fair.c 227.4 KB
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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
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 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
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 */

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

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

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

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

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

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

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

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

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

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

	return factor;
}

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

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

void sched_init_granularity(void)
{
	update_sysctl();
}

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

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

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

	w = scale_load_down(lw->weight);

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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#else	/* !CONFIG_FAIR_GROUP_SCHED */

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

#define entity_is_task(se)	1

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

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

	return &rq->cfs;
}

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

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

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

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

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

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

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#endif	/* CONFIG_FAIR_GROUP_SCHED */

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

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

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

	return min_vruntime;
}

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

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

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

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

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

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

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

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

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

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

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

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

	if (!left)
		return NULL;

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

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

	if (!next)
		return NULL;

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

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

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

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

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

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

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

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

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

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

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

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

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

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

693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737
/*
 * With new tasks being created, their initial util_avgs are extrapolated
 * based on the cfs_rq's current util_avg:
 *
 *   util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight
 *
 * However, in many cases, the above util_avg does not give a desired
 * value. Moreover, the sum of the util_avgs may be divergent, such
 * as when the series is a harmonic series.
 *
 * To solve this problem, we also cap the util_avg of successive tasks to
 * only 1/2 of the left utilization budget:
 *
 *   util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n
 *
 * where n denotes the nth task.
 *
 * For example, a simplest series from the beginning would be like:
 *
 *  task  util_avg: 512, 256, 128,  64,  32,   16,    8, ...
 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ...
 *
 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap)
 * if util_avg > util_avg_cap.
 */
void post_init_entity_util_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	struct sched_avg *sa = &se->avg;
	long cap = (long)(scale_load_down(SCHED_LOAD_SCALE) - cfs_rq->avg.util_avg) / 2;

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

			if (sa->util_avg > cap)
				sa->util_avg = cap;
		} else {
			sa->util_avg = cap;
		}
		sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
	}
}

738 739
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq);
static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq);
740
#else
741
void init_entity_runnable_average(struct sched_entity *se)
742 743
{
}
744 745 746
void post_init_entity_util_avg(struct sched_entity *se)
{
}
747 748
#endif

749
/*
750
 * Update the current task's runtime statistics.
751
 */
752
static void update_curr(struct cfs_rq *cfs_rq)
753
{
754
	struct sched_entity *curr = cfs_rq->curr;
755
	u64 now = rq_clock_task(rq_of(cfs_rq));
756
	u64 delta_exec;
757 758 759 760

	if (unlikely(!curr))
		return;

761 762
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
763
		return;
764

I
Ingo Molnar 已提交
765
	curr->exec_start = now;
766

767 768 769 770 771 772 773 774 775
	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);

776 777 778
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

779
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
780
		cpuacct_charge(curtask, delta_exec);
781
		account_group_exec_runtime(curtask, delta_exec);
782
	}
783 784

	account_cfs_rq_runtime(cfs_rq, delta_exec);
785 786
}

787 788 789 790 791
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

792
#ifdef CONFIG_SCHEDSTATS
793
static inline void
794
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
795
{
796 797 798 799 800 801 802
	u64 wait_start = rq_clock(rq_of(cfs_rq));

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

	se->statistics.wait_start = wait_start;
803 804
}

805 806 807 808
static void
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct task_struct *p;
809 810 811
	u64 delta;

	delta = rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start;
812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832

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

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

833 834 835
/*
 * Task is being enqueued - update stats:
 */
836 837
static inline void
update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
838 839 840 841 842
{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
843
	if (se != cfs_rq->curr)
844
		update_stats_wait_start(cfs_rq, se);
845 846 847
}

static inline void
848
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
849 850 851 852 853
{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
854
	if (se != cfs_rq->curr)
855
		update_stats_wait_end(cfs_rq, se);
856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887

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

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

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

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

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

static inline void
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
{
888
}
889
#endif
890 891 892 893 894

/*
 * We are picking a new current task - update its stats:
 */
static inline void
895
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
896 897 898 899
{
	/*
	 * We are starting a new run period:
	 */
900
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
901 902 903 904 905 906
}

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

907 908
#ifdef CONFIG_NUMA_BALANCING
/*
909 910 911
 * 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.
912
 */
913 914
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
915 916 917

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
918

919 920 921
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945
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)
{
946
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
947 948 949
	unsigned int scan, floor;
	unsigned int windows = 1;

950 951
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967
	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);
}

968 969 970 971 972 973 974 975 976 977 978 979
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));
}

980 981 982 983 984
struct numa_group {
	atomic_t refcount;

	spinlock_t lock; /* nr_tasks, tasks */
	int nr_tasks;
985
	pid_t gid;
986
	int active_nodes;
987 988

	struct rcu_head rcu;
989
	unsigned long total_faults;
990
	unsigned long max_faults_cpu;
991 992 993 994 995
	/*
	 * 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.
	 */
996
	unsigned long *faults_cpu;
997
	unsigned long faults[0];
998 999
};

1000 1001 1002 1003 1004 1005 1006 1007 1008
/* 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)

1009 1010 1011 1012 1013
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

1014 1015 1016 1017 1018 1019 1020
/*
 * The averaged statistics, shared & private, memory & cpu,
 * occupy the first half of the array. The second half of the
 * array is for current counters, which are averaged into the
 * first set by task_numa_placement.
 */
static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
1021
{
1022
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
1023 1024 1025 1026
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
1027
	if (!p->numa_faults)
1028 1029
		return 0;

1030 1031
	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
1032 1033
}

1034 1035 1036 1037 1038
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

1039 1040
	return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
1041 1042
}

1043 1044
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
1045 1046
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
1047 1048
}

1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060
/*
 * A node triggering more than 1/3 as many NUMA faults as the maximum is
 * considered part of a numa group's pseudo-interleaving set. Migrations
 * between these nodes are slowed down, to allow things to settle down.
 */
#define ACTIVE_NODE_FRACTION 3

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

1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125
/* Handle placement on systems where not all nodes are directly connected. */
static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
					int maxdist, bool task)
{
	unsigned long score = 0;
	int node;

	/*
	 * All nodes are directly connected, and the same distance
	 * from each other. No need for fancy placement algorithms.
	 */
	if (sched_numa_topology_type == NUMA_DIRECT)
		return 0;

	/*
	 * This code is called for each node, introducing N^2 complexity,
	 * which should be ok given the number of nodes rarely exceeds 8.
	 */
	for_each_online_node(node) {
		unsigned long faults;
		int dist = node_distance(nid, node);

		/*
		 * The furthest away nodes in the system are not interesting
		 * for placement; nid was already counted.
		 */
		if (dist == sched_max_numa_distance || node == nid)
			continue;

		/*
		 * On systems with a backplane NUMA topology, compare groups
		 * of nodes, and move tasks towards the group with the most
		 * memory accesses. When comparing two nodes at distance
		 * "hoplimit", only nodes closer by than "hoplimit" are part
		 * of each group. Skip other nodes.
		 */
		if (sched_numa_topology_type == NUMA_BACKPLANE &&
					dist > maxdist)
			continue;

		/* Add up the faults from nearby nodes. */
		if (task)
			faults = task_faults(p, node);
		else
			faults = group_faults(p, node);

		/*
		 * On systems with a glueless mesh NUMA topology, there are
		 * no fixed "groups of nodes". Instead, nodes that are not
		 * directly connected bounce traffic through intermediate
		 * nodes; a numa_group can occupy any set of nodes.
		 * The further away a node is, the less the faults count.
		 * This seems to result in good task placement.
		 */
		if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
			faults *= (sched_max_numa_distance - dist);
			faults /= (sched_max_numa_distance - LOCAL_DISTANCE);
		}

		score += faults;
	}

	return score;
}

1126 1127 1128 1129 1130 1131
/*
 * 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.
 */
1132 1133
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1134
{
1135
	unsigned long faults, total_faults;
1136

1137
	if (!p->numa_faults)
1138 1139 1140 1141 1142 1143 1144
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1145
	faults = task_faults(p, nid);
1146 1147
	faults += score_nearby_nodes(p, nid, dist, true);

1148
	return 1000 * faults / total_faults;
1149 1150
}

1151 1152
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1153
{
1154 1155 1156 1157 1158 1159 1160 1161
	unsigned long faults, total_faults;

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1162 1163
		return 0;

1164
	faults = group_faults(p, nid);
1165 1166
	faults += score_nearby_nodes(p, nid, dist, false);

1167
	return 1000 * faults / total_faults;
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
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;

	/*
1210 1211
	 * Destination node is much more heavily used than the source
	 * node? Allow migration.
1212
	 */
1213 1214
	if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) *
					ACTIVE_NODE_FRACTION)
1215 1216 1217
		return true;

	/*
1218 1219 1220 1221 1222 1223
	 * Distribute memory according to CPU & memory use on each node,
	 * with 3/4 hysteresis to avoid unnecessary memory migrations:
	 *
	 * faults_cpu(dst)   3   faults_cpu(src)
	 * --------------- * - > ---------------
	 * faults_mem(dst)   4   faults_mem(src)
1224
	 */
1225 1226
	return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 >
	       group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4;
1227 1228
}

1229
static unsigned long weighted_cpuload(const int cpu);
1230 1231
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1232
static unsigned long capacity_of(int cpu);
1233 1234
static long effective_load(struct task_group *tg, int cpu, long wl, long wg);

1235
/* Cached statistics for all CPUs within a node */
1236
struct numa_stats {
1237
	unsigned long nr_running;
1238
	unsigned long load;
1239 1240

	/* Total compute capacity of CPUs on a node */
1241
	unsigned long compute_capacity;
1242 1243

	/* Approximate capacity in terms of runnable tasks on a node */
1244
	unsigned long task_capacity;
1245
	int has_free_capacity;
1246
};
1247

1248 1249 1250 1251 1252
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1253 1254
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1255 1256 1257 1258 1259 1260 1261

	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);
1262
		ns->compute_capacity += capacity_of(cpu);
1263 1264

		cpus++;
1265 1266
	}

1267 1268 1269 1270 1271
	/*
	 * 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.
	 *
1272 1273
	 * We'll either bail at !has_free_capacity, or we'll detect a huge
	 * imbalance and bail there.
1274 1275 1276 1277
	 */
	if (!cpus)
		return;

1278 1279 1280 1281 1282 1283
	/* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
	smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
	capacity = cpus / smt; /* cores */

	ns->task_capacity = min_t(unsigned, capacity,
		DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1284
	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1285 1286
}

1287 1288
struct task_numa_env {
	struct task_struct *p;
1289

1290 1291
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1292

1293
	struct numa_stats src_stats, dst_stats;
1294

1295
	int imbalance_pct;
1296
	int dist;
1297 1298 1299

	struct task_struct *best_task;
	long best_imp;
1300 1301 1302
	int best_cpu;
};

1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313
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);

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

1314
static bool load_too_imbalanced(long src_load, long dst_load,
1315 1316
				struct task_numa_env *env)
{
1317 1318
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329
	long src_capacity, dst_capacity;

	/*
	 * The load is corrected for the CPU capacity available on each node.
	 *
	 * src_load        dst_load
	 * ------------ vs ---------
	 * src_capacity    dst_capacity
	 */
	src_capacity = env->src_stats.compute_capacity;
	dst_capacity = env->dst_stats.compute_capacity;
1330 1331

	/* We care about the slope of the imbalance, not the direction. */
1332 1333
	if (dst_load < src_load)
		swap(dst_load, src_load);
1334 1335

	/* Is the difference below the threshold? */
1336 1337
	imb = dst_load * src_capacity * 100 -
	      src_load * dst_capacity * env->imbalance_pct;
1338 1339 1340 1341 1342
	if (imb <= 0)
		return false;

	/*
	 * The imbalance is above the allowed threshold.
1343
	 * Compare it with the old imbalance.
1344
	 */
1345
	orig_src_load = env->src_stats.load;
1346
	orig_dst_load = env->dst_stats.load;
1347

1348 1349
	if (orig_dst_load < orig_src_load)
		swap(orig_dst_load, orig_src_load);
1350

1351 1352 1353 1354 1355
	old_imb = orig_dst_load * src_capacity * 100 -
		  orig_src_load * dst_capacity * env->imbalance_pct;

	/* Would this change make things worse? */
	return (imb > old_imb);
1356 1357
}

1358 1359 1360 1361 1362 1363
/*
 * 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
 */
1364 1365
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1366 1367 1368 1369
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1370
	long src_load, dst_load;
1371
	long load;
1372
	long imp = env->p->numa_group ? groupimp : taskimp;
1373
	long moveimp = imp;
1374
	int dist = env->dist;
1375
	bool assigned = false;
1376 1377

	rcu_read_lock();
1378 1379 1380 1381

	raw_spin_lock_irq(&dst_rq->lock);
	cur = dst_rq->curr;
	/*
1382
	 * No need to move the exiting task or idle task.
1383 1384
	 */
	if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1385
		cur = NULL;
1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398
	else {
		/*
		 * The task_struct must be protected here to protect the
		 * p->numa_faults access in the task_weight since the
		 * numa_faults could already be freed in the following path:
		 * finish_task_switch()
		 *     --> put_task_struct()
		 *         --> __put_task_struct()
		 *             --> task_numa_free()
		 */
		get_task_struct(cur);
	}

1399
	raw_spin_unlock_irq(&dst_rq->lock);
1400

1401 1402 1403 1404 1405 1406 1407
	/*
	 * Because we have preemption enabled we can get migrated around and
	 * end try selecting ourselves (current == env->p) as a swap candidate.
	 */
	if (cur == env->p)
		goto unlock;

1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419
	/*
	 * "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;

1420 1421
		/*
		 * If dst and source tasks are in the same NUMA group, or not
1422
		 * in any group then look only at task weights.
1423
		 */
1424
		if (cur->numa_group == env->p->numa_group) {
1425 1426
			imp = taskimp + task_weight(cur, env->src_nid, dist) -
			      task_weight(cur, env->dst_nid, dist);
1427 1428 1429 1430 1431 1432
			/*
			 * Add some hysteresis to prevent swapping the
			 * tasks within a group over tiny differences.
			 */
			if (cur->numa_group)
				imp -= imp/16;
1433
		} else {
1434 1435 1436 1437 1438 1439
			/*
			 * Compare the group weights. If a task is all by
			 * itself (not part of a group), use the task weight
			 * instead.
			 */
			if (cur->numa_group)
1440 1441
				imp += group_weight(cur, env->src_nid, dist) -
				       group_weight(cur, env->dst_nid, dist);
1442
			else
1443 1444
				imp += task_weight(cur, env->src_nid, dist) -
				       task_weight(cur, env->dst_nid, dist);
1445
		}
1446 1447
	}

1448
	if (imp <= env->best_imp && moveimp <= env->best_imp)
1449 1450 1451 1452
		goto unlock;

	if (!cur) {
		/* Is there capacity at our destination? */
1453
		if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1454
		    !env->dst_stats.has_free_capacity)
1455 1456 1457 1458 1459 1460
			goto unlock;

		goto balance;
	}

	/* Balance doesn't matter much if we're running a task per cpu */
1461 1462
	if (imp > env->best_imp && src_rq->nr_running == 1 &&
			dst_rq->nr_running == 1)
1463 1464 1465 1466 1467 1468
		goto assign;

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
balance:
1469 1470 1471
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1472

1473 1474 1475 1476 1477 1478 1479 1480 1481
	if (moveimp > imp && moveimp > env->best_imp) {
		/*
		 * If the improvement from just moving env->p direction is
		 * better than swapping tasks around, check if a move is
		 * possible. Store a slightly smaller score than moveimp,
		 * so an actually idle CPU will win.
		 */
		if (!load_too_imbalanced(src_load, dst_load, env)) {
			imp = moveimp - 1;
1482
			put_task_struct(cur);
1483 1484 1485 1486 1487 1488 1489 1490
			cur = NULL;
			goto assign;
		}
	}

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

1491
	if (cur) {
1492 1493 1494
		load = task_h_load(cur);
		dst_load -= load;
		src_load += load;
1495 1496
	}

1497
	if (load_too_imbalanced(src_load, dst_load, env))
1498 1499
		goto unlock;

1500 1501 1502 1503 1504 1505 1506
	/*
	 * One idle CPU per node is evaluated for a task numa move.
	 * Call select_idle_sibling to maybe find a better one.
	 */
	if (!cur)
		env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);

1507
assign:
1508
	assigned = true;
1509 1510 1511
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
1512 1513 1514 1515 1516 1517
	/*
	 * The dst_rq->curr isn't assigned. The protection for task_struct is
	 * finished.
	 */
	if (cur && !assigned)
		put_task_struct(cur);
1518 1519
}

1520 1521
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1522 1523 1524 1525 1526 1527 1528 1529 1530
{
	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;
1531
		task_numa_compare(env, taskimp, groupimp);
1532 1533 1534
	}
}

1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551
/* Only move tasks to a NUMA node less busy than the current node. */
static bool numa_has_capacity(struct task_numa_env *env)
{
	struct numa_stats *src = &env->src_stats;
	struct numa_stats *dst = &env->dst_stats;

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

	/*
	 * Only consider a task move if the source has a higher load
	 * than the destination, corrected for CPU capacity on each node.
	 *
	 *      src->load                dst->load
	 * --------------------- vs ---------------------
	 * src->compute_capacity    dst->compute_capacity
	 */
1552 1553 1554
	if (src->load * dst->compute_capacity * env->imbalance_pct >

	    dst->load * src->compute_capacity * 100)
1555 1556 1557 1558 1559
		return true;

	return false;
}

1560 1561 1562 1563
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1564

1565
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1566
		.src_nid = task_node(p),
1567 1568 1569 1570 1571

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
1572
		.best_cpu = -1,
1573 1574
	};
	struct sched_domain *sd;
1575
	unsigned long taskweight, groupweight;
1576
	int nid, ret, dist;
1577
	long taskimp, groupimp;
1578

1579
	/*
1580 1581 1582 1583 1584 1585
	 * 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.
1586 1587
	 */
	rcu_read_lock();
1588
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1589 1590
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1591 1592
	rcu_read_unlock();

1593 1594 1595 1596 1597 1598 1599
	/*
	 * 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)) {
1600
		p->numa_preferred_nid = task_node(p);
1601 1602 1603
		return -EINVAL;
	}

1604
	env.dst_nid = p->numa_preferred_nid;
1605 1606 1607 1608 1609 1610
	dist = env.dist = node_distance(env.src_nid, env.dst_nid);
	taskweight = task_weight(p, env.src_nid, dist);
	groupweight = group_weight(p, env.src_nid, dist);
	update_numa_stats(&env.src_stats, env.src_nid);
	taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
	groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1611
	update_numa_stats(&env.dst_stats, env.dst_nid);
1612

1613
	/* Try to find a spot on the preferred nid. */
1614 1615
	if (numa_has_capacity(&env))
		task_numa_find_cpu(&env, taskimp, groupimp);
1616

1617 1618 1619 1620 1621 1622 1623
	/*
	 * Look at other nodes in these cases:
	 * - there is no space available on the preferred_nid
	 * - the task is part of a numa_group that is interleaved across
	 *   multiple NUMA nodes; in order to better consolidate the group,
	 *   we need to check other locations.
	 */
1624
	if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) {
1625 1626 1627
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1628

1629
			dist = node_distance(env.src_nid, env.dst_nid);
1630 1631 1632 1633 1634
			if (sched_numa_topology_type == NUMA_BACKPLANE &&
						dist != env.dist) {
				taskweight = task_weight(p, env.src_nid, dist);
				groupweight = group_weight(p, env.src_nid, dist);
			}
1635

1636
			/* Only consider nodes where both task and groups benefit */
1637 1638
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1639
			if (taskimp < 0 && groupimp < 0)
1640 1641
				continue;

1642
			env.dist = dist;
1643 1644
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1645 1646
			if (numa_has_capacity(&env))
				task_numa_find_cpu(&env, taskimp, groupimp);
1647 1648 1649
		}
	}

