fair.c 214.3 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 */
669 670 671 672

/* Give new task start runnable values to heavy its load in infant time */
void init_task_runnable_average(struct task_struct *p)
{
673
	struct sched_avg *sa = &p->se.avg;
674

675 676 677 678 679 680 681 682 683 684 685 686
	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;
	sa->load_avg = scale_load_down(p->se.load.weight);
	sa->load_sum = sa->load_avg * LOAD_AVG_MAX;
	sa->util_avg = scale_load_down(SCHED_LOAD_SCALE);
	sa->util_sum = LOAD_AVG_MAX;
	/* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */
687 688 689 690 691 692 693
}
#else
void init_task_runnable_average(struct task_struct *p)
{
}
#endif

694
/*
695
 * Update the current task's runtime statistics.
696
 */
697
static void update_curr(struct cfs_rq *cfs_rq)
698
{
699
	struct sched_entity *curr = cfs_rq->curr;
700
	u64 now = rq_clock_task(rq_of(cfs_rq));
701
	u64 delta_exec;
702 703 704 705

	if (unlikely(!curr))
		return;

706 707
	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
P
Peter Zijlstra 已提交
708
		return;
709

I
Ingo Molnar 已提交
710
	curr->exec_start = now;
711

712 713 714 715 716 717 718 719 720
	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);

721 722 723
	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

724
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
725
		cpuacct_charge(curtask, delta_exec);
726
		account_group_exec_runtime(curtask, delta_exec);
727
	}
728 729

	account_cfs_rq_runtime(cfs_rq, delta_exec);
730 731
}

732 733 734 735 736
static void update_curr_fair(struct rq *rq)
{
	update_curr(cfs_rq_of(&rq->curr->se));
}

737
static inline void
738
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
739
{
740
	schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
741 742 743 744 745
}

/*
 * Task is being enqueued - update stats:
 */
746
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
747 748 749 750 751
{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
752
	if (se != cfs_rq->curr)
753
		update_stats_wait_start(cfs_rq, se);
754 755 756
}

static void
757
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
758
{
759
	schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
760
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
761 762
	schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
	schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
763
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
764 765 766
#ifdef CONFIG_SCHEDSTATS
	if (entity_is_task(se)) {
		trace_sched_stat_wait(task_of(se),
767
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
768 769
	}
#endif
770
	schedstat_set(se->statistics.wait_start, 0);
771 772 773
}

static inline void
774
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
775 776 777 778 779
{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
780
	if (se != cfs_rq->curr)
781
		update_stats_wait_end(cfs_rq, se);
782 783 784 785 786 787
}

/*
 * We are picking a new current task - update its stats:
 */
static inline void
788
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
789 790 791 792
{
	/*
	 * We are starting a new run period:
	 */
793
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
794 795 796 797 798 799
}

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

800 801
#ifdef CONFIG_NUMA_BALANCING
/*
802 803 804
 * 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.
805
 */
806 807
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
808 809 810

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
811

812 813 814
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838
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)
{
839
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
840 841 842
	unsigned int scan, floor;
	unsigned int windows = 1;

843 844
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860
	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);
}

861 862 863 864 865 866 867 868 869 870 871 872
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));
}

873 874 875 876 877
struct numa_group {
	atomic_t refcount;

	spinlock_t lock; /* nr_tasks, tasks */
	int nr_tasks;
878
	pid_t gid;
879 880

	struct rcu_head rcu;
881
	nodemask_t active_nodes;
882
	unsigned long total_faults;
883 884 885 886 887
	/*
	 * 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.
	 */
888
	unsigned long *faults_cpu;
889
	unsigned long faults[0];
890 891
};

892 893 894 895 896 897 898 899 900
/* 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)

901 902 903 904 905
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

906 907 908 909 910 911 912
/*
 * 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)
913
{
914
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
915 916 917 918
}

static inline unsigned long task_faults(struct task_struct *p, int nid)
{
919
	if (!p->numa_faults)
920 921
		return 0;

922 923
	return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)];
924 925
}

926 927 928 929 930
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

931 932
	return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] +
		p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)];
933 934
}

935 936
static inline unsigned long group_faults_cpu(struct numa_group *group, int nid)
{
937 938
	return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] +
		group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)];
939 940
}

941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005
/* 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;
}

1006 1007 1008 1009 1010 1011
/*
 * 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.
 */
1012 1013
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1014
{
1015
	unsigned long faults, total_faults;
1016

1017
	if (!p->numa_faults)
1018 1019 1020 1021 1022 1023 1024
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

1025
	faults = task_faults(p, nid);
1026 1027
	faults += score_nearby_nodes(p, nid, dist, true);

1028
	return 1000 * faults / total_faults;
1029 1030
}

1031 1032
static inline unsigned long group_weight(struct task_struct *p, int nid,
					 int dist)
1033
{
1034 1035 1036 1037 1038 1039 1040 1041
	unsigned long faults, total_faults;

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1042 1043
		return 0;

1044
	faults = group_faults(p, nid);
1045 1046
	faults += score_nearby_nodes(p, nid, dist, false);

1047
	return 1000 * faults / total_faults;
1048 1049
}

1050 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
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);
}

1113
static unsigned long weighted_cpuload(const int cpu);
1114 1115
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
1116
static unsigned long capacity_of(int cpu);
1117 1118
static long effective_load(struct task_group *tg, int cpu, long wl, long wg);

1119
/* Cached statistics for all CPUs within a node */
1120
struct numa_stats {
1121
	unsigned long nr_running;
1122
	unsigned long load;
1123 1124

	/* Total compute capacity of CPUs on a node */
1125
	unsigned long compute_capacity;
1126 1127

	/* Approximate capacity in terms of runnable tasks on a node */
1128
	unsigned long task_capacity;
1129
	int has_free_capacity;
1130
};
1131

1132 1133 1134 1135 1136
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
1137 1138
	int smt, cpu, cpus = 0;
	unsigned long capacity;
1139 1140 1141 1142 1143 1144 1145

	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);
1146
		ns->compute_capacity += capacity_of(cpu);
1147 1148

		cpus++;
1149 1150
	}

1151 1152 1153 1154 1155
	/*
	 * 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.
	 *
1156 1157
	 * We'll either bail at !has_free_capacity, or we'll detect a huge
	 * imbalance and bail there.
1158 1159 1160 1161
	 */
	if (!cpus)
		return;

1162 1163 1164 1165 1166 1167
	/* 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));
1168
	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1169 1170
}

1171 1172
struct task_numa_env {
	struct task_struct *p;
1173

1174 1175
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1176

1177
	struct numa_stats src_stats, dst_stats;
1178

1179
	int imbalance_pct;
1180
	int dist;
1181 1182 1183

	struct task_struct *best_task;
	long best_imp;
1184 1185 1186
	int best_cpu;
};

1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199
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;
}

1200
static bool load_too_imbalanced(long src_load, long dst_load,
1201 1202
				struct task_numa_env *env)
{
1203 1204
	long imb, old_imb;
	long orig_src_load, orig_dst_load;
1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215
	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;
1216 1217

	/* We care about the slope of the imbalance, not the direction. */
1218 1219
	if (dst_load < src_load)
		swap(dst_load, src_load);
1220 1221

	/* Is the difference below the threshold? */
1222 1223
	imb = dst_load * src_capacity * 100 -
	      src_load * dst_capacity * env->imbalance_pct;
1224 1225 1226 1227 1228
	if (imb <= 0)
		return false;

	/*
	 * The imbalance is above the allowed threshold.
1229
	 * Compare it with the old imbalance.
1230
	 */
1231
	orig_src_load = env->src_stats.load;
1232
	orig_dst_load = env->dst_stats.load;
1233

1234 1235
	if (orig_dst_load < orig_src_load)
		swap(orig_dst_load, orig_src_load);
1236

1237 1238 1239 1240 1241
	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);
1242 1243
}

1244 1245 1246 1247 1248 1249
/*
 * 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
 */
1250 1251
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1252 1253 1254 1255
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1256
	long src_load, dst_load;
1257
	long load;
1258
	long imp = env->p->numa_group ? groupimp : taskimp;
1259
	long moveimp = imp;
1260
	int dist = env->dist;
1261 1262

	rcu_read_lock();
1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273

	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))
1274
		cur = NULL;
1275
	raw_spin_unlock_irq(&dst_rq->lock);
1276

1277 1278 1279 1280 1281 1282 1283
	/*
	 * 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;

1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295
	/*
	 * "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;

1296 1297
		/*
		 * If dst and source tasks are in the same NUMA group, or not
1298
		 * in any group then look only at task weights.
1299
		 */
1300
		if (cur->numa_group == env->p->numa_group) {
1301 1302
			imp = taskimp + task_weight(cur, env->src_nid, dist) -
			      task_weight(cur, env->dst_nid, dist);
1303 1304 1305 1306 1307 1308
			/*
			 * Add some hysteresis to prevent swapping the
			 * tasks within a group over tiny differences.
			 */
			if (cur->numa_group)
				imp -= imp/16;
1309
		} else {
1310 1311 1312 1313 1314 1315
			/*
			 * 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)
1316 1317
				imp += group_weight(cur, env->src_nid, dist) -
				       group_weight(cur, env->dst_nid, dist);
1318
			else
1319 1320
				imp += task_weight(cur, env->src_nid, dist) -
				       task_weight(cur, env->dst_nid, dist);
1321
		}
1322 1323
	}

1324
	if (imp <= env->best_imp && moveimp <= env->best_imp)
1325 1326 1327 1328
		goto unlock;

	if (!cur) {
		/* Is there capacity at our destination? */
1329
		if (env->src_stats.nr_running <= env->src_stats.task_capacity &&
1330
		    !env->dst_stats.has_free_capacity)
1331 1332 1333 1334 1335 1336
			goto unlock;

		goto balance;
	}

	/* Balance doesn't matter much if we're running a task per cpu */
1337 1338
	if (imp > env->best_imp && src_rq->nr_running == 1 &&
			dst_rq->nr_running == 1)
1339 1340 1341 1342 1343 1344
		goto assign;

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
balance:
1345 1346 1347
	load = task_h_load(env->p);
	dst_load = env->dst_stats.load + load;
	src_load = env->src_stats.load - load;
1348

1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365
	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;

1366
	if (cur) {
1367 1368 1369
		load = task_h_load(cur);
		dst_load -= load;
		src_load += load;
1370 1371
	}

1372
	if (load_too_imbalanced(src_load, dst_load, env))
1373 1374
		goto unlock;

1375 1376 1377 1378 1379 1380 1381
	/*
	 * 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);

1382 1383 1384 1385 1386 1387
assign:
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1388 1389
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1390 1391 1392 1393 1394 1395 1396 1397 1398
{
	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;
1399
		task_numa_compare(env, taskimp, groupimp);
1400 1401 1402
	}
}

1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419
/* 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
	 */
1420 1421 1422
	if (src->load * dst->compute_capacity * env->imbalance_pct >

	    dst->load * src->compute_capacity * 100)
1423 1424 1425 1426 1427
		return true;

	return false;
}

1428 1429 1430 1431
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1432

1433
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1434
		.src_nid = task_node(p),
1435 1436 1437 1438 1439 1440

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
		.best_cpu = -1
1441 1442
	};
	struct sched_domain *sd;
1443
	unsigned long taskweight, groupweight;
1444
	int nid, ret, dist;
1445
	long taskimp, groupimp;
1446

1447
	/*
1448 1449 1450 1451 1452 1453
	 * 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.
1454 1455
	 */
	rcu_read_lock();
1456
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1457 1458
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1459 1460
	rcu_read_unlock();

1461 1462 1463 1464 1465 1466 1467
	/*
	 * 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)) {
1468
		p->numa_preferred_nid = task_node(p);
1469 1470 1471
		return -EINVAL;
	}

1472
	env.dst_nid = p->numa_preferred_nid;
1473 1474 1475 1476 1477 1478
	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;
1479
	update_numa_stats(&env.dst_stats, env.dst_nid);
1480

1481
	/* Try to find a spot on the preferred nid. */
1482 1483
	if (numa_has_capacity(&env))
		task_numa_find_cpu(&env, taskimp, groupimp);
1484

1485 1486 1487 1488 1489 1490 1491 1492 1493
	/*
	 * 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)) {
1494 1495 1496
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1497

1498
			dist = node_distance(env.src_nid, env.dst_nid);
1499 1500 1501 1502 1503
			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);
			}
1504

1505
			/* Only consider nodes where both task and groups benefit */
1506 1507
			taskimp = task_weight(p, nid, dist) - taskweight;
			groupimp = group_weight(p, nid, dist) - groupweight;
1508
			if (taskimp < 0 && groupimp < 0)
1509 1510
				continue;

1511
			env.dist = dist;
1512 1513
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1514 1515
			if (numa_has_capacity(&env))
				task_numa_find_cpu(&env, taskimp, groupimp);
1516 1517 1518
		}
	}

1519 1520 1521 1522 1523 1524 1525 1526
	/*
	 * 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.
	 */
1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539
	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;
1540

1541 1542 1543 1544 1545 1546
	/*
	 * 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);

1547
	if (env.best_task == NULL) {
1548 1549 1550
		ret = migrate_task_to(p, env.best_cpu);
		if (ret != 0)
			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
1551 1552 1553 1554
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
1555 1556
	if (ret != 0)
		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
1557 1558
	put_task_struct(env.best_task);
	return ret;
1559 1560
}

1561 1562 1563
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1564 1565
	unsigned long interval = HZ;

1566
	/* This task has no NUMA fault statistics yet */
1567
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1568 1569
		return;

1570
	/* Periodically retry migrating the task to the preferred node */
1571 1572
	interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16);
	p->numa_migrate_retry = jiffies + interval;
1573 1574

	/* Success if task is already running on preferred CPU */
1575
	if (task_node(p) == p->numa_preferred_nid)
1576 1577 1578
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1579
	task_numa_migrate(p);
1580 1581
}

1582 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
/*
 * 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);
	}
}

1614 1615 1616
/*
 * 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
1617 1618 1619
 * 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.
1620 1621
 */
#define NUMA_PERIOD_SLOTS 10
1622
#define NUMA_PERIOD_THRESHOLD 7
1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642

/*
 * 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
1643 1644 1645
	 * 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
1646
	 */
1647
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1648 1649 1650 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
		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
		 */
1681
		ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1682 1683 1684 1685 1686 1687 1688 1689
		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));
}

1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707
/*
 * 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 {
1708 1709
		delta = p->se.avg.load_sum / p->se.load.weight;
		*period = LOAD_AVG_MAX;
1710 1711 1712 1713 1714 1715 1716 1717
	}

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

	return delta;
}

1718 1719 1720 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
/*
 * 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;
1765
		nodemask_t max_group = NODE_MASK_NONE;
1766 1767 1768 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
		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. */
1799 1800
		if (!max_faults)
			break;
1801 1802 1803 1804 1805
		nodes = max_group;
	}
	return nid;
}

1806 1807
static void task_numa_placement(struct task_struct *p)
{
1808 1809
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
1810
	unsigned long fault_types[2] = { 0, 0 };
1811 1812
	unsigned long total_faults;
	u64 runtime, period;
1813
	spinlock_t *group_lock = NULL;
1814

1815 1816 1817 1818 1819
	/*
	 * 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:
	 */
1820
	seq = READ_ONCE(p->mm->numa_scan_seq);
1821 1822 1823
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
1824
	p->numa_scan_period_max = task_scan_max(p);
1825

1826 1827 1828 1829
	total_faults = p->numa_faults_locality[0] +
		       p->numa_faults_locality[1];
	runtime = numa_get_avg_runtime(p, &period);

1830 1831 1832
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
1833
		spin_lock_irq(group_lock);
1834 1835
	}

