fair.c 217.7 KB
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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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 */

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

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

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

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

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

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

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

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

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/*
 * Increase the granularity value when there are more CPUs,
 * because with more CPUs the 'effective latency' as visible
 * to users decreases. But the relationship is not linear,
 * so pick a second-best guess by going with the log2 of the
 * number of CPUs.
 *
 * This idea comes from the SD scheduler of Con Kolivas:
 */
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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
 *
 * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case
 * we're guaranteed shift stays positive because inv_weight is guaranteed to
 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22.
 *
 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus
 * weight/lw.weight <= 1, and therefore our shift will also be positive.
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 */
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static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
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{
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	u64 fact = scale_load_down(weight);
	int shift = WMULT_SHIFT;
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	__update_inv_weight(lw);
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	if (unlikely(fact >> 32)) {
		while (fact >> 32) {
			fact >>= 1;
			shift--;
		}
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	}

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


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

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

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

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

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

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

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

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static 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.
 * Note: The tables below are dependent on this value.
 */
#define LOAD_AVG_PERIOD 32
#define LOAD_AVG_MAX 47742 /* maximum possible load avg */
#define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */
669

670 671
/* Give new sched_entity start runnable values to heavy its load in infant time */
void init_entity_runnable_average(struct sched_entity *se)
672
{
673
	struct sched_avg *sa = &se->avg;
674

675 676 677 678 679 680 681
	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;
682
	sa->load_avg = scale_load_down(se->load.weight);
683 684
	sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
	sa->util_avg = scale_load_down(SCHED_LOAD_SCALE);
685
	sa->util_sum = sa->util_avg * LOAD_AVG_MAX;
686
	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
687
}
688 689 690

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);
691
#else
692
void init_entity_runnable_average(struct sched_entity *se)
693 694 695 696
{
}
#endif

697
/*
698
 * Update the current task's runtime statistics.
699
 */
700
static void update_curr(struct cfs_rq *cfs_rq)
701
{
702
	struct sched_entity *curr = cfs_rq->curr;
703
	u64 now = rq_clock_task(rq_of(cfs_rq));
704
	u64 delta_exec;
705 706 707 708

	if (unlikely(!curr))
		return;

709 710
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
711
		return;
712

I
Ingo Molnar 已提交
713
	curr->exec_start = now;
714

715 716 717 718 719 720 721 722 723
	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);

724 725 726
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

727
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
728
		cpuacct_charge(curtask, delta_exec);
729
		account_group_exec_runtime(curtask, delta_exec);
730
	}
731 732

	account_cfs_rq_runtime(cfs_rq, delta_exec);
733 734
}

735 736 737 738 739
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

740
static inline void
741
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
742
{
743
	schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
744 745 746 747 748
}

/*
 * Task is being enqueued - update stats:
 */
749
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
750 751 752 753 754
{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
755
	if (se != cfs_rq->curr)
756
		update_stats_wait_start(cfs_rq, se);
757 758 759
}

static void
760
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
761
{
762
	schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
763
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
764 765
	schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
	schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
766
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
767 768 769
#ifdef CONFIG_SCHEDSTATS
	if (entity_is_task(se)) {
		trace_sched_stat_wait(task_of(se),
770
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
771 772
	}
#endif
773
	schedstat_set(se->statistics.wait_start, 0);
774 775 776
}

static inline void
777
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
778 779 780 781 782
{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
783
	if (se != cfs_rq->curr)
784
		update_stats_wait_end(cfs_rq, se);
785 786 787 788 789 790
}

/*
 * We are picking a new current task - update its stats:
 */
static inline void
791
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
792 793 794 795
{
	/*
	 * We are starting a new run period:
	 */
796
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
797 798 799 800 801 802
}

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

803 804
#ifdef CONFIG_NUMA_BALANCING
/*
805 806 807
 * 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.
808
 */
809 810
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
811 812 813

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
814

815 816 817
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841
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)
{
842
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
843 844 845
	unsigned int scan, floor;
	unsigned int windows = 1;

846 847
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863
	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);
}

864 865 866 867 868 869 870 871 872 873 874 875
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));
}

876 877 878 879 880
struct numa_group {
	atomic_t refcount;

	spinlock_t lock; /* nr_tasks, tasks */
	int nr_tasks;
881
	pid_t gid;
882 883

	struct rcu_head rcu;
884
	nodemask_t active_nodes;
885
	unsigned long total_faults;
886 887 888 889 890
	/*
	 * 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.
	 */
891
	unsigned long *faults_cpu;
892
	unsigned long faults[0];
893 894
};

895 896 897 898 899 900 901 902 903
/* 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)

904 905 906 907 908
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

909 910 911 912 913 914 915
/*
 * 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)
916
{
917
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
918 919 920 921
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
922
	if (!p->numa_faults)
923 924
		return 0;

925 926
	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
927 928
}

929 930 931 932 933
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

934 935
	return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
936 937
}

938 939
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
940 941
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
942 943
}

944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008
/* 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;
}

1009 1010 1011 1012 1013 1014
/*
 * 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.
 */
1015 1016
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1017
{
1018
	unsigned long faults, total_faults;
1019

1020
	if (!p->numa_faults)
1021 1022 1023 1024 1025 1026 1027
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1028
	faults = task_faults(p, nid);
1029 1030
	faults += score_nearby_nodes(p, nid, dist, true);

1031
	return 1000 * faults / total_faults;
1032 1033
}

1034 1035
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1036
{
1037 1038 1039 1040 1041 1042 1043 1044
	unsigned long faults, total_faults;

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1045 1046
		return 0;

1047
	faults = group_faults(p, nid);
1048 1049
	faults += score_nearby_nodes(p, nid, dist, false);

1050
	return 1000 * faults / total_faults;
1051 1052
}

1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115
bool should_numa_migrate_memory(struct task_struct *p, struct page * page,
				int src_nid, int dst_cpu)
{
	struct numa_group *ng = p->numa_group;
	int dst_nid = cpu_to_node(dst_cpu);
	int last_cpupid, this_cpupid;

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

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

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

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

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

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

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

1116
static unsigned long weighted_cpuload(const int cpu);
1117 1118
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1119
static unsigned long capacity_of(int cpu);
1120 1121
static long effective_load(struct task_group *tg, int cpu, long wl, long wg);

1122
/* Cached statistics for all CPUs within a node */
1123
struct numa_stats {
1124
	unsigned long nr_running;
1125
	unsigned long load;
1126 1127

	/* Total compute capacity of CPUs on a node */
1128
	unsigned long compute_capacity;
1129 1130

	/* Approximate capacity in terms of runnable tasks on a node */
1131
	unsigned long task_capacity;
1132
	int has_free_capacity;
1133
};
1134

1135 1136 1137 1138 1139
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1140 1141
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1142 1143 1144 1145 1146 1147 1148

	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);
1149
		ns->compute_capacity += capacity_of(cpu);
1150 1151

		cpus++;
1152 1153
	}

1154 1155 1156 1157 1158
	/*
	 * 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.
	 *
1159 1160
	 * We'll either bail at !has_free_capacity, or we'll detect a huge
	 * imbalance and bail there.
1161 1162 1163 1164
	 */
	if (!cpus)
		return;

1165 1166 1167 1168 1169 1170
	/* 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));
1171
	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1172 1173
}

1174 1175
struct task_numa_env {
	struct task_struct *p;
1176

1177 1178
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1179

1180
	struct numa_stats src_stats, dst_stats;
1181

1182
	int imbalance_pct;
1183
	int dist;
1184 1185 1186

	struct task_struct *best_task;
	long best_imp;
1187 1188 1189
	int best_cpu;
};

1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202
static void task_numa_assign(struct task_numa_env *env,
			     struct task_struct *p, long imp)
{
	if (env->best_task)
		put_task_struct(env->best_task);
	if (p)
		get_task_struct(p);

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

1203
static bool load_too_imbalanced(long src_load, long dst_load,
1204 1205
				struct task_numa_env *env)
{
1206 1207
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218
	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;
1219 1220

	/* We care about the slope of the imbalance, not the direction. */
1221 1222
	if (dst_load < src_load)
		swap(dst_load, src_load);
1223 1224

	/* Is the difference below the threshold? */
1225 1226
	imb = dst_load * src_capacity * 100 -
	      src_load * dst_capacity * env->imbalance_pct;
1227 1228 1229 1230 1231
	if (imb <= 0)
		return false;

	/*
	 * The imbalance is above the allowed threshold.
1232
	 * Compare it with the old imbalance.
1233
	 */
1234
	orig_src_load = env->src_stats.load;
1235
	orig_dst_load = env->dst_stats.load;
1236

1237 1238
	if (orig_dst_load < orig_src_load)
		swap(orig_dst_load, orig_src_load);
1239

1240 1241 1242 1243 1244
	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);
1245 1246
}

1247 1248 1249 1250 1251 1252
/*
 * 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
 */
1253 1254
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1255 1256 1257 1258
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1259
	long src_load, dst_load;
1260
	long load;
1261
	long imp = env->p->numa_group ? groupimp : taskimp;
1262
	long moveimp = imp;
1263
	int dist = env->dist;
1264 1265

	rcu_read_lock();
1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276

	raw_spin_lock_irq(&dst_rq->lock);
	cur = dst_rq->curr;
	/*
	 * No need to move the exiting task, and this ensures that ->curr
	 * wasn't reaped and thus get_task_struct() in task_numa_assign()
	 * is safe under RCU read lock.
	 * Note that rcu_read_lock() itself can't protect from the final
	 * put_task_struct() after the last schedule().
	 */
	if ((cur->flags & PF_EXITING) || is_idle_task(cur))
1277
		cur = NULL;
1278
	raw_spin_unlock_irq(&dst_rq->lock);
1279

1280 1281 1282 1283 1284 1285 1286
	/*
	 * 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;

1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298
	/*
	 * "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;

1299 1300
		/*
		 * If dst and source tasks are in the same NUMA group, or not
1301
		 * in any group then look only at task weights.
1302
		 */
1303
		if (cur->numa_group == env->p->numa_group) {
1304 1305
			imp = taskimp + task_weight(cur, env->src_nid, dist) -
			      task_weight(cur, env->dst_nid, dist);
1306 1307 1308 1309 1310 1311
			/*
			 * Add some hysteresis to prevent swapping the
			 * tasks within a group over tiny differences.
			 */
			if (cur->numa_group)
				imp -= imp/16;
1312
		} else {
1313 1314 1315 1316 1317 1318
			/*
			 * 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)
1319 1320
				imp += group_weight(cur, env->src_nid, dist) -
				       group_weight(cur, env->dst_nid, dist);
1321
			else
1322 1323
				imp += task_weight(cur, env->src_nid, dist) -
				       task_weight(cur, env->dst_nid, dist);
1324
		}
1325 1326
	}

1327
	if (imp <= env->best_imp && moveimp <= env->best_imp)
1328 1329 1330 1331
		goto unlock;

	if (!cur) {
		/* Is there capacity at our destination? */
1332
		if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1333
		    !env->dst_stats.has_free_capacity)
1334 1335 1336 1337 1338 1339
			goto unlock;

		goto balance;
	}

	/* Balance doesn't matter much if we're running a task per cpu */
1340 1341
	if (imp > env->best_imp && src_rq->nr_running == 1 &&
			dst_rq->nr_running == 1)
1342 1343 1344 1345 1346 1347
		goto assign;

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
balance:
1348 1349 1350
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1351

1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368
	if (moveimp > imp && moveimp > env->best_imp) {
		/*
		 * If the improvement from just moving env->p direction is
		 * better than swapping tasks around, check if a move is
		 * possible. Store a slightly smaller score than moveimp,
		 * so an actually idle CPU will win.
		 */
		if (!load_too_imbalanced(src_load, dst_load, env)) {
			imp = moveimp - 1;
			cur = NULL;
			goto assign;
		}
	}

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

1369
	if (cur) {
1370 1371 1372
		load = task_h_load(cur);
		dst_load -= load;
		src_load += load;
1373 1374
	}

1375
	if (load_too_imbalanced(src_load, dst_load, env))
1376 1377
		goto unlock;

1378 1379 1380 1381 1382 1383 1384
	/*
	 * 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);

1385 1386 1387 1388 1389 1390
assign:
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1391 1392
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1393 1394 1395 1396 1397 1398 1399 1400 1401
{
	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;
1402
		task_numa_compare(env, taskimp, groupimp);
1403 1404 1405
	}
}

1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422
/* 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
	 */
1423 1424 1425
	if (src->load * dst->compute_capacity * env->imbalance_pct >

	    dst->load * src->compute_capacity * 100)
1426 1427 1428 1429 1430
		return true;

	return false;
}

1431 1432 1433 1434
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1435

1436
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1437
		.src_nid = task_node(p),
1438 1439 1440 1441 1442 1443

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
		.best_cpu = -1
1444 1445
	};
	struct sched_domain *sd;
1446
	unsigned long taskweight, groupweight;
1447
	int nid, ret, dist;
1448
	long taskimp, groupimp;
1449

1450
	/*
1451 1452 1453 1454 1455 1456
	 * 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.
1457 1458
	 */
	rcu_read_lock();
1459
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1460 1461
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1462 1463
	rcu_read_unlock();

1464 1465 1466 1467 1468 1469 1470
	/*
	 * 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)) {
1471
		p->numa_preferred_nid = task_node(p);
1472 1473 1474
		return -EINVAL;
	}

1475
	env.dst_nid = p->numa_preferred_nid;
1476 1477 1478 1479 1480 1481
	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;
1482
	update_numa_stats(&env.dst_stats, env.dst_nid);
1483

1484
	/* Try to find a spot on the preferred nid. */
1485 1486
	if (numa_has_capacity(&env))
		task_numa_find_cpu(&env, taskimp, groupimp);
1487

1488 1489 1490 1491 1492 1493 1494 1495 1496
	/*
	 * Look at other nodes in these cases:
	 * - there is no space available on the preferred_nid
	 * - the task is part of a numa_group that is interleaved across
	 *   multiple NUMA nodes; in order to better consolidate the group,
	 *   we need to check other locations.
	 */
	if (env.best_cpu == -1 || (p->numa_group &&
			nodes_weight(p->numa_group->active_nodes) > 1)) {
1497 1498 1499
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1500

1501
			dist = node_distance(env.src_nid, env.dst_nid);
1502 1503 1504 1505 1506
			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);
			}
1507

1508
			/* Only consider nodes where both task and groups benefit */
1509 1510
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1511
			if (taskimp < 0 && groupimp < 0)
1512 1513
				continue;

1514
			env.dist = dist;
1515 1516
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1517 1518
			if (numa_has_capacity(&env))
				task_numa_find_cpu(&env, taskimp, groupimp);
1519 1520 1521
		}
	}

1522 1523 1524 1525 1526 1527 1528 1529
	/*
	 * 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.
	 */
1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542
	if (p->numa_group) {
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
			nid = env.dst_nid;

		if (node_isset(nid, p->numa_group->active_nodes))
			sched_setnuma(p, env.dst_nid);
	}

	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;
1543

1544 1545 1546 1547 1548 1549
	/*
	 * 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);

1550
	if (env.best_task == NULL) {
1551 1552 1553
		ret = migrate_task_to(p, env.best_cpu);
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1554 1555 1556 1557
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
1558 1559
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1560 1561
	put_task_struct(env.best_task);
	return ret;
1562 1563
}

1564 1565 1566
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1567 1568
	unsigned long interval = HZ;

1569
	/* This task has no NUMA fault statistics yet */
1570
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1571 1572
		return;

1573
	/* Periodically retry migrating the task to the preferred node */
1574 1575
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
	p->numa_migrate_retry = jiffies + interval;
1576 1577

	/* Success if task is already running on preferred CPU */
1578
	if (task_node(p) == p->numa_preferred_nid)
1579 1580 1581
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1582
	task_numa_migrate(p);
1583 1584
}

1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616
/*
 * Find the nodes on which the workload is actively running. We do this by
 * tracking the nodes from which NUMA hinting faults are triggered. This can
 * be different from the set of nodes where the workload's memory is currently
 * located.
 *
 * The bitmask is used to make smarter decisions on when to do NUMA page
 * migrations, To prevent flip-flopping, and excessive page migrations, nodes
 * are added when they cause over 6/16 of the maximum number of faults, but
 * only removed when they drop below 3/16.
 */
static void update_numa_active_node_mask(struct numa_group *numa_group)
{
	unsigned long faults, max_faults = 0;
	int nid;

