fair.c 159.5 KB
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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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 */

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

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

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

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

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

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

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

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

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

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

	return factor;
}

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

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

void sched_init_granularity(void)
{
	update_sysctl();
}

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

#define WMULT_SHIFT	32

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

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

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

	if (!lw->inv_weight) {
		unsigned long w = scale_load_down(lw->weight);

		if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
			lw->inv_weight = 1;
		else if (unlikely(!w))
			lw->inv_weight = WMULT_CONST;
		else
			lw->inv_weight = WMULT_CONST / w;
	}

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

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


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

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

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

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

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

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

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

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static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
				       int force_update);
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static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (!cfs_rq->on_list) {
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		/*
		 * Ensure we either appear before our parent (if already
		 * enqueued) or force our parent to appear after us when it is
		 * enqueued.  The fact that we always enqueue bottom-up
		 * reduces this to two cases.
		 */
		if (cfs_rq->tg->parent &&
		    cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
			list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
				&rq_of(cfs_rq)->leaf_cfs_rq_list);
		} else {
			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
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				&rq_of(cfs_rq)->leaf_cfs_rq_list);
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		}
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		cfs_rq->on_list = 1;
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		/* We should have no load, but we need to update last_decay. */
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		update_cfs_rq_blocked_load(cfs_rq, 0);
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	}
}

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

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

/* Do the two (enqueued) entities belong to the same group ? */
static inline int
is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
	if (se->cfs_rq == pse->cfs_rq)
		return 1;

	return 0;
}

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

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

	for_each_sched_entity(se)
		depth++;

	return depth;
}

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

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

	/* First walk up until both entities are at same depth */
	se_depth = depth_se(*se);
	pse_depth = depth_se(*pse);

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

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

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

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#else	/* !CONFIG_FAIR_GROUP_SCHED */

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

#define entity_is_task(se)	1

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

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

	return &rq->cfs;
}

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

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

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

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

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

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

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

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#endif	/* CONFIG_FAIR_GROUP_SCHED */

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

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

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

	return min_vruntime;
}

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

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

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

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

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

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

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

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

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

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

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

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

	if (!left)
		return NULL;

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

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

	if (!next)
		return NULL;

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

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

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

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

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

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

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

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

	return period;
}

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

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

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#ifdef CONFIG_SMP
static inline void __update_task_entity_contrib(struct sched_entity *se);

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

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

703 704 705 706 707
/*
 * Update the current task's runtime statistics. Skip current tasks that
 * are not in our scheduling class.
 */
static inline void
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708 709
__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
	      unsigned long delta_exec)
710
{
711
	unsigned long delta_exec_weighted;
712

713 714
	schedstat_set(curr->statistics.exec_max,
		      max((u64)delta_exec, curr->statistics.exec_max));
715 716

	curr->sum_exec_runtime += delta_exec;
717
	schedstat_add(cfs_rq, exec_clock, delta_exec);
718
	delta_exec_weighted = calc_delta_fair(delta_exec, curr);
719

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720
	curr->vruntime += delta_exec_weighted;
721
	update_min_vruntime(cfs_rq);
722 723
}

724
static void update_curr(struct cfs_rq *cfs_rq)
725
{
726
	struct sched_entity *curr = cfs_rq->curr;
727
	u64 now = rq_clock_task(rq_of(cfs_rq));
728 729 730 731 732 733 734 735 736 737
	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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738
	delta_exec = (unsigned long)(now - curr->exec_start);
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739 740
	if (!delta_exec)
		return;
741

I
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742 743
	__update_curr(cfs_rq, curr, delta_exec);
	curr->exec_start = now;
744 745 746 747

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

748
		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
749
		cpuacct_charge(curtask, delta_exec);
750
		account_group_exec_runtime(curtask, delta_exec);
751
	}
752 753

	account_cfs_rq_runtime(cfs_rq, delta_exec);
754 755 756
}

static inline void
757
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
758
{
759
	schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
760 761 762 763 764
}

/*
 * Task is being enqueued - update stats:
 */
765
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
766 767 768 769 770
{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
771
	if (se != cfs_rq->curr)
772
		update_stats_wait_start(cfs_rq, se);
773 774 775
}

static void
776
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
777
{
778
	schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
779
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
780 781
	schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
	schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
782
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
783 784 785
#ifdef CONFIG_SCHEDSTATS
	if (entity_is_task(se)) {
		trace_sched_stat_wait(task_of(se),
786
			rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
787 788
	}
#endif
789
	schedstat_set(se->statistics.wait_start, 0);
790 791 792
}

static inline void
793
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
794 795 796 797 798
{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
799
	if (se != cfs_rq->curr)
800
		update_stats_wait_end(cfs_rq, se);
801 802 803 804 805 806
}

/*
 * We are picking a new current task - update its stats:
 */
static inline void
807
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
808 809 810 811
{
	/*
	 * We are starting a new run period:
	 */
812
	se->exec_start = rq_clock_task(rq_of(cfs_rq));
813 814 815 816 817 818
}

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

819 820
#ifdef CONFIG_NUMA_BALANCING
/*
821
 * numa task sample period in ms
822
 */
823
unsigned int sysctl_numa_balancing_scan_period_min = 100;
824 825
unsigned int sysctl_numa_balancing_scan_period_max = 100*50;
unsigned int sysctl_numa_balancing_scan_period_reset = 100*600;
826 827 828

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
829

830 831 832
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

833 834
static void task_numa_placement(struct task_struct *p)
{
835
	int seq;
836

837 838 839
	if (!p->mm)	/* for example, ksmd faulting in a user's mm */
		return;
	seq = ACCESS_ONCE(p->mm->numa_scan_seq);
840 841 842 843 844 845 846 847 848 849
	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.
 */
850
void task_numa_fault(int node, int pages, bool migrated)
851 852 853
{
	struct task_struct *p = current;

854 855 856
	if (!sched_feat_numa(NUMA))
		return;

857 858
	/* FIXME: Allocate task-specific structure for placement policy here */

859
	/*
860 861
	 * If pages are properly placed (did not migrate) then scan slower.
	 * This is reset periodically in case of phase changes
862
	 */
863 864 865
        if (!migrated)
		p->numa_scan_period = min(sysctl_numa_balancing_scan_period_max,
			p->numa_scan_period + jiffies_to_msecs(10));
866

867 868 869
	task_numa_placement(p);
}

870 871 872 873 874 875
static void reset_ptenuma_scan(struct task_struct *p)
{
	ACCESS_ONCE(p->mm->numa_scan_seq)++;
	p->mm->numa_scan_offset = 0;
}

