fair.c 231.7 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
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 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
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 */

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

#include "sched.h"
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/*
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 * Targeted preemption latency for CPU-bound tasks:
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 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds)
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 *
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 * NOTE: this latency value is not the same as the concept of
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 * 'timeslice length' - timeslices in CFS are of variable length
 * and have no persistent notion like in traditional, time-slice
 * based scheduling concepts.
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 *
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 * (to see the precise effective timeslice length of your workload,
 *  run vmstat and monitor the context-switches (cs) field)
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 */
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unsigned int sysctl_sched_latency = 6000000ULL;
unsigned int normalized_sysctl_sched_latency = 6000000ULL;
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/*
 * The initial- and re-scaling of tunables is configurable
 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
 *
 * Options are:
 * SCHED_TUNABLESCALING_NONE - unscaled, always *1
 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
 */
enum sched_tunable_scaling sysctl_sched_tunable_scaling
	= SCHED_TUNABLESCALING_LOG;

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/*
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 * Minimal preemption granularity for CPU-bound tasks:
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 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
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 */
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unsigned int sysctl_sched_min_granularity = 750000ULL;
unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
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/*
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 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
 */
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static unsigned int sched_nr_latency = 8;
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/*
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 * After fork, child runs first. If set to 0 (default) then
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 * parent will (try to) run first.
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 */
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unsigned int sysctl_sched_child_runs_first __read_mostly;
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/*
 * SCHED_OTHER wake-up granularity.
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 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
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 *
 * This option delays the preemption effects of decoupled workloads
 * and reduces their over-scheduling. Synchronous workloads will still
 * have immediate wakeup/sleep latencies.
 */
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unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
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unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
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const_debug unsigned int sysctl_sched_migration_cost = 500000UL;

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/*
 * The exponential sliding  window over which load is averaged for shares
 * distribution.
 * (default: 10msec)
 */
unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;

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#ifdef CONFIG_CFS_BANDWIDTH
/*
 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool
 * each time a cfs_rq requests quota.
 *
 * Note: in the case that the slice exceeds the runtime remaining (either due
 * to consumption or the quota being specified to be smaller than the slice)
 * we will always only issue the remaining available time.
 *
 * default: 5 msec, units: microseconds
  */
unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL;
#endif

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static inline void update_load_add(struct load_weight *lw, unsigned long inc)
{
	lw->weight += inc;
	lw->inv_weight = 0;
}

static inline void update_load_sub(struct load_weight *lw, unsigned long dec)
{
	lw->weight -= dec;
	lw->inv_weight = 0;
}

static inline void update_load_set(struct load_weight *lw, unsigned long w)
{
	lw->weight = w;
	lw->inv_weight = 0;
}

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/*
 * Increase the granularity value when there are more CPUs,
 * because with more CPUs the 'effective latency' as visible
 * to users decreases. But the relationship is not linear,
 * so pick a second-best guess by going with the log2 of the
 * number of CPUs.
 *
 * This idea comes from the SD scheduler of Con Kolivas:
 */
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static unsigned int get_update_sysctl_factor(void)
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{
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	unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8);
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	unsigned int factor;

	switch (sysctl_sched_tunable_scaling) {
	case SCHED_TUNABLESCALING_NONE:
		factor = 1;
		break;
	case SCHED_TUNABLESCALING_LINEAR:
		factor = cpus;
		break;
	case SCHED_TUNABLESCALING_LOG:
	default:
		factor = 1 + ilog2(cpus);
		break;
	}

	return factor;
}

static void update_sysctl(void)
{
	unsigned int factor = get_update_sysctl_factor();

#define SET_SYSCTL(name) \
	(sysctl_##name = (factor) * normalized_sysctl_##name)
	SET_SYSCTL(sched_min_granularity);
	SET_SYSCTL(sched_latency);
	SET_SYSCTL(sched_wakeup_granularity);
#undef SET_SYSCTL
}

void sched_init_granularity(void)
{
	update_sysctl();
}

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#define WMULT_CONST	(~0U)
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#define WMULT_SHIFT	32

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static void __update_inv_weight(struct load_weight *lw)
{
	unsigned long w;

	if (likely(lw->inv_weight))
		return;

	w = scale_load_down(lw->weight);

	if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
		lw->inv_weight = 1;
	else if (unlikely(!w))
		lw->inv_weight = WMULT_CONST;
	else
		lw->inv_weight = WMULT_CONST / w;
}
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/*
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 * delta_exec * weight / lw.weight
 *   OR
 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT
 *
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 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case
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 * we're guaranteed shift stays positive because inv_weight is guaranteed to
 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
 *
 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
 * weight/lw.weight <= 1, and therefore our shift will also be positive.
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 */
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static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
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{
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	u64 fact = scale_load_down(weight);
	int shift = WMULT_SHIFT;
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	__update_inv_weight(lw);
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	if (unlikely(fact >> 32)) {
		while (fact >> 32) {
			fact >>= 1;
			shift--;
		}
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	}

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	/* hint to use a 32x32->64 mul */
	fact = (u64)(u32)fact * lw->inv_weight;
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	while (fact >> 32) {
		fact >>= 1;
		shift--;
	}
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	return mul_u64_u32_shr(delta_exec, fact, shift);
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}


const struct sched_class fair_sched_class;
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/**************************************************************
 * CFS operations on generic schedulable entities:
 */

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#ifdef CONFIG_FAIR_GROUP_SCHED
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/* cpu runqueue to which this cfs_rq is attached */
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
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	return cfs_rq->rq;
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}

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/* An entity is a task if it doesn't "own" a runqueue */
#define entity_is_task(se)	(!se->my_q)
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static inline struct task_struct *task_of(struct sched_entity *se)
{
#ifdef CONFIG_SCHED_DEBUG
	WARN_ON_ONCE(!entity_is_task(se));
#endif
	return container_of(se, struct task_struct, se);
}

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/* Walk up scheduling entities hierarchy */
#define for_each_sched_entity(se) \
		for (; se; se = se->parent)

static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
{
	return p->se.cfs_rq;
}

/* runqueue on which this entity is (to be) queued */
static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
{
	return se->cfs_rq;
}

/* runqueue "owned" by this group */
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
{
	return grp->my_q;
}

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static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (!cfs_rq->on_list) {
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		/*
		 * Ensure we either appear before our parent (if already
		 * enqueued) or force our parent to appear after us when it is
		 * enqueued.  The fact that we always enqueue bottom-up
		 * reduces this to two cases.
		 */
		if (cfs_rq->tg->parent &&
		    cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
			list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
				&rq_of(cfs_rq)->leaf_cfs_rq_list);
		} else {
			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
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				&rq_of(cfs_rq)->leaf_cfs_rq_list);
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		}
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		cfs_rq->on_list = 1;
	}
}

static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (cfs_rq->on_list) {
		list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
		cfs_rq->on_list = 0;
	}
}

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/* Iterate thr' all leaf cfs_rq's on a runqueue */
#define for_each_leaf_cfs_rq(rq, cfs_rq) \
	list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)

/* Do the two (enqueued) entities belong to the same group ? */
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static inline struct cfs_rq *
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is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
	if (se->cfs_rq == pse->cfs_rq)
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		return se->cfs_rq;
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	return NULL;
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}

static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
	return se->parent;
}

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static void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
	int se_depth, pse_depth;

	/*
	 * preemption test can be made between sibling entities who are in the
	 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
	 * both tasks until we find their ancestors who are siblings of common
	 * parent.
	 */

	/* First walk up until both entities are at same depth */
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	se_depth = (*se)->depth;
	pse_depth = (*pse)->depth;
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	while (se_depth > pse_depth) {
		se_depth--;
		*se = parent_entity(*se);
	}

	while (pse_depth > se_depth) {
		pse_depth--;
		*pse = parent_entity(*pse);
	}

	while (!is_same_group(*se, *pse)) {
		*se = parent_entity(*se);
		*pse = parent_entity(*pse);
	}
}

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#else	/* !CONFIG_FAIR_GROUP_SCHED */

static inline struct task_struct *task_of(struct sched_entity *se)
{
	return container_of(se, struct task_struct, se);
}
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
	return container_of(cfs_rq, struct rq, cfs);
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}

#define entity_is_task(se)	1

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#define for_each_sched_entity(se) \
		for (; se; se = NULL)
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static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
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{
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	return &task_rq(p)->cfs;
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}

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static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
{
	struct task_struct *p = task_of(se);
	struct rq *rq = task_rq(p);

	return &rq->cfs;
}

/* runqueue "owned" by this group */
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
{
	return NULL;
}

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static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
}

static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
}

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#define for_each_leaf_cfs_rq(rq, cfs_rq) \
		for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)

static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
	return NULL;
}

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static inline void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
}

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#endif	/* CONFIG_FAIR_GROUP_SCHED */

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static __always_inline
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void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec);
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/**************************************************************
 * Scheduling class tree data structure manipulation methods:
 */

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static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime)
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{
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	s64 delta = (s64)(vruntime - max_vruntime);
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	if (delta > 0)
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		max_vruntime = vruntime;
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	return max_vruntime;
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}

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static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
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{
	s64 delta = (s64)(vruntime - min_vruntime);
	if (delta < 0)
		min_vruntime = vruntime;

	return min_vruntime;
}

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static inline int entity_before(struct sched_entity *a,
				struct sched_entity *b)
{
	return (s64)(a->vruntime - b->vruntime) < 0;
}

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static void update_min_vruntime(struct cfs_rq *cfs_rq)
{
	u64 vruntime = cfs_rq->min_vruntime;

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

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

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		if (!cfs_rq->curr)
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			vruntime = se->vruntime;
		else
			vruntime = min_vruntime(vruntime, se->vruntime);
	}

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	/* ensure we never gain time by being placed backwards. */
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	cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
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#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
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}

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/*
 * Enqueue an entity into the rb-tree:
 */
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static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
	struct rb_node *parent = NULL;
	struct sched_entity *entry;
	int leftmost = 1;

	/*
	 * Find the right place in the rbtree:
	 */
	while (*link) {
		parent = *link;
		entry = rb_entry(parent, struct sched_entity, run_node);
		/*
		 * We dont care about collisions. Nodes with
		 * the same key stay together.
		 */
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		if (entity_before(se, entry)) {
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			link = &parent->rb_left;
		} else {
			link = &parent->rb_right;
			leftmost = 0;
		}
	}

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

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static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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	if (cfs_rq->rb_leftmost == &se->run_node) {
		struct rb_node *next_node;

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

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struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq)
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{
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	struct rb_node *left = cfs_rq->rb_leftmost;

	if (!left)
		return NULL;

	return rb_entry(left, struct sched_entity, run_node);
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}

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static struct sched_entity *__pick_next_entity(struct sched_entity *se)
{
	struct rb_node *next = rb_next(&se->run_node);

	if (!next)
		return NULL;

	return rb_entry(next, struct sched_entity, run_node);
}

#ifdef CONFIG_SCHED_DEBUG
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struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
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{
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	struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
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	if (!last)
		return NULL;
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	return rb_entry(last, struct sched_entity, run_node);
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}

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

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

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

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

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

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

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

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

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

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

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

676 677 678 679 680 681 682
	sa->last_update_time = 0;
	/*
	 * sched_avg's period_contrib should be strictly less then 1024, so
	 * we give it 1023 to make sure it is almost a period (1024us), and
	 * will definitely be update (after enqueue).
	 */
	sa->period_contrib = 1023;
683
	sa->load_avg = scale_load_down(se->load.weight);
684
	sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
685 686 687 688 689
	/*
	 * At this point, util_avg won't be used in select_task_rq_fair anyway
	 */
	sa->util_avg = 0;
	sa->util_sum = 0;
690
	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
691
}
692

693 694
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
static int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq);
695
static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force);
696 697
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se);

698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726
/*
 * With new tasks being created, their initial util_avgs are extrapolated
 * based on the cfs_rq's current util_avg:
 *
 *   util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
 *
 * However, in many cases, the above util_avg does not give a desired
 * value. Moreover, the sum of the util_avgs may be divergent, such
 * as when the series is a harmonic series.
 *
 * To solve this problem, we also cap the util_avg of successive tasks to
 * only 1/2 of the left utilization budget:
 *
 *   util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
 *
 * where n denotes the nth task.
 *
 * For example, a simplest series from the beginning would be like:
 *
 *  task  util_avg: 512, 256, 128,  64,  32,   16,    8, ...
 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
 *
 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
 * if util_avg > util_avg_cap.
 */
void post_init_entity_util_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	struct sched_avg *sa = &se->avg;
727
	long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
728
	u64 now = cfs_rq_clock_task(cfs_rq);
729 730 731 732 733 734 735 736 737 738 739 740 741

	if (cap > 0) {
		if (cfs_rq->avg.util_avg != 0) {
			sa->util_avg  = cfs_rq->avg.util_avg * se->load.weight;
			sa->util_avg /= (cfs_rq->avg.load_avg + 1);

			if (sa->util_avg > cap)
				sa->util_avg = cap;
		} else {
			sa->util_avg = cap;
		}
		sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
	}
742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760

	if (entity_is_task(se)) {
		struct task_struct *p = task_of(se);
		if (p->sched_class != &fair_sched_class) {
			/*
			 * For !fair tasks do:
			 *
			update_cfs_rq_load_avg(now, cfs_rq, false);
			attach_entity_load_avg(cfs_rq, se);
			switched_from_fair(rq, p);
			 *
			 * such that the next switched_to_fair() has the
			 * expected state.
			 */
			se->avg.last_update_time = now;
			return;
		}
	}

761
	update_cfs_rq_load_avg(now, cfs_rq, false);
762
	attach_entity_load_avg(cfs_rq, se);
763
	update_tg_load_avg(cfs_rq, false);
764 765
}

766
#else /* !CONFIG_SMP */
767
void init_entity_runnable_average(struct sched_entity *se)
768 769
{
}
770 771 772
void post_init_entity_util_avg(struct sched_entity *se)
{
}
773 774 775
static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
{
}
776
#endif /* CONFIG_SMP */
777

778
/*
779
 * Update the current task's runtime statistics.
780
 */
781
static void update_curr(struct cfs_rq *cfs_rq)
782
{
783
	struct sched_entity *curr = cfs_rq->curr;
784
	u64 now = rq_clock_task(rq_of(cfs_rq));
785
	u64 delta_exec;
786 787 788 789

	if (unlikely(!curr))
		return;

790 791
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
792
		return;
793

I
Ingo Molnar 已提交
794
	curr->exec_start = now;
795

796 797 798 799 800 801 802 803 804
	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);

805 806 807
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

808
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
809
		cpuacct_charge(curtask, delta_exec);
810
		account_group_exec_runtime(curtask, delta_exec);
811
	}
812 813

	account_cfs_rq_runtime(cfs_rq, delta_exec);
814 815
}

816 817 818 819 820
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

821
#ifdef CONFIG_SCHEDSTATS
822
static inline void
823
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
824
{
825 826 827 828 829 830 831
	u64 wait_start = rq_clock(rq_of(cfs_rq));

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

	se->statistics.wait_start = wait_start;
832 833
}

834 835 836 837
static void
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *p;
838 839 840
	u64 delta;

	delta = rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start;
841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861

	if (entity_is_task(se)) {
		p = task_of(se);
		if (task_on_rq_migrating(p)) {
			/*
			 * Preserve migrating task's wait time so wait_start
			 * time stamp can be adjusted to accumulate wait time
			 * prior to migration.
			 */
			se->statistics.wait_start = delta;
			return;
		}
		trace_sched_stat_wait(p, delta);
	}

	se->statistics.wait_max = max(se->statistics.wait_max, delta);
	se->statistics.wait_count++;
	se->statistics.wait_sum += delta;
	se->statistics.wait_start = 0;
}

862 863 864
/*
 * Task is being enqueued - update stats:
 */
865 866
static inline void
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
867 868 869 870 871
{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
872
	if (se != cfs_rq->curr)
873
		update_stats_wait_start(cfs_rq, se);
874 875 876
}

static inline void
877
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
878 879 880 881 882
{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
883
	if (se != cfs_rq->curr)
884
		update_stats_wait_end(cfs_rq, se);
885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916

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

			if (tsk->state & TASK_INTERRUPTIBLE)
				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
			if (tsk->state & TASK_UNINTERRUPTIBLE)
				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
		}
	}

}
#else
static inline void
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
}

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

static inline void
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
}

static inline void
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
917
}
918
#endif
919 920 921 922 923

/*
 * We are picking a new current task - update its stats:
 */
static inline void
924
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
925 926 927 928
{
	/*
	 * We are starting a new run period:
	 */
929
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
930 931 932 933 934 935
}

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

936 937
#ifdef CONFIG_NUMA_BALANCING
/*
938 939 940
 * 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.
941
 */
942 943
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
944 945 946

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
947

948 949 950
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974
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)
{
975
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
976 977 978
	unsigned int scan, floor;
	unsigned int windows = 1;

979 980
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996
	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);
}

997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008
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));
}

1009 1010 1011 1012 1013
struct numa_group {
	atomic_t refcount;

	spinlock_t lock; /* nr_tasks, tasks */
	int nr_tasks;
1014
	pid_t gid;
1015
	int active_nodes;
1016 1017

	struct rcu_head rcu;
1018
	unsigned long total_faults;
1019
	unsigned long max_faults_cpu;
1020 1021 1022 1023 1024
	/*
	 * 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.
	 */
1025
	unsigned long *faults_cpu;
1026
	unsigned long faults[0];
1027 1028
};

1029 1030 1031 1032 1033 1034 1035 1036 1037
/* 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)

1038 1039 1040 1041 1042
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

1043 1044 1045 1046 1047 1048 1049
/*
 * 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)
1050
{
1051
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1052 1053 1054 1055
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
1056
	if (!p->numa_faults)
1057 1058
		return 0;

1059 1060
	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1061 1062
}

1063 1064 1065 1066 1067
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

1068 1069
	return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1070 1071
}

1072 1073
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
1074 1075
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1076 1077
}

1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089
/*
 * A node triggering more than 1/3 as many NUMA faults as the maximum is
 * considered part of a numa group's pseudo-interleaving set. Migrations
 * between these nodes are slowed down, to allow things to settle down.
 */
#define ACTIVE_NODE_FRACTION 3

static bool numa_is_active_node(int nid, struct numa_group *ng)
{
	return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu;
}

1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154
/* 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;
}

1155 1156 1157 1158 1159 1160
/*
 * 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.
 */
1161 1162
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1163
{
1164
	unsigned long faults, total_faults;
1165

1166
	if (!p->numa_faults)
1167 1168 1169 1170 1171 1172 1173
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1174
	faults = task_faults(p, nid);
1175 1176
	faults += score_nearby_nodes(p, nid, dist, true);

1177
	return 1000 * faults / total_faults;
1178 1179
}

1180 1181
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1182
{
1183 1184 1185 1186 1187 1188 1189 1190
	unsigned long faults, total_faults;

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1191 1192
		return 0;

1193
	faults = group_faults(p, nid);
1194 1195
	faults += score_nearby_nodes(p, nid, dist, false);

1196
	return 1000 * faults / total_faults;
1197 1198
}

1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238
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;

	/*
1239 1240
	 * Destination node is much more heavily used than the source
	 * node? Allow migration.
1241
	 */
1242 1243
	if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
					ACTIVE_NODE_FRACTION)
1244 1245 1246
		return true;

	/*
1247 1248 1249 1250 1251 1252
	 * Distribute memory according to CPU & memory use on each node,
	 * with 3/4 hysteresis to avoid unnecessary memory migrations:
	 *
	 * faults_cpu(dst)   3   faults_cpu(src)
	 * --------------- * - > ---------------
	 * faults_mem(dst)   4   faults_mem(src)
1253
	 */
1254 1255
	return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
	       group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1256 1257
}

1258
static unsigned long weighted_cpuload(const int cpu);
1259 1260
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1261
static unsigned long capacity_of(int cpu);
1262 1263
static long effective_load(struct task_group *tg, int cpu, long wl, long wg);

1264
/* Cached statistics for all CPUs within a node */
1265
struct numa_stats {
1266
	unsigned long nr_running;
1267
	unsigned long load;
1268 1269

	/* Total compute capacity of CPUs on a node */
1270
	unsigned long compute_capacity;
1271 1272

	/* Approximate capacity in terms of runnable tasks on a node */
1273
	unsigned long task_capacity;
1274
	int has_free_capacity;
1275
};
1276

1277 1278 1279 1280 1281
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1282 1283
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1284 1285 1286 1287 1288 1289 1290

	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);
1291
		ns->compute_capacity += capacity_of(cpu);
1292 1293

		cpus++;
1294 1295
	}

1296 1297 1298 1299 1300
	/*
	 * 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.
	 *
1301 1302
	 * We'll either bail at !has_free_capacity, or we'll detect a huge
	 * imbalance and bail there.
1303 1304 1305 1306
	 */
	if (!cpus)
		return;

1307 1308 1309 1310 1311 1312
	/* 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));
1313
	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1314 1315
}

1316 1317
struct task_numa_env {
	struct task_struct *p;
1318

1319 1320
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1321

1322
	struct numa_stats src_stats, dst_stats;
1323

1324
	int imbalance_pct;
1325
	int dist;
1326 1327 1328

	struct task_struct *best_task;
	long best_imp;
1329 1330 1331
	int best_cpu;
};

1332 1333 1334 1335 1336
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);
1337 1338
	if (p)
		get_task_struct(p);
1339 1340 1341 1342 1343 1344

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

1345
static bool load_too_imbalanced(long src_load, long dst_load,
1346 1347
				struct task_numa_env *env)
{
1348 1349
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360
	long src_capacity, dst_capacity;

