fair.c 213.5 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:
 */
static int get_update_sysctl_factor(void)
{
	unsigned int cpus = min_t(int, num_online_cpus(), 8);
	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 void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
				       int force_update);
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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;
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		/* We should have no load, but we need to update last_decay. */
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		update_cfs_rq_blocked_load(cfs_rq, 0);
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	}
}

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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	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)
{
	u64 period = sysctl_sched_latency;
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	unsigned long nr_latency = sched_nr_latency;
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	if (unlikely(nr_running > nr_latency)) {
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		period = sysctl_sched_min_granularity;
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		period *= nr_running;
	}

	return period;
}

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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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{
665
	return calc_delta_fair(sched_slice(cfs_rq, se), se);
666 667
}

668
#ifdef CONFIG_SMP
669
static int select_idle_sibling(struct task_struct *p, int cpu);
670 671
static unsigned long task_h_load(struct task_struct *p);

672
static inline void __update_task_entity_contrib(struct sched_entity *se);
673
static inline void __update_task_entity_utilization(struct sched_entity *se);
674 675 676 677 678 679 680

/* Give new task start runnable values to heavy its load in infant time */
void init_task_runnable_average(struct task_struct *p)
{
	u32 slice;

	slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
681 682
	p->se.avg.runnable_avg_sum = p->se.avg.running_avg_sum = slice;
	p->se.avg.avg_period = slice;
683
	__update_task_entity_contrib(&p->se);
684
	__update_task_entity_utilization(&p->se);
685 686 687 688 689 690 691
}
#else
void init_task_runnable_average(struct task_struct *p)
{
}
#endif

692
/*
693
 * Update the current task's runtime statistics.
694
 */
695
static void update_curr(struct cfs_rq *cfs_rq)
696
{
697
	struct sched_entity *curr = cfs_rq->curr;
698
	u64 now = rq_clock_task(rq_of(cfs_rq));
699
	u64 delta_exec;
700 701 702 703

	if (unlikely(!curr))
		return;

704 705
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
706
		return;
707

I
Ingo Molnar 已提交
708
	curr->exec_start = now;
709

710 711 712 713 714 715 716 717 718
	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);

719 720 721
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

722
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
723
		cpuacct_charge(curtask, delta_exec);
724
		account_group_exec_runtime(curtask, delta_exec);
725
	}
726 727

	account_cfs_rq_runtime(cfs_rq, delta_exec);
728 729
}

730 731 732 733 734
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

735
static inline void
736
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
737
{
738
	schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
739 740 741 742 743
}

/*
 * Task is being enqueued - update stats:
 */
744
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
745 746 747 748 749
{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
750
	if (se != cfs_rq->curr)
751
		update_stats_wait_start(cfs_rq, se);
752 753 754
}

static void
755
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
756
{
757
	schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
758
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
759 760
	schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
	schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
761
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
762 763 764
#ifdef CONFIG_SCHEDSTATS
	if (entity_is_task(se)) {
		trace_sched_stat_wait(task_of(se),
765
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
766 767
	}
#endif
768
	schedstat_set(se->statistics.wait_start, 0);
769 770 771
}

static inline void
772
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
773 774 775 776 777
{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
778
	if (se != cfs_rq->curr)
779
		update_stats_wait_end(cfs_rq, se);
780 781 782 783 784 785
}

/*
 * We are picking a new current task - update its stats:
 */
static inline void
786
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
787 788 789 790
{
	/*
	 * We are starting a new run period:
	 */
791
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
792 793 794 795 796 797
}

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

798 799
#ifdef CONFIG_NUMA_BALANCING
/*
800 801 802
 * 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.
803
 */
804 805
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
806 807 808

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
809

810 811 812
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836
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)
{
837
	unsigned int scan_size = ACCESS_ONCE(sysctl_numa_balancing_scan_size);
838 839 840
	unsigned int scan, floor;
	unsigned int windows = 1;

841 842
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858
	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);
}

859 860 861 862 863 864 865 866 867 868 869 870
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));
}

871 872 873 874 875
struct numa_group {
	atomic_t refcount;

	spinlock_t lock; /* nr_tasks, tasks */
	int nr_tasks;
876
	pid_t gid;
877 878

	struct rcu_head rcu;
879
	nodemask_t active_nodes;
880
	unsigned long total_faults;
881 882 883 884 885
	/*
	 * 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.
	 */
886
	unsigned long *faults_cpu;
887
	unsigned long faults[0];
888 889
};

890 891 892 893 894 895 896 897 898
/* 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)

899 900 901 902 903
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

904 905 906 907 908 909 910
/*
 * 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)
911
{
912
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
913 914 915 916
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
917
	if (!p->numa_faults)
918 919
		return 0;

920 921
	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
922 923
}

924 925 926 927 928
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

929 930
	return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
931 932
}

933 934
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
935 936
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
937 938
}

939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003
/* 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;
}

1004 1005 1006 1007 1008 1009
/*
 * 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.
 */
1010 1011
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1012
{
1013
	unsigned long faults, total_faults;
1014

1015
	if (!p->numa_faults)
1016 1017 1018 1019 1020 1021 1022
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1023
	faults = task_faults(p, nid);
1024 1025
	faults += score_nearby_nodes(p, nid, dist, true);

1026
	return 1000 * faults / total_faults;
1027 1028
}

1029 1030
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1031
{
1032 1033 1034 1035 1036 1037 1038 1039
	unsigned long faults, total_faults;

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1040 1041
		return 0;

1042
	faults = group_faults(p, nid);
1043 1044
	faults += score_nearby_nodes(p, nid, dist, false);

1045
	return 1000 * faults / total_faults;
1046 1047
}

1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 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
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);
}

1111
static unsigned long weighted_cpuload(const int cpu);
1112 1113
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1114
static unsigned long capacity_of(int cpu);
1115 1116
static long effective_load(struct task_group *tg, int cpu, long wl, long wg);

1117
/* Cached statistics for all CPUs within a node */
1118
struct numa_stats {
1119
	unsigned long nr_running;
1120
	unsigned long load;
1121 1122

	/* Total compute capacity of CPUs on a node */
1123
	unsigned long compute_capacity;
1124 1125

	/* Approximate capacity in terms of runnable tasks on a node */
1126
	unsigned long task_capacity;
1127
	int has_free_capacity;
1128
};
1129

1130 1131 1132 1133 1134
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1135 1136
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1137 1138 1139 1140 1141 1142 1143

	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);
1144
		ns->compute_capacity += capacity_of(cpu);
1145 1146

		cpus++;
1147 1148
	}

1149 1150 1151 1152 1153
	/*
	 * 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.
	 *
1154 1155
	 * We'll either bail at !has_free_capacity, or we'll detect a huge
	 * imbalance and bail there.
1156 1157 1158 1159
	 */
	if (!cpus)
		return;

1160 1161 1162 1163 1164 1165
	/* 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));
1166
	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1167 1168
}

1169 1170
struct task_numa_env {
	struct task_struct *p;
1171

1172 1173
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1174

1175
	struct numa_stats src_stats, dst_stats;
1176

1177
	int imbalance_pct;
1178
	int dist;
1179 1180 1181

	struct task_struct *best_task;
	long best_imp;
1182 1183 1184
	int best_cpu;
};

1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197
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;
}

1198
static bool load_too_imbalanced(long src_load, long dst_load,
1199 1200
				struct task_numa_env *env)
{
1201
	long src_capacity, dst_capacity;
1202 1203 1204 1205
	long orig_src_load;
	long load_a, load_b;
	long moved_load;
	long imb;
1206 1207 1208 1209 1210 1211 1212 1213 1214 1215

	/*
	 * 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;
1216 1217

	/* We care about the slope of the imbalance, not the direction. */
1218 1219 1220 1221
	load_a = dst_load;
	load_b = src_load;
	if (load_a < load_b)
		swap(load_a, load_b);
1222 1223

	/* Is the difference below the threshold? */
1224 1225
	imb = load_a * src_capacity * 100 -
		load_b * dst_capacity * env->imbalance_pct;
1226 1227 1228 1229 1230
	if (imb <= 0)
		return false;

	/*
	 * The imbalance is above the allowed threshold.
1231 1232
	 * Allow a move that brings us closer to a balanced situation,
	 * without moving things past the point of balance.
1233
	 */
1234 1235
	orig_src_load = env->src_stats.load;

1236 1237 1238 1239 1240 1241 1242 1243
	/*
	 * In a task swap, there will be one load moving from src to dst,
	 * and another moving back. This is the net sum of both moves.
	 * A simple task move will always have a positive value.
	 * Allow the move if it brings the system closer to a balanced
	 * situation, without crossing over the balance point.
	 */
	moved_load = orig_src_load - src_load;
1244

1245 1246 1247 1248 1249 1250
	if (moved_load > 0)
		/* Moving src -> dst. Did we overshoot balance? */
		return src_load * dst_capacity < dst_load * src_capacity;
	else
		/* Moving dst -> src. Did we overshoot balance? */
		return dst_load * src_capacity < src_load * dst_capacity;
1251 1252
}

1253 1254 1255 1256 1257 1258
/*
 * 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
 */
1259 1260
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1261 1262 1263 1264
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1265
	long src_load, dst_load;
1266
	long load;
1267
	long imp = env->p->numa_group ? groupimp : taskimp;
1268
	long moveimp = imp;
1269
	int dist = env->dist;
1270 1271

	rcu_read_lock();
1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282

	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))
1283
		cur = NULL;
1284
	raw_spin_unlock_irq(&dst_rq->lock);
1285

1286 1287 1288 1289 1290 1291 1292
	/*
	 * 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;

1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304
	/*
	 * "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;

1305 1306
		/*
		 * If dst and source tasks are in the same NUMA group, or not
1307
		 * in any group then look only at task weights.
1308
		 */
1309
		if (cur->numa_group == env->p->numa_group) {
1310 1311
			imp = taskimp + task_weight(cur, env->src_nid, dist) -
			      task_weight(cur, env->dst_nid, dist);
1312 1313 1314 1315 1316 1317
			/*
			 * Add some hysteresis to prevent swapping the
			 * tasks within a group over tiny differences.
			 */
			if (cur->numa_group)
				imp -= imp/16;
1318
		} else {
1319 1320 1321 1322 1323 1324
			/*
			 * 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)
1325 1326
				imp += group_weight(cur, env->src_nid, dist) -
				       group_weight(cur, env->dst_nid, dist);
1327
			else
1328 1329
				imp += task_weight(cur, env->src_nid, dist) -
				       task_weight(cur, env->dst_nid, dist);
1330
		}
1331 1332
	}

1333
	if (imp <= env->best_imp && moveimp <= env->best_imp)
1334 1335 1336 1337
		goto unlock;

	if (!cur) {
		/* Is there capacity at our destination? */
1338
		if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1339
		    !env->dst_stats.has_free_capacity)
1340 1341 1342 1343 1344 1345
			goto unlock;

		goto balance;
	}

	/* Balance doesn't matter much if we're running a task per cpu */
1346 1347
	if (imp > env->best_imp && src_rq->nr_running == 1 &&
			dst_rq->nr_running == 1)
1348 1349 1350 1351 1352 1353
		goto assign;

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
balance:
1354 1355 1356
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1357

1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374
	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;

1375
	if (cur) {
1376 1377 1378
		load = task_h_load(cur);
		dst_load -= load;
		src_load += load;
1379 1380
	}

1381
	if (load_too_imbalanced(src_load, dst_load, env))
1382 1383
		goto unlock;

1384 1385 1386 1387 1388 1389 1390
	/*
	 * 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);

1391 1392 1393 1394 1395 1396
assign:
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1397 1398
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1399 1400 1401 1402 1403 1404 1405 1406 1407
{
	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;
1408
		task_numa_compare(env, taskimp, groupimp);
1409 1410 1411
	}
}

1412 1413 1414 1415
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1416

1417
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1418
		.src_nid = task_node(p),
1419 1420 1421 1422 1423 1424

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
		.best_cpu = -1
1425 1426
	};
	struct sched_domain *sd;
1427
	unsigned long taskweight, groupweight;
1428
	int nid, ret, dist;
1429
	long taskimp, groupimp;
1430

1431
	/*
1432 1433 1434 1435 1436 1437
	 * 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.
1438 1439
	 */
	rcu_read_lock();
1440
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1441 1442
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1443 1444
	rcu_read_unlock();

1445 1446 1447 1448 1449 1450 1451
	/*
	 * 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)) {
1452
		p->numa_preferred_nid = task_node(p);
1453 1454 1455
		return -EINVAL;
	}

1456
	env.dst_nid = p->numa_preferred_nid;
1457 1458 1459 1460 1461 1462
	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;
1463
	update_numa_stats(&env.dst_stats, env.dst_nid);
1464

1465 1466
	/* Try to find a spot on the preferred nid. */
	task_numa_find_cpu(&env, taskimp, groupimp);
1467

1468 1469 1470 1471 1472 1473 1474 1475 1476
	/*
	 * 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)) {
1477 1478 1479
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1480

1481
			dist = node_distance(env.src_nid, env.dst_nid);
1482 1483 1484 1485 1486
			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);
			}
1487

1488
			/* Only consider nodes where both task and groups benefit */
1489 1490
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1491
			if (taskimp < 0 && groupimp < 0)
1492 1493
				continue;

1494
			env.dist = dist;
1495 1496
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1497
			task_numa_find_cpu(&env, taskimp, groupimp);
1498 1499 1500
		}
	}

1501 1502 1503 1504 1505 1506 1507 1508
	/*
	 * 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.
	 */
1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521
	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;
1522

1523 1524 1525 1526 1527 1528
	/*
	 * 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);

1529
	if (env.best_task == NULL) {
1530 1531 1532
		ret = migrate_task_to(p, env.best_cpu);
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1533 1534 1535 1536
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
1537 1538
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1539 1540
	put_task_struct(env.best_task);
	return ret;
1541 1542
}

1543 1544 1545
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1546 1547
	unsigned long interval = HZ;

1548
	/* This task has no NUMA fault statistics yet */
1549
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1550 1551
		return;

1552
	/* Periodically retry migrating the task to the preferred node */
1553 1554
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
	p->numa_migrate_retry = jiffies + interval;
1555 1556

	/* Success if task is already running on preferred CPU */
1557
	if (task_node(p) == p->numa_preferred_nid)
1558 1559 1560
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1561
	task_numa_migrate(p);
1562 1563
}

1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595
/*
 * 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);
	}
}

1596 1597 1598
/*
 * 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
1599 1600 1601
 * 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.
1602 1603
 */
#define NUMA_PERIOD_SLOTS 10
1604
#define NUMA_PERIOD_THRESHOLD 7
1605 1606 1607 1608 1609 1610 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 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660

/*
 * 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
	 * to automatic numa balancing. Scan slower
	 */
	if (local + shared == 0) {
		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
		 */
1661
		ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1662 1663 1664 1665 1666 1667 1668 1669
		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));
}

1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688
/*
 * 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 {
		delta = p->se.avg.runnable_avg_sum;
1689
		*period = p->se.avg.avg_period;
1690 1691 1692 1693 1694 1695 1696 1697
	}

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

	return delta;
}

1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744
/*
 * 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;
1745
		nodemask_t max_group = NODE_MASK_NONE;
1746 1747 1748 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
		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. */
1779 1780
		if (!max_faults)
			break;
1781 1782 1783 1784 1785
		nodes = max_group;
	}
	return nid;
}

1786 1787
static void task_numa_placement(struct task_struct *p)
{
1788 1789
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
1790
	unsigned long fault_types[2] = { 0, 0 };
1791 1792
	unsigned long total_faults;
	u64 runtime, period;
1793
	spinlock_t *group_lock = NULL;
1794

1795
	seq = ACCESS_ONCE(p->mm->numa_scan_seq);
1796 1797 1798
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
1799
	p->numa_scan_period_max = task_scan_max(p);
1800

1801 1802 1803 1804
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

1805 1806 1807
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
1808
		spin_lock_irq(group_lock);
1809 1810
	}

1811 1812
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
1813 1814
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1815
		unsigned long faults = 0, group_faults = 0;
1816
		int priv;
1817

1818
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1819
			long diff, f_diff, f_weight;
1820

1821 1822 1823 1824
			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);
1825

1826
			/* Decay existing window, copy faults since last scan */
1827 1828 1829
			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;
1830

1831 1832 1833 1834 1835 1836 1837 1838
			/*
			 * 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);
1839
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1840
				   (total_faults + 1);
1841 1842
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
1843

1844 1845 1846
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
1847
			p->total_numa_faults += diff;
1848
			if (p->numa_group) {
1849 1850 1851 1852 1853 1854 1855 1856 1857
				/*
				 * 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;
1858
				p->numa_group->total_faults += diff;
1859
				group_faults += p->numa_group->faults[mem_idx];
1860
			}
1861 1862
		}

1863 1864 1865 1866
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
1867 1868 1869 1870 1871 1872 1873

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

1874 1875
	update_task_scan_period(p, fault_types[0], fault_types[1]);

1876
	if (p->numa_group) {
1877
		update_numa_active_node_mask(p->numa_group);
1878
		spin_unlock_irq(group_lock);
1879
		max_nid = preferred_group_nid(p, max_group_nid);
1880 1881
	}

1882 1883 1884 1885 1886 1887 1888
	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);
1889
	}
1890 1891
}

1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902
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);
}

