fair.c 197.2 KB
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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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 */

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

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

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

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

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

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

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

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

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

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

	return factor;
}

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

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

void sched_init_granularity(void)
{
	update_sysctl();
}

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

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

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

	w = scale_load_down(lw->weight);

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

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


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

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

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

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

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

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

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

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static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
				       int force_update);
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static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (!cfs_rq->on_list) {
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		/*
		 * Ensure we either appear before our parent (if already
		 * enqueued) or force our parent to appear after us when it is
		 * enqueued.  The fact that we always enqueue bottom-up
		 * reduces this to two cases.
		 */
		if (cfs_rq->tg->parent &&
		    cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
			list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
				&rq_of(cfs_rq)->leaf_cfs_rq_list);
		} else {
			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
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				&rq_of(cfs_rq)->leaf_cfs_rq_list);
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		}
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		cfs_rq->on_list = 1;
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		/* We should have no load, but we need to update last_decay. */
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		update_cfs_rq_blocked_load(cfs_rq, 0);
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	}
}

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

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

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

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

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

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

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

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

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

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#else	/* !CONFIG_FAIR_GROUP_SCHED */

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

#define entity_is_task(se)	1

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

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

	return &rq->cfs;
}

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

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

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

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

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

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

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#endif	/* CONFIG_FAIR_GROUP_SCHED */

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

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

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

	return min_vruntime;
}

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

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

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

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

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

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

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

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

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

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

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

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

	if (!left)
		return NULL;

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

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

	if (!next)
		return NULL;

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

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

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

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

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

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

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

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

	return period;
}

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

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/*
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 * We calculate the vruntime slice of a to-be-inserted task.
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 *
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 * vs = s/w
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 */
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static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
664
	return calc_delta_fair(sched_slice(cfs_rq, se), se);
665 666
}

667
#ifdef CONFIG_SMP
668 669
static unsigned long task_h_load(struct task_struct *p);

670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688
static inline void __update_task_entity_contrib(struct sched_entity *se);

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

	p->se.avg.decay_count = 0;
	slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
	p->se.avg.runnable_avg_sum = slice;
	p->se.avg.runnable_avg_period = slice;
	__update_task_entity_contrib(&p->se);
}
#else
void init_task_runnable_average(struct task_struct *p)
{
}
#endif

689
/*
690
 * Update the current task's runtime statistics.
691
 */
692
static void update_curr(struct cfs_rq *cfs_rq)
693
{
694
	struct sched_entity *curr = cfs_rq->curr;
695
	u64 now = rq_clock_task(rq_of(cfs_rq));
696
	u64 delta_exec;
697 698 699 700

	if (unlikely(!curr))
		return;

701 702
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
703
		return;
704

I
Ingo Molnar 已提交
705
	curr->exec_start = now;
706

707 708 709 710 711 712 713 714 715
	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);

716 717 718
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

719
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
720
		cpuacct_charge(curtask, delta_exec);
721
		account_group_exec_runtime(curtask, delta_exec);
722
	}
723 724

	account_cfs_rq_runtime(cfs_rq, delta_exec);
725 726 727
}

static inline void
728
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
729
{
730
	schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
731 732 733 734 735
}

/*
 * Task is being enqueued - update stats:
 */
736
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
737 738 739 740 741
{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
742
	if (se != cfs_rq->curr)
743
		update_stats_wait_start(cfs_rq, se);
744 745 746
}

static void
747
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
748
{
749
	schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
750
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
751 752
	schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
	schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
753
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
754 755 756
#ifdef CONFIG_SCHEDSTATS
	if (entity_is_task(se)) {
		trace_sched_stat_wait(task_of(se),
757
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
758 759
	}
#endif
760
	schedstat_set(se->statistics.wait_start, 0);
761 762 763
}

static inline void
764
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
765 766 767 768 769
{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
770
	if (se != cfs_rq->curr)
771
		update_stats_wait_end(cfs_rq, se);
772 773 774 775 776 777
}

/*
 * We are picking a new current task - update its stats:
 */
static inline void
778
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
779 780 781 782
{
	/*
	 * We are starting a new run period:
	 */
783
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
784 785 786 787 788 789
}

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

790 791
#ifdef CONFIG_NUMA_BALANCING
/*
792 793 794
 * 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.
795
 */
796 797
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
798 799 800

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
801

802 803 804
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849
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)
{
	unsigned int scan, floor;
	unsigned int windows = 1;

	if (sysctl_numa_balancing_scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / sysctl_numa_balancing_scan_size;
	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);
}

850 851 852 853 854 855 856 857 858 859 860 861
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));
}

862 863 864 865 866
struct numa_group {
	atomic_t refcount;

	spinlock_t lock; /* nr_tasks, tasks */
	int nr_tasks;
867
	pid_t gid;
868 869 870
	struct list_head task_list;

	struct rcu_head rcu;
871
	nodemask_t active_nodes;
872
	unsigned long total_faults;
873 874 875 876 877
	/*
	 * 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.
	 */
878
	unsigned long *faults_cpu;
879
	unsigned long faults[0];
880 881
};

882 883 884 885 886 887 888 889 890
/* 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)

891 892 893 894 895
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

896 897
static inline int task_faults_idx(int nid, int priv)
{
898
	return NR_NUMA_HINT_FAULT_TYPES * nid + priv;
899 900 901 902
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
903
	if (!p->numa_faults_memory)
904 905
		return 0;

906 907
	return p->numa_faults_memory[task_faults_idx(nid, 0)] +
		p->numa_faults_memory[task_faults_idx(nid, 1)];
908 909
}

910 911 912 913 914
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

915 916
	return p->numa_group->faults[task_faults_idx(nid, 0)] +
		p->numa_group->faults[task_faults_idx(nid, 1)];
917 918
}

919 920 921 922 923 924
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
	return group->faults_cpu[task_faults_idx(nid, 0)] +
		group->faults_cpu[task_faults_idx(nid, 1)];
}

925 926 927 928 929 930 931 932 933 934
/*
 * 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.
 */
static inline unsigned long task_weight(struct task_struct *p, int nid)
{
	unsigned long total_faults;

935
	if (!p->numa_faults_memory)
936 937 938 939 940 941 942 943 944 945 946 947
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

	return 1000 * task_faults(p, nid) / total_faults;
}

static inline unsigned long group_weight(struct task_struct *p, int nid)
{
948
	if (!p->numa_group || !p->numa_group->total_faults)
949 950
		return 0;

951
	return 1000 * group_faults(p, nid) / p->numa_group->total_faults;
952 953
}

954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016
bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
				int src_nid, int dst_cpu)
{
	struct numa_group *ng = p->numa_group;
	int dst_nid = cpu_to_node(dst_cpu);
	int last_cpupid, this_cpupid;

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

	/*
	 * Multi-stage node selection is used in conjunction with a periodic
	 * migration fault to build a temporal task<->page relation. By using
	 * a two-stage filter we remove short/unlikely relations.
	 *
	 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate
	 * a task's usage of a particular page (n_p) per total usage of this
	 * page (n_t) (in a given time-span) to a probability.
	 *
	 * Our periodic faults will sample this probability and getting the
	 * same result twice in a row, given these samples are fully
	 * independent, is then given by P(n)^2, provided our sample period
	 * is sufficiently short compared to the usage pattern.
	 *
	 * This quadric squishes small probabilities, making it less likely we
	 * act on an unlikely task<->page relation.
	 */
	last_cpupid = page_cpupid_xchg_last(page, this_cpupid);
	if (!cpupid_pid_unset(last_cpupid) &&
				cpupid_to_nid(last_cpupid) != dst_nid)
		return false;

	/* Always allow migrate on private faults */
	if (cpupid_match_pid(p, last_cpupid))
		return true;

	/* A shared fault, but p->numa_group has not been set up yet. */
	if (!ng)
		return true;

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

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

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

1017
static unsigned long weighted_cpuload(const int cpu);
1018 1019 1020 1021 1022
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
static unsigned long power_of(int cpu);
static long effective_load(struct task_group *tg, int cpu, long wl, long wg);

1023
/* Cached statistics for all CPUs within a node */
1024
struct numa_stats {
1025
	unsigned long nr_running;
1026
	unsigned long load;
1027 1028 1029 1030 1031 1032 1033

	/* Total compute capacity of CPUs on a node */
	unsigned long power;

	/* Approximate capacity in terms of runnable tasks on a node */
	unsigned long capacity;
	int has_capacity;
1034
};
1035

1036 1037 1038 1039 1040
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1041
	int cpu, cpus = 0;
1042 1043 1044 1045 1046 1047 1048 1049

	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);
		ns->power += power_of(cpu);
1050 1051

		cpus++;
1052 1053
	}

1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064
	/*
	 * 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.
	 *
	 * We'll either bail at !has_capacity, or we'll detect a huge imbalance
	 * and bail there.
	 */
	if (!cpus)
		return;

1065 1066 1067 1068 1069
	ns->load = (ns->load * SCHED_POWER_SCALE) / ns->power;
	ns->capacity = DIV_ROUND_CLOSEST(ns->power, SCHED_POWER_SCALE);
	ns->has_capacity = (ns->nr_running < ns->capacity);
}

1070 1071
struct task_numa_env {
	struct task_struct *p;
1072

1073 1074
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1075

1076
	struct numa_stats src_stats, dst_stats;
1077

1078
	int imbalance_pct;
1079 1080 1081

	struct task_struct *best_task;
	long best_imp;
1082 1083 1084
	int best_cpu;
};

1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103
static void task_numa_assign(struct task_numa_env *env,
			     struct task_struct *p, long imp)
{
	if (env->best_task)
		put_task_struct(env->best_task);
	if (p)
		get_task_struct(p);

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

/*
 * 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
 */
1104 1105
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1106 1107 1108 1109 1110 1111
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
	long dst_load, src_load;
	long load;
1112
	long imp = (groupimp > 0) ? groupimp : taskimp;
1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130

	rcu_read_lock();
	cur = ACCESS_ONCE(dst_rq->curr);
	if (cur->pid == 0) /* idle */
		cur = NULL;

	/*
	 * "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;

1131 1132
		/*
		 * If dst and source tasks are in the same NUMA group, or not
1133
		 * in any group then look only at task weights.
1134
		 */
1135
		if (cur->numa_group == env->p->numa_group) {
1136 1137
			imp = taskimp + task_weight(cur, env->src_nid) -
			      task_weight(cur, env->dst_nid);
1138 1139 1140 1141 1142 1143
			/*
			 * Add some hysteresis to prevent swapping the
			 * tasks within a group over tiny differences.
			 */
			if (cur->numa_group)
				imp -= imp/16;
1144
		} else {
1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160
			/*
			 * Compare the group weights. If a task is all by
			 * itself (not part of a group), use the task weight
			 * instead.
			 */
			if (env->p->numa_group)
				imp = groupimp;
			else
				imp = taskimp;

			if (cur->numa_group)
				imp += group_weight(cur, env->src_nid) -
				       group_weight(cur, env->dst_nid);
			else
				imp += task_weight(cur, env->src_nid) -
				       task_weight(cur, env->dst_nid);
1161
		}
1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210
	}

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

	if (!cur) {
		/* Is there capacity at our destination? */
		if (env->src_stats.has_capacity &&
		    !env->dst_stats.has_capacity)
			goto unlock;

		goto balance;
	}

	/* Balance doesn't matter much if we're running a task per cpu */
	if (src_rq->nr_running == 1 && dst_rq->nr_running == 1)
		goto assign;

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
balance:
	dst_load = env->dst_stats.load;
	src_load = env->src_stats.load;

	/* XXX missing power terms */
	load = task_h_load(env->p);
	dst_load += load;
	src_load -= load;

	if (cur) {
		load = task_h_load(cur);
		dst_load -= load;
		src_load += load;
	}

	/* make src_load the smaller */
	if (dst_load < src_load)
		swap(dst_load, src_load);

	if (src_load * env->imbalance_pct < dst_load * 100)
		goto unlock;

assign:
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1211 1212
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1213 1214 1215 1216 1217 1218 1219 1220 1221
{
	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;
1222
		task_numa_compare(env, taskimp, groupimp);
1223 1224 1225
	}
}

1226 1227 1228 1229
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1230

1231
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1232
		.src_nid = task_node(p),
1233 1234 1235 1236 1237 1238

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
		.best_cpu = -1
1239 1240
	};
	struct sched_domain *sd;
1241
	unsigned long taskweight, groupweight;
1242
	int nid, ret;
1243
	long taskimp, groupimp;
1244

1245
	/*
1246 1247 1248 1249 1250 1251
	 * 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.
1252 1253
	 */
	rcu_read_lock();
1254
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1255 1256
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1257 1258
	rcu_read_unlock();

1259 1260 1261 1262 1263 1264 1265
	/*
	 * 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)) {
1266
		p->numa_preferred_nid = task_node(p);
1267 1268 1269
		return -EINVAL;
	}

1270 1271
	taskweight = task_weight(p, env.src_nid);
	groupweight = group_weight(p, env.src_nid);
1272
	update_numa_stats(&env.src_stats, env.src_nid);
1273
	env.dst_nid = p->numa_preferred_nid;
1274 1275
	taskimp = task_weight(p, env.dst_nid) - taskweight;
	groupimp = group_weight(p, env.dst_nid) - groupweight;
1276
	update_numa_stats(&env.dst_stats, env.dst_nid);
1277

1278 1279
	/* If the preferred nid has capacity, try to use it. */
	if (env.dst_stats.has_capacity)
1280
		task_numa_find_cpu(&env, taskimp, groupimp);
1281 1282 1283

	/* No space available on the preferred nid. Look elsewhere. */
	if (env.best_cpu == -1) {
1284 1285 1286
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1287

1288
			/* Only consider nodes where both task and groups benefit */
1289 1290 1291
			taskimp = task_weight(p, nid) - taskweight;
			groupimp = group_weight(p, nid) - groupweight;
			if (taskimp < 0 && groupimp < 0)
1292 1293
				continue;

1294 1295
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1296
			task_numa_find_cpu(&env, taskimp, groupimp);
1297 1298 1299
		}
	}

1300 1301 1302 1303
	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;

1304 1305
	sched_setnuma(p, env.dst_nid);

1306 1307 1308 1309 1310 1311
	/*
	 * 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);

1312
	if (env.best_task == NULL) {
1313 1314 1315
		ret = migrate_task_to(p, env.best_cpu);
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1316 1317 1318 1319
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
1320 1321
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1322 1323
	put_task_struct(env.best_task);
	return ret;
1324 1325
}

1326 1327 1328
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1329
	/* This task has no NUMA fault statistics yet */
1330
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults_memory))
1331 1332
		return;

1333 1334 1335 1336
	/* Periodically retry migrating the task to the preferred node */
	p->numa_migrate_retry = jiffies + HZ;

	/* Success if task is already running on preferred CPU */
1337
	if (task_node(p) == p->numa_preferred_nid)
1338 1339 1340
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1341
	task_numa_migrate(p);
1342 1343
}

1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375
/*
 * Find the nodes on which the workload is actively running. We do this by
 * tracking the nodes from which NUMA hinting faults are triggered. This can
 * be different from the set of nodes where the workload's memory is currently
 * located.
 *
 * The bitmask is used to make smarter decisions on when to do NUMA page
 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
 * are added when they cause over 6/16 of the maximum number of faults, but
 * only removed when they drop below 3/16.
 */
static void update_numa_active_node_mask(struct numa_group *numa_group)
{
	unsigned long faults, max_faults = 0;
	int nid;

	for_each_online_node(nid) {
		faults = group_faults_cpu(numa_group, nid);
		if (faults > max_faults)
			max_faults = faults;
	}

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

1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449
/*
 * 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
 * period will be for the next scan window. If local/remote ratio is below
 * NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) the
 * scan period will decrease
 */
#define NUMA_PERIOD_SLOTS 10
#define NUMA_PERIOD_THRESHOLD 3

/*
 * Increase the scan period (slow down scanning) if the majority of
 * our memory is already on our local node, or if the majority of
 * the page accesses are shared with other processes.
 * Otherwise, decrease the scan period.
 */
static void update_task_scan_period(struct task_struct *p,
			unsigned long shared, unsigned long private)
{
	unsigned int period_slot;
	int ratio;
	int diff;

	unsigned long remote = p->numa_faults_locality[0];
	unsigned long local = p->numa_faults_locality[1];

	/*
	 * If there were no record hinting faults then either the task is
	 * completely idle or all activity is areas that are not of interest
	 * to automatic numa balancing. Scan slower
	 */
	if (local + shared == 0) {
		p->numa_scan_period = min(p->numa_scan_period_max,
			p->numa_scan_period << 1);

		p->mm->numa_next_scan = jiffies +
			msecs_to_jiffies(p->numa_scan_period);

		return;
	}

	/*
	 * Prepare to scale scan period relative to the current period.
	 *	 == NUMA_PERIOD_THRESHOLD scan period stays the same
	 *       <  NUMA_PERIOD_THRESHOLD scan period decreases (scan faster)
	 *	 >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
	 */
	period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
	ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
	if (ratio >= NUMA_PERIOD_THRESHOLD) {
		int slot = ratio - NUMA_PERIOD_THRESHOLD;
		if (!slot)
			slot = 1;
		diff = slot * period_slot;
	} else {
		diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot;

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

1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477
/*
 * Get the fraction of time the task has been running since the last
 * NUMA placement cycle. The scheduler keeps similar statistics, but
 * decays those on a 32ms period, which is orders of magnitude off
 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
 * stats only if the task is so new there are no NUMA statistics yet.
 */
static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
{
	u64 runtime, delta, now;
	/* Use the start of this time slice to avoid calculations. */
	now = p->se.exec_start;
	runtime = p->se.sum_exec_runtime;

	if (p->last_task_numa_placement) {
		delta = runtime - p->last_sum_exec_runtime;
		*period = now - p->last_task_numa_placement;
	} else {
		delta = p->se.avg.runnable_avg_sum;
		*period = p->se.avg.runnable_avg_period;
	}

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

	return delta;
}

1478 1479
static void task_numa_placement(struct task_struct *p)
{
1480 1481
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
1482
	unsigned long fault_types[2] = { 0, 0 };
1483 1484
	unsigned long total_faults;
	u64 runtime, period;
1485
	spinlock_t *group_lock = NULL;
1486

1487
	seq = ACCESS_ONCE(p->mm->numa_scan_seq);
1488 1489 1490
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
1491
	p->numa_scan_period_max = task_scan_max(p);
1492

1493 1494 1495 1496
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

1497 1498 1499 1500 1501 1502
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
		spin_lock(group_lock);
	}

1503 1504
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
1505
		unsigned long faults = 0, group_faults = 0;
1506
		int priv, i;
1507

1508
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1509
			long diff, f_diff, f_weight;
1510

1511
			i = task_faults_idx(nid, priv);
1512

1513
			/* Decay existing window, copy faults since last scan */
1514
			diff = p->numa_faults_buffer_memory[i] - p->numa_faults_memory[i] / 2;
1515 1516
			fault_types[priv] += p->numa_faults_buffer_memory[i];
			p->numa_faults_buffer_memory[i] = 0;
1517