1836 1837
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
1838 1839
		/* Keep track of the offsets in numa_faults array */
		int mem_idx, membuf_idx, cpu_idx, cpubuf_idx;
1840
		unsigned long faults = 0, group_faults = 0;
1841
		int priv;
1842

1843
		for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) {
1844
			long diff, f_diff, f_weight;
1845

1846 1847 1848 1849
			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);
1850

1851
			/* Decay existing window, copy faults since last scan */
1852 1853 1854
			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;
1855

1856 1857 1858 1859 1860 1861 1862 1863
			/*
			 * 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);
1864
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1865
				   (total_faults + 1);
1866 1867
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
1868

1869 1870 1871
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
1872
			p->total_numa_faults += diff;
1873
			if (p->numa_group) {
1874 1875 1876 1877 1878 1879 1880 1881 1882
				/*
				 * 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;
1883
				p->numa_group->total_faults += diff;
1884
				group_faults += p->numa_group->faults[mem_idx];
1885
			}
1886 1887
		}

1888 1889 1890 1891
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
1892 1893 1894 1895 1896 1897 1898

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

1899 1900
	update_task_scan_period(p, fault_types[0], fault_types[1]);

1901
	if (p->numa_group) {
1902
		update_numa_active_node_mask(p->numa_group);
1903
		spin_unlock_irq(group_lock);
1904
		max_nid = preferred_group_nid(p, max_group_nid);
1905 1906
	}

1907 1908 1909 1910 1911 1912 1913
	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);
1914
	}
1915 1916
}

1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927
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);
}

1928 1929
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
1930 1931 1932 1933 1934 1935 1936 1937 1938
{
	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) +
1939
				    4*nr_node_ids*sizeof(unsigned long);
1940 1941 1942 1943 1944 1945 1946

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

		atomic_set(&grp->refcount, 1);
		spin_lock_init(&grp->lock);
1947
		grp->gid = p->pid;
1948
		/* Second half of the array tracks nids where faults happen */
1949 1950
		grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES *
						nr_node_ids;
1951

1952 1953
		node_set(task_node(current), grp->active_nodes);

1954
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
1955
			grp->faults[i] = p->numa_faults[i];
1956

1957
		grp->total_faults = p->total_numa_faults;
1958

1959 1960 1961 1962 1963
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
1964
	tsk = READ_ONCE(cpu_rq(cpu)->curr);
1965 1966

	if (!cpupid_match_pid(tsk, cpupid))
1967
		goto no_join;
1968 1969 1970

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
1971
		goto no_join;
1972 1973 1974

	my_grp = p->numa_group;
	if (grp == my_grp)
1975
		goto no_join;
1976 1977 1978 1979 1980 1981

	/*
	 * 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)
1982
		goto no_join;
1983 1984 1985 1986 1987

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1988
		goto no_join;
1989

1990 1991 1992 1993 1994 1995 1996
	/* 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;
1997

1998 1999 2000
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

2001
	if (join && !get_numa_group(grp))
2002
		goto no_join;
2003 2004 2005 2006 2007 2008

	rcu_read_unlock();

	if (!join)
		return;

2009 2010
	BUG_ON(irqs_disabled());
	double_lock_irq(&my_grp->lock, &grp->lock);
2011

2012
	for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) {
2013 2014
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
2015
	}
2016 2017
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
2018 2019 2020 2021 2022

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

	spin_unlock(&my_grp->lock);
2023
	spin_unlock_irq(&grp->lock);
2024 2025 2026 2027

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
2028 2029 2030 2031 2032
	return;

no_join:
	rcu_read_unlock();
	return;
2033 2034 2035 2036 2037
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
2038
	void *numa_faults = p->numa_faults;
2039 2040
	unsigned long flags;
	int i;
2041 2042

	if (grp) {
2043
		spin_lock_irqsave(&grp->lock, flags);
2044
		for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++)
2045
			grp->faults[i] -= p->numa_faults[i];
2046
		grp->total_faults -= p->total_numa_faults;
2047

2048
		grp->nr_tasks--;
2049
		spin_unlock_irqrestore(&grp->lock, flags);
2050
		RCU_INIT_POINTER(p->numa_group, NULL);
2051 2052 2053
		put_numa_group(grp);
	}

2054
	p->numa_faults = NULL;
2055
	kfree(numa_faults);
2056 2057
}

2058 2059 2060
/*
 * Got a PROT_NONE fault for a page on @node.
 */
2061
void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
2062 2063
{
	struct task_struct *p = current;
2064
	bool migrated = flags & TNF_MIGRATED;
2065
	int cpu_node = task_node(current);
2066
	int local = !!(flags & TNF_FAULT_LOCAL);
2067
	int priv;
2068

2069
	if (!numabalancing_enabled)
2070 2071
		return;

2072 2073 2074 2075
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

2076
	/* Allocate buffer to track faults on a per-node basis */
2077 2078
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) *
2079
			   NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids;
2080

2081 2082
		p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN);
		if (!p->numa_faults)
2083
			return;
2084

2085
		p->total_numa_faults = 0;
2086
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
2087
	}
2088

2089 2090 2091 2092 2093 2094 2095 2096
	/*
	 * 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);
2097
		if (!priv && !(flags & TNF_NO_GROUP))
2098
			task_numa_group(p, last_cpupid, flags, &priv);
2099 2100
	}

2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111
	/*
	 * 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;

2112
	task_numa_placement(p);
2113

2114 2115 2116 2117 2118
	/*
	 * 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))
2119 2120
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
2121 2122
	if (migrated)
		p->numa_pages_migrated += pages;
2123 2124
	if (flags & TNF_MIGRATE_FAIL)
		p->numa_faults_locality[2] += pages;
I
Ingo Molnar 已提交
2125

2126 2127
	p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages;
	p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages;
2128
	p->numa_faults_locality[local] += pages;
2129 2130
}

2131 2132
static void reset_ptenuma_scan(struct task_struct *p)
{
2133 2134 2135 2136 2137 2138 2139 2140
	/*
	 * 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:
	 */
2141
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2142 2143 2144
	p->mm->numa_scan_offset = 0;
}

2145 2146 2147 2148 2149 2150 2151 2152 2153
/*
 * 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;
2154
	struct vm_area_struct *vma;
2155
	unsigned long start, end;
2156
	unsigned long nr_pte_updates = 0;
2157
	long pages;
2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172

	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;

2173
	if (!mm->numa_next_scan) {
2174 2175
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2176 2177
	}

2178 2179 2180 2181 2182 2183 2184
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

2185 2186 2187 2188
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
		p->numa_scan_period = task_scan_min(p);
	}
2189

2190
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
2191 2192 2193
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

2194 2195 2196 2197 2198 2199
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

2200 2201 2202 2203 2204
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
	if (!pages)
		return;
2205

2206
	down_read(&mm->mmap_sem);
2207
	vma = find_vma(mm, start);
2208 2209
	if (!vma) {
		reset_ptenuma_scan(p);
2210
		start = 0;
2211 2212
		vma = mm->mmap;
	}
2213
	for (; vma; vma = vma->vm_next) {
2214
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2215
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2216
			continue;
2217
		}
2218

2219 2220 2221 2222 2223 2224 2225 2226 2227 2228
		/*
		 * 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
2229 2230 2231 2232 2233 2234
		/*
		 * 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;
2235

2236 2237 2238 2239
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2240 2241 2242 2243 2244 2245 2246 2247 2248
			nr_pte_updates += change_prot_numa(vma, start, end);

			/*
			 * Scan sysctl_numa_balancing_scan_size but ensure that
			 * at least one PTE is updated so that unused virtual
			 * address space is quickly skipped.
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
2249

2250 2251 2252
			start = end;
			if (pages <= 0)
				goto out;
2253 2254

			cond_resched();
2255
		} while (end != vma->vm_end);
2256
	}
2257

2258
out:
2259
	/*
P
Peter Zijlstra 已提交
2260 2261 2262 2263
	 * 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.
2264 2265
	 */
	if (vma)
2266
		mm->numa_scan_offset = start;
2267 2268 2269
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295
}

/*
 * 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) {
2296
		if (!curr->node_stamp)
2297
			curr->numa_scan_period = task_scan_min(curr);
2298
		curr->node_stamp += period;
2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309

		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)
{
}
2310 2311 2312 2313 2314 2315 2316 2317

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)
{
}
2318 2319
#endif /* CONFIG_NUMA_BALANCING */

2320 2321 2322 2323
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2324
	if (!parent_entity(se))
2325
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2326
#ifdef CONFIG_SMP
2327 2328 2329 2330 2331 2332
	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);
	}
2333
#endif
2334 2335 2336 2337 2338 2339 2340
	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);
2341
	if (!parent_entity(se))
2342
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2343 2344
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2345
		list_del_init(&se->group_node);
2346
	}
2347 2348 2349
	cfs_rq->nr_running--;
}

2350 2351
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
2352 2353 2354 2355 2356
static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
{
	long tg_weight;

	/*
2357 2358 2359
	 * 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().
2360
	 */
2361
	tg_weight = atomic_long_read(&tg->load_avg);
2362 2363
	tg_weight -= cfs_rq->tg_load_avg_contrib;
	tg_weight += cfs_rq->avg.load_avg;
2364 2365 2366 2367

	return tg_weight;
}

2368
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2369
{
2370
	long tg_weight, load, shares;
2371

2372
	tg_weight = calc_tg_weight(tg, cfs_rq);
2373
	load = cfs_rq->avg.load_avg;
2374 2375

	shares = (tg->shares * load);
2376 2377
	if (tg_weight)
		shares /= tg_weight;
2378 2379 2380 2381 2382 2383 2384 2385 2386

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

	return shares;
}
# else /* CONFIG_SMP */
2387
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2388 2389 2390 2391
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
2392 2393 2394
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
2395 2396 2397 2398
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
2399
		account_entity_dequeue(cfs_rq, se);
2400
	}
P
Peter Zijlstra 已提交
2401 2402 2403 2404 2405 2406 2407

	update_load_set(&se->load, weight);

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

2408 2409
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2410
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2411 2412 2413
{
	struct task_group *tg;
	struct sched_entity *se;
2414
	long shares;
P
Peter Zijlstra 已提交
2415 2416 2417

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
2418
	if (!se || throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
2419
		return;
2420 2421 2422 2423
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
2424
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
2425 2426 2427 2428

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
2429
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2430 2431 2432 2433
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

2434
#ifdef CONFIG_SMP
2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454
/* 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,
};

2455 2456 2457 2458 2459 2460
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472
	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
2473 2474
	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
	 * With a look-up table which covers y^n (n<PERIOD)
2475 2476 2477 2478 2479 2480
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
2481 2482
	}

2483 2484
	val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
	return val;
2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512
}

/*
 * 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];
2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542
}

/*
 * 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}]
 */
2543 2544 2545
static __always_inline int
__update_load_avg(u64 now, int cpu, struct sched_avg *sa,
		  unsigned long weight, int running)
2546
{
2547
	u64 delta, periods;
2548
	u32 contrib;
2549
	int delta_w, decayed = 0;
2550
	unsigned long scale_freq = arch_scale_freq_capacity(NULL, cpu);
2551

2552
	delta = now - sa->last_update_time;
2553 2554 2555 2556 2557
	/*
	 * 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) {
2558
		sa->last_update_time = now;
2559 2560 2561 2562 2563 2564 2565 2566 2567 2568
		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;
2569
	sa->last_update_time = now;
2570 2571

	/* delta_w is the amount already accumulated against our next period */
2572
	delta_w = sa->period_contrib;
2573 2574 2575
	if (delta + delta_w >= 1024) {
		decayed = 1;

2576 2577 2578
		/* how much left for next period will start over, we don't know yet */
		sa->period_contrib = 0;

2579 2580 2581 2582 2583 2584
		/*
		 * 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;
2585 2586
		if (weight)
			sa->load_sum += weight * delta_w;
2587
		if (running)
2588
			sa->util_sum += delta_w * scale_freq >> SCHED_CAPACITY_SHIFT;
2589 2590 2591 2592 2593 2594 2595

		delta -= delta_w;

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

2596 2597
		sa->load_sum = decay_load(sa->load_sum, periods + 1);
		sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2598 2599

		/* Efficiently calculate \sum (1..n_period) 1024*y^i */
2600 2601 2602
		contrib = __compute_runnable_contrib(periods);
		if (weight)
			sa->load_sum += weight * contrib;
2603
		if (running)
2604
			sa->util_sum += contrib * scale_freq >> SCHED_CAPACITY_SHIFT;
2605 2606 2607
	}

	/* Remainder of delta accrued against u_0` */
2608 2609
	if (weight)
		sa->load_sum += weight * delta;
2610
	if (running)
2611
		sa->util_sum += delta * scale_freq >> SCHED_CAPACITY_SHIFT;
2612

2613
	sa->period_contrib += delta;
2614

2615 2616 2617 2618
	if (decayed) {
		sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
		sa->util_avg = (sa->util_sum << SCHED_LOAD_SHIFT) / LOAD_AVG_MAX;
	}
2619

2620
	return decayed;
2621 2622
}

2623
#ifdef CONFIG_FAIR_GROUP_SCHED
2624
/*
2625 2626
 * 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).
2627
 */
2628
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2629
{
2630
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2631

2632 2633 2634
	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;
2635
	}
2636
}
2637

2638
#else /* CONFIG_FAIR_GROUP_SCHED */
2639
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2640
#endif /* CONFIG_FAIR_GROUP_SCHED */
2641

2642
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2643

2644 2645
/* 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)
2646
{
2647 2648
	int decayed;
	struct sched_avg *sa = &cfs_rq->avg;
2649

2650 2651 2652 2653
	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);
2654
	}
2655

2656 2657 2658 2659 2660 2661
	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);
		sa->util_sum = max_t(s32, sa->util_sum -
			((r * LOAD_AVG_MAX) >> SCHED_LOAD_SHIFT), 0);
	}
2662

2663 2664
	decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
		scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL);
2665

2666 2667 2668 2669
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
2670

2671
	return decayed;
2672 2673
}

2674 2675
/* Update task and its cfs_rq load average */
static inline void update_load_avg(struct sched_entity *se, int update_tg)
2676
{
2677
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
2678
	int cpu = cpu_of(rq_of(cfs_rq));
2679
	u64 now = cfs_rq_clock_task(cfs_rq);
2680

2681
	/*
2682 2683
	 * 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
2684
	 */
2685 2686
	__update_load_avg(now, cpu, &se->avg,
		se->on_rq * scale_load_down(se->load.weight), cfs_rq->curr == se);
2687

2688 2689
	if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
		update_tg_load_avg(cfs_rq, 0);
2690 2691
}

2692 2693 2694
/* 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)
2695
{
2696 2697 2698
	struct sched_avg *sa = &se->avg;
	u64 now = cfs_rq_clock_task(cfs_rq);
	int migrated = 0, decayed;
2699

2700 2701 2702
	if (sa->last_update_time == 0) {
		sa->last_update_time = now;
		migrated = 1;
2703
	}
2704 2705 2706
	else {
		__update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
			se->on_rq * scale_load_down(se->load.weight), cfs_rq->curr == se);
2707
	}
2708

2709
	decayed = update_cfs_rq_load_avg(now, cfs_rq);
2710

2711 2712 2713 2714 2715
	if (migrated) {
		cfs_rq->avg.load_avg += sa->load_avg;
		cfs_rq->avg.load_sum += sa->load_sum;
		cfs_rq->avg.util_avg += sa->util_avg;
		cfs_rq->avg.util_sum += sa->util_sum;
2716 2717
	}