1903 1904
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
1905 1906 1907 1908 1909 1910 1911 1912 1913
{
	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) +
1914
				    4*nr_node_ids*sizeof(unsigned long);
1915 1916 1917 1918 1919 1920 1921

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

		atomic_set(&grp->refcount, 1);
		spin_lock_init(&grp->lock);
1922
		grp->gid = p->pid;
1923
		/* Second half of the array tracks nids where faults happen */
1924 1925
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
1926

1927 1928
		node_set(task_node(current), grp->active_nodes);

1929
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1930
			grp->faults[i] = p->numa_faults[i];
1931

1932
		grp->total_faults = p->total_numa_faults;
1933

1934 1935 1936 1937 1938 1939 1940 1941
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
	tsk = ACCESS_ONCE(cpu_rq(cpu)->curr);

	if (!cpupid_match_pid(tsk, cpupid))
1942
		goto no_join;
1943 1944 1945

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
1946
		goto no_join;
1947 1948 1949

	my_grp = p->numa_group;
	if (grp == my_grp)
1950
		goto no_join;
1951 1952 1953 1954 1955 1956

	/*
	 * 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)
1957
		goto no_join;
1958 1959 1960 1961 1962

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1963
		goto no_join;
1964

1965 1966 1967 1968 1969 1970 1971
	/* 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;
1972

1973 1974 1975
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

1976
	if (join && !get_numa_group(grp))
1977
		goto no_join;
1978 1979 1980 1981 1982 1983

	rcu_read_unlock();

	if (!join)
		return;

1984 1985
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
1986

1987
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
1988 1989
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
1990
	}
1991 1992
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
1993 1994 1995 1996 1997

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

	spin_unlock(&my_grp->lock);
1998
	spin_unlock_irq(&grp->lock);
1999 2000 2001 2002

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2003 2004 2005 2006 2007
	return;

no_join:
	rcu_read_unlock();
	return;
2008 2009 2010 2011 2012
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
2013
	void *numa_faults = p->numa_faults;
2014 2015
	unsigned long flags;
	int i;
2016 2017

	if (grp) {
2018
		spin_lock_irqsave(&grp->lock, flags);
2019
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2020
			grp->faults[i] -= p->numa_faults[i];
2021
		grp->total_faults -= p->total_numa_faults;
2022

2023
		grp->nr_tasks--;
2024
		spin_unlock_irqrestore(&grp->lock, flags);
2025
		RCU_INIT_POINTER(p->numa_group, NULL);
2026 2027 2028
		put_numa_group(grp);
	}

2029
	p->numa_faults = NULL;
2030
	kfree(numa_faults);
2031 2032
}

2033 2034 2035
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2036
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2037 2038
{
	struct task_struct *p = current;
2039
	bool migrated = flags & TNF_MIGRATED;
2040
	int cpu_node = task_node(current);
2041
	int local = !!(flags & TNF_FAULT_LOCAL);
2042
	int priv;
2043

2044
	if (!numabalancing_enabled)
2045 2046
		return;

2047 2048 2049 2050
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2051
	/* Allocate buffer to track faults on a per-node basis */
2052 2053
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2054
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2055

2056 2057
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2058
			return;
2059

2060
		p->total_numa_faults = 0;
2061
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2062
	}
2063

2064 2065 2066 2067 2068 2069 2070 2071
	/*
	 * 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);
2072
		if (!priv && !(flags & TNF_NO_GROUP))
2073
			task_numa_group(p, last_cpupid, flags, &priv);
2074 2075
	}

2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086
	/*
	 * 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;

2087
	task_numa_placement(p);
2088

2089 2090 2091 2092 2093
	/*
	 * 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))
2094 2095
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
2096 2097 2098
	if (migrated)
		p->numa_pages_migrated += pages;

2099 2100
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2101
	p->numa_faults_locality[local] += pages;
2102 2103
}

2104 2105 2106 2107 2108 2109
static void reset_ptenuma_scan(struct task_struct *p)
{
	ACCESS_ONCE(p->mm->numa_scan_seq)++;
	p->mm->numa_scan_offset = 0;
}

2110 2111 2112 2113 2114 2115 2116 2117 2118
/*
 * 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;
2119
	struct vm_area_struct *vma;
2120
	unsigned long start, end;
2121
	unsigned long nr_pte_updates = 0;
2122
	long pages;
2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137

	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;

2138
	if (!mm->numa_next_scan) {
2139 2140
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2141 2142
	}

2143 2144 2145 2146 2147 2148 2149
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2150 2151 2152 2153
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
		p->numa_scan_period = task_scan_min(p);
	}
2154

2155
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2156 2157 2158
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2159 2160 2161 2162 2163 2164
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2165 2166 2167 2168 2169
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
	if (!pages)
		return;
2170

2171
	down_read(&mm->mmap_sem);
2172
	vma = find_vma(mm, start);
2173 2174
	if (!vma) {
		reset_ptenuma_scan(p);
2175
		start = 0;
2176 2177
		vma = mm->mmap;
	}
2178
	for (; vma; vma = vma->vm_next) {
2179
		if (!vma_migratable(vma) || !vma_policy_mof(vma))
2180 2181
			continue;

2182 2183 2184 2185 2186 2187 2188 2189 2190 2191
		/*
		 * 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
2192 2193 2194 2195 2196 2197
		/*
		 * 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;
2198

2199 2200 2201 2202
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2203 2204 2205 2206 2207 2208 2209 2210 2211
			nr_pte_updates += change_prot_numa(vma, start, end);

			/*
			 * Scan sysctl_numa_balancing_scan_size but ensure that
			 * at least one PTE is updated so that unused virtual
			 * address space is quickly skipped.
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2212

2213 2214 2215
			start = end;
			if (pages <= 0)
				goto out;
2216 2217

			cond_resched();
2218
		} while (end != vma->vm_end);
2219
	}
2220

2221
out:
2222
	/*
P
Peter Zijlstra 已提交
2223 2224 2225 2226
	 * 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.
2227 2228
	 */
	if (vma)
2229
		mm->numa_scan_offset = start;
2230 2231 2232
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258
}

/*
 * 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;

	if (now - curr->node_stamp > period) {
2259
		if (!curr->node_stamp)
2260
			curr->numa_scan_period = task_scan_min(curr);
2261
		curr->node_stamp += period;
2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272

		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)
{
}
2273 2274 2275 2276 2277 2278 2279 2280

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)
{
}
2281 2282
#endif /* CONFIG_NUMA_BALANCING */

2283 2284 2285 2286
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2287
	if (!parent_entity(se))
2288
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2289
#ifdef CONFIG_SMP
2290 2291 2292 2293 2294 2295
	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);
	}
2296
#endif
2297 2298 2299 2300 2301 2302 2303
	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);
2304
	if (!parent_entity(se))
2305
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2306 2307
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2308
		list_del_init(&se->group_node);
2309
	}
2310 2311 2312
	cfs_rq->nr_running--;
}

2313 2314
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
2315 2316 2317 2318 2319 2320 2321 2322 2323
static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
{
	long tg_weight;

	/*
	 * Use this CPU's actual weight instead of the last load_contribution
	 * to gain a more accurate current total weight. See
	 * update_cfs_rq_load_contribution().
	 */
2324
	tg_weight = atomic_long_read(&tg->load_avg);
2325
	tg_weight -= cfs_rq->tg_load_contrib;
2326 2327 2328 2329 2330
	tg_weight += cfs_rq->load.weight;

	return tg_weight;
}

2331
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2332
{
2333
	long tg_weight, load, shares;
2334

2335
	tg_weight = calc_tg_weight(tg, cfs_rq);
2336
	load = cfs_rq->load.weight;
2337 2338

	shares = (tg->shares * load);
2339 2340
	if (tg_weight)
		shares /= tg_weight;
2341 2342 2343 2344 2345 2346 2347 2348 2349

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

	return shares;
}
# else /* CONFIG_SMP */
2350
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2351 2352 2353 2354
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
2355 2356 2357
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
2358 2359 2360 2361
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
2362
		account_entity_dequeue(cfs_rq, se);
2363
	}
P
Peter Zijlstra 已提交
2364 2365 2366 2367 2368 2369 2370

	update_load_set(&se->load, weight);

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

2371 2372
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2373
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2374 2375 2376
{
	struct task_group *tg;
	struct sched_entity *se;
2377
	long shares;
P
Peter Zijlstra 已提交
2378 2379 2380

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
2381
	if (!se || throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
2382
		return;
2383 2384 2385 2386
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
2387
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
2388 2389 2390 2391

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
2392
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2393 2394 2395 2396
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

2397
#ifdef CONFIG_SMP
2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425
/*
 * We choose a half-life close to 1 scheduling period.
 * Note: The tables below are dependent on this value.
 */
#define LOAD_AVG_PERIOD 32
#define LOAD_AVG_MAX 47742 /* maximum possible load avg */
#define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */

/* 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,
};

2426 2427 2428 2429 2430 2431
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443
	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
2444 2445
	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
	 * With a look-up table which covers y^n (n<PERIOD)
2446 2447 2448 2449 2450 2451
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
2452 2453
	}

2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484
	val *= runnable_avg_yN_inv[local_n];
	/* We don't use SRR here since we always want to round down. */
	return val >> 32;
}

/*
 * 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];
2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516
}

/*
 * 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}]
 */
static __always_inline int __update_entity_runnable_avg(u64 now,
							struct sched_avg *sa,
2517 2518
							int runnable,
							int running)
2519
{
2520 2521
	u64 delta, periods;
	u32 runnable_contrib;
2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543
	int delta_w, decayed = 0;

	delta = now - sa->last_runnable_update;
	/*
	 * 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) {
		sa->last_runnable_update = now;
		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;
	sa->last_runnable_update = now;

	/* delta_w is the amount already accumulated against our next period */
2544
	delta_w = sa->avg_period % 1024;
2545 2546 2547 2548 2549 2550 2551 2552 2553 2554
	if (delta + delta_w >= 1024) {
		/* period roll-over */
		decayed = 1;

		/*
		 * 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;
2555 2556
		if (runnable)
			sa->runnable_avg_sum += delta_w;
2557 2558 2559
		if (running)
			sa->running_avg_sum += delta_w;
		sa->avg_period += delta_w;
2560 2561 2562 2563 2564 2565 2566 2567 2568

		delta -= delta_w;

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

		sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum,
						  periods + 1);
2569 2570 2571
		sa->running_avg_sum = decay_load(sa->running_avg_sum,
						  periods + 1);
		sa->avg_period = decay_load(sa->avg_period,
2572 2573 2574 2575 2576 2577
						     periods + 1);

		/* Efficiently calculate \sum (1..n_period) 1024*y^i */
		runnable_contrib = __compute_runnable_contrib(periods);
		if (runnable)
			sa->runnable_avg_sum += runnable_contrib;
2578 2579 2580
		if (running)
			sa->running_avg_sum += runnable_contrib;
		sa->avg_period += runnable_contrib;
2581 2582 2583 2584 2585
	}

	/* Remainder of delta accrued against u_0` */
	if (runnable)
		sa->runnable_avg_sum += delta;
2586 2587 2588
	if (running)
		sa->running_avg_sum += delta;
	sa->avg_period += delta;
2589 2590 2591 2592

	return decayed;
}

2593
/* Synchronize an entity's decay with its parenting cfs_rq.*/
2594
static inline u64 __synchronize_entity_decay(struct sched_entity *se)
2595 2596 2597 2598 2599
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 decays = atomic64_read(&cfs_rq->decay_counter);

	decays -= se->avg.decay_count;
2600
	se->avg.decay_count = 0;
2601
	if (!decays)
2602
		return 0;
2603 2604

	se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
2605 2606
	se->avg.utilization_avg_contrib =
		decay_load(se->avg.utilization_avg_contrib, decays);
2607 2608

	return decays;
2609 2610
}

2611 2612 2613 2614 2615
#ifdef CONFIG_FAIR_GROUP_SCHED
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
						 int force_update)
{
	struct task_group *tg = cfs_rq->tg;
2616
	long tg_contrib;
2617 2618 2619 2620

	tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg;
	tg_contrib -= cfs_rq->tg_load_contrib;

2621 2622 2623
	if (!tg_contrib)
		return;

2624 2625
	if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) {
		atomic_long_add(tg_contrib, &tg->load_avg);
2626 2627 2628
		cfs_rq->tg_load_contrib += tg_contrib;
	}
}
2629

2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640
/*
 * Aggregate cfs_rq runnable averages into an equivalent task_group
 * representation for computing load contributions.
 */
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
						  struct cfs_rq *cfs_rq)
{
	struct task_group *tg = cfs_rq->tg;
	long contrib;

	/* The fraction of a cpu used by this cfs_rq */
2641
	contrib = div_u64((u64)sa->runnable_avg_sum << NICE_0_SHIFT,
2642
			  sa->avg_period + 1);
2643 2644 2645 2646 2647 2648 2649 2650
	contrib -= cfs_rq->tg_runnable_contrib;

	if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) {
		atomic_add(contrib, &tg->runnable_avg);
		cfs_rq->tg_runnable_contrib += contrib;
	}
}

2651 2652 2653 2654
static inline void __update_group_entity_contrib(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = group_cfs_rq(se);
	struct task_group *tg = cfs_rq->tg;
2655 2656
	int runnable_avg;

2657 2658 2659
	u64 contrib;

	contrib = cfs_rq->tg_load_contrib * tg->shares;
2660 2661
	se->avg.load_avg_contrib = div_u64(contrib,
				     atomic_long_read(&tg->load_avg) + 1);
2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690

	/*
	 * For group entities we need to compute a correction term in the case
	 * that they are consuming <1 cpu so that we would contribute the same
	 * load as a task of equal weight.
	 *
	 * Explicitly co-ordinating this measurement would be expensive, but
	 * fortunately the sum of each cpus contribution forms a usable
	 * lower-bound on the true value.
	 *
	 * Consider the aggregate of 2 contributions.  Either they are disjoint
	 * (and the sum represents true value) or they are disjoint and we are
	 * understating by the aggregate of their overlap.
	 *
	 * Extending this to N cpus, for a given overlap, the maximum amount we
	 * understand is then n_i(n_i+1)/2 * w_i where n_i is the number of
	 * cpus that overlap for this interval and w_i is the interval width.
	 *
	 * On a small machine; the first term is well-bounded which bounds the
	 * total error since w_i is a subset of the period.  Whereas on a
	 * larger machine, while this first term can be larger, if w_i is the
	 * of consequential size guaranteed to see n_i*w_i quickly converge to
	 * our upper bound of 1-cpu.
	 */
	runnable_avg = atomic_read(&tg->runnable_avg);
	if (runnable_avg < NICE_0_LOAD) {
		se->avg.load_avg_contrib *= runnable_avg;
		se->avg.load_avg_contrib >>= NICE_0_SHIFT;
	}
2691
}
2692 2693 2694

static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
{
2695 2696
	__update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable,
			runnable);
2697 2698
	__update_tg_runnable_avg(&rq->avg, &rq->cfs);
}
2699
#else /* CONFIG_FAIR_GROUP_SCHED */
2700 2701
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
						 int force_update) {}
2702 2703
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
						  struct cfs_rq *cfs_rq) {}
2704
static inline void __update_group_entity_contrib(struct sched_entity *se) {}
2705
static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
2706
#endif /* CONFIG_FAIR_GROUP_SCHED */
2707

2708 2709 2710 2711 2712 2713
static inline void __update_task_entity_contrib(struct sched_entity *se)
{
	u32 contrib;

	/* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
	contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight);
2714
	contrib /= (se->avg.avg_period + 1);
2715 2716 2717
	se->avg.load_avg_contrib = scale_load(contrib);
}

2718 2719 2720 2721 2722
/* Compute the current contribution to load_avg by se, return any delta */
static long __update_entity_load_avg_contrib(struct sched_entity *se)
{
	long old_contrib = se->avg.load_avg_contrib;

2723 2724 2725
	if (entity_is_task(se)) {
		__update_task_entity_contrib(se);
	} else {
2726
		__update_tg_runnable_avg(&se->avg, group_cfs_rq(se));
2727 2728
		__update_group_entity_contrib(se);
	}
2729 2730 2731 2732

	return se->avg.load_avg_contrib - old_contrib;
}

2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749

static inline void __update_task_entity_utilization(struct sched_entity *se)
{
	u32 contrib;

	/* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
	contrib = se->avg.running_avg_sum * scale_load_down(SCHED_LOAD_SCALE);
	contrib /= (se->avg.avg_period + 1);
	se->avg.utilization_avg_contrib = scale_load(contrib);
}

static long __update_entity_utilization_avg_contrib(struct sched_entity *se)
{
	long old_contrib = se->avg.utilization_avg_contrib;

	if (entity_is_task(se))
		__update_task_entity_utilization(se);
2750 2751 2752
	else
		se->avg.utilization_avg_contrib =
					group_cfs_rq(se)->utilization_load_avg;
2753 2754 2755 2756

	return se->avg.utilization_avg_contrib - old_contrib;
}

2757 2758 2759 2760 2761 2762 2763 2764 2765
static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq,
						 long load_contrib)
{
	if (likely(load_contrib < cfs_rq->blocked_load_avg))
		cfs_rq->blocked_load_avg -= load_contrib;
	else
		cfs_rq->blocked_load_avg = 0;
}

2766 2767
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);