	/*
	 * The load is corrected for the CPU capacity available on each node.
	 *
	 * src_load        dst_load
	 * ------------ vs ---------
	 * src_capacity    dst_capacity
	 */
	src_capacity = env->src_stats.compute_capacity;
	dst_capacity = env->dst_stats.compute_capacity;
1361 1362

	/* We care about the slope of the imbalance, not the direction. */
1363 1364
	if (dst_load < src_load)
		swap(dst_load, src_load);
1365 1366

	/* Is the difference below the threshold? */
1367 1368
	imb = dst_load * src_capacity * 100 -
	      src_load * dst_capacity * env->imbalance_pct;
1369 1370 1371 1372 1373
	if (imb <= 0)
		return false;

	/*
	 * The imbalance is above the allowed threshold.
1374
	 * Compare it with the old imbalance.
1375
	 */
1376
	orig_src_load = env->src_stats.load;
1377
	orig_dst_load = env->dst_stats.load;
1378

1379 1380
	if (orig_dst_load < orig_src_load)
		swap(orig_dst_load, orig_src_load);
1381

1382 1383 1384 1385 1386
	old_imb = orig_dst_load * src_capacity * 100 -
		  orig_src_load * dst_capacity * env->imbalance_pct;

	/* Would this change make things worse? */
	return (imb > old_imb);
1387 1388
}

1389 1390 1391 1392 1393 1394
/*
 * 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
 */
1395 1396
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1397 1398 1399 1400
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1401
	long src_load, dst_load;
1402
	long load;
1403
	long imp = env->p->numa_group ? groupimp : taskimp;
1404
	long moveimp = imp;
1405
	int dist = env->dist;
1406 1407

	rcu_read_lock();
1408 1409
	cur = task_rcu_dereference(&dst_rq->curr);
	if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur)))
1410 1411
		cur = NULL;

1412 1413 1414 1415 1416 1417 1418
	/*
	 * 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;

1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430
	/*
	 * "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;

1431 1432
		/*
		 * If dst and source tasks are in the same NUMA group, or not
1433
		 * in any group then look only at task weights.
1434
		 */
1435
		if (cur->numa_group == env->p->numa_group) {
1436 1437
			imp = taskimp + task_weight(cur, env->src_nid, dist) -
			      task_weight(cur, env->dst_nid, dist);
1438 1439 1440 1441 1442 1443
			/*
			 * Add some hysteresis to prevent swapping the
			 * tasks within a group over tiny differences.
			 */
			if (cur->numa_group)
				imp -= imp/16;
1444
		} else {
1445 1446 1447 1448 1449 1450
			/*
			 * 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)
1451 1452
				imp += group_weight(cur, env->src_nid, dist) -
				       group_weight(cur, env->dst_nid, dist);
1453
			else
1454 1455
				imp += task_weight(cur, env->src_nid, dist) -
				       task_weight(cur, env->dst_nid, dist);
1456
		}
1457 1458
	}

1459
	if (imp <= env->best_imp && moveimp <= env->best_imp)
1460 1461 1462 1463
		goto unlock;

	if (!cur) {
		/* Is there capacity at our destination? */
1464
		if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1465
		    !env->dst_stats.has_free_capacity)
1466 1467 1468 1469 1470 1471
			goto unlock;

		goto balance;
	}

	/* Balance doesn't matter much if we're running a task per cpu */
1472 1473
	if (imp > env->best_imp && src_rq->nr_running == 1 &&
			dst_rq->nr_running == 1)
1474 1475 1476 1477 1478 1479
		goto assign;

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
balance:
1480 1481 1482
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1483

1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500
	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;

1501
	if (cur) {
1502 1503 1504
		load = task_h_load(cur);
		dst_load -= load;
		src_load += load;
1505 1506
	}

1507
	if (load_too_imbalanced(src_load, dst_load, env))
1508 1509
		goto unlock;

1510 1511 1512 1513 1514
	/*
	 * One idle CPU per node is evaluated for a task numa move.
	 * Call select_idle_sibling to maybe find a better one.
	 */
	if (!cur)
1515 1516
		env->dst_cpu = select_idle_sibling(env->p, env->src_cpu,
						   env->dst_cpu);
1517

1518 1519 1520 1521 1522 1523
assign:
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1524 1525
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1526 1527 1528 1529 1530 1531 1532 1533 1534
{
	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;
1535
		task_numa_compare(env, taskimp, groupimp);
1536 1537 1538
	}
}

1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555
/* Only move tasks to a NUMA node less busy than the current node. */
static bool numa_has_capacity(struct task_numa_env *env)
{
	struct numa_stats *src = &env->src_stats;
	struct numa_stats *dst = &env->dst_stats;

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

	/*
	 * Only consider a task move if the source has a higher load
	 * than the destination, corrected for CPU capacity on each node.
	 *
	 *      src->load                dst->load
	 * --------------------- vs ---------------------
	 * src->compute_capacity    dst->compute_capacity
	 */
1556 1557 1558
	if (src->load * dst->compute_capacity * env->imbalance_pct >

	    dst->load * src->compute_capacity * 100)
1559 1560 1561 1562 1563
		return true;

	return false;
}

1564 1565 1566 1567
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1568

1569
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1570
		.src_nid = task_node(p),
1571 1572 1573 1574 1575

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
1576
		.best_cpu = -1,
1577 1578
	};
	struct sched_domain *sd;
1579
	unsigned long taskweight, groupweight;
1580
	int nid, ret, dist;
1581
	long taskimp, groupimp;
1582

1583
	/*
1584 1585 1586 1587 1588 1589
	 * 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.
1590 1591
	 */
	rcu_read_lock();
1592
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1593 1594
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1595 1596
	rcu_read_unlock();

1597 1598 1599 1600 1601 1602 1603
	/*
	 * 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)) {
1604
		p->numa_preferred_nid = task_node(p);
1605 1606 1607
		return -EINVAL;
	}

1608
	env.dst_nid = p->numa_preferred_nid;
1609 1610 1611 1612 1613 1614
	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;
1615
	update_numa_stats(&env.dst_stats, env.dst_nid);
1616

1617
	/* Try to find a spot on the preferred nid. */
1618 1619
	if (numa_has_capacity(&env))
		task_numa_find_cpu(&env, taskimp, groupimp);
1620

1621 1622 1623 1624 1625 1626 1627
	/*
	 * 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.
	 */
1628
	if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
1629 1630 1631
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1632

1633
			dist = node_distance(env.src_nid, env.dst_nid);
1634 1635 1636 1637 1638
			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);
			}
1639

1640
			/* Only consider nodes where both task and groups benefit */
1641 1642
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1643
			if (taskimp < 0 && groupimp < 0)
1644 1645
				continue;

1646
			env.dist = dist;
1647 1648
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1649 1650
			if (numa_has_capacity(&env))
				task_numa_find_cpu(&env, taskimp, groupimp);
1651 1652 1653
		}
	}

1654 1655 1656 1657 1658 1659 1660 1661
	/*
	 * 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.
	 */
1662
	if (p->numa_group) {
1663 1664
		struct numa_group *ng = p->numa_group;

1665 1666 1667 1668 1669
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
			nid = env.dst_nid;

1670
		if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
1671 1672 1673 1674 1675 1676
			sched_setnuma(p, env.dst_nid);
	}

	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;
1677

1678 1679 1680 1681 1682 1683
	/*
	 * 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);

1684
	if (env.best_task == NULL) {
1685 1686 1687
		ret = migrate_task_to(p, env.best_cpu);
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1688 1689 1690 1691
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
1692 1693
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1694 1695
	put_task_struct(env.best_task);
	return ret;
1696 1697
}

1698 1699 1700
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1701 1702
	unsigned long interval = HZ;

1703
	/* This task has no NUMA fault statistics yet */
1704
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1705 1706
		return;

1707
	/* Periodically retry migrating the task to the preferred node */
1708 1709
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
	p->numa_migrate_retry = jiffies + interval;
1710 1711

	/* Success if task is already running on preferred CPU */
1712
	if (task_node(p) == p->numa_preferred_nid)
1713 1714 1715
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1716
	task_numa_migrate(p);
1717 1718
}

1719
/*
1720
 * Find out how many nodes on the workload is actively running on. Do this by
1721 1722 1723 1724
 * 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.
 */
1725
static void numa_group_count_active_nodes(struct numa_group *numa_group)
1726 1727
{
	unsigned long faults, max_faults = 0;
1728
	int nid, active_nodes = 0;
1729 1730 1731 1732 1733 1734 1735 1736 1737

	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);
1738 1739
		if (faults * ACTIVE_NODE_FRACTION > max_faults)
			active_nodes++;
1740
	}
1741 1742 1743

	numa_group->max_faults_cpu = max_faults;
	numa_group->active_nodes = active_nodes;
1744 1745
}

1746 1747 1748
/*
 * 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
1749 1750 1751
 * 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.
1752 1753
 */
#define NUMA_PERIOD_SLOTS 10
1754
#define NUMA_PERIOD_THRESHOLD 7
1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774

/*
 * 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
1775 1776 1777
	 * to automatic numa balancing. Related to that, if there were failed
	 * migration then it implies we are migrating too quickly or the local
	 * node is overloaded. In either case, scan slower
1778
	 */
1779
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812
		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
		 */
1813
		ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1814 1815 1816 1817 1818 1819 1820 1821
		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));
}

1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839
/*
 * 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 {
1840 1841
		delta = p->se.avg.load_sum / p->se.load.weight;
		*period = LOAD_AVG_MAX;
1842 1843 1844 1845 1846 1847 1848 1849
	}

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

	return delta;
}

1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896
/*
 * 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;
1897
		nodemask_t max_group = NODE_MASK_NONE;
1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930
		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. */
1931 1932
		if (!max_faults)
			break;
1933 1934 1935 1936 1937
		nodes = max_group;
	}
	return nid;
}

1938 1939
static void task_numa_placement(struct task_struct *p)
{
1940 1941
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
1942
	unsigned long fault_types[2] = { 0, 0 };
1943 1944
	unsigned long total_faults;
	u64 runtime, period;
1945
	spinlock_t *group_lock = NULL;
1946

1947 1948 1949 1950 1951
	/*
	 * The p->mm->numa_scan_seq field gets updated without
	 * exclusive access. Use READ_ONCE() here to ensure
	 * that the field is read in a single access:
	 */
1952
	seq = READ_ONCE(p->mm->numa_scan_seq);
1953 1954 1955
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
1956
	p->numa_scan_period_max = task_scan_max(p);
1957

1958 1959 1960 1961
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

1962 1963 1964
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
1965
		spin_lock_irq(group_lock);
1966 1967
	}

1968 1969
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
1970 1971
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1972
		unsigned long faults = 0, group_faults = 0;
1973
		int priv;
1974

1975
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1976
			long diff, f_diff, f_weight;
1977

1978 1979 1980 1981
			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);
1982

1983
			/* Decay existing window, copy faults since last scan */
1984 1985 1986
			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;
1987

1988 1989 1990 1991 1992 1993 1994 1995
			/*
			 * 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);
1996
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1997
				   (total_faults + 1);
1998 1999
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
2000

2001 2002 2003
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
2004
			p->total_numa_faults += diff;
2005
			if (p->numa_group) {
2006 2007 2008 2009 2010 2011 2012 2013 2014
				/*
				 * 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;
2015
				p->numa_group->total_faults += diff;
2016
				group_faults += p->numa_group->faults[mem_idx];
2017
			}
2018 2019
		}

2020 2021 2022 2023
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
2024 2025 2026 2027 2028 2029 2030

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

2031 2032
	update_task_scan_period(p, fault_types[0], fault_types[1]);

2033
	if (p->numa_group) {
2034
		numa_group_count_active_nodes(p->numa_group);
2035
		spin_unlock_irq(group_lock);
2036
		max_nid = preferred_group_nid(p, max_group_nid);
2037 2038
	}

2039 2040 2041 2042 2043 2044 2045
	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);
2046
	}
2047 2048
}

2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059
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);
}

2060 2061
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
2062 2063 2064 2065 2066 2067 2068 2069 2070
{
	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) +
2071
				    4*nr_node_ids*sizeof(unsigned long);
2072 2073 2074 2075 2076 2077

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

		atomic_set(&grp->refcount, 1);
2078 2079
		grp->active_nodes = 1;
		grp->max_faults_cpu = 0;
2080
		spin_lock_init(&grp->lock);
2081
		grp->gid = p->pid;
2082
		/* Second half of the array tracks nids where faults happen */
2083 2084
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
2085

2086
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2087
			grp->faults[i] = p->numa_faults[i];
2088

2089
		grp->total_faults = p->total_numa_faults;
2090

2091 2092 2093 2094 2095
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
2096
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
2097 2098

	if (!cpupid_match_pid(tsk, cpupid))
2099
		goto no_join;
2100 2101 2102

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
2103
		goto no_join;
2104 2105 2106

	my_grp = p->numa_group;
	if (grp == my_grp)
2107
		goto no_join;
2108 2109 2110 2111 2112 2113

	/*
	 * 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)
2114
		goto no_join;
2115 2116 2117 2118 2119

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2120
		goto no_join;
2121

2122 2123 2124 2125 2126 2127 2128
	/* 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;
2129

2130 2131 2132
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2133
	if (join && !get_numa_group(grp))
2134
		goto no_join;
2135 2136 2137 2138 2139 2140

	rcu_read_unlock();

	if (!join)
		return;

2141 2142
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2143

2144
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2145 2146
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2147
	}
2148 2149
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2150 2151 2152 2153 2154

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

	spin_unlock(&my_grp->lock);
2155
	spin_unlock_irq(&grp->lock);
2156 2157 2158 2159

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2160 2161 2162 2163 2164
	return;

no_join:
	rcu_read_unlock();
	return;
2165 2166 2167 2168 2169
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
2170
	void *numa_faults = p->numa_faults;
2171 2172
	unsigned long flags;
	int i;
2173 2174

	if (grp) {
2175
		spin_lock_irqsave(&grp->lock, flags);
2176
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2177
			grp->faults[i] -= p->numa_faults[i];
2178
		grp->total_faults -= p->total_numa_faults;
2179

2180
		grp->nr_tasks--;
2181
		spin_unlock_irqrestore(&grp->lock, flags);
2182
		RCU_INIT_POINTER(p->numa_group, NULL);
2183 2184 2185
		put_numa_group(grp);
	}

2186
	p->numa_faults = NULL;
2187
	kfree(numa_faults);
2188 2189
}

2190 2191 2192
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2193
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2194 2195
{
	struct task_struct *p = current;
2196
	bool migrated = flags & TNF_MIGRATED;
2197
	int cpu_node = task_node(current);
2198
	int local = !!(flags & TNF_FAULT_LOCAL);
2199
	struct numa_group *ng;
2200
	int priv;
2201

2202
	if (!static_branch_likely(&sched_numa_balancing))
2203 2204
		return;

2205 2206 2207 2208
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2209
	/* Allocate buffer to track faults on a per-node basis */
2210 2211
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2212
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2213

2214 2215
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2216
			return;
2217

2218
		p->total_numa_faults = 0;
2219
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2220
	}
2221

2222 2223 2224 2225 2226 2227 2228 2229
	/*
	 * 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);
2230
		if (!priv && !(flags & TNF_NO_GROUP))
2231
			task_numa_group(p, last_cpupid, flags, &priv);
2232 2233
	}

2234 2235 2236 2237 2238 2239
	/*
	 * 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.
	 */
2240 2241 2242 2243
	ng = p->numa_group;
	if (!priv && !local && ng && ng->active_nodes > 1 &&
				numa_is_active_node(cpu_node, ng) &&
				numa_is_active_node(mem_node, ng))
2244 2245
		local = 1;

2246
	task_numa_placement(p);
2247

2248 2249 2250 2251 2252
	/*
	 * 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))
2253 2254
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
2255 2256
	if (migrated)
		p->numa_pages_migrated += pages;
2257 2258
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2259

2260 2261
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2262
	p->numa_faults_locality[local] += pages;
2263 2264
}

2265 2266
static void reset_ptenuma_scan(struct task_struct *p)
{
2267 2268 2269 2270 2271 2272 2273 2274
	/*
	 * We only did a read acquisition of the mmap sem, so
	 * p->mm->numa_scan_seq is written to without exclusive access
	 * and the update is not guaranteed to be atomic. That's not
	 * much of an issue though, since this is just used for
	 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
	 * expensive, to avoid any form of compiler optimizations:
	 */
2275
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2276 2277 2278
	p->mm->numa_scan_offset = 0;
}

2279 2280 2281 2282 2283 2284 2285 2286 2287
/*
 * 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;
2288
	u64 runtime = p->se.sum_exec_runtime;
2289
	struct vm_area_struct *vma;
2290
	unsigned long start, end;
2291
	unsigned long nr_pte_updates = 0;
2292
	long pages, virtpages;
2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307

	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;

2308
	if (!mm->numa_next_scan) {
2309 2310
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2311 2312
	}

2313 2314 2315 2316 2317 2318 2319
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2320 2321 2322 2323
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
		p->numa_scan_period = task_scan_min(p);
	}
2324

2325
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2326 2327 2328
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2329 2330 2331 2332 2333 2334
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2335 2336 2337
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2338
	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2339 2340
	if (!pages)
		return;
2341

2342

2343
	down_read(&mm->mmap_sem);
2344
	vma = find_vma(mm, start);
2345 2346
	if (!vma) {
		reset_ptenuma_scan(p);
2347
		start = 0;
2348 2349
		vma = mm->mmap;
	}
2350
	for (; vma; vma = vma->vm_next) {
2351
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2352
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2353
			continue;
2354
		}
2355

2356 2357 2358 2359 2360 2361 2362 2363 2364 2365
		/*
		 * 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
2366 2367 2368 2369 2370 2371
		/*
		 * 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;
2372

2373 2374 2375 2376
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2377
			nr_pte_updates = change_prot_numa(vma, start, end);
2378 2379

			/*
2380 2381 2382 2383 2384 2385
			 * Try to scan sysctl_numa_balancing_size worth of
			 * hpages that have at least one present PTE that
			 * is not already pte-numa. If the VMA contains
			 * areas that are unused or already full of prot_numa
			 * PTEs, scan up to virtpages, to skip through those
			 * areas faster.
2386 2387 2388
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2389
			virtpages -= (end - start) >> PAGE_SHIFT;
2390

2391
			start = end;
2392
			if (pages <= 0 || virtpages <= 0)
2393
				goto out;
2394 2395

			cond_resched();
2396
		} while (end != vma->vm_end);
2397
	}
2398

2399
out:
2400
	/*
P
Peter Zijlstra 已提交
2401 2402 2403 2404
	 * 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.
2405 2406
	 */
	if (vma)
2407
		mm->numa_scan_offset = start;
2408 2409 2410
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421

	/*
	 * Make sure tasks use at least 32x as much time to run other code
	 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
	 * Usually update_task_scan_period slows down scanning enough; on an
	 * overloaded system we need to limit overhead on a per task basis.
	 */
	if (unlikely(p->se.sum_exec_runtime != runtime)) {
		u64 diff = p->se.sum_exec_runtime - runtime;
		p->node_stamp += 32 * diff;
	}
2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446
}

/*
 * 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;

2447
	if (now > curr->node_stamp + period) {
2448
		if (!curr->node_stamp)
2449
			curr->numa_scan_period = task_scan_min(curr);
2450
		curr->node_stamp += period;
2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461

		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)
{
}
2462 2463 2464 2465 2466 2467 2468 2469

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)
{
}
2470 2471
#endif /* CONFIG_NUMA_BALANCING */

2472 2473 2474 2475
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2476
	if (!parent_entity(se))
2477
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2478
#ifdef CONFIG_SMP
2479 2480 2481 2482 2483 2484
	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);
	}
2485
#endif
2486 2487 2488 2489 2490 2491 2492
	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);
2493
	if (!parent_entity(se))
2494
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2495
#ifdef CONFIG_SMP
2496 2497
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2498
		list_del_init(&se->group_node);
2499
	}
2500
#endif
2501 2502 2503
	cfs_rq->nr_running--;
}

2504 2505
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
2506
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2507
{
2508
	long tg_weight, load, shares;
2509 2510

	/*
2511 2512 2513
	 * This really should be: cfs_rq->avg.load_avg, but instead we use
	 * cfs_rq->load.weight, which is its upper bound. This helps ramp up
	 * the shares for small weight interactive tasks.
2514
	 */
2515
	load = scale_load_down(cfs_rq->load.weight);
2516

2517
	tg_weight = atomic_long_read(&tg->load_avg);
2518

2519 2520 2521
	/* Ensure tg_weight >= load */
	tg_weight -= cfs_rq->tg_load_avg_contrib;
	tg_weight += load;
2522 2523

	shares = (tg->shares * load);
2524 2525
	if (tg_weight)
		shares /= tg_weight;
2526 2527 2528 2529 2530 2531 2532 2533 2534

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

	return shares;
}
# else /* CONFIG_SMP */
2535
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2536 2537 2538 2539
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
2540

P
Peter Zijlstra 已提交
2541 2542 2543
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
2544 2545 2546 2547
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
2548
		account_entity_dequeue(cfs_rq, se);
2549
	}
P
Peter Zijlstra 已提交
2550 2551 2552 2553 2554 2555 2556

	update_load_set(&se->load, weight);

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

2557 2558
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2559
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2560 2561 2562
{
	struct task_group *tg;
	struct sched_entity *se;
2563
	long shares;
P
Peter Zijlstra 已提交
2564 2565 2566

