fair.c 226.2 KB
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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
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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
/* Group cfs_rq's load_avg is used for task_h_load and update_cfs_share */
static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
2879
{
2880
	struct sched_avg *sa = &cfs_rq->avg;
2881
	struct rq *rq = rq_of(cfs_rq);
2882
	int decayed, removed_load = 0, removed_util = 0;
2883
	int cpu = cpu_of(rq);
2884

2885
	if (atomic_long_read(&cfs_rq->removed_load_avg)) {
2886
		s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
2887 2888
		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);
2889
		removed_load = 1;
2890
	}
2891

2892 2893 2894
	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);
2895
		sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
2896
		removed_util = 1;
2897
	}
2898

2899
	decayed = __update_load_avg(now, cpu, sa,
2900
		scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2901

2902 2903 2904 2905
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
2906

2907 2908
	if (cpu == smp_processor_id() && &rq->cfs == cfs_rq &&
	    (decayed || removed_util)) {
2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927
		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),
2928
				    min(sa->util_avg, max), max);
2929
	}
2930

2931
	return decayed || removed_load;
2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951
}

/* 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);

	if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
		update_tg_load_avg(cfs_rq, 0);
2952 2953
}

2954 2955
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2956 2957 2958
	if (!sched_feat(ATTACH_AGE_LOAD))
		goto skip_aging;

2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972
	/*
	 * 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.
		 */
	}

2973
skip_aging:
2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992
	se->avg.last_update_time = cfs_rq->avg.last_update_time;
	cfs_rq->avg.load_avg += se->avg.load_avg;
	cfs_rq->avg.load_sum += se->avg.load_sum;
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
}

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

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

2993 2994 2995
/* 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)
2996
{
2997 2998
	struct sched_avg *sa = &se->avg;
	u64 now = cfs_rq_clock_task(cfs_rq);
2999
	int migrated, decayed;
3000

3001 3002
	migrated = !sa->last_update_time;
	if (!migrated) {
3003
		__update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
3004 3005
			se->on_rq * scale_load_down(se->load.weight),
			cfs_rq->curr == se, NULL);
3006
	}
3007

3008
	decayed = update_cfs_rq_load_avg(now, cfs_rq);
3009

3010 3011 3012
	cfs_rq->runnable_load_avg += sa->load_avg;
	cfs_rq->runnable_load_sum += sa->load_sum;

3013 3014
	if (migrated)
		attach_entity_load_avg(cfs_rq, se);
3015

3016 3017
	if (decayed || migrated)
		update_tg_load_avg(cfs_rq, 0);
3018 3019
}

3020 3021 3022 3023 3024 3025 3026 3027 3028
/* 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 =
3029
		max_t(s64,  cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
3030 3031
}

3032
#ifndef CONFIG_64BIT
3033 3034
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
3035
	u64 last_update_time_copy;
3036
	u64 last_update_time;
3037

3038 3039 3040 3041 3042
	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);
3043 3044 3045

	return last_update_time;
}
3046
#else
3047 3048 3049 3050
static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
	return cfs_rq->avg.last_update_time;
}
3051 3052
#endif

3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070
/*
 * 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);

3071
	__update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
3072 3073
	atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
	atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
3074
}
3075

3076 3077 3078 3079 3080 3081 3082 3083 3084 3085
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;
}

3086 3087
static int idle_balance(struct rq *this_rq);

3088 3089
#else /* CONFIG_SMP */

3090 3091 3092
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) {}
3093 3094
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
3095
static inline void remove_entity_load_avg(struct sched_entity *se) {}
3096

3097 3098 3099 3100 3101
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) {}

3102 3103 3104 3105 3106
static inline int idle_balance(struct rq *rq)
{
	return 0;
}

3107
#endif /* CONFIG_SMP */
3108

3109
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
3110 3111
{
#ifdef CONFIG_SCHEDSTATS
3112 3113 3114 3115 3116
	struct task_struct *tsk = NULL;

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

3117
	if (se->statistics.sleep_start) {
3118
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
3119 3120 3121 3122

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

3123 3124
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
3125

3126
		se->statistics.sleep_start = 0;
3127
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
3128

3129
		if (tsk) {
3130
			account_scheduler_latency(tsk, delta >> 10, 1);
3131 3132
			trace_sched_stat_sleep(tsk, delta);
		}
3133
	}
3134
	if (se->statistics.block_start) {
3135
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
3136 3137 3138 3139

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

3140 3141
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
3142

3143
		se->statistics.block_start = 0;
3144
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
3145

3146
		if (tsk) {
3147
			if (tsk->in_iowait) {
3148 3149
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
3150
				trace_sched_stat_iowait(tsk, delta);
3151 3152
			}

3153 3154
			trace_sched_stat_blocked(tsk, delta);

3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165
			/*
			 * 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
3166
		}
3167 3168 3169 3170
	}
#endif
}

P
Peter Zijlstra 已提交
3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183
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
}

3184 3185 3186
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
3187
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
3188

3189 3190 3191 3192 3193 3194
	/*
	 * 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
3195
	if (initial && sched_feat(START_DEBIT))
3196
		vruntime += sched_vslice(cfs_rq, se);
3197

3198
	/* sleeps up to a single latency don't count. */
3199
	if (!initial) {
3200
		unsigned long thresh = sysctl_sched_latency;
3201

3202 3203 3204 3205 3206 3207
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
3208

3209
		vruntime -= thresh;
3210 3211
	}

3212
	/* ensure we never gain time by being placed backwards. */
3213
	se->vruntime = max_vruntime(se->vruntime, vruntime);
3214 3215
}

3216 3217
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237
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
}

3238
static void
3239
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3240
{
3241 3242 3243
	bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING);
	bool curr = cfs_rq->curr == se;

3244
	/*
3245 3246
	 * If we're the current task, we must renormalise before calling
	 * update_curr().
3247
	 */
3248
	if (renorm && curr)
3249 3250
		se->vruntime += cfs_rq->min_vruntime;

3251 3252
	update_curr(cfs_rq);

3253
	/*
3254 3255
	 * Otherwise, renormalise after, such that we're placed at the current
	 * moment in time, instead of some random moment in the past.
3256
	 */
3257 3258 3259
	if (renorm && !curr)
		se->vruntime += cfs_rq->min_vruntime;

3260
	enqueue_entity_load_avg(cfs_rq, se);
3261 3262
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
3263

3264
	if (flags & ENQUEUE_WAKEUP) {
3265
		place_entity(cfs_rq, se, 0);
3266 3267
		if (schedstat_enabled())
			enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
3268
	}
3269

3270 3271 3272 3273 3274
	check_schedstat_required();
	if (schedstat_enabled()) {
		update_stats_enqueue(cfs_rq, se);
		check_spread(cfs_rq, se);
	}
3275
	if (!curr)
3276
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3277
	se->on_rq = 1;
3278

3279
	if (cfs_rq->nr_running == 1) {
3280
		list_add_leaf_cfs_rq(cfs_rq);
3281 3282
		check_enqueue_throttle(cfs_rq);
	}
3283 3284
}

3285
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3286
{
3287 3288
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3289
		if (cfs_rq->last != se)
3290
			break;
3291 3292

		cfs_rq->last = NULL;
3293 3294
	}
}
P
Peter Zijlstra 已提交
3295

3296 3297 3298 3299
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3300
		if (cfs_rq->next != se)
3301
			break;
3302 3303

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

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

		cfs_rq->skip = NULL;
3315 3316 3317
	}
}

P
Peter Zijlstra 已提交
3318 3319
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3320 3321 3322 3323 3324
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
3325 3326 3327

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
3328 3329
}

3330
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3331

3332
static void
3333
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3334
{
3335 3336 3337 3338
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
3339
	dequeue_entity_load_avg(cfs_rq, se);
3340

3341 3342
	if (schedstat_enabled())
		update_stats_dequeue(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
3343

P
Peter Zijlstra 已提交
3344
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3345

3346
	if (se != cfs_rq->curr)
3347
		__dequeue_entity(cfs_rq, se);
3348
	se->on_rq = 0;
3349
	account_entity_dequeue(cfs_rq, se);
3350 3351 3352 3353 3354 3355

	/*
	 * 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.
	 */
3356
	if (!(flags & DEQUEUE_SLEEP))
3357
		se->vruntime -= cfs_rq->min_vruntime;
3358

3359 3360 3361
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3362
	update_min_vruntime(cfs_rq);
3363
	update_cfs_shares(cfs_rq);
3364 3365 3366 3367 3368
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
3369
static void
I
Ingo Molnar 已提交
3370
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3371
{
3372
	unsigned long ideal_runtime, delta_exec;
3373 3374
	struct sched_entity *se;
	s64 delta;
3375

P
Peter Zijlstra 已提交
3376
	ideal_runtime = sched_slice(cfs_rq, curr);
3377
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3378
	if (delta_exec > ideal_runtime) {
3379
		resched_curr(rq_of(cfs_rq));
3380 3381 3382 3383 3384
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395
		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;

3396 3397
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
3398

3399 3400
	if (delta < 0)
		return;
3401

3402
	if (delta > ideal_runtime)
3403
		resched_curr(rq_of(cfs_rq));
3404 3405
}

3406
static void
3407
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3408
{
3409 3410 3411 3412 3413 3414 3415
	/* '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.
		 */
3416 3417
		if (schedstat_enabled())
			update_stats_wait_end(cfs_rq, se);
3418
		__dequeue_entity(cfs_rq, se);
3419
		update_load_avg(se, 1);
3420 3421
	}

3422
	update_stats_curr_start(cfs_rq, se);
3423
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
3424 3425 3426 3427 3428 3429
#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):
	 */
3430
	if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3431
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
3432 3433 3434
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
3435
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
3436 3437
}

3438 3439 3440
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

3441 3442 3443 3444 3445 3446 3447
/*
 * 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
 */
3448 3449
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3450
{
3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461
	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 */
3462

3463 3464 3465 3466 3467
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
3468 3469 3470 3471 3472 3473 3474 3475 3476 3477
		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;
		}

3478 3479 3480
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
3481

3482 3483 3484 3485 3486 3487
	/*
	 * 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;

3488 3489 3490 3491 3492 3493
	/*
	 * 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;

3494
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3495 3496

	return se;
3497 3498
}

3499
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3500

3501
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3502 3503 3504 3505 3506 3507
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
3508
		update_curr(cfs_rq);
3509

3510 3511 3512
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

3513 3514 3515 3516 3517 3518
	if (schedstat_enabled()) {
		check_spread(cfs_rq, prev);
		if (prev->on_rq)
			update_stats_wait_start(cfs_rq, prev);
	}

3519 3520 3521
	if (prev->on_rq) {
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
3522
		/* in !on_rq case, update occurred at dequeue */
3523
		update_load_avg(prev, 0);
3524
	}
3525
	cfs_rq->curr = NULL;
3526 3527
}

P
Peter Zijlstra 已提交
3528 3529
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3530 3531
{
	/*
3532
	 * Update run-time statistics of the 'current'.
3533
	 */
3534
	update_curr(cfs_rq);
3535

3536 3537 3538
	/*
	 * Ensure that runnable average is periodically updated.
	 */
3539
	update_load_avg(curr, 1);
3540
	update_cfs_shares(cfs_rq);
3541

P
Peter Zijlstra 已提交
3542 3543 3544 3545 3546
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
3547
	if (queued) {
3548
		resched_curr(rq_of(cfs_rq));
3549 3550
		return;
	}
P
Peter Zijlstra 已提交
3551 3552 3553 3554 3555 3556 3557 3558
	/*
	 * 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
3559
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
3560
		check_preempt_tick(cfs_rq, curr);
3561 3562
}

3563 3564 3565 3566 3567 3568

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

#ifdef CONFIG_CFS_BANDWIDTH
3569 3570

#ifdef HAVE_JUMP_LABEL
3571
static struct static_key __cfs_bandwidth_used;
3572 3573 3574

static inline bool cfs_bandwidth_used(void)
{
3575
	return static_key_false(&__cfs_bandwidth_used);
3576 3577
}

3578
void cfs_bandwidth_usage_inc(void)
3579
{
3580 3581 3582 3583 3584 3585
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
3586 3587 3588 3589 3590 3591 3592
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

3593 3594
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
3595 3596
#endif /* HAVE_JUMP_LABEL */