2768
/* Update a sched_entity's runnable average */
2769 2770
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq)
2771
{
2772
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
2773
	long contrib_delta, utilization_delta;
2774
	u64 now;
2775

2776 2777 2778 2779 2780 2781 2782 2783 2784
	/*
	 * For a group entity we need to use their owned cfs_rq_clock_task() in
	 * case they are the parent of a throttled hierarchy.
	 */
	if (entity_is_task(se))
		now = cfs_rq_clock_task(cfs_rq);
	else
		now = cfs_rq_clock_task(group_cfs_rq(se));

2785 2786
	if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq,
					cfs_rq->curr == se))
2787 2788 2789
		return;

	contrib_delta = __update_entity_load_avg_contrib(se);
2790
	utilization_delta = __update_entity_utilization_avg_contrib(se);
2791 2792 2793 2794

	if (!update_cfs_rq)
		return;

2795
	if (se->on_rq) {
2796
		cfs_rq->runnable_load_avg += contrib_delta;
2797 2798
		cfs_rq->utilization_load_avg += utilization_delta;
	} else {
2799
		subtract_blocked_load_contrib(cfs_rq, -contrib_delta);
2800
	}
2801 2802 2803 2804 2805 2806
}

/*
 * Decay the load contributed by all blocked children and account this so that
 * their contribution may appropriately discounted when they wake up.
 */
2807
static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
2808
{
2809
	u64 now = cfs_rq_clock_task(cfs_rq) >> 20;
2810 2811 2812
	u64 decays;

	decays = now - cfs_rq->last_decay;
2813
	if (!decays && !force_update)
2814 2815
		return;

2816 2817 2818
	if (atomic_long_read(&cfs_rq->removed_load)) {
		unsigned long removed_load;
		removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
2819 2820
		subtract_blocked_load_contrib(cfs_rq, removed_load);
	}
2821

2822 2823 2824 2825 2826 2827
	if (decays) {
		cfs_rq->blocked_load_avg = decay_load(cfs_rq->blocked_load_avg,
						      decays);
		atomic64_add(decays, &cfs_rq->decay_counter);
		cfs_rq->last_decay = now;
	}
2828 2829

	__update_cfs_rq_tg_load_contrib(cfs_rq, force_update);
2830
}
2831

2832 2833
/* Add the load generated by se into cfs_rq's child load-average */
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
2834 2835
						  struct sched_entity *se,
						  int wakeup)
2836
{
2837 2838 2839 2840
	/*
	 * We track migrations using entity decay_count <= 0, on a wake-up
	 * migration we use a negative decay count to track the remote decays
	 * accumulated while sleeping.
2841 2842 2843 2844
	 *
	 * Newly forked tasks are enqueued with se->avg.decay_count == 0, they
	 * are seen by enqueue_entity_load_avg() as a migration with an already
	 * constructed load_avg_contrib.
2845 2846
	 */
	if (unlikely(se->avg.decay_count <= 0)) {
2847
		se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq));
2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862
		if (se->avg.decay_count) {
			/*
			 * In a wake-up migration we have to approximate the
			 * time sleeping.  This is because we can't synchronize
			 * clock_task between the two cpus, and it is not
			 * guaranteed to be read-safe.  Instead, we can
			 * approximate this using our carried decays, which are
			 * explicitly atomically readable.
			 */
			se->avg.last_runnable_update -= (-se->avg.decay_count)
							<< 20;
			update_entity_load_avg(se, 0);
			/* Indicate that we're now synchronized and on-rq */
			se->avg.decay_count = 0;
		}
2863 2864
		wakeup = 0;
	} else {
2865
		__synchronize_entity_decay(se);
2866 2867
	}

2868 2869
	/* migrated tasks did not contribute to our blocked load */
	if (wakeup) {
2870
		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
2871 2872
		update_entity_load_avg(se, 0);
	}
2873

2874
	cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
2875
	cfs_rq->utilization_load_avg += se->avg.utilization_avg_contrib;
2876 2877
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !wakeup);
2878 2879
}

2880 2881 2882 2883 2884
/*
 * Remove se's load from this cfs_rq child load-average, if the entity is
 * transitioning to a blocked state we track its projected decay using
 * blocked_load_avg.
 */
2885
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
2886 2887
						  struct sched_entity *se,
						  int sleep)
2888
{
2889
	update_entity_load_avg(se, 1);
2890 2891
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !sleep);
2892

2893
	cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
2894
	cfs_rq->utilization_load_avg -= se->avg.utilization_avg_contrib;
2895 2896 2897 2898
	if (sleep) {
		cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
		se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
	} /* migrations, e.g. sleep=0 leave decay_count == 0 */
2899
}
2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920

/*
 * Update the rq's load with the elapsed running time before entering
 * idle. if the last scheduled task is not a CFS task, idle_enter will
 * be the only way to update the runnable statistic.
 */
void idle_enter_fair(struct rq *this_rq)
{
	update_rq_runnable_avg(this_rq, 1);
}

/*
 * Update the rq's load with the elapsed idle time before a task is
 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
 * be the only way to update the runnable statistic.
 */
void idle_exit_fair(struct rq *this_rq)
{
	update_rq_runnable_avg(this_rq, 0);
}

2921 2922
static int idle_balance(struct rq *this_rq);

2923 2924
#else /* CONFIG_SMP */

2925 2926
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq) {}
2927
static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
2928
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
2929 2930
					   struct sched_entity *se,
					   int wakeup) {}
2931
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
2932 2933
					   struct sched_entity *se,
					   int sleep) {}
2934 2935
static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
					      int force_update) {}
2936 2937 2938 2939 2940 2941

static inline int idle_balance(struct rq *rq)
{
	return 0;
}

2942
#endif /* CONFIG_SMP */
2943

2944
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2945 2946
{
#ifdef CONFIG_SCHEDSTATS
2947 2948 2949 2950 2951
	struct task_struct *tsk = NULL;

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

2952
	if (se->statistics.sleep_start) {
2953
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2954 2955 2956 2957

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

2958 2959
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
2960

2961
		se->statistics.sleep_start = 0;
2962
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
2963

2964
		if (tsk) {
2965
			account_scheduler_latency(tsk, delta >> 10, 1);
2966 2967
			trace_sched_stat_sleep(tsk, delta);
		}
2968
	}
2969
	if (se->statistics.block_start) {
2970
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2971 2972 2973 2974

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

2975 2976
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
2977

2978
		se->statistics.block_start = 0;
2979
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
2980

2981
		if (tsk) {
2982
			if (tsk->in_iowait) {
2983 2984
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
2985
				trace_sched_stat_iowait(tsk, delta);
2986 2987
			}

2988 2989
			trace_sched_stat_blocked(tsk, delta);

2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000
			/*
			 * 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
3001
		}
3002 3003 3004 3005
	}
#endif
}

P
Peter Zijlstra 已提交
3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018
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
}

3019 3020 3021
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3022
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3023

3024 3025 3026 3027 3028 3029
	/*
	 * 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
3030
	if (initial && sched_feat(START_DEBIT))
3031
		vruntime += sched_vslice(cfs_rq, se);
3032

3033
	/* sleeps up to a single latency don't count. */
3034
	if (!initial) {
3035
		unsigned long thresh = sysctl_sched_latency;
3036

3037 3038 3039 3040 3041 3042
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3043

3044
		vruntime -= thresh;
3045 3046
	}

3047
	/* ensure we never gain time by being placed backwards. */
3048
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3049 3050
}

3051 3052
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3053
static void
3054
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3055
{
3056 3057
	/*
	 * Update the normalized vruntime before updating min_vruntime
3058
	 * through calling update_curr().
3059
	 */
3060
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
3061 3062
		se->vruntime += cfs_rq->min_vruntime;

3063
	/*
3064
	 * Update run-time statistics of the 'current'.
3065
	 */
3066
	update_curr(cfs_rq);
3067
	enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
3068 3069
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
3070

3071
	if (flags & ENQUEUE_WAKEUP) {
3072
		place_entity(cfs_rq, se, 0);
3073
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
3074
	}
3075

3076
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
3077
	check_spread(cfs_rq, se);
3078 3079
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3080
	se->on_rq = 1;
3081

3082
	if (cfs_rq->nr_running == 1) {
3083
		list_add_leaf_cfs_rq(cfs_rq);
3084 3085
		check_enqueue_throttle(cfs_rq);
	}
3086 3087
}

3088
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3089
{
3090 3091
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3092
		if (cfs_rq->last != se)
3093
			break;
3094 3095

		cfs_rq->last = NULL;
3096 3097
	}
}
P
Peter Zijlstra 已提交
3098

3099 3100 3101 3102
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3103
		if (cfs_rq->next != se)
3104
			break;
3105 3106

		cfs_rq->next = NULL;
3107
	}
P
Peter Zijlstra 已提交
3108 3109
}

3110 3111 3112 3113
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3114
		if (cfs_rq->skip != se)
3115
			break;
3116 3117

		cfs_rq->skip = NULL;
3118 3119 3120
	}
}

P
Peter Zijlstra 已提交
3121 3122
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3123 3124 3125 3126 3127
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
3128 3129 3130

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
3131 3132
}

3133
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3134

3135
static void
3136
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3137
{
3138 3139 3140 3141
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
3142
	dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);
3143

3144
	update_stats_dequeue(cfs_rq, se);
3145
	if (flags & DEQUEUE_SLEEP) {
P
Peter Zijlstra 已提交
3146
#ifdef CONFIG_SCHEDSTATS
3147 3148 3149 3150
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
3151
				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3152
			if (tsk->state & TASK_UNINTERRUPTIBLE)
3153
				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3154
		}
3155
#endif
P
Peter Zijlstra 已提交
3156 3157
	}

P
Peter Zijlstra 已提交
3158
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3159

3160
	if (se != cfs_rq->curr)
3161
		__dequeue_entity(cfs_rq, se);
3162
	se->on_rq = 0;
3163
	account_entity_dequeue(cfs_rq, se);
3164 3165 3166 3167 3168 3169

	/*
	 * 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.
	 */
3170
	if (!(flags & DEQUEUE_SLEEP))
3171
		se->vruntime -= cfs_rq->min_vruntime;
3172

3173 3174 3175
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3176
	update_min_vruntime(cfs_rq);
3177
	update_cfs_shares(cfs_rq);
3178 3179 3180 3181 3182
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
3183
static void
I
Ingo Molnar 已提交
3184
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3185
{
3186
	unsigned long ideal_runtime, delta_exec;
3187 3188
	struct sched_entity *se;
	s64 delta;
3189

P
Peter Zijlstra 已提交
3190
	ideal_runtime = sched_slice(cfs_rq, curr);
3191
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3192
	if (delta_exec > ideal_runtime) {
3193
		resched_curr(rq_of(cfs_rq));
3194 3195 3196 3197 3198
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209
		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;

3210 3211
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
3212

3213 3214
	if (delta < 0)
		return;
3215

3216
	if (delta > ideal_runtime)
3217
		resched_curr(rq_of(cfs_rq));
3218 3219
}

3220
static void
3221
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3222
{
3223 3224 3225 3226 3227 3228 3229 3230 3231
	/* '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);
3232
		update_entity_load_avg(se, 1);
3233 3234
	}

3235
	update_stats_curr_start(cfs_rq, se);
3236
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
3237 3238 3239 3240 3241 3242
#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):
	 */
3243
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3244
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
3245 3246 3247
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
3248
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
3249 3250
}

3251 3252 3253
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

3254 3255 3256 3257 3258 3259 3260
/*
 * 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
 */
3261 3262
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3263
{
3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274
	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 */
3275

3276 3277 3278 3279 3280
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
3281 3282 3283 3284 3285 3286 3287 3288 3289 3290
		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;
		}

3291 3292 3293
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
3294

3295 3296 3297 3298 3299 3300
	/*
	 * 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;

3301 3302 3303 3304 3305 3306
	/*
	 * 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;

3307
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3308 3309

	return se;
3310 3311
}

3312
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3313

3314
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3315 3316 3317 3318 3319 3320
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
3321
		update_curr(cfs_rq);
3322

3323 3324 3325
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

P
Peter Zijlstra 已提交
3326
	check_spread(cfs_rq, prev);
3327
	if (prev->on_rq) {
3328
		update_stats_wait_start(cfs_rq, prev);
3329 3330
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
3331
		/* in !on_rq case, update occurred at dequeue */
3332
		update_entity_load_avg(prev, 1);
3333
	}
3334
	cfs_rq->curr = NULL;
3335 3336
}

P
Peter Zijlstra 已提交
3337 3338
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3339 3340
{
	/*
3341
	 * Update run-time statistics of the 'current'.
3342
	 */
3343
	update_curr(cfs_rq);
3344

3345 3346 3347
	/*
	 * Ensure that runnable average is periodically updated.
	 */
3348
	update_entity_load_avg(curr, 1);
3349
	update_cfs_rq_blocked_load(cfs_rq, 1);
3350
	update_cfs_shares(cfs_rq);
3351

P
Peter Zijlstra 已提交
3352 3353 3354 3355 3356
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
3357
	if (queued) {
3358
		resched_curr(rq_of(cfs_rq));
3359 3360
		return;
	}
P
Peter Zijlstra 已提交
3361 3362 3363 3364 3365 3366 3367 3368
	/*
	 * 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
3369
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
3370
		check_preempt_tick(cfs_rq, curr);
3371 3372
}

3373 3374 3375 3376 3377 3378

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

#ifdef CONFIG_CFS_BANDWIDTH
3379 3380

#ifdef HAVE_JUMP_LABEL
3381
static struct static_key __cfs_bandwidth_used;
3382 3383 3384

static inline bool cfs_bandwidth_used(void)
{
3385
	return static_key_false(&__cfs_bandwidth_used);
3386 3387
}

3388
void cfs_bandwidth_usage_inc(void)
3389
{
3390 3391 3392 3393 3394 3395
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
3396 3397 3398 3399 3400 3401 3402
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

3403 3404
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
3405 3406
#endif /* HAVE_JUMP_LABEL */

3407 3408 3409 3410 3411 3412 3413 3414
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
3415 3416 3417 3418 3419 3420

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

P
Paul Turner 已提交
3421 3422 3423 3424 3425 3426 3427
/*
 * 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
 */
3428
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439
{
	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);
}

3440 3441 3442 3443 3444
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

3445 3446 3447 3448 3449 3450
/* 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;

3451
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3452 3453
}

3454 3455
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3456 3457 3458
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
3459
	u64 amount = 0, min_amount, expires;
3460 3461 3462 3463 3464 3465 3466

	/* 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;
3467
	else {
P
Paul Turner 已提交
3468 3469 3470 3471 3472 3473 3474 3475
		/*
		 * If the bandwidth pool has become inactive, then at least one
		 * period must have elapsed since the last consumption.
		 * Refresh the global state and ensure bandwidth timer becomes
		 * active.
		 */
		if (!cfs_b->timer_active) {
			__refill_cfs_bandwidth_runtime(cfs_b);
3476
			__start_cfs_bandwidth(cfs_b, false);
P
Paul Turner 已提交
3477
		}
3478 3479 3480 3481 3482 3483

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
3484
	}
P
Paul Turner 已提交
3485
	expires = cfs_b->runtime_expires;
3486 3487 3488
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
3489 3490 3491 3492 3493 3494 3495
	/*
	 * 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;
3496 3497

	return cfs_rq->runtime_remaining > 0;
3498 3499
}

P
Paul Turner 已提交
3500 3501 3502 3503 3504
/*
 * 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)
3505
{
P
Paul Turner 已提交
3506 3507 3508
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
3509
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3510 3511
		return;

P
Paul Turner 已提交
3512 3513 3514 3515 3516 3517 3518 3519 3520
	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
3521 3522 3523
	 * 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
3524 3525
	 */

3526
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
3527 3528 3529 3530 3531 3532 3533 3534
		/* 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;
	}
}

3535
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
3536 3537
{
	/* dock delta_exec before expiring quota (as it could span periods) */
3538
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
3539 3540 3541
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
3542 3543
		return;

3544 3545 3546 3547 3548
	/*
	 * 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))
3549
		resched_curr(rq_of(cfs_rq));
3550 3551
}

3552
static __always_inline
3553
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3554
{
3555
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3556 3557 3558 3559 3560
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

3561 3562
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
3563
	return cfs_bandwidth_used() && cfs_rq->throttled;
3564 3565
}

3566 3567 3568
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
3569
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597
}

/*
 * 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) {
3598
		/* adjust cfs_rq_clock_task() */
3599
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3600
					     cfs_rq->throttled_clock_task;
3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611
	}
#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)];

3612 3613
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
3614
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
3615 3616 3617 3618 3619
	cfs_rq->throttle_count++;

	return 0;
}

3620
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3621 3622 3623 3624 3625 3626 3627 3628
{
	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;

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

3629
	/* freeze hierarchy runnable averages while throttled */
3630 3631 3632
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649

	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)
3650
		sub_nr_running(rq, task_delta);
3651 3652

	cfs_rq->throttled = 1;
3653
	cfs_rq->throttled_clock = rq_clock(rq);
3654
	raw_spin_lock(&cfs_b->lock);
3655 3656 3657 3658 3659
	/*
	 * 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);
3660
	if (!cfs_b->timer_active)
3661
		__start_cfs_bandwidth(cfs_b, false);
3662 3663 3664
	raw_spin_unlock(&cfs_b->lock);
}

3665
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3666 3667 3668 3669 3670 3671 3672
{
	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;

