fair.c 217.0 KB
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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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 */

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

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

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

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

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

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

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

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

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

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

	return factor;
}

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

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

void sched_init_granularity(void)
{
	update_sysctl();
}

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

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

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

	w = scale_load_down(lw->weight);

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

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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#else	/* !CONFIG_FAIR_GROUP_SCHED */

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

#define entity_is_task(se)	1

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

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

	return &rq->cfs;
}

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

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

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

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

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

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

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#endif	/* CONFIG_FAIR_GROUP_SCHED */

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

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

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

	return min_vruntime;
}

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

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

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

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

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

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

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

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

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

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

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

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

	if (!left)
		return NULL;

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

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

	if (!next)
		return NULL;

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

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

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

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

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

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

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

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

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

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

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

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

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

675 676 677 678 679 680 681
	sa->last_update_time = 0;
	/*
	 * sched_avg's period_contrib should be strictly less then 1024, so
	 * we give it 1023 to make sure it is almost a period (1024us), and
	 * will definitely be update (after enqueue).
	 */
	sa->period_contrib = 1023;
682
	sa->load_avg = scale_load_down(se->load.weight);
683 684 685 686
	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

static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq);
static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq);
691
#else
692
void init_entity_runnable_average(struct sched_entity *se)
693 694 695 696
{
}
#endif

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

	if (unlikely(!curr))
		return;

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

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

715 716 717 718 719 720 721 722 723
	schedstat_set(curr->statistics.exec_max,
		      max(delta_exec, curr->statistics.exec_max));

	curr->sum_exec_runtime += delta_exec;
	schedstat_add(cfs_rq, exec_clock, delta_exec);

	curr->vruntime += calc_delta_fair(delta_exec, curr);
	update_min_vruntime(cfs_rq);

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

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

	account_cfs_rq_runtime(cfs_rq, delta_exec);
733 734
}

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

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

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

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

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

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

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

803 804
#ifdef CONFIG_NUMA_BALANCING
/*
805 806 807
 * Approximate time to scan a full NUMA task in ms. The task scan period is
 * calculated based on the tasks virtual memory size and
 * numa_balancing_scan_size.
808
 */
809 810
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
811 812 813

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

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

818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841
static unsigned int task_nr_scan_windows(struct task_struct *p)
{
	unsigned long rss = 0;
	unsigned long nr_scan_pages;

	/*
	 * Calculations based on RSS as non-present and empty pages are skipped
	 * by the PTE scanner and NUMA hinting faults should be trapped based
	 * on resident pages
	 */
	nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT);
	rss = get_mm_rss(p->mm);
	if (!rss)
		rss = nr_scan_pages;

	rss = round_up(rss, nr_scan_pages);
	return rss / nr_scan_pages;
}

/* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */
#define MAX_SCAN_WINDOW 2560

static unsigned int task_scan_min(struct task_struct *p)
{
842
	unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size);
843 844 845
	unsigned int scan, floor;
	unsigned int windows = 1;

846 847
	if (scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / scan_size;
848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863
	floor = 1000 / windows;

	scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
	return max_t(unsigned int, floor, scan);
}

static unsigned int task_scan_max(struct task_struct *p)
{
	unsigned int smin = task_scan_min(p);
	unsigned int smax;

	/* Watch for min being lower than max due to floor calculations */
	smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p);
	return max(smin, smax);
}

864 865 866 867 868 869 870 871 872 873 874 875
static void account_numa_enqueue(struct rq *rq, struct task_struct *p)
{
	rq->nr_numa_running += (p->numa_preferred_nid != -1);
	rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p));
}

static void account_numa_dequeue(struct rq *rq, struct task_struct *p)
{
	rq->nr_numa_running -= (p->numa_preferred_nid != -1);
	rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p));
}

876 877 878 879 880
struct numa_group {
	atomic_t refcount;

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

	struct rcu_head rcu;
884
	nodemask_t active_nodes;
885
	unsigned long total_faults;
886 887 888 889 890
	/*
	 * Faults_cpu is used to decide whether memory should move
	 * towards the CPU. As a consequence, these stats are weighted
	 * more by CPU use than by memory faults.
	 */
891
	unsigned long *faults_cpu;
892
	unsigned long faults[0];
893 894
};

895 896 897 898 899 900 901 902 903
/* Shared or private faults. */
#define NR_NUMA_HINT_FAULT_TYPES 2

/* Memory and CPU locality */
#define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2)

/* Averaged statistics, and temporary buffers. */
#define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2)

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

909 910 911 912 913 914 915
/*
 * The averaged statistics, shared & private, memory & cpu,
 * occupy the first half of the array. The second half of the
 * array is for current counters, which are averaged into the
 * first set by task_numa_placement.
 */
static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv)
916
{
917
	return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv;
918 919 920 921
}

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

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

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

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

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

944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008
/* Handle placement on systems where not all nodes are directly connected. */
static unsigned long score_nearby_nodes(struct task_struct *p, int nid,
					int maxdist, bool task)
{
	unsigned long score = 0;
	int node;

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

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

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

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

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

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

		score += faults;
	}

	return score;
}

1009 1010 1011 1012 1013 1014
/*
 * These return the fraction of accesses done by a particular task, or
 * task group, on a particular numa node.  The group weight is given a
 * larger multiplier, in order to group tasks together that are almost
 * evenly spread out between numa nodes.
 */
1015 1016
static inline unsigned long task_weight(struct task_struct *p, int nid,
					int dist)
1017
{
1018
	unsigned long faults, total_faults;
1019

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

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

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

1031
	return 1000 * faults / total_faults;
1032 1033
}

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

	if (!p->numa_group)
		return 0;

	total_faults = p->numa_group->total_faults;

	if (!total_faults)
1045 1046
		return 0;

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

1050
	return 1000 * faults / total_faults;
1051 1052
}

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

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

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

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

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

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

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

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

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

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

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

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

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

	memset(ns, 0, sizeof(*ns));
	for_each_cpu(cpu, cpumask_of_node(nid)) {
		struct rq *rq = cpu_rq(cpu);

		ns->nr_running += rq->nr_running;
		ns->load += weighted_cpuload(cpu);
1149
		ns->compute_capacity += capacity_of(cpu);
1150 1151

		cpus++;
1152 1153
	}

1154 1155 1156 1157 1158
	/*
	 * If we raced with hotplug and there are no CPUs left in our mask
	 * the @ns structure is NULL'ed and task_numa_compare() will
	 * not find this node attractive.
	 *
1159 1160
	 * We'll either bail at !has_free_capacity, or we'll detect a huge
	 * imbalance and bail there.
1161 1162 1163 1164
	 */
	if (!cpus)
		return;

1165 1166 1167 1168 1169 1170
	/* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */
	smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity);
	capacity = cpus / smt; /* cores */

	ns->task_capacity = min_t(unsigned, capacity,
		DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE));
1171
	ns->has_free_capacity = (ns->nr_running < ns->task_capacity);
1172 1173
}

1174 1175
struct task_numa_env {
	struct task_struct *p;
1176

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

1180
	struct numa_stats src_stats, dst_stats;
1181

1182
	int imbalance_pct;
1183
	int dist;
1184 1185 1186

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

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

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

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

	/*
	 * The load is corrected for the CPU capacity available on each node.
	 *
	 * src_load        dst_load
	 * ------------ vs ---------
	 * src_capacity    dst_capacity
	 */
	src_capacity = env->src_stats.compute_capacity;
	dst_capacity = env->dst_stats.compute_capacity;
1219 1220

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

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

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

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

1240 1241 1242 1243 1244
	old_imb = orig_dst_load * src_capacity * 100 -
		  orig_src_load * dst_capacity * env->imbalance_pct;

	/* Would this change make things worse? */
	return (imb > old_imb);
1245 1246
}

1247 1248 1249 1250 1251 1252
/*
 * This checks if the overall compute and NUMA accesses of the system would
 * be improved if the source tasks was migrated to the target dst_cpu taking
 * into account that it might be best if task running on the dst_cpu should
 * be exchanged with the source task
 */
1253 1254
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1255 1256 1257 1258
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
1259
	long src_load, dst_load;
1260
	long load;
1261
	long imp = env->p->numa_group ? groupimp : taskimp;
1262
	long moveimp = imp;
1263
	int dist = env->dist;
1264 1265

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

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

1280 1281 1282 1283 1284 1285 1286
	/*
	 * Because we have preemption enabled we can get migrated around and
	 * end try selecting ourselves (current == env->p) as a swap candidate.
	 */
	if (cur == env->p)
		goto unlock;

1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298
	/*
	 * "imp" is the fault differential for the source task between the
	 * source and destination node. Calculate the total differential for
	 * the source task and potential destination task. The more negative
	 * the value is, the more rmeote accesses that would be expected to
	 * be incurred if the tasks were swapped.
	 */
	if (cur) {
		/* Skip this swap candidate if cannot move to the source cpu */
		if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur)))
			goto unlock;

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

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

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

		goto balance;
	}

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

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

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

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

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

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

1378 1379 1380 1381 1382 1383 1384
	/*
	 * One idle CPU per node is evaluated for a task numa move.
	 * Call select_idle_sibling to maybe find a better one.
	 */
	if (!cur)
		env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu);

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

1391 1392
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1393 1394 1395 1396 1397 1398 1399 1400 1401
{
	int cpu;

	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
		/* Skip this CPU if the source task cannot migrate */
		if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p)))
			continue;

		env->dst_cpu = cpu;
1402
		task_numa_compare(env, taskimp, groupimp);
1403 1404 1405
	}
}

1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422
/* Only move tasks to a NUMA node less busy than the current node. */
static bool numa_has_capacity(struct task_numa_env *env)
{
	struct numa_stats *src = &env->src_stats;
	struct numa_stats *dst = &env->dst_stats;

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

	/*
	 * Only consider a task move if the source has a higher load
	 * than the destination, corrected for CPU capacity on each node.
	 *
	 *      src->load                dst->load
	 * --------------------- vs ---------------------
	 * src->compute_capacity    dst->compute_capacity
	 */
1423 1424 1425
	if (src->load * dst->compute_capacity * env->imbalance_pct >

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

	return false;
}

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

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

		.imbalance_pct = 112,

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

1450
	/*
1451 1452 1453 1454 1455 1456
	 * Pick the lowest SD_NUMA domain, as that would have the smallest
	 * imbalance and would be the first to start moving tasks about.
	 *
	 * And we want to avoid any moving of tasks about, as that would create
	 * random movement of tasks -- counter the numa conditions we're trying
	 * to satisfy here.
1457 1458
	 */
	rcu_read_lock();
1459
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
1460 1461
	if (sd)
		env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1462 1463
	rcu_read_unlock();

1464 1465 1466 1467 1468 1469 1470
	/*
	 * Cpusets can break the scheduler domain tree into smaller
	 * balance domains, some of which do not cross NUMA boundaries.
	 * Tasks that are "trapped" in such domains cannot be migrated
	 * elsewhere, so there is no point in (re)trying.
	 */
	if (unlikely(!sd)) {
1471
		p->numa_preferred_nid = task_node(p);
1472 1473 1474
		return -EINVAL;
	}

1475
	env.dst_nid = p->numa_preferred_nid;
1476 1477 1478 1479 1480 1481
	dist = env.dist = node_distance(env.src_nid, env.dst_nid);
	taskweight = task_weight(p, env.src_nid, dist);
	groupweight = group_weight(p, env.src_nid, dist);
	update_numa_stats(&env.src_stats, env.src_nid);
	taskimp = task_weight(p, env.dst_nid, dist) - taskweight;
	groupimp = group_weight(p, env.dst_nid, dist) - groupweight;
1482
	update_numa_stats(&env.dst_stats, env.dst_nid);
1483

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

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

1501
			dist = node_distance(env.src_nid, env.dst_nid);
1502 1503 1504 1505 1506
			if (sched_numa_topology_type == NUMA_BACKPLANE &&
						dist != env.dist) {
				taskweight = task_weight(p, env.src_nid, dist);
				groupweight = group_weight(p, env.src_nid, dist);
			}
1507

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

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

1522 1523 1524 1525 1526 1527 1528 1529
	/*
	 * If the task is part of a workload that spans multiple NUMA nodes,
	 * and is migrating into one of the workload's active nodes, remember
	 * this node as the task's preferred numa node, so the workload can
	 * settle down.
	 * A task that migrated to a second choice node will be better off
	 * trying for a better one later. Do not set the preferred node here.
	 */
1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542
	if (p->numa_group) {
		if (env.best_cpu == -1)
			nid = env.src_nid;
		else
			nid = env.dst_nid;

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

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

1544 1545 1546 1547 1548 1549
	/*
	 * Reset the scan period if the task is being rescheduled on an
	 * alternative node to recheck if the tasks is now properly placed.
	 */
	p->numa_scan_period = task_scan_min(p);

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

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

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

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

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

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

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

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

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

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

1617 1618 1619
/*
 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS
 * increments. The more local the fault statistics are, the higher the scan
1620 1621 1622
 * period will be for the next scan window. If local/(local+remote) ratio is
 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS)
 * the scan period will decrease. Aim for 70% local accesses.
1623 1624
 */
#define NUMA_PERIOD_SLOTS 10
1625
#define NUMA_PERIOD_THRESHOLD 7
1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645

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

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

	/*
	 * If there were no record hinting faults then either the task is
	 * completely idle or all activity is areas that are not of interest
1646 1647 1648
	 * to automatic numa balancing. Related to that, if there were failed
	 * migration then it implies we are migrating too quickly or the local
	 * node is overloaded. In either case, scan slower
1649
	 */
1650
	if (local + shared == 0 || p->numa_faults_locality[2]) {
1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683
		p->numa_scan_period = min(p->numa_scan_period_max,
			p->numa_scan_period << 1);

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

		return;
	}

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

		/*
		 * Scale scan rate increases based on sharing. There is an
		 * inverse relationship between the degree of sharing and
		 * the adjustment made to the scanning period. Broadly
		 * speaking the intent is that there is little point
		 * scanning faster if shared accesses dominate as it may
		 * simply bounce migrations uselessly
		 */
1684
		ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
1685 1686 1687 1688 1689 1690 1691 1692
		diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
	}

	p->numa_scan_period = clamp(p->numa_scan_period + diff,
			task_scan_min(p), task_scan_max(p));
	memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
}

1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710
/*
 * Get the fraction of time the task has been running since the last
 * NUMA placement cycle. The scheduler keeps similar statistics, but
 * decays those on a 32ms period, which is orders of magnitude off
 * from the dozens-of-seconds NUMA balancing period. Use the scheduler
 * stats only if the task is so new there are no NUMA statistics yet.
 */
static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
{
	u64 runtime, delta, now;
	/* Use the start of this time slice to avoid calculations. */
	now = p->se.exec_start;
	runtime = p->se.sum_exec_runtime;

	if (p->last_task_numa_placement) {
		delta = runtime - p->last_sum_exec_runtime;
		*period = now - p->last_task_numa_placement;
	} else {
1711 1712
		delta = p->se.avg.load_sum / p->se.load.weight;
		*period = LOAD_AVG_MAX;
1713 1714 1715 1716 1717 1718 1719 1720
	}

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

	return delta;
}

1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767
/*
 * Determine the preferred nid for a task in a numa_group. This needs to
 * be done in a way that produces consistent results with group_weight,
 * otherwise workloads might not converge.
 */
static int preferred_group_nid(struct task_struct *p, int nid)
{
	nodemask_t nodes;
	int dist;

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

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

		dist = sched_max_numa_distance;

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

	/*
	 * Finding the preferred nid in a system with NUMA backplane
	 * interconnect topology is more involved. The goal is to locate
	 * tasks from numa_groups near each other in the system, and
	 * untangle workloads from different sides of the system. This requires
	 * searching down the hierarchy of node groups, recursively searching
	 * inside the highest scoring group of nodes. The nodemask tricks
	 * keep the complexity of the search down.
	 */
	nodes = node_online_map;
	for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) {
		unsigned long max_faults = 0;
1768
		nodemask_t max_group = NODE_MASK_NONE;
1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801
		int a, b;

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

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

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

			/* Remember the top group. */
			if (faults > max_faults) {
				max_faults = faults;
				max_group = this_group;
				/*
				 * subtle: at the smallest distance there is
				 * just one node left in each "group", the
				 * winner is the preferred nid.
				 */
				nid = a;
			}
		}
		/* Next round, evaluate the nodes within max_group. */
1802 1803
		if (!max_faults)
			break;
1804 1805 1806 1807 1808
		nodes = max_group;
	}
	return nid;
}

