fair.c 158.0 KB
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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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 */

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#include <linux/latencytop.h>
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#include <linux/sched.h>
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#include <linux/cpumask.h>
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#include <linux/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 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 3256
{
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
3257
	struct sched_domain *sd;
3258 3259
	struct sched_group *sg;
	int i;
3260 3261

	/*
3262 3263
	 * If the task is going to be woken-up on this cpu and if it is
	 * already idle, then it is the right target.
3264
	 */
3265 3266 3267 3268 3269 3270 3271 3272
	if (target == cpu && idle_cpu(cpu))
		return cpu;

	/*
	 * If the task is going to be woken-up on the cpu where it previously
	 * ran and if it is currently idle, then it the right target.
	 */
	if (target == prev_cpu && idle_cpu(prev_cpu))
3273
		return prev_cpu;
3274 3275

	/*
3276
	 * Otherwise, iterate the domains and find an elegible idle cpu.
3277
	 */
3278
	sd = rcu_dereference(per_cpu(sd_llc, target));
3279
	for_each_lower_domain(sd) {
3280 3281 3282 3283 3284 3285 3286 3287 3288 3289
		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)) {
				if (!idle_cpu(i))
					goto next;
			}
3290

3291 3292 3293 3294 3295 3296 3297 3298
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
3299 3300 3301
	return target;
}

3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312
/*
 * 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.
 */
3313
static int
3314
select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
3315
{
3316
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
3317 3318 3319
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
	int new_cpu = cpu;
3320
	int want_affine = 0;
3321
	int sync = wake_flags & WF_SYNC;
3322

3323
	if (p->nr_cpus_allowed == 1)
3324 3325
		return prev_cpu;

3326
	if (sd_flag & SD_BALANCE_WAKE) {
3327
		if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
3328 3329 3330
			want_affine = 1;
		new_cpu = prev_cpu;
	}
3331

3332
	rcu_read_lock();
3333
	for_each_domain(cpu, tmp) {
3334 3335 3336
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

3337
		/*
3338 3339
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
3340
		 */
3341 3342 3343
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
3344
			break;
3345
		}
3346

3347
		if (tmp->flags & sd_flag)
3348 3349 3350
			sd = tmp;
	}

3351
	if (affine_sd) {
3352
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
3353 3354 3355 3356
			prev_cpu = cpu;

		new_cpu = select_idle_sibling(p, prev_cpu);
		goto unlock;
3357
	}
3358

3359
	while (sd) {
3360
		int load_idx = sd->forkexec_idx;
3361
		struct sched_group *group;
3362
		int weight;
3363

3364
		if (!(sd->flags & sd_flag)) {
3365 3366 3367
			sd = sd->child;
			continue;
		}
3368

3369 3370
		if (sd_flag & SD_BALANCE_WAKE)
			load_idx = sd->wake_idx;
3371

3372
		group = find_idlest_group(sd, p, cpu, load_idx);
3373 3374 3375 3376
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
3377

3378
		new_cpu = find_idlest_cpu(group, p, cpu);
3379 3380 3381 3382
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
3383
		}
3384 3385 3386

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
3387
		weight = sd->span_weight;
3388 3389
		sd = NULL;
		for_each_domain(cpu, tmp) {
3390
			if (weight <= tmp->span_weight)
3391
				break;
3392
			if (tmp->flags & sd_flag)
3393 3394 3395
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
3396
	}
3397 3398
unlock:
	rcu_read_unlock();
3399

3400
	return new_cpu;
3401
}
3402

3403 3404 3405 3406 3407 3408
/*
 * 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
3409 3410 3411 3412 3413 3414 3415 3416 3417
/*
 * 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)
{
3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430
	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);
	}
3431
}
3432
#endif
3433 3434
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
3435 3436
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
3437 3438 3439 3440
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
3441 3442
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
3443 3444 3445 3446 3447 3448 3449 3450 3451
	 *
	 * 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.
3452
	 */
3453
	return calc_delta_fair(gran, se);
3454 3455
}

3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477
/*
 * 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
3478
	gran = wakeup_gran(curr, se);
3479 3480 3481 3482 3483 3484
	if (vdiff > gran)
		return 1;

	return 0;
}

3485 3486
static void set_last_buddy(struct sched_entity *se)
{
3487 3488 3489 3490 3491
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
3492 3493 3494 3495
}

static void set_next_buddy(struct sched_entity *se)
{
3496 3497 3498 3499 3500
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
3501 3502
}

3503 3504
static void set_skip_buddy(struct sched_entity *se)
{
3505 3506
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
3507 3508
}

3509 3510 3511
/*
 * Preempt the current task with a newly woken task if needed:
 */
3512
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
3513 3514
{
	struct task_struct *curr = rq->curr;
3515
	struct sched_entity *se = &curr->se, *pse = &p->se;
3516
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
3517
	int scale = cfs_rq->nr_running >= sched_nr_latency;
3518
	int next_buddy_marked = 0;
3519

I
Ingo Molnar 已提交
3520 3521 3522
	if (unlikely(se == pse))
		return;

3523
	/*
3524
	 * This is possible from callers such as move_task(), in which we
3525 3526 3527 3528 3529 3530 3531
	 * 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;

3532
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
3533
		set_next_buddy(pse);
3534 3535
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
3536

3537 3538 3539
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
3540 3541 3542 3543 3544 3545
	 *
	 * 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.
3546 3547 3548 3549
	 */
	if (test_tsk_need_resched(curr))
		return;

3550 3551 3552 3553 3554
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

3555
	/*
3556 3557
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
3558
	 */
3559
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
3560
		return;
3561

3562
	find_matching_se(&se, &pse);
3563
	update_curr(cfs_rq_of(se));
3564
	BUG_ON(!pse);
3565 3566 3567 3568 3569 3570 3571
	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);
3572
		goto preempt;
3573
	}
3574

3575
	return;
3576

3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592
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);
3593 3594
}

3595
static struct task_struct *pick_next_task_fair(struct rq *rq)
3596
{
P
Peter Zijlstra 已提交
3597
	struct task_struct *p;
3598 3599 3600
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

3601
	if (!cfs_rq->nr_running)
3602 3603 3604
		return NULL;

	do {
3605
		se = pick_next_entity(cfs_rq);
3606
		set_next_entity(cfs_rq, se);
3607 3608 3609
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
3610
	p = task_of(se);
3611 3612
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
3613 3614

	return p;
3615 3616 3617 3618 3619
}

/*
 * Account for a descheduled task:
 */
3620
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
3621 3622 3623 3624 3625 3626
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
3627
		put_prev_entity(cfs_rq, se);
3628 3629 3630
	}
}