3597 3598 3599 3600 3601 3602 3603 3604
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
3605 3606 3607 3608 3609 3610

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

P
Paul Turner 已提交
3611 3612 3613 3614 3615 3616 3617
/*
 * 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
 */
3618
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629
{
	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);
}

3630 3631 3632 3633 3634
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

3635 3636 3637 3638 3639 3640
/* 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;

3641
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3642 3643
}

3644 3645
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3646 3647 3648
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
3649
	u64 amount = 0, min_amount, expires;
3650 3651 3652 3653 3654 3655 3656

	/* 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;
3657
	else {
P
Peter Zijlstra 已提交
3658
		start_cfs_bandwidth(cfs_b);
3659 3660 3661 3662 3663 3664

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
3665
	}
P
Paul Turner 已提交
3666
	expires = cfs_b->runtime_expires;
3667 3668 3669
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
3670 3671 3672 3673 3674 3675 3676
	/*
	 * 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;
3677 3678

	return cfs_rq->runtime_remaining > 0;
3679 3680
}

P
Paul Turner 已提交
3681 3682 3683 3684 3685
/*
 * 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)
3686
{
P
Paul Turner 已提交
3687 3688 3689
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
3690
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3691 3692
		return;

P
Paul Turner 已提交
3693 3694 3695 3696 3697 3698 3699 3700 3701
	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
3702 3703 3704
	 * 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
3705 3706
	 */

3707
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
3708 3709 3710 3711 3712 3713 3714 3715
		/* 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;
	}
}

3716
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
3717 3718
{
	/* dock delta_exec before expiring quota (as it could span periods) */
3719
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
3720 3721 3722
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
3723 3724
		return;

3725 3726 3727 3728 3729
	/*
	 * 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))
3730
		resched_curr(rq_of(cfs_rq));
3731 3732
}

3733
static __always_inline
3734
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3735
{
3736
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3737 3738 3739 3740 3741
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

3742 3743
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
3744
	return cfs_bandwidth_used() && cfs_rq->throttled;
3745 3746
}

3747 3748 3749
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
3750
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
3751 3752 3753 3754 3755 3756 3757 3758 3759 3760 3761 3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778
}

/*
 * 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) {
3779
		/* adjust cfs_rq_clock_task() */
3780
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3781
					     cfs_rq->throttled_clock_task;
3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792
	}
#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)];

3793 3794
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
3795
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
3796 3797 3798 3799 3800
	cfs_rq->throttle_count++;

	return 0;
}

3801
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3802 3803 3804 3805 3806
{
	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
3807
	bool empty;
3808 3809 3810

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

3811
	/* freeze hierarchy runnable averages while throttled */
3812 3813 3814
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831

	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)
3832
		sub_nr_running(rq, task_delta);
3833 3834

	cfs_rq->throttled = 1;
3835
	cfs_rq->throttled_clock = rq_clock(rq);
3836
	raw_spin_lock(&cfs_b->lock);
3837
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
3838

3839 3840 3841 3842 3843
	/*
	 * 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
3844 3845 3846 3847 3848 3849 3850 3851

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

3852 3853 3854
	raw_spin_unlock(&cfs_b->lock);
}

3855
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3856 3857 3858 3859 3860 3861 3862
{
	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;

3863
	se = cfs_rq->tg->se[cpu_of(rq)];
3864 3865

	cfs_rq->throttled = 0;
3866 3867 3868

	update_rq_clock(rq);

3869
	raw_spin_lock(&cfs_b->lock);
3870
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3871 3872 3873
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

3874 3875 3876
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894
	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)
3895
		add_nr_running(rq, task_delta);
3896 3897 3898

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
3899
		resched_curr(rq);
3900 3901 3902 3903 3904 3905
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
3906 3907
	u64 runtime;
	u64 starting_runtime = remaining;
3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937

	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();

3938
	return starting_runtime - remaining;
3939 3940
}

3941 3942 3943 3944 3945 3946 3947 3948
/*
 * 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)
{
3949
	u64 runtime, runtime_expires;
3950
	int throttled;
3951 3952 3953

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
3954
		goto out_deactivate;
3955

3956
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3957
	cfs_b->nr_periods += overrun;
3958

3959 3960 3961 3962 3963 3964
	/*
	 * 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
3965 3966 3967

	__refill_cfs_bandwidth_runtime(cfs_b);

3968 3969 3970
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
3971
		return 0;
3972 3973
	}

3974 3975 3976
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

3977 3978 3979
	runtime_expires = cfs_b->runtime_expires;

	/*
3980 3981 3982 3983 3984
	 * 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.
3985
	 */
3986 3987
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
3988 3989 3990 3991 3992 3993 3994
		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);
3995 3996

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
3997
	}
3998

3999 4000 4001 4002 4003 4004 4005
	/*
	 * 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;
4006

4007 4008 4009 4010
	return 0;

out_deactivate:
	return 1;
4011
}
4012

4013 4014 4015 4016 4017 4018 4019
/* 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;

4020 4021 4022 4023
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
4024
 * hrtimer base being cleared by hrtimer_start. In the case of
4025 4026
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051
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
4052 4053 4054
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083
}

/* 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)
{
4084 4085 4086
	if (!cfs_bandwidth_used())
		return;

4087
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
4088 4089 4090 4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102
		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 */
4103 4104 4105
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
4106
		return;
4107
	}
4108

4109
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
4110
		runtime = cfs_b->runtime;
4111

4112 4113 4114 4115 4116 4117 4118 4119 4120 4121
	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)
4122
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
4123 4124 4125
	raw_spin_unlock(&cfs_b->lock);
}

4126 4127 4128 4129 4130 4131 4132
/*
 * 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)
{
4133 4134 4135
	if (!cfs_bandwidth_used())
		return;

4136 4137 4138 4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150
	/* 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() */
4151
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
4152
{
4153
	if (!cfs_bandwidth_used())
4154
		return false;
4155

4156
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
4157
		return false;
4158 4159 4160 4161 4162 4163

	/*
	 * 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))
4164
		return true;
4165 4166

	throttle_cfs_rq(cfs_rq);
4167
	return true;
4168
}
4169 4170 4171 4172 4173

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
4174

4175 4176 4177 4178 4179 4180 4181 4182 4183 4184 4185 4186
	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;

4187
	raw_spin_lock(&cfs_b->lock);
4188
	for (;;) {
P
Peter Zijlstra 已提交
4189
		overrun = hrtimer_forward_now(timer, cfs_b->period);
4190 4191 4192 4193 4194
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
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Peter Zijlstra 已提交
4195 4196
	if (idle)
		cfs_b->period_active = 0;
4197
	raw_spin_unlock(&cfs_b->lock);
4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208 4209

	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
4210
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
4211 4212 4213 4214 4215 4216 4217 4218 4219 4220 4221
	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
4222
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
4223
{
P
Peter Zijlstra 已提交
4224
	lockdep_assert_held(&cfs_b->lock);
4225

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Peter Zijlstra 已提交
4226 4227 4228 4229 4230
	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);
	}
4231 4232 4233 4234
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
4235 4236 4237 4238
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

4239 4240 4241 4242
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255
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);
	}
}

4256
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4257 4258 4259 4260 4261 4262 4263 4264 4265 4266 4267
{
	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
		 */
4268
		cfs_rq->runtime_remaining = 1;
4269 4270 4271 4272 4273 4274
		/*
		 * 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;

4275 4276 4277 4278 4279 4280
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
}

#else /* CONFIG_CFS_BANDWIDTH */
4281 4282
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
4283
	return rq_clock_task(rq_of(cfs_rq));
4284 4285
}

4286
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4287
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4288
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4289
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4290 4291 4292 4293 4294

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
4295 4296 4297 4298 4299 4300 4301 4302 4303 4304 4305

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;
}
4306 4307 4308 4309 4310

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) {}
4311 4312
#endif

4313 4314 4315 4316 4317
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) {}
4318
static inline void update_runtime_enabled(struct rq *rq) {}
4319
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4320 4321 4322

#endif /* CONFIG_CFS_BANDWIDTH */

4323 4324 4325 4326
/**************************************************
 * CFS operations on tasks:
 */

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Peter Zijlstra 已提交
4327 4328 4329 4330 4331 4332 4333 4334
#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);

4335
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
4336 4337 4338 4339 4340 4341
		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)
4342
				resched_curr(rq);
P
Peter Zijlstra 已提交
4343 4344
			return;
		}
4345
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
4346 4347
	}
}
4348 4349 4350 4351 4352 4353 4354 4355 4356 4357

/*
 * 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;

4358
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4359 4360 4361 4362 4363
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
4364
#else /* !CONFIG_SCHED_HRTICK */
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Peter Zijlstra 已提交
4365 4366 4367 4368
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
4369 4370 4371 4372

static inline void hrtick_update(struct rq *rq)
{
}
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Peter Zijlstra 已提交
4373 4374
#endif

4375 4376 4377 4378 4379
/*
 * 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:
 */
4380
static void
4381
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4382 4383
{
	struct cfs_rq *cfs_rq;
4384
	struct sched_entity *se = &p->se;
4385 4386

	for_each_sched_entity(se) {
4387
		if (se->on_rq)
4388 4389
			break;
		cfs_rq = cfs_rq_of(se);
4390
		enqueue_entity(cfs_rq, se, flags);
4391 4392 4393 4394 4395 4396 4397 4398 4399

		/*
		 * 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;
4400
		cfs_rq->h_nr_running++;
4401

4402
		flags = ENQUEUE_WAKEUP;
4403
	}
P
Peter Zijlstra 已提交
4404

P
Peter Zijlstra 已提交
4405
	for_each_sched_entity(se) {
4406
		cfs_rq = cfs_rq_of(se);
4407
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
4408

4409 4410 4411
		if (cfs_rq_throttled(cfs_rq))
			break;

4412
		update_load_avg(se, 1);
4413
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4414 4415
	}

Y
Yuyang Du 已提交
4416
	if (!se)
4417
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
4418

4419
	hrtick_update(rq);
4420 4421
}

4422 4423
static void set_next_buddy(struct sched_entity *se);

4424 4425 4426 4427 4428
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
4429
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4430 4431
{
	struct cfs_rq *cfs_rq;
4432
	struct sched_entity *se = &p->se;
4433
	int task_sleep = flags & DEQUEUE_SLEEP;
4434 4435 4436

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
4437
		dequeue_entity(cfs_rq, se, flags);
4438 4439 4440 4441 4442 4443 4444 4445 4446

		/*
		 * 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;
4447
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4448

4449
		/* Don't dequeue parent if it has other entities besides us */
4450 4451 4452 4453 4454 4455 4456
		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));
4457 4458 4459

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
4460
			break;
4461
		}
4462
		flags |= DEQUEUE_SLEEP;
4463
	}
P
Peter Zijlstra 已提交
4464

P
Peter Zijlstra 已提交
4465
	for_each_sched_entity(se) {
4466
		cfs_rq = cfs_rq_of(se);
4467
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4468

4469 4470 4471
		if (cfs_rq_throttled(cfs_rq))
			break;

4472
		update_load_avg(se, 1);
4473
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4474 4475
	}

Y
Yuyang Du 已提交
4476
	if (!se)
4477
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
4478

4479
	hrtick_update(rq);
4480 4481
}

4482
#ifdef CONFIG_SMP
4483 4484 4485 4486 4487 4488

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

/*
4489
 * The exact cpuload calculated at every tick would be:
4490
 *
4491 4492 4493 4494 4495 4496 4497
 *   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
4498 4499 4500
 *
 * decay_load_missed() below does efficient calculation of
 *
4501 4502 4503 4504 4505 4506
 *   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())
4507
 *
4508
 * The calculation is approximated on a 128 point scale.
4509 4510
 */
#define DEGRADE_SHIFT		7
4511 4512 4513 4514 4515 4516 4517 4518 4519

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 }
};
4520 4521 4522 4523 4524 4525 4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549