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

1818 1819 1820 1821 1822
	/*
	 * The p->mm->numa_scan_seq field gets updated without
	 * exclusive access. Use READ_ONCE() here to ensure
	 * that the field is read in a single access:
	 */
1823
	seq = READ_ONCE(p->mm->numa_scan_seq);
1824 1825 1826
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
1827
	p->numa_scan_period_max = task_scan_max(p);
1828

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

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

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

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

1849 1850 1851 1852
			mem_idx = task_faults_idx(NUMA_MEM, nid, priv);
			membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv);
			cpu_idx = task_faults_idx(NUMA_CPU, nid, priv);
			cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv);
1853

1854
			/* Decay existing window, copy faults since last scan */
1855 1856 1857
			diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2;
			fault_types[priv] += p->numa_faults[membuf_idx];
			p->numa_faults[membuf_idx] = 0;
1858

1859 1860 1861 1862 1863 1864 1865 1866
			/*
			 * Normalize the faults_from, so all tasks in a group
			 * count according to CPU use, instead of by the raw
			 * number of faults. Tasks with little runtime have
			 * little over-all impact on throughput, and thus their
			 * faults are less important.
			 */
			f_weight = div64_u64(runtime << 16, period + 1);
1867
			f_weight = (f_weight * p->numa_faults[cpubuf_idx]) /
1868
				   (total_faults + 1);
1869 1870
			f_diff = f_weight - p->numa_faults[cpu_idx] / 2;
			p->numa_faults[cpubuf_idx] = 0;
1871

1872 1873 1874
			p->numa_faults[mem_idx] += diff;
			p->numa_faults[cpu_idx] += f_diff;
			faults += p->numa_faults[mem_idx];
1875
			p->total_numa_faults += diff;
1876
			if (p->numa_group) {
1877 1878 1879 1880 1881 1882 1883 1884 1885
				/*
				 * safe because we can only change our own group
				 *
				 * mem_idx represents the offset for a given
				 * nid and priv in a specific region because it
				 * is at the beginning of the numa_faults array.
				 */
				p->numa_group->faults[mem_idx] += diff;
				p->numa_group->faults_cpu[mem_idx] += f_diff;
1886
				p->numa_group->total_faults += diff;
1887
				group_faults += p->numa_group->faults[mem_idx];
1888
			}
1889 1890
		}

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

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

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

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

1910 1911 1912 1913 1914 1915 1916
	if (max_faults) {
		/* Set the new preferred node */
		if (max_nid != p->numa_preferred_nid)
			sched_setnuma(p, max_nid);

		if (task_node(p) != p->numa_preferred_nid)
			numa_migrate_preferred(p);
1917
	}
1918 1919
}

1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930
static inline int get_numa_group(struct numa_group *grp)
{
	return atomic_inc_not_zero(&grp->refcount);
}

static inline void put_numa_group(struct numa_group *grp)
{
	if (atomic_dec_and_test(&grp->refcount))
		kfree_rcu(grp, rcu);
}

1931 1932
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
1933 1934 1935 1936 1937 1938 1939 1940 1941
{
	struct numa_group *grp, *my_grp;
	struct task_struct *tsk;
	bool join = false;
	int cpu = cpupid_to_cpu(cpupid);
	int i;

	if (unlikely(!p->numa_group)) {
		unsigned int size = sizeof(struct numa_group) +
1942
				    4*nr_node_ids*sizeof(unsigned long);
1943 1944 1945 1946 1947 1948 1949

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

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

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

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

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

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

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

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

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

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

	/*
	 * Only join the other group if its bigger; if we're the bigger group,
	 * the other task will join us.
	 */
	if (my_grp->nr_tasks > grp->nr_tasks)
1985
		goto no_join;
1986 1987 1988 1989 1990

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

1993 1994 1995 1996 1997 1998 1999
	/* Always join threads in the same process. */
	if (tsk->mm == current->mm)
		join = true;

	/* Simple filter to avoid false positives due to PID collisions */
	if (flags & TNF_SHARED)
		join = true;
2000

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

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

	rcu_read_unlock();

	if (!join)
		return;

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

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

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

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

	rcu_assign_pointer(p->numa_group, grp);

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

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

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

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

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

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

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

2072
	if (!numabalancing_enabled)
2073 2074
		return;

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

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

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

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

2092 2093 2094 2095 2096 2097 2098 2099
	/*
	 * First accesses are treated as private, otherwise consider accesses
	 * to be private if the accessing pid has not changed
	 */
	if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) {
		priv = 1;
	} else {
		priv = cpupid_match_pid(p, last_cpupid);
2100
		if (!priv && !(flags & TNF_NO_GROUP))
2101
			task_numa_group(p, last_cpupid, flags, &priv);
2102 2103
	}

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

2115
	task_numa_placement(p);
2116

2117 2118 2119 2120 2121
	/*
	 * Retry task to preferred node migration periodically, in case it
	 * case it previously failed, or the scheduler moved us.
	 */
	if (time_after(jiffies, p->numa_migrate_retry))
2122 2123
		numa_migrate_preferred(p);

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

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

2134 2135
static void reset_ptenuma_scan(struct task_struct *p)
{
2136 2137 2138 2139 2140 2141 2142 2143
	/*
	 * We only did a read acquisition of the mmap sem, so
	 * p->mm->numa_scan_seq is written to without exclusive access
	 * and the update is not guaranteed to be atomic. That's not
	 * much of an issue though, since this is just used for
	 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not
	 * expensive, to avoid any form of compiler optimizations:
	 */
2144
	WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
2145 2146 2147
	p->mm->numa_scan_offset = 0;
}

2148 2149 2150 2151 2152 2153 2154 2155 2156
/*
 * The expensive part of numa migration is done from task_work context.
 * Triggered from task_tick_numa().
 */
void task_numa_work(struct callback_head *work)
{
	unsigned long migrate, next_scan, now = jiffies;
	struct task_struct *p = current;
	struct mm_struct *mm = p->mm;
2157
	struct vm_area_struct *vma;
2158
	unsigned long start, end;
2159
	unsigned long nr_pte_updates = 0;
2160
	long pages;
2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175

	WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));

	work->next = work; /* protect against double add */
	/*
	 * Who cares about NUMA placement when they're dying.
	 *
	 * NOTE: make sure not to dereference p->mm before this check,
	 * exit_task_work() happens _after_ exit_mm() so we could be called
	 * without p->mm even though we still had it when we enqueued this
	 * work.
	 */
	if (p->flags & PF_EXITING)
		return;

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

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

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

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

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

2203 2204 2205 2206 2207
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
	if (!pages)
		return;
2208

2209
	down_read(&mm->mmap_sem);
2210
	vma = find_vma(mm, start);
2211 2212
	if (!vma) {
		reset_ptenuma_scan(p);
2213
		start = 0;
2214 2215
		vma = mm->mmap;
	}
2216
	for (; vma; vma = vma->vm_next) {
2217
		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
2218
			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
2219
			continue;
2220
		}
2221

2222 2223 2224 2225 2226 2227 2228 2229 2230 2231
		/*
		 * 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
2232 2233 2234 2235 2236 2237
		/*
		 * 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;
2238

2239 2240 2241 2242
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
2243 2244 2245 2246 2247 2248 2249 2250 2251
			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;
2252

2253 2254 2255
			start = end;
			if (pages <= 0)
				goto out;
2256 2257

			cond_resched();
2258
		} while (end != vma->vm_end);
2259
	}
2260

2261
out:
2262
	/*
P
Peter Zijlstra 已提交
2263 2264 2265 2266
	 * 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.
2267 2268
	 */
	if (vma)
2269
		mm->numa_scan_offset = start;
2270 2271 2272
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298
}

/*
 * 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) {
2299
		if (!curr->node_stamp)
2300
			curr->numa_scan_period = task_scan_min(curr);
2301
		curr->node_stamp += period;
2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312

		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)
{
}
2313 2314 2315 2316 2317 2318 2319 2320

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)
{
}
2321 2322
#endif /* CONFIG_NUMA_BALANCING */

2323 2324 2325 2326
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
2327
	if (!parent_entity(se))
2328
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
2329
#ifdef CONFIG_SMP
2330 2331 2332 2333 2334 2335
	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);
	}
2336
#endif
2337 2338 2339 2340 2341 2342 2343
	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);
2344
	if (!parent_entity(se))
2345
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
2346 2347
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
2348
		list_del_init(&se->group_node);
2349
	}
2350 2351 2352
	cfs_rq->nr_running--;
}

2353 2354
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
2355 2356 2357 2358 2359
static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
{
	long tg_weight;

	/*
2360 2361 2362
	 * 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().
2363
	 */
2364
	tg_weight = atomic_long_read(&tg->load_avg);
2365
	tg_weight -= cfs_rq->tg_load_avg_contrib;
2366
	tg_weight += cfs_rq_load_avg(cfs_rq);
2367 2368 2369 2370

	return tg_weight;
}

2371
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2372
{
2373
	long tg_weight, load, shares;
2374

2375
	tg_weight = calc_tg_weight(tg, cfs_rq);
2376
	load = cfs_rq_load_avg(cfs_rq);
2377 2378

	shares = (tg->shares * load);
2379 2380
	if (tg_weight)
		shares /= tg_weight;
2381 2382 2383 2384 2385 2386 2387 2388 2389

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

	return shares;
}
# else /* CONFIG_SMP */
2390
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
2391 2392 2393 2394
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
2395 2396 2397
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
2398 2399 2400 2401
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
2402
		account_entity_dequeue(cfs_rq, se);
2403
	}
P
Peter Zijlstra 已提交
2404 2405 2406 2407 2408 2409 2410

	update_load_set(&se->load, weight);

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

2411 2412
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

2413
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2414 2415 2416
{
	struct task_group *tg;
	struct sched_entity *se;
2417
	long shares;
P
Peter Zijlstra 已提交
2418 2419 2420

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
2421
	if (!se || throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
2422
		return;
2423 2424 2425 2426
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
2427
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
2428 2429 2430 2431

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
2432
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
2433 2434 2435 2436
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

2437
#ifdef CONFIG_SMP
2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457
/* 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,
};

2458 2459 2460 2461 2462 2463
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475
	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
2476 2477
	 *    y^n = 1/2^(n/PERIOD) * y^(n%PERIOD)
	 * With a look-up table which covers y^n (n<PERIOD)
2478 2479 2480 2481 2482 2483
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
2484 2485
	}

2486 2487
	val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32);
	return val;
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 2513 2514 2515
}

/*
 * 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];
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 2543 2544 2545
}

/*
 * 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}]
 */
2546 2547
static __always_inline int
__update_load_avg(u64 now, int cpu, struct sched_avg *sa,
2548
		  unsigned long weight, int running, struct cfs_rq *cfs_rq)
2549
{
2550
	u64 delta, periods;
2551
	u32 contrib;
2552
	int delta_w, decayed = 0;
2553
	unsigned long scale_freq = arch_scale_freq_capacity(NULL, cpu);
2554

2555
	delta = now - sa->last_update_time;
2556 2557 2558 2559 2560
	/*
	 * 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) {
2561
		sa->last_update_time = now;
2562 2563 2564 2565 2566 2567 2568 2569 2570 2571
		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;
2572
	sa->last_update_time = now;
2573 2574

	/* delta_w is the amount already accumulated against our next period */
2575
	delta_w = sa->period_contrib;
2576 2577 2578
	if (delta + delta_w >= 1024) {
		decayed = 1;

2579 2580 2581
		/* how much left for next period will start over, we don't know yet */
		sa->period_contrib = 0;

2582 2583 2584 2585 2586 2587
		/*
		 * 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;
2588
		if (weight) {
2589
			sa->load_sum += weight * delta_w;
2590 2591 2592
			if (cfs_rq)
				cfs_rq->runnable_load_sum += weight * delta_w;
		}
2593
		if (running)
2594
			sa->util_sum += delta_w * scale_freq >> SCHED_CAPACITY_SHIFT;
2595 2596 2597 2598 2599 2600 2601

		delta -= delta_w;

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

2602
		sa->load_sum = decay_load(sa->load_sum, periods + 1);
2603 2604 2605 2606
		if (cfs_rq) {
			cfs_rq->runnable_load_sum =
				decay_load(cfs_rq->runnable_load_sum, periods + 1);
		}
2607
		sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1);
2608 2609

		/* Efficiently calculate \sum (1..n_period) 1024*y^i */
2610
		contrib = __compute_runnable_contrib(periods);
2611
		if (weight) {
2612
			sa->load_sum += weight * contrib;
2613 2614 2615
			if (cfs_rq)
				cfs_rq->runnable_load_sum += weight * contrib;
		}
2616
		if (running)
2617
			sa->util_sum += contrib * scale_freq >> SCHED_CAPACITY_SHIFT;
2618 2619 2620
	}

	/* Remainder of delta accrued against u_0` */
2621
	if (weight) {
2622
		sa->load_sum += weight * delta;
2623 2624 2625
		if (cfs_rq)
			cfs_rq->runnable_load_sum += weight * delta;
	}
2626
	if (running)
2627
		sa->util_sum += delta * scale_freq >> SCHED_CAPACITY_SHIFT;
2628

2629
	sa->period_contrib += delta;
2630

2631 2632
	if (decayed) {
		sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX);
2633 2634 2635 2636
		if (cfs_rq) {
			cfs_rq->runnable_load_avg =
				div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX);
		}
2637 2638
		sa->util_avg = (sa->util_sum << SCHED_LOAD_SHIFT) / LOAD_AVG_MAX;
	}
2639

2640
	return decayed;
2641 2642
}

2643
#ifdef CONFIG_FAIR_GROUP_SCHED
2644
/*
2645 2646
 * 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).
2647
 */
2648
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
2649
{
2650
	long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;
2651

2652 2653 2654
	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;
2655
	}
2656
}
2657

2658
#else /* CONFIG_FAIR_GROUP_SCHED */
2659
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
2660
#endif /* CONFIG_FAIR_GROUP_SCHED */
2661

2662
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
2663

2664 2665
/* 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)
2666
{
2667
	struct sched_avg *sa = &cfs_rq->avg;
2668
	int decayed;
2669

2670 2671 2672 2673
	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);
2674
	}
2675

2676 2677 2678 2679 2680 2681
	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);
	}
2682

2683
	decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2684
		scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq);
2685

2686 2687 2688 2689
#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->load_last_update_time_copy = sa->last_update_time;
#endif
2690

2691
	return decayed;
2692 2693
}

2694 2695
/* Update task and its cfs_rq load average */
static inline void update_load_avg(struct sched_entity *se, int update_tg)
2696
{
2697
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
2698
	u64 now = cfs_rq_clock_task(cfs_rq);
2699
	int cpu = cpu_of(rq_of(cfs_rq));
2700

2701
	/*
2702 2703
	 * 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
2704
	 */
2705
	__update_load_avg(now, cpu, &se->avg,
2706 2707
			  se->on_rq * scale_load_down(se->load.weight),
			  cfs_rq->curr == se, NULL);
2708

2709 2710
	if (update_cfs_rq_load_avg(now, cfs_rq) && update_tg)
		update_tg_load_avg(cfs_rq, 0);
2711 2712
}

2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733
static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	se->avg.last_update_time = cfs_rq->avg.last_update_time;
	cfs_rq->avg.load_avg += se->avg.load_avg;
	cfs_rq->avg.load_sum += se->avg.load_sum;
	cfs_rq->avg.util_avg += se->avg.util_avg;
	cfs_rq->avg.util_sum += se->avg.util_sum;
}

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

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

2734 2735 2736
/* 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)
2737
{
2738 2739
	struct sched_avg *sa = &se->avg;
	u64 now = cfs_rq_clock_task(cfs_rq);
2740
	int migrated, decayed;
2741

2742 2743
	migrated = !sa->last_update_time;
	if (!migrated) {
2744
		__update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa,
2745 2746
			se->on_rq * scale_load_down(se->load.weight),
			cfs_rq->curr == se, NULL);
2747
	}
2748

2749
	decayed = update_cfs_rq_load_avg(now, cfs_rq);
2750

2751 2752 2753
	cfs_rq->runnable_load_avg += sa->load_avg;
	cfs_rq->runnable_load_sum += sa->load_sum;

2754 2755
	if (migrated)
		attach_entity_load_avg(cfs_rq, se);
2756

2757 2758
	if (decayed || migrated)
		update_tg_load_avg(cfs_rq, 0);
2759 2760
}

2761 2762 2763 2764 2765 2766 2767 2768 2769
/* Remove the runnable load generated by se from cfs_rq's runnable load average */
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_avg(se, 1);

	cfs_rq->runnable_load_avg =
		max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0);
	cfs_rq->runnable_load_sum =
2770
		max_t(s64,  cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
2771 2772
}