1518 1519 1520 1521 1522 1523 1524 1525 1526 1527
			/*
			 * 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);
			f_weight = (f_weight * p->numa_faults_buffer_cpu[i]) /
				   (total_faults + 1);
1528
			f_diff = f_weight - p->numa_faults_cpu[i] / 2;
1529 1530
			p->numa_faults_buffer_cpu[i] = 0;

1531 1532
			p->numa_faults_memory[i] += diff;
			p->numa_faults_cpu[i] += f_diff;
1533
			faults += p->numa_faults_memory[i];
1534
			p->total_numa_faults += diff;
1535 1536
			if (p->numa_group) {
				/* safe because we can only change our own group */
1537
				p->numa_group->faults[i] += diff;
1538
				p->numa_group->faults_cpu[i] += f_diff;
1539 1540
				p->numa_group->total_faults += diff;
				group_faults += p->numa_group->faults[i];
1541
			}
1542 1543
		}

1544 1545 1546 1547
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
1548 1549 1550 1551 1552 1553 1554

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

1555 1556
	update_task_scan_period(p, fault_types[0], fault_types[1]);

1557
	if (p->numa_group) {
1558
		update_numa_active_node_mask(p->numa_group);
1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571
		/*
		 * If the preferred task and group nids are different,
		 * iterate over the nodes again to find the best place.
		 */
		if (max_nid != max_group_nid) {
			unsigned long weight, max_weight = 0;

			for_each_online_node(nid) {
				weight = task_weight(p, nid) + group_weight(p, nid);
				if (weight > max_weight) {
					max_weight = weight;
					max_nid = nid;
				}
1572 1573
			}
		}
1574 1575

		spin_unlock(group_lock);
1576 1577
	}

1578
	/* Preferred node as the node with the most faults */
1579
	if (max_faults && max_nid != p->numa_preferred_nid) {
1580
		/* Update the preferred nid and migrate task if possible */
1581
		sched_setnuma(p, max_nid);
1582
		numa_migrate_preferred(p);
1583
	}
1584 1585
}

1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596
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);
}

1597 1598
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
1599 1600 1601 1602 1603 1604 1605 1606 1607
{
	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) +
1608
				    4*nr_node_ids*sizeof(unsigned long);
1609 1610 1611 1612 1613 1614 1615 1616

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

		atomic_set(&grp->refcount, 1);
		spin_lock_init(&grp->lock);
		INIT_LIST_HEAD(&grp->task_list);
1617
		grp->gid = p->pid;
1618
		/* Second half of the array tracks nids where faults happen */
1619 1620
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
1621

1622 1623
		node_set(task_node(current), grp->active_nodes);

1624
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1625
			grp->faults[i] = p->numa_faults_memory[i];
1626

1627
		grp->total_faults = p->total_numa_faults;
1628

1629 1630 1631 1632 1633 1634 1635 1636 1637
		list_add(&p->numa_entry, &grp->task_list);
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

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

	if (!cpupid_match_pid(tsk, cpupid))
1638
		goto no_join;
1639 1640 1641

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
1642
		goto no_join;
1643 1644 1645

	my_grp = p->numa_group;
	if (grp == my_grp)
1646
		goto no_join;
1647 1648 1649 1650 1651 1652

	/*
	 * 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)
1653
		goto no_join;
1654 1655 1656 1657 1658

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1659
		goto no_join;
1660

1661 1662 1663 1664 1665 1666 1667
	/* 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;
1668

1669 1670 1671
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

1672
	if (join && !get_numa_group(grp))
1673
		goto no_join;
1674 1675 1676 1677 1678 1679

	rcu_read_unlock();

	if (!join)
		return;

1680 1681
	double_lock(&my_grp->lock, &grp->lock);

1682
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
1683 1684
		my_grp->faults[i] -= p->numa_faults_memory[i];
		grp->faults[i] += p->numa_faults_memory[i];
1685
	}
1686 1687
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698

	list_move(&p->numa_entry, &grp->task_list);
	my_grp->nr_tasks--;
	grp->nr_tasks++;

	spin_unlock(&my_grp->lock);
	spin_unlock(&grp->lock);

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
1699 1700 1701 1702 1703
	return;

no_join:
	rcu_read_unlock();
	return;
1704 1705 1706 1707 1708 1709
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
	int i;
1710
	void *numa_faults = p->numa_faults_memory;
1711 1712

	if (grp) {
1713
		spin_lock(&grp->lock);
1714
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1715
			grp->faults[i] -= p->numa_faults_memory[i];
1716
		grp->total_faults -= p->total_numa_faults;
1717

1718 1719 1720 1721 1722 1723 1724
		list_del(&p->numa_entry);
		grp->nr_tasks--;
		spin_unlock(&grp->lock);
		rcu_assign_pointer(p->numa_group, NULL);
		put_numa_group(grp);
	}

1725 1726
	p->numa_faults_memory = NULL;
	p->numa_faults_buffer_memory = NULL;
1727 1728
	p->numa_faults_cpu= NULL;
	p->numa_faults_buffer_cpu = NULL;
1729
	kfree(numa_faults);
1730 1731
}

1732 1733 1734
/*
 * Got a PROT_NONE fault for a page on @node.
 */
1735
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
1736 1737
{
	struct task_struct *p = current;
1738
	bool migrated = flags & TNF_MIGRATED;
1739
	int cpu_node = task_node(current);
1740
	int priv;
1741

1742
	if (!numabalancing_enabled)
1743 1744
		return;

1745 1746 1747 1748
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

1749 1750 1751 1752
	/* Do not worry about placement if exiting */
	if (p->state == TASK_DEAD)
		return;

1753
	/* Allocate buffer to track faults on a per-node basis */
1754
	if (unlikely(!p->numa_faults_memory)) {
1755 1756
		int size = sizeof(*p->numa_faults_memory) *
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
1757

1758
		p->numa_faults_memory = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
1759
		if (!p->numa_faults_memory)
1760
			return;
1761

1762
		BUG_ON(p->numa_faults_buffer_memory);
1763 1764 1765 1766 1767 1768
		/*
		 * 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.
		 */
1769 1770 1771
		p->numa_faults_cpu = p->numa_faults_memory + (2 * nr_node_ids);
		p->numa_faults_buffer_memory = p->numa_faults_memory + (4 * nr_node_ids);
		p->numa_faults_buffer_cpu = p->numa_faults_memory + (6 * nr_node_ids);
1772
		p->total_numa_faults = 0;
1773
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1774
	}
1775

1776 1777 1778 1779 1780 1781 1782 1783
	/*
	 * 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);
1784
		if (!priv && !(flags & TNF_NO_GROUP))
1785
			task_numa_group(p, last_cpupid, flags, &priv);
1786 1787
	}

1788
	task_numa_placement(p);
1789

1790 1791 1792 1793 1794
	/*
	 * 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))
1795 1796
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
1797 1798 1799
	if (migrated)
		p->numa_pages_migrated += pages;

1800 1801
	p->numa_faults_buffer_memory[task_faults_idx(mem_node, priv)] += pages;
	p->numa_faults_buffer_cpu[task_faults_idx(cpu_node, priv)] += pages;
1802
	p->numa_faults_locality[!!(flags & TNF_FAULT_LOCAL)] += pages;
1803 1804
}

1805 1806 1807 1808 1809 1810
static void reset_ptenuma_scan(struct task_struct *p)
{
	ACCESS_ONCE(p->mm->numa_scan_seq)++;
	p->mm->numa_scan_offset = 0;
}

1811 1812 1813 1814 1815 1816 1817 1818 1819
/*
 * 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;
1820
	struct vm_area_struct *vma;
1821
	unsigned long start, end;
1822
	unsigned long nr_pte_updates = 0;
1823
	long pages;
1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838

	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;

1839
	if (!mm->numa_next_scan) {
1840 1841
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
1842 1843
	}

1844 1845 1846 1847 1848 1849 1850
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

1851 1852 1853 1854
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
		p->numa_scan_period = task_scan_min(p);
	}
1855

1856
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
1857 1858 1859
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

1860 1861 1862 1863 1864 1865
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

1866 1867 1868 1869 1870
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
	if (!pages)
		return;
1871

1872
	down_read(&mm->mmap_sem);
1873
	vma = find_vma(mm, start);
1874 1875
	if (!vma) {
		reset_ptenuma_scan(p);
1876
		start = 0;
1877 1878
		vma = mm->mmap;
	}
1879
	for (; vma; vma = vma->vm_next) {
1880
		if (!vma_migratable(vma) || !vma_policy_mof(p, vma))
1881 1882
			continue;

1883 1884 1885 1886 1887 1888 1889 1890 1891 1892
		/*
		 * 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
1893 1894 1895 1896 1897 1898
		/*
		 * 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;
1899

1900 1901 1902 1903
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
1904 1905 1906 1907 1908 1909 1910 1911 1912
			nr_pte_updates += change_prot_numa(vma, start, end);

			/*
			 * Scan sysctl_numa_balancing_scan_size but ensure that
			 * at least one PTE is updated so that unused virtual
			 * address space is quickly skipped.
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
1913

1914 1915 1916 1917
			start = end;
			if (pages <= 0)
				goto out;
		} while (end != vma->vm_end);
1918
	}
1919

1920
out:
1921
	/*
P
Peter Zijlstra 已提交
1922 1923 1924 1925
	 * 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.
1926 1927
	 */
	if (vma)
1928
		mm->numa_scan_offset = start;
1929 1930 1931
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957
}

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

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

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

	if (now - curr->node_stamp > period) {
1958
		if (!curr->node_stamp)
1959
			curr->numa_scan_period = task_scan_min(curr);
1960
		curr->node_stamp += period;
1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971

		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)
{
}
1972 1973 1974 1975 1976 1977 1978 1979

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)
{
}
1980 1981
#endif /* CONFIG_NUMA_BALANCING */

1982 1983 1984 1985
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
1986
	if (!parent_entity(se))
1987
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
1988
#ifdef CONFIG_SMP
1989 1990 1991 1992 1993 1994
	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);
	}
1995
#endif
1996 1997 1998 1999 2000 2001 2002
	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);
2003
	if (!parent_entity(se))
2004
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2005 2006
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2007
		list_del_init(&se->group_node);
2008
	}
2009 2010 2011
	cfs_rq->nr_running--;
}

2012 2013
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
2014 2015 2016 2017 2018 2019 2020 2021 2022
static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
{
	long tg_weight;

	/*
	 * Use this CPU's actual weight instead of the last load_contribution
	 * to gain a more accurate current total weight. See
	 * update_cfs_rq_load_contribution().
	 */
2023
	tg_weight = atomic_long_read(&tg->load_avg);
2024
	tg_weight -= cfs_rq->tg_load_contrib;
2025 2026 2027 2028 2029
	tg_weight += cfs_rq->load.weight;

	return tg_weight;
}

2030
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2031
{
2032
	long tg_weight, load, shares;
2033

2034
	tg_weight = calc_tg_weight(tg, cfs_rq);
2035
	load = cfs_rq->load.weight;
2036 2037

	shares = (tg->shares * load);
2038 2039
	if (tg_weight)
		shares /= tg_weight;
2040 2041 2042 2043 2044 2045 2046 2047 2048

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

	return shares;
}
# else /* CONFIG_SMP */
2049
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2050 2051 2052 2053
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
2054 2055 2056
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
2057 2058 2059 2060
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
2061
		account_entity_dequeue(cfs_rq, se);
2062
	}
P
Peter Zijlstra 已提交
2063 2064 2065 2066 2067 2068 2069

	update_load_set(&se->load, weight);

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

2070 2071
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2072
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2073 2074 2075
{
	struct task_group *tg;
	struct sched_entity *se;
2076
	long shares;
P
Peter Zijlstra 已提交
2077 2078 2079

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
2080
	if (!se || throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
2081
		return;
2082 2083 2084 2085
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
2086
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
2087 2088 2089 2090

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
2091
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2092 2093 2094 2095
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

2096
#ifdef CONFIG_SMP
2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124
/*
 * We choose a half-life close to 1 scheduling period.
 * Note: The tables below are dependent on this value.
 */
#define LOAD_AVG_PERIOD 32
#define LOAD_AVG_MAX 47742 /* maximum possible load avg */
#define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */

/* Precomputed fixed inverse multiplies for multiplication by y^n */
static const u32 runnable_avg_yN_inv[] = {
	0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6,
	0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85,
	0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581,
	0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9,
	0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80,
	0x85aac367, 0x82cd8698,
};

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

2125 2126 2127 2128 2129 2130
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150
	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
	 *    y^n = 1/2^(n/PERIOD) * k^(n%PERIOD)
	 * With a look-up table which covers k^n (n<PERIOD)
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
2151 2152
	}

2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183
	val *= runnable_avg_yN_inv[local_n];
	/* We don't use SRR here since we always want to round down. */
	return val >> 32;
}

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

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

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

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

	contrib = decay_load(contrib, n);
	return contrib + runnable_avg_yN_sum[n];
2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217
}

/*
 * We can represent the historical contribution to runnable average as the
 * coefficients of a geometric series.  To do this we sub-divide our runnable
 * history into segments of approximately 1ms (1024us); label the segment that
 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
 *
 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
 *      p0            p1           p2
 *     (now)       (~1ms ago)  (~2ms ago)
 *
 * Let u_i denote the fraction of p_i that the entity was runnable.
 *
 * We then designate the fractions u_i as our co-efficients, yielding the
 * following representation of historical load:
 *   u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
 *
 * We choose y based on the with of a reasonably scheduling period, fixing:
 *   y^32 = 0.5
 *
 * This means that the contribution to load ~32ms ago (u_32) will be weighted
 * approximately half as much as the contribution to load within the last ms
 * (u_0).
 *
 * When a period "rolls over" and we have new u_0`, multiplying the previous
 * sum again by y is sufficient to update:
 *   load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
 *            = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
 */
static __always_inline int __update_entity_runnable_avg(u64 now,
							struct sched_avg *sa,
							int runnable)
{
2218 2219
	u64 delta, periods;
	u32 runnable_contrib;
2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252
	int delta_w, decayed = 0;

	delta = now - sa->last_runnable_update;
	/*
	 * This should only happen when time goes backwards, which it
	 * unfortunately does during sched clock init when we swap over to TSC.
	 */
	if ((s64)delta < 0) {
		sa->last_runnable_update = now;
		return 0;
	}

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

	/* delta_w is the amount already accumulated against our next period */
	delta_w = sa->runnable_avg_period % 1024;
	if (delta + delta_w >= 1024) {
		/* period roll-over */
		decayed = 1;

		/*
		 * Now that we know we're crossing a period boundary, figure
		 * out how much from delta we need to complete the current
		 * period and accrue it.
		 */
		delta_w = 1024 - delta_w;
2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272
		if (runnable)
			sa->runnable_avg_sum += delta_w;
		sa->runnable_avg_period += delta_w;

		delta -= delta_w;

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

		sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum,
						  periods + 1);
		sa->runnable_avg_period = decay_load(sa->runnable_avg_period,
						     periods + 1);

		/* Efficiently calculate \sum (1..n_period) 1024*y^i */
		runnable_contrib = __compute_runnable_contrib(periods);
		if (runnable)
			sa->runnable_avg_sum += runnable_contrib;
		sa->runnable_avg_period += runnable_contrib;
2273 2274 2275 2276 2277 2278 2279 2280 2281 2282
	}

	/* Remainder of delta accrued against u_0` */
	if (runnable)
		sa->runnable_avg_sum += delta;
	sa->runnable_avg_period += delta;

	return decayed;
}

2283
/* Synchronize an entity's decay with its parenting cfs_rq.*/
2284
static inline u64 __synchronize_entity_decay(struct sched_entity *se)
2285 2286 2287 2288 2289 2290
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 decays = atomic64_read(&cfs_rq->decay_counter);

	decays -= se->avg.decay_count;
	if (!decays)
2291
		return 0;
2292 2293 2294

	se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
	se->avg.decay_count = 0;
2295 2296

	return decays;
2297 2298
}

2299 2300 2301 2302 2303
#ifdef CONFIG_FAIR_GROUP_SCHED
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
						 int force_update)
{
	struct task_group *tg = cfs_rq->tg;
2304
	long tg_contrib;
2305 2306 2307 2308

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

2309 2310
	if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) {
		atomic_long_add(tg_contrib, &tg->load_avg);
2311 2312 2313
		cfs_rq->tg_load_contrib += tg_contrib;
	}
}
2314

2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325
/*
 * Aggregate cfs_rq runnable averages into an equivalent task_group
 * representation for computing load contributions.
 */
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
						  struct cfs_rq *cfs_rq)
{
	struct task_group *tg = cfs_rq->tg;
	long contrib;

	/* The fraction of a cpu used by this cfs_rq */
2326
	contrib = div_u64((u64)sa->runnable_avg_sum << NICE_0_SHIFT,
2327 2328 2329 2330 2331 2332 2333 2334 2335
			  sa->runnable_avg_period + 1);
	contrib -= cfs_rq->tg_runnable_contrib;

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

2336 2337 2338 2339
static inline void __update_group_entity_contrib(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = group_cfs_rq(se);
	struct task_group *tg = cfs_rq->tg;
2340 2341
	int runnable_avg;

2342 2343 2344
	u64 contrib;

	contrib = cfs_rq->tg_load_contrib * tg->shares;
2345 2346
	se->avg.load_avg_contrib = div_u64(contrib,
				     atomic_long_read(&tg->load_avg) + 1);
2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375

	/*
	 * For group entities we need to compute a correction term in the case
	 * that they are consuming <1 cpu so that we would contribute the same
	 * load as a task of equal weight.
	 *
	 * Explicitly co-ordinating this measurement would be expensive, but
	 * fortunately the sum of each cpus contribution forms a usable
	 * lower-bound on the true value.
	 *
	 * Consider the aggregate of 2 contributions.  Either they are disjoint
	 * (and the sum represents true value) or they are disjoint and we are
	 * understating by the aggregate of their overlap.
	 *
	 * Extending this to N cpus, for a given overlap, the maximum amount we
	 * understand is then n_i(n_i+1)/2 * w_i where n_i is the number of
	 * cpus that overlap for this interval and w_i is the interval width.
	 *
	 * On a small machine; the first term is well-bounded which bounds the
	 * total error since w_i is a subset of the period.  Whereas on a
	 * larger machine, while this first term can be larger, if w_i is the
	 * of consequential size guaranteed to see n_i*w_i quickly converge to
	 * our upper bound of 1-cpu.
	 */
	runnable_avg = atomic_read(&tg->runnable_avg);
	if (runnable_avg < NICE_0_LOAD) {
		se->avg.load_avg_contrib *= runnable_avg;
		se->avg.load_avg_contrib >>= NICE_0_SHIFT;
	}
2376
}
2377
#else /* CONFIG_FAIR_GROUP_SCHED */
2378 2379
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
						 int force_update) {}
2380 2381
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
						  struct cfs_rq *cfs_rq) {}
2382
static inline void __update_group_entity_contrib(struct sched_entity *se) {}
2383
#endif /* CONFIG_FAIR_GROUP_SCHED */
2384