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

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

1617 1618 1619
/*
 * 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
1620 1621 1622
 * 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.
1623 1624
 */
#define NUMA_PERIOD_SLOTS 10
1625
#define NUMA_PERIOD_THRESHOLD 7
1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645

/*
 * 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
1646 1647 1648
	 * 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
1649
	 */
1650
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683
		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
		 */
1684
		ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1685 1686 1687 1688 1689 1690 1691 1692
		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));
}

1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710
/*
 * 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 {
1711 1712
		delta = p->se.avg.load_sum / p->se.load.weight;
		*period = LOAD_AVG_MAX;
1713 1714 1715 1716 1717 1718 1719 1720
	}

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

	return delta;
}

1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767
/*
 * 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;
1768
		nodemask_t max_group = NODE_MASK_NONE;
1769 1770 1771 1772 1773 1774 1775 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
		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. */
1802 1803
		if (!max_faults)
			break;
1804 1805 1806 1807 1808
		nodes = max_group;
	}
	return nid;
}

1809 1810
static void task_numa_placement(struct task_struct *p)
{
1811 1812
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
1813
	unsigned long fault_types[2] = { 0, 0 };
1814 1815
	unsigned long total_faults;
	u64 runtime, period;
1816
	spinlock_t *group_lock = NULL;
1817

1818 1819 1820 1821 1822
	/*
	 * 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:
	 */
1823
	seq = READ_ONCE(p->mm->numa_scan_seq);
1824 1825 1826
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
1827
	p->numa_scan_period_max = task_scan_max(p);
1828

1829 1830 1831 1832
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

1833 1834 1835
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
1836
		spin_lock_irq(group_lock);
1837 1838
	}

1839 1840
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
1841 1842
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1843
		unsigned long faults = 0, group_faults = 0;
1844
		int priv;
1845

1846
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1847
			long diff, f_diff, f_weight;
1848

1849 1850 1851 1852
			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);
1853

1854
			/* Decay existing window, copy faults since last scan */
1855 1856 1857
			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;
1858

1859 1860 1861 1862 1863 1864 1865 1866
			/*
			 * 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);
1867
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1868
				   (total_faults + 1);
1869 1870
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
1871

1872 1873 1874
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
1875
			p->total_numa_faults += diff;
1876
			if (p->numa_group) {
1877 1878 1879 1880 1881 1882 1883 1884 1885
				/*
				 * 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;
1886
				p->numa_group->total_faults += diff;
1887
				group_faults += p->numa_group->faults[mem_idx];
1888
			}
1889 1890
		}

1891 1892 1893 1894
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
1895 1896 1897 1898 1899 1900 1901

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

1902 1903
	update_task_scan_period(p, fault_types[0], fault_types[1]);

1904
	if (p->numa_group) {
1905
		update_numa_active_node_mask(p->numa_group);
1906
		spin_unlock_irq(group_lock);
1907
		max_nid = preferred_group_nid(p, max_group_nid);
1908 1909
	}

1910 1911 1912 1913 1914 1915 1916
	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);
1917
	}
1918 1919
}

1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930
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);
}

1931 1932
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
1933 1934 1935 1936 1937 1938 1939 1940 1941
{
	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) +
1942
				    4*nr_node_ids*sizeof(unsigned long);
1943 1944 1945 1946 1947 1948 1949

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

		atomic_set(&grp->refcount, 1);
		spin_lock_init(&grp->lock);
1950
		grp->gid = p->pid;
1951
		/* Second half of the array tracks nids where faults happen */
1952 1953
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
1954

1955 1956
		node_set(task_node(current), grp->active_nodes);

1957
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1958
			grp->faults[i] = p->numa_faults[i];
1959

1960
		grp->total_faults = p->total_numa_faults;
1961

1962 1963 1964 1965 1966
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
1967
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
1968 1969

	if (!cpupid_match_pid(tsk, cpupid))
1970
		goto no_join;
1971 1972 1973

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
1974
		goto no_join;
1975 1976 1977

	my_grp = p->numa_group;
	if (grp == my_grp)
1978
		goto no_join;
1979 1980 1981 1982 1983 1984

	/*
	 * 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)
1985
		goto no_join;
1986 1987 1988 1989 1990

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1991
		goto no_join;
1992

1993 1994 1995 1996 1997 1998 1999
	/* 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;
2000

2001 2002 2003
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2004
	if (join && !get_numa_group(grp))
2005
		goto no_join;
2006 2007 2008 2009 2010 2011

	rcu_read_unlock();

	if (!join)
		return;

2012 2013
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2014

2015
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2016 2017
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2018
	}
2019 2020
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2021 2022 2023 2024 2025

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

	spin_unlock(&my_grp->lock);
2026
	spin_unlock_irq(&grp->lock);
2027 2028 2029 2030

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2031 2032 2033 2034 2035
	return;

no_join:
	rcu_read_unlock();
	return;
2036 2037 2038 2039 2040
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
2041
	void *numa_faults = p->numa_faults;
2042 2043
	unsigned long flags;
	int i;
2044 2045

	if (grp) {
2046
		spin_lock_irqsave(&grp->lock, flags);
2047
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2048
			grp->faults[i] -= p->numa_faults[i];
2049
		grp->total_faults -= p->total_numa_faults;
2050

2051
		grp->nr_tasks--;
2052
		spin_unlock_irqrestore(&grp->lock, flags);
2053
		RCU_INIT_POINTER(p->numa_group, NULL);
2054 2055 2056
		put_numa_group(grp);
	}

2057
	p->numa_faults = NULL;
2058
	kfree(numa_faults);
2059 2060
}

2061 2062 2063
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2064
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2065 2066
{
	struct task_struct *p = current;
2067
	bool migrated = flags & TNF_MIGRATED;
2068
	int cpu_node = task_node(current);
2069
	int local = !!(flags & TNF_FAULT_LOCAL);
2070
	int priv;
2071

2072
	if (!static_branch_likely(&sched_numa_balancing))
2073 2074
		return;

2075 2076 2077 2078
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2079
	/* Allocate buffer to track faults on a per-node basis */
2080 2081
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2082
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2083

2084 2085
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2086
			return;
2087

2088
		p->total_numa_faults = 0;
2089
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2090
	}
2091

2092 2093 2094 2095 2096 2097 2098 2099
	/*
	 * 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);
2100
		if (!priv && !(flags & TNF_NO_GROUP))
2101
			task_numa_group(p, last_cpupid, flags, &priv);
2102 2103
	}

2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114
	/*
	 * If a workload spans multiple NUMA nodes, a shared fault that
	 * occurs wholly within the set of nodes that the workload is
	 * actively using should be counted as local. This allows the
	 * scan rate to slow down when a workload has settled down.
	 */
	if (!priv && !local && p->numa_group &&
			node_isset(cpu_node, p->numa_group->active_nodes) &&
			node_isset(mem_node, p->numa_group->active_nodes))
		local = 1;

2115
	task_numa_placement(p);
2116

2117 2118 2119 2120 2121
	/*
	 * 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))
2122 2123
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
2124 2125
	if (migrated)
		p->numa_pages_migrated += pages;
2126 2127
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2128

2129 2130
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2131
	p->numa_faults_locality[local] += pages;
2132 2133
}

2134 2135
static void reset_ptenuma_scan(struct task_struct *p)
{
2136 2137 2138 2139 2140 2141 2142 2143
	/*
	 * 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:
	 */
2144
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2145 2146 2147
	p->mm->numa_scan_offset = 0;
}

2148 2149 2150 2151 2152 2153 2154 2155 2156
/*
 * 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;
2157
	struct vm_area_struct *vma;
2158
	unsigned long start, end;
2159
	unsigned long nr_pte_updates = 0;
2160
	long pages, virtpages;
2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175

	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;

2176
	if (!mm->numa_next_scan) {
2177 2178
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2179 2180
	}

2181 2182 2183 2184 2185 2186 2187
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2188 2189 2190 2191
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
		p->numa_scan_period = task_scan_min(p);
	}
2192

2193
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2194 2195 2196
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2197 2198 2199 2200 2201 2202
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2203 2204 2205
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
2206
	virtpages = pages * 8;	   /* Scan up to this much virtual space */
2207 2208
	if (!pages)
		return;
2209

2210

2211
	down_read(&mm->mmap_sem);
2212
	vma = find_vma(mm, start);
2213 2214
	if (!vma) {
		reset_ptenuma_scan(p);
2215
		start = 0;
2216 2217
		vma = mm->mmap;
	}
2218
	for (; vma; vma = vma->vm_next) {
2219
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2220
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2221
			continue;
2222
		}
2223

2224 2225 2226 2227 2228 2229 2230 2231 2232 2233
		/*
		 * 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
2234 2235 2236 2237 2238 2239
		/*
		 * 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;
2240

2241 2242 2243 2244
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2245
			nr_pte_updates = change_prot_numa(vma, start, end);
2246 2247

			/*
2248 2249 2250 2251 2252 2253
			 * 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.
2254 2255 2256
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2257
			virtpages -= (end - start) >> PAGE_SHIFT;
2258

2259
			start = end;
2260
			if (pages <= 0 || virtpages <= 0)
2261
				goto out;
2262 2263

			cond_resched();
2264
		} while (end != vma->vm_end);
2265
	}
2266

2267
out:
2268
	/*
P
Peter Zijlstra 已提交
2269 2270 2271 2272
	 * 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.
2273 2274
	 */
	if (vma)
2275
		mm->numa_scan_offset = start;
2276 2277 2278
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304
}

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

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

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

	if (now - curr->node_stamp > period) {
2305
		if (!curr->node_stamp)
2306
			curr->numa_scan_period = task_scan_min(curr);
2307
		curr->node_stamp += period;
2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318

		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)
{
}
2319 2320 2321 2322 2323 2324 2325 2326

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)
{
}
2327 2328
#endif /* CONFIG_NUMA_BALANCING */

2329 2330 2331 2332
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2333
	if (!parent_entity(se))
2334
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2335
#ifdef CONFIG_SMP
2336 2337 2338 2339 2340 2341
	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);
	}
2342
#endif
2343 2344 2345 2346 2347 2348 2349
	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);
2350
	if (!parent_entity(se))
2351
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2352 2353
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2354
		list_del_init(&se->group_node);
2355
	}
2356 2357 2358
	cfs_rq->nr_running--;
}

2359 2360
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
2361 2362 2363 2364 2365
static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
{
	long tg_weight;

	/*
2366 2367 2368
	 * 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().
2369
	 */
2370
	tg_weight = atomic_long_read(&tg->load_avg);
2371
	tg_weight -= cfs_rq->tg_load_avg_contrib;
2372
	tg_weight += cfs_rq_load_avg(cfs_rq);
2373 2374 2375 2376

	return tg_weight;
}

2377
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2378
{
2379
	long tg_weight, load, shares;
2380

2381
	tg_weight = calc_tg_weight(tg, cfs_rq);
2382
	load = cfs_rq_load_avg(cfs_rq);
2383 2384

	shares = (tg->shares * load);
2385 2386
	if (tg_weight)
		shares /= tg_weight;
2387 2388 2389 2390 2391 2392 2393 2394 2395

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

	return shares;
}
# else /* CONFIG_SMP */
2396
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2397 2398 2399 2400
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
2401 2402 2403
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
2404 2405 2406 2407
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
2408
		account_entity_dequeue(cfs_rq, se);
2409
	}
P
Peter Zijlstra 已提交
2410 2411 2412 2413 2414 2415 2416

	update_load_set(&se->load, weight);

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

2417 2418
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2419
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2420 2421 2422
{
	struct task_group *tg;
	struct sched_entity *se;
2423
	long shares;
P
Peter Zijlstra 已提交
2424 2425 2426

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
2427
	if (!se || throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
2428
		return;
2429 2430 2431 2432
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
2433
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
2434 2435 2436 2437

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
2438
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2439 2440 2441 2442
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

2443
#ifdef CONFIG_SMP
2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463
/* 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,
};

2464 2465 2466 2467 2468 2469
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481
	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
2482 2483
	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
	 * With a look-up table which covers y^n (n<PERIOD)
2484 2485 2486 2487 2488 2489
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
2490 2491
	}

2492 2493
	val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
	return val;
2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521
}

/*
 * 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];
2522 2523
}

2524 2525 2526 2527
#if (SCHED_LOAD_SHIFT - SCHED_LOAD_RESOLUTION) != 10 || SCHED_CAPACITY_SHIFT != 10
#error "load tracking assumes 2^10 as unit"
#endif

2528
#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)
2529

2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557
/*
 * 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}]
 */
2558 2559
static __always_inline int
__update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2560
		  unsigned long weight, int running, struct cfs_rq *cfs_rq)
2561
{
2562
	u64 delta, scaled_delta, periods;
2563
	u32 contrib;
2564
	unsigned int delta_w, scaled_delta_w, decayed = 0;
2565
	unsigned long scale_freq, scale_cpu;
2566

2567
	delta = now - sa->last_update_time;
2568 2569 2570 2571 2572
	/*
	 * 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) {
2573
		sa->last_update_time = now;
2574 2575 2576 2577 2578 2579 2580 2581 2582 2583
		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;
2584
	sa->last_update_time = now;
2585

2586 2587 2588
	scale_freq = arch_scale_freq_capacity(NULL, cpu);
	scale_cpu = arch_scale_cpu_capacity(NULL, cpu);

2589
	/* delta_w is the amount already accumulated against our next period */
2590
	delta_w = sa->period_contrib;
2591 2592 2593
	if (delta + delta_w >= 1024) {
		decayed = 1;

2594 2595 2596
		/* how much left for next period will start over, we don't know yet */
		sa->period_contrib = 0;

2597 2598 2599 2600 2601 2602
		/*
		 * 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;
2603
		scaled_delta_w = cap_scale(delta_w, scale_freq);
2604
		if (weight) {
2605 2606 2607 2608 2609
			sa->load_sum += weight * scaled_delta_w;
			if (cfs_rq) {
				cfs_rq->runnable_load_sum +=
						weight * scaled_delta_w;
			}
2610
		}
2611
		if (running)
2612
			sa->util_sum += scaled_delta_w * scale_cpu;
2613 2614 2615 2616 2617 2618 2619

		delta -= delta_w;

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

2620
		sa->load_sum = decay_load(sa->load_sum, periods + 1);
2621 2622 2623 2624
		if (cfs_rq) {
			cfs_rq->runnable_load_sum =
				decay_load(cfs_rq->runnable_load_sum, periods + 1);
		}
2625
		sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2626 2627

		/* Efficiently calculate \sum (1..n_period) 1024*y^i */
2628
		contrib = __compute_runnable_contrib(periods);
2629
		contrib = cap_scale(contrib, scale_freq);
2630
		if (weight) {
2631
			sa->load_sum += weight * contrib;
2632 2633 2634
			if (cfs_rq)
				cfs_rq->runnable_load_sum += weight * contrib;
		}
2635
		if (running)
2636
			sa->util_sum += contrib * scale_cpu;
2637 2638 2639
	}

	/* Remainder of delta accrued against u_0` */
2640
	scaled_delta = cap_scale(delta, scale_freq);
2641
	if (weight) {
2642
		sa->load_sum += weight * scaled_delta;
2643
		if (cfs_rq)
2644
			cfs_rq->runnable_load_sum += weight * scaled_delta;
2645
	}
2646
	if (running)
2647
		sa->util_sum += scaled_delta * scale_cpu;
2648

2649
	sa->period_contrib += delta;
2650

2651 2652
	if (decayed) {
		sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2653 2654 2655 2656
		if (cfs_rq) {
			cfs_rq->runnable_load_avg =
				div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
		}
2657
		sa->util_avg = sa->util_sum / LOAD_AVG_MAX;
2658
	}
2659

2660
	return decayed;
2661 2662
}

2663
#ifdef CONFIG_FAIR_GROUP_SCHED
2664
/*
2665 2666
 * 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).
2667
 */
2668
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2669
{
2670
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2671

2672 2673 2674
	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;
2675
	}
2676
}
2677

2678
#else /* CONFIG_FAIR_GROUP_SCHED */
2679
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2680
#endif /* CONFIG_FAIR_GROUP_SCHED */
2681

2682
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2683

2684 2685
/* 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)
2686
{
2687
	struct sched_avg *sa = &cfs_rq->avg;
2688
	int decayed;
2689

2690 2691 2692 2693
	if (atomic_long_read(&cfs_rq->removed_load_avg)) {
		long r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
		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);
2694
	}
2695

2696 2697 2698
	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);
2699
		sa->util_sum = max_t(s32, sa->util_sum - r * LOAD_AVG_MAX, 0);
2700
	}
2701