1650 1651 1652 1653 1654 1655 1656 1657
	/*
	 * If the task is part of a workload that spans multiple NUMA nodes,
	 * and is migrating into one of the workload's active nodes, remember
	 * this node as the task's preferred numa node, so the workload can
	 * settle down.
	 * A task that migrated to a second choice node will be better off
	 * trying for a better one later. Do not set the preferred node here.
	 */
1658
	if (p->numa_group) {
1659 1660
		struct numa_group *ng = p->numa_group;

1661 1662 1663 1664 1665
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
			nid = env.dst_nid;

1666
		if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng))
1667 1668 1669 1670 1671 1672
			sched_setnuma(p, env.dst_nid);
	}

	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;
1673

1674 1675 1676 1677 1678 1679
	/*
	 * 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);

1680
	if (env.best_task == NULL) {
1681 1682 1683
		ret = migrate_task_to(p, env.best_cpu);
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1684 1685 1686 1687
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
1688 1689
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1690 1691
	put_task_struct(env.best_task);
	return ret;
1692 1693
}

1694 1695 1696
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1697 1698
	unsigned long interval = HZ;

1699
	/* This task has no NUMA fault statistics yet */
1700
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1701 1702
		return;

1703
	/* Periodically retry migrating the task to the preferred node */
1704 1705
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
	p->numa_migrate_retry = jiffies + interval;
1706 1707

	/* Success if task is already running on preferred CPU */
1708
	if (task_node(p) == p->numa_preferred_nid)
1709 1710 1711
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1712
	task_numa_migrate(p);
1713 1714
}

1715
/*
1716
 * Find out how many nodes on the workload is actively running on. Do this by
1717 1718 1719 1720
 * 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.
 */
1721
static void numa_group_count_active_nodes(struct numa_group *numa_group)
1722 1723
{
	unsigned long faults, max_faults = 0;
1724
	int nid, active_nodes = 0;
1725 1726 1727 1728 1729 1730 1731 1732 1733

	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);
1734 1735
		if (faults * ACTIVE_NODE_FRACTION > max_faults)
			active_nodes++;
1736
	}
1737 1738 1739

	numa_group->max_faults_cpu = max_faults;
	numa_group->active_nodes = active_nodes;
1740 1741
}

1742 1743 1744
/*
 * 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
1745 1746 1747
 * period will be for the next scan window. If local/(local+remote) ratio is
 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
 * the scan period will decrease. Aim for 70% local accesses.
1748 1749
 */
#define NUMA_PERIOD_SLOTS 10
1750
#define NUMA_PERIOD_THRESHOLD 7
1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770

/*
 * 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
1771 1772 1773
	 * to automatic numa balancing. Related to that, if there were failed
	 * migration then it implies we are migrating too quickly or the local
	 * node is overloaded. In either case, scan slower
1774
	 */
1775
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808
		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
		 */
1809
		ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1810 1811 1812 1813 1814 1815 1816 1817
		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));
}

1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835
/*
 * 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 {
1836 1837
		delta = p->se.avg.load_sum / p->se.load.weight;
		*period = LOAD_AVG_MAX;
1838 1839 1840 1841 1842 1843 1844 1845
	}

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

	return delta;
}

1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892
/*
 * Determine the preferred nid for a task in a numa_group. This needs to
 * be done in a way that produces consistent results with group_weight,
 * otherwise workloads might not converge.
 */
static int preferred_group_nid(struct task_struct *p, int nid)
{
	nodemask_t nodes;
	int dist;

	/* Direct connections between all NUMA nodes. */
	if (sched_numa_topology_type == NUMA_DIRECT)
		return nid;

	/*
	 * On a system with glueless mesh NUMA topology, group_weight
	 * scores nodes according to the number of NUMA hinting faults on
	 * both the node itself, and on nearby nodes.
	 */
	if (sched_numa_topology_type == NUMA_GLUELESS_MESH) {
		unsigned long score, max_score = 0;
		int node, max_node = nid;

		dist = sched_max_numa_distance;

		for_each_online_node(node) {
			score = group_weight(p, node, dist);
			if (score > max_score) {
				max_score = score;
				max_node = node;
			}
		}
		return max_node;
	}

	/*
	 * Finding the preferred nid in a system with NUMA backplane
	 * interconnect topology is more involved. The goal is to locate
	 * tasks from numa_groups near each other in the system, and
	 * untangle workloads from different sides of the system. This requires
	 * searching down the hierarchy of node groups, recursively searching
	 * inside the highest scoring group of nodes. The nodemask tricks
	 * keep the complexity of the search down.
	 */
	nodes = node_online_map;
	for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
		unsigned long max_faults = 0;
1893
		nodemask_t max_group = NODE_MASK_NONE;
1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926
		int a, b;

		/* Are there nodes at this distance from each other? */
		if (!find_numa_distance(dist))
			continue;

		for_each_node_mask(a, nodes) {
			unsigned long faults = 0;
			nodemask_t this_group;
			nodes_clear(this_group);

			/* Sum group's NUMA faults; includes a==b case. */
			for_each_node_mask(b, nodes) {
				if (node_distance(a, b) < dist) {
					faults += group_faults(p, b);
					node_set(b, this_group);
					node_clear(b, nodes);
				}
			}

			/* Remember the top group. */
			if (faults > max_faults) {
				max_faults = faults;
				max_group = this_group;
				/*
				 * subtle: at the smallest distance there is
				 * just one node left in each "group", the
				 * winner is the preferred nid.
				 */
				nid = a;
			}
		}
		/* Next round, evaluate the nodes within max_group. */
1927 1928
		if (!max_faults)
			break;
1929 1930 1931 1932 1933
		nodes = max_group;
	}
	return nid;
}

1934 1935
static void task_numa_placement(struct task_struct *p)
{
1936 1937
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
1938
	unsigned long fault_types[2] = { 0, 0 };
1939 1940
	unsigned long total_faults;
	u64 runtime, period;
1941
	spinlock_t *group_lock = NULL;
1942

1943 1944 1945 1946 1947
	/*
	 * The p->mm->numa_scan_seq field gets updated without
	 * exclusive access. Use READ_ONCE() here to ensure
	 * that the field is read in a single access:
	 */
1948
	seq = READ_ONCE(p->mm->numa_scan_seq);
1949 1950 1951
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
1952
	p->numa_scan_period_max = task_scan_max(p);
1953

1954 1955 1956 1957
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

1958 1959 1960
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
1961
		spin_lock_irq(group_lock);
1962 1963
	}

1964 1965
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
1966 1967
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1968
		unsigned long faults = 0, group_faults = 0;
1969
		int priv;
1970

1971
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1972
			long diff, f_diff, f_weight;
1973

1974 1975 1976 1977
			mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
			membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
			cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
			cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1978

1979
			/* Decay existing window, copy faults since last scan */
1980 1981 1982
			diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
			fault_types[priv] += p->numa_faults[membuf_idx];
			p->numa_faults[membuf_idx] = 0;
1983

1984 1985 1986 1987 1988 1989 1990 1991
			/*
			 * 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);
1992
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1993
				   (total_faults + 1);
1994 1995
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
1996

1997 1998 1999
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
2000
			p->total_numa_faults += diff;
2001
			if (p->numa_group) {
2002 2003 2004 2005 2006 2007 2008 2009 2010
				/*
				 * safe because we can only change our own group
				 *
				 * mem_idx represents the offset for a given
				 * nid and priv in a specific region because it
				 * is at the beginning of the numa_faults array.
				 */
				p->numa_group->faults[mem_idx] += diff;
				p->numa_group->faults_cpu[mem_idx] += f_diff;
2011
				p->numa_group->total_faults += diff;
2012
				group_faults += p->numa_group->faults[mem_idx];
2013
			}
2014 2015
		}

2016 2017 2018 2019
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
2020 2021 2022 2023 2024 2025 2026

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

2027 2028
	update_task_scan_period(p, fault_types[0], fault_types[1]);

2029
	if (p->numa_group) {
2030
		numa_group_count_active_nodes(p->numa_group);
2031
		spin_unlock_irq(group_lock);
2032
		max_nid = preferred_group_nid(p, max_group_nid);
2033 2034
	}

2035 2036 2037 2038 2039 2040 2041
	if (max_faults) {
		/* Set the new preferred node */
		if (max_nid != p->numa_preferred_nid)
			sched_setnuma(p, max_nid);

		if (task_node(p) != p->numa_preferred_nid)
			numa_migrate_preferred(p);
2042
	}
2043 2044
}

2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055
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);
}

2056 2057
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
2058 2059 2060 2061 2062 2063 2064 2065 2066
{
	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) +
2067
				    4*nr_node_ids*sizeof(unsigned long);
2068 2069 2070 2071 2072 2073

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

		atomic_set(&grp->refcount, 1);
2074 2075
		grp->active_nodes = 1;
		grp->max_faults_cpu = 0;
2076
		spin_lock_init(&grp->lock);
2077
		grp->gid = p->pid;
2078
		/* Second half of the array tracks nids where faults happen */
2079 2080
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
2081

2082
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2083
			grp->faults[i] = p->numa_faults[i];
2084

2085
		grp->total_faults = p->total_numa_faults;
2086

2087 2088 2089 2090 2091
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
2092
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
2093 2094

	if (!cpupid_match_pid(tsk, cpupid))
2095
		goto no_join;
2096 2097 2098

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
2099
		goto no_join;
2100 2101 2102

	my_grp = p->numa_group;
	if (grp == my_grp)
2103
		goto no_join;
2104 2105 2106 2107 2108 2109

	/*
	 * 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)
2110
		goto no_join;
2111 2112 2113 2114 2115

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
2116
		goto no_join;
2117

2118 2119 2120 2121 2122 2123 2124
	/* 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;
2125

2126 2127 2128
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2129
	if (join && !get_numa_group(grp))
2130
		goto no_join;
2131 2132 2133 2134 2135 2136

	rcu_read_unlock();

	if (!join)
		return;

2137 2138
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2139

2140
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2141 2142
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2143
	}
2144 2145
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2146 2147 2148 2149 2150

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

	spin_unlock(&my_grp->lock);
2151
	spin_unlock_irq(&grp->lock);
2152 2153 2154 2155

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2156 2157 2158 2159 2160
	return;

no_join:
	rcu_read_unlock();
	return;
2161 2162 2163 2164 2165
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
2166
	void *numa_faults = p->numa_faults;
2167 2168
	unsigned long flags;
	int i;
2169 2170

	if (grp) {
2171
		spin_lock_irqsave(&grp->lock, flags);
2172
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2173
			grp->faults[i] -= p->numa_faults[i];
2174
		grp->total_faults -= p->total_numa_faults;
2175

2176
		grp->nr_tasks--;
2177
		spin_unlock_irqrestore(&grp->lock, flags);
2178
		RCU_INIT_POINTER(p->numa_group, NULL);
2179 2180 2181
		put_numa_group(grp);
	}

2182
	p->numa_faults = NULL;
2183
	kfree(numa_faults);
2184 2185
}

2186 2187 2188
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2189
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2190 2191
{
	struct task_struct *p = current;
2192
	bool migrated = flags & TNF_MIGRATED;
2193
	int cpu_node = task_node(current);
2194
	int local = !!(flags & TNF_FAULT_LOCAL);
2195
	struct numa_group *ng;
2196
	int priv;
2197

2198
	if (!static_branch_likely(&sched_numa_balancing))
2199 2200
		return;

2201 2202 2203 2204
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2205
	/* Allocate buffer to track faults on a per-node basis */
2206 2207
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2208
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2209

2210 2211
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2212
			return;
2213

2214
		p->total_numa_faults = 0;
2215
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2216
	}
2217

2218 2219 2220 2221 2222 2223 2224 2225
	/*
	 * 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);
2226
		if (!priv && !(flags & TNF_NO_GROUP))
2227
			task_numa_group(p, last_cpupid, flags, &priv);
2228 2229
	}

2230 2231 2232 2233 2234 2235
	/*
	 * If a workload spans multiple NUMA nodes, a shared fault that
	 * occurs wholly within the set of nodes that the workload is
	 * actively using should be counted as local. This allows the
	 * scan rate to slow down when a workload has settled down.
	 */
2236 2237 2238 2239
	ng = p->numa_group;
	if (!priv && !local && ng && ng->active_nodes > 1 &&
				numa_is_active_node(cpu_node, ng) &&
				numa_is_active_node(mem_node, ng))
2240 2241
		local = 1;

2242
	task_numa_placement(p);
2243

2244 2245 2246 2247 2248
	/*
	 * 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))
2249 2250
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
2251 2252
	if (migrated)
		p->numa_pages_migrated += pages;
2253 2254
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2255

2256 2257
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2258
	p->numa_faults_locality[local] += pages;
2259 2260
}

2261 2262
static void reset_ptenuma_scan(struct task_struct *p)
{
2263 2264 2265 2266 2267 2268 2269 2270
	/*
	 * We only did a read acquisition of the mmap sem, so
	 * p->mm->numa_scan_seq is written to without exclusive access
	 * and the update is not guaranteed to be atomic. That's not
	 * much of an issue though, since this is just used for
	 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
	 * expensive, to avoid any form of compiler optimizations:
	 */
2271
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2272 2273 2274
	p->mm->numa_scan_offset = 0;
}

2275 2276 2277 2278 2279 2280 2281 2282 2283
/*
 * 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;
2284
	u64 runtime = p->se.sum_exec_runtime;
2285
	struct vm_area_struct *vma;
2286
	unsigned long start, end;
2287
	unsigned long nr_pte_updates = 0;
2288
	long pages, virtpages;
2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303

	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;

2304
	if (!mm->numa_next_scan) {
2305 2306
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2307 2308
	}

2309 2310 2311 2312 2313 2314 2315
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2316 2317 2318 2319
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
		p->numa_scan_period = task_scan_min(p);
	}
2320

2321
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2322 2323 2324
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2325 2326 2327 2328 2329 2330
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2331 2332 2333
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2334
	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2335 2336
	if (!pages)
		return;
2337

2338

2339
	down_read(&mm->mmap_sem);
2340
	vma = find_vma(mm, start);
2341 2342
	if (!vma) {
		reset_ptenuma_scan(p);
2343
		start = 0;
2344 2345
		vma = mm->mmap;
	}
2346
	for (; vma; vma = vma->vm_next) {
2347
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2348
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2349
			continue;
2350
		}
2351

2352 2353 2354 2355 2356 2357 2358 2359 2360 2361
		/*
		 * 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
2362 2363 2364 2365 2366 2367
		/*
		 * 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;
2368

2369 2370 2371 2372
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2373
			nr_pte_updates = change_prot_numa(vma, start, end);
2374 2375

			/*
2376 2377 2378 2379 2380 2381
			 * Try to scan sysctl_numa_balancing_size worth of
			 * hpages that have at least one present PTE that
			 * is not already pte-numa. If the VMA contains
			 * areas that are unused or already full of prot_numa
			 * PTEs, scan up to virtpages, to skip through those
			 * areas faster.
2382 2383 2384
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2385
			virtpages -= (end - start) >> PAGE_SHIFT;
2386

2387
			start = end;
2388
			if (pages <= 0 || virtpages <= 0)
2389
				goto out;
2390 2391

			cond_resched();
2392
		} while (end != vma->vm_end);
2393
	}
2394

2395
out:
2396
	/*
P
Peter Zijlstra 已提交
2397 2398 2399 2400
	 * 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.
2401 2402
	 */
	if (vma)
2403
		mm->numa_scan_offset = start;
2404 2405 2406
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417

	/*
	 * Make sure tasks use at least 32x as much time to run other code
	 * than they used here, to limit NUMA PTE scanning overhead to 3% max.
	 * Usually update_task_scan_period slows down scanning enough; on an
	 * overloaded system we need to limit overhead on a per task basis.
	 */
	if (unlikely(p->se.sum_exec_runtime != runtime)) {
		u64 diff = p->se.sum_exec_runtime - runtime;
		p->node_stamp += 32 * diff;
	}
2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442
}

/*
 * 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;

2443
	if (now > curr->node_stamp + period) {
2444
		if (!curr->node_stamp)
2445
			curr->numa_scan_period = task_scan_min(curr);
2446
		curr->node_stamp += period;
2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457

		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)
{
}
2458 2459 2460 2461 2462 2463 2464 2465

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)
{
}
2466 2467
#endif /* CONFIG_NUMA_BALANCING */

2468 2469 2470 2471
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2472
	if (!parent_entity(se))
2473
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2474
#ifdef CONFIG_SMP
2475 2476 2477 2478 2479 2480
	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);
	}
2481
#endif
2482 2483 2484 2485 2486 2487 2488
	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);
2489
	if (!parent_entity(se))
2490
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2491
#ifdef CONFIG_SMP
2492 2493
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2494
		list_del_init(&se->group_node);
2495
	}
2496
#endif
2497 2498 2499
	cfs_rq->nr_running--;
}

2500 2501
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
2502 2503 2504 2505 2506
static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
{
	long tg_weight;

	/*
2507 2508 2509
	 * Use this CPU's real-time load instead of the last load contribution
	 * as the updating of the contribution is delayed, and we will use the
	 * the real-time load to calc the share. See update_tg_load_avg().
2510
	 */
2511
	tg_weight = atomic_long_read(&tg->load_avg);
2512
	tg_weight -= cfs_rq->tg_load_avg_contrib;
2513
	tg_weight += cfs_rq->load.weight;
2514 2515 2516 2517

	return tg_weight;
}

2518
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2519
{
2520
	long tg_weight, load, shares;
2521

2522
	tg_weight = calc_tg_weight(tg, cfs_rq);
2523
	load = cfs_rq->load.weight;
2524 2525

	shares = (tg->shares * load);
2526 2527
	if (tg_weight)
		shares /= tg_weight;
2528 2529 2530 2531 2532 2533 2534 2535 2536

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

	return shares;
}
# else /* CONFIG_SMP */
2537
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2538 2539 2540 2541
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
2542 2543 2544
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
2545 2546 2547 2548
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
2549
		account_entity_dequeue(cfs_rq, se);
2550
	}
P
Peter Zijlstra 已提交
2551 2552 2553 2554 2555 2556 2557

	update_load_set(&se->load, weight);

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

2558 2559
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2560
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2561 2562 2563
{
	struct task_group *tg;
	struct sched_entity *se;
2564
	long shares;
P
Peter Zijlstra 已提交
2565 2566 2567

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
2568
	if (!se || throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
2569
		return;
2570 2571 2572 2573
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
2574
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
2575 2576 2577 2578

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
2579
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2580 2581 2582 2583
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

2584
#ifdef CONFIG_SMP
2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604
/* 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,
};

2605 2606 2607 2608 2609 2610
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622
	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
2623 2624
	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
	 * With a look-up table which covers y^n (n<PERIOD)
2625 2626 2627 2628 2629 2630
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
2631 2632
	}

2633 2634
	val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
	return val;
2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662
}

/*
 * 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];
2663 2664
}

2665 2666 2667 2668
#if (SCHED_LOAD_SHIFT - SCHED_LOAD_RESOLUTION) != 10 || SCHED_CAPACITY_SHIFT != 10
#error "load tracking assumes 2^10 as unit"
#endif

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

2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698
/*
 * We can represent the historical contribution to runnable average as the
 * coefficients of a geometric series.  To do this we sub-divide our runnable
 * history into segments of approximately 1ms (1024us); label the segment that
 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g.
 *
 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ...
 *      p0            p1           p2
 *     (now)       (~1ms ago)  (~2ms ago)
 *
 * Let u_i denote the fraction of p_i that the entity was runnable.
 *
 * We then designate the fractions u_i as our co-efficients, yielding the
 * following representation of historical load:
 *   u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ...
 *
 * We choose y based on the with of a reasonably scheduling period, fixing:
 *   y^32 = 0.5
 *
 * This means that the contribution to load ~32ms ago (u_32) will be weighted
 * approximately half as much as the contribution to load within the last ms
 * (u_0).
 *
 * When a period "rolls over" and we have new u_0`, multiplying the previous
 * sum again by y is sufficient to update:
 *   load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
 *            = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
 */
2699 2700
static __always_inline int
__update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2701
		  unsigned long weight, int running, struct cfs_rq *cfs_rq)
2702
{
2703
	u64 delta, scaled_delta, periods;
2704
	u32 contrib;
2705
	unsigned int delta_w, scaled_delta_w, decayed = 0;
2706
	unsigned long scale_freq, scale_cpu;
2707

