fair.c 187.7 KB
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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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 */

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#include <linux/latencytop.h>
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#include <linux/sched.h>
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#include <linux/cpumask.h>
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#include <linux/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:
 */
static int get_update_sysctl_factor(void)
{
	unsigned int cpus = min_t(int, num_online_cpus(), 8);
	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();
}

#if BITS_PER_LONG == 32
# define WMULT_CONST	(~0UL)
#else
# define WMULT_CONST	(1UL << 32)
#endif

#define WMULT_SHIFT	32

/*
 * Shift right and round:
 */
#define SRR(x, y) (((x) + (1UL << ((y) - 1))) >> (y))

/*
 * delta *= weight / lw
 */
static unsigned long
calc_delta_mine(unsigned long delta_exec, unsigned long weight,
		struct load_weight *lw)
{
	u64 tmp;

	/*
	 * weight can be less than 2^SCHED_LOAD_RESOLUTION for task group sched
	 * entities since MIN_SHARES = 2. Treat weight as 1 if less than
	 * 2^SCHED_LOAD_RESOLUTION.
	 */
	if (likely(weight > (1UL << SCHED_LOAD_RESOLUTION)))
		tmp = (u64)delta_exec * scale_load_down(weight);
	else
		tmp = (u64)delta_exec;

	if (!lw->inv_weight) {
		unsigned long 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;
	}

	/*
	 * Check whether we'd overflow the 64-bit multiplication:
	 */
	if (unlikely(tmp > WMULT_CONST))
		tmp = SRR(SRR(tmp, WMULT_SHIFT/2) * lw->inv_weight,
			WMULT_SHIFT/2);
	else
		tmp = SRR(tmp * lw->inv_weight, WMULT_SHIFT);

	return (unsigned long)min(tmp, (u64)(unsigned long)LONG_MAX);
}


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 void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
				       int force_update);
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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;
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		/* We should have no load, but we need to update last_decay. */
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		update_cfs_rq_blocked_load(cfs_rq, 0);
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	}
}

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 ? */
static inline int
is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
	if (se->cfs_rq == pse->cfs_rq)
		return 1;

	return 0;
}

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

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/* return depth at which a sched entity is present in the hierarchy */
static inline int depth_se(struct sched_entity *se)
{
	int depth = 0;

	for_each_sched_entity(se)
		depth++;

	return depth;
}

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 */
	se_depth = depth_se(*se);
	pse_depth = depth_se(*pse);

	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 int
is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
	return 1;
}

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
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long 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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	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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 */
static inline unsigned long
calc_delta_fair(unsigned long delta, struct sched_entity *se)
{
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	if (unlikely(se->load.weight != NICE_0_LOAD))
		delta = calc_delta_mine(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)
{
	u64 period = sysctl_sched_latency;
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	unsigned long nr_latency = sched_nr_latency;
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	if (unlikely(nr_running > nr_latency)) {
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		period = sysctl_sched_min_granularity;
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		period *= nr_running;
	}

	return period;
}

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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;
		}
		slice = calc_delta_mine(slice, se->load.weight, load);
	}
	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 unsigned long task_h_load(struct task_struct *p);

686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704
static inline void __update_task_entity_contrib(struct sched_entity *se);

/* Give new task start runnable values to heavy its load in infant time */
void init_task_runnable_average(struct task_struct *p)
{
	u32 slice;

	p->se.avg.decay_count = 0;
	slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
	p->se.avg.runnable_avg_sum = slice;
	p->se.avg.runnable_avg_period = slice;
	__update_task_entity_contrib(&p->se);
}
#else
void init_task_runnable_average(struct task_struct *p)
{
}
#endif

705 706 707 708 709
/*
 * Update the current task's runtime statistics. Skip current tasks that
 * are not in our scheduling class.
 */
static inline void
I
Ingo Molnar 已提交
710 711
__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
	      unsigned long delta_exec)
712
{
713
	unsigned long delta_exec_weighted;
714

715 716
	schedstat_set(curr->statistics.exec_max,
		      max((u64)delta_exec, curr->statistics.exec_max));
717 718

	curr->sum_exec_runtime += delta_exec;
719
	schedstat_add(cfs_rq, exec_clock, delta_exec);
720
	delta_exec_weighted = calc_delta_fair(delta_exec, curr);
721

I
Ingo Molnar 已提交
722
	curr->vruntime += delta_exec_weighted;
723
	update_min_vruntime(cfs_rq);
724 725
}

726
static void update_curr(struct cfs_rq *cfs_rq)
727
{
728
	struct sched_entity *curr = cfs_rq->curr;
729
	u64 now = rq_clock_task(rq_of(cfs_rq));
730 731 732 733 734 735 736 737 738 739
	unsigned long delta_exec;

	if (unlikely(!curr))
		return;

	/*
	 * Get the amount of time the current task was running
	 * since the last time we changed load (this cannot
	 * overflow on 32 bits):
	 */
I
Ingo Molnar 已提交
740
	delta_exec = (unsigned long)(now - curr->exec_start);
P
Peter Zijlstra 已提交
741 742
	if (!delta_exec)
		return;
743

I
Ingo Molnar 已提交
744 745
	__update_curr(cfs_rq, curr, delta_exec);
	curr->exec_start = now;
746 747 748 749

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

750
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
751
		cpuacct_charge(curtask, delta_exec);
752
		account_group_exec_runtime(curtask, delta_exec);
753
	}
754 755

	account_cfs_rq_runtime(cfs_rq, delta_exec);
756 757 758
}

static inline void
759
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
760
{
761
	schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
762 763 764 765 766
}

/*
 * Task is being enqueued - update stats:
 */
767
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
768 769 770 771 772
{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
773
	if (se != cfs_rq->curr)
774
		update_stats_wait_start(cfs_rq, se);
775 776 777
}

static void
778
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
779
{
780
	schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
781
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
782 783
	schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
	schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
784
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
785 786 787
#ifdef CONFIG_SCHEDSTATS
	if (entity_is_task(se)) {
		trace_sched_stat_wait(task_of(se),
788
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
789 790
	}
#endif
791
	schedstat_set(se->statistics.wait_start, 0);
792 793 794
}

static inline void
795
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
796 797 798 799 800
{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
801
	if (se != cfs_rq->curr)
802
		update_stats_wait_end(cfs_rq, se);
803 804 805 806 807 808
}

/*
 * We are picking a new current task - update its stats:
 */
static inline void
809
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
810 811 812 813
{
	/*
	 * We are starting a new run period:
	 */
814
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
815 816 817 818 819 820
}

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

821 822
#ifdef CONFIG_NUMA_BALANCING
/*
823 824 825
 * 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.
826
 */
827 828
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
829 830 831

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
832

833 834 835
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

836 837 838 839 840 841 842 843
/*
 * After skipping a page migration on a shared page, skip N more numa page
 * migrations unconditionally. This reduces the number of NUMA migrations
 * in shared memory workloads, and has the effect of pulling tasks towards
 * where their memory lives, over pulling the memory towards the task.
 */
unsigned int sysctl_numa_balancing_migrate_deferred = 16;

844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888
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)
{
	unsigned int scan, floor;
	unsigned int windows = 1;

	if (sysctl_numa_balancing_scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / sysctl_numa_balancing_scan_size;
	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);
}

889 890 891 892 893 894 895
/*
 * Once a preferred node is selected the scheduler balancer will prefer moving
 * a task to that node for sysctl_numa_balancing_settle_count number of PTE
 * scans. This will give the process the chance to accumulate more faults on
 * the preferred node but still allow the scheduler to move the task again if
 * the nodes CPUs are overloaded.
 */
896
unsigned int sysctl_numa_balancing_settle_count __read_mostly = 4;
897

898 899 900 901 902 903 904 905 906 907 908 909
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));
}

910 911 912 913 914
struct numa_group {
	atomic_t refcount;

	spinlock_t lock; /* nr_tasks, tasks */
	int nr_tasks;
915
	pid_t gid;
916 917 918
	struct list_head task_list;

	struct rcu_head rcu;
919 920
	unsigned long total_faults;
	unsigned long faults[0];
921 922
};

923 924 925 926 927
pid_t task_numa_group_id(struct task_struct *p)
{
	return p->numa_group ? p->numa_group->gid : 0;
}

928 929 930 931 932 933 934 935 936 937 938 939 940 941
static inline int task_faults_idx(int nid, int priv)
{
	return 2 * nid + priv;
}

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

	return p->numa_faults[task_faults_idx(nid, 0)] +
		p->numa_faults[task_faults_idx(nid, 1)];
}

942 943 944 945 946
static inline unsigned long group_faults(struct task_struct *p, int nid)
{
	if (!p->numa_group)
		return 0;

947
	return p->numa_group->faults[2*nid] + p->numa_group->faults[2*nid+1];
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
}

/*
 * 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.
 */
static inline unsigned long task_weight(struct task_struct *p, int nid)
{
	unsigned long total_faults;

	if (!p->numa_faults)
		return 0;

	total_faults = p->total_numa_faults;

	if (!total_faults)
		return 0;

	return 1000 * task_faults(p, nid) / total_faults;
}

static inline unsigned long group_weight(struct task_struct *p, int nid)
{
973
	if (!p->numa_group || !p->numa_group->total_faults)
974 975
		return 0;

976
	return 1000 * group_faults(p, nid) / p->numa_group->total_faults;
977 978
}

979
static unsigned long weighted_cpuload(const int cpu);
980 981 982 983 984
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
static unsigned long power_of(int cpu);
static long effective_load(struct task_group *tg, int cpu, long wl, long wg);

985
/* Cached statistics for all CPUs within a node */
986
struct numa_stats {
987
	unsigned long nr_running;
988
	unsigned long load;
989 990 991 992 993 994 995

	/* Total compute capacity of CPUs on a node */
	unsigned long power;

	/* Approximate capacity in terms of runnable tasks on a node */
	unsigned long capacity;
	int has_capacity;
996
};
997

998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018
/*
 * XXX borrowed from update_sg_lb_stats
 */
static void update_numa_stats(struct numa_stats *ns, int nid)
{
	int cpu;

	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);
		ns->power += power_of(cpu);
	}

	ns->load = (ns->load * SCHED_POWER_SCALE) / ns->power;
	ns->capacity = DIV_ROUND_CLOSEST(ns->power, SCHED_POWER_SCALE);
	ns->has_capacity = (ns->nr_running < ns->capacity);
}

1019 1020
struct task_numa_env {
	struct task_struct *p;
1021

1022 1023
	int src_cpu, src_nid;
	int dst_cpu, dst_nid;
1024

1025
	struct numa_stats src_stats, dst_stats;
1026

1027 1028 1029 1030
	int imbalance_pct, idx;

	struct task_struct *best_task;
	long best_imp;
1031 1032 1033
	int best_cpu;
};

1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052
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;
}

/*
 * 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
 */
1053 1054
static void task_numa_compare(struct task_numa_env *env,
			      long taskimp, long groupimp)
1055 1056 1057 1058 1059 1060
{
	struct rq *src_rq = cpu_rq(env->src_cpu);
	struct rq *dst_rq = cpu_rq(env->dst_cpu);
	struct task_struct *cur;
	long dst_load, src_load;
	long load;
1061
	long imp = (groupimp > 0) ? groupimp : taskimp;
1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079

	rcu_read_lock();
	cur = ACCESS_ONCE(dst_rq->curr);
	if (cur->pid == 0) /* idle */
		cur = NULL;

	/*
	 * "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;

1080 1081
		/*
		 * If dst and source tasks are in the same NUMA group, or not
1082
		 * in any group then look only at task weights.
1083
		 */
1084
		if (cur->numa_group == env->p->numa_group) {
1085 1086
			imp = taskimp + task_weight(cur, env->src_nid) -
			      task_weight(cur, env->dst_nid);
1087 1088 1089 1090 1091 1092
			/*
			 * Add some hysteresis to prevent swapping the
			 * tasks within a group over tiny differences.
			 */
			if (cur->numa_group)
				imp -= imp/16;
1093
		} else {
1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109
			/*
			 * Compare the group weights. If a task is all by
			 * itself (not part of a group), use the task weight
			 * instead.
			 */
			if (env->p->numa_group)
				imp = groupimp;
			else
				imp = taskimp;

			if (cur->numa_group)
				imp += group_weight(cur, env->src_nid) -
				       group_weight(cur, env->dst_nid);
			else
				imp += task_weight(cur, env->src_nid) -
				       task_weight(cur, env->dst_nid);
1110
		}
1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159
	}

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

	if (!cur) {
		/* Is there capacity at our destination? */
		if (env->src_stats.has_capacity &&
		    !env->dst_stats.has_capacity)
			goto unlock;

		goto balance;
	}

	/* Balance doesn't matter much if we're running a task per cpu */
	if (src_rq->nr_running == 1 && dst_rq->nr_running == 1)
		goto assign;

	/*
	 * In the overloaded case, try and keep the load balanced.
	 */
balance:
	dst_load = env->dst_stats.load;
	src_load = env->src_stats.load;

	/* XXX missing power terms */
	load = task_h_load(env->p);
	dst_load += load;
	src_load -= load;

	if (cur) {
		load = task_h_load(cur);
		dst_load -= load;
		src_load += load;
	}

	/* make src_load the smaller */
	if (dst_load < src_load)
		swap(dst_load, src_load);

	if (src_load * env->imbalance_pct < dst_load * 100)
		goto unlock;

assign:
	task_numa_assign(env, cur, imp);
unlock:
	rcu_read_unlock();
}

1160 1161
static void task_numa_find_cpu(struct task_numa_env *env,
				long taskimp, long groupimp)
1162 1163 1164 1165 1166 1167 1168 1169 1170
{
	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;
1171
		task_numa_compare(env, taskimp, groupimp);
1172 1173 1174
	}
}

1175 1176 1177 1178
static int task_numa_migrate(struct task_struct *p)
{
	struct task_numa_env env = {
		.p = p,
1179

1180
		.src_cpu = task_cpu(p),
I
Ingo Molnar 已提交
1181
		.src_nid = task_node(p),
1182 1183 1184 1185 1186 1187

		.imbalance_pct = 112,

		.best_task = NULL,
		.best_imp = 0,
		.best_cpu = -1
1188 1189
	};
	struct sched_domain *sd;
1190
	unsigned long taskweight, groupweight;
1191
	int nid, ret;
1192
	long taskimp, groupimp;
1193

1194
	/*
1195 1196 1197 1198 1199 1200
	 * 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.
1201 1202
	 */
	rcu_read_lock();
1203 1204
	sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu));
	env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2;
1205 1206
	rcu_read_unlock();

1207 1208
	taskweight = task_weight(p, env.src_nid);
	groupweight = group_weight(p, env.src_nid);
1209
	update_numa_stats(&env.src_stats, env.src_nid);
1210
	env.dst_nid = p->numa_preferred_nid;
1211 1212
	taskimp = task_weight(p, env.dst_nid) - taskweight;
	groupimp = group_weight(p, env.dst_nid) - groupweight;
1213
	update_numa_stats(&env.dst_stats, env.dst_nid);
1214

1215 1216
	/* If the preferred nid has capacity, try to use it. */
	if (env.dst_stats.has_capacity)
1217
		task_numa_find_cpu(&env, taskimp, groupimp);
1218 1219 1220

	/* No space available on the preferred nid. Look elsewhere. */
	if (env.best_cpu == -1) {
1221 1222 1223
		for_each_online_node(nid) {
			if (nid == env.src_nid || nid == p->numa_preferred_nid)
				continue;
1224

1225
			/* Only consider nodes where both task and groups benefit */
1226 1227 1228
			taskimp = task_weight(p, nid) - taskweight;
			groupimp = group_weight(p, nid) - groupweight;
			if (taskimp < 0 && groupimp < 0)
1229 1230
				continue;

1231 1232
			env.dst_nid = nid;
			update_numa_stats(&env.dst_stats, env.dst_nid);
1233
			task_numa_find_cpu(&env, taskimp, groupimp);
1234 1235 1236
		}
	}

1237 1238 1239 1240
	/* No better CPU than the current one was found. */
	if (env.best_cpu == -1)
		return -EAGAIN;

1241 1242
	sched_setnuma(p, env.dst_nid);

1243 1244 1245 1246 1247 1248
	/*
	 * 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);

1249 1250 1251 1252 1253 1254 1255 1256
	if (env.best_task == NULL) {
		int ret = migrate_task_to(p, env.best_cpu);
		return ret;
	}

	ret = migrate_swap(p, env.best_task);
	put_task_struct(env.best_task);
	return ret;
1257 1258
}

1259 1260 1261
/* Attempt to migrate a task to a CPU on the preferred node. */
static void numa_migrate_preferred(struct task_struct *p)
{
1262 1263
	/* This task has no NUMA fault statistics yet */
	if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults))
1264 1265
		return;

1266 1267 1268 1269 1270
	/* Periodically retry migrating the task to the preferred node */
	p->numa_migrate_retry = jiffies + HZ;

	/* Success if task is already running on preferred CPU */
	if (cpu_to_node(task_cpu(p)) == p->numa_preferred_nid)
1271 1272 1273
		return;

	/* Otherwise, try migrate to a CPU on the preferred node */
1274
	task_numa_migrate(p);
1275 1276
}

1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351
/*
 * 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
 * period will be for the next scan window. If local/remote ratio is below
 * NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) the
 * scan period will decrease
 */
#define NUMA_PERIOD_SLOTS 10
#define NUMA_PERIOD_THRESHOLD 3

/*
 * 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
	 * to automatic numa balancing. Scan slower
	 */
	if (local + shared == 0) {
		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
		 */
		period_slot = DIV_ROUND_UP(diff, NUMA_PERIOD_SLOTS);
		ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared));
		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));
}