2702
	decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2703
		scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2704

2705 2706 2707 2708
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
2709

2710
	return decayed;
2711 2712
}

2713 2714
/* Update task and its cfs_rq load average */
static inline void update_load_avg(struct sched_entity *se, int update_tg)
2715
{
2716
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
2717
	u64 now = cfs_rq_clock_task(cfs_rq);
2718
	int cpu = cpu_of(rq_of(cfs_rq));
2719

2720
	/*
2721 2722
	 * 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
2723
	 */
2724
	__update_load_avg(now, cpu, &se->avg,
2725 2726
			  se->on_rq * scale_load_down(se->load.weight),
			  cfs_rq->curr == se, NULL);
2727

2728 2729
	if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
		update_tg_load_avg(cfs_rq, 0);
2730 2731
}

2732 2733
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2734 2735 2736
	if (!sched_feat(ATTACH_AGE_LOAD))
		goto skip_aging;

2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750
	/*
	 * 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.
		 */
	}

2751
skip_aging:
2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770
	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);
}

2771 2772 2773
/* 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)
2774
{
2775 2776
	struct sched_avg *sa = &se->avg;
	u64 now = cfs_rq_clock_task(cfs_rq);
2777
	int migrated, decayed;
2778

2779 2780
	migrated = !sa->last_update_time;
	if (!migrated) {
2781
		__update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2782 2783
			se->on_rq * scale_load_down(se->load.weight),
			cfs_rq->curr == se, NULL);
2784
	}
2785

2786
	decayed = update_cfs_rq_load_avg(now, cfs_rq);
2787

2788 2789 2790
	cfs_rq->runnable_load_avg += sa->load_avg;
	cfs_rq->runnable_load_sum += sa->load_sum;

2791 2792
	if (migrated)
		attach_entity_load_avg(cfs_rq, se);
2793

2794 2795
	if (decayed || migrated)
		update_tg_load_avg(cfs_rq, 0);
2796 2797
}

2798 2799 2800 2801 2802 2803 2804 2805 2806
/* 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 =
2807
		max_t(s64,  cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2808 2809
}

2810
/*
2811 2812
 * Task first catches up with cfs_rq, and then subtract
 * itself from the cfs_rq (task must be off the queue now).
2813
 */
2814
void remove_entity_load_avg(struct sched_entity *se)
2815
{
2816 2817 2818 2819 2820
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 last_update_time;

#ifndef CONFIG_64BIT
	u64 last_update_time_copy;
2821

2822 2823 2824 2825 2826 2827 2828 2829 2830
	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);
#else
	last_update_time = cfs_rq->avg.last_update_time;
#endif

2831
	__update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2832 2833
	atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
	atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2834
}
2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853

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

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

2854 2855 2856 2857 2858 2859 2860 2861 2862 2863
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;
}

2864 2865
static int idle_balance(struct rq *this_rq);

2866 2867
#else /* CONFIG_SMP */

2868 2869 2870
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) {}
2871 2872
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2873
static inline void remove_entity_load_avg(struct sched_entity *se) {}
2874

2875 2876 2877 2878 2879
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) {}

2880 2881 2882 2883 2884
static inline int idle_balance(struct rq *rq)
{
	return 0;
}

2885
#endif /* CONFIG_SMP */
2886

2887
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2888 2889
{
#ifdef CONFIG_SCHEDSTATS
2890 2891 2892 2893 2894
	struct task_struct *tsk = NULL;

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

2895
	if (se->statistics.sleep_start) {
2896
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2897 2898 2899 2900

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

2901 2902
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
2903

2904
		se->statistics.sleep_start = 0;
2905
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
2906

2907
		if (tsk) {
2908
			account_scheduler_latency(tsk, delta >> 10, 1);
2909 2910
			trace_sched_stat_sleep(tsk, delta);
		}
2911
	}
2912
	if (se->statistics.block_start) {
2913
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2914 2915 2916 2917

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

2918 2919
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
2920

2921
		se->statistics.block_start = 0;
2922
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
2923

2924
		if (tsk) {
2925
			if (tsk->in_iowait) {
2926 2927
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
2928
				trace_sched_stat_iowait(tsk, delta);
2929 2930
			}

2931 2932
			trace_sched_stat_blocked(tsk, delta);

2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943
			/*
			 * 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
2944
		}
2945 2946 2947 2948
	}
#endif
}

P
Peter Zijlstra 已提交
2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961
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
}

2962 2963 2964
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
2965
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
2966

2967 2968 2969 2970 2971 2972
	/*
	 * 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
2973
	if (initial && sched_feat(START_DEBIT))
2974
		vruntime += sched_vslice(cfs_rq, se);
2975

2976
	/* sleeps up to a single latency don't count. */
2977
	if (!initial) {
2978
		unsigned long thresh = sysctl_sched_latency;
2979

2980 2981 2982 2983 2984 2985
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
2986

2987
		vruntime -= thresh;
2988 2989
	}

2990
	/* ensure we never gain time by being placed backwards. */
2991
	se->vruntime = max_vruntime(se->vruntime, vruntime);
2992 2993
}

2994 2995
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

2996
static void
2997
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2998
{
2999 3000
	/*
	 * Update the normalized vruntime before updating min_vruntime
3001
	 * through calling update_curr().
3002
	 */
3003
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
3004 3005
		se->vruntime += cfs_rq->min_vruntime;

3006
	/*
3007
	 * Update run-time statistics of the 'current'.
3008
	 */
3009
	update_curr(cfs_rq);
3010
	enqueue_entity_load_avg(cfs_rq, se);
3011 3012
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
3013

3014
	if (flags & ENQUEUE_WAKEUP) {
3015
		place_entity(cfs_rq, se, 0);
3016
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
3017
	}
3018

3019
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
3020
	check_spread(cfs_rq, se);
3021 3022
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
3023
	se->on_rq = 1;
3024

3025
	if (cfs_rq->nr_running == 1) {
3026
		list_add_leaf_cfs_rq(cfs_rq);
3027 3028
		check_enqueue_throttle(cfs_rq);
	}
3029 3030
}

3031
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
3032
{
3033 3034
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3035
		if (cfs_rq->last != se)
3036
			break;
3037 3038

		cfs_rq->last = NULL;
3039 3040
	}
}
P
Peter Zijlstra 已提交
3041

3042 3043 3044 3045
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3046
		if (cfs_rq->next != se)
3047
			break;
3048 3049

		cfs_rq->next = NULL;
3050
	}
P
Peter Zijlstra 已提交
3051 3052
}

3053 3054 3055 3056
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3057
		if (cfs_rq->skip != se)
3058
			break;
3059 3060

		cfs_rq->skip = NULL;
3061 3062 3063
	}
}

P
Peter Zijlstra 已提交
3064 3065
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3066 3067 3068 3069 3070
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
3071 3072 3073

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
3074 3075
}

3076
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3077

3078
static void
3079
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3080
{
3081 3082 3083 3084
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
3085
	dequeue_entity_load_avg(cfs_rq, se);
3086

3087
	update_stats_dequeue(cfs_rq, se);
3088
	if (flags & DEQUEUE_SLEEP) {
P
Peter Zijlstra 已提交
3089
#ifdef CONFIG_SCHEDSTATS
3090 3091 3092 3093
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
3094
				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3095
			if (tsk->state & TASK_UNINTERRUPTIBLE)
3096
				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3097
		}
3098
#endif
P
Peter Zijlstra 已提交
3099 3100
	}

P
Peter Zijlstra 已提交
3101
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3102

3103
	if (se != cfs_rq->curr)
3104
		__dequeue_entity(cfs_rq, se);
3105
	se->on_rq = 0;
3106
	account_entity_dequeue(cfs_rq, se);
3107 3108 3109 3110 3111 3112

	/*
	 * 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.
	 */
3113
	if (!(flags & DEQUEUE_SLEEP))
3114
		se->vruntime -= cfs_rq->min_vruntime;
3115

3116 3117 3118
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3119
	update_min_vruntime(cfs_rq);
3120
	update_cfs_shares(cfs_rq);
3121 3122 3123 3124 3125
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
3126
static void
I
Ingo Molnar 已提交
3127
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3128
{
3129
	unsigned long ideal_runtime, delta_exec;
3130 3131
	struct sched_entity *se;
	s64 delta;
3132

P
Peter Zijlstra 已提交
3133
	ideal_runtime = sched_slice(cfs_rq, curr);
3134
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3135
	if (delta_exec > ideal_runtime) {
3136
		resched_curr(rq_of(cfs_rq));
3137 3138 3139 3140 3141
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152
		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;

3153 3154
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
3155

3156 3157
	if (delta < 0)
		return;
3158

3159
	if (delta > ideal_runtime)
3160
		resched_curr(rq_of(cfs_rq));
3161 3162
}

3163
static void
3164
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3165
{
3166 3167 3168 3169 3170 3171 3172 3173 3174
	/* 'current' is not kept within the tree. */
	if (se->on_rq) {
		/*
		 * Any task has to be enqueued before it get to execute on
		 * a CPU. So account for the time it spent waiting on the
		 * runqueue.
		 */
		update_stats_wait_end(cfs_rq, se);
		__dequeue_entity(cfs_rq, se);
3175
		update_load_avg(se, 1);
3176 3177
	}

3178
	update_stats_curr_start(cfs_rq, se);
3179
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
3180 3181 3182 3183 3184 3185
#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):
	 */
3186
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3187
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
3188 3189 3190
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
3191
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
3192 3193
}

3194 3195 3196
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

3197 3198 3199 3200 3201 3202 3203
/*
 * 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
 */
3204 3205
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3206
{
3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217
	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 */
3218

3219 3220 3221 3222 3223
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
3224 3225 3226 3227 3228 3229 3230 3231 3232 3233
		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;
		}

3234 3235 3236
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
3237

3238 3239 3240 3241 3242 3243
	/*
	 * 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;

3244 3245 3246 3247 3248 3249
	/*
	 * 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;

3250
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3251 3252

	return se;
3253 3254
}

3255
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3256

3257
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3258 3259 3260 3261 3262 3263
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
3264
		update_curr(cfs_rq);
3265

3266 3267 3268
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

P
Peter Zijlstra 已提交
3269
	check_spread(cfs_rq, prev);
3270
	if (prev->on_rq) {
3271
		update_stats_wait_start(cfs_rq, prev);
3272 3273
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
3274
		/* in !on_rq case, update occurred at dequeue */
3275
		update_load_avg(prev, 0);
3276
	}
3277
	cfs_rq->curr = NULL;
3278 3279
}

P
Peter Zijlstra 已提交
3280 3281
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3282 3283
{
	/*
3284
	 * Update run-time statistics of the 'current'.
3285
	 */
3286
	update_curr(cfs_rq);
3287

3288 3289 3290
	/*
	 * Ensure that runnable average is periodically updated.
	 */
3291
	update_load_avg(curr, 1);
3292
	update_cfs_shares(cfs_rq);
3293

P
Peter Zijlstra 已提交
3294 3295 3296 3297 3298
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
3299
	if (queued) {
3300
		resched_curr(rq_of(cfs_rq));
3301 3302
		return;
	}
P
Peter Zijlstra 已提交
3303 3304 3305 3306 3307 3308 3309 3310
	/*
	 * 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
3311
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
3312
		check_preempt_tick(cfs_rq, curr);
3313 3314
}

3315 3316 3317 3318 3319 3320

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

#ifdef CONFIG_CFS_BANDWIDTH
3321 3322

#ifdef HAVE_JUMP_LABEL
3323
static struct static_key __cfs_bandwidth_used;
3324 3325 3326

static inline bool cfs_bandwidth_used(void)
{
3327
	return static_key_false(&__cfs_bandwidth_used);
3328 3329
}

3330
void cfs_bandwidth_usage_inc(void)
3331
{
3332 3333 3334 3335 3336 3337
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
3338 3339 3340 3341 3342 3343 3344
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

3345 3346
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
3347 3348
#endif /* HAVE_JUMP_LABEL */

3349 3350 3351 3352 3353 3354 3355 3356
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
3357 3358 3359 3360 3361 3362

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

P
Paul Turner 已提交
3363 3364 3365 3366 3367 3368 3369
/*
 * 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
 */
3370
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381
{
	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);
}

3382 3383 3384 3385 3386
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

3387 3388 3389 3390 3391 3392
/* 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;

3393
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3394 3395
}

3396 3397
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3398 3399 3400
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
3401
	u64 amount = 0, min_amount, expires;
3402 3403 3404 3405 3406 3407 3408

	/* 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;
3409
	else {
P
Peter Zijlstra 已提交
3410
		start_cfs_bandwidth(cfs_b);
3411 3412 3413 3414 3415 3416

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
3417
	}
P
Paul Turner 已提交
3418
	expires = cfs_b->runtime_expires;
3419 3420 3421
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
3422 3423 3424 3425 3426 3427 3428
	/*
	 * 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;
3429 3430

	return cfs_rq->runtime_remaining > 0;
3431 3432
}

P
Paul Turner 已提交
3433 3434 3435 3436 3437
/*
 * 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)
3438
{
P
Paul Turner 已提交
3439 3440 3441
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
3442
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3443 3444
		return;

P
Paul Turner 已提交
3445 3446 3447 3448 3449 3450 3451 3452 3453
	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
3454 3455 3456
	 * 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
3457 3458
	 */

3459
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
3460 3461 3462 3463 3464 3465 3466 3467
		/* 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;
	}
}

3468
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
3469 3470
{
	/* dock delta_exec before expiring quota (as it could span periods) */
3471
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
3472 3473 3474
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
3475 3476
		return;

3477 3478 3479 3480 3481
	/*
	 * 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))
3482
		resched_curr(rq_of(cfs_rq));
3483 3484
}

3485
static __always_inline
3486
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3487
{
3488
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3489 3490 3491 3492 3493
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

3494 3495
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
3496
	return cfs_bandwidth_used() && cfs_rq->throttled;
3497 3498
}

3499 3500 3501
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
3502
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530
}

/*
 * 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) {
3531
		/* adjust cfs_rq_clock_task() */
3532
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3533
					     cfs_rq->throttled_clock_task;
3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544
	}
#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)];

3545 3546
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
3547
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
3548 3549 3550 3551 3552
	cfs_rq->throttle_count++;

	return 0;
}

3553
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3554 3555 3556 3557 3558
{
	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
3559
	bool empty;
3560 3561 3562

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

3563
	/* freeze hierarchy runnable averages while throttled */
3564 3565 3566
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583

	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)
3584
		sub_nr_running(rq, task_delta);
3585 3586

	cfs_rq->throttled = 1;
3587
	cfs_rq->throttled_clock = rq_clock(rq);
3588
	raw_spin_lock(&cfs_b->lock);
3589
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
3590

3591 3592 3593 3594 3595
	/*
	 * 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
3596 3597 3598 3599 3600 3601 3602 3603

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

3604 3605 3606
	raw_spin_unlock(&cfs_b->lock);
}

3607
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3608 3609 3610 3611 3612 3613 3614
{
	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;

3615
	se = cfs_rq->tg->se[cpu_of(rq)];
3616 3617

	cfs_rq->throttled = 0;
3618 3619 3620

	update_rq_clock(rq);

3621
	raw_spin_lock(&cfs_b->lock);
3622
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3623 3624 3625
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

3626 3627 3628
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646
	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)
3647
		add_nr_running(rq, task_delta);
3648 3649 3650

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
3651
		resched_curr(rq);
3652 3653 3654 3655 3656 3657
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
3658 3659
	u64 runtime;
	u64 starting_runtime = remaining;
3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689

	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();

3690
	return starting_runtime - remaining;
3691 3692
}

3693 3694 3695 3696 3697 3698 3699 3700
/*
 * 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)
{
3701
	u64 runtime, runtime_expires;
3702
	int throttled;
3703 3704 3705

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
3706
		goto out_deactivate;
3707

3708
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3709
	cfs_b->nr_periods += overrun;
3710

3711 3712 3713 3714 3715 3716
	/*
	 * 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
3717 3718 3719

	__refill_cfs_bandwidth_runtime(cfs_b);

3720 3721 3722
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
3723
		return 0;
3724 3725
	}

3726 3727 3728
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

3729 3730 3731
	runtime_expires = cfs_b->runtime_expires;

	/*
3732 3733 3734 3735 3736
	 * 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.
3737
	 */
3738 3739
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
3740 3741 3742 3743 3744 3745 3746
		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);
3747 3748

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
3749
	}
3750

3751 3752 3753 3754 3755 3756 3757
	/*
	 * 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;
3758