876 877 878 879 880 881 882 883 884
/*
 * 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;
885
	struct vm_area_struct *vma;
886 887
	unsigned long start, end;
	long pages;
888 889 890 891 892 893 894 895 896 897 898 899 900 901 902

	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;

903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920
	/*
	 * 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;
	}

921 922 923 924 925 926 927 928 929 930 931 932 933
	/*
	 * 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);
	}

934 935 936 937 938 939 940 941 942 943
	/*
	 * 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;

944
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
945 946 947
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

948 949 950 951 952 953 954 955
	/*
	 * 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;

956 957 958 959 960
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
	if (!pages)
		return;
961

962
	down_read(&mm->mmap_sem);
963
	vma = find_vma(mm, start);
964 965
	if (!vma) {
		reset_ptenuma_scan(p);
966
		start = 0;
967 968
		vma = mm->mmap;
	}
969
	for (; vma; vma = vma->vm_next) {
970 971 972 973
		if (!vma_migratable(vma))
			continue;

		/* Skip small VMAs. They are not likely to be of relevance */
974
		if (vma->vm_end - vma->vm_start < HPAGE_SIZE)
975 976
			continue;

977 978 979 980 981
		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);
982

983 984 985 986
			start = end;
			if (pages <= 0)
				goto out;
		} while (end != vma->vm_end);
987
	}
988

989
out:
990 991 992 993 994 995 996
	/*
	 * 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)
997
		mm->numa_scan_offset = start;
998 999 1000
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026
}

/*
 * 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) {
1027 1028
		if (!curr->node_stamp)
			curr->numa_scan_period = sysctl_numa_balancing_scan_period_min;
1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042
		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 */

1043 1044 1045 1046
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
1047
	if (!parent_entity(se))
1048
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
1049 1050
#ifdef CONFIG_SMP
	if (entity_is_task(se))
1051
		list_add(&se->group_node, &rq_of(cfs_rq)->cfs_tasks);
1052
#endif
1053 1054 1055 1056 1057 1058 1059
	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);
1060
	if (!parent_entity(se))
1061
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
1062
	if (entity_is_task(se))
1063
		list_del_init(&se->group_node);
1064 1065 1066
	cfs_rq->nr_running--;
}

1067 1068
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
1069 1070 1071 1072 1073 1074 1075 1076 1077
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().
	 */
1078
	tg_weight = atomic_long_read(&tg->load_avg);
1079
	tg_weight -= cfs_rq->tg_load_contrib;
1080 1081 1082 1083 1084
	tg_weight += cfs_rq->load.weight;

	return tg_weight;
}

1085
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1086
{
1087
	long tg_weight, load, shares;
1088

1089
	tg_weight = calc_tg_weight(tg, cfs_rq);
1090
	load = cfs_rq->load.weight;
1091 1092

	shares = (tg->shares * load);
1093 1094
	if (tg_weight)
		shares /= tg_weight;
1095 1096 1097 1098 1099 1100 1101 1102 1103

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

	return shares;
}
# else /* CONFIG_SMP */
1104
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1105 1106 1107 1108
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
1109 1110 1111
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
1112 1113 1114 1115
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
1116
		account_entity_dequeue(cfs_rq, se);
1117
	}
P
Peter Zijlstra 已提交
1118 1119 1120 1121 1122 1123 1124

	update_load_set(&se->load, weight);

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

1125 1126
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

1127
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
1128 1129 1130
{
	struct task_group *tg;
	struct sched_entity *se;
1131
	long shares;
P
Peter Zijlstra 已提交
1132 1133 1134

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
1135
	if (!se || throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
1136
		return;
1137 1138 1139 1140
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
1141
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
1142 1143 1144 1145

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
1146
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
1147 1148 1149 1150
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

1151
#ifdef CONFIG_SMP
1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179
/*
 * 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,
};

1180 1181 1182 1183 1184 1185
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205
	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;
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 1235 1236 1237 1238
	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];
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 1270 1271 1272
}

/*
 * 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)
{
1273 1274
	u64 delta, periods;
	u32 runnable_contrib;
1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307
	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;
1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327
		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;
1328 1329 1330 1331 1332 1333 1334 1335 1336 1337
	}

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

	return decayed;
}

1338
/* Synchronize an entity's decay with its parenting cfs_rq.*/
1339
static inline u64 __synchronize_entity_decay(struct sched_entity *se)
1340 1341 1342 1343 1344 1345
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 decays = atomic64_read(&cfs_rq->decay_counter);

	decays -= se->avg.decay_count;
	if (!decays)
1346
		return 0;
1347 1348 1349

	se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
	se->avg.decay_count = 0;
1350 1351

	return decays;
1352 1353
}

1354 1355 1356 1357 1358
#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;
1359
	long tg_contrib;
1360 1361 1362 1363

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

1364 1365
	if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) {
		atomic_long_add(tg_contrib, &tg->load_avg);
1366 1367 1368
		cfs_rq->tg_load_contrib += tg_contrib;
	}
}
1369

1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390
/*
 * 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;
	}
}

1391 1392 1393 1394
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;
1395 1396
	int runnable_avg;

1397 1398 1399
	u64 contrib;

	contrib = cfs_rq->tg_load_contrib * tg->shares;
1400 1401
	se->avg.load_avg_contrib = div_u64(contrib,
				     atomic_long_read(&tg->load_avg) + 1);
1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430

	/*
	 * 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;
	}
1431
}
1432 1433 1434
#else
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
						 int force_update) {}
1435 1436
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
						  struct cfs_rq *cfs_rq) {}
1437
static inline void __update_group_entity_contrib(struct sched_entity *se) {}
1438 1439
#endif

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

1450 1451 1452 1453 1454
/* 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;

1455 1456 1457
	if (entity_is_task(se)) {
		__update_task_entity_contrib(se);
	} else {
1458
		__update_tg_runnable_avg(&se->avg, group_cfs_rq(se));
1459 1460
		__update_group_entity_contrib(se);
	}
1461 1462 1463 1464

	return se->avg.load_avg_contrib - old_contrib;
}

1465 1466 1467 1468 1469 1470 1471 1472 1473
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;
}

1474 1475
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);

1476
/* Update a sched_entity's runnable average */
1477 1478
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq)
1479
{
1480 1481
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	long contrib_delta;
1482
	u64 now;
1483

1484 1485 1486 1487 1488 1489 1490 1491 1492 1493
	/*
	 * 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))
1494 1495 1496
		return;

	contrib_delta = __update_entity_load_avg_contrib(se);
1497 1498 1499 1500

	if (!update_cfs_rq)
		return;