/*
 * 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;
}

4550 4551 4552 4553 4554 4555 4556
/**
 * __update_cpu_load - update the rq->cpu_load[] statistics
 * @this_rq: The rq to update statistics for
 * @this_load: The current load
 * @pending_updates: The number of missed updates
 * @active: !0 for NOHZ_FULL
 *
4557
 * Update rq->cpu_load[] statistics. This function is usually called every
4558 4559 4560 4561 4562 4563 4564 4565 4566 4567 4568 4569 4570 4571 4572 4573 4574 4575 4576 4577 4578 4579 4580 4581 4582 4583 4584
 * scheduler tick (TICK_NSEC).
 *
 * This function computes a decaying average:
 *
 *   load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
 *
 * Because of NOHZ it might not get called on every tick which gives need for
 * the @pending_updates argument.
 *
 *   load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
 *             = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
 *             = A * (A * load[i]_n-2 + B) + B
 *             = A * (A * (A * load[i]_n-3 + B) + B) + B
 *             = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
 *             = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
 *             = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
 *             = (1 - 1/2^i)^n * (load[i]_0 - load) + load
 *
 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
 * any change in load would have resulted in the tick being turned back on.
 *
 * For regular NOHZ, this reduces to:
 *
 *   load[i]_n = (1 - 1/2^i)^n * load[i]_0
 *
 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
 * term. See the @active paramter.
4585 4586
 */
static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
4587
			      unsigned long pending_updates, int active)
4588
{
4589
	unsigned long tickless_load = active ? this_rq->cpu_load[0] : 0;
4590 4591 4592 4593 4594 4595 4596 4597 4598 4599 4600
	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 */

4601
		old_load = this_rq->cpu_load[i];
4602
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
4603 4604 4605 4606 4607 4608 4609 4610 4611
		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;
		}
4612 4613 4614 4615 4616 4617 4618 4619 4620 4621 4622 4623 4624 4625 4626
		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);
}

4627 4628 4629 4630 4631 4632
/* 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);
}

4633
#ifdef CONFIG_NO_HZ_COMMON
4634 4635 4636 4637 4638 4639 4640 4641 4642 4643 4644 4645 4646 4647 4648 4649 4650 4651 4652
static void __update_cpu_load_nohz(struct rq *this_rq,
				   unsigned long curr_jiffies,
				   unsigned long load,
				   int active)
{
	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.
		 */
		__update_cpu_load(this_rq, load, pending_updates, active);
	}
}

4653 4654 4655 4656 4657 4658 4659 4660 4661 4662 4663 4664 4665 4666 4667 4668 4669
/*
 * There is no sane way to deal with nohz on smp when using jiffies because the
 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading
 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}.
 *
 * Therefore we cannot use the delta approach from the regular tick since that
 * would seriously skew the load calculation. However we'll make do for those
 * updates happening while idle (nohz_idle_balance) or coming out of idle
 * (tick_nohz_idle_exit).
 *
 * This means we might still be one tick off for nohz periods.
 */

/*
 * Called from nohz_idle_balance() to update the load ratings before doing the
 * idle balance.
 */
4670
static void update_cpu_load_idle(struct rq *this_rq)
4671 4672 4673 4674
{
	/*
	 * bail if there's load or we're actually up-to-date.
	 */
4675
	if (weighted_cpuload(cpu_of(this_rq)))
4676 4677
		return;

4678
	__update_cpu_load_nohz(this_rq, READ_ONCE(jiffies), 0, 0);
4679 4680 4681 4682 4683
}

/*
 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
 */
4684
void update_cpu_load_nohz(int active)
4685 4686
{
	struct rq *this_rq = this_rq();
4687
	unsigned long curr_jiffies = READ_ONCE(jiffies);
4688
	unsigned long load = active ? weighted_cpuload(cpu_of(this_rq)) : 0;
4689 4690 4691 4692 4693

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

	raw_spin_lock(&this_rq->lock);
4694
	__update_cpu_load_nohz(this_rq, curr_jiffies, load, active);
4695 4696 4697 4698 4699 4700 4701 4702 4703
	raw_spin_unlock(&this_rq->lock);
}
#endif /* CONFIG_NO_HZ */

/*
 * Called from scheduler_tick()
 */
void update_cpu_load_active(struct rq *this_rq)
{
4704
	unsigned long load = weighted_cpuload(cpu_of(this_rq));
4705
	/*
4706
	 * See the mess around update_cpu_load_idle() / update_cpu_load_nohz().
4707 4708
	 */
	this_rq->last_load_update_tick = jiffies;
4709
	__update_cpu_load(this_rq, load, 1, 1);
4710 4711
}

4712 4713 4714 4715 4716 4717 4718 4719 4720 4721 4722 4723 4724 4725 4726 4727 4728 4729 4730 4731 4732 4733 4734 4735 4736 4737 4738 4739 4740 4741 4742 4743 4744
/*
 * 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);
}

4745
static unsigned long capacity_of(int cpu)
4746
{
4747
	return cpu_rq(cpu)->cpu_capacity;
4748 4749
}

4750 4751 4752 4753 4754
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

4755 4756 4757
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
4758
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4759
	unsigned long load_avg = weighted_cpuload(cpu);
4760 4761

	if (nr_running)
4762
		return load_avg / nr_running;
4763 4764 4765 4766

	return 0;
}

4767 4768 4769 4770 4771 4772 4773
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.
	 */
4774
	if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4775
		current->wakee_flips >>= 1;
4776 4777 4778 4779 4780 4781 4782 4783
		current->wakee_flip_decay_ts = jiffies;
	}

	if (current->last_wakee != p) {
		current->last_wakee = p;
		current->wakee_flips++;
	}
}
4784

4785
static void task_waking_fair(struct task_struct *p)
4786 4787 4788
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
4789 4790 4791 4792
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
4793

4794 4795 4796 4797 4798 4799 4800 4801
	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
4802

4803
	se->vruntime -= min_vruntime;
4804
	record_wakee(p);
4805 4806
}

4807
#ifdef CONFIG_FAIR_GROUP_SCHED
4808 4809 4810 4811 4812 4813
/*
 * 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.
4814 4815 4816 4817 4818 4819 4820 4821 4822 4823 4824 4825 4826 4827 4828 4829 4830 4831 4832 4833 4834 4835 4836 4837 4838 4839 4840 4841 4842 4843 4844 4845 4846 4847 4848 4849 4850 4851 4852 4853 4854 4855 4856
 *
 * 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.
4857
 */
P
Peter Zijlstra 已提交
4858
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4859
{
P
Peter Zijlstra 已提交
4860
	struct sched_entity *se = tg->se[cpu];
4861

4862
	if (!tg->parent)	/* the trivial, non-cgroup case */
4863 4864
		return wl;

P
Peter Zijlstra 已提交
4865
	for_each_sched_entity(se) {
4866
		long w, W;
P
Peter Zijlstra 已提交
4867

4868
		tg = se->my_q->tg;
4869

4870 4871 4872 4873
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
4874

4875 4876 4877
		/*
		 * w = rw_i + @wl
		 */
4878
		w = cfs_rq_load_avg(se->my_q) + wl;
4879

4880 4881 4882 4883
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
4884
			wl = (w * (long)tg->shares) / W;
4885 4886
		else
			wl = tg->shares;
4887

4888 4889 4890 4891 4892
		/*
		 * 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().
		 */
4893 4894
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
4895 4896 4897 4898

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
4899
		wl -= se->avg.load_avg;
4900 4901 4902 4903 4904 4905 4906 4907

		/*
		 * 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
4908 4909
		wg = 0;
	}
4910

P
Peter Zijlstra 已提交
4911
	return wl;
4912 4913
}
#else
P
Peter Zijlstra 已提交
4914

4915
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
P
Peter Zijlstra 已提交
4916
{
4917
	return wl;
4918
}
P
Peter Zijlstra 已提交
4919

4920 4921
#endif

M
Mike Galbraith 已提交
4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933
/*
 * 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.
 */
4934 4935
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
4936 4937
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
4938
	int factor = this_cpu_read(sd_llc_size);
4939

M
Mike Galbraith 已提交
4940 4941 4942 4943 4944
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
4945 4946
}

4947
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4948
{
4949
	s64 this_load, load;
4950
	s64 this_eff_load, prev_eff_load;
4951 4952
	int idx, this_cpu, prev_cpu;
	struct task_group *tg;
4953
	unsigned long weight;
4954
	int balanced;
4955

4956 4957 4958 4959 4960
	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);
4961

4962 4963 4964 4965 4966
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
4967 4968
	if (sync) {
		tg = task_group(current);
4969
		weight = current->se.avg.load_avg;
4970

4971
		this_load += effective_load(tg, this_cpu, -weight, -weight);
4972 4973
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
4974

4975
	tg = task_group(p);
4976
	weight = p->se.avg.load_avg;
4977

4978 4979
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4980 4981 4982
	 * 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.
4983 4984 4985 4986
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
4987 4988
	this_eff_load = 100;
	this_eff_load *= capacity_of(prev_cpu);
4989

4990 4991
	prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= capacity_of(this_cpu);
4992

4993
	if (this_load > 0) {
4994 4995 4996 4997
		this_eff_load *= this_load +
			effective_load(tg, this_cpu, weight, weight);

		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4998
	}
4999

5000
	balanced = this_eff_load <= prev_eff_load;
5001

5002
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
5003

5004 5005
	if (!balanced)
		return 0;
5006

5007 5008 5009 5010
	schedstat_inc(sd, ttwu_move_affine);
	schedstat_inc(p, se.statistics.nr_wakeups_affine);

	return 1;
5011 5012
}

5013 5014 5015 5016 5017
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
5018
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
5019
		  int this_cpu, int sd_flag)
5020
{
5021
	struct sched_group *idlest = NULL, *group = sd->groups;
5022
	unsigned long min_load = ULONG_MAX, this_load = 0;
5023
	int load_idx = sd->forkexec_idx;
5024
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
5025

5026 5027 5028
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

5029 5030 5031 5032
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
5033

5034 5035
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
5036
					tsk_cpus_allowed(p)))
5037 5038 5039 5040 5041 5042 5043 5044 5045 5046 5047 5048 5049 5050 5051 5052 5053 5054
			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;
		}

5055
		/* Adjust by relative CPU capacity of the group */
5056
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
5057 5058 5059 5060 5061 5062 5063 5064 5065 5066 5067 5068 5069 5070 5071 5072 5073 5074 5075 5076 5077

		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;
5078 5079 5080 5081
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
5082 5083 5084
	int i;

	/* Traverse only the allowed CPUs */
5085
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
5086 5087 5088 5089 5090 5091 5092 5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103 5104 5105 5106 5107
		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;
			}
5108
		} else if (shallowest_idle_cpu == -1) {
5109 5110 5111 5112 5113
			load = weighted_cpuload(i);
			if (load < min_load || (load == min_load && i == this_cpu)) {
				min_load = load;
				least_loaded_cpu = i;
			}
5114 5115 5116
		}
	}

5117
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
5118
}
5119

5120 5121 5122
/*
 * Try and locate an idle CPU in the sched_domain.
 */
5123
static int select_idle_sibling(struct task_struct *p, int target)
5124
{
5125
	struct sched_domain *sd;
5126
	struct sched_group *sg;
5127
	int i = task_cpu(p);
5128

5129 5130
	if (idle_cpu(target))
		return target;
5131 5132

	/*
5133
	 * If the prevous cpu is cache affine and idle, don't be stupid.
5134
	 */
5135 5136
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
5137 5138

	/*
5139 5140 5141 5142 5143 5144 5145 5146 5147 5148 5149 5150 5151
	 * 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.
5152
	 */
5153
	sd = rcu_dereference(per_cpu(sd_llc, target));
5154
	for_each_lower_domain(sd) {
5155 5156 5157 5158 5159 5160
		sg = sd->groups;
		do {
			if (!cpumask_intersects(sched_group_cpus(sg),
						tsk_cpus_allowed(p)))
				goto next;

5161
			/* Ensure the entire group is idle */
5162
			for_each_cpu(i, sched_group_cpus(sg)) {
5163
				if (i == target || !idle_cpu(i))
5164 5165
					goto next;
			}
5166

5167 5168 5169 5170
			/*
			 * It doesn't matter which cpu we pick, the
			 * whole group is idle.
			 */
5171 5172 5173 5174 5175 5176 5177 5178
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
5179 5180
	return target;
}
5181

