fair.c 157.8 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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/*
 * 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 min_vruntime, u64 vruntime)
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{
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	s64 delta = (s64)(vruntime - min_vruntime);
	if (delta > 0)
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		min_vruntime = vruntime;

	return min_vruntime;
}

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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);
	}

	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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/*
 * Update the current task's runtime statistics. Skip current tasks that
 * are not in our scheduling class.
 */
static inline void
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__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
	      unsigned long delta_exec)
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{
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	unsigned long delta_exec_weighted;
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	schedstat_set(curr->statistics.exec_max,
		      max((u64)delta_exec, curr->statistics.exec_max));
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	curr->sum_exec_runtime += delta_exec;
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	schedstat_add(cfs_rq, exec_clock, delta_exec);
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	delta_exec_weighted = calc_delta_fair(delta_exec, curr);
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	curr->vruntime += delta_exec_weighted;
682
	update_min_vruntime(cfs_rq);
683 684
}

685
static void update_curr(struct cfs_rq *cfs_rq)
686
{
687
	struct sched_entity *curr = cfs_rq->curr;
688
	u64 now = rq_of(cfs_rq)->clock_task;
689 690 691 692 693 694 695 696 697 698
	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):
	 */
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699
	delta_exec = (unsigned long)(now - curr->exec_start);
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700 701
	if (!delta_exec)
		return;
702

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703 704
	__update_curr(cfs_rq, curr, delta_exec);
	curr->exec_start = now;
705 706 707 708

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

709
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
710
		cpuacct_charge(curtask, delta_exec);
711
		account_group_exec_runtime(curtask, delta_exec);
712
	}
713 714

	account_cfs_rq_runtime(cfs_rq, delta_exec);
715 716 717
}

static inline void
718
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
719
{
720
	schedstat_set(se->statistics.wait_start, rq_of(cfs_rq)->clock);
721 722 723 724 725
}

/*
 * Task is being enqueued - update stats:
 */
726
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
727 728 729 730 731
{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
732
	if (se != cfs_rq->curr)
733
		update_stats_wait_start(cfs_rq, se);
734 735 736
}

static void
737
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
738
{
739 740 741 742 743
	schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
			rq_of(cfs_rq)->clock - se->statistics.wait_start));
	schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
	schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
			rq_of(cfs_rq)->clock - se->statistics.wait_start);
744 745 746
#ifdef CONFIG_SCHEDSTATS
	if (entity_is_task(se)) {
		trace_sched_stat_wait(task_of(se),
747
			rq_of(cfs_rq)->clock - se->statistics.wait_start);
748 749
	}
#endif
750
	schedstat_set(se->statistics.wait_start, 0);
751 752 753
}

static inline void
754
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
755 756 757 758 759
{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
760
	if (se != cfs_rq->curr)
761
		update_stats_wait_end(cfs_rq, se);
762 763 764 765 766 767
}

/*
 * We are picking a new current task - update its stats:
 */
static inline void
768
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
769 770 771 772
{
	/*
	 * We are starting a new run period:
	 */
773
	se->exec_start = rq_of(cfs_rq)->clock_task;
774 775 776 777 778 779
}

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

780 781
#ifdef CONFIG_NUMA_BALANCING
/*
782
 * numa task sample period in ms
783
 */
784
unsigned int sysctl_numa_balancing_scan_period_min = 100;
785 786
unsigned int sysctl_numa_balancing_scan_period_max = 100*50;
unsigned int sysctl_numa_balancing_scan_period_reset = 100*600;
787 788 789

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
790

791 792 793
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

794 795
static void task_numa_placement(struct task_struct *p)
{
796
	int seq;
797

798 799 800
	if (!p->mm)	/* for example, ksmd faulting in a user's mm */
		return;
	seq = ACCESS_ONCE(p->mm->numa_scan_seq);
801 802 803 804 805 806 807 808 809 810
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;

	/* FIXME: Scheduling placement policy hints go here */
}

/*
 * Got a PROT_NONE fault for a page on @node.
 */
811
void task_numa_fault(int node, int pages, bool migrated)
812 813 814
{
	struct task_struct *p = current;

815 816 817
	if (!sched_feat_numa(NUMA))
		return;

818 819
	/* FIXME: Allocate task-specific structure for placement policy here */

820
	/*
821 822
	 * If pages are properly placed (did not migrate) then scan slower.
	 * This is reset periodically in case of phase changes
823
	 */
824 825 826
        if (!migrated)
		p->numa_scan_period = min(sysctl_numa_balancing_scan_period_max,
			p->numa_scan_period + jiffies_to_msecs(10));
827

828 829 830
	task_numa_placement(p);
}

831 832 833 834 835 836
static void reset_ptenuma_scan(struct task_struct *p)
{
	ACCESS_ONCE(p->mm->numa_scan_seq)++;
	p->mm->numa_scan_offset = 0;
}

837 838 839 840 841 842 843 844 845
/*
 * 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;
846
	struct vm_area_struct *vma;
847 848
	unsigned long start, end;
	long pages;
849 850 851 852 853 854 855 856 857 858 859 860 861 862 863

	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;

864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881
	/*
	 * We do not care about task placement until a task runs on a node
	 * other than the first one used by the address space. This is
	 * largely because migrations are driven by what CPU the task
	 * is running on. If it's never scheduled on another node, it'll
	 * not migrate so why bother trapping the fault.
	 */
	if (mm->first_nid == NUMA_PTE_SCAN_INIT)
		mm->first_nid = numa_node_id();
	if (mm->first_nid != NUMA_PTE_SCAN_ACTIVE) {
		/* Are we running on a new node yet? */
		if (numa_node_id() == mm->first_nid &&
		    !sched_feat_numa(NUMA_FORCE))
			return;

		mm->first_nid = NUMA_PTE_SCAN_ACTIVE;
	}

882 883 884 885 886 887 888 889 890 891 892 893 894
	/*
	 * Reset the scan period if enough time has gone by. Objective is that
	 * scanning will be reduced if pages are properly placed. As tasks
	 * can enter different phases this needs to be re-examined. Lacking
	 * proper tracking of reference behaviour, this blunt hammer is used.
	 */
	migrate = mm->numa_next_reset;
	if (time_after(now, migrate)) {
		p->numa_scan_period = sysctl_numa_balancing_scan_period_min;
		next_scan = now + msecs_to_jiffies(sysctl_numa_balancing_scan_period_reset);
		xchg(&mm->numa_next_reset, next_scan);
	}

895 896 897 898 899 900 901 902 903 904
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

	if (p->numa_scan_period == 0)
		p->numa_scan_period = sysctl_numa_balancing_scan_period_min;

905
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
906 907 908
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

909 910 911 912 913 914 915 916
	/*
	 * Do not set pte_numa if the current running node is rate-limited.
	 * This loses statistics on the fault but if we are unwilling to
	 * migrate to this node, it is less likely we can do useful work
	 */
	if (migrate_ratelimited(numa_node_id()))
		return;

917 918 919 920 921
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
	if (!pages)
		return;
922

923
	down_read(&mm->mmap_sem);
924
	vma = find_vma(mm, start);
925 926
	if (!vma) {
		reset_ptenuma_scan(p);
927
		start = 0;
928 929
		vma = mm->mmap;
	}
930
	for (; vma; vma = vma->vm_next) {
931 932 933 934
		if (!vma_migratable(vma))
			continue;

		/* Skip small VMAs. They are not likely to be of relevance */
935
		if (vma->vm_end - vma->vm_start < HPAGE_SIZE)
936 937
			continue;

938 939 940 941 942
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
			pages -= change_prot_numa(vma, start, end);
943

944 945 946 947
			start = end;
			if (pages <= 0)
				goto out;
		} while (end != vma->vm_end);
948
	}
949

950
out:
951 952 953 954 955 956 957
	/*
	 * 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.
	 */
	if (vma)
958
		mm->numa_scan_offset = start;
959 960 961
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987
}

/*
 * 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) {
988 989
		if (!curr->node_stamp)
			curr->numa_scan_period = sysctl_numa_balancing_scan_period_min;
990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003
		curr->node_stamp = now;

		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)
{
}
#endif /* CONFIG_NUMA_BALANCING */

1004 1005 1006 1007
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
1008
	if (!parent_entity(se))
1009
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
1010 1011
#ifdef CONFIG_SMP
	if (entity_is_task(se))
1012
		list_add(&se->group_node, &rq_of(cfs_rq)->cfs_tasks);
1013
#endif
1014 1015 1016 1017 1018 1019 1020
	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);
1021
	if (!parent_entity(se))
1022
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
1023
	if (entity_is_task(se))
1024
		list_del_init(&se->group_node);
1025 1026 1027
	cfs_rq->nr_running--;
}

1028 1029
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
1030 1031 1032 1033 1034 1035 1036 1037 1038
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().
	 */
1039 1040
	tg_weight = atomic64_read(&tg->load_avg);
	tg_weight -= cfs_rq->tg_load_contrib;
1041 1042 1043 1044 1045
	tg_weight += cfs_rq->load.weight;

	return tg_weight;
}

1046
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1047
{
1048
	long tg_weight, load, shares;
1049

1050
	tg_weight = calc_tg_weight(tg, cfs_rq);
1051
	load = cfs_rq->load.weight;
1052 1053

	shares = (tg->shares * load);
1054 1055
	if (tg_weight)
		shares /= tg_weight;
1056 1057 1058 1059 1060 1061 1062 1063 1064

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

	return shares;
}
# else /* CONFIG_SMP */
1065
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1066 1067 1068 1069
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
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1070 1071 1072
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
1073 1074 1075 1076
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
1077
		account_entity_dequeue(cfs_rq, se);
1078
	}
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1079 1080 1081 1082 1083 1084 1085

	update_load_set(&se->load, weight);

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

1086 1087
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

1088
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
1089 1090 1091
{
	struct task_group *tg;
	struct sched_entity *se;
1092
	long shares;
P
Peter Zijlstra 已提交
1093 1094 1095

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
1096
	if (!se || throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
1097
		return;
1098 1099 1100 1101
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
1102
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
1103 1104 1105 1106

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
1107
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
1108 1109 1110 1111
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

1112 1113
/* Only depends on SMP, FAIR_GROUP_SCHED may be removed when useful in lb */
#if defined(CONFIG_SMP) && defined(CONFIG_FAIR_GROUP_SCHED)
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
/*
 * 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,
};

1142 1143 1144 1145 1146 1147
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167
	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;
1168 1169
	}

1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200
	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];
1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234
}

/*
 * 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)
{
1235 1236
	u64 delta, periods;
	u32 runnable_contrib;
1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269
	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;
1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289
		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;
1290 1291 1292 1293 1294 1295 1296 1297 1298 1299
	}

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

	return decayed;
}

1300
/* Synchronize an entity's decay with its parenting cfs_rq.*/
1301
static inline u64 __synchronize_entity_decay(struct sched_entity *se)
1302 1303 1304 1305 1306 1307
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 decays = atomic64_read(&cfs_rq->decay_counter);

	decays -= se->avg.decay_count;
	if (!decays)
1308
		return 0;
1309 1310 1311

	se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
	se->avg.decay_count = 0;
1312 1313

	return decays;
1314 1315
}

1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330
#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;
	s64 tg_contrib;

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

	if (force_update || abs64(tg_contrib) > cfs_rq->tg_load_contrib / 8) {
		atomic64_add(tg_contrib, &tg->load_avg);
		cfs_rq->tg_load_contrib += tg_contrib;
	}
}
1331

1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352
/*
 * 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;
	}
}

1353 1354 1355 1356
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;
1357 1358
	int runnable_avg;

1359 1360 1361 1362 1363
	u64 contrib;

	contrib = cfs_rq->tg_load_contrib * tg->shares;
	se->avg.load_avg_contrib = div64_u64(contrib,
					     atomic64_read(&tg->load_avg) + 1);
1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392

	/*
	 * 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;
	}
1393
}
1394 1395 1396
#else
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
						 int force_update) {}
1397 1398
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
						  struct cfs_rq *cfs_rq) {}
1399
static inline void __update_group_entity_contrib(struct sched_entity *se) {}
1400 1401
#endif

1402 1403 1404 1405 1406 1407 1408 1409 1410 1411
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);
}

1412 1413 1414 1415 1416
/* 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;