3759 3760 3761 3762
	return 0;

out_deactivate:
	return 1;
3763
}
3764

3765 3766 3767 3768 3769 3770 3771
/* 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;

3772 3773 3774 3775
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3776
 * hrtimer base being cleared by hrtimer_start. In the case of
3777 3778
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803
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
3804 3805 3806
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
3807 3808 3809 3810 3811 3812 3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831 3832 3833 3834 3835
}

/* 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)
{
3836 3837 3838
	if (!cfs_bandwidth_used())
		return;

3839
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854
		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 */
3855 3856 3857
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
3858
		return;
3859
	}
3860

3861
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3862
		runtime = cfs_b->runtime;
3863

3864 3865 3866 3867 3868 3869 3870 3871 3872 3873
	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)
3874
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
3875 3876 3877
	raw_spin_unlock(&cfs_b->lock);
}

3878 3879 3880 3881 3882 3883 3884
/*
 * 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)
{
3885 3886 3887
	if (!cfs_bandwidth_used())
		return;

3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902
	/* 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() */
3903
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3904
{
3905
	if (!cfs_bandwidth_used())
3906
		return false;
3907

3908
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3909
		return false;
3910 3911 3912 3913 3914 3915

	/*
	 * 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))
3916
		return true;
3917 3918

	throttle_cfs_rq(cfs_rq);
3919
	return true;
3920
}
3921 3922 3923 3924 3925

static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, slack_timer);
P
Peter Zijlstra 已提交
3926

3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938
	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;

3939
	raw_spin_lock(&cfs_b->lock);
3940
	for (;;) {
P
Peter Zijlstra 已提交
3941
		overrun = hrtimer_forward_now(timer, cfs_b->period);
3942 3943 3944 3945 3946
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
P
Peter Zijlstra 已提交
3947 3948
	if (idle)
		cfs_b->period_active = 0;
3949
	raw_spin_unlock(&cfs_b->lock);
3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961

	return idle ? HRTIMER_NORESTART : HRTIMER_RESTART;
}

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

	INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
3962
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
3963 3964 3965 3966 3967 3968 3969 3970 3971 3972 3973
	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);
}

P
Peter Zijlstra 已提交
3974
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3975
{
P
Peter Zijlstra 已提交
3976
	lockdep_assert_held(&cfs_b->lock);
3977

P
Peter Zijlstra 已提交
3978 3979 3980 3981 3982
	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);
	}
3983 3984 3985 3986
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
3987 3988 3989 3990
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

3991 3992 3993 3994
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

3995 3996 3997 3998 3999 4000 4001 4002 4003 4004 4005 4006 4007
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);
	}
}

4008
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019
{
	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
		 */
4020
		cfs_rq->runtime_remaining = 1;
4021 4022 4023 4024 4025 4026
		/*
		 * 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;

4027 4028 4029 4030 4031 4032
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
}

#else /* CONFIG_CFS_BANDWIDTH */
4033 4034
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
4035
	return rq_clock_task(rq_of(cfs_rq));
4036 4037
}

4038
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4039
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4040
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4041
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4042 4043 4044 4045 4046

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057

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;
}
4058 4059 4060 4061 4062

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) {}
4063 4064
#endif

4065 4066 4067 4068 4069
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) {}
4070
static inline void update_runtime_enabled(struct rq *rq) {}
4071
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4072 4073 4074

#endif /* CONFIG_CFS_BANDWIDTH */

4075 4076 4077 4078
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
4079 4080 4081 4082 4083 4084 4085 4086
#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);

4087
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
4088 4089 4090 4091 4092 4093
		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)
4094
				resched_curr(rq);
P
Peter Zijlstra 已提交
4095 4096
			return;
		}
4097
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
4098 4099
	}
}
4100 4101 4102 4103 4104 4105 4106 4107 4108 4109

/*
 * 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;

4110
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4111 4112 4113 4114 4115
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
4116
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
4117 4118 4119 4120
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
4121 4122 4123 4124

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
4125 4126
#endif

4127 4128 4129 4130 4131
/*
 * 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:
 */
4132
static void
4133
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4134 4135
{
	struct cfs_rq *cfs_rq;
4136
	struct sched_entity *se = &p->se;
4137 4138

	for_each_sched_entity(se) {
4139
		if (se->on_rq)
4140 4141
			break;
		cfs_rq = cfs_rq_of(se);
4142
		enqueue_entity(cfs_rq, se, flags);
4143 4144 4145 4146 4147 4148 4149 4150 4151

		/*
		 * 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;
4152
		cfs_rq->h_nr_running++;
4153

4154
		flags = ENQUEUE_WAKEUP;
4155
	}
P
Peter Zijlstra 已提交
4156

P
Peter Zijlstra 已提交
4157
	for_each_sched_entity(se) {
4158
		cfs_rq = cfs_rq_of(se);
4159
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
4160

4161 4162 4163
		if (cfs_rq_throttled(cfs_rq))
			break;

4164
		update_load_avg(se, 1);
4165
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4166 4167
	}

Y
Yuyang Du 已提交
4168
	if (!se)
4169
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
4170

4171
	hrtick_update(rq);
4172 4173
}

4174 4175
static void set_next_buddy(struct sched_entity *se);

4176 4177 4178 4179 4180
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
4181
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4182 4183
{
	struct cfs_rq *cfs_rq;
4184
	struct sched_entity *se = &p->se;
4185
	int task_sleep = flags & DEQUEUE_SLEEP;
4186 4187 4188

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
4189
		dequeue_entity(cfs_rq, se, flags);
4190 4191 4192 4193 4194 4195 4196 4197 4198

		/*
		 * 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;
4199
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4200

4201
		/* Don't dequeue parent if it has other entities besides us */
4202 4203 4204 4205 4206 4207 4208
		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));
4209 4210 4211

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
4212
			break;
4213
		}
4214
		flags |= DEQUEUE_SLEEP;
4215
	}
P
Peter Zijlstra 已提交
4216

P
Peter Zijlstra 已提交
4217
	for_each_sched_entity(se) {
4218
		cfs_rq = cfs_rq_of(se);
4219
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4220

4221 4222 4223
		if (cfs_rq_throttled(cfs_rq))
			break;

4224
		update_load_avg(se, 1);
4225
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4226 4227
	}

Y
Yuyang Du 已提交
4228
	if (!se)
4229
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
4230

4231
	hrtick_update(rq);
4232 4233
}

4234
#ifdef CONFIG_SMP
4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 4256 4257 4258 4259 4260 4261 4262 4263 4264 4265 4266 4267 4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282 4283 4284 4285 4286 4287 4288 4289 4290 4291 4292 4293 4294 4295 4296 4297 4298 4299 4300 4301 4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 4315 4316 4317 4318 4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329 4330 4331 4332 4333 4334 4335 4336 4337 4338 4339 4340 4341 4342

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

/*
 * The exact cpuload at various idx values, calculated at every tick would be
 * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
 *
 * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
 * on nth tick when cpu may be busy, then we have:
 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
 * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
 *
 * decay_load_missed() below does efficient calculation of
 * load = ((2^idx - 1) / 2^idx)^(n-1) * load
 * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
 *
 * The calculation is approximated on a 128 point scale.
 * degrade_zero_ticks is the number of ticks after which load at any
 * particular idx is approximated to be zero.
 * degrade_factor is a precomputed table, a row for each load idx.
 * Each column corresponds to degradation factor for a power of two ticks,
 * based on 128 point scale.
 * Example:
 * row 2, col 3 (=12) says that the degradation at load idx 2 after
 * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
 *
 * With this power of 2 load factors, we can degrade the load n times
 * by looking at 1 bits in n and doing as many mult/shift instead of
 * n mult/shifts needed by the exact degradation.
 */
#define DEGRADE_SHIFT		7
static const unsigned char
		degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
static const unsigned char
		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},
					{112, 98, 75, 43, 15, 1, 0},
					{120, 112, 98, 76, 45, 16, 2} };

/*
 * 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;
}

/*
 * Update rq->cpu_load[] statistics. This function is usually called every
 * scheduler tick (TICK_NSEC). With tickless idle this will not be called
 * every tick. We fix it up based on jiffies.
 */
static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
			      unsigned long pending_updates)
{
	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 */

		old_load = this_rq->cpu_load[i];
		old_load = decay_load_missed(old_load, pending_updates - 1, i);
		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);
}

4343 4344 4345 4346 4347 4348
/* 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);
}

4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368
#ifdef CONFIG_NO_HZ_COMMON
/*
 * 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.
 */
static void update_idle_cpu_load(struct rq *this_rq)
{
4369
	unsigned long curr_jiffies = READ_ONCE(jiffies);
4370
	unsigned long load = weighted_cpuload(cpu_of(this_rq));
4371 4372 4373 4374 4375 4376 4377 4378 4379 4380 4381 4382 4383 4384 4385 4386 4387 4388 4389 4390
	unsigned long pending_updates;

	/*
	 * bail if there's load or we're actually up-to-date.
	 */
	if (load || curr_jiffies == this_rq->last_load_update_tick)
		return;

	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
	this_rq->last_load_update_tick = curr_jiffies;

	__update_cpu_load(this_rq, load, pending_updates);
}

/*
 * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
 */
void update_cpu_load_nohz(void)
{
	struct rq *this_rq = this_rq();
4391
	unsigned long curr_jiffies = READ_ONCE(jiffies);
4392 4393 4394 4395 4396 4397 4398 4399 4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415
	unsigned long pending_updates;

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

	raw_spin_lock(&this_rq->lock);
	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
	if (pending_updates) {
		this_rq->last_load_update_tick = curr_jiffies;
		/*
		 * We were idle, this means load 0, the current load might be
		 * !0 due to remote wakeups and the sort.
		 */
		__update_cpu_load(this_rq, 0, pending_updates);
	}
	raw_spin_unlock(&this_rq->lock);
}
#endif /* CONFIG_NO_HZ */

/*
 * Called from scheduler_tick()
 */
void update_cpu_load_active(struct rq *this_rq)
{
4416
	unsigned long load = weighted_cpuload(cpu_of(this_rq));
4417 4418 4419 4420 4421 4422 4423
	/*
	 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
	 */
	this_rq->last_load_update_tick = jiffies;
	__update_cpu_load(this_rq, load, 1);
}

4424 4425 4426 4427 4428 4429 4430 4431 4432 4433 4434 4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445 4446 4447 4448 4449 4450 4451 4452 4453 4454 4455 4456
/*
 * 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);
}

4457
static unsigned long capacity_of(int cpu)
4458
{
4459
	return cpu_rq(cpu)->cpu_capacity;
4460 4461
}

4462 4463 4464 4465 4466
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

4467 4468 4469
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
4470
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4471
	unsigned long load_avg = weighted_cpuload(cpu);
4472 4473

	if (nr_running)
4474
		return load_avg / nr_running;
4475 4476 4477 4478

	return 0;
}

4479 4480 4481 4482 4483 4484 4485
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.
	 */
4486
	if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4487
		current->wakee_flips >>= 1;
4488 4489 4490 4491 4492 4493 4494 4495
		current->wakee_flip_decay_ts = jiffies;
	}

	if (current->last_wakee != p) {
		current->last_wakee = p;
		current->wakee_flips++;
	}
}
4496

4497
static void task_waking_fair(struct task_struct *p)
4498 4499 4500
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
4501 4502 4503 4504
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
4505

4506 4507 4508 4509 4510 4511 4512 4513
	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
4514

4515
	se->vruntime -= min_vruntime;
4516
	record_wakee(p);
4517 4518
}

4519
#ifdef CONFIG_FAIR_GROUP_SCHED
4520 4521 4522 4523 4524 4525
/*
 * 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.
4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550 4551 4552 4553 4554 4555 4556 4557 4558 4559 4560 4561 4562 4563 4564 4565 4566 4567 4568
 *
 * 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.
4569
 */
P
Peter Zijlstra 已提交
4570
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4571
{
P
Peter Zijlstra 已提交
4572
	struct sched_entity *se = tg->se[cpu];
4573

4574
	if (!tg->parent)	/* the trivial, non-cgroup case */
4575 4576
		return wl;

P
Peter Zijlstra 已提交
4577
	for_each_sched_entity(se) {
4578
		long w, W;
P
Peter Zijlstra 已提交
4579

4580
		tg = se->my_q->tg;
4581

4582 4583 4584 4585
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
4586

4587 4588 4589
		/*
		 * w = rw_i + @wl
		 */
4590
		w = cfs_rq_load_avg(se->my_q) + wl;
4591

4592 4593 4594 4595
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
4596
			wl = (w * (long)tg->shares) / W;
4597 4598
		else
			wl = tg->shares;
4599

4600 4601 4602 4603 4604
		/*
		 * 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().
		 */
4605 4606
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
4607 4608 4609 4610

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
4611
		wl -= se->avg.load_avg;
4612 4613 4614 4615 4616 4617 4618 4619

		/*
		 * 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
4620 4621
		wg = 0;
	}
4622

P
Peter Zijlstra 已提交
4623
	return wl;
4624 4625
}
#else
P
Peter Zijlstra 已提交
4626

4627
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
P
Peter Zijlstra 已提交
4628
{
4629
	return wl;
4630
}
P
Peter Zijlstra 已提交
4631

4632 4633
#endif

M
Mike Galbraith 已提交
4634 4635 4636 4637 4638 4639 4640 4641 4642 4643 4644 4645
/*
 * 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.
 */
4646 4647
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
4648 4649
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
4650
	int factor = this_cpu_read(sd_llc_size);
4651

M
Mike Galbraith 已提交
4652 4653 4654 4655 4656
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
4657 4658
}

4659
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4660
{
4661
	s64 this_load, load;
4662
	s64 this_eff_load, prev_eff_load;
4663 4664
	int idx, this_cpu, prev_cpu;
	struct task_group *tg;
4665
	unsigned long weight;
4666
	int balanced;
4667

4668 4669 4670 4671 4672
	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);
4673

4674 4675 4676 4677 4678
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
4679 4680
	if (sync) {
		tg = task_group(current);
4681
		weight = current->se.avg.load_avg;
4682

4683
		this_load += effective_load(tg, this_cpu, -weight, -weight);
4684 4685
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
4686

4687
	tg = task_group(p);
4688
	weight = p->se.avg.load_avg;
4689

4690 4691
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4692 4693 4694
	 * 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.
4695 4696 4697 4698
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
4699 4700
	this_eff_load = 100;
	this_eff_load *= capacity_of(prev_cpu);
4701

4702 4703
	prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= capacity_of(this_cpu);
4704

4705
	if (this_load > 0) {
4706 4707 4708 4709
		this_eff_load *= this_load +
			effective_load(tg, this_cpu, weight, weight);

		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4710
	}
4711

4712
	balanced = this_eff_load <= prev_eff_load;
4713

4714
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4715

4716 4717
	if (!balanced)
		return 0;
4718

4719 4720 4721 4722
	schedstat_inc(sd, ttwu_move_affine);
	schedstat_inc(p, se.statistics.nr_wakeups_affine);

	return 1;
4723 4724
}

4725 4726 4727 4728 4729
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
4730
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4731
		  int this_cpu, int sd_flag)
4732
{
4733
	struct sched_group *idlest = NULL, *group = sd->groups;
4734
	unsigned long min_load = ULONG_MAX, this_load = 0;
4735
	int load_idx = sd->forkexec_idx;
4736
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
4737

4738 4739 4740
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

4741 4742 4743 4744
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
4745

4746 4747
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
4748
					tsk_cpus_allowed(p)))
4749 4750 4751 4752 4753 4754 4755 4756 4757 4758 4759 4760 4761 4762 4763 4764 4765 4766
			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;
		}

4767
		/* Adjust by relative CPU capacity of the group */
4768
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4769 4770 4771 4772 4773 4774 4775 4776 4777 4778 4779 4780 4781 4782 4783 4784 4785 4786 4787 4788 4789

		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;
4790 4791 4792 4793
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
4794 4795 4796
	int i;

	/* Traverse only the allowed CPUs */
4797
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4798 4799 4800 4801 4802 4803 4804 4805 4806 4807 4808 4809 4810 4811 4812 4813 4814 4815 4816 4817 4818 4819
		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;
			}
4820
		} else if (shallowest_idle_cpu == -1) {
4821 4822 4823 4824 4825
			load = weighted_cpuload(i);
			if (load < min_load || (load == min_load && i == this_cpu)) {
				min_load = load;
				least_loaded_cpu = i;
			}
4826 4827 4828
		}
	}