2708
	delta = now - sa->last_update_time;
2709 2710 2711 2712 2713
	/*
	 * This should only happen when time goes backwards, which it
	 * unfortunately does during sched clock init when we swap over to TSC.
	 */
	if ((s64)delta < 0) {
2714
		sa->last_update_time = now;
2715 2716 2717 2718 2719 2720 2721 2722 2723 2724
		return 0;
	}

	/*
	 * Use 1024ns as the unit of measurement since it's a reasonable
	 * approximation of 1us and fast to compute.
	 */
	delta >>= 10;
	if (!delta)
		return 0;
2725
	sa->last_update_time = now;
2726

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

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

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

2738 2739 2740 2741 2742 2743
		/*
		 * Now that we know we're crossing a period boundary, figure
		 * out how much from delta we need to complete the current
		 * period and accrue it.
		 */
		delta_w = 1024 - delta_w;
2744
		scaled_delta_w = cap_scale(delta_w, scale_freq);
2745
		if (weight) {
2746 2747 2748 2749 2750
			sa->load_sum += weight * scaled_delta_w;
			if (cfs_rq) {
				cfs_rq->runnable_load_sum +=
						weight * scaled_delta_w;
			}
2751
		}
2752
		if (running)
2753
			sa->util_sum += scaled_delta_w * scale_cpu;
2754 2755 2756 2757 2758 2759 2760

		delta -= delta_w;

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

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

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

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

2790
	sa->period_contrib += delta;
2791

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

2801
	return decayed;
2802 2803
}

2804
#ifdef CONFIG_FAIR_GROUP_SCHED
2805
/*
2806 2807
 * Updating tg's load_avg is necessary before update_cfs_share (which is done)
 * and effective_load (which is not done because it is too costly).
2808
 */
2809
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2810
{
2811
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2812

2813 2814 2815 2816 2817 2818
	/*
	 * No need to update load_avg for root_task_group as it is not used.
	 */
	if (cfs_rq->tg == &root_task_group)
		return;

2819 2820 2821
	if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
		atomic_long_add(delta, &cfs_rq->tg->load_avg);
		cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
2822
	}
2823
}
2824

2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870
/*
 * Called within set_task_rq() right before setting a task's cpu. The
 * caller only guarantees p->pi_lock is held; no other assumptions,
 * including the state of rq->lock, should be made.
 */
void set_task_rq_fair(struct sched_entity *se,
		      struct cfs_rq *prev, struct cfs_rq *next)
{
	if (!sched_feat(ATTACH_AGE_LOAD))
		return;

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

#ifndef CONFIG_64BIT
		u64 p_last_update_time_copy;
		u64 n_last_update_time_copy;

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

			smp_rmb();

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

		} while (p_last_update_time != p_last_update_time_copy ||
			 n_last_update_time != n_last_update_time_copy);
#else
		p_last_update_time = prev->avg.last_update_time;
		n_last_update_time = next->avg.last_update_time;
#endif
		__update_load_avg(p_last_update_time, cpu_of(rq_of(prev)),
				  &se->avg, 0, 0, NULL);
		se->avg.last_update_time = n_last_update_time;
	}
}
2871
#else /* CONFIG_FAIR_GROUP_SCHED */
2872
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2873
#endif /* CONFIG_FAIR_GROUP_SCHED */
2874

2875
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2876

2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905
static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
{
	struct rq *rq = rq_of(cfs_rq);
	int cpu = cpu_of(rq);

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

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

2906
/* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
2907 2908
static inline int
update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
2909
{
2910
	struct sched_avg *sa = &cfs_rq->avg;
2911
	int decayed, removed_load = 0, removed_util = 0;
2912

2913
	if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2914
		s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2915 2916
		sa->load_avg = max_t(long, sa->load_avg - r, 0);
		sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
2917
		removed_load = 1;
2918
	}
2919

2920 2921 2922
	if (atomic_long_read(&cfs_rq->removed_util_avg)) {
		long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0);
		sa->util_avg = max_t(long, sa->util_avg - r, 0);
2923
		sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
2924
		removed_util = 1;
2925
	}
2926

2927
	decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2928
		scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2929

2930 2931 2932 2933
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
2934

2935 2936
	if (update_freq && (decayed || removed_util))
		cfs_rq_util_change(cfs_rq);
2937

2938
	return decayed || removed_load;
2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956
}

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

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

2957
	if (update_cfs_rq_load_avg(now, cfs_rq, true) && update_tg)
2958
		update_tg_load_avg(cfs_rq, 0);
2959 2960
}

2961 2962
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2963 2964 2965
	if (!sched_feat(ATTACH_AGE_LOAD))
		goto skip_aging;

2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979
	/*
	 * If we got migrated (either between CPUs or between cgroups) we'll
	 * have aged the average right before clearing @last_update_time.
	 */
	if (se->avg.last_update_time) {
		__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
				  &se->avg, 0, 0, NULL);

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

2980
skip_aging:
2981 2982 2983 2984 2985
	se->avg.last_update_time = cfs_rq->avg.last_update_time;
	cfs_rq->avg.load_avg += se->avg.load_avg;
	cfs_rq->avg.load_sum += se->avg.load_sum;
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
2986 2987

	cfs_rq_util_change(cfs_rq);
2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999
}

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

	cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
	cfs_rq->avg.load_sum = max_t(s64,  cfs_rq->avg.load_sum - se->avg.load_sum, 0);
	cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
	cfs_rq->avg.util_sum = max_t(s32,  cfs_rq->avg.util_sum - se->avg.util_sum, 0);
3000 3001

	cfs_rq_util_change(cfs_rq);
3002 3003
}

3004 3005 3006
/* Add the load generated by se into cfs_rq's load average */
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
3007
{
3008 3009
	struct sched_avg *sa = &se->avg;
	u64 now = cfs_rq_clock_task(cfs_rq);
3010
	int migrated, decayed;
3011

3012 3013
	migrated = !sa->last_update_time;
	if (!migrated) {
3014
		__update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
3015 3016
			se->on_rq * scale_load_down(se->load.weight),
			cfs_rq->curr == se, NULL);
3017
	}
3018

3019
	decayed = update_cfs_rq_load_avg(now, cfs_rq, !migrated);
3020

3021 3022 3023
	cfs_rq->runnable_load_avg += sa->load_avg;
	cfs_rq->runnable_load_sum += sa->load_sum;

3024 3025
	if (migrated)
		attach_entity_load_avg(cfs_rq, se);
3026

3027 3028
	if (decayed || migrated)
		update_tg_load_avg(cfs_rq, 0);
3029 3030
}

3031 3032 3033 3034 3035 3036 3037 3038 3039
/* Remove the runnable load generated by se from cfs_rq's runnable load average */
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_avg(se, 1);

	cfs_rq->runnable_load_avg =
		max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
	cfs_rq->runnable_load_sum =
3040
		max_t(s64,  cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
3041 3042
}

3043
#ifndef CONFIG_64BIT
3044 3045
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
3046
	u64 last_update_time_copy;
3047
	u64 last_update_time;
3048

3049 3050 3051 3052 3053
	do {
		last_update_time_copy = cfs_rq->load_last_update_time_copy;
		smp_rmb();
		last_update_time = cfs_rq->avg.last_update_time;
	} while (last_update_time != last_update_time_copy);
3054 3055 3056

	return last_update_time;
}
3057
#else
3058 3059 3060 3061
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.last_update_time;
}
3062 3063
#endif

3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081
/*
 * Task first catches up with cfs_rq, and then subtract
 * itself from the cfs_rq (task must be off the queue now).
 */
void remove_entity_load_avg(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 last_update_time;

	/*
	 * Newly created task or never used group entity should not be removed
	 * from its (source) cfs_rq
	 */
	if (se->avg.last_update_time == 0)
		return;

	last_update_time = cfs_rq_last_update_time(cfs_rq);

3082
	__update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
3083 3084
	atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
	atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
3085
}
3086

3087 3088 3089 3090 3091 3092 3093 3094 3095 3096
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
{
	return cfs_rq->runnable_load_avg;
}

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

3097 3098
static int idle_balance(struct rq *this_rq);

3099 3100
#else /* CONFIG_SMP */

3101 3102 3103
static inline void update_load_avg(struct sched_entity *se, int update_tg) {}
static inline void
enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3104 3105
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3106
static inline void remove_entity_load_avg(struct sched_entity *se) {}
3107

3108 3109 3110 3111 3112
static inline void
attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
static inline void
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}

3113 3114 3115 3116 3117
static inline int idle_balance(struct rq *rq)
{
	return 0;
}

3118
#endif /* CONFIG_SMP */
3119

3120
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
3121 3122
{
#ifdef CONFIG_SCHEDSTATS
3123 3124 3125 3126 3127
	struct task_struct *tsk = NULL;

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

3128
	if (se->statistics.sleep_start) {
3129
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
3130 3131 3132 3133

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

3134 3135
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
3136

3137
		se->statistics.sleep_start = 0;
3138
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
3139

3140
		if (tsk) {
3141
			account_scheduler_latency(tsk, delta >> 10, 1);
3142 3143
			trace_sched_stat_sleep(tsk, delta);
		}
3144
	}
3145
	if (se->statistics.block_start) {
3146
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
3147 3148 3149 3150

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

3151 3152
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
3153

3154
		se->statistics.block_start = 0;
3155
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
3156

3157
		if (tsk) {
3158
			if (tsk->in_iowait) {
3159 3160
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
3161
				trace_sched_stat_iowait(tsk, delta);
3162 3163
			}

3164 3165
			trace_sched_stat_blocked(tsk, delta);

3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176
			/*
			 * 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
3177
		}
3178 3179 3180 3181
	}
#endif
}

P
Peter Zijlstra 已提交
3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194
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
}

3195 3196 3197
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3198
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3199

3200 3201 3202 3203 3204 3205
	/*
	 * 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
3206
	if (initial && sched_feat(START_DEBIT))
3207
		vruntime += sched_vslice(cfs_rq, se);
3208

3209
	/* sleeps up to a single latency don't count. */
3210
	if (!initial) {
3211
		unsigned long thresh = sysctl_sched_latency;
3212

3213 3214 3215 3216 3217 3218
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3219

3220
		vruntime -= thresh;
3221 3222
	}

3223
	/* ensure we never gain time by being placed backwards. */
3224
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3225 3226
}

3227 3228
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248
static inline void check_schedstat_required(void)
{
#ifdef CONFIG_SCHEDSTATS
	if (schedstat_enabled())
		return;

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

3249
static void
3250
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3251
{
3252 3253 3254
	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING);
	bool curr = cfs_rq->curr == se;

3255
	/*
3256 3257
	 * If we're the current task, we must renormalise before calling
	 * update_curr().
3258
	 */
3259
	if (renorm && curr)
3260 3261
		se->vruntime += cfs_rq->min_vruntime;

3262 3263
	update_curr(cfs_rq);

3264
	/*
3265 3266
	 * Otherwise, renormalise after, such that we're placed at the current
	 * moment in time, instead of some random moment in the past.
3267
	 */
3268 3269 3270
	if (renorm && !curr)
		se->vruntime += cfs_rq->min_vruntime;

3271
	enqueue_entity_load_avg(cfs_rq, se);
3272 3273
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
3274

3275
	if (flags & ENQUEUE_WAKEUP) {
3276
		place_entity(cfs_rq, se, 0);
3277 3278
		if (schedstat_enabled())
			enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
3279
	}
3280

3281 3282 3283 3284 3285
	check_schedstat_required();
	if (schedstat_enabled()) {
		update_stats_enqueue(cfs_rq, se);
		check_spread(cfs_rq, se);
	}
3286
	if (!curr)
3287
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3288
	se->on_rq = 1;
3289

3290
	if (cfs_rq->nr_running == 1) {
3291
		list_add_leaf_cfs_rq(cfs_rq);
3292 3293
		check_enqueue_throttle(cfs_rq);
	}
3294 3295
}

3296
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3297
{
3298 3299
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3300
		if (cfs_rq->last != se)
3301
			break;
3302 3303

		cfs_rq->last = NULL;
3304 3305
	}
}
P
Peter Zijlstra 已提交
3306

3307 3308 3309 3310
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3311
		if (cfs_rq->next != se)
3312
			break;
3313 3314

		cfs_rq->next = NULL;
3315
	}
P
Peter Zijlstra 已提交
3316 3317
}

3318 3319 3320 3321
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3322
		if (cfs_rq->skip != se)
3323
			break;
3324 3325

		cfs_rq->skip = NULL;
3326 3327 3328
	}
}

P
Peter Zijlstra 已提交
3329 3330
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3331 3332 3333 3334 3335
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
3336 3337 3338

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
3339 3340
}

3341
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3342

3343
static void
3344
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3345
{
3346 3347 3348 3349
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
3350
	dequeue_entity_load_avg(cfs_rq, se);
3351

3352 3353
	if (schedstat_enabled())
		update_stats_dequeue(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
3354

P
Peter Zijlstra 已提交
3355
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3356

3357
	if (se != cfs_rq->curr)
3358
		__dequeue_entity(cfs_rq, se);
3359
	se->on_rq = 0;
3360
	account_entity_dequeue(cfs_rq, se);
3361 3362 3363 3364 3365 3366

	/*
	 * 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.
	 */
3367
	if (!(flags & DEQUEUE_SLEEP))
3368
		se->vruntime -= cfs_rq->min_vruntime;
3369

3370 3371 3372
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3373
	update_min_vruntime(cfs_rq);
3374
	update_cfs_shares(cfs_rq);
3375 3376 3377 3378 3379
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
3380
static void
I
Ingo Molnar 已提交
3381
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3382
{
3383
	unsigned long ideal_runtime, delta_exec;
3384 3385
	struct sched_entity *se;
	s64 delta;
3386

P
Peter Zijlstra 已提交
3387
	ideal_runtime = sched_slice(cfs_rq, curr);
3388
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3389
	if (delta_exec > ideal_runtime) {
3390
		resched_curr(rq_of(cfs_rq));
3391 3392 3393 3394 3395
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406
		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;

3407 3408
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
3409

3410 3411
	if (delta < 0)
		return;
3412

3413
	if (delta > ideal_runtime)
3414
		resched_curr(rq_of(cfs_rq));
3415 3416
}

3417
static void
3418
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3419
{
3420 3421 3422 3423 3424 3425 3426
	/* '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.
		 */
3427 3428
		if (schedstat_enabled())
			update_stats_wait_end(cfs_rq, se);
3429
		__dequeue_entity(cfs_rq, se);
3430
		update_load_avg(se, 1);
3431 3432
	}

3433
	update_stats_curr_start(cfs_rq, se);
3434
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
3435 3436 3437 3438 3439 3440
#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):
	 */
3441
	if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3442
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
3443 3444 3445
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
3446
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
3447 3448
}

3449 3450 3451
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

3452 3453 3454 3455 3456 3457 3458
/*
 * 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
 */
3459 3460
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3461
{
3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472
	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 */
3473

3474 3475 3476 3477 3478
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
3479 3480 3481 3482 3483 3484 3485 3486 3487 3488
		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;
		}

3489 3490 3491
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
3492

3493 3494 3495 3496 3497 3498
	/*
	 * 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;

3499 3500 3501 3502 3503 3504
	/*
	 * 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;

3505
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3506 3507

	return se;
3508 3509
}

3510
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3511

3512
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3513 3514 3515 3516 3517 3518
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
3519
		update_curr(cfs_rq);
3520

3521 3522 3523
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

3524 3525 3526 3527 3528 3529
	if (schedstat_enabled()) {
		check_spread(cfs_rq, prev);
		if (prev->on_rq)
			update_stats_wait_start(cfs_rq, prev);
	}

3530 3531 3532
	if (prev->on_rq) {
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
3533
		/* in !on_rq case, update occurred at dequeue */
3534
		update_load_avg(prev, 0);
3535
	}
3536
	cfs_rq->curr = NULL;
3537 3538
}

P
Peter Zijlstra 已提交
3539 3540
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3541 3542
{
	/*
3543
	 * Update run-time statistics of the 'current'.
3544
	 */
3545
	update_curr(cfs_rq);
3546

3547 3548 3549
	/*
	 * Ensure that runnable average is periodically updated.
	 */
3550
	update_load_avg(curr, 1);
3551
	update_cfs_shares(cfs_rq);
3552

P
Peter Zijlstra 已提交
3553 3554 3555 3556 3557
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
3558
	if (queued) {
3559
		resched_curr(rq_of(cfs_rq));
3560 3561
		return;
	}
P
Peter Zijlstra 已提交
3562 3563 3564 3565 3566 3567 3568 3569
	/*
	 * 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
3570
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
3571
		check_preempt_tick(cfs_rq, curr);
3572 3573
}

3574 3575 3576 3577 3578 3579

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

#ifdef CONFIG_CFS_BANDWIDTH
3580 3581

#ifdef HAVE_JUMP_LABEL
3582
static struct static_key __cfs_bandwidth_used;
3583 3584 3585

static inline bool cfs_bandwidth_used(void)
{
3586
	return static_key_false(&__cfs_bandwidth_used);
3587 3588
}

3589
void cfs_bandwidth_usage_inc(void)
3590
{
3591 3592 3593 3594 3595 3596
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
3597 3598 3599 3600 3601 3602 3603
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

3604 3605
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
3606 3607
#endif /* HAVE_JUMP_LABEL */

3608 3609 3610 3611 3612 3613 3614 3615
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
3616 3617 3618 3619 3620 3621

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

P
Paul Turner 已提交
3622 3623 3624 3625 3626 3627 3628
/*
 * 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
 */
3629
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640
{
	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);
}

3641 3642 3643 3644 3645
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

3646 3647 3648 3649 3650 3651
/* 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;

3652
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3653 3654
}

3655 3656
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3657 3658 3659
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
3660
	u64 amount = 0, min_amount, expires;
3661 3662 3663 3664 3665 3666 3667

	/* 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;
3668
	else {
P
Peter Zijlstra 已提交
3669
		start_cfs_bandwidth(cfs_b);
3670 3671 3672 3673 3674 3675

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
3676
	}
P
Paul Turner 已提交
3677
	expires = cfs_b->runtime_expires;
3678 3679 3680
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
3681 3682 3683 3684 3685 3686 3687
	/*
	 * 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;
3688 3689

	return cfs_rq->runtime_remaining > 0;
3690 3691
}

P
Paul Turner 已提交
3692 3693 3694 3695 3696
/*
 * 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)
3697
{
P
Paul Turner 已提交
3698 3699 3700
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
3701
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3702 3703
		return;

P
Paul Turner 已提交
3704 3705 3706 3707 3708 3709 3710 3711 3712
	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
3713 3714 3715
	 * whether the global deadline has advanced. It is valid to compare
	 * cfs_b->runtime_expires without any locks since we only care about
	 * exact equality, so a partial write will still work.
P
Paul Turner 已提交
3716 3717
	 */

3718
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
3719 3720 3721 3722 3723 3724 3725 3726
		/* 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;
	}
}

3727
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
3728 3729
{
	/* dock delta_exec before expiring quota (as it could span periods) */
3730
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
3731 3732 3733
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
3734 3735
		return;

3736 3737 3738 3739 3740
	/*
	 * 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))
3741
		resched_curr(rq_of(cfs_rq));
3742 3743
}

3744
static __always_inline
3745
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3746
{
3747
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3748 3749 3750 3751 3752
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