3673
	se = cfs_rq->tg->se[cpu_of(rq)];
3674 3675

	cfs_rq->throttled = 0;
3676 3677 3678

	update_rq_clock(rq);

3679
	raw_spin_lock(&cfs_b->lock);
3680
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3681 3682 3683
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

3684 3685 3686
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704
	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)
3705
		add_nr_running(rq, task_delta);
3706 3707 3708

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
3709
		resched_curr(rq);
3710 3711 3712 3713 3714 3715
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
3716 3717
	u64 runtime;
	u64 starting_runtime = remaining;
3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747

	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();

3748
	return starting_runtime - remaining;
3749 3750
}

3751 3752 3753 3754 3755 3756 3757 3758
/*
 * 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)
{
3759
	u64 runtime, runtime_expires;
3760
	int throttled;
3761 3762 3763

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
3764
		goto out_deactivate;
3765

3766
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3767
	cfs_b->nr_periods += overrun;
3768

3769 3770 3771 3772 3773 3774
	/*
	 * 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
3775

3776 3777 3778 3779 3780 3781 3782
	/*
	 * if we have relooped after returning idle once, we need to update our
	 * status as actually running, so that other cpus doing
	 * __start_cfs_bandwidth will stop trying to cancel us.
	 */
	cfs_b->timer_active = 1;

P
Paul Turner 已提交
3783 3784
	__refill_cfs_bandwidth_runtime(cfs_b);

3785 3786 3787
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
3788
		return 0;
3789 3790
	}

3791 3792 3793
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

3794 3795 3796
	runtime_expires = cfs_b->runtime_expires;

	/*
3797 3798 3799 3800 3801
	 * 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.
3802
	 */
3803 3804
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
3805 3806 3807 3808 3809 3810 3811
		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);
3812 3813

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
3814
	}
3815

3816 3817 3818 3819 3820 3821 3822
	/*
	 * 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;
3823

3824 3825 3826 3827 3828
	return 0;

out_deactivate:
	cfs_b->timer_active = 0;
	return 1;
3829
}
3830

3831 3832 3833 3834 3835 3836 3837
/* 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;

3838 3839 3840 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
 * hrtimer base being cleared by __hrtimer_start_range_ns. In the case of
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
3845 3846 3847 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 3873 3874 3875 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
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;

	start_bandwidth_timer(&cfs_b->slack_timer,
				ns_to_ktime(cfs_bandwidth_slack_period));
}

/* 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)
{
3901 3902 3903
	if (!cfs_bandwidth_used())
		return;

3904
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3905 3906 3907 3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919
		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 */
3920 3921 3922
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
3923
		return;
3924
	}
3925

3926
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3927
		runtime = cfs_b->runtime;
3928

3929 3930 3931 3932 3933 3934 3935 3936 3937 3938
	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)
3939
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
3940 3941 3942
	raw_spin_unlock(&cfs_b->lock);
}

3943 3944 3945 3946 3947 3948 3949
/*
 * 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)
{
3950 3951 3952
	if (!cfs_bandwidth_used())
		return;

3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967
	/* 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() */
3968
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3969
{
3970
	if (!cfs_bandwidth_used())
3971
		return false;
3972

3973
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3974
		return false;
3975 3976 3977 3978 3979 3980

	/*
	 * 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))
3981
		return true;
3982 3983

	throttle_cfs_rq(cfs_rq);
3984
	return true;
3985
}
3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996 3997 3998 3999 4000 4001 4002 4003

static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, slack_timer);
	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);
	ktime_t now;
	int overrun;
	int idle = 0;

4004
	raw_spin_lock(&cfs_b->lock);
4005 4006 4007 4008 4009 4010 4011 4012 4013
	for (;;) {
		now = hrtimer_cb_get_time(timer);
		overrun = hrtimer_forward(timer, now, cfs_b->period);

		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
4014
	raw_spin_unlock(&cfs_b->lock);
4015 4016 4017 4018 4019 4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039

	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);
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	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);
}

/* requires cfs_b->lock, may release to reprogram timer */
4040
void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b, bool force)
4041 4042 4043 4044 4045 4046 4047
{
	/*
	 * The timer may be active because we're trying to set a new bandwidth
	 * period or because we're racing with the tear-down path
	 * (timer_active==0 becomes visible before the hrtimer call-back
	 * terminates).  In either case we ensure that it's re-programmed
	 */
4048 4049 4050
	while (unlikely(hrtimer_active(&cfs_b->period_timer)) &&
	       hrtimer_try_to_cancel(&cfs_b->period_timer) < 0) {
		/* bounce the lock to allow do_sched_cfs_period_timer to run */
4051
		raw_spin_unlock(&cfs_b->lock);
4052
		cpu_relax();
4053 4054
		raw_spin_lock(&cfs_b->lock);
		/* if someone else restarted the timer then we're done */
4055
		if (!force && cfs_b->timer_active)
4056 4057 4058 4059 4060 4061 4062 4063 4064
			return;
	}

	cfs_b->timer_active = 1;
	start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period);
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4065 4066 4067 4068
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4069 4070 4071 4072
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083 4084 4085
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);
	}
}

4086
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4087 4088 4089 4090 4091 4092 4093 4094 4095 4096 4097
{
	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
		 */
4098
		cfs_rq->runtime_remaining = 1;
4099 4100 4101 4102 4103 4104
		/*
		 * 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;

4105 4106 4107 4108 4109 4110
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
}

#else /* CONFIG_CFS_BANDWIDTH */
4111 4112
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
4113
	return rq_clock_task(rq_of(cfs_rq));
4114 4115
}

4116
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4117
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4118
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4119
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4120 4121 4122 4123 4124

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135

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;
}
4136 4137 4138 4139 4140

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) {}
4141 4142
#endif

4143 4144 4145 4146 4147
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) {}
4148
static inline void update_runtime_enabled(struct rq *rq) {}
4149
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4150 4151 4152

#endif /* CONFIG_CFS_BANDWIDTH */

4153 4154 4155 4156
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
4157 4158 4159 4160 4161 4162 4163 4164
#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);

4165
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
4166 4167 4168 4169 4170 4171
		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)
4172
				resched_curr(rq);
P
Peter Zijlstra 已提交
4173 4174
			return;
		}
4175
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
4176 4177
	}
}
4178 4179 4180 4181 4182 4183 4184 4185 4186 4187

/*
 * 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;

4188
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4189 4190 4191 4192 4193
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
4194
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
4195 4196 4197 4198
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
4199 4200 4201 4202

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
4203 4204
#endif

4205 4206 4207 4208 4209
/*
 * 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:
 */
4210
static void
4211
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4212 4213
{
	struct cfs_rq *cfs_rq;
4214
	struct sched_entity *se = &p->se;
4215 4216

	for_each_sched_entity(se) {
4217
		if (se->on_rq)
4218 4219
			break;
		cfs_rq = cfs_rq_of(se);
4220
		enqueue_entity(cfs_rq, se, flags);
4221 4222 4223 4224 4225 4226 4227 4228 4229

		/*
		 * 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;
4230
		cfs_rq->h_nr_running++;
4231

4232
		flags = ENQUEUE_WAKEUP;
4233
	}
P
Peter Zijlstra 已提交
4234

P
Peter Zijlstra 已提交
4235
	for_each_sched_entity(se) {
4236
		cfs_rq = cfs_rq_of(se);
4237
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
4238

4239 4240 4241
		if (cfs_rq_throttled(cfs_rq))
			break;

4242
		update_cfs_shares(cfs_rq);
4243
		update_entity_load_avg(se, 1);
P
Peter Zijlstra 已提交
4244 4245
	}

4246 4247
	if (!se) {
		update_rq_runnable_avg(rq, rq->nr_running);
4248
		add_nr_running(rq, 1);
4249
	}
4250
	hrtick_update(rq);
4251 4252
}

4253 4254
static void set_next_buddy(struct sched_entity *se);

4255 4256 4257 4258 4259
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
4260
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4261 4262
{
	struct cfs_rq *cfs_rq;
4263
	struct sched_entity *se = &p->se;
4264
	int task_sleep = flags & DEQUEUE_SLEEP;
4265 4266 4267

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
4268
		dequeue_entity(cfs_rq, se, flags);
4269 4270 4271 4272 4273 4274 4275 4276 4277

		/*
		 * 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;
4278
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4279

4280
		/* Don't dequeue parent if it has other entities besides us */
4281 4282 4283 4284 4285 4286 4287
		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));
4288 4289 4290

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
4291
			break;
4292
		}
4293
		flags |= DEQUEUE_SLEEP;
4294
	}
P
Peter Zijlstra 已提交
4295

P
Peter Zijlstra 已提交
4296
	for_each_sched_entity(se) {
4297
		cfs_rq = cfs_rq_of(se);
4298
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4299

4300 4301 4302
		if (cfs_rq_throttled(cfs_rq))
			break;

4303
		update_cfs_shares(cfs_rq);
4304
		update_entity_load_avg(se, 1);
P
Peter Zijlstra 已提交
4305 4306
	}

4307
	if (!se) {
4308
		sub_nr_running(rq, 1);
4309 4310
		update_rq_runnable_avg(rq, 1);
	}
4311
	hrtick_update(rq);
4312 4313
}

4314
#ifdef CONFIG_SMP
4315 4316 4317
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
4318
	return cpu_rq(cpu)->cfs.runnable_load_avg;
4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329 4330 4331 4332 4333 4334 4335 4336 4337 4338 4339 4340 4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351 4352 4353
}

/*
 * 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);
}

4354
static unsigned long capacity_of(int cpu)
4355
{
4356
	return cpu_rq(cpu)->cpu_capacity;
4357 4358 4359 4360 4361
}

static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
4362
	unsigned long nr_running = ACCESS_ONCE(rq->cfs.h_nr_running);
4363
	unsigned long load_avg = rq->cfs.runnable_load_avg;
4364 4365

	if (nr_running)
4366
		return load_avg / nr_running;
4367 4368 4369 4370

	return 0;
}

4371 4372 4373 4374 4375 4376 4377
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.
	 */
4378
	if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4379
		current->wakee_flips >>= 1;
4380 4381 4382 4383 4384 4385 4386 4387
		current->wakee_flip_decay_ts = jiffies;
	}

	if (current->last_wakee != p) {
		current->last_wakee = p;
		current->wakee_flips++;
	}
}
4388

4389
static void task_waking_fair(struct task_struct *p)
4390 4391 4392
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
4393 4394 4395 4396
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
4397

4398 4399 4400 4401 4402 4403 4404 4405
	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
4406

4407
	se->vruntime -= min_vruntime;
4408
	record_wakee(p);
4409 4410
}

4411
#ifdef CONFIG_FAIR_GROUP_SCHED
4412 4413 4414 4415 4416 4417
/*
 * 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.
4418 4419 4420 4421 4422 4423 4424 4425 4426 4427 4428 4429 4430 4431 4432 4433 4434 4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445 4446 4447 4448 4449 4450 4451 4452 4453 4454 4455 4456 4457 4458 4459 4460
 *
 * 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.
4461
 */
P
Peter Zijlstra 已提交
4462
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4463
{
P
Peter Zijlstra 已提交
4464
	struct sched_entity *se = tg->se[cpu];
4465

4466
	if (!tg->parent)	/* the trivial, non-cgroup case */
4467 4468
		return wl;

P
Peter Zijlstra 已提交
4469
	for_each_sched_entity(se) {
4470
		long w, W;
P
Peter Zijlstra 已提交
4471

4472
		tg = se->my_q->tg;
4473

4474 4475 4476 4477
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
4478

4479 4480 4481 4482
		/*
		 * w = rw_i + @wl
		 */
		w = se->my_q->load.weight + wl;
4483

4484 4485 4486 4487
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
4488
			wl = (w * (long)tg->shares) / W;
4489 4490
		else
			wl = tg->shares;
4491

4492 4493 4494 4495 4496
		/*
		 * 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().
		 */
4497 4498
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
4499 4500 4501 4502

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
4503
		wl -= se->load.weight;
4504 4505 4506 4507 4508 4509 4510 4511

		/*
		 * 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
4512 4513
		wg = 0;
	}
4514

P
Peter Zijlstra 已提交
4515
	return wl;
4516 4517
}
#else
P
Peter Zijlstra 已提交
4518

4519
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
P
Peter Zijlstra 已提交
4520
{
4521
	return wl;
4522
}
P
Peter Zijlstra 已提交
4523

4524 4525
#endif

4526 4527
static int wake_wide(struct task_struct *p)
{
4528
	int factor = this_cpu_read(sd_llc_size);
4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547

	/*
	 * Yeah, it's the switching-frequency, could means many wakee or
	 * rapidly switch, use factor here will just help to automatically
	 * adjust the loose-degree, so bigger node will lead to more pull.
	 */
	if (p->wakee_flips > factor) {
		/*
		 * wakee is somewhat hot, it needs certain amount of cpu
		 * resource, so if waker is far more hot, prefer to leave
		 * it alone.
		 */
		if (current->wakee_flips > (factor * p->wakee_flips))
			return 1;
	}

	return 0;
}

4548
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4549
{
4550
	s64 this_load, load;
4551
	s64 this_eff_load, prev_eff_load;
4552 4553
	int idx, this_cpu, prev_cpu;
	struct task_group *tg;
4554
	unsigned long weight;
4555
	int balanced;
4556

4557 4558 4559 4560 4561 4562 4563
	/*
	 * If we wake multiple tasks be careful to not bounce
	 * ourselves around too much.
	 */
	if (wake_wide(p))
		return 0;

4564 4565 4566 4567 4568
	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);
4569

4570 4571 4572 4573 4574
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
4575 4576 4577 4578
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

4579
		this_load += effective_load(tg, this_cpu, -weight, -weight);
4580 4581
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
4582

4583 4584
	tg = task_group(p);
	weight = p->se.load.weight;
4585

4586 4587
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4588 4589 4590
	 * 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.
4591 4592 4593 4594
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
4595 4596
	this_eff_load = 100;
	this_eff_load *= capacity_of(prev_cpu);
4597

4598 4599
	prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= capacity_of(this_cpu);
4600

4601
	if (this_load > 0) {
4602 4603 4604 4605
		this_eff_load *= this_load +
			effective_load(tg, this_cpu, weight, weight);

		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4606
	}
4607

4608
	balanced = this_eff_load <= prev_eff_load;
4609

4610
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4611

4612 4613
	if (!balanced)
		return 0;
4614

4615 4616 4617 4618
	schedstat_inc(sd, ttwu_move_affine);
	schedstat_inc(p, se.statistics.nr_wakeups_affine);

	return 1;
4619 4620
}

4621 4622 4623 4624 4625
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
4626
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4627
		  int this_cpu, int sd_flag)
4628
{
4629
	struct sched_group *idlest = NULL, *group = sd->groups;
4630
	unsigned long min_load = ULONG_MAX, this_load = 0;
4631
	int load_idx = sd->forkexec_idx;
4632
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
4633

4634 4635 4636
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

4637 4638 4639 4640
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
4641

4642 4643
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
4644
					tsk_cpus_allowed(p)))
4645 4646 4647 4648 4649 4650 4651 4652 4653 4654 4655 4656 4657 4658 4659 4660 4661 4662
			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;
		}

4663
		/* Adjust by relative CPU capacity of the group */
4664
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4665 4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680 4681 4682 4683 4684 4685

		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;
4686 4687 4688 4689
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
4690 4691 4692
	int i;

	/* Traverse only the allowed CPUs */
4693
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4694 4695 4696 4697 4698 4699 4700 4701 4702 4703 4704 4705 4706 4707 4708 4709 4710 4711 4712 4713 4714 4715
		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;
			}
4716
		} else if (shallowest_idle_cpu == -1) {
4717 4718 4719 4720 4721
			load = weighted_cpuload(i);
			if (load < min_load || (load == min_load && i == this_cpu)) {
				min_load = load;
				least_loaded_cpu = i;
			}
4722 4723 4724
		}
	}

4725
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
4726
}
4727

4728 4729 4730
/*
 * Try and locate an idle CPU in the sched_domain.
 */
4731
static int select_idle_sibling(struct task_struct *p, int target)
4732
{
4733
	struct sched_domain *sd;
4734
	struct sched_group *sg;
4735
	int i = task_cpu(p);
4736

4737 4738
	if (idle_cpu(target))
		return target;
4739 4740

	/*
4741
	 * If the prevous cpu is cache affine and idle, don't be stupid.
4742
	 */
4743 4744
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
4745 4746

	/*
4747
	 * Otherwise, iterate the domains and find an elegible idle cpu.
4748
	 */
4749
	sd = rcu_dereference(per_cpu(sd_llc, target));
4750
	for_each_lower_domain(sd) {
4751 4752 4753 4754 4755 4756 4757
		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)) {
4758
				if (i == target || !idle_cpu(i))
4759 4760
					goto next;
			}
4761

4762 4763 4764 4765 4766 4767 4768 4769
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
4770 4771 4772
	return target;
}

4773
/*
4774 4775 4776
 * 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.
4777
 *
4778 4779
 * 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.
4780
 *
4781
 * Returns the target cpu number.
4782 4783 4784
 *
 * preempt must be disabled.
 */
4785
static int
4786
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
4787
{
4788
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
4789 4790
	int cpu = smp_processor_id();
	int new_cpu = cpu;
4791
	int want_affine = 0;
4792
	int sync = wake_flags & WF_SYNC;
4793