3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649 3650 3651 3652 3653 3654 3655
/*
 * 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);
3656 3657 3658 3659 3660 3661
		/*
		 * 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;
3662 3663 3664 3665 3666
	}

	set_skip_buddy(se);
}

3667 3668 3669 3670
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

3671 3672
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
3673 3674 3675 3676 3677 3678 3679 3680 3681 3682
		return false;

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

	yield_task_fair(rq);

	return true;
}

3683
#ifdef CONFIG_SMP
3684
/**************************************************
P
Peter Zijlstra 已提交
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 3794 3795 3796 3797 3798 3799 3800
 * 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.]
 */ 
3801

3802 3803
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

3804
#define LBF_ALL_PINNED	0x01
3805
#define LBF_NEED_BREAK	0x02
3806
#define LBF_SOME_PINNED 0x04
3807 3808 3809 3810 3811

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
3812
	int			src_cpu;
3813 3814 3815 3816

	int			dst_cpu;
	struct rq		*dst_rq;

3817 3818
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
3819
	enum cpu_idle_type	idle;
3820
	long			imbalance;
3821 3822 3823
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

3824
	unsigned int		flags;
3825 3826 3827 3828

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
3829 3830
};

3831
/*
3832
 * move_task - move a task from one runqueue to another runqueue.
3833 3834
 * Both runqueues must be locked.
 */
3835
static void move_task(struct task_struct *p, struct lb_env *env)
3836
{
3837 3838 3839 3840
	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);
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 3868 3869 3870 3871 3872 3873 3874
/*
 * 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;
}

3875 3876 3877 3878
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
3879
int can_migrate_task(struct task_struct *p, struct lb_env *env)
3880 3881 3882 3883 3884 3885 3886 3887
{
	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.
	 */
3888
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
3889 3890
		int new_dst_cpu;

3891
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909

		/*
		 * 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;
		}
3910 3911
		return 0;
	}
3912 3913

	/* Record that we found atleast one task that could run on dst_cpu */
3914
	env->flags &= ~LBF_ALL_PINNED;
3915

3916
	if (task_running(env->src_rq, p)) {
3917
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
3918 3919 3920 3921 3922 3923 3924 3925 3926
		return 0;
	}

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

3927
	tsk_cache_hot = task_hot(p, env->src_rq->clock_task, env->sd);
3928
	if (!tsk_cache_hot ||
3929
		env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
3930 3931
#ifdef CONFIG_SCHEDSTATS
		if (tsk_cache_hot) {
3932
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
3933
			schedstat_inc(p, se.statistics.nr_forced_migrations);
3934 3935 3936 3937 3938 3939
		}
#endif
		return 1;
	}

	if (tsk_cache_hot) {
3940
		schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
3941 3942 3943 3944 3945
		return 0;
	}
	return 1;
}

3946 3947 3948 3949 3950 3951 3952
/*
 * 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.
 */
3953
static int move_one_task(struct lb_env *env)
3954 3955 3956
{
	struct task_struct *p, *n;

3957 3958 3959
	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;
3960

3961 3962
		if (!can_migrate_task(p, env))
			continue;
3963

3964 3965 3966 3967 3968 3969 3970 3971
		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;
3972 3973 3974 3975
	}
	return 0;
}

3976 3977
static unsigned long task_h_load(struct task_struct *p);

3978 3979
static const unsigned int sched_nr_migrate_break = 32;

3980
/*
3981
 * move_tasks tries to move up to imbalance weighted load from busiest to
3982 3983 3984 3985 3986 3987
 * 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)
3988
{
3989 3990
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
3991 3992
	unsigned long load;
	int pulled = 0;
3993

3994
	if (env->imbalance <= 0)
3995
		return 0;
3996

3997 3998
	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
3999

4000 4001
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
4002
		if (env->loop > env->loop_max)
4003
			break;
4004 4005

		/* take a breather every nr_migrate tasks */
4006
		if (env->loop > env->loop_break) {
4007
			env->loop_break += sched_nr_migrate_break;
4008
			env->flags |= LBF_NEED_BREAK;
4009
			break;
4010
		}
4011

4012
		if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
4013 4014 4015
			goto next;

		load = task_h_load(p);
4016

4017
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
4018 4019
			goto next;

4020
		if ((load / 2) > env->imbalance)
4021
			goto next;
4022

4023 4024
		if (!can_migrate_task(p, env))
			goto next;
4025

4026
		move_task(p, env);
4027
		pulled++;
4028
		env->imbalance -= load;
4029 4030

#ifdef CONFIG_PREEMPT
4031 4032 4033 4034 4035
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
		 * kernels will stop after the first task is pulled to minimize
		 * the critical section.
		 */
4036
		if (env->idle == CPU_NEWLY_IDLE)
4037
			break;
4038 4039
#endif

4040 4041 4042 4043
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
4044
		if (env->imbalance <= 0)
4045
			break;
4046 4047 4048

		continue;
next:
4049
		list_move_tail(&p->se.group_node, tasks);
4050
	}
4051

4052
	/*
4053 4054 4055
	 * 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().
4056
	 */
4057
	schedstat_add(env->sd, lb_gained[env->idle], pulled);
4058

4059
	return pulled;
4060 4061
}

P
Peter Zijlstra 已提交
4062
#ifdef CONFIG_FAIR_GROUP_SCHED
4063 4064 4065
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
4066
static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
4067
{
4068 4069
	struct sched_entity *se = tg->se[cpu];
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
4070

4071 4072 4073
	/* throttled entities do not contribute to load */
	if (throttled_hierarchy(cfs_rq))
		return;
4074

4075
	update_cfs_rq_blocked_load(cfs_rq, 1);
4076

4077 4078 4079 4080 4081 4082 4083 4084 4085 4086 4087 4088 4089 4090
	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 {
4091
		struct rq *rq = rq_of(cfs_rq);
4092 4093
		update_rq_runnable_avg(rq, rq->nr_running);
	}
4094 4095
}

4096
static void update_blocked_averages(int cpu)
4097 4098
{
	struct rq *rq = cpu_rq(cpu);
4099 4100
	struct cfs_rq *cfs_rq;
	unsigned long flags;
4101

4102 4103
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
4104 4105 4106 4107
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
4108
	for_each_leaf_cfs_rq(rq, cfs_rq) {
4109 4110 4111 4112 4113 4114
		/*
		 * 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);
4115
	}
4116 4117

	raw_spin_unlock_irqrestore(&rq->lock, flags);
4118 4119
}

4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144
/*
 * 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)
{
4145 4146 4147 4148 4149 4150 4151 4152
	struct rq *rq = cpu_rq(cpu);
	unsigned long now = jiffies;