1352 1353
static void task_numa_placement(struct task_struct *p)
{
1354 1355
	int seq, nid, max_nid = -1, max_group_nid = -1;
	unsigned long max_faults = 0, max_group_faults = 0;
1356
	unsigned long fault_types[2] = { 0, 0 };
1357
	spinlock_t *group_lock = NULL;
1358

1359
	seq = ACCESS_ONCE(p->mm->numa_scan_seq);
1360 1361 1362
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
1363
	p->numa_scan_period_max = task_scan_max(p);
1364

1365 1366 1367 1368 1369 1370
	/* If the task is part of a group prevent parallel updates to group stats */
	if (p->numa_group) {
		group_lock = &p->numa_group->lock;
		spin_lock(group_lock);
	}

1371 1372
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
1373
		unsigned long faults = 0, group_faults = 0;
1374
		int priv, i;
1375

1376
		for (priv = 0; priv < 2; priv++) {
1377 1378
			long diff;

1379
			i = task_faults_idx(nid, priv);
1380
			diff = -p->numa_faults[i];
1381

1382 1383 1384
			/* Decay existing window, copy faults since last scan */
			p->numa_faults[i] >>= 1;
			p->numa_faults[i] += p->numa_faults_buffer[i];
1385
			fault_types[priv] += p->numa_faults_buffer[i];
1386
			p->numa_faults_buffer[i] = 0;
1387 1388

			faults += p->numa_faults[i];
1389
			diff += p->numa_faults[i];
1390
			p->total_numa_faults += diff;
1391 1392
			if (p->numa_group) {
				/* safe because we can only change our own group */
1393 1394 1395
				p->numa_group->faults[i] += diff;
				p->numa_group->total_faults += diff;
				group_faults += p->numa_group->faults[i];
1396
			}
1397 1398
		}

1399 1400 1401 1402
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
1403 1404 1405 1406 1407 1408 1409

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

1410 1411
	update_task_scan_period(p, fault_types[0], fault_types[1]);

1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425
	if (p->numa_group) {
		/*
		 * If the preferred task and group nids are different,
		 * iterate over the nodes again to find the best place.
		 */
		if (max_nid != max_group_nid) {
			unsigned long weight, max_weight = 0;

			for_each_online_node(nid) {
				weight = task_weight(p, nid) + group_weight(p, nid);
				if (weight > max_weight) {
					max_weight = weight;
					max_nid = nid;
				}
1426 1427
			}
		}
1428 1429

		spin_unlock(group_lock);
1430 1431
	}

1432
	/* Preferred node as the node with the most faults */
1433
	if (max_faults && max_nid != p->numa_preferred_nid) {
1434
		/* Update the preferred nid and migrate task if possible */
1435
		sched_setnuma(p, max_nid);
1436
		numa_migrate_preferred(p);
1437
	}
1438 1439
}

1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450
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);
}

1451 1452
static void task_numa_group(struct task_struct *p, int cpupid, int flags,
			int *priv)
1453 1454 1455 1456 1457 1458 1459 1460 1461
{
	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) +
1462
				    2*nr_node_ids*sizeof(unsigned long);
1463 1464 1465 1466 1467 1468 1469 1470

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

		atomic_set(&grp->refcount, 1);
		spin_lock_init(&grp->lock);
		INIT_LIST_HEAD(&grp->task_list);
1471
		grp->gid = p->pid;
1472 1473

		for (i = 0; i < 2*nr_node_ids; i++)
1474
			grp->faults[i] = p->numa_faults[i];
1475

1476
		grp->total_faults = p->total_numa_faults;
1477

1478 1479 1480 1481 1482 1483 1484 1485 1486
		list_add(&p->numa_entry, &grp->task_list);
		grp->nr_tasks++;
		rcu_assign_pointer(p->numa_group, grp);
	}

	rcu_read_lock();
	tsk = ACCESS_ONCE(cpu_rq(cpu)->curr);

	if (!cpupid_match_pid(tsk, cpupid))
1487
		goto no_join;
1488 1489 1490

	grp = rcu_dereference(tsk->numa_group);
	if (!grp)
1491
		goto no_join;
1492 1493 1494

	my_grp = p->numa_group;
	if (grp == my_grp)
1495
		goto no_join;
1496 1497 1498 1499 1500 1501

	/*
	 * 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)
1502
		goto no_join;
1503 1504 1505 1506 1507

	/*
	 * Tie-break on the grp address.
	 */
	if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp)
1508
		goto no_join;
1509

1510 1511 1512 1513 1514 1515 1516
	/* 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;
1517

1518 1519 1520
	/* Update priv based on whether false sharing was detected */
	*priv = !join;

1521
	if (join && !get_numa_group(grp))
1522
		goto no_join;
1523 1524 1525 1526 1527 1528

	rcu_read_unlock();

	if (!join)
		return;

1529 1530
	double_lock(&my_grp->lock, &grp->lock);

1531
	for (i = 0; i < 2*nr_node_ids; i++) {
1532 1533
		my_grp->faults[i] -= p->numa_faults[i];
		grp->faults[i] += p->numa_faults[i];
1534
	}
1535 1536
	my_grp->total_faults -= p->total_numa_faults;
	grp->total_faults += p->total_numa_faults;
1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547

	list_move(&p->numa_entry, &grp->task_list);
	my_grp->nr_tasks--;
	grp->nr_tasks++;

	spin_unlock(&my_grp->lock);
	spin_unlock(&grp->lock);

	rcu_assign_pointer(p->numa_group, grp);

	put_numa_group(my_grp);
1548 1549 1550 1551 1552
	return;

no_join:
	rcu_read_unlock();
	return;
1553 1554 1555 1556 1557 1558
}

void task_numa_free(struct task_struct *p)
{
	struct numa_group *grp = p->numa_group;
	int i;
1559
	void *numa_faults = p->numa_faults;
1560 1561

	if (grp) {
1562
		spin_lock(&grp->lock);
1563
		for (i = 0; i < 2*nr_node_ids; i++)
1564 1565
			grp->faults[i] -= p->numa_faults[i];
		grp->total_faults -= p->total_numa_faults;
1566

1567 1568 1569 1570 1571 1572 1573
		list_del(&p->numa_entry);
		grp->nr_tasks--;
		spin_unlock(&grp->lock);
		rcu_assign_pointer(p->numa_group, NULL);
		put_numa_group(grp);
	}

1574 1575 1576
	p->numa_faults = NULL;
	p->numa_faults_buffer = NULL;
	kfree(numa_faults);
1577 1578
}

1579 1580 1581
/*
 * Got a PROT_NONE fault for a page on @node.
 */
1582
void task_numa_fault(int last_cpupid, int node, int pages, int flags)
1583 1584
{
	struct task_struct *p = current;
1585
	bool migrated = flags & TNF_MIGRATED;
1586
	int priv;
1587

1588
	if (!numabalancing_enabled)
1589 1590
		return;

1591 1592 1593 1594
	/* for example, ksmd faulting in a user's mm */
	if (!p->mm)
		return;

1595 1596 1597 1598
	/* Do not worry about placement if exiting */
	if (p->state == TASK_DEAD)
		return;

1599 1600
	/* Allocate buffer to track faults on a per-node basis */
	if (unlikely(!p->numa_faults)) {
1601
		int size = sizeof(*p->numa_faults) * 2 * nr_node_ids;
1602

1603 1604
		/* numa_faults and numa_faults_buffer share the allocation */
		p->numa_faults = kzalloc(size * 2, GFP_KERNEL|__GFP_NOWARN);
1605 1606
		if (!p->numa_faults)
			return;
1607 1608

		BUG_ON(p->numa_faults_buffer);
1609
		p->numa_faults_buffer = p->numa_faults + (2 * nr_node_ids);
1610
		p->total_numa_faults = 0;
1611
		memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality));
1612
	}
1613

1614 1615 1616 1617 1618 1619 1620 1621
	/*
	 * 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);
1622
		if (!priv && !(flags & TNF_NO_GROUP))
1623
			task_numa_group(p, last_cpupid, flags, &priv);
1624 1625
	}

1626
	task_numa_placement(p);
1627

1628 1629 1630 1631 1632
	/*
	 * 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))
1633 1634
		numa_migrate_preferred(p);

I
Ingo Molnar 已提交
1635 1636 1637
	if (migrated)
		p->numa_pages_migrated += pages;

1638
	p->numa_faults_buffer[task_faults_idx(node, priv)] += pages;
1639
	p->numa_faults_locality[!!(flags & TNF_FAULT_LOCAL)] += pages;
1640 1641
}

1642 1643 1644 1645 1646 1647
static void reset_ptenuma_scan(struct task_struct *p)
{
	ACCESS_ONCE(p->mm->numa_scan_seq)++;
	p->mm->numa_scan_offset = 0;
}

1648 1649 1650 1651 1652 1653 1654 1655 1656
/*
 * 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;
1657
	struct vm_area_struct *vma;
1658
	unsigned long start, end;
1659
	unsigned long nr_pte_updates = 0;
1660
	long pages;
1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675

	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;

1676
	if (!mm->numa_next_scan) {
1677 1678
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
1679 1680
	}

1681 1682 1683 1684 1685 1686 1687
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

1688 1689 1690 1691
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
		p->numa_scan_period = task_scan_min(p);
	}
1692

1693
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
1694 1695 1696
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

1697 1698 1699 1700 1701 1702
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

1703 1704 1705 1706 1707
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
	if (!pages)
		return;
1708

1709
	down_read(&mm->mmap_sem);
1710
	vma = find_vma(mm, start);
1711 1712
	if (!vma) {
		reset_ptenuma_scan(p);
1713
		start = 0;
1714 1715
		vma = mm->mmap;
	}
1716
	for (; vma; vma = vma->vm_next) {
1717
		if (!vma_migratable(vma) || !vma_policy_mof(p, vma))
1718 1719
			continue;

1720 1721 1722 1723 1724 1725 1726 1727 1728 1729
		/*
		 * 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;

1730 1731 1732 1733
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
1734 1735 1736 1737 1738 1739 1740 1741 1742
			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;
1743

1744 1745 1746 1747
			start = end;
			if (pages <= 0)
				goto out;
		} while (end != vma->vm_end);
1748
	}
1749

1750
out:
1751
	/*
P
Peter Zijlstra 已提交
1752 1753 1754 1755
	 * 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.
1756 1757
	 */
	if (vma)
1758
		mm->numa_scan_offset = start;
1759 1760 1761
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787
}

/*
 * 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) {
1788
		if (!curr->node_stamp)
1789
			curr->numa_scan_period = task_scan_min(curr);
1790
		curr->node_stamp += period;
1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801

		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)
{
}
1802 1803 1804 1805 1806 1807 1808 1809

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)
{
}
1810 1811
#endif /* CONFIG_NUMA_BALANCING */

1812 1813 1814 1815
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
1816
	if (!parent_entity(se))
1817
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
1818
#ifdef CONFIG_SMP
1819 1820 1821 1822 1823 1824
	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);
	}
1825
#endif
1826 1827 1828 1829 1830 1831 1832
	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);
1833
	if (!parent_entity(se))
1834
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
1835 1836
	if (entity_is_task(se)) {
		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
1837
		list_del_init(&se->group_node);
1838
	}
1839 1840 1841
	cfs_rq->nr_running--;
}

1842 1843
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
1844 1845 1846 1847 1848 1849 1850 1851 1852
static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
{
	long tg_weight;

	/*
	 * Use this CPU's actual weight instead of the last load_contribution
	 * to gain a more accurate current total weight. See
	 * update_cfs_rq_load_contribution().
	 */
1853
	tg_weight = atomic_long_read(&tg->load_avg);
1854
	tg_weight -= cfs_rq->tg_load_contrib;
1855 1856 1857 1858 1859
	tg_weight += cfs_rq->load.weight;

	return tg_weight;
}

1860
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1861
{
1862
	long tg_weight, load, shares;
1863

1864
	tg_weight = calc_tg_weight(tg, cfs_rq);
1865
	load = cfs_rq->load.weight;
1866 1867

	shares = (tg->shares * load);
1868 1869
	if (tg_weight)
		shares /= tg_weight;
1870 1871 1872 1873 1874 1875 1876 1877 1878

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

	return shares;
}
# else /* CONFIG_SMP */
1879
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1880 1881 1882 1883
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
1884 1885 1886
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
1887 1888 1889 1890
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
1891
		account_entity_dequeue(cfs_rq, se);
1892
	}
P
Peter Zijlstra 已提交
1893 1894 1895 1896 1897 1898 1899

	update_load_set(&se->load, weight);

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

1900 1901
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

1902
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
1903 1904 1905
{
	struct task_group *tg;
	struct sched_entity *se;
1906
	long shares;
P
Peter Zijlstra 已提交
1907 1908 1909

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
1910
	if (!se || throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
1911
		return;
1912 1913 1914 1915
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
1916
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
1917 1918 1919 1920

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
1921
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
1922 1923 1924 1925
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

1926
#ifdef CONFIG_SMP
1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954
/*
 * 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 */

/* 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,
};

1955 1956 1957 1958 1959 1960
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980
	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
	 *    y^n = 1/2^(n/PERIOD) * k^(n%PERIOD)
	 * With a look-up table which covers k^n (n<PERIOD)
	 *
	 * To achieve constant time decay_load.
	 */
	if (unlikely(local_n >= LOAD_AVG_PERIOD)) {
		val >>= local_n / LOAD_AVG_PERIOD;
		local_n %= LOAD_AVG_PERIOD;
1981 1982
	}

1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
	val *= runnable_avg_yN_inv[local_n];
	/* We don't use SRR here since we always want to round down. */
	return val >> 32;
}

/*
 * 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];
2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047
}

/*
 * 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}]
 */
static __always_inline int __update_entity_runnable_avg(u64 now,
							struct sched_avg *sa,
							int runnable)
{
2048 2049
	u64 delta, periods;
	u32 runnable_contrib;
2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082
	int delta_w, decayed = 0;

	delta = now - sa->last_runnable_update;
	/*
	 * 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) {
		sa->last_runnable_update = now;
		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;
	sa->last_runnable_update = now;

	/* delta_w is the amount already accumulated against our next period */
	delta_w = sa->runnable_avg_period % 1024;
	if (delta + delta_w >= 1024) {
		/* period roll-over */
		decayed = 1;

		/*
		 * 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;
2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102
		if (runnable)
			sa->runnable_avg_sum += delta_w;
		sa->runnable_avg_period += delta_w;

		delta -= delta_w;

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

		sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum,
						  periods + 1);
		sa->runnable_avg_period = decay_load(sa->runnable_avg_period,
						     periods + 1);

		/* Efficiently calculate \sum (1..n_period) 1024*y^i */
		runnable_contrib = __compute_runnable_contrib(periods);
		if (runnable)
			sa->runnable_avg_sum += runnable_contrib;
		sa->runnable_avg_period += runnable_contrib;
2103 2104 2105 2106 2107 2108 2109 2110 2111 2112
	}

	/* Remainder of delta accrued against u_0` */
	if (runnable)
		sa->runnable_avg_sum += delta;
	sa->runnable_avg_period += delta;

	return decayed;
}

2113
/* Synchronize an entity's decay with its parenting cfs_rq.*/
2114
static inline u64 __synchronize_entity_decay(struct sched_entity *se)
2115 2116 2117 2118 2119 2120
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 decays = atomic64_read(&cfs_rq->decay_counter);

	decays -= se->avg.decay_count;
	if (!decays)
2121
		return 0;
2122 2123 2124

	se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
	se->avg.decay_count = 0;
2125 2126

	return decays;
2127 2128
}

2129 2130 2131 2132 2133
#ifdef CONFIG_FAIR_GROUP_SCHED
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
						 int force_update)
{
	struct task_group *tg = cfs_rq->tg;
2134
	long tg_contrib;
2135 2136 2137 2138

	tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg;
	tg_contrib -= cfs_rq->tg_load_contrib;

2139 2140
	if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) {
		atomic_long_add(tg_contrib, &tg->load_avg);
2141 2142 2143
		cfs_rq->tg_load_contrib += tg_contrib;
	}
}
2144

2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165
/*
 * Aggregate cfs_rq runnable averages into an equivalent task_group
 * representation for computing load contributions.
 */
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
						  struct cfs_rq *cfs_rq)
{
	struct task_group *tg = cfs_rq->tg;
	long contrib;

	/* The fraction of a cpu used by this cfs_rq */
	contrib = div_u64(sa->runnable_avg_sum << NICE_0_SHIFT,
			  sa->runnable_avg_period + 1);
	contrib -= cfs_rq->tg_runnable_contrib;

	if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) {
		atomic_add(contrib, &tg->runnable_avg);
		cfs_rq->tg_runnable_contrib += contrib;
	}
}

2166 2167 2168 2169
static inline void __update_group_entity_contrib(struct sched_entity *se)
{
	struct cfs_rq *cfs_rq = group_cfs_rq(se);
	struct task_group *tg = cfs_rq->tg;
2170 2171
	int runnable_avg;

2172 2173 2174
	u64 contrib;

	contrib = cfs_rq->tg_load_contrib * tg->shares;
2175 2176
	se->avg.load_avg_contrib = div_u64(contrib,
				     atomic_long_read(&tg->load_avg) + 1);
2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205