5182
/*
5183
 * cpu_util returns the amount of capacity of a CPU that is used by CFS
5184
 * tasks. The unit of the return value must be the one of capacity so we can
5185 5186
 * compare the utilization with the capacity of the CPU that is available for
 * CFS task (ie cpu_capacity).
5187 5188 5189 5190 5191 5192 5193 5194 5195 5196 5197 5198 5199 5200 5201 5202 5203 5204 5205 5206
 *
 * 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).
5207
 */
5208
static int cpu_util(int cpu)
5209
{
5210
	unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
5211 5212
	unsigned long capacity = capacity_orig_of(cpu);

5213
	return (util >= capacity) ? capacity : util;
5214
}
5215

5216
/*
5217 5218 5219
 * 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.
5220
 *
5221 5222
 * 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.
5223
 *
5224
 * Returns the target cpu number.
5225 5226 5227
 *
 * preempt must be disabled.
 */
5228
static int
5229
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
5230
{
5231
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
5232
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
5233
	int new_cpu = prev_cpu;
5234
	int want_affine = 0;
5235
	int sync = wake_flags & WF_SYNC;
5236

5237
	if (sd_flag & SD_BALANCE_WAKE)
M
Mike Galbraith 已提交
5238
		want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
5239

5240
	rcu_read_lock();
5241
	for_each_domain(cpu, tmp) {
5242
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
5243
			break;
5244

5245
		/*
5246 5247
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
5248
		 */
5249 5250 5251
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
5252
			break;
5253
		}
5254

5255
		if (tmp->flags & sd_flag)
5256
			sd = tmp;
M
Mike Galbraith 已提交
5257 5258
		else if (!want_affine)
			break;
5259 5260
	}

M
Mike Galbraith 已提交
5261 5262 5263 5264
	if (affine_sd) {
		sd = NULL; /* Prefer wake_affine over balance flags */
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
			new_cpu = cpu;
5265
	}
5266

M
Mike Galbraith 已提交
5267 5268 5269 5270 5271
	if (!sd) {
		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
			new_cpu = select_idle_sibling(p, new_cpu);

	} else while (sd) {
5272
		struct sched_group *group;
5273
		int weight;
5274

5275
		if (!(sd->flags & sd_flag)) {
5276 5277 5278
			sd = sd->child;
			continue;
		}
5279

5280
		group = find_idlest_group(sd, p, cpu, sd_flag);
5281 5282 5283 5284
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
5285

5286
		new_cpu = find_idlest_cpu(group, p, cpu);
5287 5288 5289 5290
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
5291
		}
5292 5293 5294

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
5295
		weight = sd->span_weight;
5296 5297
		sd = NULL;
		for_each_domain(cpu, tmp) {
5298
			if (weight <= tmp->span_weight)
5299
				break;
5300
			if (tmp->flags & sd_flag)
5301 5302 5303
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
5304
	}
5305
	rcu_read_unlock();
5306

5307
	return new_cpu;
5308
}
5309 5310 5311 5312

/*
 * 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
5313
 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
5314
 */
5315
static void migrate_task_rq_fair(struct task_struct *p)
5316
{
5317
	/*
5318 5319 5320 5321 5322
	 * 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.
5323
	 */
5324 5325 5326 5327
	remove_entity_load_avg(&p->se);

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
5328 5329

	/* We have migrated, no longer consider this task hot */
5330
	p->se.exec_start = 0;
5331
}
5332 5333 5334 5335 5336

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
5337 5338
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
5339 5340
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5341 5342 5343 5344
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
5345 5346
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
5347 5348 5349 5350 5351 5352 5353 5354 5355
	 *
	 * 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.
5356
	 */
5357
	return calc_delta_fair(gran, se);
5358 5359
}

5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379 5380 5381
/*
 * 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
5382
	gran = wakeup_gran(curr, se);
5383 5384 5385 5386 5387 5388
	if (vdiff > gran)
		return 1;

	return 0;
}

5389 5390
static void set_last_buddy(struct sched_entity *se)
{
5391 5392 5393 5394 5395
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
5396 5397 5398 5399
}

static void set_next_buddy(struct sched_entity *se)
{
5400 5401 5402 5403 5404
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
5405 5406
}

5407 5408
static void set_skip_buddy(struct sched_entity *se)
{
5409 5410
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
5411 5412
}

5413 5414 5415
/*
 * Preempt the current task with a newly woken task if needed:
 */
5416
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5417 5418
{
	struct task_struct *curr = rq->curr;
5419
	struct sched_entity *se = &curr->se, *pse = &p->se;
5420
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5421
	int scale = cfs_rq->nr_running >= sched_nr_latency;
5422
	int next_buddy_marked = 0;
5423

I
Ingo Molnar 已提交
5424 5425 5426
	if (unlikely(se == pse))
		return;

5427
	/*
5428
	 * This is possible from callers such as attach_tasks(), in which we
5429 5430 5431 5432 5433 5434 5435
	 * 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;

5436
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
5437
		set_next_buddy(pse);
5438 5439
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
5440

5441 5442 5443
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
5444 5445 5446 5447 5448 5449
	 *
	 * 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.
5450 5451 5452 5453
	 */
	if (test_tsk_need_resched(curr))
		return;

5454 5455 5456 5457 5458
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

5459
	/*
5460 5461
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
5462
	 */
5463
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5464
		return;
5465

5466
	find_matching_se(&se, &pse);
5467
	update_curr(cfs_rq_of(se));
5468
	BUG_ON(!pse);
5469 5470 5471 5472 5473 5474 5475
	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);
5476
		goto preempt;
5477
	}
5478

5479
	return;
5480

5481
preempt:
5482
	resched_curr(rq);
5483 5484 5485 5486 5487 5488 5489 5490 5491 5492 5493 5494 5495 5496
	/*
	 * 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);
5497 5498
}

5499 5500
static struct task_struct *
pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5501 5502 5503
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
5504
	struct task_struct *p;
5505
	int new_tasks;
5506

5507
again:
5508 5509
#ifdef CONFIG_FAIR_GROUP_SCHED
	if (!cfs_rq->nr_running)
5510
		goto idle;
5511

5512
	if (prev->sched_class != &fair_sched_class)
5513 5514 5515 5516 5517 5518 5519 5520 5521 5522 5523 5524 5525 5526 5527 5528 5529 5530 5531
		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.
		 */
5532 5533 5534 5535 5536
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
5537

5538 5539 5540 5541 5542 5543 5544 5545 5546
			/*
			 * 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;
		}
5547 5548 5549 5550 5551 5552 5553 5554 5555 5556 5557 5558 5559 5560 5561 5562 5563 5564 5565 5566 5567 5568 5569 5570 5571 5572 5573 5574 5575 5576 5577 5578 5579 5580 5581 5582 5583 5584 5585 5586

		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
5587

5588
	if (!cfs_rq->nr_running)
5589
		goto idle;
5590

5591
	put_prev_task(rq, prev);
5592

5593
	do {
5594
		se = pick_next_entity(cfs_rq, NULL);
5595
		set_next_entity(cfs_rq, se);
5596 5597 5598
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
5599
	p = task_of(se);
5600

5601 5602
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
5603 5604

	return p;
5605 5606

idle:
5607 5608 5609 5610 5611 5612 5613
	/*
	 * 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);
5614
	new_tasks = idle_balance(rq);
5615
	lockdep_pin_lock(&rq->lock);
5616 5617 5618 5619 5620
	/*
	 * 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.
	 */
5621
	if (new_tasks < 0)
5622 5623
		return RETRY_TASK;

5624
	if (new_tasks > 0)
5625 5626 5627
		goto again;

	return NULL;
5628 5629 5630 5631 5632
}

/*
 * Account for a descheduled task:
 */
5633
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5634 5635 5636 5637 5638 5639
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5640
		put_prev_entity(cfs_rq, se);
5641 5642 5643
	}
}

5644 5645 5646 5647 5648 5649 5650 5651 5652 5653 5654 5655 5656 5657 5658 5659 5660 5661 5662 5663 5664 5665 5666 5667 5668
/*
 * 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);
5669 5670 5671 5672 5673
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
5674
		rq_clock_skip_update(rq, true);
5675 5676 5677 5678 5679
	}

	set_skip_buddy(se);
}

5680 5681 5682 5683
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

5684 5685
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5686 5687 5688 5689 5690 5691 5692 5693 5694 5695
		return false;

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

	yield_task_fair(rq);

	return true;
}

5696
#ifdef CONFIG_SMP
5697
/**************************************************
P
Peter Zijlstra 已提交
5698 5699 5700 5701 5702 5703 5704 5705 5706 5707 5708 5709 5710 5711 5712 5713
 * 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
5714
 * is derived from the nice value as per sched_prio_to_weight[].
P
Peter Zijlstra 已提交
5715 5716 5717 5718 5719 5720
 *
 * 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)
 *
5721
 * C_i is the compute capacity of cpu i, typically it is the
P
Peter Zijlstra 已提交
5722 5723 5724 5725 5726 5727
 * 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):
 *
5728
 *   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
5729 5730 5731 5732 5733 5734 5735 5736 5737 5738 5739 5740 5741 5742 5743 5744 5745 5746 5747 5748 5749 5750 5751 5752 5753 5754 5755 5756 5757 5758 5759 5760 5761 5762 5763 5764 5765 5766 5767 5768 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
 *
 * 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.]
 */ 
5814

5815 5816
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

5817 5818
enum fbq_type { regular, remote, all };

5819
#define LBF_ALL_PINNED	0x01
5820
#define LBF_NEED_BREAK	0x02
5821 5822
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
5823 5824 5825 5826 5827

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
5828
	int			src_cpu;
5829 5830 5831 5832

	int			dst_cpu;
	struct rq		*dst_rq;

5833 5834
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
5835
	enum cpu_idle_type	idle;
5836
	long			imbalance;
5837 5838 5839
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

5840
	unsigned int		flags;
5841 5842 5843 5844

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
5845 5846

	enum fbq_type		fbq_type;
5847
	struct list_head	tasks;
5848 5849
};

5850 5851 5852
/*
 * Is this task likely cache-hot:
 */
5853
static int task_hot(struct task_struct *p, struct lb_env *env)
5854 5855 5856
{
	s64 delta;

5857 5858
	lockdep_assert_held(&env->src_rq->lock);

5859 5860 5861 5862 5863 5864 5865 5866 5867
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
5868
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5869 5870 5871 5872 5873 5874 5875 5876 5877
			(&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;

5878
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5879 5880 5881 5882

	return delta < (s64)sysctl_sched_migration_cost;
}

5883
#ifdef CONFIG_NUMA_BALANCING
5884
/*
5885 5886 5887
 * 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.
5888
 */
5889
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5890
{
5891
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
5892
	unsigned long src_faults, dst_faults;
5893 5894
	int src_nid, dst_nid;

5895
	if (!static_branch_likely(&sched_numa_balancing))
5896 5897
		return -1;

5898
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5899
		return -1;
5900 5901 5902 5903

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

5904
	if (src_nid == dst_nid)
5905
		return -1;
5906

5907 5908 5909 5910 5911 5912 5913
	/* 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;
	}
5914

5915 5916
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
5917
		return 0;
5918

5919 5920 5921 5922 5923 5924
	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);
5925 5926
	}

5927
	return dst_faults < src_faults;
5928 5929
}

5930
#else
5931
static inline int migrate_degrades_locality(struct task_struct *p,
5932 5933
					     struct lb_env *env)
{
5934
	return -1;
5935
}
5936 5937
#endif

5938 5939 5940 5941
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
5942
int can_migrate_task(struct task_struct *p, struct lb_env *env)
5943
{
5944
	int tsk_cache_hot;
5945 5946 5947

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

5948 5949
	/*
	 * We do not migrate tasks that are:
5950
	 * 1) throttled_lb_pair, or
5951
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5952 5953
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
5954
	 */
5955 5956 5957
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

5958
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5959
		int cpu;
5960

5961
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5962

5963 5964
		env->flags |= LBF_SOME_PINNED;

5965 5966 5967 5968 5969 5970 5971 5972
		/*
		 * 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.
		 */
5973
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5974 5975
			return 0;

5976 5977 5978
		/* 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))) {
5979
				env->flags |= LBF_DST_PINNED;
5980 5981 5982
				env->new_dst_cpu = cpu;
				break;
			}
5983
		}
5984

5985 5986
		return 0;
	}
5987 5988

	/* Record that we found atleast one task that could run on dst_cpu */
5989
	env->flags &= ~LBF_ALL_PINNED;
5990