4829
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
4830
}
4831

4832 4833 4834
/*
 * Try and locate an idle CPU in the sched_domain.
 */
4835
static int select_idle_sibling(struct task_struct *p, int target)
4836
{
4837
	struct sched_domain *sd;
4838
	struct sched_group *sg;
4839
	int i = task_cpu(p);
4840

4841 4842
	if (idle_cpu(target))
		return target;
4843 4844

	/*
4845
	 * If the prevous cpu is cache affine and idle, don't be stupid.
4846
	 */
4847 4848
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
4849 4850

	/*
4851
	 * Otherwise, iterate the domains and find an elegible idle cpu.
4852
	 */
4853
	sd = rcu_dereference(per_cpu(sd_llc, target));
4854
	for_each_lower_domain(sd) {
4855 4856 4857 4858 4859 4860 4861
		sg = sd->groups;
		do {
			if (!cpumask_intersects(sched_group_cpus(sg),
						tsk_cpus_allowed(p)))
				goto next;

			for_each_cpu(i, sched_group_cpus(sg)) {
4862
				if (i == target || !idle_cpu(i))
4863 4864
					goto next;
			}
4865

4866 4867 4868 4869 4870 4871 4872 4873
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
4874 4875
	return target;
}
4876

4877
/*
4878
 * cpu_util returns the amount of capacity of a CPU that is used by CFS
4879
 * tasks. The unit of the return value must be the one of capacity so we can
4880 4881
 * compare the utilization with the capacity of the CPU that is available for
 * CFS task (ie cpu_capacity).
4882 4883 4884 4885 4886 4887 4888 4889 4890 4891 4892 4893 4894 4895 4896 4897 4898 4899 4900 4901
 *
 * 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).
4902
 */
4903
static int cpu_util(int cpu)
4904
{
4905
	unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
4906 4907
	unsigned long capacity = capacity_orig_of(cpu);

4908
	return (util >= capacity) ? capacity : util;
4909
}
4910

4911
/*
4912 4913 4914
 * 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.
4915
 *
4916 4917
 * 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.
4918
 *
4919
 * Returns the target cpu number.
4920 4921 4922
 *
 * preempt must be disabled.
 */
4923
static int
4924
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
4925
{
4926
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
4927
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
4928
	int new_cpu = prev_cpu;
4929
	int want_affine = 0;
4930
	int sync = wake_flags & WF_SYNC;
4931

4932
	if (sd_flag & SD_BALANCE_WAKE)
M
Mike Galbraith 已提交
4933
		want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
4934

4935
	rcu_read_lock();
4936
	for_each_domain(cpu, tmp) {
4937
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
4938
			break;
4939

4940
		/*
4941 4942
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
4943
		 */
4944 4945 4946
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
4947
			break;
4948
		}
4949

4950
		if (tmp->flags & sd_flag)
4951
			sd = tmp;
M
Mike Galbraith 已提交
4952 4953
		else if (!want_affine)
			break;
4954 4955
	}

M
Mike Galbraith 已提交
4956 4957 4958 4959
	if (affine_sd) {
		sd = NULL; /* Prefer wake_affine over balance flags */
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
			new_cpu = cpu;
4960
	}
4961

M
Mike Galbraith 已提交
4962 4963 4964 4965 4966
	if (!sd) {
		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
			new_cpu = select_idle_sibling(p, new_cpu);

	} else while (sd) {
4967
		struct sched_group *group;
4968
		int weight;
4969

4970
		if (!(sd->flags & sd_flag)) {
4971 4972 4973
			sd = sd->child;
			continue;
		}
4974

4975
		group = find_idlest_group(sd, p, cpu, sd_flag);
4976 4977 4978 4979
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
4980

4981
		new_cpu = find_idlest_cpu(group, p, cpu);
4982 4983 4984 4985
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
4986
		}
4987 4988 4989

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
4990
		weight = sd->span_weight;
4991 4992
		sd = NULL;
		for_each_domain(cpu, tmp) {
4993
			if (weight <= tmp->span_weight)
4994
				break;
4995
			if (tmp->flags & sd_flag)
4996 4997 4998
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
4999
	}
5000
	rcu_read_unlock();
5001

5002
	return new_cpu;
5003
}
5004 5005 5006 5007 5008 5009 5010

/*
 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and
 * cfs_rq_of(p) references at time of call are still valid and identify the
 * previous cpu.  However, the caller only guarantees p->pi_lock is held; no
 * other assumptions, including the state of rq->lock, should be made.
 */
5011
static void migrate_task_rq_fair(struct task_struct *p, int next_cpu)
5012
{
5013
	/*
5014 5015 5016 5017 5018
	 * 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.
5019
	 */
5020 5021 5022 5023
	remove_entity_load_avg(&p->se);

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
5024 5025

	/* We have migrated, no longer consider this task hot */
5026
	p->se.exec_start = 0;
5027
}
5028 5029 5030 5031 5032

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
5033 5034
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
5035 5036
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
5037 5038 5039 5040
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
5041 5042
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
5043 5044 5045 5046 5047 5048 5049 5050 5051
	 *
	 * 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.
5052
	 */
5053
	return calc_delta_fair(gran, se);
5054 5055
}

5056 5057 5058 5059 5060 5061 5062 5063 5064 5065 5066 5067 5068 5069 5070 5071 5072 5073 5074 5075 5076 5077
/*
 * 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
5078
	gran = wakeup_gran(curr, se);
5079 5080 5081 5082 5083 5084
	if (vdiff > gran)
		return 1;

	return 0;
}

5085 5086
static void set_last_buddy(struct sched_entity *se)
{
5087 5088 5089 5090 5091
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
5092 5093 5094 5095
}

static void set_next_buddy(struct sched_entity *se)
{
5096 5097 5098 5099 5100
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
5101 5102
}

5103 5104
static void set_skip_buddy(struct sched_entity *se)
{
5105 5106
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
5107 5108
}

5109 5110 5111
/*
 * Preempt the current task with a newly woken task if needed:
 */
5112
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5113 5114
{
	struct task_struct *curr = rq->curr;
5115
	struct sched_entity *se = &curr->se, *pse = &p->se;
5116
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5117
	int scale = cfs_rq->nr_running >= sched_nr_latency;
5118
	int next_buddy_marked = 0;
5119

I
Ingo Molnar 已提交
5120 5121 5122
	if (unlikely(se == pse))
		return;

5123
	/*
5124
	 * This is possible from callers such as attach_tasks(), in which we
5125 5126 5127 5128 5129 5130 5131
	 * 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;

5132
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
5133
		set_next_buddy(pse);
5134 5135
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
5136

5137 5138 5139
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
5140 5141 5142 5143 5144 5145
	 *
	 * 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.
5146 5147 5148 5149
	 */
	if (test_tsk_need_resched(curr))
		return;

5150 5151 5152 5153 5154
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

5155
	/*
5156 5157
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
5158
	 */
5159
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5160
		return;
5161

5162
	find_matching_se(&se, &pse);
5163
	update_curr(cfs_rq_of(se));
5164
	BUG_ON(!pse);
5165 5166 5167 5168 5169 5170 5171
	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);
5172
		goto preempt;
5173
	}
5174

5175
	return;
5176

5177
preempt:
5178
	resched_curr(rq);
5179 5180 5181 5182 5183 5184 5185 5186 5187 5188 5189 5190 5191 5192
	/*
	 * 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);
5193 5194
}

5195 5196
static struct task_struct *
pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5197 5198 5199
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
5200
	struct task_struct *p;
5201
	int new_tasks;
5202

5203
again:
5204 5205
#ifdef CONFIG_FAIR_GROUP_SCHED
	if (!cfs_rq->nr_running)
5206
		goto idle;
5207

5208
	if (prev->sched_class != &fair_sched_class)
5209 5210 5211 5212 5213 5214 5215 5216 5217 5218 5219 5220 5221 5222 5223 5224 5225 5226 5227
		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.
		 */
5228 5229 5230 5231 5232
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
5233

5234 5235 5236 5237 5238 5239 5240 5241 5242
			/*
			 * 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;
		}
5243 5244 5245 5246 5247 5248 5249 5250 5251 5252 5253 5254 5255 5256 5257 5258 5259 5260 5261 5262 5263 5264 5265 5266 5267 5268 5269 5270 5271 5272 5273 5274 5275 5276 5277 5278 5279 5280 5281 5282

		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
5283

5284
	if (!cfs_rq->nr_running)
5285
		goto idle;
5286

5287
	put_prev_task(rq, prev);
5288

5289
	do {
5290
		se = pick_next_entity(cfs_rq, NULL);
5291
		set_next_entity(cfs_rq, se);
5292 5293 5294
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
5295
	p = task_of(se);
5296

5297 5298
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
5299 5300

	return p;
5301 5302

idle:
5303 5304 5305 5306 5307 5308 5309
	/*
	 * 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);
5310
	new_tasks = idle_balance(rq);
5311
	lockdep_pin_lock(&rq->lock);
5312 5313 5314 5315 5316
	/*
	 * 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.
	 */
5317
	if (new_tasks < 0)
5318 5319
		return RETRY_TASK;

5320
	if (new_tasks > 0)
5321 5322 5323
		goto again;

	return NULL;
5324 5325 5326 5327 5328
}

/*
 * Account for a descheduled task:
 */
5329
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5330 5331 5332 5333 5334 5335
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5336
		put_prev_entity(cfs_rq, se);
5337 5338 5339
	}
}

5340 5341 5342 5343 5344 5345 5346 5347 5348 5349 5350 5351 5352 5353 5354 5355 5356 5357 5358 5359 5360 5361 5362 5363 5364
/*
 * 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);
5365 5366 5367 5368 5369
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
5370
		rq_clock_skip_update(rq, true);
5371 5372 5373 5374 5375
	}

	set_skip_buddy(se);
}

5376 5377 5378 5379
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

5380 5381
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5382 5383 5384 5385 5386 5387 5388 5389 5390 5391
		return false;

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

	yield_task_fair(rq);

	return true;
}

5392
#ifdef CONFIG_SMP
5393
/**************************************************
P
Peter Zijlstra 已提交
5394 5395 5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416
 * Fair scheduling class load-balancing methods.
 *
 * BASICS
 *
 * The purpose of load-balancing is to achieve the same basic fairness the
 * per-cpu scheduler provides, namely provide a proportional amount of compute
 * time to each task. This is expressed in the following equation:
 *
 *   W_i,n/P_i == W_j,n/P_j for all i,j                               (1)
 *
 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight
 * W_i,0 is defined as:
 *
 *   W_i,0 = \Sum_j w_i,j                                             (2)
 *
 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight
 * is derived from the nice value as per prio_to_weight[].
 *
 * The weight average is an exponential decay average of the instantaneous
 * weight:
 *
 *   W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0               (3)
 *
5417
 * C_i is the compute capacity of cpu i, typically it is the
P
Peter Zijlstra 已提交
5418 5419 5420 5421 5422 5423
 * 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):
 *
5424
 *   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
5425 5426 5427 5428 5429 5430 5431 5432 5433 5434 5435 5436 5437 5438 5439 5440 5441 5442 5443 5444 5445 5446 5447 5448 5449 5450 5451 5452 5453 5454 5455 5456 5457 5458 5459 5460 5461 5462 5463 5464 5465 5466 5467 5468 5469 5470 5471 5472 5473 5474 5475 5476 5477 5478 5479 5480 5481 5482 5483 5484 5485 5486 5487 5488 5489 5490 5491 5492 5493 5494 5495 5496 5497 5498 5499 5500 5501 5502 5503 5504 5505 5506 5507 5508 5509
 *
 * 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.]
 */ 
5510

5511 5512
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

5513 5514
enum fbq_type { regular, remote, all };

5515
#define LBF_ALL_PINNED	0x01
5516
#define LBF_NEED_BREAK	0x02
5517 5518
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
5519 5520 5521 5522 5523

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
5524
	int			src_cpu;
5525 5526 5527 5528

	int			dst_cpu;
	struct rq		*dst_rq;

5529 5530
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
5531
	enum cpu_idle_type	idle;
5532
	long			imbalance;
5533 5534 5535
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

5536
	unsigned int		flags;
5537 5538 5539 5540

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
5541 5542

	enum fbq_type		fbq_type;
5543
	struct list_head	tasks;
5544 5545
};

5546 5547 5548
/*
 * Is this task likely cache-hot:
 */
5549
static int task_hot(struct task_struct *p, struct lb_env *env)
5550 5551 5552
{
	s64 delta;

5553 5554
	lockdep_assert_held(&env->src_rq->lock);

5555 5556 5557 5558 5559 5560 5561 5562 5563
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
5564
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5565 5566 5567 5568 5569 5570 5571 5572 5573
			(&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;

5574
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5575 5576 5577 5578

	return delta < (s64)sysctl_sched_migration_cost;
}

5579
#ifdef CONFIG_NUMA_BALANCING
5580
/*
5581 5582 5583
 * 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.
5584
 */
5585
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5586
{
5587
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
5588
	unsigned long src_faults, dst_faults;
5589 5590
	int src_nid, dst_nid;

5591
	if (!static_branch_likely(&sched_numa_balancing))
5592 5593
		return -1;

5594
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5595
		return -1;
5596 5597 5598 5599

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

5600
	if (src_nid == dst_nid)
5601
		return -1;
5602

5603 5604 5605 5606 5607 5608 5609
	/* 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;
	}
5610

5611 5612
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
5613
		return 0;
5614

5615 5616 5617 5618 5619 5620
	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);
5621 5622
	}

5623
	return dst_faults < src_faults;
5624 5625
}

5626
#else
5627
static inline int migrate_degrades_locality(struct task_struct *p,
5628 5629
					     struct lb_env *env)
{
5630
	return -1;
5631
}
5632 5633
#endif

5634 5635 5636 5637
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
5638
int can_migrate_task(struct task_struct *p, struct lb_env *env)
5639
{
5640
	int tsk_cache_hot;
5641 5642 5643

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

5644 5645
	/*
	 * We do not migrate tasks that are:
5646
	 * 1) throttled_lb_pair, or
5647
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5648 5649
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
5650
	 */
5651 5652 5653
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

5654
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5655
		int cpu;
5656

5657
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5658

5659 5660
		env->flags |= LBF_SOME_PINNED;

5661 5662 5663 5664 5665 5666 5667 5668
		/*
		 * 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.
		 */
5669
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5670 5671
			return 0;

5672 5673 5674
		/* 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))) {
5675
				env->flags |= LBF_DST_PINNED;
5676 5677 5678
				env->new_dst_cpu = cpu;
				break;
			}
5679
		}
5680

5681 5682
		return 0;
	}
5683 5684

	/* Record that we found atleast one task that could run on dst_cpu */
5685
	env->flags &= ~LBF_ALL_PINNED;
5686

5687
	if (task_running(env->src_rq, p)) {
5688
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5689 5690 5691 5692 5693
		return 0;
	}

	/*
	 * Aggressive migration if:
5694 5695 5696
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
5697
	 */
5698 5699 5700
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
5701

5702
	if (tsk_cache_hot <= 0 ||
5703
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5704
		if (tsk_cache_hot == 1) {
5705 5706 5707
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
			schedstat_inc(p, se.statistics.nr_forced_migrations);
		}
5708 5709 5710
		return 1;
	}

Z
Zhang Hang 已提交
5711 5712
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
5713 5714
}

5715
/*
5716 5717 5718 5719 5720 5721 5722 5723 5724 5725 5726
 * detach_task() -- detach the task for the migration specified in env
 */
static void detach_task(struct task_struct *p, struct lb_env *env)
{
	lockdep_assert_held(&env->src_rq->lock);

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

5727
/*
5728
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5729 5730
 * part of active balancing operations within "domain".
 *
5731
 * Returns a task if successful and NULL otherwise.
5732
 */
5733
static struct task_struct *detach_one_task(struct lb_env *env)
5734 5735 5736
{
	struct task_struct *p, *n;

5737 5738
	lockdep_assert_held(&env->src_rq->lock);

5739 5740 5741
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
5742

5743
		detach_task(p, env);
5744

5745
		/*
5746
		 * Right now, this is only the second place where
5747
		 * lb_gained[env->idle] is updated (other is detach_tasks)
5748
		 * so we can safely collect stats here rather than
5749
		 * inside detach_tasks().
5750 5751
		 */
		schedstat_inc(env->sd, lb_gained[env->idle]);
5752
		return p;
5753
	}
5754
	return NULL;
5755 5756
}

5757 5758
static const unsigned int sched_nr_migrate_break = 32;