1417 1418 1419
	if (entity_is_task(se)) {
		__update_task_entity_contrib(se);
	} else {
1420
		__update_tg_runnable_avg(&se->avg, group_cfs_rq(se));
1421 1422
		__update_group_entity_contrib(se);
	}
1423 1424 1425 1426

	return se->avg.load_avg_contrib - old_contrib;
}

1427 1428 1429 1430 1431 1432 1433 1434 1435
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;
}

1436 1437
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);

1438
/* Update a sched_entity's runnable average */
1439 1440
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq)
1441
{
1442 1443
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	long contrib_delta;
1444
	u64 now;
1445

1446 1447 1448 1449 1450 1451 1452 1453 1454 1455
	/*
	 * 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))
1456 1457 1458
		return;

	contrib_delta = __update_entity_load_avg_contrib(se);
1459 1460 1461 1462

	if (!update_cfs_rq)
		return;

1463 1464
	if (se->on_rq)
		cfs_rq->runnable_load_avg += contrib_delta;
1465 1466 1467 1468 1469 1470 1471 1472
	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.
 */
1473
static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
1474
{
1475
	u64 now = cfs_rq_clock_task(cfs_rq) >> 20;
1476 1477 1478
	u64 decays;

	decays = now - cfs_rq->last_decay;
1479
	if (!decays && !force_update)
1480 1481
		return;

1482 1483 1484 1485
	if (atomic64_read(&cfs_rq->removed_load)) {
		u64 removed_load = atomic64_xchg(&cfs_rq->removed_load, 0);
		subtract_blocked_load_contrib(cfs_rq, removed_load);
	}
1486

1487 1488 1489 1490 1491 1492
	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;
	}
1493 1494

	__update_cfs_rq_tg_load_contrib(cfs_rq, force_update);
1495
}
1496 1497 1498 1499

static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
{
	__update_entity_runnable_avg(rq->clock_task, &rq->avg, runnable);
1500
	__update_tg_runnable_avg(&rq->avg, &rq->cfs);
1501
}
1502 1503 1504

/* 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,
1505 1506
						  struct sched_entity *se,
						  int wakeup)
1507
{
1508 1509 1510 1511 1512 1513
	/*
	 * 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.
	 */
	if (unlikely(se->avg.decay_count <= 0)) {
1514
		se->avg.last_runnable_update = rq_of(cfs_rq)->clock_task;
1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529
		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;
		}
1530 1531 1532 1533 1534
		wakeup = 0;
	} else {
		__synchronize_entity_decay(se);
	}

1535 1536
	/* migrated tasks did not contribute to our blocked load */
	if (wakeup) {
1537
		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
1538 1539
		update_entity_load_avg(se, 0);
	}
1540

1541
	cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
1542 1543
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !wakeup);
1544 1545
}

1546 1547 1548 1549 1550
/*
 * 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.
 */
1551
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
1552 1553
						  struct sched_entity *se,
						  int sleep)
1554
{
1555
	update_entity_load_avg(se, 1);
1556 1557
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !sleep);
1558

1559
	cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
1560 1561 1562 1563
	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 */
1564
}
1565
#else
1566 1567
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq) {}
1568
static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
1569
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
1570 1571
					   struct sched_entity *se,
					   int wakeup) {}
1572
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
1573 1574
					   struct sched_entity *se,
					   int sleep) {}
1575 1576
static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
					      int force_update) {}
1577 1578
#endif

1579
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
1580 1581
{
#ifdef CONFIG_SCHEDSTATS
1582 1583 1584 1585 1586
	struct task_struct *tsk = NULL;

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

1587 1588
	if (se->statistics.sleep_start) {
		u64 delta = rq_of(cfs_rq)->clock - se->statistics.sleep_start;
1589 1590 1591 1592

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

1593 1594
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
1595

1596
		se->statistics.sleep_start = 0;
1597
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
1598

1599
		if (tsk) {
1600
			account_scheduler_latency(tsk, delta >> 10, 1);
1601 1602
			trace_sched_stat_sleep(tsk, delta);
		}
1603
	}
1604 1605
	if (se->statistics.block_start) {
		u64 delta = rq_of(cfs_rq)->clock - se->statistics.block_start;
1606 1607 1608 1609

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

1610 1611
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
1612

1613
		se->statistics.block_start = 0;
1614
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
1615

1616
		if (tsk) {
1617
			if (tsk->in_iowait) {
1618 1619
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
1620
				trace_sched_stat_iowait(tsk, delta);
1621 1622
			}

1623 1624
			trace_sched_stat_blocked(tsk, delta);

1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635
			/*
			 * 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
1636
		}
1637 1638 1639 1640
	}
#endif
}

P
Peter Zijlstra 已提交
1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653
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
}

1654 1655 1656
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
1657
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
1658

1659 1660 1661 1662 1663 1664
	/*
	 * 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
1665
	if (initial && sched_feat(START_DEBIT))
1666
		vruntime += sched_vslice(cfs_rq, se);
1667

1668
	/* sleeps up to a single latency don't count. */
1669
	if (!initial) {
1670
		unsigned long thresh = sysctl_sched_latency;
1671

1672 1673 1674 1675 1676 1677
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
1678

1679
		vruntime -= thresh;
1680 1681
	}

1682
	/* ensure we never gain time by being placed backwards. */
1683
	se->vruntime = max_vruntime(se->vruntime, vruntime);
1684 1685
}

1686 1687
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

1688
static void
1689
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1690
{
1691 1692 1693 1694
	/*
	 * Update the normalized vruntime before updating min_vruntime
	 * through callig update_curr().
	 */
1695
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
1696 1697
		se->vruntime += cfs_rq->min_vruntime;

1698
	/*
1699
	 * Update run-time statistics of the 'current'.
1700
	 */
1701
	update_curr(cfs_rq);
1702
	enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
1703 1704
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
1705

1706
	if (flags & ENQUEUE_WAKEUP) {
1707
		place_entity(cfs_rq, se, 0);
1708
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
1709
	}
1710

1711
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
1712
	check_spread(cfs_rq, se);
1713 1714
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
1715
	se->on_rq = 1;
1716

1717
	if (cfs_rq->nr_running == 1) {
1718
		list_add_leaf_cfs_rq(cfs_rq);
1719 1720
		check_enqueue_throttle(cfs_rq);
	}
1721 1722
}

1723
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
1724
{
1725 1726 1727 1728 1729 1730 1731 1732
	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
1733

1734 1735 1736 1737 1738 1739 1740 1741 1742
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
1743 1744
}

1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755
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
1756 1757
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
1758 1759 1760 1761 1762
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
1763 1764 1765

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
1766 1767
}

1768
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
1769

1770
static void
1771
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1772
{
1773 1774 1775 1776
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
1777
	dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);
1778

1779
	update_stats_dequeue(cfs_rq, se);
1780
	if (flags & DEQUEUE_SLEEP) {
P
Peter Zijlstra 已提交
1781
#ifdef CONFIG_SCHEDSTATS
1782 1783 1784 1785
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
1786
				se->statistics.sleep_start = rq_of(cfs_rq)->clock;
1787
			if (tsk->state & TASK_UNINTERRUPTIBLE)
1788
				se->statistics.block_start = rq_of(cfs_rq)->clock;
1789
		}
1790
#endif
P
Peter Zijlstra 已提交
1791 1792
	}

P
Peter Zijlstra 已提交
1793
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
1794

1795
	if (se != cfs_rq->curr)
1796
		__dequeue_entity(cfs_rq, se);
1797
	se->on_rq = 0;
1798
	account_entity_dequeue(cfs_rq, se);
1799 1800 1801 1802 1803 1804

	/*
	 * 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.
	 */
1805
	if (!(flags & DEQUEUE_SLEEP))
1806
		se->vruntime -= cfs_rq->min_vruntime;
1807

1808 1809 1810
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

1811
	update_min_vruntime(cfs_rq);
1812
	update_cfs_shares(cfs_rq);
1813 1814 1815 1816 1817
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
1818
static void
I
Ingo Molnar 已提交
1819
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
1820
{
1821
	unsigned long ideal_runtime, delta_exec;
1822 1823
	struct sched_entity *se;
	s64 delta;
1824

P
Peter Zijlstra 已提交
1825
	ideal_runtime = sched_slice(cfs_rq, curr);
1826
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
1827
	if (delta_exec > ideal_runtime) {
1828
		resched_task(rq_of(cfs_rq)->curr);
1829 1830 1831 1832 1833
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844
		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;

1845 1846
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
1847

1848 1849
	if (delta < 0)
		return;
1850

1851 1852
	if (delta > ideal_runtime)
		resched_task(rq_of(cfs_rq)->curr);
1853 1854
}

1855
static void
1856
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
1857
{
1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868
	/* '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);
	}

1869
	update_stats_curr_start(cfs_rq, se);
1870
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
1871 1872 1873 1874 1875 1876
#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):
	 */
1877
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
1878
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
1879 1880 1881
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
1882
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
1883 1884
}

1885 1886 1887
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

1888 1889 1890 1891 1892 1893 1894
/*
 * 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
 */
1895
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
1896
{
1897
	struct sched_entity *se = __pick_first_entity(cfs_rq);
1898
	struct sched_entity *left = se;
1899

1900 1901 1902 1903 1904 1905 1906 1907 1908
	/*
	 * 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;
	}
1909

1910 1911 1912 1913 1914 1915
	/*
	 * 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;

1916 1917 1918 1919 1920 1921
	/*
	 * 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;

1922
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
1923 1924

	return se;
1925 1926
}

1927 1928
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq);

1929
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
1930 1931 1932 1933 1934 1935
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
1936
		update_curr(cfs_rq);
1937

1938 1939 1940
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

P
Peter Zijlstra 已提交
1941
	check_spread(cfs_rq, prev);
1942
	if (prev->on_rq) {
1943
		update_stats_wait_start(cfs_rq, prev);
1944 1945
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
1946
		/* in !on_rq case, update occurred at dequeue */
1947
		update_entity_load_avg(prev, 1);
1948
	}
1949
	cfs_rq->curr = NULL;
1950 1951
}

P
Peter Zijlstra 已提交
1952 1953
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
1954 1955
{
	/*
1956
	 * Update run-time statistics of the 'current'.
1957
	 */
1958
	update_curr(cfs_rq);
1959

1960 1961 1962
	/*
	 * Ensure that runnable average is periodically updated.
	 */
1963
	update_entity_load_avg(curr, 1);
1964
	update_cfs_rq_blocked_load(cfs_rq, 1);
1965

P
Peter Zijlstra 已提交
1966 1967 1968 1969 1970
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
1971 1972 1973 1974
	if (queued) {
		resched_task(rq_of(cfs_rq)->curr);
		return;
	}
P
Peter Zijlstra 已提交
1975 1976 1977 1978 1979 1980 1981 1982
	/*
	 * 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
1983
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
1984
		check_preempt_tick(cfs_rq, curr);
1985 1986
}

1987 1988 1989 1990 1991 1992

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

#ifdef CONFIG_CFS_BANDWIDTH
1993 1994

#ifdef HAVE_JUMP_LABEL
1995
static struct static_key __cfs_bandwidth_used;
1996 1997 1998

static inline bool cfs_bandwidth_used(void)
{
1999
	return static_key_false(&__cfs_bandwidth_used);
2000 2001 2002 2003 2004 2005
}

void account_cfs_bandwidth_used(int enabled, int was_enabled)
{
	/* only need to count groups transitioning between enabled/!enabled */
	if (enabled && !was_enabled)
2006
		static_key_slow_inc(&__cfs_bandwidth_used);
2007
	else if (!enabled && was_enabled)
2008
		static_key_slow_dec(&__cfs_bandwidth_used);
2009 2010 2011 2012 2013 2014 2015 2016 2017 2018
}
#else /* HAVE_JUMP_LABEL */
static bool cfs_bandwidth_used(void)
{
	return true;
}

void account_cfs_bandwidth_used(int enabled, int was_enabled) {}
#endif /* HAVE_JUMP_LABEL */

2019 2020 2021 2022 2023 2024 2025 2026
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
2027 2028 2029 2030 2031 2032

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

P
Paul Turner 已提交
2033 2034 2035 2036 2037 2038 2039
/*
 * 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
 */
2040
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051
{
	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);
}