2773
/*
2774 2775
 * Task first catches up with cfs_rq, and then subtract
 * itself from the cfs_rq (task must be off the queue now).
2776
 */
2777
void remove_entity_load_avg(struct sched_entity *se)
2778
{
2779 2780 2781 2782 2783
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 last_update_time;

#ifndef CONFIG_64BIT
	u64 last_update_time_copy;
2784

2785 2786 2787 2788 2789 2790 2791 2792 2793
	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

2794
	__update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
2795 2796
	atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
	atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
2797
}
2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816

/*
 * 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)
{
}

2817 2818 2819 2820 2821 2822 2823 2824 2825 2826
static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
{
	return cfs_rq->runnable_load_avg;
}

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

2827 2828
static int idle_balance(struct rq *this_rq);

2829 2830
#else /* CONFIG_SMP */

2831 2832 2833
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) {}
2834 2835
static inline void
dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
2836
static inline void remove_entity_load_avg(struct sched_entity *se) {}
2837

2838 2839 2840 2841 2842
static inline void
attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
static inline void
detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}

2843 2844 2845 2846 2847
static inline int idle_balance(struct rq *rq)
{
	return 0;
}

2848
#endif /* CONFIG_SMP */
2849

2850
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2851 2852
{
#ifdef CONFIG_SCHEDSTATS
2853 2854 2855 2856 2857
	struct task_struct *tsk = NULL;

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

2858
	if (se->statistics.sleep_start) {
2859
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2860 2861 2862 2863

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

2864 2865
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
2866

2867
		se->statistics.sleep_start = 0;
2868
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
2869

2870
		if (tsk) {
2871
			account_scheduler_latency(tsk, delta >> 10, 1);
2872 2873
			trace_sched_stat_sleep(tsk, delta);
		}
2874
	}
2875
	if (se->statistics.block_start) {
2876
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2877 2878 2879 2880

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

2881 2882
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
2883

2884
		se->statistics.block_start = 0;
2885
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
2886

2887
		if (tsk) {
2888
			if (tsk->in_iowait) {
2889 2890
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
2891
				trace_sched_stat_iowait(tsk, delta);
2892 2893
			}

2894 2895
			trace_sched_stat_blocked(tsk, delta);

2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906
			/*
			 * 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
2907
		}
2908 2909 2910 2911
	}
#endif
}

P
Peter Zijlstra 已提交
2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924
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
}

2925 2926 2927
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
2928
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
2929

2930 2931 2932 2933 2934 2935
	/*
	 * 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
2936
	if (initial && sched_feat(START_DEBIT))
2937
		vruntime += sched_vslice(cfs_rq, se);
2938

2939
	/* sleeps up to a single latency don't count. */
2940
	if (!initial) {
2941
		unsigned long thresh = sysctl_sched_latency;
2942

2943 2944 2945 2946 2947 2948
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
2949

2950
		vruntime -= thresh;
2951 2952
	}

2953
	/* ensure we never gain time by being placed backwards. */
2954
	se->vruntime = max_vruntime(se->vruntime, vruntime);
2955 2956
}

2957 2958
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

2959
static void
2960
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2961
{
2962 2963
	/*
	 * Update the normalized vruntime before updating min_vruntime
2964
	 * through calling update_curr().
2965
	 */
2966
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
2967 2968
		se->vruntime += cfs_rq->min_vruntime;

2969
	/*
2970
	 * Update run-time statistics of the 'current'.
2971
	 */
2972
	update_curr(cfs_rq);
2973
	enqueue_entity_load_avg(cfs_rq, se);
2974 2975
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
2976

2977
	if (flags & ENQUEUE_WAKEUP) {
2978
		place_entity(cfs_rq, se, 0);
2979
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
2980
	}
2981

2982
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
2983
	check_spread(cfs_rq, se);
2984 2985
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
2986
	se->on_rq = 1;
2987

2988
	if (cfs_rq->nr_running == 1) {
2989
		list_add_leaf_cfs_rq(cfs_rq);
2990 2991
		check_enqueue_throttle(cfs_rq);
	}
2992 2993
}

2994
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
2995
{
2996 2997
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
2998
		if (cfs_rq->last != se)
2999
			break;
3000 3001

		cfs_rq->last = NULL;
3002 3003
	}
}
P
Peter Zijlstra 已提交
3004

3005 3006 3007 3008
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3009
		if (cfs_rq->next != se)
3010
			break;
3011 3012

		cfs_rq->next = NULL;
3013
	}
P
Peter Zijlstra 已提交
3014 3015
}

3016 3017 3018 3019
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
3020
		if (cfs_rq->skip != se)
3021
			break;
3022 3023

		cfs_rq->skip = NULL;
3024 3025 3026
	}
}

P
Peter Zijlstra 已提交
3027 3028
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
3029 3030 3031 3032 3033
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
3034 3035 3036

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
3037 3038
}

3039
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3040

3041
static void
3042
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
3043
{
3044 3045 3046 3047
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
3048
	dequeue_entity_load_avg(cfs_rq, se);
3049

3050
	update_stats_dequeue(cfs_rq, se);
3051
	if (flags & DEQUEUE_SLEEP) {
P
Peter Zijlstra 已提交
3052
#ifdef CONFIG_SCHEDSTATS
3053 3054 3055 3056
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
3057
				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
3058
			if (tsk->state & TASK_UNINTERRUPTIBLE)
3059
				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
3060
		}
3061
#endif
P
Peter Zijlstra 已提交
3062 3063
	}

P
Peter Zijlstra 已提交
3064
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3065

3066
	if (se != cfs_rq->curr)
3067
		__dequeue_entity(cfs_rq, se);
3068
	se->on_rq = 0;
3069
	account_entity_dequeue(cfs_rq, se);
3070 3071 3072 3073 3074 3075

	/*
	 * 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.
	 */
3076
	if (!(flags & DEQUEUE_SLEEP))
3077
		se->vruntime -= cfs_rq->min_vruntime;
3078

3079 3080 3081
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

3082
	update_min_vruntime(cfs_rq);
3083
	update_cfs_shares(cfs_rq);
3084 3085 3086 3087 3088
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
3089
static void
I
Ingo Molnar 已提交
3090
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3091
{
3092
	unsigned long ideal_runtime, delta_exec;
3093 3094
	struct sched_entity *se;
	s64 delta;
3095

P
Peter Zijlstra 已提交
3096
	ideal_runtime = sched_slice(cfs_rq, curr);
3097
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
3098
	if (delta_exec > ideal_runtime) {
3099
		resched_curr(rq_of(cfs_rq));
3100 3101 3102 3103 3104
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115
		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;

3116 3117
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
3118

3119 3120
	if (delta < 0)
		return;
3121

3122
	if (delta > ideal_runtime)
3123
		resched_curr(rq_of(cfs_rq));
3124 3125
}

3126
static void
3127
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
3128
{
3129 3130 3131 3132 3133 3134 3135 3136 3137
	/* '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);
3138
		update_load_avg(se, 1);
3139 3140
	}

3141
	update_stats_curr_start(cfs_rq, se);
3142
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
3143 3144 3145 3146 3147 3148
#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):
	 */
3149
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
3150
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
3151 3152 3153
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
3154
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
3155 3156
}

3157 3158 3159
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

3160 3161 3162 3163 3164 3165 3166
/*
 * 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
 */
3167 3168
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
3169
{
3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180
	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 */
3181

3182 3183 3184 3185 3186
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
3187 3188 3189 3190 3191 3192 3193 3194 3195 3196
		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;
		}

3197 3198 3199
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
3200

3201 3202 3203 3204 3205 3206
	/*
	 * 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;

3207 3208 3209 3210 3211 3212
	/*
	 * 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;

3213
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
3214 3215

	return se;
3216 3217
}

3218
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);
3219

3220
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
3221 3222 3223 3224 3225 3226
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
3227
		update_curr(cfs_rq);
3228

3229 3230 3231
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

P
Peter Zijlstra 已提交
3232
	check_spread(cfs_rq, prev);
3233
	if (prev->on_rq) {
3234
		update_stats_wait_start(cfs_rq, prev);
3235 3236
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
3237
		/* in !on_rq case, update occurred at dequeue */
3238
		update_load_avg(prev, 0);
3239
	}
3240
	cfs_rq->curr = NULL;
3241 3242
}

P
Peter Zijlstra 已提交
3243 3244
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
3245 3246
{
	/*
3247
	 * Update run-time statistics of the 'current'.
3248
	 */
3249
	update_curr(cfs_rq);
3250

3251 3252 3253
	/*
	 * Ensure that runnable average is periodically updated.
	 */
3254
	update_load_avg(curr, 1);
3255
	update_cfs_shares(cfs_rq);
3256

P
Peter Zijlstra 已提交
3257 3258 3259 3260 3261
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
3262
	if (queued) {
3263
		resched_curr(rq_of(cfs_rq));
3264 3265
		return;
	}
P
Peter Zijlstra 已提交
3266 3267 3268 3269 3270 3271 3272 3273
	/*
	 * 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
3274
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
3275
		check_preempt_tick(cfs_rq, curr);
3276 3277
}

3278 3279 3280 3281 3282 3283

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

#ifdef CONFIG_CFS_BANDWIDTH
3284 3285

#ifdef HAVE_JUMP_LABEL
3286
static struct static_key __cfs_bandwidth_used;
3287 3288 3289

static inline bool cfs_bandwidth_used(void)
{
3290
	return static_key_false(&__cfs_bandwidth_used);
3291 3292
}

3293
void cfs_bandwidth_usage_inc(void)
3294
{
3295 3296 3297 3298 3299 3300
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
3301 3302 3303 3304 3305 3306 3307
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

3308 3309
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
3310 3311
#endif /* HAVE_JUMP_LABEL */

3312 3313 3314 3315 3316 3317 3318 3319
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
3320 3321 3322 3323 3324 3325

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

P
Paul Turner 已提交
3326 3327 3328 3329 3330 3331 3332
/*
 * 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
 */
3333
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344
{
	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);
}

3345 3346 3347 3348 3349
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

3350 3351 3352 3353 3354 3355
/* 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;

3356
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
3357 3358
}

3359 3360
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3361 3362 3363
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
3364
	u64 amount = 0, min_amount, expires;
3365 3366 3367 3368 3369 3370 3371

	/* 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;
3372
	else {
P
Peter Zijlstra 已提交
3373
		start_cfs_bandwidth(cfs_b);
3374 3375 3376 3377 3378 3379

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
3380
	}
P
Paul Turner 已提交
3381
	expires = cfs_b->runtime_expires;
3382 3383 3384
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
3385 3386 3387 3388 3389 3390 3391
	/*
	 * 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;
3392 3393

	return cfs_rq->runtime_remaining > 0;
3394 3395
}

P
Paul Turner 已提交
3396 3397 3398 3399 3400
/*
 * 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)
3401
{
P
Paul Turner 已提交
3402 3403 3404
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
3405
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
3406 3407
		return;

P
Paul Turner 已提交
3408 3409 3410 3411 3412 3413 3414 3415 3416
	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
3417 3418 3419
	 * 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
3420 3421
	 */

3422
	if (cfs_rq->runtime_expires != cfs_b->runtime_expires) {
P
Paul Turner 已提交
3423 3424 3425 3426 3427 3428 3429 3430
		/* 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;
	}
}

3431
static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
P
Paul Turner 已提交
3432 3433
{
	/* dock delta_exec before expiring quota (as it could span periods) */
3434
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
3435 3436 3437
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
3438 3439
		return;

3440 3441 3442 3443 3444
	/*
	 * 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))
3445
		resched_curr(rq_of(cfs_rq));
3446 3447
}

3448
static __always_inline
3449
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec)
3450
{
3451
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3452 3453 3454 3455 3456
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

3457 3458
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
3459
	return cfs_bandwidth_used() && cfs_rq->throttled;
3460 3461
}

3462 3463 3464
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
3465
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493
}

/*
 * 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) {
3494
		/* adjust cfs_rq_clock_task() */
3495
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3496
					     cfs_rq->throttled_clock_task;
3497 3498 3499 3500 3501 3502 3503 3504 3505 3506 3507
	}
#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)];

3508 3509
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
3510
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
3511 3512 3513 3514 3515
	cfs_rq->throttle_count++;

	return 0;
}

3516
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3517 3518 3519 3520 3521
{
	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
3522
	bool empty;
3523 3524 3525

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

3526
	/* freeze hierarchy runnable averages while throttled */
3527 3528 3529
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546

	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)
3547
		sub_nr_running(rq, task_delta);
3548 3549

	cfs_rq->throttled = 1;
3550
	cfs_rq->throttled_clock = rq_clock(rq);
3551
	raw_spin_lock(&cfs_b->lock);
3552
	empty = list_empty(&cfs_b->throttled_cfs_rq);
P
Peter Zijlstra 已提交
3553

3554 3555 3556 3557 3558
	/*
	 * 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
3559 3560 3561 3562 3563 3564 3565 3566

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

3567 3568 3569
	raw_spin_unlock(&cfs_b->lock);
}

3570
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3571 3572 3573 3574 3575 3576 3577
{
	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;

3578
	se = cfs_rq->tg->se[cpu_of(rq)];
3579 3580

	cfs_rq->throttled = 0;
3581 3582 3583

	update_rq_clock(rq);

3584
	raw_spin_lock(&cfs_b->lock);
3585
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3586 3587 3588
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

3589 3590 3591
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609
	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)
3610
		add_nr_running(rq, task_delta);
3611 3612 3613

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
3614
		resched_curr(rq);
3615 3616 3617 3618 3619 3620
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
3621 3622
	u64 runtime;
	u64 starting_runtime = remaining;
3623 3624 3625 3626 3627 3628 3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649 3650 3651 3652

	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();

3653
	return starting_runtime - remaining;
3654 3655
}

3656 3657 3658 3659 3660 3661 3662 3663
/*
 * 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)
{
3664
	u64 runtime, runtime_expires;
3665
	int throttled;
3666 3667 3668

	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
3669
		goto out_deactivate;
3670

3671
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
3672
	cfs_b->nr_periods += overrun;
3673

3674 3675 3676 3677 3678 3679
	/*
	 * 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
3680 3681 3682

	__refill_cfs_bandwidth_runtime(cfs_b);

3683 3684 3685
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
3686
		return 0;
3687 3688
	}

3689 3690 3691
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

3692 3693 3694
	runtime_expires = cfs_b->runtime_expires;

	/*
3695 3696 3697 3698 3699
	 * 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.
3700
	 */
3701 3702
	while (throttled && cfs_b->runtime > 0) {
		runtime = cfs_b->runtime;
3703 3704 3705 3706 3707 3708 3709
		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);
3710 3711

		cfs_b->runtime -= min(runtime, cfs_b->runtime);
3712
	}
3713

3714 3715 3716 3717 3718 3719 3720
	/*
	 * 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;
3721

3722 3723 3724 3725
	return 0;

out_deactivate:
	return 1;
3726
}
3727

3728 3729 3730 3731 3732 3733 3734
/* 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;

3735 3736 3737 3738
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
3739
 * hrtimer base being cleared by hrtimer_start. In the case of
3740 3741
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754 3755 3756 3757 3758 3759 3760 3761 3762 3763 3764 3765 3766
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
3767 3768 3769
	hrtimer_start(&cfs_b->slack_timer,
			ns_to_ktime(cfs_bandwidth_slack_period),
			HRTIMER_MODE_REL);
3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798
}

/* 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)
{
3799 3800 3801
	if (!cfs_bandwidth_used())
		return;

3802
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814 3815 3816 3817
		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 */
3818 3819 3820
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
3821
		return;
3822
	}
3823

3824
	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice)
3825
		runtime = cfs_b->runtime;
3826

3827 3828 3829 3830 3831 3832 3833 3834 3835 3836
	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)
3837
		cfs_b->runtime -= min(runtime, cfs_b->runtime);
3838 3839 3840
	raw_spin_unlock(&cfs_b->lock);
}

3841 3842 3843 3844 3845 3846 3847
/*
 * 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)
{
3848 3849 3850
	if (!cfs_bandwidth_used())
		return;

3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861 3862 3863 3864 3865
	/* 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() */
3866
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
3867
{
3868
	if (!cfs_bandwidth_used())
3869
		return false;
3870

3871
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
3872
		return false;
3873 3874 3875 3876 3877 3878