2718 2719
	if (decayed || migrated)
		update_tg_load_avg(cfs_rq, 0);
2720 2721
}

2722
/*
2723 2724
 * Task first catches up with cfs_rq, and then subtract
 * itself from the cfs_rq (task must be off the queue now).
2725
 */
2726
void remove_entity_load_avg(struct sched_entity *se)
2727
{
2728 2729 2730 2731 2732
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 last_update_time;

#ifndef CONFIG_64BIT
	u64 last_update_time_copy;
2733

2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745
	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

	__update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0);
	atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
	atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2746
}
2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765

/*
 * 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)
{
}

2766 2767
static int idle_balance(struct rq *this_rq);

2768 2769
#else /* CONFIG_SMP */

2770 2771 2772 2773
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) {}
static inline void remove_entity_load_avg(struct sched_entity *se) {}
2774 2775 2776 2777 2778 2779

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

2780
#endif /* CONFIG_SMP */
2781

2782
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2783 2784
{
#ifdef CONFIG_SCHEDSTATS
2785 2786 2787 2788 2789
	struct task_struct *tsk = NULL;

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

2790
	if (se->statistics.sleep_start) {
2791
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2792 2793 2794 2795

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

2796 2797
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
2798

2799
		se->statistics.sleep_start = 0;
2800
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
2801

2802
		if (tsk) {
2803
			account_scheduler_latency(tsk, delta >> 10, 1);
2804 2805
			trace_sched_stat_sleep(tsk, delta);
		}
2806
	}
2807
	if (se->statistics.block_start) {
2808
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2809 2810 2811 2812

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

2813 2814
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
2815

2816
		se->statistics.block_start = 0;
2817
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
2818

2819
		if (tsk) {
2820
			if (tsk->in_iowait) {
2821 2822
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
2823
				trace_sched_stat_iowait(tsk, delta);
2824 2825
			}

2826 2827
			trace_sched_stat_blocked(tsk, delta);

2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838
			/*
			 * 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
2839
		}
2840 2841 2842 2843
	}
#endif
}

P
Peter Zijlstra 已提交
2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856
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
}

2857 2858 2859
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
2860
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
2861

2862 2863 2864 2865 2866 2867
	/*
	 * 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
2868
	if (initial && sched_feat(START_DEBIT))
2869
		vruntime += sched_vslice(cfs_rq, se);
2870

2871
	/* sleeps up to a single latency don't count. */
2872
	if (!initial) {
2873
		unsigned long thresh = sysctl_sched_latency;
2874

2875 2876 2877 2878 2879 2880
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
2881

2882
		vruntime -= thresh;
2883 2884
	}

2885
	/* ensure we never gain time by being placed backwards. */
2886
	se->vruntime = max_vruntime(se->vruntime, vruntime);
2887 2888
}

2889 2890
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

2891
static void
2892
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2893
{
2894 2895
	/*
	 * Update the normalized vruntime before updating min_vruntime
2896
	 * through calling update_curr().
2897
	 */
2898
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
2899 2900
		se->vruntime += cfs_rq->min_vruntime;

2901
	/*
2902
	 * Update run-time statistics of the 'current'.
2903
	 */
2904
	update_curr(cfs_rq);
2905
	enqueue_entity_load_avg(cfs_rq, se);
2906 2907
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
2908

2909
	if (flags & ENQUEUE_WAKEUP) {
2910
		place_entity(cfs_rq, se, 0);
2911
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
2912
	}
2913

2914
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
2915
	check_spread(cfs_rq, se);
2916 2917
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
2918
	se->on_rq = 1;
2919

2920
	if (cfs_rq->nr_running == 1) {
2921
		list_add_leaf_cfs_rq(cfs_rq);
2922 2923
		check_enqueue_throttle(cfs_rq);
	}
2924 2925
}

2926
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
2927
{
2928 2929
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
2930
		if (cfs_rq->last != se)
2931
			break;
2932 2933

		cfs_rq->last = NULL;
2934 2935
	}
}
P
Peter Zijlstra 已提交
2936

2937 2938 2939 2940
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
2941
		if (cfs_rq->next != se)
2942
			break;
2943 2944

		cfs_rq->next = NULL;
2945
	}
P
Peter Zijlstra 已提交
2946 2947
}

2948 2949 2950 2951
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
2952
		if (cfs_rq->skip != se)
2953
			break;
2954 2955

		cfs_rq->skip = NULL;
2956 2957 2958
	}
}

P
Peter Zijlstra 已提交
2959 2960
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2961 2962 2963 2964 2965
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
2966 2967 2968

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
2969 2970
}

2971
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
2972

2973
static void
2974
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2975
{
2976 2977 2978 2979
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
2980
	update_load_avg(se, 1);
2981

2982
	update_stats_dequeue(cfs_rq, se);
2983
	if (flags & DEQUEUE_SLEEP) {
P
Peter Zijlstra 已提交
2984
#ifdef CONFIG_SCHEDSTATS
2985 2986 2987 2988
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
2989
				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
2990
			if (tsk->state & TASK_UNINTERRUPTIBLE)
2991
				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
2992
		}
2993
#endif
P
Peter Zijlstra 已提交
2994 2995
	}

P
Peter Zijlstra 已提交
2996
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
2997

2998
	if (se != cfs_rq->curr)
2999
		__dequeue_entity(cfs_rq, se);
3000
	se->on_rq = 0;
3001
	account_entity_dequeue(cfs_rq, se);
3002 3003 3004 3005 3006 3007

	/*
	 * 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.
	 */
3008
	if (!(flags & DEQUEUE_SLEEP))
3009
		se->vruntime -= cfs_rq->min_vruntime;
3010

3011 3012 3013
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3014
	update_min_vruntime(cfs_rq);
3015
	update_cfs_shares(cfs_rq);
3016 3017 3018 3019 3020
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
3021
static void
I
Ingo Molnar 已提交
3022
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3023
{
3024
	unsigned long ideal_runtime, delta_exec;
3025 3026
	struct sched_entity *se;
	s64 delta;
3027

P
Peter Zijlstra 已提交
3028
	ideal_runtime = sched_slice(cfs_rq, curr);
3029
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3030
	if (delta_exec > ideal_runtime) {
3031
		resched_curr(rq_of(cfs_rq));
3032 3033 3034 3035 3036
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047
		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;

3048 3049
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
3050

3051 3052
	if (delta < 0)
		return;
3053

3054
	if (delta > ideal_runtime)
3055
		resched_curr(rq_of(cfs_rq));
3056 3057
}

3058
static void
3059
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3060
{
3061 3062 3063 3064 3065 3066 3067 3068 3069
	/* '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);
3070
		update_load_avg(se, 1);
3071 3072
	}

3073
	update_stats_curr_start(cfs_rq, se);
3074
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
3075 3076 3077 3078 3079 3080
#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):
	 */
3081
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3082
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
3083 3084 3085
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
3086
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
3087 3088
}

3089 3090 3091
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

3092 3093 3094 3095 3096 3097 3098
/*
 * 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
 */
3099 3100
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3101
{
3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112
	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 */
3113

3114 3115 3116 3117 3118
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
3119 3120 3121 3122 3123 3124 3125 3126 3127 3128
		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;
		}

3129 3130 3131
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
3132

3133 3134 3135 3136 3137 3138
	/*
	 * 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;

3139 3140 3141 3142 3143 3144
	/*
	 * 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;

3145
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3146 3147

	return se;
3148 3149
}

3150
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3151

3152
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3153 3154 3155 3156 3157 3158
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
3159
		update_curr(cfs_rq);
3160

3161 3162 3163
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

P
Peter Zijlstra 已提交
3164
	check_spread(cfs_rq, prev);
3165
	if (prev->on_rq) {
3166
		update_stats_wait_start(cfs_rq, prev);
3167 3168
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
3169
		/* in !on_rq case, update occurred at dequeue */
3170
		update_load_avg(prev, 0);
3171
	}
3172
	cfs_rq->curr = NULL;
3173 3174
}

P
Peter Zijlstra 已提交
3175 3176
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3177 3178
{
	/*
3179
	 * Update run-time statistics of the 'current'.
3180
	 */
3181
	update_curr(cfs_rq);
3182

3183 3184 3185
	/*
	 * Ensure that runnable average is periodically updated.
	 */
3186
	update_load_avg(curr, 1);
3187
	update_cfs_shares(cfs_rq);
3188

P
Peter Zijlstra 已提交
3189 3190 3191 3192 3193
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
3194
	if (queued) {
3195
		resched_curr(rq_of(cfs_rq));
3196 3197
		return;
	}
P
Peter Zijlstra 已提交
3198 3199 3200 3201 3202 3203 3204 3205
	/*
	 * 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
3206
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
3207
		check_preempt_tick(cfs_rq, curr);
3208 3209
}

3210 3211 3212 3213 3214 3215

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

#ifdef CONFIG_CFS_BANDWIDTH
3216 3217

#ifdef HAVE_JUMP_LABEL
3218
static struct static_key __cfs_bandwidth_used;
3219 3220 3221

static inline bool cfs_bandwidth_used(void)
{
3222
	return static_key_false(&__cfs_bandwidth_used);
3223 3224
}

3225
void cfs_bandwidth_usage_inc(void)
3226
{
3227 3228 3229 3230 3231 3232
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
3233 3234 3235 3236 3237 3238 3239
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

3240 3241
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
3242 3243
#endif /* HAVE_JUMP_LABEL */

3244 3245 3246 3247 3248 3249 3250 3251
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
3252 3253 3254 3255 3256 3257

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

P
Paul Turner 已提交
3258 3259 3260 3261 3262 3263 3264
/*
 * 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
 */
3265
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276
{
	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);
}

3277 3278 3279 3280 3281
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

3282 3283 3284 3285 3286 3287
/* 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;

3288
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3289 3290
}

3291 3292
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3293 3294 3295
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
3296
	u64 amount = 0, min_amount, expires;
3297 3298 3299 3300 3301 3302 3303

	/* 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;
3304
	else {
P
Peter Zijlstra 已提交
3305
		start_cfs_bandwidth(cfs_b);
3306 3307 3308 3309 3310 3311

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
3312
	}
P
Paul Turner 已提交
3313
	expires = cfs_b->runtime_expires;
3314 3315 3316
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
3317 3318 3319 3320 3321 3322 3323
	/*
	 * 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;
3324 3325

	return cfs_rq->runtime_remaining > 0;
3326 3327
}

P
Paul Turner 已提交
3328 3329 3330 3331 3332
/*
 * 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)
3333
{
P
Paul Turner 已提交
3334 3335 3336
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
3337
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3338 3339
		return;

P
Paul Turner 已提交
3340 3341 3342 3343 3344 3345 3346 3347 3348
	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
3349 3350 3351
	 * 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
3352 3353
	 */

3354
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
3355 3356 3357 3358 3359 3360 3361 3362
		/* 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;
	}
}

3363
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
3364 3365
{
	/* dock delta_exec before expiring quota (as it could span periods) */
3366
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
3367 3368 3369
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
3370 3371
		return;

3372 3373 3374 3375 3376
	/*
	 * 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))
3377
		resched_curr(rq_of(cfs_rq));
3378 3379
}

3380
static __always_inline
3381
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3382
{
3383
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3384 3385 3386 3387 3388
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

3389 3390
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
3391
	return cfs_bandwidth_used() && cfs_rq->throttled;
3392 3393
}

3394 3395 3396
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
3397
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425
}

/*
 * 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) {
3426
		/* adjust cfs_rq_clock_task() */
3427
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3428
					     cfs_rq->throttled_clock_task;
3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439
	}
#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)];

3440 3441
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
3442
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
3443 3444 3445 3446 3447
	cfs_rq->throttle_count++;

	return 0;
}

3448
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3449 3450 3451 3452 3453
{
	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
3454
	bool empty;
3455 3456 3457

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

3458
	/* freeze hierarchy runnable averages while throttled */
3459 3460 3461
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477 3478

	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)
3479
		sub_nr_running(rq, task_delta);
3480 3481

	cfs_rq->throttled = 1;
3482
	cfs_rq->throttled_clock = rq_clock(rq);
3483
	raw_spin_lock(&cfs_b->lock);
3484
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
3485

3486 3487 3488 3489 3490
	/*
	 * 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
3491 3492 3493 3494 3495 3496 3497 3498

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

3499 3500 3501
	raw_spin_unlock(&cfs_b->lock);
}

3502
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3503 3504 3505 3506 3507 3508 3509
{
	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;

3510
	se = cfs_rq->tg->se[cpu_of(rq)];
3511 3512

	cfs_rq->throttled = 0;
3513 3514 3515

	update_rq_clock(rq);

3516
	raw_spin_lock(&cfs_b->lock);
3517
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3518 3519 3520
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

3521 3522 3523
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

3524 3525 3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541
	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)
3542
		add_nr_running(rq, task_delta);
3543 3544 3545

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
3546
		resched_curr(rq);
3547 3548 3549 3550 3551 3552
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
3553 3554
	u64 runtime;
	u64 starting_runtime = remaining;
3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584

	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();

3585
	return starting_runtime - remaining;
3586 3587
}

3588 3589 3590 3591 3592 3593 3594 3595
/*
 * 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)
{
3596
	u64 runtime, runtime_expires;
3597
	int throttled;
3598 3599 3600

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
3601
		goto out_deactivate;
3602

3603
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3604
	cfs_b->nr_periods += overrun;
3605

3606 3607 3608 3609 3610 3611
	/*
	 * 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
3612 3613 3614

	__refill_cfs_bandwidth_runtime(cfs_b);

3615 3616 3617
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
3618
		return 0;
3619 3620
	}

3621 3622 3623
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

3624 3625 3626
	runtime_expires = cfs_b->runtime_expires;

	/*
3627 3628 3629 3630 3631
	 * 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.
3632
	 */
3633 3634
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
3635 3636 3637 3638 3639 3640 3641
		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);
3642 3643

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
3644
	}
3645

3646 3647 3648 3649 3650 3651 3652
	/*
	 * 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;
3653

3654 3655 3656 3657
	return 0;

out_deactivate:
	return 1;
3658
}
3659

3660 3661 3662 3663 3664 3665 3666
/* 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;

3667 3668 3669 3670
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3671
 * hrtimer base being cleared by hrtimer_start. In the case of
3672 3673
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698
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
3699 3700 3701
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730
}

/* 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)
{
3731 3732 3733
	if (!cfs_bandwidth_used())
		return;

3734
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749
		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 */
3750 3751 3752
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
3753
		return;
3754
	}
3755

3756
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3757
		runtime = cfs_b->runtime;
3758

3759 3760 3761 3762 3763 3764 3765 3766 3767 3768
	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)
3769
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
3770 3771 3772
	raw_spin_unlock(&cfs_b->lock);
}

3773 3774 3775 3776 3777 3778 3779
/*
 * 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)
{
3780 3781 3782
	if (!cfs_bandwidth_used())
		return;

3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797
	/* 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() */
3798
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3799
{
3800
	if (!cfs_bandwidth_used())
3801
		return false;
3802

3803
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3804
		return false;
3805 3806 3807 3808 3809 3810

	/*
	 * 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))
3811
		return true;
3812 3813

	throttle_cfs_rq(cfs_rq);
3814
	return true;
3815
}
3816 3817 3818 3819 3820

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
3821

3822 3823 3824 3825 3826 3827 3828 3829 3830 3831 3832 3833
	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;

3834
	raw_spin_lock(&cfs_b->lock);
3835
	for (;;) {
P
Peter Zijlstra 已提交
3836
		overrun = hrtimer_forward_now(timer, cfs_b->period);
3837 3838 3839 3840 3841
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
P
Peter Zijlstra 已提交
3842 3843
	if (idle)
		cfs_b->period_active = 0;
3844
	raw_spin_unlock(&cfs_b->lock);
3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856

	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
3857
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
3858 3859 3860 3861 3862 3863 3864 3865 3866 3867 3868
	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
3869
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3870
{
P
Peter Zijlstra 已提交
3871
	lockdep_assert_held(&cfs_b->lock);
3872