2052 2053 2054 2055 2056
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

2057 2058 2059 2060 2061 2062 2063 2064 2065
/* 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;

	return rq_of(cfs_rq)->clock_task - cfs_rq->throttled_clock_task_time;
}

2066 2067
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2068 2069 2070
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
2071
	u64 amount = 0, min_amount, expires;
2072 2073 2074 2075 2076 2077 2078

	/* 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;
2079
	else {
P
Paul Turner 已提交
2080 2081 2082 2083 2084 2085 2086 2087
		/*
		 * 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);
2088
			__start_cfs_bandwidth(cfs_b);
P
Paul Turner 已提交
2089
		}
2090 2091 2092 2093 2094 2095

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
2096
	}
P
Paul Turner 已提交
2097
	expires = cfs_b->runtime_expires;
2098 2099 2100
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
2101 2102 2103 2104 2105 2106 2107
	/*
	 * 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;
2108 2109

	return cfs_rq->runtime_remaining > 0;
2110 2111
}

P
Paul Turner 已提交
2112 2113 2114 2115 2116
/*
 * 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)
2117
{
P
Paul Turner 已提交
2118 2119 2120 2121 2122
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);
	struct rq *rq = rq_of(cfs_rq);

	/* if the deadline is ahead of our clock, nothing to do */
	if (likely((s64)(rq->clock - cfs_rq->runtime_expires) < 0))
2123 2124
		return;

P
Paul Turner 已提交
2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149
	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) */
2150
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
2151 2152 2153
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
2154 2155
		return;

2156 2157 2158 2159 2160 2161
	/*
	 * 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);
2162 2163
}

2164 2165
static __always_inline
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec)
2166
{
2167
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
2168 2169 2170 2171 2172
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

2173 2174
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
2175
	return cfs_bandwidth_used() && cfs_rq->throttled;
2176 2177
}

2178 2179 2180
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
2181
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209
}

/*
 * 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) {
2210 2211 2212
		/* adjust cfs_rq_clock_task() */
		cfs_rq->throttled_clock_task_time += rq->clock_task -
					     cfs_rq->throttled_clock_task;
2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223
	}
#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)];

2224 2225
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
2226
		cfs_rq->throttled_clock_task = rq->clock_task;
2227 2228 2229 2230 2231
	cfs_rq->throttle_count++;

	return 0;
}

2232
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
2233 2234 2235 2236 2237 2238 2239 2240
{
	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))];

2241
	/* freeze hierarchy runnable averages while throttled */
2242 2243 2244
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264

	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;
2265
	cfs_rq->throttled_clock = rq->clock;
2266 2267 2268 2269 2270
	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);
}

2271
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282
{
	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;

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

	cfs_rq->throttled = 0;
	raw_spin_lock(&cfs_b->lock);
2283
	cfs_b->throttled_time += rq->clock - cfs_rq->throttled_clock;
2284 2285 2286
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

2287 2288 2289 2290
	update_rq_clock(rq);
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353
	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;
}

2354 2355 2356 2357 2358 2359 2360 2361
/*
 * 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)
{
2362 2363
	u64 runtime, runtime_expires;
	int idle = 1, throttled;
2364 2365 2366 2367 2368 2369

	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;

2370 2371 2372
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
	/* idle depends on !throttled (for the case of a large deficit) */
	idle = cfs_b->idle && !throttled;
2373
	cfs_b->nr_periods += overrun;
2374

P
Paul Turner 已提交
2375 2376 2377 2378 2379 2380
	/* if we're going inactive then everything else can be deferred */
	if (idle)
		goto out_unlock;

	__refill_cfs_bandwidth_runtime(cfs_b);

2381 2382 2383 2384 2385 2386
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
		goto out_unlock;
	}

2387 2388 2389
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413
	/*
	 * 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);
	}
2414

2415 2416 2417 2418 2419 2420 2421 2422 2423
	/* 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;
2424 2425 2426 2427 2428 2429 2430
out_unlock:
	if (idle)
		cfs_b->timer_active = 0;
	raw_spin_unlock(&cfs_b->lock);

	return idle;
}
2431

2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495
/* 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;

/* are we near the end of the current quota period? */
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)
{
2496 2497 2498
	if (!cfs_bandwidth_used())
		return;

2499
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536
		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 */
	if (runtime_refresh_within(cfs_b, min_bandwidth_expiration))
		return;

	raw_spin_lock(&cfs_b->lock);
	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);
}

2537 2538 2539 2540 2541 2542 2543
/*
 * 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)
{
2544 2545 2546
	if (!cfs_bandwidth_used())
		return;

2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563
	/* 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)
{
2564 2565 2566
	if (!cfs_bandwidth_used())
		return;

2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578
	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);
}
2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663

static inline u64 default_cfs_period(void);
static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun);
static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b);

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
	 */
	while (unlikely(hrtimer_active(&cfs_b->period_timer))) {
		raw_spin_unlock(&cfs_b->lock);
		/* ensure cfs_b->lock is available while we wait */
		hrtimer_cancel(&cfs_b->period_timer);

		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);
}

2664
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684
{
	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 */
2685 2686 2687 2688 2689 2690 2691
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
	return rq_of(cfs_rq)->clock_task;
}

static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
				     unsigned long delta_exec) {}
2692 2693
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
2694
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2695 2696 2697 2698 2699

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710

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;
}
2711 2712 2713 2714 2715

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) {}
2716 2717
#endif

2718 2719 2720 2721 2722
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) {}
2723
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
2724 2725 2726

#endif /* CONFIG_CFS_BANDWIDTH */

2727 2728 2729 2730
/**************************************************
 * CFS operations on tasks:
 */

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Peter Zijlstra 已提交
2731 2732 2733 2734 2735 2736 2737 2738
#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);

2739
	if (cfs_rq->nr_running > 1) {
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Peter Zijlstra 已提交
2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753
		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.
		 */
2754
		if (rq->curr != p)
2755
			delta = max_t(s64, 10000LL, delta);
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Peter Zijlstra 已提交
2756

2757
		hrtick_start(rq, delta);
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2758 2759
	}
}
2760 2761 2762 2763 2764 2765 2766 2767 2768 2769

/*
 * 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;

2770
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
2771 2772 2773 2774 2775
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
2776
#else /* !CONFIG_SCHED_HRTICK */
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2777 2778 2779 2780
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
2781 2782 2783 2784

static inline void hrtick_update(struct rq *rq)
{
}
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2785 2786
#endif

2787 2788 2789 2790 2791
/*
 * 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:
 */
2792
static void
2793
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
2794 2795
{
	struct cfs_rq *cfs_rq;
2796
	struct sched_entity *se = &p->se;
2797 2798

	for_each_sched_entity(se) {
2799
		if (se->on_rq)
2800 2801
			break;
		cfs_rq = cfs_rq_of(se);
2802
		enqueue_entity(cfs_rq, se, flags);
2803 2804 2805 2806 2807 2808 2809 2810 2811

		/*
		 * 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;
2812
		cfs_rq->h_nr_running++;
2813

2814
		flags = ENQUEUE_WAKEUP;
2815
	}
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2816

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2817
	for_each_sched_entity(se) {
2818
		cfs_rq = cfs_rq_of(se);
2819
		cfs_rq->h_nr_running++;
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Peter Zijlstra 已提交
2820

2821 2822 2823
		if (cfs_rq_throttled(cfs_rq))
			break;

2824
		update_cfs_shares(cfs_rq);
2825
		update_entity_load_avg(se, 1);
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Peter Zijlstra 已提交
2826 2827
	}

2828 2829
	if (!se) {
		update_rq_runnable_avg(rq, rq->nr_running);
2830
		inc_nr_running(rq);
2831
	}
2832
	hrtick_update(rq);
2833 2834
}

2835 2836
static void set_next_buddy(struct sched_entity *se);

2837 2838 2839 2840 2841
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
2842
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
2843 2844
{
	struct cfs_rq *cfs_rq;
2845
	struct sched_entity *se = &p->se;
2846
	int task_sleep = flags & DEQUEUE_SLEEP;
2847 2848 2849

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
2850
		dequeue_entity(cfs_rq, se, flags);
2851 2852 2853 2854 2855 2856 2857 2858 2859

		/*
		 * 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;
2860
		cfs_rq->h_nr_running--;
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2861

2862
		/* Don't dequeue parent if it has other entities besides us */
2863 2864 2865 2866 2867 2868 2869
		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));
2870 2871 2872

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
2873
			break;
2874
		}
2875
		flags |= DEQUEUE_SLEEP;
2876
	}
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2877

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2878
	for_each_sched_entity(se) {
2879
		cfs_rq = cfs_rq_of(se);
2880
		cfs_rq->h_nr_running--;
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Peter Zijlstra 已提交
2881

2882 2883 2884
		if (cfs_rq_throttled(cfs_rq))
			break;

2885
		update_cfs_shares(cfs_rq);
2886
		update_entity_load_avg(se, 1);
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Peter Zijlstra 已提交
2887 2888
	}

2889
	if (!se) {
2890
		dec_nr_running(rq);
2891 2892
		update_rq_runnable_avg(rq, 1);
	}
2893
	hrtick_update(rq);
2894 2895
}

2896
#ifdef CONFIG_SMP
2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
	return cpu_rq(cpu)->load.weight;
}

/*
 * 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);

	if (nr_running)
		return rq->load.weight / nr_running;

	return 0;
}

2952

2953
static void task_waking_fair(struct task_struct *p)
2954 2955 2956
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
2957 2958 2959 2960
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
2961

2962 2963 2964 2965 2966 2967 2968 2969
	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
2970

2971
	se->vruntime -= min_vruntime;
2972 2973
}

2974
#ifdef CONFIG_FAIR_GROUP_SCHED
2975 2976 2977 2978 2979 2980
/*
 * 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.
2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023
 *
 * 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.
3024
 */
P
Peter Zijlstra 已提交
3025
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
3026
{
P
Peter Zijlstra 已提交
3027
	struct sched_entity *se = tg->se[cpu];
3028

3029
	if (!tg->parent)	/* the trivial, non-cgroup case */
3030 3031
		return wl;

P
Peter Zijlstra 已提交
3032
	for_each_sched_entity(se) {
3033
		long w, W;
P
Peter Zijlstra 已提交
3034

3035
		tg = se->my_q->tg;
3036

3037 3038 3039 3040
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
3041

3042 3043 3044 3045
		/*
		 * w = rw_i + @wl
		 */
		w = se->my_q->load.weight + wl;
3046

3047 3048 3049 3050 3051
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
			wl = (w * tg->shares) / W;
3052 3053
		else
			wl = tg->shares;
3054

3055 3056 3057 3058 3059
		/*
		 * 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().
		 */
3060 3061
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
3062 3063 3064 3065

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
3066
		wl -= se->load.weight;
3067 3068 3069 3070 3071 3072 3073 3074

		/*
		 * 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
3075 3076
		wg = 0;
	}
3077

P
Peter Zijlstra 已提交
3078
	return wl;
3079 3080
}
#else
P
Peter Zijlstra 已提交
3081

3082 3083
static inline unsigned long effective_load(struct task_group *tg, int cpu,
		unsigned long wl, unsigned long wg)
P
Peter Zijlstra 已提交
3084
{
3085
	return wl;
3086
}
P
Peter Zijlstra 已提交
3087

3088 3089
#endif

3090
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
3091
{
3092
	s64 this_load, load;
3093
	int idx, this_cpu, prev_cpu;
3094
	unsigned long tl_per_task;
3095
	struct task_group *tg;
3096
	unsigned long weight;
3097
	int balanced;
3098

3099 3100 3101 3102 3103
	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);
3104

3105 3106 3107 3108 3109
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
3110 3111 3112 3113
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

3114
		this_load += effective_load(tg, this_cpu, -weight, -weight);
3115 3116
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
3117

3118 3119
	tg = task_group(p);
	weight = p->se.load.weight;
3120

3121 3122
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
3123 3124 3125
	 * 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.
3126 3127 3128 3129
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
3130 3131
	if (this_load > 0) {
		s64 this_eff_load, prev_eff_load;
3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144

		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;
3145

3146
	/*
I
Ingo Molnar 已提交
3147 3148 3149
	 * If the currently running task will sleep within
	 * a reasonable amount of time then attract this newly
	 * woken task:
3150
	 */
3151 3152
	if (sync && balanced)
		return 1;
3153