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

	rq->h_load_throttle = now;

4153
	rcu_read_lock();
4154
	walk_tg_tree(tg_load_down, tg_nop, (void *)cpu);
4155
	rcu_read_unlock();
4156 4157
}

4158
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
4159
{
4160 4161
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
	unsigned long load;
P
Peter Zijlstra 已提交
4162

4163 4164
	load = p->se.load.weight;
	load = div_u64(load * cfs_rq->h_load, cfs_rq->load.weight + 1);
P
Peter Zijlstra 已提交
4165

4166
	return load;
P
Peter Zijlstra 已提交
4167 4168
}
#else
4169
static inline void update_blocked_averages(int cpu)
4170 4171 4172
{
}

4173
static inline void update_h_load(long cpu)
P
Peter Zijlstra 已提交
4174 4175 4176
{
}

4177
static unsigned long task_h_load(struct task_struct *p)
4178
{
4179
	return p->se.load.weight;
4180
}
P
Peter Zijlstra 已提交
4181
#endif
4182 4183 4184 4185 4186 4187 4188 4189 4190 4191 4192 4193 4194 4195 4196 4197 4198

/********** 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;
4199
	unsigned long this_has_capacity;
4200
	unsigned int  this_idle_cpus;
4201 4202

	/* Statistics of the busiest group */
4203
	unsigned int  busiest_idle_cpus;
4204 4205 4206
	unsigned long max_load;
	unsigned long busiest_load_per_task;
	unsigned long busiest_nr_running;
4207
	unsigned long busiest_group_capacity;
4208
	unsigned long busiest_has_capacity;
4209
	unsigned int  busiest_group_weight;
4210 4211 4212 4213 4214 4215 4216 4217 4218 4219 4220 4221 4222

	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;
4223 4224
	unsigned long idle_cpus;
	unsigned long group_weight;
4225
	int group_imb; /* Is there an imbalance in the group ? */
4226
	int group_has_capacity; /* Is there extra capacity in the group? */
4227 4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 4256
};

/**
 * 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)
{
4257
	return SCHED_POWER_SCALE;
4258 4259 4260 4261 4262 4263 4264 4265 4266
}

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)
{
4267
	unsigned long weight = sd->span_weight;
4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282
	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);
4283
	u64 total, available, age_stamp, avg;
4284

4285 4286 4287 4288 4289 4290 4291 4292
	/*
	 * 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);
4293

4294
	if (unlikely(total < avg)) {
4295 4296 4297
		/* Ensures that power won't end up being negative */
		available = 0;
	} else {
4298
		available = total - avg;
4299
	}
4300

4301 4302
	if (unlikely((s64)total < SCHED_POWER_SCALE))
		total = SCHED_POWER_SCALE;
4303

4304
	total >>= SCHED_POWER_SHIFT;
4305 4306 4307 4308 4309 4310

	return div_u64(available, total);
}

static void update_cpu_power(struct sched_domain *sd, int cpu)
{
4311
	unsigned long weight = sd->span_weight;
4312
	unsigned long power = SCHED_POWER_SCALE;
4313 4314 4315 4316 4317 4318 4319 4320
	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);

4321
		power >>= SCHED_POWER_SHIFT;
4322 4323
	}

4324
	sdg->sgp->power_orig = power;
4325 4326 4327 4328 4329 4330

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

4331
	power >>= SCHED_POWER_SHIFT;
4332

4333
	power *= scale_rt_power(cpu);
4334
	power >>= SCHED_POWER_SHIFT;
4335 4336 4337 4338

	if (!power)
		power = 1;

4339
	cpu_rq(cpu)->cpu_power = power;
4340
	sdg->sgp->power = power;
4341 4342
}

4343
void update_group_power(struct sched_domain *sd, int cpu)
4344 4345 4346 4347
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
	unsigned long power;
4348 4349 4350 4351 4352
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
	sdg->sgp->next_update = jiffies + interval;
4353 4354 4355 4356 4357 4358 4359 4360

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

	power = 0;

P
Peter Zijlstra 已提交
4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371 4372 4373 4374 4375 4376 4377 4378 4379 4380
	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);
	}
4381

4382
	sdg->sgp->power_orig = sdg->sgp->power = power;
4383 4384
}

4385 4386 4387 4388 4389 4390 4391 4392 4393 4394 4395
/*
 * 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)
{
	/*
4396
	 * Only siblings can have significantly less than SCHED_POWER_SCALE
4397
	 */
P
Peter Zijlstra 已提交
4398
	if (!(sd->flags & SD_SHARE_CPUPOWER))
4399 4400 4401 4402 4403
		return 0;

	/*
	 * If ~90% of the cpu_power is still there, we're good.
	 */
4404
	if (group->sgp->power * 32 > group->sgp->power_orig * 29)
4405 4406 4407 4408 4409
		return 1;

	return 0;
}

4410 4411
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
4412
 * @env: The load balancing environment.
4413 4414 4415 4416 4417 4418
 * @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.
 */
4419 4420
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
4421
			int local_group, int *balance, struct sg_lb_stats *sgs)
4422
{
4423 4424
	unsigned long nr_running, max_nr_running, min_nr_running;
	unsigned long load, max_cpu_load, min_cpu_load;
4425
	unsigned int balance_cpu = -1, first_idle_cpu = 0;
4426
	unsigned long avg_load_per_task = 0;
4427
	int i;
4428

4429
	if (local_group)
P
Peter Zijlstra 已提交
4430
		balance_cpu = group_balance_cpu(group);
4431 4432 4433 4434

	/* Tally up the load of all CPUs in the group */
	max_cpu_load = 0;
	min_cpu_load = ~0UL;
4435
	max_nr_running = 0;
4436
	min_nr_running = ~0UL;
4437

4438
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
4439 4440
		struct rq *rq = cpu_rq(i);

4441 4442
		nr_running = rq->nr_running;