3753 3754
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
3755
	return cfs_bandwidth_used() && cfs_rq->throttled;
3756 3757
}

3758 3759 3760
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
3761
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789
}

/*
 * 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) {
3790
		/* adjust cfs_rq_clock_task() */
3791
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3792
					     cfs_rq->throttled_clock_task;
3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803
	}
#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)];

3804 3805
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
3806
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
3807 3808 3809 3810 3811
	cfs_rq->throttle_count++;

	return 0;
}

3812
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3813 3814 3815 3816 3817
{
	struct rq *rq = rq_of(cfs_rq);
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
	struct sched_entity *se;
	long task_delta, dequeue = 1;
P
Peter Zijlstra 已提交
3818
	bool empty;
3819 3820 3821

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

3822
	/* freeze hierarchy runnable averages while throttled */
3823 3824 3825
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
3826 3827 3828 3829 3830 3831 3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842

	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)
3843
		sub_nr_running(rq, task_delta);
3844 3845

	cfs_rq->throttled = 1;
3846
	cfs_rq->throttled_clock = rq_clock(rq);
3847
	raw_spin_lock(&cfs_b->lock);
3848
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
3849

3850 3851 3852 3853 3854
	/*
	 * Add to the _head_ of the list, so that an already-started
	 * distribute_cfs_runtime will not see us
	 */
	list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
3855 3856 3857 3858 3859 3860 3861 3862

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

3863 3864 3865
	raw_spin_unlock(&cfs_b->lock);
}

3866
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3867 3868 3869 3870 3871 3872 3873
{
	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;

3874
	se = cfs_rq->tg->se[cpu_of(rq)];
3875 3876

	cfs_rq->throttled = 0;
3877 3878 3879

	update_rq_clock(rq);

3880
	raw_spin_lock(&cfs_b->lock);
3881
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3882 3883 3884
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

3885 3886 3887
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905
	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)
3906
		add_nr_running(rq, task_delta);
3907 3908 3909

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
3910
		resched_curr(rq);
3911 3912 3913 3914 3915 3916
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
3917 3918
	u64 runtime;
	u64 starting_runtime = remaining;
3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946 3947 3948

	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();

3949
	return starting_runtime - remaining;
3950 3951
}

3952 3953 3954 3955 3956 3957 3958 3959
/*
 * 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)
{
3960
	u64 runtime, runtime_expires;
3961
	int throttled;
3962 3963 3964

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
3965
		goto out_deactivate;
3966

3967
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3968
	cfs_b->nr_periods += overrun;
3969

3970 3971 3972 3973 3974 3975
	/*
	 * idle depends on !throttled (for the case of a large deficit), and if
	 * we're going inactive then everything else can be deferred
	 */
	if (cfs_b->idle && !throttled)
		goto out_deactivate;
P
Paul Turner 已提交
3976 3977 3978

	__refill_cfs_bandwidth_runtime(cfs_b);

3979 3980 3981
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
3982
		return 0;
3983 3984
	}

3985 3986 3987
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

3988 3989 3990
	runtime_expires = cfs_b->runtime_expires;

	/*
3991 3992 3993 3994 3995
	 * This check is repeated as we are holding onto the new bandwidth while
	 * we unthrottle. This can potentially race with an unthrottled group
	 * trying to acquire new bandwidth from the global pool. This can result
	 * in us over-using our runtime if it is all used during this loop, but
	 * only by limited amounts in that extreme case.
3996
	 */
3997 3998
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
3999 4000 4001 4002 4003 4004 4005
		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);
4006 4007

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4008
	}
4009

4010 4011 4012 4013 4014 4015 4016
	/*
	 * 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;
4017

4018 4019 4020 4021
	return 0;

out_deactivate:
	return 1;
4022
}
4023

4024 4025 4026 4027 4028 4029 4030
/* 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;

4031 4032 4033 4034
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4035
 * hrtimer base being cleared by hrtimer_start. In the case of
4036 4037
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061 4062
static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
{
	struct hrtimer *refresh_timer = &cfs_b->period_timer;
	u64 remaining;

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

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

	return 0;
}

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

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

P
Peter Zijlstra 已提交
4063 4064 4065
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
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
}

/* 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)
{
4095 4096 4097
	if (!cfs_bandwidth_used())
		return;

4098
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4099 4100 4101 4102 4103 4104 4105 4106 4107 4108 4109 4110 4111 4112 4113
		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 */
4114 4115 4116
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
4117
		return;
4118
	}
4119

4120
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4121
		runtime = cfs_b->runtime;
4122

4123 4124 4125 4126 4127 4128 4129 4130 4131 4132
	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)
4133
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4134 4135 4136
	raw_spin_unlock(&cfs_b->lock);
}

4137 4138 4139 4140 4141 4142 4143
/*
 * 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)
{
4144 4145 4146
	if (!cfs_bandwidth_used())
		return;

4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161
	/* 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() */
4162
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4163
{
4164
	if (!cfs_bandwidth_used())
4165
		return false;
4166

4167
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4168
		return false;
4169 4170 4171 4172 4173 4174

	/*
	 * 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))
4175
		return true;
4176 4177

	throttle_cfs_rq(cfs_rq);
4178
	return true;
4179
}
4180 4181 4182 4183 4184

static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, slack_timer);
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Peter Zijlstra 已提交
4185

4186 4187 4188 4189 4190 4191 4192 4193 4194 4195 4196 4197
	do_sched_cfs_slack_timer(cfs_b);

	return HRTIMER_NORESTART;
}

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

4198
	raw_spin_lock(&cfs_b->lock);
4199
	for (;;) {
P
Peter Zijlstra 已提交
4200
		overrun = hrtimer_forward_now(timer, cfs_b->period);
4201 4202 4203 4204 4205
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
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Peter Zijlstra 已提交
4206 4207
	if (idle)
		cfs_b->period_active = 0;
4208
	raw_spin_unlock(&cfs_b->lock);
4209 4210 4211 4212 4213 4214 4215 4216 4217 4218 4219 4220

	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);
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Peter Zijlstra 已提交
4221
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232
	cfs_b->period_timer.function = sched_cfs_period_timer;
	hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	cfs_b->slack_timer.function = sched_cfs_slack_timer;
}

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

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Peter Zijlstra 已提交
4233
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4234
{
P
Peter Zijlstra 已提交
4235
	lockdep_assert_held(&cfs_b->lock);
4236

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Peter Zijlstra 已提交
4237 4238 4239 4240 4241
	if (!cfs_b->period_active) {
		cfs_b->period_active = 1;
		hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
		hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
	}
4242 4243 4244 4245
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4246 4247 4248 4249
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4250 4251 4252 4253
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

4254 4255 4256 4257 4258 4259 4260 4261 4262 4263 4264 4265 4266
static void __maybe_unused update_runtime_enabled(struct rq *rq)
{
	struct cfs_rq *cfs_rq;

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

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

4267
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278
{
	struct cfs_rq *cfs_rq;

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

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
4279
		cfs_rq->runtime_remaining = 1;
4280 4281 4282 4283 4284 4285
		/*
		 * Offline rq is schedulable till cpu is completely disabled
		 * in take_cpu_down(), so we prevent new cfs throttling here.
		 */
		cfs_rq->runtime_enabled = 0;

4286 4287 4288 4289 4290 4291
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
}

#else /* CONFIG_CFS_BANDWIDTH */
4292 4293
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
4294
	return rq_clock_task(rq_of(cfs_rq));
4295 4296
}

4297
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4298
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4299
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4300
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4301 4302 4303 4304 4305

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
4306 4307 4308 4309 4310 4311 4312 4313 4314 4315 4316

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;
}
4317 4318 4319 4320 4321

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) {}
4322 4323
#endif

4324 4325 4326 4327 4328
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) {}
4329
static inline void update_runtime_enabled(struct rq *rq) {}
4330
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4331 4332 4333

#endif /* CONFIG_CFS_BANDWIDTH */

4334 4335 4336 4337
/**************************************************
 * CFS operations on tasks:
 */

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Peter Zijlstra 已提交
4338 4339 4340 4341 4342 4343 4344 4345
#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);

4346
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
4347 4348 4349 4350 4351 4352
		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)
4353
				resched_curr(rq);
P
Peter Zijlstra 已提交
4354 4355
			return;
		}
4356
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
4357 4358
	}
}
4359 4360 4361 4362 4363 4364 4365 4366 4367 4368

/*
 * 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;

4369
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4370 4371 4372 4373 4374
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
4375
#else /* !CONFIG_SCHED_HRTICK */
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Peter Zijlstra 已提交
4376 4377 4378 4379
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
4380 4381 4382 4383

static inline void hrtick_update(struct rq *rq)
{
}
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Peter Zijlstra 已提交
4384 4385
#endif

4386 4387 4388 4389 4390
/*
 * 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:
 */
4391
static void
4392
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4393 4394
{
	struct cfs_rq *cfs_rq;
4395
	struct sched_entity *se = &p->se;
4396 4397

	for_each_sched_entity(se) {
4398
		if (se->on_rq)
4399 4400
			break;
		cfs_rq = cfs_rq_of(se);
4401
		enqueue_entity(cfs_rq, se, flags);
4402 4403 4404 4405 4406 4407 4408 4409 4410

		/*
		 * 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;
4411
		cfs_rq->h_nr_running++;
4412

4413
		flags = ENQUEUE_WAKEUP;
4414
	}
P
Peter Zijlstra 已提交
4415

P
Peter Zijlstra 已提交
4416
	for_each_sched_entity(se) {
4417
		cfs_rq = cfs_rq_of(se);
4418
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
4419

4420 4421 4422
		if (cfs_rq_throttled(cfs_rq))
			break;

4423
		update_load_avg(se, 1);
4424
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4425 4426
	}

Y
Yuyang Du 已提交
4427
	if (!se)
4428
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
4429

4430
	hrtick_update(rq);
4431 4432
}

4433 4434
static void set_next_buddy(struct sched_entity *se);

4435 4436 4437 4438 4439
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
4440
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4441 4442
{
	struct cfs_rq *cfs_rq;
4443
	struct sched_entity *se = &p->se;
4444
	int task_sleep = flags & DEQUEUE_SLEEP;
4445 4446 4447

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
4448
		dequeue_entity(cfs_rq, se, flags);
4449 4450 4451 4452 4453 4454 4455 4456 4457

		/*
		 * 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;
4458
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4459

4460
		/* Don't dequeue parent if it has other entities besides us */
4461 4462 4463 4464 4465 4466 4467
		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));
4468 4469 4470

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
4471
			break;
4472
		}
4473
		flags |= DEQUEUE_SLEEP;
4474
	}
P
Peter Zijlstra 已提交
4475

P
Peter Zijlstra 已提交
4476
	for_each_sched_entity(se) {
4477
		cfs_rq = cfs_rq_of(se);
4478
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4479

4480 4481 4482
		if (cfs_rq_throttled(cfs_rq))
			break;

4483
		update_load_avg(se, 1);
4484
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4485 4486
	}

Y
Yuyang Du 已提交
4487
	if (!se)
4488
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
4489

4490
	hrtick_update(rq);
4491 4492
}

4493
#ifdef CONFIG_SMP
4494 4495 4496 4497 4498 4499

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

/*
4500
 * The exact cpuload calculated at every tick would be:
4501
 *
4502 4503 4504 4505 4506 4507 4508
 *   load' = (1 - 1/2^i) * load + (1/2^i) * cur_load
 *
 * If a cpu misses updates for n ticks (as it was idle) and update gets
 * called on the n+1-th tick when cpu may be busy, then we have:
 *
 *   load_n   = (1 - 1/2^i)^n * load_0
 *   load_n+1 = (1 - 1/2^i)   * load_n + (1/2^i) * cur_load
4509 4510 4511
 *
 * decay_load_missed() below does efficient calculation of
 *
4512 4513 4514 4515 4516 4517
 *   load' = (1 - 1/2^i)^n * load
 *
 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
 * This allows us to precompute the above in said factors, thereby allowing the
 * reduction of an arbitrary n in O(log_2 n) steps. (See also
 * fixed_power_int())
4518
 *
4519
 * The calculation is approximated on a 128 point scale.
4520 4521
 */
#define DEGRADE_SHIFT		7
4522 4523 4524 4525 4526 4527 4528 4529 4530

static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
	{   0,   0,  0,  0,  0,  0, 0, 0 },
	{  64,  32,  8,  0,  0,  0, 0, 0 },
	{  96,  72, 40, 12,  1,  0, 0, 0 },
	{ 112,  98, 75, 43, 15,  1, 0, 0 },
	{ 120, 112, 98, 76, 45, 16, 2, 0 }
};
4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550 4551 4552 4553 4554 4555 4556 4557 4558 4559 4560

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

	if (!missed_updates)
		return load;

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

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

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

		missed_updates >>= 1;
		j++;
	}
	return load;
}

4561
/**
4562
 * __cpu_load_update - update the rq->cpu_load[] statistics
4563 4564 4565 4566
 * @this_rq: The rq to update statistics for
 * @this_load: The current load
 * @pending_updates: The number of missed updates
 *
4567
 * Update rq->cpu_load[] statistics. This function is usually called every
4568 4569 4570 4571 4572 4573 4574 4575 4576 4577 4578 4579 4580 4581 4582 4583 4584 4585 4586 4587 4588 4589 4590 4591 4592 4593
 * scheduler tick (TICK_NSEC).
 *
 * This function computes a decaying average:
 *
 *   load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
 *
 * Because of NOHZ it might not get called on every tick which gives need for
 * the @pending_updates argument.
 *
 *   load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
 *             = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
 *             = A * (A * load[i]_n-2 + B) + B
 *             = A * (A * (A * load[i]_n-3 + B) + B) + B
 *             = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
 *             = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
 *             = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
 *             = (1 - 1/2^i)^n * (load[i]_0 - load) + load
 *
 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
 * any change in load would have resulted in the tick being turned back on.
 *
 * For regular NOHZ, this reduces to:
 *
 *   load[i]_n = (1 - 1/2^i)^n * load[i]_0
 *
 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
4594
 * term.
4595
 */
4596 4597
static void cpu_load_update(struct rq *this_rq, unsigned long this_load,
			    unsigned long pending_updates)
4598
{
4599
	unsigned long tickless_load = this_rq->cpu_load[0];
4600 4601 4602 4603 4604 4605 4606 4607 4608 4609 4610
	int i, scale;

	this_rq->nr_load_updates++;

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

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

4611
		old_load = this_rq->cpu_load[i];
4612
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
4613 4614 4615 4616 4617 4618 4619 4620 4621
		if (tickless_load) {
			old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
			/*
			 * old_load can never be a negative value because a
			 * decayed tickless_load cannot be greater than the
			 * original tickless_load.
			 */
			old_load += tickless_load;
		}
4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636
		new_load = this_load;
		/*
		 * Round up the averaging division if load is increasing. This
		 * prevents us from getting stuck on 9 if the load is 10, for
		 * example.
		 */
		if (new_load > old_load)
			new_load += scale - 1;

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

	sched_avg_update(this_rq);
}

4637 4638 4639 4640 4641 4642
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
	return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
}

4643
#ifdef CONFIG_NO_HZ_COMMON
4644 4645 4646 4647 4648 4649 4650 4651 4652 4653 4654 4655 4656 4657 4658 4659 4660
/*
 * There is no sane way to deal with nohz on smp when using jiffies because the
 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
 *
 * Therefore we need to avoid the delta approach from the regular tick when
 * possible since that would seriously skew the load calculation. This is why we
 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on
 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle
 * loop exit, nohz_idle_balance, nohz full exit...)
 *
 * This means we might still be one tick off for nohz periods.
 */

static void cpu_load_update_nohz(struct rq *this_rq,
				 unsigned long curr_jiffies,
				 unsigned long load)
4661 4662 4663 4664 4665 4666 4667 4668 4669 4670 4671
{
	unsigned long pending_updates;

	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
	if (pending_updates) {
		this_rq->last_load_update_tick = curr_jiffies;
		/*
		 * In the regular NOHZ case, we were idle, this means load 0.
		 * In the NOHZ_FULL case, we were non-idle, we should consider
		 * its weighted load.
		 */
4672
		cpu_load_update(this_rq, load, pending_updates);
4673 4674 4675
	}
}

4676 4677 4678 4679
/*
 * Called from nohz_idle_balance() to update the load ratings before doing the
 * idle balance.
 */
4680
static void cpu_load_update_idle(struct rq *this_rq)
4681 4682 4683 4684
{
	/*
	 * bail if there's load or we're actually up-to-date.
	 */
4685
	if (weighted_cpuload(cpu_of(this_rq)))
4686 4687
		return;

4688
	cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0);
4689 4690 4691
}

/*
4692 4693 4694 4695
 * Record CPU load on nohz entry so we know the tickless load to account
 * on nohz exit. cpu_load[0] happens then to be updated more frequently
 * than other cpu_load[idx] but it should be fine as cpu_load readers
 * shouldn't rely into synchronized cpu_load[*] updates.
4696
 */
4697
void cpu_load_update_nohz_start(void)
4698 4699
{
	struct rq *this_rq = this_rq();
4700 4701 4702 4703 4704 4705 4706 4707 4708 4709 4710 4711 4712 4713

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

/*
 * Account the tickless load in the end of a nohz frame.
 */
void cpu_load_update_nohz_stop(void)
{
4714
	unsigned long curr_jiffies = READ_ONCE(jiffies);
4715 4716
	struct rq *this_rq = this_rq();
	unsigned long load;
4717 4718 4719 4720

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

4721
	load = weighted_cpuload(cpu_of(this_rq));
4722
	raw_spin_lock(&this_rq->lock);
4723
	cpu_load_update_nohz(this_rq, curr_jiffies, load);
4724 4725
	raw_spin_unlock(&this_rq->lock);
}
4726 4727 4728 4729 4730 4731 4732 4733 4734 4735 4736 4737
#else /* !CONFIG_NO_HZ_COMMON */
static inline void cpu_load_update_nohz(struct rq *this_rq,
					unsigned long curr_jiffies,
					unsigned long load) { }
#endif /* CONFIG_NO_HZ_COMMON */

static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load)
{
	/* See the mess around cpu_load_update_nohz(). */
	this_rq->last_load_update_tick = READ_ONCE(jiffies);
	cpu_load_update(this_rq, load, 1);
}
4738 4739 4740 4741

/*
 * Called from scheduler_tick()
 */
4742
void cpu_load_update_active(struct rq *this_rq)
4743
{
4744
	unsigned long load = weighted_cpuload(cpu_of(this_rq));
4745 4746 4747 4748 4749

	if (tick_nohz_tick_stopped())
		cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load);
	else
		cpu_load_update_periodic(this_rq, load);
4750 4751
}

4752 4753 4754 4755 4756 4757 4758 4759 4760 4761 4762 4763 4764 4765 4766 4767 4768 4769 4770 4771 4772 4773 4774 4775 4776 4777 4778 4779 4780 4781 4782 4783 4784
/*
 * 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);
}

4785
static unsigned long capacity_of(int cpu)
4786
{
4787
	return cpu_rq(cpu)->cpu_capacity;
4788 4789
}

4790 4791 4792 4793 4794
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

4795 4796 4797
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
4798
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4799
	unsigned long load_avg = weighted_cpuload(cpu);
4800 4801

	if (nr_running)
4802
		return load_avg / nr_running;
4803 4804 4805 4806

	return 0;
}

4807 4808 4809 4810 4811 4812 4813
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.
	 */
4814
	if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4815
		current->wakee_flips >>= 1;
4816 4817 4818 4819 4820 4821 4822 4823
		current->wakee_flip_decay_ts = jiffies;
	}

	if (current->last_wakee != p) {
		current->last_wakee = p;
		current->wakee_flips++;
	}
}
4824

4825
static void task_waking_fair(struct task_struct *p)
4826 4827 4828
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
4829 4830 4831 4832
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
4833

4834 4835 4836 4837 4838 4839 4840 4841
	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
4842