3154
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
3155 3156
	tl_per_task = cpu_avg_load_per_task(this_cpu);

3157 3158 3159
	if (balanced ||
	    (this_load <= load &&
	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
3160 3161 3162 3163 3164
		/*
		 * This domain has SD_WAKE_AFFINE and
		 * p is cache cold in this domain, and
		 * there is no bad imbalance.
		 */
3165
		schedstat_inc(sd, ttwu_move_affine);
3166
		schedstat_inc(p, se.statistics.nr_wakeups_affine);
3167 3168 3169 3170 3171 3172

		return 1;
	}
	return 0;
}

3173 3174 3175 3176 3177
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
3178
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
3179
		  int this_cpu, int load_idx)
3180
{
3181
	struct sched_group *idlest = NULL, *group = sd->groups;
3182 3183
	unsigned long min_load = ULONG_MAX, this_load = 0;
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
3184

3185 3186 3187 3188
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
3189

3190 3191
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
3192
					tsk_cpus_allowed(p)))
3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211
			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 */
3212
		avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;
3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237

		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 */
3238
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
3239 3240 3241 3242 3243
		load = weighted_cpuload(i);

		if (load < min_load || (load == min_load && i == this_cpu)) {
			min_load = load;
			idlest = i;
3244 3245 3246
		}
	}

3247 3248
	return idlest;
}
3249

3250 3251 3252
/*
 * Try and locate an idle CPU in the sched_domain.
 */
3253
static int select_idle_sibling(struct task_struct *p, int target)
3254
{
3255
	struct sched_domain *sd;
3256
	struct sched_group *sg;
3257
	int i = task_cpu(p);
3258

3259 3260
	if (idle_cpu(target))
		return target;
3261 3262

	/*
3263
	 * If the prevous cpu is cache affine and idle, don't be stupid.
3264
	 */
3265 3266
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
3267 3268

	/*
3269
	 * Otherwise, iterate the domains and find an elegible idle cpu.
3270
	 */
3271
	sd = rcu_dereference(per_cpu(sd_llc, target));
3272
	for_each_lower_domain(sd) {
3273 3274 3275 3276 3277 3278 3279
		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)) {
3280
				if (i == target || !idle_cpu(i))
3281 3282
					goto next;
			}
3283

3284 3285 3286 3287 3288 3289 3290 3291
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
3292 3293 3294
	return target;
}

3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305
/*
 * 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.
 */
3306
static int
3307
select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
3308
{
3309
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
3310 3311 3312
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
	int new_cpu = cpu;
3313
	int want_affine = 0;
3314
	int sync = wake_flags & WF_SYNC;
3315

3316
	if (p->nr_cpus_allowed == 1)
3317 3318
		return prev_cpu;

3319
	if (sd_flag & SD_BALANCE_WAKE) {
3320
		if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
3321 3322 3323
			want_affine = 1;
		new_cpu = prev_cpu;
	}
3324

3325
	rcu_read_lock();
3326
	for_each_domain(cpu, tmp) {
3327 3328 3329
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

3330
		/*
3331 3332
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
3333
		 */
3334 3335 3336
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
3337
			break;
3338
		}
3339

3340
		if (tmp->flags & sd_flag)
3341 3342 3343
			sd = tmp;
	}

3344
	if (affine_sd) {
3345
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
3346 3347 3348 3349
			prev_cpu = cpu;

		new_cpu = select_idle_sibling(p, prev_cpu);
		goto unlock;
3350
	}
3351

3352
	while (sd) {
3353
		int load_idx = sd->forkexec_idx;
3354
		struct sched_group *group;
3355
		int weight;
3356

3357
		if (!(sd->flags & sd_flag)) {
3358 3359 3360
			sd = sd->child;
			continue;
		}
3361

3362 3363
		if (sd_flag & SD_BALANCE_WAKE)
			load_idx = sd->wake_idx;
3364

3365
		group = find_idlest_group(sd, p, cpu, load_idx);
3366 3367 3368 3369
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
3370

3371
		new_cpu = find_idlest_cpu(group, p, cpu);
3372 3373 3374 3375
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
3376
		}
3377 3378 3379

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
3380
		weight = sd->span_weight;
3381 3382
		sd = NULL;
		for_each_domain(cpu, tmp) {
3383
			if (weight <= tmp->span_weight)
3384
				break;
3385
			if (tmp->flags & sd_flag)
3386 3387 3388
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
3389
	}
3390 3391
unlock:
	rcu_read_unlock();
3392

3393
	return new_cpu;
3394
}
3395

3396 3397 3398 3399 3400 3401
/*
 * Load-tracking only depends on SMP, FAIR_GROUP_SCHED dependency below may be
 * removed when useful for applications beyond shares distribution (e.g.
 * load-balance).
 */
#ifdef CONFIG_FAIR_GROUP_SCHED
3402 3403 3404 3405 3406 3407 3408 3409 3410
/*
 * 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)
{
3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423
	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);
		atomic64_add(se->avg.load_avg_contrib, &cfs_rq->removed_load);
	}
3424
}
3425
#endif
3426 3427
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
3428 3429
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
3430 3431 3432 3433
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
3434 3435
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
3436 3437 3438 3439 3440 3441 3442 3443 3444
	 *
	 * 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.
3445
	 */
3446
	return calc_delta_fair(gran, se);
3447 3448
}

3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470
/*
 * 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
3471
	gran = wakeup_gran(curr, se);
3472 3473 3474 3475 3476 3477
	if (vdiff > gran)
		return 1;

	return 0;
}

3478 3479
static void set_last_buddy(struct sched_entity *se)
{
3480 3481 3482 3483 3484
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
3485 3486 3487 3488
}

static void set_next_buddy(struct sched_entity *se)
{
3489 3490 3491 3492 3493
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
3494 3495
}

3496 3497
static void set_skip_buddy(struct sched_entity *se)
{
3498 3499
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
3500 3501
}

3502 3503 3504
/*
 * Preempt the current task with a newly woken task if needed:
 */
3505
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
3506 3507
{
	struct task_struct *curr = rq->curr;
3508
	struct sched_entity *se = &curr->se, *pse = &p->se;
3509
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
3510
	int scale = cfs_rq->nr_running >= sched_nr_latency;
3511
	int next_buddy_marked = 0;
3512

I
Ingo Molnar 已提交
3513 3514 3515
	if (unlikely(se == pse))
		return;

3516
	/*
3517
	 * This is possible from callers such as move_task(), in which we
3518 3519 3520 3521 3522 3523 3524
	 * 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;

3525
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
3526
		set_next_buddy(pse);
3527 3528
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
3529

3530 3531 3532
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
3533 3534 3535 3536 3537 3538
	 *
	 * 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.
3539 3540 3541 3542
	 */
	if (test_tsk_need_resched(curr))
		return;

3543 3544 3545 3546 3547
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

3548
	/*
3549 3550
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
3551
	 */
3552
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
3553
		return;
3554

3555
	find_matching_se(&se, &pse);
3556
	update_curr(cfs_rq_of(se));
3557
	BUG_ON(!pse);
3558 3559 3560 3561 3562 3563 3564
	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);
3565
		goto preempt;
3566
	}
3567

3568
	return;
3569

3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585
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);
3586 3587
}

3588
static struct task_struct *pick_next_task_fair(struct rq *rq)
3589
{
P
Peter Zijlstra 已提交
3590
	struct task_struct *p;
3591 3592 3593
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

3594
	if (!cfs_rq->nr_running)
3595 3596 3597
		return NULL;

	do {
3598
		se = pick_next_entity(cfs_rq);
3599
		set_next_entity(cfs_rq, se);
3600 3601 3602
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
3603
	p = task_of(se);
3604 3605
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
3606 3607

	return p;
3608 3609 3610 3611 3612
}

/*
 * Account for a descheduled task:
 */
3613
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
3614 3615 3616 3617 3618 3619
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
3620
		put_prev_entity(cfs_rq, se);
3621 3622 3623
	}
}

3624 3625 3626 3627 3628 3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648
/*
 * 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);
3649 3650 3651 3652 3653 3654
		/*
		 * 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;
3655 3656 3657 3658 3659
	}

	set_skip_buddy(se);
}

3660 3661 3662 3663
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

3664 3665
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
3666 3667 3668 3669 3670 3671 3672 3673 3674 3675
		return false;

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

	yield_task_fair(rq);

	return true;
}

3676
#ifdef CONFIG_SMP
3677
/**************************************************
P
Peter Zijlstra 已提交
3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754 3755 3756 3757 3758 3759 3760 3761 3762 3763 3764 3765 3766 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
 * 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.]
 */ 
3794

3795 3796
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

3797
#define LBF_ALL_PINNED	0x01
3798
#define LBF_NEED_BREAK	0x02
3799
#define LBF_SOME_PINNED 0x04
3800 3801 3802 3803 3804

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
3805
	int			src_cpu;
3806 3807 3808 3809

	int			dst_cpu;
	struct rq		*dst_rq;

3810 3811
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
3812
	enum cpu_idle_type	idle;
3813
	long			imbalance;
3814 3815 3816
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

3817
	unsigned int		flags;
3818 3819 3820 3821

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
3822 3823
};

3824
/*
3825
 * move_task - move a task from one runqueue to another runqueue.
3826 3827
 * Both runqueues must be locked.
 */
3828
static void move_task(struct task_struct *p, struct lb_env *env)
3829
{
3830 3831 3832 3833
	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);
3834 3835
}

3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861 3862 3863 3864 3865 3866 3867
/*
 * 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;
}

3868 3869 3870 3871
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
3872
int can_migrate_task(struct task_struct *p, struct lb_env *env)
3873 3874 3875 3876 3877 3878 3879 3880
{
	int tsk_cache_hot = 0;
	/*
	 * We do not migrate tasks that are:
	 * 1) running (obviously), or
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
	 * 3) are cache-hot on their current CPU.
	 */
3881
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
3882 3883
		int new_dst_cpu;

3884
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902

		/*
		 * 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.
		 */
		if (!env->dst_grpmask || (env->flags & LBF_SOME_PINNED))
			return 0;

		new_dst_cpu = cpumask_first_and(env->dst_grpmask,
						tsk_cpus_allowed(p));
		if (new_dst_cpu < nr_cpu_ids) {
			env->flags |= LBF_SOME_PINNED;
			env->new_dst_cpu = new_dst_cpu;
		}
3903 3904
		return 0;
	}
3905 3906

	/* Record that we found atleast one task that could run on dst_cpu */
3907
	env->flags &= ~LBF_ALL_PINNED;
3908

3909
	if (task_running(env->src_rq, p)) {
3910
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
3911 3912 3913 3914 3915 3916 3917 3918 3919
		return 0;
	}

	/*
	 * Aggressive migration if:
	 * 1) task is cache cold, or
	 * 2) too many balance attempts have failed.
	 */

3920
	tsk_cache_hot = task_hot(p, env->src_rq->clock_task, env->sd);
3921
	if (!tsk_cache_hot ||
3922
		env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
3923 3924
#ifdef CONFIG_SCHEDSTATS
		if (tsk_cache_hot) {
3925
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
3926
			schedstat_inc(p, se.statistics.nr_forced_migrations);
3927 3928 3929 3930 3931 3932
		}
#endif
		return 1;
	}

	if (tsk_cache_hot) {
3933
		schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
3934 3935 3936 3937 3938
		return 0;
	}
	return 1;
}

3939 3940 3941 3942 3943 3944 3945
/*
 * 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.
 */
3946
static int move_one_task(struct lb_env *env)
3947 3948 3949
{
	struct task_struct *p, *n;

3950 3951 3952
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (throttled_lb_pair(task_group(p), env->src_rq->cpu, env->dst_cpu))
			continue;
3953

3954 3955
		if (!can_migrate_task(p, env))
			continue;
3956

3957 3958 3959 3960 3961 3962 3963 3964
		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;
3965 3966 3967 3968
	}
	return 0;
}

3969 3970
static unsigned long task_h_load(struct task_struct *p);

3971 3972
static const unsigned int sched_nr_migrate_break = 32;

3973
/*
3974
 * move_tasks tries to move up to imbalance weighted load from busiest to
3975 3976 3977 3978 3979 3980
 * 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)
3981
{
3982 3983
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
3984 3985
	unsigned long load;
	int pulled = 0;
3986