	/*
	 * For group entities we need to compute a correction term in the case
	 * that they are consuming <1 cpu so that we would contribute the same
	 * load as a task of equal weight.
	 *
	 * Explicitly co-ordinating this measurement would be expensive, but
	 * fortunately the sum of each cpus contribution forms a usable
	 * lower-bound on the true value.
	 *
	 * Consider the aggregate of 2 contributions.  Either they are disjoint
	 * (and the sum represents true value) or they are disjoint and we are
	 * understating by the aggregate of their overlap.
	 *
	 * Extending this to N cpus, for a given overlap, the maximum amount we
	 * understand is then n_i(n_i+1)/2 * w_i where n_i is the number of
	 * cpus that overlap for this interval and w_i is the interval width.
	 *
	 * On a small machine; the first term is well-bounded which bounds the
	 * total error since w_i is a subset of the period.  Whereas on a
	 * larger machine, while this first term can be larger, if w_i is the
	 * of consequential size guaranteed to see n_i*w_i quickly converge to
	 * our upper bound of 1-cpu.
	 */
	runnable_avg = atomic_read(&tg->runnable_avg);
	if (runnable_avg < NICE_0_LOAD) {
		se->avg.load_avg_contrib *= runnable_avg;
		se->avg.load_avg_contrib >>= NICE_0_SHIFT;
	}
2206
}
2207 2208 2209
#else
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
						 int force_update) {}
2210 2211
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
						  struct cfs_rq *cfs_rq) {}
2212
static inline void __update_group_entity_contrib(struct sched_entity *se) {}
2213 2214
#endif

2215 2216 2217 2218 2219 2220 2221 2222 2223 2224
static inline void __update_task_entity_contrib(struct sched_entity *se)
{
	u32 contrib;

	/* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
	contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight);
	contrib /= (se->avg.runnable_avg_period + 1);
	se->avg.load_avg_contrib = scale_load(contrib);
}

2225 2226 2227 2228 2229
/* Compute the current contribution to load_avg by se, return any delta */
static long __update_entity_load_avg_contrib(struct sched_entity *se)
{
	long old_contrib = se->avg.load_avg_contrib;

2230 2231 2232
	if (entity_is_task(se)) {
		__update_task_entity_contrib(se);
	} else {
2233
		__update_tg_runnable_avg(&se->avg, group_cfs_rq(se));
2234 2235
		__update_group_entity_contrib(se);
	}
2236 2237 2238 2239

	return se->avg.load_avg_contrib - old_contrib;
}

2240 2241 2242 2243 2244 2245 2246 2247 2248
static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq,
						 long load_contrib)
{
	if (likely(load_contrib < cfs_rq->blocked_load_avg))
		cfs_rq->blocked_load_avg -= load_contrib;
	else
		cfs_rq->blocked_load_avg = 0;
}

2249 2250
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);

2251
/* Update a sched_entity's runnable average */
2252 2253
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq)
2254
{
2255 2256
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	long contrib_delta;
2257
	u64 now;
2258

2259 2260 2261 2262 2263 2264 2265 2266 2267 2268
	/*
	 * For a group entity we need to use their owned cfs_rq_clock_task() in
	 * case they are the parent of a throttled hierarchy.
	 */
	if (entity_is_task(se))
		now = cfs_rq_clock_task(cfs_rq);
	else
		now = cfs_rq_clock_task(group_cfs_rq(se));

	if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq))
2269 2270 2271
		return;

	contrib_delta = __update_entity_load_avg_contrib(se);
2272 2273 2274 2275

	if (!update_cfs_rq)
		return;

2276 2277
	if (se->on_rq)
		cfs_rq->runnable_load_avg += contrib_delta;
2278 2279 2280 2281 2282 2283 2284 2285
	else
		subtract_blocked_load_contrib(cfs_rq, -contrib_delta);
}

/*
 * Decay the load contributed by all blocked children and account this so that
 * their contribution may appropriately discounted when they wake up.
 */
2286
static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
2287
{
2288
	u64 now = cfs_rq_clock_task(cfs_rq) >> 20;
2289 2290 2291
	u64 decays;

	decays = now - cfs_rq->last_decay;
2292
	if (!decays && !force_update)
2293 2294
		return;

2295 2296 2297
	if (atomic_long_read(&cfs_rq->removed_load)) {
		unsigned long removed_load;
		removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
2298 2299
		subtract_blocked_load_contrib(cfs_rq, removed_load);
	}
2300

2301 2302 2303 2304 2305 2306
	if (decays) {
		cfs_rq->blocked_load_avg = decay_load(cfs_rq->blocked_load_avg,
						      decays);
		atomic64_add(decays, &cfs_rq->decay_counter);
		cfs_rq->last_decay = now;
	}
2307 2308

	__update_cfs_rq_tg_load_contrib(cfs_rq, force_update);
2309
}
2310 2311 2312

static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
{
2313
	__update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable);
2314
	__update_tg_runnable_avg(&rq->avg, &rq->cfs);
2315
}
2316 2317 2318

/* Add the load generated by se into cfs_rq's child load-average */
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
2319 2320
						  struct sched_entity *se,
						  int wakeup)
2321
{
2322 2323 2324 2325
	/*
	 * We track migrations using entity decay_count <= 0, on a wake-up
	 * migration we use a negative decay count to track the remote decays
	 * accumulated while sleeping.
2326 2327 2328 2329
	 *
	 * Newly forked tasks are enqueued with se->avg.decay_count == 0, they
	 * are seen by enqueue_entity_load_avg() as a migration with an already
	 * constructed load_avg_contrib.
2330 2331
	 */
	if (unlikely(se->avg.decay_count <= 0)) {
2332
		se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq));
2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347
		if (se->avg.decay_count) {
			/*
			 * In a wake-up migration we have to approximate the
			 * time sleeping.  This is because we can't synchronize
			 * clock_task between the two cpus, and it is not
			 * guaranteed to be read-safe.  Instead, we can
			 * approximate this using our carried decays, which are
			 * explicitly atomically readable.
			 */
			se->avg.last_runnable_update -= (-se->avg.decay_count)
							<< 20;
			update_entity_load_avg(se, 0);
			/* Indicate that we're now synchronized and on-rq */
			se->avg.decay_count = 0;
		}
2348 2349
		wakeup = 0;
	} else {
2350 2351 2352 2353 2354 2355 2356
		/*
		 * Task re-woke on same cpu (or else migrate_task_rq_fair()
		 * would have made count negative); we must be careful to avoid
		 * double-accounting blocked time after synchronizing decays.
		 */
		se->avg.last_runnable_update += __synchronize_entity_decay(se)
							<< 20;
2357 2358
	}

2359 2360
	/* migrated tasks did not contribute to our blocked load */
	if (wakeup) {
2361
		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
2362 2363
		update_entity_load_avg(se, 0);
	}
2364

2365
	cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
2366 2367
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !wakeup);
2368 2369
}

2370 2371 2372 2373 2374
/*
 * Remove se's load from this cfs_rq child load-average, if the entity is
 * transitioning to a blocked state we track its projected decay using
 * blocked_load_avg.
 */
2375
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
2376 2377
						  struct sched_entity *se,
						  int sleep)
2378
{
2379
	update_entity_load_avg(se, 1);
2380 2381
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !sleep);
2382

2383
	cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
2384 2385 2386 2387
	if (sleep) {
		cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
		se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
	} /* migrations, e.g. sleep=0 leave decay_count == 0 */
2388
}
2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409

/*
 * 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_rq_runnable_avg(this_rq, 1);
}

/*
 * 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)
{
	update_rq_runnable_avg(this_rq, 0);
}

2410
#else
2411 2412
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq) {}
2413
static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
2414
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
2415 2416
					   struct sched_entity *se,
					   int wakeup) {}
2417
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
2418 2419
					   struct sched_entity *se,
					   int sleep) {}
2420 2421
static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
					      int force_update) {}
2422 2423
#endif

2424
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
2425 2426
{
#ifdef CONFIG_SCHEDSTATS
2427 2428 2429 2430 2431
	struct task_struct *tsk = NULL;

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

2432
	if (se->statistics.sleep_start) {
2433
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
2434 2435 2436 2437

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

2438 2439
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
2440

2441
		se->statistics.sleep_start = 0;
2442
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
2443

2444
		if (tsk) {
2445
			account_scheduler_latency(tsk, delta >> 10, 1);
2446 2447
			trace_sched_stat_sleep(tsk, delta);
		}
2448
	}
2449
	if (se->statistics.block_start) {
2450
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
2451 2452 2453 2454

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

2455 2456
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
2457

2458
		se->statistics.block_start = 0;
2459
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
2460

2461
		if (tsk) {
2462
			if (tsk->in_iowait) {
2463 2464
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
2465
				trace_sched_stat_iowait(tsk, delta);
2466 2467
			}

2468 2469
			trace_sched_stat_blocked(tsk, delta);

2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480
			/*
			 * 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
2481
		}
2482 2483 2484 2485
	}
#endif
}

P
Peter Zijlstra 已提交
2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498
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
}

2499 2500 2501
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
2502
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
2503

2504 2505 2506 2507 2508 2509
	/*
	 * 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
2510
	if (initial && sched_feat(START_DEBIT))
2511
		vruntime += sched_vslice(cfs_rq, se);
2512

2513
	/* sleeps up to a single latency don't count. */
2514
	if (!initial) {
2515
		unsigned long thresh = sysctl_sched_latency;
2516

2517 2518 2519 2520 2521 2522
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
2523

2524
		vruntime -= thresh;
2525 2526
	}

2527
	/* ensure we never gain time by being placed backwards. */
2528
	se->vruntime = max_vruntime(se->vruntime, vruntime);
2529 2530
}

2531 2532
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

2533
static void
2534
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2535
{
2536 2537
	/*
	 * Update the normalized vruntime before updating min_vruntime
2538
	 * through calling update_curr().
2539
	 */
2540
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
2541 2542
		se->vruntime += cfs_rq->min_vruntime;

2543
	/*
2544
	 * Update run-time statistics of the 'current'.
2545
	 */
2546
	update_curr(cfs_rq);
2547
	enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
2548 2549
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
2550

2551
	if (flags & ENQUEUE_WAKEUP) {
2552
		place_entity(cfs_rq, se, 0);
2553
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
2554
	}
2555

2556
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
2557
	check_spread(cfs_rq, se);
2558 2559
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
2560
	se->on_rq = 1;
2561

2562
	if (cfs_rq->nr_running == 1) {
2563
		list_add_leaf_cfs_rq(cfs_rq);
2564 2565
		check_enqueue_throttle(cfs_rq);
	}
2566 2567
}

2568
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
2569
{
2570 2571 2572 2573 2574 2575 2576 2577
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
		if (cfs_rq->last == se)
			cfs_rq->last = NULL;
		else
			break;
	}
}
P
Peter Zijlstra 已提交
2578

2579 2580 2581 2582 2583 2584 2585 2586 2587
static void __clear_buddies_next(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
		if (cfs_rq->next == se)
			cfs_rq->next = NULL;
		else
			break;
	}
P
Peter Zijlstra 已提交
2588 2589
}

2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
		if (cfs_rq->skip == se)
			cfs_rq->skip = NULL;
		else
			break;
	}
}

P
Peter Zijlstra 已提交
2601 2602
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2603 2604 2605 2606 2607
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
2608 2609 2610

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
2611 2612
}

2613
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
2614

2615
static void
2616
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2617
{
2618 2619 2620 2621
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
2622
	dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);
2623

2624
	update_stats_dequeue(cfs_rq, se);
2625
	if (flags & DEQUEUE_SLEEP) {
P
Peter Zijlstra 已提交
2626
#ifdef CONFIG_SCHEDSTATS
2627 2628 2629 2630
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
2631
				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
2632
			if (tsk->state & TASK_UNINTERRUPTIBLE)
2633
				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
2634
		}
2635
#endif
P
Peter Zijlstra 已提交
2636 2637
	}

P
Peter Zijlstra 已提交
2638
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
2639

2640
	if (se != cfs_rq->curr)
2641
		__dequeue_entity(cfs_rq, se);
2642
	se->on_rq = 0;
2643
	account_entity_dequeue(cfs_rq, se);
2644 2645 2646 2647 2648 2649

	/*
	 * 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.
	 */
2650
	if (!(flags & DEQUEUE_SLEEP))
2651
		se->vruntime -= cfs_rq->min_vruntime;
2652

2653 2654 2655
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

2656
	update_min_vruntime(cfs_rq);
2657
	update_cfs_shares(cfs_rq);
2658 2659 2660 2661 2662
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
2663
static void
I
Ingo Molnar 已提交
2664
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
2665
{
2666
	unsigned long ideal_runtime, delta_exec;
2667 2668
	struct sched_entity *se;
	s64 delta;
2669

P
Peter Zijlstra 已提交
2670
	ideal_runtime = sched_slice(cfs_rq, curr);
2671
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
2672
	if (delta_exec > ideal_runtime) {
2673
		resched_task(rq_of(cfs_rq)->curr);
2674 2675 2676 2677 2678
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689
		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;

2690 2691
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
2692

2693 2694
	if (delta < 0)
		return;
2695

2696 2697
	if (delta > ideal_runtime)
		resched_task(rq_of(cfs_rq)->curr);
2698 2699
}

2700
static void
2701
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
2702
{
2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713
	/* '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);
	}

2714
	update_stats_curr_start(cfs_rq, se);
2715
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
2716 2717 2718 2719 2720 2721
#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):
	 */
2722
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
2723
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
2724 2725 2726
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
2727
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
2728 2729
}

2730 2731 2732
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

2733 2734 2735 2736 2737 2738 2739
/*
 * 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
 */
2740
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
2741
{
2742
	struct sched_entity *se = __pick_first_entity(cfs_rq);
2743
	struct sched_entity *left = se;
2744

2745 2746 2747 2748 2749 2750 2751 2752 2753
	/*
	 * Avoid running the skip buddy, if running something else can
	 * be done without getting too unfair.
	 */
	if (cfs_rq->skip == se) {
		struct sched_entity *second = __pick_next_entity(se);
		if (second && wakeup_preempt_entity(second, left) < 1)
			se = second;
	}
2754

2755 2756 2757 2758 2759 2760
	/*
	 * 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;

2761 2762 2763 2764 2765 2766
	/*
	 * 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;

2767
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
2768 2769

	return se;
2770 2771
}

2772 2773
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq);

2774
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
2775 2776 2777 2778 2779 2780
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
2781
		update_curr(cfs_rq);
2782

2783 2784 2785
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

P
Peter Zijlstra 已提交
2786
	check_spread(cfs_rq, prev);
2787
	if (prev->on_rq) {
2788
		update_stats_wait_start(cfs_rq, prev);
2789 2790
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
2791
		/* in !on_rq case, update occurred at dequeue */
2792
		update_entity_load_avg(prev, 1);
2793
	}
2794
	cfs_rq->curr = NULL;
2795 2796
}

P
Peter Zijlstra 已提交
2797 2798
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
2799 2800
{
	/*
2801
	 * Update run-time statistics of the 'current'.
2802
	 */
2803
	update_curr(cfs_rq);
2804

2805 2806 2807
	/*
	 * Ensure that runnable average is periodically updated.
	 */
2808
	update_entity_load_avg(curr, 1);
2809
	update_cfs_rq_blocked_load(cfs_rq, 1);
2810
	update_cfs_shares(cfs_rq);
2811

P
Peter Zijlstra 已提交
2812 2813 2814 2815 2816
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
2817 2818 2819 2820
	if (queued) {
		resched_task(rq_of(cfs_rq)->curr);
		return;
	}
P
Peter Zijlstra 已提交
2821 2822 2823 2824 2825 2826 2827 2828
	/*
	 * 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
2829
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
2830
		check_preempt_tick(cfs_rq, curr);
2831 2832
}

2833 2834 2835 2836 2837 2838

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

#ifdef CONFIG_CFS_BANDWIDTH
2839 2840

#ifdef HAVE_JUMP_LABEL
2841
static struct static_key __cfs_bandwidth_used;
2842 2843 2844

static inline bool cfs_bandwidth_used(void)
{
2845
	return static_key_false(&__cfs_bandwidth_used);
2846 2847
}

2848
void cfs_bandwidth_usage_inc(void)
2849
{
2850 2851 2852 2853 2854 2855
	static_key_slow_inc(&__cfs_bandwidth_used);
}

void cfs_bandwidth_usage_dec(void)
{
	static_key_slow_dec(&__cfs_bandwidth_used);
2856 2857 2858 2859 2860 2861 2862
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

2863 2864
void cfs_bandwidth_usage_inc(void) {}
void cfs_bandwidth_usage_dec(void) {}
2865 2866
#endif /* HAVE_JUMP_LABEL */

2867 2868 2869 2870 2871 2872 2873 2874
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
2875 2876 2877 2878 2879 2880

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

P
Paul Turner 已提交
2881 2882 2883 2884 2885 2886 2887
/*
 * 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
 */
2888
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899
{
	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);
}

2900 2901 2902 2903 2904
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

2905 2906 2907 2908 2909 2910
/* 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;

2911
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
2912 2913
}

2914 2915
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2916 2917 2918
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
2919
	u64 amount = 0, min_amount, expires;
2920 2921 2922 2923 2924 2925 2926

	/* 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;
2927
	else {
P
Paul Turner 已提交
2928 2929 2930 2931 2932 2933 2934 2935
		/*
		 * If the bandwidth pool has become inactive, then at least one
		 * period must have elapsed since the last consumption.
		 * Refresh the global state and ensure bandwidth timer becomes
		 * active.
		 */
		if (!cfs_b->timer_active) {
			__refill_cfs_bandwidth_runtime(cfs_b);
2936
			__start_cfs_bandwidth(cfs_b);
P
Paul Turner 已提交
2937
		}
2938 2939 2940 2941 2942 2943

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
2944
	}
P
Paul Turner 已提交
2945
	expires = cfs_b->runtime_expires;
2946 2947 2948
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
2949 2950 2951 2952 2953 2954 2955
	/*
	 * 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;
2956 2957

	return cfs_rq->runtime_remaining > 0;
2958 2959
}

P
Paul Turner 已提交
2960 2961 2962 2963 2964
/*
 * 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)
2965
{
P
Paul Turner 已提交
2966 2967 2968
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
2969
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
2970 2971
		return;