4443 4444
		/* Bias balancing toward cpus of our domain */
		if (local_group) {
P
Peter Zijlstra 已提交
4445 4446
			if (idle_cpu(i) && !first_idle_cpu &&
					cpumask_test_cpu(i, sched_group_mask(group))) {
4447
				first_idle_cpu = 1;
4448 4449
				balance_cpu = i;
			}
4450 4451

			load = target_load(i, load_idx);
4452 4453
		} else {
			load = source_load(i, load_idx);
4454
			if (load > max_cpu_load)
4455 4456 4457
				max_cpu_load = load;
			if (min_cpu_load > load)
				min_cpu_load = load;
4458 4459 4460 4461 4462

			if (nr_running > max_nr_running)
				max_nr_running = nr_running;
			if (min_nr_running > nr_running)
				min_nr_running = nr_running;
4463 4464 4465
		}

		sgs->group_load += load;
4466
		sgs->sum_nr_running += nr_running;
4467
		sgs->sum_weighted_load += weighted_cpuload(i);
4468 4469
		if (idle_cpu(i))
			sgs->idle_cpus++;
4470 4471 4472 4473 4474 4475 4476 4477
	}

	/*
	 * 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.
	 */
4478
	if (local_group) {
4479
		if (env->idle != CPU_NEWLY_IDLE) {
4480
			if (balance_cpu != env->dst_cpu) {
4481 4482 4483
				*balance = 0;
				return;
			}
4484
			update_group_power(env->sd, env->dst_cpu);
4485
		} else if (time_after_eq(jiffies, group->sgp->next_update))
4486
			update_group_power(env->sd, env->dst_cpu);
4487 4488 4489
	}

	/* Adjust by relative CPU power of the group */
4490
	sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / group->sgp->power;
4491 4492 4493

	/*
	 * Consider the group unbalanced when the imbalance is larger
P
Peter Zijlstra 已提交
4494
	 * than the average weight of a task.
4495 4496 4497 4498 4499 4500
	 *
	 * 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?
	 */
4501 4502
	if (sgs->sum_nr_running)
		avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
4503

4504 4505
	if ((max_cpu_load - min_cpu_load) >= avg_load_per_task &&
	    (max_nr_running - min_nr_running) > 1)
4506 4507
		sgs->group_imb = 1;

4508
	sgs->group_capacity = DIV_ROUND_CLOSEST(group->sgp->power,
4509
						SCHED_POWER_SCALE);
4510
	if (!sgs->group_capacity)
4511
		sgs->group_capacity = fix_small_capacity(env->sd, group);
4512
	sgs->group_weight = group->group_weight;
4513 4514 4515

	if (sgs->group_capacity > sgs->sum_nr_running)
		sgs->group_has_capacity = 1;
4516 4517
}

4518 4519
/**
 * update_sd_pick_busiest - return 1 on busiest group
4520
 * @env: The load balancing environment.
4521 4522
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
4523
 * @sgs: sched_group statistics
4524 4525 4526 4527
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
 */
4528
static bool update_sd_pick_busiest(struct lb_env *env,
4529 4530
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
4531
				   struct sg_lb_stats *sgs)
4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546
{
	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.
	 */
4547 4548
	if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
	    env->dst_cpu < group_first_cpu(sg)) {
4549 4550 4551 4552 4553 4554 4555 4556 4557 4558
		if (!sds->busiest)
			return true;

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

	return false;
}

4559
/**
4560
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
4561
 * @env: The load balancing environment.
4562 4563 4564
 * @balance: Should we balance.
 * @sds: variable to hold the statistics for this sched_domain.
 */
4565
static inline void update_sd_lb_stats(struct lb_env *env,
4566
					int *balance, struct sd_lb_stats *sds)
4567
{
4568 4569
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
4570 4571 4572 4573 4574 4575
	struct sg_lb_stats sgs;
	int load_idx, prefer_sibling = 0;

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

4576
	load_idx = get_sd_load_idx(env->sd, env->idle);
4577 4578 4579 4580

	do {
		int local_group;

4581
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
4582
		memset(&sgs, 0, sizeof(sgs));
4583
		update_sg_lb_stats(env, sg, load_idx, local_group, balance, &sgs);
4584

P
Peter Zijlstra 已提交
4585
		if (local_group && !(*balance))
4586 4587 4588
			return;

		sds->total_load += sgs.group_load;
4589
		sds->total_pwr += sg->sgp->power;
4590 4591 4592

		/*
		 * In case the child domain prefers tasks go to siblings
4593
		 * first, lower the sg capacity to one so that we'll try
4594 4595 4596 4597 4598 4599
		 * 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).
4600
		 */
4601
		if (prefer_sibling && !local_group && sds->this_has_capacity)
4602 4603 4604 4605
			sgs.group_capacity = min(sgs.group_capacity, 1UL);

		if (local_group) {
			sds->this_load = sgs.avg_load;
4606
			sds->this = sg;
4607 4608
			sds->this_nr_running = sgs.sum_nr_running;
			sds->this_load_per_task = sgs.sum_weighted_load;
4609
			sds->this_has_capacity = sgs.group_has_capacity;
4610
			sds->this_idle_cpus = sgs.idle_cpus;
4611
		} else if (update_sd_pick_busiest(env, sds, sg, &sgs)) {
4612
			sds->max_load = sgs.avg_load;
4613
			sds->busiest = sg;
4614
			sds->busiest_nr_running = sgs.sum_nr_running;
4615
			sds->busiest_idle_cpus = sgs.idle_cpus;
4616
			sds->busiest_group_capacity = sgs.group_capacity;
4617
			sds->busiest_load_per_task = sgs.sum_weighted_load;
4618
			sds->busiest_has_capacity = sgs.group_has_capacity;
4619
			sds->busiest_group_weight = sgs.group_weight;
4620 4621 4622
			sds->group_imb = sgs.group_imb;
		}

4623
		sg = sg->next;
4624
	} while (sg != env->sd->groups);
4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636 4637 4638 4639 4640 4641 4642 4643
}

/**
 * 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.
 *
4644 4645 4646
 * Returns 1 when packing is required and a task should be moved to
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
4647
 * @env: The load balancing environment.
4648 4649
 * @sds: Statistics of the sched_domain which is to be packed
 */
4650
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
4651 4652 4653
{
	int busiest_cpu;

4654
	if (!(env->sd->flags & SD_ASYM_PACKING))
4655 4656 4657 4658 4659 4660
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
4661
	if (env->dst_cpu > busiest_cpu)
4662 4663
		return 0;

4664 4665 4666
	env->imbalance = DIV_ROUND_CLOSEST(
		sds->max_load * sds->busiest->sgp->power, SCHED_POWER_SCALE);

4667
	return 1;
4668 4669 4670 4671 4672 4673
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
4674
 * @env: The load balancing environment.
4675 4676
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
4677 4678
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
4679 4680 4681
{
	unsigned long tmp, pwr_now = 0, pwr_move = 0;
	unsigned int imbn = 2;
4682
	unsigned long scaled_busy_load_per_task;
4683 4684 4685 4686 4687 4688