3987
	if (env->imbalance <= 0)
3988
		return 0;
3989

3990 3991
	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
3992

3993 3994
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
3995
		if (env->loop > env->loop_max)
3996
			break;
3997 3998

		/* take a breather every nr_migrate tasks */
3999
		if (env->loop > env->loop_break) {
4000
			env->loop_break += sched_nr_migrate_break;
4001
			env->flags |= LBF_NEED_BREAK;
4002
			break;
4003
		}
4004

4005
		if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
4006 4007 4008
			goto next;

		load = task_h_load(p);
4009

4010
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
4011 4012
			goto next;

4013
		if ((load / 2) > env->imbalance)
4014
			goto next;
4015

4016 4017
		if (!can_migrate_task(p, env))
			goto next;
4018

4019
		move_task(p, env);
4020
		pulled++;
4021
		env->imbalance -= load;
4022 4023

#ifdef CONFIG_PREEMPT
4024 4025 4026 4027 4028
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
		 * kernels will stop after the first task is pulled to minimize
		 * the critical section.
		 */
4029
		if (env->idle == CPU_NEWLY_IDLE)
4030
			break;
4031 4032
#endif

4033 4034 4035 4036
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
4037
		if (env->imbalance <= 0)
4038
			break;
4039 4040 4041

		continue;
next:
4042
		list_move_tail(&p->se.group_node, tasks);
4043
	}
4044

4045
	/*
4046 4047 4048
	 * 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().
4049
	 */
4050
	schedstat_add(env->sd, lb_gained[env->idle], pulled);
4051

4052
	return pulled;
4053 4054
}

P
Peter Zijlstra 已提交
4055
#ifdef CONFIG_FAIR_GROUP_SCHED
4056 4057 4058
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
4059
static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
4060
{
4061 4062
	struct sched_entity *se = tg->se[cpu];
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
4063

4064 4065 4066
	/* throttled entities do not contribute to load */
	if (throttled_hierarchy(cfs_rq))
		return;
4067

4068
	update_cfs_rq_blocked_load(cfs_rq, 1);
4069

4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083
	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 {
4084
		struct rq *rq = rq_of(cfs_rq);
4085 4086
		update_rq_runnable_avg(rq, rq->nr_running);
	}
4087 4088
}

4089
static void update_blocked_averages(int cpu)
4090 4091
{
	struct rq *rq = cpu_rq(cpu);
4092 4093
	struct cfs_rq *cfs_rq;
	unsigned long flags;
4094

4095 4096
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
4097 4098 4099 4100
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
4101
	for_each_leaf_cfs_rq(rq, cfs_rq) {
4102 4103 4104 4105 4106 4107
		/*
		 * 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);
4108
	}
4109 4110

	raw_spin_unlock_irqrestore(&rq->lock, flags);
4111 4112
}

4113 4114 4115 4116 4117 4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137
/*
 * Compute the cpu's hierarchical load factor for each task group.
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
static int tg_load_down(struct task_group *tg, void *data)
{
	unsigned long load;
	long cpu = (long)data;

	if (!tg->parent) {
		load = cpu_rq(cpu)->load.weight;
	} else {
		load = tg->parent->cfs_rq[cpu]->h_load;
		load *= tg->se[cpu]->load.weight;
		load /= tg->parent->cfs_rq[cpu]->load.weight + 1;
	}

	tg->cfs_rq[cpu]->h_load = load;

	return 0;
}

static void update_h_load(long cpu)
{
4138 4139 4140 4141 4142 4143 4144 4145
	struct rq *rq = cpu_rq(cpu);
	unsigned long now = jiffies;

	if (rq->h_load_throttle == now)
		return;

	rq->h_load_throttle = now;

4146
	rcu_read_lock();
4147
	walk_tg_tree(tg_load_down, tg_nop, (void *)cpu);
4148
	rcu_read_unlock();
4149 4150
}

4151
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
4152
{
4153 4154
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
	unsigned long load;
P
Peter Zijlstra 已提交
4155

4156 4157
	load = p->se.load.weight;
	load = div_u64(load * cfs_rq->h_load, cfs_rq->load.weight + 1);
P
Peter Zijlstra 已提交
4158

4159
	return load;
P
Peter Zijlstra 已提交
4160 4161
}
#else
4162
static inline void update_blocked_averages(int cpu)
4163 4164 4165
{
}

4166
static inline void update_h_load(long cpu)
P
Peter Zijlstra 已提交
4167 4168 4169
{
}

4170
static unsigned long task_h_load(struct task_struct *p)
4171
{
4172
	return p->se.load.weight;
4173
}
P
Peter Zijlstra 已提交
4174
#endif
4175 4176 4177 4178 4179 4180 4181 4182 4183 4184 4185 4186 4187 4188 4189 4190 4191

/********** Helpers for find_busiest_group ************************/
/*
 * 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 *this;  /* 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 */

	/** Statistics of this group */
	unsigned long this_load;
	unsigned long this_load_per_task;
	unsigned long this_nr_running;
4192
	unsigned long this_has_capacity;
4193
	unsigned int  this_idle_cpus;
4194 4195

	/* Statistics of the busiest group */
4196
	unsigned int  busiest_idle_cpus;
4197 4198 4199
	unsigned long max_load;
	unsigned long busiest_load_per_task;
	unsigned long busiest_nr_running;
4200
	unsigned long busiest_group_capacity;
4201
	unsigned long busiest_has_capacity;
4202
	unsigned int  busiest_group_weight;
4203 4204 4205 4206 4207 4208 4209 4210 4211 4212 4213 4214 4215

	int group_imb; /* Is there imbalance in this sd */
};

/*
 * 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_nr_running; /* Nr tasks running in the group */
	unsigned long sum_weighted_load; /* Weighted load of group's tasks */
	unsigned long group_capacity;
4216 4217
	unsigned long idle_cpus;
	unsigned long group_weight;
4218
	int group_imb; /* Is there an imbalance in the group ? */
4219
	int group_has_capacity; /* Is there extra capacity in the group? */
4220 4221 4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249
};

/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
 * @idle: The Idle status of the CPU for whose sd load_icx is obtained.
 */
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;
}

unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
{
4250
	return SCHED_POWER_SCALE;
4251 4252 4253 4254 4255 4256 4257 4258 4259
}

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

unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
{
4260
	unsigned long weight = sd->span_weight;
4261 4262 4263 4264 4265 4266 4267 4268 4269 4270 4271 4272 4273 4274 4275
	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);
}

unsigned long scale_rt_power(int cpu)
{
	struct rq *rq = cpu_rq(cpu);
4276
	u64 total, available, age_stamp, avg;
4277

4278 4279 4280 4281 4282 4283 4284 4285
	/*
	 * 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);

	total = sched_avg_period() + (rq->clock - age_stamp);
4286

4287
	if (unlikely(total < avg)) {
4288 4289 4290
		/* Ensures that power won't end up being negative */
		available = 0;
	} else {
4291
		available = total - avg;
4292
	}
4293

4294 4295
	if (unlikely((s64)total < SCHED_POWER_SCALE))
		total = SCHED_POWER_SCALE;
4296

4297
	total >>= SCHED_POWER_SHIFT;
4298 4299 4300 4301 4302 4303

	return div_u64(available, total);
}

static void update_cpu_power(struct sched_domain *sd, int cpu)
{
4304
	unsigned long weight = sd->span_weight;
4305
	unsigned long power = SCHED_POWER_SCALE;
4306 4307 4308 4309 4310 4311 4312 4313
	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);

4314
		power >>= SCHED_POWER_SHIFT;
4315 4316
	}

4317
	sdg->sgp->power_orig = power;
4318 4319 4320 4321 4322 4323

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

4324
	power >>= SCHED_POWER_SHIFT;
4325

4326
	power *= scale_rt_power(cpu);
4327
	power >>= SCHED_POWER_SHIFT;
4328 4329 4330 4331

	if (!power)
		power = 1;

4332
	cpu_rq(cpu)->cpu_power = power;
4333
	sdg->sgp->power = power;
4334 4335
}

4336
void update_group_power(struct sched_domain *sd, int cpu)
4337 4338 4339 4340
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
	unsigned long power;
4341 4342 4343 4344 4345
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
	sdg->sgp->next_update = jiffies + interval;
4346 4347 4348 4349 4350 4351 4352 4353

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

	power = 0;

P
Peter Zijlstra 已提交
4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371 4372 4373
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

		for_each_cpu(cpu, sched_group_cpus(sdg))
			power += power_of(cpu);
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
			power += group->sgp->power;
			group = group->next;
		} while (group != child->groups);
	}
4374

4375
	sdg->sgp->power_orig = sdg->sgp->power = power;
4376 4377
}

4378 4379 4380 4381 4382 4383 4384 4385 4386 4387 4388
/*
 * 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)
{
	/*
4389
	 * Only siblings can have significantly less than SCHED_POWER_SCALE
4390
	 */
P
Peter Zijlstra 已提交
4391
	if (!(sd->flags & SD_SHARE_CPUPOWER))
4392 4393 4394 4395 4396
		return 0;

	/*
	 * If ~90% of the cpu_power is still there, we're good.
	 */
4397
	if (group->sgp->power * 32 > group->sgp->power_orig * 29)
4398 4399 4400 4401 4402
		return 1;

	return 0;
}

4403 4404
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
4405
 * @env: The load balancing environment.
4406 4407 4408 4409 4410 4411
 * @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.
 * @balance: Should we balance.
 * @sgs: variable to hold the statistics for this group.
 */
4412 4413
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
4414
			int local_group, int *balance, struct sg_lb_stats *sgs)
4415
{
4416 4417
	unsigned long nr_running, max_nr_running, min_nr_running;
	unsigned long load, max_cpu_load, min_cpu_load;
4418
	unsigned int balance_cpu = -1, first_idle_cpu = 0;
4419
	unsigned long avg_load_per_task = 0;
4420
	int i;
4421

4422
	if (local_group)
P
Peter Zijlstra 已提交
4423
		balance_cpu = group_balance_cpu(group);
4424 4425 4426 4427

	/* Tally up the load of all CPUs in the group */
	max_cpu_load = 0;
	min_cpu_load = ~0UL;
4428
	max_nr_running = 0;
4429
	min_nr_running = ~0UL;
4430

4431
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
4432 4433
		struct rq *rq = cpu_rq(i);

4434 4435
		nr_running = rq->nr_running;

4436 4437
		/* Bias balancing toward cpus of our domain */
		if (local_group) {
P
Peter Zijlstra 已提交
4438 4439
			if (idle_cpu(i) && !first_idle_cpu &&
					cpumask_test_cpu(i, sched_group_mask(group))) {
4440
				first_idle_cpu = 1;
4441 4442
				balance_cpu = i;
			}
4443 4444

			load = target_load(i, load_idx);
4445 4446
		} else {
			load = source_load(i, load_idx);
4447
			if (load > max_cpu_load)
4448 4449 4450
				max_cpu_load = load;
			if (min_cpu_load > load)
				min_cpu_load = load;
4451 4452 4453 4454 4455

			if (nr_running > max_nr_running)
				max_nr_running = nr_running;
			if (min_nr_running > nr_running)
				min_nr_running = nr_running;
4456 4457 4458
		}

		sgs->group_load += load;
4459
		sgs->sum_nr_running += nr_running;
4460
		sgs->sum_weighted_load += weighted_cpuload(i);
4461 4462
		if (idle_cpu(i))
			sgs->idle_cpus++;
4463 4464 4465 4466 4467 4468 4469 4470
	}

	/*
	 * First idle cpu or the first cpu(busiest) in this sched group
	 * is eligible for doing load balancing at this and above
	 * domains. In the newly idle case, we will allow all the cpu's
	 * to do the newly idle load balance.
	 */
4471
	if (local_group) {
4472
		if (env->idle != CPU_NEWLY_IDLE) {
4473
			if (balance_cpu != env->dst_cpu) {
4474 4475 4476
				*balance = 0;
				return;
			}
4477
			update_group_power(env->sd, env->dst_cpu);
4478
		} else if (time_after_eq(jiffies, group->sgp->next_update))
4479
			update_group_power(env->sd, env->dst_cpu);
4480 4481 4482
	}

	/* Adjust by relative CPU power of the group */
4483
	sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / group->sgp->power;
4484 4485 4486