4843
	se->vruntime -= min_vruntime;
4844
	record_wakee(p);
4845 4846
}

4847
#ifdef CONFIG_FAIR_GROUP_SCHED
4848 4849 4850 4851 4852 4853
/*
 * 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.
4854 4855 4856 4857 4858 4859 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
 *
 * 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.
4897
 */
P
Peter Zijlstra 已提交
4898
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4899
{
P
Peter Zijlstra 已提交
4900
	struct sched_entity *se = tg->se[cpu];
4901

4902
	if (!tg->parent)	/* the trivial, non-cgroup case */
4903 4904
		return wl;

P
Peter Zijlstra 已提交
4905
	for_each_sched_entity(se) {
4906
		long w, W;
P
Peter Zijlstra 已提交
4907

4908
		tg = se->my_q->tg;
4909

4910 4911 4912 4913
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
4914

4915 4916 4917
		/*
		 * w = rw_i + @wl
		 */
4918
		w = cfs_rq_load_avg(se->my_q) + wl;
4919

4920 4921 4922 4923
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
4924
			wl = (w * (long)tg->shares) / W;
4925 4926
		else
			wl = tg->shares;
4927

4928 4929 4930 4931 4932
		/*
		 * 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().
		 */
4933 4934
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
4935 4936 4937 4938

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
4939
		wl -= se->avg.load_avg;
4940 4941 4942 4943 4944 4945 4946 4947

		/*
		 * 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
4948 4949
		wg = 0;
	}
4950

P
Peter Zijlstra 已提交
4951
	return wl;
4952 4953
}
#else
P
Peter Zijlstra 已提交
4954

4955
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
P
Peter Zijlstra 已提交
4956
{
4957
	return wl;
4958
}
P
Peter Zijlstra 已提交
4959

4960 4961
#endif

M
Mike Galbraith 已提交
4962 4963 4964 4965 4966 4967 4968 4969 4970 4971 4972 4973
/*
 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.
 * A waker of many should wake a different task than the one last awakened
 * at a frequency roughly N times higher than one of its wakees.  In order
 * to determine whether we should let the load spread vs consolodating to
 * shared cache, we look for a minimum 'flip' frequency of llc_size in one
 * partner, and a factor of lls_size higher frequency in the other.  With
 * both conditions met, we can be relatively sure that the relationship is
 * non-monogamous, with partner count exceeding socket size.  Waker/wakee
 * being client/server, worker/dispatcher, interrupt source or whatever is
 * irrelevant, spread criteria is apparent partner count exceeds socket size.
 */
4974 4975
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
4976 4977
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
4978
	int factor = this_cpu_read(sd_llc_size);
4979

M
Mike Galbraith 已提交
4980 4981 4982 4983 4984
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
4985 4986
}

4987
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4988
{
4989
	s64 this_load, load;
4990
	s64 this_eff_load, prev_eff_load;
4991 4992
	int idx, this_cpu, prev_cpu;
	struct task_group *tg;
4993
	unsigned long weight;
4994
	int balanced;
4995

4996 4997 4998 4999 5000
	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);
5001

5002 5003 5004 5005 5006
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
5007 5008
	if (sync) {
		tg = task_group(current);
5009
		weight = current->se.avg.load_avg;
5010

5011
		this_load += effective_load(tg, this_cpu, -weight, -weight);
5012 5013
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
5014

5015
	tg = task_group(p);
5016
	weight = p->se.avg.load_avg;
5017

5018 5019
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
5020 5021 5022
	 * 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.
5023 5024 5025 5026
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
5027 5028
	this_eff_load = 100;
	this_eff_load *= capacity_of(prev_cpu);
5029

5030 5031
	prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= capacity_of(this_cpu);
5032

5033
	if (this_load > 0) {
5034 5035 5036 5037
		this_eff_load *= this_load +
			effective_load(tg, this_cpu, weight, weight);

		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
5038
	}
5039

5040
	balanced = this_eff_load <= prev_eff_load;
5041

5042
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
5043

5044 5045
	if (!balanced)
		return 0;
5046

5047 5048 5049 5050
	schedstat_inc(sd, ttwu_move_affine);
	schedstat_inc(p, se.statistics.nr_wakeups_affine);

	return 1;
5051 5052
}

5053 5054 5055 5056 5057
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
5058
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5059
		  int this_cpu, int sd_flag)
5060
{
5061
	struct sched_group *idlest = NULL, *group = sd->groups;
5062
	unsigned long min_load = ULONG_MAX, this_load = 0;
5063
	int load_idx = sd->forkexec_idx;
5064
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
5065

5066 5067 5068
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

5069 5070 5071 5072
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
5073

5074 5075
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
5076
					tsk_cpus_allowed(p)))
5077 5078 5079 5080 5081 5082 5083 5084 5085 5086 5087 5088 5089 5090 5091 5092 5093 5094
			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;
		}

5095
		/* Adjust by relative CPU capacity of the group */
5096
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
5097 5098 5099 5100 5101 5102 5103 5104 5105 5106 5107 5108 5109 5110 5111 5112 5113 5114 5115 5116 5117

		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;
5118 5119 5120 5121
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
5122 5123 5124
	int i;

	/* Traverse only the allowed CPUs */
5125
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5126 5127 5128 5129 5130 5131 5132 5133 5134 5135 5136 5137 5138 5139 5140 5141 5142 5143 5144 5145 5146 5147
		if (idle_cpu(i)) {
			struct rq *rq = cpu_rq(i);
			struct cpuidle_state *idle = idle_get_state(rq);
			if (idle && idle->exit_latency < min_exit_latency) {
				/*
				 * We give priority to a CPU whose idle state
				 * has the smallest exit latency irrespective
				 * of any idle timestamp.
				 */
				min_exit_latency = idle->exit_latency;
				latest_idle_timestamp = rq->idle_stamp;
				shallowest_idle_cpu = i;
			} else if ((!idle || idle->exit_latency == min_exit_latency) &&
				   rq->idle_stamp > latest_idle_timestamp) {
				/*
				 * If equal or no active idle state, then
				 * the most recently idled CPU might have
				 * a warmer cache.
				 */
				latest_idle_timestamp = rq->idle_stamp;
				shallowest_idle_cpu = i;
			}
5148
		} else if (shallowest_idle_cpu == -1) {
5149 5150 5151 5152 5153
			load = weighted_cpuload(i);
			if (load < min_load || (load == min_load && i == this_cpu)) {
				min_load = load;
				least_loaded_cpu = i;
			}
5154 5155 5156
		}
	}

5157
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5158
}
5159

5160 5161 5162
/*
 * Try and locate an idle CPU in the sched_domain.
 */
5163
static int select_idle_sibling(struct task_struct *p, int target)
5164
{
5165
	struct sched_domain *sd;
5166
	struct sched_group *sg;
5167
	int i = task_cpu(p);
5168

5169 5170
	if (idle_cpu(target))
		return target;
5171 5172

	/*
5173
	 * If the prevous cpu is cache affine and idle, don't be stupid.
5174
	 */
5175 5176
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
5177 5178

	/*
5179 5180 5181 5182 5183 5184 5185 5186 5187 5188 5189 5190 5191
	 * Otherwise, iterate the domains and find an eligible idle cpu.
	 *
	 * A completely idle sched group at higher domains is more
	 * desirable than an idle group at a lower level, because lower
	 * domains have smaller groups and usually share hardware
	 * resources which causes tasks to contend on them, e.g. x86
	 * hyperthread siblings in the lowest domain (SMT) can contend
	 * on the shared cpu pipeline.
	 *
	 * However, while we prefer idle groups at higher domains
	 * finding an idle cpu at the lowest domain is still better than
	 * returning 'target', which we've already established, isn't
	 * idle.
5192
	 */
5193
	sd = rcu_dereference(per_cpu(sd_llc, target));
5194
	for_each_lower_domain(sd) {
5195 5196 5197 5198 5199 5200
		sg = sd->groups;
		do {
			if (!cpumask_intersects(sched_group_cpus(sg),
						tsk_cpus_allowed(p)))
				goto next;

5201
			/* Ensure the entire group is idle */
5202
			for_each_cpu(i, sched_group_cpus(sg)) {
5203
				if (i == target || !idle_cpu(i))
5204 5205
					goto next;
			}
5206

5207 5208 5209 5210
			/*
			 * It doesn't matter which cpu we pick, the
			 * whole group is idle.
			 */
5211 5212 5213 5214 5215 5216 5217 5218
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
5219 5220
	return target;
}
5221

5222
/*
5223
 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5224
 * tasks. The unit of the return value must be the one of capacity so we can
5225 5226
 * compare the utilization with the capacity of the CPU that is available for
 * CFS task (ie cpu_capacity).
5227 5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238 5239 5240 5241 5242 5243 5244 5245 5246
 *
 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
 * recent utilization of currently non-runnable tasks on a CPU. It represents
 * the amount of utilization of a CPU in the range [0..capacity_orig] where
 * capacity_orig is the cpu_capacity available at the highest frequency
 * (arch_scale_freq_capacity()).
 * The utilization of a CPU converges towards a sum equal to or less than the
 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
 * the running time on this CPU scaled by capacity_curr.
 *
 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
 * higher than capacity_orig because of unfortunate rounding in
 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until
 * the average stabilizes with the new running time. We need to check that the
 * utilization stays within the range of [0..capacity_orig] and cap it if
 * necessary. Without utilization capping, a group could be seen as overloaded
 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
 * available capacity. We allow utilization to overshoot capacity_curr (but not
 * capacity_orig) as it useful for predicting the capacity required after task
 * migrations (scheduler-driven DVFS).
5247
 */
5248
static int cpu_util(int cpu)
5249
{
5250
	unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
5251 5252
	unsigned long capacity = capacity_orig_of(cpu);

5253
	return (util >= capacity) ? capacity : util;
5254
}
5255

5256
/*
5257 5258 5259
 * 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.
5260
 *
5261 5262
 * 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.
5263
 *
5264
 * Returns the target cpu number.
5265 5266 5267
 *
 * preempt must be disabled.
 */
5268
static int
5269
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5270
{
5271
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5272
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
5273
	int new_cpu = prev_cpu;
5274
	int want_affine = 0;
5275
	int sync = wake_flags & WF_SYNC;
5276

5277
	if (sd_flag & SD_BALANCE_WAKE)
M
Mike Galbraith 已提交
5278
		want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
5279

5280
	rcu_read_lock();
5281
	for_each_domain(cpu, tmp) {
5282
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
5283
			break;
5284

5285
		/*
5286 5287
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
5288
		 */
5289 5290 5291
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
5292
			break;
5293
		}
5294

5295
		if (tmp->flags & sd_flag)
5296
			sd = tmp;
M
Mike Galbraith 已提交
5297 5298
		else if (!want_affine)
			break;
5299 5300
	}

M
Mike Galbraith 已提交
5301 5302 5303 5304
	if (affine_sd) {
		sd = NULL; /* Prefer wake_affine over balance flags */
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
			new_cpu = cpu;
5305
	}
5306

M
Mike Galbraith 已提交
5307 5308 5309 5310 5311
	if (!sd) {
		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
			new_cpu = select_idle_sibling(p, new_cpu);

	} else while (sd) {
5312
		struct sched_group *group;
5313
		int weight;
5314

5315
		if (!(sd->flags & sd_flag)) {
5316 5317 5318
			sd = sd->child;
			continue;
		}
5319

5320
		group = find_idlest_group(sd, p, cpu, sd_flag);
5321 5322 5323 5324
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
5325

5326
		new_cpu = find_idlest_cpu(group, p, cpu);
5327 5328 5329 5330
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
5331
		}
5332 5333 5334

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
5335
		weight = sd->span_weight;
5336 5337
		sd = NULL;
		for_each_domain(cpu, tmp) {
5338
			if (weight <= tmp->span_weight)
5339
				break;
5340
			if (tmp->flags & sd_flag)
5341 5342 5343
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
5344
	}
5345
	rcu_read_unlock();
5346

5347
	return new_cpu;
5348
}
5349 5350 5351 5352

/*
 * 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
5353
 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5354
 */
5355
static void migrate_task_rq_fair(struct task_struct *p)
5356
{
5357
	/*
5358 5359 5360 5361 5362
	 * We are supposed to update the task to "current" time, then its up to date
	 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting
	 * what current time is, so simply throw away the out-of-date time. This
	 * will result in the wakee task is less decayed, but giving the wakee more
	 * load sounds not bad.
5363
	 */
5364 5365 5366 5367
	remove_entity_load_avg(&p->se);

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
5368 5369

	/* We have migrated, no longer consider this task hot */
5370
	p->se.exec_start = 0;
5371
}
5372 5373 5374 5375 5376

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
5377 5378
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
5379 5380
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5381 5382 5383 5384
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
5385 5386
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
5387 5388 5389 5390 5391 5392 5393 5394 5395
	 *
	 * 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.
5396
	 */
5397
	return calc_delta_fair(gran, se);
5398 5399
}

5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418 5419 5420 5421
/*
 * 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
5422
	gran = wakeup_gran(curr, se);
5423 5424 5425 5426 5427 5428
	if (vdiff > gran)
		return 1;

	return 0;
}

5429 5430
static void set_last_buddy(struct sched_entity *se)
{
5431 5432 5433 5434 5435
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
5436 5437 5438 5439
}

static void set_next_buddy(struct sched_entity *se)
{
5440 5441 5442 5443 5444
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
5445 5446
}

5447 5448
static void set_skip_buddy(struct sched_entity *se)
{
5449 5450
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
5451 5452
}

5453 5454 5455
/*
 * Preempt the current task with a newly woken task if needed:
 */
5456
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5457 5458
{
	struct task_struct *curr = rq->curr;
5459
	struct sched_entity *se = &curr->se, *pse = &p->se;
5460
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5461
	int scale = cfs_rq->nr_running >= sched_nr_latency;
5462
	int next_buddy_marked = 0;
5463

I
Ingo Molnar 已提交
5464 5465 5466
	if (unlikely(se == pse))
		return;

5467
	/*
5468
	 * This is possible from callers such as attach_tasks(), in which we
5469 5470 5471 5472 5473 5474 5475
	 * 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;

5476
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
5477
		set_next_buddy(pse);
5478 5479
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
5480

5481 5482 5483
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
5484 5485 5486 5487 5488 5489
	 *
	 * 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.
5490 5491 5492 5493
	 */
	if (test_tsk_need_resched(curr))
		return;

5494 5495 5496 5497 5498
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

5499
	/*
5500 5501
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
5502
	 */
5503
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5504
		return;
5505

5506
	find_matching_se(&se, &pse);
5507
	update_curr(cfs_rq_of(se));
5508
	BUG_ON(!pse);
5509 5510 5511 5512 5513 5514 5515
	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);
5516
		goto preempt;
5517
	}
5518

5519
	return;
5520

5521
preempt:
5522
	resched_curr(rq);
5523 5524 5525 5526 5527 5528 5529 5530 5531 5532 5533 5534 5535 5536
	/*
	 * 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);
5537 5538
}

5539 5540
static struct task_struct *
pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5541 5542 5543
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
5544
	struct task_struct *p;
5545
	int new_tasks;
5546

5547
again:
5548 5549
#ifdef CONFIG_FAIR_GROUP_SCHED
	if (!cfs_rq->nr_running)
5550
		goto idle;
5551

5552
	if (prev->sched_class != &fair_sched_class)
5553 5554 5555 5556 5557 5558 5559 5560 5561 5562 5563 5564 5565 5566 5567 5568 5569 5570 5571
		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.
		 */
5572 5573 5574 5575 5576
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
5577

5578 5579 5580 5581 5582 5583 5584 5585 5586
			/*
			 * 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;
		}
5587 5588 5589 5590 5591 5592 5593 5594 5595 5596 5597 5598 5599 5600 5601 5602 5603 5604 5605 5606 5607 5608 5609 5610 5611 5612 5613 5614 5615 5616 5617 5618 5619 5620 5621 5622 5623 5624 5625 5626

		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
5627

5628
	if (!cfs_rq->nr_running)
5629
		goto idle;
5630

5631
	put_prev_task(rq, prev);
5632

5633
	do {
5634
		se = pick_next_entity(cfs_rq, NULL);
5635
		set_next_entity(cfs_rq, se);
5636 5637 5638
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
5639
	p = task_of(se);
5640

5641 5642
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
5643 5644

	return p;
5645 5646

idle:
5647 5648 5649 5650 5651 5652 5653
	/*
	 * This is OK, because current is on_cpu, which avoids it being picked
	 * for load-balance and preemption/IRQs are still disabled avoiding
	 * further scheduler activity on it and we're being very careful to
	 * re-start the picking loop.
	 */
	lockdep_unpin_lock(&rq->lock);
5654
	new_tasks = idle_balance(rq);
5655
	lockdep_pin_lock(&rq->lock);
5656 5657 5658 5659 5660
	/*
	 * Because idle_balance() releases (and re-acquires) rq->lock, it is
	 * possible for any higher priority task to appear. In that case we
	 * must re-start the pick_next_entity() loop.
	 */
5661
	if (new_tasks < 0)
5662 5663
		return RETRY_TASK;

5664
	if (new_tasks > 0)
5665 5666 5667
		goto again;

	return NULL;
5668 5669 5670 5671 5672
}

/*
 * Account for a descheduled task:
 */
5673
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5674 5675 5676 5677 5678 5679
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5680
		put_prev_entity(cfs_rq, se);
5681 5682 5683
	}
}

5684 5685 5686 5687 5688 5689 5690 5691 5692 5693 5694 5695 5696 5697 5698 5699 5700 5701 5702 5703 5704 5705 5706 5707 5708
/*
 * 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);
5709 5710 5711 5712 5713
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
5714
		rq_clock_skip_update(rq, true);
5715 5716 5717 5718 5719
	}

	set_skip_buddy(se);
}

5720 5721 5722 5723
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

5724 5725
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5726 5727 5728 5729 5730 5731 5732 5733 5734 5735
		return false;

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

	yield_task_fair(rq);

	return true;
}

5736
#ifdef CONFIG_SMP
5737
/**************************************************
P
Peter Zijlstra 已提交
5738 5739 5740 5741 5742 5743 5744 5745 5746 5747 5748 5749 5750 5751 5752 5753
 * 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
5754
 * is derived from the nice value as per sched_prio_to_weight[].
P
Peter Zijlstra 已提交
5755 5756 5757 5758 5759 5760
 *
 * 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)
 *
5761
 * C_i is the compute capacity of cpu i, typically it is the
P
Peter Zijlstra 已提交
5762 5763 5764 5765 5766 5767
 * 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):
 *
5768
 *   imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j }    (4)
P
Peter Zijlstra 已提交
5769 5770 5771 5772 5773 5774 5775 5776 5777 5778 5779 5780 5781 5782 5783 5784 5785 5786 5787 5788 5789 5790 5791 5792 5793 5794 5795 5796 5797 5798 5799 5800 5801 5802 5803 5804 5805 5806 5807 5808 5809 5810 5811 5812 5813 5814 5815 5816 5817 5818 5819 5820 5821 5822 5823 5824 5825 5826 5827 5828 5829 5830 5831 5832 5833 5834 5835 5836 5837 5838 5839 5840 5841 5842 5843 5844 5845 5846 5847 5848 5849 5850 5851 5852 5853
 *
 * 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.]
 */ 
5854

5855 5856
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

5857 5858
enum fbq_type { regular, remote, all };

5859
#define LBF_ALL_PINNED	0x01
5860
#define LBF_NEED_BREAK	0x02
5861 5862
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
5863 5864 5865 5866 5867

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
5868
	int			src_cpu;
5869 5870 5871 5872

	int			dst_cpu;
	struct rq		*dst_rq;

5873 5874
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
5875
	enum cpu_idle_type	idle;
5876
	long			imbalance;
5877 5878 5879
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