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
2567
	if (!se || throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
2568
		return;
2569 2570 2571 2572
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
2573
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
2574 2575 2576 2577

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
2578
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2579 2580 2581 2582
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

2583
#ifdef CONFIG_SMP
2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603
/* 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,
};

2604 2605 2606 2607 2608 2609 2610 2611 2612 2613
/*
 * Precomputed \Sum y^k { 1<=k<=n, where n%32=0). Values are rolled down to
 * lower integers. See Documentation/scheduler/sched-avg.txt how these
 * were generated:
 */
static const u32 __accumulated_sum_N32[] = {
	    0, 23371, 35056, 40899, 43820, 45281,
	46011, 46376, 46559, 46650, 46696, 46719,
};

2614 2615 2616 2617 2618 2619
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631
	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
2632 2633
	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
	 * With a look-up table which covers y^n (n<PERIOD)
2634 2635 2636 2637 2638 2639
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
2640 2641
	}

2642 2643
	val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
	return val;
2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661
}

/*
 * 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;

2662 2663 2664
	/* Since n < LOAD_AVG_MAX_N, n/LOAD_AVG_PERIOD < 11 */
	contrib = __accumulated_sum_N32[n/LOAD_AVG_PERIOD];
	n %= LOAD_AVG_PERIOD;
2665 2666
	contrib = decay_load(contrib, n);
	return contrib + runnable_avg_yN_sum[n];
2667 2668
}

2669
#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2670

2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698
/*
 * 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}]
 */
2699 2700
static __always_inline int
__update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2701
		  unsigned long weight, int running, struct cfs_rq *cfs_rq)
2702
{
2703
	u64 delta, scaled_delta, periods;
2704
	u32 contrib;
2705
	unsigned int delta_w, scaled_delta_w, decayed = 0;
2706
	unsigned long scale_freq, scale_cpu;
2707

2708
	delta = now - sa->last_update_time;
2709 2710 2711 2712 2713
	/*
	 * 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) {
2714
		sa->last_update_time = now;
2715 2716 2717 2718 2719 2720 2721 2722 2723 2724
		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;
2725
	sa->last_update_time = now;
2726

2727 2728 2729
	scale_freq = arch_scale_freq_capacity(NULL, cpu);
	scale_cpu = arch_scale_cpu_capacity(NULL, cpu);

2730
	/* delta_w is the amount already accumulated against our next period */
2731
	delta_w = sa->period_contrib;
2732 2733 2734
	if (delta + delta_w >= 1024) {
		decayed = 1;

2735 2736 2737
		/* how much left for next period will start over, we don't know yet */
		sa->period_contrib = 0;

2738 2739 2740 2741 2742 2743
		/*
		 * 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;
2744
		scaled_delta_w = cap_scale(delta_w, scale_freq);
2745
		if (weight) {
2746 2747 2748 2749 2750
			sa->load_sum += weight * scaled_delta_w;
			if (cfs_rq) {
				cfs_rq->runnable_load_sum +=
						weight * scaled_delta_w;
			}
2751
		}
2752
		if (running)
2753
			sa->util_sum += scaled_delta_w * scale_cpu;
2754 2755 2756 2757 2758 2759 2760

		delta -= delta_w;

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

2761
		sa->load_sum = decay_load(sa->load_sum, periods + 1);
2762 2763 2764 2765
		if (cfs_rq) {
			cfs_rq->runnable_load_sum =
				decay_load(cfs_rq->runnable_load_sum, periods + 1);
		}
2766
		sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2767 2768

		/* Efficiently calculate \sum (1..n_period) 1024*y^i */
2769
		contrib = __compute_runnable_contrib(periods);
2770
		contrib = cap_scale(contrib, scale_freq);
2771
		if (weight) {
2772
			sa->load_sum += weight * contrib;
2773 2774 2775
			if (cfs_rq)
				cfs_rq->runnable_load_sum += weight * contrib;
		}
2776
		if (running)
2777
			sa->util_sum += contrib * scale_cpu;
2778 2779 2780
	}

	/* Remainder of delta accrued against u_0` */
2781
	scaled_delta = cap_scale(delta, scale_freq);
2782
	if (weight) {
2783
		sa->load_sum += weight * scaled_delta;
2784
		if (cfs_rq)
2785
			cfs_rq->runnable_load_sum += weight * scaled_delta;
2786
	}
2787
	if (running)
2788
		sa->util_sum += scaled_delta * scale_cpu;
2789

2790
	sa->period_contrib += delta;
2791

2792 2793
	if (decayed) {
		sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2794 2795 2796 2797
		if (cfs_rq) {
			cfs_rq->runnable_load_avg =
				div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
		}
2798
		sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2799
	}
2800

2801
	return decayed;
2802 2803
}

2804
#ifdef CONFIG_FAIR_GROUP_SCHED
2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819
/**
 * update_tg_load_avg - update the tg's load avg
 * @cfs_rq: the cfs_rq whose avg changed
 * @force: update regardless of how small the difference
 *
 * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
 * However, because tg->load_avg is a global value there are performance
 * considerations.
 *
 * In order to avoid having to look at the other cfs_rq's, we use a
 * differential update where we store the last value we propagated. This in
 * turn allows skipping updates if the differential is 'small'.
 *
 * Updating tg's load_avg is necessary before update_cfs_share() (which is
 * done) and effective_load() (which is not done because it is too costly).
2820
 */
2821
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2822
{
2823
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2824

2825 2826 2827 2828 2829 2830
	/*
	 * No need to update load_avg for root_task_group as it is not used.
	 */
	if (cfs_rq->tg == &root_task_group)
		return;

2831 2832 2833
	if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
		atomic_long_add(delta, &cfs_rq->tg->load_avg);
		cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2834
	}
2835
}
2836

2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882
/*
 * Called within set_task_rq() right before setting a task's cpu. The
 * caller only guarantees p->pi_lock is held; no other assumptions,
 * including the state of rq->lock, should be made.
 */
void set_task_rq_fair(struct sched_entity *se,
		      struct cfs_rq *prev, struct cfs_rq *next)
{
	if (!sched_feat(ATTACH_AGE_LOAD))
		return;

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

#ifndef CONFIG_64BIT
		u64 p_last_update_time_copy;
		u64 n_last_update_time_copy;

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

			smp_rmb();

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

		} while (p_last_update_time != p_last_update_time_copy ||
			 n_last_update_time != n_last_update_time_copy);
#else
		p_last_update_time = prev->avg.last_update_time;
		n_last_update_time = next->avg.last_update_time;
#endif
		__update_load_avg(p_last_update_time, cpu_of(rq_of(prev)),
				  &se->avg, 0, 0, NULL);
		se->avg.last_update_time = n_last_update_time;
	}
}
2883
#else /* CONFIG_FAIR_GROUP_SCHED */
2884
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2885
#endif /* CONFIG_FAIR_GROUP_SCHED */
2886

2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915
static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
{
	struct rq *rq = rq_of(cfs_rq);
	int cpu = cpu_of(rq);

	if (cpu == smp_processor_id() && &rq->cfs == cfs_rq) {
		unsigned long max = rq->cpu_capacity_orig;

		/*
		 * There are a few boundary cases this might miss but it should
		 * get called often enough that that should (hopefully) not be
		 * a real problem -- added to that it only calls on the local
		 * CPU, so if we enqueue remotely we'll miss an update, but
		 * the next tick/schedule should update.
		 *
		 * It will not get called when we go idle, because the idle
		 * thread is a different class (!fair), nor will the utilization
		 * number include things like RT tasks.
		 *
		 * As is, the util number is not freq-invariant (we'd have to
		 * implement arch_scale_freq_capacity() for that).
		 *
		 * See cpu_util().
		 */
		cpufreq_update_util(rq_clock(rq),
				    min(cfs_rq->avg.util_avg, max), max);
	}
}

2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932
/*
 * Unsigned subtract and clamp on underflow.
 *
 * Explicitly do a load-store to ensure the intermediate value never hits
 * memory. This allows lockless observations without ever seeing the negative
 * values.
 */
#define sub_positive(_ptr, _val) do {				\
	typeof(_ptr) ptr = (_ptr);				\
	typeof(*ptr) val = (_val);				\
	typeof(*ptr) res, var = READ_ONCE(*ptr);		\
	res = var - val;					\
	if (res > var)						\
		res = 0;					\
	WRITE_ONCE(*ptr, res);					\
} while (0)

2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944
/**
 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages
 * @now: current time, as per cfs_rq_clock_task()
 * @cfs_rq: cfs_rq to update
 * @update_freq: should we call cfs_rq_util_change() or will the call do so
 *
 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable)
 * avg. The immediate corollary is that all (fair) tasks must be attached, see
 * post_init_entity_util_avg().
 *
 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
 *
2945 2946 2947 2948
 * Returns true if the load decayed or we removed load.
 *
 * Since both these conditions indicate a changed cfs_rq->avg.load we should
 * call update_tg_load_avg() when this function returns true.
2949
 */
2950 2951
static inline int
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
2952
{
2953
	struct sched_avg *sa = &cfs_rq->avg;
2954
	int decayed, removed_load = 0, removed_util = 0;
2955

2956
	if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2957
		s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2958 2959
		sub_positive(&sa->load_avg, r);
		sub_positive(&sa->load_sum, r * LOAD_AVG_MAX);
2960
		removed_load = 1;
2961
	}
2962

2963 2964
	if (atomic_long_read(&cfs_rq->removed_util_avg)) {
		long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
2965 2966
		sub_positive(&sa->util_avg, r);
		sub_positive(&sa->util_sum, r * LOAD_AVG_MAX);
2967
		removed_util = 1;
2968
	}
2969

2970
	decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2971
		scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2972

2973 2974 2975 2976
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
2977

2978 2979
	if (update_freq && (decayed || removed_util))
		cfs_rq_util_change(cfs_rq);
2980

2981
	return decayed || removed_load;
2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999
}

/* Update task and its cfs_rq load average */
static inline void update_load_avg(struct sched_entity *se, int update_tg)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 now = cfs_rq_clock_task(cfs_rq);
	struct rq *rq = rq_of(cfs_rq);
	int cpu = cpu_of(rq);

	/*
	 * Track task load average for carrying it to new CPU after migrated, and
	 * track group sched_entity load average for task_h_load calc in migration
	 */
	__update_load_avg(now, cpu, &se->avg,
			  se->on_rq * scale_load_down(se->load.weight),
			  cfs_rq->curr == se, NULL);

3000
	if (update_cfs_rq_load_avg(now, cfs_rq, true) && update_tg)
3001
		update_tg_load_avg(cfs_rq, 0);
3002 3003
}

3004 3005 3006 3007 3008 3009 3010 3011
/**
 * attach_entity_load_avg - attach this entity to its cfs_rq load avg
 * @cfs_rq: cfs_rq to attach to
 * @se: sched_entity to attach
 *
 * Must call update_cfs_rq_load_avg() before this, since we rely on
 * cfs_rq->avg.last_update_time being current.
 */
3012 3013
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3014 3015 3016
	if (!sched_feat(ATTACH_AGE_LOAD))
		goto skip_aging;

3017 3018 3019
	/*
	 * If we got migrated (either between CPUs or between cgroups) we'll
	 * have aged the average right before clearing @last_update_time.
3020 3021
	 *
	 * Or we're fresh through post_init_entity_util_avg().
3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032
	 */
	if (se->avg.last_update_time) {
		__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
				  &se->avg, 0, 0, NULL);

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

3033
skip_aging:
3034 3035 3036 3037 3038
	se->avg.last_update_time = cfs_rq->avg.last_update_time;
	cfs_rq->avg.load_avg += se->avg.load_avg;
	cfs_rq->avg.load_sum += se->avg.load_sum;
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
3039 3040

	cfs_rq_util_change(cfs_rq);
3041 3042
}

3043 3044 3045 3046 3047 3048 3049 3050
/**
 * detach_entity_load_avg - detach this entity from its cfs_rq load avg
 * @cfs_rq: cfs_rq to detach from
 * @se: sched_entity to detach
 *
 * Must call update_cfs_rq_load_avg() before this, since we rely on
 * cfs_rq->avg.last_update_time being current.
 */
3051 3052 3053 3054 3055 3056
static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
			  &se->avg, se->on_rq * scale_load_down(se->load.weight),
			  cfs_rq->curr == se, NULL);

3057 3058 3059 3060
	sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg);
	sub_positive(&cfs_rq->avg.load_sum, se->avg.load_sum);
	sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
	sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
3061 3062

	cfs_rq_util_change(cfs_rq);
3063 3064
}

3065 3066 3067
/* Add the load generated by se into cfs_rq's load average */
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3068
{
3069 3070
	struct sched_avg *sa = &se->avg;
	u64 now = cfs_rq_clock_task(cfs_rq);
3071
	int migrated, decayed;
3072

3073 3074
	migrated = !sa->last_update_time;
	if (!migrated) {
3075
		__update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
3076 3077
			se->on_rq * scale_load_down(se->load.weight),
			cfs_rq->curr == se, NULL);
3078
	}
3079

3080
	decayed = update_cfs_rq_load_avg(now, cfs_rq, !migrated);
3081

3082 3083 3084
	cfs_rq->runnable_load_avg += sa->load_avg;
	cfs_rq->runnable_load_sum += sa->load_sum;

3085 3086
	if (migrated)
		attach_entity_load_avg(cfs_rq, se);
3087

3088 3089
	if (decayed || migrated)
		update_tg_load_avg(cfs_rq, 0);
3090 3091
}

3092 3093 3094 3095 3096 3097 3098 3099 3100
/* Remove the runnable load generated by se from cfs_rq's runnable load average */
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_avg(se, 1);

	cfs_rq->runnable_load_avg =
		max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
	cfs_rq->runnable_load_sum =
3101
		max_t(s64,  cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
3102 3103
}

3104
#ifndef CONFIG_64BIT
3105 3106
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
3107
	u64 last_update_time_copy;
3108
	u64 last_update_time;
3109

3110 3111 3112 3113 3114
	do {
		last_update_time_copy = cfs_rq->load_last_update_time_copy;
		smp_rmb();
		last_update_time = cfs_rq->avg.last_update_time;
	} while (last_update_time != last_update_time_copy);
3115 3116 3117

	return last_update_time;
}
3118
#else
3119 3120 3121 3122
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.last_update_time;
}
3123 3124
#endif

3125 3126 3127 3128 3129 3130 3131 3132 3133 3134
/*
 * Task first catches up with cfs_rq, and then subtract
 * itself from the cfs_rq (task must be off the queue now).
 */
void remove_entity_load_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 last_update_time;

	/*
3135 3136 3137 3138 3139 3140 3141
	 * tasks cannot exit without having gone through wake_up_new_task() ->
	 * post_init_entity_util_avg() which will have added things to the
	 * cfs_rq, so we can remove unconditionally.
	 *
	 * Similarly for groups, they will have passed through
	 * post_init_entity_util_avg() before unregister_sched_fair_group()
	 * calls this.
3142 3143 3144 3145
	 */

	last_update_time = cfs_rq_last_update_time(cfs_rq);

3146
	__update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
3147 3148
	atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
	atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
3149
}
3150

3151 3152 3153 3154 3155 3156 3157 3158 3159 3160
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
{
	return cfs_rq->runnable_load_avg;
}

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

3161 3162
static int idle_balance(struct rq *this_rq);

3163 3164
#else /* CONFIG_SMP */

3165 3166 3167 3168 3169 3170
static inline int
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
{
	return 0;
}

3171 3172 3173 3174 3175 3176 3177 3178
static inline void update_load_avg(struct sched_entity *se, int not_used)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	struct rq *rq = rq_of(cfs_rq);

	cpufreq_trigger_update(rq_clock(rq));
}

3179 3180
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3181 3182
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3183
static inline void remove_entity_load_avg(struct sched_entity *se) {}
3184

3185 3186 3187 3188 3189
static inline void
attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
static inline void
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}

3190 3191 3192 3193 3194
static inline int idle_balance(struct rq *rq)
{
	return 0;
}

3195
#endif /* CONFIG_SMP */
3196

3197
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
3198 3199
{
#ifdef CONFIG_SCHEDSTATS
3200 3201 3202 3203 3204
	struct task_struct *tsk = NULL;

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

3205
	if (se->statistics.sleep_start) {
3206
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
3207 3208 3209 3210

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

3211 3212
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
3213

3214
		se->statistics.sleep_start = 0;
3215
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
3216

3217
		if (tsk) {
3218
			account_scheduler_latency(tsk, delta >> 10, 1);
3219 3220
			trace_sched_stat_sleep(tsk, delta);
		}
3221
	}
3222
	if (se->statistics.block_start) {
3223
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
3224 3225 3226 3227

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

3228 3229
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
3230

3231
		se->statistics.block_start = 0;
3232
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
3233

3234
		if (tsk) {
3235
			if (tsk->in_iowait) {
3236 3237
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
3238
				trace_sched_stat_iowait(tsk, delta);
3239 3240
			}

3241 3242
			trace_sched_stat_blocked(tsk, delta);

3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253
			/*
			 * 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
3254
		}
3255 3256 3257 3258
	}
#endif
}

P
Peter Zijlstra 已提交
3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271
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
}

3272 3273 3274
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3275
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3276

3277 3278 3279 3280 3281 3282
	/*
	 * 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
3283
	if (initial && sched_feat(START_DEBIT))
3284
		vruntime += sched_vslice(cfs_rq, se);
3285

3286
	/* sleeps up to a single latency don't count. */
3287
	if (!initial) {
3288
		unsigned long thresh = sysctl_sched_latency;
3289

3290 3291 3292 3293 3294 3295
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3296

3297
		vruntime -= thresh;
3298 3299
	}

3300
	/* ensure we never gain time by being placed backwards. */
3301
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3302 3303
}

3304 3305
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317
static inline void check_schedstat_required(void)
{
#ifdef CONFIG_SCHEDSTATS
	if (schedstat_enabled())
		return;

	/* Force schedstat enabled if a dependent tracepoint is active */
	if (trace_sched_stat_wait_enabled()    ||
			trace_sched_stat_sleep_enabled()   ||
			trace_sched_stat_iowait_enabled()  ||
			trace_sched_stat_blocked_enabled() ||
			trace_sched_stat_runtime_enabled())  {
3318
		printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, "
3319 3320 3321 3322 3323 3324 3325
			     "stat_blocked and stat_runtime require the "
			     "kernel parameter schedstats=enabled or "
			     "kernel.sched_schedstats=1\n");
	}
#endif
}

3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344

/*
 * MIGRATION
 *
 *	dequeue
 *	  update_curr()
 *	    update_min_vruntime()
 *	  vruntime -= min_vruntime
 *
 *	enqueue
 *	  update_curr()
 *	    update_min_vruntime()
 *	  vruntime += min_vruntime
 *
 * this way the vruntime transition between RQs is done when both
 * min_vruntime are up-to-date.
 *
 * WAKEUP (remote)
 *
3345
 *	->migrate_task_rq_fair() (p->state == TASK_WAKING)
3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356
 *	  vruntime -= min_vruntime
 *
 *	enqueue
 *	  update_curr()
 *	    update_min_vruntime()
 *	  vruntime += min_vruntime
 *
 * this way we don't have the most up-to-date min_vruntime on the originating
 * CPU and an up-to-date min_vruntime on the destination CPU.
 */

3357
static void
3358
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3359
{
3360 3361 3362
	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED);
	bool curr = cfs_rq->curr == se;

3363
	/*
3364 3365
	 * If we're the current task, we must renormalise before calling
	 * update_curr().
3366
	 */
3367
	if (renorm && curr)
3368 3369
		se->vruntime += cfs_rq->min_vruntime;

3370 3371
	update_curr(cfs_rq);

3372
	/*
3373 3374 3375 3376
	 * Otherwise, renormalise after, such that we're placed at the current
	 * moment in time, instead of some random moment in the past. Being
	 * placed in the past could significantly boost this task to the
	 * fairness detriment of existing tasks.
3377
	 */
3378 3379 3380
	if (renorm && !curr)
		se->vruntime += cfs_rq->min_vruntime;

3381
	enqueue_entity_load_avg(cfs_rq, se);
3382 3383
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
3384

3385
	if (flags & ENQUEUE_WAKEUP) {
3386
		place_entity(cfs_rq, se, 0);
3387 3388
		if (schedstat_enabled())
			enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
3389
	}
3390

3391 3392 3393 3394 3395
	check_schedstat_required();
	if (schedstat_enabled()) {
		update_stats_enqueue(cfs_rq, se);
		check_spread(cfs_rq, se);
	}
3396
	if (!curr)
3397
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3398
	se->on_rq = 1;
3399

3400
	if (cfs_rq->nr_running == 1) {
3401
		list_add_leaf_cfs_rq(cfs_rq);
3402 3403
		check_enqueue_throttle(cfs_rq);
	}
3404 3405
}

3406
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3407
{
3408 3409
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3410
		if (cfs_rq->last != se)
3411
			break;
3412 3413

		cfs_rq->last = NULL;
3414 3415
	}
}
P
Peter Zijlstra 已提交
3416

3417 3418 3419 3420
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3421
		if (cfs_rq->next != se)
3422
			break;
3423 3424

		cfs_rq->next = NULL;
3425
	}
P
Peter Zijlstra 已提交
3426 3427
}

3428 3429 3430 3431
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3432
		if (cfs_rq->skip != se)
3433
			break;
3434 3435

		cfs_rq->skip = NULL;
3436 3437 3438
	}
}

P
Peter Zijlstra 已提交
3439 3440
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3441 3442 3443 3444 3445
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
3446 3447 3448