5991
	if (task_running(env->src_rq, p)) {
5992
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5993 5994 5995 5996 5997
		return 0;
	}

	/*
	 * Aggressive migration if:
5998 5999 6000
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
6001
	 */
6002 6003 6004
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
6005

6006
	if (tsk_cache_hot <= 0 ||
6007
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
6008
		if (tsk_cache_hot == 1) {
6009 6010 6011
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
			schedstat_inc(p, se.statistics.nr_forced_migrations);
		}
6012 6013 6014
		return 1;
	}

Z
Zhang Hang 已提交
6015 6016
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
6017 6018
}

6019
/*
6020 6021 6022 6023 6024 6025 6026
 * 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;
6027
	deactivate_task(env->src_rq, p, 0);
6028 6029 6030
	set_task_cpu(p, env->dst_cpu);
}

6031
/*
6032
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
6033 6034
 * part of active balancing operations within "domain".
 *
6035
 * Returns a task if successful and NULL otherwise.
6036
 */
6037
static struct task_struct *detach_one_task(struct lb_env *env)
6038 6039 6040
{
	struct task_struct *p, *n;

6041 6042
	lockdep_assert_held(&env->src_rq->lock);

6043 6044 6045
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
6046

6047
		detach_task(p, env);
6048

6049
		/*
6050
		 * Right now, this is only the second place where
6051
		 * lb_gained[env->idle] is updated (other is detach_tasks)
6052
		 * so we can safely collect stats here rather than
6053
		 * inside detach_tasks().
6054 6055
		 */
		schedstat_inc(env->sd, lb_gained[env->idle]);
6056
		return p;
6057
	}
6058
	return NULL;
6059 6060
}

6061 6062
static const unsigned int sched_nr_migrate_break = 32;

6063
/*
6064 6065
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
6066
 *
6067
 * Returns number of detached tasks if successful and 0 otherwise.
6068
 */
6069
static int detach_tasks(struct lb_env *env)
6070
{
6071 6072
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
6073
	unsigned long load;
6074 6075 6076
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
6077

6078
	if (env->imbalance <= 0)
6079
		return 0;
6080

6081
	while (!list_empty(tasks)) {
6082 6083 6084 6085 6086 6087 6088
		/*
		 * 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;

6089
		p = list_first_entry(tasks, struct task_struct, se.group_node);
6090

6091 6092
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
6093
		if (env->loop > env->loop_max)
6094
			break;
6095 6096

		/* take a breather every nr_migrate tasks */
6097
		if (env->loop > env->loop_break) {
6098
			env->loop_break += sched_nr_migrate_break;
6099
			env->flags |= LBF_NEED_BREAK;
6100
			break;
6101
		}
6102

6103
		if (!can_migrate_task(p, env))
6104 6105 6106
			goto next;

		load = task_h_load(p);
6107

6108
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
6109 6110
			goto next;

6111
		if ((load / 2) > env->imbalance)
6112
			goto next;
6113

6114 6115 6116 6117
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
6118
		env->imbalance -= load;
6119 6120

#ifdef CONFIG_PREEMPT
6121 6122
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
6123
		 * kernels will stop after the first task is detached to minimize
6124 6125
		 * the critical section.
		 */
6126
		if (env->idle == CPU_NEWLY_IDLE)
6127
			break;
6128 6129
#endif

6130 6131 6132 6133
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
6134
		if (env->imbalance <= 0)
6135
			break;
6136 6137 6138

		continue;
next:
6139
		list_move_tail(&p->se.group_node, tasks);
6140
	}
6141

6142
	/*
6143 6144 6145
	 * 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().
6146
	 */
6147
	schedstat_add(env->sd, lb_gained[env->idle], detached);
6148

6149 6150 6151 6152 6153 6154 6155 6156 6157 6158 6159 6160
	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);
6161
	p->on_rq = TASK_ON_RQ_QUEUED;
6162 6163 6164 6165 6166 6167 6168 6169 6170 6171 6172 6173 6174 6175 6176 6177 6178 6179 6180 6181 6182 6183 6184 6185 6186 6187 6188 6189
	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);
6190

6191 6192 6193 6194
		attach_task(env->dst_rq, p);
	}

	raw_spin_unlock(&env->dst_rq->lock);
6195 6196
}

P
Peter Zijlstra 已提交
6197
#ifdef CONFIG_FAIR_GROUP_SCHED
6198
static void update_blocked_averages(int cpu)
6199 6200
{
	struct rq *rq = cpu_rq(cpu);
6201 6202
	struct cfs_rq *cfs_rq;
	unsigned long flags;
6203

6204 6205
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
6206

6207 6208 6209 6210
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
6211
	for_each_leaf_cfs_rq(rq, cfs_rq) {
6212 6213 6214
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
6215

6216 6217 6218
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
			update_tg_load_avg(cfs_rq, 0);
	}
6219
	raw_spin_unlock_irqrestore(&rq->lock, flags);
6220 6221
}

6222
/*
6223
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
6224 6225 6226
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
6227
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
6228
{
6229 6230
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
6231
	unsigned long now = jiffies;
6232
	unsigned long load;
6233

6234
	if (cfs_rq->last_h_load_update == now)
6235 6236
		return;

6237 6238 6239 6240 6241 6242 6243
	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;
	}
6244

6245
	if (!se) {
6246
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
6247 6248 6249 6250 6251
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
6252 6253
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
6254 6255 6256 6257
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
6258 6259
}

6260
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
6261
{
6262
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
6263

6264
	update_cfs_rq_h_load(cfs_rq);
6265
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
6266
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
6267 6268
}
#else
6269
static inline void update_blocked_averages(int cpu)
6270
{
6271 6272 6273 6274 6275 6276 6277 6278
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
	unsigned long flags;

	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
	raw_spin_unlock_irqrestore(&rq->lock, flags);
6279 6280
}

6281
static unsigned long task_h_load(struct task_struct *p)
6282
{
6283
	return p->se.avg.load_avg;
6284
}
P
Peter Zijlstra 已提交
6285
#endif
6286 6287

/********** Helpers for find_busiest_group ************************/
6288 6289 6290 6291 6292 6293 6294

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

6295 6296 6297 6298 6299 6300 6301
/*
 * 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
6302
	unsigned long load_per_task;
6303
	unsigned long group_capacity;
6304
	unsigned long group_util; /* Total utilization of the group */
6305 6306 6307
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
6308
	enum group_type group_type;
6309
	int group_no_capacity;
6310 6311 6312 6313
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
6314 6315
};

J
Joonsoo Kim 已提交
6316 6317 6318 6319 6320 6321 6322 6323
/*
 * 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 */
6324
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
6325 6326 6327
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6328
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
6329 6330
};

6331 6332 6333 6334 6335 6336 6337 6338 6339 6340 6341 6342
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,
6343
		.total_capacity = 0UL,
6344 6345
		.busiest_stat = {
			.avg_load = 0UL,
6346 6347
			.sum_nr_running = 0,
			.group_type = group_other,
6348 6349 6350 6351
		},
	};
}

6352 6353 6354
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
6355
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6356 6357
 *
 * Return: The load index.
6358 6359 6360 6361 6362 6363 6364 6365 6366 6367 6368 6369 6370 6371 6372 6373 6374 6375 6376 6377 6378 6379
 */
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;
}

6380
static unsigned long scale_rt_capacity(int cpu)
6381 6382
{
	struct rq *rq = cpu_rq(cpu);
6383
	u64 total, used, age_stamp, avg;
6384
	s64 delta;
6385

6386 6387 6388 6389
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
6390 6391
	age_stamp = READ_ONCE(rq->age_stamp);
	avg = READ_ONCE(rq->rt_avg);
6392
	delta = __rq_clock_broken(rq) - age_stamp;
6393

6394 6395 6396 6397
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
6398

6399
	used = div_u64(avg, total);
6400

6401 6402
	if (likely(used < SCHED_CAPACITY_SCALE))
		return SCHED_CAPACITY_SCALE - used;
6403

6404
	return 1;
6405 6406
}

6407
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6408
{
6409
	unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6410 6411
	struct sched_group *sdg = sd->groups;

6412
	cpu_rq(cpu)->cpu_capacity_orig = capacity;
6413

6414
	capacity *= scale_rt_capacity(cpu);
6415
	capacity >>= SCHED_CAPACITY_SHIFT;
6416

6417 6418
	if (!capacity)
		capacity = 1;
6419

6420 6421
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
6422 6423
}

6424
void update_group_capacity(struct sched_domain *sd, int cpu)
6425 6426 6427
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
6428
	unsigned long capacity;
6429 6430 6431 6432
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
6433
	sdg->sgc->next_update = jiffies + interval;
6434 6435

	if (!child) {
6436
		update_cpu_capacity(sd, cpu);
6437 6438 6439
		return;
	}

6440
	capacity = 0;
6441

P
Peter Zijlstra 已提交
6442 6443 6444 6445 6446 6447
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

6448
		for_each_cpu(cpu, sched_group_cpus(sdg)) {
6449
			struct sched_group_capacity *sgc;
6450
			struct rq *rq = cpu_rq(cpu);
6451

6452
			/*
6453
			 * build_sched_domains() -> init_sched_groups_capacity()
6454 6455 6456
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
6457 6458
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
6459
			 *
6460
			 * This avoids capacity from being 0 and
6461 6462 6463
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
6464
				capacity += capacity_of(cpu);
6465 6466
				continue;
			}
6467

6468 6469
			sgc = rq->sd->groups->sgc;
			capacity += sgc->capacity;
6470
		}
P
Peter Zijlstra 已提交
6471 6472 6473 6474 6475 6476 6477 6478
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
6479
			capacity += group->sgc->capacity;
P
Peter Zijlstra 已提交
6480 6481 6482
			group = group->next;
		} while (group != child->groups);
	}
6483

6484
	sdg->sgc->capacity = capacity;
6485 6486
}

6487
/*
6488 6489 6490
 * 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
6491 6492
 */
static inline int
6493
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6494
{
6495 6496
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
6497 6498
}

6499 6500 6501 6502 6503 6504 6505 6506 6507 6508 6509 6510 6511 6512 6513 6514
/*
 * 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
6515 6516
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
6517 6518
 *
 * When this is so detected; this group becomes a candidate for busiest; see
6519
 * update_sd_pick_busiest(). And calculate_imbalance() and
6520
 * find_busiest_group() avoid some of the usual balance conditions to allow it
6521 6522 6523 6524 6525 6526 6527
 * 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.
 */

6528
static inline int sg_imbalanced(struct sched_group *group)
6529
{
6530
	return group->sgc->imbalance;
6531 6532
}

6533
/*
6534 6535 6536
 * 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
6537 6538
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
6539 6540 6541 6542 6543
 * 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.
6544
 */
6545 6546
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6547
{
6548 6549
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
6550

6551
	if ((sgs->group_capacity * 100) >
6552
			(sgs->group_util * env->sd->imbalance_pct))
6553
		return true;
6554

6555 6556 6557 6558 6559 6560 6561 6562 6563 6564 6565 6566 6567 6568 6569 6570
	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;
6571

6572
	if ((sgs->group_capacity * 100) <
6573
			(sgs->group_util * env->sd->imbalance_pct))
6574
		return true;
6575

6576
	return false;
6577 6578
}

6579 6580 6581
static inline enum
group_type group_classify(struct sched_group *group,
			  struct sg_lb_stats *sgs)
6582
{
6583
	if (sgs->group_no_capacity)
6584 6585 6586 6587 6588 6589 6590 6591
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

6592 6593
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6594
 * @env: The load balancing environment.
6595 6596 6597 6598
 * @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.
6599
 * @overload: Indicate more than one runnable task for any CPU.
6600
 */
6601 6602
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
6603 6604
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
6605
{
6606
	unsigned long load;
6607
	int i, nr_running;
6608

6609 6610
	memset(sgs, 0, sizeof(*sgs));

6611
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6612 6613 6614
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
6615
		if (local_group)
6616
			load = target_load(i, load_idx);
6617
		else
6618 6619 6620
			load = source_load(i, load_idx);

		sgs->group_load += load;
6621
		sgs->group_util += cpu_util(i);
6622
		sgs->sum_nr_running += rq->cfs.h_nr_running;
6623

6624 6625
		nr_running = rq->nr_running;
		if (nr_running > 1)
6626 6627
			*overload = true;