P
Paul Turner 已提交
2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996
	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
	 * whether the global deadline has advanced.
	 */

	if ((s64)(cfs_rq->runtime_expires - cfs_b->runtime_expires) >= 0) {
		/* 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;
	}
}

static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
				     unsigned long delta_exec)
{
	/* dock delta_exec before expiring quota (as it could span periods) */
2997
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
2998 2999 3000
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
3001 3002
		return;

3003 3004 3005 3006 3007 3008
	/*
	 * 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))
		resched_task(rq_of(cfs_rq)->curr);
3009 3010
}

3011 3012
static __always_inline
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec)
3013
{
3014
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
3015 3016 3017 3018 3019
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

3020 3021
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
3022
	return cfs_bandwidth_used() && cfs_rq->throttled;
3023 3024
}

3025 3026 3027
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
3028
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056
}

/*
 * 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) {
3057
		/* adjust cfs_rq_clock_task() */
3058
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
3059
					     cfs_rq->throttled_clock_task;
3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070
	}
#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)];

3071 3072
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
3073
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
3074 3075 3076 3077 3078
	cfs_rq->throttle_count++;

	return 0;
}

3079
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
3080 3081 3082 3083 3084 3085 3086 3087
{
	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;

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

3088
	/* freeze hierarchy runnable averages while throttled */
3089 3090 3091
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111

	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)
		rq->nr_running -= task_delta;

	cfs_rq->throttled = 1;
3112
	cfs_rq->throttled_clock = rq_clock(rq);
3113 3114 3115 3116 3117
	raw_spin_lock(&cfs_b->lock);
	list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);
	raw_spin_unlock(&cfs_b->lock);
}

3118
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
3119 3120 3121 3122 3123 3124 3125
{
	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;

3126
	se = cfs_rq->tg->se[cpu_of(rq)];
3127 3128

	cfs_rq->throttled = 0;
3129 3130 3131

	update_rq_clock(rq);

3132
	raw_spin_lock(&cfs_b->lock);
3133
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
3134 3135 3136
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

3137 3138 3139
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202
	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)
		rq->nr_running += task_delta;

	/* determine whether we need to wake up potentially idle cpu */
	if (rq->curr == rq->idle && rq->cfs.nr_running)
		resched_task(rq->curr);
}

static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
		u64 remaining, u64 expires)
{
	struct cfs_rq *cfs_rq;
	u64 runtime = remaining;

	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();

	return remaining;
}

3203 3204 3205 3206 3207 3208 3209 3210
/*
 * 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)
{
3211 3212
	u64 runtime, runtime_expires;
	int idle = 1, throttled;
3213 3214 3215 3216 3217 3218

	raw_spin_lock(&cfs_b->lock);
	/* no need to continue the timer with no bandwidth constraint */
	if (cfs_b->quota == RUNTIME_INF)
		goto out_unlock;

3219 3220 3221
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
	/* idle depends on !throttled (for the case of a large deficit) */
	idle = cfs_b->idle && !throttled;
3222
	cfs_b->nr_periods += overrun;
3223

P
Paul Turner 已提交
3224 3225 3226 3227
	/* if we're going inactive then everything else can be deferred */
	if (idle)
		goto out_unlock;

3228 3229 3230 3231 3232 3233 3234
	/*
	 * if we have relooped after returning idle once, we need to update our
	 * status as actually running, so that other cpus doing
	 * __start_cfs_bandwidth will stop trying to cancel us.
	 */
	cfs_b->timer_active = 1;

P
Paul Turner 已提交
3235 3236
	__refill_cfs_bandwidth_runtime(cfs_b);

3237 3238 3239 3240 3241 3242
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
		goto out_unlock;
	}

3243 3244 3245
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269
	/*
	 * There are throttled entities so we must first use the new bandwidth
	 * to unthrottle them before making it generally available.  This
	 * ensures that all existing debts will be paid before a new cfs_rq is
	 * allowed to run.
	 */
	runtime = cfs_b->runtime;
	runtime_expires = cfs_b->runtime_expires;
	cfs_b->runtime = 0;

	/*
	 * 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.
	 */
	while (throttled && runtime > 0) {
		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);
	}
3270

3271 3272 3273 3274 3275 3276 3277 3278 3279
	/* return (any) remaining runtime */
	cfs_b->runtime = runtime;
	/*
	 * 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;
3280 3281 3282 3283 3284 3285 3286
out_unlock:
	if (idle)
		cfs_b->timer_active = 0;
	raw_spin_unlock(&cfs_b->lock);

	return idle;
}
3287

3288 3289 3290 3291 3292 3293 3294
/* 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;

3295 3296 3297 3298 3299 3300 3301
/*
 * Are we near the end of the current quota period?
 *
 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
 * hrtimer base being cleared by __hrtimer_start_range_ns. In the case of
 * migrate_hrtimers, base is never cleared, so we are fine.
 */
3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357
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;

	start_bandwidth_timer(&cfs_b->slack_timer,
				ns_to_ktime(cfs_bandwidth_slack_period));
}

/* 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)
{
3358 3359 3360
	if (!cfs_bandwidth_used())
		return;

3361
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376
		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 */
3377 3378 3379
	raw_spin_lock(&cfs_b->lock);
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
		raw_spin_unlock(&cfs_b->lock);
3380
		return;
3381
	}
3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400

	if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
		runtime = cfs_b->runtime;
		cfs_b->runtime = 0;
	}
	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)
		cfs_b->runtime = runtime;
	raw_spin_unlock(&cfs_b->lock);
}

3401 3402 3403 3404 3405 3406 3407
/*
 * 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)
{
3408 3409 3410
	if (!cfs_bandwidth_used())
		return;

3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427
	/* 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() */
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq)
{
3428 3429 3430
	if (!cfs_bandwidth_used())
		return;

3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442
	if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0))
		return;

	/*
	 * 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))
		return;

	throttle_cfs_rq(cfs_rq);
}
3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 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 3494 3495 3496 3497 3498 3499 3500 3501 3502

static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer)
{
	struct cfs_bandwidth *cfs_b =
		container_of(timer, struct cfs_bandwidth, slack_timer);
	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);
	ktime_t now;
	int overrun;
	int idle = 0;

	for (;;) {
		now = hrtimer_cb_get_time(timer);
		overrun = hrtimer_forward(timer, now, cfs_b->period);

		if (!overrun)
			break;

		idle = do_sched_cfs_period_timer(cfs_b, overrun);
	}

	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);
	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	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);
}

/* requires cfs_b->lock, may release to reprogram timer */
void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
	/*
	 * The timer may be active because we're trying to set a new bandwidth
	 * period or because we're racing with the tear-down path
	 * (timer_active==0 becomes visible before the hrtimer call-back
	 * terminates).  In either case we ensure that it's re-programmed
	 */
3503 3504 3505
	while (unlikely(hrtimer_active(&cfs_b->period_timer)) &&
	       hrtimer_try_to_cancel(&cfs_b->period_timer) < 0) {
		/* bounce the lock to allow do_sched_cfs_period_timer to run */
3506
		raw_spin_unlock(&cfs_b->lock);
3507
		cpu_relax();
3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523
		raw_spin_lock(&cfs_b->lock);
		/* if someone else restarted the timer then we're done */
		if (cfs_b->timer_active)
			return;
	}

	cfs_b->timer_active = 1;
	start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period);
}

static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
{
	hrtimer_cancel(&cfs_b->period_timer);
	hrtimer_cancel(&cfs_b->slack_timer);
}

3524
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
3525 3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544
{
	struct cfs_rq *cfs_rq;

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

		if (!cfs_rq->runtime_enabled)
			continue;

		/*
		 * clock_task is not advancing so we just need to make sure
		 * there's some valid quota amount
		 */
		cfs_rq->runtime_remaining = cfs_b->quota;
		if (cfs_rq_throttled(cfs_rq))
			unthrottle_cfs_rq(cfs_rq);
	}
}

#else /* CONFIG_CFS_BANDWIDTH */
3545 3546
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
3547
	return rq_clock_task(rq_of(cfs_rq));
3548 3549 3550 3551
}

static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
				     unsigned long delta_exec) {}
3552 3553
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
3554
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
3555 3556 3557 3558 3559

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570

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;
}
3571 3572 3573 3574 3575

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) {}
3576 3577
#endif

3578 3579 3580 3581 3582
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) {}
3583
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
3584 3585 3586

#endif /* CONFIG_CFS_BANDWIDTH */

3587 3588 3589 3590
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
3591 3592 3593 3594 3595 3596 3597 3598
#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);

3599
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613
		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)
				resched_task(p);
			return;
		}

		/*
		 * Don't schedule slices shorter than 10000ns, that just
		 * doesn't make sense. Rely on vruntime for fairness.
		 */
3614
		if (rq->curr != p)
3615
			delta = max_t(s64, 10000LL, delta);
P
Peter Zijlstra 已提交
3616

3617
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
3618 3619
	}
}
3620 3621 3622 3623 3624 3625 3626 3627 3628 3629

/*
 * 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;

3630
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
3631 3632 3633 3634 3635
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
3636
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
3637 3638 3639 3640
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
3641 3642 3643 3644

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
3645 3646
#endif

3647 3648 3649 3650 3651
/*
 * 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:
 */
3652
static void
3653
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
3654 3655
{
	struct cfs_rq *cfs_rq;
3656
	struct sched_entity *se = &p->se;
3657 3658

	for_each_sched_entity(se) {
3659
		if (se->on_rq)
3660 3661
			break;
		cfs_rq = cfs_rq_of(se);
3662
		enqueue_entity(cfs_rq, se, flags);
3663 3664 3665 3666 3667 3668 3669 3670 3671

		/*
		 * 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;
3672
		cfs_rq->h_nr_running++;
3673

3674
		flags = ENQUEUE_WAKEUP;
3675
	}
P
Peter Zijlstra 已提交
3676

P
Peter Zijlstra 已提交
3677
	for_each_sched_entity(se) {
3678
		cfs_rq = cfs_rq_of(se);
3679
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
3680

3681 3682 3683
		if (cfs_rq_throttled(cfs_rq))
			break;

3684
		update_cfs_shares(cfs_rq);
3685
		update_entity_load_avg(se, 1);
P
Peter Zijlstra 已提交
3686 3687
	}

3688 3689
	if (!se) {
		update_rq_runnable_avg(rq, rq->nr_running);
3690
		inc_nr_running(rq);
3691
	}
3692
	hrtick_update(rq);
3693 3694
}

3695 3696
static void set_next_buddy(struct sched_entity *se);

3697 3698 3699 3700 3701
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
3702
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
3703 3704
{
	struct cfs_rq *cfs_rq;
3705
	struct sched_entity *se = &p->se;
3706
	int task_sleep = flags & DEQUEUE_SLEEP;
3707 3708 3709

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
3710
		dequeue_entity(cfs_rq, se, flags);
3711 3712 3713 3714 3715 3716 3717 3718 3719

		/*
		 * 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;
3720
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
3721

3722
		/* Don't dequeue parent if it has other entities besides us */
3723 3724 3725 3726 3727 3728 3729
		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));
3730 3731 3732

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
3733
			break;
3734
		}
3735
		flags |= DEQUEUE_SLEEP;
3736
	}
P
Peter Zijlstra 已提交
3737

P
Peter Zijlstra 已提交
3738
	for_each_sched_entity(se) {
3739
		cfs_rq = cfs_rq_of(se);
3740
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
3741

3742 3743 3744
		if (cfs_rq_throttled(cfs_rq))
			break;

3745
		update_cfs_shares(cfs_rq);
3746
		update_entity_load_avg(se, 1);
P
Peter Zijlstra 已提交
3747 3748
	}

3749
	if (!se) {
3750
		dec_nr_running(rq);
3751 3752
		update_rq_runnable_avg(rq, 1);
	}
3753
	hrtick_update(rq);
3754 3755
}

3756
#ifdef CONFIG_SMP
3757 3758 3759
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
3760
	return cpu_rq(cpu)->cfs.runnable_load_avg;
3761 3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804
}

/*
 * 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);
}

static unsigned long power_of(int cpu)
{
	return cpu_rq(cpu)->cpu_power;
}

static unsigned long cpu_avg_load_per_task(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
	unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
3805
	unsigned long load_avg = rq->cfs.runnable_load_avg;
3806 3807

	if (nr_running)
3808
		return load_avg / nr_running;
3809 3810 3811 3812

	return 0;
}

3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829
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.
	 */
	if (jiffies > current->wakee_flip_decay_ts + HZ) {
		current->wakee_flips = 0;
		current->wakee_flip_decay_ts = jiffies;
	}

	if (current->last_wakee != p) {
		current->last_wakee = p;
		current->wakee_flips++;
	}
}
3830

3831
static void task_waking_fair(struct task_struct *p)
3832 3833 3834
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
3835 3836 3837 3838
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
3839

3840 3841 3842 3843 3844 3845 3846 3847
	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
3848

3849
	se->vruntime -= min_vruntime;
3850
	record_wakee(p);
3851 3852
}

3853
#ifdef CONFIG_FAIR_GROUP_SCHED
3854 3855 3856 3857 3858 3859
/*
 * 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.
3860 3861 3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902
 *
 * 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.
3903
 */
P
Peter Zijlstra 已提交
3904
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
3905
{
P
Peter Zijlstra 已提交
3906
	struct sched_entity *se = tg->se[cpu];
3907

3908
	if (!tg->parent || !wl)	/* the trivial, non-cgroup case */
3909 3910
		return wl;

P
Peter Zijlstra 已提交
3911
	for_each_sched_entity(se) {
3912
		long w, W;
P
Peter Zijlstra 已提交
3913

3914
		tg = se->my_q->tg;
3915

3916 3917 3918 3919
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
3920

3921 3922 3923 3924
		/*
		 * w = rw_i + @wl
		 */
		w = se->my_q->load.weight + wl;
3925

3926 3927 3928 3929 3930
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
			wl = (w * tg->shares) / W;
3931 3932
		else
			wl = tg->shares;
3933

3934 3935 3936 3937 3938
		/*
		 * 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().
		 */
3939 3940
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
3941 3942 3943 3944

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
3945
		wl -= se->load.weight;
3946 3947 3948 3949 3950 3951 3952 3953

		/*
		 * 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
3954 3955
		wg = 0;
	}
3956

P
Peter Zijlstra 已提交
3957
	return wl;
3958 3959
}
#else
P
Peter Zijlstra 已提交
3960

3961
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
P
Peter Zijlstra 已提交
3962
{
3963
	return wl;
3964
}
P
Peter Zijlstra 已提交
3965

3966 3967
#endif

3968 3969
static int wake_wide(struct task_struct *p)
{
3970
	int factor = this_cpu_read(sd_llc_size);
3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989

	/*
	 * Yeah, it's the switching-frequency, could means many wakee or
	 * rapidly switch, use factor here will just help to automatically
	 * adjust the loose-degree, so bigger node will lead to more pull.
	 */
	if (p->wakee_flips > factor) {
		/*
		 * wakee is somewhat hot, it needs certain amount of cpu
		 * resource, so if waker is far more hot, prefer to leave
		 * it alone.
		 */
		if (current->wakee_flips > (factor * p->wakee_flips))
			return 1;
	}

	return 0;
}

3990
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
3991
{
3992
	s64 this_load, load;
3993
	int idx, this_cpu, prev_cpu;
3994
	unsigned long tl_per_task;
3995
	struct task_group *tg;
3996
	unsigned long weight;
3997
	int balanced;
3998

3999 4000 4001 4002 4003 4004 4005
	/*
	 * If we wake multiple tasks be careful to not bounce
	 * ourselves around too much.
	 */
	if (wake_wide(p))
		return 0;

4006 4007 4008 4009 4010
	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);
4011

4012 4013 4014 4015 4016
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
4017 4018 4019 4020
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

4021
		this_load += effective_load(tg, this_cpu, -weight, -weight);
4022 4023
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
4024

4025 4026
	tg = task_group(p);
	weight = p->se.load.weight;
4027

4028 4029
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
4030 4031 4032
	 * 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.
4033 4034 4035 4036
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
4037 4038
	if (this_load > 0) {
		s64 this_eff_load, prev_eff_load;
4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051

		this_eff_load = 100;
		this_eff_load *= power_of(prev_cpu);
		this_eff_load *= this_load +
			effective_load(tg, this_cpu, weight, weight);

		prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
		prev_eff_load *= power_of(this_cpu);
		prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);

		balanced = this_eff_load <= prev_eff_load;
	} else
		balanced = true;
4052

4053
	/*
I
Ingo Molnar 已提交
4054 4055 4056
	 * If the currently running task will sleep within
	 * a reasonable amount of time then attract this newly
	 * woken task:
4057
	 */
4058 4059
	if (sync && balanced)
		return 1;
4060

4061
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
4062 4063
	tl_per_task = cpu_avg_load_per_task(this_cpu);

4064 4065 4066
	if (balanced ||
	    (this_load <= load &&
	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
4067 4068 4069 4070 4071
		/*
		 * This domain has SD_WAKE_AFFINE and
		 * p is cache cold in this domain, and
		 * there is no bad imbalance.
		 */
4072
		schedstat_inc(sd, ttwu_move_affine);
4073
		schedstat_inc(p, se.statistics.nr_wakeups_affine);
4074 4075 4076 4077 4078 4079

		return 1;
	}
	return 0;
}

4080 4081 4082 4083 4084
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
4085
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
4086
		  int this_cpu, int load_idx)
4087
{
4088
	struct sched_group *idlest = NULL, *group = sd->groups;
4089 4090
	unsigned long min_load = ULONG_MAX, this_load = 0;
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
4091