	/*
	 * 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))
3879
		return true;
3880 3881

	throttle_cfs_rq(cfs_rq);
3882
	return true;
3883
}
3884 3885 3886 3887 3888

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
3889

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

3902
	raw_spin_lock(&cfs_b->lock);
3903
	for (;;) {
P
Peter Zijlstra 已提交
3904
		overrun = hrtimer_forward_now(timer, cfs_b->period);
3905 3906 3907 3908 3909
		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}
P
Peter Zijlstra 已提交
3910 3911
	if (idle)
		cfs_b->period_active = 0;
3912
	raw_spin_unlock(&cfs_b->lock);
3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924

	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
3925
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936
	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
3937
void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
3938
{
P
Peter Zijlstra 已提交
3939
	lockdep_assert_held(&cfs_b->lock);
3940

P
Peter Zijlstra 已提交
3941 3942 3943 3944 3945
	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);
	}
3946 3947 3948 3949
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
3950 3951 3952 3953
	/* init_cfs_bandwidth() was not called */
	if (!cfs_b->throttled_cfs_rq.next)
		return;

3954 3955 3956 3957
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970
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);
	}
}

3971
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982
{
	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
		 */
3983
		cfs_rq->runtime_remaining = 1;
3984 3985 3986 3987 3988 3989
		/*
		 * 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;

3990 3991 3992 3993 3994 3995
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
}

#else /* CONFIG_CFS_BANDWIDTH */
3996 3997
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
3998
	return rq_clock_task(rq_of(cfs_rq));
3999 4000
}

4001
static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {}
4002
static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; }
4003
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
4004
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
4005 4006 4007 4008 4009

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020

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;
}
4021 4022 4023 4024 4025

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) {}
4026 4027
#endif

4028 4029 4030 4031 4032
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) {}
4033
static inline void update_runtime_enabled(struct rq *rq) {}
4034
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
4035 4036 4037

#endif /* CONFIG_CFS_BANDWIDTH */

4038 4039 4040 4041
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
4042 4043 4044 4045 4046 4047 4048 4049
#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);

4050
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
4051 4052 4053 4054 4055 4056
		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)
4057
				resched_curr(rq);
P
Peter Zijlstra 已提交
4058 4059
			return;
		}
4060
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
4061 4062
	}
}
4063 4064 4065 4066 4067 4068 4069 4070 4071 4072

/*
 * 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;

4073
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
4074 4075 4076 4077 4078
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
4079
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
4080 4081 4082 4083
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
4084 4085 4086 4087

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
4088 4089
#endif

4090 4091 4092 4093 4094
/*
 * 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:
 */
4095
static void
4096
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4097 4098
{
	struct cfs_rq *cfs_rq;
4099
	struct sched_entity *se = &p->se;
4100 4101

	for_each_sched_entity(se) {
4102
		if (se->on_rq)
4103 4104
			break;
		cfs_rq = cfs_rq_of(se);
4105
		enqueue_entity(cfs_rq, se, flags);
4106 4107 4108 4109 4110 4111 4112 4113 4114

		/*
		 * 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;
4115
		cfs_rq->h_nr_running++;
4116

4117
		flags = ENQUEUE_WAKEUP;
4118
	}
P
Peter Zijlstra 已提交
4119

P
Peter Zijlstra 已提交
4120
	for_each_sched_entity(se) {
4121
		cfs_rq = cfs_rq_of(se);
4122
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
4123

4124 4125 4126
		if (cfs_rq_throttled(cfs_rq))
			break;

4127
		update_load_avg(se, 1);
4128
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4129 4130
	}

Y
Yuyang Du 已提交
4131
	if (!se)
4132
		add_nr_running(rq, 1);
Y
Yuyang Du 已提交
4133

4134
	hrtick_update(rq);
4135 4136
}

4137 4138
static void set_next_buddy(struct sched_entity *se);

4139 4140 4141 4142 4143
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
4144
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
4145 4146
{
	struct cfs_rq *cfs_rq;
4147
	struct sched_entity *se = &p->se;
4148
	int task_sleep = flags & DEQUEUE_SLEEP;
4149 4150 4151

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
4152
		dequeue_entity(cfs_rq, se, flags);
4153 4154 4155 4156 4157 4158 4159 4160 4161

		/*
		 * 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;
4162
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4163

4164
		/* Don't dequeue parent if it has other entities besides us */
4165 4166 4167 4168 4169 4170 4171
		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));
4172 4173 4174

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
4175
			break;
4176
		}
4177
		flags |= DEQUEUE_SLEEP;
4178
	}
P
Peter Zijlstra 已提交
4179

P
Peter Zijlstra 已提交
4180
	for_each_sched_entity(se) {
4181
		cfs_rq = cfs_rq_of(se);
4182
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
4183

4184 4185 4186
		if (cfs_rq_throttled(cfs_rq))
			break;

4187
		update_load_avg(se, 1);
4188
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
4189 4190
	}

Y
Yuyang Du 已提交
4191
	if (!se)
4192
		sub_nr_running(rq, 1);
Y
Yuyang Du 已提交
4193

4194
	hrtick_update(rq);
4195 4196
}

4197
#ifdef CONFIG_SMP
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 4258 4259 4260 4261 4262 4263 4264 4265 4266 4267 4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282 4283 4284 4285 4286 4287 4288 4289 4290 4291 4292 4293 4294 4295 4296 4297 4298 4299 4300 4301 4302 4303 4304 4305

/*
 * 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);
}

4306 4307 4308 4309 4310 4311
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
	return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs);
}

4312 4313 4314 4315 4316 4317 4318 4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329 4330 4331
#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)
{
4332
	unsigned long curr_jiffies = READ_ONCE(jiffies);
4333
	unsigned long load = weighted_cpuload(cpu_of(this_rq));
4334 4335 4336 4337 4338 4339 4340 4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351 4352 4353
	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();
4354
	unsigned long curr_jiffies = READ_ONCE(jiffies);
4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371 4372 4373 4374 4375 4376 4377 4378
	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)
{
4379
	unsigned long load = weighted_cpuload(cpu_of(this_rq));
4380 4381 4382 4383 4384 4385 4386
	/*
	 * 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);
}

4387 4388 4389 4390 4391 4392 4393 4394 4395 4396 4397 4398 4399 4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415 4416 4417 4418 4419
/*
 * 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);
}

4420
static unsigned long capacity_of(int cpu)
4421
{
4422
	return cpu_rq(cpu)->cpu_capacity;
4423 4424
}

4425 4426 4427 4428 4429
static unsigned long capacity_orig_of(int cpu)
{
	return cpu_rq(cpu)->cpu_capacity_orig;
}

4430 4431 4432
static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
4433
	unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running);
4434
	unsigned long load_avg = weighted_cpuload(cpu);
4435 4436

	if (nr_running)
4437
		return load_avg / nr_running;
4438 4439 4440 4441

	return 0;
}

4442 4443 4444 4445 4446 4447 4448
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.
	 */
4449
	if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) {
4450
		current->wakee_flips >>= 1;
4451 4452 4453 4454 4455 4456 4457 4458
		current->wakee_flip_decay_ts = jiffies;
	}

	if (current->last_wakee != p) {
		current->last_wakee = p;
		current->wakee_flips++;
	}
}
4459

4460
static void task_waking_fair(struct task_struct *p)
4461 4462 4463
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
4464 4465 4466 4467
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
4468

4469 4470 4471 4472 4473 4474 4475 4476
	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
4477

4478
	se->vruntime -= min_vruntime;
4479
	record_wakee(p);
4480 4481
}

4482
#ifdef CONFIG_FAIR_GROUP_SCHED
4483 4484 4485 4486 4487 4488
/*
 * 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.
4489 4490 4491 4492 4493 4494 4495 4496 4497 4498 4499 4500 4501 4502 4503 4504 4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517 4518 4519 4520 4521 4522 4523 4524 4525 4526 4527 4528 4529 4530 4531
 *
 * 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.
4532
 */
P
Peter Zijlstra 已提交
4533
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
4534
{
P
Peter Zijlstra 已提交
4535
	struct sched_entity *se = tg->se[cpu];
4536

4537
	if (!tg->parent)	/* the trivial, non-cgroup case */
4538 4539
		return wl;

P
Peter Zijlstra 已提交
4540
	for_each_sched_entity(se) {
4541
		long w, W;
P
Peter Zijlstra 已提交
4542

4543
		tg = se->my_q->tg;
4544

4545 4546 4547 4548
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
4549

4550 4551 4552
		/*
		 * w = rw_i + @wl
		 */
4553
		w = cfs_rq_load_avg(se->my_q) + wl;
4554

4555 4556 4557 4558
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
4559
			wl = (w * (long)tg->shares) / W;
4560 4561
		else
			wl = tg->shares;
4562

4563 4564 4565 4566 4567
		/*
		 * 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().
		 */
4568 4569
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
4570 4571 4572 4573

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
4574
		wl -= se->avg.load_avg;
4575 4576 4577 4578 4579 4580 4581 4582

		/*
		 * 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
4583 4584
		wg = 0;
	}
4585

P
Peter Zijlstra 已提交
4586
	return wl;
4587 4588
}
#else
P
Peter Zijlstra 已提交
4589

4590
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
P
Peter Zijlstra 已提交
4591
{
4592
	return wl;
4593
}
P
Peter Zijlstra 已提交
4594

4595 4596
#endif

M
Mike Galbraith 已提交
4597 4598 4599 4600 4601 4602 4603 4604 4605 4606 4607 4608
/*
 * 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.
 */
4609 4610
static int wake_wide(struct task_struct *p)
{
M
Mike Galbraith 已提交
4611 4612
	unsigned int master = current->wakee_flips;
	unsigned int slave = p->wakee_flips;
4613
	int factor = this_cpu_read(sd_llc_size);
4614

M
Mike Galbraith 已提交
4615 4616 4617 4618 4619
	if (master < slave)
		swap(master, slave);
	if (slave < factor || master < slave * factor)
		return 0;
	return 1;
4620 4621
}

4622
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
4623
{
4624
	s64 this_load, load;
4625
	s64 this_eff_load, prev_eff_load;
4626 4627
	int idx, this_cpu, prev_cpu;
	struct task_group *tg;
4628
	unsigned long weight;
4629
	int balanced;
4630

4631 4632 4633 4634 4635
	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);
4636

4637 4638 4639 4640 4641
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
4642 4643
	if (sync) {
		tg = task_group(current);
4644
		weight = current->se.avg.load_avg;
4645

4646
		this_load += effective_load(tg, this_cpu, -weight, -weight);
4647 4648
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
4649

4650
	tg = task_group(p);
4651
	weight = p->se.avg.load_avg;
4652

4653 4654
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4655 4656 4657
	 * 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.
4658 4659 4660 4661
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
4662 4663
	this_eff_load = 100;
	this_eff_load *= capacity_of(prev_cpu);
4664

4665 4666
	prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
	prev_eff_load *= capacity_of(this_cpu);
4667

4668
	if (this_load > 0) {
4669 4670 4671 4672
		this_eff_load *= this_load +
			effective_load(tg, this_cpu, weight, weight);

		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
4673
	}
4674

4675
	balanced = this_eff_load <= prev_eff_load;
4676

4677
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4678

4679 4680
	if (!balanced)
		return 0;
4681

4682 4683 4684 4685
	schedstat_inc(sd, ttwu_move_affine);
	schedstat_inc(p, se.statistics.nr_wakeups_affine);

	return 1;
4686 4687
}

4688 4689 4690 4691 4692
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
4693
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4694
		  int this_cpu, int sd_flag)
4695
{
4696
	struct sched_group *idlest = NULL, *group = sd->groups;
4697
	unsigned long min_load = ULONG_MAX, this_load = 0;
4698
	int load_idx = sd->forkexec_idx;
4699
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
4700

4701 4702 4703
	if (sd_flag & SD_BALANCE_WAKE)
		load_idx = sd->wake_idx;

4704 4705 4706 4707
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
4708

4709 4710
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
4711
					tsk_cpus_allowed(p)))
4712 4713 4714 4715 4716 4717 4718 4719 4720 4721 4722 4723 4724 4725 4726 4727 4728 4729
			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;
		}

4730
		/* Adjust by relative CPU capacity of the group */
4731
		avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity;
4732 4733 4734 4735 4736 4737 4738 4739 4740 4741 4742 4743 4744 4745 4746 4747 4748 4749 4750 4751 4752

		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;
4753 4754 4755 4756
	unsigned int min_exit_latency = UINT_MAX;
	u64 latest_idle_timestamp = 0;
	int least_loaded_cpu = this_cpu;
	int shallowest_idle_cpu = -1;
4757 4758 4759
	int i;

	/* Traverse only the allowed CPUs */
4760
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4761 4762 4763 4764 4765 4766 4767 4768 4769 4770 4771 4772 4773 4774 4775 4776 4777 4778 4779 4780 4781 4782
		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;
			}
4783
		} else if (shallowest_idle_cpu == -1) {
4784 4785 4786 4787 4788
			load = weighted_cpuload(i);
			if (load < min_load || (load == min_load && i == this_cpu)) {
				min_load = load;
				least_loaded_cpu = i;
			}
4789 4790 4791
		}
	}

4792
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
4793
}
4794

4795 4796 4797
/*
 * Try and locate an idle CPU in the sched_domain.
 */
4798
static int select_idle_sibling(struct task_struct *p, int target)
4799
{
4800
	struct sched_domain *sd;
4801
	struct sched_group *sg;
4802
	int i = task_cpu(p);
4803

4804 4805
	if (idle_cpu(target))
		return target;
4806 4807

	/*
4808
	 * If the prevous cpu is cache affine and idle, don't be stupid.
4809
	 */
4810 4811
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
4812 4813

	/*
4814
	 * Otherwise, iterate the domains and find an elegible idle cpu.
4815
	 */
4816
	sd = rcu_dereference(per_cpu(sd_llc, target));
4817
	for_each_lower_domain(sd) {
4818 4819 4820 4821 4822 4823 4824
		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)) {
4825
				if (i == target || !idle_cpu(i))
4826 4827
					goto next;
			}
4828

4829 4830 4831 4832 4833 4834 4835 4836
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
4837 4838
	return target;
}
4839 4840 4841 4842 4843
/*
 * 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).
4844
 * cfs.avg.util_avg is the sum of running time of runnable tasks on a
4845 4846 4847
 * 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.
4848 4849
 * Nevertheless, cfs.avg.util_avg can be higher than SCHED_LOAD_SCALE
 * because of unfortunate rounding in util_avg or just
4850 4851 4852 4853 4854 4855 4856 4857
 * 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)
{
4858
	unsigned long usage = cpu_rq(cpu)->cfs.avg.util_avg;
4859 4860 4861 4862 4863 4864 4865
	unsigned long capacity = capacity_orig_of(cpu);

	if (usage >= SCHED_LOAD_SCALE)
		return capacity;

	return (usage * capacity) >> SCHED_LOAD_SHIFT;
}
4866

4867
/*
4868 4869 4870
 * 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.
4871
 *
4872 4873
 * 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.
4874
 *
4875
 * Returns the target cpu number.
4876 4877 4878
 *
 * preempt must be disabled.
 */
4879
static int
4880
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
4881
{
4882
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
4883
	int cpu = smp_processor_id();
M
Mike Galbraith 已提交
4884
	int new_cpu = prev_cpu;
4885
	int want_affine = 0;
4886
	int sync = wake_flags & WF_SYNC;
4887

4888
	if (sd_flag & SD_BALANCE_WAKE)
M
Mike Galbraith 已提交
4889
		want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p));
4890

4891
	rcu_read_lock();
4892
	for_each_domain(cpu, tmp) {
4893
		if (!(tmp->flags & SD_LOAD_BALANCE))
M
Mike Galbraith 已提交
4894
			break;
4895

4896
		/*
4897 4898
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
4899
		 */
4900 4901 4902
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
4903
			break;
4904
		}
4905

4906
		if (tmp->flags & sd_flag)
4907
			sd = tmp;
M
Mike Galbraith 已提交
4908 4909
		else if (!want_affine)
			break;
4910 4911
	}

M
Mike Galbraith 已提交
4912 4913 4914 4915
	if (affine_sd) {
		sd = NULL; /* Prefer wake_affine over balance flags */
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
			new_cpu = cpu;
4916
	}
4917

M
Mike Galbraith 已提交
4918 4919 4920 4921 4922
	if (!sd) {
		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */
			new_cpu = select_idle_sibling(p, new_cpu);

	} else while (sd) {
4923
		struct sched_group *group;
4924
		int weight;
4925

4926
		if (!(sd->flags & sd_flag)) {
4927 4928 4929
			sd = sd->child;
			continue;
		}
4930