2385 2386 2387 2388 2389 2390 2391 2392 2393 2394
static inline void __update_task_entity_contrib(struct sched_entity *se)
{
	u32 contrib;

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

2395 2396 2397 2398 2399
/* Compute the current contribution to load_avg by se, return any delta */
static long __update_entity_load_avg_contrib(struct sched_entity *se)
{
	long old_contrib = se->avg.load_avg_contrib;

2400 2401 2402
	if (entity_is_task(se)) {
		__update_task_entity_contrib(se);
	} else {
2403
		__update_tg_runnable_avg(&se->avg, group_cfs_rq(se));
2404 2405
		__update_group_entity_contrib(se);
	}
2406 2407 2408 2409

	return se->avg.load_avg_contrib - old_contrib;
}

2410 2411 2412 2413 2414 2415 2416 2417 2418
static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq,
						 long load_contrib)
{
	if (likely(load_contrib < cfs_rq->blocked_load_avg))
		cfs_rq->blocked_load_avg -= load_contrib;
	else
		cfs_rq->blocked_load_avg = 0;
}

2419 2420
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);

2421
/* Update a sched_entity's runnable average */
2422 2423
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq)
2424
{
2425 2426
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	long contrib_delta;
2427
	u64 now;
2428

2429 2430 2431 2432 2433 2434 2435 2436 2437 2438
	/*
	 * For a group entity we need to use their owned cfs_rq_clock_task() in
	 * case they are the parent of a throttled hierarchy.
	 */
	if (entity_is_task(se))
		now = cfs_rq_clock_task(cfs_rq);
	else
		now = cfs_rq_clock_task(group_cfs_rq(se));

	if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq))
2439 2440 2441
		return;

	contrib_delta = __update_entity_load_avg_contrib(se);
2442 2443 2444 2445

	if (!update_cfs_rq)
		return;

2446 2447
	if (se->on_rq)
		cfs_rq->runnable_load_avg += contrib_delta;
2448 2449 2450 2451 2452 2453 2454 2455
	else
		subtract_blocked_load_contrib(cfs_rq, -contrib_delta);
}

/*
 * Decay the load contributed by all blocked children and account this so that
 * their contribution may appropriately discounted when they wake up.
 */
2456
static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
2457
{
2458
	u64 now = cfs_rq_clock_task(cfs_rq) >> 20;
2459 2460 2461
	u64 decays;

	decays = now - cfs_rq->last_decay;
2462
	if (!decays && !force_update)
2463 2464
		return;

2465 2466 2467
	if (atomic_long_read(&cfs_rq->removed_load)) {
		unsigned long removed_load;
		removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
2468 2469
		subtract_blocked_load_contrib(cfs_rq, removed_load);
	}
2470

2471 2472 2473 2474 2475 2476
	if (decays) {
		cfs_rq->blocked_load_avg = decay_load(cfs_rq->blocked_load_avg,
						      decays);
		atomic64_add(decays, &cfs_rq->decay_counter);
		cfs_rq->last_decay = now;
	}
2477 2478

	__update_cfs_rq_tg_load_contrib(cfs_rq, force_update);
2479
}
2480 2481 2482

static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
{
2483
	__update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable);
2484
	__update_tg_runnable_avg(&rq->avg, &rq->cfs);
2485
}
2486 2487 2488

/* Add the load generated by se into cfs_rq's child load-average */
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
2489 2490
						  struct sched_entity *se,
						  int wakeup)
2491
{
2492 2493 2494 2495
	/*
	 * We track migrations using entity decay_count <= 0, on a wake-up
	 * migration we use a negative decay count to track the remote decays
	 * accumulated while sleeping.
2496 2497 2498 2499
	 *
	 * Newly forked tasks are enqueued with se->avg.decay_count == 0, they
	 * are seen by enqueue_entity_load_avg() as a migration with an already
	 * constructed load_avg_contrib.
2500 2501
	 */
	if (unlikely(se->avg.decay_count <= 0)) {
2502
		se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq));
2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517
		if (se->avg.decay_count) {
			/*
			 * In a wake-up migration we have to approximate the
			 * time sleeping.  This is because we can't synchronize
			 * clock_task between the two cpus, and it is not
			 * guaranteed to be read-safe.  Instead, we can
			 * approximate this using our carried decays, which are
			 * explicitly atomically readable.
			 */
			se->avg.last_runnable_update -= (-se->avg.decay_count)
							<< 20;
			update_entity_load_avg(se, 0);
			/* Indicate that we're now synchronized and on-rq */
			se->avg.decay_count = 0;
		}
2518 2519
		wakeup = 0;
	} else {
2520
		__synchronize_entity_decay(se);
2521 2522
	}

2523 2524
	/* migrated tasks did not contribute to our blocked load */
	if (wakeup) {
2525
		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
2526 2527
		update_entity_load_avg(se, 0);
	}
2528

2529
	cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
2530 2531
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !wakeup);
2532 2533
}

2534 2535 2536 2537 2538
/*
 * Remove se's load from this cfs_rq child load-average, if the entity is
 * transitioning to a blocked state we track its projected decay using
 * blocked_load_avg.
 */
2539
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
2540 2541
						  struct sched_entity *se,
						  int sleep)
2542
{
2543
	update_entity_load_avg(se, 1);
2544 2545
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !sleep);
2546

2547
	cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
2548 2549 2550 2551
	if (sleep) {
		cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
		se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
	} /* migrations, e.g. sleep=0 leave decay_count == 0 */
2552
}
2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573

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

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

2574 2575
static int idle_balance(struct rq *this_rq);

2576 2577
#else /* CONFIG_SMP */

2578 2579
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq) {}
2580
static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
2581
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
2582 2583
					   struct sched_entity *se,
					   int wakeup) {}
2584
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
2585 2586
					   struct sched_entity *se,
					   int sleep) {}
2587 2588
static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
					      int force_update) {}
2589 2590 2591 2592 2593 2594

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

2595
#endif /* CONFIG_SMP */
2596

2597
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2598 2599
{
#ifdef CONFIG_SCHEDSTATS
2600 2601 2602 2603 2604
	struct task_struct *tsk = NULL;

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

2605
	if (se->statistics.sleep_start) {
2606
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2607 2608 2609 2610

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

2611 2612
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
2613

2614
		se->statistics.sleep_start = 0;
2615
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
2616

2617
		if (tsk) {
2618
			account_scheduler_latency(tsk, delta >> 10, 1);
2619 2620
			trace_sched_stat_sleep(tsk, delta);
		}
2621
	}
2622
	if (se->statistics.block_start) {
2623
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2624 2625 2626 2627

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

2628 2629
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
2630

2631
		se->statistics.block_start = 0;
2632
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
2633

2634
		if (tsk) {
2635
			if (tsk->in_iowait) {
2636 2637
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
2638
				trace_sched_stat_iowait(tsk, delta);
2639 2640
			}

2641 2642
			trace_sched_stat_blocked(tsk, delta);

2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653
			/*
			 * 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
2654
		}
2655 2656 2657 2658
	}
#endif
}

P
Peter Zijlstra 已提交
2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671
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
}

2672 2673 2674
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
2675
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
2676

2677 2678 2679 2680 2681 2682
	/*
	 * 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
2683
	if (initial && sched_feat(START_DEBIT))
2684
		vruntime += sched_vslice(cfs_rq, se);
2685

2686
	/* sleeps up to a single latency don't count. */
2687
	if (!initial) {
2688
		unsigned long thresh = sysctl_sched_latency;
2689

2690 2691 2692 2693 2694 2695
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
2696

2697
		vruntime -= thresh;
2698 2699
	}

2700
	/* ensure we never gain time by being placed backwards. */
2701
	se->vruntime = max_vruntime(se->vruntime, vruntime);
2702 2703
}

2704 2705
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

2706
static void
2707
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2708
{
2709 2710
	/*
	 * Update the normalized vruntime before updating min_vruntime
2711
	 * through calling update_curr().
2712
	 */
2713
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
2714 2715
		se->vruntime += cfs_rq->min_vruntime;

2716
	/*
2717
	 * Update run-time statistics of the 'current'.
2718
	 */
2719
	update_curr(cfs_rq);
2720
	enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
2721 2722
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
2723

2724
	if (flags & ENQUEUE_WAKEUP) {
2725
		place_entity(cfs_rq, se, 0);
2726
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
2727
	}
2728

2729
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
2730
	check_spread(cfs_rq, se);
2731 2732
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
2733
	se->on_rq = 1;
2734

2735
	if (cfs_rq->nr_running == 1) {
2736
		list_add_leaf_cfs_rq(cfs_rq);
2737 2738
		check_enqueue_throttle(cfs_rq);
	}
2739 2740
}

2741
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
2742
{
2743 2744
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
2745
		if (cfs_rq->last != se)
2746
			break;
2747 2748

		cfs_rq->last = NULL;
2749 2750
	}
}
P
Peter Zijlstra 已提交
2751

2752 2753 2754 2755
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
2756
		if (cfs_rq->next != se)
2757
			break;
2758 2759

		cfs_rq->next = NULL;
2760
	}
P
Peter Zijlstra 已提交
2761 2762
}

2763 2764 2765 2766
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
2767
		if (cfs_rq->skip != se)
2768
			break;
2769 2770

		cfs_rq->skip = NULL;
2771 2772 2773
	}
}

P
Peter Zijlstra 已提交
2774 2775
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2776 2777 2778 2779 2780
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
2781 2782 2783

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
2784 2785
}

2786
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
2787

2788
static void
2789
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2790
{
2791 2792 2793 2794
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
2795
	dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);
2796

2797
	update_stats_dequeue(cfs_rq, se);
2798
	if (flags & DEQUEUE_SLEEP) {
P
Peter Zijlstra 已提交
2799
#ifdef CONFIG_SCHEDSTATS
2800 2801 2802 2803
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
2804
				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
2805
			if (tsk->state & TASK_UNINTERRUPTIBLE)
2806
				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
2807
		}
2808
#endif
P
Peter Zijlstra 已提交
2809 2810
	}

P
Peter Zijlstra 已提交
2811
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
2812

2813
	if (se != cfs_rq->curr)
2814
		__dequeue_entity(cfs_rq, se);
2815
	se->on_rq = 0;
2816
	account_entity_dequeue(cfs_rq, se);
2817 2818 2819 2820 2821 2822

	/*
	 * 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.
	 */
2823
	if (!(flags & DEQUEUE_SLEEP))
2824
		se->vruntime -= cfs_rq->min_vruntime;
2825

2826 2827 2828
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

2829
	update_min_vruntime(cfs_rq);
2830
	update_cfs_shares(cfs_rq);
2831 2832 2833 2834 2835
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
2836
static void
I
Ingo Molnar 已提交
2837
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
2838
{
2839
	unsigned long ideal_runtime, delta_exec;
2840 2841
	struct sched_entity *se;
	s64 delta;
2842

P
Peter Zijlstra 已提交
2843
	ideal_runtime = sched_slice(cfs_rq, curr);
2844
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
2845
	if (delta_exec > ideal_runtime) {
2846
		resched_task(rq_of(cfs_rq)->curr);
2847 2848 2849 2850 2851
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862
		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;

2863 2864
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
2865

2866 2867
	if (delta < 0)
		return;
2868

2869 2870
	if (delta > ideal_runtime)
		resched_task(rq_of(cfs_rq)->curr);
2871 2872
}

2873
static void
2874
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
2875
{
2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886
	/* 'current' is not kept within the tree. */
	if (se->on_rq) {
		/*
		 * Any task has to be enqueued before it get to execute on
		 * a CPU. So account for the time it spent waiting on the
		 * runqueue.
		 */
		update_stats_wait_end(cfs_rq, se);
		__dequeue_entity(cfs_rq, se);
	}

2887
	update_stats_curr_start(cfs_rq, se);
2888
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
2889 2890 2891 2892 2893 2894
#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):
	 */
2895
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
2896
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
2897 2898 2899
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
2900
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
2901 2902
}

2903 2904 2905
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

2906 2907 2908 2909 2910 2911 2912
/*
 * 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
 */
2913 2914
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
2915
{
2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926
	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 */
2927

2928 2929 2930 2931 2932
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
2933 2934 2935 2936 2937 2938 2939 2940 2941 2942
		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;
		}

2943 2944 2945
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
2946

2947 2948 2949 2950 2951 2952
	/*
	 * 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;

2953 2954 2955 2956 2957 2958
	/*
	 * 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;

2959
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
2960 2961

	return se;
2962 2963
}

2964
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
2965

2966
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
2967 2968 2969 2970 2971 2972
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
2973
		update_curr(cfs_rq);
2974

2975 2976 2977
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

P
Peter Zijlstra 已提交
2978
	check_spread(cfs_rq, prev);
2979
	if (prev->on_rq) {
2980
		update_stats_wait_start(cfs_rq, prev);
2981 2982
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
2983
		/* in !on_rq case, update occurred at dequeue */
2984
		update_entity_load_avg(prev, 1);
2985
	}
2986
	cfs_rq->curr = NULL;
2987 2988
}

P
Peter Zijlstra 已提交
2989 2990
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
2991 2992
{
	/*
2993
	 * Update run-time statistics of the 'current'.
2994
	 */
2995
	update_curr(cfs_rq);
2996

2997 2998 2999
	/*
	 * Ensure that runnable average is periodically updated.
	 */
3000
	update_entity_load_avg(curr, 1);
3001
	update_cfs_rq_blocked_load(cfs_rq, 1);
3002
	update_cfs_shares(cfs_rq);
3003

P
Peter Zijlstra 已提交
3004 3005 3006 3007 3008
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
3009 3010 3011 3012
	if (queued) {
		resched_task(rq_of(cfs_rq)->curr);
		return;
	}
P
Peter Zijlstra 已提交
3013 3014 3015 3016 3017 3018 3019 3020
	/*
	 * 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
3021
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
3022
		check_preempt_tick(cfs_rq, curr);
3023 3024
}

3025 3026 3027 3028 3029 3030

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

#ifdef CONFIG_CFS_BANDWIDTH
3031 3032

#ifdef HAVE_JUMP_LABEL
3033
static struct static_key __cfs_bandwidth_used;
3034 3035 3036

static inline bool cfs_bandwidth_used(void)
{
3037
	return static_key_false(&__cfs_bandwidth_used);
3038 3039
}

3040
void cfs_bandwidth_usage_inc(void)
3041
{
3042 3043 3044 3045 3046 3047
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
3048 3049 3050 3051 3052 3053 3054
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

3055 3056
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
3057 3058
#endif /* HAVE_JUMP_LABEL */

3059 3060 3061 3062 3063 3064 3065 3066
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
3067 3068 3069 3070 3071 3072

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

P
Paul Turner 已提交
3073 3074 3075 3076 3077 3078 3079
/*
 * 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
 */
3080
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091
{
	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);
}

3092 3093 3094 3095 3096
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

3097 3098 3099 3100 3101 3102
/* rq->task_clock normalized against any time this cfs_rq has spent throttled */
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
	if (unlikely(cfs_rq->throttle_count))
		return cfs_rq->throttled_clock_task;

3103
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3104 3105
}

3106 3107
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3108 3109 3110
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
3111
	u64 amount = 0, min_amount, expires;
3112 3113 3114 3115 3116 3117 3118

	/* 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;
3119
	else {
P
Paul Turner 已提交
3120 3121 3122 3123 3124 3125 3126 3127
		/*
		 * If the bandwidth pool has become inactive, then at least one
		 * period must have elapsed since the last consumption.
		 * Refresh the global state and ensure bandwidth timer becomes
		 * active.
		 */
		if (!cfs_b->timer_active) {
			__refill_cfs_bandwidth_runtime(cfs_b);
3128
			__start_cfs_bandwidth(cfs_b);
P
Paul Turner 已提交
3129
		}
3130 3131 3132 3133 3134 3135

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
3136
	}
P
Paul Turner 已提交
3137
	expires = cfs_b->runtime_expires;
3138 3139 3140
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
3141 3142 3143 3144 3145 3146 3147
	/*
	 * 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;
3148 3149

	return cfs_rq->runtime_remaining > 0;
3150 3151
}

P
Paul Turner 已提交
3152 3153 3154 3155 3156
/*
 * 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)
3157
{
P
Paul Turner 已提交
3158 3159 3160
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
3161
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3162 3163
		return;

P
Paul Turner 已提交
3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184
	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
	 * whether the global deadline has advanced.
	 */

	if ((s64)(cfs_rq->runtime_expires - cfs_b->runtime_expires) >= 0) {
		/* 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;
	}
}

3185
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
3186 3187
{
	/* dock delta_exec before expiring quota (as it could span periods) */
3188
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
3189 3190 3191
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
3192 3193
		return;

3194 3195 3196 3197 3198 3199
	/*
	 * 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))
		resched_task(rq_of(cfs_rq)->curr);
3200 3201
}

3202
static __always_inline
3203
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3204
{
3205
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3206 3207 3208 3209 3210
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

3211 3212
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
3213
	return cfs_bandwidth_used() && cfs_rq->throttled;
3214 3215
}

3216 3217 3218
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
3219
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247
}

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

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

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

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

	cfs_rq->throttle_count--;
#ifdef CONFIG_SMP
	if (!cfs_rq->throttle_count) {
3248
		/* adjust cfs_rq_clock_task() */
3249
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3250
					     cfs_rq->throttled_clock_task;
3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261
	}
#endif

	return 0;
}

static int tg_throttle_down(struct task_group *tg, void *data)
{
	struct rq *rq = data;
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];

3262 3263
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
3264
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
3265 3266 3267 3268 3269
	cfs_rq->throttle_count++;

	return 0;
}

3270
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3271 3272 3273 3274 3275 3276 3277 3278
{
	struct rq *rq = rq_of(cfs_rq);
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
	struct sched_entity *se;
	long task_delta, dequeue = 1;

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

3279
	/* freeze hierarchy runnable averages while throttled */
3280 3281 3282
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302

	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)
		rq->nr_running -= task_delta;

	cfs_rq->throttled = 1;
3303
	cfs_rq->throttled_clock = rq_clock(rq);
3304 3305
	raw_spin_lock(&cfs_b->lock);
	list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
3306 3307
	if (!cfs_b->timer_active)
		__start_cfs_bandwidth(cfs_b);
3308 3309 3310
	raw_spin_unlock(&cfs_b->lock);
}

3311
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3312 3313 3314 3315 3316 3317 3318
{
	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;

3319
	se = cfs_rq->tg->se[cpu_of(rq)];
3320 3321

	cfs_rq->throttled = 0;
3322 3323 3324

	update_rq_clock(rq);

3325
	raw_spin_lock(&cfs_b->lock);
3326
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3327 3328 3329
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

3330 3331 3332
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395
	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)
		rq->nr_running += task_delta;

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
		resched_task(rq->curr);
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
	u64 runtime = remaining;