4794 4795
	if (sd_flag & SD_BALANCE_WAKE)
		want_affine = cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
4796

4797
	rcu_read_lock();
4798
	for_each_domain(cpu, tmp) {
4799 4800 4801
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

4802
		/*
4803 4804
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
4805
		 */
4806 4807 4808
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
4809
			break;
4810
		}
4811

4812
		if (tmp->flags & sd_flag)
4813 4814 4815
			sd = tmp;
	}

4816 4817
	if (affine_sd && cpu != prev_cpu && wake_affine(affine_sd, p, sync))
		prev_cpu = cpu;
4818

4819
	if (sd_flag & SD_BALANCE_WAKE) {
4820 4821
		new_cpu = select_idle_sibling(p, prev_cpu);
		goto unlock;
4822
	}
4823

4824 4825
	while (sd) {
		struct sched_group *group;
4826
		int weight;
4827

4828
		if (!(sd->flags & sd_flag)) {
4829 4830 4831
			sd = sd->child;
			continue;
		}
4832

4833
		group = find_idlest_group(sd, p, cpu, sd_flag);
4834 4835 4836 4837
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
4838

4839
		new_cpu = find_idlest_cpu(group, p, cpu);
4840 4841 4842 4843
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
4844
		}
4845 4846 4847

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
4848
		weight = sd->span_weight;
4849 4850
		sd = NULL;
		for_each_domain(cpu, tmp) {
4851
			if (weight <= tmp->span_weight)
4852
				break;
4853
			if (tmp->flags & sd_flag)
4854 4855 4856
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
4857
	}
4858 4859
unlock:
	rcu_read_unlock();
4860

4861
	return new_cpu;
4862
}
4863 4864 4865 4866 4867 4868 4869 4870 4871 4872

/*
 * 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
 * previous cpu.  However, the caller only guarantees p->pi_lock is held; no
 * other assumptions, including the state of rq->lock, should be made.
 */
static void
migrate_task_rq_fair(struct task_struct *p, int next_cpu)
{
4873 4874 4875 4876 4877 4878 4879 4880 4881 4882 4883
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	/*
	 * Load tracking: accumulate removed load so that it can be processed
	 * when we next update owning cfs_rq under rq->lock.  Tasks contribute
	 * to blocked load iff they have a positive decay-count.  It can never
	 * be negative here since on-rq tasks have decay-count == 0.
	 */
	if (se->avg.decay_count) {
		se->avg.decay_count = -__synchronize_entity_decay(se);
4884 4885
		atomic_long_add(se->avg.load_avg_contrib,
						&cfs_rq->removed_load);
4886
	}
4887 4888 4889

	/* We have migrated, no longer consider this task hot */
	se->exec_start = 0;
4890
}
4891 4892
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
4893 4894
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
4895 4896 4897 4898
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
4899 4900
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
4901 4902 4903 4904 4905 4906 4907 4908 4909
	 *
	 * 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.
4910
	 */
4911
	return calc_delta_fair(gran, se);
4912 4913
}

4914 4915 4916 4917 4918 4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935
/*
 * 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
4936
	gran = wakeup_gran(curr, se);
4937 4938 4939 4940 4941 4942
	if (vdiff > gran)
		return 1;

	return 0;
}

4943 4944
static void set_last_buddy(struct sched_entity *se)
{
4945 4946 4947 4948 4949
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
4950 4951 4952 4953
}

static void set_next_buddy(struct sched_entity *se)
{
4954 4955 4956 4957 4958
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
4959 4960
}

4961 4962
static void set_skip_buddy(struct sched_entity *se)
{
4963 4964
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
4965 4966
}

4967 4968 4969
/*
 * Preempt the current task with a newly woken task if needed:
 */
4970
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
4971 4972
{
	struct task_struct *curr = rq->curr;
4973
	struct sched_entity *se = &curr->se, *pse = &p->se;
4974
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
4975
	int scale = cfs_rq->nr_running >= sched_nr_latency;
4976
	int next_buddy_marked = 0;
4977

I
Ingo Molnar 已提交
4978 4979 4980
	if (unlikely(se == pse))
		return;

4981
	/*
4982
	 * This is possible from callers such as attach_tasks(), in which we
4983 4984 4985 4986 4987 4988 4989
	 * 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;

4990
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
4991
		set_next_buddy(pse);
4992 4993
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
4994

4995 4996 4997
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
4998 4999 5000 5001 5002 5003
	 *
	 * 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.
5004 5005 5006 5007
	 */
	if (test_tsk_need_resched(curr))
		return;

5008 5009 5010 5011 5012
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

5013
	/*
5014 5015
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
5016
	 */
5017
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5018
		return;
5019

5020
	find_matching_se(&se, &pse);
5021
	update_curr(cfs_rq_of(se));
5022
	BUG_ON(!pse);
5023 5024 5025 5026 5027 5028 5029
	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);
5030
		goto preempt;
5031
	}
5032

5033
	return;
5034

5035
preempt:
5036
	resched_curr(rq);
5037 5038 5039 5040 5041 5042 5043 5044 5045 5046 5047 5048 5049 5050
	/*
	 * 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);
5051 5052
}

5053 5054
static struct task_struct *
pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5055 5056 5057
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
5058
	struct task_struct *p;
5059
	int new_tasks;
5060

5061
again:
5062 5063
#ifdef CONFIG_FAIR_GROUP_SCHED
	if (!cfs_rq->nr_running)
5064
		goto idle;
5065

5066
	if (prev->sched_class != &fair_sched_class)
5067 5068 5069 5070 5071 5072 5073 5074 5075 5076 5077 5078 5079 5080 5081 5082 5083 5084 5085 5086 5087 5088 5089 5090 5091 5092 5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103 5104 5105 5106 5107 5108 5109 5110 5111 5112 5113 5114 5115 5116 5117 5118 5119 5120 5121 5122 5123 5124 5125 5126 5127 5128 5129 5130 5131 5132 5133 5134 5135 5136 5137
		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.
		 */
		if (curr && curr->on_rq)
			update_curr(cfs_rq);
		else
			curr = NULL;

		/*
		 * 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;

		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
5138

5139
	if (!cfs_rq->nr_running)
5140
		goto idle;
5141

5142
	put_prev_task(rq, prev);
5143

5144
	do {
5145
		se = pick_next_entity(cfs_rq, NULL);
5146
		set_next_entity(cfs_rq, se);
5147 5148 5149
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
5150
	p = task_of(se);
5151

5152 5153
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
5154 5155

	return p;
5156 5157

idle:
5158
	new_tasks = idle_balance(rq);
5159 5160 5161 5162 5163
	/*
	 * 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.
	 */
5164
	if (new_tasks < 0)
5165 5166
		return RETRY_TASK;

5167
	if (new_tasks > 0)
5168 5169 5170
		goto again;

	return NULL;
5171 5172 5173 5174 5175
}

/*
 * Account for a descheduled task:
 */
5176
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5177 5178 5179 5180 5181 5182
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5183
		put_prev_entity(cfs_rq, se);
5184 5185 5186
	}
}

5187 5188 5189 5190 5191 5192 5193 5194 5195 5196 5197 5198 5199 5200 5201 5202 5203 5204 5205 5206 5207 5208 5209 5210 5211
/*
 * 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);
5212 5213 5214 5215 5216
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
5217
		rq_clock_skip_update(rq, true);
5218 5219 5220 5221 5222
	}

	set_skip_buddy(se);
}

5223 5224 5225 5226
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

5227 5228
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5229 5230 5231 5232 5233 5234 5235 5236 5237 5238
		return false;

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

	yield_task_fair(rq);

	return true;
}

5239
#ifdef CONFIG_SMP
5240
/**************************************************
P
Peter Zijlstra 已提交
5241 5242 5243 5244 5245 5246 5247 5248 5249 5250 5251 5252 5253 5254 5255 5256 5257 5258 5259 5260 5261 5262 5263
 * 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)
 *
5264
 * C_i is the compute capacity of cpu i, typically it is the
P
Peter Zijlstra 已提交
5265 5266 5267 5268 5269 5270
 * 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):
 *
5271
 *   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
5272 5273 5274 5275 5276 5277 5278 5279 5280 5281 5282 5283 5284 5285 5286 5287 5288 5289 5290 5291 5292 5293 5294 5295 5296 5297 5298 5299 5300 5301 5302 5303 5304 5305 5306 5307 5308 5309 5310 5311 5312 5313 5314 5315 5316 5317 5318 5319 5320 5321 5322 5323 5324 5325 5326 5327 5328 5329 5330 5331 5332 5333 5334 5335 5336 5337 5338 5339 5340 5341 5342 5343 5344 5345 5346 5347 5348 5349 5350 5351 5352 5353 5354 5355 5356
 *
 * 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.]
 */ 
5357

5358 5359
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

5360 5361
enum fbq_type { regular, remote, all };

5362
#define LBF_ALL_PINNED	0x01
5363
#define LBF_NEED_BREAK	0x02
5364 5365
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
5366 5367 5368 5369 5370

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
5371
	int			src_cpu;
5372 5373 5374 5375

	int			dst_cpu;
	struct rq		*dst_rq;

5376 5377
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
5378
	enum cpu_idle_type	idle;
5379
	long			imbalance;
5380 5381 5382
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

5383
	unsigned int		flags;
5384 5385 5386 5387

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
5388 5389

	enum fbq_type		fbq_type;
5390
	struct list_head	tasks;
5391 5392
};

5393 5394 5395
/*
 * Is this task likely cache-hot:
 */
5396
static int task_hot(struct task_struct *p, struct lb_env *env)
5397 5398 5399
{
	s64 delta;

5400 5401
	lockdep_assert_held(&env->src_rq->lock);

5402 5403 5404 5405 5406 5407 5408 5409 5410
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
5411
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5412 5413 5414 5415 5416 5417 5418 5419 5420
			(&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;

5421
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5422 5423 5424 5425

	return delta < (s64)sysctl_sched_migration_cost;
}

5426 5427 5428 5429
#ifdef CONFIG_NUMA_BALANCING
/* Returns true if the destination node has incurred more faults */
static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
{
5430
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
5431 5432
	int src_nid, dst_nid;

5433
	if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults ||
5434 5435 5436 5437 5438 5439 5440
	    !(env->sd->flags & SD_NUMA)) {
		return false;
	}

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

5441
	if (src_nid == dst_nid)
5442 5443
		return false;

5444 5445 5446 5447
	if (numa_group) {
		/* Task is already in the group's interleave set. */
		if (node_isset(src_nid, numa_group->active_nodes))
			return false;
5448

5449 5450 5451
		/* Task is moving into the group's interleave set. */
		if (node_isset(dst_nid, numa_group->active_nodes))
			return true;
5452

5453 5454 5455 5456 5457
		return group_faults(p, dst_nid) > group_faults(p, src_nid);
	}

	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
5458 5459
		return true;

5460
	return task_faults(p, dst_nid) > task_faults(p, src_nid);
5461
}
5462 5463 5464 5465


static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
{
5466
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
5467 5468 5469 5470 5471
	int src_nid, dst_nid;

	if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER))
		return false;

5472
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5473 5474 5475 5476 5477
		return false;

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

5478
	if (src_nid == dst_nid)
5479 5480
		return false;

5481 5482 5483 5484 5485 5486 5487 5488 5489 5490 5491 5492
	if (numa_group) {
		/* Task is moving within/into the group's interleave set. */
		if (node_isset(dst_nid, numa_group->active_nodes))
			return false;

		/* Task is moving out of the group's interleave set. */
		if (node_isset(src_nid, numa_group->active_nodes))
			return true;

		return group_faults(p, dst_nid) < group_faults(p, src_nid);
	}

5493 5494 5495 5496
	/* Migrating away from the preferred node is always bad. */
	if (src_nid == p->numa_preferred_nid)
		return true;

5497
	return task_faults(p, dst_nid) < task_faults(p, src_nid);
5498 5499
}

5500 5501 5502 5503 5504 5505
#else
static inline bool migrate_improves_locality(struct task_struct *p,
					     struct lb_env *env)
{
	return false;
}
5506 5507 5508 5509 5510 5511

static inline bool migrate_degrades_locality(struct task_struct *p,
					     struct lb_env *env)
{
	return false;
}
5512 5513
#endif

5514 5515 5516 5517
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
5518
int can_migrate_task(struct task_struct *p, struct lb_env *env)
5519 5520
{
	int tsk_cache_hot = 0;
5521 5522 5523

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

5524 5525
	/*
	 * We do not migrate tasks that are:
5526
	 * 1) throttled_lb_pair, or
5527
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5528 5529
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
5530
	 */
5531 5532 5533
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

5534
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5535
		int cpu;
5536

5537
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5538

5539 5540
		env->flags |= LBF_SOME_PINNED;

5541 5542 5543 5544 5545 5546 5547 5548
		/*
		 * 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.
		 */
5549
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5550 5551
			return 0;

5552 5553 5554
		/* 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))) {
5555
				env->flags |= LBF_DST_PINNED;
5556 5557 5558
				env->new_dst_cpu = cpu;
				break;
			}
5559
		}
5560

5561 5562
		return 0;
	}
5563 5564

	/* Record that we found atleast one task that could run on dst_cpu */
5565
	env->flags &= ~LBF_ALL_PINNED;
5566

5567
	if (task_running(env->src_rq, p)) {
5568
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5569 5570 5571 5572 5573
		return 0;
	}

	/*
	 * Aggressive migration if:
5574 5575 5576
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
5577
	 */
5578
	tsk_cache_hot = task_hot(p, env);
5579 5580
	if (!tsk_cache_hot)
		tsk_cache_hot = migrate_degrades_locality(p, env);
5581

5582 5583
	if (migrate_improves_locality(p, env) || !tsk_cache_hot ||
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5584 5585 5586 5587
		if (tsk_cache_hot) {
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
			schedstat_inc(p, se.statistics.nr_forced_migrations);
		}
5588 5589 5590
		return 1;
	}

Z
Zhang Hang 已提交
5591 5592
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
5593 5594
}

5595
/*
5596 5597 5598 5599 5600 5601 5602 5603 5604 5605 5606
 * 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);

	deactivate_task(env->src_rq, p, 0);
	p->on_rq = TASK_ON_RQ_MIGRATING;
	set_task_cpu(p, env->dst_cpu);
}

5607
/*
5608
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5609 5610
 * part of active balancing operations within "domain".
 *
5611
 * Returns a task if successful and NULL otherwise.
5612
 */
5613
static struct task_struct *detach_one_task(struct lb_env *env)
5614 5615 5616
{
	struct task_struct *p, *n;

5617 5618
	lockdep_assert_held(&env->src_rq->lock);

5619 5620 5621
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
5622

5623
		detach_task(p, env);
5624

5625
		/*
5626
		 * Right now, this is only the second place where
5627
		 * lb_gained[env->idle] is updated (other is detach_tasks)
5628
		 * so we can safely collect stats here rather than
5629
		 * inside detach_tasks().
5630 5631
		 */
		schedstat_inc(env->sd, lb_gained[env->idle]);
5632
		return p;
5633
	}
5634
	return NULL;
5635 5636
}

5637 5638
static const unsigned int sched_nr_migrate_break = 32;

5639
/*
5640 5641
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
5642
 *
5643
 * Returns number of detached tasks if successful and 0 otherwise.
5644
 */
5645
static int detach_tasks(struct lb_env *env)
5646
{
5647 5648
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
5649
	unsigned long load;
5650 5651 5652
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
5653

5654
	if (env->imbalance <= 0)
5655
		return 0;
5656

5657 5658
	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
5659

5660 5661
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
5662
		if (env->loop > env->loop_max)
5663
			break;
5664 5665

		/* take a breather every nr_migrate tasks */
5666
		if (env->loop > env->loop_break) {
5667
			env->loop_break += sched_nr_migrate_break;
5668
			env->flags |= LBF_NEED_BREAK;
5669
			break;
5670
		}
5671

5672
		if (!can_migrate_task(p, env))
5673 5674 5675
			goto next;

		load = task_h_load(p);
5676

5677
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5678 5679
			goto next;

5680
		if ((load / 2) > env->imbalance)
5681
			goto next;
5682

5683 5684 5685 5686
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
5687
		env->imbalance -= load;
5688 5689

#ifdef CONFIG_PREEMPT
5690 5691
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
5692
		 * kernels will stop after the first task is detached to minimize
5693 5694
		 * the critical section.
		 */
5695
		if (env->idle == CPU_NEWLY_IDLE)
5696
			break;
5697 5698
#endif

5699 5700 5701 5702
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
5703
		if (env->imbalance <= 0)
5704
			break;
5705 5706 5707

		continue;
next:
5708
		list_move_tail(&p->se.group_node, tasks);
5709
	}
5710

5711
	/*
5712 5713 5714
	 * 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().
5715
	 */
5716
	schedstat_add(env->sd, lb_gained[env->idle], detached);
5717

5718 5719 5720 5721 5722 5723 5724 5725 5726 5727 5728 5729 5730 5731 5732 5733 5734 5735 5736 5737 5738 5739 5740 5741 5742 5743 5744 5745 5746 5747 5748 5749 5750 5751 5752 5753 5754 5755 5756 5757 5758
	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);
	p->on_rq = TASK_ON_RQ_QUEUED;
	activate_task(rq, p, 0);
	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);
5759