	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;
4689
	} else {
4690
		sds->this_load_per_task =
4691 4692
			cpu_avg_load_per_task(env->dst_cpu);
	}
4693

4694
	scaled_busy_load_per_task = sds->busiest_load_per_task
4695
					 * SCHED_POWER_SCALE;
4696
	scaled_busy_load_per_task /= sds->busiest->sgp->power;
4697 4698 4699

	if (sds->max_load - sds->this_load + scaled_busy_load_per_task >=
			(scaled_busy_load_per_task * imbn)) {
4700
		env->imbalance = sds->busiest_load_per_task;
4701 4702 4703 4704 4705 4706 4707 4708 4709
		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.
	 */

4710
	pwr_now += sds->busiest->sgp->power *
4711
			min(sds->busiest_load_per_task, sds->max_load);
4712
	pwr_now += sds->this->sgp->power *
4713
			min(sds->this_load_per_task, sds->this_load);
4714
	pwr_now /= SCHED_POWER_SCALE;
4715 4716

	/* Amount of load we'd subtract */
4717
	tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
4718
		sds->busiest->sgp->power;
4719
	if (sds->max_load > tmp)
4720
		pwr_move += sds->busiest->sgp->power *
4721 4722 4723
			min(sds->busiest_load_per_task, sds->max_load - tmp);

	/* Amount of load we'd add */
4724
	if (sds->max_load * sds->busiest->sgp->power <
4725
		sds->busiest_load_per_task * SCHED_POWER_SCALE)
4726 4727
		tmp = (sds->max_load * sds->busiest->sgp->power) /
			sds->this->sgp->power;
4728
	else
4729
		tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
4730 4731
			sds->this->sgp->power;
	pwr_move += sds->this->sgp->power *
4732
			min(sds->this_load_per_task, sds->this_load + tmp);
4733
	pwr_move /= SCHED_POWER_SCALE;
4734 4735 4736

	/* Move if we gain throughput */
	if (pwr_move > pwr_now)
4737
		env->imbalance = sds->busiest_load_per_task;
4738 4739 4740 4741 4742
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
4743
 * @env: load balance environment
4744 4745
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
4746
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
4747
{
4748 4749 4750 4751 4752 4753 4754 4755
	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);
	}

4756 4757 4758 4759 4760 4761
	/*
	 * 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) {
4762 4763
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
4764 4765
	}

4766 4767 4768 4769 4770 4771 4772
	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);

4773
		load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
4774

4775
		load_above_capacity /= sds->busiest->sgp->power;
4776 4777 4778 4779 4780 4781 4782 4783 4784 4785 4786 4787 4788
	}

	/*
	 * 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);
4789 4790

	/* How much load to actually move to equalise the imbalance */
4791
	env->imbalance = min(max_pull * sds->busiest->sgp->power,
4792
		(sds->avg_load - sds->this_load) * sds->this->sgp->power)
4793
			/ SCHED_POWER_SCALE;
4794 4795 4796

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
4797
	 * there is no guarantee that any tasks will be moved so we'll have
4798 4799 4800
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
4801 4802
	if (env->imbalance < sds->busiest_load_per_task)
		return fix_small_imbalance(env, sds);
4803 4804

}
4805

4806 4807 4808 4809 4810 4811 4812 4813 4814 4815 4816 4817
/******* 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.
 *
4818
 * @env: The load balancing environment.
4819 4820 4821 4822 4823 4824 4825 4826 4827
 * @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 *
4828
find_busiest_group(struct lb_env *env, int *balance)
4829 4830 4831 4832 4833 4834 4835 4836 4837
{
	struct sd_lb_stats sds;

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

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
4838
	update_sd_lb_stats(env, balance, &sds);
4839

4840 4841 4842
	/*
	 * this_cpu is not the appropriate cpu to perform load balancing at
	 * this level.
4843
	 */
P
Peter Zijlstra 已提交
4844
	if (!(*balance))
4845 4846
		goto ret;

4847 4848
	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(env, &sds))
4849 4850
		return sds.busiest;

4851
	/* There is no busy sibling group to pull tasks from */
4852 4853 4854
	if (!sds.busiest || sds.busiest_nr_running == 0)
		goto out_balanced;

4855
	sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
4856

P
Peter Zijlstra 已提交
4857 4858 4859 4860 4861 4862 4863 4864
	/*
	 * 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;

4865
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
4866
	if (env->idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
4867 4868 4869
			!sds.busiest_has_capacity)
		goto force_balance;

4870 4871 4872 4873
	/*
	 * If the local group is more busy than the selected busiest group
	 * don't try and pull any tasks.
	 */
4874 4875 4876
	if (sds.this_load >= sds.max_load)
		goto out_balanced;

4877 4878 4879 4880
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
4881 4882 4883
	if (sds.this_load >= sds.avg_load)
		goto out_balanced;

4884
	if (env->idle == CPU_IDLE) {
4885 4886 4887 4888 4889 4890
		/*
		 * 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.
		 */
4891
		if ((sds.this_idle_cpus <= sds.busiest_idle_cpus + 1) &&
4892 4893
		    sds.busiest_nr_running <= sds.busiest_group_weight)
			goto out_balanced;
4894 4895 4896 4897 4898
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
4899
		if (100 * sds.max_load <= env->sd->imbalance_pct * sds.this_load)
4900
			goto out_balanced;
4901
	}
4902

4903
force_balance:
4904
	/* Looks like there is an imbalance. Compute it */
4905
	calculate_imbalance(env, &sds);
4906 4907 4908 4909
	return sds.busiest;

out_balanced:
ret:
4910
	env->imbalance = 0;
4911 4912 4913 4914 4915 4916
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
4917
static struct rq *find_busiest_queue(struct lb_env *env,
4918
				     struct sched_group *group)
4919 4920 4921 4922 4923 4924 4925
{
	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);
4926 4927
		unsigned long capacity = DIV_ROUND_CLOSEST(power,
							   SCHED_POWER_SCALE);
4928 4929
		unsigned long wl;

4930
		if (!capacity)
4931
			capacity = fix_small_capacity(env->sd, group);
4932

4933
		if (!cpumask_test_cpu(i, env->cpus))
4934 4935 4936
			continue;

		rq = cpu_rq(i);
4937
		wl = weighted_cpuload(i);
4938

4939 4940 4941 4942
		/*
		 * When comparing with imbalance, use weighted_cpuload()
		 * which is not scaled with the cpu power.
		 */
4943
		if (capacity && rq->nr_running == 1 && wl > env->imbalance)
4944 4945
			continue;