	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();

	return remaining;
}

3396 3397 3398 3399 3400 3401 3402 3403
/*
 * 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)
{
3404 3405
	u64 runtime, runtime_expires;
	int idle = 1, throttled;
3406 3407 3408 3409 3410 3411

	raw_spin_lock(&cfs_b->lock);
	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
		goto out_unlock;

3412 3413 3414
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
	/* idle depends on !throttled (for the case of a large deficit) */
	idle = cfs_b->idle && !throttled;
3415
	cfs_b->nr_periods += overrun;
3416

P
Paul Turner 已提交
3417 3418 3419 3420
	/* if we're going inactive then everything else can be deferred */
	if (idle)
		goto out_unlock;

3421 3422 3423 3424 3425 3426 3427
	/*
	 * if we have relooped after returning idle once, we need to update our
	 * status as actually running, so that other cpus doing
	 * __start_cfs_bandwidth will stop trying to cancel us.
	 */
	cfs_b->timer_active = 1;

P
Paul Turner 已提交
3428 3429
	__refill_cfs_bandwidth_runtime(cfs_b);

3430 3431 3432 3433 3434 3435
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
		goto out_unlock;
	}

3436 3437 3438
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

3439 3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462
	/*
	 * There are throttled entities so we must first use the new bandwidth
	 * to unthrottle them before making it generally available.  This
	 * ensures that all existing debts will be paid before a new cfs_rq is
	 * allowed to run.
	 */
	runtime = cfs_b->runtime;
	runtime_expires = cfs_b->runtime_expires;
	cfs_b->runtime = 0;

	/*
	 * 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.
	 */
	while (throttled && runtime > 0) {
		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);
	}
3463

3464 3465 3466 3467 3468 3469 3470 3471 3472
	/* return (any) remaining runtime */
	cfs_b->runtime = runtime;
	/*
	 * 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;
3473 3474 3475 3476 3477 3478 3479
out_unlock:
	if (idle)
		cfs_b->timer_active = 0;
	raw_spin_unlock(&cfs_b->lock);

	return idle;
}
3480

3481 3482 3483 3484 3485 3486 3487
/* 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;

3488 3489 3490 3491 3492 3493 3494
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
 * hrtimer base being cleared by __hrtimer_start_range_ns. In the case of
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
3495 3496 3497 3498 3499 3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546 3547 3548 3549 3550
static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
{
	struct hrtimer *refresh_timer = &cfs_b->period_timer;
	u64 remaining;

	/* if the call-back is running a quota refresh is already occurring */
	if (hrtimer_callback_running(refresh_timer))
		return 1;

	/* is a quota refresh about to occur? */
	remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
	if (remaining < min_expire)
		return 1;

	return 0;
}

static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b)
{
	u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration;

	/* if there's a quota refresh soon don't bother with slack */
	if (runtime_refresh_within(cfs_b, min_left))
		return;

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

/* we know any runtime found here is valid as update_curr() precedes return */
static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
	s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime;

	if (slack_runtime <= 0)
		return;

	raw_spin_lock(&cfs_b->lock);
	if (cfs_b->quota != RUNTIME_INF &&
	    cfs_rq->runtime_expires == cfs_b->runtime_expires) {
		cfs_b->runtime += slack_runtime;

		/* we are under rq->lock, defer unthrottling using a timer */
		if (cfs_b->runtime > sched_cfs_bandwidth_slice() &&
		    !list_empty(&cfs_b->throttled_cfs_rq))
			start_cfs_slack_bandwidth(cfs_b);
	}
	raw_spin_unlock(&cfs_b->lock);

	/* even if it's not valid for return we don't want to try again */
	cfs_rq->runtime_remaining -= slack_runtime;
}

static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
3551 3552 3553
	if (!cfs_bandwidth_used())
		return;

3554
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569
		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 */
3570 3571 3572
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
3573
		return;
3574
	}
3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593

	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
		runtime = cfs_b->runtime;
		cfs_b->runtime = 0;
	}
	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)
		cfs_b->runtime = runtime;
	raw_spin_unlock(&cfs_b->lock);
}

3594 3595 3596 3597 3598 3599 3600
/*
 * 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)
{
3601 3602 3603
	if (!cfs_bandwidth_used())
		return;

3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617 3618
	/* an active group must be handled by the update_curr()->put() path */
	if (!cfs_rq->runtime_enabled || cfs_rq->curr)
		return;

	/* ensure the group is not already throttled */
	if (cfs_rq_throttled(cfs_rq))
		return;

	/* update runtime allocation */
	account_cfs_rq_runtime(cfs_rq, 0);
	if (cfs_rq->runtime_remaining <= 0)
		throttle_cfs_rq(cfs_rq);
}

/* conditionally throttle active cfs_rq's from put_prev_entity() */
3619
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3620
{
3621
	if (!cfs_bandwidth_used())
3622
		return false;
3623

3624
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3625
		return false;
3626 3627 3628 3629 3630 3631

	/*
	 * 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))
3632
		return true;
3633 3634

	throttle_cfs_rq(cfs_rq);
3635
	return true;
3636
}
3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649 3650 3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689 3690 3691 3692 3693 3694 3695 3696

static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, slack_timer);
	do_sched_cfs_slack_timer(cfs_b);

	return HRTIMER_NORESTART;
}

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

	for (;;) {
		now = hrtimer_cb_get_time(timer);
		overrun = hrtimer_forward(timer, now, cfs_b->period);

		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}

	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
}

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

	INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	cfs_b->period_timer.function = sched_cfs_period_timer;
	hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	cfs_b->slack_timer.function = sched_cfs_slack_timer;
}

static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
	cfs_rq->runtime_enabled = 0;
	INIT_LIST_HEAD(&cfs_rq->throttled_list);
}

/* requires cfs_b->lock, may release to reprogram timer */
void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
	/*
	 * The timer may be active because we're trying to set a new bandwidth
	 * period or because we're racing with the tear-down path
	 * (timer_active==0 becomes visible before the hrtimer call-back
	 * terminates).  In either case we ensure that it's re-programmed
	 */
3697 3698 3699
	while (unlikely(hrtimer_active(&cfs_b->period_timer)) &&
	       hrtimer_try_to_cancel(&cfs_b->period_timer) < 0) {
		/* bounce the lock to allow do_sched_cfs_period_timer to run */
3700
		raw_spin_unlock(&cfs_b->lock);
3701
		cpu_relax();
3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717
		raw_spin_lock(&cfs_b->lock);
		/* if someone else restarted the timer then we're done */
		if (cfs_b->timer_active)
			return;
	}

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

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

3718
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738
{
	struct cfs_rq *cfs_rq;

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

		if (!cfs_rq->runtime_enabled)
			continue;

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
		cfs_rq->runtime_remaining = cfs_b->quota;
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
}

#else /* CONFIG_CFS_BANDWIDTH */
3739 3740
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
3741
	return rq_clock_task(rq_of(cfs_rq));
3742 3743
}

3744
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
3745
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
3746
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
3747
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
3748 3749 3750 3751 3752

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
3753 3754 3755 3756 3757 3758 3759 3760 3761 3762 3763

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;
}
3764 3765 3766 3767 3768

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) {}
3769 3770
#endif

3771 3772 3773 3774 3775
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) {}
3776
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
3777 3778 3779

#endif /* CONFIG_CFS_BANDWIDTH */

3780 3781 3782 3783
/**************************************************
 * CFS operations on tasks:
 */

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Peter Zijlstra 已提交
3784 3785 3786 3787 3788 3789 3790 3791
#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);

3792
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804 3805 3806
		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)
				resched_task(p);
			return;
		}

		/*
		 * Don't schedule slices shorter than 10000ns, that just
		 * doesn't make sense. Rely on vruntime for fairness.
		 */
3807
		if (rq->curr != p)
3808
			delta = max_t(s64, 10000LL, delta);
P
Peter Zijlstra 已提交
3809

3810
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
3811 3812
	}
}
3813 3814 3815 3816 3817 3818 3819 3820 3821 3822

/*
 * 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;

3823
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
3824 3825 3826 3827 3828
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
3829
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
3830 3831 3832 3833
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
3834 3835 3836 3837

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
3838 3839
#endif

3840 3841 3842 3843 3844
/*
 * 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:
 */
3845
static void
3846
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
3847 3848
{
	struct cfs_rq *cfs_rq;
3849
	struct sched_entity *se = &p->se;
3850 3851

	for_each_sched_entity(se) {
3852
		if (se->on_rq)
3853 3854
			break;
		cfs_rq = cfs_rq_of(se);
3855
		enqueue_entity(cfs_rq, se, flags);
3856 3857 3858 3859 3860 3861 3862 3863 3864

		/*
		 * end evaluation on encountering a throttled cfs_rq
		 *
		 * note: in the case of encountering a throttled cfs_rq we will
		 * post the final h_nr_running increment below.
		*/
		if (cfs_rq_throttled(cfs_rq))
			break;
3865
		cfs_rq->h_nr_running++;
3866

3867
		flags = ENQUEUE_WAKEUP;
3868
	}
P
Peter Zijlstra 已提交
3869

P
Peter Zijlstra 已提交
3870
	for_each_sched_entity(se) {
3871
		cfs_rq = cfs_rq_of(se);
3872
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
3873

3874 3875 3876
		if (cfs_rq_throttled(cfs_rq))
			break;

3877
		update_cfs_shares(cfs_rq);
3878
		update_entity_load_avg(se, 1);
P
Peter Zijlstra 已提交
3879 3880
	}

3881 3882
	if (!se) {
		update_rq_runnable_avg(rq, rq->nr_running);
3883
		inc_nr_running(rq);
3884
	}
3885
	hrtick_update(rq);
3886 3887
}

3888 3889
static void set_next_buddy(struct sched_entity *se);

3890 3891 3892 3893 3894
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
3895
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
3896 3897
{
	struct cfs_rq *cfs_rq;
3898
	struct sched_entity *se = &p->se;
3899
	int task_sleep = flags & DEQUEUE_SLEEP;
3900 3901 3902

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
3903
		dequeue_entity(cfs_rq, se, flags);
3904 3905 3906 3907 3908 3909 3910 3911 3912

		/*
		 * 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;
3913
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
3914

3915
		/* Don't dequeue parent if it has other entities besides us */
3916 3917 3918 3919 3920 3921 3922
		if (cfs_rq->load.weight) {
			/*
			 * Bias pick_next to pick a task from this cfs_rq, as
			 * p is sleeping when it is within its sched_slice.
			 */
			if (task_sleep && parent_entity(se))
				set_next_buddy(parent_entity(se));
3923 3924 3925

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
3926
			break;
3927
		}
3928
		flags |= DEQUEUE_SLEEP;
3929
	}
P
Peter Zijlstra 已提交
3930

P
Peter Zijlstra 已提交
3931
	for_each_sched_entity(se) {
3932
		cfs_rq = cfs_rq_of(se);
3933
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
3934

3935 3936 3937
		if (cfs_rq_throttled(cfs_rq))
			break;

3938
		update_cfs_shares(cfs_rq);
3939
		update_entity_load_avg(se, 1);
P
Peter Zijlstra 已提交
3940 3941
	}

3942
	if (!se) {
3943
		dec_nr_running(rq);
3944 3945
		update_rq_runnable_avg(rq, 1);
	}
3946
	hrtick_update(rq);
3947 3948
}

3949
#ifdef CONFIG_SMP
3950 3951 3952
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
3953
	return cpu_rq(cpu)->cfs.runnable_load_avg;
3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996 3997
}

/*
 * 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);
}

static unsigned long power_of(int cpu)
{
	return cpu_rq(cpu)->cpu_power;
}

static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
	unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
3998
	unsigned long load_avg = rq->cfs.runnable_load_avg;
3999 4000

	if (nr_running)
4001
		return load_avg / nr_running;
4002 4003 4004 4005

	return 0;
}

4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020 4021 4022
static void record_wakee(struct task_struct *p)
{
	/*
	 * Rough decay (wiping) for cost saving, don't worry
	 * about the boundary, really active task won't care
	 * about the loss.
	 */
	if (jiffies > current->wakee_flip_decay_ts + HZ) {
		current->wakee_flips = 0;
		current->wakee_flip_decay_ts = jiffies;
	}

	if (current->last_wakee != p) {
		current->last_wakee = p;
		current->wakee_flips++;
	}
}
4023

4024
static void task_waking_fair(struct task_struct *p)
4025 4026 4027
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
4028 4029 4030 4031
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
4032

4033 4034 4035 4036 4037 4038 4039 4040
	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
4041

4042
	se->vruntime -= min_vruntime;
4043
	record_wakee(p);
4044 4045
}

4046
#ifdef CONFIG_FAIR_GROUP_SCHED
4047 4048 4049 4050 4051 4052
/*
 * 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.
4053 4054 4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083 4084 4085 4086 4087 4088 4089 4090 4091 4092 4093 4094 4095
 *
 * 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.
4096
 */
P
Peter Zijlstra 已提交
4097
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4098
{
P
Peter Zijlstra 已提交
4099
	struct sched_entity *se = tg->se[cpu];
4100

4101
	if (!tg->parent)	/* the trivial, non-cgroup case */
4102 4103
		return wl;

P
Peter Zijlstra 已提交
4104
	for_each_sched_entity(se) {
4105
		long w, W;
P
Peter Zijlstra 已提交
4106

4107
		tg = se->my_q->tg;
4108

4109 4110 4111 4112
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
4113

4114 4115 4116 4117
		/*
		 * w = rw_i + @wl
		 */
		w = se->my_q->load.weight + wl;
4118

4119 4120 4121 4122 4123
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
			wl = (w * tg->shares) / W;
4124 4125
		else
			wl = tg->shares;
4126

4127 4128 4129 4130 4131
		/*
		 * 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().
		 */
4132 4133
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
4134 4135 4136 4137

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
4138
		wl -= se->load.weight;
4139 4140 4141 4142 4143 4144 4145 4146

		/*
		 * 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
4147 4148
		wg = 0;
	}
4149

P
Peter Zijlstra 已提交
4150
	return wl;
4151 4152
}
#else
P
Peter Zijlstra 已提交
4153

4154
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
P
Peter Zijlstra 已提交
4155
{
4156
	return wl;
4157
}
P
Peter Zijlstra 已提交
4158

4159 4160
#endif

4161 4162
static int wake_wide(struct task_struct *p)
{
4163
	int factor = this_cpu_read(sd_llc_size);
4164 4165 4166 4167 4168 4169 4170 4171 4172 4173 4174 4175 4176 4177 4178 4179 4180 4181 4182

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

	return 0;
}

4183
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4184
{
4185
	s64 this_load, load;
4186
	int idx, this_cpu, prev_cpu;
4187
	unsigned long tl_per_task;
4188
	struct task_group *tg;
4189
	unsigned long weight;
4190
	int balanced;
4191

4192 4193 4194 4195 4196 4197 4198
	/*
	 * If we wake multiple tasks be careful to not bounce
	 * ourselves around too much.
	 */
	if (wake_wide(p))
		return 0;

4199 4200 4201 4202 4203
	idx	  = sd->wake_idx;
	this_cpu  = smp_processor_id();
	prev_cpu  = task_cpu(p);
	load	  = source_load(prev_cpu, idx);
	this_load = target_load(this_cpu, idx);
4204

4205 4206 4207 4208 4209
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
4210 4211 4212 4213
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

4214
		this_load += effective_load(tg, this_cpu, -weight, -weight);
4215 4216
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
4217

4218 4219
	tg = task_group(p);
	weight = p->se.load.weight;
4220

4221 4222
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4223 4224 4225
	 * 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.
4226 4227 4228 4229
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
4230 4231
	if (this_load > 0) {
		s64 this_eff_load, prev_eff_load;
4232 4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244

		this_eff_load = 100;
		this_eff_load *= power_of(prev_cpu);
		this_eff_load *= this_load +
			effective_load(tg, this_cpu, weight, weight);

		prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
		prev_eff_load *= power_of(this_cpu);
		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);

		balanced = this_eff_load <= prev_eff_load;
	} else
		balanced = true;
4245

4246
	/*
I
Ingo Molnar 已提交
4247 4248 4249
	 * If the currently running task will sleep within
	 * a reasonable amount of time then attract this newly
	 * woken task:
4250
	 */
4251 4252
	if (sync && balanced)
		return 1;
4253

4254
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4255 4256
	tl_per_task = cpu_avg_load_per_task(this_cpu);

4257 4258 4259
	if (balanced ||
	    (this_load <= load &&
	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
4260 4261 4262 4263 4264
		/*
		 * This domain has SD_WAKE_AFFINE and
		 * p is cache cold in this domain, and
		 * there is no bad imbalance.
		 */
4265
		schedstat_inc(sd, ttwu_move_affine);
4266
		schedstat_inc(p, se.statistics.nr_wakeups_affine);
4267 4268 4269 4270 4271 4272

		return 1;
	}
	return 0;
}

4273 4274 4275 4276 4277
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
4278
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4279
		  int this_cpu, int sd_flag)
4280
{
4281
	struct sched_group *idlest = NULL, *group = sd->groups;
4282
	unsigned long min_load = ULONG_MAX, this_load = 0;
4283
	int load_idx = sd->forkexec_idx;
4284
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
4285

4286 4287 4288
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

4289 4290 4291 4292
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
4293

4294 4295
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
4296
					tsk_cpus_allowed(p)))
4297 4298 4299 4300 4301 4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 4315
			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;
		}

		/* Adjust by relative CPU power of the group */
4316
		avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;
4317 4318 4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329 4330 4331 4332 4333 4334 4335 4336 4337 4338 4339 4340 4341

		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;
	int idlest = -1;
	int i;

	/* Traverse only the allowed CPUs */
4342
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4343 4344 4345 4346 4347
		load = weighted_cpuload(i);

		if (load < min_load || (load == min_load && i == this_cpu)) {
			min_load = load;
			idlest = i;
4348 4349 4350
		}
	}

4351 4352
	return idlest;
}
4353

4354 4355 4356
/*
 * Try and locate an idle CPU in the sched_domain.
 */
4357
static int select_idle_sibling(struct task_struct *p, int target)
4358
{
4359
	struct sched_domain *sd;
4360
	struct sched_group *sg;
4361
	int i = task_cpu(p);
4362

4363 4364
	if (idle_cpu(target))
		return target;
4365 4366

	/*
4367
	 * If the prevous cpu is cache affine and idle, don't be stupid.
4368
	 */
4369 4370
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
4371 4372

	/*
4373
	 * Otherwise, iterate the domains and find an elegible idle cpu.
4374
	 */
4375
	sd = rcu_dereference(per_cpu(sd_llc, target));
4376
	for_each_lower_domain(sd) {
4377 4378 4379 4380 4381 4382 4383
		sg = sd->groups;
		do {
			if (!cpumask_intersects(sched_group_cpus(sg),
						tsk_cpus_allowed(p)))
				goto next;

			for_each_cpu(i, sched_group_cpus(sg)) {
4384
				if (i == target || !idle_cpu(i))
4385 4386
					goto next;
			}
4387