5760 5761 5762 5763
		attach_task(env->dst_rq, p);
	}

	raw_spin_unlock(&env->dst_rq->lock);
5764 5765
}

P
Peter Zijlstra 已提交
5766
#ifdef CONFIG_FAIR_GROUP_SCHED
5767 5768 5769
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
5770
static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
5771
{
5772 5773
	struct sched_entity *se = tg->se[cpu];
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
5774

5775 5776 5777
	/* throttled entities do not contribute to load */
	if (throttled_hierarchy(cfs_rq))
		return;
5778

5779
	update_cfs_rq_blocked_load(cfs_rq, 1);
5780

5781 5782 5783 5784 5785 5786 5787 5788 5789 5790 5791 5792 5793 5794
	if (se) {
		update_entity_load_avg(se, 1);
		/*
		 * We pivot on our runnable average having decayed to zero for
		 * list removal.  This generally implies that all our children
		 * have also been removed (modulo rounding error or bandwidth
		 * control); however, such cases are rare and we can fix these
		 * at enqueue.
		 *
		 * TODO: fix up out-of-order children on enqueue.
		 */
		if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running)
			list_del_leaf_cfs_rq(cfs_rq);
	} else {
5795
		struct rq *rq = rq_of(cfs_rq);
5796 5797
		update_rq_runnable_avg(rq, rq->nr_running);
	}
5798 5799
}

5800
static void update_blocked_averages(int cpu)
5801 5802
{
	struct rq *rq = cpu_rq(cpu);
5803 5804
	struct cfs_rq *cfs_rq;
	unsigned long flags;
5805

5806 5807
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
5808 5809 5810 5811
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
5812
	for_each_leaf_cfs_rq(rq, cfs_rq) {
5813 5814 5815 5816 5817 5818
		/*
		 * Note: We may want to consider periodically releasing
		 * rq->lock about these updates so that creating many task
		 * groups does not result in continually extending hold time.
		 */
		__update_blocked_averages_cpu(cfs_rq->tg, rq->cpu);
5819
	}
5820 5821

	raw_spin_unlock_irqrestore(&rq->lock, flags);
5822 5823
}

5824
/*
5825
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5826 5827 5828
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
5829
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
5830
{
5831 5832
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
5833
	unsigned long now = jiffies;
5834
	unsigned long load;
5835

5836
	if (cfs_rq->last_h_load_update == now)
5837 5838
		return;

5839 5840 5841 5842 5843 5844 5845
	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;
	}
5846

5847
	if (!se) {
5848
		cfs_rq->h_load = cfs_rq->runnable_load_avg;
5849 5850 5851 5852 5853 5854 5855 5856 5857 5858 5859
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
		load = div64_ul(load * se->avg.load_avg_contrib,
				cfs_rq->runnable_load_avg + 1);
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
5860 5861
}

5862
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
5863
{
5864
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
5865

5866
	update_cfs_rq_h_load(cfs_rq);
5867 5868
	return div64_ul(p->se.avg.load_avg_contrib * cfs_rq->h_load,
			cfs_rq->runnable_load_avg + 1);
P
Peter Zijlstra 已提交
5869 5870
}
#else
5871
static inline void update_blocked_averages(int cpu)
5872 5873 5874
{
}

5875
static unsigned long task_h_load(struct task_struct *p)
5876
{
5877
	return p->se.avg.load_avg_contrib;
5878
}
P
Peter Zijlstra 已提交
5879
#endif
5880 5881

/********** Helpers for find_busiest_group ************************/
5882 5883 5884 5885 5886 5887 5888

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

5889 5890 5891 5892 5893 5894 5895
/*
 * 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
5896
	unsigned long load_per_task;
5897
	unsigned long group_capacity;
5898
	unsigned int sum_nr_running; /* Nr tasks running in the group */
5899
	unsigned int group_capacity_factor;
5900 5901
	unsigned int idle_cpus;
	unsigned int group_weight;
5902
	enum group_type group_type;
5903
	int group_has_free_capacity;
5904 5905 5906 5907
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
5908 5909
};

J
Joonsoo Kim 已提交
5910 5911 5912 5913 5914 5915 5916 5917
/*
 * 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 */
5918
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
5919 5920 5921
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
5922
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
5923 5924
};

5925 5926 5927 5928 5929 5930 5931 5932 5933 5934 5935 5936
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,
5937
		.total_capacity = 0UL,
5938 5939
		.busiest_stat = {
			.avg_load = 0UL,
5940 5941
			.sum_nr_running = 0,
			.group_type = group_other,
5942 5943 5944 5945
		},
	};
}

5946 5947 5948
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
5949
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
5950 5951
 *
 * Return: The load index.
5952 5953 5954 5955 5956 5957 5958 5959 5960 5961 5962 5963 5964 5965 5966 5967 5968 5969 5970 5971 5972 5973
 */
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;
}

5974
static unsigned long default_scale_capacity(struct sched_domain *sd, int cpu)
5975
{
5976
	return SCHED_CAPACITY_SCALE;
5977 5978
}

5979
unsigned long __weak arch_scale_freq_capacity(struct sched_domain *sd, int cpu)
5980
{
5981
	return default_scale_capacity(sd, cpu);
5982 5983
}

5984
static unsigned long default_scale_cpu_capacity(struct sched_domain *sd, int cpu)
5985
{
5986 5987
	if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1))
		return sd->smt_gain / sd->span_weight;
5988

5989
	return SCHED_CAPACITY_SCALE;
5990 5991
}

5992
unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
5993
{
5994
	return default_scale_cpu_capacity(sd, cpu);
5995 5996
}

5997
static unsigned long scale_rt_capacity(int cpu)
5998 5999
{
	struct rq *rq = cpu_rq(cpu);
6000
	u64 total, available, age_stamp, avg;
6001
	s64 delta;
6002

6003 6004 6005 6006 6007 6008
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
	age_stamp = ACCESS_ONCE(rq->age_stamp);
	avg = ACCESS_ONCE(rq->rt_avg);
6009
	delta = __rq_clock_broken(rq) - age_stamp;
6010

6011 6012 6013 6014
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
6015

6016
	if (unlikely(total < avg)) {
6017
		/* Ensures that capacity won't end up being negative */
6018 6019
		available = 0;
	} else {
6020
		available = total - avg;
6021
	}
6022

6023 6024
	if (unlikely((s64)total < SCHED_CAPACITY_SCALE))
		total = SCHED_CAPACITY_SCALE;
6025

6026
	total >>= SCHED_CAPACITY_SHIFT;
6027 6028 6029 6030

	return div_u64(available, total);
}

6031
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6032
{
6033
	unsigned long capacity = SCHED_CAPACITY_SCALE;
6034 6035
	struct sched_group *sdg = sd->groups;

6036 6037 6038 6039
	if (sched_feat(ARCH_CAPACITY))
		capacity *= arch_scale_cpu_capacity(sd, cpu);
	else
		capacity *= default_scale_cpu_capacity(sd, cpu);
6040

6041
	capacity >>= SCHED_CAPACITY_SHIFT;
6042

6043
	sdg->sgc->capacity_orig = capacity;
6044

6045
	capacity *= scale_rt_capacity(cpu);
6046
	capacity >>= SCHED_CAPACITY_SHIFT;
6047

6048 6049
	if (!capacity)
		capacity = 1;
6050

6051 6052
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
6053 6054
}

6055
void update_group_capacity(struct sched_domain *sd, int cpu)
6056 6057 6058
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
6059
	unsigned long capacity, capacity_orig;
6060 6061 6062 6063
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
6064
	sdg->sgc->next_update = jiffies + interval;
6065 6066

	if (!child) {
6067
		update_cpu_capacity(sd, cpu);
6068 6069 6070
		return;
	}

6071
	capacity_orig = capacity = 0;
6072

P
Peter Zijlstra 已提交
6073 6074 6075 6076 6077 6078
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

6079
		for_each_cpu(cpu, sched_group_cpus(sdg)) {
6080
			struct sched_group_capacity *sgc;
6081
			struct rq *rq = cpu_rq(cpu);
6082

6083
			/*
6084
			 * build_sched_domains() -> init_sched_groups_capacity()
6085 6086 6087
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
6088 6089
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
6090
			 *
6091
			 * This avoids capacity/capacity_orig from being 0 and
6092 6093
			 * causing divide-by-zero issues on boot.
			 *
6094
			 * Runtime updates will correct capacity_orig.
6095 6096
			 */
			if (unlikely(!rq->sd)) {
6097 6098
				capacity_orig += capacity_of(cpu);
				capacity += capacity_of(cpu);
6099 6100
				continue;
			}
6101

6102 6103 6104
			sgc = rq->sd->groups->sgc;
			capacity_orig += sgc->capacity_orig;
			capacity += sgc->capacity;
6105
		}
P
Peter Zijlstra 已提交
6106 6107 6108 6109 6110 6111 6112 6113
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
6114 6115
			capacity_orig += group->sgc->capacity_orig;
			capacity += group->sgc->capacity;
P
Peter Zijlstra 已提交
6116 6117 6118
			group = group->next;
		} while (group != child->groups);
	}
6119

6120 6121
	sdg->sgc->capacity_orig = capacity_orig;
	sdg->sgc->capacity = capacity;
6122 6123
}

6124 6125 6126 6127 6128 6129 6130 6131 6132 6133 6134
/*
 * Try and fix up capacity for tiny siblings, this is needed when
 * things like SD_ASYM_PACKING need f_b_g to select another sibling
 * which on its own isn't powerful enough.
 *
 * See update_sd_pick_busiest() and check_asym_packing().
 */
static inline int
fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
{
	/*
6135
	 * Only siblings can have significantly less than SCHED_CAPACITY_SCALE
6136
	 */
6137
	if (!(sd->flags & SD_SHARE_CPUCAPACITY))
6138 6139 6140
		return 0;

	/*
6141
	 * If ~90% of the cpu_capacity is still there, we're good.
6142
	 */
6143
	if (group->sgc->capacity * 32 > group->sgc->capacity_orig * 29)
6144 6145 6146 6147 6148
		return 1;

	return 0;
}

6149 6150 6151 6152 6153 6154 6155 6156 6157 6158 6159 6160 6161 6162 6163 6164
/*
 * 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
6165 6166
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
6167 6168
 *
 * When this is so detected; this group becomes a candidate for busiest; see
6169
 * update_sd_pick_busiest(). And calculate_imbalance() and
6170
 * find_busiest_group() avoid some of the usual balance conditions to allow it
6171 6172 6173 6174 6175 6176 6177
 * 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.
 */

6178
static inline int sg_imbalanced(struct sched_group *group)
6179
{
6180
	return group->sgc->imbalance;
6181 6182
}

6183
/*
6184
 * Compute the group capacity factor.
6185
 *
6186
 * Avoid the issue where N*frac(smt_capacity) >= 1 creates 'phantom' cores by
6187
 * first dividing out the smt factor and computing the actual number of cores
6188
 * and limit unit capacity with that.
6189
 */
6190
static inline int sg_capacity_factor(struct lb_env *env, struct sched_group *group)
6191
{
6192
	unsigned int capacity_factor, smt, cpus;
6193
	unsigned int capacity, capacity_orig;
6194

6195 6196
	capacity = group->sgc->capacity;
	capacity_orig = group->sgc->capacity_orig;
6197
	cpus = group->group_weight;
6198

6199
	/* smt := ceil(cpus / capacity), assumes: 1 < smt_capacity < 2 */
6200
	smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, capacity_orig);
6201
	capacity_factor = cpus / smt; /* cores */
6202

6203
	capacity_factor = min_t(unsigned,
6204
		capacity_factor, DIV_ROUND_CLOSEST(capacity, SCHED_CAPACITY_SCALE));
6205 6206
	if (!capacity_factor)
		capacity_factor = fix_small_capacity(env->sd, group);
6207

6208
	return capacity_factor;
6209 6210
}

6211 6212 6213 6214 6215 6216 6217 6218 6219 6220 6221 6222
static enum group_type
group_classify(struct sched_group *group, struct sg_lb_stats *sgs)
{
	if (sgs->sum_nr_running > sgs->group_capacity_factor)
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

6223 6224
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6225
 * @env: The load balancing environment.
6226 6227 6228 6229
 * @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.
6230
 * @overload: Indicate more than one runnable task for any CPU.
6231
 */
6232 6233
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
6234 6235
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
6236
{
6237
	unsigned long load;
6238
	int i;
6239

6240 6241
	memset(sgs, 0, sizeof(*sgs));

6242
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6243 6244 6245
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
6246
		if (local_group)
6247
			load = target_load(i, load_idx);
6248
		else
6249 6250 6251
			load = source_load(i, load_idx);

		sgs->group_load += load;
6252
		sgs->sum_nr_running += rq->cfs.h_nr_running;
6253 6254 6255 6256

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

6257 6258 6259 6260
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
6261
		sgs->sum_weighted_load += weighted_cpuload(i);
6262 6263
		if (idle_cpu(i))
			sgs->idle_cpus++;
6264 6265
	}

6266 6267
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
6268
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6269

6270
	if (sgs->sum_nr_running)
6271
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6272

6273
	sgs->group_weight = group->group_weight;
6274
	sgs->group_capacity_factor = sg_capacity_factor(env, group);
6275
	sgs->group_type = group_classify(group, sgs);
6276

6277
	if (sgs->group_capacity_factor > sgs->sum_nr_running)
6278
		sgs->group_has_free_capacity = 1;
6279 6280
}

6281 6282
/**
 * update_sd_pick_busiest - return 1 on busiest group
6283
 * @env: The load balancing environment.
6284 6285
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
6286
 * @sgs: sched_group statistics
6287 6288 6289
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
6290 6291 6292
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
6293
 */
6294
static bool update_sd_pick_busiest(struct lb_env *env,
6295 6296
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
6297
				   struct sg_lb_stats *sgs)
6298
{
6299
	struct sg_lb_stats *busiest = &sds->busiest_stat;
6300

6301
	if (sgs->group_type > busiest->group_type)
6302 6303
		return true;

6304 6305 6306 6307 6308 6309 6310 6311
	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))
6312 6313 6314 6315 6316 6317 6318
		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.
	 */
6319
	if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6320 6321 6322 6323 6324 6325 6326 6327 6328 6329
		if (!sds->busiest)
			return true;

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

	return false;
}

6330 6331 6332 6333 6334 6335 6336 6337 6338 6339 6340 6341 6342 6343 6344 6345 6346 6347 6348 6349 6350 6351 6352 6353 6354 6355 6356 6357 6358 6359
#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 */

6360
/**
6361
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6362
 * @env: The load balancing environment.
6363 6364
 * @sds: variable to hold the statistics for this sched_domain.
 */
6365
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6366
{
6367 6368
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
6369
	struct sg_lb_stats tmp_sgs;
6370
	int load_idx, prefer_sibling = 0;
6371
	bool overload = false;
6372 6373 6374 6375

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

6376
	load_idx = get_sd_load_idx(env->sd, env->idle);
6377 6378

	do {
J
Joonsoo Kim 已提交
6379
		struct sg_lb_stats *sgs = &tmp_sgs;
6380 6381
		int local_group;

6382
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
6383 6384 6385
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
6386 6387

			if (env->idle != CPU_NEWLY_IDLE ||
6388 6389
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
6390
		}
6391

6392 6393
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
6394

6395 6396 6397
		if (local_group)
			goto next_group;

6398 6399
		/*
		 * In case the child domain prefers tasks go to siblings
6400
		 * first, lower the sg capacity factor to one so that we'll try
6401 6402
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
6403
		 * these excess tasks, i.e. nr_running < group_capacity_factor. The
6404 6405 6406
		 * 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).
6407
		 */
6408
		if (prefer_sibling && sds->local &&
6409
		    sds->local_stat.group_has_free_capacity) {
6410
			sgs->group_capacity_factor = min(sgs->group_capacity_factor, 1U);
6411 6412
			sgs->group_type = group_classify(sg, sgs);
		}
6413

6414
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6415
			sds->busiest = sg;
J
Joonsoo Kim 已提交
6416
			sds->busiest_stat = *sgs;
6417 6418
		}

6419 6420 6421
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
6422
		sds->total_capacity += sgs->group_capacity;
6423

6424
		sg = sg->next;
6425
	} while (sg != env->sd->groups);
6426 6427 6428

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6429 6430 6431 6432 6433 6434 6435

	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;
	}

6436 6437 6438 6439 6440 6441 6442 6443 6444 6445 6446 6447 6448 6449 6450 6451 6452 6453 6454
}

/**
 * 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.
 *
6455
 * Return: 1 when packing is required and a task should be moved to
6456 6457
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
6458
 * @env: The load balancing environment.
6459 6460
 * @sds: Statistics of the sched_domain which is to be packed
 */
6461
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6462 6463 6464
{
	int busiest_cpu;

6465
	if (!(env->sd->flags & SD_ASYM_PACKING))
6466 6467 6468 6469 6470 6471
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
6472
	if (env->dst_cpu > busiest_cpu)
6473 6474
		return 0;

6475
	env->imbalance = DIV_ROUND_CLOSEST(
6476
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6477
		SCHED_CAPACITY_SCALE);
6478

6479
	return 1;
6480 6481 6482 6483 6484 6485
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
6486
 * @env: The load balancing environment.
6487 6488
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
6489 6490
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6491
{
6492
	unsigned long tmp, capa_now = 0, capa_move = 0;
6493
	unsigned int imbn = 2;
6494
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
6495
	struct sg_lb_stats *local, *busiest;
6496