P
Peter Zijlstra 已提交
3873 3874 3875 3876 3877
	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);
	}
3878 3879 3880 3881
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
3882 3883 3884 3885
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

3886 3887 3888 3889
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902
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);
	}
}

3903
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
3904 3905 3906 3907 3908 3909 3910 3911 3912 3913 3914
{
	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
		 */
3915
		cfs_rq->runtime_remaining = 1;
3916 3917 3918 3919 3920 3921
		/*
		 * 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;

3922 3923 3924 3925 3926 3927
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
}

#else /* CONFIG_CFS_BANDWIDTH */
3928 3929
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
3930
	return rq_clock_task(rq_of(cfs_rq));
3931 3932
}

3933
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
3934
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
3935
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
3936
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
3937 3938 3939 3940 3941

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952

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;
}
3953 3954 3955 3956 3957

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) {}
3958 3959
#endif

3960 3961 3962 3963 3964
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) {}
3965
static inline void update_runtime_enabled(struct rq *rq) {}
3966
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
3967 3968 3969

#endif /* CONFIG_CFS_BANDWIDTH */

3970 3971 3972 3973
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
3974 3975 3976 3977 3978 3979 3980 3981
#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);

3982
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
3983 3984 3985 3986 3987 3988
		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)
3989
				resched_curr(rq);
P
Peter Zijlstra 已提交
3990 3991
			return;
		}
3992
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
3993 3994
	}
}
3995 3996 3997 3998 3999 4000 4001 4002 4003 4004

/*
 * 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;

4005
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4006 4007 4008 4009 4010
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
4011
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
4012 4013 4014 4015
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
4016 4017 4018 4019

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
4020 4021
#endif

4022 4023 4024 4025 4026
/*
 * 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:
 */
4027
static void
4028
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4029 4030
{
	struct cfs_rq *cfs_rq;
4031
	struct sched_entity *se = &p->se;
4032 4033

	for_each_sched_entity(se) {
4034
		if (se->on_rq)
4035 4036
			break;
		cfs_rq = cfs_rq_of(se);
4037
		enqueue_entity(cfs_rq, se, flags);
4038 4039 4040 4041 4042 4043 4044 4045 4046

		/*
		 * 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;
4047
		cfs_rq->h_nr_running++;
4048

4049
		flags = ENQUEUE_WAKEUP;
4050
	}
P
Peter Zijlstra 已提交
4051

P
Peter Zijlstra 已提交
4052
	for_each_sched_entity(se) {
4053
		cfs_rq = cfs_rq_of(se);
4054
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
4055

4056 4057 4058
		if (cfs_rq_throttled(cfs_rq))
			break;

4059
		update_load_avg(se, 1);
4060
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4061 4062
	}

Y
Yuyang Du 已提交
4063
	if (!se)
4064
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
4065

4066
	hrtick_update(rq);
4067 4068
}

4069 4070
static void set_next_buddy(struct sched_entity *se);

4071 4072 4073 4074 4075
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
4076
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4077 4078
{
	struct cfs_rq *cfs_rq;
4079
	struct sched_entity *se = &p->se;
4080
	int task_sleep = flags & DEQUEUE_SLEEP;
4081 4082 4083

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
4084
		dequeue_entity(cfs_rq, se, flags);
4085 4086 4087 4088 4089 4090 4091 4092 4093

		/*
		 * 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;
4094
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4095

4096
		/* Don't dequeue parent if it has other entities besides us */
4097 4098 4099 4100 4101 4102 4103
		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));
4104 4105 4106

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
4107
			break;
4108
		}
4109
		flags |= DEQUEUE_SLEEP;
4110
	}
P
Peter Zijlstra 已提交
4111

P
Peter Zijlstra 已提交
4112
	for_each_sched_entity(se) {
4113
		cfs_rq = cfs_rq_of(se);
4114
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4115

4116 4117 4118
		if (cfs_rq_throttled(cfs_rq))
			break;

4119
		update_load_avg(se, 1);
4120
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4121 4122
	}

Y
Yuyang Du 已提交
4123
	if (!se)
4124
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
4125

4126
	hrtick_update(rq);
4127 4128
}

4129
#ifdef CONFIG_SMP
4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170 4171 4172 4173 4174 4175 4176 4177 4178 4179 4180 4181 4182 4183 4184 4185 4186 4187 4188 4189 4190 4191 4192 4193 4194 4195 4196 4197 4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208 4209 4210 4211 4212 4213 4214 4215 4216 4217 4218 4219 4220 4221 4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 4256 4257

/*
 * 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);
}

#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)
{
4258
	unsigned long curr_jiffies = READ_ONCE(jiffies);
4259
	unsigned long load = this_rq->cfs.avg.load_avg;
4260 4261 4262 4263 4264 4265 4266 4267 4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279
	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();
4280
	unsigned long curr_jiffies = READ_ONCE(jiffies);
4281 4282 4283 4284 4285 4286 4287 4288 4289 4290 4291 4292 4293 4294 4295 4296 4297 4298 4299 4300 4301 4302 4303 4304
	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)
{
4305
	unsigned long load = this_rq->cfs.avg.load_avg;
4306 4307 4308 4309 4310 4311 4312
	/*
	 * 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);
}

4313 4314 4315
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
4316
	return cpu_rq(cpu)->cfs.avg.load_avg;
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 4343 4344 4345 4346 4347 4348 4349 4350 4351
}

/*
 * 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);
}

4352
static unsigned long capacity_of(int cpu)
4353
{
4354
	return cpu_rq(cpu)->cpu_capacity;
4355 4356
}

4357 4358 4359 4360 4361
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

4362 4363 4364
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
4365
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4366
	unsigned long load_avg = rq->cfs.avg.load_avg;
4367 4368

	if (nr_running)
4369
		return load_avg / nr_running;
4370 4371 4372 4373

	return 0;
}

4374 4375 4376 4377 4378 4379 4380
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.
	 */
4381
	if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4382
		current->wakee_flips >>= 1;
4383 4384 4385 4386 4387 4388 4389 4390
		current->wakee_flip_decay_ts = jiffies;
	}

	if (current->last_wakee != p) {
		current->last_wakee = p;
		current->wakee_flips++;
	}
}
4391

4392
static void task_waking_fair(struct task_struct *p)
4393 4394 4395
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
4396 4397 4398 4399
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
4400

4401 4402 4403 4404 4405 4406 4407 4408
	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
4409

4410
	se->vruntime -= min_vruntime;
4411
	record_wakee(p);
4412 4413
}

4414
#ifdef CONFIG_FAIR_GROUP_SCHED
4415 4416 4417 4418 4419 4420
/*
 * 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.
4421 4422 4423 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 4457 4458 4459 4460 4461 4462 4463
 *
 * 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.
4464
 */
P
Peter Zijlstra 已提交
4465
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4466
{
P
Peter Zijlstra 已提交
4467
	struct sched_entity *se = tg->se[cpu];
4468

4469
	if (!tg->parent)	/* the trivial, non-cgroup case */
4470 4471
		return wl;

P
Peter Zijlstra 已提交
4472
	for_each_sched_entity(se) {
4473
		long w, W;
P
Peter Zijlstra 已提交
4474

4475
		tg = se->my_q->tg;
4476

4477 4478 4479 4480
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
4481

4482 4483 4484
		/*
		 * w = rw_i + @wl
		 */
4485
		w = se->my_q->avg.load_avg + wl;
4486

4487 4488 4489 4490
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
4491
			wl = (w * (long)tg->shares) / W;
4492 4493
		else
			wl = tg->shares;
4494

4495 4496 4497 4498 4499
		/*
		 * 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().
		 */
4500 4501
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
4502 4503 4504 4505

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
4506
		wl -= se->avg.load_avg;
4507 4508 4509 4510 4511 4512 4513 4514

		/*
		 * 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
4515 4516
		wg = 0;
	}
4517

P
Peter Zijlstra 已提交
4518
	return wl;
4519 4520
}
#else
P
Peter Zijlstra 已提交
4521

4522
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
P
Peter Zijlstra 已提交
4523
{
4524
	return wl;
4525
}
P
Peter Zijlstra 已提交
4526

4527 4528
#endif

M
Mike Galbraith 已提交
4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540
/*
 * 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.
 */
4541 4542
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
4543 4544
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
4545
	int factor = this_cpu_read(sd_llc_size);
4546

M
Mike Galbraith 已提交
4547 4548 4549 4550 4551
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
4552 4553
}

4554
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4555
{
4556
	s64 this_load, load;
4557
	s64 this_eff_load, prev_eff_load;
4558 4559
	int idx, this_cpu, prev_cpu;
	struct task_group *tg;
4560
	unsigned long weight;
4561
	int balanced;
4562

4563 4564 4565 4566 4567
	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);
4568

4569 4570 4571 4572 4573
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
4574 4575
	if (sync) {
		tg = task_group(current);
4576
		weight = current->se.avg.load_avg;
4577

4578
		this_load += effective_load(tg, this_cpu, -weight, -weight);
4579 4580
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
4581

4582
	tg = task_group(p);
4583
	weight = p->se.avg.load_avg;
4584

4585 4586
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4587 4588 4589
	 * 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.
4590 4591 4592 4593
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
4594 4595
	this_eff_load = 100;
	this_eff_load *= capacity_of(prev_cpu);
4596

4597 4598
	prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= capacity_of(this_cpu);
4599

4600
	if (this_load > 0) {
4601 4602 4603 4604
		this_eff_load *= this_load +
			effective_load(tg, this_cpu, weight, weight);

		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4605
	}
4606

4607
	balanced = this_eff_load <= prev_eff_load;
4608

4609
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4610

4611 4612
	if (!balanced)
		return 0;
4613

4614 4615 4616 4617
	schedstat_inc(sd, ttwu_move_affine);
	schedstat_inc(p, se.statistics.nr_wakeups_affine);

	return 1;
4618 4619
}

4620 4621 4622 4623 4624
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
4625
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4626
		  int this_cpu, int sd_flag)
4627
{
4628
	struct sched_group *idlest = NULL, *group = sd->groups;
4629
	unsigned long min_load = ULONG_MAX, this_load = 0;
4630
	int load_idx = sd->forkexec_idx;
4631
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
4632

4633 4634 4635
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

4636 4637 4638 4639
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
4640

4641 4642
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
4643
					tsk_cpus_allowed(p)))
4644 4645 4646 4647 4648 4649 4650 4651 4652 4653 4654 4655 4656 4657 4658 4659 4660 4661
			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;
		}

4662
		/* Adjust by relative CPU capacity of the group */
4663
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4664 4665 4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680 4681 4682 4683 4684

		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;
4685 4686 4687 4688
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
4689 4690 4691
	int i;

	/* Traverse only the allowed CPUs */
4692
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4693 4694 4695 4696 4697 4698 4699 4700 4701 4702 4703 4704 4705 4706 4707 4708 4709 4710 4711 4712 4713 4714
		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;
			}
4715
		} else if (shallowest_idle_cpu == -1) {
4716 4717 4718 4719 4720
			load = weighted_cpuload(i);
			if (load < min_load || (load == min_load && i == this_cpu)) {
				min_load = load;
				least_loaded_cpu = i;
			}
4721 4722 4723
		}
	}

4724
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
4725
}
4726

4727 4728 4729
/*
 * Try and locate an idle CPU in the sched_domain.
 */
4730
static int select_idle_sibling(struct task_struct *p, int target)
4731
{
4732
	struct sched_domain *sd;
4733
	struct sched_group *sg;
4734
	int i = task_cpu(p);
4735

4736 4737
	if (idle_cpu(target))
		return target;
4738 4739

	/*
4740
	 * If the prevous cpu is cache affine and idle, don't be stupid.
4741
	 */
4742 4743
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
4744 4745

	/*
4746
	 * Otherwise, iterate the domains and find an elegible idle cpu.
4747
	 */
4748
	sd = rcu_dereference(per_cpu(sd_llc, target));
4749
	for_each_lower_domain(sd) {
4750 4751 4752 4753 4754 4755 4756
		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)) {
4757
				if (i == target || !idle_cpu(i))
4758 4759
					goto next;
			}
4760

4761 4762 4763 4764 4765 4766 4767 4768
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
4769 4770
	return target;
}
4771 4772 4773 4774 4775
/*
 * get_cpu_usage returns the amount of capacity of a CPU that is used by CFS
 * tasks. The unit of the return value must be the one of capacity so we can
 * compare the usage with the capacity of the CPU that is available for CFS
 * task (ie cpu_capacity).
4776
 * cfs.avg.util_avg is the sum of running time of runnable tasks on a
4777 4778 4779
 * CPU. It represents the amount of utilization of a CPU in the range
 * [0..SCHED_LOAD_SCALE].  The usage of a CPU can't be higher than the full
 * capacity of the CPU because it's about the running time on this CPU.
4780 4781
 * Nevertheless, cfs.avg.util_avg can be higher than SCHED_LOAD_SCALE
 * because of unfortunate rounding in util_avg or just
4782 4783 4784 4785 4786 4787 4788 4789
 * after migrating tasks until the average stabilizes with the new running
 * time. So we need to check that the usage stays into the range
 * [0..cpu_capacity_orig] and cap if necessary.
 * Without capping the usage, a group could be seen as overloaded (CPU0 usage
 * at 121% + CPU1 usage at 80%) whereas CPU1 has 20% of available capacity
 */
static int get_cpu_usage(int cpu)
{
4790
	unsigned long usage = cpu_rq(cpu)->cfs.avg.util_avg;
4791 4792 4793 4794 4795 4796 4797
	unsigned long capacity = capacity_orig_of(cpu);

	if (usage >= SCHED_LOAD_SCALE)
		return capacity;

	return (usage * capacity) >> SCHED_LOAD_SHIFT;
}
4798

4799
/*
4800 4801 4802
 * 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.
4803
 *
4804 4805
 * 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.
4806
 *
4807
 * Returns the target cpu number.
4808 4809 4810
 *
 * preempt must be disabled.
 */
4811
static int
4812
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
4813
{
4814
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
4815
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
4816
	int new_cpu = prev_cpu;
4817
	int want_affine = 0;
4818
	int sync = wake_flags & WF_SYNC;
4819

4820
	if (sd_flag & SD_BALANCE_WAKE)
M
Mike Galbraith 已提交
4821
		want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
4822

4823
	rcu_read_lock();
4824
	for_each_domain(cpu, tmp) {
4825
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
4826
			break;
4827

4828
		/*
4829 4830
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
4831
		 */
4832 4833 4834
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
4835
			break;
4836
		}
4837

4838
		if (tmp->flags & sd_flag)
4839
			sd = tmp;
M
Mike Galbraith 已提交
4840 4841
		else if (!want_affine)
			break;
4842 4843
	}

M
Mike Galbraith 已提交
4844 4845 4846 4847
	if (affine_sd) {
		sd = NULL; /* Prefer wake_affine over balance flags */
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
			new_cpu = cpu;
4848
	}
4849

M
Mike Galbraith 已提交
4850 4851 4852 4853 4854
	if (!sd) {
		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
			new_cpu = select_idle_sibling(p, new_cpu);

	} else while (sd) {
4855
		struct sched_group *group;
4856
		int weight;
4857

4858
		if (!(sd->flags & sd_flag)) {
4859 4860 4861
			sd = sd->child;
			continue;
		}
4862

4863
		group = find_idlest_group(sd, p, cpu, sd_flag);
4864 4865 4866 4867
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
4868

4869
		new_cpu = find_idlest_cpu(group, p, cpu);
4870 4871 4872 4873
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
4874
		}
4875 4876 4877