4388 4389 4390 4391 4392 4393 4394 4395
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
4396 4397 4398
	return target;
}

4399
/*
4400 4401 4402
 * 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.
4403
 *
4404 4405
 * 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.
4406
 *
4407
 * Returns the target cpu number.
4408 4409 4410
 *
 * preempt must be disabled.
 */
4411
static int
4412
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
4413
{
4414
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
4415 4416
	int cpu = smp_processor_id();
	int new_cpu = cpu;
4417
	int want_affine = 0;
4418
	int sync = wake_flags & WF_SYNC;
4419

4420
	if (p->nr_cpus_allowed == 1)
4421 4422
		return prev_cpu;

4423
	if (sd_flag & SD_BALANCE_WAKE) {
4424
		if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
4425 4426 4427
			want_affine = 1;
		new_cpu = prev_cpu;
	}
4428

4429
	rcu_read_lock();
4430
	for_each_domain(cpu, tmp) {
4431 4432 4433
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

4434
		/*
4435 4436
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
4437
		 */
4438 4439 4440
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
4441
			break;
4442
		}
4443

4444
		if (tmp->flags & sd_flag)
4445 4446 4447
			sd = tmp;
	}

4448
	if (affine_sd) {
4449
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
4450 4451 4452 4453
			prev_cpu = cpu;

		new_cpu = select_idle_sibling(p, prev_cpu);
		goto unlock;
4454
	}
4455

4456 4457
	while (sd) {
		struct sched_group *group;
4458
		int weight;
4459

4460
		if (!(sd->flags & sd_flag)) {
4461 4462 4463
			sd = sd->child;
			continue;
		}
4464

4465
		group = find_idlest_group(sd, p, cpu, sd_flag);
4466 4467 4468 4469
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
4470

4471
		new_cpu = find_idlest_cpu(group, p, cpu);
4472 4473 4474 4475
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
4476
		}
4477 4478 4479

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
4480
		weight = sd->span_weight;
4481 4482
		sd = NULL;
		for_each_domain(cpu, tmp) {
4483
			if (weight <= tmp->span_weight)
4484
				break;
4485
			if (tmp->flags & sd_flag)
4486 4487 4488
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
4489
	}
4490 4491
unlock:
	rcu_read_unlock();
4492

4493
	return new_cpu;
4494
}
4495 4496 4497 4498 4499 4500 4501 4502 4503 4504

/*
 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
 * cfs_rq_of(p) references at time of call are still valid and identify the
 * previous cpu.  However, the caller only guarantees p->pi_lock is held; no
 * other assumptions, including the state of rq->lock, should be made.
 */
static void
migrate_task_rq_fair(struct task_struct *p, int next_cpu)
{
4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	/*
	 * Load tracking: accumulate removed load so that it can be processed
	 * when we next update owning cfs_rq under rq->lock.  Tasks contribute
	 * to blocked load iff they have a positive decay-count.  It can never
	 * be negative here since on-rq tasks have decay-count == 0.
	 */
	if (se->avg.decay_count) {
		se->avg.decay_count = -__synchronize_entity_decay(se);
4516 4517
		atomic_long_add(se->avg.load_avg_contrib,
						&cfs_rq->removed_load);
4518
	}
4519
}
4520 4521
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
4522 4523
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
4524 4525 4526 4527
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
4528 4529
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
4530 4531 4532 4533 4534 4535 4536 4537 4538
	 *
	 * 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.
4539
	 */
4540
	return calc_delta_fair(gran, se);
4541 4542
}

4543 4544 4545 4546 4547 4548 4549 4550 4551 4552 4553 4554 4555 4556 4557 4558 4559 4560 4561 4562 4563 4564
/*
 * 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
4565
	gran = wakeup_gran(curr, se);
4566 4567 4568 4569 4570 4571
	if (vdiff > gran)
		return 1;

	return 0;
}

4572 4573
static void set_last_buddy(struct sched_entity *se)
{
4574 4575 4576 4577 4578
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
4579 4580 4581 4582
}

static void set_next_buddy(struct sched_entity *se)
{
4583 4584 4585 4586 4587
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
4588 4589
}

4590 4591
static void set_skip_buddy(struct sched_entity *se)
{
4592 4593
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
4594 4595
}

4596 4597 4598
/*
 * Preempt the current task with a newly woken task if needed:
 */
4599
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
4600 4601
{
	struct task_struct *curr = rq->curr;
4602
	struct sched_entity *se = &curr->se, *pse = &p->se;
4603
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
4604
	int scale = cfs_rq->nr_running >= sched_nr_latency;
4605
	int next_buddy_marked = 0;
4606

I
Ingo Molnar 已提交
4607 4608 4609
	if (unlikely(se == pse))
		return;

4610
	/*
4611
	 * This is possible from callers such as move_task(), in which we
4612 4613 4614 4615 4616 4617 4618
	 * 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;

4619
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
4620
		set_next_buddy(pse);
4621 4622
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
4623

4624 4625 4626
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
4627 4628 4629 4630 4631 4632
	 *
	 * 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.
4633 4634 4635 4636
	 */
	if (test_tsk_need_resched(curr))
		return;

4637 4638 4639 4640 4641
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

4642
	/*
4643 4644
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
4645
	 */
4646
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
4647
		return;
4648

4649
	find_matching_se(&se, &pse);
4650
	update_curr(cfs_rq_of(se));
4651
	BUG_ON(!pse);
4652 4653 4654 4655 4656 4657 4658
	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);
4659
		goto preempt;
4660
	}
4661

4662
	return;
4663

4664 4665 4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679
preempt:
	resched_task(curr);
	/*
	 * 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);
4680 4681
}

4682 4683
static struct task_struct *
pick_next_task_fair(struct rq *rq, struct task_struct *prev)
4684 4685 4686
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
4687 4688
	struct task_struct *p;

4689
again:
4690 4691
#ifdef CONFIG_FAIR_GROUP_SCHED
	if (!cfs_rq->nr_running)
4692
		goto idle;
4693

4694
	if (prev->sched_class != &fair_sched_class)
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 4720 4721 4722 4723 4724 4725 4726 4727 4728 4729 4730 4731 4732 4733 4734 4735 4736 4737 4738 4739 4740 4741 4742 4743 4744 4745 4746 4747 4748 4749 4750 4751 4752 4753 4754 4755 4756 4757 4758 4759 4760 4761 4762 4763 4764 4765
		goto simple;

	/*
	 * Because of the set_next_buddy() in dequeue_task_fair() it is rather
	 * likely that a next task is from the same cgroup as the current.
	 *
	 * Therefore attempt to avoid putting and setting the entire cgroup
	 * hierarchy, only change the part that actually changes.
	 */

	do {
		struct sched_entity *curr = cfs_rq->curr;

		/*
		 * Since we got here without doing put_prev_entity() we also
		 * have to consider cfs_rq->curr. If it is still a runnable
		 * entity, update_curr() will update its vruntime, otherwise
		 * forget we've ever seen it.
		 */
		if (curr && curr->on_rq)
			update_curr(cfs_rq);
		else
			curr = NULL;

		/*
		 * This call to check_cfs_rq_runtime() will do the throttle and
		 * dequeue its entity in the parent(s). Therefore the 'simple'
		 * nr_running test will indeed be correct.
		 */
		if (unlikely(check_cfs_rq_runtime(cfs_rq)))
			goto simple;

		se = pick_next_entity(cfs_rq, curr);
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

	p = task_of(se);

	/*
	 * Since we haven't yet done put_prev_entity and if the selected task
	 * is a different task than we started out with, try and touch the
	 * least amount of cfs_rqs.
	 */
	if (prev != p) {
		struct sched_entity *pse = &prev->se;

		while (!(cfs_rq = is_same_group(se, pse))) {
			int se_depth = se->depth;
			int pse_depth = pse->depth;

			if (se_depth <= pse_depth) {
				put_prev_entity(cfs_rq_of(pse), pse);
				pse = parent_entity(pse);
			}
			if (se_depth >= pse_depth) {
				set_next_entity(cfs_rq_of(se), se);
				se = parent_entity(se);
			}
		}

		put_prev_entity(cfs_rq, pse);
		set_next_entity(cfs_rq, se);
	}

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

	return p;
simple:
	cfs_rq = &rq->cfs;
#endif
4766

4767
	if (!cfs_rq->nr_running)
4768
		goto idle;
4769

4770
	put_prev_task(rq, prev);
4771

4772
	do {
4773
		se = pick_next_entity(cfs_rq, NULL);
4774
		set_next_entity(cfs_rq, se);
4775 4776 4777
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
4778
	p = task_of(se);
4779

4780 4781
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
4782 4783

	return p;
4784 4785

idle:
4786
	if (idle_balance(rq)) /* drops rq->lock */
4787 4788 4789
		goto again;

	return NULL;
4790 4791 4792 4793 4794
}

/*
 * Account for a descheduled task:
 */
4795
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
4796 4797 4798 4799 4800 4801
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
4802
		put_prev_entity(cfs_rq, se);
4803 4804 4805
	}
}

4806 4807 4808 4809 4810 4811 4812 4813 4814 4815 4816 4817 4818 4819 4820 4821 4822 4823 4824 4825 4826 4827 4828 4829 4830
/*
 * 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);
4831 4832 4833 4834 4835 4836
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
		 rq->skip_clock_update = 1;
4837 4838 4839 4840 4841
	}

	set_skip_buddy(se);
}

4842 4843 4844 4845
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

4846 4847
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
4848 4849 4850 4851 4852 4853 4854 4855 4856 4857
		return false;

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

	yield_task_fair(rq);

	return true;
}

4858
#ifdef CONFIG_SMP
4859
/**************************************************
P
Peter Zijlstra 已提交
4860 4861 4862 4863 4864 4865 4866 4867 4868 4869 4870 4871 4872 4873 4874 4875 4876 4877 4878 4879 4880 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 4916 4917 4918 4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935 4936 4937 4938 4939 4940 4941 4942 4943 4944 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
 * Fair scheduling class load-balancing methods.
 *
 * BASICS
 *
 * The purpose of load-balancing is to achieve the same basic fairness the
 * per-cpu scheduler provides, namely provide a proportional amount of compute
 * time to each task. This is expressed in the following equation:
 *
 *   W_i,n/P_i == W_j,n/P_j for all i,j                               (1)
 *
 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
 * W_i,0 is defined as:
 *
 *   W_i,0 = \Sum_j w_i,j                                             (2)
 *
 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
 * is derived from the nice value as per prio_to_weight[].
 *
 * The weight average is an exponential decay average of the instantaneous
 * weight:
 *
 *   W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0               (3)
 *
 * P_i is the cpu power (or compute capacity) of cpu i, typically it is the
 * 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):
 *
 *   imb_i,j = max{ avg(W/P), W_i/P_i } - min{ avg(W/P), W_j/P_j }    (4)
 *
 * 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.]
 */ 
4976

4977 4978
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

4979 4980
enum fbq_type { regular, remote, all };

4981
#define LBF_ALL_PINNED	0x01
4982
#define LBF_NEED_BREAK	0x02
4983 4984
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
4985 4986 4987 4988 4989

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
4990
	int			src_cpu;
4991 4992 4993 4994

	int			dst_cpu;
	struct rq		*dst_rq;

4995 4996
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
4997
	enum cpu_idle_type	idle;
4998
	long			imbalance;
4999 5000 5001
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

5002
	unsigned int		flags;
5003 5004 5005 5006

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
5007 5008

	enum fbq_type		fbq_type;
5009 5010
};

5011
/*
5012
 * move_task - move a task from one runqueue to another runqueue.
5013 5014
 * Both runqueues must be locked.
 */
5015
static void move_task(struct task_struct *p, struct lb_env *env)
5016
{
5017 5018 5019 5020
	deactivate_task(env->src_rq, p, 0);
	set_task_cpu(p, env->dst_cpu);
	activate_task(env->dst_rq, p, 0);
	check_preempt_curr(env->dst_rq, p, 0);
5021 5022
}

5023 5024 5025 5026 5027 5028 5029 5030 5031 5032 5033 5034 5035 5036 5037 5038 5039 5040 5041 5042 5043 5044 5045 5046 5047 5048 5049 5050 5051 5052 5053 5054
/*
 * Is this task likely cache-hot:
 */
static int
task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
{
	s64 delta;

	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
	if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running &&
			(&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;

	delta = now - p->se.exec_start;

	return delta < (s64)sysctl_sched_migration_cost;
}

5055 5056 5057 5058 5059 5060
#ifdef CONFIG_NUMA_BALANCING
/* Returns true if the destination node has incurred more faults */
static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
{
	int src_nid, dst_nid;

5061
	if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults_memory ||
5062 5063 5064 5065 5066 5067 5068
	    !(env->sd->flags & SD_NUMA)) {
		return false;
	}

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

5069
	if (src_nid == dst_nid)
5070 5071
		return false;

5072 5073 5074 5075
	/* Always encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
		return true;

5076 5077 5078
	/* If both task and group weight improve, this move is a winner. */
	if (task_weight(p, dst_nid) > task_weight(p, src_nid) &&
	    group_weight(p, dst_nid) > group_weight(p, src_nid))
5079 5080 5081 5082
		return true;

	return false;
}
5083 5084 5085 5086 5087 5088 5089 5090 5091


static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
{
	int src_nid, dst_nid;

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

5092
	if (!p->numa_faults_memory || !(env->sd->flags & SD_NUMA))
5093 5094 5095 5096 5097
		return false;

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

5098
	if (src_nid == dst_nid)
5099 5100
		return false;

5101 5102 5103 5104
	/* Migrating away from the preferred node is always bad. */
	if (src_nid == p->numa_preferred_nid)
		return true;

5105 5106 5107
	/* If either task or group weight get worse, don't do it. */
	if (task_weight(p, dst_nid) < task_weight(p, src_nid) ||
	    group_weight(p, dst_nid) < group_weight(p, src_nid))
5108 5109 5110 5111 5112
		return true;

	return false;
}

5113 5114 5115 5116 5117 5118
#else
static inline bool migrate_improves_locality(struct task_struct *p,
					     struct lb_env *env)
{
	return false;
}
5119 5120 5121 5122 5123 5124

static inline bool migrate_degrades_locality(struct task_struct *p,
					     struct lb_env *env)
{
	return false;
}
5125 5126
#endif

5127 5128 5129 5130
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
5131
int can_migrate_task(struct task_struct *p, struct lb_env *env)
5132 5133 5134 5135
{
	int tsk_cache_hot = 0;
	/*
	 * We do not migrate tasks that are:
5136
	 * 1) throttled_lb_pair, or
5137
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5138 5139
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
5140
	 */
5141 5142 5143
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

5144
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5145
		int cpu;
5146

5147
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5148

5149 5150
		env->flags |= LBF_SOME_PINNED;

5151 5152 5153 5154 5155 5156 5157 5158
		/*
		 * 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.
		 */
5159
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5160 5161
			return 0;

5162 5163 5164
		/* 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))) {
5165
				env->flags |= LBF_DST_PINNED;
5166 5167 5168
				env->new_dst_cpu = cpu;
				break;
			}
5169
		}
5170

5171 5172
		return 0;
	}
5173 5174

	/* Record that we found atleast one task that could run on dst_cpu */
5175
	env->flags &= ~LBF_ALL_PINNED;
5176

5177
	if (task_running(env->src_rq, p)) {
5178
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5179 5180 5181 5182 5183
		return 0;
	}

	/*
	 * Aggressive migration if:
5184 5185 5186
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
5187
	 */
5188
	tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd);
5189 5190
	if (!tsk_cache_hot)
		tsk_cache_hot = migrate_degrades_locality(p, env);
5191 5192 5193 5194 5195 5196 5197 5198 5199 5200 5201

	if (migrate_improves_locality(p, env)) {
#ifdef CONFIG_SCHEDSTATS
		if (tsk_cache_hot) {
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
			schedstat_inc(p, se.statistics.nr_forced_migrations);
		}
#endif
		return 1;
	}

5202
	if (!tsk_cache_hot ||
5203
		env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
Z
Zhang Hang 已提交
5204

5205
		if (tsk_cache_hot) {
5206
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
5207
			schedstat_inc(p, se.statistics.nr_forced_migrations);
5208
		}
Z
Zhang Hang 已提交
5209

5210 5211 5212
		return 1;
	}

Z
Zhang Hang 已提交
5213 5214
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
5215 5216
}

5217 5218 5219 5220 5221 5222 5223
/*
 * move_one_task tries to move exactly one task from busiest to this_rq, as
 * part of active balancing operations within "domain".
 * Returns 1 if successful and 0 otherwise.
 *
 * Called with both runqueues locked.
 */
5224
static int move_one_task(struct lb_env *env)
5225 5226 5227
{
	struct task_struct *p, *n;

5228 5229 5230
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
5231

5232 5233 5234 5235 5236 5237 5238 5239
		move_task(p, env);
		/*
		 * Right now, this is only the second place move_task()
		 * is called, so we can safely collect move_task()
		 * stats here rather than inside move_task().
		 */
		schedstat_inc(env->sd, lb_gained[env->idle]);
		return 1;
5240 5241 5242 5243
	}
	return 0;
}

5244 5245
static const unsigned int sched_nr_migrate_break = 32;

5246
/*
5247
 * move_tasks tries to move up to imbalance weighted load from busiest to
5248 5249 5250 5251 5252 5253
 * this_rq, as part of a balancing operation within domain "sd".
 * Returns 1 if successful and 0 otherwise.
 *
 * Called with both runqueues locked.
 */
static int move_tasks(struct lb_env *env)
5254
{
5255 5256
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
5257 5258
	unsigned long load;
	int pulled = 0;
5259

5260
	if (env->imbalance <= 0)
5261
		return 0;
5262

5263 5264
	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
5265

5266 5267
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
5268
		if (env->loop > env->loop_max)
5269
			break;
5270 5271

		/* take a breather every nr_migrate tasks */
5272
		if (env->loop > env->loop_break) {
5273
			env->loop_break += sched_nr_migrate_break;
5274
			env->flags |= LBF_NEED_BREAK;
5275
			break;
5276
		}
5277

5278
		if (!can_migrate_task(p, env))
5279 5280 5281
			goto next;

		load = task_h_load(p);
5282

5283
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5284 5285
			goto next;

5286
		if ((load / 2) > env->imbalance)
5287
			goto next;
5288

5289
		move_task(p, env);
5290
		pulled++;
5291
		env->imbalance -= load;
5292 5293

#ifdef CONFIG_PREEMPT
5294 5295 5296 5297 5298
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
		 * kernels will stop after the first task is pulled to minimize
		 * the critical section.
		 */
5299
		if (env->idle == CPU_NEWLY_IDLE)
5300
			break;
5301 5302
#endif

5303 5304 5305 5306
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
5307
		if (env->imbalance <= 0)
5308
			break;
5309 5310 5311

		continue;
next:
5312
		list_move_tail(&p->se.group_node, tasks);
5313
	}
5314

5315
	/*
5316 5317 5318
	 * Right now, this is one of only two places move_task() is called,
	 * so we can safely collect move_task() stats here rather than
	 * inside move_task().
5319
	 */
5320
	schedstat_add(env->sd, lb_gained[env->idle], pulled);
5321