4092 4093 4094 4095
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
4096

4097 4098
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
4099
					tsk_cpus_allowed(p)))
4100 4101 4102 4103 4104 4105 4106 4107 4108 4109 4110 4111 4112 4113 4114 4115 4116 4117 4118
			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;
		}

		/* Adjust by relative CPU power of the group */
4119
		avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;
4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144

		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;
	int idlest = -1;
	int i;

	/* Traverse only the allowed CPUs */
4145
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
4146 4147 4148 4149 4150
		load = weighted_cpuload(i);

		if (load < min_load || (load == min_load && i == this_cpu)) {
			min_load = load;
			idlest = i;
4151 4152 4153
		}
	}

4154 4155
	return idlest;
}
4156

4157 4158 4159
/*
 * Try and locate an idle CPU in the sched_domain.
 */
4160
static int select_idle_sibling(struct task_struct *p, int target)
4161
{
4162
	struct sched_domain *sd;
4163
	struct sched_group *sg;
4164
	int i = task_cpu(p);
4165

4166 4167
	if (idle_cpu(target))
		return target;
4168 4169

	/*
4170
	 * If the prevous cpu is cache affine and idle, don't be stupid.
4171
	 */
4172 4173
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
4174 4175

	/*
4176
	 * Otherwise, iterate the domains and find an elegible idle cpu.
4177
	 */
4178
	sd = rcu_dereference(per_cpu(sd_llc, target));
4179
	for_each_lower_domain(sd) {
4180 4181 4182 4183 4184 4185 4186
		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)) {
4187
				if (i == target || !idle_cpu(i))
4188 4189
					goto next;
			}
4190

4191 4192 4193 4194 4195 4196 4197 4198
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
4199 4200 4201
	return target;
}

4202 4203 4204 4205 4206 4207 4208 4209 4210 4211 4212
/*
 * sched_balance_self: balance the current task (running on cpu) in domains
 * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
 * SD_BALANCE_EXEC.
 *
 * Balance, ie. select the least loaded group.
 *
 * Returns the target CPU number, or the same CPU if no balancing is needed.
 *
 * preempt must be disabled.
 */
4213
static int
4214
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
4215
{
4216
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
4217 4218
	int cpu = smp_processor_id();
	int new_cpu = cpu;
4219
	int want_affine = 0;
4220
	int sync = wake_flags & WF_SYNC;
4221

4222
	if (p->nr_cpus_allowed == 1)
4223 4224
		return prev_cpu;

4225
	if (sd_flag & SD_BALANCE_WAKE) {
4226
		if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
4227 4228 4229
			want_affine = 1;
		new_cpu = prev_cpu;
	}
4230

4231
	rcu_read_lock();
4232
	for_each_domain(cpu, tmp) {
4233 4234 4235
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

4236
		/*
4237 4238
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
4239
		 */
4240 4241 4242
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
4243
			break;
4244
		}
4245

4246
		if (tmp->flags & sd_flag)
4247 4248 4249
			sd = tmp;
	}

4250
	if (affine_sd) {
4251
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
4252 4253 4254 4255
			prev_cpu = cpu;

		new_cpu = select_idle_sibling(p, prev_cpu);
		goto unlock;
4256
	}
4257

4258
	while (sd) {
4259
		int load_idx = sd->forkexec_idx;
4260
		struct sched_group *group;
4261
		int weight;
4262

4263
		if (!(sd->flags & sd_flag)) {
4264 4265 4266
			sd = sd->child;
			continue;
		}
4267

4268 4269
		if (sd_flag & SD_BALANCE_WAKE)
			load_idx = sd->wake_idx;
4270

4271
		group = find_idlest_group(sd, p, cpu, load_idx);
4272 4273 4274 4275
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
4276

4277
		new_cpu = find_idlest_cpu(group, p, cpu);
4278 4279 4280 4281
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
4282
		}
4283 4284 4285

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
4286
		weight = sd->span_weight;
4287 4288
		sd = NULL;
		for_each_domain(cpu, tmp) {
4289
			if (weight <= tmp->span_weight)
4290
				break;
4291
			if (tmp->flags & sd_flag)
4292 4293 4294
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
4295
	}
4296 4297
unlock:
	rcu_read_unlock();
4298

4299
	return new_cpu;
4300
}
4301 4302 4303 4304 4305 4306 4307 4308 4309 4310

/*
 * 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.
 */
static void
migrate_task_rq_fair(struct task_struct *p, int next_cpu)
{
4311 4312 4313 4314 4315 4316 4317 4318 4319 4320 4321
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	/*
	 * Load tracking: accumulate removed load so that it can be processed
	 * when we next update owning cfs_rq under rq->lock.  Tasks contribute
	 * to blocked load iff they have a positive decay-count.  It can never
	 * be negative here since on-rq tasks have decay-count == 0.
	 */
	if (se->avg.decay_count) {
		se->avg.decay_count = -__synchronize_entity_decay(se);
4322 4323
		atomic_long_add(se->avg.load_avg_contrib,
						&cfs_rq->removed_load);
4324
	}
4325
}
4326 4327
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
4328 4329
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
4330 4331 4332 4333
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
4334 4335
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
4336 4337 4338 4339 4340 4341 4342 4343 4344
	 *
	 * 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.
4345
	 */
4346
	return calc_delta_fair(gran, se);
4347 4348
}

4349 4350 4351 4352 4353 4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370
/*
 * 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
4371
	gran = wakeup_gran(curr, se);
4372 4373 4374 4375 4376 4377
	if (vdiff > gran)
		return 1;

	return 0;
}

4378 4379
static void set_last_buddy(struct sched_entity *se)
{
4380 4381 4382 4383 4384
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
4385 4386 4387 4388
}

static void set_next_buddy(struct sched_entity *se)
{
4389 4390 4391 4392 4393
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
4394 4395
}

4396 4397
static void set_skip_buddy(struct sched_entity *se)
{
4398 4399
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
4400 4401
}

4402 4403 4404
/*
 * Preempt the current task with a newly woken task if needed:
 */
4405
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
4406 4407
{
	struct task_struct *curr = rq->curr;
4408
	struct sched_entity *se = &curr->se, *pse = &p->se;
4409
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
4410
	int scale = cfs_rq->nr_running >= sched_nr_latency;
4411
	int next_buddy_marked = 0;
4412

I
Ingo Molnar 已提交
4413 4414 4415
	if (unlikely(se == pse))
		return;

4416
	/*
4417
	 * This is possible from callers such as move_task(), in which we
4418 4419 4420 4421 4422 4423 4424
	 * 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;

4425
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
4426
		set_next_buddy(pse);
4427 4428
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
4429

4430 4431 4432
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
4433 4434 4435 4436 4437 4438
	 *
	 * 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.
4439 4440 4441 4442
	 */
	if (test_tsk_need_resched(curr))
		return;

4443 4444 4445 4446 4447
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

4448
	/*
4449 4450
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
4451
	 */
4452
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
4453
		return;
4454

4455
	find_matching_se(&se, &pse);
4456
	update_curr(cfs_rq_of(se));
4457
	BUG_ON(!pse);
4458 4459 4460 4461 4462 4463 4464
	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);
4465
		goto preempt;
4466
	}
4467

4468
	return;
4469

4470 4471 4472 4473 4474 4475 4476 4477 4478 4479 4480 4481 4482 4483 4484 4485
preempt:
	resched_task(curr);
	/*
	 * 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);
4486 4487
}

4488
static struct task_struct *pick_next_task_fair(struct rq *rq)
4489
{
P
Peter Zijlstra 已提交
4490
	struct task_struct *p;
4491 4492 4493
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

4494
	if (!cfs_rq->nr_running)
4495 4496 4497
		return NULL;

	do {
4498
		se = pick_next_entity(cfs_rq);
4499
		set_next_entity(cfs_rq, se);
4500 4501 4502
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
4503
	p = task_of(se);
4504 4505
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
4506 4507

	return p;
4508 4509 4510 4511 4512
}

/*
 * Account for a descheduled task:
 */
4513
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
4514 4515 4516 4517 4518 4519
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
4520
		put_prev_entity(cfs_rq, se);
4521 4522 4523
	}
}

4524 4525 4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548
/*
 * 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);
4549 4550 4551 4552 4553 4554
		/*
		 * Tell update_rq_clock() that we've just updated,
		 * so we don't do microscopic update in schedule()
		 * and double the fastpath cost.
		 */
		 rq->skip_clock_update = 1;
4555 4556 4557 4558 4559
	}

	set_skip_buddy(se);
}

4560 4561 4562 4563
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

4564 4565
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
4566 4567 4568 4569 4570 4571 4572 4573 4574 4575
		return false;

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

	yield_task_fair(rq);

	return true;
}

4576
#ifdef CONFIG_SMP
4577
/**************************************************
P
Peter Zijlstra 已提交
4578 4579 4580 4581 4582 4583 4584 4585 4586 4587 4588 4589 4590 4591 4592 4593 4594 4595 4596 4597 4598 4599 4600 4601 4602 4603 4604 4605 4606 4607 4608 4609 4610 4611 4612 4613 4614 4615 4616 4617 4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636 4637 4638 4639 4640 4641 4642 4643 4644 4645 4646 4647 4648 4649 4650 4651 4652 4653 4654 4655 4656 4657 4658 4659 4660 4661 4662 4663 4664 4665 4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680 4681 4682 4683 4684 4685 4686 4687 4688 4689 4690 4691 4692 4693
 * 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)
 *
 * P_i is the cpu power (or compute capacity) of cpu i, typically it is the
 * 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):
 *
 *   imb_i,j = max{ avg(W/P), W_i/P_i } - min{ avg(W/P), W_j/P_j }    (4)
 *
 * 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.]
 */ 
4694

4695 4696
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

4697 4698
enum fbq_type { regular, remote, all };

4699
#define LBF_ALL_PINNED	0x01
4700
#define LBF_NEED_BREAK	0x02
4701 4702
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
4703 4704 4705 4706 4707

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
4708
	int			src_cpu;
4709 4710 4711 4712

	int			dst_cpu;
	struct rq		*dst_rq;

4713 4714
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
4715
	enum cpu_idle_type	idle;
4716
	long			imbalance;
4717 4718 4719
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

4720
	unsigned int		flags;
4721 4722 4723 4724

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
4725 4726

	enum fbq_type		fbq_type;
4727 4728
};

4729
/*
4730
 * move_task - move a task from one runqueue to another runqueue.
4731 4732
 * Both runqueues must be locked.
 */
4733
static void move_task(struct task_struct *p, struct lb_env *env)
4734
{
4735 4736 4737 4738
	deactivate_task(env->src_rq, p, 0);
	set_task_cpu(p, env->dst_cpu);
	activate_task(env->dst_rq, p, 0);
	check_preempt_curr(env->dst_rq, p, 0);
4739 4740
}

4741 4742 4743 4744 4745 4746 4747 4748 4749 4750 4751 4752 4753 4754 4755 4756 4757 4758 4759 4760 4761 4762 4763 4764 4765 4766 4767 4768 4769 4770 4771 4772
/*
 * Is this task likely cache-hot:
 */
static int
task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
{
	s64 delta;

	if (p->sched_class != &fair_sched_class)
		return 0;

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

	/*
	 * Buddy candidates are cache hot:
	 */
	if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running &&
			(&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;

	delta = now - p->se.exec_start;

	return delta < (s64)sysctl_sched_migration_cost;
}

4773 4774 4775 4776 4777 4778 4779 4780 4781 4782 4783 4784 4785 4786
#ifdef CONFIG_NUMA_BALANCING
/* Returns true if the destination node has incurred more faults */
static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
{
	int src_nid, dst_nid;

	if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults ||
	    !(env->sd->flags & SD_NUMA)) {
		return false;
	}

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

4787
	if (src_nid == dst_nid)
4788 4789
		return false;

4790 4791 4792 4793
	/* Always encourage migration to the preferred node. */
	if (dst_nid == p->numa_preferred_nid)
		return true;

4794 4795 4796
	/* If both task and group weight improve, this move is a winner. */
	if (task_weight(p, dst_nid) > task_weight(p, src_nid) &&
	    group_weight(p, dst_nid) > group_weight(p, src_nid))
4797 4798 4799 4800
		return true;

	return false;
}
4801 4802 4803 4804 4805 4806 4807 4808 4809 4810 4811 4812 4813 4814 4815


static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
{
	int src_nid, dst_nid;

	if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER))
		return false;

	if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
		return false;

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

4816
	if (src_nid == dst_nid)
4817 4818
		return false;

4819 4820 4821 4822
	/* Migrating away from the preferred node is always bad. */
	if (src_nid == p->numa_preferred_nid)
		return true;

4823 4824 4825
	/* If either task or group weight get worse, don't do it. */
	if (task_weight(p, dst_nid) < task_weight(p, src_nid) ||
	    group_weight(p, dst_nid) < group_weight(p, src_nid))
4826 4827 4828 4829 4830
		return true;

	return false;
}

4831 4832 4833 4834 4835 4836
#else
static inline bool migrate_improves_locality(struct task_struct *p,
					     struct lb_env *env)
{
	return false;
}
4837 4838 4839 4840 4841 4842

static inline bool migrate_degrades_locality(struct task_struct *p,
					     struct lb_env *env)
{
	return false;
}
4843 4844
#endif

4845 4846 4847 4848
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
4849
int can_migrate_task(struct task_struct *p, struct lb_env *env)
4850 4851 4852 4853
{
	int tsk_cache_hot = 0;
	/*
	 * We do not migrate tasks that are:
4854
	 * 1) throttled_lb_pair, or
4855
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
4856 4857
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
4858
	 */
4859 4860 4861
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

4862
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
4863
		int cpu;
4864

4865
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
4866

4867 4868
		env->flags |= LBF_SOME_PINNED;

4869 4870 4871 4872 4873 4874 4875 4876
		/*
		 * 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.
		 */
4877
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
4878 4879
			return 0;

4880 4881 4882
		/* 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))) {
4883
				env->flags |= LBF_DST_PINNED;
4884 4885 4886
				env->new_dst_cpu = cpu;
				break;
			}
4887
		}
4888

4889 4890
		return 0;
	}
4891 4892

	/* Record that we found atleast one task that could run on dst_cpu */
4893
	env->flags &= ~LBF_ALL_PINNED;
4894

4895
	if (task_running(env->src_rq, p)) {
4896
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
4897 4898 4899 4900 4901
		return 0;
	}

	/*
	 * Aggressive migration if:
4902 4903 4904
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
4905
	 */
4906
	tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd);
4907 4908
	if (!tsk_cache_hot)
		tsk_cache_hot = migrate_degrades_locality(p, env);
4909 4910 4911 4912 4913 4914 4915 4916 4917 4918 4919

	if (migrate_improves_locality(p, env)) {
#ifdef CONFIG_SCHEDSTATS
		if (tsk_cache_hot) {
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
			schedstat_inc(p, se.statistics.nr_forced_migrations);
		}
#endif
		return 1;
	}

4920
	if (!tsk_cache_hot ||
4921
		env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
Z
Zhang Hang 已提交
4922

4923
		if (tsk_cache_hot) {
4924
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
4925
			schedstat_inc(p, se.statistics.nr_forced_migrations);
4926
		}
Z
Zhang Hang 已提交
4927

4928 4929 4930
		return 1;
	}

Z
Zhang Hang 已提交
4931 4932
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
4933 4934
}

4935 4936 4937 4938 4939 4940 4941
/*
 * move_one_task tries to move exactly one task from busiest to this_rq, as
 * part of active balancing operations within "domain".
 * Returns 1 if successful and 0 otherwise.
 *
 * Called with both runqueues locked.
 */
4942
static int move_one_task(struct lb_env *env)
4943 4944 4945
{
	struct task_struct *p, *n;

4946 4947 4948
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
4949

4950 4951 4952 4953 4954 4955 4956 4957
		move_task(p, env);
		/*
		 * Right now, this is only the second place move_task()
		 * is called, so we can safely collect move_task()
		 * stats here rather than inside move_task().
		 */
		schedstat_inc(env->sd, lb_gained[env->idle]);
		return 1;
4958 4959 4960 4961
	}
	return 0;
}

4962 4963
static const unsigned int sched_nr_migrate_break = 32;

4964
/*
4965
 * move_tasks tries to move up to imbalance weighted load from busiest to
4966 4967 4968 4969 4970 4971
 * this_rq, as part of a balancing operation within domain "sd".
 * Returns 1 if successful and 0 otherwise.
 *
 * Called with both runqueues locked.
 */
static int move_tasks(struct lb_env *env)
4972
{
4973 4974
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
4975 4976
	unsigned long load;
	int pulled = 0;
4977

4978
	if (env->imbalance <= 0)
4979
		return 0;
4980

4981 4982
	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
4983

4984 4985
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
4986
		if (env->loop > env->loop_max)
4987
			break;
4988 4989

		/* take a breather every nr_migrate tasks */
4990
		if (env->loop > env->loop_break) {
4991
			env->loop_break += sched_nr_migrate_break;
4992
			env->flags |= LBF_NEED_BREAK;
4993
			break;
4994
		}
4995

4996
		if (!can_migrate_task(p, env))
4997 4998 4999
			goto next;

		load = task_h_load(p);
5000

5001
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
5002 5003
			goto next;

5004
		if ((load / 2) > env->imbalance)
5005
			goto next;
5006

5007
		move_task(p, env);
5008
		pulled++;
5009
		env->imbalance -= load;
5010 5011

#ifdef CONFIG_PREEMPT
5012 5013 5014 5015 5016
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
		 * kernels will stop after the first task is pulled to minimize
		 * the critical section.
		 */
5017
		if (env->idle == CPU_NEWLY_IDLE)
5018
			break;
5019 5020
#endif