1501 1502
	if (se->on_rq)
		cfs_rq->runnable_load_avg += contrib_delta;
1503 1504 1505 1506 1507 1508 1509 1510
	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.
 */
1511
static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
1512
{
1513
	u64 now = cfs_rq_clock_task(cfs_rq) >> 20;
1514 1515 1516
	u64 decays;

	decays = now - cfs_rq->last_decay;
1517
	if (!decays && !force_update)
1518 1519
		return;

1520 1521 1522
	if (atomic_long_read(&cfs_rq->removed_load)) {
		unsigned long removed_load;
		removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
1523 1524
		subtract_blocked_load_contrib(cfs_rq, removed_load);
	}
1525

1526 1527 1528 1529 1530 1531
	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;
	}
1532 1533

	__update_cfs_rq_tg_load_contrib(cfs_rq, force_update);
1534
}
1535 1536 1537

static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
{
1538
	__update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable);
1539
	__update_tg_runnable_avg(&rq->avg, &rq->cfs);
1540
}
1541 1542 1543

/* 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,
1544 1545
						  struct sched_entity *se,
						  int wakeup)
1546
{
1547 1548 1549 1550
	/*
	 * 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.
1551 1552 1553 1554
	 *
	 * Newly forked tasks are enqueued with se->avg.decay_count == 0, they
	 * are seen by enqueue_entity_load_avg() as a migration with an already
	 * constructed load_avg_contrib.
1555 1556
	 */
	if (unlikely(se->avg.decay_count <= 0)) {
1557
		se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq));
1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572
		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;
		}
1573 1574
		wakeup = 0;
	} else {
1575 1576 1577 1578 1579 1580 1581
		/*
		 * Task re-woke on same cpu (or else migrate_task_rq_fair()
		 * would have made count negative); we must be careful to avoid
		 * double-accounting blocked time after synchronizing decays.
		 */
		se->avg.last_runnable_update += __synchronize_entity_decay(se)
							<< 20;
1582 1583
	}

1584 1585
	/* migrated tasks did not contribute to our blocked load */
	if (wakeup) {
1586
		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
1587 1588
		update_entity_load_avg(se, 0);
	}
1589

1590
	cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
1591 1592
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !wakeup);
1593 1594
}

1595 1596 1597 1598 1599
/*
 * 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.
 */
1600
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
1601 1602
						  struct sched_entity *se,
						  int sleep)
1603
{
1604
	update_entity_load_avg(se, 1);
1605 1606
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !sleep);
1607

1608
	cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
1609 1610 1611 1612
	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 */
1613
}
1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634

/*
 * Update the rq's load with the elapsed running time before entering
 * idle. if the last scheduled task is not a CFS task, idle_enter will
 * be the only way to update the runnable statistic.
 */
void idle_enter_fair(struct rq *this_rq)
{
	update_rq_runnable_avg(this_rq, 1);
}

/*
 * Update the rq's load with the elapsed idle time before a task is
 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
 * be the only way to update the runnable statistic.
 */
void idle_exit_fair(struct rq *this_rq)
{
	update_rq_runnable_avg(this_rq, 0);
}

1635
#else
1636 1637
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq) {}
1638
static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
1639
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
1640 1641
					   struct sched_entity *se,
					   int wakeup) {}
1642
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
1643 1644
					   struct sched_entity *se,
					   int sleep) {}
1645 1646
static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
					      int force_update) {}
1647 1648
#endif

1649
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
1650 1651
{
#ifdef CONFIG_SCHEDSTATS
1652 1653 1654 1655 1656
	struct task_struct *tsk = NULL;

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

1657
	if (se->statistics.sleep_start) {
1658
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
1659 1660 1661 1662

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

1663 1664
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
1665

1666
		se->statistics.sleep_start = 0;
1667
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
1668

1669
		if (tsk) {
1670
			account_scheduler_latency(tsk, delta >> 10, 1);
1671 1672
			trace_sched_stat_sleep(tsk, delta);
		}
1673
	}
1674
	if (se->statistics.block_start) {
1675
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
1676 1677 1678 1679

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

1680 1681
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
1682

1683
		se->statistics.block_start = 0;
1684
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
1685

1686
		if (tsk) {
1687
			if (tsk->in_iowait) {
1688 1689
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
1690
				trace_sched_stat_iowait(tsk, delta);
1691 1692
			}

1693 1694
			trace_sched_stat_blocked(tsk, delta);

1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705
			/*
			 * 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
1706
		}
1707 1708 1709 1710
	}
#endif
}

P
Peter Zijlstra 已提交
1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723
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
}

1724 1725 1726
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
1727
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
1728

1729 1730 1731 1732 1733 1734
	/*
	 * 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
1735
	if (initial && sched_feat(START_DEBIT))
1736
		vruntime += sched_vslice(cfs_rq, se);
1737

1738
	/* sleeps up to a single latency don't count. */
1739
	if (!initial) {
1740
		unsigned long thresh = sysctl_sched_latency;
1741

1742 1743 1744 1745 1746 1747
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
1748

1749
		vruntime -= thresh;
1750 1751
	}

1752
	/* ensure we never gain time by being placed backwards. */
1753
	se->vruntime = max_vruntime(se->vruntime, vruntime);
1754 1755
}

1756 1757
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

1758
static void
1759
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1760
{
1761 1762 1763 1764
	/*
	 * Update the normalized vruntime before updating min_vruntime
	 * through callig update_curr().
	 */
1765
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
1766 1767
		se->vruntime += cfs_rq->min_vruntime;

1768
	/*
1769
	 * Update run-time statistics of the 'current'.
1770
	 */
1771
	update_curr(cfs_rq);
1772
	enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
1773 1774
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
1775

1776
	if (flags & ENQUEUE_WAKEUP) {
1777
		place_entity(cfs_rq, se, 0);
1778
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
1779
	}
1780

1781
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
1782
	check_spread(cfs_rq, se);
1783 1784
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
1785
	se->on_rq = 1;
1786

1787
	if (cfs_rq->nr_running == 1) {
1788
		list_add_leaf_cfs_rq(cfs_rq);
1789 1790
		check_enqueue_throttle(cfs_rq);
	}
1791 1792
}

1793
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
1794
{
1795 1796 1797 1798 1799 1800 1801 1802
	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
1803

1804 1805 1806 1807 1808 1809 1810 1811 1812
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
1813 1814
}

1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825
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;
	}
}