4931
		group = find_idlest_group(sd, p, cpu, sd_flag);
4932 4933 4934 4935
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
4936

4937
		new_cpu = find_idlest_cpu(group, p, cpu);
4938 4939 4940 4941
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
4942
		}
4943 4944 4945

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
4946
		weight = sd->span_weight;
4947 4948
		sd = NULL;
		for_each_domain(cpu, tmp) {
4949
			if (weight <= tmp->span_weight)
4950
				break;
4951
			if (tmp->flags & sd_flag)
4952 4953 4954
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
4955
	}
4956
	rcu_read_unlock();
4957

4958
	return new_cpu;
4959
}
4960 4961 4962 4963 4964 4965 4966

/*
 * 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.
 */
4967
static void migrate_task_rq_fair(struct task_struct *p, int next_cpu)
4968
{
4969
	/*
4970 4971 4972 4973 4974
	 * 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.
4975
	 */
4976 4977 4978 4979
	remove_entity_load_avg(&p->se);

	/* Tell new CPU we are migrated */
	p->se.avg.last_update_time = 0;
4980 4981

	/* We have migrated, no longer consider this task hot */
4982
	p->se.exec_start = 0;
4983
}
4984 4985 4986 4987 4988

static void task_dead_fair(struct task_struct *p)
{
	remove_entity_load_avg(&p->se);
}
4989 4990
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
4991 4992
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
4993 4994 4995 4996
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
4997 4998
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
4999 5000 5001 5002 5003 5004 5005 5006 5007
	 *
	 * 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.
5008
	 */
5009
	return calc_delta_fair(gran, se);
5010 5011
}

5012 5013 5014 5015 5016 5017 5018 5019 5020 5021 5022 5023 5024 5025 5026 5027 5028 5029 5030 5031 5032 5033
/*
 * 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
5034
	gran = wakeup_gran(curr, se);
5035 5036 5037 5038 5039 5040
	if (vdiff > gran)
		return 1;

	return 0;
}

5041 5042
static void set_last_buddy(struct sched_entity *se)
{
5043 5044 5045 5046 5047
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
5048 5049 5050 5051
}

static void set_next_buddy(struct sched_entity *se)
{
5052 5053 5054 5055 5056
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
5057 5058
}

5059 5060
static void set_skip_buddy(struct sched_entity *se)
{
5061 5062
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
5063 5064
}

5065 5066 5067
/*
 * Preempt the current task with a newly woken task if needed:
 */
5068
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
5069 5070
{
	struct task_struct *curr = rq->curr;
5071
	struct sched_entity *se = &curr->se, *pse = &p->se;
5072
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
5073
	int scale = cfs_rq->nr_running >= sched_nr_latency;
5074
	int next_buddy_marked = 0;
5075

I
Ingo Molnar 已提交
5076 5077 5078
	if (unlikely(se == pse))
		return;

5079
	/*
5080
	 * This is possible from callers such as attach_tasks(), in which we
5081 5082 5083 5084 5085 5086 5087
	 * 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;

5088
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
5089
		set_next_buddy(pse);
5090 5091
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
5092

5093 5094 5095
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
5096 5097 5098 5099 5100 5101
	 *
	 * 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.
5102 5103 5104 5105
	 */
	if (test_tsk_need_resched(curr))
		return;

5106 5107 5108 5109 5110
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

5111
	/*
5112 5113
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
5114
	 */
5115
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
5116
		return;
5117

5118
	find_matching_se(&se, &pse);
5119
	update_curr(cfs_rq_of(se));
5120
	BUG_ON(!pse);
5121 5122 5123 5124 5125 5126 5127
	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);
5128
		goto preempt;
5129
	}
5130

5131
	return;
5132

5133
preempt:
5134
	resched_curr(rq);
5135 5136 5137 5138 5139 5140 5141 5142 5143 5144 5145 5146 5147 5148
	/*
	 * 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);
5149 5150
}

5151 5152
static struct task_struct *
pick_next_task_fair(struct rq *rq, struct task_struct *prev)
5153 5154 5155
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;
5156
	struct task_struct *p;
5157
	int new_tasks;
5158

5159
again:
5160 5161
#ifdef CONFIG_FAIR_GROUP_SCHED
	if (!cfs_rq->nr_running)
5162
		goto idle;
5163

5164
	if (prev->sched_class != &fair_sched_class)
5165 5166 5167 5168 5169 5170 5171 5172 5173 5174 5175 5176 5177 5178 5179 5180 5181 5182 5183
		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.
		 */
5184 5185 5186 5187 5188
		if (curr) {
			if (curr->on_rq)
				update_curr(cfs_rq);
			else
				curr = NULL;
5189

5190 5191 5192 5193 5194 5195 5196 5197 5198
			/*
			 * 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;
		}
5199 5200 5201 5202 5203 5204 5205 5206 5207 5208 5209 5210 5211 5212 5213 5214 5215 5216 5217 5218 5219 5220 5221 5222 5223 5224 5225 5226 5227 5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238

		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
5239

5240
	if (!cfs_rq->nr_running)
5241
		goto idle;
5242

5243
	put_prev_task(rq, prev);
5244

5245
	do {
5246
		se = pick_next_entity(cfs_rq, NULL);
5247
		set_next_entity(cfs_rq, se);
5248 5249 5250
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
5251
	p = task_of(se);
5252

5253 5254
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
5255 5256

	return p;
5257 5258

idle:
5259 5260 5261 5262 5263 5264 5265
	/*
	 * 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);
5266
	new_tasks = idle_balance(rq);
5267
	lockdep_pin_lock(&rq->lock);
5268 5269 5270 5271 5272
	/*
	 * 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.
	 */
5273
	if (new_tasks < 0)
5274 5275
		return RETRY_TASK;

5276
	if (new_tasks > 0)
5277 5278 5279
		goto again;

	return NULL;
5280 5281 5282 5283 5284
}

/*
 * Account for a descheduled task:
 */
5285
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
5286 5287 5288 5289 5290 5291
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
5292
		put_prev_entity(cfs_rq, se);
5293 5294 5295
	}
}

5296 5297 5298 5299 5300 5301 5302 5303 5304 5305 5306 5307 5308 5309 5310 5311 5312 5313 5314 5315 5316 5317 5318 5319 5320
/*
 * 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);
5321 5322 5323 5324 5325
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
5326
		rq_clock_skip_update(rq, true);
5327 5328 5329 5330 5331
	}

	set_skip_buddy(se);
}

5332 5333 5334 5335
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

5336 5337
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
5338 5339 5340 5341 5342 5343 5344 5345 5346 5347
		return false;

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

	yield_task_fair(rq);

	return true;
}

5348
#ifdef CONFIG_SMP
5349
/**************************************************
P
Peter Zijlstra 已提交
5350 5351 5352 5353 5354 5355 5356 5357 5358 5359 5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372
 * 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)
 *
5373
 * C_i is the compute capacity of cpu i, typically it is the
P
Peter Zijlstra 已提交
5374 5375 5376 5377 5378 5379
 * 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):
 *
5380
 *   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
5381 5382 5383 5384 5385 5386 5387 5388 5389 5390 5391 5392 5393 5394 5395 5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418 5419 5420 5421 5422 5423 5424 5425 5426 5427 5428 5429 5430 5431 5432 5433 5434 5435 5436 5437 5438 5439 5440 5441 5442 5443 5444 5445 5446 5447 5448 5449 5450 5451 5452 5453 5454 5455 5456 5457 5458 5459 5460 5461 5462 5463 5464 5465
 *
 * 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.]
 */ 
5466

5467 5468
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

5469 5470
enum fbq_type { regular, remote, all };

5471
#define LBF_ALL_PINNED	0x01
5472
#define LBF_NEED_BREAK	0x02
5473 5474
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
5475 5476 5477 5478 5479

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
5480
	int			src_cpu;
5481 5482 5483 5484

	int			dst_cpu;
	struct rq		*dst_rq;

5485 5486
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
5487
	enum cpu_idle_type	idle;
5488
	long			imbalance;
5489 5490 5491
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

5492
	unsigned int		flags;
5493 5494 5495 5496

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
5497 5498

	enum fbq_type		fbq_type;
5499
	struct list_head	tasks;
5500 5501
};

5502 5503 5504
/*
 * Is this task likely cache-hot:
 */
5505
static int task_hot(struct task_struct *p, struct lb_env *env)
5506 5507 5508
{
	s64 delta;

5509 5510
	lockdep_assert_held(&env->src_rq->lock);

5511 5512 5513 5514 5515 5516 5517 5518 5519
	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
5520
	if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running &&
5521 5522 5523 5524 5525 5526 5527 5528 5529
			(&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;

5530
	delta = rq_clock_task(env->src_rq) - p->se.exec_start;
5531 5532 5533 5534

	return delta < (s64)sysctl_sched_migration_cost;
}

5535
#ifdef CONFIG_NUMA_BALANCING
5536
/*
5537 5538 5539
 * 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.
5540
 */
5541
static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
5542
{
5543
	struct numa_group *numa_group = rcu_dereference(p->numa_group);
5544
	unsigned long src_faults, dst_faults;
5545 5546
	int src_nid, dst_nid;

5547
	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
5548 5549 5550 5551
		return -1;

	if (!sched_feat(NUMA))
		return -1;
5552 5553 5554 5555

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

5556
	if (src_nid == dst_nid)
5557
		return -1;
5558

5559 5560 5561 5562 5563 5564 5565
	/* 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;
	}
5566

5567 5568
	/* Encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
5569
		return 0;
5570

5571 5572 5573 5574 5575 5576
	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);
5577 5578
	}

5579
	return dst_faults < src_faults;
5580 5581
}

5582
#else
5583
static inline int migrate_degrades_locality(struct task_struct *p,
5584 5585
					     struct lb_env *env)
{
5586
	return -1;
5587
}
5588 5589
#endif

5590 5591 5592 5593
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
5594
int can_migrate_task(struct task_struct *p, struct lb_env *env)
5595
{
5596
	int tsk_cache_hot;
5597 5598 5599

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

5600 5601
	/*
	 * We do not migrate tasks that are:
5602
	 * 1) throttled_lb_pair, or
5603
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
5604 5605
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
5606
	 */
5607 5608 5609
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

5610
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
5611
		int cpu;
5612

5613
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
5614

5615 5616
		env->flags |= LBF_SOME_PINNED;

5617 5618 5619 5620 5621 5622 5623 5624
		/*
		 * 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.
		 */
5625
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
5626 5627
			return 0;

5628 5629 5630
		/* 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))) {
5631
				env->flags |= LBF_DST_PINNED;
5632 5633 5634
				env->new_dst_cpu = cpu;
				break;
			}
5635
		}
5636

5637 5638
		return 0;
	}
5639 5640

	/* Record that we found atleast one task that could run on dst_cpu */
5641
	env->flags &= ~LBF_ALL_PINNED;
5642

5643
	if (task_running(env->src_rq, p)) {
5644
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
5645 5646 5647 5648 5649
		return 0;
	}

	/*
	 * Aggressive migration if:
5650 5651 5652
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
5653
	 */
5654 5655 5656
	tsk_cache_hot = migrate_degrades_locality(p, env);
	if (tsk_cache_hot == -1)
		tsk_cache_hot = task_hot(p, env);
5657

5658
	if (tsk_cache_hot <= 0 ||
5659
	    env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
5660
		if (tsk_cache_hot == 1) {
5661 5662 5663
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
			schedstat_inc(p, se.statistics.nr_forced_migrations);
		}
5664 5665 5666
		return 1;
	}

Z
Zhang Hang 已提交
5667 5668
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
5669 5670
}

5671
/*
5672 5673 5674 5675 5676 5677 5678 5679 5680 5681 5682
 * 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);
}

5683
/*
5684
 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as
5685 5686
 * part of active balancing operations within "domain".
 *
5687
 * Returns a task if successful and NULL otherwise.
5688
 */
5689
static struct task_struct *detach_one_task(struct lb_env *env)
5690 5691 5692
{
	struct task_struct *p, *n;

5693 5694
	lockdep_assert_held(&env->src_rq->lock);

5695 5696 5697
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
5698

5699
		detach_task(p, env);
5700

5701
		/*
5702
		 * Right now, this is only the second place where
5703
		 * lb_gained[env->idle] is updated (other is detach_tasks)
5704
		 * so we can safely collect stats here rather than
5705
		 * inside detach_tasks().
5706 5707
		 */
		schedstat_inc(env->sd, lb_gained[env->idle]);
5708
		return p;
5709
	}
5710
	return NULL;
5711 5712
}

5713 5714
static const unsigned int sched_nr_migrate_break = 32;

5715
/*
5716 5717
 * detach_tasks() -- tries to detach up to imbalance weighted load from
 * busiest_rq, as part of a balancing operation within domain "sd".
5718
 *
5719
 * Returns number of detached tasks if successful and 0 otherwise.
5720
 */
5721
static int detach_tasks(struct lb_env *env)
5722
{
5723 5724
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
5725
	unsigned long load;
5726 5727 5728
	int detached = 0;

	lockdep_assert_held(&env->src_rq->lock);
5729

5730
	if (env->imbalance <= 0)
5731
		return 0;
5732

5733
	while (!list_empty(tasks)) {
5734 5735 5736 5737 5738 5739 5740
		/*
		 * 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;

5741
		p = list_first_entry(tasks, struct task_struct, se.group_node);
5742

5743 5744
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
5745
		if (env->loop > env->loop_max)
5746
			break;
5747 5748

		/* take a breather every nr_migrate tasks */
5749
		if (env->loop > env->loop_break) {
5750
			env->loop_break += sched_nr_migrate_break;
5751
			env->flags |= LBF_NEED_BREAK;
5752
			break;
5753
		}
5754

5755
		if (!can_migrate_task(p, env))
5756 5757 5758
			goto next;

		load = task_h_load(p);
5759

5760
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5761 5762
			goto next;

5763
		if ((load / 2) > env->imbalance)
5764
			goto next;
5765

5766 5767 5768 5769
		detach_task(p, env);
		list_add(&p->se.group_node, &env->tasks);

		detached++;
5770
		env->imbalance -= load;
5771 5772

#ifdef CONFIG_PREEMPT
5773 5774
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
5775
		 * kernels will stop after the first task is detached to minimize
5776 5777
		 * the critical section.
		 */
5778
		if (env->idle == CPU_NEWLY_IDLE)
5779
			break;
5780 5781
#endif

5782 5783 5784 5785
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
5786
		if (env->imbalance <= 0)
5787
			break;
5788 5789 5790

		continue;
next:
5791
		list_move_tail(&p->se.group_node, tasks);
5792
	}
5793

5794
	/*
5795 5796 5797
	 * 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().
5798
	 */
5799
	schedstat_add(env->sd, lb_gained[env->idle], detached);
5800

5801 5802 5803 5804 5805 5806 5807 5808 5809 5810 5811 5812 5813 5814 5815 5816 5817 5818 5819 5820 5821 5822 5823 5824 5825 5826 5827 5828 5829 5830 5831 5832 5833 5834 5835 5836 5837 5838 5839 5840 5841
	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);
5842

5843 5844 5845 5846
		attach_task(env->dst_rq, p);
	}

	raw_spin_unlock(&env->dst_rq->lock);
5847 5848
}

P
Peter Zijlstra 已提交
5849
#ifdef CONFIG_FAIR_GROUP_SCHED
5850
static void update_blocked_averages(int cpu)
5851 5852
{
	struct rq *rq = cpu_rq(cpu);
5853 5854
	struct cfs_rq *cfs_rq;
	unsigned long flags;
5855

5856 5857
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
5858

5859 5860 5861 5862
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
5863
	for_each_leaf_cfs_rq(rq, cfs_rq) {
5864 5865 5866
		/* throttled entities do not contribute to load */
		if (throttled_hierarchy(cfs_rq))
			continue;
5867

5868 5869 5870
		if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq))
			update_tg_load_avg(cfs_rq, 0);
	}
5871
	raw_spin_unlock_irqrestore(&rq->lock, flags);
5872 5873
}

5874
/*
5875
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5876 5877 5878
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
5879
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
5880
{
5881 5882
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
5883
	unsigned long now = jiffies;
5884
	unsigned long load;
5885

5886
	if (cfs_rq->last_h_load_update == now)
5887 5888
		return;

5889 5890 5891 5892 5893 5894 5895
	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;
	}
5896

5897
	if (!se) {
5898
		cfs_rq->h_load = cfs_rq_load_avg(cfs_rq);
5899 5900 5901 5902 5903
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
5904 5905
		load = div64_ul(load * se->avg.load_avg,
			cfs_rq_load_avg(cfs_rq) + 1);
5906 5907 5908 5909
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
5910 5911
}