5880
	unsigned int		flags;
5881 5882 5883 5884

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
5885 5886

	enum fbq_type		fbq_type;
5887
	struct list_head	tasks;
5888 5889
};

5890 5891 5892
/*
 * Is this task likely cache-hot:
 */
5893
static int task_hot(struct task_struct *p, struct lb_env *env)
5894 5895 5896
{
	s64 delta;

5897 5898
	lockdep_assert_held(&env->src_rq->lock);

5899 5900 5901 5902 5903 5904 5905 5906 5907
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
5908
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5909 5910 5911 5912 5913 5914 5915 5916 5917
			(&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;

5918
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5919 5920 5921 5922

	return delta < (s64)sysctl_sched_migration_cost;
}

5923
#ifdef CONFIG_NUMA_BALANCING
5924
/*
5925 5926 5927
 * Returns 1, if task migration degrades locality
 * Returns 0, if task migration improves locality i.e migration preferred.
 * Returns -1, if task migration is not affected by locality.
5928
 */
5929
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5930
{
5931
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
5932
	unsigned long src_faults, dst_faults;
5933 5934
	int src_nid, dst_nid;

5935
	if (!static_branch_likely(&sched_numa_balancing))
5936 5937
		return -1;

5938
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5939
		return -1;
5940 5941 5942 5943

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

5944
	if (src_nid == dst_nid)
5945
		return -1;
5946

5947 5948 5949 5950 5951 5952 5953
	/* Migrating away from the preferred node is always bad. */
	if (src_nid == p->numa_preferred_nid) {
		if (env->src_rq->nr_running > env->src_rq->nr_preferred_running)
			return 1;
		else
			return -1;
	}
5954

5955 5956
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
5957
		return 0;
5958

5959 5960 5961 5962 5963 5964
	if (numa_group) {
		src_faults = group_faults(p, src_nid);
		dst_faults = group_faults(p, dst_nid);
	} else {
		src_faults = task_faults(p, src_nid);
		dst_faults = task_faults(p, dst_nid);
5965 5966
	}

5967
	return dst_faults < src_faults;
5968 5969
}

5970
#else
5971
static inline int migrate_degrades_locality(struct task_struct *p,
5972 5973
					     struct lb_env *env)
{
5974
	return -1;
5975
}
5976 5977
#endif

5978 5979 5980 5981
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
5982
int can_migrate_task(struct task_struct *p, struct lb_env *env)
5983
{
5984
	int tsk_cache_hot;
5985 5986 5987

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

5988 5989
	/*
	 * We do not migrate tasks that are:
5990
	 * 1) throttled_lb_pair, or
5991
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5992 5993
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
5994
	 */
5995 5996 5997
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

5998
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5999
		int cpu;
6000

6001
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
6002

6003 6004
		env->flags |= LBF_SOME_PINNED;

6005 6006 6007 6008 6009 6010 6011 6012
		/*
		 * 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.
		 */
6013
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
6014 6015
			return 0;

6016 6017 6018
		/* 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))) {
6019
				env->flags |= LBF_DST_PINNED;
6020 6021 6022
				env->new_dst_cpu = cpu;
				break;
			}
6023
		}
6024

6025 6026
		return 0;
	}
6027 6028

	/* Record that we found atleast one task that could run on dst_cpu */
6029
	env->flags &= ~LBF_ALL_PINNED;
6030

6031
	if (task_running(env->src_rq, p)) {
6032
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
6033 6034 6035 6036 6037
		return 0;
	}

	/*
	 * Aggressive migration if:
6038 6039 6040
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
6041
	 */
6042 6043 6044
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
6045

6046
	if (tsk_cache_hot <= 0 ||
6047
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6048
		if (tsk_cache_hot == 1) {
6049 6050 6051
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
			schedstat_inc(p, se.statistics.nr_forced_migrations);
		}
6052 6053 6054
		return 1;
	}

Z
Zhang Hang 已提交
6055 6056
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
6057 6058
}

6059
/*
6060 6061 6062 6063 6064 6065 6066
 * detach_task() -- detach the task for the migration specified in env
 */
static void detach_task(struct task_struct *p, struct lb_env *env)
{
	lockdep_assert_held(&env->src_rq->lock);

	p->on_rq = TASK_ON_RQ_MIGRATING;
6067
	deactivate_task(env->src_rq, p, 0);
6068 6069 6070
	set_task_cpu(p, env->dst_cpu);
}

6071
/*
6072
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6073 6074
 * part of active balancing operations within "domain".
 *
6075
 * Returns a task if successful and NULL otherwise.
6076
 */
6077
static struct task_struct *detach_one_task(struct lb_env *env)
6078 6079 6080
{
	struct task_struct *p, *n;

6081 6082
	lockdep_assert_held(&env->src_rq->lock);

6083 6084 6085
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
6086

6087
		detach_task(p, env);
6088

6089
		/*
6090
		 * Right now, this is only the second place where
6091
		 * lb_gained[env->idle] is updated (other is detach_tasks)
6092
		 * so we can safely collect stats here rather than
6093
		 * inside detach_tasks().
6094 6095
		 */
		schedstat_inc(env->sd, lb_gained[env->idle]);
6096
		return p;
6097
	}
6098
	return NULL;
6099 6100
}

6101 6102
static const unsigned int sched_nr_migrate_break = 32;

6103
/*
6104 6105
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
6106
 *
6107
 * Returns number of detached tasks if successful and 0 otherwise.
6108
 */
6109
static int detach_tasks(struct lb_env *env)
6110
{
6111 6112
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
6113
	unsigned long load;
6114 6115 6116
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
6117

6118
	if (env->imbalance <= 0)
6119
		return 0;
6120

6121
	while (!list_empty(tasks)) {
6122 6123 6124 6125 6126 6127 6128
		/*
		 * We don't want to steal all, otherwise we may be treated likewise,
		 * which could at worst lead to a livelock crash.
		 */
		if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
			break;

6129
		p = list_first_entry(tasks, struct task_struct, se.group_node);
6130

6131 6132
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
6133
		if (env->loop > env->loop_max)
6134
			break;
6135 6136

		/* take a breather every nr_migrate tasks */
6137
		if (env->loop > env->loop_break) {
6138
			env->loop_break += sched_nr_migrate_break;
6139
			env->flags |= LBF_NEED_BREAK;
6140
			break;
6141
		}
6142

6143
		if (!can_migrate_task(p, env))
6144 6145 6146
			goto next;

		load = task_h_load(p);
6147

6148
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6149 6150
			goto next;

6151
		if ((load / 2) > env->imbalance)
6152
			goto next;
6153

6154 6155 6156 6157
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
6158
		env->imbalance -= load;
6159 6160

#ifdef CONFIG_PREEMPT
6161 6162
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
6163
		 * kernels will stop after the first task is detached to minimize
6164 6165
		 * the critical section.
		 */
6166
		if (env->idle == CPU_NEWLY_IDLE)
6167
			break;
6168 6169
#endif

6170 6171 6172 6173
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
6174
		if (env->imbalance <= 0)
6175
			break;
6176 6177 6178

		continue;
next:
6179
		list_move_tail(&p->se.group_node, tasks);
6180
	}
6181

6182
	/*
6183 6184 6185
	 * Right now, this is one of only two places we collect this stat
	 * so we can safely collect detach_one_task() stats here rather
	 * than inside detach_one_task().
6186
	 */
6187
	schedstat_add(env->sd, lb_gained[env->idle], detached);
6188

6189 6190 6191 6192 6193 6194 6195 6196 6197 6198 6199 6200
	return detached;
}

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

	BUG_ON(task_rq(p) != rq);
	activate_task(rq, p, 0);
6201
	p->on_rq = TASK_ON_RQ_QUEUED;
6202 6203 6204 6205 6206 6207 6208 6209 6210 6211 6212 6213 6214 6215 6216 6217 6218 6219 6220 6221 6222 6223 6224 6225 6226 6227 6228 6229
	check_preempt_curr(rq, p, 0);
}

/*
 * attach_one_task() -- attaches the task returned from detach_one_task() to
 * its new rq.
 */
static void attach_one_task(struct rq *rq, struct task_struct *p)
{
	raw_spin_lock(&rq->lock);
	attach_task(rq, p);
	raw_spin_unlock(&rq->lock);
}

/*
 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their
 * new rq.
 */
static void attach_tasks(struct lb_env *env)
{
	struct list_head *tasks = &env->tasks;
	struct task_struct *p;

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

	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
		list_del_init(&p->se.group_node);
6230

6231 6232 6233 6234
		attach_task(env->dst_rq, p);
	}

	raw_spin_unlock(&env->dst_rq->lock);
6235 6236
}

P
Peter Zijlstra 已提交
6237
#ifdef CONFIG_FAIR_GROUP_SCHED
6238
static void update_blocked_averages(int cpu)
6239 6240
{
	struct rq *rq = cpu_rq(cpu);
6241 6242
	struct cfs_rq *cfs_rq;
	unsigned long flags;
6243

6244 6245
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
6246

6247 6248 6249 6250
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
6251
	for_each_leaf_cfs_rq(rq, cfs_rq) {
6252 6253 6254
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
6255

6256
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true))
6257 6258
			update_tg_load_avg(cfs_rq, 0);
	}
6259
	raw_spin_unlock_irqrestore(&rq->lock, flags);
6260 6261
}

6262
/*
6263
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6264 6265 6266
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
6267
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6268
{
6269 6270
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6271
	unsigned long now = jiffies;
6272
	unsigned long load;
6273

6274
	if (cfs_rq->last_h_load_update == now)
6275 6276
		return;

6277 6278 6279 6280 6281 6282 6283
	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;
	}
6284

6285
	if (!se) {
6286
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6287 6288 6289 6290 6291
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
6292 6293
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
6294 6295 6296 6297
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
6298 6299
}

6300
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
6301
{
6302
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
6303

6304
	update_cfs_rq_h_load(cfs_rq);
6305
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6306
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
6307 6308
}
#else
6309
static inline void update_blocked_averages(int cpu)
6310
{
6311 6312 6313 6314 6315 6316
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
	unsigned long flags;

	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
6317
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true);
6318
	raw_spin_unlock_irqrestore(&rq->lock, flags);
6319 6320
}

6321
static unsigned long task_h_load(struct task_struct *p)
6322
{
6323
	return p->se.avg.load_avg;
6324
}
P
Peter Zijlstra 已提交
6325
#endif
6326 6327

/********** Helpers for find_busiest_group ************************/
6328 6329 6330 6331 6332 6333 6334

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

6335 6336 6337 6338 6339 6340 6341
/*
 * 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
6342
	unsigned long load_per_task;
6343
	unsigned long group_capacity;
6344
	unsigned long group_util; /* Total utilization of the group */
6345 6346 6347
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
6348
	enum group_type group_type;
6349
	int group_no_capacity;
6350 6351 6352 6353
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
6354 6355
};

J
Joonsoo Kim 已提交
6356 6357 6358 6359 6360 6361 6362 6363
/*
 * 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 */
6364
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
6365 6366 6367
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6368
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
6369 6370
};

6371 6372 6373 6374 6375 6376 6377 6378 6379 6380 6381 6382
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,
6383
		.total_capacity = 0UL,
6384 6385
		.busiest_stat = {
			.avg_load = 0UL,
6386 6387
			.sum_nr_running = 0,
			.group_type = group_other,
6388 6389 6390 6391
		},
	};
}

6392 6393 6394
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
6395
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6396 6397
 *
 * Return: The load index.
6398 6399 6400 6401 6402 6403 6404 6405 6406 6407 6408 6409 6410 6411 6412 6413 6414 6415 6416 6417 6418 6419
 */
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;
}

6420
static unsigned long scale_rt_capacity(int cpu)
6421 6422
{
	struct rq *rq = cpu_rq(cpu);
6423
	u64 total, used, age_stamp, avg;
6424
	s64 delta;
6425

6426 6427 6428 6429
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
6430 6431
	age_stamp = READ_ONCE(rq->age_stamp);
	avg = READ_ONCE(rq->rt_avg);
6432
	delta = __rq_clock_broken(rq) - age_stamp;
6433

6434 6435 6436 6437
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
6438

6439
	used = div_u64(avg, total);
6440

6441 6442
	if (likely(used < SCHED_CAPACITY_SCALE))
		return SCHED_CAPACITY_SCALE - used;
6443

6444
	return 1;
6445 6446
}

6447
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6448
{
6449
	unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6450 6451
	struct sched_group *sdg = sd->groups;

6452
	cpu_rq(cpu)->cpu_capacity_orig = capacity;
6453

6454
	capacity *= scale_rt_capacity(cpu);
6455
	capacity >>= SCHED_CAPACITY_SHIFT;
6456

6457 6458
	if (!capacity)
		capacity = 1;
6459

6460 6461
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
6462 6463
}

6464
void update_group_capacity(struct sched_domain *sd, int cpu)
6465 6466 6467
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
6468
	unsigned long capacity;
6469 6470 6471 6472
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
6473
	sdg->sgc->next_update = jiffies + interval;
6474 6475

	if (!child) {
6476
		update_cpu_capacity(sd, cpu);
6477 6478 6479
		return;
	}

6480
	capacity = 0;
6481

P
Peter Zijlstra 已提交
6482 6483 6484 6485 6486 6487
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

6488
		for_each_cpu(cpu, sched_group_cpus(sdg)) {
6489
			struct sched_group_capacity *sgc;
6490
			struct rq *rq = cpu_rq(cpu);
6491

6492
			/*
6493
			 * build_sched_domains() -> init_sched_groups_capacity()
6494 6495 6496
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
6497 6498
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
6499
			 *
6500
			 * This avoids capacity from being 0 and
6501 6502 6503
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
6504
				capacity += capacity_of(cpu);
6505 6506
				continue;
			}
6507

6508 6509
			sgc = rq->sd->groups->sgc;
			capacity += sgc->capacity;
6510
		}
P
Peter Zijlstra 已提交
6511 6512 6513 6514 6515 6516 6517 6518
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
6519
			capacity += group->sgc->capacity;
P
Peter Zijlstra 已提交
6520 6521 6522
			group = group->next;
		} while (group != child->groups);
	}
6523

6524
	sdg->sgc->capacity = capacity;
6525 6526
}

6527
/*
6528 6529 6530
 * Check whether the capacity of the rq has been noticeably reduced by side
 * activity. The imbalance_pct is used for the threshold.
 * Return true is the capacity is reduced
6531 6532
 */
static inline int
6533
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6534
{
6535 6536
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
6537 6538
}

6539 6540 6541 6542 6543 6544 6545 6546 6547 6548 6549 6550 6551 6552 6553 6554
/*
 * 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
6555 6556
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
6557 6558
 *
 * When this is so detected; this group becomes a candidate for busiest; see
6559
 * update_sd_pick_busiest(). And calculate_imbalance() and
6560
 * find_busiest_group() avoid some of the usual balance conditions to allow it
6561 6562 6563 6564 6565 6566 6567
 * 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.
 */

6568
static inline int sg_imbalanced(struct sched_group *group)
6569
{
6570
	return group->sgc->imbalance;
6571 6572
}

6573
/*
6574 6575 6576
 * group_has_capacity returns true if the group has spare capacity that could
 * be used by some tasks.
 * We consider that a group has spare capacity if the  * number of task is
6577 6578
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
6579 6580 6581 6582 6583
 * For the latter, we use a threshold to stabilize the state, to take into
 * account the variance of the tasks' load and to return true if the available
 * capacity in meaningful for the load balancer.
 * As an example, an available capacity of 1% can appear but it doesn't make
 * any benefit for the load balance.
6584
 */
6585 6586
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6587
{
6588 6589
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
6590

6591
	if ((sgs->group_capacity * 100) >
6592
			(sgs->group_util * env->sd->imbalance_pct))
6593
		return true;
6594

6595 6596 6597 6598 6599 6600 6601 6602 6603 6604 6605 6606 6607 6608 6609 6610
	return false;
}

/*
 *  group_is_overloaded returns true if the group has more tasks than it can
 *  handle.
 *  group_is_overloaded is not equals to !group_has_capacity because a group
 *  with the exact right number of tasks, has no more spare capacity but is not
 *  overloaded so both group_has_capacity and group_is_overloaded return
 *  false.
 */
static inline bool
group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
{
	if (sgs->sum_nr_running <= sgs->group_weight)
		return false;
6611

6612
	if ((sgs->group_capacity * 100) <
6613
			(sgs->group_util * env->sd->imbalance_pct))
6614
		return true;
6615

6616
	return false;
6617 6618
}

6619 6620 6621
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
6622
{
6623
	if (sgs->group_no_capacity)
6624 6625 6626 6627 6628 6629 6630 6631
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

6632 6633
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6634
 * @env: The load balancing environment.
6635 6636 6637 6638
 * @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.
6639
 * @overload: Indicate more than one runnable task for any CPU.
6640
 */
6641 6642
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
6643 6644
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
6645
{
6646
	unsigned long load;
6647
	int i, nr_running;
6648

6649 6650
	memset(sgs, 0, sizeof(*sgs));

6651
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6652 6653 6654
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
6655
		if (local_group)
6656
			load = target_load(i, load_idx);
6657
		else
6658 6659 6660
			load = source_load(i, load_idx);

		sgs->group_load += load;
6661
		sgs->group_util += cpu_util(i);
6662
		sgs->sum_nr_running += rq->cfs.h_nr_running;
6663

6664 6665
		nr_running = rq->nr_running;
		if (nr_running > 1)
6666 6667
			*overload = true;

6668 6669 6670 6671
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
6672
		sgs->sum_weighted_load += weighted_cpuload(i);
6673 6674 6675 6676
		/*
		 * No need to call idle_cpu() if nr_running is not 0
		 */
		if (!nr_running && idle_cpu(i))
6677
			sgs->idle_cpus++;
6678 6679
	}

6680 6681
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
6682
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6683

6684
	if (sgs->sum_nr_running)
6685
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6686

6687
	sgs->group_weight = group->group_weight;
6688

6689
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
6690
	sgs->group_type = group_classify(group, sgs);
6691 6692
}

6693 6694
/**
 * update_sd_pick_busiest - return 1 on busiest group
6695
 * @env: The load balancing environment.
6696 6697
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
6698
 * @sgs: sched_group statistics
6699 6700 6701
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
6702 6703 6704
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
6705
 */
6706
static bool update_sd_pick_busiest(struct lb_env *env,
6707 6708
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
6709
				   struct sg_lb_stats *sgs)
6710
{
6711
	struct sg_lb_stats *busiest = &sds->busiest_stat;
6712

6713
	if (sgs->group_type > busiest->group_type)
6714 6715
		return true;

6716 6717 6718 6719 6720 6721 6722 6723
	if (sgs->group_type < busiest->group_type)
		return false;

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

	/* This is the busiest node in its class. */
	if (!(env->sd->flags & SD_ASYM_PACKING))
6724 6725
		return true;

6726 6727 6728
	/* No ASYM_PACKING if target cpu is already busy */
	if (env->idle == CPU_NOT_IDLE)
		return true;
6729 6730 6731 6732 6733
	/*
	 * 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.
	 */
6734
	if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6735 6736 6737
		if (!sds->busiest)
			return true;

6738 6739
		/* Prefer to move from highest possible cpu's work */
		if (group_first_cpu(sds->busiest) < group_first_cpu(sg))
6740 6741 6742 6743 6744 6745
			return true;
	}

	return false;
}

6746 6747 6748 6749 6750 6751 6752 6753 6754 6755 6756 6757 6758 6759 6760 6761 6762 6763 6764 6765 6766 6767 6768 6769 6770 6771 6772 6773 6774 6775
#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 */

6776
/**
6777
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6778
 * @env: The load balancing environment.
6779 6780
 * @sds: variable to hold the statistics for this sched_domain.
 */
6781
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6782
{
6783 6784
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
6785
	struct sg_lb_stats tmp_sgs;
6786
	int load_idx, prefer_sibling = 0;
6787
	bool overload = false;
6788 6789 6790 6791