4946 4947 4948 4949 4950 4951
		/*
		 * 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.
		 */
4952
		wl = (wl * SCHED_POWER_SCALE) / power;
4953

4954 4955 4956 4957 4958 4959 4960 4961 4962 4963 4964 4965 4966 4967 4968 4969
		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. */
4970
DEFINE_PER_CPU(cpumask_var_t, load_balance_tmpmask);
4971

4972
static int need_active_balance(struct lb_env *env)
4973
{
4974 4975 4976
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
4977 4978 4979 4980 4981 4982

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
4983
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
4984
			return 1;
4985 4986 4987 4988 4989
	}

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

4990 4991
static int active_load_balance_cpu_stop(void *data);

4992 4993 4994 4995 4996 4997 4998 4999
/*
 * 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)
{
5000 5001
	int ld_moved, cur_ld_moved, active_balance = 0;
	int lb_iterations, max_lb_iterations;
5002 5003 5004 5005 5006
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
	struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);

5007 5008
	struct lb_env env = {
		.sd		= sd,
5009 5010
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
5011
		.dst_grpmask    = sched_group_cpus(sd->groups),
5012
		.idle		= idle,
5013
		.loop_break	= sched_nr_migrate_break,
5014
		.cpus		= cpus,
5015 5016
	};

5017
	cpumask_copy(cpus, cpu_active_mask);
5018
	max_lb_iterations = cpumask_weight(env.dst_grpmask);
5019 5020 5021 5022

	schedstat_inc(sd, lb_count[idle]);

redo:
5023
	group = find_busiest_group(&env, balance);
5024 5025 5026 5027 5028 5029 5030 5031 5032

	if (*balance == 0)
		goto out_balanced;

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

5033
	busiest = find_busiest_queue(&env, group);
5034 5035 5036 5037 5038
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

5039
	BUG_ON(busiest == env.dst_rq);
5040

5041
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
5042 5043

	ld_moved = 0;
5044
	lb_iterations = 1;
5045 5046 5047 5048 5049 5050 5051
	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.
		 */
5052
		env.flags |= LBF_ALL_PINNED;
5053 5054 5055
		env.src_cpu   = busiest->cpu;
		env.src_rq    = busiest;
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
5056

5057
		update_h_load(env.src_cpu);
5058
more_balance:
5059
		local_irq_save(flags);
5060
		double_rq_lock(env.dst_rq, busiest);
5061 5062 5063 5064 5065 5066 5067

		/*
		 * 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;
5068
		double_rq_unlock(env.dst_rq, busiest);
5069 5070
		local_irq_restore(flags);

5071 5072 5073 5074 5075
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

5076 5077 5078
		/*
		 * some other cpu did the load balance for us.
		 */
5079 5080 5081 5082 5083 5084 5085 5086 5087 5088 5089 5090 5091 5092 5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103
		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) {

5104
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
5105 5106 5107 5108 5109 5110 5111 5112 5113 5114
			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;
		}
5115 5116

		/* All tasks on this runqueue were pinned by CPU affinity */
5117
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
5118
			cpumask_clear_cpu(cpu_of(busiest), cpus);
5119 5120 5121
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
5122
				goto redo;
5123
			}
5124 5125 5126 5127 5128 5129
			goto out_balanced;
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
5130 5131 5132 5133 5134 5135 5136 5137
		/*
		 * 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++;
5138

5139
		if (need_active_balance(&env)) {
5140 5141
			raw_spin_lock_irqsave(&busiest->lock, flags);

5142 5143 5144
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
5145 5146
			 */
			if (!cpumask_test_cpu(this_cpu,
5147
					tsk_cpus_allowed(busiest->curr))) {
5148 5149
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
5150
				env.flags |= LBF_ALL_PINNED;
5151 5152 5153
				goto out_one_pinned;
			}

5154 5155 5156 5157 5158
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
5159 5160 5161 5162 5163 5164
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
5165

5166
			if (active_balance) {
5167 5168 5169
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
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 5197 5198 5199 5200 5201 5202 5203

			/*
			 * 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 */
5204
	if (((env.flags & LBF_ALL_PINNED) &&
5205
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
5206 5207 5208
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

5209
	ld_moved = 0;
5210 5211 5212 5213 5214 5215 5216 5217
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.
 */
5218
void idle_balance(int this_cpu, struct rq *this_rq)
5219 5220 5221 5222 5223 5224 5225 5226 5227 5228
{
	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;

5229 5230
	update_rq_runnable_avg(this_rq, 1);

5231 5232 5233 5234 5235
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

5236
	update_blocked_averages(this_cpu);
5237
	rcu_read_lock();
5238 5239
	for_each_domain(this_cpu, sd) {
		unsigned long interval;
5240
		int balance = 1;
5241 5242 5243 5244

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

5245
		if (sd->flags & SD_BALANCE_NEWIDLE) {
5246
			/* If we've pulled tasks over stop searching: */
5247 5248 5249
			pulled_task = load_balance(this_cpu, this_rq,
						   sd, CPU_NEWLY_IDLE, &balance);
		}
5250 5251 5252 5253

		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
5254 5255
		if (pulled_task) {
			this_rq->idle_stamp = 0;
5256
			break;
N
Nikhil Rao 已提交
5257
		}
5258
	}
5259
	rcu_read_unlock();
5260 5261 5262

	raw_spin_lock(&this_rq->lock);

5263 5264 5265 5266 5267 5268 5269 5270 5271 5272
	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;
	}
}

/*
5273 5274 5275 5276
 * 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.
5277
 */
5278
static int active_load_balance_cpu_stop(void *data)
5279
{
5280 5281
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
5282
	int target_cpu = busiest_rq->push_cpu;
5283
	struct rq *target_rq = cpu_rq(target_cpu);
5284
	struct sched_domain *sd;
5285 5286 5287 5288 5289 5290 5291

	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;
5292 5293 5294

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
5295
		goto out_unlock;
5296 5297 5298 5299 5300 5301 5302 5303 5304 5305 5306 5307

	/*
	 * 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. */
5308
	rcu_read_lock();
5309 5310 5311 5312 5313 5314 5315
	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)) {
5316 5317
		struct lb_env env = {
			.sd		= sd,
5318 5319 5320 5321
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
5322 5323 5324
			.idle		= CPU_IDLE,
		};

5325 5326
		schedstat_inc(sd, alb_count);

5327
		if (move_one_task(&env))
5328 5329 5330 5331
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
5332
	rcu_read_unlock();
5333
	double_unlock_balance(busiest_rq, target_rq);
5334 5335 5336 5337
out_unlock:
	busiest_rq->active_balance = 0;
	raw_spin_unlock_irq(&busiest_rq->lock);
	return 0;
5338 5339 5340
}