5322
	return pulled;
5323 5324
}

P
Peter Zijlstra 已提交
5325
#ifdef CONFIG_FAIR_GROUP_SCHED
5326 5327 5328
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
5329
static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
5330
{
5331 5332
	struct sched_entity *se = tg->se[cpu];
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
5333

5334 5335 5336
	/* throttled entities do not contribute to load */
	if (throttled_hierarchy(cfs_rq))
		return;
5337

5338
	update_cfs_rq_blocked_load(cfs_rq, 1);
5339

5340 5341 5342 5343 5344 5345 5346 5347 5348 5349 5350 5351 5352 5353
	if (se) {
		update_entity_load_avg(se, 1);
		/*
		 * We pivot on our runnable average having decayed to zero for
		 * list removal.  This generally implies that all our children
		 * have also been removed (modulo rounding error or bandwidth
		 * control); however, such cases are rare and we can fix these
		 * at enqueue.
		 *
		 * TODO: fix up out-of-order children on enqueue.
		 */
		if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running)
			list_del_leaf_cfs_rq(cfs_rq);
	} else {
5354
		struct rq *rq = rq_of(cfs_rq);
5355 5356
		update_rq_runnable_avg(rq, rq->nr_running);
	}
5357 5358
}

5359
static void update_blocked_averages(int cpu)
5360 5361
{
	struct rq *rq = cpu_rq(cpu);
5362 5363
	struct cfs_rq *cfs_rq;
	unsigned long flags;
5364

5365 5366
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
5367 5368 5369 5370
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
5371
	for_each_leaf_cfs_rq(rq, cfs_rq) {
5372 5373 5374 5375 5376 5377
		/*
		 * Note: We may want to consider periodically releasing
		 * rq->lock about these updates so that creating many task
		 * groups does not result in continually extending hold time.
		 */
		__update_blocked_averages_cpu(cfs_rq->tg, rq->cpu);
5378
	}
5379 5380

	raw_spin_unlock_irqrestore(&rq->lock, flags);
5381 5382
}

5383
/*
5384
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5385 5386 5387
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
5388
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
5389
{
5390 5391
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
5392
	unsigned long now = jiffies;
5393
	unsigned long load;
5394

5395
	if (cfs_rq->last_h_load_update == now)
5396 5397
		return;

5398 5399 5400 5401 5402 5403 5404
	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;
	}
5405

5406
	if (!se) {
5407
		cfs_rq->h_load = cfs_rq->runnable_load_avg;
5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
		load = div64_ul(load * se->avg.load_avg_contrib,
				cfs_rq->runnable_load_avg + 1);
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
5419 5420
}

5421
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
5422
{
5423
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
5424

5425
	update_cfs_rq_h_load(cfs_rq);
5426 5427
	return div64_ul(p->se.avg.load_avg_contrib * cfs_rq->h_load,
			cfs_rq->runnable_load_avg + 1);
P
Peter Zijlstra 已提交
5428 5429
}
#else
5430
static inline void update_blocked_averages(int cpu)
5431 5432 5433
{
}

5434
static unsigned long task_h_load(struct task_struct *p)
5435
{
5436
	return p->se.avg.load_avg_contrib;
5437
}
P
Peter Zijlstra 已提交
5438
#endif
5439 5440 5441 5442 5443 5444 5445 5446 5447

/********** Helpers for find_busiest_group ************************/
/*
 * 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
5448
	unsigned long load_per_task;
5449
	unsigned long group_power;
5450 5451 5452 5453
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int group_capacity;
	unsigned int idle_cpus;
	unsigned int group_weight;
5454
	int group_imb; /* Is there an imbalance in the group ? */
5455
	int group_has_capacity; /* Is there extra capacity in the group? */
5456 5457 5458 5459
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
5460 5461
};

J
Joonsoo Kim 已提交
5462 5463 5464 5465 5466 5467 5468 5469 5470 5471 5472 5473
/*
 * 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 */
	unsigned long total_pwr;	/* Total power of all groups in sd */
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
5474
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
5475 5476
};

5477 5478 5479 5480 5481 5482 5483 5484 5485 5486 5487 5488 5489 5490 5491 5492 5493 5494 5495
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,
		.total_pwr = 0UL,
		.busiest_stat = {
			.avg_load = 0UL,
		},
	};
}

5496 5497 5498
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
5499
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
5500 5501
 *
 * Return: The load index.
5502 5503 5504 5505 5506 5507 5508 5509 5510 5511 5512 5513 5514 5515 5516 5517 5518 5519 5520 5521 5522 5523
 */
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;
}

5524
static unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
5525
{
5526
	return SCHED_POWER_SCALE;
5527 5528 5529 5530 5531 5532 5533
}

unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu)
{
	return default_scale_freq_power(sd, cpu);
}

5534
static unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
5535
{
5536
	unsigned long weight = sd->span_weight;
5537 5538 5539 5540 5541 5542 5543 5544 5545 5546 5547 5548
	unsigned long smt_gain = sd->smt_gain;

	smt_gain /= weight;

	return smt_gain;
}

unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
{
	return default_scale_smt_power(sd, cpu);
}

5549
static unsigned long scale_rt_power(int cpu)
5550 5551
{
	struct rq *rq = cpu_rq(cpu);
5552
	u64 total, available, age_stamp, avg;
5553

5554 5555 5556 5557 5558 5559 5560
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
	age_stamp = ACCESS_ONCE(rq->age_stamp);
	avg = ACCESS_ONCE(rq->rt_avg);

5561
	total = sched_avg_period() + (rq_clock(rq) - age_stamp);
5562

5563
	if (unlikely(total < avg)) {
5564 5565 5566
		/* Ensures that power won't end up being negative */
		available = 0;
	} else {
5567
		available = total - avg;
5568
	}
5569

5570 5571
	if (unlikely((s64)total < SCHED_POWER_SCALE))
		total = SCHED_POWER_SCALE;
5572

5573
	total >>= SCHED_POWER_SHIFT;
5574 5575 5576 5577 5578 5579

	return div_u64(available, total);
}

static void update_cpu_power(struct sched_domain *sd, int cpu)
{
5580
	unsigned long weight = sd->span_weight;
5581
	unsigned long power = SCHED_POWER_SCALE;
5582 5583 5584 5585 5586 5587 5588 5589
	struct sched_group *sdg = sd->groups;

	if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
		if (sched_feat(ARCH_POWER))
			power *= arch_scale_smt_power(sd, cpu);
		else
			power *= default_scale_smt_power(sd, cpu);

5590
		power >>= SCHED_POWER_SHIFT;
5591 5592
	}

5593
	sdg->sgp->power_orig = power;
5594 5595 5596 5597 5598 5599

	if (sched_feat(ARCH_POWER))
		power *= arch_scale_freq_power(sd, cpu);
	else
		power *= default_scale_freq_power(sd, cpu);

5600
	power >>= SCHED_POWER_SHIFT;
5601

5602
	power *= scale_rt_power(cpu);
5603
	power >>= SCHED_POWER_SHIFT;
5604 5605 5606 5607

	if (!power)
		power = 1;

5608
	cpu_rq(cpu)->cpu_power = power;
5609
	sdg->sgp->power = power;
5610 5611
}

5612
void update_group_power(struct sched_domain *sd, int cpu)
5613 5614 5615
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
5616
	unsigned long power, power_orig;
5617 5618 5619 5620 5621
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
	sdg->sgp->next_update = jiffies + interval;
5622 5623 5624 5625 5626 5627

	if (!child) {
		update_cpu_power(sd, cpu);
		return;
	}

5628
	power_orig = power = 0;
5629

P
Peter Zijlstra 已提交
5630 5631 5632 5633 5634 5635
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

5636
		for_each_cpu(cpu, sched_group_cpus(sdg)) {
5637 5638
			struct sched_group_power *sgp;
			struct rq *rq = cpu_rq(cpu);
5639

5640 5641 5642 5643 5644 5645 5646 5647 5648 5649 5650 5651 5652 5653 5654 5655 5656 5657
			/*
			 * build_sched_domains() -> init_sched_groups_power()
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
			 * Use power_of(), which is set irrespective of domains
			 * in update_cpu_power().
			 *
			 * This avoids power/power_orig from being 0 and
			 * causing divide-by-zero issues on boot.
			 *
			 * Runtime updates will correct power_orig.
			 */
			if (unlikely(!rq->sd)) {
				power_orig += power_of(cpu);
				power += power_of(cpu);
				continue;
			}
5658

5659 5660 5661
			sgp = rq->sd->groups->sgp;
			power_orig += sgp->power_orig;
			power += sgp->power;
5662
		}
P
Peter Zijlstra 已提交
5663 5664 5665 5666 5667 5668 5669 5670
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
5671
			power_orig += group->sgp->power_orig;
P
Peter Zijlstra 已提交
5672 5673 5674 5675
			power += group->sgp->power;
			group = group->next;
		} while (group != child->groups);
	}
5676

5677 5678
	sdg->sgp->power_orig = power_orig;
	sdg->sgp->power = power;
5679 5680
}

5681 5682 5683 5684 5685 5686 5687 5688 5689 5690 5691
/*
 * Try and fix up capacity for tiny siblings, this is needed when
 * things like SD_ASYM_PACKING need f_b_g to select another sibling
 * which on its own isn't powerful enough.
 *
 * See update_sd_pick_busiest() and check_asym_packing().
 */
static inline int
fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
{
	/*
5692
	 * Only siblings can have significantly less than SCHED_POWER_SCALE
5693
	 */
P
Peter Zijlstra 已提交
5694
	if (!(sd->flags & SD_SHARE_CPUPOWER))
5695 5696 5697 5698 5699
		return 0;

	/*
	 * If ~90% of the cpu_power is still there, we're good.
	 */
5700
	if (group->sgp->power * 32 > group->sgp->power_orig * 29)
5701 5702 5703 5704 5705
		return 1;

	return 0;
}

5706 5707 5708 5709 5710 5711 5712 5713 5714 5715 5716 5717 5718 5719 5720 5721
/*
 * 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
5722 5723
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
5724 5725
 *
 * When this is so detected; this group becomes a candidate for busiest; see
5726
 * update_sd_pick_busiest(). And calculate_imbalance() and
5727
 * find_busiest_group() avoid some of the usual balance conditions to allow it
5728 5729 5730 5731 5732 5733 5734
 * 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.
 */

5735
static inline int sg_imbalanced(struct sched_group *group)
5736
{
5737
	return group->sgp->imbalance;
5738 5739
}

5740 5741 5742
/*
 * Compute the group capacity.
 *
5743 5744 5745
 * Avoid the issue where N*frac(smt_power) >= 1 creates 'phantom' cores by
 * first dividing out the smt factor and computing the actual number of cores
 * and limit power unit capacity with that.
5746 5747 5748
 */
static inline int sg_capacity(struct lb_env *env, struct sched_group *group)
{
5749 5750 5751 5752 5753 5754
	unsigned int capacity, smt, cpus;
	unsigned int power, power_orig;

	power = group->sgp->power;
	power_orig = group->sgp->power_orig;
	cpus = group->group_weight;
5755

5756 5757 5758
	/* smt := ceil(cpus / power), assumes: 1 < smt_power < 2 */
	smt = DIV_ROUND_UP(SCHED_POWER_SCALE * cpus, power_orig);
	capacity = cpus / smt; /* cores */
5759

5760
	capacity = min_t(unsigned, capacity, DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE));
5761 5762 5763 5764 5765 5766
	if (!capacity)
		capacity = fix_small_capacity(env->sd, group);

	return capacity;
}

5767 5768
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
5769
 * @env: The load balancing environment.
5770 5771 5772 5773 5774
 * @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.
 */
5775 5776
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
5777
			int local_group, struct sg_lb_stats *sgs)
5778
{
5779
	unsigned long load;
5780
	int i;
5781

5782 5783
	memset(sgs, 0, sizeof(*sgs));

5784
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
5785 5786 5787
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
5788
		if (local_group)
5789
			load = target_load(i, load_idx);
5790
		else
5791 5792 5793
			load = source_load(i, load_idx);

		sgs->group_load += load;
5794
		sgs->sum_nr_running += rq->nr_running;
5795 5796 5797 5798
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
5799
		sgs->sum_weighted_load += weighted_cpuload(i);
5800 5801
		if (idle_cpu(i))
			sgs->idle_cpus++;
5802 5803 5804
	}

	/* Adjust by relative CPU power of the group */
5805 5806
	sgs->group_power = group->sgp->power;
	sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / sgs->group_power;
5807

5808
	if (sgs->sum_nr_running)
5809
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
5810

5811
	sgs->group_weight = group->group_weight;
5812

5813 5814 5815
	sgs->group_imb = sg_imbalanced(group);
	sgs->group_capacity = sg_capacity(env, group);

5816 5817
	if (sgs->group_capacity > sgs->sum_nr_running)
		sgs->group_has_capacity = 1;
5818 5819
}

5820 5821
/**
 * update_sd_pick_busiest - return 1 on busiest group
5822
 * @env: The load balancing environment.
5823 5824
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
5825
 * @sgs: sched_group statistics
5826 5827 5828
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
5829 5830 5831
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
5832
 */
5833
static bool update_sd_pick_busiest(struct lb_env *env,
5834 5835
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
5836
				   struct sg_lb_stats *sgs)
5837
{
J
Joonsoo Kim 已提交
5838
	if (sgs->avg_load <= sds->busiest_stat.avg_load)
5839 5840 5841 5842 5843 5844 5845 5846 5847 5848 5849 5850 5851
		return false;

	if (sgs->sum_nr_running > sgs->group_capacity)
		return true;

	if (sgs->group_imb)
		return true;

	/*
	 * ASYM_PACKING needs to move all the work to the lowest
	 * numbered CPUs in the group, therefore mark all groups
	 * higher than ourself as busy.
	 */
5852 5853
	if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
	    env->dst_cpu < group_first_cpu(sg)) {
5854 5855 5856 5857 5858 5859 5860 5861 5862 5863
		if (!sds->busiest)
			return true;

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

	return false;
}

5864 5865 5866 5867 5868 5869 5870 5871 5872 5873 5874 5875 5876 5877 5878 5879 5880 5881 5882 5883 5884 5885 5886 5887 5888 5889 5890 5891 5892 5893
#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 */

5894
/**
5895
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
5896
 * @env: The load balancing environment.
5897 5898
 * @sds: variable to hold the statistics for this sched_domain.
 */
5899
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
5900
{
5901 5902
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
5903
	struct sg_lb_stats tmp_sgs;
5904 5905 5906 5907 5908
	int load_idx, prefer_sibling = 0;

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

5909
	load_idx = get_sd_load_idx(env->sd, env->idle);
5910 5911

	do {
J
Joonsoo Kim 已提交
5912
		struct sg_lb_stats *sgs = &tmp_sgs;
5913 5914
		int local_group;

5915
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
5916 5917 5918
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
5919 5920 5921 5922

			if (env->idle != CPU_NEWLY_IDLE ||
			    time_after_eq(jiffies, sg->sgp->next_update))
				update_group_power(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
5923
		}
5924

J
Joonsoo Kim 已提交
5925
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs);
5926

5927 5928 5929
		if (local_group)
			goto next_group;

5930 5931
		/*
		 * In case the child domain prefers tasks go to siblings
5932
		 * first, lower the sg capacity to one so that we'll try
5933 5934 5935 5936 5937 5938
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
		 * these excess tasks, i.e. nr_running < group_capacity. 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).
5939
		 */
5940 5941
		if (prefer_sibling && sds->local &&
		    sds->local_stat.group_has_capacity)
5942
			sgs->group_capacity = min(sgs->group_capacity, 1U);
5943

5944
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
5945
			sds->busiest = sg;
J
Joonsoo Kim 已提交
5946
			sds->busiest_stat = *sgs;
5947 5948
		}

5949 5950 5951 5952 5953
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
		sds->total_pwr += sgs->group_power;

5954
		sg = sg->next;
5955
	} while (sg != env->sd->groups);
5956 5957 5958

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
5959 5960 5961 5962 5963 5964 5965 5966 5967 5968 5969 5970 5971 5972 5973 5974 5975 5976 5977
}

/**
 * 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.
 *
5978
 * Return: 1 when packing is required and a task should be moved to
5979 5980
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
5981
 * @env: The load balancing environment.
5982 5983
 * @sds: Statistics of the sched_domain which is to be packed
 */
5984
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
5985 5986 5987
{
	int busiest_cpu;

5988
	if (!(env->sd->flags & SD_ASYM_PACKING))
5989 5990 5991 5992 5993 5994
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
5995
	if (env->dst_cpu > busiest_cpu)
5996 5997
		return 0;

5998
	env->imbalance = DIV_ROUND_CLOSEST(
5999 6000
		sds->busiest_stat.avg_load * sds->busiest_stat.group_power,
		SCHED_POWER_SCALE);
6001

6002
	return 1;
6003 6004 6005 6006 6007 6008
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
6009
 * @env: The load balancing environment.
6010 6011
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
6012 6013
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6014 6015 6016
{
	unsigned long tmp, pwr_now = 0, pwr_move = 0;
	unsigned int imbn = 2;
6017
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
6018
	struct sg_lb_stats *local, *busiest;
6019

J
Joonsoo Kim 已提交
6020 6021
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6022

J
Joonsoo Kim 已提交
6023 6024 6025 6026
	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;
6027

J
Joonsoo Kim 已提交
6028 6029
	scaled_busy_load_per_task =
		(busiest->load_per_task * SCHED_POWER_SCALE) /
6030
		busiest->group_power;
J
Joonsoo Kim 已提交
6031

6032 6033
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
6034
		env->imbalance = busiest->load_per_task;
6035 6036 6037 6038 6039 6040 6041 6042 6043
		return;
	}

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

6044
	pwr_now += busiest->group_power *
J
Joonsoo Kim 已提交
6045
			min(busiest->load_per_task, busiest->avg_load);
6046
	pwr_now += local->group_power *
J
Joonsoo Kim 已提交
6047
			min(local->load_per_task, local->avg_load);
6048
	pwr_now /= SCHED_POWER_SCALE;
6049 6050

	/* Amount of load we'd subtract */
J
Joonsoo Kim 已提交
6051
	tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
6052
		busiest->group_power;
J
Joonsoo Kim 已提交
6053
	if (busiest->avg_load > tmp) {
6054
		pwr_move += busiest->group_power *
J
Joonsoo Kim 已提交
6055 6056 6057
			    min(busiest->load_per_task,
				busiest->avg_load - tmp);
	}
6058 6059

	/* Amount of load we'd add */
6060
	if (busiest->avg_load * busiest->group_power <
J
Joonsoo Kim 已提交
6061
	    busiest->load_per_task * SCHED_POWER_SCALE) {
6062 6063
		tmp = (busiest->avg_load * busiest->group_power) /
		      local->group_power;
J
Joonsoo Kim 已提交
6064 6065
	} else {
		tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
6066
		      local->group_power;
J
Joonsoo Kim 已提交
6067
	}
6068 6069
	pwr_move += local->group_power *
		    min(local->load_per_task, local->avg_load + tmp);
6070
	pwr_move /= SCHED_POWER_SCALE;
6071 6072 6073

