this_rq->cpu;
7776 7777
	struct rq *rq;
	int balance_cpu;
7778 7779 7780
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
7781

7782 7783 7784
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
7785 7786

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7787
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7788 7789 7790 7791 7792 7793 7794
			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.
		 */
7795
		if (need_resched())
7796 7797
			break;

V
Vincent Guittot 已提交
7798 7799
		rq = cpu_rq(balance_cpu);

7800 7801 7802 7803 7804 7805 7806 7807 7808 7809 7810
		/*
		 * 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);
		}
7811

7812 7813 7814 7815
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
7816
	}
7817 7818 7819 7820 7821 7822 7823 7824

	/*
	 * 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;
7825 7826
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7827 7828 7829
}

/*
7830
 * Current heuristic for kicking the idle load balancer in the presence
7831
 * of an idle cpu in the system.
7832
 *   - This rq has more than one task.
7833 7834 7835 7836
 *   - 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.
7837 7838
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
7839
 */
7840
static inline bool nohz_kick_needed(struct rq *rq)
7841 7842
{
	unsigned long now = jiffies;
7843
	struct sched_domain *sd;
7844
	struct sched_group_capacity *sgc;
7845
	int nr_busy, cpu = rq->cpu;
7846
	bool kick = false;
7847

7848
	if (unlikely(rq->idle_balance))
7849
		return false;
7850

7851 7852 7853 7854
       /*
	* 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.
	*/
7855
	set_cpu_sd_state_busy();
7856
	nohz_balance_exit_idle(cpu);
7857 7858 7859 7860 7861 7862

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
7863
		return false;
7864 7865

	if (time_before(now, nohz.next_balance))
7866
		return false;
7867

7868
	if (rq->nr_running >= 2)
7869
		return true;
7870

7871
	rcu_read_lock();
7872 7873
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
	if (sd) {
7874 7875
		sgc = sd->groups->sgc;
		nr_busy = atomic_read(&sgc->nr_busy_cpus);
7876

7877 7878 7879 7880 7881
		if (nr_busy > 1) {
			kick = true;
			goto unlock;
		}

7882
	}
7883

7884 7885 7886 7887 7888 7889 7890 7891
	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
			kick = true;
			goto unlock;
		}
	}
7892

7893
	sd = rcu_dereference(per_cpu(sd_asym, cpu));
7894
	if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
7895 7896 7897 7898
				  sched_domain_span(sd)) < cpu)) {
		kick = true;
		goto unlock;
	}
7899

7900
unlock:
7901
	rcu_read_unlock();
7902
	return kick;
7903 7904
}
#else
7905
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7906 7907 7908 7909 7910 7911
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
7912 7913
static void run_rebalance_domains(struct softirq_action *h)
{
7914
	struct rq *this_rq = this_rq();
7915
	enum cpu_idle_type idle = this_rq->idle_balance ?
7916 7917 7918
						CPU_IDLE : CPU_NOT_IDLE;

	/*
7919
	 * If this cpu has a pending nohz_balance_kick, then do the
7920
	 * balancing on behalf of the other idle cpus whose ticks are
7921 7922 7923 7924
	 * 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.
7925
	 */
7926
	nohz_idle_balance(this_rq, idle);
7927
	rebalance_domains(this_rq, idle);
7928 7929 7930 7931 7932
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
7933
void trigger_load_balance(struct rq *rq)
7934 7935
{
	/* Don't need to rebalance while attached to NULL domain */
7936 7937 7938 7939
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
7940
		raise_softirq(SCHED_SOFTIRQ);
7941
#ifdef CONFIG_NO_HZ_COMMON
7942
	if (nohz_kick_needed(rq))
7943
		nohz_balancer_kick();
7944
#endif
7945 7946
}

7947 7948 7949
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
7950 7951

	update_runtime_enabled(rq);
7952 7953 7954 7955 7956
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
7957 7958 7959

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
7960 7961
}

7962
#endif /* CONFIG_SMP */
7963

7964 7965 7966
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
7967
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
7968 7969 7970 7971 7972 7973
{
	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
7974
		entity_tick(cfs_rq, se, queued);
7975
	}
7976

7977
	if (static_branch_unlikely(&sched_numa_balancing))
7978
		task_tick_numa(rq, curr);
7979 7980 7981
}

/*
P
Peter Zijlstra 已提交
7982 7983 7984
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
7985
 */
P
Peter Zijlstra 已提交
7986
static void task_fork_fair(struct task_struct *p)
7987
{
7988 7989
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
7990
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
7991 7992 7993
	struct rq *rq = this_rq();
	unsigned long flags;

7994
	raw_spin_lock_irqsave(&rq->lock, flags);
7995

7996 7997
	update_rq_clock(rq);

7998 7999 8000
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

8001 8002 8003 8004 8005 8006 8007 8008 8009
	/*
	 * 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();
8010

8011
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
8012

8013 8014
	if (curr)
		se->vruntime = curr->vruntime;
8015
	place_entity(cfs_rq, se, 1);
8016

P
Peter Zijlstra 已提交
8017
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
8018
		/*
8019 8020 8021
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
8022
		swap(curr->vruntime, se->vruntime);
8023
		resched_curr(rq);
8024
	}
8025

8026 8027
	se->vruntime -= cfs_rq->min_vruntime;

8028
	raw_spin_unlock_irqrestore(&rq->lock, flags);
8029 8030
}

8031 8032 8033 8034
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
8035 8036
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8037
{
8038
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
8039 8040
		return;

8041 8042 8043 8044 8045
	/*
	 * 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
8046
	if (rq->curr == p) {
8047
		if (p->prio > oldprio)
8048
			resched_curr(rq);
8049
	} else
8050
		check_preempt_curr(rq, p, 0);
8051 8052
}