#ifdef CONFIG_NO_HZ
5341 5342 5343 5344 5345 5346
/*
 * 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.
 */
5347
static struct {
5348
	cpumask_var_t idle_cpus_mask;
5349
	atomic_t nr_cpus;
5350 5351
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
5352

5353
static inline int find_new_ilb(int call_cpu)
5354
{
5355
	int ilb = cpumask_first(nohz.idle_cpus_mask);
5356

5357 5358 5359 5360
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
5361 5362
}

5363 5364 5365 5366 5367 5368 5369 5370 5371 5372 5373
/*
 * 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++;

5374
	ilb_cpu = find_new_ilb(cpu);
5375

5376 5377
	if (ilb_cpu >= nr_cpu_ids)
		return;
5378

5379
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
5380 5381 5382 5383 5384 5385 5386 5387
		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);
5388 5389 5390
	return;
}

5391
static inline void nohz_balance_exit_idle(int cpu)
5392 5393 5394 5395 5396 5397 5398 5399
{
	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));
	}
}

5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418 5419 5420 5421 5422 5423 5424 5425 5426 5427 5428 5429
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();
}

5430
/*
5431
 * This routine will record that the cpu is going idle with tick stopped.
5432
 * This info will be used in performing idle load balancing in the future.
5433
 */
5434
void nohz_balance_enter_idle(int cpu)
5435
{
5436 5437 5438 5439 5440 5441
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

5442 5443
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
5444

5445 5446 5447
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
5448
}
5449 5450 5451 5452 5453 5454

static int __cpuinit sched_ilb_notifier(struct notifier_block *nfb,
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
5455
		nohz_balance_exit_idle(smp_processor_id());
5456 5457 5458 5459 5460
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
5461 5462 5463 5464
#endif

static DEFINE_SPINLOCK(balancing);

5465 5466 5467 5468
/*
 * 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.
 */
5469
void update_max_interval(void)
5470 5471 5472 5473
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

5474 5475 5476 5477 5478 5479 5480 5481 5482 5483 5484
/*
 * 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;
5485
	struct sched_domain *sd;
5486 5487 5488 5489 5490
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
	int need_serialize;

5491
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
5492

5493
	rcu_read_lock();
5494 5495 5496 5497 5498 5499 5500 5501 5502 5503
	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);
5504
		interval = clamp(interval, 1UL, max_load_balance_interval);
5505 5506 5507 5508 5509 5510 5511 5512 5513 5514 5515 5516

		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
5517
				 * longer idle.
5518 5519 5520 5521 5522 5523 5524 5525 5526 5527 5528 5529 5530 5531 5532 5533 5534 5535 5536 5537 5538
				 */
				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;
	}
5539
	rcu_read_unlock();
5540 5541 5542 5543 5544 5545 5546 5547 5548 5549

	/*
	 * 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;
}

5550
#ifdef CONFIG_NO_HZ
5551
/*
5552
 * In CONFIG_NO_HZ case, the idle balance kickee will do the
5553 5554
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
5555 5556 5557 5558 5559 5560
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;

5561 5562 5563
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
5564 5565

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
5566
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
5567 5568 5569 5570 5571 5572 5573
			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.
		 */
5574
		if (need_resched())
5575 5576
			break;

V
Vincent Guittot 已提交
5577 5578 5579 5580 5581 5582
		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);
5583 5584 5585 5586 5587 5588 5589

		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;
5590 5591
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
5592 5593 5594
}

/*
5595 5596 5597 5598 5599 5600 5601
 * 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.
5602 5603 5604 5605
 */
static inline int nohz_kick_needed(struct rq *rq, int cpu)
{
	unsigned long now = jiffies;
5606
	struct sched_domain *sd;
5607

5608
	if (unlikely(idle_cpu(cpu)))
5609 5610
		return 0;

5611 5612 5613 5614
       /*
	* 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.
	*/
5615
	set_cpu_sd_state_busy();
5616
	nohz_balance_exit_idle(cpu);
5617 5618 5619 5620 5621 5622 5623

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
		return 0;
5624 5625

	if (time_before(now, nohz.next_balance))
5626 5627
		return 0;

5628 5629
	if (rq->nr_running >= 2)
		goto need_kick;
5630

5631
	rcu_read_lock();
5632 5633 5634 5635
	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);
5636

5637
		if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1)
5638
			goto need_kick_unlock;
5639 5640 5641 5642

		if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight
		    && (cpumask_first_and(nohz.idle_cpus_mask,
					  sched_domain_span(sd)) < cpu))
5643
			goto need_kick_unlock;
5644 5645 5646

		if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING)))
			break;
5647
	}
5648
	rcu_read_unlock();
5649
	return 0;
5650 5651 5652

need_kick_unlock:
	rcu_read_unlock();
5653 5654
need_kick:
	return 1;
5655 5656 5657 5658 5659 5660 5661 5662 5663
}
#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).
 */
5664 5665 5666 5667
static void run_rebalance_domains(struct softirq_action *h)
{
	int this_cpu = smp_processor_id();
	struct rq *this_rq = cpu_rq(this_cpu);
5668
	enum cpu_idle_type idle = this_rq->idle_balance ?
5669 5670 5671 5672 5673
						CPU_IDLE : CPU_NOT_IDLE;

	rebalance_domains(this_cpu, idle);

	/*
5674
	 * If this cpu has a pending nohz_balance_kick, then do the
5675 5676 5677
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
5678
	nohz_idle_balance(this_cpu, idle);
5679 5680 5681 5682
}

static inline int on_null_domain(int cpu)
{
5683
	return !rcu_dereference_sched(cpu_rq(cpu)->sd);
5684 5685 5686 5687 5688
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
5689
void trigger_load_balance(struct rq *rq, int cpu)
5690 5691 5692 5693 5694
{
	/* 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);
5695
#ifdef CONFIG_NO_HZ
5696
	if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
5697 5698
		nohz_balancer_kick(cpu);
#endif
5699 5700
}

5701 5702 5703 5704 5705 5706 5707 5708
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
5709 5710 5711

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
5712 5713
}

5714
#endif /* CONFIG_SMP */
5715

5716 5717 5718
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
5719
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
5720 5721 5722 5723 5724 5725
{
	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
5726
		entity_tick(cfs_rq, se, queued);
5727
	}
5728