	/* Move if we gain throughput */
	if (pwr_move > pwr_now)
J
Joonsoo Kim 已提交
6074
		env->imbalance = busiest->load_per_task;
6075 6076 6077 6078 6079
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
6080
 * @env: load balance environment
6081 6082
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
6083
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6084
{
6085
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
6086 6087 6088 6089
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6090

J
Joonsoo Kim 已提交
6091
	if (busiest->group_imb) {
6092 6093 6094 6095
		/*
		 * 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
6096 6097
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
6098 6099
	}

6100 6101 6102 6103 6104
	/*
	 * In the presence of smp nice balancing, certain scenarios can have
	 * max load less than avg load(as we skip the groups at or below
	 * its cpu_power, while calculating max_load..)
	 */
6105 6106
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
6107 6108
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
6109 6110
	}

J
Joonsoo Kim 已提交
6111
	if (!busiest->group_imb) {
6112 6113
		/*
		 * Don't want to pull so many tasks that a group would go idle.
6114 6115
		 * Except of course for the group_imb case, since then we might
		 * have to drop below capacity to reach cpu-load equilibrium.
6116
		 */
J
Joonsoo Kim 已提交
6117 6118
		load_above_capacity =
			(busiest->sum_nr_running - busiest->group_capacity);
6119

6120
		load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
6121
		load_above_capacity /= busiest->group_power;
6122 6123 6124 6125 6126 6127 6128 6129 6130 6131
	}

	/*
	 * We're trying to get all the cpus to the average_load, so we don't
	 * want to push ourselves above the average load, nor do we wish to
	 * reduce the max loaded cpu below the average load. At the same time,
	 * we also don't want to reduce the group load below the group capacity
	 * (so that we can implement power-savings policies etc). Thus we look
	 * for the minimum possible imbalance.
	 */
6132
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6133 6134

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
6135
	env->imbalance = min(
6136 6137
		max_pull * busiest->group_power,
		(sds->avg_load - local->avg_load) * local->group_power
J
Joonsoo Kim 已提交
6138
	) / SCHED_POWER_SCALE;
6139 6140 6141

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
6142
	 * there is no guarantee that any tasks will be moved so we'll have
6143 6144 6145
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
6146
	if (env->imbalance < busiest->load_per_task)
6147
		return fix_small_imbalance(env, sds);
6148
}
6149

6150 6151 6152 6153 6154 6155 6156 6157 6158 6159 6160 6161
/******* find_busiest_group() helpers end here *********************/

/**
 * find_busiest_group - Returns the busiest group within the sched_domain
 * if there is an imbalance. If there isn't an imbalance, and
 * the user has opted for power-savings, it returns a group whose
 * CPUs can be put to idle by rebalancing those tasks elsewhere, if
 * such a group exists.
 *
 * Also calculates the amount of weighted load which should be moved
 * to restore balance.
 *
6162
 * @env: The load balancing environment.
6163
 *
6164
 * Return:	- The busiest group if imbalance exists.
6165 6166 6167 6168
 *		- If no imbalance and user has opted for power-savings balance,
 *		   return the least loaded group whose CPUs can be
 *		   put to idle by rebalancing its tasks onto our group.
 */
J
Joonsoo Kim 已提交
6169
static struct sched_group *find_busiest_group(struct lb_env *env)
6170
{
J
Joonsoo Kim 已提交
6171
	struct sg_lb_stats *local, *busiest;
6172 6173
	struct sd_lb_stats sds;

6174
	init_sd_lb_stats(&sds);
6175 6176 6177 6178 6179

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
6180
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
6181 6182
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
6183

6184 6185
	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(env, &sds))
6186 6187
		return sds.busiest;

6188
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
6189
	if (!sds.busiest || busiest->sum_nr_running == 0)
6190 6191
		goto out_balanced;

6192
	sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
6193

P
Peter Zijlstra 已提交
6194 6195
	/*
	 * If the busiest group is imbalanced the below checks don't
6196
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
6197 6198
	 * isn't true due to cpus_allowed constraints and the like.
	 */
J
Joonsoo Kim 已提交
6199
	if (busiest->group_imb)
P
Peter Zijlstra 已提交
6200 6201
		goto force_balance;

6202
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
J
Joonsoo Kim 已提交
6203 6204
	if (env->idle == CPU_NEWLY_IDLE && local->group_has_capacity &&
	    !busiest->group_has_capacity)
6205 6206
		goto force_balance;

6207 6208 6209 6210
	/*
	 * If the local group is more busy than the selected busiest group
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
6211
	if (local->avg_load >= busiest->avg_load)
6212 6213
		goto out_balanced;

6214 6215 6216 6217
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
6218
	if (local->avg_load >= sds.avg_load)
6219 6220
		goto out_balanced;

6221
	if (env->idle == CPU_IDLE) {
6222 6223 6224 6225 6226 6227
		/*
		 * This cpu is idle. If the busiest group load doesn't
		 * have more tasks than the number of available cpu's and
		 * there is no imbalance between this and busiest group
		 * wrt to idle cpu's, it is balanced.
		 */
J
Joonsoo Kim 已提交
6228 6229
		if ((local->idle_cpus < busiest->idle_cpus) &&
		    busiest->sum_nr_running <= busiest->group_weight)
6230
			goto out_balanced;
6231 6232 6233 6234 6235
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
6236 6237
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
6238
			goto out_balanced;
6239
	}
6240

6241
force_balance:
6242
	/* Looks like there is an imbalance. Compute it */
6243
	calculate_imbalance(env, &sds);
6244 6245 6246
	return sds.busiest;

out_balanced:
6247
	env->imbalance = 0;
6248 6249 6250 6251 6252 6253
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
6254
static struct rq *find_busiest_queue(struct lb_env *env,
6255
				     struct sched_group *group)
6256 6257
{
	struct rq *busiest = NULL, *rq;
6258
	unsigned long busiest_load = 0, busiest_power = 1;
6259 6260
	int i;

6261
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6262 6263 6264 6265 6266
		unsigned long power, capacity, wl;
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
6267

6268 6269 6270 6271 6272 6273 6274 6275 6276 6277 6278 6279 6280 6281 6282 6283 6284 6285 6286 6287 6288 6289 6290 6291
		/*
		 * 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;

		power = power_of(i);
		capacity = DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE);
6292
		if (!capacity)
6293
			capacity = fix_small_capacity(env->sd, group);
6294

6295
		wl = weighted_cpuload(i);
6296

6297 6298 6299 6300
		/*
		 * When comparing with imbalance, use weighted_cpuload()
		 * which is not scaled with the cpu power.
		 */
6301
		if (capacity && rq->nr_running == 1 && wl > env->imbalance)
6302 6303
			continue;

6304 6305 6306 6307 6308
		/*
		 * For the load comparisons with the other cpu's, consider
		 * the weighted_cpuload() scaled with the cpu power, so that
		 * the load can be moved away from the cpu that is potentially
		 * running at a lower capacity.
6309 6310 6311 6312 6313
		 *
		 * Thus we're looking for max(wl_i / power_i), crosswise
		 * multiplication to rid ourselves of the division works out
		 * to: wl_i * power_j > wl_j * power_i;  where j is our
		 * previous maximum.
6314
		 */
6315 6316 6317
		if (wl * busiest_power > busiest_load * power) {
			busiest_load = wl;
			busiest_power = power;
6318 6319 6320 6321 6322 6323 6324 6325 6326 6327 6328 6329 6330 6331
			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. */
6332
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6333

6334
static int need_active_balance(struct lb_env *env)
6335
{
6336 6337 6338
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
6339 6340 6341 6342 6343 6344

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
6345
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6346
			return 1;
6347 6348 6349 6350 6351
	}

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

6352 6353
static int active_load_balance_cpu_stop(void *data);

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 6381 6382 6383 6384
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.
	 */
6385
	return balance_cpu == env->dst_cpu;
6386 6387
}

6388 6389 6390 6391 6392 6393
/*
 * 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,
6394
			int *continue_balancing)
6395
{
6396
	int ld_moved, cur_ld_moved, active_balance = 0;
6397
	struct sched_domain *sd_parent = sd->parent;
6398 6399 6400
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
6401
	struct cpumask *cpus = __get_cpu_var(load_balance_mask);
6402

6403 6404
	struct lb_env env = {
		.sd		= sd,
6405 6406
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
6407
		.dst_grpmask    = sched_group_cpus(sd->groups),
6408
		.idle		= idle,
6409
		.loop_break	= sched_nr_migrate_break,
6410
		.cpus		= cpus,
6411
		.fbq_type	= all,
6412 6413
	};

6414 6415 6416 6417
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
6418
	if (idle == CPU_NEWLY_IDLE)
6419 6420
		env.dst_grpmask = NULL;

6421 6422 6423 6424 6425
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
6426 6427
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
6428
		goto out_balanced;
6429
	}
6430

6431
	group = find_busiest_group(&env);
6432 6433 6434 6435 6436
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

6437
	busiest = find_busiest_queue(&env, group);
6438 6439 6440 6441 6442
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

6443
	BUG_ON(busiest == env.dst_rq);
6444

6445
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
6446 6447 6448 6449 6450 6451 6452 6453 6454

	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.
		 */
6455
		env.flags |= LBF_ALL_PINNED;
6456 6457 6458
		env.src_cpu   = busiest->cpu;
		env.src_rq    = busiest;
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
6459

6460
more_balance:
6461
		local_irq_save(flags);
6462
		double_rq_lock(env.dst_rq, busiest);
6463 6464 6465 6466 6467 6468 6469

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
		cur_ld_moved = move_tasks(&env);
		ld_moved += cur_ld_moved;
6470
		double_rq_unlock(env.dst_rq, busiest);
6471 6472 6473 6474 6475
		local_irq_restore(flags);

		/*
		 * some other cpu did the load balance for us.
		 */
6476 6477 6478
		if (cur_ld_moved && env.dst_cpu != smp_processor_id())
			resched_cpu(env.dst_cpu);

6479 6480 6481 6482 6483
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

6484 6485 6486 6487 6488 6489 6490 6491 6492 6493 6494 6495 6496 6497 6498 6499 6500 6501 6502
		/*
		 * 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.
		 */
6503
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
6504

6505 6506 6507
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

6508
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
6509
			env.dst_cpu	 = env.new_dst_cpu;
6510
			env.flags	&= ~LBF_DST_PINNED;
6511 6512
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
6513

6514 6515 6516 6517 6518 6519
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
6520

6521 6522 6523 6524 6525 6526 6527 6528 6529 6530 6531 6532
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
			int *group_imbalance = &sd_parent->groups->sgp->imbalance;

			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) {
				*group_imbalance = 1;
			} else if (*group_imbalance)
				*group_imbalance = 0;
		}

6533
		/* All tasks on this runqueue were pinned by CPU affinity */
6534
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
6535
			cpumask_clear_cpu(cpu_of(busiest), cpus);
6536 6537 6538
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
6539
				goto redo;
6540
			}
6541 6542 6543 6544 6545 6546
			goto out_balanced;
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
6547 6548 6549 6550 6551 6552 6553 6554
		/*
		 * 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++;
6555

6556
		if (need_active_balance(&env)) {
6557 6558
			raw_spin_lock_irqsave(&busiest->lock, flags);

6559 6560 6561
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
6562 6563
			 */
			if (!cpumask_test_cpu(this_cpu,
6564
					tsk_cpus_allowed(busiest->curr))) {
6565 6566
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
6567
				env.flags |= LBF_ALL_PINNED;
6568 6569 6570
				goto out_one_pinned;
			}

6571 6572 6573 6574 6575
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
6576 6577 6578 6579 6580 6581
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
6582

6583
			if (active_balance) {
6584 6585 6586
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
6587
			}
6588 6589 6590 6591 6592 6593 6594 6595 6596 6597 6598 6599 6600 6601 6602 6603 6604 6605 6606 6607 6608 6609 6610 6611 6612 6613 6614 6615 6616 6617 6618 6619 6620

			/*
			 * We've kicked active balancing, reset the failure
			 * counter.
			 */
			sd->nr_balance_failed = sd->cache_nice_tries+1;
		}
	} else
		sd->nr_balance_failed = 0;

	if (likely(!active_balance)) {
		/* We were unbalanced, so reset the balancing interval */
		sd->balance_interval = sd->min_interval;
	} else {
		/*
		 * If we've begun active balancing, start to back off. This
		 * case may not be covered by the all_pinned logic if there
		 * is only 1 task on the busy runqueue (because we don't call
		 * move_tasks).
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
	schedstat_inc(sd, lb_balanced[idle]);

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
6621
	if (((env.flags & LBF_ALL_PINNED) &&
6622
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
6623 6624 6625
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

6626
	ld_moved = 0;
6627 6628 6629 6630 6631 6632 6633 6634
out:
	return ld_moved;
}

/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
6635
static int idle_balance(struct rq *this_rq)
6636 6637 6638 6639
{
	struct sched_domain *sd;
	int pulled_task = 0;
	unsigned long next_balance = jiffies + HZ;
6640
	u64 curr_cost = 0;
6641
	int this_cpu = this_rq->cpu;
6642

6643 6644 6645 6646 6647 6648 6649
	idle_enter_fair(this_rq);
	/*
	 * 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);

6650
	if (this_rq->avg_idle < sysctl_sched_migration_cost)
6651
		goto out;
6652

6653 6654 6655 6656 6657
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

6658
	update_blocked_averages(this_cpu);
6659
	rcu_read_lock();
6660 6661
	for_each_domain(this_cpu, sd) {
		unsigned long interval;
6662
		int continue_balancing = 1;
6663
		u64 t0, domain_cost;
6664 6665 6666 6667

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

6668 6669 6670
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost)
			break;

6671
		if (sd->flags & SD_BALANCE_NEWIDLE) {
6672 6673
			t0 = sched_clock_cpu(this_cpu);

6674
			/* If we've pulled tasks over stop searching: */
6675
			pulled_task = load_balance(this_cpu, this_rq,
6676 6677
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
6678 6679 6680 6681 6682 6683

			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;
6684
		}
6685 6686 6687 6688

		interval = msecs_to_jiffies(sd->balance_interval);
		if (time_after(next_balance, sd->last_balance + interval))
			next_balance = sd->last_balance + interval;
6689
		if (pulled_task)
6690 6691
			break;
	}
6692
	rcu_read_unlock();
6693 6694 6695

	raw_spin_lock(&this_rq->lock);

6696 6697 6698 6699
	/*
	 * While browsing the domains, we released the rq lock.
	 * A task could have be enqueued in the meantime
	 */
6700 6701 6702 6703
	if (this_rq->nr_running && !pulled_task) {
		pulled_task = 1;
		goto out;
	}
6704

6705 6706 6707 6708 6709 6710 6711
	if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
		/*
		 * We are going idle. next_balance may be set based on
		 * a busy processor. So reset next_balance.
		 */
		this_rq->next_balance = next_balance;
	}
6712 6713 6714

	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;
6715

6716 6717 6718 6719
out:
	if (pulled_task)
		this_rq->idle_stamp = 0;

6720
	return pulled_task;
6721 6722 6723
}

/*
6724 6725 6726 6727
 * 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.
6728
 */
6729
static int active_load_balance_cpu_stop(void *data)
6730
{
6731 6732
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
6733
	int target_cpu = busiest_rq->push_cpu;
6734
	struct rq *target_rq = cpu_rq(target_cpu);
6735
	struct sched_domain *sd;
6736 6737 6738 6739 6740 6741 6742

	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;
6743 6744 6745

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
6746
		goto out_unlock;
6747 6748 6749 6750 6751 6752 6753 6754 6755 6756 6757 6758

	/*
	 * 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);

	/* move a task from busiest_rq to target_rq */
	double_lock_balance(busiest_rq, target_rq);

	/* Search for an sd spanning us and the target CPU. */
6759
	rcu_read_lock();
6760 6761 6762 6763 6764 6765 6766
	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)) {
6767 6768
		struct lb_env env = {
			.sd		= sd,
6769 6770 6771 6772
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
6773 6774 6775
			.idle		= CPU_IDLE,
		};

6776 6777
		schedstat_inc(sd, alb_count);

6778
		if (move_one_task(&env))
6779 6780 6781 6782
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
6783
	rcu_read_unlock();
6784
	double_unlock_balance(busiest_rq, target_rq);
6785 6786 6787 6788
out_unlock:
	busiest_rq->active_balance = 0;
	raw_spin_unlock_irq(&busiest_rq->lock);
	return 0;
6789 6790
}

6791
#ifdef CONFIG_NO_HZ_COMMON
6792 6793 6794 6795 6796 6797
/*
 * 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.
 */
6798
static struct {
6799
	cpumask_var_t idle_cpus_mask;
6800
	atomic_t nr_cpus;
6801 6802
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
6803

6804
static inline int find_new_ilb(void)
6805
{
6806
	int ilb = cpumask_first(nohz.idle_cpus_mask);
6807

6808 6809 6810 6811
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
6812 6813
}

6814 6815 6816 6817 6818
/*
 * 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).
 */
6819
static void nohz_balancer_kick(void)
6820 6821 6822 6823 6824
{
	int ilb_cpu;

	nohz.next_balance++;

6825
	ilb_cpu = find_new_ilb();
6826

6827 6828
	if (ilb_cpu >= nr_cpu_ids)
		return;
6829

6830
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
6831 6832 6833 6834 6835 6836 6837 6838
		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);
6839 6840 6841
	return;
}

6842
static inline void nohz_balance_exit_idle(int cpu)
6843 6844 6845 6846 6847 6848 6849 6850
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
		cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
		atomic_dec(&nohz.nr_cpus);
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

6851 6852 6853
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
6854
	int cpu = smp_processor_id();
6855 6856

	rcu_read_lock();
6857
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
6858 6859 6860 6861 6862

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

6863
	atomic_inc(&sd->groups->sgp->nr_busy_cpus);
V
Vincent Guittot 已提交
6864
unlock:
6865 6866 6867 6868 6869 6870
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
6871
	int cpu = smp_processor_id();
6872 6873

	rcu_read_lock();
6874
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
6875 6876 6877 6878 6879

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

6880
	atomic_dec(&sd->groups->sgp->nr_busy_cpus);
V
Vincent Guittot 已提交
6881
unlock:
6882 6883 6884
	rcu_read_unlock();
}

6885
/*
6886
 * This routine will record that the cpu is going idle with tick stopped.
6887
 * This info will be used in performing idle load balancing in the future.
6888
 */
6889
void nohz_balance_enter_idle(int cpu)
6890
{
6891 6892 6893 6894 6895 6896
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

6897 6898
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
6899

6900 6901 6902
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
6903
}
6904

6905
static int sched_ilb_notifier(struct notifier_block *nfb,
6906 6907 6908 6909
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
6910
		nohz_balance_exit_idle(smp_processor_id());
6911 6912 6913 6914 6915
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
6916 6917 6918 6919
#endif

static DEFINE_SPINLOCK(balancing);