5912
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
5913
{
5914
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
5915

5916
	update_cfs_rq_h_load(cfs_rq);
5917
	return div64_ul(p->se.avg.load_avg * cfs_rq->h_load,
5918
			cfs_rq_load_avg(cfs_rq) + 1);
P
Peter Zijlstra 已提交
5919 5920
}
#else
5921
static inline void update_blocked_averages(int cpu)
5922
{
5923 5924 5925 5926 5927 5928 5929 5930
	struct rq *rq = cpu_rq(cpu);
	struct cfs_rq *cfs_rq = &rq->cfs;
	unsigned long flags;

	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
	update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
	raw_spin_unlock_irqrestore(&rq->lock, flags);
5931 5932
}

5933
static unsigned long task_h_load(struct task_struct *p)
5934
{
5935
	return p->se.avg.load_avg;
5936
}
P
Peter Zijlstra 已提交
5937
#endif
5938 5939

/********** Helpers for find_busiest_group ************************/
5940 5941 5942 5943 5944 5945 5946

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

5947 5948 5949 5950 5951 5952 5953
/*
 * 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
5954
	unsigned long load_per_task;
5955
	unsigned long group_capacity;
5956
	unsigned long group_usage; /* Total usage of the group */
5957 5958 5959
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int idle_cpus;
	unsigned int group_weight;
5960
	enum group_type group_type;
5961
	int group_no_capacity;
5962 5963 5964 5965
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
5966 5967
};

J
Joonsoo Kim 已提交
5968 5969 5970 5971 5972 5973 5974 5975
/*
 * 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 */
5976
	unsigned long total_capacity;	/* Total capacity of all groups in sd */
J
Joonsoo Kim 已提交
5977 5978 5979
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
5980
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
5981 5982
};

5983 5984 5985 5986 5987 5988 5989 5990 5991 5992 5993 5994
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,
5995
		.total_capacity = 0UL,
5996 5997
		.busiest_stat = {
			.avg_load = 0UL,
5998 5999
			.sum_nr_running = 0,
			.group_type = group_other,
6000 6001 6002 6003
		},
	};
}

6004 6005 6006
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
6007
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
6008 6009
 *
 * Return: The load index.
6010 6011 6012 6013 6014 6015 6016 6017 6018 6019 6020 6021 6022 6023 6024 6025 6026 6027 6028 6029 6030 6031
 */
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;
}

6032
static unsigned long default_scale_cpu_capacity(struct sched_domain *sd, int cpu)
6033
{
6034 6035
	if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1))
		return sd->smt_gain / sd->span_weight;
6036

6037
	return SCHED_CAPACITY_SCALE;
6038 6039
}

6040
unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
6041
{
6042
	return default_scale_cpu_capacity(sd, cpu);
6043 6044
}

6045
static unsigned long scale_rt_capacity(int cpu)
6046 6047
{
	struct rq *rq = cpu_rq(cpu);
6048
	u64 total, used, age_stamp, avg;
6049
	s64 delta;
6050

6051 6052 6053 6054
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
6055 6056
	age_stamp = READ_ONCE(rq->age_stamp);
	avg = READ_ONCE(rq->rt_avg);
6057
	delta = __rq_clock_broken(rq) - age_stamp;
6058

6059 6060 6061 6062
	if (unlikely(delta < 0))
		delta = 0;

	total = sched_avg_period() + delta;
6063

6064
	used = div_u64(avg, total);
6065

6066 6067
	if (likely(used < SCHED_CAPACITY_SCALE))
		return SCHED_CAPACITY_SCALE - used;
6068

6069
	return 1;
6070 6071
}

6072
static void update_cpu_capacity(struct sched_domain *sd, int cpu)
6073
{
6074
	unsigned long capacity = SCHED_CAPACITY_SCALE;
6075 6076
	struct sched_group *sdg = sd->groups;

6077 6078 6079 6080
	if (sched_feat(ARCH_CAPACITY))
		capacity *= arch_scale_cpu_capacity(sd, cpu);
	else
		capacity *= default_scale_cpu_capacity(sd, cpu);
6081

6082
	capacity >>= SCHED_CAPACITY_SHIFT;
6083

6084
	cpu_rq(cpu)->cpu_capacity_orig = capacity;
6085

6086
	capacity *= scale_rt_capacity(cpu);
6087
	capacity >>= SCHED_CAPACITY_SHIFT;
6088

6089 6090
	if (!capacity)
		capacity = 1;
6091

6092 6093
	cpu_rq(cpu)->cpu_capacity = capacity;
	sdg->sgc->capacity = capacity;
6094 6095
}

6096
void update_group_capacity(struct sched_domain *sd, int cpu)
6097 6098 6099
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
6100
	unsigned long capacity;
6101 6102 6103 6104
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
6105
	sdg->sgc->next_update = jiffies + interval;
6106 6107

	if (!child) {
6108
		update_cpu_capacity(sd, cpu);
6109 6110 6111
		return;
	}

6112
	capacity = 0;
6113

P
Peter Zijlstra 已提交
6114 6115 6116 6117 6118 6119
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

6120
		for_each_cpu(cpu, sched_group_cpus(sdg)) {
6121
			struct sched_group_capacity *sgc;
6122
			struct rq *rq = cpu_rq(cpu);
6123

6124
			/*
6125
			 * build_sched_domains() -> init_sched_groups_capacity()
6126 6127 6128
			 * gets here before we've attached the domains to the
			 * runqueues.
			 *
6129 6130
			 * Use capacity_of(), which is set irrespective of domains
			 * in update_cpu_capacity().
6131
			 *
6132
			 * This avoids capacity from being 0 and
6133 6134 6135
			 * causing divide-by-zero issues on boot.
			 */
			if (unlikely(!rq->sd)) {
6136
				capacity += capacity_of(cpu);
6137 6138
				continue;
			}
6139

6140 6141
			sgc = rq->sd->groups->sgc;
			capacity += sgc->capacity;
6142
		}
P
Peter Zijlstra 已提交
6143 6144 6145 6146 6147 6148 6149 6150
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
6151
			capacity += group->sgc->capacity;
P
Peter Zijlstra 已提交
6152 6153 6154
			group = group->next;
		} while (group != child->groups);
	}
6155

6156
	sdg->sgc->capacity = capacity;
6157 6158
}

6159
/*
6160 6161 6162
 * 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
6163 6164
 */
static inline int
6165
check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
6166
{
6167 6168
	return ((rq->cpu_capacity * sd->imbalance_pct) <
				(rq->cpu_capacity_orig * 100));
6169 6170
}

6171 6172 6173 6174 6175 6176 6177 6178 6179 6180 6181 6182 6183 6184 6185 6186
/*
 * 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
6187 6188
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
6189 6190
 *
 * When this is so detected; this group becomes a candidate for busiest; see
6191
 * update_sd_pick_busiest(). And calculate_imbalance() and
6192
 * find_busiest_group() avoid some of the usual balance conditions to allow it
6193 6194 6195 6196 6197 6198 6199
 * 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.
 */

6200
static inline int sg_imbalanced(struct sched_group *group)
6201
{
6202
	return group->sgc->imbalance;
6203 6204
}

6205
/*
6206 6207 6208 6209 6210 6211 6212 6213 6214 6215
 * 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.
6216
 */
6217 6218
static inline bool
group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
6219
{
6220 6221
	if (sgs->sum_nr_running < sgs->group_weight)
		return true;
6222

6223 6224 6225
	if ((sgs->group_capacity * 100) >
			(sgs->group_usage * env->sd->imbalance_pct))
		return true;
6226

6227 6228 6229 6230 6231 6232 6233 6234 6235 6236 6237 6238 6239 6240 6241 6242
	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;
6243

6244 6245 6246
	if ((sgs->group_capacity * 100) <
			(sgs->group_usage * env->sd->imbalance_pct))
		return true;
6247

6248
	return false;
6249 6250
}

6251 6252 6253
static enum group_type group_classify(struct lb_env *env,
		struct sched_group *group,
		struct sg_lb_stats *sgs)
6254
{
6255
	if (sgs->group_no_capacity)
6256 6257 6258 6259 6260 6261 6262 6263
		return group_overloaded;

	if (sg_imbalanced(group))
		return group_imbalanced;

	return group_other;
}

6264 6265
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
6266
 * @env: The load balancing environment.
6267 6268 6269 6270
 * @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.
6271
 * @overload: Indicate more than one runnable task for any CPU.
6272
 */
6273 6274
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
6275 6276
			int local_group, struct sg_lb_stats *sgs,
			bool *overload)
6277
{
6278
	unsigned long load;
6279
	int i;
6280

6281 6282
	memset(sgs, 0, sizeof(*sgs));

6283
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6284 6285 6286
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
6287
		if (local_group)
6288
			load = target_load(i, load_idx);
6289
		else
6290 6291 6292
			load = source_load(i, load_idx);

		sgs->group_load += load;
6293
		sgs->group_usage += get_cpu_usage(i);
6294
		sgs->sum_nr_running += rq->cfs.h_nr_running;
6295 6296 6297 6298

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

6299 6300 6301 6302
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
6303
		sgs->sum_weighted_load += weighted_cpuload(i);
6304 6305
		if (idle_cpu(i))
			sgs->idle_cpus++;
6306 6307
	}

6308 6309
	/* Adjust by relative CPU capacity of the group */
	sgs->group_capacity = group->sgc->capacity;
6310
	sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
6311

6312
	if (sgs->sum_nr_running)
6313
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
6314

6315
	sgs->group_weight = group->group_weight;
6316

6317 6318
	sgs->group_no_capacity = group_is_overloaded(env, sgs);
	sgs->group_type = group_classify(env, group, sgs);
6319 6320
}

6321 6322
/**
 * update_sd_pick_busiest - return 1 on busiest group
6323
 * @env: The load balancing environment.
6324 6325
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
6326
 * @sgs: sched_group statistics
6327 6328 6329
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
6330 6331 6332
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
6333
 */
6334
static bool update_sd_pick_busiest(struct lb_env *env,
6335 6336
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
6337
				   struct sg_lb_stats *sgs)
6338
{
6339
	struct sg_lb_stats *busiest = &sds->busiest_stat;
6340

6341
	if (sgs->group_type > busiest->group_type)
6342 6343
		return true;

6344 6345 6346 6347 6348 6349 6350 6351
	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))
6352 6353 6354 6355 6356 6357 6358
		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.
	 */
6359
	if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) {
6360 6361 6362 6363 6364 6365 6366 6367 6368 6369
		if (!sds->busiest)
			return true;

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

	return false;
}

6370 6371 6372 6373 6374 6375 6376 6377 6378 6379 6380 6381 6382 6383 6384 6385 6386 6387 6388 6389 6390 6391 6392 6393 6394 6395 6396 6397 6398 6399
#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 */

6400
/**
6401
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
6402
 * @env: The load balancing environment.
6403 6404
 * @sds: variable to hold the statistics for this sched_domain.
 */
6405
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
6406
{
6407 6408
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
6409
	struct sg_lb_stats tmp_sgs;
6410
	int load_idx, prefer_sibling = 0;
6411
	bool overload = false;
6412 6413 6414 6415

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

6416
	load_idx = get_sd_load_idx(env->sd, env->idle);
6417 6418

	do {
J
Joonsoo Kim 已提交
6419
		struct sg_lb_stats *sgs = &tmp_sgs;
6420 6421
		int local_group;

6422
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
6423 6424 6425
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
6426 6427

			if (env->idle != CPU_NEWLY_IDLE ||
6428 6429
			    time_after_eq(jiffies, sg->sgc->next_update))
				update_group_capacity(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
6430
		}
6431

6432 6433
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
						&overload);
6434

6435 6436 6437
		if (local_group)
			goto next_group;

6438 6439
		/*
		 * In case the child domain prefers tasks go to siblings
6440
		 * first, lower the sg capacity so that we'll try
6441 6442
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
6443 6444 6445 6446
		 * 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).
6447
		 */
6448
		if (prefer_sibling && sds->local &&
6449 6450 6451 6452
		    group_has_capacity(env, &sds->local_stat) &&
		    (sgs->sum_nr_running > 1)) {
			sgs->group_no_capacity = 1;
			sgs->group_type = group_overloaded;
6453
		}
6454

6455
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
6456
			sds->busiest = sg;
J
Joonsoo Kim 已提交
6457
			sds->busiest_stat = *sgs;
6458 6459
		}

6460 6461 6462
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
6463
		sds->total_capacity += sgs->group_capacity;
6464

6465
		sg = sg->next;
6466
	} while (sg != env->sd->groups);
6467 6468 6469

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
6470 6471 6472 6473 6474 6475 6476

	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;
	}

6477 6478 6479 6480 6481 6482 6483 6484 6485 6486 6487 6488 6489 6490 6491 6492 6493 6494 6495
}

/**
 * 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.
 *
6496
 * Return: 1 when packing is required and a task should be moved to
6497 6498
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
6499
 * @env: The load balancing environment.
6500 6501
 * @sds: Statistics of the sched_domain which is to be packed
 */
6502
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
6503 6504 6505
{
	int busiest_cpu;

6506
	if (!(env->sd->flags & SD_ASYM_PACKING))
6507 6508 6509 6510 6511 6512
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
6513
	if (env->dst_cpu > busiest_cpu)
6514 6515
		return 0;

6516
	env->imbalance = DIV_ROUND_CLOSEST(
6517
		sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity,
6518
		SCHED_CAPACITY_SCALE);
6519

6520
	return 1;
6521 6522 6523 6524 6525 6526
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
6527
 * @env: The load balancing environment.
6528 6529
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
6530 6531
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6532
{
6533
	unsigned long tmp, capa_now = 0, capa_move = 0;
6534
	unsigned int imbn = 2;
6535
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
6536
	struct sg_lb_stats *local, *busiest;
6537

J
Joonsoo Kim 已提交
6538 6539
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6540

J
Joonsoo Kim 已提交
6541 6542 6543 6544
	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;
6545

J
Joonsoo Kim 已提交
6546
	scaled_busy_load_per_task =
6547
		(busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6548
		busiest->group_capacity;
J
Joonsoo Kim 已提交
6549

6550 6551
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
6552
		env->imbalance = busiest->load_per_task;
6553 6554 6555 6556 6557
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
6558
	 * however we may be able to increase total CPU capacity used by
6559 6560 6561
	 * moving them.
	 */

6562
	capa_now += busiest->group_capacity *
J
Joonsoo Kim 已提交
6563
			min(busiest->load_per_task, busiest->avg_load);
6564
	capa_now += local->group_capacity *
J
Joonsoo Kim 已提交
6565
			min(local->load_per_task, local->avg_load);
6566
	capa_now /= SCHED_CAPACITY_SCALE;
6567 6568

	/* Amount of load we'd subtract */
6569
	if (busiest->avg_load > scaled_busy_load_per_task) {
6570
		capa_move += busiest->group_capacity *
J
Joonsoo Kim 已提交
6571
			    min(busiest->load_per_task,
6572
				busiest->avg_load - scaled_busy_load_per_task);
J
Joonsoo Kim 已提交
6573
	}
6574 6575

	/* Amount of load we'd add */
6576
	if (busiest->avg_load * busiest->group_capacity <
6577
	    busiest->load_per_task * SCHED_CAPACITY_SCALE) {
6578 6579
		tmp = (busiest->avg_load * busiest->group_capacity) /
		      local->group_capacity;
J
Joonsoo Kim 已提交
6580
	} else {
6581
		tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) /
6582
		      local->group_capacity;
J
Joonsoo Kim 已提交
6583
	}
6584
	capa_move += local->group_capacity *
6585
		    min(local->load_per_task, local->avg_load + tmp);
6586
	capa_move /= SCHED_CAPACITY_SCALE;
6587 6588

	/* Move if we gain throughput */
6589
	if (capa_move > capa_now)
J
Joonsoo Kim 已提交
6590
		env->imbalance = busiest->load_per_task;
6591 6592 6593 6594 6595
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
6596
 * @env: load balance environment
6597 6598
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
6599
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
6600
{
6601
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
6602 6603 6604 6605
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
6606

6607
	if (busiest->group_type == group_imbalanced) {
6608 6609 6610 6611
		/*
		 * 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
6612 6613
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
6614 6615
	}

6616 6617 6618
	/*
	 * 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
6619
	 * its cpu_capacity, while calculating max_load..)
6620
	 */
6621 6622
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
6623 6624
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
6625 6626
	}