6628 6629 6630 6631
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
6632
		sgs->sum_weighted_load += weighted_cpuload(i);
6633 6634 6635 6636
		/*
		 * No need to call idle_cpu() if nr_running is not 0
		 */
		if (!nr_running && idle_cpu(i))
6637
			sgs->idle_cpus++;
6638 6639
	}

6640 6641
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
6642
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6643

6644
	if (sgs->sum_nr_running)
6645
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6646

6647
	sgs->group_weight = group->group_weight;
6648

6649
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
6650
	sgs->group_type = group_classify(group, sgs);
6651 6652
}

6653 6654
/**
 * update_sd_pick_busiest - return 1 on busiest group
6655
 * @env: The load balancing environment.
6656 6657
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
6658
 * @sgs: sched_group statistics
6659 6660 6661
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
6662 6663 6664
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
6665
 */
6666
static bool update_sd_pick_busiest(struct lb_env *env,
6667 6668
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
6669
				   struct sg_lb_stats *sgs)
6670
{
6671
	struct sg_lb_stats *busiest = &sds->busiest_stat;
6672

6673
	if (sgs->group_type > busiest->group_type)
6674 6675
		return true;

6676 6677 6678 6679 6680 6681 6682 6683
	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))
6684 6685
		return true;

6686 6687 6688
	/* No ASYM_PACKING if target cpu is already busy */
	if (env->idle == CPU_NOT_IDLE)
		return true;
6689 6690 6691 6692 6693
	/*
	 * 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.
	 */
6694
	if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6695 6696 6697
		if (!sds->busiest)
			return true;

6698 6699
		/* Prefer to move from highest possible cpu's work */
		if (group_first_cpu(sds->busiest) < group_first_cpu(sg))
6700 6701 6702 6703 6704 6705
			return true;
	}

	return false;
}

6706 6707 6708 6709 6710 6711 6712 6713 6714 6715 6716 6717 6718 6719 6720 6721 6722 6723 6724 6725 6726 6727 6728 6729 6730 6731 6732 6733 6734 6735
#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 */

6736
/**
6737
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6738
 * @env: The load balancing environment.
6739 6740
 * @sds: variable to hold the statistics for this sched_domain.
 */
6741
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6742
{
6743 6744
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
6745
	struct sg_lb_stats tmp_sgs;
6746
	int load_idx, prefer_sibling = 0;
6747
	bool overload = false;
6748 6749 6750 6751

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

6752
	load_idx = get_sd_load_idx(env->sd, env->idle);
6753 6754

	do {
J
Joonsoo Kim 已提交
6755
		struct sg_lb_stats *sgs = &tmp_sgs;
6756 6757
		int local_group;

6758
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
6759 6760 6761
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
6762 6763

			if (env->idle != CPU_NEWLY_IDLE ||
6764 6765
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
6766
		}
6767

6768 6769
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
6770

6771 6772 6773
		if (local_group)
			goto next_group;

6774 6775
		/*
		 * In case the child domain prefers tasks go to siblings
6776
		 * first, lower the sg capacity so that we'll try
6777 6778
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
6779 6780 6781 6782
		 * 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).
6783
		 */
6784
		if (prefer_sibling && sds->local &&
6785 6786 6787
		    group_has_capacity(env, &sds->local_stat) &&
		    (sgs->sum_nr_running > 1)) {
			sgs->group_no_capacity = 1;
6788
			sgs->group_type = group_classify(sg, sgs);
6789
		}
6790

6791
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6792
			sds->busiest = sg;
J
Joonsoo Kim 已提交
6793
			sds->busiest_stat = *sgs;
6794 6795
		}

6796 6797 6798
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
6799
		sds->total_capacity += sgs->group_capacity;
6800

6801
		sg = sg->next;
6802
	} while (sg != env->sd->groups);
6803 6804 6805

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6806 6807 6808 6809 6810 6811 6812

	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;
	}

6813 6814 6815 6816 6817 6818 6819 6820 6821 6822 6823 6824 6825 6826 6827 6828 6829 6830 6831
}

/**
 * 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.
 *
6832
 * Return: 1 when packing is required and a task should be moved to
6833 6834
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
6835
 * @env: The load balancing environment.
6836 6837
 * @sds: Statistics of the sched_domain which is to be packed
 */
6838
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6839 6840 6841
{
	int busiest_cpu;

6842
	if (!(env->sd->flags & SD_ASYM_PACKING))
6843 6844
		return 0;

6845 6846 6847
	if (env->idle == CPU_NOT_IDLE)
		return 0;

6848 6849 6850 6851
	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
6852
	if (env->dst_cpu > busiest_cpu)
6853 6854
		return 0;

6855
	env->imbalance = DIV_ROUND_CLOSEST(
6856
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6857
		SCHED_CAPACITY_SCALE);
6858

6859
	return 1;
6860 6861 6862 6863 6864 6865
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
6866
 * @env: The load balancing environment.
6867 6868
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
6869 6870
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6871
{
6872
	unsigned long tmp, capa_now = 0, capa_move = 0;
6873
	unsigned int imbn = 2;
6874
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
6875
	struct sg_lb_stats *local, *busiest;
6876

J
Joonsoo Kim 已提交
6877 6878
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6879

J
Joonsoo Kim 已提交
6880 6881 6882 6883
	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;
6884

J
Joonsoo Kim 已提交
6885
	scaled_busy_load_per_task =
6886
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6887
		busiest->group_capacity;
J
Joonsoo Kim 已提交
6888

6889 6890
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
6891
		env->imbalance = busiest->load_per_task;
6892 6893 6894 6895 6896
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
6897
	 * however we may be able to increase total CPU capacity used by
6898 6899 6900
	 * moving them.
	 */

6901
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
6902
			min(busiest->load_per_task, busiest->avg_load);
6903
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
6904
			min(local->load_per_task, local->avg_load);
6905
	capa_now /= SCHED_CAPACITY_SCALE;
6906 6907

	/* Amount of load we'd subtract */
6908
	if (busiest->avg_load > scaled_busy_load_per_task) {
6909
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
6910
			    min(busiest->load_per_task,
6911
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
6912
	}
6913 6914

	/* Amount of load we'd add */
6915
	if (busiest->avg_load * busiest->group_capacity <
6916
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6917 6918
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
6919
	} else {
6920
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6921
		      local->group_capacity;
J
Joonsoo Kim 已提交
6922
	}
6923
	capa_move += local->group_capacity *
6924
		    min(local->load_per_task, local->avg_load + tmp);
6925
	capa_move /= SCHED_CAPACITY_SCALE;
6926 6927

	/* Move if we gain throughput */
6928
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
6929
		env->imbalance = busiest->load_per_task;
6930 6931 6932 6933 6934
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
6935
 * @env: load balance environment
6936 6937
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
6938
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6939
{
6940
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
6941 6942 6943 6944
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6945

6946
	if (busiest->group_type == group_imbalanced) {
6947 6948 6949 6950
		/*
		 * 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
6951 6952
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
6953 6954
	}

6955 6956 6957
	/*
	 * 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
6958
	 * its cpu_capacity, while calculating max_load..)
6959
	 */
6960 6961
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
6962 6963
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
6964 6965
	}

6966 6967 6968 6969 6970
	/*
	 * If there aren't any idle cpus, avoid creating some.
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
6971 6972 6973 6974 6975 6976
		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;
6977 6978 6979 6980 6981 6982 6983 6984 6985 6986
	}

	/*
	 * 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.
	 */
6987
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6988 6989

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
6990
	env->imbalance = min(
6991 6992
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
6993
	) / SCHED_CAPACITY_SCALE;
6994 6995 6996

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
6997
	 * there is no guarantee that any tasks will be moved so we'll have
6998 6999 7000
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
7001
	if (env->imbalance < busiest->load_per_task)
7002
		return fix_small_imbalance(env, sds);
7003
}
7004

7005 7006 7007 7008 7009 7010 7011 7012 7013 7014 7015 7016
/******* 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.
 *
7017
 * @env: The load balancing environment.
7018
 *
7019
 * Return:	- The busiest group if imbalance exists.
7020 7021 7022 7023
 *		- 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
7024
static struct sched_group *find_busiest_group(struct lb_env *env)
7025
{
J
Joonsoo Kim 已提交
7026
	struct sg_lb_stats *local, *busiest;
7027 7028
	struct sd_lb_stats sds;

7029
	init_sd_lb_stats(&sds);
7030 7031 7032 7033 7034

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
7035
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
7036 7037
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
7038

7039
	/* ASYM feature bypasses nice load balance check */
7040
	if (check_asym_packing(env, &sds))
7041 7042
		return sds.busiest;

7043
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
7044
	if (!sds.busiest || busiest->sum_nr_running == 0)
7045 7046
		goto out_balanced;

7047 7048
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
7049

P
Peter Zijlstra 已提交
7050 7051
	/*
	 * If the busiest group is imbalanced the below checks don't
7052
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
7053 7054
	 * isn't true due to cpus_allowed constraints and the like.
	 */
7055
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
7056 7057
		goto force_balance;

7058
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
7059 7060
	if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
	    busiest->group_no_capacity)
7061 7062
		goto force_balance;

7063
	/*
7064
	 * If the local group is busier than the selected busiest group
7065 7066
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
7067
	if (local->avg_load >= busiest->avg_load)
7068 7069
		goto out_balanced;

7070 7071 7072 7073
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
7074
	if (local->avg_load >= sds.avg_load)
7075 7076
		goto out_balanced;

7077
	if (env->idle == CPU_IDLE) {
7078
		/*
7079 7080 7081 7082 7083
		 * 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
7084
		 */
7085 7086
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
7087
			goto out_balanced;
7088 7089 7090 7091 7092
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
7093 7094
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
7095
			goto out_balanced;
7096
	}
7097

7098
force_balance:
7099
	/* Looks like there is an imbalance. Compute it */
7100
	calculate_imbalance(env, &sds);
7101 7102 7103
	return sds.busiest;

out_balanced:
7104
	env->imbalance = 0;
7105 7106 7107 7108 7109 7110
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
7111
static struct rq *find_busiest_queue(struct lb_env *env,
7112
				     struct sched_group *group)
7113 7114
{
	struct rq *busiest = NULL, *rq;
7115
	unsigned long busiest_load = 0, busiest_capacity = 1;
7116 7117
	int i;

7118
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
7119
		unsigned long capacity, wl;
7120 7121 7122 7123
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
7124

7125 7126 7127 7128 7129 7130 7131 7132 7133 7134 7135 7136 7137 7138 7139 7140 7141 7142 7143 7144 7145 7146
		/*
		 * 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;

7147
		capacity = capacity_of(i);
7148

7149
		wl = weighted_cpuload(i);
7150

7151 7152
		/*
		 * When comparing with imbalance, use weighted_cpuload()
7153
		 * which is not scaled with the cpu capacity.
7154
		 */
7155 7156 7157

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
7158 7159
			continue;

7160 7161
		/*
		 * For the load comparisons with the other cpu's, consider
7162 7163 7164
		 * 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.
7165
		 *
7166
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
7167
		 * multiplication to rid ourselves of the division works out
7168 7169
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
7170
		 */
7171
		if (wl * busiest_capacity > busiest_load * capacity) {
7172
			busiest_load = wl;
7173
			busiest_capacity = capacity;
7174 7175 7176 7177 7178 7179 7180 7181 7182 7183 7184 7185 7186 7187
			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. */
7188
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
7189

7190
static int need_active_balance(struct lb_env *env)
7191
{
7192 7193 7194
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
7195 7196 7197 7198 7199 7200

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
7201
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
7202
			return 1;
7203 7204
	}

7205 7206 7207 7208 7209 7210 7211 7212 7213 7214 7215 7216 7217
	/*
	 * 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;
	}

7218 7219 7220
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

7221 7222
static int active_load_balance_cpu_stop(void *data);

7223 7224 7225 7226 7227 7228 7229 7230 7231 7232 7233 7234 7235 7236 7237 7238 7239 7240 7241 7242 7243 7244 7245 7246 7247 7248 7249 7250 7251 7252 7253
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.
	 */
7254
	return balance_cpu == env->dst_cpu;
7255 7256
}