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
3449 3450
}

3451
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3452

3453
static void
3454
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3455
{
3456 3457 3458 3459
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
3460
	dequeue_entity_load_avg(cfs_rq, se);
3461

3462 3463
	if (schedstat_enabled())
		update_stats_dequeue(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
3464

P
Peter Zijlstra 已提交
3465
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3466

3467
	if (se != cfs_rq->curr)
3468
		__dequeue_entity(cfs_rq, se);
3469
	se->on_rq = 0;
3470
	account_entity_dequeue(cfs_rq, se);
3471 3472 3473 3474 3475 3476

	/*
	 * 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.
	 */
3477
	if (!(flags & DEQUEUE_SLEEP))
3478
		se->vruntime -= cfs_rq->min_vruntime;
3479

3480 3481 3482
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3483
	update_min_vruntime(cfs_rq);
3484
	update_cfs_shares(cfs_rq);
3485 3486 3487 3488 3489
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
3490
static void
I
Ingo Molnar 已提交
3491
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3492
{
3493
	unsigned long ideal_runtime, delta_exec;
3494 3495
	struct sched_entity *se;
	s64 delta;
3496

P
Peter Zijlstra 已提交
3497
	ideal_runtime = sched_slice(cfs_rq, curr);
3498
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3499
	if (delta_exec > ideal_runtime) {
3500
		resched_curr(rq_of(cfs_rq));
3501 3502 3503 3504 3505
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516
		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;

3517 3518
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
3519

3520 3521
	if (delta < 0)
		return;
3522

3523
	if (delta > ideal_runtime)
3524
		resched_curr(rq_of(cfs_rq));
3525 3526
}

3527
static void
3528
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3529
{
3530 3531 3532 3533 3534 3535 3536
	/* '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.
		 */
3537 3538
		if (schedstat_enabled())
			update_stats_wait_end(cfs_rq, se);
3539
		__dequeue_entity(cfs_rq, se);
3540
		update_load_avg(se, 1);
3541 3542
	}

3543
	update_stats_curr_start(cfs_rq, se);
3544
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
3545 3546 3547 3548 3549 3550
#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):
	 */
3551
	if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3552
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
3553 3554 3555
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
3556
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
3557 3558
}

3559 3560 3561
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

3562 3563 3564 3565 3566 3567 3568
/*
 * 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
 */
3569 3570
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3571
{
3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582
	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 */
3583

3584 3585 3586 3587 3588
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
3589 3590 3591 3592 3593 3594 3595 3596 3597 3598
		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;
		}

3599 3600 3601
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
3602

3603 3604 3605 3606 3607 3608
	/*
	 * 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;

3609 3610 3611 3612 3613 3614
	/*
	 * 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;

3615
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3616 3617

	return se;
3618 3619
}

3620
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3621

3622
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3623 3624 3625 3626 3627 3628
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
3629
		update_curr(cfs_rq);
3630

3631 3632 3633
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

3634 3635 3636 3637 3638 3639
	if (schedstat_enabled()) {
		check_spread(cfs_rq, prev);
		if (prev->on_rq)
			update_stats_wait_start(cfs_rq, prev);
	}

3640 3641 3642
	if (prev->on_rq) {
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
3643
		/* in !on_rq case, update occurred at dequeue */
3644
		update_load_avg(prev, 0);
3645
	}
3646
	cfs_rq->curr = NULL;
3647 3648
}

P
Peter Zijlstra 已提交
3649 3650
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3651 3652
{
	/*
3653
	 * Update run-time statistics of the 'current'.
3654
	 */
3655
	update_curr(cfs_rq);
3656

3657 3658 3659
	/*
	 * Ensure that runnable average is periodically updated.
	 */
3660
	update_load_avg(curr, 1);
3661
	update_cfs_shares(cfs_rq);
3662

P
Peter Zijlstra 已提交
3663 3664 3665 3666 3667
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
3668
	if (queued) {
3669
		resched_curr(rq_of(cfs_rq));
3670 3671
		return;
	}
P
Peter Zijlstra 已提交
3672 3673 3674 3675 3676 3677 3678 3679
	/*
	 * 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
3680
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
3681
		check_preempt_tick(cfs_rq, curr);
3682 3683
}

3684 3685 3686 3687 3688 3689

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

#ifdef CONFIG_CFS_BANDWIDTH
3690 3691

#ifdef HAVE_JUMP_LABEL
3692
static struct static_key __cfs_bandwidth_used;
3693 3694 3695

static inline bool cfs_bandwidth_used(void)
{
3696
	return static_key_false(&__cfs_bandwidth_used);
3697 3698
}

3699
void cfs_bandwidth_usage_inc(void)
3700
{
3701 3702 3703 3704 3705 3706
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
3707 3708 3709 3710 3711 3712 3713
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

3714 3715
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
3716 3717
#endif /* HAVE_JUMP_LABEL */

3718 3719 3720 3721 3722 3723 3724 3725
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
3726 3727 3728 3729 3730 3731

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

P
Paul Turner 已提交
3732 3733 3734 3735 3736 3737 3738
/*
 * 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
 */
3739
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750
{
	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);
}

3751 3752 3753 3754 3755
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

3756 3757 3758 3759
/* 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))
3760
		return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time;
3761

3762
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3763 3764
}

3765 3766
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3767 3768 3769
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
3770
	u64 amount = 0, min_amount, expires;
3771 3772 3773 3774 3775 3776 3777

	/* 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;
3778
	else {
P
Peter Zijlstra 已提交
3779
		start_cfs_bandwidth(cfs_b);
3780 3781 3782 3783 3784 3785

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
3786
	}
P
Paul Turner 已提交
3787
	expires = cfs_b->runtime_expires;
3788 3789 3790
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
3791 3792 3793 3794 3795 3796 3797
	/*
	 * 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;
3798 3799

	return cfs_rq->runtime_remaining > 0;
3800 3801
}

P
Paul Turner 已提交
3802 3803 3804 3805 3806
/*
 * 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)
3807
{
P
Paul Turner 已提交
3808 3809 3810
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
3811
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3812 3813
		return;

P
Paul Turner 已提交
3814 3815 3816 3817 3818 3819 3820 3821 3822
	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
3823 3824 3825
	 * 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
3826 3827
	 */

3828
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
3829 3830 3831 3832 3833 3834 3835 3836
		/* 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;
	}
}

3837
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
3838 3839
{
	/* dock delta_exec before expiring quota (as it could span periods) */
3840
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
3841 3842 3843
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
3844 3845
		return;

3846 3847 3848 3849 3850
	/*
	 * 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))
3851
		resched_curr(rq_of(cfs_rq));
3852 3853
}

3854
static __always_inline
3855
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3856
{
3857
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3858 3859 3860 3861 3862
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

3863 3864
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
3865
	return cfs_bandwidth_used() && cfs_rq->throttled;
3866 3867
}

3868 3869 3870
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
3871
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
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
}

/*
 * Ensure that neither of the group entities corresponding to src_cpu or
 * dest_cpu are members of a throttled hierarchy when performing group
 * load-balance operations.
 */
static inline int throttled_lb_pair(struct task_group *tg,
				    int src_cpu, int dest_cpu)
{
	struct cfs_rq *src_cfs_rq, *dest_cfs_rq;

	src_cfs_rq = tg->cfs_rq[src_cpu];
	dest_cfs_rq = tg->cfs_rq[dest_cpu];

	return throttled_hierarchy(src_cfs_rq) ||
	       throttled_hierarchy(dest_cfs_rq);
}

/* updated child weight may affect parent so we have to do this bottom up */
static int tg_unthrottle_up(struct task_group *tg, void *data)
{
	struct rq *rq = data;
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

	cfs_rq->throttle_count--;
	if (!cfs_rq->throttle_count) {
3899
		/* adjust cfs_rq_clock_task() */
3900
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3901
					     cfs_rq->throttled_clock_task;
3902 3903 3904 3905 3906 3907 3908 3909 3910 3911
	}

	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)];

3912 3913
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
3914
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
3915 3916 3917 3918 3919
	cfs_rq->throttle_count++;

	return 0;
}

3920
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3921 3922 3923 3924 3925
{
	struct rq *rq = rq_of(cfs_rq);
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
	struct sched_entity *se;
	long task_delta, dequeue = 1;
P
Peter Zijlstra 已提交
3926
	bool empty;
3927 3928 3929

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

3930
	/* freeze hierarchy runnable averages while throttled */
3931 3932 3933
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950

	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)
3951
		sub_nr_running(rq, task_delta);
3952 3953

	cfs_rq->throttled = 1;
3954
	cfs_rq->throttled_clock = rq_clock(rq);
3955
	raw_spin_lock(&cfs_b->lock);
3956
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
3957

3958 3959 3960 3961 3962
	/*
	 * Add to the _head_ of the list, so that an already-started
	 * distribute_cfs_runtime will not see us
	 */
	list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
3963 3964 3965 3966 3967 3968 3969 3970

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

3971 3972 3973
	raw_spin_unlock(&cfs_b->lock);
}

3974
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3975 3976 3977 3978 3979 3980 3981
{
	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;

3982
	se = cfs_rq->tg->se[cpu_of(rq)];
3983 3984

	cfs_rq->throttled = 0;
3985 3986 3987

	update_rq_clock(rq);

3988
	raw_spin_lock(&cfs_b->lock);
3989
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3990 3991 3992
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

3993 3994 3995
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

3996 3997 3998 3999 4000 4001 4002 4003 4004 4005 4006 4007 4008 4009 4010 4011 4012 4013
	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)
4014
		add_nr_running(rq, task_delta);
4015 4016 4017

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
4018
		resched_curr(rq);
4019 4020 4021 4022 4023 4024
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
4025 4026
	u64 runtime;
	u64 starting_runtime = remaining;
4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056

	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();

4057
	return starting_runtime - remaining;
4058 4059
}

4060 4061 4062 4063 4064 4065 4066 4067
/*
 * 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)
{
4068
	u64 runtime, runtime_expires;
4069
	int throttled;
4070 4071 4072

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
4073
		goto out_deactivate;
4074

4075
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
4076
	cfs_b->nr_periods += overrun;
4077

4078 4079 4080 4081 4082 4083
	/*
	 * 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
4084 4085 4086

	__refill_cfs_bandwidth_runtime(cfs_b);

4087 4088 4089
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
4090
		return 0;
4091 4092
	}

4093 4094 4095
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

4096 4097 4098
	runtime_expires = cfs_b->runtime_expires;

	/*
4099 4100 4101 4102 4103
	 * 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.
4104
	 */
4105 4106
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
4107 4108 4109 4110 4111 4112 4113
		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);
4114 4115

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4116
	}
4117

4118 4119 4120 4121 4122 4123 4124
	/*
	 * 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;
4125

4126 4127 4128 4129
	return 0;

out_deactivate:
	return 1;
4130
}
4131

4132 4133 4134 4135 4136 4137 4138
/* 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;

4139 4140 4141 4142
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4143
 * hrtimer base being cleared by hrtimer_start. In the case of
4144 4145
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
4146 4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170
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;

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Peter Zijlstra 已提交
4171 4172 4173
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
4174 4175 4176 4177 4178 4179 4180 4181 4182 4183 4184 4185 4186 4187 4188 4189 4190 4191 4192 4193 4194 4195 4196 4197 4198 4199 4200 4201 4202
}

/* 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)
{
4203 4204 4205
	if (!cfs_bandwidth_used())
		return;

4206
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4207 4208 4209 4210 4211 4212 4213 4214 4215 4216 4217 4218 4219 4220 4221
		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 */
4222 4223 4224
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
4225
		return;
4226
	}
4227

4228
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4229
		runtime = cfs_b->runtime;
4230

4231 4232 4233 4234 4235 4236 4237 4238 4239 4240
	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)
4241
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4242 4243 4244
	raw_spin_unlock(&cfs_b->lock);
}

4245 4246 4247 4248 4249 4250 4251
/*
 * 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)
{
4252 4253 4254
	if (!cfs_bandwidth_used())
		return;

4255 4256 4257 4258 4259 4260 4261 4262 4263 4264 4265 4266 4267 4268
	/* 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);
}

4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282
static void sync_throttle(struct task_group *tg, int cpu)
{
	struct cfs_rq *pcfs_rq, *cfs_rq;

	if (!cfs_bandwidth_used())
		return;

	if (!tg->parent)
		return;

	cfs_rq = tg->cfs_rq[cpu];
	pcfs_rq = tg->parent->cfs_rq[cpu];

	cfs_rq->throttle_count = pcfs_rq->throttle_count;
4283
	cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu));
4284 4285
}

4286
/* conditionally throttle active cfs_rq's from put_prev_entity() */
4287
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4288
{
4289
	if (!cfs_bandwidth_used())
4290
		return false;
4291

4292
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4293
		return false;
4294 4295 4296 4297 4298 4299

	/*
	 * 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))
4300
		return true;
4301 4302

	throttle_cfs_rq(cfs_rq);
4303
	return true;
4304
}
4305 4306 4307 4308 4309

static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, slack_timer);
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Peter Zijlstra 已提交
4310

4311 4312 4313 4314 4315 4316 4317 4318 4319 4320 4321 4322
	do_sched_cfs_slack_timer(cfs_b);

	return HRTIMER_NORESTART;
}

static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, period_timer);
	int overrun;
	int idle = 0;

4323
	raw_spin_lock(&cfs_b->lock);
4324
	for (;;) {
P
Peter Zijlstra 已提交
4325
		overrun = hrtimer_forward_now(timer, cfs_b->period);
4326 4327 4328 4329 4330
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
P
Peter Zijlstra 已提交
4331 4332
	if (idle)
		cfs_b->period_active = 0;
4333
	raw_spin_unlock(&cfs_b->lock);
4334 4335 4336 4337 4338 4339 4340 4341 4342 4343 4344 4345

	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
}

void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
	raw_spin_lock_init(&cfs_b->lock);
	cfs_b->runtime = 0;
	cfs_b->quota = RUNTIME_INF;
	cfs_b->period = ns_to_ktime(default_cfs_period());

	INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
4346
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4347 4348 4349 4350 4351 4352 4353 4354 4355 4356 4357
	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);
}

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Peter Zijlstra 已提交
4358
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4359
{
P
Peter Zijlstra 已提交
4360
	lockdep_assert_held(&cfs_b->lock);
4361

P
Peter Zijlstra 已提交
4362 4363 4364 4365 4366
	if (!cfs_b->period_active) {
		cfs_b->period_active = 1;
		hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
		hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
	}
4367 4368 4369 4370
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4371 4372 4373 4374
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4375 4376 4377 4378
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

4379 4380 4381 4382 4383 4384 4385 4386 4387 4388 4389 4390 4391
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);
	}
}

4392
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4393 4394 4395 4396 4397 4398 4399 4400 4401 4402 4403
{
	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
		 */
4404
		cfs_rq->runtime_remaining = 1;
4405 4406 4407 4408 4409 4410
		/*
		 * 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;

4411 4412 4413 4414 4415 4416
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
}

#else /* CONFIG_CFS_BANDWIDTH */
4417 4418
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
4419
	return rq_clock_task(rq_of(cfs_rq));
4420 4421
}

4422
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4423
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4424
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4425
static inline void sync_throttle(struct task_group *tg, int cpu) {}
4426
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4427 4428 4429 4430 4431

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
4432 4433 4434 4435 4436 4437 4438 4439 4440 4441 4442

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;
}
4443 4444 4445 4446 4447

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) {}
4448 4449
#endif

4450 4451 4452 4453 4454
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) {}
4455
static inline void update_runtime_enabled(struct rq *rq) {}
4456
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4457 4458 4459

#endif /* CONFIG_CFS_BANDWIDTH */

4460 4461 4462 4463
/**************************************************
 * CFS operations on tasks:
 */

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Peter Zijlstra 已提交
4464 4465 4466 4467 4468 4469 4470 4471
#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);

4472
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
4473 4474 4475 4476 4477 4478
		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)
4479
				resched_curr(rq);
P
Peter Zijlstra 已提交
4480 4481
			return;
		}
4482
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
4483 4484
	}
}
4485 4486 4487 4488 4489 4490 4491 4492 4493 4494

/*
 * 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;

4495
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4496 4497 4498 4499 4500
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
4501
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
4502 4503 4504 4505
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
4506 4507 4508 4509

static inline void hrtick_update(struct rq *rq)
{
}
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Peter Zijlstra 已提交
4510 4511
#endif

4512 4513 4514 4515 4516
/*
 * 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:
 */
4517
static void
4518
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4519 4520
{
	struct cfs_rq *cfs_rq;
4521
	struct sched_entity *se = &p->se;
4522 4523

	for_each_sched_entity(se) {
4524
		if (se->on_rq)
4525 4526
			break;
		cfs_rq = cfs_rq_of(se);
4527
		enqueue_entity(cfs_rq, se, flags);
4528 4529 4530 4531 4532 4533

		/*
		 * 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.
4534
		 */
4535 4536
		if (cfs_rq_throttled(cfs_rq))
			break;
4537
		cfs_rq->h_nr_running++;
4538

4539
		flags = ENQUEUE_WAKEUP;
4540
	}
P
Peter Zijlstra 已提交
4541

P
Peter Zijlstra 已提交
4542
	for_each_sched_entity(se) {
4543
		cfs_rq = cfs_rq_of(se);
4544
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
4545

4546 4547 4548
		if (cfs_rq_throttled(cfs_rq))
			break;

4549
		update_load_avg(se, 1);
4550
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4551 4552
	}

Y
Yuyang Du 已提交
4553
	if (!se)
4554
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
4555

4556
	hrtick_update(rq);
4557 4558
}

4559 4560
static void set_next_buddy(struct sched_entity *se);

4561 4562 4563 4564 4565
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
4566
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4567 4568
{
	struct cfs_rq *cfs_rq;
4569
	struct sched_entity *se = &p->se;
4570
	int task_sleep = flags & DEQUEUE_SLEEP;
4571 4572 4573

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
4574
		dequeue_entity(cfs_rq, se, flags);
4575 4576 4577 4578 4579 4580 4581 4582 4583

		/*
		 * 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;
4584
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4585

4586
		/* Don't dequeue parent if it has other entities besides us */
4587
		if (cfs_rq->load.weight) {
4588 4589
			/* Avoid re-evaluating load for this entity: */
			se = parent_entity(se);
4590 4591 4592 4593
			/*
			 * Bias pick_next to pick a task from this cfs_rq, as
			 * p is sleeping when it is within its sched_slice.
			 */
4594 4595
			if (task_sleep && se && !throttled_hierarchy(cfs_rq))
				set_next_buddy(se);
4596
			break;
4597
		}
4598
		flags |= DEQUEUE_SLEEP;
4599
	}
P
Peter Zijlstra 已提交
4600

P
Peter Zijlstra 已提交
4601
	for_each_sched_entity(se) {
4602
		cfs_rq = cfs_rq_of(se);
4603
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4604

4605 4606 4607
		if (cfs_rq_throttled(cfs_rq))
			break;

4608
		update_load_avg(se, 1);
4609
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4610 4611
	}

Y
Yuyang Du 已提交
4612
	if (!se)
4613
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
4614

4615
	hrtick_update(rq);
4616 4617
}

4618
#ifdef CONFIG_SMP
4619
#ifdef CONFIG_NO_HZ_COMMON
4620 4621 4622 4623 4624
/*
 * per rq 'load' arrray crap; XXX kill this.
 */

/*
4625
 * The exact cpuload calculated at every tick would be:
4626
 *
4627 4628 4629 4630 4631 4632 4633
 *   load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
 *
 * If a cpu misses updates for n ticks (as it was idle) and update gets
 * called on the n+1-th tick when cpu may be busy, then we have:
 *
 *   load_n   = (1 - 1/2^i)^n * load_0
 *   load_n+1 = (1 - 1/2^i)   * load_n + (1/2^i) * cur_load
4634 4635 4636
 *
 * decay_load_missed() below does efficient calculation of
 *
4637 4638 4639 4640 4641 4642
 *   load' = (1 - 1/2^i)^n * load
 *
 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
 * This allows us to precompute the above in said factors, thereby allowing the
 * reduction of an arbitrary n in O(log_2 n) steps. (See also
 * fixed_power_int())
4643
 *
4644
 * The calculation is approximated on a 128 point scale.
4645 4646
 */
#define DEGRADE_SHIFT		7
4647 4648 4649 4650 4651 4652 4653 4654 4655

static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
	{   0,   0,  0,  0,  0,  0, 0, 0 },
	{  64,  32,  8,  0,  0,  0, 0, 0 },
	{  96,  72, 40, 12,  1,  0, 0, 0 },
	{ 112,  98, 75, 43, 15,  1, 0, 0 },
	{ 120, 112, 98, 76, 45, 16, 2, 0 }
};
4656 4657 4658 4659 4660 4661 4662 4663 4664 4665 4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680 4681 4682 4683 4684

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

	if (!missed_updates)
		return load;

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

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

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

		missed_updates >>= 1;
		j++;
	}
	return load;
}
4685
#endif /* CONFIG_NO_HZ_COMMON */
4686