5021 5022 5023 5024
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
5025
		if (env->imbalance <= 0)
5026
			break;
5027 5028 5029

		continue;
next:
5030
		list_move_tail(&p->se.group_node, tasks);
5031
	}
5032

5033
	/*
5034 5035 5036
	 * Right now, this is one of only two places move_task() is called,
	 * so we can safely collect move_task() stats here rather than
	 * inside move_task().
5037
	 */
5038
	schedstat_add(env->sd, lb_gained[env->idle], pulled);
5039

5040
	return pulled;
5041 5042
}

P
Peter Zijlstra 已提交
5043
#ifdef CONFIG_FAIR_GROUP_SCHED
5044 5045 5046
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
5047
static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
5048
{
5049 5050
	struct sched_entity *se = tg->se[cpu];
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
5051

5052 5053 5054
	/* throttled entities do not contribute to load */
	if (throttled_hierarchy(cfs_rq))
		return;
5055

5056
	update_cfs_rq_blocked_load(cfs_rq, 1);
5057

5058 5059 5060 5061 5062 5063 5064 5065 5066 5067 5068 5069 5070 5071
	if (se) {
		update_entity_load_avg(se, 1);
		/*
		 * We pivot on our runnable average having decayed to zero for
		 * list removal.  This generally implies that all our children
		 * have also been removed (modulo rounding error or bandwidth
		 * control); however, such cases are rare and we can fix these
		 * at enqueue.
		 *
		 * TODO: fix up out-of-order children on enqueue.
		 */
		if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running)
			list_del_leaf_cfs_rq(cfs_rq);
	} else {
5072
		struct rq *rq = rq_of(cfs_rq);
5073 5074
		update_rq_runnable_avg(rq, rq->nr_running);
	}
5075 5076
}

5077
static void update_blocked_averages(int cpu)
5078 5079
{
	struct rq *rq = cpu_rq(cpu);
5080 5081
	struct cfs_rq *cfs_rq;
	unsigned long flags;
5082

5083 5084
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
5085 5086 5087 5088
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
5089
	for_each_leaf_cfs_rq(rq, cfs_rq) {
5090 5091 5092 5093 5094 5095
		/*
		 * Note: We may want to consider periodically releasing
		 * rq->lock about these updates so that creating many task
		 * groups does not result in continually extending hold time.
		 */
		__update_blocked_averages_cpu(cfs_rq->tg, rq->cpu);
5096
	}
5097 5098

	raw_spin_unlock_irqrestore(&rq->lock, flags);
5099 5100
}

5101
/*
5102
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
5103 5104 5105
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
5106
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
5107
{
5108 5109
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
5110
	unsigned long now = jiffies;
5111
	unsigned long load;
5112

5113
	if (cfs_rq->last_h_load_update == now)
5114 5115
		return;

5116 5117 5118 5119 5120 5121 5122
	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;
	}
5123

5124
	if (!se) {
5125
		cfs_rq->h_load = cfs_rq->runnable_load_avg;
5126 5127 5128 5129 5130 5131 5132 5133 5134 5135 5136
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
		load = div64_ul(load * se->avg.load_avg_contrib,
				cfs_rq->runnable_load_avg + 1);
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
5137 5138
}

5139
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
5140
{
5141
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
5142

5143
	update_cfs_rq_h_load(cfs_rq);
5144 5145
	return div64_ul(p->se.avg.load_avg_contrib * cfs_rq->h_load,
			cfs_rq->runnable_load_avg + 1);
P
Peter Zijlstra 已提交
5146 5147
}
#else
5148
static inline void update_blocked_averages(int cpu)
5149 5150 5151
{
}

5152
static unsigned long task_h_load(struct task_struct *p)
5153
{
5154
	return p->se.avg.load_avg_contrib;
5155
}
P
Peter Zijlstra 已提交
5156
#endif
5157 5158 5159 5160 5161 5162 5163 5164 5165

/********** Helpers for find_busiest_group ************************/
/*
 * 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
5166
	unsigned long load_per_task;
5167
	unsigned long group_power;
5168 5169 5170 5171
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int group_capacity;
	unsigned int idle_cpus;
	unsigned int group_weight;
5172
	int group_imb; /* Is there an imbalance in the group ? */
5173
	int group_has_capacity; /* Is there extra capacity in the group? */
5174 5175 5176 5177
#ifdef CONFIG_NUMA_BALANCING
	unsigned int nr_numa_running;
	unsigned int nr_preferred_running;
#endif
5178 5179
};

J
Joonsoo Kim 已提交
5180 5181 5182 5183 5184 5185 5186 5187 5188 5189 5190 5191
/*
 * 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 */
	unsigned long total_pwr;	/* Total power of all groups in sd */
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
5192
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
5193 5194
};

5195 5196 5197 5198 5199 5200 5201 5202 5203 5204 5205 5206 5207 5208 5209 5210 5211 5212 5213
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,
		.total_pwr = 0UL,
		.busiest_stat = {
			.avg_load = 0UL,
		},
	};
}

5214 5215 5216
/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
5217
 * @idle: The idle status of the CPU for whose sd load_idx is obtained.
5218 5219
 *
 * Return: The load index.
5220 5221 5222 5223 5224 5225 5226 5227 5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238 5239 5240 5241
 */
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;
}

5242
static unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
5243
{
5244
	return SCHED_POWER_SCALE;
5245 5246 5247 5248 5249 5250 5251
}

unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu)
{
	return default_scale_freq_power(sd, cpu);
}

5252
static unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
5253
{
5254
	unsigned long weight = sd->span_weight;
5255 5256 5257 5258 5259 5260 5261 5262 5263 5264 5265 5266
	unsigned long smt_gain = sd->smt_gain;

	smt_gain /= weight;

	return smt_gain;
}

unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
{
	return default_scale_smt_power(sd, cpu);
}

5267
static unsigned long scale_rt_power(int cpu)
5268 5269
{
	struct rq *rq = cpu_rq(cpu);
5270
	u64 total, available, age_stamp, avg;
5271

5272 5273 5274 5275 5276 5277 5278
	/*
	 * Since we're reading these variables without serialization make sure
	 * we read them once before doing sanity checks on them.
	 */
	age_stamp = ACCESS_ONCE(rq->age_stamp);
	avg = ACCESS_ONCE(rq->rt_avg);

5279
	total = sched_avg_period() + (rq_clock(rq) - age_stamp);
5280

5281
	if (unlikely(total < avg)) {
5282 5283 5284
		/* Ensures that power won't end up being negative */
		available = 0;
	} else {
5285
		available = total - avg;
5286
	}
5287

5288 5289
	if (unlikely((s64)total < SCHED_POWER_SCALE))
		total = SCHED_POWER_SCALE;
5290

5291
	total >>= SCHED_POWER_SHIFT;
5292 5293 5294 5295 5296 5297

	return div_u64(available, total);
}

static void update_cpu_power(struct sched_domain *sd, int cpu)
{
5298
	unsigned long weight = sd->span_weight;
5299
	unsigned long power = SCHED_POWER_SCALE;
5300 5301 5302 5303 5304 5305 5306 5307
	struct sched_group *sdg = sd->groups;

	if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
		if (sched_feat(ARCH_POWER))
			power *= arch_scale_smt_power(sd, cpu);
		else
			power *= default_scale_smt_power(sd, cpu);

5308
		power >>= SCHED_POWER_SHIFT;
5309 5310
	}

5311
	sdg->sgp->power_orig = power;
5312 5313 5314 5315 5316 5317

	if (sched_feat(ARCH_POWER))
		power *= arch_scale_freq_power(sd, cpu);
	else
		power *= default_scale_freq_power(sd, cpu);

5318
	power >>= SCHED_POWER_SHIFT;
5319

5320
	power *= scale_rt_power(cpu);
5321
	power >>= SCHED_POWER_SHIFT;
5322 5323 5324 5325

	if (!power)
		power = 1;

5326
	cpu_rq(cpu)->cpu_power = power;
5327
	sdg->sgp->power = power;
5328 5329
}

5330
void update_group_power(struct sched_domain *sd, int cpu)
5331 5332 5333
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
5334
	unsigned long power, power_orig;
5335 5336 5337 5338 5339
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
	sdg->sgp->next_update = jiffies + interval;
5340 5341 5342 5343 5344 5345

	if (!child) {
		update_cpu_power(sd, cpu);
		return;
	}

5346
	power_orig = power = 0;
5347

P
Peter Zijlstra 已提交
5348 5349 5350 5351 5352 5353
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

5354 5355 5356 5357 5358 5359
		for_each_cpu(cpu, sched_group_cpus(sdg)) {
			struct sched_group *sg = cpu_rq(cpu)->sd->groups;

			power_orig += sg->sgp->power_orig;
			power += sg->sgp->power;
		}
P
Peter Zijlstra 已提交
5360 5361 5362 5363 5364 5365 5366 5367
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
5368
			power_orig += group->sgp->power_orig;
P
Peter Zijlstra 已提交
5369 5370 5371 5372
			power += group->sgp->power;
			group = group->next;
		} while (group != child->groups);
	}
5373

5374 5375
	sdg->sgp->power_orig = power_orig;
	sdg->sgp->power = power;
5376 5377
}

5378 5379 5380 5381 5382 5383 5384 5385 5386 5387 5388
/*
 * Try and fix up capacity for tiny siblings, this is needed when
 * things like SD_ASYM_PACKING need f_b_g to select another sibling
 * which on its own isn't powerful enough.
 *
 * See update_sd_pick_busiest() and check_asym_packing().
 */
static inline int
fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
{
	/*
5389
	 * Only siblings can have significantly less than SCHED_POWER_SCALE
5390
	 */
P
Peter Zijlstra 已提交
5391
	if (!(sd->flags & SD_SHARE_CPUPOWER))
5392 5393 5394 5395 5396
		return 0;

	/*
	 * If ~90% of the cpu_power is still there, we're good.
	 */
5397
	if (group->sgp->power * 32 > group->sgp->power_orig * 29)
5398 5399 5400 5401 5402
		return 1;

	return 0;
}

5403 5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418
/*
 * 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
5419 5420
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
5421 5422
 *
 * When this is so detected; this group becomes a candidate for busiest; see
5423
 * update_sd_pick_busiest(). And calculate_imbalance() and
5424
 * find_busiest_group() avoid some of the usual balance conditions to allow it
5425 5426 5427 5428 5429 5430 5431
 * 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.
 */

5432
static inline int sg_imbalanced(struct sched_group *group)
5433
{
5434
	return group->sgp->imbalance;
5435 5436
}

5437 5438 5439
/*
 * Compute the group capacity.
 *
5440 5441 5442
 * Avoid the issue where N*frac(smt_power) >= 1 creates 'phantom' cores by
 * first dividing out the smt factor and computing the actual number of cores
 * and limit power unit capacity with that.
5443 5444 5445
 */
static inline int sg_capacity(struct lb_env *env, struct sched_group *group)
{
5446 5447 5448 5449 5450 5451
	unsigned int capacity, smt, cpus;
	unsigned int power, power_orig;

	power = group->sgp->power;
	power_orig = group->sgp->power_orig;
	cpus = group->group_weight;
5452

5453 5454 5455
	/* smt := ceil(cpus / power), assumes: 1 < smt_power < 2 */
	smt = DIV_ROUND_UP(SCHED_POWER_SCALE * cpus, power_orig);
	capacity = cpus / smt; /* cores */
5456

5457
	capacity = min_t(unsigned, capacity, DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE));
5458 5459 5460 5461 5462 5463
	if (!capacity)
		capacity = fix_small_capacity(env->sd, group);

	return capacity;
}

5464 5465
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
5466
 * @env: The load balancing environment.
5467 5468 5469 5470 5471
 * @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.
 */
5472 5473
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
5474
			int local_group, struct sg_lb_stats *sgs)
5475
{
5476 5477
	unsigned long nr_running;
	unsigned long load;
5478
	int i;
5479

5480 5481
	memset(sgs, 0, sizeof(*sgs));

5482
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
5483 5484
		struct rq *rq = cpu_rq(i);

5485 5486
		nr_running = rq->nr_running;

5487
		/* Bias balancing toward cpus of our domain */
5488
		if (local_group)
5489
			load = target_load(i, load_idx);
5490
		else
5491 5492 5493
			load = source_load(i, load_idx);

		sgs->group_load += load;
5494
		sgs->sum_nr_running += nr_running;
5495 5496 5497 5498
#ifdef CONFIG_NUMA_BALANCING
		sgs->nr_numa_running += rq->nr_numa_running;
		sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
5499
		sgs->sum_weighted_load += weighted_cpuload(i);
5500 5501
		if (idle_cpu(i))
			sgs->idle_cpus++;
5502 5503 5504
	}

	/* Adjust by relative CPU power of the group */
5505 5506
	sgs->group_power = group->sgp->power;
	sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / sgs->group_power;
5507

5508
	if (sgs->sum_nr_running)
5509
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
5510

5511
	sgs->group_weight = group->group_weight;
5512

5513 5514 5515
	sgs->group_imb = sg_imbalanced(group);
	sgs->group_capacity = sg_capacity(env, group);

5516 5517
	if (sgs->group_capacity > sgs->sum_nr_running)
		sgs->group_has_capacity = 1;
5518 5519
}

5520 5521
/**
 * update_sd_pick_busiest - return 1 on busiest group
5522
 * @env: The load balancing environment.
5523 5524
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
5525
 * @sgs: sched_group statistics
5526 5527 5528
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
5529 5530 5531
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
5532
 */
5533
static bool update_sd_pick_busiest(struct lb_env *env,
5534 5535
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
5536
				   struct sg_lb_stats *sgs)
5537
{
J
Joonsoo Kim 已提交
5538
	if (sgs->avg_load <= sds->busiest_stat.avg_load)
5539 5540 5541 5542 5543 5544 5545 5546 5547 5548 5549 5550 5551
		return false;

	if (sgs->sum_nr_running > sgs->group_capacity)
		return true;

	if (sgs->group_imb)
		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.
	 */
5552 5553
	if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
	    env->dst_cpu < group_first_cpu(sg)) {
5554 5555 5556 5557 5558 5559 5560 5561 5562 5563
		if (!sds->busiest)
			return true;

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

	return false;
}

5564 5565 5566 5567 5568 5569 5570 5571 5572 5573 5574 5575 5576 5577 5578 5579 5580 5581 5582 5583 5584 5585 5586 5587 5588 5589 5590 5591 5592 5593
#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 */

5594
/**
5595
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
5596
 * @env: The load balancing environment.
5597 5598
 * @sds: variable to hold the statistics for this sched_domain.
 */
5599
static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds)
5600
{
5601 5602
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
5603
	struct sg_lb_stats tmp_sgs;
5604 5605 5606 5607 5608
	int load_idx, prefer_sibling = 0;

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

5609
	load_idx = get_sd_load_idx(env->sd, env->idle);
5610 5611

	do {
J
Joonsoo Kim 已提交
5612
		struct sg_lb_stats *sgs = &tmp_sgs;
5613 5614
		int local_group;

5615
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
5616 5617 5618
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
5619 5620 5621 5622

			if (env->idle != CPU_NEWLY_IDLE ||
			    time_after_eq(jiffies, sg->sgp->next_update))
				update_group_power(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
5623
		}
5624

J
Joonsoo Kim 已提交
5625
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs);
5626

5627 5628 5629
		if (local_group)
			goto next_group;

5630 5631
		/*
		 * In case the child domain prefers tasks go to siblings
5632
		 * first, lower the sg capacity to one so that we'll try
5633 5634 5635 5636 5637 5638
		 * and move all the excess tasks away. We lower the capacity
		 * of a group only if the local group has the capacity to fit
		 * these excess tasks, i.e. nr_running < group_capacity. 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).
5639
		 */
5640 5641
		if (prefer_sibling && sds->local &&
		    sds->local_stat.group_has_capacity)
5642
			sgs->group_capacity = min(sgs->group_capacity, 1U);
5643

5644
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
5645
			sds->busiest = sg;
J
Joonsoo Kim 已提交
5646
			sds->busiest_stat = *sgs;
5647 5648
		}

5649 5650 5651 5652 5653
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
		sds->total_pwr += sgs->group_power;

5654
		sg = sg->next;
5655
	} while (sg != env->sd->groups);
5656 5657 5658

	if (env->sd->flags & SD_NUMA)
		env->fbq_type = fbq_classify_group(&sds->busiest_stat);
5659 5660 5661 5662 5663 5664 5665 5666 5667 5668 5669 5670 5671 5672 5673 5674 5675 5676 5677
}

/**
 * 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.
 *
5678
 * Return: 1 when packing is required and a task should be moved to
5679 5680
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
5681
 * @env: The load balancing environment.
5682 5683
 * @sds: Statistics of the sched_domain which is to be packed
 */
5684
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
5685 5686 5687
{
	int busiest_cpu;

5688
	if (!(env->sd->flags & SD_ASYM_PACKING))
5689 5690 5691 5692 5693 5694
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
5695
	if (env->dst_cpu > busiest_cpu)
5696 5697
		return 0;

5698
	env->imbalance = DIV_ROUND_CLOSEST(
5699 5700
		sds->busiest_stat.avg_load * sds->busiest_stat.group_power,
		SCHED_POWER_SCALE);
5701

5702
	return 1;
5703 5704 5705 5706 5707 5708
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
5709
 * @env: The load balancing environment.
5710 5711
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
5712 5713
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
5714 5715 5716
{
	unsigned long tmp, pwr_now = 0, pwr_move = 0;
	unsigned int imbn = 2;
5717
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
5718
	struct sg_lb_stats *local, *busiest;
5719

J
Joonsoo Kim 已提交
5720 5721
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
5722

J
Joonsoo Kim 已提交
5723 5724 5725 5726
	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;
5727