6627 6628 6629 6630 6631
	/*
	 * If there aren't any idle cpus, avoid creating some.
	 */
	if (busiest->group_type == group_overloaded &&
	    local->group_type   == group_overloaded) {
6632 6633 6634 6635 6636 6637
		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;
6638 6639 6640 6641 6642 6643 6644 6645 6646 6647
	}

	/*
	 * 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.
	 */
6648
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
6649 6650

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
6651
	env->imbalance = min(
6652 6653
		max_pull * busiest->group_capacity,
		(sds->avg_load - local->avg_load) * local->group_capacity
6654
	) / SCHED_CAPACITY_SCALE;
6655 6656 6657

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
6658
	 * there is no guarantee that any tasks will be moved so we'll have
6659 6660 6661
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
6662
	if (env->imbalance < busiest->load_per_task)
6663
		return fix_small_imbalance(env, sds);
6664
}
6665

6666 6667 6668 6669 6670 6671 6672 6673 6674 6675 6676 6677
/******* 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.
 *
6678
 * @env: The load balancing environment.
6679
 *
6680
 * Return:	- The busiest group if imbalance exists.
6681 6682 6683 6684
 *		- 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
6685
static struct sched_group *find_busiest_group(struct lb_env *env)
6686
{
J
Joonsoo Kim 已提交
6687
	struct sg_lb_stats *local, *busiest;
6688 6689
	struct sd_lb_stats sds;

6690
	init_sd_lb_stats(&sds);
6691 6692 6693 6694 6695

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
6696
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
6697 6698
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
6699

6700
	/* ASYM feature bypasses nice load balance check */
6701 6702
	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(env, &sds))
6703 6704
		return sds.busiest;

6705
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
6706
	if (!sds.busiest || busiest->sum_nr_running == 0)
6707 6708
		goto out_balanced;

6709 6710
	sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load)
						/ sds.total_capacity;
6711

P
Peter Zijlstra 已提交
6712 6713
	/*
	 * If the busiest group is imbalanced the below checks don't
6714
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
6715 6716
	 * isn't true due to cpus_allowed constraints and the like.
	 */
6717
	if (busiest->group_type == group_imbalanced)
P
Peter Zijlstra 已提交
6718 6719
		goto force_balance;

6720
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
6721 6722
	if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
	    busiest->group_no_capacity)
6723 6724
		goto force_balance;

6725
	/*
6726
	 * If the local group is busier than the selected busiest group
6727 6728
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
6729
	if (local->avg_load >= busiest->avg_load)
6730 6731
		goto out_balanced;

6732 6733 6734 6735
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
6736
	if (local->avg_load >= sds.avg_load)
6737 6738
		goto out_balanced;

6739
	if (env->idle == CPU_IDLE) {
6740
		/*
6741 6742 6743 6744 6745
		 * 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
6746
		 */
6747 6748
		if ((busiest->group_type != group_overloaded) &&
				(local->idle_cpus <= (busiest->idle_cpus + 1)))
6749
			goto out_balanced;
6750 6751 6752 6753 6754
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
6755 6756
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
6757
			goto out_balanced;
6758
	}
6759

6760
force_balance:
6761
	/* Looks like there is an imbalance. Compute it */
6762
	calculate_imbalance(env, &sds);
6763 6764 6765
	return sds.busiest;

out_balanced:
6766
	env->imbalance = 0;
6767 6768 6769 6770 6771 6772
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
6773
static struct rq *find_busiest_queue(struct lb_env *env,
6774
				     struct sched_group *group)
6775 6776
{
	struct rq *busiest = NULL, *rq;
6777
	unsigned long busiest_load = 0, busiest_capacity = 1;
6778 6779
	int i;

6780
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
6781
		unsigned long capacity, wl;
6782 6783 6784 6785
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
6786

6787 6788 6789 6790 6791 6792 6793 6794 6795 6796 6797 6798 6799 6800 6801 6802 6803 6804 6805 6806 6807 6808
		/*
		 * 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;

6809
		capacity = capacity_of(i);
6810

6811
		wl = weighted_cpuload(i);
6812

6813 6814
		/*
		 * When comparing with imbalance, use weighted_cpuload()
6815
		 * which is not scaled with the cpu capacity.
6816
		 */
6817 6818 6819

		if (rq->nr_running == 1 && wl > env->imbalance &&
		    !check_cpu_capacity(rq, env->sd))
6820 6821
			continue;

6822 6823
		/*
		 * For the load comparisons with the other cpu's, consider
6824 6825 6826
		 * 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.
6827
		 *
6828
		 * Thus we're looking for max(wl_i / capacity_i), crosswise
6829
		 * multiplication to rid ourselves of the division works out
6830 6831
		 * to: wl_i * capacity_j > wl_j * capacity_i;  where j is
		 * our previous maximum.
6832
		 */
6833
		if (wl * busiest_capacity > busiest_load * capacity) {
6834
			busiest_load = wl;
6835
			busiest_capacity = capacity;
6836 6837 6838 6839 6840 6841 6842 6843 6844 6845 6846 6847 6848 6849
			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. */
6850
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6851

6852
static int need_active_balance(struct lb_env *env)
6853
{
6854 6855 6856
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
6857 6858 6859 6860 6861 6862

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
6863
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6864
			return 1;
6865 6866
	}

6867 6868 6869 6870 6871 6872 6873 6874 6875 6876 6877 6878 6879
	/*
	 * 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;
	}

6880 6881 6882
	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

6883 6884
static int active_load_balance_cpu_stop(void *data);

6885 6886 6887 6888 6889 6890 6891 6892 6893 6894 6895 6896 6897 6898 6899 6900 6901 6902 6903 6904 6905 6906 6907 6908 6909 6910 6911 6912 6913 6914 6915
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.
	 */
6916
	return balance_cpu == env->dst_cpu;
6917 6918
}

6919 6920 6921 6922 6923 6924
/*
 * 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,
6925
			int *continue_balancing)
6926
{
6927
	int ld_moved, cur_ld_moved, active_balance = 0;
6928
	struct sched_domain *sd_parent = sd->parent;
6929 6930 6931
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
6932
	struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
6933

6934 6935
	struct lb_env env = {
		.sd		= sd,
6936 6937
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
6938
		.dst_grpmask    = sched_group_cpus(sd->groups),
6939
		.idle		= idle,
6940
		.loop_break	= sched_nr_migrate_break,
6941
		.cpus		= cpus,
6942
		.fbq_type	= all,
6943
		.tasks		= LIST_HEAD_INIT(env.tasks),
6944 6945
	};

6946 6947 6948 6949
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
6950
	if (idle == CPU_NEWLY_IDLE)
6951 6952
		env.dst_grpmask = NULL;

6953 6954 6955 6956 6957
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
6958 6959
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
6960
		goto out_balanced;
6961
	}
6962

6963
	group = find_busiest_group(&env);
6964 6965 6966 6967 6968
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

6969
	busiest = find_busiest_queue(&env, group);
6970 6971 6972 6973 6974
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

6975
	BUG_ON(busiest == env.dst_rq);
6976

6977
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
6978

6979 6980 6981
	env.src_cpu = busiest->cpu;
	env.src_rq = busiest;

6982 6983 6984 6985 6986 6987 6988 6989
	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.
		 */
6990
		env.flags |= LBF_ALL_PINNED;
6991
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
6992

6993
more_balance:
6994
		raw_spin_lock_irqsave(&busiest->lock, flags);
6995 6996 6997 6998 6999

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
7000
		cur_ld_moved = detach_tasks(&env);
7001 7002

		/*
7003 7004 7005 7006 7007
		 * 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.
7008
		 */
7009 7010 7011 7012 7013 7014 7015 7016

		raw_spin_unlock(&busiest->lock);

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

7017
		local_irq_restore(flags);
7018

7019 7020 7021 7022 7023
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

7024 7025 7026 7027 7028 7029 7030 7031 7032 7033 7034 7035 7036 7037 7038 7039 7040 7041 7042
		/*
		 * 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.
		 */
7043
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
7044

7045 7046 7047
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

7048
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
7049
			env.dst_cpu	 = env.new_dst_cpu;
7050
			env.flags	&= ~LBF_DST_PINNED;
7051 7052
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
7053

7054 7055 7056 7057 7058 7059
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
7060

7061 7062 7063 7064
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
7065
			int *group_imbalance = &sd_parent->groups->sgc->imbalance;
7066

7067
			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
7068 7069 7070
				*group_imbalance = 1;
		}

7071
		/* All tasks on this runqueue were pinned by CPU affinity */
7072
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
7073
			cpumask_clear_cpu(cpu_of(busiest), cpus);
7074 7075 7076
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
7077
				goto redo;
7078
			}
7079
			goto out_all_pinned;
7080 7081 7082 7083 7084
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
7085 7086 7087 7088 7089 7090 7091 7092
		/*
		 * 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++;
7093

7094
		if (need_active_balance(&env)) {
7095 7096
			raw_spin_lock_irqsave(&busiest->lock, flags);

7097 7098 7099
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
7100 7101
			 */
			if (!cpumask_test_cpu(this_cpu,
7102
					tsk_cpus_allowed(busiest->curr))) {
7103 7104
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
7105
				env.flags |= LBF_ALL_PINNED;
7106 7107 7108
				goto out_one_pinned;
			}

7109 7110 7111 7112 7113
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
7114 7115 7116 7117 7118 7119
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
7120

7121
			if (active_balance) {
7122 7123 7124
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
7125
			}
7126 7127 7128 7129 7130 7131 7132 7133 7134 7135 7136 7137 7138 7139 7140 7141 7142 7143

			/*
			 * 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
7144
		 * detach_tasks).
7145 7146 7147 7148 7149 7150 7151 7152
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
7153 7154 7155 7156 7157 7158 7159 7160 7161 7162 7163 7164 7165 7166 7167 7168 7169
	/*
	 * 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.
	 */
7170 7171 7172 7173 7174 7175
	schedstat_inc(sd, lb_balanced[idle]);

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
7176
	if (((env.flags & LBF_ALL_PINNED) &&
7177
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
7178 7179 7180
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

7181
	ld_moved = 0;
7182 7183 7184 7185
out:
	return ld_moved;
}

7186 7187 7188 7189 7190 7191 7192 7193 7194 7195 7196 7197 7198 7199 7200 7201 7202 7203 7204 7205 7206 7207 7208 7209 7210 7211 7212
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;
}

7213 7214 7215 7216
/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
7217
static int idle_balance(struct rq *this_rq)
7218
{
7219 7220
	unsigned long next_balance = jiffies + HZ;
	int this_cpu = this_rq->cpu;
7221 7222
	struct sched_domain *sd;
	int pulled_task = 0;
7223
	u64 curr_cost = 0;
7224

7225
	idle_enter_fair(this_rq);
7226

7227 7228 7229 7230 7231 7232
	/*
	 * 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);

7233 7234
	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
	    !this_rq->rd->overload) {
7235 7236 7237 7238 7239 7240
		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);
		if (sd)
			update_next_balance(sd, 0, &next_balance);
		rcu_read_unlock();

7241
		goto out;
7242
	}
7243

7244 7245
	raw_spin_unlock(&this_rq->lock);

7246
	update_blocked_averages(this_cpu);
7247
	rcu_read_lock();
7248
	for_each_domain(this_cpu, sd) {
7249
		int continue_balancing = 1;
7250
		u64 t0, domain_cost;
7251 7252 7253 7254

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

7255 7256
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
			update_next_balance(sd, 0, &next_balance);
7257
			break;
7258
		}
7259

7260
		if (sd->flags & SD_BALANCE_NEWIDLE) {
7261 7262
			t0 = sched_clock_cpu(this_cpu);

7263
			pulled_task = load_balance(this_cpu, this_rq,
7264 7265
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
7266 7267 7268 7269 7270 7271

			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;
7272
		}
7273

7274
		update_next_balance(sd, 0, &next_balance);
7275 7276 7277 7278 7279 7280

		/*
		 * Stop searching for tasks to pull if there are
		 * now runnable tasks on this rq.
		 */
		if (pulled_task || this_rq->nr_running > 0)
7281 7282
			break;
	}
7283
	rcu_read_unlock();
7284 7285 7286

	raw_spin_lock(&this_rq->lock);

7287 7288 7289
	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

7290
	/*
7291 7292 7293
	 * 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.
7294
	 */
7295
	if (this_rq->cfs.h_nr_running && !pulled_task)
7296
		pulled_task = 1;
7297

7298 7299 7300
out:
	/* Move the next balance forward */
	if (time_after(this_rq->next_balance, next_balance))
7301
		this_rq->next_balance = next_balance;
7302

7303
	/* Is there a task of a high priority class? */
7304
	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
7305 7306 7307 7308
		pulled_task = -1;

	if (pulled_task) {
		idle_exit_fair(this_rq);
7309
		this_rq->idle_stamp = 0;
7310
	}
7311

7312
	return pulled_task;
7313 7314 7315
}

/*
7316 7317 7318 7319
 * 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.
7320
 */
7321
static int active_load_balance_cpu_stop(void *data)
7322
{
7323 7324
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
7325
	int target_cpu = busiest_rq->push_cpu;
7326
	struct rq *target_rq = cpu_rq(target_cpu);
7327
	struct sched_domain *sd;
7328
	struct task_struct *p = NULL;
7329 7330 7331 7332 7333 7334 7335

	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;
7336 7337 7338

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
7339
		goto out_unlock;
7340 7341 7342 7343 7344 7345 7346 7347 7348

	/*
	 * 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. */
7349
	rcu_read_lock();
7350 7351 7352 7353 7354 7355 7356
	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)) {
7357 7358
		struct lb_env env = {
			.sd		= sd,
7359 7360 7361 7362
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
7363 7364 7365
			.idle		= CPU_IDLE,
		};

7366 7367
		schedstat_inc(sd, alb_count);

7368 7369
		p = detach_one_task(&env);
		if (p)
7370 7371 7372 7373
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
7374
	rcu_read_unlock();
7375 7376
out_unlock:
	busiest_rq->active_balance = 0;
7377 7378 7379 7380 7381 7382 7383
	raw_spin_unlock(&busiest_rq->lock);

	if (p)
		attach_one_task(target_rq, p);

	local_irq_enable();

7384
	return 0;
7385 7386
}

7387 7388 7389 7390 7391
static inline int on_null_domain(struct rq *rq)
{
	return unlikely(!rcu_dereference_sched(rq->sd));
}

7392
#ifdef CONFIG_NO_HZ_COMMON
7393 7394 7395 7396 7397 7398
/*
 * 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.
 */
7399
static struct {
7400
	cpumask_var_t idle_cpus_mask;
7401
	atomic_t nr_cpus;
7402 7403
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
7404

7405
static inline int find_new_ilb(void)
7406
{
7407
	int ilb = cpumask_first(nohz.idle_cpus_mask);
7408

7409 7410 7411 7412
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
7413 7414
}

7415 7416 7417 7418 7419
/*
 * 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).
 */
7420
static void nohz_balancer_kick(void)
7421 7422 7423 7424 7425
{
	int ilb_cpu;

	nohz.next_balance++;

7426
	ilb_cpu = find_new_ilb();
7427

7428 7429
	if (ilb_cpu >= nr_cpu_ids)
		return;
7430

7431
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
7432 7433 7434 7435 7436 7437 7438 7439
		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);
7440 7441 7442
	return;
}

7443
static inline void nohz_balance_exit_idle(int cpu)
7444 7445
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
7446 7447 7448 7449 7450 7451 7452
		/*
		 * 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);
		}
7453 7454 7455 7456
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

7457 7458 7459
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
7460
	int cpu = smp_processor_id();
7461 7462

	rcu_read_lock();
7463
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7464 7465 7466 7467 7468

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

7469
	atomic_inc(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7470
unlock:
7471 7472 7473 7474 7475 7476
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;
7477
	int cpu = smp_processor_id();
7478 7479

	rcu_read_lock();
7480
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
V
Vincent Guittot 已提交
7481 7482 7483 7484 7485

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

7486
	atomic_dec(&sd->groups->sgc->nr_busy_cpus);
V
Vincent Guittot 已提交
7487
unlock:
7488 7489 7490
	rcu_read_unlock();
}

7491
/*
7492
 * This routine will record that the cpu is going idle with tick stopped.
7493
 * This info will be used in performing idle load balancing in the future.
7494
 */
7495
void nohz_balance_enter_idle(int cpu)
7496
{
7497 7498 7499 7500 7501 7502
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

7503 7504
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
7505

7506 7507 7508 7509 7510 7511
	/*
	 * If we're a completely isolated CPU, we don't play.
	 */
	if (on_null_domain(cpu_rq(cpu)))
		return;