6920 6921 6922 6923
/*
 * 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.
 */
6924
void update_max_interval(void)
6925 6926 6927 6928
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

6929 6930 6931 6932
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
6933
 * Balancing parameters are set up in init_sched_domains.
6934
 */
6935
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
6936
{
6937
	int continue_balancing = 1;
6938
	int cpu = rq->cpu;
6939
	unsigned long interval;
6940
	struct sched_domain *sd;
6941 6942 6943
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
6944 6945
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
6946

6947
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
6948

6949
	rcu_read_lock();
6950
	for_each_domain(cpu, sd) {
6951 6952 6953 6954 6955 6956 6957 6958 6959 6960 6961 6962
		/*
		 * 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;

6963 6964 6965
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

6966 6967 6968 6969 6970 6971 6972 6973 6974 6975 6976
		/*
		 * 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;
		}

6977 6978 6979 6980 6981 6982
		interval = sd->balance_interval;
		if (idle != CPU_IDLE)
			interval *= sd->busy_factor;

		/* scale ms to jiffies */
		interval = msecs_to_jiffies(interval);
6983
		interval = clamp(interval, 1UL, max_load_balance_interval);
6984 6985 6986 6987 6988 6989 6990 6991 6992

		need_serialize = sd->flags & SD_SERIALIZE;

		if (need_serialize) {
			if (!spin_trylock(&balancing))
				goto out;
		}

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
6993
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
6994
				/*
6995
				 * The LBF_DST_PINNED logic could have changed
6996 6997
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
6998
				 */
6999
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7000 7001 7002 7003 7004 7005 7006 7007 7008 7009
			}
			sd->last_balance = jiffies;
		}
		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;
		}
7010 7011
	}
	if (need_decay) {
7012
		/*
7013 7014
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
7015
		 */
7016 7017
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
7018
	}
7019
	rcu_read_unlock();
7020 7021 7022 7023 7024 7025 7026 7027 7028 7029

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

7030
#ifdef CONFIG_NO_HZ_COMMON
7031
/*
7032
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7033 7034
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
7035
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7036
{
7037
	int this_cpu = this_rq->cpu;
7038 7039 7040
	struct rq *rq;
	int balance_cpu;

7041 7042 7043
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
7044 7045

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7046
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7047 7048 7049 7050 7051 7052 7053
			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.
		 */
7054
		if (need_resched())
7055 7056
			break;

V
Vincent Guittot 已提交
7057 7058 7059 7060 7061 7062
		rq = cpu_rq(balance_cpu);

		raw_spin_lock_irq(&rq->lock);
		update_rq_clock(rq);
		update_idle_cpu_load(rq);
		raw_spin_unlock_irq(&rq->lock);
7063

7064
		rebalance_domains(rq, CPU_IDLE);
7065 7066 7067 7068 7069

		if (time_after(this_rq->next_balance, rq->next_balance))
			this_rq->next_balance = rq->next_balance;
	}
	nohz.next_balance = this_rq->next_balance;
7070 7071
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7072 7073 7074
}

/*
7075 7076 7077 7078 7079 7080 7081
 * Current heuristic for kicking the idle load balancer in the presence
 * of an idle cpu is the system.
 *   - This rq has more than one task.
 *   - At any scheduler domain level, this cpu's scheduler group has multiple
 *     busy cpu's exceeding the group's power.
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
7082
 */
7083
static inline int nohz_kick_needed(struct rq *rq)
7084 7085
{
	unsigned long now = jiffies;
7086
	struct sched_domain *sd;
7087
	struct sched_group_power *sgp;
7088
	int nr_busy, cpu = rq->cpu;
7089

7090
	if (unlikely(rq->idle_balance))
7091 7092
		return 0;

7093 7094 7095 7096
       /*
	* 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.
	*/
7097
	set_cpu_sd_state_busy();
7098
	nohz_balance_exit_idle(cpu);
7099 7100 7101 7102 7103 7104 7105

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
		return 0;
7106 7107

	if (time_before(now, nohz.next_balance))
7108 7109
		return 0;

7110 7111
	if (rq->nr_running >= 2)
		goto need_kick;
7112

7113
	rcu_read_lock();
7114
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
7115

7116 7117 7118
	if (sd) {
		sgp = sd->groups->sgp;
		nr_busy = atomic_read(&sgp->nr_busy_cpus);
7119

7120
		if (nr_busy > 1)
7121
			goto need_kick_unlock;
7122
	}
7123 7124 7125 7126 7127 7128 7129

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

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

7130
	rcu_read_unlock();
7131
	return 0;
7132 7133 7134

need_kick_unlock:
	rcu_read_unlock();
7135 7136
need_kick:
	return 1;
7137 7138
}
#else
7139
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7140 7141 7142 7143 7144 7145
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
7146 7147
static void run_rebalance_domains(struct softirq_action *h)
{
7148
	struct rq *this_rq = this_rq();
7149
	enum cpu_idle_type idle = this_rq->idle_balance ?
7150 7151
						CPU_IDLE : CPU_NOT_IDLE;

7152
	rebalance_domains(this_rq, idle);
7153 7154

	/*
7155
	 * If this cpu has a pending nohz_balance_kick, then do the
7156 7157 7158
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
7159
	nohz_idle_balance(this_rq, idle);
7160 7161
}

7162
static inline int on_null_domain(struct rq *rq)
7163
{
7164
	return !rcu_dereference_sched(rq->sd);
7165 7166 7167 7168 7169
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
7170
void trigger_load_balance(struct rq *rq)
7171 7172
{
	/* Don't need to rebalance while attached to NULL domain */
7173 7174 7175 7176
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
7177
		raise_softirq(SCHED_SOFTIRQ);
7178
#ifdef CONFIG_NO_HZ_COMMON
7179
	if (nohz_kick_needed(rq))
7180
		nohz_balancer_kick();
7181
#endif
7182 7183
}

7184 7185 7186 7187 7188 7189 7190 7191
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
7192 7193 7194

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
7195 7196
}

7197
#endif /* CONFIG_SMP */
7198

7199 7200 7201
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
7202
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
7203 7204 7205 7206 7207 7208
{
	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
7209
		entity_tick(cfs_rq, se, queued);
7210
	}
7211

7212
	if (numabalancing_enabled)
7213
		task_tick_numa(rq, curr);
7214

7215
	update_rq_runnable_avg(rq, 1);
7216 7217 7218
}

/*
P
Peter Zijlstra 已提交
7219 7220 7221
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
7222
 */
P
Peter Zijlstra 已提交
7223
static void task_fork_fair(struct task_struct *p)
7224
{
7225 7226
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
7227
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
7228 7229 7230
	struct rq *rq = this_rq();
	unsigned long flags;

7231
	raw_spin_lock_irqsave(&rq->lock, flags);
7232

7233 7234
	update_rq_clock(rq);

7235 7236 7237
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

7238 7239 7240 7241 7242 7243 7244 7245 7246
	/*
	 * Not only the cpu but also the task_group of the parent might have
	 * been changed after parent->se.parent,cfs_rq were copied to
	 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
	 * of child point to valid ones.
	 */
	rcu_read_lock();
	__set_task_cpu(p, this_cpu);
	rcu_read_unlock();
7247

7248
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
7249

7250 7251
	if (curr)
		se->vruntime = curr->vruntime;
7252
	place_entity(cfs_rq, se, 1);
7253

P
Peter Zijlstra 已提交
7254
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
7255
		/*
7256 7257 7258
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
7259
		swap(curr->vruntime, se->vruntime);
7260
		resched_task(rq->curr);
7261
	}
7262

7263 7264
	se->vruntime -= cfs_rq->min_vruntime;

7265
	raw_spin_unlock_irqrestore(&rq->lock, flags);
7266 7267
}

7268 7269 7270 7271
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
7272 7273
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
7274
{
P
Peter Zijlstra 已提交
7275 7276 7277
	if (!p->se.on_rq)
		return;

7278 7279 7280 7281 7282
	/*
	 * 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
7283
	if (rq->curr == p) {
7284 7285 7286
		if (p->prio > oldprio)
			resched_task(rq->curr);
	} else
7287
		check_preempt_curr(rq, p, 0);
7288 7289
}

P
Peter Zijlstra 已提交
7290 7291 7292 7293 7294 7295 7296 7297 7298 7299 7300 7301 7302 7303 7304 7305 7306 7307 7308 7309 7310 7311
static void switched_from_fair(struct rq *rq, struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	/*
	 * Ensure the task's vruntime is normalized, so that when its
	 * switched back to the fair class the enqueue_entity(.flags=0) will
	 * do the right thing.
	 *
	 * If it was on_rq, then the dequeue_entity(.flags=0) will already
	 * have normalized the vruntime, if it was !on_rq, then only when
	 * the task is sleeping will it still have non-normalized vruntime.
	 */
	if (!se->on_rq && p->state != TASK_RUNNING) {
		/*
		 * 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;
	}
7312

7313
#ifdef CONFIG_SMP
7314 7315 7316 7317 7318
	/*
	* Remove our load from contribution when we leave sched_fair
	* and ensure we don't carry in an old decay_count if we
	* switch back.
	*/
7319 7320 7321
	if (se->avg.decay_count) {
		__synchronize_entity_decay(se);
		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
7322 7323
	}
#endif
P
Peter Zijlstra 已提交
7324 7325
}

7326 7327 7328
/*
 * We switched to the sched_fair class.
 */
P
Peter Zijlstra 已提交
7329
static void switched_to_fair(struct rq *rq, struct task_struct *p)
7330
{
7331 7332 7333 7334 7335 7336 7337 7338 7339
	struct sched_entity *se = &p->se;
#ifdef CONFIG_FAIR_GROUP_SCHED
	/*
	 * 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
	if (!se->on_rq)
P
Peter Zijlstra 已提交
7340 7341
		return;

7342 7343 7344 7345 7346
	/*
	 * We were most likely switched from sched_rt, so
	 * kick off the schedule if running, otherwise just see
	 * if we can still preempt the current task.
	 */
P
Peter Zijlstra 已提交
7347
	if (rq->curr == p)
7348 7349
		resched_task(rq->curr);
	else
7350
		check_preempt_curr(rq, p, 0);
7351 7352
}

7353 7354 7355 7356 7357 7358 7359 7360 7361
/* 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;

7362 7363 7364 7365 7366 7367 7368
	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);
	}
7369 7370
}

7371 7372 7373 7374 7375 7376 7377
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
7378
#ifdef CONFIG_SMP
7379
	atomic64_set(&cfs_rq->decay_counter, 1);
7380
	atomic_long_set(&cfs_rq->removed_load, 0);
7381
#endif
7382 7383
}

P
Peter Zijlstra 已提交
7384
#ifdef CONFIG_FAIR_GROUP_SCHED
7385
static void task_move_group_fair(struct task_struct *p, int on_rq)
P
Peter Zijlstra 已提交
7386
{
P
Peter Zijlstra 已提交
7387
	struct sched_entity *se = &p->se;
7388
	struct cfs_rq *cfs_rq;
P
Peter Zijlstra 已提交
7389

7390 7391 7392 7393 7394 7395 7396 7397 7398 7399 7400 7401 7402
	/*
	 * If the task was not on the rq at the time of this cgroup movement
	 * it must have been asleep, sleeping tasks keep their ->vruntime
	 * absolute on their old rq until wakeup (needed for the fair sleeper
	 * bonus in place_entity()).
	 *
	 * If it was on the rq, we've just 'preempted' it, which does convert
	 * ->vruntime to a relative base.
	 *
	 * Make sure both cases convert their relative position when migrating
	 * to another cgroup's rq. This does somewhat interfere with the
	 * fair sleeper stuff for the first placement, but who cares.
	 */
7403 7404 7405 7406 7407 7408
	/*
	 * When !on_rq, vruntime of the task has usually NOT been normalized.
	 * But there are some cases where it has already been normalized:
	 *
	 * - Moving a forked child which is waiting for being woken up by
	 *   wake_up_new_task().
7409 7410
	 * - Moving a task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
7411 7412 7413 7414
	 *
	 * To prevent boost or penalty in the new cfs_rq caused by delta
	 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
	 */
P
Peter Zijlstra 已提交
7415
	if (!on_rq && (!se->sum_exec_runtime || p->state == TASK_WAKING))
7416 7417
		on_rq = 1;

7418
	if (!on_rq)
P
Peter Zijlstra 已提交
7419
		se->vruntime -= cfs_rq_of(se)->min_vruntime;
7420
	set_task_rq(p, task_cpu(p));
P
Peter Zijlstra 已提交
7421
	se->depth = se->parent ? se->parent->depth + 1 : 0;
7422
	if (!on_rq) {
P
Peter Zijlstra 已提交
7423 7424
		cfs_rq = cfs_rq_of(se);
		se->vruntime += cfs_rq->min_vruntime;
7425 7426 7427 7428 7429 7430
#ifdef CONFIG_SMP
		/*
		 * migrate_task_rq_fair() will have removed our previous
		 * contribution, but we must synchronize for ongoing future
		 * decay.
		 */
P
Peter Zijlstra 已提交
7431 7432
		se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
		cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
7433 7434
#endif
	}
P
Peter Zijlstra 已提交
7435
}
7436 7437 7438 7439 7440 7441 7442 7443 7444 7445 7446 7447 7448 7449 7450 7451 7452 7453 7454 7455 7456 7457 7458 7459 7460 7461 7462 7463 7464 7465 7466 7467 7468 7469 7470 7471 7472 7473 7474 7475 7476 7477 7478 7479 7480 7481 7482 7483 7484 7485 7486 7487 7488 7489 7490 7491 7492 7493 7494 7495 7496 7497 7498 7499 7500 7501 7502 7503 7504 7505 7506 7507 7508 7509 7510 7511 7512 7513 7514 7515 7516 7517 7518 7519 7520 7521 7522 7523 7524 7525 7526 7527

void free_fair_sched_group(struct task_group *tg)
{
	int i;

	destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));

	for_each_possible_cpu(i) {
		if (tg->cfs_rq)
			kfree(tg->cfs_rq[i]);
		if (tg->se)
			kfree(tg->se[i]);
	}

	kfree(tg->cfs_rq);
	kfree(tg->se);
}

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
	struct cfs_rq *cfs_rq;
	struct sched_entity *se;
	int i;

	tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
	if (!tg->cfs_rq)
		goto err;
	tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
	if (!tg->se)
		goto err;

	tg->shares = NICE_0_LOAD;

	init_cfs_bandwidth(tg_cfs_bandwidth(tg));

	for_each_possible_cpu(i) {
		cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
				      GFP_KERNEL, cpu_to_node(i));
		if (!cfs_rq)
			goto err;

		se = kzalloc_node(sizeof(struct sched_entity),
				  GFP_KERNEL, cpu_to_node(i));
		if (!se)
			goto err_free_rq;

		init_cfs_rq(cfs_rq);
		init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

void unregister_fair_sched_group(struct task_group *tg, int cpu)
{
	struct rq *rq = cpu_rq(cpu);
	unsigned long flags;

	/*
	* Only empty task groups can be destroyed; so we can speculatively
	* check on_list without danger of it being re-added.
	*/
	if (!tg->cfs_rq[cpu]->on_list)
		return;

	raw_spin_lock_irqsave(&rq->lock, flags);
	list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
	raw_spin_unlock_irqrestore(&rq->lock, flags);
}

void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
			struct sched_entity *se, int cpu,
			struct sched_entity *parent)
{
	struct rq *rq = cpu_rq(cpu);

	cfs_rq->tg = tg;
	cfs_rq->rq = rq;
	init_cfs_rq_runtime(cfs_rq);

	tg->cfs_rq[cpu] = cfs_rq;
	tg->se[cpu] = se;

	/* se could be NULL for root_task_group */
	if (!se)
		return;

P
Peter Zijlstra 已提交
7528
	if (!parent) {
7529
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
7530 7531
		se->depth = 0;
	} else {
7532
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
7533 7534
		se->depth = parent->depth + 1;
	}
7535 7536

	se->my_q = cfs_rq;
7537 7538
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
7539 7540 7541 7542 7543 7544 7545 7546 7547 7548 7549 7550 7551 7552 7553 7554 7555 7556 7557 7558 7559 7560 7561 7562 7563 7564 7565 7566 7567 7568
	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);
7569 7570 7571

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
7572
		for_each_sched_entity(se)
7573 7574 7575 7576 7577 7578 7579 7580 7581 7582 7583 7584 7585 7586 7587 7588 7589 7590 7591 7592 7593
			update_cfs_shares(group_cfs_rq(se));
		raw_spin_unlock_irqrestore(&rq->lock, flags);
	}

done:
	mutex_unlock(&shares_mutex);
	return 0;
}
#else /* CONFIG_FAIR_GROUP_SCHED */

void free_fair_sched_group(struct task_group *tg) { }

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
	return 1;
}

void unregister_fair_sched_group(struct task_group *tg, int cpu) { }

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
7594

7595
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
7596 7597 7598 7599 7600 7601 7602 7603 7604
{
	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)
7605
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
7606 7607 7608 7609

	return rr_interval;
}

7610 7611 7612
/*
 * All the scheduling class methods:
 */
7613
const struct sched_class fair_sched_class = {
7614
	.next			= &idle_sched_class,
7615 7616 7617
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
7618
	.yield_to_task		= yield_to_task_fair,
7619

I
Ingo Molnar 已提交
7620
	.check_preempt_curr	= check_preempt_wakeup,
7621 7622 7623 7624

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

7625
#ifdef CONFIG_SMP
L
Li Zefan 已提交
7626
	.select_task_rq		= select_task_rq_fair,
7627
	.migrate_task_rq	= migrate_task_rq_fair,
7628

7629 7630
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
7631 7632

	.task_waking		= task_waking_fair,
7633
#endif
7634

7635
	.set_curr_task          = set_curr_task_fair,
7636
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
7637
	.task_fork		= task_fork_fair,
7638 7639

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
7640
	.switched_from		= switched_from_fair,
7641
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
7642

7643 7644
	.get_rr_interval	= get_rr_interval_fair,

P
Peter Zijlstra 已提交
7645
#ifdef CONFIG_FAIR_GROUP_SCHED
7646
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
7647
#endif
7648 7649 7650
};

#ifdef CONFIG_SCHED_DEBUG
7651
void print_cfs_stats(struct seq_file *m, int cpu)
7652 7653 7654
{
	struct cfs_rq *cfs_rq;

7655
	rcu_read_lock();
7656
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
7657
		print_cfs_rq(m, cpu, cfs_rq);
7658
	rcu_read_unlock();
7659 7660
}
#endif
7661 7662 7663 7664 7665 7666

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

7667
#ifdef CONFIG_NO_HZ_COMMON
7668
	nohz.next_balance = jiffies;
7669
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
7670
	cpu_notifier(sched_ilb_notifier, 0);
7671 7672 7673 7674
#endif
#endif /* SMP */

}