J
Joonsoo Kim 已提交
5728 5729
	scaled_busy_load_per_task =
		(busiest->load_per_task * SCHED_POWER_SCALE) /
5730
		busiest->group_power;
J
Joonsoo Kim 已提交
5731

5732 5733
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
5734
		env->imbalance = busiest->load_per_task;
5735 5736 5737 5738 5739 5740 5741 5742 5743
		return;
	}

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

5744
	pwr_now += busiest->group_power *
J
Joonsoo Kim 已提交
5745
			min(busiest->load_per_task, busiest->avg_load);
5746
	pwr_now += local->group_power *
J
Joonsoo Kim 已提交
5747
			min(local->load_per_task, local->avg_load);
5748
	pwr_now /= SCHED_POWER_SCALE;
5749 5750

	/* Amount of load we'd subtract */
J
Joonsoo Kim 已提交
5751
	tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
5752
		busiest->group_power;
J
Joonsoo Kim 已提交
5753
	if (busiest->avg_load > tmp) {
5754
		pwr_move += busiest->group_power *
J
Joonsoo Kim 已提交
5755 5756 5757
			    min(busiest->load_per_task,
				busiest->avg_load - tmp);
	}
5758 5759

	/* Amount of load we'd add */
5760
	if (busiest->avg_load * busiest->group_power <
J
Joonsoo Kim 已提交
5761
	    busiest->load_per_task * SCHED_POWER_SCALE) {
5762 5763
		tmp = (busiest->avg_load * busiest->group_power) /
		      local->group_power;
J
Joonsoo Kim 已提交
5764 5765
	} else {
		tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
5766
		      local->group_power;
J
Joonsoo Kim 已提交
5767
	}
5768 5769
	pwr_move += local->group_power *
		    min(local->load_per_task, local->avg_load + tmp);
5770
	pwr_move /= SCHED_POWER_SCALE;
5771 5772 5773

	/* Move if we gain throughput */
	if (pwr_move > pwr_now)
J
Joonsoo Kim 已提交
5774
		env->imbalance = busiest->load_per_task;
5775 5776 5777 5778 5779
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
5780
 * @env: load balance environment
5781 5782
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
5783
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
5784
{
5785
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
5786 5787 5788 5789
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
5790

J
Joonsoo Kim 已提交
5791
	if (busiest->group_imb) {
5792 5793 5794 5795
		/*
		 * 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
5796 5797
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
5798 5799
	}

5800 5801 5802 5803 5804
	/*
	 * 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
	 * its cpu_power, while calculating max_load..)
	 */
5805 5806
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
5807 5808
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
5809 5810
	}

J
Joonsoo Kim 已提交
5811
	if (!busiest->group_imb) {
5812 5813
		/*
		 * Don't want to pull so many tasks that a group would go idle.
5814 5815
		 * Except of course for the group_imb case, since then we might
		 * have to drop below capacity to reach cpu-load equilibrium.
5816
		 */
J
Joonsoo Kim 已提交
5817 5818
		load_above_capacity =
			(busiest->sum_nr_running - busiest->group_capacity);
5819

5820
		load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
5821
		load_above_capacity /= busiest->group_power;
5822 5823 5824 5825 5826 5827 5828 5829 5830 5831
	}

	/*
	 * 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.
	 */
5832
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
5833 5834

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
5835
	env->imbalance = min(
5836 5837
		max_pull * busiest->group_power,
		(sds->avg_load - local->avg_load) * local->group_power
J
Joonsoo Kim 已提交
5838
	) / SCHED_POWER_SCALE;
5839 5840 5841

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
5842
	 * there is no guarantee that any tasks will be moved so we'll have
5843 5844 5845
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
5846
	if (env->imbalance < busiest->load_per_task)
5847
		return fix_small_imbalance(env, sds);
5848
}
5849

5850 5851 5852 5853 5854 5855 5856 5857 5858 5859 5860 5861
/******* 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.
 *
5862
 * @env: The load balancing environment.
5863
 *
5864
 * Return:	- The busiest group if imbalance exists.
5865 5866 5867 5868
 *		- 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
5869
static struct sched_group *find_busiest_group(struct lb_env *env)
5870
{
J
Joonsoo Kim 已提交
5871
	struct sg_lb_stats *local, *busiest;
5872 5873
	struct sd_lb_stats sds;

5874
	init_sd_lb_stats(&sds);
5875 5876 5877 5878 5879

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
5880
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
5881 5882
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
5883

5884 5885
	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(env, &sds))
5886 5887
		return sds.busiest;

5888
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
5889
	if (!sds.busiest || busiest->sum_nr_running == 0)
5890 5891
		goto out_balanced;

5892
	sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
5893

P
Peter Zijlstra 已提交
5894 5895
	/*
	 * If the busiest group is imbalanced the below checks don't
5896
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
5897 5898
	 * isn't true due to cpus_allowed constraints and the like.
	 */
J
Joonsoo Kim 已提交
5899
	if (busiest->group_imb)
P
Peter Zijlstra 已提交
5900 5901
		goto force_balance;

5902
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
J
Joonsoo Kim 已提交
5903 5904
	if (env->idle == CPU_NEWLY_IDLE && local->group_has_capacity &&
	    !busiest->group_has_capacity)
5905 5906
		goto force_balance;

5907 5908 5909 5910
	/*
	 * If the local group is more busy than the selected busiest group
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
5911
	if (local->avg_load >= busiest->avg_load)
5912 5913
		goto out_balanced;

5914 5915 5916 5917
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
5918
	if (local->avg_load >= sds.avg_load)
5919 5920
		goto out_balanced;

5921
	if (env->idle == CPU_IDLE) {
5922 5923 5924 5925 5926 5927
		/*
		 * This cpu is idle. If the busiest group load doesn't
		 * have more tasks than the number of available cpu's and
		 * there is no imbalance between this and busiest group
		 * wrt to idle cpu's, it is balanced.
		 */
J
Joonsoo Kim 已提交
5928 5929
		if ((local->idle_cpus < busiest->idle_cpus) &&
		    busiest->sum_nr_running <= busiest->group_weight)
5930
			goto out_balanced;
5931 5932 5933 5934 5935
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
5936 5937
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
5938
			goto out_balanced;
5939
	}
5940

5941
force_balance:
5942
	/* Looks like there is an imbalance. Compute it */
5943
	calculate_imbalance(env, &sds);
5944 5945 5946
	return sds.busiest;

out_balanced:
5947
	env->imbalance = 0;
5948 5949 5950 5951 5952 5953
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
5954
static struct rq *find_busiest_queue(struct lb_env *env,
5955
				     struct sched_group *group)
5956 5957
{
	struct rq *busiest = NULL, *rq;
5958
	unsigned long busiest_load = 0, busiest_power = 1;
5959 5960
	int i;

5961
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
5962 5963 5964 5965 5966
		unsigned long power, capacity, wl;
		enum fbq_type rt;

		rq = cpu_rq(i);
		rt = fbq_classify_rq(rq);
5967

5968 5969 5970 5971 5972 5973 5974 5975 5976 5977 5978 5979 5980 5981 5982 5983 5984 5985 5986 5987 5988 5989 5990 5991
		/*
		 * 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;

		power = power_of(i);
		capacity = DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE);
5992
		if (!capacity)
5993
			capacity = fix_small_capacity(env->sd, group);
5994

5995
		wl = weighted_cpuload(i);
5996

5997 5998 5999 6000
		/*
		 * When comparing with imbalance, use weighted_cpuload()
		 * which is not scaled with the cpu power.
		 */
6001
		if (capacity && rq->nr_running == 1 && wl > env->imbalance)
6002 6003
			continue;

6004 6005 6006 6007 6008
		/*
		 * For the load comparisons with the other cpu's, consider
		 * the weighted_cpuload() scaled with the cpu power, so that
		 * the load can be moved away from the cpu that is potentially
		 * running at a lower capacity.
6009 6010 6011 6012 6013
		 *
		 * Thus we're looking for max(wl_i / power_i), crosswise
		 * multiplication to rid ourselves of the division works out
		 * to: wl_i * power_j > wl_j * power_i;  where j is our
		 * previous maximum.
6014
		 */
6015 6016 6017
		if (wl * busiest_power > busiest_load * power) {
			busiest_load = wl;
			busiest_power = power;
6018 6019 6020 6021 6022 6023 6024 6025 6026 6027 6028 6029 6030 6031
			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. */
6032
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
6033

6034
static int need_active_balance(struct lb_env *env)
6035
{
6036 6037 6038
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
6039 6040 6041 6042 6043 6044

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
6045
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
6046
			return 1;
6047 6048 6049 6050 6051
	}

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

6052 6053
static int active_load_balance_cpu_stop(void *data);

6054 6055 6056 6057 6058 6059 6060 6061 6062 6063 6064 6065 6066 6067 6068 6069 6070 6071 6072 6073 6074 6075 6076 6077 6078 6079 6080 6081 6082 6083 6084
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.
	 */
6085
	return balance_cpu == env->dst_cpu;
6086 6087
}

6088 6089 6090 6091 6092 6093
/*
 * 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,
6094
			int *continue_balancing)
6095
{
6096
	int ld_moved, cur_ld_moved, active_balance = 0;
6097
	struct sched_domain *sd_parent = sd->parent;
6098 6099 6100
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
6101
	struct cpumask *cpus = __get_cpu_var(load_balance_mask);
6102

6103 6104
	struct lb_env env = {
		.sd		= sd,
6105 6106
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
6107
		.dst_grpmask    = sched_group_cpus(sd->groups),
6108
		.idle		= idle,
6109
		.loop_break	= sched_nr_migrate_break,
6110
		.cpus		= cpus,
6111
		.fbq_type	= all,
6112 6113
	};

6114 6115 6116 6117
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
6118
	if (idle == CPU_NEWLY_IDLE)
6119 6120
		env.dst_grpmask = NULL;

6121 6122 6123 6124 6125
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
6126 6127
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
6128
		goto out_balanced;
6129
	}
6130

6131
	group = find_busiest_group(&env);
6132 6133 6134 6135 6136
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

6137
	busiest = find_busiest_queue(&env, group);
6138 6139 6140 6141 6142
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

6143
	BUG_ON(busiest == env.dst_rq);
6144

6145
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
6146 6147 6148 6149 6150 6151 6152 6153 6154

	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.
		 */
6155
		env.flags |= LBF_ALL_PINNED;
6156 6157 6158
		env.src_cpu   = busiest->cpu;
		env.src_rq    = busiest;
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
6159

6160
more_balance:
6161
		local_irq_save(flags);
6162
		double_rq_lock(env.dst_rq, busiest);
6163 6164 6165 6166 6167 6168 6169

		/*
		 * cur_ld_moved - load moved in current iteration
		 * ld_moved     - cumulative load moved across iterations
		 */
		cur_ld_moved = move_tasks(&env);
		ld_moved += cur_ld_moved;
6170
		double_rq_unlock(env.dst_rq, busiest);
6171 6172 6173 6174 6175
		local_irq_restore(flags);

		/*
		 * some other cpu did the load balance for us.
		 */
6176 6177 6178
		if (cur_ld_moved && env.dst_cpu != smp_processor_id())
			resched_cpu(env.dst_cpu);

6179 6180 6181 6182 6183
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

6184 6185 6186 6187 6188 6189 6190 6191 6192 6193 6194 6195 6196 6197 6198 6199 6200 6201 6202
		/*
		 * 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.
		 */
6203
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
6204

6205 6206 6207
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

6208
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
6209
			env.dst_cpu	 = env.new_dst_cpu;
6210
			env.flags	&= ~LBF_DST_PINNED;
6211 6212
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
6213

6214 6215 6216 6217 6218 6219
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
6220

6221 6222 6223 6224 6225 6226 6227 6228 6229 6230 6231 6232
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
			int *group_imbalance = &sd_parent->groups->sgp->imbalance;

			if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) {
				*group_imbalance = 1;
			} else if (*group_imbalance)
				*group_imbalance = 0;
		}

6233
		/* All tasks on this runqueue were pinned by CPU affinity */
6234
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
6235
			cpumask_clear_cpu(cpu_of(busiest), cpus);
6236 6237 6238
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
6239
				goto redo;
6240
			}
6241 6242 6243 6244 6245 6246
			goto out_balanced;
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
6247 6248 6249 6250 6251 6252 6253 6254
		/*
		 * 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++;
6255

6256
		if (need_active_balance(&env)) {
6257 6258
			raw_spin_lock_irqsave(&busiest->lock, flags);

6259 6260 6261
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
6262 6263
			 */
			if (!cpumask_test_cpu(this_cpu,
6264
					tsk_cpus_allowed(busiest->curr))) {
6265 6266
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
6267
				env.flags |= LBF_ALL_PINNED;
6268 6269 6270
				goto out_one_pinned;
			}

6271 6272 6273 6274 6275
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
6276 6277 6278 6279 6280 6281
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
6282

6283
			if (active_balance) {
6284 6285 6286
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
6287
			}
6288 6289 6290 6291 6292 6293 6294 6295 6296 6297 6298 6299 6300 6301 6302 6303 6304 6305 6306 6307 6308 6309 6310 6311 6312 6313 6314 6315 6316 6317 6318 6319 6320

			/*
			 * 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
		 * move_tasks).
		 */
		if (sd->balance_interval < sd->max_interval)
			sd->balance_interval *= 2;
	}

	goto out;

out_balanced:
	schedstat_inc(sd, lb_balanced[idle]);

	sd->nr_balance_failed = 0;

out_one_pinned:
	/* tune up the balancing interval */
6321
	if (((env.flags & LBF_ALL_PINNED) &&
6322
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
6323 6324 6325
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

6326
	ld_moved = 0;
6327 6328 6329 6330 6331 6332 6333 6334
out:
	return ld_moved;
}

/*
 * idle_balance is called by schedule() if this_cpu is about to become
 * idle. Attempts to pull tasks from other CPUs.
 */
6335
void idle_balance(int this_cpu, struct rq *this_rq)
6336 6337 6338 6339
{
	struct sched_domain *sd;
	int pulled_task = 0;
	unsigned long next_balance = jiffies + HZ;
6340
	u64 curr_cost = 0;
6341

6342
	this_rq->idle_stamp = rq_clock(this_rq);
6343 6344 6345 6346

	if (this_rq->avg_idle < sysctl_sched_migration_cost)
		return;

6347 6348 6349 6350 6351
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

6352
	update_blocked_averages(this_cpu);
6353
	rcu_read_lock();
6354 6355
	for_each_domain(this_cpu, sd) {
		unsigned long interval;
6356
		int continue_balancing = 1;
6357
		u64 t0, domain_cost;
6358 6359 6360 6361

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

6362 6363 6364
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost)
			break;

6365
		if (sd->flags & SD_BALANCE_NEWIDLE) {
6366 6367
			t0 = sched_clock_cpu(this_cpu);

6368
			/* If we've pulled tasks over stop searching: */
6369
			pulled_task = load_balance(this_cpu, this_rq,
6370 6371
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
6372 6373 6374 6375 6376 6377

			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;
6378
		}
6379 6380 6381 6382

		interval = msecs_to_jiffies(sd->balance_interval);
		if (time_after(next_balance, sd->last_balance + interval))
			next_balance = sd->last_balance + interval;
N
Nikhil Rao 已提交
6383 6384
		if (pulled_task) {
			this_rq->idle_stamp = 0;
6385
			break;
N
Nikhil Rao 已提交
6386
		}
6387
	}
6388
	rcu_read_unlock();
6389 6390 6391

	raw_spin_lock(&this_rq->lock);

6392 6393 6394 6395 6396 6397 6398
	if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
		/*
		 * We are going idle. next_balance may be set based on
		 * a busy processor. So reset next_balance.
		 */
		this_rq->next_balance = next_balance;
	}
6399 6400 6401

	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;
6402 6403 6404
}

/*
6405 6406 6407 6408
 * 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.
6409
 */
6410
static int active_load_balance_cpu_stop(void *data)
6411
{
6412 6413
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
6414
	int target_cpu = busiest_rq->push_cpu;
6415
	struct rq *target_rq = cpu_rq(target_cpu);
6416
	struct sched_domain *sd;
6417 6418 6419 6420 6421 6422 6423

	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;
6424 6425 6426

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
6427
		goto out_unlock;
6428 6429 6430 6431 6432 6433 6434 6435 6436 6437 6438 6439

	/*
	 * 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);

	/* move a task from busiest_rq to target_rq */
	double_lock_balance(busiest_rq, target_rq);

	/* Search for an sd spanning us and the target CPU. */
6440
	rcu_read_lock();
6441 6442 6443 6444 6445 6446 6447
	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)) {
6448 6449
		struct lb_env env = {
			.sd		= sd,
6450 6451 6452 6453
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
6454 6455 6456
			.idle		= CPU_IDLE,
		};

6457 6458
		schedstat_inc(sd, alb_count);

6459
		if (move_one_task(&env))
6460 6461 6462 6463
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
6464
	rcu_read_unlock();
6465
	double_unlock_balance(busiest_rq, target_rq);
6466 6467 6468 6469
out_unlock:
	busiest_rq->active_balance = 0;
	raw_spin_unlock_irq(&busiest_rq->lock);
	return 0;
6470 6471
}

6472
#ifdef CONFIG_NO_HZ_COMMON
6473 6474 6475 6476 6477 6478
/*
 * 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.
 */
6479
static struct {
6480
	cpumask_var_t idle_cpus_mask;
6481
	atomic_t nr_cpus;
6482 6483
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
6484

6485
static inline int find_new_ilb(int call_cpu)
6486
{
6487
	int ilb = cpumask_first(nohz.idle_cpus_mask);
6488

6489 6490 6491 6492
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
6493 6494
}