	/*
	 * Consider the group unbalanced when the imbalance is larger
P
Peter Zijlstra 已提交
4487
	 * than the average weight of a task.
4488 4489 4490 4491 4492 4493
	 *
	 * APZ: with cgroup the avg task weight can vary wildly and
	 *      might not be a suitable number - should we keep a
	 *      normalized nr_running number somewhere that negates
	 *      the hierarchy?
	 */
4494 4495
	if (sgs->sum_nr_running)
		avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
4496

4497 4498
	if ((max_cpu_load - min_cpu_load) >= avg_load_per_task &&
	    (max_nr_running - min_nr_running) > 1)
4499 4500
		sgs->group_imb = 1;

4501
	sgs->group_capacity = DIV_ROUND_CLOSEST(group->sgp->power,
4502
						SCHED_POWER_SCALE);
4503
	if (!sgs->group_capacity)
4504
		sgs->group_capacity = fix_small_capacity(env->sd, group);
4505
	sgs->group_weight = group->group_weight;
4506 4507 4508

	if (sgs->group_capacity > sgs->sum_nr_running)
		sgs->group_has_capacity = 1;
4509 4510
}

4511 4512
/**
 * update_sd_pick_busiest - return 1 on busiest group
4513
 * @env: The load balancing environment.
4514 4515
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
4516
 * @sgs: sched_group statistics
4517 4518 4519 4520
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
 */
4521
static bool update_sd_pick_busiest(struct lb_env *env,
4522 4523
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
4524
				   struct sg_lb_stats *sgs)
4525 4526 4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539
{
	if (sgs->avg_load <= sds->max_load)
		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.
	 */
4540 4541
	if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
	    env->dst_cpu < group_first_cpu(sg)) {
4542 4543 4544 4545 4546 4547 4548 4549 4550 4551
		if (!sds->busiest)
			return true;

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

	return false;
}

4552
/**
4553
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
4554
 * @env: The load balancing environment.
4555 4556 4557
 * @balance: Should we balance.
 * @sds: variable to hold the statistics for this sched_domain.
 */
4558
static inline void update_sd_lb_stats(struct lb_env *env,
4559
					int *balance, struct sd_lb_stats *sds)
4560
{
4561 4562
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
4563 4564 4565 4566 4567 4568
	struct sg_lb_stats sgs;
	int load_idx, prefer_sibling = 0;

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

4569
	load_idx = get_sd_load_idx(env->sd, env->idle);
4570 4571 4572 4573

	do {
		int local_group;

4574
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
4575
		memset(&sgs, 0, sizeof(sgs));
4576
		update_sg_lb_stats(env, sg, load_idx, local_group, balance, &sgs);
4577

P
Peter Zijlstra 已提交
4578
		if (local_group && !(*balance))
4579 4580 4581
			return;

		sds->total_load += sgs.group_load;
4582
		sds->total_pwr += sg->sgp->power;
4583 4584 4585

		/*
		 * In case the child domain prefers tasks go to siblings
4586
		 * first, lower the sg capacity to one so that we'll try
4587 4588 4589 4590 4591 4592
		 * 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).
4593
		 */
4594
		if (prefer_sibling && !local_group && sds->this_has_capacity)
4595 4596 4597 4598
			sgs.group_capacity = min(sgs.group_capacity, 1UL);

		if (local_group) {
			sds->this_load = sgs.avg_load;
4599
			sds->this = sg;
4600 4601
			sds->this_nr_running = sgs.sum_nr_running;
			sds->this_load_per_task = sgs.sum_weighted_load;
4602
			sds->this_has_capacity = sgs.group_has_capacity;
4603
			sds->this_idle_cpus = sgs.idle_cpus;
4604
		} else if (update_sd_pick_busiest(env, sds, sg, &sgs)) {
4605
			sds->max_load = sgs.avg_load;
4606
			sds->busiest = sg;
4607
			sds->busiest_nr_running = sgs.sum_nr_running;
4608
			sds->busiest_idle_cpus = sgs.idle_cpus;
4609
			sds->busiest_group_capacity = sgs.group_capacity;
4610
			sds->busiest_load_per_task = sgs.sum_weighted_load;
4611
			sds->busiest_has_capacity = sgs.group_has_capacity;
4612
			sds->busiest_group_weight = sgs.group_weight;
4613 4614 4615
			sds->group_imb = sgs.group_imb;
		}

4616
		sg = sg->next;
4617
	} while (sg != env->sd->groups);
4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636
}

/**
 * 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.
 *
4637 4638 4639
 * Returns 1 when packing is required and a task should be moved to
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
4640
 * @env: The load balancing environment.
4641 4642
 * @sds: Statistics of the sched_domain which is to be packed
 */
4643
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
4644 4645 4646
{
	int busiest_cpu;

4647
	if (!(env->sd->flags & SD_ASYM_PACKING))
4648 4649 4650 4651 4652 4653
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
4654
	if (env->dst_cpu > busiest_cpu)
4655 4656
		return 0;

4657 4658 4659
	env->imbalance = DIV_ROUND_CLOSEST(
		sds->max_load * sds->busiest->sgp->power, SCHED_POWER_SCALE);

4660
	return 1;
4661 4662 4663 4664 4665 4666
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
4667
 * @env: The load balancing environment.
4668 4669
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
4670 4671
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
4672 4673 4674
{
	unsigned long tmp, pwr_now = 0, pwr_move = 0;
	unsigned int imbn = 2;
4675
	unsigned long scaled_busy_load_per_task;
4676 4677 4678 4679 4680 4681

	if (sds->this_nr_running) {
		sds->this_load_per_task /= sds->this_nr_running;
		if (sds->busiest_load_per_task >
				sds->this_load_per_task)
			imbn = 1;
4682
	} else {
4683
		sds->this_load_per_task =
4684 4685
			cpu_avg_load_per_task(env->dst_cpu);
	}
4686

4687
	scaled_busy_load_per_task = sds->busiest_load_per_task
4688
					 * SCHED_POWER_SCALE;
4689
	scaled_busy_load_per_task /= sds->busiest->sgp->power;
4690 4691 4692

	if (sds->max_load - sds->this_load + scaled_busy_load_per_task >=
			(scaled_busy_load_per_task * imbn)) {
4693
		env->imbalance = sds->busiest_load_per_task;
4694 4695 4696 4697 4698 4699 4700 4701 4702
		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.
	 */

4703
	pwr_now += sds->busiest->sgp->power *
4704
			min(sds->busiest_load_per_task, sds->max_load);
4705
	pwr_now += sds->this->sgp->power *
4706
			min(sds->this_load_per_task, sds->this_load);
4707
	pwr_now /= SCHED_POWER_SCALE;
4708 4709

	/* Amount of load we'd subtract */
4710
	tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
4711
		sds->busiest->sgp->power;
4712
	if (sds->max_load > tmp)
4713
		pwr_move += sds->busiest->sgp->power *
4714 4715 4716
			min(sds->busiest_load_per_task, sds->max_load - tmp);

	/* Amount of load we'd add */
4717
	if (sds->max_load * sds->busiest->sgp->power <
4718
		sds->busiest_load_per_task * SCHED_POWER_SCALE)
4719 4720
		tmp = (sds->max_load * sds->busiest->sgp->power) /
			sds->this->sgp->power;
4721
	else
4722
		tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
4723 4724
			sds->this->sgp->power;
	pwr_move += sds->this->sgp->power *
4725
			min(sds->this_load_per_task, sds->this_load + tmp);
4726
	pwr_move /= SCHED_POWER_SCALE;
4727 4728 4729

	/* Move if we gain throughput */
	if (pwr_move > pwr_now)
4730
		env->imbalance = sds->busiest_load_per_task;
4731 4732 4733 4734 4735
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
4736
 * @env: load balance environment
4737 4738
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
4739
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
4740
{
4741 4742 4743 4744 4745 4746 4747 4748
	unsigned long max_pull, load_above_capacity = ~0UL;

	sds->busiest_load_per_task /= sds->busiest_nr_running;
	if (sds->group_imb) {
		sds->busiest_load_per_task =
			min(sds->busiest_load_per_task, sds->avg_load);
	}

4749 4750 4751 4752 4753 4754
	/*
	 * 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..)
	 */
	if (sds->max_load < sds->avg_load) {
4755 4756
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
4757 4758
	}

4759 4760 4761 4762 4763 4764 4765
	if (!sds->group_imb) {
		/*
		 * Don't want to pull so many tasks that a group would go idle.
		 */
		load_above_capacity = (sds->busiest_nr_running -
						sds->busiest_group_capacity);

4766
		load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
4767

4768
		load_above_capacity /= sds->busiest->sgp->power;
4769 4770 4771 4772 4773 4774 4775 4776 4777 4778 4779 4780 4781
	}

	/*
	 * 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.
	 * Be careful of negative numbers as they'll appear as very large values
	 * with unsigned longs.
	 */
	max_pull = min(sds->max_load - sds->avg_load, load_above_capacity);
4782 4783

	/* How much load to actually move to equalise the imbalance */
4784
	env->imbalance = min(max_pull * sds->busiest->sgp->power,
4785
		(sds->avg_load - sds->this_load) * sds->this->sgp->power)
4786
			/ SCHED_POWER_SCALE;
4787 4788 4789

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
4790
	 * there is no guarantee that any tasks will be moved so we'll have
4791 4792 4793
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
4794 4795
	if (env->imbalance < sds->busiest_load_per_task)
		return fix_small_imbalance(env, sds);
4796 4797

}
4798

4799 4800 4801 4802 4803 4804 4805 4806 4807 4808 4809 4810
/******* 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.
 *
4811
 * @env: The load balancing environment.
4812 4813 4814 4815 4816 4817 4818 4819 4820
 * @balance: Pointer to a variable indicating if this_cpu
 *	is the appropriate cpu to perform load balancing at this_level.
 *
 * Returns:	- the busiest group if imbalance exists.
 *		- 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.
 */
static struct sched_group *
4821
find_busiest_group(struct lb_env *env, int *balance)
4822 4823 4824 4825 4826 4827 4828 4829 4830
{
	struct sd_lb_stats sds;

	memset(&sds, 0, sizeof(sds));

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
4831
	update_sd_lb_stats(env, balance, &sds);
4832

4833 4834 4835
	/*
	 * this_cpu is not the appropriate cpu to perform load balancing at
	 * this level.
4836
	 */
P
Peter Zijlstra 已提交
4837
	if (!(*balance))
4838 4839
		goto ret;

4840 4841
	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(env, &sds))
4842 4843
		return sds.busiest;

4844
	/* There is no busy sibling group to pull tasks from */
4845 4846 4847
	if (!sds.busiest || sds.busiest_nr_running == 0)
		goto out_balanced;

4848
	sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
4849

P
Peter Zijlstra 已提交
4850 4851 4852 4853 4854 4855 4856 4857
	/*
	 * If the busiest group is imbalanced the below checks don't
	 * work because they assumes all things are equal, which typically
	 * isn't true due to cpus_allowed constraints and the like.
	 */
	if (sds.group_imb)
		goto force_balance;

4858
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
4859
	if (env->idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
4860 4861 4862
			!sds.busiest_has_capacity)
		goto force_balance;

4863 4864 4865 4866
	/*
	 * If the local group is more busy than the selected busiest group
	 * don't try and pull any tasks.
	 */
4867 4868 4869
	if (sds.this_load >= sds.max_load)
		goto out_balanced;

4870 4871 4872 4873
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
4874 4875 4876
	if (sds.this_load >= sds.avg_load)
		goto out_balanced;

4877
	if (env->idle == CPU_IDLE) {
4878 4879 4880 4881 4882 4883
		/*
		 * 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.
		 */
4884
		if ((sds.this_idle_cpus <= sds.busiest_idle_cpus + 1) &&
4885 4886
		    sds.busiest_nr_running <= sds.busiest_group_weight)
			goto out_balanced;
4887 4888 4889 4890 4891
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
4892
		if (100 * sds.max_load <= env->sd->imbalance_pct * sds.this_load)
4893
			goto out_balanced;
4894
	}
4895