8053
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
8054 8055 8056 8057
{
	struct sched_entity *se = &p->se;

	/*
8058 8059 8060 8061 8062 8063 8064 8065 8066 8067
	 * 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
8068
	 *
8069 8070 8071 8072
	 * - 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
8073
	 */
8074 8075 8076 8077 8078 8079 8080 8081 8082 8083 8084 8085
	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
8086 8087 8088 8089 8090 8091 8092
		/*
		 * 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;
	}
8093

8094
	/* Catch up with the cfs_rq and remove our load when we leave */
8095
	detach_entity_load_avg(cfs_rq, se);
P
Peter Zijlstra 已提交
8096 8097
}

8098
static void attach_task_cfs_rq(struct task_struct *p)
8099
{
8100
	struct sched_entity *se = &p->se;
8101
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
8102 8103

#ifdef CONFIG_FAIR_GROUP_SCHED
8104 8105 8106 8107 8108 8109
	/*
	 * 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
8110

8111
	/* Synchronize task with its cfs_rq */
8112 8113 8114 8115 8116
	attach_entity_load_avg(cfs_rq, se);

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
8117

8118 8119 8120 8121 8122 8123 8124 8125
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);
8126

8127
	if (task_on_rq_queued(p)) {
8128
		/*
8129 8130 8131
		 * 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.
8132
		 */
8133 8134 8135 8136
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
8137
	}
8138 8139
}

8140 8141 8142 8143 8144 8145 8146 8147 8148
/* 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;

8149 8150 8151 8152 8153 8154 8155
	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);
	}
8156 8157
}

8158 8159 8160 8161 8162 8163 8164
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
8165
#ifdef CONFIG_SMP
8166 8167
	atomic_long_set(&cfs_rq->removed_load_avg, 0);
	atomic_long_set(&cfs_rq->removed_util_avg, 0);
8168
#endif
8169 8170
}

P
Peter Zijlstra 已提交
8171
#ifdef CONFIG_FAIR_GROUP_SCHED
8172
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
8173
{
8174
	detach_task_cfs_rq(p);
8175
	set_task_rq(p, task_cpu(p));
8176 8177 8178 8179 8180

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
8181
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
8182
}
8183 8184 8185 8186 8187 8188 8189 8190 8191 8192

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]);
8193 8194 8195
		if (tg->se) {
			if (tg->se[i])
				remove_entity_load_avg(tg->se[i]);
8196
			kfree(tg->se[i]);
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 8233
	}

	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]);
8234
		init_entity_runnable_average(se);
8235 8236 8237 8238 8239 8240 8241 8242 8243 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 8274 8275 8276 8277 8278
	}

	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;

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Peter Zijlstra 已提交
8279
	if (!parent) {
8280
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
8281 8282
		se->depth = 0;
	} else {
8283
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
8284 8285
		se->depth = parent->depth + 1;
	}
8286 8287

	se->my_q = cfs_rq;
8288 8289
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
8290 8291 8292 8293 8294 8295 8296 8297 8298 8299 8300 8301 8302 8303 8304 8305 8306 8307 8308 8309 8310 8311 8312 8313 8314 8315 8316 8317 8318 8319
	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);
8320 8321 8322

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
8323
		for_each_sched_entity(se)
8324 8325 8326 8327 8328 8329 8330 8331 8332 8333 8334 8335 8336 8337 8338 8339 8340 8341 8342 8343 8344
			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
8345

8346
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8347 8348 8349 8350 8351 8352 8353 8354 8355
{
	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)
8356
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8357 8358 8359 8360

	return rr_interval;
}

8361 8362 8363
/*
 * All the scheduling class methods:
 */
8364
const struct sched_class fair_sched_class = {
8365
	.next			= &idle_sched_class,
8366 8367 8368
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
8369
	.yield_to_task		= yield_to_task_fair,
8370

I
Ingo Molnar 已提交
8371
	.check_preempt_curr	= check_preempt_wakeup,
8372 8373 8374 8375

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

8376
#ifdef CONFIG_SMP
L
Li Zefan 已提交
8377
	.select_task_rq		= select_task_rq_fair,
8378
	.migrate_task_rq	= migrate_task_rq_fair,
8379

8380 8381
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
8382 8383

	.task_waking		= task_waking_fair,
8384
	.task_dead		= task_dead_fair,
8385
	.set_cpus_allowed	= set_cpus_allowed_common,
8386
#endif
8387

8388
	.set_curr_task          = set_curr_task_fair,
8389
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
8390
	.task_fork		= task_fork_fair,
8391 8392

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
8393
	.switched_from		= switched_from_fair,
8394
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
8395

8396 8397
	.get_rr_interval	= get_rr_interval_fair,

8398 8399
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
8400
#ifdef CONFIG_FAIR_GROUP_SCHED
8401
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
8402
#endif
8403 8404 8405
};

#ifdef CONFIG_SCHED_DEBUG
8406
void print_cfs_stats(struct seq_file *m, int cpu)
8407 8408 8409
{
	struct cfs_rq *cfs_rq;

8410
	rcu_read_lock();
8411
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8412
		print_cfs_rq(m, cpu, cfs_rq);
8413
	rcu_read_unlock();
8414
}
8415 8416 8417 8418 8419 8420 8421 8422 8423 8424 8425 8426 8427 8428 8429 8430 8431 8432 8433 8434 8435

#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 */
8436 8437 8438 8439 8440 8441

__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

8442
#ifdef CONFIG_NO_HZ_COMMON
8443
	nohz.next_balance = jiffies;
8444
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8445
	cpu_notifier(sched_ilb_notifier, 0);
8446 8447 8448 8449
#endif
#endif /* SMP */

}