6495 6496 6497 6498 6499 6500 6501 6502 6503 6504 6505
/*
 * 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).
 */
static void nohz_balancer_kick(int cpu)
{
	int ilb_cpu;

	nohz.next_balance++;

6506
	ilb_cpu = find_new_ilb(cpu);
6507

6508 6509
	if (ilb_cpu >= nr_cpu_ids)
		return;
6510

6511
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
6512 6513 6514 6515 6516 6517 6518 6519
		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);
6520 6521 6522
	return;
}

6523
static inline void nohz_balance_exit_idle(int cpu)
6524 6525 6526 6527 6528 6529 6530 6531
{
	if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) {
		cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
		atomic_dec(&nohz.nr_cpus);
		clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
	}
}

6532 6533 6534 6535 6536
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;

	rcu_read_lock();
N
Nathan Zimmer 已提交
6537
	sd = rcu_dereference_check_sched_domain(this_rq()->sd);
V
Vincent Guittot 已提交
6538 6539 6540 6541 6542 6543

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

	for (; sd; sd = sd->parent)
6544
		atomic_inc(&sd->groups->sgp->nr_busy_cpus);
V
Vincent Guittot 已提交
6545
unlock:
6546 6547 6548 6549 6550 6551 6552 6553
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;

	rcu_read_lock();
N
Nathan Zimmer 已提交
6554
	sd = rcu_dereference_check_sched_domain(this_rq()->sd);
V
Vincent Guittot 已提交
6555 6556 6557 6558 6559 6560

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

	for (; sd; sd = sd->parent)
6561
		atomic_dec(&sd->groups->sgp->nr_busy_cpus);
V
Vincent Guittot 已提交
6562
unlock:
6563 6564 6565
	rcu_read_unlock();
}

6566
/*
6567
 * This routine will record that the cpu is going idle with tick stopped.
6568
 * This info will be used in performing idle load balancing in the future.
6569
 */
6570
void nohz_balance_enter_idle(int cpu)
6571
{
6572 6573 6574 6575 6576 6577
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

6578 6579
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
6580

6581 6582 6583
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
6584
}
6585

6586
static int sched_ilb_notifier(struct notifier_block *nfb,
6587 6588 6589 6590
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
6591
		nohz_balance_exit_idle(smp_processor_id());
6592 6593 6594 6595 6596
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
6597 6598 6599 6600
#endif

static DEFINE_SPINLOCK(balancing);

6601 6602 6603 6604
/*
 * 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.
 */
6605
void update_max_interval(void)
6606 6607 6608 6609
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

6610 6611 6612 6613
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
6614
 * Balancing parameters are set up in init_sched_domains.
6615 6616 6617
 */
static void rebalance_domains(int cpu, enum cpu_idle_type idle)
{
6618
	int continue_balancing = 1;
6619 6620
	struct rq *rq = cpu_rq(cpu);
	unsigned long interval;
6621
	struct sched_domain *sd;
6622 6623 6624
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
6625 6626
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
6627

6628
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
6629

6630
	rcu_read_lock();
6631
	for_each_domain(cpu, sd) {
6632 6633 6634 6635 6636 6637 6638 6639 6640 6641 6642 6643
		/*
		 * 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;

6644 6645 6646
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

6647 6648 6649 6650 6651 6652 6653 6654 6655 6656 6657
		/*
		 * 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;
		}

6658 6659 6660 6661 6662 6663
		interval = sd->balance_interval;
		if (idle != CPU_IDLE)
			interval *= sd->busy_factor;

		/* scale ms to jiffies */
		interval = msecs_to_jiffies(interval);
6664
		interval = clamp(interval, 1UL, max_load_balance_interval);
6665 6666 6667 6668 6669 6670 6671 6672 6673

		need_serialize = sd->flags & SD_SERIALIZE;

		if (need_serialize) {
			if (!spin_trylock(&balancing))
				goto out;
		}

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
6674
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
6675
				/*
6676
				 * The LBF_DST_PINNED logic could have changed
6677 6678
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
6679
				 */
6680
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
6681 6682 6683 6684 6685 6686 6687 6688 6689 6690
			}
			sd->last_balance = jiffies;
		}
		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;
		}
6691 6692
	}
	if (need_decay) {
6693
		/*
6694 6695
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
6696
		 */
6697 6698
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
6699
	}
6700
	rcu_read_unlock();
6701 6702 6703 6704 6705 6706 6707 6708 6709 6710

	/*
	 * 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;
}

6711
#ifdef CONFIG_NO_HZ_COMMON
6712
/*
6713
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
6714 6715
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
6716 6717 6718 6719 6720 6721
static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle)
{
	struct rq *this_rq = cpu_rq(this_cpu);
	struct rq *rq;
	int balance_cpu;

6722 6723 6724
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
6725 6726

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
6727
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
6728 6729 6730 6731 6732 6733 6734
			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.
		 */
6735
		if (need_resched())
6736 6737
			break;

V
Vincent Guittot 已提交
6738 6739 6740 6741 6742 6743
		rq = cpu_rq(balance_cpu);

		raw_spin_lock_irq(&rq->lock);
		update_rq_clock(rq);
		update_idle_cpu_load(rq);
		raw_spin_unlock_irq(&rq->lock);
6744 6745 6746 6747 6748 6749 6750

		rebalance_domains(balance_cpu, CPU_IDLE);

		if (time_after(this_rq->next_balance, rq->next_balance))
			this_rq->next_balance = rq->next_balance;
	}
	nohz.next_balance = this_rq->next_balance;
6751 6752
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
6753 6754 6755
}

/*
6756 6757 6758 6759 6760 6761 6762
 * Current heuristic for kicking the idle load balancer in the presence
 * of an idle cpu is the system.
 *   - This rq has more than one task.
 *   - At any scheduler domain level, this cpu's scheduler group has multiple
 *     busy cpu's exceeding the group's power.
 *   - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
 *     domain span are idle.
6763 6764 6765 6766
 */
static inline int nohz_kick_needed(struct rq *rq, int cpu)
{
	unsigned long now = jiffies;
6767
	struct sched_domain *sd;
6768

6769
	if (unlikely(idle_cpu(cpu)))
6770 6771
		return 0;

6772 6773 6774 6775
       /*
	* 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.
	*/
6776
	set_cpu_sd_state_busy();
6777
	nohz_balance_exit_idle(cpu);
6778 6779 6780 6781 6782 6783 6784

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
		return 0;
6785 6786

	if (time_before(now, nohz.next_balance))
6787 6788
		return 0;

6789 6790
	if (rq->nr_running >= 2)
		goto need_kick;
6791

6792
	rcu_read_lock();
6793 6794 6795 6796
	for_each_domain(cpu, sd) {
		struct sched_group *sg = sd->groups;
		struct sched_group_power *sgp = sg->sgp;
		int nr_busy = atomic_read(&sgp->nr_busy_cpus);
6797

6798
		if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1)
6799
			goto need_kick_unlock;
6800 6801 6802 6803

		if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight
		    && (cpumask_first_and(nohz.idle_cpus_mask,
					  sched_domain_span(sd)) < cpu))
6804
			goto need_kick_unlock;
6805 6806 6807

		if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING)))
			break;
6808
	}
6809
	rcu_read_unlock();
6810
	return 0;
6811 6812 6813

need_kick_unlock:
	rcu_read_unlock();
6814 6815
need_kick:
	return 1;
6816 6817 6818 6819 6820 6821 6822 6823 6824
}
#else
static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle) { }
#endif

/*
 * run_rebalance_domains is triggered when needed from the scheduler tick.
 * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
 */
6825 6826 6827 6828
static void run_rebalance_domains(struct softirq_action *h)
{
	int this_cpu = smp_processor_id();
	struct rq *this_rq = cpu_rq(this_cpu);
6829
	enum cpu_idle_type idle = this_rq->idle_balance ?
6830 6831 6832 6833 6834
						CPU_IDLE : CPU_NOT_IDLE;

	rebalance_domains(this_cpu, idle);

	/*
6835
	 * If this cpu has a pending nohz_balance_kick, then do the
6836 6837 6838
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
6839
	nohz_idle_balance(this_cpu, idle);
6840 6841 6842 6843
}

static inline int on_null_domain(int cpu)
{
6844
	return !rcu_dereference_sched(cpu_rq(cpu)->sd);
6845 6846 6847 6848 6849
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
6850
void trigger_load_balance(struct rq *rq, int cpu)
6851 6852 6853 6854 6855
{
	/* Don't need to rebalance while attached to NULL domain */
	if (time_after_eq(jiffies, rq->next_balance) &&
	    likely(!on_null_domain(cpu)))
		raise_softirq(SCHED_SOFTIRQ);
6856
#ifdef CONFIG_NO_HZ_COMMON
6857
	if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
6858 6859
		nohz_balancer_kick(cpu);
#endif
6860 6861
}

6862 6863 6864 6865 6866 6867 6868 6869
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
6870 6871 6872

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
6873 6874
}

6875
#endif /* CONFIG_SMP */
6876

6877 6878 6879
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
6880
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
6881 6882 6883 6884 6885 6886
{
	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
6887
		entity_tick(cfs_rq, se, queued);
6888
	}
6889

6890
	if (numabalancing_enabled)
6891
		task_tick_numa(rq, curr);
6892

6893
	update_rq_runnable_avg(rq, 1);
6894 6895 6896
}

/*
P
Peter Zijlstra 已提交
6897 6898 6899
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
6900
 */
P
Peter Zijlstra 已提交
6901
static void task_fork_fair(struct task_struct *p)
6902
{
6903 6904
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
6905
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
6906 6907 6908
	struct rq *rq = this_rq();
	unsigned long flags;

6909
	raw_spin_lock_irqsave(&rq->lock, flags);
6910

6911 6912
	update_rq_clock(rq);

6913 6914 6915
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

6916 6917 6918 6919 6920 6921 6922 6923 6924
	/*
	 * 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();
6925

6926
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
6927

6928 6929
	if (curr)
		se->vruntime = curr->vruntime;
6930
	place_entity(cfs_rq, se, 1);
6931

P
Peter Zijlstra 已提交
6932
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
6933
		/*
6934 6935 6936
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
6937
		swap(curr->vruntime, se->vruntime);
6938
		resched_task(rq->curr);
6939
	}
6940

6941 6942
	se->vruntime -= cfs_rq->min_vruntime;

6943
	raw_spin_unlock_irqrestore(&rq->lock, flags);
6944 6945
}

6946 6947 6948 6949
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
6950 6951
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
6952
{
P
Peter Zijlstra 已提交
6953 6954 6955
	if (!p->se.on_rq)
		return;

6956 6957 6958 6959 6960
	/*
	 * 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
6961
	if (rq->curr == p) {
6962 6963 6964
		if (p->prio > oldprio)
			resched_task(rq->curr);
	} else
6965
		check_preempt_curr(rq, p, 0);
6966 6967
}

P
Peter Zijlstra 已提交
6968 6969 6970 6971 6972 6973 6974 6975 6976 6977 6978 6979 6980 6981 6982 6983 6984 6985 6986 6987 6988 6989
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);

	/*
	 * Ensure the task's vruntime is normalized, so that when its
	 * switched back to the fair class the enqueue_entity(.flags=0) will
	 * do the right thing.
	 *
	 * If it was on_rq, then the dequeue_entity(.flags=0) will already
	 * have normalized the vruntime, if it was !on_rq, then only when
	 * the task is sleeping will it still have non-normalized vruntime.
	 */
	if (!se->on_rq && p->state != TASK_RUNNING) {
		/*
		 * 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;
	}
6990

6991
#ifdef CONFIG_SMP
6992 6993 6994 6995 6996
	/*
	* Remove our load from contribution when we leave sched_fair
	* and ensure we don't carry in an old decay_count if we
	* switch back.
	*/
6997 6998 6999
	if (se->avg.decay_count) {
		__synchronize_entity_decay(se);
		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
7000 7001
	}
#endif
P
Peter Zijlstra 已提交
7002 7003
}

7004 7005 7006
/*
 * We switched to the sched_fair class.
 */
P
Peter Zijlstra 已提交
7007
static void switched_to_fair(struct rq *rq, struct task_struct *p)
7008
{
P
Peter Zijlstra 已提交
7009 7010 7011
	if (!p->se.on_rq)
		return;

7012 7013 7014 7015 7016
	/*
	 * 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
7017
	if (rq->curr == p)
7018 7019
		resched_task(rq->curr);
	else
7020
		check_preempt_curr(rq, p, 0);
7021 7022
}

7023 7024 7025 7026 7027 7028 7029 7030 7031
/* 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;

7032 7033 7034 7035 7036 7037 7038
	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);
	}
7039 7040
}

7041 7042 7043 7044 7045 7046 7047
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
7048
#ifdef CONFIG_SMP
7049
	atomic64_set(&cfs_rq->decay_counter, 1);
7050
	atomic_long_set(&cfs_rq->removed_load, 0);
7051
#endif
7052 7053
}

P
Peter Zijlstra 已提交
7054
#ifdef CONFIG_FAIR_GROUP_SCHED
7055
static void task_move_group_fair(struct task_struct *p, int on_rq)
P
Peter Zijlstra 已提交
7056
{
7057
	struct cfs_rq *cfs_rq;
7058 7059 7060 7061 7062 7063 7064 7065 7066 7067 7068 7069 7070
	/*
	 * 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.
	 */
7071 7072 7073 7074 7075 7076
	/*
	 * When !on_rq, vruntime of the task has usually NOT been normalized.
	 * 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().
7077 7078
	 * - Moving a task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
7079 7080 7081 7082
	 *
	 * To prevent boost or penalty in the new cfs_rq caused by delta
	 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
	 */
7083
	if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING))
7084 7085
		on_rq = 1;

7086 7087 7088
	if (!on_rq)
		p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
	set_task_rq(p, task_cpu(p));
7089 7090 7091 7092 7093 7094 7095 7096 7097 7098 7099 7100 7101
	if (!on_rq) {
		cfs_rq = cfs_rq_of(&p->se);
		p->se.vruntime += cfs_rq->min_vruntime;
#ifdef CONFIG_SMP
		/*
		 * migrate_task_rq_fair() will have removed our previous
		 * contribution, but we must synchronize for ongoing future
		 * decay.
		 */
		p->se.avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
		cfs_rq->blocked_load_avg += p->se.avg.load_avg_contrib;
#endif
	}
P
Peter Zijlstra 已提交
7102
}
7103 7104 7105 7106 7107 7108 7109 7110 7111 7112 7113 7114 7115 7116 7117 7118 7119 7120 7121 7122 7123 7124 7125 7126 7127 7128 7129 7130 7131 7132 7133 7134 7135 7136 7137 7138 7139 7140 7141 7142 7143 7144 7145 7146 7147 7148 7149 7150 7151 7152 7153 7154 7155 7156 7157 7158 7159 7160 7161 7162 7163 7164 7165 7166 7167 7168 7169 7170 7171 7172 7173 7174 7175 7176 7177 7178 7179 7180 7181 7182 7183 7184 7185 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 7213 7214 7215 7216 7217 7218 7219 7220 7221 7222 7223 7224 7225 7226 7227 7228 7229 7230 7231

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

	destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));

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

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

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

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

	tg->shares = NICE_0_LOAD;

	init_cfs_bandwidth(tg_cfs_bandwidth(tg));

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

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

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

	return 1;

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

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

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

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

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

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

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

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

	if (!parent)
		se->cfs_rq = &rq->cfs;
	else
		se->cfs_rq = parent->my_q;

	se->my_q = cfs_rq;
	update_load_set(&se->load, 0);
	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);
7232 7233 7234

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
7235
		for_each_sched_entity(se)
7236 7237 7238 7239 7240 7241 7242 7243 7244 7245 7246 7247 7248 7249 7250 7251 7252 7253 7254 7255 7256
			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
7257

7258
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
7259 7260 7261 7262 7263 7264 7265 7266 7267
{
	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)
7268
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
7269 7270 7271 7272

	return rr_interval;
}

7273 7274 7275
/*
 * All the scheduling class methods:
 */
7276
const struct sched_class fair_sched_class = {
7277
	.next			= &idle_sched_class,
7278 7279 7280
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
7281
	.yield_to_task		= yield_to_task_fair,
7282

I
Ingo Molnar 已提交
7283
	.check_preempt_curr	= check_preempt_wakeup,
7284 7285 7286 7287

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

7288
#ifdef CONFIG_SMP
L
Li Zefan 已提交
7289
	.select_task_rq		= select_task_rq_fair,
7290
	.migrate_task_rq	= migrate_task_rq_fair,
7291

7292 7293
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
7294 7295

	.task_waking		= task_waking_fair,
7296
#endif
7297

7298
	.set_curr_task          = set_curr_task_fair,
7299
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
7300
	.task_fork		= task_fork_fair,
7301 7302

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
7303
	.switched_from		= switched_from_fair,
7304
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
7305

7306 7307
	.get_rr_interval	= get_rr_interval_fair,

P
Peter Zijlstra 已提交
7308
#ifdef CONFIG_FAIR_GROUP_SCHED
7309
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
7310
#endif
7311 7312 7313
};

#ifdef CONFIG_SCHED_DEBUG
7314
void print_cfs_stats(struct seq_file *m, int cpu)
7315 7316 7317
{
	struct cfs_rq *cfs_rq;

7318
	rcu_read_lock();
7319
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
7320
		print_cfs_rq(m, cpu, cfs_rq);
7321
	rcu_read_unlock();
7322 7323
}
#endif
7324 7325 7326 7327 7328 7329

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

7330
#ifdef CONFIG_NO_HZ_COMMON
7331
	nohz.next_balance = jiffies;
7332
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
7333
	cpu_notifier(sched_ilb_notifier, 0);
7334 7335 7336 7337
#endif
#endif /* SMP */

}