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

6792
	load_idx = get_sd_load_idx(env->sd, env->idle);
6793 6794

	do {
J
Joonsoo Kim 已提交
6795
		struct sg_lb_stats *sgs = &tmp_sgs;
6796 6797
		int local_group;

6798
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
6799 6800 6801
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
6802 6803

			if (env->idle != CPU_NEWLY_IDLE ||
6804 6805
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
6806
		}
6807

6808 6809
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
6810

6811 6812 6813
		if (local_group)
			goto next_group;

6814 6815
		/*
		 * In case the child domain prefers tasks go to siblings
6816
		 * first, lower the sg capacity so that we'll try
6817 6818
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
6819 6820 6821 6822
		 * these excess tasks. The extra check prevents the case where
		 * you always pull from the heaviest group when it is already
		 * under-utilized (possible with a large weight task outweighs
		 * the tasks on the system).
6823
		 */
6824
		if (prefer_sibling && sds->local &&
6825 6826 6827
		    group_has_capacity(env, &sds->local_stat) &&
		    (sgs->sum_nr_running > 1)) {
			sgs->group_no_capacity = 1;
6828
			sgs->group_type = group_classify(sg, sgs);
6829
		}
6830

6831
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6832
			sds->busiest = sg;
J
Joonsoo Kim 已提交
6833
			sds->busiest_stat = *sgs;
6834 6835
		}

6836 6837 6838
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
6839
		sds->total_capacity += sgs->group_capacity;
6840

6841
		sg = sg->next;
6842
	} while (sg != env->sd->groups);
6843 6844 6845

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6846 6847 6848 6849 6850 6851 6852

	if (!env->sd->parent) {
		/* update overload indicator if we are at root domain */
		if (env->dst_rq->rd->overload != overload)
			env->dst_rq->rd->overload = overload;
	}

6853 6854 6855 6856 6857 6858 6859 6860 6861 6862 6863 6864 6865 6866 6867 6868 6869 6870 6871
}

/**
 * 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.
 *
6872
 * Return: 1 when packing is required and a task should be moved to
6873 6874
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
6875
 * @env: The load balancing environment.
6876 6877
 * @sds: Statistics of the sched_domain which is to be packed
 */
6878
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6879 6880 6881
{
	int busiest_cpu;

6882
	if (!(env->sd->flags & SD_ASYM_PACKING))
6883 6884
		return 0;

6885 6886 6887
	if (env->idle == CPU_NOT_IDLE)
		return 0;

6888 6889 6890 6891
	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
6892
	if (env->dst_cpu > busiest_cpu)
6893 6894
		return 0;

6895
	env->imbalance = DIV_ROUND_CLOSEST(
6896
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6897
		SCHED_CAPACITY_SCALE);
6898

6899
	return 1;
6900 6901 6902 6903 6904 6905
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
6906
 * @env: The load balancing environment.
6907 6908
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
6909 6910
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6911
{
6912
	unsigned long tmp, capa_now = 0, capa_move = 0;
6913
	unsigned int imbn = 2;
6914
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
6915
	struct sg_lb_stats *local, *busiest;
6916

J
Joonsoo Kim 已提交
6917 6918
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6919

J
Joonsoo Kim 已提交
6920 6921 6922 6923
	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;
6924

J
Joonsoo Kim 已提交
6925
	scaled_busy_load_per_task =
6926
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6927
		busiest->group_capacity;
J
Joonsoo Kim 已提交
6928

6929 6930
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
6931
		env->imbalance = busiest->load_per_task;
6932 6933 6934 6935 6936
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
6937
	 * however we may be able to increase total CPU capacity used by
6938 6939 6940
	 * moving them.
	 */

6941
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
6942
			min(busiest->load_per_task, busiest->avg_load);
6943
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
6944
			min(local->load_per_task, local->avg_load);
6945
	capa_now /= SCHED_CAPACITY_SCALE;
6946 6947

	/* Amount of load we'd subtract */
6948
	if (busiest->avg_load > scaled_busy_load_per_task) {
6949
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
6950
			    min(busiest->load_per_task,
6951
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
6952
	}
6953 6954

	/* Amount of load we'd add */
6955
	if (busiest->avg_load * busiest->group_capacity <
6956
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6957 6958
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
6959
	} else {
6960
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6961
		      local->group_capacity;
J
Joonsoo Kim 已提交
6962
	}
6963
	capa_move += local->group_capacity *
6964
		    min(local->load_per_task, local->avg_load + tmp);
6965
	capa_move /= SCHED_CAPACITY_SCALE;
6966 6967

	/* Move if we gain throughput */
6968
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
6969
		env->imbalance = busiest->load_per_task;
6970 6971 6972 6973 6974
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
6975
 * @env: load balance environment
6976 6977
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
6978
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6979
{
6980
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
6981 6982 6983 6984
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6985

6986
	if (busiest->group_type == group_imbalanced) {
6987 6988 6989 6990
		/*
		 * 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
6991 6992
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
6993 6994
	}

6995 6996 6997
	/*
	 * 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
6998
	 * its cpu_capacity, while calculating max_load..)
6999
	 */
7000 7001
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
7002 7003
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
7004 7005
	}

7006 7007 7008 7009 7010
	/*
	 * If there aren't any idle cpus, avoid creating some.
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
7011 7012 7013 7014 7015 7016
		load_above_capacity = busiest->sum_nr_running *
					SCHED_LOAD_SCALE;
		if (load_above_capacity > busiest->group_capacity)
			load_above_capacity -= busiest->group_capacity;
		else
			load_above_capacity = ~0UL;
7017 7018 7019 7020 7021 7022 7023 7024 7025 7026
	}

	/*
	 * 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.
	 */
7027
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
7028 7029

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
7030
	env->imbalance = min(
7031 7032
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
7033
	) / SCHED_CAPACITY_SCALE;
7034 7035 7036

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
7037
	 * there is no guarantee that any tasks will be moved so we'll have
7038 7039 7040
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
7041
	if (env->imbalance < busiest->load_per_task)
7042
		return fix_small_imbalance(env, sds);
7043
}
7044

7045 7046 7047 7048 7049 7050 7051 7052 7053 7054 7055 7056
/******* 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.
 *
7057
 * @env: The load balancing environment.
7058
 *
7059
 * Return:	- The busiest group if imbalance exists.
7060 7061 7062 7063
 *		- 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
7064
static struct sched_group *find_busiest_group(struct lb_env *env)
7065
{
J
Joonsoo Kim 已提交
7066
	struct sg_lb_stats *local, *busiest;
7067 7068
	struct sd_lb_stats sds;

7069
	init_sd_lb_stats(&sds);
7070 7071 7072 7073 7074

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
7075
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
7076 7077
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
7078

7079
	/* ASYM feature bypasses nice load balance check */
7080
	if (check_asym_packing(env, &sds))
7081 7082
		return sds.busiest;

7083
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
7084
	if (!sds.busiest || busiest->sum_nr_running == 0)
7085 7086
		goto out_balanced;

7087 7088
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
7089

P
Peter Zijlstra 已提交
7090 7091
	/*
	 * If the busiest group is imbalanced the below checks don't
7092
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
7093 7094
	 * isn't true due to cpus_allowed constraints and the like.
	 */
7095
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
7096 7097
		goto force_balance;

7098
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7099 7100
	if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
	    busiest->group_no_capacity)
7101 7102
		goto force_balance;

7103
	/*
7104
	 * If the local group is busier than the selected busiest group
7105 7106
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
7107
	if (local->avg_load >= busiest->avg_load)
7108 7109
		goto out_balanced;

7110 7111 7112 7113
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
7114
	if (local->avg_load >= sds.avg_load)
7115 7116
		goto out_balanced;

7117
	if (env->idle == CPU_IDLE) {
7118
		/*
7119 7120 7121 7122 7123
		 * This cpu is idle. If the busiest group is not overloaded
		 * and there is no imbalance between this and busiest group
		 * wrt idle cpus, it is balanced. The imbalance becomes
		 * significant if the diff is greater than 1 otherwise we
		 * might end up to just move the imbalance on another group
7124
		 */
7125 7126
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
7127
			goto out_balanced;
7128 7129 7130 7131 7132
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
7133 7134
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
7135
			goto out_balanced;
7136
	}
7137

7138
force_balance:
7139
	/* Looks like there is an imbalance. Compute it */
7140
	calculate_imbalance(env, &sds);
7141 7142 7143
	return sds.busiest;

out_balanced:
7144
	env->imbalance = 0;
7145 7146 7147 7148 7149 7150
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
7151
static struct rq *find_busiest_queue(struct lb_env *env,
7152
				     struct sched_group *group)
7153 7154
{
	struct rq *busiest = NULL, *rq;
7155
	unsigned long busiest_load = 0, busiest_capacity = 1;
7156 7157
	int i;

7158
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7159
		unsigned long capacity, wl;
7160 7161 7162 7163
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
7164

7165 7166 7167 7168 7169 7170 7171 7172 7173 7174 7175 7176 7177 7178 7179 7180 7181 7182 7183 7184 7185 7186
		/*
		 * 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;

7187
		capacity = capacity_of(i);
7188

7189
		wl = weighted_cpuload(i);
7190

7191 7192
		/*
		 * When comparing with imbalance, use weighted_cpuload()
7193
		 * which is not scaled with the cpu capacity.
7194
		 */
7195 7196 7197

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
7198 7199
			continue;

7200 7201
		/*
		 * For the load comparisons with the other cpu's, consider
7202 7203 7204
		 * the weighted_cpuload() scaled with the cpu capacity, so
		 * that the load can be moved away from the cpu that is
		 * potentially running at a lower capacity.
7205
		 *
7206
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
7207
		 * multiplication to rid ourselves of the division works out
7208 7209
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
7210
		 */
7211
		if (wl * busiest_capacity > busiest_load * capacity) {
7212
			busiest_load = wl;
7213
			busiest_capacity = capacity;
7214 7215 7216 7217 7218 7219 7220 7221 7222 7223 7224 7225 7226 7227
			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. */
7228
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
7229

7230
static int need_active_balance(struct lb_env *env)
7231
{
7232 7233 7234
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
7235 7236 7237 7238 7239 7240

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
7241
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7242
			return 1;
7243 7244
	}

7245 7246 7247 7248 7249 7250 7251 7252 7253 7254 7255 7256 7257
	/*
	 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
	 * It's worth migrating the task if the src_cpu's capacity is reduced
	 * because of other sched_class or IRQs if more capacity stays
	 * available on dst_cpu.
	 */
	if ((env->idle != CPU_NOT_IDLE) &&
	    (env->src_rq->cfs.h_nr_running == 1)) {
		if ((check_cpu_capacity(env->src_rq, sd)) &&
		    (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
			return 1;
	}

7258 7259 7260
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

7261 7262
static int active_load_balance_cpu_stop(void *data);

7263 7264 7265 7266 7267 7268 7269 7270 7271 7272 7273 7274 7275 7276 7277 7278 7279 7280 7281 7282 7283 7284 7285 7286 7287 7288 7289 7290 7291 7292 7293
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.
	 */
7294
	return balance_cpu == env->dst_cpu;
7295 7296
}

7297 7298 7299 7300 7301 7302
/*
 * 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,
7303
			int *continue_balancing)
7304
{
7305
	int ld_moved, cur_ld_moved, active_balance = 0;
7306
	struct sched_domain *sd_parent = sd->parent;
7307 7308 7309
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
7310
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7311

7312 7313
	struct lb_env env = {
		.sd		= sd,
7314 7315
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
7316
		.dst_grpmask    = sched_group_cpus(sd->groups),
7317
		.idle		= idle,
7318
		.loop_break	= sched_nr_migrate_break,
7319
		.cpus		= cpus,
7320
		.fbq_type	= all,
7321
		.tasks		= LIST_HEAD_INIT(env.tasks),
7322 7323
	};

7324 7325 7326 7327
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
7328
	if (idle == CPU_NEWLY_IDLE)
7329 7330
		env.dst_grpmask = NULL;

7331 7332 7333 7334 7335
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
7336 7337
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
7338
		goto out_balanced;
7339
	}
7340

7341
	group = find_busiest_group(&env);
7342 7343 7344 7345 7346
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

7347
	busiest = find_busiest_queue(&env, group);
7348 7349 7350 7351 7352
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

7353
	BUG_ON(busiest == env.dst_rq);
7354

7355
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7356

7357 7358 7359
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

7360 7361 7362 7363 7364 7365 7366 7367
	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.
		 */
7368
		env.flags |= LBF_ALL_PINNED;
7369
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
7370

7371
more_balance:
7372
		raw_spin_lock_irqsave(&busiest->lock, flags);
7373 7374 7375 7376 7377

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
7378
		cur_ld_moved = detach_tasks(&env);
7379 7380

		/*
7381 7382 7383 7384 7385
		 * We've detached some tasks from busiest_rq. Every
		 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
		 * unlock busiest->lock, and we are able to be sure
		 * that nobody can manipulate the tasks in parallel.
		 * See task_rq_lock() family for the details.
7386
		 */
7387 7388 7389 7390 7391 7392 7393 7394

		raw_spin_unlock(&busiest->lock);

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

7395
		local_irq_restore(flags);
7396

7397 7398 7399 7400 7401
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

7402 7403 7404 7405 7406 7407 7408 7409 7410 7411 7412 7413 7414 7415 7416 7417 7418 7419 7420
		/*
		 * 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.
		 */
7421
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7422

7423 7424 7425
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

7426
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
7427
			env.dst_cpu	 = env.new_dst_cpu;
7428
			env.flags	&= ~LBF_DST_PINNED;
7429 7430
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
7431

7432 7433 7434 7435 7436 7437
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
7438

7439 7440 7441 7442
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
7443
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7444

7445
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7446 7447 7448
				*group_imbalance = 1;
		}

7449
		/* All tasks on this runqueue were pinned by CPU affinity */
7450
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
7451
			cpumask_clear_cpu(cpu_of(busiest), cpus);
7452 7453 7454
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
7455
				goto redo;
7456
			}
7457
			goto out_all_pinned;
7458 7459 7460 7461 7462
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
7463 7464 7465 7466 7467 7468 7469 7470
		/*
		 * 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++;
7471

7472
		if (need_active_balance(&env)) {
7473 7474
			raw_spin_lock_irqsave(&busiest->lock, flags);

7475 7476 7477
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
7478 7479
			 */
			if (!cpumask_test_cpu(this_cpu,
7480
					tsk_cpus_allowed(busiest->curr))) {
7481 7482
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
7483
				env.flags |= LBF_ALL_PINNED;
7484 7485 7486
				goto out_one_pinned;
			}

7487 7488 7489 7490 7491
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
7492 7493 7494 7495 7496 7497
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
7498

7499
			if (active_balance) {
7500 7501 7502
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
7503
			}
7504

7505
			/* We've kicked active balancing, force task migration. */
7506 7507 7508 7509 7510 7511 7512 7513 7514 7515 7516 7517 7518
			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
7519
		 * detach_tasks).
7520 7521 7522 7523 7524 7525 7526 7527
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
7528 7529 7530 7531 7532 7533 7534 7535 7536 7537 7538 7539 7540 7541 7542 7543 7544
	/*
	 * We reach balance although we may have faced some affinity
	 * constraints. Clear the imbalance flag if it was set.
	 */
	if (sd_parent) {
		int *group_imbalance = &sd_parent->groups->sgc->imbalance;

		if (*group_imbalance)
			*group_imbalance = 0;
	}

out_all_pinned:
	/*
	 * We reach balance because all tasks are pinned at this level so
	 * we can't migrate them. Let the imbalance flag set so parent level
	 * can try to migrate them.
	 */
7545 7546 7547 7548 7549 7550
	schedstat_inc(sd, lb_balanced[idle]);

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
7551
	if (((env.flags & LBF_ALL_PINNED) &&
7552
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
7553 7554 7555
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

7556
	ld_moved = 0;
7557 7558 7559 7560
out:
	return ld_moved;
}

7561 7562 7563 7564 7565 7566 7567 7568 7569 7570 7571 7572 7573 7574 7575 7576 7577 7578 7579 7580 7581 7582 7583 7584 7585 7586 7587
static inline unsigned long
get_sd_balance_interval(struct sched_domain *sd, int cpu_busy)
{
	unsigned long interval = sd->balance_interval;

	if (cpu_busy)
		interval *= sd->busy_factor;

	/* scale ms to jiffies */
	interval = msecs_to_jiffies(interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);

	return interval;
}

static inline void
update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance)
{
	unsigned long interval, next;

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

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

7588 7589 7590 7591
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
7592
static int idle_balance(struct rq *this_rq)
7593
{
7594 7595
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
7596 7597
	struct sched_domain *sd;
	int pulled_task = 0;
7598
	u64 curr_cost = 0;
7599

7600 7601 7602 7603 7604 7605
	/*
	 * 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);

7606 7607
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
7608 7609 7610 7611 7612 7613
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
			update_next_balance(sd, 0, &next_balance);
		rcu_read_unlock();

7614
		goto out;
7615
	}
7616

7617 7618
	raw_spin_unlock(&this_rq->lock);

7619
	update_blocked_averages(this_cpu);
7620
	rcu_read_lock();
7621
	for_each_domain(this_cpu, sd) {
7622
		int continue_balancing = 1;
7623
		u64 t0, domain_cost;
7624 7625 7626 7627

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

7628 7629
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
			update_next_balance(sd, 0, &next_balance);
7630
			break;
7631
		}
7632

7633
		if (sd->flags & SD_BALANCE_NEWIDLE) {
7634 7635
			t0 = sched_clock_cpu(this_cpu);

7636
			pulled_task = load_balance(this_cpu, this_rq,
7637 7638
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
7639 7640 7641 7642 7643 7644

			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;
7645
		}
7646

7647
		update_next_balance(sd, 0, &next_balance);
7648 7649 7650 7651 7652 7653

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
7654 7655
			break;
	}
7656
	rcu_read_unlock();
7657 7658 7659

	raw_spin_lock(&this_rq->lock);

7660 7661 7662
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

7663
	/*
7664 7665 7666
	 * While browsing the domains, we released the rq lock, a task could
	 * have been enqueued in the meantime. Since we're not going idle,
	 * pretend we pulled a task.
7667
	 */
7668
	if (this_rq->cfs.h_nr_running && !pulled_task)
7669
		pulled_task = 1;
7670

7671 7672 7673
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
7674
		this_rq->next_balance = next_balance;
7675

7676
	/* Is there a task of a high priority class? */
7677
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7678 7679
		pulled_task = -1;

7680
	if (pulled_task)
7681 7682
		this_rq->idle_stamp = 0;

7683
	return pulled_task;
7684 7685 7686
}

/*
7687 7688 7689 7690
 * 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.
7691
 */
7692
static int active_load_balance_cpu_stop(void *data)
7693
{
7694 7695
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
7696
	int target_cpu = busiest_rq->push_cpu;
7697
	struct rq *target_rq = cpu_rq(target_cpu);
7698
	struct sched_domain *sd;
7699
	struct task_struct *p = NULL;
7700 7701 7702 7703 7704 7705 7706

	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;
7707 7708 7709

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
7710
		goto out_unlock;
7711 7712 7713 7714 7715 7716 7717 7718 7719

	/*
	 * This condition is "impossible", if it occurs
	 * we need to fix it. Originally reported by
	 * Bjorn Helgaas on a 128-cpu setup.
	 */
	BUG_ON(busiest_rq == target_rq);

	/* Search for an sd spanning us and the target CPU. */
7720
	rcu_read_lock();
7721 7722 7723 7724 7725 7726 7727
	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)) {
7728 7729
		struct lb_env env = {
			.sd		= sd,
7730 7731 7732 7733
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
7734 7735 7736
			.idle		= CPU_IDLE,
		};

7737 7738
		schedstat_inc(sd, alb_count);