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Peter Zijlstra 已提交
1826 1827
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
1828 1829 1830 1831 1832
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
1833 1834 1835

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
1836 1837
}

1838
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
1839

1840
static void
1841
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1842
{
1843 1844 1845 1846
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
1847
	dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);
1848

1849
	update_stats_dequeue(cfs_rq, se);
1850
	if (flags & DEQUEUE_SLEEP) {
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Peter Zijlstra 已提交
1851
#ifdef CONFIG_SCHEDSTATS
1852 1853 1854 1855
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
1856
				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
1857
			if (tsk->state & TASK_UNINTERRUPTIBLE)
1858
				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
1859
		}
1860
#endif
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Peter Zijlstra 已提交
1861 1862
	}

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Peter Zijlstra 已提交
1863
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
1864

1865
	if (se != cfs_rq->curr)
1866
		__dequeue_entity(cfs_rq, se);
1867
	se->on_rq = 0;
1868
	account_entity_dequeue(cfs_rq, se);
1869 1870 1871 1872 1873 1874

	/*
	 * 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.
	 */
1875
	if (!(flags & DEQUEUE_SLEEP))
1876
		se->vruntime -= cfs_rq->min_vruntime;
1877

1878 1879 1880
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

1881
	update_min_vruntime(cfs_rq);
1882
	update_cfs_shares(cfs_rq);
1883 1884 1885 1886 1887
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
1888
static void
I
Ingo Molnar 已提交
1889
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
1890
{
1891
	unsigned long ideal_runtime, delta_exec;
1892 1893
	struct sched_entity *se;
	s64 delta;
1894

P
Peter Zijlstra 已提交
1895
	ideal_runtime = sched_slice(cfs_rq, curr);
1896
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
1897
	if (delta_exec > ideal_runtime) {
1898
		resched_task(rq_of(cfs_rq)->curr);
1899 1900 1901 1902 1903
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914
		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;

1915 1916
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
1917

1918 1919
	if (delta < 0)
		return;
1920

1921 1922
	if (delta > ideal_runtime)
		resched_task(rq_of(cfs_rq)->curr);
1923 1924
}

1925
static void
1926
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
1927
{
1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938
	/* '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);
	}

1939
	update_stats_curr_start(cfs_rq, se);
1940
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
1941 1942 1943 1944 1945 1946
#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):
	 */
1947
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
1948
		se->statistics.slice_max = max(se->statistics.slice_max,
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Ingo Molnar 已提交
1949 1950 1951
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
1952
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
1953 1954
}

1955 1956 1957
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

1958 1959 1960 1961 1962 1963 1964
/*
 * 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
 */
1965
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
1966
{
1967
	struct sched_entity *se = __pick_first_entity(cfs_rq);
1968
	struct sched_entity *left = se;
1969

1970 1971 1972 1973 1974 1975 1976 1977 1978
	/*
	 * 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;
	}
1979

1980 1981 1982 1983 1984 1985
	/*
	 * 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;

1986 1987 1988 1989 1990 1991
	/*
	 * 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;

1992
	clear_buddies(cfs_rq, se);
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Peter Zijlstra 已提交
1993 1994

	return se;
1995 1996
}

1997 1998
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq);

1999
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
2000 2001 2002 2003 2004 2005
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
2006
		update_curr(cfs_rq);
2007

2008 2009 2010
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

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Peter Zijlstra 已提交
2011
	check_spread(cfs_rq, prev);
2012
	if (prev->on_rq) {
2013
		update_stats_wait_start(cfs_rq, prev);
2014 2015
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
2016
		/* in !on_rq case, update occurred at dequeue */
2017
		update_entity_load_avg(prev, 1);
2018
	}
2019
	cfs_rq->curr = NULL;
2020 2021
}

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Peter Zijlstra 已提交
2022 2023
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
2024 2025
{
	/*
2026
	 * Update run-time statistics of the 'current'.
2027
	 */
2028
	update_curr(cfs_rq);
2029

2030 2031 2032
	/*
	 * Ensure that runnable average is periodically updated.
	 */
2033
	update_entity_load_avg(curr, 1);
2034
	update_cfs_rq_blocked_load(cfs_rq, 1);
2035

P
Peter Zijlstra 已提交
2036 2037 2038 2039 2040
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
2041 2042 2043 2044
	if (queued) {
		resched_task(rq_of(cfs_rq)->curr);
		return;
	}
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Peter Zijlstra 已提交
2045 2046 2047 2048 2049 2050 2051 2052
	/*
	 * 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
2053
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
2054
		check_preempt_tick(cfs_rq, curr);
2055 2056
}

2057 2058 2059 2060 2061 2062

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

#ifdef CONFIG_CFS_BANDWIDTH
2063 2064

#ifdef HAVE_JUMP_LABEL
2065
static struct static_key __cfs_bandwidth_used;
2066 2067 2068

static inline bool cfs_bandwidth_used(void)
{
2069
	return static_key_false(&__cfs_bandwidth_used);
2070 2071 2072 2073 2074 2075
}

void account_cfs_bandwidth_used(int enabled, int was_enabled)
{
	/* only need to count groups transitioning between enabled/!enabled */
	if (enabled && !was_enabled)
2076
		static_key_slow_inc(&__cfs_bandwidth_used);
2077
	else if (!enabled && was_enabled)
2078
		static_key_slow_dec(&__cfs_bandwidth_used);
2079 2080 2081 2082 2083 2084 2085 2086 2087 2088
}
#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 */

2089 2090 2091 2092 2093 2094 2095 2096
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
2097 2098 2099 2100 2101 2102

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

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2103 2104 2105 2106 2107 2108 2109
/*
 * 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
 */
2110
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
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2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121
{
	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);
}

2122 2123 2124 2125 2126
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

2127 2128 2129 2130 2131 2132
/* 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;

2133
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
2134 2135
}

2136 2137
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2138 2139 2140
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
2141
	u64 amount = 0, min_amount, expires;
2142 2143 2144 2145 2146 2147 2148

	/* 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;
2149
	else {
P
Paul Turner 已提交
2150 2151 2152 2153 2154 2155 2156 2157
		/*
		 * 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);
2158
			__start_cfs_bandwidth(cfs_b);
P
Paul Turner 已提交
2159
		}
2160 2161 2162 2163 2164 2165

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
2166
	}
P
Paul Turner 已提交
2167
	expires = cfs_b->runtime_expires;
2168 2169 2170
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
2171 2172 2173 2174 2175 2176 2177
	/*
	 * 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;
2178 2179

	return cfs_rq->runtime_remaining > 0;
2180 2181
}

P
Paul Turner 已提交
2182 2183 2184 2185 2186
/*
 * 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)
2187
{
P
Paul Turner 已提交
2188 2189 2190
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
2191
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
2192 2193
		return;