4687
/**
4688
 * __cpu_load_update - update the rq->cpu_load[] statistics
4689 4690 4691 4692
 * @this_rq: The rq to update statistics for
 * @this_load: The current load
 * @pending_updates: The number of missed updates
 *
4693
 * Update rq->cpu_load[] statistics. This function is usually called every
4694 4695 4696 4697 4698 4699 4700 4701 4702 4703 4704 4705 4706 4707 4708 4709 4710 4711 4712 4713 4714 4715 4716 4717 4718 4719
 * scheduler tick (TICK_NSEC).
 *
 * This function computes a decaying average:
 *
 *   load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
 *
 * Because of NOHZ it might not get called on every tick which gives need for
 * the @pending_updates argument.
 *
 *   load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
 *             = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
 *             = A * (A * load[i]_n-2 + B) + B
 *             = A * (A * (A * load[i]_n-3 + B) + B) + B
 *             = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
 *             = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
 *             = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
 *             = (1 - 1/2^i)^n * (load[i]_0 - load) + load
 *
 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
 * any change in load would have resulted in the tick being turned back on.
 *
 * For regular NOHZ, this reduces to:
 *
 *   load[i]_n = (1 - 1/2^i)^n * load[i]_0
 *
 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
4720
 * term.
4721
 */
4722 4723
static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
			    unsigned long pending_updates)
4724
{
4725
	unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0];
4726 4727 4728 4729 4730 4731 4732 4733 4734 4735 4736
	int i, scale;

	this_rq->nr_load_updates++;

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

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

4737
		old_load = this_rq->cpu_load[i];
4738
#ifdef CONFIG_NO_HZ_COMMON
4739
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
4740 4741 4742 4743 4744 4745 4746 4747 4748
		if (tickless_load) {
			old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
			/*
			 * old_load can never be a negative value because a
			 * decayed tickless_load cannot be greater than the
			 * original tickless_load.
			 */
			old_load += tickless_load;
		}
4749
#endif
4750 4751 4752 4753 4754 4755 4756 4757 4758 4759 4760 4761 4762 4763 4764
		new_load = this_load;
		/*
		 * Round up the averaging division if load is increasing. This
		 * prevents us from getting stuck on 9 if the load is 10, for
		 * example.
		 */
		if (new_load > old_load)
			new_load += scale - 1;

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

	sched_avg_update(this_rq);
}

4765 4766 4767 4768 4769 4770
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
	return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
}

4771
#ifdef CONFIG_NO_HZ_COMMON
4772 4773 4774 4775 4776 4777 4778 4779 4780 4781 4782 4783 4784 4785 4786 4787 4788
/*
 * There is no sane way to deal with nohz on smp when using jiffies because the
 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
 *
 * Therefore we need to avoid the delta approach from the regular tick when
 * possible since that would seriously skew the load calculation. This is why we
 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
 * loop exit, nohz_idle_balance, nohz full exit...)
 *
 * This means we might still be one tick off for nohz periods.
 */

static void cpu_load_update_nohz(struct rq *this_rq,
				 unsigned long curr_jiffies,
				 unsigned long load)
4789 4790 4791 4792 4793 4794 4795 4796 4797 4798 4799
{
	unsigned long pending_updates;

	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
	if (pending_updates) {
		this_rq->last_load_update_tick = curr_jiffies;
		/*
		 * In the regular NOHZ case, we were idle, this means load 0.
		 * In the NOHZ_FULL case, we were non-idle, we should consider
		 * its weighted load.
		 */
4800
		cpu_load_update(this_rq, load, pending_updates);
4801 4802 4803
	}
}

4804 4805 4806 4807
/*
 * Called from nohz_idle_balance() to update the load ratings before doing the
 * idle balance.
 */
4808
static void cpu_load_update_idle(struct rq *this_rq)
4809 4810 4811 4812
{
	/*
	 * bail if there's load or we're actually up-to-date.
	 */
4813
	if (weighted_cpuload(cpu_of(this_rq)))
4814 4815
		return;

4816
	cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
4817 4818 4819
}

/*
4820 4821 4822 4823
 * Record CPU load on nohz entry so we know the tickless load to account
 * on nohz exit. cpu_load[0] happens then to be updated more frequently
 * than other cpu_load[idx] but it should be fine as cpu_load readers
 * shouldn't rely into synchronized cpu_load[*] updates.
4824
 */
4825
void cpu_load_update_nohz_start(void)
4826 4827
{
	struct rq *this_rq = this_rq();
4828 4829 4830 4831 4832 4833 4834 4835 4836 4837 4838 4839 4840 4841

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

/*
 * Account the tickless load in the end of a nohz frame.
 */
void cpu_load_update_nohz_stop(void)
{
4842
	unsigned long curr_jiffies = READ_ONCE(jiffies);
4843 4844
	struct rq *this_rq = this_rq();
	unsigned long load;
4845 4846 4847 4848

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

4849
	load = weighted_cpuload(cpu_of(this_rq));
4850
	raw_spin_lock(&this_rq->lock);
4851
	update_rq_clock(this_rq);
4852
	cpu_load_update_nohz(this_rq, curr_jiffies, load);
4853 4854
	raw_spin_unlock(&this_rq->lock);
}
4855 4856 4857 4858 4859 4860 4861 4862
#else /* !CONFIG_NO_HZ_COMMON */
static inline void cpu_load_update_nohz(struct rq *this_rq,
					unsigned long curr_jiffies,
					unsigned long load) { }
#endif /* CONFIG_NO_HZ_COMMON */

static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load)
{
4863
#ifdef CONFIG_NO_HZ_COMMON
4864 4865
	/* See the mess around cpu_load_update_nohz(). */
	this_rq->last_load_update_tick = READ_ONCE(jiffies);
4866
#endif
4867 4868
	cpu_load_update(this_rq, load, 1);
}
4869 4870 4871 4872

/*
 * Called from scheduler_tick()
 */
4873
void cpu_load_update_active(struct rq *this_rq)
4874
{
4875
	unsigned long load = weighted_cpuload(cpu_of(this_rq));
4876 4877 4878 4879 4880

	if (tick_nohz_tick_stopped())
		cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
	else
		cpu_load_update_periodic(this_rq, load);
4881 4882
}

4883 4884 4885 4886 4887 4888 4889 4890 4891 4892 4893 4894 4895 4896 4897 4898 4899 4900 4901 4902 4903 4904 4905 4906 4907 4908 4909 4910 4911 4912 4913 4914 4915
/*
 * 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);
}

4916
static unsigned long capacity_of(int cpu)
4917
{
4918
	return cpu_rq(cpu)->cpu_capacity;
4919 4920
}

4921 4922 4923 4924 4925
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

4926 4927 4928
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
4929
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4930
	unsigned long load_avg = weighted_cpuload(cpu);
4931 4932

	if (nr_running)
4933
		return load_avg / nr_running;
4934 4935 4936 4937

	return 0;
}

4938
#ifdef CONFIG_FAIR_GROUP_SCHED
4939 4940 4941 4942 4943 4944
/*
 * 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.
4945 4946 4947 4948 4949 4950 4951 4952 4953 4954 4955 4956 4957 4958 4959 4960 4961 4962 4963 4964 4965 4966 4967 4968 4969 4970 4971 4972 4973 4974 4975 4976 4977 4978 4979 4980 4981 4982 4983 4984 4985 4986 4987
 *
 * 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.
4988
 */
P
Peter Zijlstra 已提交
4989
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4990
{
P
Peter Zijlstra 已提交
4991
	struct sched_entity *se = tg->se[cpu];
4992

4993
	if (!tg->parent)	/* the trivial, non-cgroup case */
4994 4995
		return wl;

P
Peter Zijlstra 已提交
4996
	for_each_sched_entity(se) {
4997 4998
		struct cfs_rq *cfs_rq = se->my_q;
		long W, w = cfs_rq_load_avg(cfs_rq);
P
Peter Zijlstra 已提交
4999

5000
		tg = cfs_rq->tg;
5001

5002 5003 5004
		/*
		 * W = @wg + \Sum rw_j
		 */
5005 5006 5007 5008 5009
		W = wg + atomic_long_read(&tg->load_avg);

		/* Ensure \Sum rw_j >= rw_i */
		W -= cfs_rq->tg_load_avg_contrib;
		W += w;
P
Peter Zijlstra 已提交
5010

5011 5012 5013
		/*
		 * w = rw_i + @wl
		 */
5014
		w += wl;
5015

5016 5017 5018 5019
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
5020
			wl = (w * (long)tg->shares) / W;
5021 5022
		else
			wl = tg->shares;
5023

5024 5025 5026 5027 5028
		/*
		 * 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().
		 */
5029 5030
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
5031 5032 5033 5034

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
5035
		wl -= se->avg.load_avg;
5036 5037 5038 5039 5040 5041 5042 5043

		/*
		 * 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
5044 5045
		wg = 0;
	}
5046

P
Peter Zijlstra 已提交
5047
	return wl;
5048 5049
}
#else
P
Peter Zijlstra 已提交
5050

5051
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
P
Peter Zijlstra 已提交
5052
{
5053
	return wl;
5054
}
P
Peter Zijlstra 已提交
5055

5056 5057
#endif

P
Peter Zijlstra 已提交
5058 5059 5060 5061 5062 5063 5064 5065 5066 5067 5068 5069 5070 5071 5072 5073 5074
static void record_wakee(struct task_struct *p)
{
	/*
	 * Only decay a single time; tasks that have less then 1 wakeup per
	 * jiffy will not have built up many flips.
	 */
	if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
		current->wakee_flips >>= 1;
		current->wakee_flip_decay_ts = jiffies;
	}

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

M
Mike Galbraith 已提交
5075 5076
/*
 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
P
Peter Zijlstra 已提交
5077
 *
M
Mike Galbraith 已提交
5078
 * A waker of many should wake a different task than the one last awakened
P
Peter Zijlstra 已提交
5079 5080 5081 5082 5083 5084 5085 5086 5087 5088 5089 5090
 * at a frequency roughly N times higher than one of its wakees.
 *
 * In order to determine whether we should let the load spread vs consolidating
 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one
 * partner, and a factor of lls_size higher frequency in the other.
 *
 * With both conditions met, we can be relatively sure that the relationship is
 * non-monogamous, with partner count exceeding socket size.
 *
 * Waker/wakee being client/server, worker/dispatcher, interrupt source or
 * whatever is irrelevant, spread criteria is apparent partner count exceeds
 * socket size.
M
Mike Galbraith 已提交
5091
 */
5092 5093
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
5094 5095
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
5096
	int factor = this_cpu_read(sd_llc_size);
5097

M
Mike Galbraith 已提交
5098 5099 5100 5101 5102
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
5103 5104
}

5105 5106
static int wake_affine(struct sched_domain *sd, struct task_struct *p,
		       int prev_cpu, int sync)
5107
{
5108
	s64 this_load, load;
5109
	s64 this_eff_load, prev_eff_load;
5110
	int idx, this_cpu;
5111
	struct task_group *tg;
5112
	unsigned long weight;
5113
	int balanced;
5114

5115 5116 5117 5118
	idx	  = sd->wake_idx;
	this_cpu  = smp_processor_id();
	load	  = source_load(prev_cpu, idx);
	this_load = target_load(this_cpu, idx);
5119

5120 5121 5122 5123 5124
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
5125 5126
	if (sync) {
		tg = task_group(current);
5127
		weight = current->se.avg.load_avg;
5128

5129
		this_load += effective_load(tg, this_cpu, -weight, -weight);
5130 5131
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
5132

5133
	tg = task_group(p);
5134
	weight = p->se.avg.load_avg;
5135

5136 5137
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5138 5139 5140
	 * 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.
5141 5142 5143 5144
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
5145 5146
	this_eff_load = 100;
	this_eff_load *= capacity_of(prev_cpu);
5147

5148 5149
	prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= capacity_of(this_cpu);
5150

5151
	if (this_load > 0) {
5152 5153 5154 5155
		this_eff_load *= this_load +
			effective_load(tg, this_cpu, weight, weight);

		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
5156
	}
5157

5158
	balanced = this_eff_load <= prev_eff_load;
5159

5160
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
5161

5162 5163
	if (!balanced)
		return 0;
5164

5165 5166 5167 5168
	schedstat_inc(sd, ttwu_move_affine);
	schedstat_inc(p, se.statistics.nr_wakeups_affine);

	return 1;
5169 5170
}

5171 5172 5173 5174 5175
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
5176
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5177
		  int this_cpu, int sd_flag)
5178
{
5179
	struct sched_group *idlest = NULL, *group = sd->groups;
5180
	unsigned long min_load = ULONG_MAX, this_load = 0;
5181
	int load_idx = sd->forkexec_idx;
5182
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
5183

5184 5185 5186
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

5187 5188 5189 5190
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
5191

5192 5193
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
5194
					tsk_cpus_allowed(p)))
5195 5196 5197 5198 5199 5200 5201 5202 5203 5204 5205 5206 5207 5208 5209 5210 5211 5212
			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;
		}

5213
		/* Adjust by relative CPU capacity of the group */
5214
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
5215 5216 5217 5218 5219 5220 5221 5222 5223 5224 5225 5226 5227 5228 5229 5230 5231 5232 5233 5234 5235

		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;
5236 5237 5238 5239
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
5240 5241
	int i;

5242 5243 5244 5245
	/* Check if we have any choice: */
	if (group->group_weight == 1)
		return cpumask_first(sched_group_cpus(group));

5246
	/* Traverse only the allowed CPUs */
5247
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5248 5249 5250 5251 5252 5253 5254 5255 5256 5257 5258 5259 5260 5261 5262 5263 5264 5265 5266 5267 5268 5269
		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;
			}
5270
		} else if (shallowest_idle_cpu == -1) {
5271 5272 5273 5274 5275
			load = weighted_cpuload(i);
			if (load < min_load || (load == min_load && i == this_cpu)) {
				min_load = load;
				least_loaded_cpu = i;
			}
5276 5277 5278
		}
	}

5279
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5280
}
5281

5282 5283 5284
/*
 * Try and locate an idle CPU in the sched_domain.
 */
5285
static int select_idle_sibling(struct task_struct *p, int prev, int target)
5286
{
5287
	struct sched_domain *sd;
5288
	struct sched_group *sg;
5289

5290 5291
	if (idle_cpu(target))
		return target;
5292 5293

	/*
5294
	 * If the prevous cpu is cache affine and idle, don't be stupid.
5295
	 */
5296 5297
	if (prev != target && cpus_share_cache(prev, target) && idle_cpu(prev))
		return prev;
5298 5299

	/*
5300 5301 5302 5303 5304 5305 5306 5307 5308 5309 5310 5311 5312
	 * Otherwise, iterate the domains and find an eligible idle cpu.
	 *
	 * A completely idle sched group at higher domains is more
	 * desirable than an idle group at a lower level, because lower
	 * domains have smaller groups and usually share hardware
	 * resources which causes tasks to contend on them, e.g. x86
	 * hyperthread siblings in the lowest domain (SMT) can contend
	 * on the shared cpu pipeline.
	 *
	 * However, while we prefer idle groups at higher domains
	 * finding an idle cpu at the lowest domain is still better than
	 * returning 'target', which we've already established, isn't
	 * idle.
5313
	 */
5314
	sd = rcu_dereference(per_cpu(sd_llc, target));
5315
	for_each_lower_domain(sd) {
5316 5317
		sg = sd->groups;
		do {
5318 5319
			int i;

5320 5321 5322 5323
			if (!cpumask_intersects(sched_group_cpus(sg),
						tsk_cpus_allowed(p)))
				goto next;

5324
			/* Ensure the entire group is idle */
5325
			for_each_cpu(i, sched_group_cpus(sg)) {
5326
				if (i == target || !idle_cpu(i))
5327 5328
					goto next;
			}
5329

5330 5331 5332 5333
			/*
			 * It doesn't matter which cpu we pick, the
			 * whole group is idle.
			 */
5334 5335 5336 5337 5338 5339 5340 5341
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
5342 5343
	return target;
}
5344

5345
/*
5346
 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5347
 * tasks. The unit of the return value must be the one of capacity so we can
5348 5349
 * compare the utilization with the capacity of the CPU that is available for
 * CFS task (ie cpu_capacity).
5350 5351 5352 5353 5354 5355 5356 5357 5358 5359 5360 5361 5362 5363 5364 5365 5366 5367 5368 5369
 *
 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
 * recent utilization of currently non-runnable tasks on a CPU. It represents
 * the amount of utilization of a CPU in the range [0..capacity_orig] where
 * capacity_orig is the cpu_capacity available at the highest frequency
 * (arch_scale_freq_capacity()).
 * The utilization of a CPU converges towards a sum equal to or less than the
 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
 * the running time on this CPU scaled by capacity_curr.
 *
 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
 * higher than capacity_orig because of unfortunate rounding in
 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
 * the average stabilizes with the new running time. We need to check that the
 * utilization stays within the range of [0..capacity_orig] and cap it if
 * necessary. Without utilization capping, a group could be seen as overloaded
 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
 * available capacity. We allow utilization to overshoot capacity_curr (but not
 * capacity_orig) as it useful for predicting the capacity required after task
 * migrations (scheduler-driven DVFS).
5370
 */
5371
static int cpu_util(int cpu)
5372
{
5373
	unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
5374 5375
	unsigned long capacity = capacity_orig_of(cpu);

5376
	return (util >= capacity) ? capacity : util;
5377
}
5378

5379
/*
5380 5381 5382
 * 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.
5383
 *
5384 5385
 * 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.
5386
 *
5387
 * Returns the target cpu number.
5388 5389 5390
 *
 * preempt must be disabled.
 */
5391
static int
5392
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5393
{
5394
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5395
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
5396
	int new_cpu = prev_cpu;
5397
	int want_affine = 0;
5398
	int sync = wake_flags & WF_SYNC;
5399

P
Peter Zijlstra 已提交
5400 5401
	if (sd_flag & SD_BALANCE_WAKE) {
		record_wakee(p);
M
Mike Galbraith 已提交
5402
		want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
P
Peter Zijlstra 已提交
5403
	}
5404

5405
	rcu_read_lock();
5406
	for_each_domain(cpu, tmp) {
5407
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
5408
			break;
5409

5410
		/*
5411 5412
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
5413
		 */
5414 5415 5416
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
5417
			break;
5418
		}
5419

5420
		if (tmp->flags & sd_flag)
5421
			sd = tmp;
M
Mike Galbraith 已提交
5422 5423
		else if (!want_affine)
			break;
5424 5425
	}

M
Mike Galbraith 已提交
5426 5427
	if (affine_sd) {
		sd = NULL; /* Prefer wake_affine over balance flags */
5428
		if (cpu != prev_cpu && wake_affine(affine_sd, p, prev_cpu, sync))
M
Mike Galbraith 已提交
5429
			new_cpu = cpu;
5430
	}
5431

M
Mike Galbraith 已提交
5432 5433
	if (!sd) {
		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
5434
			new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
M
Mike Galbraith 已提交
5435 5436

	} else while (sd) {
5437
		struct sched_group *group;
5438
		int weight;
5439

5440
		if (!(sd->flags & sd_flag)) {
5441 5442 5443
			sd = sd->child;
			continue;
		}
5444

5445
		group = find_idlest_group(sd, p, cpu, sd_flag);
5446 5447 5448 5449
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
5450

5451
		new_cpu = find_idlest_cpu(group, p, cpu);
5452 5453 5454 5455
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
5456
		}
5457 5458 5459

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
5460
		weight = sd->span_weight;
5461 5462
		sd = NULL;
		for_each_domain(cpu, tmp) {
5463
			if (weight <= tmp->span_weight)
5464
				break;
5465
			if (tmp->flags & sd_flag)
5466 5467 5468
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
5469
	}
5470
	rcu_read_unlock();
5471

5472
	return new_cpu;
5473
}
5474 5475 5476 5477

/*
 * 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
5478
 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5479
 */
5480
static void migrate_task_rq_fair(struct task_struct *p)
5481
{
5482 5483 5484 5485 5486 5487 5488 5489 5490 5491 5492 5493 5494 5495 5496 5497 5498 5499 5500 5501 5502 5503 5504 5505 5506 5507
	/*
	 * As blocked tasks retain absolute vruntime the migration needs to
	 * deal with this by subtracting the old and adding the new
	 * min_vruntime -- the latter is done by enqueue_entity() when placing
	 * the task on the new runqueue.
	 */
	if (p->state == TASK_WAKING) {
		struct sched_entity *se = &p->se;
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
		u64 min_vruntime;

#ifndef CONFIG_64BIT
		u64 min_vruntime_copy;

		do {
			min_vruntime_copy = cfs_rq->min_vruntime_copy;
			smp_rmb();
			min_vruntime = cfs_rq->min_vruntime;
		} while (min_vruntime != min_vruntime_copy);
#else
		min_vruntime = cfs_rq->min_vruntime;
#endif

		se->vruntime -= min_vruntime;
	}

5508
	/*
5509 5510 5511 5512 5513
	 * We are supposed to update the task to "current" time, then its up to date
	 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
	 * what current time is, so simply throw away the out-of-date time. This
	 * will result in the wakee task is less decayed, but giving the wakee more
	 * load sounds not bad.
5514
	 */
5515 5516 5517 5518
	remove_entity_load_avg(&p->se);

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
5519 5520

	/* We have migrated, no longer consider this task hot */
5521
	p->se.exec_start = 0;
5522
}
5523 5524 5525 5526 5527

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
5528 5529
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
5530 5531
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5532 5533 5534 5535
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
5536 5537
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
5538 5539 5540 5541 5542 5543 5544 5545 5546
	 *
	 * 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.
5547
	 */
5548
	return calc_delta_fair(gran, se);
5549 5550
}

5551 5552 5553 5554 5555 5556 5557 5558 5559 5560 5561 5562 5563 5564 5565 5566 5567 5568 5569 5570 5571 5572
/*
 * 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
5573
	gran = wakeup_gran(curr, se);
5574 5575 5576 5577 5578 5579
	if (vdiff > gran)
		return 1;

	return 0;
}

5580 5581
static void set_last_buddy(struct sched_entity *se)
{
5582 5583 5584 5585 5586
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
5587 5588 5589 5590
}

static void set_next_buddy(struct sched_entity *se)
{
5591 5592 5593 5594 5595
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
5596 5597
}