7257 7258 7259 7260 7261 7262
/*
 * 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,
7263
			int *continue_balancing)
7264
{
7265
	int ld_moved, cur_ld_moved, active_balance = 0;
7266
	struct sched_domain *sd_parent = sd->parent;
7267 7268 7269
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
7270
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
7271

7272 7273
	struct lb_env env = {
		.sd		= sd,
7274 7275
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
7276
		.dst_grpmask    = sched_group_cpus(sd->groups),
7277
		.idle		= idle,
7278
		.loop_break	= sched_nr_migrate_break,
7279
		.cpus		= cpus,
7280
		.fbq_type	= all,
7281
		.tasks		= LIST_HEAD_INIT(env.tasks),
7282 7283
	};

7284 7285 7286 7287
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
7288
	if (idle == CPU_NEWLY_IDLE)
7289 7290
		env.dst_grpmask = NULL;

7291 7292 7293 7294 7295
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
7296 7297
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
7298
		goto out_balanced;
7299
	}
7300

7301
	group = find_busiest_group(&env);
7302 7303 7304 7305 7306
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

7307
	busiest = find_busiest_queue(&env, group);
7308 7309 7310 7311 7312
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

7313
	BUG_ON(busiest == env.dst_rq);
7314

7315
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7316

7317 7318 7319
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

7320 7321 7322 7323 7324 7325 7326 7327
	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.
		 */
7328
		env.flags |= LBF_ALL_PINNED;
7329
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
7330

7331
more_balance:
7332
		raw_spin_lock_irqsave(&busiest->lock, flags);
7333 7334 7335 7336 7337

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
7338
		cur_ld_moved = detach_tasks(&env);
7339 7340

		/*
7341 7342 7343 7344 7345
		 * 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.
7346
		 */
7347 7348 7349 7350 7351 7352 7353 7354

		raw_spin_unlock(&busiest->lock);

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

7355
		local_irq_restore(flags);
7356

7357 7358 7359 7360 7361
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

7362 7363 7364 7365 7366 7367 7368 7369 7370 7371 7372 7373 7374 7375 7376 7377 7378 7379 7380
		/*
		 * 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.
		 */
7381
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7382

7383 7384 7385
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

7386
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
7387
			env.dst_cpu	 = env.new_dst_cpu;
7388
			env.flags	&= ~LBF_DST_PINNED;
7389 7390
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
7391

7392 7393 7394 7395 7396 7397
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
7398

7399 7400 7401 7402
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
7403
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7404

7405
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7406 7407 7408
				*group_imbalance = 1;
		}

7409
		/* All tasks on this runqueue were pinned by CPU affinity */
7410
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
7411
			cpumask_clear_cpu(cpu_of(busiest), cpus);
7412 7413 7414
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
7415
				goto redo;
7416
			}
7417
			goto out_all_pinned;
7418 7419 7420 7421 7422
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
7423 7424 7425 7426 7427 7428 7429 7430
		/*
		 * 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++;
7431

7432
		if (need_active_balance(&env)) {
7433 7434
			raw_spin_lock_irqsave(&busiest->lock, flags);

7435 7436 7437
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
7438 7439
			 */
			if (!cpumask_test_cpu(this_cpu,
7440
					tsk_cpus_allowed(busiest->curr))) {
7441 7442
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
7443
				env.flags |= LBF_ALL_PINNED;
7444 7445 7446
				goto out_one_pinned;
			}

7447 7448 7449 7450 7451
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
7452 7453 7454 7455 7456 7457
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
7458

7459
			if (active_balance) {
7460 7461 7462
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
7463
			}
7464

7465
			/* We've kicked active balancing, force task migration. */
7466 7467 7468 7469 7470 7471 7472 7473 7474 7475 7476 7477 7478
			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
7479
		 * detach_tasks).
7480 7481 7482 7483 7484 7485 7486 7487
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
7488 7489 7490 7491 7492 7493 7494 7495 7496 7497 7498 7499 7500 7501 7502 7503 7504
	/*
	 * 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.
	 */
7505 7506 7507 7508 7509 7510
	schedstat_inc(sd, lb_balanced[idle]);

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
7511
	if (((env.flags & LBF_ALL_PINNED) &&
7512
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
7513 7514 7515
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

7516
	ld_moved = 0;
7517 7518 7519 7520
out:
	return ld_moved;
}

7521 7522 7523 7524 7525 7526 7527 7528 7529 7530 7531 7532 7533 7534 7535 7536 7537 7538 7539 7540 7541 7542 7543 7544 7545 7546 7547
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;
}

7548 7549 7550 7551
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
7552
static int idle_balance(struct rq *this_rq)
7553
{
7554 7555
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
7556 7557
	struct sched_domain *sd;
	int pulled_task = 0;
7558
	u64 curr_cost = 0;
7559

7560 7561 7562 7563 7564 7565
	/*
	 * 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);

7566 7567
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
7568 7569 7570 7571 7572 7573
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
			update_next_balance(sd, 0, &next_balance);
		rcu_read_unlock();

7574
		goto out;
7575
	}
7576

7577 7578
	raw_spin_unlock(&this_rq->lock);

7579
	update_blocked_averages(this_cpu);
7580
	rcu_read_lock();
7581
	for_each_domain(this_cpu, sd) {
7582
		int continue_balancing = 1;
7583
		u64 t0, domain_cost;
7584 7585 7586 7587

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

7588 7589
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
			update_next_balance(sd, 0, &next_balance);
7590
			break;
7591
		}
7592

7593
		if (sd->flags & SD_BALANCE_NEWIDLE) {
7594 7595
			t0 = sched_clock_cpu(this_cpu);

7596
			pulled_task = load_balance(this_cpu, this_rq,
7597 7598
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
7599 7600 7601 7602 7603 7604

			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;
7605
		}
7606

7607
		update_next_balance(sd, 0, &next_balance);
7608 7609 7610 7611 7612 7613

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
7614 7615
			break;
	}
7616
	rcu_read_unlock();
7617 7618 7619

	raw_spin_lock(&this_rq->lock);

7620 7621 7622
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

7623
	/*
7624 7625 7626
	 * 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.
7627
	 */
7628
	if (this_rq->cfs.h_nr_running && !pulled_task)
7629
		pulled_task = 1;
7630

7631 7632 7633
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
7634
		this_rq->next_balance = next_balance;
7635

7636
	/* Is there a task of a high priority class? */
7637
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7638 7639
		pulled_task = -1;

7640
	if (pulled_task)
7641 7642
		this_rq->idle_stamp = 0;

7643
	return pulled_task;
7644 7645 7646
}

/*
7647 7648 7649 7650
 * 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.
7651
 */
7652
static int active_load_balance_cpu_stop(void *data)
7653
{
7654 7655
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
7656
	int target_cpu = busiest_rq->push_cpu;
7657
	struct rq *target_rq = cpu_rq(target_cpu);
7658
	struct sched_domain *sd;
7659
	struct task_struct *p = NULL;
7660 7661 7662 7663 7664 7665 7666

	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;
7667 7668 7669

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
7670
		goto out_unlock;
7671 7672 7673 7674 7675 7676 7677 7678 7679

	/*
	 * 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. */
7680
	rcu_read_lock();
7681 7682 7683 7684 7685 7686 7687
	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)) {
7688 7689
		struct lb_env env = {
			.sd		= sd,
7690 7691 7692 7693
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
7694 7695 7696
			.idle		= CPU_IDLE,
		};

7697 7698
		schedstat_inc(sd, alb_count);

7699
		p = detach_one_task(&env);
7700
		if (p) {
7701
			schedstat_inc(sd, alb_pushed);
7702 7703 7704
			/* Active balancing done, reset the failure counter. */
			sd->nr_balance_failed = 0;
		} else {
7705
			schedstat_inc(sd, alb_failed);
7706
		}
7707
	}
7708
	rcu_read_unlock();
7709 7710
out_unlock:
	busiest_rq->active_balance = 0;
7711 7712 7713 7714 7715 7716 7717
	raw_spin_unlock(&busiest_rq->lock);

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

7718
	return 0;
7719 7720
}

7721 7722 7723 7724 7725
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

7726
#ifdef CONFIG_NO_HZ_COMMON
7727 7728 7729 7730 7731 7732
/*
 * 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.
 */
7733
static struct {
7734
	cpumask_var_t idle_cpus_mask;
7735
	atomic_t nr_cpus;
7736 7737
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
7738

7739
static inline int find_new_ilb(void)
7740
{
7741
	int ilb = cpumask_first(nohz.idle_cpus_mask);
7742

7743 7744 7745 7746
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
7747 7748
}

7749 7750 7751 7752 7753
/*
 * 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).
 */
7754
static void nohz_balancer_kick(void)
7755 7756 7757 7758 7759
{
	int ilb_cpu;

	nohz.next_balance++;

7760
	ilb_cpu = find_new_ilb();
7761

7762 7763
	if (ilb_cpu >= nr_cpu_ids)
		return;
7764

7765
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7766 7767 7768 7769 7770 7771 7772 7773
		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);
7774 7775 7776
	return;
}

7777
static inline void nohz_balance_exit_idle(int cpu)
7778 7779
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7780 7781 7782 7783 7784 7785 7786
		/*
		 * 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);
		}
7787 7788 7789 7790
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

7791 7792 7793
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
7794
	int cpu = smp_processor_id();
7795 7796

	rcu_read_lock();
7797
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7798 7799 7800 7801 7802

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

7803
	atomic_inc(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7804
unlock:
7805 7806 7807 7808 7809 7810
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
7811
	int cpu = smp_processor_id();
7812 7813

	rcu_read_lock();
7814
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7815 7816 7817 7818 7819

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

7820
	atomic_dec(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7821
unlock:
7822 7823 7824
	rcu_read_unlock();
}

7825
/*
7826
 * This routine will record that the cpu is going idle with tick stopped.
7827
 * This info will be used in performing idle load balancing in the future.
7828
 */
7829
void nohz_balance_enter_idle(int cpu)
7830
{
7831 7832 7833 7834 7835 7836
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

7837 7838
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
7839

7840 7841 7842 7843 7844 7845
	/*
	 * If we're a completely isolated CPU, we don't play.
	 */
	if (on_null_domain(cpu_rq(cpu)))
		return;

7846 7847 7848
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7849
}
7850

7851
static int sched_ilb_notifier(struct notifier_block *nfb,
7852 7853 7854 7855
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
7856
		nohz_balance_exit_idle(smp_processor_id());
7857 7858 7859 7860 7861
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
7862 7863 7864 7865
#endif

static DEFINE_SPINLOCK(balancing);

7866 7867 7868 7869
/*
 * 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.
 */
7870
void update_max_interval(void)
7871 7872 7873 7874
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

7875 7876 7877 7878
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
7879
 * Balancing parameters are set up in init_sched_domains.
7880
 */
7881
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7882
{
7883
	int continue_balancing = 1;
7884
	int cpu = rq->cpu;
7885
	unsigned long interval;
7886
	struct sched_domain *sd;
7887 7888 7889
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
7890 7891
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
7892

7893
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
7894

7895
	rcu_read_lock();
7896
	for_each_domain(cpu, sd) {
7897 7898 7899 7900 7901 7902 7903 7904 7905 7906 7907 7908
		/*
		 * 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;

7909 7910 7911
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

7912 7913 7914 7915 7916 7917 7918 7919 7920 7921 7922
		/*
		 * 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;
		}

7923
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7924 7925 7926 7927 7928 7929 7930 7931

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

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
7932
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7933
				/*
7934
				 * The LBF_DST_PINNED logic could have changed
7935 7936
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
7937
				 */
7938
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7939 7940
			}
			sd->last_balance = jiffies;
7941
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7942 7943 7944 7945 7946 7947 7948 7949
		}
		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;
		}
7950 7951
	}
	if (need_decay) {
7952
		/*
7953 7954
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
7955
		 */
7956 7957
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
7958
	}
7959
	rcu_read_unlock();
7960 7961 7962 7963 7964 7965

	/*
	 * 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.
	 */
7966
	if (likely(update_next_balance)) {
7967
		rq->next_balance = next_balance;
7968 7969 7970 7971 7972 7973 7974 7975 7976 7977 7978 7979 7980 7981

#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
	}
7982 7983
}

7984
#ifdef CONFIG_NO_HZ_COMMON
7985
/*
7986
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7987 7988
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
7989
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7990
{
7991
	int this_cpu = this_rq->cpu;
7992 7993
	struct rq *rq;
	int balance_cpu;
7994 7995 7996
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
7997