7512 7513 7514
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
7515
}
7516

7517
static int sched_ilb_notifier(struct notifier_block *nfb,
7518 7519 7520 7521
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
7522
		nohz_balance_exit_idle(smp_processor_id());
7523 7524 7525 7526 7527
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
7528 7529 7530 7531
#endif

static DEFINE_SPINLOCK(balancing);

7532 7533 7534 7535
/*
 * 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.
 */
7536
void update_max_interval(void)
7537 7538 7539 7540
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

7541 7542 7543 7544
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
7545
 * Balancing parameters are set up in init_sched_domains.
7546
 */
7547
static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
7548
{
7549
	int continue_balancing = 1;
7550
	int cpu = rq->cpu;
7551
	unsigned long interval;
7552
	struct sched_domain *sd;
7553 7554 7555
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
7556 7557
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
7558

7559
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
7560

7561
	rcu_read_lock();
7562
	for_each_domain(cpu, sd) {
7563 7564 7565 7566 7567 7568 7569 7570 7571 7572 7573 7574
		/*
		 * 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;

7575 7576 7577
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

7578 7579 7580 7581 7582 7583 7584 7585 7586 7587 7588
		/*
		 * 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;
		}

7589
		interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7590 7591 7592 7593 7594 7595 7596 7597

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

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
7598
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
7599
				/*
7600
				 * The LBF_DST_PINNED logic could have changed
7601 7602
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
7603
				 */
7604
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
7605 7606
			}
			sd->last_balance = jiffies;
7607
			interval = get_sd_balance_interval(sd, idle != CPU_IDLE);
7608 7609 7610 7611 7612 7613 7614 7615
		}
		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;
		}
7616 7617
	}
	if (need_decay) {
7618
		/*
7619 7620
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
7621
		 */
7622 7623
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
7624
	}
7625
	rcu_read_unlock();
7626 7627 7628 7629 7630 7631 7632 7633 7634 7635

	/*
	 * 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;
}

7636
#ifdef CONFIG_NO_HZ_COMMON
7637
/*
7638
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
7639 7640
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
7641
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
7642
{
7643
	int this_cpu = this_rq->cpu;
7644 7645 7646
	struct rq *rq;
	int balance_cpu;

7647 7648 7649
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
7650 7651

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
7652
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
7653 7654 7655 7656 7657 7658 7659
			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.
		 */
7660
		if (need_resched())
7661 7662
			break;

V
Vincent Guittot 已提交
7663 7664
		rq = cpu_rq(balance_cpu);

7665 7666 7667 7668 7669 7670 7671 7672 7673 7674 7675
		/*
		 * 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);
		}
7676 7677 7678 7679 7680

		if (time_after(this_rq->next_balance, rq->next_balance))
			this_rq->next_balance = rq->next_balance;
	}
	nohz.next_balance = this_rq->next_balance;
7681 7682
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
7683 7684 7685
}

/*
7686
 * Current heuristic for kicking the idle load balancer in the presence
7687
 * of an idle cpu in the system.
7688
 *   - This rq has more than one task.
7689 7690 7691 7692
 *   - 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.
7693 7694
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
7695
 */
7696
static inline bool nohz_kick_needed(struct rq *rq)
7697 7698
{
	unsigned long now = jiffies;
7699
	struct sched_domain *sd;
7700
	struct sched_group_capacity *sgc;
7701
	int nr_busy, cpu = rq->cpu;
7702
	bool kick = false;
7703

7704
	if (unlikely(rq->idle_balance))
7705
		return false;
7706

7707 7708 7709 7710
       /*
	* 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.
	*/
7711
	set_cpu_sd_state_busy();
7712
	nohz_balance_exit_idle(cpu);
7713 7714 7715 7716 7717 7718

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
7719
		return false;
7720 7721

	if (time_before(now, nohz.next_balance))
7722
		return false;
7723

7724
	if (rq->nr_running >= 2)
7725
		return true;
7726

7727
	rcu_read_lock();
7728 7729
	sd = rcu_dereference(per_cpu(sd_busy, cpu));
	if (sd) {
7730 7731
		sgc = sd->groups->sgc;
		nr_busy = atomic_read(&sgc->nr_busy_cpus);
7732

7733 7734 7735 7736 7737
		if (nr_busy > 1) {
			kick = true;
			goto unlock;
		}

7738
	}
7739

7740 7741 7742 7743 7744 7745 7746 7747
	sd = rcu_dereference(rq->sd);
	if (sd) {
		if ((rq->cfs.h_nr_running >= 1) &&
				check_cpu_capacity(rq, sd)) {
			kick = true;
			goto unlock;
		}
	}
7748

7749
	sd = rcu_dereference(per_cpu(sd_asym, cpu));
7750
	if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
7751 7752 7753 7754
				  sched_domain_span(sd)) < cpu)) {
		kick = true;
		goto unlock;
	}
7755

7756
unlock:
7757
	rcu_read_unlock();
7758
	return kick;
7759 7760
}
#else
7761
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
7762 7763 7764 7765 7766 7767
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
7768 7769
static void run_rebalance_domains(struct softirq_action *h)
{
7770
	struct rq *this_rq = this_rq();
7771
	enum cpu_idle_type idle = this_rq->idle_balance ?
7772 7773 7774
						CPU_IDLE : CPU_NOT_IDLE;

	/*
7775
	 * If this cpu has a pending nohz_balance_kick, then do the
7776
	 * balancing on behalf of the other idle cpus whose ticks are
7777 7778 7779 7780
	 * 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.
7781
	 */
7782
	nohz_idle_balance(this_rq, idle);
7783
	rebalance_domains(this_rq, idle);
7784 7785 7786 7787 7788
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
7789
void trigger_load_balance(struct rq *rq)
7790 7791
{
	/* Don't need to rebalance while attached to NULL domain */
7792 7793 7794 7795
	if (unlikely(on_null_domain(rq)))
		return;

	if (time_after_eq(jiffies, rq->next_balance))
7796
		raise_softirq(SCHED_SOFTIRQ);
7797
#ifdef CONFIG_NO_HZ_COMMON
7798
	if (nohz_kick_needed(rq))
7799
		nohz_balancer_kick();
7800
#endif
7801 7802
}

7803 7804 7805
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
7806 7807

	update_runtime_enabled(rq);
7808 7809 7810 7811 7812
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
7813 7814 7815

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
7816 7817
}

7818
#endif /* CONFIG_SMP */
7819

7820 7821 7822
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
7823
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
7824 7825 7826 7827 7828 7829
{
	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
7830
		entity_tick(cfs_rq, se, queued);
7831
	}
7832

7833
	if (numabalancing_enabled)
7834
		task_tick_numa(rq, curr);
7835 7836 7837
}

/*
P
Peter Zijlstra 已提交
7838 7839 7840
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
7841
 */
P
Peter Zijlstra 已提交
7842
static void task_fork_fair(struct task_struct *p)
7843
{
7844 7845
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
7846
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
7847 7848 7849
	struct rq *rq = this_rq();
	unsigned long flags;

7850
	raw_spin_lock_irqsave(&rq->lock, flags);
7851

7852 7853
	update_rq_clock(rq);

7854 7855 7856
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

7857 7858 7859 7860 7861 7862 7863 7864 7865
	/*
	 * 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();
7866

7867
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
7868

7869 7870
	if (curr)
		se->vruntime = curr->vruntime;
7871
	place_entity(cfs_rq, se, 1);
7872

P
Peter Zijlstra 已提交
7873
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
7874
		/*
7875 7876 7877
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
7878
		swap(curr->vruntime, se->vruntime);
7879
		resched_curr(rq);
7880
	}
7881

7882 7883
	se->vruntime -= cfs_rq->min_vruntime;

7884
	raw_spin_unlock_irqrestore(&rq->lock, flags);
7885 7886
}

7887 7888 7889 7890
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
7891 7892
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
7893
{
7894
	if (!task_on_rq_queued(p))
P
Peter Zijlstra 已提交
7895 7896
		return;

7897 7898 7899 7900 7901
	/*
	 * 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
7902
	if (rq->curr == p) {
7903
		if (p->prio > oldprio)
7904
			resched_curr(rq);
7905
	} else
7906
		check_preempt_curr(rq, p, 0);
7907 7908
}

P
Peter Zijlstra 已提交
7909 7910 7911 7912 7913 7914
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);

	/*
7915
	 * Ensure the task's vruntime is normalized, so that when it's
P
Peter Zijlstra 已提交
7916 7917 7918
	 * switched back to the fair class the enqueue_entity(.flags=0) will
	 * do the right thing.
	 *
7919 7920
	 * 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
7921 7922
	 * the task is sleeping will it still have non-normalized vruntime.
	 */
7923
	if (!task_on_rq_queued(p) && p->state != TASK_RUNNING) {
P
Peter Zijlstra 已提交
7924 7925 7926 7927 7928 7929 7930
		/*
		 * 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;
	}
7931

7932
	/* Catch up with the cfs_rq and remove our load when we leave */
7933
	detach_entity_load_avg(cfs_rq, se);
P
Peter Zijlstra 已提交
7934 7935 7936
}

static void switched_to_fair(struct rq *rq, struct task_struct *p)
7937
{
7938
	struct sched_entity *se = &p->se;
7939 7940

#ifdef CONFIG_FAIR_GROUP_SCHED
7941 7942 7943 7944 7945 7946
	/*
	 * 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
7947 7948 7949 7950 7951 7952 7953 7954 7955 7956 7957 7958 7959 7960

	if (!task_on_rq_queued(p)) {

		/*
		 * Ensure the task has a non-normalized vruntime when it is switched
		 * back to the fair class with !queued, so that enqueue_entity() at
		 * wake-up time will do the right thing.
		 *
		 * If it's queued, then the enqueue_entity(.flags=0) makes the task
		 * has non-normalized vruntime, if it's !queued, then it still has
		 * normalized vruntime.
		 */
		if (p->state != TASK_RUNNING)
			se->vruntime += cfs_rq_of(se)->min_vruntime;
P
Peter Zijlstra 已提交
7961
		return;
7962
	}
P
Peter Zijlstra 已提交
7963

7964 7965 7966 7967 7968
	/*
	 * 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
7969
	if (rq->curr == p)
7970
		resched_curr(rq);
7971
	else
7972
		check_preempt_curr(rq, p, 0);
7973 7974
}

7975 7976 7977 7978 7979 7980 7981 7982 7983
/* 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;

7984 7985 7986 7987 7988 7989 7990
	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);
	}
7991 7992
}

7993 7994 7995 7996 7997 7998 7999
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
8000
#ifdef CONFIG_SMP
8001 8002
	atomic_long_set(&cfs_rq->removed_load_avg, 0);
	atomic_long_set(&cfs_rq->removed_util_avg, 0);
8003
#endif
8004 8005
}

P
Peter Zijlstra 已提交
8006
#ifdef CONFIG_FAIR_GROUP_SCHED
8007
static void task_move_group_fair(struct task_struct *p, int queued)
P
Peter Zijlstra 已提交
8008
{
P
Peter Zijlstra 已提交
8009
	struct sched_entity *se = &p->se;
8010
	struct cfs_rq *cfs_rq;
P
Peter Zijlstra 已提交
8011

8012 8013 8014 8015 8016 8017 8018 8019 8020 8021 8022 8023 8024
	/*
	 * 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.
	 */
8025
	/*
8026
	 * When !queued, vruntime of the task has usually NOT been normalized.
8027 8028 8029 8030
	 * 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().
8031 8032
	 * - Moving a task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
8033 8034 8035 8036
	 *
	 * To prevent boost or penalty in the new cfs_rq caused by delta
	 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
	 */
8037 8038
	if (!queued && (!se->sum_exec_runtime || p->state == TASK_WAKING))
		queued = 1;
8039

8040
	cfs_rq = cfs_rq_of(se);
8041
	if (!queued)
8042 8043 8044 8045
		se->vruntime -= cfs_rq->min_vruntime;

	/* Synchronize task with its prev cfs_rq */
	detach_entity_load_avg(cfs_rq, se);
8046
	set_task_rq(p, task_cpu(p));
P
Peter Zijlstra 已提交
8047
	se->depth = se->parent ? se->parent->depth + 1 : 0;
8048 8049
	cfs_rq = cfs_rq_of(se);
	if (!queued)
P
Peter Zijlstra 已提交
8050
		se->vruntime += cfs_rq->min_vruntime;
8051

8052 8053
	/* Virtually synchronize task with its new cfs_rq */
	attach_entity_load_avg(cfs_rq, se);
P
Peter Zijlstra 已提交
8054
}
8055 8056 8057 8058 8059 8060 8061 8062 8063 8064

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]);
8065 8066 8067
		if (tg->se) {
			if (tg->se[i])
				remove_entity_load_avg(tg->se[i]);
8068
			kfree(tg->se[i]);
8069
		}
8070 8071 8072 8073 8074 8075 8076 8077 8078 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
	}

	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]);
8106
		init_entity_runnable_average(se);
8107 8108 8109 8110 8111 8112 8113 8114 8115 8116 8117 8118 8119 8120 8121 8122 8123 8124 8125 8126 8127 8128 8129 8130 8131 8132 8133 8134 8135 8136 8137 8138 8139 8140 8141 8142 8143 8144 8145 8146 8147 8148 8149 8150
	}

	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
8151
	if (!parent) {
8152
		se->cfs_rq = &rq->cfs;
P
Peter Zijlstra 已提交
8153 8154
		se->depth = 0;
	} else {
8155
		se->cfs_rq = parent->my_q;
P
Peter Zijlstra 已提交
8156 8157
		se->depth = parent->depth + 1;
	}
8158 8159

	se->my_q = cfs_rq;
8160 8161
	/* guarantee group entities always have weight */
	update_load_set(&se->load, NICE_0_LOAD);
8162 8163 8164 8165 8166 8167 8168 8169 8170 8171 8172 8173 8174 8175 8176 8177 8178 8179 8180 8181 8182 8183 8184 8185 8186 8187 8188 8189 8190 8191
	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);
8192 8193 8194

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
8195
		for_each_sched_entity(se)
8196 8197 8198 8199 8200 8201 8202 8203 8204 8205 8206 8207 8208 8209 8210 8211 8212 8213 8214 8215 8216
			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
8217

8218
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
8219 8220 8221 8222 8223 8224 8225 8226 8227
{
	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)
8228
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
8229 8230 8231 8232

	return rr_interval;
}

8233 8234 8235
/*
 * All the scheduling class methods:
 */
8236
const struct sched_class fair_sched_class = {
8237
	.next			= &idle_sched_class,
8238 8239 8240
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
8241
	.yield_to_task		= yield_to_task_fair,
8242

I
Ingo Molnar 已提交
8243
	.check_preempt_curr	= check_preempt_wakeup,
8244 8245 8246 8247

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

8248
#ifdef CONFIG_SMP
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8249
	.select_task_rq		= select_task_rq_fair,
8250
	.migrate_task_rq	= migrate_task_rq_fair,
8251

8252 8253
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
8254 8255

	.task_waking		= task_waking_fair,
8256
	.task_dead		= task_dead_fair,
8257
	.set_cpus_allowed	= set_cpus_allowed_common,
8258
#endif
8259

8260
	.set_curr_task          = set_curr_task_fair,
8261
	.task_tick		= task_tick_fair,
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	.task_fork		= task_fork_fair,
8263 8264

	.prio_changed		= prio_changed_fair,
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	.switched_from		= switched_from_fair,
8266
	.switched_to		= switched_to_fair,
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8268 8269
	.get_rr_interval	= get_rr_interval_fair,

8270 8271
	.update_curr		= update_curr_fair,

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8272
#ifdef CONFIG_FAIR_GROUP_SCHED
8273
	.task_move_group	= task_move_group_fair,
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#endif
8275 8276 8277
};

#ifdef CONFIG_SCHED_DEBUG
8278
void print_cfs_stats(struct seq_file *m, int cpu)
8279 8280 8281
{
	struct cfs_rq *cfs_rq;

8282
	rcu_read_lock();
8283
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
8284
		print_cfs_rq(m, cpu, cfs_rq);
8285
	rcu_read_unlock();
8286
}
8287 8288 8289 8290 8291 8292 8293 8294 8295 8296 8297 8298 8299 8300 8301 8302 8303 8304 8305 8306 8307

#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 */
8308 8309 8310 8311 8312 8313

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

8314
#ifdef CONFIG_NO_HZ_COMMON
8315
	nohz.next_balance = jiffies;
8316
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
8317
	cpu_notifier(sched_ilb_notifier, 0);
8318 8319 8320 8321
#endif
#endif /* SMP */

}