5598 5599
static void set_skip_buddy(struct sched_entity *se)
{
5600 5601
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
5602 5603
}

5604 5605 5606
/*
 * Preempt the current task with a newly woken task if needed:
 */
5607
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5608 5609
{
	struct task_struct *curr = rq->curr;
5610
	struct sched_entity *se = &curr->se, *pse = &p->se;
5611
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5612
	int scale = cfs_rq->nr_running >= sched_nr_latency;
5613
	int next_buddy_marked = 0;
5614

I
Ingo Molnar 已提交
5615 5616 5617
	if (unlikely(se == pse))
		return;

5618
	/*
5619
	 * This is possible from callers such as attach_tasks(), in which we
5620 5621 5622 5623 5624 5625 5626
	 * 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;

5627
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
5628
		set_next_buddy(pse);
5629 5630
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
5631

5632 5633 5634
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
5635 5636 5637 5638 5639 5640
	 *
	 * 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.
5641 5642 5643 5644
	 */
	if (test_tsk_need_resched(curr))
		return;

5645 5646 5647 5648 5649
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

5650
	/*
5651 5652
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
5653
	 */
5654
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5655
		return;
5656

5657
	find_matching_se(&se, &pse);
5658
	update_curr(cfs_rq_of(se));
5659
	BUG_ON(!pse);
5660 5661 5662 5663 5664 5665 5666
	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);
5667
		goto preempt;
5668
	}
5669

5670
	return;
5671

5672
preempt:
5673
	resched_curr(rq);
5674 5675 5676 5677 5678 5679 5680 5681 5682 5683 5684 5685 5686 5687
	/*
	 * 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);
5688 5689
}

5690
static struct task_struct *
5691
pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct pin_cookie cookie)
5692 5693 5694
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
5695
	struct task_struct *p;
5696
	int new_tasks;
5697

5698
again:
5699 5700
#ifdef CONFIG_FAIR_GROUP_SCHED
	if (!cfs_rq->nr_running)
5701
		goto idle;
5702

5703
	if (prev->sched_class != &fair_sched_class)
5704 5705 5706 5707 5708 5709 5710 5711 5712 5713 5714 5715 5716 5717 5718 5719 5720 5721 5722
		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.
		 */
5723 5724 5725 5726 5727
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
5728

5729 5730 5731 5732 5733 5734 5735 5736 5737
			/*
			 * 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;
		}
5738 5739 5740 5741 5742 5743 5744 5745 5746 5747 5748 5749 5750 5751 5752 5753 5754 5755 5756 5757 5758 5759 5760 5761 5762 5763 5764 5765 5766 5767 5768 5769 5770 5771 5772 5773 5774 5775 5776 5777

		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
5778

5779
	if (!cfs_rq->nr_running)
5780
		goto idle;
5781

5782
	put_prev_task(rq, prev);
5783

5784
	do {
5785
		se = pick_next_entity(cfs_rq, NULL);
5786
		set_next_entity(cfs_rq, se);
5787 5788 5789
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
5790
	p = task_of(se);
5791

5792 5793
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
5794 5795

	return p;
5796 5797

idle:
5798 5799 5800 5801 5802 5803
	/*
	 * This is OK, because current is on_cpu, which avoids it being picked
	 * for load-balance and preemption/IRQs are still disabled avoiding
	 * further scheduler activity on it and we're being very careful to
	 * re-start the picking loop.
	 */
5804
	lockdep_unpin_lock(&rq->lock, cookie);
5805
	new_tasks = idle_balance(rq);
5806
	lockdep_repin_lock(&rq->lock, cookie);
5807 5808 5809 5810 5811
	/*
	 * 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.
	 */
5812
	if (new_tasks < 0)
5813 5814
		return RETRY_TASK;

5815
	if (new_tasks > 0)
5816 5817 5818
		goto again;

	return NULL;
5819 5820 5821 5822 5823
}

/*
 * Account for a descheduled task:
 */
5824
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5825 5826 5827 5828 5829 5830
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5831
		put_prev_entity(cfs_rq, se);
5832 5833 5834
	}
}

5835 5836 5837 5838 5839 5840 5841 5842 5843 5844 5845 5846 5847 5848 5849 5850 5851 5852 5853 5854 5855 5856 5857 5858 5859
/*
 * 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);
5860 5861 5862 5863 5864
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
5865
		rq_clock_skip_update(rq, true);
5866 5867 5868 5869 5870
	}

	set_skip_buddy(se);
}

5871 5872 5873 5874
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

5875 5876
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5877 5878 5879 5880 5881 5882 5883 5884 5885 5886
		return false;

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

	yield_task_fair(rq);

	return true;
}

5887
#ifdef CONFIG_SMP
5888
/**************************************************
P
Peter Zijlstra 已提交
5889 5890 5891 5892 5893 5894 5895 5896 5897 5898 5899 5900 5901 5902 5903 5904
 * 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
5905
 * is derived from the nice value as per sched_prio_to_weight[].
P
Peter Zijlstra 已提交
5906 5907 5908 5909 5910 5911
 *
 * 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)
 *
5912
 * C_i is the compute capacity of cpu i, typically it is the
P
Peter Zijlstra 已提交
5913 5914 5915 5916 5917 5918
 * 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):
 *
5919
 *   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
5920 5921 5922 5923 5924 5925 5926 5927 5928 5929 5930 5931 5932 5933 5934 5935 5936 5937 5938 5939 5940 5941 5942 5943 5944 5945 5946 5947 5948 5949 5950 5951 5952 5953 5954 5955 5956 5957 5958 5959 5960 5961 5962 5963 5964 5965 5966 5967 5968 5969 5970 5971 5972 5973 5974 5975 5976 5977 5978 5979 5980 5981 5982 5983 5984 5985 5986 5987 5988 5989 5990 5991 5992 5993 5994 5995 5996 5997 5998 5999 6000 6001 6002 6003 6004
 *
 * 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.]
 */ 
6005

6006 6007
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

6008 6009
enum fbq_type { regular, remote, all };

6010
#define LBF_ALL_PINNED	0x01
6011
#define LBF_NEED_BREAK	0x02
6012 6013
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
6014 6015 6016 6017 6018

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
6019
	int			src_cpu;
6020 6021 6022 6023

	int			dst_cpu;
	struct rq		*dst_rq;

6024 6025
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
6026
	enum cpu_idle_type	idle;
6027
	long			imbalance;
6028 6029 6030
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

6031
	unsigned int		flags;
6032 6033 6034 6035

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
6036 6037

	enum fbq_type		fbq_type;
6038
	struct list_head	tasks;
6039 6040
};

6041 6042 6043
/*
 * Is this task likely cache-hot:
 */
6044
static int task_hot(struct task_struct *p, struct lb_env *env)
6045 6046 6047
{
	s64 delta;

6048 6049
	lockdep_assert_held(&env->src_rq->lock);

6050 6051 6052 6053 6054 6055 6056 6057 6058
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
6059
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
6060 6061 6062 6063 6064 6065 6066 6067 6068
			(&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;

6069
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
6070 6071 6072 6073

	return delta < (s64)sysctl_sched_migration_cost;
}

6074
#ifdef CONFIG_NUMA_BALANCING
6075
/*
6076 6077 6078
 * Returns 1, if task migration degrades locality
 * Returns 0, if task migration improves locality i.e migration preferred.
 * Returns -1, if task migration is not affected by locality.
6079
 */
6080
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
6081
{
6082
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
6083
	unsigned long src_faults, dst_faults;
6084 6085
	int src_nid, dst_nid;

6086
	if (!static_branch_likely(&sched_numa_balancing))
6087 6088
		return -1;

6089
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
6090
		return -1;
6091 6092 6093 6094

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

6095
	if (src_nid == dst_nid)
6096
		return -1;
6097

6098 6099 6100 6101 6102 6103 6104
	/* Migrating away from the preferred node is always bad. */
	if (src_nid == p->numa_preferred_nid) {
		if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
			return 1;
		else
			return -1;
	}
6105

6106 6107
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
6108
		return 0;
6109

6110 6111 6112 6113 6114 6115
	if (numa_group) {
		src_faults = group_faults(p, src_nid);
		dst_faults = group_faults(p, dst_nid);
	} else {
		src_faults = task_faults(p, src_nid);
		dst_faults = task_faults(p, dst_nid);
6116 6117
	}

6118
	return dst_faults < src_faults;
6119 6120
}

6121
#else
6122
static inline int migrate_degrades_locality(struct task_struct *p,
6123 6124
					     struct lb_env *env)
{
6125
	return -1;
6126
}
6127 6128
#endif

6129 6130 6131 6132
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
6133
int can_migrate_task(struct task_struct *p, struct lb_env *env)
6134
{
6135
	int tsk_cache_hot;
6136 6137 6138

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

6139 6140
	/*
	 * We do not migrate tasks that are:
6141
	 * 1) throttled_lb_pair, or
6142
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
6143 6144
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
6145
	 */
6146 6147 6148
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

6149
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
6150
		int cpu;
6151

6152
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
6153

6154 6155
		env->flags |= LBF_SOME_PINNED;

6156 6157 6158 6159 6160 6161 6162 6163
		/*
		 * 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.
		 */
6164
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
6165 6166
			return 0;

6167 6168 6169
		/* 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))) {
6170
				env->flags |= LBF_DST_PINNED;
6171 6172 6173
				env->new_dst_cpu = cpu;
				break;
			}
6174
		}
6175

6176 6177
		return 0;
	}
6178 6179

	/* Record that we found atleast one task that could run on dst_cpu */
6180
	env->flags &= ~LBF_ALL_PINNED;
6181

6182
	if (task_running(env->src_rq, p)) {
6183
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
6184 6185 6186 6187 6188
		return 0;
	}

	/*
	 * Aggressive migration if:
6189 6190 6191
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
6192
	 */
6193 6194 6195
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
6196

6197
	if (tsk_cache_hot <= 0 ||
6198
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6199
		if (tsk_cache_hot == 1) {
6200 6201 6202
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
			schedstat_inc(p, se.statistics.nr_forced_migrations);
		}
6203 6204 6205
		return 1;
	}

Z
Zhang Hang 已提交
6206 6207
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
6208 6209
}

6210
/*
6211 6212 6213 6214 6215 6216 6217
 * detach_task() -- detach the task for the migration specified in env
 */
static void detach_task(struct task_struct *p, struct lb_env *env)
{
	lockdep_assert_held(&env->src_rq->lock);

	p->on_rq = TASK_ON_RQ_MIGRATING;
6218
	deactivate_task(env->src_rq, p, 0);
6219 6220 6221
	set_task_cpu(p, env->dst_cpu);
}

6222
/*
6223
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6224 6225
 * part of active balancing operations within "domain".
 *
6226
 * Returns a task if successful and NULL otherwise.
6227
 */
6228
static struct task_struct *detach_one_task(struct lb_env *env)
6229 6230 6231
{
	struct task_struct *p, *n;

6232 6233
	lockdep_assert_held(&env->src_rq->lock);

6234 6235 6236
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
6237

6238
		detach_task(p, env);
6239

6240
		/*
6241
		 * Right now, this is only the second place where
6242
		 * lb_gained[env->idle] is updated (other is detach_tasks)
6243
		 * so we can safely collect stats here rather than
6244
		 * inside detach_tasks().
6245 6246
		 */
		schedstat_inc(env->sd, lb_gained[env->idle]);
6247
		return p;
6248
	}
6249
	return NULL;
6250 6251
}

6252 6253
static const unsigned int sched_nr_migrate_break = 32;

6254
/*
6255 6256
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
6257
 *
6258
 * Returns number of detached tasks if successful and 0 otherwise.
6259
 */
6260
static int detach_tasks(struct lb_env *env)
6261
{
6262 6263
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
6264
	unsigned long load;
6265 6266 6267
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
6268

6269
	if (env->imbalance <= 0)
6270
		return 0;
6271

6272
	while (!list_empty(tasks)) {
6273 6274 6275 6276 6277 6278 6279
		/*
		 * We don't want to steal all, otherwise we may be treated likewise,
		 * which could at worst lead to a livelock crash.
		 */
		if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
			break;

6280
		p = list_first_entry(tasks, struct task_struct, se.group_node);
6281

6282 6283
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
6284
		if (env->loop > env->loop_max)
6285
			break;
6286 6287

		/* take a breather every nr_migrate tasks */
6288
		if (env->loop > env->loop_break) {
6289
			env->loop_break += sched_nr_migrate_break;
6290
			env->flags |= LBF_NEED_BREAK;
6291
			break;
6292
		}
6293

6294
		if (!can_migrate_task(p, env))
6295 6296 6297
			goto next;

		load = task_h_load(p);
6298

6299
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6300 6301
			goto next;

6302
		if ((load / 2) > env->imbalance)
6303
			goto next;
6304

6305 6306 6307 6308
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
6309
		env->imbalance -= load;
6310 6311

#ifdef CONFIG_PREEMPT
6312 6313
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
6314
		 * kernels will stop after the first task is detached to minimize
6315 6316
		 * the critical section.
		 */
6317
		if (env->idle == CPU_NEWLY_IDLE)
6318
			break;
6319 6320
#endif

6321 6322 6323 6324
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
6325
		if (env->imbalance <= 0)
6326
			break;
6327 6328 6329

		continue;
next:
6330
		list_move_tail(&p->se.group_node, tasks);
6331
	}
6332

6333
	/*
6334 6335 6336
	 * 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().
6337
	 */
6338
	schedstat_add(env->sd, lb_gained[env->idle], detached);
6339

6340 6341 6342 6343 6344 6345 6346 6347 6348 6349 6350 6351
	return detached;
}

/*
 * attach_task() -- attach the task detached by detach_task() to its new rq.
 */
static void attach_task(struct rq *rq, struct task_struct *p)
{
	lockdep_assert_held(&rq->lock);

	BUG_ON(task_rq(p) != rq);
	activate_task(rq, p, 0);
6352
	p->on_rq = TASK_ON_RQ_QUEUED;
6353 6354 6355 6356 6357 6358 6359 6360 6361 6362 6363 6364 6365 6366 6367 6368 6369 6370 6371 6372 6373 6374 6375 6376 6377 6378 6379 6380
	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);
6381

6382 6383 6384 6385
		attach_task(env->dst_rq, p);
	}

	raw_spin_unlock(&env->dst_rq->lock);
6386 6387
}

P
Peter Zijlstra 已提交
6388
#ifdef CONFIG_FAIR_GROUP_SCHED
6389
static void update_blocked_averages(int cpu)
6390 6391
{
	struct rq *rq = cpu_rq(cpu);
6392 6393
	struct cfs_rq *cfs_rq;
	unsigned long flags;
6394

6395 6396
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
6397

6398 6399 6400 6401
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
6402
	for_each_leaf_cfs_rq(rq, cfs_rq) {
6403 6404 6405
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
6406

6407
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true))
6408 6409
			update_tg_load_avg(cfs_rq, 0);
	}
6410
	raw_spin_unlock_irqrestore(&rq->lock, flags);
6411 6412
}

6413
/*
6414
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6415 6416 6417
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
6418
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6419
{
6420 6421
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6422
	unsigned long now = jiffies;
6423
	unsigned long load;
6424

6425
	if (cfs_rq->last_h_load_update == now)
6426 6427
		return;

6428 6429 6430 6431 6432 6433 6434
	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;
	}
6435

6436
	if (!se) {
6437
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6438 6439 6440 6441 6442
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
6443 6444
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
6445 6446 6447 6448
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
6449 6450
}

6451
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
6452
{
6453
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
6454

6455
	update_cfs_rq_h_load(cfs_rq);
6456
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6457
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
6458 6459
}
#else
6460
static inline void update_blocked_averages(int cpu)
6461
{
6462 6463 6464 6465 6466 6467
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
	unsigned long flags;

	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
6468
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true);
6469
	raw_spin_unlock_irqrestore(&rq->lock, flags);
6470 6471
}

6472
static unsigned long task_h_load(struct task_struct *p)
6473
{
6474
	return p->se.avg.load_avg;
6475
}
P
Peter Zijlstra 已提交
6476
#endif
6477 6478

/********** Helpers for find_busiest_group ************************/
6479 6480 6481 6482 6483 6484 6485

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

6486 6487 6488 6489 6490 6491 6492
/*
 * 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
6493
	unsigned long load_per_task;
6494
	unsigned long group_capacity;
6495
	unsigned long group_util; /* Total utilization of the group */
6496 6497 6498
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
6499
	enum group_type group_type;
6500
	int group_no_capacity;
6501 6502 6503 6504
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
6505 6506
};

J
Joonsoo Kim 已提交
6507 6508 6509 6510 6511 6512 6513 6514
/*
 * 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 */
6515
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
6516 6517 6518
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6519
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
6520 6521
};

6522 6523 6524 6525 6526 6527 6528 6529 6530 6531 6532 6533
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,
6534
		.total_capacity = 0UL,
6535 6536
		.busiest_stat = {
			.avg_load = 0UL,
6537 6538
			.sum_nr_running = 0,
			.group_type = group_other,
6539 6540 6541 6542
		},
	};
}

6543 6544 6545
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
6546
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6547 6548
 *
 * Return: The load index.
6549 6550 6551 6552 6553 6554 6555 6556 6557 6558 6559 6560 6561 6562 6563 6564 6565 6566 6567 6568 6569 6570
 */
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;
}

6571
static unsigned long scale_rt_capacity(int cpu)
6572 6573
{
	struct rq *rq = cpu_rq(cpu);
6574
	u64 total, used, age_stamp, avg;
6575
	s64 delta;
6576

6577 6578 6579 6580
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
6581 6582
	age_stamp = READ_ONCE(rq->age_stamp);
	avg = READ_ONCE(rq->rt_avg);
6583
	delta = __rq_clock_broken(rq) - age_stamp;
6584

6585 6586 6587 6588
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
6589

6590
	used = div_u64(avg, total);
6591

6592 6593
	if (likely(used < SCHED_CAPACITY_SCALE))
		return SCHED_CAPACITY_SCALE - used;
6594

6595
	return 1;
6596 6597
}

6598
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6599
{
6600
	unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6601 6602
	struct sched_group *sdg = sd->groups;

6603
	cpu_rq(cpu)->cpu_capacity_orig = capacity;
6604

6605
	capacity *= scale_rt_capacity(cpu);
6606
	capacity >>= SCHED_CAPACITY_SHIFT;
6607

6608 6609
	if (!capacity)
		capacity = 1;
6610

6611 6612
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
6613 6614
}

6615
void update_group_capacity(struct sched_domain *sd, int cpu)
6616 6617 6618
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
6619
	unsigned long capacity;
6620 6621 6622 6623
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
6624
	sdg->sgc->next_update = jiffies + interval;
6625 6626

	if (!child) {
6627
		update_cpu_capacity(sd, cpu);
6628 6629 6630
		return;
	}

6631
	capacity = 0;
6632

P
Peter Zijlstra 已提交
6633 6634 6635 6636 6637 6638
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

6639
		for_each_cpu(cpu, sched_group_cpus(sdg)) {
6640
			struct sched_group_capacity *sgc;
6641
			struct rq *rq = cpu_rq(cpu);
6642

6643
			/*
6644
			 * build_sched_domains() -> init_sched_groups_capacity()
6645 6646 6647
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
6648 6649
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
6650
			 *
6651
			 * This avoids capacity from being 0 and
6652 6653 6654
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
6655
				capacity += capacity_of(cpu);
6656 6657
				continue;
			}
6658

6659 6660
			sgc = rq->sd->groups->sgc;
			capacity += sgc->capacity;
6661
		}
P
Peter Zijlstra 已提交
6662 6663 6664 6665 6666 6667 6668 6669
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
6670
			capacity += group->sgc->capacity;
P
Peter Zijlstra 已提交
6671 6672 6673
			group = group->next;
		} while (group != child->groups);
	}
6674

6675
	sdg->sgc->capacity = capacity;
6676 6677
}

6678
/*
6679 6680 6681
 * Check whether the capacity of the rq has been noticeably reduced by side
 * activity. The imbalance_pct is used for the threshold.
 * Return true is the capacity is reduced
6682 6683
 */
static inline int
6684
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6685
{
6686 6687
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
6688 6689
}

6690 6691 6692 6693 6694 6695 6696 6697 6698 6699 6700 6701 6702 6703 6704 6705
/*
 * 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
6706 6707
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
6708 6709
 *
 * When this is so detected; this group becomes a candidate for busiest; see
6710
 * update_sd_pick_busiest(). And calculate_imbalance() and
6711
 * find_busiest_group() avoid some of the usual balance conditions to allow it
6712 6713 6714 6715 6716 6717 6718
 * 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.
 */

6719
static inline int sg_imbalanced(struct sched_group *group)
6720
{
6721
	return group->sgc->imbalance;
6722 6723
}

6724
/*
6725 6726 6727
 * group_has_capacity returns true if the group has spare capacity that could
 * be used by some tasks.
 * We consider that a group has spare capacity if the  * number of task is
6728 6729
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
6730 6731 6732 6733 6734
 * For the latter, we use a threshold to stabilize the state, to take into
 * account the variance of the tasks' load and to return true if the available
 * capacity in meaningful for the load balancer.
 * As an example, an available capacity of 1% can appear but it doesn't make
 * any benefit for the load balance.
6735
 */
6736 6737
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6738
{
6739 6740
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
6741

6742
	if ((sgs->group_capacity * 100) >
6743
			(sgs->group_util * env->sd->imbalance_pct))
6744
		return true;
6745

6746 6747 6748 6749 6750 6751 6752 6753 6754 6755 6756 6757 6758 6759 6760 6761
	return false;
}