7998 7999 8000
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
8001 8002

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
8003
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
8004 8005 8006 8007 8008 8009 8010
			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.
		 */
8011
		if (need_resched())
8012 8013
			break;

V
Vincent Guittot 已提交
8014 8015
		rq = cpu_rq(balance_cpu);

8016 8017 8018 8019 8020 8021 8022
		/*
		 * 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);
8023
			update_cpu_load_idle(rq);
8024 8025 8026
			raw_spin_unlock_irq(&rq->lock);
			rebalance_domains(rq, CPU_IDLE);
		}
8027

8028 8029 8030 8031
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
8032
	}
8033 8034 8035 8036 8037 8038 8039 8040

	/*
	 * 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;
8041 8042
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
8043 8044 8045
}

/*
8046
 * Current heuristic for kicking the idle load balancer in the presence
8047
 * of an idle cpu in the system.
8048
 *   - This rq has more than one task.
8049 8050 8051 8052
 *   - 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.
8053 8054
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
8055
 */
8056
static inline bool nohz_kick_needed(struct rq *rq)
8057 8058
{
	unsigned long now = jiffies;
8059
	struct sched_domain *sd;
8060
	struct sched_group_capacity *sgc;
8061
	int nr_busy, cpu = rq->cpu;
8062
	bool kick = false;
8063

8064
	if (unlikely(rq->idle_balance))
8065
		return false;
8066

8067 8068 8069 8070
       /*
	* 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.
	*/
8071
	set_cpu_sd_state_busy();
8072
	nohz_balance_exit_idle(cpu);
8073 8074 8075 8076 8077 8078

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
8079
		return false;
8080 8081

	if (time_before(now, nohz.next_balance))
8082
		return false;
8083

8084
	if (rq->nr_running >= 2)
8085
		return true;
8086

8087
	rcu_read_lock();
8088 8089
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
	if (sd) {
8090 8091
		sgc = sd->groups->sgc;
		nr_busy = atomic_read(&sgc->nr_busy_cpus);
8092

8093 8094 8095 8096 8097
		if (nr_busy > 1) {
			kick = true;
			goto unlock;
		}

8098
	}
8099

8100 8101 8102 8103 8104 8105 8106 8107
	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
			kick = true;
			goto unlock;
		}
	}
8108

8109
	sd = rcu_dereference(per_cpu(sd_asym, cpu));
8110
	if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
8111 8112 8113 8114
				  sched_domain_span(sd)) < cpu)) {
		kick = true;
		goto unlock;
	}
8115

8116
unlock:
8117
	rcu_read_unlock();
8118
	return kick;
8119 8120
}
#else
8121
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
8122 8123 8124 8125 8126 8127
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
8128 8129
static void run_rebalance_domains(struct softirq_action *h)
{
8130
	struct rq *this_rq = this_rq();
8131
	enum cpu_idle_type idle = this_rq->idle_balance ?
8132 8133 8134
						CPU_IDLE : CPU_NOT_IDLE;

	/*
8135
	 * If this cpu has a pending nohz_balance_kick, then do the
8136
	 * balancing on behalf of the other idle cpus whose ticks are
8137 8138 8139 8140
	 * 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.
8141
	 */
8142
	nohz_idle_balance(this_rq, idle);
8143
	rebalance_domains(this_rq, idle);
8144 8145 8146 8147 8148
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
8149
void trigger_load_balance(struct rq *rq)
8150 8151
{
	/* Don't need to rebalance while attached to NULL domain */
8152 8153 8154 8155
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
8156
		raise_softirq(SCHED_SOFTIRQ);
8157
#ifdef CONFIG_NO_HZ_COMMON
8158
	if (nohz_kick_needed(rq))
8159
		nohz_balancer_kick();
8160
#endif
8161 8162
}

8163 8164 8165
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
8166 8167

	update_runtime_enabled(rq);
8168 8169 8170 8171 8172
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
8173 8174 8175

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
8176 8177
}

8178
#endif /* CONFIG_SMP */
8179

8180 8181 8182
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
8183
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
8184 8185 8186 8187 8188 8189
{
	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
8190
		entity_tick(cfs_rq, se, queued);
8191
	}
8192

8193
	if (static_branch_unlikely(&sched_numa_balancing))
8194
		task_tick_numa(rq, curr);
8195 8196 8197
}

/*
P
Peter Zijlstra 已提交
8198 8199 8200
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
8201
 */
P
Peter Zijlstra 已提交
8202
static void task_fork_fair(struct task_struct *p)
8203
{
8204 8205
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
8206
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
8207 8208 8209
	struct rq *rq = this_rq();
	unsigned long flags;

8210
	raw_spin_lock_irqsave(&rq->lock, flags);
8211

8212 8213
	update_rq_clock(rq);

8214 8215 8216
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

8217 8218 8219 8220 8221 8222 8223 8224 8225
	/*
	 * 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();
8226

8227
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
8228

8229 8230
	if (curr)
		se->vruntime = curr->vruntime;
8231
	place_entity(cfs_rq, se, 1);
8232

P
Peter Zijlstra 已提交
8233
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
8234
		/*
8235 8236 8237
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
8238
		swap(curr->vruntime, se->vruntime);
8239
		resched_curr(rq);
8240
	}
8241

8242 8243
	se->vruntime -= cfs_rq->min_vruntime;

8244
	raw_spin_unlock_irqrestore(&rq->lock, flags);
8245 8246
}

8247 8248 8249 8250
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
8251 8252
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
8253
{
8254
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
8255 8256
		return;

8257 8258 8259 8260 8261
	/*
	 * 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
8262
	if (rq->curr == p) {
8263
		if (p->prio > oldprio)
8264
			resched_curr(rq);
8265
	} else
8266
		check_preempt_curr(rq, p, 0);
8267 8268
}

8269
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
8270 8271 8272 8273
{
	struct sched_entity *se = &p->se;

	/*
8274 8275 8276 8277 8278 8279 8280 8281 8282 8283
	 * 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
8284
	 *
8285 8286 8287 8288
	 * - 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
8289
	 */
8290 8291 8292 8293 8294 8295 8296 8297 8298 8299 8300 8301
	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
8302 8303 8304 8305 8306 8307 8308
		/*
		 * 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;
	}
8309

8310
	/* Catch up with the cfs_rq and remove our load when we leave */
8311
	detach_entity_load_avg(cfs_rq, se);
P
Peter Zijlstra 已提交
8312 8313
}

8314
static void attach_task_cfs_rq(struct task_struct *p)
8315
{
8316
	struct sched_entity *se = &p->se;
8317
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
8318 8319

#ifdef CONFIG_FAIR_GROUP_SCHED
8320 8321 8322 8323 8324 8325
	/*
	 * 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
8326

8327
	/* Synchronize task with its cfs_rq */
8328 8329 8330 8331 8332
	attach_entity_load_avg(cfs_rq, se);

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
8333

8334 8335 8336 8337 8338 8339 8340 8341
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);
8342

8343
	if (task_on_rq_queued(p)) {
8344
		/*
8345 8346 8347
		 * 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.
8348
		 */
8349 8350 8351 8352
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
8353
	}
8354 8355
}

8356 8357 8358 8359 8360 8361 8362 8363 8364
/* 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;

8365 8366 8367 8368 8369 8370 8371
	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);
	}
8372 8373
}

8374 8375 8376 8377 8378 8379 8380
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
8381
#ifdef CONFIG_SMP
8382 8383
	atomic_long_set(&cfs_rq->removed_load_avg, 0);
	atomic_long_set(&cfs_rq->removed_util_avg, 0);
8384
#endif
8385 8386
}

P
Peter Zijlstra 已提交
8387
#ifdef CONFIG_FAIR_GROUP_SCHED
8388
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
8389
{
8390
	detach_task_cfs_rq(p);
8391
	set_task_rq(p, task_cpu(p));
8392 8393 8394 8395 8396

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
8397
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
8398
}
8399 8400 8401 8402 8403 8404 8405 8406 8407 8408

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]);
8409
		if (tg->se)
8410 8411 8412 8413 8414 8415 8416 8417 8418 8419 8420 8421 8422 8423 8424 8425 8426 8427 8428 8429 8430 8431 8432 8433 8434 8435 8436 8437 8438 8439 8440 8441 8442 8443 8444 8445 8446
			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]);
8447
		init_entity_runnable_average(se);
8448
		post_init_entity_util_avg(se);
8449 8450 8451 8452 8453 8454 8455 8456 8457 8458
	}

	return 1;

err_free_rq:
	kfree(cfs_rq);
err:
	return 0;
}

8459
void unregister_fair_sched_group(struct task_group *tg)
8460 8461
{
	unsigned long flags;
8462 8463
	struct rq *rq;
	int cpu;
8464

8465 8466 8467
	for_each_possible_cpu(cpu) {
		if (tg->se[cpu])
			remove_entity_load_avg(tg->se[cpu]);
8468

8469 8470 8471 8472 8473 8474 8475 8476 8477 8478 8479 8480 8481
		/*
		 * 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);
	}
8482 8483 8484 8485 8486 8487 8488 8489 8490 8491 8492 8493 8494 8495 8496 8497 8498 8499 8500
}

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
8501
	if (!parent) {
8502
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
8503 8504
		se->depth = 0;
	} else {
8505
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
8506 8507
		se->depth = parent->depth + 1;
	}
8508 8509

	se->my_q = cfs_rq;
8510 8511
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
8512 8513 8514 8515 8516 8517 8518 8519 8520 8521 8522 8523 8524 8525 8526 8527 8528 8529 8530 8531 8532 8533 8534 8535 8536 8537 8538 8539 8540 8541
	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);
8542 8543 8544

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
8545
		for_each_sched_entity(se)
8546 8547 8548 8549 8550 8551 8552 8553 8554 8555 8556 8557 8558 8559 8560 8561 8562
			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;
}

8563
void unregister_fair_sched_group(struct task_group *tg) { }
8564 8565 8566

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
8567

8568
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8569 8570 8571 8572 8573 8574 8575 8576 8577
{
	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)
8578
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8579 8580 8581 8582

	return rr_interval;
}

8583 8584 8585
/*
 * All the scheduling class methods:
 */
8586
const struct sched_class fair_sched_class = {
8587
	.next			= &idle_sched_class,
8588 8589 8590
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
8591
	.yield_to_task		= yield_to_task_fair,
8592

I
Ingo Molnar 已提交
8593
	.check_preempt_curr	= check_preempt_wakeup,
8594 8595 8596 8597

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

8598
#ifdef CONFIG_SMP
L
Li Zefan 已提交
8599
	.select_task_rq		= select_task_rq_fair,
8600
	.migrate_task_rq	= migrate_task_rq_fair,
8601

8602 8603
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
8604 8605

	.task_waking		= task_waking_fair,
8606
	.task_dead		= task_dead_fair,
8607
	.set_cpus_allowed	= set_cpus_allowed_common,
8608
#endif
8609

8610
	.set_curr_task          = set_curr_task_fair,
8611
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
8612
	.task_fork		= task_fork_fair,
8613 8614

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
8615
	.switched_from		= switched_from_fair,
8616
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
8617

8618 8619
	.get_rr_interval	= get_rr_interval_fair,

8620 8621
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
8622
#ifdef CONFIG_FAIR_GROUP_SCHED
8623
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
8624
#endif
8625 8626 8627
};

#ifdef CONFIG_SCHED_DEBUG
8628
void print_cfs_stats(struct seq_file *m, int cpu)
8629 8630 8631
{
	struct cfs_rq *cfs_rq;

8632
	rcu_read_lock();
8633
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8634
		print_cfs_rq(m, cpu, cfs_rq);
8635
	rcu_read_unlock();
8636
}
8637 8638 8639 8640 8641 8642 8643 8644 8645 8646 8647 8648 8649 8650 8651 8652 8653 8654 8655 8656 8657

#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 */
8658 8659 8660 8661 8662 8663

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

8664
#ifdef CONFIG_NO_HZ_COMMON
8665
	nohz.next_balance = jiffies;
8666
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8667
	cpu_notifier(sched_ilb_notifier, 0);
8668 8669 8670 8671
#endif
#endif /* SMP */

}