P
Paul Turner 已提交
2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218
	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) */
2219
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
2220 2221 2222
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
2223 2224
		return;

2225 2226 2227 2228 2229 2230
	/*
	 * 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);
2231 2232
}

2233 2234
static __always_inline
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec)
2235
{
2236
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
2237 2238 2239 2240 2241
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

2242 2243
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
2244
	return cfs_bandwidth_used() && cfs_rq->throttled;
2245 2246
}

2247 2248 2249
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
2250
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278
}

/*
 * 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) {
2279
		/* adjust cfs_rq_clock_task() */
2280
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
2281
					     cfs_rq->throttled_clock_task;
2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292
	}
#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)];

2293 2294
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
2295
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
2296 2297 2298 2299 2300
	cfs_rq->throttle_count++;

	return 0;
}

2301
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
2302 2303 2304 2305 2306 2307 2308 2309
{
	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))];

2310
	/* freeze hierarchy runnable averages while throttled */
2311 2312 2313
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333

	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;
2334
	cfs_rq->throttled_clock = rq_clock(rq);
2335 2336 2337 2338 2339
	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);
}

2340
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
2341 2342 2343 2344 2345 2346 2347
{
	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;

2348
	se = cfs_rq->tg->se[cpu_of(rq)];
2349 2350

	cfs_rq->throttled = 0;
2351 2352 2353

	update_rq_clock(rq);

2354
	raw_spin_lock(&cfs_b->lock);
2355
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
2356 2357 2358
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

2359 2360 2361
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424
	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;
}

2425 2426 2427 2428 2429 2430 2431 2432
/*
 * 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)
{
2433 2434
	u64 runtime, runtime_expires;
	int idle = 1, throttled;
2435 2436 2437 2438 2439 2440

	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;

2441 2442 2443
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
	/* idle depends on !throttled (for the case of a large deficit) */
	idle = cfs_b->idle && !throttled;
2444
	cfs_b->nr_periods += overrun;
2445

P
Paul Turner 已提交
2446 2447 2448 2449 2450 2451
	/* if we're going inactive then everything else can be deferred */
	if (idle)
		goto out_unlock;

	__refill_cfs_bandwidth_runtime(cfs_b);

2452 2453 2454 2455 2456 2457
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
		goto out_unlock;
	}

2458 2459 2460
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484
	/*
	 * 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);
	}
2485

2486 2487 2488 2489 2490 2491 2492 2493 2494
	/* 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;
2495 2496 2497 2498 2499 2500 2501
out_unlock:
	if (idle)
		cfs_b->timer_active = 0;
	raw_spin_unlock(&cfs_b->lock);

	return idle;
}
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 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566
/* 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)
{
2567 2568 2569
	if (!cfs_bandwidth_used())
		return;

2570
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
2571 2572 2573 2574 2575 2576 2577 2578 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
		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);
}

2608 2609 2610 2611 2612 2613 2614
/*
 * 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)
{
2615 2616 2617
	if (!cfs_bandwidth_used())
		return;

2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634
	/* 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)
{
2635 2636 2637
	if (!cfs_bandwidth_used())
		return;

2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649
	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);
}
2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730

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);
}

2731
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751
{
	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 */
2752 2753
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
2754
	return rq_clock_task(rq_of(cfs_rq));
2755 2756 2757 2758
}

static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
				     unsigned long delta_exec) {}
2759 2760
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
2761
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2762 2763 2764 2765 2766

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777

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;
}
2778 2779 2780 2781 2782

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) {}
2783 2784
#endif

2785 2786 2787 2788 2789
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) {}
2790
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
2791 2792 2793

#endif /* CONFIG_CFS_BANDWIDTH */

2794 2795 2796 2797
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
2798 2799 2800 2801 2802 2803 2804 2805
#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);

2806
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820
		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.
		 */
2821
		if (rq->curr != p)
2822
			delta = max_t(s64, 10000LL, delta);
P
Peter Zijlstra 已提交
2823

2824
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
2825 2826
	}
}
2827 2828 2829 2830 2831 2832 2833 2834 2835 2836

/*
 * 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;

2837
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
2838 2839 2840 2841 2842
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
2843
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
2844 2845 2846 2847
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
2848 2849 2850 2851

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
2852 2853
#endif

2854 2855 2856 2857 2858
/*
 * 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:
 */
2859
static void
2860
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
2861 2862
{
	struct cfs_rq *cfs_rq;
2863
	struct sched_entity *se = &p->se;
2864 2865

	for_each_sched_entity(se) {
2866
		if (se->on_rq)
2867 2868
			break;
		cfs_rq = cfs_rq_of(se);
2869
		enqueue_entity(cfs_rq, se, flags);
2870 2871 2872 2873 2874 2875 2876 2877 2878

		/*
		 * 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;
2879
		cfs_rq->h_nr_running++;
2880

2881
		flags = ENQUEUE_WAKEUP;
2882
	}
P
Peter Zijlstra 已提交
2883

P
Peter Zijlstra 已提交
2884
	for_each_sched_entity(se) {
2885
		cfs_rq = cfs_rq_of(se);
2886
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
2887

2888 2889 2890
		if (cfs_rq_throttled(cfs_rq))
			break;

2891
		update_cfs_shares(cfs_rq);
2892
		update_entity_load_avg(se, 1);
P
Peter Zijlstra 已提交
2893 2894
	}

2895 2896
	if (!se) {
		update_rq_runnable_avg(rq, rq->nr_running);
2897
		inc_nr_running(rq);
2898
	}
2899
	hrtick_update(rq);
2900 2901
}

2902 2903
static void set_next_buddy(struct sched_entity *se);

2904 2905 2906 2907 2908
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
2909
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
2910 2911
{
	struct cfs_rq *cfs_rq;
2912
	struct sched_entity *se = &p->se;
2913
	int task_sleep = flags & DEQUEUE_SLEEP;
2914 2915 2916

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
2917
		dequeue_entity(cfs_rq, se, flags);
2918 2919 2920 2921 2922 2923 2924 2925 2926

		/*
		 * 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;
2927
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
2928

2929
		/* Don't dequeue parent if it has other entities besides us */
2930 2931 2932 2933 2934 2935 2936
		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));
2937 2938 2939

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
2940
			break;
2941
		}
2942
		flags |= DEQUEUE_SLEEP;
2943
	}
P
Peter Zijlstra 已提交
2944