/*
 *  group_is_overloaded returns true if the group has more tasks than it can
 *  handle.
 *  group_is_overloaded is not equals to !group_has_capacity because a group
 *  with the exact right number of tasks, has no more spare capacity but is not
 *  overloaded so both group_has_capacity and group_is_overloaded return
 *  false.
 */
static inline bool
group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
{
	if (sgs->sum_nr_running <= sgs->group_weight)
		return false;
6762

6763
	if ((sgs->group_capacity * 100) <
6764
			(sgs->group_util * env->sd->imbalance_pct))
6765
		return true;
6766

6767
	return false;
6768 6769
}

6770 6771 6772
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
6773
{
6774
	if (sgs->group_no_capacity)
6775 6776 6777 6778 6779 6780 6781 6782
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

6783 6784
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6785
 * @env: The load balancing environment.
6786 6787 6788 6789
 * @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.
6790
 * @overload: Indicate more than one runnable task for any CPU.
6791
 */
6792 6793
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
6794 6795
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
6796
{
6797
	unsigned long load;
6798
	int i, nr_running;
6799

6800 6801
	memset(sgs, 0, sizeof(*sgs));

6802
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6803 6804 6805
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
6806
		if (local_group)
6807
			load = target_load(i, load_idx);
6808
		else
6809 6810 6811
			load = source_load(i, load_idx);

		sgs->group_load += load;
6812
		sgs->group_util += cpu_util(i);
6813
		sgs->sum_nr_running += rq->cfs.h_nr_running;
6814

6815 6816
		nr_running = rq->nr_running;
		if (nr_running > 1)
6817 6818
			*overload = true;

6819 6820 6821 6822
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
6823
		sgs->sum_weighted_load += weighted_cpuload(i);
6824 6825 6826 6827
		/*
		 * No need to call idle_cpu() if nr_running is not 0
		 */
		if (!nr_running && idle_cpu(i))
6828
			sgs->idle_cpus++;
6829 6830
	}

6831 6832
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
6833
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6834

6835
	if (sgs->sum_nr_running)
6836
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6837

6838
	sgs->group_weight = group->group_weight;
6839

6840
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
6841
	sgs->group_type = group_classify(group, sgs);
6842 6843
}

6844 6845
/**
 * update_sd_pick_busiest - return 1 on busiest group
6846
 * @env: The load balancing environment.
6847 6848
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
6849
 * @sgs: sched_group statistics
6850 6851 6852
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
6853 6854 6855
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
6856
 */
6857
static bool update_sd_pick_busiest(struct lb_env *env,
6858 6859
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
6860
				   struct sg_lb_stats *sgs)
6861
{
6862
	struct sg_lb_stats *busiest = &sds->busiest_stat;
6863

6864
	if (sgs->group_type > busiest->group_type)
6865 6866
		return true;

6867 6868 6869 6870 6871 6872 6873 6874
	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))
6875 6876
		return true;

6877 6878 6879
	/* No ASYM_PACKING if target cpu is already busy */
	if (env->idle == CPU_NOT_IDLE)
		return true;
6880 6881 6882 6883 6884
	/*
	 * 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.
	 */
6885
	if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6886 6887 6888
		if (!sds->busiest)
			return true;

6889 6890
		/* Prefer to move from highest possible cpu's work */
		if (group_first_cpu(sds->busiest) < group_first_cpu(sg))
6891 6892 6893 6894 6895 6896
			return true;
	}

	return false;
}

6897 6898 6899 6900 6901 6902 6903 6904 6905 6906 6907 6908 6909 6910 6911 6912 6913 6914 6915 6916 6917 6918 6919 6920 6921 6922 6923 6924 6925 6926
#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 */

6927
/**
6928
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6929
 * @env: The load balancing environment.
6930 6931
 * @sds: variable to hold the statistics for this sched_domain.
 */
6932
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6933
{
6934 6935
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
6936
	struct sg_lb_stats tmp_sgs;
6937
	int load_idx, prefer_sibling = 0;
6938
	bool overload = false;
6939 6940 6941 6942

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

6943
	load_idx = get_sd_load_idx(env->sd, env->idle);
6944 6945

	do {
J
Joonsoo Kim 已提交
6946
		struct sg_lb_stats *sgs = &tmp_sgs;
6947 6948
		int local_group;

6949
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
6950 6951 6952
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
6953 6954

			if (env->idle != CPU_NEWLY_IDLE ||
6955 6956
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
6957
		}
6958

6959 6960
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
6961

6962 6963 6964
		if (local_group)
			goto next_group;

6965 6966
		/*
		 * In case the child domain prefers tasks go to siblings
6967
		 * first, lower the sg capacity so that we'll try
6968 6969
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
6970 6971 6972 6973
		 * these excess tasks. The extra check prevents the case where
		 * you always pull from the heaviest group when it is already
		 * under-utilized (possible with a large weight task outweighs
		 * the tasks on the system).
6974
		 */
6975
		if (prefer_sibling && sds->local &&
6976 6977 6978
		    group_has_capacity(env, &sds->local_stat) &&
		    (sgs->sum_nr_running > 1)) {
			sgs->group_no_capacity = 1;
6979
			sgs->group_type = group_classify(sg, sgs);
6980
		}
6981

6982
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6983
			sds->busiest = sg;
J
Joonsoo Kim 已提交
6984
			sds->busiest_stat = *sgs;
6985 6986
		}

6987 6988 6989
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
6990
		sds->total_capacity += sgs->group_capacity;
6991

6992
		sg = sg->next;
6993
	} while (sg != env->sd->groups);
6994 6995 6996

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6997 6998 6999 7000 7001 7002 7003

	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;
	}

7004 7005 7006 7007 7008 7009 7010 7011 7012 7013 7014 7015 7016 7017 7018 7019 7020 7021 7022
}

/**
 * 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.
 *
7023
 * Return: 1 when packing is required and a task should be moved to
7024 7025
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
7026
 * @env: The load balancing environment.
7027 7028
 * @sds: Statistics of the sched_domain which is to be packed
 */
7029
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
7030 7031 7032
{
	int busiest_cpu;

7033
	if (!(env->sd->flags & SD_ASYM_PACKING))
7034 7035
		return 0;

7036 7037 7038
	if (env->idle == CPU_NOT_IDLE)
		return 0;

7039 7040 7041 7042
	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
7043
	if (env->dst_cpu > busiest_cpu)
7044 7045
		return 0;

7046
	env->imbalance = DIV_ROUND_CLOSEST(
7047
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
7048
		SCHED_CAPACITY_SCALE);
7049

7050
	return 1;
7051 7052 7053 7054 7055 7056
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
7057
 * @env: The load balancing environment.
7058 7059
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
7060 7061
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7062
{
7063
	unsigned long tmp, capa_now = 0, capa_move = 0;
7064
	unsigned int imbn = 2;
7065
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
7066
	struct sg_lb_stats *local, *busiest;
7067

J
Joonsoo Kim 已提交
7068 7069
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
7070

J
Joonsoo Kim 已提交
7071 7072 7073 7074
	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;
7075

J
Joonsoo Kim 已提交
7076
	scaled_busy_load_per_task =
7077
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7078
		busiest->group_capacity;
J
Joonsoo Kim 已提交
7079

7080 7081
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
7082
		env->imbalance = busiest->load_per_task;
7083 7084 7085 7086 7087
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
7088
	 * however we may be able to increase total CPU capacity used by
7089 7090 7091
	 * moving them.
	 */

7092
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
7093
			min(busiest->load_per_task, busiest->avg_load);
7094
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
7095
			min(local->load_per_task, local->avg_load);
7096
	capa_now /= SCHED_CAPACITY_SCALE;
7097 7098

	/* Amount of load we'd subtract */
7099
	if (busiest->avg_load > scaled_busy_load_per_task) {
7100
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
7101
			    min(busiest->load_per_task,
7102
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
7103
	}
7104 7105

	/* Amount of load we'd add */
7106
	if (busiest->avg_load * busiest->group_capacity <
7107
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
7108 7109
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
7110
	} else {
7111
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
7112
		      local->group_capacity;
J
Joonsoo Kim 已提交
7113
	}
7114
	capa_move += local->group_capacity *
7115
		    min(local->load_per_task, local->avg_load + tmp);
7116
	capa_move /= SCHED_CAPACITY_SCALE;
7117 7118

	/* Move if we gain throughput */
7119
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
7120
		env->imbalance = busiest->load_per_task;
7121 7122 7123 7124 7125
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
7126
 * @env: load balance environment
7127 7128
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
7129
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
7130
{
7131
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
7132 7133 7134 7135
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
7136

7137
	if (busiest->group_type == group_imbalanced) {
7138 7139 7140 7141
		/*
		 * 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
7142 7143
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
7144 7145
	}

7146
	/*
7147 7148 7149 7150
	 * Avg load of busiest sg can be less and avg load of local sg can
	 * be greater than avg load across all sgs of sd because avg load
	 * factors in sg capacity and sgs with smaller group_type are
	 * skipped when updating the busiest sg:
7151
	 */
7152 7153
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
7154 7155
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
7156 7157
	}

7158 7159 7160 7161 7162
	/*
	 * If there aren't any idle cpus, avoid creating some.
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
7163
		load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE;
7164
		if (load_above_capacity > busiest->group_capacity) {
7165
			load_above_capacity -= busiest->group_capacity;
7166 7167 7168
			load_above_capacity *= NICE_0_LOAD;
			load_above_capacity /= busiest->group_capacity;
		} else
7169
			load_above_capacity = ~0UL;
7170 7171 7172 7173 7174 7175
	}

	/*
	 * 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,
7176 7177
	 * we also don't want to reduce the group load below the group
	 * capacity. Thus we look for the minimum possible imbalance.
7178
	 */
7179
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7180 7181

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
7182
	env->imbalance = min(
7183 7184
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
7185
	) / SCHED_CAPACITY_SCALE;
7186 7187 7188

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
7189
	 * there is no guarantee that any tasks will be moved so we'll have
7190 7191 7192
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
7193
	if (env->imbalance < busiest->load_per_task)
7194
		return fix_small_imbalance(env, sds);
7195
}
7196

7197 7198 7199 7200
/******* find_busiest_group() helpers end here *********************/

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
7201
 * if there is an imbalance.
7202 7203 7204 7205
 *
 * Also calculates the amount of weighted load which should be moved
 * to restore balance.
 *
7206
 * @env: The load balancing environment.
7207
 *
7208
 * Return:	- The busiest group if imbalance exists.
7209
 */
J
Joonsoo Kim 已提交
7210
static struct sched_group *find_busiest_group(struct lb_env *env)
7211
{
J
Joonsoo Kim 已提交
7212
	struct sg_lb_stats *local, *busiest;
7213 7214
	struct sd_lb_stats sds;

7215
	init_sd_lb_stats(&sds);
7216 7217 7218 7219 7220

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
7221
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
7222 7223
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
7224

7225
	/* ASYM feature bypasses nice load balance check */
7226
	if (check_asym_packing(env, &sds))
7227 7228
		return sds.busiest;

7229
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
7230
	if (!sds.busiest || busiest->sum_nr_running == 0)
7231 7232
		goto out_balanced;

7233 7234
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
7235

P
Peter Zijlstra 已提交
7236 7237
	/*
	 * If the busiest group is imbalanced the below checks don't
7238
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
7239 7240
	 * isn't true due to cpus_allowed constraints and the like.
	 */
7241
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
7242 7243
		goto force_balance;

7244
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7245 7246
	if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
	    busiest->group_no_capacity)
7247 7248
		goto force_balance;

7249
	/*
7250
	 * If the local group is busier than the selected busiest group
7251 7252
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
7253
	if (local->avg_load >= busiest->avg_load)
7254 7255
		goto out_balanced;

7256 7257 7258 7259
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
7260
	if (local->avg_load >= sds.avg_load)
7261 7262
		goto out_balanced;

7263
	if (env->idle == CPU_IDLE) {
7264
		/*
7265 7266 7267 7268 7269
		 * 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
7270
		 */
7271 7272
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
7273
			goto out_balanced;
7274 7275 7276 7277 7278
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
7279 7280
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
7281
			goto out_balanced;
7282
	}
7283

7284
force_balance:
7285
	/* Looks like there is an imbalance. Compute it */
7286
	calculate_imbalance(env, &sds);
7287 7288 7289
	return sds.busiest;

out_balanced:
7290
	env->imbalance = 0;
7291 7292 7293 7294 7295 7296
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
7297
static struct rq *find_busiest_queue(struct lb_env *env,
7298
				     struct sched_group *group)
7299 7300
{
	struct rq *busiest = NULL, *rq;
7301
	unsigned long busiest_load = 0, busiest_capacity = 1;
7302 7303
	int i;

7304
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7305
		unsigned long capacity, wl;
7306 7307 7308 7309
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
7310

7311 7312 7313 7314 7315 7316 7317 7318 7319 7320 7321 7322 7323 7324 7325 7326 7327 7328 7329 7330 7331 7332
		/*
		 * 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;

7333
		capacity = capacity_of(i);
7334

7335
		wl = weighted_cpuload(i);
7336

7337 7338
		/*
		 * When comparing with imbalance, use weighted_cpuload()
7339
		 * which is not scaled with the cpu capacity.
7340
		 */
7341 7342 7343

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
7344 7345
			continue;

7346 7347
		/*
		 * For the load comparisons with the other cpu's, consider
7348 7349 7350
		 * 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.
7351
		 *
7352
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
7353
		 * multiplication to rid ourselves of the division works out
7354 7355
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
7356
		 */
7357
		if (wl * busiest_capacity > busiest_load * capacity) {
7358
			busiest_load = wl;
7359
			busiest_capacity = capacity;
7360 7361 7362 7363 7364 7365 7366 7367 7368 7369 7370 7371 7372 7373
			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. */
7374
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
7375

7376
static int need_active_balance(struct lb_env *env)
7377
{
7378 7379 7380
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
7381 7382 7383 7384 7385 7386

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
7387
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7388
			return 1;
7389 7390
	}

7391 7392 7393 7394 7395 7396 7397 7398 7399 7400 7401 7402 7403
	/*
	 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
	 * It's worth migrating the task if the src_cpu's capacity is reduced
	 * because of other sched_class or IRQs if more capacity stays
	 * available on dst_cpu.
	 */
	if ((env->idle != CPU_NOT_IDLE) &&
	    (env->src_rq->cfs.h_nr_running == 1)) {
		if ((check_cpu_capacity(env->src_rq, sd)) &&
		    (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
			return 1;
	}

7404 7405 7406
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

7407 7408
static int active_load_balance_cpu_stop(void *data);

7409 7410 7411 7412 7413 7414 7415 7416 7417 7418 7419 7420 7421 7422 7423 7424 7425 7426 7427 7428 7429 7430 7431 7432 7433 7434 7435 7436 7437 7438 7439
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.
	 */
7440
	return balance_cpu == env->dst_cpu;
7441 7442
}

7443 7444 7445 7446 7447 7448
/*
 * 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,
7449
			int *continue_balancing)
7450
{
7451
	int ld_moved, cur_ld_moved, active_balance = 0;
7452
	struct sched_domain *sd_parent = sd->parent;
7453 7454 7455
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
7456
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7457

7458 7459
	struct lb_env env = {
		.sd		= sd,
7460 7461
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
7462
		.dst_grpmask    = sched_group_cpus(sd->groups),
7463
		.idle		= idle,
7464
		.loop_break	= sched_nr_migrate_break,
7465
		.cpus		= cpus,
7466
		.fbq_type	= all,
7467
		.tasks		= LIST_HEAD_INIT(env.tasks),
7468 7469
	};

7470 7471 7472 7473
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
7474
	if (idle == CPU_NEWLY_IDLE)
7475 7476
		env.dst_grpmask = NULL;

7477 7478 7479 7480 7481
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
7482 7483
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
7484
		goto out_balanced;
7485
	}
7486

7487
	group = find_busiest_group(&env);
7488 7489 7490 7491 7492
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

7493
	busiest = find_busiest_queue(&env, group);
7494 7495 7496 7497 7498
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

7499
	BUG_ON(busiest == env.dst_rq);
7500

7501
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7502

7503 7504 7505
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

7506 7507 7508 7509 7510 7511 7512 7513
	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.
		 */
7514
		env.flags |= LBF_ALL_PINNED;
7515
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
7516

7517
more_balance:
7518
		raw_spin_lock_irqsave(&busiest->lock, flags);
7519 7520 7521 7522 7523

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
7524
		cur_ld_moved = detach_tasks(&env);
7525 7526

		/*
7527 7528 7529 7530 7531
		 * 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.
7532
		 */
7533 7534 7535 7536 7537 7538 7539 7540

		raw_spin_unlock(&busiest->lock);

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

7541
		local_irq_restore(flags);
7542

7543 7544 7545 7546 7547
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

7548 7549 7550 7551 7552 7553 7554 7555 7556 7557 7558 7559 7560 7561 7562 7563 7564 7565 7566
		/*
		 * 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.
		 */
7567
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7568

7569 7570 7571
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

7572
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
7573
			env.dst_cpu	 = env.new_dst_cpu;
7574
			env.flags	&= ~LBF_DST_PINNED;
7575 7576
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
7577

7578 7579 7580 7581 7582 7583
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
7584

7585 7586 7587 7588
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
7589
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7590

7591
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7592 7593 7594
				*group_imbalance = 1;
		}

7595
		/* All tasks on this runqueue were pinned by CPU affinity */
7596
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
7597
			cpumask_clear_cpu(cpu_of(busiest), cpus);
7598 7599 7600
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
7601
				goto redo;
7602
			}
7603
			goto out_all_pinned;
7604 7605 7606 7607 7608
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
7609 7610 7611 7612 7613 7614 7615 7616
		/*
		 * 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++;
7617

7618
		if (need_active_balance(&env)) {
7619 7620
			raw_spin_lock_irqsave(&busiest->lock, flags);

7621 7622 7623
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
7624 7625
			 */
			if (!cpumask_test_cpu(this_cpu,
7626
					tsk_cpus_allowed(busiest->curr))) {
7627 7628
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
7629
				env.flags |= LBF_ALL_PINNED;
7630 7631 7632
				goto out_one_pinned;
			}

7633 7634 7635 7636 7637
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
7638 7639 7640 7641 7642 7643
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
7644

7645
			if (active_balance) {
7646 7647 7648
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
7649
			}
7650

7651
			/* We've kicked active balancing, force task migration. */
7652 7653 7654 7655 7656 7657 7658 7659 7660 7661 7662 7663 7664
			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
7665
		 * detach_tasks).
7666 7667 7668 7669 7670 7671 7672 7673
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
7674 7675 7676 7677 7678 7679 7680 7681 7682 7683 7684 7685 7686 7687 7688 7689 7690
	/*
	 * 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.
	 */
7691 7692 7693 7694 7695 7696
	schedstat_inc(sd, lb_balanced[idle]);

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
7697
	if (((env.flags & LBF_ALL_PINNED) &&
7698
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
7699 7700 7701
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

7702
	ld_moved = 0;
7703 7704 7705 7706
out:
	return ld_moved;
}

7707 7708 7709 7710 7711 7712 7713 7714 7715 7716 7717 7718 7719 7720 7721 7722
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
7723
update_next_balance(struct sched_domain *sd, unsigned long *next_balance)
7724 7725 7726
{
	unsigned long interval, next;

7727 7728
	/* used by idle balance, so cpu_busy = 0 */
	interval = get_sd_balance_interval(sd, 0);
7729 7730 7731 7732 7733 7734
	next = sd->last_balance + interval;

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

7735 7736 7737 7738
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
7739
static int idle_balance(struct rq *this_rq)
7740
{
7741 7742
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
7743 7744
	struct sched_domain *sd;
	int pulled_task = 0;
7745
	u64 curr_cost = 0;
7746

7747 7748 7749 7750 7751 7752
	/*
	 * 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);

7753 7754
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
7755 7756 7757
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
7758
			update_next_balance(sd, &next_balance);
7759 7760
		rcu_read_unlock();

7761
		goto out;
7762
	}
7763

7764 7765
	raw_spin_unlock(&this_rq->lock);

7766
	update_blocked_averages(this_cpu);
7767
	rcu_read_lock();
7768
	for_each_domain(this_cpu, sd) {
7769
		int continue_balancing = 1;
7770
		u64 t0, domain_cost;
7771 7772 7773 7774

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

7775
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
7776
			update_next_balance(sd, &next_balance);
7777
			break;
7778
		}
7779

7780
		if (sd->flags & SD_BALANCE_NEWIDLE) {
7781 7782
			t0 = sched_clock_cpu(this_cpu);

7783
			pulled_task = load_balance(this_cpu, this_rq,
7784 7785
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
7786 7787 7788 7789 7790 7791

			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;
7792
		}
7793

7794
		update_next_balance(sd, &next_balance);
7795 7796 7797 7798 7799 7800

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
7801 7802
			break;
	}
7803
	rcu_read_unlock();
7804 7805 7806

	raw_spin_lock(&this_rq->lock);

7807 7808 7809
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

7810
	/*
7811 7812 7813
	 * 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.
7814
	 */
7815
	if (this_rq->cfs.h_nr_running && !pulled_task)
7816
		pulled_task = 1;
7817

7818 7819 7820
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
7821
		this_rq->next_balance = next_balance;
7822

7823
	/* Is there a task of a high priority class? */
7824
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7825 7826
		pulled_task = -1;

7827
	if (pulled_task)
7828 7829
		this_rq->idle_stamp = 0;