J
Joonsoo Kim 已提交
6497 6498
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6499

J
Joonsoo Kim 已提交
6500 6501 6502 6503
	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;
6504

J
Joonsoo Kim 已提交
6505
	scaled_busy_load_per_task =
6506
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6507
		busiest->group_capacity;
J
Joonsoo Kim 已提交
6508

6509 6510
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
6511
		env->imbalance = busiest->load_per_task;
6512 6513 6514 6515 6516
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
6517
	 * however we may be able to increase total CPU capacity used by
6518 6519 6520
	 * moving them.
	 */

6521
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
6522
			min(busiest->load_per_task, busiest->avg_load);
6523
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
6524
			min(local->load_per_task, local->avg_load);
6525
	capa_now /= SCHED_CAPACITY_SCALE;
6526 6527

	/* Amount of load we'd subtract */
6528
	if (busiest->avg_load > scaled_busy_load_per_task) {
6529
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
6530
			    min(busiest->load_per_task,
6531
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
6532
	}
6533 6534

	/* Amount of load we'd add */
6535
	if (busiest->avg_load * busiest->group_capacity <
6536
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6537 6538
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
6539
	} else {
6540
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6541
		      local->group_capacity;
J
Joonsoo Kim 已提交
6542
	}
6543
	capa_move += local->group_capacity *
6544
		    min(local->load_per_task, local->avg_load + tmp);
6545
	capa_move /= SCHED_CAPACITY_SCALE;
6546 6547

	/* Move if we gain throughput */
6548
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
6549
		env->imbalance = busiest->load_per_task;
6550 6551 6552 6553 6554
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
6555
 * @env: load balance environment
6556 6557
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
6558
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6559
{
6560
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
6561 6562 6563 6564
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6565

6566
	if (busiest->group_type == group_imbalanced) {
6567 6568 6569 6570
		/*
		 * 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
6571 6572
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
6573 6574
	}

6575 6576 6577
	/*
	 * 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
6578
	 * its cpu_capacity, while calculating max_load..)
6579
	 */
6580 6581
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
6582 6583
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
6584 6585
	}

6586 6587 6588 6589 6590
	/*
	 * If there aren't any idle cpus, avoid creating some.
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
J
Joonsoo Kim 已提交
6591
		load_above_capacity =
6592
			(busiest->sum_nr_running - busiest->group_capacity_factor);
6593

6594
		load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_CAPACITY_SCALE);
6595
		load_above_capacity /= busiest->group_capacity;
6596 6597 6598 6599 6600 6601 6602 6603 6604 6605
	}

	/*
	 * 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.
	 */
6606
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6607 6608

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
6609
	env->imbalance = min(
6610 6611
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
6612
	) / SCHED_CAPACITY_SCALE;
6613 6614 6615

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
6616
	 * there is no guarantee that any tasks will be moved so we'll have
6617 6618 6619
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
6620
	if (env->imbalance < busiest->load_per_task)
6621
		return fix_small_imbalance(env, sds);
6622
}
6623

6624 6625 6626 6627 6628 6629 6630 6631 6632 6633 6634 6635
/******* 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.
 *
6636
 * @env: The load balancing environment.
6637
 *
6638
 * Return:	- The busiest group if imbalance exists.
6639 6640 6641 6642
 *		- 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
6643
static struct sched_group *find_busiest_group(struct lb_env *env)
6644
{
J
Joonsoo Kim 已提交
6645
	struct sg_lb_stats *local, *busiest;
6646 6647
	struct sd_lb_stats sds;

6648
	init_sd_lb_stats(&sds);
6649 6650 6651 6652 6653

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
6654
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
6655 6656
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
6657

6658 6659
	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(env, &sds))
6660 6661
		return sds.busiest;

6662
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
6663
	if (!sds.busiest || busiest->sum_nr_running == 0)
6664 6665
		goto out_balanced;

6666 6667
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
6668

P
Peter Zijlstra 已提交
6669 6670
	/*
	 * If the busiest group is imbalanced the below checks don't
6671
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
6672 6673
	 * isn't true due to cpus_allowed constraints and the like.
	 */
6674
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
6675 6676
		goto force_balance;

6677
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6678 6679
	if (env->idle == CPU_NEWLY_IDLE && local->group_has_free_capacity &&
	    !busiest->group_has_free_capacity)
6680 6681
		goto force_balance;

6682
	/*
6683
	 * If the local group is busier than the selected busiest group
6684 6685
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
6686
	if (local->avg_load >= busiest->avg_load)
6687 6688
		goto out_balanced;

6689 6690 6691 6692
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
6693
	if (local->avg_load >= sds.avg_load)
6694 6695
		goto out_balanced;

6696
	if (env->idle == CPU_IDLE) {
6697
		/*
6698 6699 6700 6701 6702
		 * 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
6703
		 */
6704 6705
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
6706
			goto out_balanced;
6707 6708 6709 6710 6711
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
6712 6713
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
6714
			goto out_balanced;
6715
	}
6716

6717
force_balance:
6718
	/* Looks like there is an imbalance. Compute it */
6719
	calculate_imbalance(env, &sds);
6720 6721 6722
	return sds.busiest;

out_balanced:
6723
	env->imbalance = 0;
6724 6725 6726 6727 6728 6729
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
6730
static struct rq *find_busiest_queue(struct lb_env *env,
6731
				     struct sched_group *group)
6732 6733
{
	struct rq *busiest = NULL, *rq;
6734
	unsigned long busiest_load = 0, busiest_capacity = 1;
6735 6736
	int i;

6737
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6738
		unsigned long capacity, capacity_factor, wl;
6739 6740 6741 6742
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
6743

6744 6745 6746 6747 6748 6749 6750 6751 6752 6753 6754 6755 6756 6757 6758 6759 6760 6761 6762 6763 6764 6765
		/*
		 * 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;

6766
		capacity = capacity_of(i);
6767
		capacity_factor = DIV_ROUND_CLOSEST(capacity, SCHED_CAPACITY_SCALE);
6768 6769
		if (!capacity_factor)
			capacity_factor = fix_small_capacity(env->sd, group);
6770

6771
		wl = weighted_cpuload(i);
6772

6773 6774
		/*
		 * When comparing with imbalance, use weighted_cpuload()
6775
		 * which is not scaled with the cpu capacity.
6776
		 */
6777
		if (capacity_factor && rq->nr_running == 1 && wl > env->imbalance)
6778 6779
			continue;

6780 6781
		/*
		 * For the load comparisons with the other cpu's, consider
6782 6783 6784
		 * 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.
6785
		 *
6786
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
6787
		 * multiplication to rid ourselves of the division works out
6788 6789
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
6790
		 */
6791
		if (wl * busiest_capacity > busiest_load * capacity) {
6792
			busiest_load = wl;
6793
			busiest_capacity = capacity;
6794 6795 6796 6797 6798 6799 6800 6801 6802 6803 6804 6805 6806 6807
			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. */
6808
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6809

6810
static int need_active_balance(struct lb_env *env)
6811
{
6812 6813 6814
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
6815 6816 6817 6818 6819 6820

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
6821
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6822
			return 1;
6823 6824 6825 6826 6827
	}

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

6828 6829
static int active_load_balance_cpu_stop(void *data);

6830 6831 6832 6833 6834 6835 6836 6837 6838 6839 6840 6841 6842 6843 6844 6845 6846 6847 6848 6849 6850 6851 6852 6853 6854 6855 6856 6857 6858 6859 6860
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.
	 */
6861
	return balance_cpu == env->dst_cpu;
6862 6863
}

6864 6865 6866 6867 6868 6869
/*
 * 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,
6870
			int *continue_balancing)
6871
{
6872
	int ld_moved, cur_ld_moved, active_balance = 0;
6873
	struct sched_domain *sd_parent = sd->parent;
6874 6875 6876
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
6877
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
6878

6879 6880
	struct lb_env env = {
		.sd		= sd,
6881 6882
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
6883
		.dst_grpmask    = sched_group_cpus(sd->groups),
6884
		.idle		= idle,
6885
		.loop_break	= sched_nr_migrate_break,
6886
		.cpus		= cpus,
6887
		.fbq_type	= all,
6888
		.tasks		= LIST_HEAD_INIT(env.tasks),
6889 6890
	};

6891 6892 6893 6894
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
6895
	if (idle == CPU_NEWLY_IDLE)
6896 6897
		env.dst_grpmask = NULL;

6898 6899 6900 6901 6902
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
6903 6904
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
6905
		goto out_balanced;
6906
	}
6907

6908
	group = find_busiest_group(&env);
6909 6910 6911 6912 6913
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

6914
	busiest = find_busiest_queue(&env, group);
6915 6916 6917 6918 6919
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

6920
	BUG_ON(busiest == env.dst_rq);
6921

6922
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
6923 6924 6925 6926 6927 6928 6929 6930 6931

	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.
		 */
6932
		env.flags |= LBF_ALL_PINNED;
6933 6934 6935
		env.src_cpu   = busiest->cpu;
		env.src_rq    = busiest;
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
6936

6937
more_balance:
6938
		raw_spin_lock_irqsave(&busiest->lock, flags);
6939 6940 6941 6942 6943

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
6944
		cur_ld_moved = detach_tasks(&env);
6945 6946

		/*
6947 6948 6949 6950 6951
		 * 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.
6952
		 */
6953 6954 6955 6956 6957 6958 6959 6960

		raw_spin_unlock(&busiest->lock);

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

6961
		local_irq_restore(flags);
6962

6963 6964 6965 6966 6967
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

6968 6969 6970 6971 6972 6973 6974 6975 6976 6977 6978 6979 6980 6981 6982 6983 6984 6985 6986
		/*
		 * 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.
		 */
6987
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
6988

6989 6990 6991
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

6992
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
6993
			env.dst_cpu	 = env.new_dst_cpu;
6994
			env.flags	&= ~LBF_DST_PINNED;
6995 6996
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
6997

6998 6999 7000 7001 7002 7003
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
7004

7005 7006 7007 7008
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
7009
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7010

7011
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7012 7013 7014
				*group_imbalance = 1;
		}

7015
		/* All tasks on this runqueue were pinned by CPU affinity */
7016
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
7017
			cpumask_clear_cpu(cpu_of(busiest), cpus);
7018 7019 7020
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
7021
				goto redo;
7022
			}
7023
			goto out_all_pinned;
7024 7025 7026 7027 7028
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
7029 7030 7031 7032 7033 7034 7035 7036
		/*
		 * 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++;
7037

7038
		if (need_active_balance(&env)) {
7039 7040
			raw_spin_lock_irqsave(&busiest->lock, flags);

7041 7042 7043
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
7044 7045
			 */
			if (!cpumask_test_cpu(this_cpu,
7046
					tsk_cpus_allowed(busiest->curr))) {
7047 7048
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
7049
				env.flags |= LBF_ALL_PINNED;
7050 7051 7052
				goto out_one_pinned;
			}

7053 7054 7055 7056 7057
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
7058 7059 7060 7061 7062 7063
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
7064

7065
			if (active_balance) {
7066 7067 7068
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
7069
			}
7070 7071 7072 7073 7074 7075 7076 7077 7078 7079 7080 7081 7082 7083 7084 7085 7086 7087

			/*
			 * 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
7088
		 * detach_tasks).
7089 7090 7091 7092 7093 7094 7095 7096
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
7097 7098 7099 7100 7101 7102 7103 7104 7105 7106 7107 7108 7109 7110 7111 7112 7113
	/*
	 * 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.
	 */
7114 7115 7116 7117 7118 7119
	schedstat_inc(sd, lb_balanced[idle]);

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
7120
	if (((env.flags & LBF_ALL_PINNED) &&
7121
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
7122 7123 7124
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

7125
	ld_moved = 0;
7126 7127 7128 7129
out:
	return ld_moved;
}

7130 7131 7132 7133 7134 7135 7136 7137 7138 7139 7140 7141 7142 7143 7144 7145 7146 7147 7148 7149 7150 7151 7152 7153 7154 7155 7156
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;
}

7157 7158 7159 7160
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
7161
static int idle_balance(struct rq *this_rq)
7162
{
7163 7164
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
7165 7166
	struct sched_domain *sd;
	int pulled_task = 0;
7167
	u64 curr_cost = 0;
7168

7169
	idle_enter_fair(this_rq);
7170

7171 7172 7173 7174 7175 7176
	/*
	 * 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);

7177 7178
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
7179 7180 7181 7182 7183 7184
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
			update_next_balance(sd, 0, &next_balance);
		rcu_read_unlock();

7185
		goto out;
7186
	}
7187

7188 7189 7190 7191 7192
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

7193
	update_blocked_averages(this_cpu);
7194
	rcu_read_lock();
7195
	for_each_domain(this_cpu, sd) {
7196
		int continue_balancing = 1;
7197
		u64 t0, domain_cost;
7198 7199 7200 7201

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

7202 7203
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
			update_next_balance(sd, 0, &next_balance);
7204
			break;
7205
		}
7206

7207
		if (sd->flags & SD_BALANCE_NEWIDLE) {
7208 7209
			t0 = sched_clock_cpu(this_cpu);

7210
			pulled_task = load_balance(this_cpu, this_rq,
7211 7212
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
7213 7214 7215 7216 7217 7218

			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;
7219
		}
7220

7221
		update_next_balance(sd, 0, &next_balance);
7222 7223 7224 7225 7226 7227

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
7228 7229
			break;
	}
7230
	rcu_read_unlock();
7231 7232 7233

	raw_spin_lock(&this_rq->lock);

7234 7235 7236
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

7237
	/*
7238 7239 7240
	 * 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.
7241
	 */
7242
	if (this_rq->cfs.h_nr_running && !pulled_task)
7243
		pulled_task = 1;
7244

7245 7246 7247
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
7248
		this_rq->next_balance = next_balance;
7249

7250
	/* Is there a task of a high priority class? */
7251
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7252 7253 7254 7255
		pulled_task = -1;

	if (pulled_task) {
		idle_exit_fair(this_rq);
7256
		this_rq->idle_stamp = 0;
7257
	}
7258

7259
	return pulled_task;
7260 7261 7262
}

/*
7263 7264 7265 7266
 * 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.
7267
 */
7268
static int active_load_balance_cpu_stop(void *data)
7269
{
7270 7271
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
7272
	int target_cpu = busiest_rq->push_cpu;
7273
	struct rq *target_rq = cpu_rq(target_cpu);
7274
	struct sched_domain *sd;
7275
	struct task_struct *p = NULL;
7276 7277 7278 7279 7280 7281 7282

	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;
7283 7284 7285

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
7286
		goto out_unlock;
7287 7288 7289 7290 7291 7292 7293 7294 7295

	/*
	 * 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. */
7296
	rcu_read_lock();
7297 7298 7299 7300 7301 7302 7303
	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)) {
7304 7305
		struct lb_env env = {
			.sd		= sd,
7306 7307 7308 7309
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
7310 7311 7312
			.idle		= CPU_IDLE,
		};

7313 7314
		schedstat_inc(sd, alb_count);

7315 7316
		p = detach_one_task(&env);
		if (p)
7317 7318 7319 7320
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
7321
	rcu_read_unlock();
7322 7323
out_unlock:
	busiest_rq->active_balance = 0;
7324 7325 7326 7327 7328 7329 7330
	raw_spin_unlock(&busiest_rq->lock);

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

7331
	return 0;
7332 7333
}

7334 7335 7336 7337 7338
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

7339
#ifdef CONFIG_NO_HZ_COMMON
7340 7341 7342 7343 7344 7345
/*
 * 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.
 */
7346
static struct {
7347
	cpumask_var_t idle_cpus_mask;
7348
	atomic_t nr_cpus;
7349 7350
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
7351

7352
static inline int find_new_ilb(void)
7353
{
7354
	int ilb = cpumask_first(nohz.idle_cpus_mask);
7355

7356 7357 7358 7359
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
7360 7361
}

7362 7363 7364 7365 7366
/*
 * 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).
 */
7367
static void nohz_balancer_kick(void)
7368 7369 7370 7371 7372
{
	int ilb_cpu;

	nohz.next_balance++;

7373
	ilb_cpu = find_new_ilb();
7374

7375 7376
	if (ilb_cpu >= nr_cpu_ids)
		return;
7377

7378
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7379 7380 7381 7382 7383 7384 7385 7386
		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);
7387 7388 7389
	return;
}

7390
static inline void nohz_balance_exit_idle(int cpu)
7391 7392
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7393 7394 7395 7396 7397 7398 7399
		/*
		 * 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);
		}
7400 7401 7402 7403
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

7404 7405 7406
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
7407
	int cpu = smp_processor_id();
7408 7409

	rcu_read_lock();
7410
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7411 7412 7413 7414 7415

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

7416
	atomic_inc(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7417
unlock:
7418 7419 7420 7421 7422 7423
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
7424
	int cpu = smp_processor_id();
7425 7426

	rcu_read_lock();
7427
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7428 7429 7430 7431 7432

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

7433
	atomic_dec(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7434
unlock:
7435 7436 7437
	rcu_read_unlock();
}

7438
/*
7439
 * This routine will record that the cpu is going idle with tick stopped.
7440
 * This info will be used in performing idle load balancing in the future.
7441
 */
7442
void nohz_balance_enter_idle(int cpu)
7443
{
7444 7445 7446 7447 7448 7449
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