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
4878
		weight = sd->span_weight;
4879 4880
		sd = NULL;
		for_each_domain(cpu, tmp) {
4881
			if (weight <= tmp->span_weight)
4882
				break;
4883
			if (tmp->flags & sd_flag)
4884 4885 4886
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
4887
	}
4888
	rcu_read_unlock();
4889

4890
	return new_cpu;
4891
}
4892 4893 4894 4895 4896 4897 4898

/*
 * 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.
 */
4899
static void migrate_task_rq_fair(struct task_struct *p, int next_cpu)
4900
{
4901
	/*
4902 4903 4904 4905 4906
	 * 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.
4907
	 */
4908 4909 4910 4911
	remove_entity_load_avg(&p->se);

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
4912 4913

	/* We have migrated, no longer consider this task hot */
4914
	p->se.exec_start = 0;
4915
}
4916 4917
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
4918 4919
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
4920 4921 4922 4923
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
4924 4925
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
4926 4927 4928 4929 4930 4931 4932 4933 4934
	 *
	 * 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.
4935
	 */
4936
	return calc_delta_fair(gran, se);
4937 4938
}

4939 4940 4941 4942 4943 4944 4945 4946 4947 4948 4949 4950 4951 4952 4953 4954 4955 4956 4957 4958 4959 4960
/*
 * 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
4961
	gran = wakeup_gran(curr, se);
4962 4963 4964 4965 4966 4967
	if (vdiff > gran)
		return 1;

	return 0;
}

4968 4969
static void set_last_buddy(struct sched_entity *se)
{
4970 4971 4972 4973 4974
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
4975 4976 4977 4978
}

static void set_next_buddy(struct sched_entity *se)
{
4979 4980 4981 4982 4983
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
4984 4985
}

4986 4987
static void set_skip_buddy(struct sched_entity *se)
{
4988 4989
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
4990 4991
}

4992 4993 4994
/*
 * Preempt the current task with a newly woken task if needed:
 */
4995
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
4996 4997
{
	struct task_struct *curr = rq->curr;
4998
	struct sched_entity *se = &curr->se, *pse = &p->se;
4999
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5000
	int scale = cfs_rq->nr_running >= sched_nr_latency;
5001
	int next_buddy_marked = 0;
5002

I
Ingo Molnar 已提交
5003 5004 5005
	if (unlikely(se == pse))
		return;

5006
	/*
5007
	 * This is possible from callers such as attach_tasks(), in which we
5008 5009 5010 5011 5012 5013 5014
	 * 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;

5015
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
5016
		set_next_buddy(pse);
5017 5018
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
5019

5020 5021 5022
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
5023 5024 5025 5026 5027 5028
	 *
	 * 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.
5029 5030 5031 5032
	 */
	if (test_tsk_need_resched(curr))
		return;

5033 5034 5035 5036 5037
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

5038
	/*
5039 5040
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
5041
	 */
5042
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5043
		return;
5044

5045
	find_matching_se(&se, &pse);
5046
	update_curr(cfs_rq_of(se));
5047
	BUG_ON(!pse);
5048 5049 5050 5051 5052 5053 5054
	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);
5055
		goto preempt;
5056
	}
5057

5058
	return;
5059

5060
preempt:
5061
	resched_curr(rq);
5062 5063 5064 5065 5066 5067 5068 5069 5070 5071 5072 5073 5074 5075
	/*
	 * 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);
5076 5077
}

5078 5079
static struct task_struct *
pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5080 5081 5082
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
5083
	struct task_struct *p;
5084
	int new_tasks;
5085

5086
again:
5087 5088
#ifdef CONFIG_FAIR_GROUP_SCHED
	if (!cfs_rq->nr_running)
5089
		goto idle;
5090

5091
	if (prev->sched_class != &fair_sched_class)
5092 5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103 5104 5105 5106 5107 5108 5109 5110
		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.
		 */
5111 5112 5113 5114 5115
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
5116

5117 5118 5119 5120 5121 5122 5123 5124 5125
			/*
			 * 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;
		}
5126 5127 5128 5129 5130 5131 5132 5133 5134 5135 5136 5137 5138 5139 5140 5141 5142 5143 5144 5145 5146 5147 5148 5149 5150 5151 5152 5153 5154 5155 5156 5157 5158 5159 5160 5161 5162 5163 5164 5165

		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
5166

5167
	if (!cfs_rq->nr_running)
5168
		goto idle;
5169

5170
	put_prev_task(rq, prev);
5171

5172
	do {
5173
		se = pick_next_entity(cfs_rq, NULL);
5174
		set_next_entity(cfs_rq, se);
5175 5176 5177
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
5178
	p = task_of(se);
5179

5180 5181
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
5182 5183

	return p;
5184 5185

idle:
5186 5187 5188 5189 5190 5191 5192
	/*
	 * 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);
5193
	new_tasks = idle_balance(rq);
5194
	lockdep_pin_lock(&rq->lock);
5195 5196 5197 5198 5199
	/*
	 * 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.
	 */
5200
	if (new_tasks < 0)
5201 5202
		return RETRY_TASK;

5203
	if (new_tasks > 0)
5204 5205 5206
		goto again;

	return NULL;
5207 5208 5209 5210 5211
}

/*
 * Account for a descheduled task:
 */
5212
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5213 5214 5215 5216 5217 5218
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5219
		put_prev_entity(cfs_rq, se);
5220 5221 5222
	}
}

5223 5224 5225 5226 5227 5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238 5239 5240 5241 5242 5243 5244 5245 5246 5247
/*
 * 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);
5248 5249 5250 5251 5252
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
5253
		rq_clock_skip_update(rq, true);
5254 5255 5256 5257 5258
	}

	set_skip_buddy(se);
}

5259 5260 5261 5262
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

5263 5264
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5265 5266 5267 5268 5269 5270 5271 5272 5273 5274
		return false;

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

	yield_task_fair(rq);

	return true;
}

5275
#ifdef CONFIG_SMP
5276
/**************************************************
P
Peter Zijlstra 已提交
5277 5278 5279 5280 5281 5282 5283 5284 5285 5286 5287 5288 5289 5290 5291 5292 5293 5294 5295 5296 5297 5298 5299
 * 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)
 *
5300
 * C_i is the compute capacity of cpu i, typically it is the
P
Peter Zijlstra 已提交
5301 5302 5303 5304 5305 5306
 * 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):
 *
5307
 *   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
5308 5309 5310 5311 5312 5313 5314 5315 5316 5317 5318 5319 5320 5321 5322 5323 5324 5325 5326 5327 5328 5329 5330 5331 5332 5333 5334 5335 5336 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 5365 5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379 5380 5381 5382 5383 5384 5385 5386 5387 5388 5389 5390 5391 5392
 *
 * 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.]
 */ 
5393

5394 5395
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

5396 5397
enum fbq_type { regular, remote, all };

5398
#define LBF_ALL_PINNED	0x01
5399
#define LBF_NEED_BREAK	0x02
5400 5401
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
5402 5403 5404 5405 5406

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
5407
	int			src_cpu;
5408 5409 5410 5411

	int			dst_cpu;
	struct rq		*dst_rq;

5412 5413
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
5414
	enum cpu_idle_type	idle;
5415
	long			imbalance;
5416 5417 5418
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

5419
	unsigned int		flags;
5420 5421 5422 5423

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
5424 5425

	enum fbq_type		fbq_type;
5426
	struct list_head	tasks;
5427 5428
};

5429 5430 5431
/*
 * Is this task likely cache-hot:
 */
5432
static int task_hot(struct task_struct *p, struct lb_env *env)
5433 5434 5435
{
	s64 delta;

5436 5437
	lockdep_assert_held(&env->src_rq->lock);

5438 5439 5440 5441 5442 5443 5444 5445 5446
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
5447
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5448 5449 5450 5451 5452 5453 5454 5455 5456
			(&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;

5457
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5458 5459 5460 5461

	return delta < (s64)sysctl_sched_migration_cost;
}

5462
#ifdef CONFIG_NUMA_BALANCING
5463
/*
5464 5465 5466
 * 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.
5467
 */
5468
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5469
{
5470
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
5471
	unsigned long src_faults, dst_faults;
5472 5473
	int src_nid, dst_nid;

5474
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5475 5476 5477 5478
		return -1;

	if (!sched_feat(NUMA))
		return -1;
5479 5480 5481 5482

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

5483
	if (src_nid == dst_nid)
5484
		return -1;
5485

5486 5487 5488 5489 5490 5491 5492
	/* 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;
	}
5493

5494 5495
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
5496
		return 0;
5497

5498 5499 5500 5501 5502 5503
	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);
5504 5505
	}

5506
	return dst_faults < src_faults;
5507 5508
}

5509
#else
5510
static inline int migrate_degrades_locality(struct task_struct *p,
5511 5512
					     struct lb_env *env)
{
5513
	return -1;
5514
}
5515 5516
#endif

5517 5518 5519 5520
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
5521
int can_migrate_task(struct task_struct *p, struct lb_env *env)
5522
{
5523
	int tsk_cache_hot;
5524 5525 5526

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

5527 5528
	/*
	 * We do not migrate tasks that are:
5529
	 * 1) throttled_lb_pair, or
5530
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5531 5532
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
5533
	 */
5534 5535 5536
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

5537
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5538
		int cpu;
5539

5540
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5541

5542 5543
		env->flags |= LBF_SOME_PINNED;

5544 5545 5546 5547 5548 5549 5550 5551
		/*
		 * 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.
		 */
5552
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5553 5554
			return 0;

5555 5556 5557
		/* 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))) {
5558
				env->flags |= LBF_DST_PINNED;
5559 5560 5561
				env->new_dst_cpu = cpu;
				break;
			}
5562
		}
5563

5564 5565
		return 0;
	}
5566 5567

	/* Record that we found atleast one task that could run on dst_cpu */
5568
	env->flags &= ~LBF_ALL_PINNED;
5569

5570
	if (task_running(env->src_rq, p)) {
5571
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5572 5573 5574 5575 5576
		return 0;
	}

	/*
	 * Aggressive migration if:
5577 5578 5579
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
5580
	 */
5581 5582 5583
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
5584

5585
	if (tsk_cache_hot <= 0 ||
5586
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5587
		if (tsk_cache_hot == 1) {
5588 5589 5590
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
			schedstat_inc(p, se.statistics.nr_forced_migrations);
		}
5591 5592 5593
		return 1;
	}

Z
Zhang Hang 已提交
5594 5595
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
5596 5597
}

5598
/*
5599 5600 5601 5602 5603 5604 5605 5606 5607 5608 5609
 * 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);
}

5610
/*
5611
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5612 5613
 * part of active balancing operations within "domain".
 *
5614
 * Returns a task if successful and NULL otherwise.
5615
 */
5616
static struct task_struct *detach_one_task(struct lb_env *env)
5617 5618 5619
{
	struct task_struct *p, *n;

5620 5621
	lockdep_assert_held(&env->src_rq->lock);

5622 5623 5624
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
5625

5626
		detach_task(p, env);
5627

5628
		/*
5629
		 * Right now, this is only the second place where
5630
		 * lb_gained[env->idle] is updated (other is detach_tasks)
5631
		 * so we can safely collect stats here rather than
5632
		 * inside detach_tasks().
5633 5634
		 */
		schedstat_inc(env->sd, lb_gained[env->idle]);
5635
		return p;
5636
	}
5637
	return NULL;
5638 5639
}

5640 5641
static const unsigned int sched_nr_migrate_break = 32;

5642
/*
5643 5644
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
5645
 *
5646
 * Returns number of detached tasks if successful and 0 otherwise.
5647
 */
5648
static int detach_tasks(struct lb_env *env)
5649
{
5650 5651
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
5652
	unsigned long load;
5653 5654 5655
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
5656

5657
	if (env->imbalance <= 0)
5658
		return 0;
5659

5660
	while (!list_empty(tasks)) {
5661 5662 5663 5664 5665 5666 5667
		/*
		 * 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;

5668
		p = list_first_entry(tasks, struct task_struct, se.group_node);
5669

5670 5671
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
5672
		if (env->loop > env->loop_max)
5673
			break;
5674 5675

		/* take a breather every nr_migrate tasks */
5676
		if (env->loop > env->loop_break) {
5677
			env->loop_break += sched_nr_migrate_break;
5678
			env->flags |= LBF_NEED_BREAK;
5679
			break;
5680
		}
5681

5682
		if (!can_migrate_task(p, env))
5683 5684 5685
			goto next;

		load = task_h_load(p);
5686

5687
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5688 5689
			goto next;

5690
		if ((load / 2) > env->imbalance)
5691
			goto next;
5692

5693 5694 5695 5696
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
5697
		env->imbalance -= load;
5698 5699

#ifdef CONFIG_PREEMPT
5700 5701
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
5702
		 * kernels will stop after the first task is detached to minimize
5703 5704
		 * the critical section.
		 */
5705
		if (env->idle == CPU_NEWLY_IDLE)
5706
			break;
5707 5708
#endif

5709 5710 5711 5712
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
5713
		if (env->imbalance <= 0)
5714
			break;
5715 5716 5717

		continue;
next:
5718
		list_move_tail(&p->se.group_node, tasks);
5719
	}
5720

5721
	/*
5722 5723 5724
	 * 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().
5725
	 */
5726
	schedstat_add(env->sd, lb_gained[env->idle], detached);
5727

5728 5729 5730 5731 5732 5733 5734 5735 5736 5737 5738 5739 5740 5741 5742 5743 5744 5745 5746 5747 5748 5749 5750 5751 5752 5753 5754 5755 5756 5757 5758 5759 5760 5761 5762 5763 5764 5765 5766 5767 5768
	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);
5769

5770 5771 5772 5773
		attach_task(env->dst_rq, p);
	}

	raw_spin_unlock(&env->dst_rq->lock);
5774 5775
}

P
Peter Zijlstra 已提交
5776
#ifdef CONFIG_FAIR_GROUP_SCHED
5777
static void update_blocked_averages(int cpu)
5778 5779
{
	struct rq *rq = cpu_rq(cpu);
5780 5781
	struct cfs_rq *cfs_rq;
	unsigned long flags;
5782

5783 5784
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
5785

5786 5787 5788 5789
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
5790
	for_each_leaf_cfs_rq(rq, cfs_rq) {
5791 5792 5793
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
5794

5795 5796 5797
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
			update_tg_load_avg(cfs_rq, 0);
	}
5798
	raw_spin_unlock_irqrestore(&rq->lock, flags);
5799 5800
}

5801
/*
5802
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5803 5804 5805
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
5806
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
5807
{
5808 5809
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
5810
	unsigned long now = jiffies;
5811
	unsigned long load;
5812

5813
	if (cfs_rq->last_h_load_update == now)
5814 5815
		return;

5816 5817 5818 5819 5820 5821 5822
	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;
	}
5823

5824
	if (!se) {
5825
		cfs_rq->h_load = cfs_rq->avg.load_avg;
5826 5827 5828 5829 5830
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
5831
		load = div64_ul(load * se->avg.load_avg, cfs_rq->avg.load_avg + 1);
5832 5833 5834 5835
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
5836 5837
}

5838
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
5839
{
5840
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
5841

5842
	update_cfs_rq_h_load(cfs_rq);
5843 5844
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
			cfs_rq->avg.load_avg + 1);
P
Peter Zijlstra 已提交
5845 5846
}
#else
5847
static inline void update_blocked_averages(int cpu)
5848 5849 5850
{
}

5851
static unsigned long task_h_load(struct task_struct *p)
5852
{
5853
	return p->se.avg.load_avg;
5854
}
P
Peter Zijlstra 已提交
5855
#endif
5856 5857

/********** Helpers for find_busiest_group ************************/
5858 5859 5860 5861 5862 5863 5864