P
Peter Zijlstra 已提交
2945
	for_each_sched_entity(se) {
2946
		cfs_rq = cfs_rq_of(se);
2947
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
2948

2949 2950 2951
		if (cfs_rq_throttled(cfs_rq))
			break;

2952
		update_cfs_shares(cfs_rq);
2953
		update_entity_load_avg(se, 1);
P
Peter Zijlstra 已提交
2954 2955
	}

2956
	if (!se) {
2957
		dec_nr_running(rq);
2958 2959
		update_rq_runnable_avg(rq, 1);
	}
2960
	hrtick_update(rq);
2961 2962
}

2963
#ifdef CONFIG_SMP
2964 2965 2966
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
2967
	return cpu_rq(cpu)->cfs.runnable_load_avg;
2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011
}

/*
 * 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);
3012
	unsigned long load_avg = rq->cfs.runnable_load_avg;
3013 3014

	if (nr_running)
3015
		return load_avg / nr_running;
3016 3017 3018 3019

	return 0;
}

3020

3021
static void task_waking_fair(struct task_struct *p)
3022 3023 3024
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
3025 3026 3027 3028
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
3029

3030 3031 3032 3033 3034 3035 3036 3037
	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
3038

3039
	se->vruntime -= min_vruntime;
3040 3041
}

3042
#ifdef CONFIG_FAIR_GROUP_SCHED
3043 3044 3045 3046 3047 3048
/*
 * 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.
3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091
 *
 * 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.
3092
 */
P
Peter Zijlstra 已提交
3093
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
3094
{
P
Peter Zijlstra 已提交
3095
	struct sched_entity *se = tg->se[cpu];
3096

3097
	if (!tg->parent)	/* the trivial, non-cgroup case */
3098 3099
		return wl;

P
Peter Zijlstra 已提交
3100
	for_each_sched_entity(se) {
3101
		long w, W;
P
Peter Zijlstra 已提交
3102

3103
		tg = se->my_q->tg;
3104

3105 3106 3107 3108
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
3109

3110 3111 3112 3113
		/*
		 * w = rw_i + @wl
		 */
		w = se->my_q->load.weight + wl;
3114

3115 3116 3117 3118 3119
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
			wl = (w * tg->shares) / W;
3120 3121
		else
			wl = tg->shares;
3122

3123 3124 3125 3126 3127
		/*
		 * 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().
		 */
3128 3129
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
3130 3131 3132 3133

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
3134
		wl -= se->load.weight;
3135 3136 3137 3138 3139 3140 3141 3142

		/*
		 * 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
3143 3144
		wg = 0;
	}
3145

P
Peter Zijlstra 已提交
3146
	return wl;
3147 3148
}
#else
P
Peter Zijlstra 已提交
3149

3150 3151
static inline unsigned long effective_load(struct task_group *tg, int cpu,
		unsigned long wl, unsigned long wg)
P
Peter Zijlstra 已提交
3152
{
3153
	return wl;
3154
}
P
Peter Zijlstra 已提交
3155

3156 3157
#endif

3158
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
3159
{
3160
	s64 this_load, load;
3161
	int idx, this_cpu, prev_cpu;
3162
	unsigned long tl_per_task;
3163
	struct task_group *tg;
3164
	unsigned long weight;
3165
	int balanced;
3166

3167 3168 3169 3170 3171
	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);
3172

3173 3174 3175 3176 3177
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
3178 3179 3180 3181
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

3182
		this_load += effective_load(tg, this_cpu, -weight, -weight);
3183 3184
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
3185

3186 3187
	tg = task_group(p);
	weight = p->se.load.weight;
3188

3189 3190
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
3191 3192 3193
	 * 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.
3194 3195 3196 3197
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
3198 3199
	if (this_load > 0) {
		s64 this_eff_load, prev_eff_load;
3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212

		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;
3213

3214
	/*
I
Ingo Molnar 已提交
3215 3216 3217
	 * If the currently running task will sleep within
	 * a reasonable amount of time then attract this newly
	 * woken task:
3218
	 */
3219 3220
	if (sync && balanced)
		return 1;
3221

3222
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
3223 3224
	tl_per_task = cpu_avg_load_per_task(this_cpu);

3225 3226 3227
	if (balanced ||
	    (this_load <= load &&
	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
3228 3229 3230 3231 3232
		/*
		 * This domain has SD_WAKE_AFFINE and
		 * p is cache cold in this domain, and
		 * there is no bad imbalance.
		 */
3233
		schedstat_inc(sd, ttwu_move_affine);
3234
		schedstat_inc(p, se.statistics.nr_wakeups_affine);
3235 3236 3237 3238 3239 3240

		return 1;
	}
	return 0;
}

3241 3242 3243 3244 3245
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
3246
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
3247
		  int this_cpu, int load_idx)
3248
{
3249
	struct sched_group *idlest = NULL, *group = sd->groups;
3250 3251
	unsigned long min_load = ULONG_MAX, this_load = 0;
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
3252

3253 3254 3255 3256
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
3257

3258 3259
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
3260
					tsk_cpus_allowed(p)))
3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279
			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 */
3280
		avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;
3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305

		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 */
3306
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
3307 3308 3309 3310 3311
		load = weighted_cpuload(i);

		if (load < min_load || (load == min_load && i == this_cpu)) {
			min_load = load;
			idlest = i;
3312 3313 3314
		}
	}

3315 3316
	return idlest;
}
3317

3318 3319 3320
/*
 * Try and locate an idle CPU in the sched_domain.
 */
3321
static int select_idle_sibling(struct task_struct *p, int target)
3322
{
3323
	struct sched_domain *sd;
3324
	struct sched_group *sg;
3325
	int i = task_cpu(p);
3326

3327 3328
	if (idle_cpu(target))
		return target;
3329 3330

	/*
3331
	 * If the prevous cpu is cache affine and idle, don't be stupid.
3332
	 */
3333 3334
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
3335 3336

	/*
3337
	 * Otherwise, iterate the domains and find an elegible idle cpu.
3338
	 */
3339
	sd = rcu_dereference(per_cpu(sd_llc, target));
3340
	for_each_lower_domain(sd) {
3341 3342 3343 3344 3345 3346 3347
		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)) {
3348
				if (i == target || !idle_cpu(i))
3349 3350
					goto next;
			}
3351

3352 3353 3354 3355 3356 3357 3358 3359
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
3360 3361 3362
	return target;
}