5759
/*
5760 5761
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
5762
 *
5763
 * Returns number of detached tasks if successful and 0 otherwise.
5764
 */
5765
static int detach_tasks(struct lb_env *env)
5766
{
5767 5768
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
5769
	unsigned long load;
5770 5771 5772
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
5773

5774
	if (env->imbalance <= 0)
5775
		return 0;
5776

5777
	while (!list_empty(tasks)) {
5778 5779 5780 5781 5782 5783 5784
		/*
		 * 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;

5785
		p = list_first_entry(tasks, struct task_struct, se.group_node);
5786

5787 5788
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
5789
		if (env->loop > env->loop_max)
5790
			break;
5791 5792

		/* take a breather every nr_migrate tasks */
5793
		if (env->loop > env->loop_break) {
5794
			env->loop_break += sched_nr_migrate_break;
5795
			env->flags |= LBF_NEED_BREAK;
5796
			break;
5797
		}
5798

5799
		if (!can_migrate_task(p, env))
5800 5801 5802
			goto next;

		load = task_h_load(p);
5803

5804
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5805 5806
			goto next;

5807
		if ((load / 2) > env->imbalance)
5808
			goto next;
5809

5810 5811 5812 5813
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
5814
		env->imbalance -= load;
5815 5816

#ifdef CONFIG_PREEMPT
5817 5818
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
5819
		 * kernels will stop after the first task is detached to minimize
5820 5821
		 * the critical section.
		 */
5822
		if (env->idle == CPU_NEWLY_IDLE)
5823
			break;
5824 5825
#endif

5826 5827 5828 5829
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
5830
		if (env->imbalance <= 0)
5831
			break;
5832 5833 5834

		continue;
next:
5835
		list_move_tail(&p->se.group_node, tasks);
5836
	}
5837

5838
	/*
5839 5840 5841
	 * 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().
5842
	 */
5843
	schedstat_add(env->sd, lb_gained[env->idle], detached);
5844

5845 5846 5847 5848 5849 5850 5851 5852 5853 5854 5855 5856 5857 5858 5859 5860 5861 5862 5863 5864 5865 5866 5867 5868 5869 5870 5871 5872 5873 5874 5875 5876 5877 5878 5879 5880 5881 5882 5883 5884 5885
	return detached;
}

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

	BUG_ON(task_rq(p) != rq);
	p->on_rq = TASK_ON_RQ_QUEUED;
	activate_task(rq, p, 0);
	check_preempt_curr(rq, p, 0);
}

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

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

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

	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
		list_del_init(&p->se.group_node);
5886

5887 5888 5889 5890
		attach_task(env->dst_rq, p);
	}

	raw_spin_unlock(&env->dst_rq->lock);
5891 5892
}

P
Peter Zijlstra 已提交
5893
#ifdef CONFIG_FAIR_GROUP_SCHED
5894
static void update_blocked_averages(int cpu)
5895 5896
{
	struct rq *rq = cpu_rq(cpu);
5897 5898
	struct cfs_rq *cfs_rq;
	unsigned long flags;
5899

5900 5901
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
5902

5903 5904 5905 5906
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
5907
	for_each_leaf_cfs_rq(rq, cfs_rq) {
5908 5909 5910
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
5911

5912 5913 5914
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
			update_tg_load_avg(cfs_rq, 0);
	}
5915
	raw_spin_unlock_irqrestore(&rq->lock, flags);
5916 5917
}

5918
/*
5919
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5920 5921 5922
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
5923
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
5924
{
5925 5926
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
5927
	unsigned long now = jiffies;
5928
	unsigned long load;
5929

5930
	if (cfs_rq->last_h_load_update == now)
5931 5932
		return;

5933 5934 5935 5936 5937 5938 5939
	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;
	}
5940

5941
	if (!se) {
5942
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
5943 5944 5945 5946 5947
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
5948 5949
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
5950 5951 5952 5953
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
5954 5955
}

5956
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
5957
{
5958
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
5959

5960
	update_cfs_rq_h_load(cfs_rq);
5961
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
5962
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
5963 5964
}
#else
5965
static inline void update_blocked_averages(int cpu)
5966
{
5967 5968 5969 5970 5971 5972 5973 5974
	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);
5975 5976
}

5977
static unsigned long task_h_load(struct task_struct *p)
5978
{
5979
	return p->se.avg.load_avg;
5980
}
P
Peter Zijlstra 已提交
5981
#endif
5982 5983

/********** Helpers for find_busiest_group ************************/
5984 5985 5986 5987 5988 5989 5990

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

5991 5992 5993 5994 5995 5996 5997
/*
 * 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
5998
	unsigned long load_per_task;
5999
	unsigned long group_capacity;
6000
	unsigned long group_util; /* Total utilization of the group */
6001 6002 6003
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
6004
	enum group_type group_type;
6005
	int group_no_capacity;
6006 6007 6008 6009
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
6010 6011
};

J
Joonsoo Kim 已提交
6012 6013 6014 6015 6016 6017 6018 6019
/*
 * 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 */
6020
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
6021 6022 6023
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
6024
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
6025 6026
};

6027 6028 6029 6030 6031 6032 6033 6034 6035 6036 6037 6038
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,
6039
		.total_capacity = 0UL,
6040 6041
		.busiest_stat = {
			.avg_load = 0UL,
6042 6043
			.sum_nr_running = 0,
			.group_type = group_other,
6044 6045 6046 6047
		},
	};
}

6048 6049 6050
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
6051
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6052 6053
 *
 * Return: The load index.
6054 6055 6056 6057 6058 6059 6060 6061 6062 6063 6064 6065 6066 6067 6068 6069 6070 6071 6072 6073 6074 6075
 */
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;
}

6076
static unsigned long scale_rt_capacity(int cpu)
6077 6078
{
	struct rq *rq = cpu_rq(cpu);
6079
	u64 total, used, age_stamp, avg;
6080
	s64 delta;
6081

6082 6083 6084 6085
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
6086 6087
	age_stamp = READ_ONCE(rq->age_stamp);
	avg = READ_ONCE(rq->rt_avg);
6088
	delta = __rq_clock_broken(rq) - age_stamp;
6089

6090 6091 6092 6093
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
6094

6095
	used = div_u64(avg, total);
6096

6097 6098
	if (likely(used < SCHED_CAPACITY_SCALE))
		return SCHED_CAPACITY_SCALE - used;
6099

6100
	return 1;
6101 6102
}

6103
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6104
{
6105
	unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);
6106 6107
	struct sched_group *sdg = sd->groups;

6108
	cpu_rq(cpu)->cpu_capacity_orig = capacity;
6109

6110
	capacity *= scale_rt_capacity(cpu);
6111
	capacity >>= SCHED_CAPACITY_SHIFT;
6112

6113 6114
	if (!capacity)
		capacity = 1;
6115

6116 6117
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
6118 6119
}

6120
void update_group_capacity(struct sched_domain *sd, int cpu)
6121 6122 6123
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
6124
	unsigned long capacity;
6125 6126 6127 6128
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
6129
	sdg->sgc->next_update = jiffies + interval;
6130 6131

	if (!child) {
6132
		update_cpu_capacity(sd, cpu);
6133 6134 6135
		return;
	}

6136
	capacity = 0;
6137

P
Peter Zijlstra 已提交
6138 6139 6140 6141 6142 6143
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

6144
		for_each_cpu(cpu, sched_group_cpus(sdg)) {
6145
			struct sched_group_capacity *sgc;
6146
			struct rq *rq = cpu_rq(cpu);
6147

6148
			/*
6149
			 * build_sched_domains() -> init_sched_groups_capacity()
6150 6151 6152
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
6153 6154
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
6155
			 *
6156
			 * This avoids capacity from being 0 and
6157 6158 6159
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
6160
				capacity += capacity_of(cpu);
6161 6162
				continue;
			}
6163

6164 6165
			sgc = rq->sd->groups->sgc;
			capacity += sgc->capacity;
6166
		}
P
Peter Zijlstra 已提交
6167 6168 6169 6170 6171 6172 6173 6174
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
6175
			capacity += group->sgc->capacity;
P
Peter Zijlstra 已提交
6176 6177 6178
			group = group->next;
		} while (group != child->groups);
	}
6179

6180
	sdg->sgc->capacity = capacity;
6181 6182
}

6183
/*
6184 6185 6186
 * 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
6187 6188
 */
static inline int
6189
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6190
{
6191 6192
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
6193 6194
}

6195 6196 6197 6198 6199 6200 6201 6202 6203 6204 6205 6206 6207 6208 6209 6210
/*
 * 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
6211 6212
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
6213 6214
 *
 * When this is so detected; this group becomes a candidate for busiest; see
6215
 * update_sd_pick_busiest(). And calculate_imbalance() and
6216
 * find_busiest_group() avoid some of the usual balance conditions to allow it
6217 6218 6219 6220 6221 6222 6223
 * 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.
 */

6224
static inline int sg_imbalanced(struct sched_group *group)
6225
{
6226
	return group->sgc->imbalance;
6227 6228
}

6229
/*
6230 6231 6232
 * 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
6233 6234
 * smaller than the number of CPUs or if the utilization is lower than the
 * available capacity for CFS tasks.
6235 6236 6237 6238 6239
 * 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.
6240
 */
6241 6242
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6243
{
6244 6245
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
6246

6247
	if ((sgs->group_capacity * 100) >
6248
			(sgs->group_util * env->sd->imbalance_pct))
6249
		return true;
6250

6251 6252 6253 6254 6255 6256 6257 6258 6259 6260 6261 6262 6263 6264 6265 6266
	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;
6267

6268
	if ((sgs->group_capacity * 100) <
6269
			(sgs->group_util * env->sd->imbalance_pct))
6270
		return true;
6271

6272
	return false;
6273 6274
}

6275 6276 6277
static enum group_type group_classify(struct lb_env *env,
		struct sched_group *group,
		struct sg_lb_stats *sgs)
6278
{
6279
	if (sgs->group_no_capacity)
6280 6281 6282 6283 6284 6285 6286 6287
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

6288 6289
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6290
 * @env: The load balancing environment.
6291 6292 6293 6294
 * @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.
6295
 * @overload: Indicate more than one runnable task for any CPU.
6296
 */
6297 6298
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
6299 6300
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
6301
{
6302
	unsigned long load;
6303
	int i;
6304

6305 6306
	memset(sgs, 0, sizeof(*sgs));

6307
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6308 6309 6310
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
6311
		if (local_group)
6312
			load = target_load(i, load_idx);
6313
		else
6314 6315 6316
			load = source_load(i, load_idx);

		sgs->group_load += load;
6317
		sgs->group_util += cpu_util(i);
6318
		sgs->sum_nr_running += rq->cfs.h_nr_running;
6319 6320 6321 6322

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

6323 6324 6325 6326
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
6327
		sgs->sum_weighted_load += weighted_cpuload(i);
6328 6329
		if (idle_cpu(i))
			sgs->idle_cpus++;
6330 6331
	}

6332 6333
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
6334
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6335

6336
	if (sgs->sum_nr_running)
6337
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6338

6339
	sgs->group_weight = group->group_weight;
6340

6341 6342
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
	sgs->group_type = group_classify(env, group, sgs);
6343 6344
}

6345 6346
/**
 * update_sd_pick_busiest - return 1 on busiest group
6347
 * @env: The load balancing environment.
6348 6349
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
6350
 * @sgs: sched_group statistics
6351 6352 6353
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
6354 6355 6356
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
6357
 */
6358
static bool update_sd_pick_busiest(struct lb_env *env,
6359 6360
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
6361
				   struct sg_lb_stats *sgs)
6362
{
6363
	struct sg_lb_stats *busiest = &sds->busiest_stat;
6364

6365
	if (sgs->group_type > busiest->group_type)
6366 6367
		return true;

6368 6369 6370 6371 6372 6373 6374 6375
	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))
6376 6377 6378 6379 6380 6381 6382
		return true;

	/*
	 * ASYM_PACKING needs to move all the work to the lowest
	 * numbered CPUs in the group, therefore mark all groups
	 * higher than ourself as busy.
	 */
6383
	if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6384 6385 6386 6387 6388 6389 6390 6391 6392 6393
		if (!sds->busiest)
			return true;

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

	return false;
}

6394 6395 6396 6397 6398 6399 6400 6401 6402 6403 6404 6405 6406 6407 6408 6409 6410 6411 6412 6413 6414 6415 6416 6417 6418 6419 6420 6421 6422 6423
#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 */

6424
/**
6425
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6426
 * @env: The load balancing environment.
6427 6428
 * @sds: variable to hold the statistics for this sched_domain.
 */
6429
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6430
{
6431 6432
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
6433
	struct sg_lb_stats tmp_sgs;
6434
	int load_idx, prefer_sibling = 0;
6435
	bool overload = false;
6436 6437 6438 6439

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

6440
	load_idx = get_sd_load_idx(env->sd, env->idle);
6441 6442

	do {
J
Joonsoo Kim 已提交
6443
		struct sg_lb_stats *sgs = &tmp_sgs;
6444 6445
		int local_group;

6446
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
6447 6448 6449
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
6450 6451

			if (env->idle != CPU_NEWLY_IDLE ||
6452 6453
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
6454
		}
6455

6456 6457
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
6458

6459 6460 6461
		if (local_group)
			goto next_group;

6462 6463
		/*
		 * In case the child domain prefers tasks go to siblings
6464
		 * first, lower the sg capacity so that we'll try
6465 6466
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
6467 6468 6469 6470
		 * 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).
6471
		 */
6472
		if (prefer_sibling && sds->local &&
6473 6474 6475 6476
		    group_has_capacity(env, &sds->local_stat) &&
		    (sgs->sum_nr_running > 1)) {
			sgs->group_no_capacity = 1;
			sgs->group_type = group_overloaded;
6477
		}
6478

6479
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6480
			sds->busiest = sg;
J
Joonsoo Kim 已提交
6481
			sds->busiest_stat = *sgs;
6482 6483
		}

6484 6485 6486
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
6487
		sds->total_capacity += sgs->group_capacity;
6488

6489
		sg = sg->next;
6490
	} while (sg != env->sd->groups);
6491 6492 6493

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6494 6495 6496 6497 6498 6499 6500

	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;
	}

6501 6502 6503 6504 6505 6506 6507 6508 6509 6510 6511 6512 6513 6514 6515 6516 6517 6518 6519
}

/**
 * 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.
 *
6520
 * Return: 1 when packing is required and a task should be moved to
6521 6522
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
6523
 * @env: The load balancing environment.
6524 6525
 * @sds: Statistics of the sched_domain which is to be packed
 */
6526
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6527 6528 6529
{
	int busiest_cpu;

6530
	if (!(env->sd->flags & SD_ASYM_PACKING))
6531 6532 6533 6534 6535 6536
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
6537
	if (env->dst_cpu > busiest_cpu)
6538 6539
		return 0;

6540
	env->imbalance = DIV_ROUND_CLOSEST(
6541
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6542
		SCHED_CAPACITY_SCALE);
6543

6544
	return 1;
6545 6546 6547 6548 6549 6550
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
6551
 * @env: The load balancing environment.
6552 6553
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
6554 6555
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6556
{
6557
	unsigned long tmp, capa_now = 0, capa_move = 0;
6558
	unsigned int imbn = 2;
6559
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
6560
	struct sg_lb_stats *local, *busiest;
6561

J
Joonsoo Kim 已提交
6562 6563
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6564

J
Joonsoo Kim 已提交
6565 6566 6567 6568
	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;
6569

J
Joonsoo Kim 已提交
6570
	scaled_busy_load_per_task =
6571
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6572
		busiest->group_capacity;
J
Joonsoo Kim 已提交
6573

6574 6575
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
6576
		env->imbalance = busiest->load_per_task;
6577 6578 6579 6580 6581
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
6582
	 * however we may be able to increase total CPU capacity used by
6583 6584 6585
	 * moving them.
	 */

6586
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
6587
			min(busiest->load_per_task, busiest->avg_load);
6588
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
6589
			min(local->load_per_task, local->avg_load);
6590
	capa_now /= SCHED_CAPACITY_SCALE;
6591 6592

	/* Amount of load we'd subtract */
6593
	if (busiest->avg_load > scaled_busy_load_per_task) {
6594
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
6595
			    min(busiest->load_per_task,
6596
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
6597
	}
6598 6599

	/* Amount of load we'd add */
6600
	if (busiest->avg_load * busiest->group_capacity <
6601
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6602 6603
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
6604
	} else {
6605
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6606
		      local->group_capacity;
J
Joonsoo Kim 已提交
6607
	}
6608
	capa_move += local->group_capacity *
6609
		    min(local->load_per_task, local->avg_load + tmp);
6610
	capa_move /= SCHED_CAPACITY_SCALE;
6611 6612