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

5865 5866 5867 5868 5869 5870 5871
/*
 * 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
5872
	unsigned long load_per_task;
5873
	unsigned long group_capacity;
5874
	unsigned long group_usage; /* Total usage of the group */
5875 5876 5877
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
5878
	enum group_type group_type;
5879
	int group_no_capacity;
5880 5881 5882 5883
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
5884 5885
};

J
Joonsoo Kim 已提交
5886 5887 5888 5889 5890 5891 5892 5893
/*
 * 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 */
5894
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
5895 5896 5897
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
5898
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
5899 5900
};

5901 5902 5903 5904 5905 5906 5907 5908 5909 5910 5911 5912
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,
5913
		.total_capacity = 0UL,
5914 5915
		.busiest_stat = {
			.avg_load = 0UL,
5916 5917
			.sum_nr_running = 0,
			.group_type = group_other,
5918 5919 5920 5921
		},
	};
}

5922 5923 5924
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
5925
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
5926 5927
 *
 * Return: The load index.
5928 5929 5930 5931 5932 5933 5934 5935 5936 5937 5938 5939 5940 5941 5942 5943 5944 5945 5946 5947 5948 5949
 */
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;
}

5950
static unsigned long default_scale_cpu_capacity(struct sched_domain *sd, int cpu)
5951
{
5952 5953
	if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1))
		return sd->smt_gain / sd->span_weight;
5954

5955
	return SCHED_CAPACITY_SCALE;
5956 5957
}

5958
unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
5959
{
5960
	return default_scale_cpu_capacity(sd, cpu);
5961 5962
}

5963
static unsigned long scale_rt_capacity(int cpu)
5964 5965
{
	struct rq *rq = cpu_rq(cpu);
5966
	u64 total, used, age_stamp, avg;
5967
	s64 delta;
5968

5969 5970 5971 5972
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
5973 5974
	age_stamp = READ_ONCE(rq->age_stamp);
	avg = READ_ONCE(rq->rt_avg);
5975
	delta = __rq_clock_broken(rq) - age_stamp;
5976

5977 5978 5979 5980
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
5981

5982
	used = div_u64(avg, total);
5983

5984 5985
	if (likely(used < SCHED_CAPACITY_SCALE))
		return SCHED_CAPACITY_SCALE - used;
5986

5987
	return 1;
5988 5989
}

5990
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
5991
{
5992
	unsigned long capacity = SCHED_CAPACITY_SCALE;
5993 5994
	struct sched_group *sdg = sd->groups;

5995 5996 5997 5998
	if (sched_feat(ARCH_CAPACITY))
		capacity *= arch_scale_cpu_capacity(sd, cpu);
	else
		capacity *= default_scale_cpu_capacity(sd, cpu);
5999

6000
	capacity >>= SCHED_CAPACITY_SHIFT;
6001

6002
	cpu_rq(cpu)->cpu_capacity_orig = capacity;
6003

6004
	capacity *= scale_rt_capacity(cpu);
6005
	capacity >>= SCHED_CAPACITY_SHIFT;
6006

6007 6008
	if (!capacity)
		capacity = 1;
6009

6010 6011
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
6012 6013
}

6014
void update_group_capacity(struct sched_domain *sd, int cpu)
6015 6016 6017
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
6018
	unsigned long capacity;
6019 6020 6021 6022
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
6023
	sdg->sgc->next_update = jiffies + interval;
6024 6025

	if (!child) {
6026
		update_cpu_capacity(sd, cpu);
6027 6028 6029
		return;
	}

6030
	capacity = 0;
6031

P
Peter Zijlstra 已提交
6032 6033 6034 6035 6036 6037
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

6038
		for_each_cpu(cpu, sched_group_cpus(sdg)) {
6039
			struct sched_group_capacity *sgc;
6040
			struct rq *rq = cpu_rq(cpu);
6041

6042
			/*
6043
			 * build_sched_domains() -> init_sched_groups_capacity()
6044 6045 6046
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
6047 6048
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
6049
			 *
6050
			 * This avoids capacity from being 0 and
6051 6052 6053
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
6054
				capacity += capacity_of(cpu);
6055 6056
				continue;
			}
6057

6058 6059
			sgc = rq->sd->groups->sgc;
			capacity += sgc->capacity;
6060
		}
P
Peter Zijlstra 已提交
6061 6062 6063 6064 6065 6066 6067 6068
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
6069
			capacity += group->sgc->capacity;
P
Peter Zijlstra 已提交
6070 6071 6072
			group = group->next;
		} while (group != child->groups);
	}
6073

6074
	sdg->sgc->capacity = capacity;
6075 6076
}

6077
/*
6078 6079 6080
 * 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
6081 6082
 */
static inline int
6083
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6084
{
6085 6086
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
6087 6088
}

6089 6090 6091 6092 6093 6094 6095 6096 6097 6098 6099 6100 6101 6102 6103 6104
/*
 * 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
6105 6106
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
6107 6108
 *
 * When this is so detected; this group becomes a candidate for busiest; see
6109
 * update_sd_pick_busiest(). And calculate_imbalance() and
6110
 * find_busiest_group() avoid some of the usual balance conditions to allow it
6111 6112 6113 6114 6115 6116 6117
 * 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.
 */

6118
static inline int sg_imbalanced(struct sched_group *group)
6119
{
6120
	return group->sgc->imbalance;
6121 6122
}

6123
/*
6124 6125 6126 6127 6128 6129 6130 6131 6132 6133
 * 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
 * smaller than the number of CPUs or if the usage is lower than the available
 * capacity for CFS tasks.
 * 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.
6134
 */
6135 6136
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6137
{
6138 6139
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
6140

6141 6142 6143
	if ((sgs->group_capacity * 100) >
			(sgs->group_usage * env->sd->imbalance_pct))
		return true;
6144

6145 6146 6147 6148 6149 6150 6151 6152 6153 6154 6155 6156 6157 6158 6159 6160
	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;
6161

6162 6163 6164
	if ((sgs->group_capacity * 100) <
			(sgs->group_usage * env->sd->imbalance_pct))
		return true;
6165

6166
	return false;
6167 6168
}

6169 6170 6171
static enum group_type group_classify(struct lb_env *env,
		struct sched_group *group,
		struct sg_lb_stats *sgs)
6172
{
6173
	if (sgs->group_no_capacity)
6174 6175 6176 6177 6178 6179 6180 6181
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

6182 6183
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6184
 * @env: The load balancing environment.
6185 6186 6187 6188
 * @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.
6189
 * @overload: Indicate more than one runnable task for any CPU.
6190
 */
6191 6192
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
6193 6194
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
6195
{
6196
	unsigned long load;
6197
	int i;
6198

6199 6200
	memset(sgs, 0, sizeof(*sgs));

6201
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6202 6203 6204
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
6205
		if (local_group)
6206
			load = target_load(i, load_idx);
6207
		else
6208 6209 6210
			load = source_load(i, load_idx);

		sgs->group_load += load;
6211
		sgs->group_usage += get_cpu_usage(i);
6212
		sgs->sum_nr_running += rq->cfs.h_nr_running;
6213 6214 6215 6216

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

6217 6218 6219 6220
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
6221
		sgs->sum_weighted_load += weighted_cpuload(i);
6222 6223
		if (idle_cpu(i))
			sgs->idle_cpus++;
6224 6225
	}

6226 6227
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
6228
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6229

6230
	if (sgs->sum_nr_running)
6231
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6232

6233
	sgs->group_weight = group->group_weight;
6234

6235 6236
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
	sgs->group_type = group_classify(env, group, sgs);
6237 6238
}

6239 6240
/**
 * update_sd_pick_busiest - return 1 on busiest group
6241
 * @env: The load balancing environment.
6242 6243
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
6244
 * @sgs: sched_group statistics
6245 6246 6247
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
6248 6249 6250
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
6251
 */
6252
static bool update_sd_pick_busiest(struct lb_env *env,
6253 6254
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
6255
				   struct sg_lb_stats *sgs)
6256
{
6257
	struct sg_lb_stats *busiest = &sds->busiest_stat;
6258

6259
	if (sgs->group_type > busiest->group_type)
6260 6261
		return true;

6262 6263 6264 6265 6266 6267 6268 6269
	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))
6270 6271 6272 6273 6274 6275 6276
		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.
	 */
6277
	if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6278 6279 6280 6281 6282 6283 6284 6285 6286 6287
		if (!sds->busiest)
			return true;

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

	return false;
}

6288 6289 6290 6291 6292 6293 6294 6295 6296 6297 6298 6299 6300 6301 6302 6303 6304 6305 6306 6307 6308 6309 6310 6311 6312 6313 6314 6315 6316 6317
#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 */

6318
/**
6319
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6320
 * @env: The load balancing environment.
6321 6322
 * @sds: variable to hold the statistics for this sched_domain.
 */
6323
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6324
{
6325 6326
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
6327
	struct sg_lb_stats tmp_sgs;
6328
	int load_idx, prefer_sibling = 0;
6329
	bool overload = false;
6330 6331 6332 6333

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

6334
	load_idx = get_sd_load_idx(env->sd, env->idle);
6335 6336

	do {
J
Joonsoo Kim 已提交
6337
		struct sg_lb_stats *sgs = &tmp_sgs;
6338 6339
		int local_group;

6340
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
6341 6342 6343
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
6344 6345

			if (env->idle != CPU_NEWLY_IDLE ||
6346 6347
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
6348
		}
6349

6350 6351
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
6352

6353 6354 6355
		if (local_group)
			goto next_group;

6356 6357
		/*
		 * In case the child domain prefers tasks go to siblings
6358
		 * first, lower the sg capacity so that we'll try
6359 6360
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
6361 6362 6363 6364
		 * 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).
6365
		 */
6366
		if (prefer_sibling && sds->local &&
6367 6368 6369 6370
		    group_has_capacity(env, &sds->local_stat) &&
		    (sgs->sum_nr_running > 1)) {
			sgs->group_no_capacity = 1;
			sgs->group_type = group_overloaded;
6371
		}
6372

6373
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6374
			sds->busiest = sg;
J
Joonsoo Kim 已提交
6375
			sds->busiest_stat = *sgs;
6376 6377
		}

6378 6379 6380
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
6381
		sds->total_capacity += sgs->group_capacity;
6382

6383
		sg = sg->next;
6384
	} while (sg != env->sd->groups);
6385 6386 6387

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6388 6389 6390 6391 6392 6393 6394

	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;
	}

6395 6396 6397 6398 6399 6400 6401 6402 6403 6404 6405 6406 6407 6408 6409 6410 6411 6412 6413
}

/**
 * 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.
 *
6414
 * Return: 1 when packing is required and a task should be moved to
6415 6416
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
6417
 * @env: The load balancing environment.
6418 6419
 * @sds: Statistics of the sched_domain which is to be packed
 */
6420
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6421 6422 6423
{
	int busiest_cpu;

6424
	if (!(env->sd->flags & SD_ASYM_PACKING))
6425 6426 6427 6428 6429 6430
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
6431
	if (env->dst_cpu > busiest_cpu)
6432 6433
		return 0;

6434
	env->imbalance = DIV_ROUND_CLOSEST(
6435
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6436
		SCHED_CAPACITY_SCALE);
6437

6438
	return 1;
6439 6440 6441 6442 6443 6444
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
6445
 * @env: The load balancing environment.
6446 6447
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
6448 6449
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6450
{
6451
	unsigned long tmp, capa_now = 0, capa_move = 0;
6452
	unsigned int imbn = 2;
6453
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
6454
	struct sg_lb_stats *local, *busiest;
6455

J
Joonsoo Kim 已提交
6456 6457
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6458

J
Joonsoo Kim 已提交
6459 6460 6461 6462
	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;
6463

J
Joonsoo Kim 已提交
6464
	scaled_busy_load_per_task =
6465
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6466
		busiest->group_capacity;
J
Joonsoo Kim 已提交
6467

6468 6469
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
6470
		env->imbalance = busiest->load_per_task;
6471 6472 6473 6474 6475
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
6476
	 * however we may be able to increase total CPU capacity used by
6477 6478 6479
	 * moving them.
	 */

6480
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
6481
			min(busiest->load_per_task, busiest->avg_load);
6482
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
6483
			min(local->load_per_task, local->avg_load);
6484
	capa_now /= SCHED_CAPACITY_SCALE;
6485 6486

	/* Amount of load we'd subtract */
6487
	if (busiest->avg_load > scaled_busy_load_per_task) {
6488
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
6489
			    min(busiest->load_per_task,
6490
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
6491
	}
6492 6493

	/* Amount of load we'd add */
6494
	if (busiest->avg_load * busiest->group_capacity <
6495
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6496 6497
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
6498
	} else {
6499
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6500
		      local->group_capacity;
J
Joonsoo Kim 已提交
6501
	}
6502
	capa_move += local->group_capacity *
6503
		    min(local->load_per_task, local->avg_load + tmp);
6504
	capa_move /= SCHED_CAPACITY_SCALE;
6505 6506

	/* Move if we gain throughput */
6507
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
6508
		env->imbalance = busiest->load_per_task;
6509 6510 6511 6512 6513
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
6514
 * @env: load balance environment
6515 6516
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
6517
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6518
{
6519
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
6520 6521 6522 6523
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6524

6525
	if (busiest->group_type == group_imbalanced) {
6526 6527 6528 6529
		/*
		 * 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
6530 6531
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
6532 6533
	}

6534 6535 6536
	/*
	 * 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
6537
	 * its cpu_capacity, while calculating max_load..)
6538
	 */
6539 6540
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
6541 6542
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
6543 6544
	}

6545 6546 6547 6548 6549
	/*
	 * If there aren't any idle cpus, avoid creating some.
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
6550 6551 6552 6553 6554 6555
		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;
6556 6557 6558 6559 6560 6561 6562 6563 6564 6565
	}

	/*
	 * 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.
	 */
6566
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6567 6568

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
6569
	env->imbalance = min(
6570 6571
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
6572
	) / SCHED_CAPACITY_SCALE;
6573 6574 6575

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
6576
	 * there is no guarantee that any tasks will be moved so we'll have
6577 6578 6579
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
6580
	if (env->imbalance < busiest->load_per_task)
6581
		return fix_small_imbalance(env, sds);
6582
}
6583

6584 6585 6586 6587 6588 6589 6590 6591 6592 6593 6594 6595
/******* 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.
 *
6596
 * @env: The load balancing environment.
6597
 *
6598
 * Return:	- The busiest group if imbalance exists.
6599 6600 6601 6602
 *		- 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
6603
static struct sched_group *find_busiest_group(struct lb_env *env)
6604
{
J
Joonsoo Kim 已提交
6605
	struct sg_lb_stats *local, *busiest;
6606 6607
	struct sd_lb_stats sds;

6608
	init_sd_lb_stats(&sds);
6609 6610 6611 6612 6613

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
6614
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
6615 6616
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
6617

6618
	/* ASYM feature bypasses nice load balance check */
6619 6620
	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(env, &sds))
6621 6622
		return sds.busiest;

6623
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
6624
	if (!sds.busiest || busiest->sum_nr_running == 0)
6625 6626
		goto out_balanced;

6627 6628
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
6629

P
Peter Zijlstra 已提交
6630 6631
	/*
	 * If the busiest group is imbalanced the below checks don't
6632
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
6633 6634
	 * isn't true due to cpus_allowed constraints and the like.
	 */
6635
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
6636 6637
		goto force_balance;

6638
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6639 6640
	if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
	    busiest->group_no_capacity)
6641 6642
		goto force_balance;

6643
	/*
6644
	 * If the local group is busier than the selected busiest group
6645 6646
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
6647
	if (local->avg_load >= busiest->avg_load)
6648 6649
		goto out_balanced;

6650 6651 6652 6653
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
6654
	if (local->avg_load >= sds.avg_load)
6655 6656
		goto out_balanced;