3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373
/*
 * 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.
 */
3374
static int
3375
select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
3376
{
3377
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
3378 3379 3380
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
	int new_cpu = cpu;
3381
	int want_affine = 0;
3382
	int sync = wake_flags & WF_SYNC;
3383

3384
	if (p->nr_cpus_allowed == 1)
3385 3386
		return prev_cpu;

3387
	if (sd_flag & SD_BALANCE_WAKE) {
3388
		if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
3389 3390 3391
			want_affine = 1;
		new_cpu = prev_cpu;
	}
3392

3393
	rcu_read_lock();
3394
	for_each_domain(cpu, tmp) {
3395 3396 3397
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

3398
		/*
3399 3400
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
3401
		 */
3402 3403 3404
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
3405
			break;
3406
		}
3407

3408
		if (tmp->flags & sd_flag)
3409 3410 3411
			sd = tmp;
	}

3412
	if (affine_sd) {
3413
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
3414 3415 3416 3417
			prev_cpu = cpu;

		new_cpu = select_idle_sibling(p, prev_cpu);
		goto unlock;
3418
	}
3419

3420
	while (sd) {
3421
		int load_idx = sd->forkexec_idx;
3422
		struct sched_group *group;
3423
		int weight;
3424

3425
		if (!(sd->flags & sd_flag)) {
3426 3427 3428
			sd = sd->child;
			continue;
		}
3429

3430 3431
		if (sd_flag & SD_BALANCE_WAKE)
			load_idx = sd->wake_idx;
3432

3433
		group = find_idlest_group(sd, p, cpu, load_idx);
3434 3435 3436 3437
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
3438

3439
		new_cpu = find_idlest_cpu(group, p, cpu);
3440 3441 3442 3443
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
3444
		}
3445 3446 3447

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
3448
		weight = sd->span_weight;
3449 3450
		sd = NULL;
		for_each_domain(cpu, tmp) {
3451
			if (weight <= tmp->span_weight)
3452
				break;
3453
			if (tmp->flags & sd_flag)
3454 3455 3456
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
3457
	}
3458 3459
unlock:
	rcu_read_unlock();
3460

3461
	return new_cpu;
3462
}
3463 3464 3465 3466 3467 3468 3469 3470 3471 3472

/*
 * 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)
{
3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483
	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);
3484 3485
		atomic_long_add(se->avg.load_avg_contrib,
						&cfs_rq->removed_load);
3486
	}
3487
}
3488 3489
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
3490 3491
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
3492 3493 3494 3495
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
3496 3497
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
3498 3499 3500 3501 3502 3503 3504 3505 3506
	 *
	 * 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.
3507
	 */
3508
	return calc_delta_fair(gran, se);
3509 3510
}

3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532
/*
 * 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
3533
	gran = wakeup_gran(curr, se);
3534 3535 3536 3537 3538 3539
	if (vdiff > gran)
		return 1;

	return 0;
}

3540 3541
static void set_last_buddy(struct sched_entity *se)
{
3542 3543 3544 3545 3546
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
3547 3548 3549 3550
}

static void set_next_buddy(struct sched_entity *se)
{
3551 3552 3553 3554 3555
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
3556 3557
}

3558 3559
static void set_skip_buddy(struct sched_entity *se)
{
3560 3561
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
3562 3563
}

3564 3565 3566
/*
 * Preempt the current task with a newly woken task if needed:
 */
3567
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
3568 3569
{
	struct task_struct *curr = rq->curr;
3570
	struct sched_entity *se = &curr->se, *pse = &p->se;
3571
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
3572
	int scale = cfs_rq->nr_running >= sched_nr_latency;
3573
	int next_buddy_marked = 0;
3574

I
Ingo Molnar 已提交
3575 3576 3577
	if (unlikely(se == pse))
		return;

3578
	/*
3579
	 * This is possible from callers such as move_task(), in which we
3580 3581 3582 3583 3584 3585 3586
	 * 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;

3587
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
3588
		set_next_buddy(pse);
3589 3590
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
3591

3592 3593 3594
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
3595 3596 3597 3598 3599 3600
	 *
	 * 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.
3601 3602 3603 3604
	 */
	if (test_tsk_need_resched(curr))
		return;

3605 3606 3607 3608 3609
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

3610
	/*
3611 3612
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
3613
	 */
3614
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
3615
		return;
3616

3617
	find_matching_se(&se, &pse);
3618
	update_curr(cfs_rq_of(se));
3619
	BUG_ON(!pse);
3620 3621 3622 3623 3624 3625 3626
	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);
3627
		goto preempt;
3628
	}
3629

3630
	return;
3631

3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647
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);
3648 3649
}

3650
static struct task_struct *pick_next_task_fair(struct rq *rq)
3651
{
P
Peter Zijlstra 已提交
3652
	struct task_struct *p;
3653 3654 3655
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

3656
	if (!cfs_rq->nr_running)
3657 3658 3659
		return NULL;

	do {
3660
		se = pick_next_entity(cfs_rq);
3661
		set_next_entity(cfs_rq, se);
3662 3663 3664
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
3665
	p = task_of(se);
3666 3667
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
3668 3669

	return p;
3670 3671 3672 3673 3674
}

/*
 * Account for a descheduled task:
 */
3675
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
3676 3677 3678 3679 3680 3681
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
3682
		put_prev_entity(cfs_rq, se);
3683 3684 3685
	}
}

3686 3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710
/*
 * 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);
3711 3712 3713 3714 3715 3716
		/*
		 * 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;
3717 3718 3719 3720 3721
	}

	set_skip_buddy(se);
}

3722 3723 3724 3725
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

3726 3727
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
3728 3729 3730 3731 3732 3733 3734 3735 3736 3737
		return false;

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

	yield_task_fair(rq);

	return true;
}

3738
#ifdef CONFIG_SMP
3739
/**************************************************
P
Peter Zijlstra 已提交
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 3801 3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831 3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855
 * 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.]
 */ 
3856

3857 3858
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

3859
#define LBF_ALL_PINNED	0x01
3860
#define LBF_NEED_BREAK	0x02
3861
#define LBF_SOME_PINNED 0x04
3862 3863 3864 3865 3866

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
3867
	int			src_cpu;
3868 3869 3870 3871

	int			dst_cpu;
	struct rq		*dst_rq;

3872 3873
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
3874
	enum cpu_idle_type	idle;
3875
	long			imbalance;
3876 3877 3878
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

3879
	unsigned int		flags;
3880 3881 3882 3883

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
3884 3885
};