4896
force_balance:
4897
	/* Looks like there is an imbalance. Compute it */
4898
	calculate_imbalance(env, &sds);
4899 4900 4901 4902
	return sds.busiest;

out_balanced:
ret:
4903
	env->imbalance = 0;
4904 4905 4906 4907 4908 4909
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
4910
static struct rq *find_busiest_queue(struct lb_env *env,
4911
				     struct sched_group *group)
4912 4913 4914 4915 4916 4917 4918
{
	struct rq *busiest = NULL, *rq;
	unsigned long max_load = 0;
	int i;

	for_each_cpu(i, sched_group_cpus(group)) {
		unsigned long power = power_of(i);
4919 4920
		unsigned long capacity = DIV_ROUND_CLOSEST(power,
							   SCHED_POWER_SCALE);
4921 4922
		unsigned long wl;

4923
		if (!capacity)
4924
			capacity = fix_small_capacity(env->sd, group);
4925

4926
		if (!cpumask_test_cpu(i, env->cpus))
4927 4928 4929
			continue;

		rq = cpu_rq(i);
4930
		wl = weighted_cpuload(i);
4931

4932 4933 4934 4935
		/*
		 * When comparing with imbalance, use weighted_cpuload()
		 * which is not scaled with the cpu power.
		 */
4936
		if (capacity && rq->nr_running == 1 && wl > env->imbalance)
4937 4938
			continue;

4939 4940 4941 4942 4943 4944
		/*
		 * 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.
		 */
4945
		wl = (wl * SCHED_POWER_SCALE) / power;
4946

4947 4948 4949 4950 4951 4952 4953 4954 4955 4956 4957 4958 4959 4960 4961 4962
		if (wl > max_load) {
			max_load = wl;
			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. */
4963
DEFINE_PER_CPU(cpumask_var_t, load_balance_tmpmask);
4964

4965
static int need_active_balance(struct lb_env *env)
4966
{
4967 4968 4969
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
4970 4971 4972 4973 4974 4975

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
4976
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
4977
			return 1;
4978 4979 4980 4981 4982
	}

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

4983 4984
static int active_load_balance_cpu_stop(void *data);

4985 4986 4987 4988 4989 4990 4991 4992
/*
 * 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,
			int *balance)
{
4993 4994
	int ld_moved, cur_ld_moved, active_balance = 0;
	int lb_iterations, max_lb_iterations;
4995 4996 4997 4998 4999
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
	struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);

5000 5001
	struct lb_env env = {
		.sd		= sd,
5002 5003
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
5004
		.dst_grpmask    = sched_group_cpus(sd->groups),
5005
		.idle		= idle,
5006
		.loop_break	= sched_nr_migrate_break,
5007
		.cpus		= cpus,
5008 5009
	};

5010
	cpumask_copy(cpus, cpu_active_mask);
5011
	max_lb_iterations = cpumask_weight(env.dst_grpmask);
5012 5013 5014 5015

	schedstat_inc(sd, lb_count[idle]);

redo:
5016
	group = find_busiest_group(&env, balance);
5017 5018 5019 5020 5021 5022 5023 5024 5025

	if (*balance == 0)
		goto out_balanced;

	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

5026
	busiest = find_busiest_queue(&env, group);
5027 5028 5029 5030 5031
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

5032
	BUG_ON(busiest == env.dst_rq);
5033

5034
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
5035 5036

	ld_moved = 0;
5037
	lb_iterations = 1;
5038 5039 5040 5041 5042 5043 5044
	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.
		 */
5045
		env.flags |= LBF_ALL_PINNED;
5046 5047 5048
		env.src_cpu   = busiest->cpu;
		env.src_rq    = busiest;
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
5049

5050
		update_h_load(env.src_cpu);
5051
more_balance:
5052
		local_irq_save(flags);
5053
		double_rq_lock(env.dst_rq, busiest);
5054 5055 5056 5057 5058 5059 5060

		/*
		 * 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;
5061
		double_rq_unlock(env.dst_rq, busiest);
5062 5063
		local_irq_restore(flags);

5064 5065 5066 5067 5068
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

5069 5070 5071
		/*
		 * some other cpu did the load balance for us.
		 */
5072 5073 5074 5075 5076 5077 5078 5079 5080 5081 5082 5083 5084 5085 5086 5087 5088 5089 5090 5091 5092 5093 5094 5095 5096
		if (cur_ld_moved && env.dst_cpu != smp_processor_id())
			resched_cpu(env.dst_cpu);

		/*
		 * 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.
		 */
		if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0 &&
				lb_iterations++ < max_lb_iterations) {

5097
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
5098 5099 5100 5101 5102 5103 5104 5105 5106 5107
			env.dst_cpu	 = env.new_dst_cpu;
			env.flags	&= ~LBF_SOME_PINNED;
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
5108 5109

		/* All tasks on this runqueue were pinned by CPU affinity */
5110
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
5111
			cpumask_clear_cpu(cpu_of(busiest), cpus);
5112 5113 5114
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
5115
				goto redo;
5116
			}
5117 5118 5119 5120 5121 5122
			goto out_balanced;
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
5123 5124 5125 5126 5127 5128 5129 5130
		/*
		 * 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++;
5131

5132
		if (need_active_balance(&env)) {
5133 5134
			raw_spin_lock_irqsave(&busiest->lock, flags);

5135 5136 5137
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
5138 5139
			 */
			if (!cpumask_test_cpu(this_cpu,
5140
					tsk_cpus_allowed(busiest->curr))) {
5141 5142
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
5143
				env.flags |= LBF_ALL_PINNED;
5144 5145 5146
				goto out_one_pinned;
			}

5147 5148 5149 5150 5151
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
5152 5153 5154 5155 5156 5157
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
5158

5159
			if (active_balance) {
5160 5161 5162
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
5163
			}
5164 5165 5166 5167 5168 5169 5170 5171 5172 5173 5174 5175 5176 5177 5178 5179 5180 5181 5182 5183 5184 5185 5186 5187 5188 5189 5190 5191 5192 5193 5194 5195 5196

			/*
			 * 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 */
5197
	if (((env.flags & LBF_ALL_PINNED) &&
5198
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
5199 5200 5201
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

5202
	ld_moved = 0;
5203 5204 5205 5206 5207 5208 5209 5210
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.
 */
5211
void idle_balance(int this_cpu, struct rq *this_rq)
5212 5213 5214 5215 5216 5217 5218 5219 5220 5221
{
	struct sched_domain *sd;
	int pulled_task = 0;
	unsigned long next_balance = jiffies + HZ;

	this_rq->idle_stamp = this_rq->clock;

	if (this_rq->avg_idle < sysctl_sched_migration_cost)
		return;

5222 5223
	update_rq_runnable_avg(this_rq, 1);

5224 5225 5226 5227 5228
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

5229
	update_blocked_averages(this_cpu);
5230
	rcu_read_lock();
5231 5232
	for_each_domain(this_cpu, sd) {
		unsigned long interval;
5233
		int balance = 1;
5234 5235 5236 5237

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

5238
		if (sd->flags & SD_BALANCE_NEWIDLE) {
5239
			/* If we've pulled tasks over stop searching: */
5240 5241 5242
			pulled_task = load_balance(this_cpu, this_rq,
						   sd, CPU_NEWLY_IDLE, &balance);
		}
5243 5244 5245 5246

		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
5247 5248
		if (pulled_task) {
			this_rq->idle_stamp = 0;
5249
			break;
N
Nikhil Rao 已提交
5250
		}
5251
	}
5252
	rcu_read_unlock();
5253 5254 5255

	raw_spin_lock(&this_rq->lock);

5256 5257 5258 5259 5260 5261 5262 5263 5264 5265
	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;
	}
}

/*
5266 5267 5268 5269
 * 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.
5270
 */
5271
static int active_load_balance_cpu_stop(void *data)
5272
{
5273 5274
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
5275
	int target_cpu = busiest_rq->push_cpu;
5276
	struct rq *target_rq = cpu_rq(target_cpu);
5277
	struct sched_domain *sd;
5278 5279 5280 5281 5282 5283 5284

	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;
5285 5286 5287

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
5288
		goto out_unlock;
5289 5290 5291 5292 5293 5294 5295 5296 5297 5298 5299 5300

	/*
	 * 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. */
5301
	rcu_read_lock();
5302 5303 5304 5305 5306 5307 5308
	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)) {
5309 5310
		struct lb_env env = {
			.sd		= sd,
5311 5312 5313 5314
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
5315 5316 5317
			.idle		= CPU_IDLE,
		};

5318 5319
		schedstat_inc(sd, alb_count);

5320
		if (move_one_task(&env))
5321 5322 5323 5324
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
5325
	rcu_read_unlock();
5326
	double_unlock_balance(busiest_rq, target_rq);
5327 5328 5329 5330
out_unlock:
	busiest_rq->active_balance = 0;
	raw_spin_unlock_irq(&busiest_rq->lock);
	return 0;
5331 5332 5333
}

#ifdef CONFIG_NO_HZ
5334 5335 5336 5337 5338 5339
/*
 * 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.
 */
5340
static struct {
5341
	cpumask_var_t idle_cpus_mask;
5342
	atomic_t nr_cpus;
5343 5344
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
5345

5346
static inline int find_new_ilb(int call_cpu)
5347
{
5348
	int ilb = cpumask_first(nohz.idle_cpus_mask);
5349

5350 5351 5352 5353
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
5354 5355
}

5356 5357 5358 5359 5360 5361 5362 5363 5364 5365 5366
/*
 * 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++;

5367
	ilb_cpu = find_new_ilb(cpu);
5368

5369 5370
	if (ilb_cpu >= nr_cpu_ids)
		return;
5371

5372
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
5373 5374 5375 5376 5377 5378 5379 5380
		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);
5381 5382 5383
	return;
}

5384
static inline void nohz_balance_exit_idle(int cpu)
5385 5386 5387 5388 5389 5390 5391 5392
{
	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));
	}
}

5393 5394 5395 5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418 5419 5420 5421 5422
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;
	int cpu = smp_processor_id();

	if (!test_bit(NOHZ_IDLE, nohz_flags(cpu)))
		return;
	clear_bit(NOHZ_IDLE, nohz_flags(cpu));

	rcu_read_lock();
	for_each_domain(cpu, sd)
		atomic_inc(&sd->groups->sgp->nr_busy_cpus);
	rcu_read_unlock();
}

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

	if (test_bit(NOHZ_IDLE, nohz_flags(cpu)))
		return;
	set_bit(NOHZ_IDLE, nohz_flags(cpu));

	rcu_read_lock();
	for_each_domain(cpu, sd)
		atomic_dec(&sd->groups->sgp->nr_busy_cpus);
	rcu_read_unlock();
}

5423
/*
5424
 * This routine will record that the cpu is going idle with tick stopped.
5425
 * This info will be used in performing idle load balancing in the future.
5426
 */
5427
void nohz_balance_enter_idle(int cpu)
5428
{
5429 5430 5431 5432 5433 5434
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

5435 5436
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
5437

5438 5439 5440
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
5441
}
5442 5443 5444 5445 5446 5447

static int __cpuinit sched_ilb_notifier(struct notifier_block *nfb,
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
5448
		nohz_balance_exit_idle(smp_processor_id());
5449 5450 5451 5452 5453
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
5454 5455 5456 5457
#endif

static DEFINE_SPINLOCK(balancing);

5458 5459 5460 5461
/*
 * 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.
 */
5462
void update_max_interval(void)
5463 5464 5465 5466
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

5467 5468 5469 5470 5471 5472 5473 5474 5475 5476 5477
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
 * Balancing parameters are set up in arch_init_sched_domains.
 */
static void rebalance_domains(int cpu, enum cpu_idle_type idle)
{
	int balance = 1;
	struct rq *rq = cpu_rq(cpu);
	unsigned long interval;
5478
	struct sched_domain *sd;
5479 5480 5481 5482 5483
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
	int need_serialize;

5484
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
5485

5486
	rcu_read_lock();
5487 5488 5489 5490 5491 5492 5493 5494 5495 5496
	for_each_domain(cpu, sd) {
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

		interval = sd->balance_interval;
		if (idle != CPU_IDLE)
			interval *= sd->busy_factor;

		/* scale ms to jiffies */
		interval = msecs_to_jiffies(interval);
5497
		interval = clamp(interval, 1UL, max_load_balance_interval);
5498 5499 5500 5501 5502 5503 5504 5505 5506 5507 5508 5509

		need_serialize = sd->flags & SD_SERIALIZE;