6657
	if (env->idle == CPU_IDLE) {
6658
		/*
6659 6660 6661 6662 6663
		 * 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
6664
		 */
6665 6666
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
6667
			goto out_balanced;
6668 6669 6670 6671 6672
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
6673 6674
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
6675
			goto out_balanced;
6676
	}
6677

6678
force_balance:
6679
	/* Looks like there is an imbalance. Compute it */
6680
	calculate_imbalance(env, &sds);
6681 6682 6683
	return sds.busiest;

out_balanced:
6684
	env->imbalance = 0;
6685 6686 6687 6688 6689 6690
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
6691
static struct rq *find_busiest_queue(struct lb_env *env,
6692
				     struct sched_group *group)
6693 6694
{
	struct rq *busiest = NULL, *rq;
6695
	unsigned long busiest_load = 0, busiest_capacity = 1;
6696 6697
	int i;

6698
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6699
		unsigned long capacity, wl;
6700 6701 6702 6703
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
6704

6705 6706 6707 6708 6709 6710 6711 6712 6713 6714 6715 6716 6717 6718 6719 6720 6721 6722 6723 6724 6725 6726
		/*
		 * 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;

6727
		capacity = capacity_of(i);
6728

6729
		wl = weighted_cpuload(i);
6730

6731 6732
		/*
		 * When comparing with imbalance, use weighted_cpuload()
6733
		 * which is not scaled with the cpu capacity.
6734
		 */
6735 6736 6737

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
6738 6739
			continue;

6740 6741
		/*
		 * For the load comparisons with the other cpu's, consider
6742 6743 6744
		 * 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.
6745
		 *
6746
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
6747
		 * multiplication to rid ourselves of the division works out
6748 6749
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
6750
		 */
6751
		if (wl * busiest_capacity > busiest_load * capacity) {
6752
			busiest_load = wl;
6753
			busiest_capacity = capacity;
6754 6755 6756 6757 6758 6759 6760 6761 6762 6763 6764 6765 6766 6767
			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. */
6768
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6769

6770
static int need_active_balance(struct lb_env *env)
6771
{
6772 6773 6774
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
6775 6776 6777 6778 6779 6780

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
6781
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6782
			return 1;
6783 6784
	}

6785 6786 6787 6788 6789 6790 6791 6792 6793 6794 6795 6796 6797
	/*
	 * 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;
	}

6798 6799 6800
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

6801 6802
static int active_load_balance_cpu_stop(void *data);

6803 6804 6805 6806 6807 6808 6809 6810 6811 6812 6813 6814 6815 6816 6817 6818 6819 6820 6821 6822 6823 6824 6825 6826 6827 6828 6829 6830 6831 6832 6833
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.
	 */
6834
	return balance_cpu == env->dst_cpu;
6835 6836
}

6837 6838 6839 6840 6841 6842
/*
 * 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,
6843
			int *continue_balancing)
6844
{
6845
	int ld_moved, cur_ld_moved, active_balance = 0;
6846
	struct sched_domain *sd_parent = sd->parent;
6847 6848 6849
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
6850
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
6851

6852 6853
	struct lb_env env = {
		.sd		= sd,
6854 6855
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
6856
		.dst_grpmask    = sched_group_cpus(sd->groups),
6857
		.idle		= idle,
6858
		.loop_break	= sched_nr_migrate_break,
6859
		.cpus		= cpus,
6860
		.fbq_type	= all,
6861
		.tasks		= LIST_HEAD_INIT(env.tasks),
6862 6863
	};

6864 6865 6866 6867
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
6868
	if (idle == CPU_NEWLY_IDLE)
6869 6870
		env.dst_grpmask = NULL;

6871 6872 6873 6874 6875
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
6876 6877
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
6878
		goto out_balanced;
6879
	}
6880

6881
	group = find_busiest_group(&env);
6882 6883 6884 6885 6886
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

6887
	busiest = find_busiest_queue(&env, group);
6888 6889 6890 6891 6892
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

6893
	BUG_ON(busiest == env.dst_rq);
6894

6895
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
6896

6897 6898 6899
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

6900 6901 6902 6903 6904 6905 6906 6907
	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.
		 */
6908
		env.flags |= LBF_ALL_PINNED;
6909
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
6910

6911
more_balance:
6912
		raw_spin_lock_irqsave(&busiest->lock, flags);
6913 6914 6915 6916 6917

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
6918
		cur_ld_moved = detach_tasks(&env);
6919 6920

		/*
6921 6922 6923 6924 6925
		 * 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.
6926
		 */
6927 6928 6929 6930 6931 6932 6933 6934

		raw_spin_unlock(&busiest->lock);

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

6935
		local_irq_restore(flags);
6936

6937 6938 6939 6940 6941
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

6942 6943 6944 6945 6946 6947 6948 6949 6950 6951 6952 6953 6954 6955 6956 6957 6958 6959 6960
		/*
		 * 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.
		 */
6961
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
6962

6963 6964 6965
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

6966
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
6967
			env.dst_cpu	 = env.new_dst_cpu;
6968
			env.flags	&= ~LBF_DST_PINNED;
6969 6970
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
6971

6972 6973 6974 6975 6976 6977
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
6978

6979 6980 6981 6982
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
6983
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
6984

6985
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
6986 6987 6988
				*group_imbalance = 1;
		}

6989
		/* All tasks on this runqueue were pinned by CPU affinity */
6990
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
6991
			cpumask_clear_cpu(cpu_of(busiest), cpus);
6992 6993 6994
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
6995
				goto redo;
6996
			}
6997
			goto out_all_pinned;
6998 6999 7000 7001 7002
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
7003 7004 7005 7006 7007 7008 7009 7010
		/*
		 * 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++;
7011

7012
		if (need_active_balance(&env)) {
7013 7014
			raw_spin_lock_irqsave(&busiest->lock, flags);

7015 7016 7017
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
7018 7019
			 */
			if (!cpumask_test_cpu(this_cpu,
7020
					tsk_cpus_allowed(busiest->curr))) {
7021 7022
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
7023
				env.flags |= LBF_ALL_PINNED;
7024 7025 7026
				goto out_one_pinned;
			}

7027 7028 7029 7030 7031
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
7032 7033 7034 7035 7036 7037
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
7038

7039
			if (active_balance) {
7040 7041 7042
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
7043
			}
7044 7045 7046 7047 7048 7049 7050 7051 7052 7053 7054 7055 7056 7057 7058 7059 7060 7061

			/*
			 * 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
7062
		 * detach_tasks).
7063 7064 7065 7066 7067 7068 7069 7070
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
7071 7072 7073 7074 7075 7076 7077 7078 7079 7080 7081 7082 7083 7084 7085 7086 7087
	/*
	 * 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.
	 */
7088 7089 7090 7091 7092 7093
	schedstat_inc(sd, lb_balanced[idle]);

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
7094
	if (((env.flags & LBF_ALL_PINNED) &&
7095
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
7096 7097 7098
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

7099
	ld_moved = 0;
7100 7101 7102 7103
out:
	return ld_moved;
}

7104 7105 7106 7107 7108 7109 7110 7111 7112 7113 7114 7115 7116 7117 7118 7119 7120 7121 7122 7123 7124 7125 7126 7127 7128 7129 7130
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;
}

7131 7132 7133 7134
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
7135
static int idle_balance(struct rq *this_rq)
7136
{
7137 7138
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
7139 7140
	struct sched_domain *sd;
	int pulled_task = 0;
7141
	u64 curr_cost = 0;
7142

7143
	idle_enter_fair(this_rq);
7144

7145 7146 7147 7148 7149 7150
	/*
	 * 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);

7151 7152
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
7153 7154 7155 7156 7157 7158
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
			update_next_balance(sd, 0, &next_balance);
		rcu_read_unlock();

7159
		goto out;
7160
	}
7161

7162 7163
	raw_spin_unlock(&this_rq->lock);

7164
	update_blocked_averages(this_cpu);
7165
	rcu_read_lock();
7166
	for_each_domain(this_cpu, sd) {
7167
		int continue_balancing = 1;
7168
		u64 t0, domain_cost;
7169 7170 7171 7172

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

7173 7174
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
			update_next_balance(sd, 0, &next_balance);
7175
			break;
7176
		}
7177

7178
		if (sd->flags & SD_BALANCE_NEWIDLE) {
7179 7180
			t0 = sched_clock_cpu(this_cpu);

7181
			pulled_task = load_balance(this_cpu, this_rq,
7182 7183
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
7184 7185 7186 7187 7188 7189

			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;
7190
		}
7191

7192
		update_next_balance(sd, 0, &next_balance);
7193 7194 7195 7196 7197 7198

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
7199 7200
			break;
	}
7201
	rcu_read_unlock();
7202 7203 7204

	raw_spin_lock(&this_rq->lock);

7205 7206 7207
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

7208
	/*
7209 7210 7211
	 * 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.
7212
	 */
7213
	if (this_rq->cfs.h_nr_running && !pulled_task)
7214
		pulled_task = 1;
7215

7216 7217 7218
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
7219
		this_rq->next_balance = next_balance;
7220

7221
	/* Is there a task of a high priority class? */
7222
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7223 7224 7225 7226
		pulled_task = -1;

	if (pulled_task) {
		idle_exit_fair(this_rq);
7227
		this_rq->idle_stamp = 0;
7228
	}
7229

7230
	return pulled_task;
7231 7232 7233
}

/*
7234 7235 7236 7237
 * 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.
7238
 */
7239
static int active_load_balance_cpu_stop(void *data)
7240
{
7241 7242
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
7243
	int target_cpu = busiest_rq->push_cpu;
7244
	struct rq *target_rq = cpu_rq(target_cpu);
7245
	struct sched_domain *sd;
7246
	struct task_struct *p = NULL;
7247 7248 7249 7250 7251 7252 7253

	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;
7254 7255 7256

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
7257
		goto out_unlock;
7258 7259 7260 7261 7262 7263 7264 7265 7266

	/*
	 * 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. */
7267
	rcu_read_lock();
7268 7269 7270 7271 7272 7273 7274
	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)) {
7275 7276
		struct lb_env env = {
			.sd		= sd,
7277 7278 7279 7280
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
7281 7282 7283
			.idle		= CPU_IDLE,
		};

7284 7285
		schedstat_inc(sd, alb_count);

7286 7287
		p = detach_one_task(&env);
		if (p)
7288 7289 7290 7291
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
7292
	rcu_read_unlock();
7293 7294
out_unlock:
	busiest_rq->active_balance = 0;
7295 7296 7297 7298 7299 7300 7301
	raw_spin_unlock(&busiest_rq->lock);

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

7302
	return 0;
7303 7304
}

7305 7306 7307 7308 7309
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

7310
#ifdef CONFIG_NO_HZ_COMMON
7311 7312 7313 7314 7315 7316
/*
 * 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.
 */
7317
static struct {
7318
	cpumask_var_t idle_cpus_mask;
7319
	atomic_t nr_cpus;
7320 7321
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
7322

7323
static inline int find_new_ilb(void)
7324
{
7325
	int ilb = cpumask_first(nohz.idle_cpus_mask);
7326

7327 7328 7329 7330
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
7331 7332
}

7333 7334 7335 7336 7337
/*
 * 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).
 */
7338
static void nohz_balancer_kick(void)
7339 7340 7341 7342 7343
{
	int ilb_cpu;

	nohz.next_balance++;

7344
	ilb_cpu = find_new_ilb();
7345

7346 7347
	if (ilb_cpu >= nr_cpu_ids)
		return;
7348

7349
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7350 7351 7352 7353 7354 7355 7356 7357
		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);
7358 7359 7360
	return;
}

7361
static inline void nohz_balance_exit_idle(int cpu)
7362 7363
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7364 7365 7366 7367 7368 7369 7370
		/*
		 * 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);
		}
7371 7372 7373 7374
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

7375 7376 7377
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
7378
	int cpu = smp_processor_id();
7379 7380

	rcu_read_lock();
7381
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7382 7383 7384 7385 7386

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

7387
	atomic_inc(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7388
unlock:
7389 7390 7391 7392 7393 7394
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
7395
	int cpu = smp_processor_id();
7396 7397

	rcu_read_lock();
7398
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7399 7400 7401 7402 7403

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

7404
	atomic_dec(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7405
unlock:
7406 7407 7408
	rcu_read_unlock();
}

7409
/*
7410
 * This routine will record that the cpu is going idle with tick stopped.
7411
 * This info will be used in performing idle load balancing in the future.
7412
 */
7413
void nohz_balance_enter_idle(int cpu)
7414
{
7415 7416 7417 7418 7419 7420
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

7421 7422
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
7423

7424 7425 7426 7427 7428 7429
	/*
	 * If we're a completely isolated CPU, we don't play.
	 */
	if (on_null_domain(cpu_rq(cpu)))
		return;

7430 7431 7432
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7433
}
7434

7435
static int sched_ilb_notifier(struct notifier_block *nfb,
7436 7437 7438 7439
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
7440
		nohz_balance_exit_idle(smp_processor_id());
7441 7442 7443 7444 7445
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
7446 7447 7448 7449
#endif

static DEFINE_SPINLOCK(balancing);

7450 7451 7452 7453
/*
 * 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.
 */
7454
void update_max_interval(void)
7455 7456 7457 7458
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

7459 7460 7461 7462
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
7463
 * Balancing parameters are set up in init_sched_domains.
7464
 */
7465
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7466
{
7467
	int continue_balancing = 1;
7468
	int cpu = rq->cpu;
7469
	unsigned long interval;
7470
	struct sched_domain *sd;
7471 7472 7473
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
7474 7475
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
7476

7477
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
7478

7479
	rcu_read_lock();
7480
	for_each_domain(cpu, sd) {
7481 7482 7483 7484 7485 7486 7487 7488 7489 7490 7491 7492
		/*
		 * 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;

7493 7494 7495
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

7496 7497 7498 7499 7500 7501 7502 7503 7504 7505 7506
		/*
		 * 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;
		}

7507
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7508 7509 7510 7511 7512 7513 7514 7515

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

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
7516
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7517
				/*
7518
				 * The LBF_DST_PINNED logic could have changed
7519 7520
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
7521
				 */
7522
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7523 7524
			}
			sd->last_balance = jiffies;
7525
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7526 7527 7528 7529 7530 7531 7532 7533
		}
		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;
		}
7534 7535
	}
	if (need_decay) {
7536
		/*
7537 7538
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
7539
		 */
7540 7541
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
7542
	}
7543
	rcu_read_unlock();
7544 7545 7546 7547 7548 7549 7550 7551 7552 7553

	/*
	 * next_balance will be updated only when there is a need.
	 * When the cpu is attached to null domain for ex, it will not be
	 * updated.
	 */
	if (likely(update_next_balance))
		rq->next_balance = next_balance;
}

7554
#ifdef CONFIG_NO_HZ_COMMON
7555
/*
7556
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7557 7558
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
7559
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7560
{
7561
	int this_cpu = this_rq->cpu;
7562 7563 7564
	struct rq *rq;
	int balance_cpu;

7565 7566 7567
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
7568 7569

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7570
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7571 7572 7573 7574 7575 7576 7577
			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.
		 */
7578
		if (need_resched())
7579 7580
			break;

V
Vincent Guittot 已提交
7581 7582
		rq = cpu_rq(balance_cpu);

7583 7584 7585 7586 7587 7588 7589 7590 7591 7592 7593
		/*
		 * 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);
		}
7594 7595 7596 7597 7598

		if (time_after(this_rq->next_balance, rq->next_balance))
			this_rq->next_balance = rq->next_balance;
	}
	nohz.next_balance = this_rq->next_balance;
7599 7600
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7601 7602 7603
}