	/* Move if we gain throughput */
6613
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
6614
		env->imbalance = busiest->load_per_task;
6615 6616 6617 6618 6619
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
6620
 * @env: load balance environment
6621 6622
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
6623
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6624
{
6625
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
6626 6627 6628 6629
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6630

6631
	if (busiest->group_type == group_imbalanced) {
6632 6633 6634 6635
		/*
		 * 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
6636 6637
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
6638 6639
	}

6640 6641 6642
	/*
	 * 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
6643
	 * its cpu_capacity, while calculating max_load..)
6644
	 */
6645 6646
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
6647 6648
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
6649 6650
	}

6651 6652 6653 6654 6655
	/*
	 * If there aren't any idle cpus, avoid creating some.
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
6656 6657 6658 6659 6660 6661
		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;
6662 6663 6664 6665 6666 6667 6668 6669 6670 6671
	}

	/*
	 * 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.
	 */
6672
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6673 6674

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
6675
	env->imbalance = min(
6676 6677
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
6678
	) / SCHED_CAPACITY_SCALE;
6679 6680 6681

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
6682
	 * there is no guarantee that any tasks will be moved so we'll have
6683 6684 6685
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
6686
	if (env->imbalance < busiest->load_per_task)
6687
		return fix_small_imbalance(env, sds);
6688
}
6689

6690 6691 6692 6693 6694 6695 6696 6697 6698 6699 6700 6701
/******* 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.
 *
6702
 * @env: The load balancing environment.
6703
 *
6704
 * Return:	- The busiest group if imbalance exists.
6705 6706 6707 6708
 *		- 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
6709
static struct sched_group *find_busiest_group(struct lb_env *env)
6710
{
J
Joonsoo Kim 已提交
6711
	struct sg_lb_stats *local, *busiest;
6712 6713
	struct sd_lb_stats sds;

6714
	init_sd_lb_stats(&sds);
6715 6716 6717 6718 6719

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
6720
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
6721 6722
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
6723

6724
	/* ASYM feature bypasses nice load balance check */
6725 6726
	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(env, &sds))
6727 6728
		return sds.busiest;

6729
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
6730
	if (!sds.busiest || busiest->sum_nr_running == 0)
6731 6732
		goto out_balanced;

6733 6734
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
6735

P
Peter Zijlstra 已提交
6736 6737
	/*
	 * If the busiest group is imbalanced the below checks don't
6738
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
6739 6740
	 * isn't true due to cpus_allowed constraints and the like.
	 */
6741
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
6742 6743
		goto force_balance;

6744
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6745 6746
	if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
	    busiest->group_no_capacity)
6747 6748
		goto force_balance;

6749
	/*
6750
	 * If the local group is busier than the selected busiest group
6751 6752
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
6753
	if (local->avg_load >= busiest->avg_load)
6754 6755
		goto out_balanced;

6756 6757 6758 6759
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
6760
	if (local->avg_load >= sds.avg_load)
6761 6762
		goto out_balanced;

6763
	if (env->idle == CPU_IDLE) {
6764
		/*
6765 6766 6767 6768 6769
		 * 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
6770
		 */
6771 6772
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
6773
			goto out_balanced;
6774 6775 6776 6777 6778
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
6779 6780
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
6781
			goto out_balanced;
6782
	}
6783

6784
force_balance:
6785
	/* Looks like there is an imbalance. Compute it */
6786
	calculate_imbalance(env, &sds);
6787 6788 6789
	return sds.busiest;

out_balanced:
6790
	env->imbalance = 0;
6791 6792 6793 6794 6795 6796
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
6797
static struct rq *find_busiest_queue(struct lb_env *env,
6798
				     struct sched_group *group)
6799 6800
{
	struct rq *busiest = NULL, *rq;
6801
	unsigned long busiest_load = 0, busiest_capacity = 1;
6802 6803
	int i;

6804
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6805
		unsigned long capacity, wl;
6806 6807 6808 6809
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
6810

6811 6812 6813 6814 6815 6816 6817 6818 6819 6820 6821 6822 6823 6824 6825 6826 6827 6828 6829 6830 6831 6832
		/*
		 * 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;

6833
		capacity = capacity_of(i);
6834

6835
		wl = weighted_cpuload(i);
6836

6837 6838
		/*
		 * When comparing with imbalance, use weighted_cpuload()
6839
		 * which is not scaled with the cpu capacity.
6840
		 */
6841 6842 6843

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
6844 6845
			continue;

6846 6847
		/*
		 * For the load comparisons with the other cpu's, consider
6848 6849 6850
		 * 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.
6851
		 *
6852
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
6853
		 * multiplication to rid ourselves of the division works out
6854 6855
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
6856
		 */
6857
		if (wl * busiest_capacity > busiest_load * capacity) {
6858
			busiest_load = wl;
6859
			busiest_capacity = capacity;
6860 6861 6862 6863 6864 6865 6866 6867 6868 6869 6870 6871 6872 6873
			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. */
6874
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6875

6876
static int need_active_balance(struct lb_env *env)
6877
{
6878 6879 6880
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
6881 6882 6883 6884 6885 6886

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
6887
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6888
			return 1;
6889 6890
	}

6891 6892 6893 6894 6895 6896 6897 6898 6899 6900 6901 6902 6903
	/*
	 * 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;
	}

6904 6905 6906
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

6907 6908
static int active_load_balance_cpu_stop(void *data);

6909 6910 6911 6912 6913 6914 6915 6916 6917 6918 6919 6920 6921 6922 6923 6924 6925 6926 6927 6928 6929 6930 6931 6932 6933 6934 6935 6936 6937 6938 6939
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.
	 */
6940
	return balance_cpu == env->dst_cpu;
6941 6942
}

6943 6944 6945 6946 6947 6948
/*
 * 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,
6949
			int *continue_balancing)
6950
{
6951
	int ld_moved, cur_ld_moved, active_balance = 0;
6952
	struct sched_domain *sd_parent = sd->parent;
6953 6954 6955
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
6956
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
6957

6958 6959
	struct lb_env env = {
		.sd		= sd,
6960 6961
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
6962
		.dst_grpmask    = sched_group_cpus(sd->groups),
6963
		.idle		= idle,
6964
		.loop_break	= sched_nr_migrate_break,
6965
		.cpus		= cpus,
6966
		.fbq_type	= all,
6967
		.tasks		= LIST_HEAD_INIT(env.tasks),
6968 6969
	};

6970 6971 6972 6973
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
6974
	if (idle == CPU_NEWLY_IDLE)
6975 6976
		env.dst_grpmask = NULL;

6977 6978 6979 6980 6981
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
6982 6983
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
6984
		goto out_balanced;
6985
	}
6986

6987
	group = find_busiest_group(&env);
6988 6989 6990 6991 6992
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

6993
	busiest = find_busiest_queue(&env, group);
6994 6995 6996 6997 6998
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

6999
	BUG_ON(busiest == env.dst_rq);
7000

7001
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
7002

7003 7004 7005
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

7006 7007 7008 7009 7010 7011 7012 7013
	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.
		 */
7014
		env.flags |= LBF_ALL_PINNED;
7015
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
7016

7017
more_balance:
7018
		raw_spin_lock_irqsave(&busiest->lock, flags);
7019 7020 7021 7022 7023

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
7024
		cur_ld_moved = detach_tasks(&env);
7025 7026

		/*
7027 7028 7029 7030 7031
		 * 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.
7032
		 */
7033 7034 7035 7036 7037 7038 7039 7040

		raw_spin_unlock(&busiest->lock);

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

7041
		local_irq_restore(flags);
7042

7043 7044 7045 7046 7047
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

7048 7049 7050 7051 7052 7053 7054 7055 7056 7057 7058 7059 7060 7061 7062 7063 7064 7065 7066
		/*
		 * 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.
		 */
7067
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7068

7069 7070 7071
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

7072
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
7073
			env.dst_cpu	 = env.new_dst_cpu;
7074
			env.flags	&= ~LBF_DST_PINNED;
7075 7076
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
7077

7078 7079 7080 7081 7082 7083
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
7084

7085 7086 7087 7088
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
7089
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7090

7091
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7092 7093 7094
				*group_imbalance = 1;
		}

7095
		/* All tasks on this runqueue were pinned by CPU affinity */
7096
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
7097
			cpumask_clear_cpu(cpu_of(busiest), cpus);
7098 7099 7100
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
7101
				goto redo;
7102
			}
7103
			goto out_all_pinned;
7104 7105 7106 7107 7108
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
7109 7110 7111 7112 7113 7114 7115 7116
		/*
		 * 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++;
7117

7118
		if (need_active_balance(&env)) {
7119 7120
			raw_spin_lock_irqsave(&busiest->lock, flags);

7121 7122 7123
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
7124 7125
			 */
			if (!cpumask_test_cpu(this_cpu,
7126
					tsk_cpus_allowed(busiest->curr))) {
7127 7128
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
7129
				env.flags |= LBF_ALL_PINNED;
7130 7131 7132
				goto out_one_pinned;
			}

7133 7134 7135 7136 7137
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
7138 7139 7140 7141 7142 7143
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
7144

7145
			if (active_balance) {
7146 7147 7148
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
7149
			}
7150 7151 7152 7153 7154 7155 7156 7157 7158 7159 7160 7161 7162 7163 7164 7165 7166 7167

			/*
			 * We've kicked active balancing, reset the failure
			 * counter.
			 */
			sd->nr_balance_failed = sd->cache_nice_tries+1;
		}
	} else
		sd->nr_balance_failed = 0;

	if (likely(!active_balance)) {
		/* We were unbalanced, so reset the balancing interval */
		sd->balance_interval = sd->min_interval;
	} else {
		/*
		 * If we've begun active balancing, start to back off. This
		 * case may not be covered by the all_pinned logic if there
		 * is only 1 task on the busy runqueue (because we don't call
7168
		 * detach_tasks).
7169 7170 7171 7172 7173 7174 7175 7176
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
7177 7178 7179 7180 7181 7182 7183 7184 7185 7186 7187 7188 7189 7190 7191 7192 7193
	/*
	 * 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.
	 */
7194 7195 7196 7197 7198 7199
	schedstat_inc(sd, lb_balanced[idle]);

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
7200
	if (((env.flags & LBF_ALL_PINNED) &&
7201
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
7202 7203 7204
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

7205
	ld_moved = 0;
7206 7207 7208 7209
out:
	return ld_moved;
}

7210 7211 7212 7213 7214 7215 7216 7217 7218 7219 7220 7221 7222 7223 7224 7225 7226 7227 7228 7229 7230 7231 7232 7233 7234 7235 7236
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;
}

7237 7238 7239 7240
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
7241
static int idle_balance(struct rq *this_rq)
7242
{
7243 7244
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
7245 7246
	struct sched_domain *sd;
	int pulled_task = 0;
7247
	u64 curr_cost = 0;
7248

7249
	idle_enter_fair(this_rq);
7250

7251 7252 7253 7254 7255 7256
	/*
	 * 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);

7257 7258
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
7259 7260 7261 7262 7263 7264
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
			update_next_balance(sd, 0, &next_balance);
		rcu_read_unlock();

7265
		goto out;
7266
	}
7267

7268 7269
	raw_spin_unlock(&this_rq->lock);

7270
	update_blocked_averages(this_cpu);
7271
	rcu_read_lock();
7272
	for_each_domain(this_cpu, sd) {
7273
		int continue_balancing = 1;
7274
		u64 t0, domain_cost;
7275 7276 7277 7278

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

7279 7280
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
			update_next_balance(sd, 0, &next_balance);
7281
			break;
7282
		}
7283

7284
		if (sd->flags & SD_BALANCE_NEWIDLE) {
7285 7286
			t0 = sched_clock_cpu(this_cpu);

7287
			pulled_task = load_balance(this_cpu, this_rq,
7288 7289
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
7290 7291 7292 7293 7294 7295

			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;
7296
		}
7297

7298
		update_next_balance(sd, 0, &next_balance);
7299 7300 7301 7302 7303 7304

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
7305 7306
			break;
	}
7307
	rcu_read_unlock();
7308 7309 7310

	raw_spin_lock(&this_rq->lock);

7311 7312 7313
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

7314
	/*
7315 7316 7317
	 * 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.
7318
	 */
7319
	if (this_rq->cfs.h_nr_running && !pulled_task)
7320
		pulled_task = 1;
7321

7322 7323 7324
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
7325
		this_rq->next_balance = next_balance;
7326

7327
	/* Is there a task of a high priority class? */
7328
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7329 7330 7331 7332
		pulled_task = -1;

	if (pulled_task) {
		idle_exit_fair(this_rq);
7333
		this_rq->idle_stamp = 0;
7334
	}
7335

7336
	return pulled_task;
7337 7338 7339
}

/*
7340 7341 7342 7343
 * 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.
7344
 */
7345
static int active_load_balance_cpu_stop(void *data)
7346
{
7347 7348
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
7349
	int target_cpu = busiest_rq->push_cpu;
7350
	struct rq *target_rq = cpu_rq(target_cpu);
7351
	struct sched_domain *sd;
7352
	struct task_struct *p = NULL;
7353 7354 7355 7356 7357 7358 7359

	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;
7360 7361 7362

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
7363
		goto out_unlock;
7364 7365 7366 7367 7368 7369 7370 7371 7372

	/*
	 * 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. */
7373
	rcu_read_lock();
7374 7375 7376 7377 7378 7379 7380
	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)) {
7381 7382
		struct lb_env env = {
			.sd		= sd,
7383 7384 7385 7386
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
7387 7388 7389
			.idle		= CPU_IDLE,
		};

7390 7391
		schedstat_inc(sd, alb_count);

7392 7393
		p = detach_one_task(&env);
		if (p)
7394 7395 7396 7397
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
7398
	rcu_read_unlock();
7399 7400
out_unlock:
	busiest_rq->active_balance = 0;
7401 7402 7403 7404 7405 7406 7407
	raw_spin_unlock(&busiest_rq->lock);

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

7408
	return 0;
7409 7410
}

7411 7412 7413 7414 7415
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

7416
#ifdef CONFIG_NO_HZ_COMMON
7417 7418 7419 7420 7421 7422
/*
 * 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.
 */
7423
static struct {
7424
	cpumask_var_t idle_cpus_mask;
7425
	atomic_t nr_cpus;
7426 7427
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
7428

7429
static inline int find_new_ilb(void)
7430
{
7431
	int ilb = cpumask_first(nohz.idle_cpus_mask);
7432

7433 7434 7435 7436
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
7437 7438
}

7439 7440 7441 7442 7443
/*
 * 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).
 */
7444
static void nohz_balancer_kick(void)
7445 7446 7447 7448 7449
{
	int ilb_cpu;

	nohz.next_balance++;

7450
	ilb_cpu = find_new_ilb();
7451

7452 7453
	if (ilb_cpu >= nr_cpu_ids)
		return;
7454

7455
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7456 7457 7458 7459 7460 7461 7462 7463
		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);
7464 7465 7466
	return;
}

7467
static inline void nohz_balance_exit_idle(int cpu)
7468 7469
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7470 7471 7472 7473 7474 7475 7476
		/*
		 * 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);
		}
7477 7478 7479 7480
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

7481 7482 7483
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
7484
	int cpu = smp_processor_id();
7485 7486

	rcu_read_lock();
7487
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7488 7489 7490 7491 7492

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

7493
	atomic_inc(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7494
unlock:
7495 7496 7497 7498 7499 7500
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
7501
	int cpu = smp_processor_id();
7502 7503

	rcu_read_lock();
7504
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7505 7506 7507 7508 7509

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

7510
	atomic_dec(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7511
unlock:
7512 7513 7514
	rcu_read_unlock();
}

7515
/*
7516
 * This routine will record that the cpu is going idle with tick stopped.
7517
 * This info will be used in performing idle load balancing in the future.
7518
 */
7519
void nohz_balance_enter_idle(int cpu)
7520
{
7521 7522 7523 7524 7525 7526
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

7527 7528
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
7529

7530 7531 7532 7533 7534 7535
	/*
	 * If we're a completely isolated CPU, we don't play.
	 */
	if (on_null_domain(cpu_rq(cpu)))
		return;

7536 7537 7538
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7539
}
7540

7541
static int sched_ilb_notifier(struct notifier_block *nfb,
7542 7543 7544 7545
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
7546
		nohz_balance_exit_idle(smp_processor_id());
7547 7548 7549 7550 7551
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
7552 7553 7554 7555
#endif

static DEFINE_SPINLOCK(balancing);