7830
	return pulled_task;
7831 7832 7833
}

/*
7834 7835 7836 7837
 * 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.
7838
 */
7839
static int active_load_balance_cpu_stop(void *data)
7840
{
7841 7842
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
7843
	int target_cpu = busiest_rq->push_cpu;
7844
	struct rq *target_rq = cpu_rq(target_cpu);
7845
	struct sched_domain *sd;
7846
	struct task_struct *p = NULL;
7847 7848 7849 7850 7851 7852 7853

	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;
7854 7855 7856

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
7857
		goto out_unlock;
7858 7859 7860 7861 7862 7863 7864 7865 7866

	/*
	 * 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. */
7867
	rcu_read_lock();
7868 7869 7870 7871 7872 7873 7874
	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)) {
7875 7876
		struct lb_env env = {
			.sd		= sd,
7877 7878 7879 7880
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
7881 7882 7883
			.idle		= CPU_IDLE,
		};

7884 7885
		schedstat_inc(sd, alb_count);

7886
		p = detach_one_task(&env);
7887
		if (p) {
7888
			schedstat_inc(sd, alb_pushed);
7889 7890 7891
			/* Active balancing done, reset the failure counter. */
			sd->nr_balance_failed = 0;
		} else {
7892
			schedstat_inc(sd, alb_failed);
7893
		}
7894
	}
7895
	rcu_read_unlock();
7896 7897
out_unlock:
	busiest_rq->active_balance = 0;
7898 7899 7900 7901 7902 7903 7904
	raw_spin_unlock(&busiest_rq->lock);

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

7905
	return 0;
7906 7907
}

7908 7909 7910 7911 7912
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

7913
#ifdef CONFIG_NO_HZ_COMMON
7914 7915 7916 7917 7918 7919
/*
 * 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.
 */
7920
static struct {
7921
	cpumask_var_t idle_cpus_mask;
7922
	atomic_t nr_cpus;
7923 7924
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
7925

7926
static inline int find_new_ilb(void)
7927
{
7928
	int ilb = cpumask_first(nohz.idle_cpus_mask);
7929

7930 7931 7932 7933
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
7934 7935
}

7936 7937 7938 7939 7940
/*
 * 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).
 */
7941
static void nohz_balancer_kick(void)
7942 7943 7944 7945 7946
{
	int ilb_cpu;

	nohz.next_balance++;

7947
	ilb_cpu = find_new_ilb();
7948

7949 7950
	if (ilb_cpu >= nr_cpu_ids)
		return;
7951

7952
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7953 7954 7955 7956 7957 7958 7959 7960
		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);
7961 7962 7963
	return;
}

7964
void nohz_balance_exit_idle(unsigned int cpu)
7965 7966
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7967 7968 7969 7970 7971 7972 7973
		/*
		 * 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);
		}
7974 7975 7976 7977
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

7978 7979 7980
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
7981
	int cpu = smp_processor_id();
7982 7983

	rcu_read_lock();
7984
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7985 7986 7987 7988 7989

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

7990
	atomic_inc(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7991
unlock:
7992 7993 7994 7995 7996 7997
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
7998
	int cpu = smp_processor_id();
7999 8000

	rcu_read_lock();
8001
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
8002 8003 8004 8005 8006

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

8007
	atomic_dec(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
8008
unlock:
8009 8010 8011
	rcu_read_unlock();
}

8012
/*
8013
 * This routine will record that the cpu is going idle with tick stopped.
8014
 * This info will be used in performing idle load balancing in the future.
8015
 */
8016
void nohz_balance_enter_idle(int cpu)
8017
{
8018 8019 8020 8021 8022 8023
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

8024 8025
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
8026

8027 8028 8029 8030 8031 8032
	/*
	 * If we're a completely isolated CPU, we don't play.
	 */
	if (on_null_domain(cpu_rq(cpu)))
		return;

8033 8034 8035
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
8036 8037 8038 8039 8040
}
#endif

static DEFINE_SPINLOCK(balancing);

8041 8042 8043 8044
/*
 * 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.
 */
8045
void update_max_interval(void)
8046 8047 8048 8049
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

8050 8051 8052 8053
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
8054
 * Balancing parameters are set up in init_sched_domains.
8055
 */
8056
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
8057
{
8058
	int continue_balancing = 1;
8059
	int cpu = rq->cpu;
8060
	unsigned long interval;
8061
	struct sched_domain *sd;
8062 8063 8064
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
8065 8066
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
8067

8068
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
8069

8070
	rcu_read_lock();
8071
	for_each_domain(cpu, sd) {
8072 8073 8074 8075 8076 8077 8078 8079 8080 8081 8082 8083
		/*
		 * 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;

8084 8085 8086
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

8087 8088 8089 8090 8091 8092 8093 8094 8095 8096 8097
		/*
		 * 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;
		}

8098
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8099 8100 8101 8102 8103 8104 8105 8106

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

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
8107
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
8108
				/*
8109
				 * The LBF_DST_PINNED logic could have changed
8110 8111
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
8112
				 */
8113
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
8114 8115
			}
			sd->last_balance = jiffies;
8116
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
8117 8118 8119 8120 8121 8122 8123 8124
		}
		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;
		}
8125 8126
	}
	if (need_decay) {
8127
		/*
8128 8129
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
8130
		 */
8131 8132
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
8133
	}
8134
	rcu_read_unlock();
8135 8136 8137 8138 8139 8140

	/*
	 * 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.
	 */
8141
	if (likely(update_next_balance)) {
8142
		rq->next_balance = next_balance;
8143 8144 8145 8146 8147 8148 8149 8150 8151 8152 8153 8154 8155 8156

#ifdef CONFIG_NO_HZ_COMMON
		/*
		 * If this CPU has been elected to perform the nohz idle
		 * balance. Other idle CPUs have already rebalanced with
		 * nohz_idle_balance() and nohz.next_balance has been
		 * updated accordingly. This CPU is now running the idle load
		 * balance for itself and we need to update the
		 * nohz.next_balance accordingly.
		 */
		if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
			nohz.next_balance = rq->next_balance;
#endif
	}
8157 8158
}

8159
#ifdef CONFIG_NO_HZ_COMMON
8160
/*
8161
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8162 8163
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
8164
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
8165
{
8166
	int this_cpu = this_rq->cpu;
8167 8168
	struct rq *rq;
	int balance_cpu;
8169 8170 8171
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
8172

8173 8174 8175
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
8176 8177

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8178
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8179 8180 8181 8182 8183 8184 8185
			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.
		 */
8186
		if (need_resched())
8187 8188
			break;

V
Vincent Guittot 已提交
8189 8190
		rq = cpu_rq(balance_cpu);

8191 8192 8193 8194 8195 8196 8197
		/*
		 * 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);
8198
			cpu_load_update_idle(rq);
8199 8200 8201
			raw_spin_unlock_irq(&rq->lock);
			rebalance_domains(rq, CPU_IDLE);
		}
8202

8203 8204 8205 8206
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
8207
	}
8208 8209 8210 8211 8212 8213 8214 8215

	/*
	 * next_balance will be updated only when there is a need.
	 * When the CPU is attached to null domain for ex, it will not be
	 * updated.
	 */
	if (likely(update_next_balance))
		nohz.next_balance = next_balance;
8216 8217
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8218 8219 8220
}

/*
8221
 * Current heuristic for kicking the idle load balancer in the presence
8222
 * of an idle cpu in the system.
8223
 *   - This rq has more than one task.
8224 8225 8226 8227
 *   - This rq has at least one CFS task and the capacity of the CPU is
 *     significantly reduced because of RT tasks or IRQs.
 *   - At parent of LLC scheduler domain level, this cpu's scheduler group has
 *     multiple busy cpu.
8228 8229
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
8230
 */
8231
static inline bool nohz_kick_needed(struct rq *rq)
8232 8233
{
	unsigned long now = jiffies;
8234
	struct sched_domain *sd;
8235
	struct sched_group_capacity *sgc;
8236
	int nr_busy, cpu = rq->cpu;
8237
	bool kick = false;
8238

8239
	if (unlikely(rq->idle_balance))
8240
		return false;
8241

8242 8243 8244 8245
       /*
	* 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.
	*/
8246
	set_cpu_sd_state_busy();
8247
	nohz_balance_exit_idle(cpu);
8248 8249 8250 8251 8252 8253

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
8254
		return false;
8255 8256

	if (time_before(now, nohz.next_balance))
8257
		return false;
8258

8259
	if (rq->nr_running >= 2)
8260
		return true;
8261

8262
	rcu_read_lock();
8263 8264
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
	if (sd) {
8265 8266
		sgc = sd->groups->sgc;
		nr_busy = atomic_read(&sgc->nr_busy_cpus);
8267

8268 8269 8270 8271 8272
		if (nr_busy > 1) {
			kick = true;
			goto unlock;
		}

8273
	}
8274

8275 8276 8277 8278 8279 8280 8281 8282
	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
			kick = true;
			goto unlock;
		}
	}
8283

8284
	sd = rcu_dereference(per_cpu(sd_asym, cpu));
8285
	if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
8286 8287 8288 8289
				  sched_domain_span(sd)) < cpu)) {
		kick = true;
		goto unlock;
	}
8290

8291
unlock:
8292
	rcu_read_unlock();
8293
	return kick;
8294 8295
}
#else
8296
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8297 8298 8299 8300 8301 8302
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
8303 8304
static void run_rebalance_domains(struct softirq_action *h)
{
8305
	struct rq *this_rq = this_rq();
8306
	enum cpu_idle_type idle = this_rq->idle_balance ?
8307 8308 8309
						CPU_IDLE : CPU_NOT_IDLE;

	/*
8310
	 * If this cpu has a pending nohz_balance_kick, then do the
8311
	 * balancing on behalf of the other idle cpus whose ticks are
8312 8313 8314 8315
	 * stopped. Do nohz_idle_balance *before* rebalance_domains to
	 * give the idle cpus a chance to load balance. Else we may
	 * load balance only within the local sched_domain hierarchy
	 * and abort nohz_idle_balance altogether if we pull some load.
8316
	 */
8317
	nohz_idle_balance(this_rq, idle);
8318
	rebalance_domains(this_rq, idle);
8319 8320 8321 8322 8323
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
8324
void trigger_load_balance(struct rq *rq)
8325 8326
{
	/* Don't need to rebalance while attached to NULL domain */
8327 8328 8329 8330
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
8331
		raise_softirq(SCHED_SOFTIRQ);
8332
#ifdef CONFIG_NO_HZ_COMMON
8333
	if (nohz_kick_needed(rq))
8334
		nohz_balancer_kick();
8335
#endif
8336 8337
}

8338 8339 8340
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
8341 8342

	update_runtime_enabled(rq);
8343 8344 8345 8346 8347
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
8348 8349 8350

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
8351 8352
}

8353
#endif /* CONFIG_SMP */
8354

8355 8356 8357
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
8358
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8359 8360 8361 8362 8363 8364
{
	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
8365
		entity_tick(cfs_rq, se, queued);
8366
	}
8367

8368
	if (static_branch_unlikely(&sched_numa_balancing))
8369
		task_tick_numa(rq, curr);
8370 8371 8372
}

/*
P
Peter Zijlstra 已提交
8373 8374 8375
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
8376
 */
P
Peter Zijlstra 已提交
8377
static void task_fork_fair(struct task_struct *p)
8378
{
8379 8380
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
P
Peter Zijlstra 已提交
8381
	struct rq *rq = this_rq();
8382

8383
	raw_spin_lock(&rq->lock);
8384 8385
	update_rq_clock(rq);

8386 8387
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;
8388 8389
	if (curr) {
		update_curr(cfs_rq);
8390
		se->vruntime = curr->vruntime;
8391
	}
8392
	place_entity(cfs_rq, se, 1);
8393

P
Peter Zijlstra 已提交
8394
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
8395
		/*
8396 8397 8398
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
8399
		swap(curr->vruntime, se->vruntime);
8400
		resched_curr(rq);
8401
	}
8402

8403
	se->vruntime -= cfs_rq->min_vruntime;
8404
	raw_spin_unlock(&rq->lock);
8405 8406
}

8407 8408 8409 8410
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
8411 8412
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8413
{
8414
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
8415 8416
		return;

8417 8418 8419 8420 8421
	/*
	 * 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
8422
	if (rq->curr == p) {
8423
		if (p->prio > oldprio)
8424
			resched_curr(rq);
8425
	} else
8426
		check_preempt_curr(rq, p, 0);
8427 8428
}

8429
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
8430 8431 8432 8433
{
	struct sched_entity *se = &p->se;

	/*
8434 8435 8436 8437 8438 8439 8440 8441 8442 8443
	 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
	 * the dequeue_entity(.flags=0) will already have normalized the
	 * vruntime.
	 */
	if (p->on_rq)
		return true;

	/*
	 * When !on_rq, vruntime of the task has usually NOT been normalized.
	 * But there are some cases where it has already been normalized:
P
Peter Zijlstra 已提交
8444
	 *
8445 8446 8447 8448
	 * - A forked child which is waiting for being woken up by
	 *   wake_up_new_task().
	 * - A task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
P
Peter Zijlstra 已提交
8449
	 */
8450 8451 8452 8453 8454 8455 8456 8457 8458 8459
	if (!se->sum_exec_runtime || p->state == TASK_WAKING)
		return true;

	return false;
}

static void detach_task_cfs_rq(struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
8460
	u64 now = cfs_rq_clock_task(cfs_rq);
8461 8462

	if (!vruntime_normalized(p)) {
P
Peter Zijlstra 已提交
8463 8464 8465 8466 8467 8468 8469
		/*
		 * 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;
	}
8470

8471
	/* Catch up with the cfs_rq and remove our load when we leave */
8472
	update_cfs_rq_load_avg(now, cfs_rq, false);
8473
	detach_entity_load_avg(cfs_rq, se);
8474
	update_tg_load_avg(cfs_rq, false);
P
Peter Zijlstra 已提交
8475 8476
}

8477
static void attach_task_cfs_rq(struct task_struct *p)
8478
{
8479
	struct sched_entity *se = &p->se;
8480
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
8481
	u64 now = cfs_rq_clock_task(cfs_rq);
8482 8483

#ifdef CONFIG_FAIR_GROUP_SCHED
8484 8485 8486 8487 8488 8489
	/*
	 * 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
8490

8491
	/* Synchronize task with its cfs_rq */
8492
	update_cfs_rq_load_avg(now, cfs_rq, false);
8493
	attach_entity_load_avg(cfs_rq, se);
8494
	update_tg_load_avg(cfs_rq, false);
8495 8496 8497 8498

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
8499

8500 8501 8502 8503 8504 8505 8506 8507
static void switched_from_fair(struct rq *rq, struct task_struct *p)
{
	detach_task_cfs_rq(p);
}

static void switched_to_fair(struct rq *rq, struct task_struct *p)
{
	attach_task_cfs_rq(p);
8508

8509
	if (task_on_rq_queued(p)) {
8510
		/*
8511 8512 8513
		 * 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.
8514
		 */
8515 8516 8517 8518
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
8519
	}
8520 8521
}

8522 8523 8524 8525 8526 8527 8528 8529 8530
/* 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;

8531 8532 8533 8534 8535 8536 8537
	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);
	}
8538 8539
}

8540 8541 8542 8543 8544 8545 8546
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
8547
#ifdef CONFIG_SMP
8548 8549
	atomic_long_set(&cfs_rq->removed_load_avg, 0);
	atomic_long_set(&cfs_rq->removed_util_avg, 0);
8550
#endif
8551 8552
}

P
Peter Zijlstra 已提交
8553
#ifdef CONFIG_FAIR_GROUP_SCHED
8554 8555 8556 8557 8558 8559 8560 8561
static void task_set_group_fair(struct task_struct *p)
{
	struct sched_entity *se = &p->se;

	set_task_rq(p, task_cpu(p));
	se->depth = se->parent ? se->parent->depth + 1 : 0;
}

8562
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
8563
{
8564
	detach_task_cfs_rq(p);
8565
	set_task_rq(p, task_cpu(p));
8566 8567 8568 8569 8570

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
8571
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
8572
}
8573

8574 8575 8576 8577 8578 8579 8580 8581 8582 8583 8584 8585 8586
static void task_change_group_fair(struct task_struct *p, int type)
{
	switch (type) {
	case TASK_SET_GROUP:
		task_set_group_fair(p);
		break;

	case TASK_MOVE_GROUP:
		task_move_group_fair(p);
		break;
	}
}

8587 8588 8589 8590 8591 8592 8593 8594 8595
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]);
8596
		if (tg->se)
8597 8598 8599 8600 8601 8602 8603 8604 8605 8606
			kfree(tg->se[i]);
	}

	kfree(tg->cfs_rq);
	kfree(tg->se);
}

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
	struct sched_entity *se;
8607 8608
	struct cfs_rq *cfs_rq;
	struct rq *rq;
8609 8610 8611 8612 8613 8614 8615 8616 8617 8618 8619 8620 8621 8622
	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) {
8623 8624
		rq = cpu_rq(i);

8625 8626 8627 8628 8629 8630 8631 8632 8633 8634 8635 8636
		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]);
8637
		init_entity_runnable_average(se);
8638 8639 8640 8641 8642 8643 8644 8645 8646 8647
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

8648 8649 8650 8651 8652 8653 8654 8655 8656 8657 8658 8659
void online_fair_sched_group(struct task_group *tg)
{
	struct sched_entity *se;
	struct rq *rq;
	int i;

	for_each_possible_cpu(i) {
		rq = cpu_rq(i);
		se = tg->se[i];

		raw_spin_lock_irq(&rq->lock);
		post_init_entity_util_avg(se);
8660
		sync_throttle(tg, i);
8661 8662 8663 8664
		raw_spin_unlock_irq(&rq->lock);
	}
}

8665
void unregister_fair_sched_group(struct task_group *tg)
8666 8667
{
	unsigned long flags;
8668 8669
	struct rq *rq;
	int cpu;
8670

8671 8672 8673
	for_each_possible_cpu(cpu) {
		if (tg->se[cpu])
			remove_entity_load_avg(tg->se[cpu]);
8674

8675 8676 8677 8678 8679 8680 8681 8682 8683 8684 8685 8686 8687
		/*
		 * Only empty task groups can be destroyed; so we can speculatively
		 * check on_list without danger of it being re-added.
		 */
		if (!tg->cfs_rq[cpu]->on_list)
			continue;

		rq = cpu_rq(cpu);

		raw_spin_lock_irqsave(&rq->lock, flags);
		list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
		raw_spin_unlock_irqrestore(&rq->lock, flags);
	}
8688 8689 8690 8691 8692 8693 8694 8695 8696 8697 8698 8699 8700 8701 8702 8703 8704 8705 8706
}

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
8707
	if (!parent) {
8708
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
8709 8710
		se->depth = 0;
	} else {
8711
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
8712 8713
		se->depth = parent->depth + 1;
	}
8714 8715

	se->my_q = cfs_rq;
8716 8717
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
8718 8719 8720 8721 8722 8723 8724 8725 8726 8727 8728 8729 8730 8731 8732 8733 8734 8735 8736 8737 8738 8739 8740 8741 8742 8743 8744 8745 8746 8747
	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);
8748 8749 8750

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
8751
		for_each_sched_entity(se)
8752 8753 8754 8755 8756 8757 8758 8759 8760 8761 8762 8763 8764 8765 8766 8767 8768
			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;
}

8769 8770
void online_fair_sched_group(struct task_group *tg) { }

8771
void unregister_fair_sched_group(struct task_group *tg) { }
8772 8773 8774

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
8775

8776
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8777 8778 8779 8780 8781 8782 8783 8784 8785
{
	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)
8786
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8787 8788 8789 8790

	return rr_interval;
}

8791 8792 8793
/*
 * All the scheduling class methods:
 */
8794
const struct sched_class fair_sched_class = {
8795
	.next			= &idle_sched_class,
8796 8797 8798
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
8799
	.yield_to_task		= yield_to_task_fair,
8800

I
Ingo Molnar 已提交
8801
	.check_preempt_curr	= check_preempt_wakeup,
8802 8803 8804 8805

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

8806
#ifdef CONFIG_SMP
L
Li Zefan 已提交
8807
	.select_task_rq		= select_task_rq_fair,
8808
	.migrate_task_rq	= migrate_task_rq_fair,
8809

8810 8811
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
8812

8813
	.task_dead		= task_dead_fair,
8814
	.set_cpus_allowed	= set_cpus_allowed_common,
8815
#endif
8816

8817
	.set_curr_task          = set_curr_task_fair,
8818
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
8819
	.task_fork		= task_fork_fair,
8820 8821

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
8822
	.switched_from		= switched_from_fair,
8823
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
8824

8825 8826
	.get_rr_interval	= get_rr_interval_fair,

8827 8828
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
8829
#ifdef CONFIG_FAIR_GROUP_SCHED
8830
	.task_change_group	= task_change_group_fair,
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Peter Zijlstra 已提交
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#endif
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};

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

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	rcu_read_lock();
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	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
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		print_cfs_rq(m, cpu, cfs_rq);
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	rcu_read_unlock();
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}
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#ifdef CONFIG_NUMA_BALANCING
void show_numa_stats(struct task_struct *p, struct seq_file *m)
{
	int node;
	unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;

	for_each_online_node(node) {
		if (p->numa_faults) {
			tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
			tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
		}
		if (p->numa_group) {
			gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
			gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
		}
		print_numa_stats(m, node, tsf, tpf, gsf, gpf);
	}
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_SCHED_DEBUG */
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__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

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#ifdef CONFIG_NO_HZ_COMMON
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	nohz.next_balance = jiffies;
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	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
#endif
#endif /* SMP */

}