/*
7604
 * Current heuristic for kicking the idle load balancer in the presence
7605
 * of an idle cpu in the system.
7606
 *   - This rq has more than one task.
7607 7608 7609 7610
 *   - 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.
7611 7612
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
7613
 */
7614
static inline bool nohz_kick_needed(struct rq *rq)
7615 7616
{
	unsigned long now = jiffies;
7617
	struct sched_domain *sd;
7618
	struct sched_group_capacity *sgc;
7619
	int nr_busy, cpu = rq->cpu;
7620
	bool kick = false;
7621

7622
	if (unlikely(rq->idle_balance))
7623
		return false;
7624

7625 7626 7627 7628
       /*
	* 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.
	*/
7629
	set_cpu_sd_state_busy();
7630
	nohz_balance_exit_idle(cpu);
7631 7632 7633 7634 7635 7636

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
7637
		return false;
7638 7639

	if (time_before(now, nohz.next_balance))
7640
		return false;
7641

7642
	if (rq->nr_running >= 2)
7643
		return true;
7644

7645
	rcu_read_lock();
7646 7647
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
	if (sd) {
7648 7649
		sgc = sd->groups->sgc;
		nr_busy = atomic_read(&sgc->nr_busy_cpus);
7650

7651 7652 7653 7654 7655
		if (nr_busy > 1) {
			kick = true;
			goto unlock;
		}

7656
	}
7657

7658 7659 7660 7661 7662 7663 7664 7665
	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
			kick = true;
			goto unlock;
		}
	}
7666

7667
	sd = rcu_dereference(per_cpu(sd_asym, cpu));
7668
	if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
7669 7670 7671 7672
				  sched_domain_span(sd)) < cpu)) {
		kick = true;
		goto unlock;
	}
7673

7674
unlock:
7675
	rcu_read_unlock();
7676
	return kick;
7677 7678
}
#else
7679
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7680 7681 7682 7683 7684 7685
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
7686 7687
static void run_rebalance_domains(struct softirq_action *h)
{
7688
	struct rq *this_rq = this_rq();
7689
	enum cpu_idle_type idle = this_rq->idle_balance ?
7690 7691 7692
						CPU_IDLE : CPU_NOT_IDLE;

	/*
7693
	 * If this cpu has a pending nohz_balance_kick, then do the
7694
	 * balancing on behalf of the other idle cpus whose ticks are
7695 7696 7697 7698
	 * 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.
7699
	 */
7700
	nohz_idle_balance(this_rq, idle);
7701
	rebalance_domains(this_rq, idle);
7702 7703 7704 7705 7706
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
7707
void trigger_load_balance(struct rq *rq)
7708 7709
{
	/* Don't need to rebalance while attached to NULL domain */
7710 7711 7712 7713
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
7714
		raise_softirq(SCHED_SOFTIRQ);
7715
#ifdef CONFIG_NO_HZ_COMMON
7716
	if (nohz_kick_needed(rq))
7717
		nohz_balancer_kick();
7718
#endif
7719 7720
}

7721 7722 7723
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
7724 7725

	update_runtime_enabled(rq);
7726 7727 7728 7729 7730
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
7731 7732 7733

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
7734 7735
}

7736
#endif /* CONFIG_SMP */
7737

7738 7739 7740
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
7741
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
7742 7743 7744 7745 7746 7747
{
	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
7748
		entity_tick(cfs_rq, se, queued);
7749
	}
7750

7751
	if (numabalancing_enabled)
7752
		task_tick_numa(rq, curr);
7753 7754 7755
}

/*
P
Peter Zijlstra 已提交
7756 7757 7758
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
7759
 */
P
Peter Zijlstra 已提交
7760
static void task_fork_fair(struct task_struct *p)
7761
{
7762 7763
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
7764
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
7765 7766 7767
	struct rq *rq = this_rq();
	unsigned long flags;

7768
	raw_spin_lock_irqsave(&rq->lock, flags);
7769

7770 7771
	update_rq_clock(rq);

7772 7773 7774
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

7775 7776 7777 7778 7779 7780 7781 7782 7783
	/*
	 * 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();
7784

7785
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
7786

7787 7788
	if (curr)
		se->vruntime = curr->vruntime;
7789
	place_entity(cfs_rq, se, 1);
7790

P
Peter Zijlstra 已提交
7791
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
7792
		/*
7793 7794 7795
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
7796
		swap(curr->vruntime, se->vruntime);
7797
		resched_curr(rq);
7798
	}
7799

7800 7801
	se->vruntime -= cfs_rq->min_vruntime;

7802
	raw_spin_unlock_irqrestore(&rq->lock, flags);
7803 7804
}

7805 7806 7807 7808
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
7809 7810
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
7811
{
7812
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
7813 7814
		return;

7815 7816 7817 7818 7819
	/*
	 * 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
7820
	if (rq->curr == p) {
7821
		if (p->prio > oldprio)
7822
			resched_curr(rq);
7823
	} else
7824
		check_preempt_curr(rq, p, 0);
7825 7826
}

P
Peter Zijlstra 已提交
7827 7828 7829 7830 7831 7832
static void switched_from_fair(struct rq *rq, struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	/*
7833
	 * Ensure the task's vruntime is normalized, so that when it's
P
Peter Zijlstra 已提交
7834 7835 7836
	 * switched back to the fair class the enqueue_entity(.flags=0) will
	 * do the right thing.
	 *
7837 7838
	 * If it's queued, then the dequeue_entity(.flags=0) will already
	 * have normalized the vruntime, if it's !queued, then only when
P
Peter Zijlstra 已提交
7839 7840
	 * the task is sleeping will it still have non-normalized vruntime.
	 */
7841
	if (!task_on_rq_queued(p) && p->state != TASK_RUNNING) {
P
Peter Zijlstra 已提交
7842 7843 7844 7845 7846 7847 7848
		/*
		 * 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;
	}
7849

7850
#ifdef CONFIG_SMP
7851 7852 7853 7854 7855 7856 7857 7858 7859 7860 7861 7862
	/* Catch up with the cfs_rq and remove our load when we leave */
	__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq), &se->avg,
		se->on_rq * scale_load_down(se->load.weight), cfs_rq->curr == se);

	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);
7863
#endif
P
Peter Zijlstra 已提交
7864 7865
}

7866 7867 7868
/*
 * We switched to the sched_fair class.
 */
P
Peter Zijlstra 已提交
7869
static void switched_to_fair(struct rq *rq, struct task_struct *p)
7870
{
7871
#ifdef CONFIG_FAIR_GROUP_SCHED
7872
	struct sched_entity *se = &p->se;
7873 7874 7875 7876 7877 7878
	/*
	 * 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
7879
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
7880 7881
		return;

7882 7883 7884 7885 7886
	/*
	 * We were most likely switched from sched_rt, so
	 * kick off the schedule if running, otherwise just see
	 * if we can still preempt the current task.
	 */
P
Peter Zijlstra 已提交
7887
	if (rq->curr == p)
7888
		resched_curr(rq);
7889
	else
7890
		check_preempt_curr(rq, p, 0);
7891 7892
}

7893 7894 7895 7896 7897 7898 7899 7900 7901
/* 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;

7902 7903 7904 7905 7906 7907 7908
	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);
	}
7909 7910
}

7911 7912 7913 7914 7915 7916 7917
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
7918
#ifdef CONFIG_SMP
7919 7920
	atomic_long_set(&cfs_rq->removed_load_avg, 0);
	atomic_long_set(&cfs_rq->removed_util_avg, 0);
7921
#endif
7922 7923
}

P
Peter Zijlstra 已提交
7924
#ifdef CONFIG_FAIR_GROUP_SCHED
7925
static void task_move_group_fair(struct task_struct *p, int queued)
P
Peter Zijlstra 已提交
7926
{
P
Peter Zijlstra 已提交
7927
	struct sched_entity *se = &p->se;
7928
	struct cfs_rq *cfs_rq;
P
Peter Zijlstra 已提交
7929

7930 7931 7932 7933 7934 7935 7936 7937 7938 7939 7940 7941 7942
	/*
	 * If the task was not on the rq at the time of this cgroup movement
	 * it must have been asleep, sleeping tasks keep their ->vruntime
	 * absolute on their old rq until wakeup (needed for the fair sleeper
	 * bonus in place_entity()).
	 *
	 * If it was on the rq, we've just 'preempted' it, which does convert
	 * ->vruntime to a relative base.
	 *
	 * Make sure both cases convert their relative position when migrating
	 * to another cgroup's rq. This does somewhat interfere with the
	 * fair sleeper stuff for the first placement, but who cares.
	 */
7943
	/*
7944
	 * When !queued, vruntime of the task has usually NOT been normalized.
7945 7946 7947 7948
	 * But there are some cases where it has already been normalized:
	 *
	 * - Moving a forked child which is waiting for being woken up by
	 *   wake_up_new_task().
7949 7950
	 * - Moving a task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
7951 7952 7953 7954
	 *
	 * To prevent boost or penalty in the new cfs_rq caused by delta
	 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
	 */
7955 7956
	if (!queued && (!se->sum_exec_runtime || p->state == TASK_WAKING))
		queued = 1;
7957

7958
	if (!queued)
P
Peter Zijlstra 已提交
7959
		se->vruntime -= cfs_rq_of(se)->min_vruntime;
7960
	set_task_rq(p, task_cpu(p));
P
Peter Zijlstra 已提交
7961
	se->depth = se->parent ? se->parent->depth + 1 : 0;
7962
	if (!queued) {
P
Peter Zijlstra 已提交
7963 7964
		cfs_rq = cfs_rq_of(se);
		se->vruntime += cfs_rq->min_vruntime;
7965

7966
#ifdef CONFIG_SMP
7967 7968 7969 7970 7971 7972
		/* Virtually synchronize task with its new cfs_rq */
		p->se.avg.last_update_time = cfs_rq->avg.last_update_time;
		cfs_rq->avg.load_avg += p->se.avg.load_avg;
		cfs_rq->avg.load_sum += p->se.avg.load_sum;
		cfs_rq->avg.util_avg += p->se.avg.util_avg;
		cfs_rq->avg.util_sum += p->se.avg.util_sum;
7973 7974
#endif
	}
P
Peter Zijlstra 已提交
7975
}
7976 7977 7978 7979 7980 7981 7982 7983 7984 7985 7986 7987 7988 7989 7990 7991 7992 7993 7994 7995 7996 7997 7998 7999 8000 8001 8002 8003 8004 8005 8006 8007 8008 8009 8010 8011 8012 8013 8014 8015 8016 8017 8018 8019 8020 8021 8022 8023 8024 8025 8026 8027 8028 8029 8030 8031 8032 8033 8034 8035 8036 8037 8038 8039 8040 8041 8042 8043 8044 8045 8046 8047 8048 8049 8050 8051 8052 8053 8054 8055 8056 8057 8058 8059 8060 8061 8062 8063 8064 8065 8066 8067

void free_fair_sched_group(struct task_group *tg)
{
	int i;

	destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));

	for_each_possible_cpu(i) {
		if (tg->cfs_rq)
			kfree(tg->cfs_rq[i]);
		if (tg->se)
			kfree(tg->se[i]);
	}

	kfree(tg->cfs_rq);
	kfree(tg->se);
}

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
	struct cfs_rq *cfs_rq;
	struct sched_entity *se;
	int i;

	tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL);
	if (!tg->cfs_rq)
		goto err;
	tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL);
	if (!tg->se)
		goto err;

	tg->shares = NICE_0_LOAD;

	init_cfs_bandwidth(tg_cfs_bandwidth(tg));

	for_each_possible_cpu(i) {
		cfs_rq = kzalloc_node(sizeof(struct cfs_rq),
				      GFP_KERNEL, cpu_to_node(i));
		if (!cfs_rq)
			goto err;

		se = kzalloc_node(sizeof(struct sched_entity),
				  GFP_KERNEL, cpu_to_node(i));
		if (!se)
			goto err_free_rq;

		init_cfs_rq(cfs_rq);
		init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
	}

	return 1;

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

void unregister_fair_sched_group(struct task_group *tg, int cpu)
{
	struct rq *rq = cpu_rq(cpu);
	unsigned long flags;

	/*
	* Only empty task groups can be destroyed; so we can speculatively
	* check on_list without danger of it being re-added.
	*/
	if (!tg->cfs_rq[cpu]->on_list)
		return;

	raw_spin_lock_irqsave(&rq->lock, flags);
	list_del_leaf_cfs_rq(tg->cfs_rq[cpu]);
	raw_spin_unlock_irqrestore(&rq->lock, flags);
}

void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
			struct sched_entity *se, int cpu,
			struct sched_entity *parent)
{
	struct rq *rq = cpu_rq(cpu);

	cfs_rq->tg = tg;
	cfs_rq->rq = rq;
	init_cfs_rq_runtime(cfs_rq);

	tg->cfs_rq[cpu] = cfs_rq;
	tg->se[cpu] = se;

	/* se could be NULL for root_task_group */
	if (!se)
		return;

P
Peter Zijlstra 已提交
8068
	if (!parent) {
8069
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
8070 8071
		se->depth = 0;
	} else {
8072
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
8073 8074
		se->depth = parent->depth + 1;
	}
8075 8076

	se->my_q = cfs_rq;
8077 8078
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
8079 8080 8081 8082 8083 8084 8085 8086 8087 8088 8089 8090 8091 8092 8093 8094 8095 8096 8097 8098 8099 8100 8101 8102 8103 8104 8105 8106 8107 8108
	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);
8109 8110 8111

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
8112
		for_each_sched_entity(se)
8113 8114 8115 8116 8117 8118 8119 8120 8121 8122 8123 8124 8125 8126 8127 8128 8129 8130 8131 8132 8133
			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
8134

8135
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8136 8137 8138 8139 8140 8141 8142 8143 8144
{
	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)
8145
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8146 8147 8148 8149

	return rr_interval;
}

8150 8151 8152
/*
 * All the scheduling class methods:
 */
8153
const struct sched_class fair_sched_class = {
8154
	.next			= &idle_sched_class,
8155 8156 8157
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
8158
	.yield_to_task		= yield_to_task_fair,
8159

I
Ingo Molnar 已提交
8160
	.check_preempt_curr	= check_preempt_wakeup,
8161 8162 8163 8164

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

8165
#ifdef CONFIG_SMP
L
Li Zefan 已提交
8166
	.select_task_rq		= select_task_rq_fair,
8167
	.migrate_task_rq	= migrate_task_rq_fair,
8168

8169 8170
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
8171 8172

	.task_waking		= task_waking_fair,
8173
#endif
8174

8175
	.set_curr_task          = set_curr_task_fair,
8176
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
8177
	.task_fork		= task_fork_fair,
8178 8179

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
8180
	.switched_from		= switched_from_fair,
8181
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
8182

8183 8184
	.get_rr_interval	= get_rr_interval_fair,

8185 8186
	.update_curr		= update_curr_fair,

P
Peter Zijlstra 已提交
8187
#ifdef CONFIG_FAIR_GROUP_SCHED
8188
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
8189
#endif
8190 8191 8192
};

#ifdef CONFIG_SCHED_DEBUG
8193
void print_cfs_stats(struct seq_file *m, int cpu)
8194 8195 8196
{
	struct cfs_rq *cfs_rq;

8197
	rcu_read_lock();
8198
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8199
		print_cfs_rq(m, cpu, cfs_rq);
8200
	rcu_read_unlock();
8201
}
8202 8203 8204 8205 8206 8207 8208 8209 8210 8211 8212 8213 8214 8215 8216 8217 8218 8219 8220 8221 8222

#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 */
8223 8224 8225 8226 8227 8228

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

8229
#ifdef CONFIG_NO_HZ_COMMON
8230
	nohz.next_balance = jiffies;
8231
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8232
	cpu_notifier(sched_ilb_notifier, 0);
8233 8234 8235 8236
#endif
#endif /* SMP */

}