7556 7557 7558 7559
/*
 * 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.
 */
7560
void update_max_interval(void)
7561 7562 7563 7564
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

7565 7566 7567 7568
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
7569
 * Balancing parameters are set up in init_sched_domains.
7570
 */
7571
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7572
{
7573
	int continue_balancing = 1;
7574
	int cpu = rq->cpu;
7575
	unsigned long interval;
7576
	struct sched_domain *sd;
7577 7578 7579
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
7580 7581
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
7582

7583
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
7584

7585
	rcu_read_lock();
7586
	for_each_domain(cpu, sd) {
7587 7588 7589 7590 7591 7592 7593 7594 7595 7596 7597 7598
		/*
		 * 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;

7599 7600 7601
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

7602 7603 7604 7605 7606 7607 7608 7609 7610 7611 7612
		/*
		 * 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;
		}

7613
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7614 7615 7616 7617 7618 7619 7620 7621

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

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
7622
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7623
				/*
7624
				 * The LBF_DST_PINNED logic could have changed
7625 7626
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
7627
				 */
7628
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7629 7630
			}
			sd->last_balance = jiffies;
7631
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7632 7633 7634 7635 7636 7637 7638 7639
		}
		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;
		}
7640 7641
	}
	if (need_decay) {
7642
		/*
7643 7644
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
7645
		 */
7646 7647
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
7648
	}
7649
	rcu_read_unlock();
7650 7651 7652 7653 7654 7655

	/*
	 * 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.
	 */
7656
	if (likely(update_next_balance)) {
7657
		rq->next_balance = next_balance;
7658 7659 7660 7661 7662 7663 7664 7665 7666 7667 7668 7669 7670 7671

#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
	}
7672 7673
}

7674
#ifdef CONFIG_NO_HZ_COMMON
7675
/*
7676
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7677 7678
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
7679
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7680
{
7681
	int this_cpu = this_rq->cpu;
7682 7683
	struct rq *rq;
	int balance_cpu;
7684 7685 7686
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
7687

7688 7689 7690
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
7691 7692

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7693
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7694 7695 7696 7697 7698 7699 7700
			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.
		 */
7701
		if (need_resched())
7702 7703
			break;

V
Vincent Guittot 已提交
7704 7705
		rq = cpu_rq(balance_cpu);

7706 7707 7708 7709 7710 7711 7712 7713 7714 7715 7716
		/*
		 * If time for next balance is due,
		 * do the balance.
		 */
		if (time_after_eq(jiffies, rq->next_balance)) {
			raw_spin_lock_irq(&rq->lock);
			update_rq_clock(rq);
			update_idle_cpu_load(rq);
			raw_spin_unlock_irq(&rq->lock);
			rebalance_domains(rq, CPU_IDLE);
		}
7717

7718 7719 7720 7721
		if (time_after(next_balance, rq->next_balance)) {
			next_balance = rq->next_balance;
			update_next_balance = 1;
		}
7722
	}
7723 7724 7725 7726 7727 7728 7729 7730

	/*
	 * 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;
7731 7732
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7733 7734 7735
}

/*
7736
 * Current heuristic for kicking the idle load balancer in the presence
7737
 * of an idle cpu in the system.
7738
 *   - This rq has more than one task.
7739 7740 7741 7742
 *   - 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.
7743 7744
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
7745
 */
7746
static inline bool nohz_kick_needed(struct rq *rq)
7747 7748
{
	unsigned long now = jiffies;
7749
	struct sched_domain *sd;
7750
	struct sched_group_capacity *sgc;
7751
	int nr_busy, cpu = rq->cpu;
7752
	bool kick = false;
7753

7754
	if (unlikely(rq->idle_balance))
7755
		return false;
7756

7757 7758 7759 7760
       /*
	* 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.
	*/
7761
	set_cpu_sd_state_busy();
7762
	nohz_balance_exit_idle(cpu);
7763 7764 7765 7766 7767 7768

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
7769
		return false;
7770 7771

	if (time_before(now, nohz.next_balance))
7772
		return false;
7773

7774
	if (rq->nr_running >= 2)
7775
		return true;
7776

7777
	rcu_read_lock();
7778 7779
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
	if (sd) {
7780 7781
		sgc = sd->groups->sgc;
		nr_busy = atomic_read(&sgc->nr_busy_cpus);
7782

7783 7784 7785 7786 7787
		if (nr_busy > 1) {
			kick = true;
			goto unlock;
		}

7788
	}
7789

7790 7791 7792 7793 7794 7795 7796 7797
	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
			kick = true;
			goto unlock;
		}
	}
7798

7799
	sd = rcu_dereference(per_cpu(sd_asym, cpu));
7800
	if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
7801 7802 7803 7804
				  sched_domain_span(sd)) < cpu)) {
		kick = true;
		goto unlock;
	}
7805

7806
unlock:
7807
	rcu_read_unlock();
7808
	return kick;
7809 7810
}
#else
7811
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7812 7813 7814 7815 7816 7817
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
7818 7819
static void run_rebalance_domains(struct softirq_action *h)
{
7820
	struct rq *this_rq = this_rq();
7821
	enum cpu_idle_type idle = this_rq->idle_balance ?
7822 7823 7824
						CPU_IDLE : CPU_NOT_IDLE;

	/*
7825
	 * If this cpu has a pending nohz_balance_kick, then do the
7826
	 * balancing on behalf of the other idle cpus whose ticks are
7827 7828 7829 7830
	 * 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.
7831
	 */
7832
	nohz_idle_balance(this_rq, idle);
7833
	rebalance_domains(this_rq, idle);
7834 7835 7836 7837 7838
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
7839
void trigger_load_balance(struct rq *rq)
7840 7841
{
	/* Don't need to rebalance while attached to NULL domain */
7842 7843 7844 7845
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
7846
		raise_softirq(SCHED_SOFTIRQ);
7847
#ifdef CONFIG_NO_HZ_COMMON
7848
	if (nohz_kick_needed(rq))
7849
		nohz_balancer_kick();
7850
#endif
7851 7852
}

7853 7854 7855
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
7856 7857

	update_runtime_enabled(rq);
7858 7859 7860 7861 7862
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
7863 7864 7865

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
7866 7867
}

7868
#endif /* CONFIG_SMP */
7869

7870 7871 7872
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
7873
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
7874 7875 7876 7877 7878 7879
{
	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
7880
		entity_tick(cfs_rq, se, queued);
7881
	}
7882

7883
	if (!static_branch_unlikely(&sched_numa_balancing))
7884
		task_tick_numa(rq, curr);
7885 7886 7887
}

/*
P
Peter Zijlstra 已提交
7888 7889 7890
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
7891
 */
P
Peter Zijlstra 已提交
7892
static void task_fork_fair(struct task_struct *p)
7893
{
7894 7895
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
7896
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
7897 7898 7899
	struct rq *rq = this_rq();
	unsigned long flags;

7900
	raw_spin_lock_irqsave(&rq->lock, flags);
7901

7902 7903
	update_rq_clock(rq);

7904 7905 7906
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

7907 7908 7909 7910 7911 7912 7913 7914 7915
	/*
	 * 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();
7916

7917
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
7918

7919 7920
	if (curr)
		se->vruntime = curr->vruntime;
7921
	place_entity(cfs_rq, se, 1);
7922

P
Peter Zijlstra 已提交
7923
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
7924
		/*
7925 7926 7927
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
7928
		swap(curr->vruntime, se->vruntime);
7929
		resched_curr(rq);
7930
	}
7931

7932 7933
	se->vruntime -= cfs_rq->min_vruntime;

7934
	raw_spin_unlock_irqrestore(&rq->lock, flags);
7935 7936
}

7937 7938 7939 7940
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
7941 7942
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
7943
{
7944
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
7945 7946
		return;

7947 7948 7949 7950 7951
	/*
	 * 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
7952
	if (rq->curr == p) {
7953
		if (p->prio > oldprio)
7954
			resched_curr(rq);
7955
	} else
7956
		check_preempt_curr(rq, p, 0);
7957 7958
}

7959
static inline bool vruntime_normalized(struct task_struct *p)
P
Peter Zijlstra 已提交
7960 7961 7962 7963
{
	struct sched_entity *se = &p->se;

	/*
7964 7965 7966 7967 7968 7969 7970 7971 7972 7973
	 * 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
7974
	 *
7975 7976 7977 7978
	 * - 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
7979
	 */
7980 7981 7982 7983 7984 7985 7986 7987 7988 7989 7990 7991
	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
7992 7993 7994 7995 7996 7997 7998
		/*
		 * 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;
	}
7999

8000
	/* Catch up with the cfs_rq and remove our load when we leave */
8001
	detach_entity_load_avg(cfs_rq, se);
P
Peter Zijlstra 已提交
8002 8003
}

8004
static void attach_task_cfs_rq(struct task_struct *p)
8005
{
8006
	struct sched_entity *se = &p->se;
8007
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
8008 8009

#ifdef CONFIG_FAIR_GROUP_SCHED
8010 8011 8012 8013 8014 8015
	/*
	 * 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
8016

8017
	/* Synchronize task with its cfs_rq */
8018 8019 8020 8021 8022
	attach_entity_load_avg(cfs_rq, se);

	if (!vruntime_normalized(p))
		se->vruntime += cfs_rq->min_vruntime;
}
8023

8024 8025 8026 8027 8028 8029 8030 8031
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);
8032

8033
	if (task_on_rq_queued(p)) {
8034
		/*
8035 8036 8037
		 * 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.
8038
		 */
8039 8040 8041 8042
		if (rq->curr == p)
			resched_curr(rq);
		else
			check_preempt_curr(rq, p, 0);
8043
	}
8044 8045
}

8046 8047 8048 8049 8050 8051 8052 8053 8054
/* 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;

8055 8056 8057 8058 8059 8060 8061
	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);
	}
8062 8063
}

8064 8065 8066 8067 8068 8069 8070
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
8071
#ifdef CONFIG_SMP
8072 8073
	atomic_long_set(&cfs_rq->removed_load_avg, 0);
	atomic_long_set(&cfs_rq->removed_util_avg, 0);
8074
#endif
8075 8076
}

P
Peter Zijlstra 已提交
8077
#ifdef CONFIG_FAIR_GROUP_SCHED
8078
static void task_move_group_fair(struct task_struct *p)
P
Peter Zijlstra 已提交
8079
{
8080
	detach_task_cfs_rq(p);
8081
	set_task_rq(p, task_cpu(p));
8082 8083 8084 8085 8086

#ifdef CONFIG_SMP
	/* Tell se's cfs_rq has been changed -- migrated */
	p->se.avg.last_update_time = 0;
#endif
8087
	attach_task_cfs_rq(p);
P
Peter Zijlstra 已提交
8088
}
8089 8090 8091 8092 8093 8094 8095 8096 8097 8098

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]);
8099 8100 8101
		if (tg->se) {
			if (tg->se[i])
				remove_entity_load_avg(tg->se[i]);
8102
			kfree(tg->se[i]);
8103
		}
8104 8105 8106 8107 8108 8109 8110 8111 8112 8113 8114 8115 8116 8117 8118 8119 8120 8121 8122 8123 8124 8125 8126 8127 8128 8129 8130 8131 8132 8133 8134 8135 8136 8137 8138 8139
	}

	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]);
8140
		init_entity_runnable_average(se);
8141 8142 8143 8144 8145 8146 8147 8148 8149 8150 8151 8152 8153 8154 8155 8156 8157 8158 8159 8160 8161 8162 8163 8164 8165 8166 8167 8168 8169 8170 8171 8172 8173 8174 8175 8176 8177 8178 8179 8180 8181 8182 8183 8184
	}

	return 1;

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

void unregister_fair_sched_group(struct task_group *tg, int cpu)
{
	struct rq *rq = cpu_rq(cpu);
	unsigned long flags;

	/*
	* Only empty task groups can be destroyed; so we can speculatively
	* check on_list without danger of it being re-added.
	*/
	if (!tg->cfs_rq[cpu]->on_list)
		return;

	raw_spin_lock_irqsave(&rq->lock, flags);
	list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
	raw_spin_unlock_irqrestore(&rq->lock, flags);
}

void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
			struct sched_entity *se, int cpu,
			struct sched_entity *parent)
{
	struct rq *rq = cpu_rq(cpu);

	cfs_rq->tg = tg;
	cfs_rq->rq = rq;
	init_cfs_rq_runtime(cfs_rq);

	tg->cfs_rq[cpu] = cfs_rq;
	tg->se[cpu] = se;

	/* se could be NULL for root_task_group */
	if (!se)
		return;

P
Peter Zijlstra 已提交
8185
	if (!parent) {
8186
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
8187 8188
		se->depth = 0;
	} else {
8189
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
8190 8191
		se->depth = parent->depth + 1;
	}
8192 8193

	se->my_q = cfs_rq;
8194 8195
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
8196 8197 8198 8199 8200 8201 8202 8203 8204 8205 8206 8207 8208 8209 8210 8211 8212 8213 8214 8215 8216 8217 8218 8219 8220 8221 8222 8223 8224 8225
	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);
8226 8227 8228

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
8229
		for_each_sched_entity(se)
8230 8231 8232 8233 8234 8235 8236 8237 8238 8239 8240 8241 8242 8243 8244 8245 8246 8247 8248 8249 8250
			update_cfs_shares(group_cfs_rq(se));
		raw_spin_unlock_irqrestore(&rq->lock, flags);
	}

done:
	mutex_unlock(&shares_mutex);
	return 0;
}
#else /* CONFIG_FAIR_GROUP_SCHED */

void free_fair_sched_group(struct task_group *tg) { }

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
	return 1;
}

void unregister_fair_sched_group(struct task_group *tg, int cpu) { }

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
8251

8252
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8253 8254 8255 8256 8257 8258 8259 8260 8261
{
	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)
8262
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8263 8264 8265 8266

	return rr_interval;
}

8267 8268 8269
/*
 * All the scheduling class methods:
 */
8270
const struct sched_class fair_sched_class = {
8271
	.next			= &idle_sched_class,
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	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
8275
	.yield_to_task		= yield_to_task_fair,
8276

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Ingo Molnar 已提交
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	.check_preempt_curr	= check_preempt_wakeup,
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	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

8282
#ifdef CONFIG_SMP
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Li Zefan 已提交
8283
	.select_task_rq		= select_task_rq_fair,
8284
	.migrate_task_rq	= migrate_task_rq_fair,
8285

8286 8287
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
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	.task_waking		= task_waking_fair,
8290
	.task_dead		= task_dead_fair,
8291
	.set_cpus_allowed	= set_cpus_allowed_common,
8292
#endif
8293

8294
	.set_curr_task          = set_curr_task_fair,
8295
	.task_tick		= task_tick_fair,
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Peter Zijlstra 已提交
8296
	.task_fork		= task_fork_fair,
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	.prio_changed		= prio_changed_fair,
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	.switched_from		= switched_from_fair,
8300
	.switched_to		= switched_to_fair,
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Peter Zijlstra 已提交
8301

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	.get_rr_interval	= get_rr_interval_fair,

8304 8305
	.update_curr		= update_curr_fair,

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Peter Zijlstra 已提交
8306
#ifdef CONFIG_FAIR_GROUP_SCHED
8307
	.task_move_group	= task_move_group_fair,
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Peter Zijlstra 已提交
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#endif
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};

#ifdef CONFIG_SCHED_DEBUG
8312
void print_cfs_stats(struct seq_file *m, int cpu)
8313 8314 8315
{
	struct cfs_rq *cfs_rq;

8316
	rcu_read_lock();
8317
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8318
		print_cfs_rq(m, cpu, cfs_rq);
8319
	rcu_read_unlock();
8320
}
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#ifdef CONFIG_NUMA_BALANCING
void show_numa_stats(struct task_struct *p, struct seq_file *m)
{
	int node;
	unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0;

	for_each_online_node(node) {
		if (p->numa_faults) {
			tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)];
			tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)];
		}
		if (p->numa_group) {
			gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)],
			gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)];
		}
		print_numa_stats(m, node, tsf, tpf, gsf, gpf);
	}
}
#endif /* CONFIG_NUMA_BALANCING */
#endif /* CONFIG_SCHED_DEBUG */
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__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

8348
#ifdef CONFIG_NO_HZ_COMMON
8349
	nohz.next_balance = jiffies;
8350
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8351
	cpu_notifier(sched_ilb_notifier, 0);
8352 8353 8354 8355
#endif
#endif /* SMP */

}