5729 5730
	if (sched_feat_numa(NUMA))
		task_tick_numa(rq, curr);
5731

5732
	update_rq_runnable_avg(rq, 1);
5733 5734 5735
}

/*
P
Peter Zijlstra 已提交
5736 5737 5738
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
5739
 */
P
Peter Zijlstra 已提交
5740
static void task_fork_fair(struct task_struct *p)
5741
{
5742 5743
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
5744
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
5745 5746 5747
	struct rq *rq = this_rq();
	unsigned long flags;

5748
	raw_spin_lock_irqsave(&rq->lock, flags);
5749

5750 5751
	update_rq_clock(rq);

5752 5753 5754
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

5755 5756
	if (unlikely(task_cpu(p) != this_cpu)) {
		rcu_read_lock();
P
Peter Zijlstra 已提交
5757
		__set_task_cpu(p, this_cpu);
5758 5759
		rcu_read_unlock();
	}
5760

5761
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
5762

5763 5764
	if (curr)
		se->vruntime = curr->vruntime;
5765
	place_entity(cfs_rq, se, 1);
5766

P
Peter Zijlstra 已提交
5767
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
5768
		/*
5769 5770 5771
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
5772
		swap(curr->vruntime, se->vruntime);
5773
		resched_task(rq->curr);
5774
	}
5775

5776 5777
	se->vruntime -= cfs_rq->min_vruntime;

5778
	raw_spin_unlock_irqrestore(&rq->lock, flags);
5779 5780
}

5781 5782 5783 5784
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
5785 5786
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
5787
{
P
Peter Zijlstra 已提交
5788 5789 5790
	if (!p->se.on_rq)
		return;

5791 5792 5793 5794 5795
	/*
	 * 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
5796
	if (rq->curr == p) {
5797 5798 5799
		if (p->prio > oldprio)
			resched_task(rq->curr);
	} else
5800
		check_preempt_curr(rq, p, 0);
5801 5802
}

P
Peter Zijlstra 已提交
5803 5804 5805 5806 5807 5808 5809 5810 5811 5812 5813 5814 5815 5816 5817 5818 5819 5820 5821 5822 5823 5824
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;
	}
5825 5826 5827 5828 5829 5830 5831 5832 5833 5834 5835 5836 5837 5838

#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
5839 5840
}

5841 5842 5843
/*
 * We switched to the sched_fair class.
 */
P
Peter Zijlstra 已提交
5844
static void switched_to_fair(struct rq *rq, struct task_struct *p)
5845
{
P
Peter Zijlstra 已提交
5846 5847 5848
	if (!p->se.on_rq)
		return;

5849 5850 5851 5852 5853
	/*
	 * 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
5854
	if (rq->curr == p)
5855 5856
		resched_task(rq->curr);
	else
5857
		check_preempt_curr(rq, p, 0);
5858 5859
}

5860 5861 5862 5863 5864 5865 5866 5867 5868
/* 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;

5869 5870 5871 5872 5873 5874 5875
	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);
	}
5876 5877
}

5878 5879 5880 5881 5882 5883 5884
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
5885 5886
#if defined(CONFIG_FAIR_GROUP_SCHED) && defined(CONFIG_SMP)
	atomic64_set(&cfs_rq->decay_counter, 1);
5887
	atomic64_set(&cfs_rq->removed_load, 0);
5888
#endif
5889 5890
}

P
Peter Zijlstra 已提交
5891
#ifdef CONFIG_FAIR_GROUP_SCHED
5892
static void task_move_group_fair(struct task_struct *p, int on_rq)
P
Peter Zijlstra 已提交
5893
{
5894
	struct cfs_rq *cfs_rq;
5895 5896 5897 5898 5899 5900 5901 5902 5903 5904 5905 5906 5907
	/*
	 * 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.
	 */
5908 5909 5910 5911 5912 5913
	/*
	 * 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().
5914 5915
	 * - Moving a task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
5916 5917 5918 5919
	 *
	 * To prevent boost or penalty in the new cfs_rq caused by delta
	 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
	 */
5920
	if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING))
5921 5922
		on_rq = 1;

5923 5924 5925
	if (!on_rq)
		p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
	set_task_rq(p, task_cpu(p));
5926 5927 5928 5929 5930 5931 5932 5933 5934 5935 5936 5937 5938
	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
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 6062 6063 6064 6065 6066 6067 6068

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);
6069
		for_each_sched_entity(se)
6070 6071 6072 6073 6074 6075 6076 6077 6078 6079 6080 6081 6082 6083 6084 6085 6086 6087 6088 6089 6090
			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
6091

6092
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
6093 6094 6095 6096 6097 6098 6099 6100 6101
{
	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)
6102
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
6103 6104 6105 6106

	return rr_interval;
}

6107 6108 6109
/*
 * All the scheduling class methods:
 */
6110
const struct sched_class fair_sched_class = {
6111
	.next			= &idle_sched_class,
6112 6113 6114
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
6115
	.yield_to_task		= yield_to_task_fair,
6116

I
Ingo Molnar 已提交
6117
	.check_preempt_curr	= check_preempt_wakeup,
6118 6119 6120 6121

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

6122
#ifdef CONFIG_SMP
L
Li Zefan 已提交
6123
	.select_task_rq		= select_task_rq_fair,
6124
#ifdef CONFIG_FAIR_GROUP_SCHED
6125
	.migrate_task_rq	= migrate_task_rq_fair,
6126
#endif
6127 6128
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
6129 6130

	.task_waking		= task_waking_fair,
6131
#endif
6132

6133
	.set_curr_task          = set_curr_task_fair,
6134
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
6135
	.task_fork		= task_fork_fair,
6136 6137

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
6138
	.switched_from		= switched_from_fair,
6139
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
6140

6141 6142
	.get_rr_interval	= get_rr_interval_fair,

P
Peter Zijlstra 已提交
6143
#ifdef CONFIG_FAIR_GROUP_SCHED
6144
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
6145
#endif
6146 6147 6148
};

#ifdef CONFIG_SCHED_DEBUG
6149
void print_cfs_stats(struct seq_file *m, int cpu)
6150 6151 6152
{
	struct cfs_rq *cfs_rq;

6153
	rcu_read_lock();
6154
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
6155
		print_cfs_rq(m, cpu, cfs_rq);
6156
	rcu_read_unlock();
6157 6158
}
#endif
6159 6160 6161 6162 6163 6164 6165

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

#ifdef CONFIG_NO_HZ
6166
	nohz.next_balance = jiffies;
6167
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
6168
	cpu_notifier(sched_ilb_notifier, 0);
6169 6170 6171 6172
#endif
#endif /* SMP */

}