7739
		p = detach_one_task(&env);
7740
		if (p) {
7741
			schedstat_inc(sd, alb_pushed);
7742 7743 7744
			/* Active balancing done, reset the failure counter. */
			sd->nr_balance_failed = 0;
		} else {
7745
			schedstat_inc(sd, alb_failed);
7746
		}
7747
	}
7748
	rcu_read_unlock();
7749 7750
out_unlock:
	busiest_rq->active_balance = 0;
7751 7752 7753 7754 7755 7756 7757
	raw_spin_unlock(&busiest_rq->lock);

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

7758
	return 0;
7759 7760
}

7761 7762 7763 7764 7765
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

7766
#ifdef CONFIG_NO_HZ_COMMON
7767 7768 7769 7770 7771 7772
/*
 * 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.
 */
7773
static struct {
7774
	cpumask_var_t idle_cpus_mask;
7775
	atomic_t nr_cpus;
7776 7777
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
7778

7779
static inline int find_new_ilb(void)
7780
{
7781
	int ilb = cpumask_first(nohz.idle_cpus_mask);
7782

7783 7784 7785 7786
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
7787 7788
}

7789 7790 7791 7792 7793
/*
 * 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).
 */
7794
static void nohz_balancer_kick(void)
7795 7796 7797 7798 7799
{
	int ilb_cpu;

	nohz.next_balance++;

7800
	ilb_cpu = find_new_ilb();
7801

7802 7803
	if (ilb_cpu >= nr_cpu_ids)
		return;
7804

7805
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7806 7807 7808 7809 7810 7811 7812 7813
		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);
7814 7815 7816
	return;
}

7817
static inline void nohz_balance_exit_idle(int cpu)
7818 7819
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7820 7821 7822 7823 7824 7825 7826
		/*
		 * Completely isolated CPUs don't ever set, so we must test.
		 */
		if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) {
			cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
			atomic_dec(&nohz.nr_cpus);
		}
7827 7828 7829 7830
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

7831 7832 7833
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
7834
	int cpu = smp_processor_id();
7835 7836

	rcu_read_lock();
7837
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7838 7839 7840 7841 7842

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

7843
	atomic_inc(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7844
unlock:
7845 7846 7847 7848 7849 7850
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
7851
	int cpu = smp_processor_id();
7852 7853

	rcu_read_lock();
7854
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7855 7856 7857 7858 7859

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

7860
	atomic_dec(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7861
unlock:
7862 7863 7864
	rcu_read_unlock();
}

7865
/*
7866
 * This routine will record that the cpu is going idle with tick stopped.
7867
 * This info will be used in performing idle load balancing in the future.
7868
 */
7869
void nohz_balance_enter_idle(int cpu)
7870
{
7871 7872 7873 7874 7875 7876
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

7877 7878
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
7879

7880 7881 7882 7883 7884 7885
	/*
	 * If we're a completely isolated CPU, we don't play.
	 */
	if (on_null_domain(cpu_rq(cpu)))
		return;

7886 7887 7888
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7889
}
7890

7891
static int sched_ilb_notifier(struct notifier_block *nfb,
7892 7893 7894 7895
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
7896
		nohz_balance_exit_idle(smp_processor_id());
7897 7898 7899 7900 7901
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
7902 7903 7904 7905
#endif

static DEFINE_SPINLOCK(balancing);

7906 7907 7908 7909
/*
 * 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.
 */
7910
void update_max_interval(void)
7911 7912 7913 7914
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

7915 7916 7917 7918
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
7919
 * Balancing parameters are set up in init_sched_domains.
7920
 */
7921
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7922
{
7923
	int continue_balancing = 1;
7924
	int cpu = rq->cpu;
7925
	unsigned long interval;
7926
	struct sched_domain *sd;
7927 7928 7929
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
7930 7931
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
7932

7933
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
7934

7935
	rcu_read_lock();
7936
	for_each_domain(cpu, sd) {
7937 7938 7939 7940 7941 7942 7943 7944 7945 7946 7947 7948
		/*
		 * 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;

7949 7950 7951
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

7952 7953 7954 7955 7956 7957 7958 7959 7960 7961 7962
		/*
		 * 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;
		}

7963
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7964 7965 7966 7967 7968 7969 7970 7971

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

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
7972
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7973
				/*
7974
				 * The LBF_DST_PINNED logic could have changed
7975 7976
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
7977
				 */
7978
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7979 7980
			}
			sd->last_balance = jiffies;
7981
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7982 7983 7984 7985 7986 7987 7988 7989
		}
		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;
		}
7990 7991
	}
	if (need_decay) {
7992
		/*
7993 7994
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
7995
		 */
7996 7997
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
7998
	}
7999
	rcu_read_unlock();
8000 8001 8002 8003 8004 8005

	/*
	 * 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.
	 */
8006
	if (likely(update_next_balance)) {
8007
		rq->next_balance = next_balance;
8008 8009 8010 8011 8012 8013 8014 8015 8016 8017 8018 8019 8020 8021

#ifdef CONFIG_NO_HZ_COMMON
		/*
		 * If this CPU has been elected to perform the nohz idle
		 * balance. Other idle CPUs have already rebalanced with
		 * nohz_idle_balance() and nohz.next_balance has been
		 * updated accordingly. This CPU is now running the idle load
		 * balance for itself and we need to update the
		 * nohz.next_balance accordingly.
		 */
		if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance))
			nohz.next_balance = rq->next_balance;
#endif
	}
8022 8023
}

8024
#ifdef CONFIG_NO_HZ_COMMON
8025
/*
8026
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
8027 8028
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
8029
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
8030
{
8031
	int this_cpu = this_rq->cpu;
8032 8033
	struct rq *rq;
	int balance_cpu;
8034 8035 8036
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
8037

8038 8039 8040
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
8041 8042

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8043
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8044 8045 8046 8047 8048 8049 8050
			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.
		 */
8051
		if (need_resched())
8052 8053
			break;

V
Vincent Guittot 已提交
8054 8055
		rq = cpu_rq(balance_cpu);

8056 8057 8058 8059 8060 8061 8062
		/*
		 * If time for next balance is due,
		 * do the balance.
		 */
		if (time_after_eq(jiffies, rq->next_balance)) {
			raw_spin_lock_irq(&rq->lock);
			update_rq_clock(rq);
8063
			cpu_load_update_idle(rq);
8064 8065 8066
			raw_spin_unlock_irq(&rq->lock);
			rebalance_domains(rq, CPU_IDLE);
		}
8067

8068 8069 8070 8071
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
8072
	}
8073 8074 8075 8076 8077 8078 8079 8080

	/*
	 * next_balance will be updated only when there is a need.
	 * When the CPU is attached to null domain for ex, it will not be
	 * updated.
	 */
	if (likely(update_next_balance))
		nohz.next_balance = next_balance;
8081 8082
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8083 8084 8085
}

/*
8086
 * Current heuristic for kicking the idle load balancer in the presence
8087
 * of an idle cpu in the system.
8088
 *   - This rq has more than one task.
8089 8090 8091 8092
 *   - This rq has at least one CFS task and the capacity of the CPU is
 *     significantly reduced because of RT tasks or IRQs.
 *   - At parent of LLC scheduler domain level, this cpu's scheduler group has
 *     multiple busy cpu.
8093 8094
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
8095
 */
8096
static inline bool nohz_kick_needed(struct rq *rq)
8097 8098
{
	unsigned long now = jiffies;
8099
	struct sched_domain *sd;
8100
	struct sched_group_capacity *sgc;
8101
	int nr_busy, cpu = rq->cpu;
8102
	bool kick = false;
8103

8104
	if (unlikely(rq->idle_balance))
8105
		return false;
8106

8107 8108 8109 8110
       /*
	* 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.
	*/
8111
	set_cpu_sd_state_busy();
8112
	nohz_balance_exit_idle(cpu);
8113 8114 8115 8116 8117 8118

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
8119
		return false;
8120 8121

	if (time_before(now, nohz.next_balance))
8122
		return false;
8123

8124
	if (rq->nr_running >= 2)
8125
		return true;
8126

8127
	rcu_read_lock();
8128 8129
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
	if (sd) {
8130 8131
		sgc = sd->groups->sgc;
		nr_busy = atomic_read(&sgc->nr_busy_cpus);
8132

8133 8134 8135 8136 8137
		if (nr_busy > 1) {
			kick = true;
			goto unlock;
		}

8138
	}
8139

8140 8141 8142 8143 8144 8145 8146 8147
	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
			kick = true;
			goto unlock;
		}
	}
8148

8149
	sd = rcu_dereference(per_cpu(sd_asym, cpu));
8150
	if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
8151 8152 8153 8154
				  sched_domain_span(sd)) < cpu)) {
		kick = true;
		goto unlock;
	}
8155

8156
unlock:
8157
	rcu_read_unlock();
8158
	return kick;
8159 8160
}
#else
8161
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8162 8163 8164 8165 8166 8167
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
8168 8169
static void run_rebalance_domains(struct softirq_action *h)
{
8170
	struct rq *this_rq = this_rq();
8171
	enum cpu_idle_type idle = this_rq->idle_balance ?
8172 8173 8174
						CPU_IDLE : CPU_NOT_IDLE;

	/*
8175
	 * If this cpu has a pending nohz_balance_kick, then do the
8176
	 * balancing on behalf of the other idle cpus whose ticks are
8177 8178 8179 8180
	 * stopped. Do nohz_idle_balance *before* rebalance_domains to
	 * give the idle cpus a chance to load balance. Else we may
	 * load balance only within the local sched_domain hierarchy
	 * and abort nohz_idle_balance altogether if we pull some load.
8181
	 */
8182
	nohz_idle_balance(this_rq, idle);
8183
	rebalance_domains(this_rq, idle);
8184 8185 8186 8187 8188
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
8189
void trigger_load_balance(struct rq *rq)
8190 8191
{
	/* Don't need to rebalance while attached to NULL domain */
8192 8193 8194 8195
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
8196
		raise_softirq(SCHED_SOFTIRQ);
8197
#ifdef CONFIG_NO_HZ_COMMON
8198
	if (nohz_kick_needed(rq))
8199
		nohz_balancer_kick();
8200
#endif
8201 8202
}

8203 8204 8205
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
8206 8207

	update_runtime_enabled(rq);
8208 8209 8210 8211 8212
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
8213 8214 8215

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
8216 8217
}

8218
#endif /* CONFIG_SMP */
8219

8220 8221 8222
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
8223
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8224 8225 8226 8227 8228 8229
{
	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
8230
		entity_tick(cfs_rq, se, queued);
8231
	}
8232

8233
	if (static_branch_unlikely(&sched_numa_balancing))
8234
		task_tick_numa(rq, curr);
8235 8236 8237
}

/*
P
Peter Zijlstra 已提交
8238 8239 8240
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
8241
 */
P
Peter Zijlstra 已提交
8242
static void task_fork_fair(struct task_struct *p)
8243
{
8244 8245
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
8246
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
8247 8248 8249
	struct rq *rq = this_rq();
	unsigned long flags;

8250
	raw_spin_lock_irqsave(&rq->lock, flags);
8251

8252 8253
	update_rq_clock(rq);

8254 8255 8256
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

8257 8258 8259 8260 8261 8262 8263 8264 8265
	/*
	 * 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();
8266

8267
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
8268

8269 8270
	if (curr)
		se->vruntime = curr->vruntime;
8271
	place_entity(cfs_rq, se, 1);
8272

P
Peter Zijlstra 已提交
8273
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
8274
		/*
8275 8276 8277
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
8278
		swap(curr->vruntime, se->vruntime);
8279
		resched_curr(rq);
8280
	}
8281

8282 8283
	se->vruntime -= cfs_rq->min_vruntime;

8284
	raw_spin_unlock_irqrestore(&rq->lock, flags);
8285 8286
}

8287 8288 8289 8290
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
8291 8292
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8293
{
8294
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
8295 8296
		return;

8297 8298 8299 8300 8301
	/*
	 * 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
8302
	if (rq->curr == p) {
8303
		if (p->prio > oldprio)
8304
			resched_curr(rq);
8305
	} else
8306
		check_preempt_curr(rq, p, 0);
8307 8308
}

8309
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
8310 8311 8312 8313
{
	struct sched_entity *se = &p->se;

	/*
8314 8315 8316 8317 8318 8319 8320 8321 8322 8323
	 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases,
	 * the dequeue_entity(.flags=0) will already have normalized the
	 * vruntime.
	 */
	if (p->on_rq)
		return true;

	/*
	 * When !on_rq, vruntime of the task has usually NOT been normalized.
	 * But there are some cases where it has already been normalized:
P
Peter Zijlstra 已提交
8324
	 *
8325 8326 8327 8328
	 * - A forked child which is waiting for being woken up by
	 *   wake_up_new_task().
	 * - A task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
P
Peter Zijlstra 已提交
8329
	 */
8330 8331 8332 8333 8334 8335 8336 8337 8338 8339 8340 8341
	if (!se->sum_exec_runtime || p->state == TASK_WAKING)
		return true;

	return false;
}

static void detach_task_cfs_rq(struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	if (!vruntime_normalized(p)) {
P
Peter Zijlstra 已提交
8342 8343 8344 8345 8346 8347 8348
		/*
		 * 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;
	}
8349

8350
	/* Catch up with the cfs_rq and remove our load when we leave */
8351
	detach_entity_load_avg(cfs_rq, se);
P
Peter Zijlstra 已提交
8352 8353
}

8354
static void attach_task_cfs_rq(struct task_struct *p)
8355
{
8356
	struct sched_entity *se = &p->se;
8357
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
8358 8359

#ifdef CONFIG_FAIR_GROUP_SCHED
8360 8361 8362 8363 8364 8365
	/*
	 * 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
8366

8367
	/* Synchronize task with its cfs_rq */
8368 8369 8370 8371 8372
	attach_entity_load_avg(cfs_rq, se);

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
8373

8374 8375 8376 8377 8378 8379 8380 8381
static void switched_from_fair(struct rq *rq, struct task_struct *p)
{
	detach_task_cfs_rq(p);
}

static void switched_to_fair(struct rq *rq, struct task_struct *p)
{
	attach_task_cfs_rq(p);
8382

8383
	if (task_on_rq_queued(p)) {
8384
		/*
8385 8386 8387
		 * 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.
8388
		 */
8389 8390 8391 8392
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
8393
	}
8394 8395
}

8396 8397 8398 8399 8400 8401 8402 8403 8404
/* 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;

8405 8406 8407 8408 8409 8410 8411
	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);
	}
8412 8413
}

8414 8415 8416 8417 8418 8419 8420
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
8421
#ifdef CONFIG_SMP
8422 8423
	atomic_long_set(&cfs_rq->removed_load_avg, 0);
	atomic_long_set(&cfs_rq->removed_util_avg, 0);
8424
#endif
8425 8426
}

P
Peter Zijlstra 已提交
8427
#ifdef CONFIG_FAIR_GROUP_SCHED
8428
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
8429
{
8430
	detach_task_cfs_rq(p);
8431
	set_task_rq(p, task_cpu(p));
8432 8433 8434 8435 8436

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
8437
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
8438
}
8439 8440 8441 8442 8443 8444 8445 8446 8447 8448

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]);
8449
		if (tg->se)
8450 8451 8452 8453 8454 8455 8456 8457 8458 8459 8460 8461 8462 8463 8464 8465 8466 8467 8468 8469 8470 8471 8472 8473 8474 8475 8476 8477 8478 8479 8480 8481 8482 8483 8484 8485 8486
			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]);
8487
		init_entity_runnable_average(se);
8488
		post_init_entity_util_avg(se);
8489 8490 8491 8492 8493 8494 8495 8496 8497 8498
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

8499
void unregister_fair_sched_group(struct task_group *tg)
8500 8501
{
	unsigned long flags;
8502 8503
	struct rq *rq;
	int cpu;
8504

8505 8506 8507
	for_each_possible_cpu(cpu) {
		if (tg->se[cpu])
			remove_entity_load_avg(tg->se[cpu]);
8508

8509 8510 8511 8512 8513 8514 8515 8516 8517 8518 8519 8520 8521
		/*
		 * Only empty task groups can be destroyed; so we can speculatively
		 * check on_list without danger of it being re-added.
		 */
		if (!tg->cfs_rq[cpu]->on_list)
			continue;

		rq = cpu_rq(cpu);

		raw_spin_lock_irqsave(&rq->lock, flags);
		list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
		raw_spin_unlock_irqrestore(&rq->lock, flags);
	}
8522 8523 8524 8525 8526 8527 8528 8529 8530 8531 8532 8533 8534 8535 8536 8537 8538 8539 8540
}

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
8541
	if (!parent) {
8542
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
8543 8544
		se->depth = 0;
	} else {
8545
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
8546 8547
		se->depth = parent->depth + 1;
	}
8548 8549

	se->my_q = cfs_rq;
8550 8551
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
8552 8553 8554 8555 8556 8557 8558 8559 8560 8561 8562 8563 8564 8565 8566 8567 8568 8569 8570 8571 8572 8573 8574 8575 8576 8577 8578 8579 8580 8581
	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);
8582 8583 8584

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
8585
		for_each_sched_entity(se)
8586 8587 8588 8589 8590 8591 8592 8593 8594 8595 8596 8597 8598 8599 8600 8601 8602
			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;
}

8603
void unregister_fair_sched_group(struct task_group *tg) { }
8604 8605 8606

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
8607

8608
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8609 8610 8611 8612 8613 8614 8615 8616 8617
{
	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)
8618
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8619 8620 8621 8622

	return rr_interval;
}

8623 8624 8625
/*
 * All the scheduling class methods:
 */
8626
const struct sched_class fair_sched_class = {
8627
	.next			= &idle_sched_class,
8628 8629 8630
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
8631
	.yield_to_task		= yield_to_task_fair,
8632

I
Ingo Molnar 已提交
8633
	.check_preempt_curr	= check_preempt_wakeup,
8634 8635 8636 8637

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

8638
#ifdef CONFIG_SMP
L
Li Zefan 已提交
8639
	.select_task_rq		= select_task_rq_fair,
8640
	.migrate_task_rq	= migrate_task_rq_fair,
8641

8642 8643
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
8644 8645

	.task_waking		= task_waking_fair,
8646
	.task_dead		= task_dead_fair,
8647
	.set_cpus_allowed	= set_cpus_allowed_common,
8648
#endif
8649

8650
	.set_curr_task          = set_curr_task_fair,
8651
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
8652
	.task_fork		= task_fork_fair,
8653 8654

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
8655
	.switched_from		= switched_from_fair,
8656
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
8657

8658 8659
	.get_rr_interval	= get_rr_interval_fair,

8660 8661
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
8662
#ifdef CONFIG_FAIR_GROUP_SCHED
8663
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
8664
#endif
8665 8666 8667
};

#ifdef CONFIG_SCHED_DEBUG
8668
void print_cfs_stats(struct seq_file *m, int cpu)
8669 8670 8671
{
	struct cfs_rq *cfs_rq;

8672
	rcu_read_lock();
8673
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8674
		print_cfs_rq(m, cpu, cfs_rq);
8675
	rcu_read_unlock();
8676
}
8677 8678 8679 8680 8681 8682 8683 8684 8685 8686 8687 8688 8689 8690 8691 8692 8693 8694 8695 8696 8697

#ifdef CONFIG_NUMA_BALANCING
void show_numa_stats(struct task_struct *p, struct seq_file *m)
{
	int node;
	unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;

	for_each_online_node(node) {
		if (p->numa_faults) {
			tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
			tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
		}
		if (p->numa_group) {
			gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
			gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
		}
		print_numa_stats(m, node, tsf, tpf, gsf, gpf);
	}
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_SCHED_DEBUG */
8698 8699 8700 8701 8702 8703

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

8704
#ifdef CONFIG_NO_HZ_COMMON
8705
	nohz.next_balance = jiffies;
8706
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8707
	cpu_notifier(sched_ilb_notifier, 0);
8708 8709 8710 8711
#endif
#endif /* SMP */

}