7450 7451
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
7452

7453 7454 7455 7456 7457 7458
	/*
	 * If we're a completely isolated CPU, we don't play.
	 */
	if (on_null_domain(cpu_rq(cpu)))
		return;

7459 7460 7461
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7462
}
7463

7464
static int sched_ilb_notifier(struct notifier_block *nfb,
7465 7466 7467 7468
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
7469
		nohz_balance_exit_idle(smp_processor_id());
7470 7471 7472 7473 7474
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
7475 7476 7477 7478
#endif

static DEFINE_SPINLOCK(balancing);

7479 7480 7481 7482
/*
 * 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.
 */
7483
void update_max_interval(void)
7484 7485 7486 7487
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

7488 7489 7490 7491
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
7492
 * Balancing parameters are set up in init_sched_domains.
7493
 */
7494
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7495
{
7496
	int continue_balancing = 1;
7497
	int cpu = rq->cpu;
7498
	unsigned long interval;
7499
	struct sched_domain *sd;
7500 7501 7502
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
7503 7504
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
7505

7506
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
7507

7508
	rcu_read_lock();
7509
	for_each_domain(cpu, sd) {
7510 7511 7512 7513 7514 7515 7516 7517 7518 7519 7520 7521
		/*
		 * 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;

7522 7523 7524
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

7525 7526 7527 7528 7529 7530 7531 7532 7533 7534 7535
		/*
		 * 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;
		}

7536
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7537 7538 7539 7540 7541 7542 7543 7544

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

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
7545
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7546
				/*
7547
				 * The LBF_DST_PINNED logic could have changed
7548 7549
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
7550
				 */
7551
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7552 7553
			}
			sd->last_balance = jiffies;
7554
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7555 7556 7557 7558 7559 7560 7561 7562
		}
		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;
		}
7563 7564
	}
	if (need_decay) {
7565
		/*
7566 7567
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
7568
		 */
7569 7570
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
7571
	}
7572
	rcu_read_unlock();
7573 7574 7575 7576 7577 7578 7579 7580 7581 7582

	/*
	 * next_balance will be updated only when there is a need.
	 * When the cpu is attached to null domain for ex, it will not be
	 * updated.
	 */
	if (likely(update_next_balance))
		rq->next_balance = next_balance;
}

7583
#ifdef CONFIG_NO_HZ_COMMON
7584
/*
7585
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7586 7587
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
7588
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7589
{
7590
	int this_cpu = this_rq->cpu;
7591 7592 7593
	struct rq *rq;
	int balance_cpu;

7594 7595 7596
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
7597 7598

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7599
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7600 7601 7602 7603 7604 7605 7606
			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.
		 */
7607
		if (need_resched())
7608 7609
			break;

V
Vincent Guittot 已提交
7610 7611
		rq = cpu_rq(balance_cpu);

7612 7613 7614 7615 7616 7617 7618 7619 7620 7621 7622
		/*
		 * 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);
		}
7623 7624 7625 7626 7627

		if (time_after(this_rq->next_balance, rq->next_balance))
			this_rq->next_balance = rq->next_balance;
	}
	nohz.next_balance = this_rq->next_balance;
7628 7629
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7630 7631 7632
}

/*
7633 7634 7635 7636
 * Current heuristic for kicking the idle load balancer in the presence
 * of an idle cpu is the system.
 *   - This rq has more than one task.
 *   - At any scheduler domain level, this cpu's scheduler group has multiple
7637
 *     busy cpu's exceeding the group's capacity.
7638 7639
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
7640
 */
7641
static inline int nohz_kick_needed(struct rq *rq)
7642 7643
{
	unsigned long now = jiffies;
7644
	struct sched_domain *sd;
7645
	struct sched_group_capacity *sgc;
7646
	int nr_busy, cpu = rq->cpu;
7647

7648
	if (unlikely(rq->idle_balance))
7649 7650
		return 0;

7651 7652 7653 7654
       /*
	* 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.
	*/
7655
	set_cpu_sd_state_busy();
7656
	nohz_balance_exit_idle(cpu);
7657 7658 7659 7660 7661 7662 7663

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
		return 0;
7664 7665

	if (time_before(now, nohz.next_balance))
7666 7667
		return 0;

7668 7669
	if (rq->nr_running >= 2)
		goto need_kick;
7670

7671
	rcu_read_lock();
7672
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
7673

7674
	if (sd) {
7675 7676
		sgc = sd->groups->sgc;
		nr_busy = atomic_read(&sgc->nr_busy_cpus);
7677

7678
		if (nr_busy > 1)
7679
			goto need_kick_unlock;
7680
	}
7681 7682 7683 7684 7685 7686 7687

	sd = rcu_dereference(per_cpu(sd_asym, cpu));

	if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
				  sched_domain_span(sd)) < cpu))
		goto need_kick_unlock;

7688
	rcu_read_unlock();
7689
	return 0;
7690 7691 7692

need_kick_unlock:
	rcu_read_unlock();
7693 7694
need_kick:
	return 1;
7695 7696
}
#else
7697
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7698 7699 7700 7701 7702 7703
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
7704 7705
static void run_rebalance_domains(struct softirq_action *h)
{
7706
	struct rq *this_rq = this_rq();
7707
	enum cpu_idle_type idle = this_rq->idle_balance ?
7708 7709
						CPU_IDLE : CPU_NOT_IDLE;

7710
	rebalance_domains(this_rq, idle);
7711 7712

	/*
7713
	 * If this cpu has a pending nohz_balance_kick, then do the
7714 7715 7716
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
7717
	nohz_idle_balance(this_rq, idle);
7718 7719 7720 7721 7722
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
7723
void trigger_load_balance(struct rq *rq)
7724 7725
{
	/* Don't need to rebalance while attached to NULL domain */
7726 7727 7728 7729
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
7730
		raise_softirq(SCHED_SOFTIRQ);
7731
#ifdef CONFIG_NO_HZ_COMMON
7732
	if (nohz_kick_needed(rq))
7733
		nohz_balancer_kick();
7734
#endif
7735 7736
}

7737 7738 7739
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
7740 7741

	update_runtime_enabled(rq);
7742 7743 7744 7745 7746
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
7747 7748 7749

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
7750 7751
}

7752
#endif /* CONFIG_SMP */
7753

7754 7755 7756
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
7757
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
7758 7759 7760 7761 7762 7763
{
	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
7764
		entity_tick(cfs_rq, se, queued);
7765
	}
7766

7767
	if (numabalancing_enabled)
7768
		task_tick_numa(rq, curr);
7769

7770
	update_rq_runnable_avg(rq, 1);
7771 7772 7773
}

/*
P
Peter Zijlstra 已提交
7774 7775 7776
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
7777
 */
P
Peter Zijlstra 已提交
7778
static void task_fork_fair(struct task_struct *p)
7779
{
7780 7781
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
7782
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
7783 7784 7785
	struct rq *rq = this_rq();
	unsigned long flags;

7786
	raw_spin_lock_irqsave(&rq->lock, flags);
7787

7788 7789
	update_rq_clock(rq);

7790 7791 7792
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

7793 7794 7795 7796 7797 7798 7799 7800 7801
	/*
	 * 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();
7802

7803
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
7804

7805 7806
	if (curr)
		se->vruntime = curr->vruntime;
7807
	place_entity(cfs_rq, se, 1);
7808

P
Peter Zijlstra 已提交
7809
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
7810
		/*
7811 7812 7813
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
7814
		swap(curr->vruntime, se->vruntime);
7815
		resched_curr(rq);
7816
	}
7817

7818 7819
	se->vruntime -= cfs_rq->min_vruntime;

7820
	raw_spin_unlock_irqrestore(&rq->lock, flags);
7821 7822
}

7823 7824 7825 7826
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
7827 7828
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
7829
{
7830
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
7831 7832
		return;

7833 7834 7835 7836 7837
	/*
	 * 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
7838
	if (rq->curr == p) {
7839
		if (p->prio > oldprio)
7840
			resched_curr(rq);
7841
	} else
7842
		check_preempt_curr(rq, p, 0);
7843 7844
}

P
Peter Zijlstra 已提交
7845 7846 7847 7848 7849 7850
static void switched_from_fair(struct rq *rq, struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	/*
7851
	 * Ensure the task's vruntime is normalized, so that when it's
P
Peter Zijlstra 已提交
7852 7853 7854
	 * switched back to the fair class the enqueue_entity(.flags=0) will
	 * do the right thing.
	 *
7855 7856
	 * If it's queued, then the dequeue_entity(.flags=0) will already
	 * have normalized the vruntime, if it's !queued, then only when
P
Peter Zijlstra 已提交
7857 7858
	 * the task is sleeping will it still have non-normalized vruntime.
	 */
7859
	if (!task_on_rq_queued(p) && p->state != TASK_RUNNING) {
P
Peter Zijlstra 已提交
7860 7861 7862 7863 7864 7865 7866
		/*
		 * 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;
	}
7867

7868
#ifdef CONFIG_SMP
7869 7870 7871 7872 7873
	/*
	* Remove our load from contribution when we leave sched_fair
	* and ensure we don't carry in an old decay_count if we
	* switch back.
	*/
7874 7875 7876
	if (se->avg.decay_count) {
		__synchronize_entity_decay(se);
		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
7877 7878
	}
#endif
P
Peter Zijlstra 已提交
7879 7880
}

7881 7882 7883
/*
 * We switched to the sched_fair class.
 */
P
Peter Zijlstra 已提交
7884
static void switched_to_fair(struct rq *rq, struct task_struct *p)
7885
{
7886
#ifdef CONFIG_FAIR_GROUP_SCHED
7887
	struct sched_entity *se = &p->se;
7888 7889 7890 7891 7892 7893
	/*
	 * 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
7894
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
7895 7896
		return;

7897 7898 7899 7900 7901
	/*
	 * 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.
	 */
P
Peter Zijlstra 已提交
7902
	if (rq->curr == p)
7903
		resched_curr(rq);
7904
	else
7905
		check_preempt_curr(rq, p, 0);
7906 7907
}

7908 7909 7910 7911 7912 7913 7914 7915 7916
/* 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;

7917 7918 7919 7920 7921 7922 7923
	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);
	}
7924 7925
}

7926 7927 7928 7929 7930 7931 7932
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
7933
#ifdef CONFIG_SMP
7934
	atomic64_set(&cfs_rq->decay_counter, 1);
7935
	atomic_long_set(&cfs_rq->removed_load, 0);
7936
#endif
7937 7938
}

P
Peter Zijlstra 已提交
7939
#ifdef CONFIG_FAIR_GROUP_SCHED
7940
static void task_move_group_fair(struct task_struct *p, int queued)
P
Peter Zijlstra 已提交
7941
{
P
Peter Zijlstra 已提交
7942
	struct sched_entity *se = &p->se;
7943
	struct cfs_rq *cfs_rq;
P
Peter Zijlstra 已提交
7944

7945 7946 7947 7948 7949 7950 7951 7952 7953 7954 7955 7956 7957
	/*
	 * If the task was not on the rq at the time of this cgroup movement
	 * it must have been asleep, sleeping tasks keep their ->vruntime
	 * absolute on their old rq until wakeup (needed for the fair sleeper
	 * bonus in place_entity()).
	 *
	 * If it was on the rq, we've just 'preempted' it, which does convert
	 * ->vruntime to a relative base.
	 *
	 * Make sure both cases convert their relative position when migrating
	 * to another cgroup's rq. This does somewhat interfere with the
	 * fair sleeper stuff for the first placement, but who cares.
	 */
7958
	/*
7959
	 * When !queued, vruntime of the task has usually NOT been normalized.
7960 7961 7962 7963
	 * But there are some cases where it has already been normalized:
	 *
	 * - Moving a forked child which is waiting for being woken up by
	 *   wake_up_new_task().
7964 7965
	 * - Moving a task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
7966 7967 7968 7969
	 *
	 * To prevent boost or penalty in the new cfs_rq caused by delta
	 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
	 */
7970 7971
	if (!queued && (!se->sum_exec_runtime || p->state == TASK_WAKING))
		queued = 1;
7972

7973
	if (!queued)
P
Peter Zijlstra 已提交
7974
		se->vruntime -= cfs_rq_of(se)->min_vruntime;
7975
	set_task_rq(p, task_cpu(p));
P
Peter Zijlstra 已提交
7976
	se->depth = se->parent ? se->parent->depth + 1 : 0;
7977
	if (!queued) {
P
Peter Zijlstra 已提交
7978 7979
		cfs_rq = cfs_rq_of(se);
		se->vruntime += cfs_rq->min_vruntime;
7980 7981 7982 7983 7984 7985
#ifdef CONFIG_SMP
		/*
		 * migrate_task_rq_fair() will have removed our previous
		 * contribution, but we must synchronize for ongoing future
		 * decay.
		 */
P
Peter Zijlstra 已提交
7986 7987
		se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
		cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
7988 7989
#endif
	}
P
Peter Zijlstra 已提交
7990
}
7991 7992 7993 7994 7995 7996 7997 7998 7999 8000 8001 8002 8003 8004 8005 8006 8007 8008 8009 8010 8011 8012 8013 8014 8015 8016 8017 8018 8019 8020 8021 8022 8023 8024 8025 8026 8027 8028 8029 8030 8031 8032 8033 8034 8035 8036 8037 8038 8039 8040 8041 8042 8043 8044 8045 8046 8047 8048 8049 8050 8051 8052 8053 8054 8055 8056 8057 8058 8059 8060 8061 8062 8063 8064 8065 8066 8067 8068 8069 8070 8071 8072 8073 8074 8075 8076 8077 8078 8079 8080 8081 8082

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]);
		if (tg->se)
			kfree(tg->se[i]);
	}

	kfree(tg->cfs_rq);
	kfree(tg->se);
}

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
	struct 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]);
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

void unregister_fair_sched_group(struct task_group *tg, int cpu)
{
	struct rq *rq = cpu_rq(cpu);
	unsigned long flags;

	/*
	* Only empty task groups can be destroyed; so we can speculatively
	* check on_list without danger of it being re-added.
	*/
	if (!tg->cfs_rq[cpu]->on_list)
		return;

	raw_spin_lock_irqsave(&rq->lock, flags);
	list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
	raw_spin_unlock_irqrestore(&rq->lock, flags);
}

void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
			struct sched_entity *se, int cpu,
			struct sched_entity *parent)
{
	struct rq *rq = cpu_rq(cpu);

	cfs_rq->tg = tg;
	cfs_rq->rq = rq;
	init_cfs_rq_runtime(cfs_rq);

	tg->cfs_rq[cpu] = cfs_rq;
	tg->se[cpu] = se;

	/* se could be NULL for root_task_group */
	if (!se)
		return;

P
Peter Zijlstra 已提交
8083
	if (!parent) {
8084
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
8085 8086
		se->depth = 0;
	} else {
8087
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
8088 8089
		se->depth = parent->depth + 1;
	}
8090 8091

	se->my_q = cfs_rq;
8092 8093
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
8094 8095 8096 8097 8098 8099 8100 8101 8102 8103 8104 8105 8106 8107 8108 8109 8110 8111 8112 8113 8114 8115 8116 8117 8118 8119 8120 8121 8122 8123
	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);
8124 8125 8126

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
8127
		for_each_sched_entity(se)
8128 8129 8130 8131 8132 8133 8134 8135 8136 8137 8138 8139 8140 8141 8142 8143 8144 8145 8146 8147 8148
			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 */

P
Peter Zijlstra 已提交
8149

8150
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8151 8152 8153 8154 8155 8156 8157 8158 8159
{
	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)
8160
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8161 8162 8163 8164

	return rr_interval;
}

8165 8166 8167
/*
 * All the scheduling class methods:
 */
8168
const struct sched_class fair_sched_class = {
8169
	.next			= &idle_sched_class,
8170 8171 8172
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
8173
	.yield_to_task		= yield_to_task_fair,
8174

I
Ingo Molnar 已提交
8175
	.check_preempt_curr	= check_preempt_wakeup,
8176 8177 8178 8179

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

8180
#ifdef CONFIG_SMP
L
Li Zefan 已提交
8181
	.select_task_rq		= select_task_rq_fair,
8182
	.migrate_task_rq	= migrate_task_rq_fair,
8183

8184 8185
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
8186 8187

	.task_waking		= task_waking_fair,
8188
#endif
8189

8190
	.set_curr_task          = set_curr_task_fair,
8191
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
8192
	.task_fork		= task_fork_fair,
8193 8194

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
8195
	.switched_from		= switched_from_fair,
8196
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
8197

8198 8199
	.get_rr_interval	= get_rr_interval_fair,

8200 8201
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
8202
#ifdef CONFIG_FAIR_GROUP_SCHED
8203
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
8204
#endif
8205 8206 8207
};

#ifdef CONFIG_SCHED_DEBUG
8208
void print_cfs_stats(struct seq_file *m, int cpu)
8209 8210 8211
{
	struct cfs_rq *cfs_rq;

8212
	rcu_read_lock();
8213
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8214
		print_cfs_rq(m, cpu, cfs_rq);
8215
	rcu_read_unlock();
8216 8217
}
#endif
8218 8219 8220 8221 8222 8223

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

8224
#ifdef CONFIG_NO_HZ_COMMON
8225
	nohz.next_balance = jiffies;
8226
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8227
	cpu_notifier(sched_ilb_notifier, 0);
8228 8229 8230 8231
#endif
#endif /* SMP */

}