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

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
			if (load_balance(cpu, rq, sd, idle, &balance)) {
				/*
				 * We've pulled tasks over so either we're no
5510
				 * longer idle.
5511 5512 5513 5514 5515 5516 5517 5518 5519 5520 5521 5522 5523 5524 5525 5526 5527 5528 5529 5530 5531
				 */
				idle = CPU_NOT_IDLE;
			}
			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;
		}

		/*
		 * Stop the load balance at this level. There is another
		 * CPU in our sched group which is doing load balancing more
		 * actively.
		 */
		if (!balance)
			break;
	}
5532
	rcu_read_unlock();
5533 5534 5535 5536 5537 5538 5539 5540 5541 5542

	/*
	 * 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;
}

5543
#ifdef CONFIG_NO_HZ
5544
/*
5545
 * In CONFIG_NO_HZ case, the idle balance kickee will do the
5546 5547
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
5548 5549 5550 5551 5552 5553
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;

5554 5555 5556
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
5557 5558

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
5559
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
5560 5561 5562 5563 5564 5565 5566
			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.
		 */
5567
		if (need_resched())
5568 5569
			break;

V
Vincent Guittot 已提交
5570 5571 5572 5573 5574 5575
		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);
5576 5577 5578 5579 5580 5581 5582

		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;
5583 5584
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
5585 5586 5587
}

/*
5588 5589 5590 5591 5592 5593 5594
 * 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.
5595 5596 5597 5598
 */
static inline int nohz_kick_needed(struct rq *rq, int cpu)
{
	unsigned long now = jiffies;
5599
	struct sched_domain *sd;
5600

5601
	if (unlikely(idle_cpu(cpu)))
5602 5603
		return 0;

5604 5605 5606 5607
       /*
	* 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.
	*/
5608
	set_cpu_sd_state_busy();
5609
	nohz_balance_exit_idle(cpu);
5610 5611 5612 5613 5614 5615 5616

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
		return 0;
5617 5618

	if (time_before(now, nohz.next_balance))
5619 5620
		return 0;

5621 5622
	if (rq->nr_running >= 2)
		goto need_kick;
5623

5624
	rcu_read_lock();
5625 5626 5627 5628
	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);
5629

5630
		if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1)
5631
			goto need_kick_unlock;
5632 5633 5634 5635

		if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight
		    && (cpumask_first_and(nohz.idle_cpus_mask,
					  sched_domain_span(sd)) < cpu))
5636
			goto need_kick_unlock;
5637 5638 5639

		if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING)))
			break;
5640
	}
5641
	rcu_read_unlock();
5642
	return 0;
5643 5644 5645

need_kick_unlock:
	rcu_read_unlock();
5646 5647
need_kick:
	return 1;
5648 5649 5650 5651 5652 5653 5654 5655 5656
}
#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).
 */
5657 5658 5659 5660
static void run_rebalance_domains(struct softirq_action *h)
{
	int this_cpu = smp_processor_id();
	struct rq *this_rq = cpu_rq(this_cpu);
5661
	enum cpu_idle_type idle = this_rq->idle_balance ?
5662 5663 5664 5665 5666
						CPU_IDLE : CPU_NOT_IDLE;

	rebalance_domains(this_cpu, idle);

	/*
5667
	 * If this cpu has a pending nohz_balance_kick, then do the
5668 5669 5670
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
5671
	nohz_idle_balance(this_cpu, idle);
5672 5673 5674 5675
}

static inline int on_null_domain(int cpu)
{
5676
	return !rcu_dereference_sched(cpu_rq(cpu)->sd);
5677 5678 5679 5680 5681
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
5682
void trigger_load_balance(struct rq *rq, int cpu)
5683 5684 5685 5686 5687
{
	/* 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);
5688
#ifdef CONFIG_NO_HZ
5689
	if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
5690 5691
		nohz_balancer_kick(cpu);
#endif
5692 5693
}

5694 5695 5696 5697 5698 5699 5700 5701
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
5702 5703 5704

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
5705 5706
}

5707
#endif /* CONFIG_SMP */
5708

5709 5710 5711
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
5712
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
5713 5714 5715 5716 5717 5718
{
	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
5719
		entity_tick(cfs_rq, se, queued);
5720
	}
5721

5722 5723
	if (sched_feat_numa(NUMA))
		task_tick_numa(rq, curr);
5724

5725
	update_rq_runnable_avg(rq, 1);
5726 5727 5728
}

/*
P
Peter Zijlstra 已提交
5729 5730 5731
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
5732
 */
P
Peter Zijlstra 已提交
5733
static void task_fork_fair(struct task_struct *p)
5734
{
5735 5736
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
5737
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
5738 5739 5740
	struct rq *rq = this_rq();
	unsigned long flags;

5741
	raw_spin_lock_irqsave(&rq->lock, flags);
5742

5743 5744
	update_rq_clock(rq);

5745 5746 5747
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

5748 5749
	if (unlikely(task_cpu(p) != this_cpu)) {
		rcu_read_lock();
P
Peter Zijlstra 已提交
5750
		__set_task_cpu(p, this_cpu);
5751 5752
		rcu_read_unlock();
	}
5753

5754
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
5755

5756 5757
	if (curr)
		se->vruntime = curr->vruntime;
5758
	place_entity(cfs_rq, se, 1);
5759

P
Peter Zijlstra 已提交
5760
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
5761
		/*
5762 5763 5764
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
5765
		swap(curr->vruntime, se->vruntime);
5766
		resched_task(rq->curr);
5767
	}
5768

5769 5770
	se->vruntime -= cfs_rq->min_vruntime;

5771
	raw_spin_unlock_irqrestore(&rq->lock, flags);
5772 5773
}

5774 5775 5776 5777
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
5778 5779
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
5780
{
P
Peter Zijlstra 已提交
5781 5782 5783
	if (!p->se.on_rq)
		return;

5784 5785 5786 5787 5788
	/*
	 * 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
5789
	if (rq->curr == p) {
5790 5791 5792
		if (p->prio > oldprio)
			resched_task(rq->curr);
	} else
5793
		check_preempt_curr(rq, p, 0);
5794 5795
}

P
Peter Zijlstra 已提交
5796 5797 5798 5799 5800 5801 5802 5803 5804 5805 5806 5807 5808 5809 5810 5811 5812 5813 5814 5815 5816 5817
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;
	}
5818 5819 5820 5821 5822 5823 5824 5825 5826 5827 5828 5829 5830 5831

#if defined(CONFIG_FAIR_GROUP_SCHED) && defined(CONFIG_SMP)
	/*
	* 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.
	*/
	if (p->se.avg.decay_count) {
		struct cfs_rq *cfs_rq = cfs_rq_of(&p->se);
		__synchronize_entity_decay(&p->se);
		subtract_blocked_load_contrib(cfs_rq,
				p->se.avg.load_avg_contrib);
	}
#endif
P
Peter Zijlstra 已提交
5832 5833
}

5834 5835 5836
/*
 * We switched to the sched_fair class.
 */
P
Peter Zijlstra 已提交
5837
static void switched_to_fair(struct rq *rq, struct task_struct *p)
5838
{
P
Peter Zijlstra 已提交
5839 5840 5841
	if (!p->se.on_rq)
		return;

5842 5843 5844 5845 5846
	/*
	 * 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
5847
	if (rq->curr == p)
5848 5849
		resched_task(rq->curr);
	else
5850
		check_preempt_curr(rq, p, 0);
5851 5852
}

5853 5854 5855 5856 5857 5858 5859 5860 5861
/* 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;

5862 5863 5864 5865 5866 5867 5868
	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);
	}
5869 5870
}

5871 5872 5873 5874 5875 5876 5877
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
5878 5879
#if defined(CONFIG_FAIR_GROUP_SCHED) && defined(CONFIG_SMP)
	atomic64_set(&cfs_rq->decay_counter, 1);
5880
	atomic64_set(&cfs_rq->removed_load, 0);
5881
#endif
5882 5883
}

P
Peter Zijlstra 已提交
5884
#ifdef CONFIG_FAIR_GROUP_SCHED
5885
static void task_move_group_fair(struct task_struct *p, int on_rq)
P
Peter Zijlstra 已提交
5886
{
5887
	struct cfs_rq *cfs_rq;
5888 5889 5890 5891 5892 5893 5894 5895 5896 5897 5898 5899 5900
	/*
	 * 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.
	 */
5901 5902 5903 5904 5905 5906
	/*
	 * 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().
5907 5908
	 * - Moving a task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
5909 5910 5911 5912
	 *
	 * To prevent boost or penalty in the new cfs_rq caused by delta
	 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
	 */
5913
	if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING))
5914 5915
		on_rq = 1;

5916 5917 5918
	if (!on_rq)
		p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
	set_task_rq(p, task_cpu(p));
5919 5920 5921 5922 5923 5924 5925 5926 5927 5928 5929 5930 5931
	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
5932
}
5933 5934 5935 5936 5937 5938 5939 5940 5941 5942 5943 5944 5945 5946 5947 5948 5949 5950 5951 5952 5953 5954 5955 5956 5957 5958 5959 5960 5961 5962 5963 5964 5965 5966 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 5992 5993 5994 5995 5996 5997 5998 5999 6000 6001 6002 6003 6004 6005 6006 6007 6008 6009 6010 6011 6012 6013 6014 6015 6016 6017 6018 6019 6020 6021 6022 6023 6024 6025 6026 6027 6028 6029 6030 6031 6032 6033 6034 6035 6036 6037 6038 6039 6040 6041 6042 6043 6044 6045 6046 6047 6048 6049 6050 6051 6052 6053 6054 6055 6056 6057 6058 6059 6060 6061

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);
6062
		for_each_sched_entity(se)
6063 6064 6065 6066 6067 6068 6069 6070 6071 6072 6073 6074 6075 6076 6077 6078 6079 6080 6081 6082 6083
			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 */

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Peter Zijlstra 已提交
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6085
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
6086 6087 6088 6089 6090 6091 6092 6093 6094
{
	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)
6095
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
6096 6097 6098 6099

	return rr_interval;
}

6100 6101 6102
/*
 * All the scheduling class methods:
 */
6103
const struct sched_class fair_sched_class = {
6104
	.next			= &idle_sched_class,
6105 6106 6107
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
6108
	.yield_to_task		= yield_to_task_fair,
6109

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Ingo Molnar 已提交
6110
	.check_preempt_curr	= check_preempt_wakeup,
6111 6112 6113 6114

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

6115
#ifdef CONFIG_SMP
L
Li Zefan 已提交
6116
	.select_task_rq		= select_task_rq_fair,
6117
#ifdef CONFIG_FAIR_GROUP_SCHED
6118
	.migrate_task_rq	= migrate_task_rq_fair,
6119
#endif
6120 6121
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
6122 6123

	.task_waking		= task_waking_fair,
6124
#endif
6125

6126
	.set_curr_task          = set_curr_task_fair,
6127
	.task_tick		= task_tick_fair,
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Peter Zijlstra 已提交
6128
	.task_fork		= task_fork_fair,
6129 6130

	.prio_changed		= prio_changed_fair,
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Peter Zijlstra 已提交
6131
	.switched_from		= switched_from_fair,
6132
	.switched_to		= switched_to_fair,
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Peter Zijlstra 已提交
6133

6134 6135
	.get_rr_interval	= get_rr_interval_fair,

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Peter Zijlstra 已提交
6136
#ifdef CONFIG_FAIR_GROUP_SCHED
6137
	.task_move_group	= task_move_group_fair,
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Peter Zijlstra 已提交
6138
#endif
6139 6140 6141
};

#ifdef CONFIG_SCHED_DEBUG
6142
void print_cfs_stats(struct seq_file *m, int cpu)
6143 6144 6145
{
	struct cfs_rq *cfs_rq;

6146
	rcu_read_lock();
6147
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
6148
		print_cfs_rq(m, cpu, cfs_rq);
6149
	rcu_read_unlock();
6150 6151
}
#endif
6152 6153 6154 6155 6156 6157 6158

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

#ifdef CONFIG_NO_HZ
6159
	nohz.next_balance = jiffies;
6160
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
6161
	cpu_notifier(sched_ilb_notifier, 0);
6162 6163 6164 6165
#endif
#endif /* SMP */

}