3886
/*
3887
 * move_task - move a task from one runqueue to another runqueue.
3888 3889
 * Both runqueues must be locked.
 */
3890
static void move_task(struct task_struct *p, struct lb_env *env)
3891
{
3892 3893 3894 3895
	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);
3896 3897
}

3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929
/*
 * 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;
}

3930 3931 3932 3933
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
3934
int can_migrate_task(struct task_struct *p, struct lb_env *env)
3935 3936 3937 3938
{
	int tsk_cache_hot = 0;
	/*
	 * We do not migrate tasks that are:
3939
	 * 1) throttled_lb_pair, or
3940
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
3941 3942
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
3943
	 */
3944 3945 3946
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

3947
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
3948
		int cpu;
3949

3950
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962

		/*
		 * 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;

3963 3964 3965 3966 3967 3968 3969
		/* Prevent to re-select dst_cpu via env's cpus */
		for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) {
			if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) {
				env->flags |= LBF_SOME_PINNED;
				env->new_dst_cpu = cpu;
				break;
			}
3970
		}
3971

3972 3973
		return 0;
	}
3974 3975

	/* Record that we found atleast one task that could run on dst_cpu */
3976
	env->flags &= ~LBF_ALL_PINNED;
3977

3978
	if (task_running(env->src_rq, p)) {
3979
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
3980 3981 3982 3983 3984 3985 3986 3987 3988
		return 0;
	}

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

3989
	tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd);
3990
	if (!tsk_cache_hot ||
3991
		env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
Z
Zhang Hang 已提交
3992

3993
		if (tsk_cache_hot) {
3994
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
3995
			schedstat_inc(p, se.statistics.nr_forced_migrations);
3996
		}
Z
Zhang Hang 已提交
3997

3998 3999 4000
		return 1;
	}

Z
Zhang Hang 已提交
4001 4002
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
4003 4004
}

4005 4006 4007 4008 4009 4010 4011
/*
 * 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.
 */
4012
static int move_one_task(struct lb_env *env)
4013 4014 4015
{
	struct task_struct *p, *n;

4016 4017 4018
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
4019

4020 4021 4022 4023 4024 4025 4026 4027
		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;
4028 4029 4030 4031
	}
	return 0;
}

4032 4033
static unsigned long task_h_load(struct task_struct *p);

4034 4035
static const unsigned int sched_nr_migrate_break = 32;

4036
/*
4037
 * move_tasks tries to move up to imbalance weighted load from busiest to
4038 4039 4040 4041 4042 4043
 * 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)
4044
{
4045 4046
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
4047 4048
	unsigned long load;
	int pulled = 0;
4049

4050
	if (env->imbalance <= 0)
4051
		return 0;
4052

4053 4054
	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
4055

4056 4057
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
4058
		if (env->loop > env->loop_max)
4059
			break;
4060 4061

		/* take a breather every nr_migrate tasks */
4062
		if (env->loop > env->loop_break) {
4063
			env->loop_break += sched_nr_migrate_break;
4064
			env->flags |= LBF_NEED_BREAK;
4065
			break;
4066
		}
4067

4068
		if (!can_migrate_task(p, env))
4069 4070 4071
			goto next;

		load = task_h_load(p);
4072

4073
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
4074 4075
			goto next;

4076
		if ((load / 2) > env->imbalance)
4077
			goto next;
4078

4079
		move_task(p, env);
4080
		pulled++;
4081
		env->imbalance -= load;
4082 4083

#ifdef CONFIG_PREEMPT
4084 4085 4086 4087 4088
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
		 * kernels will stop after the first task is pulled to minimize
		 * the critical section.
		 */
4089
		if (env->idle == CPU_NEWLY_IDLE)
4090
			break;
4091 4092
#endif

4093 4094 4095 4096
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
4097
		if (env->imbalance <= 0)
4098
			break;
4099 4100 4101

		continue;
next:
4102
		list_move_tail(&p->se.group_node, tasks);
4103
	}
4104

4105
	/*
4106 4107 4108
	 * 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().
4109
	 */
4110
	schedstat_add(env->sd, lb_gained[env->idle], pulled);
4111

4112
	return pulled;
4113 4114
}

P
Peter Zijlstra 已提交
4115
#ifdef CONFIG_FAIR_GROUP_SCHED
4116 4117 4118
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
4119
static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
4120
{
4121 4122
	struct sched_entity *se = tg->se[cpu];
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
4123

4124 4125 4126
	/* throttled entities do not contribute to load */
	if (throttled_hierarchy(cfs_rq))
		return;
4127

4128
	update_cfs_rq_blocked_load(cfs_rq, 1);
4129

4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143
	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 {
4144
		struct rq *rq = rq_of(cfs_rq);
4145 4146
		update_rq_runnable_avg(rq, rq->nr_running);
	}
4147 4148
}

4149
static void update_blocked_averages(int cpu)
4150 4151
{
	struct rq *rq = cpu_rq(cpu);
4152 4153
	struct cfs_rq *cfs_rq;
	unsigned long flags;
4154

4155 4156
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
4157 4158 4159 4160
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
4161
	for_each_leaf_cfs_rq(rq, cfs_rq) {
4162 4163 4164 4165 4166 4167
		/*
		 * 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);
4168
	}
4169 4170

	raw_spin_unlock_irqrestore(&rq->lock, flags);
4171 4172
}

4173 4174 4175 4176 4177 4178 4179 4180 4181 4182 4183
/*
 * 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) {
4184
		load = cpu_rq(cpu)->avg.load_avg_contrib;
4185 4186
	} else {
		load = tg->parent->cfs_rq[cpu]->h_load;
4187 4188
		load = div64_ul(load * tg->se[cpu]->avg.load_avg_contrib,
				tg->parent->cfs_rq[cpu]->runnable_load_avg + 1);
4189 4190 4191 4192 4193 4194 4195 4196 4197
	}

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

	return 0;
}

static void update_h_load(long cpu)
{
4198 4199 4200 4201 4202 4203 4204 4205
	struct rq *rq = cpu_rq(cpu);
	unsigned long now = jiffies;

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

	rq->h_load_throttle = now;

4206
	rcu_read_lock();
4207
	walk_tg_tree(tg_load_down, tg_nop, (void *)cpu);
4208
	rcu_read_unlock();
4209 4210
}

4211
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
4212
{
4213
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
4214

4215 4216
	return div64_ul(p->se.avg.load_avg_contrib * cfs_rq->h_load,
			cfs_rq->runnable_load_avg + 1);
P
Peter Zijlstra 已提交
4217 4218
}
#else
4219
static inline void update_blocked_averages(int cpu)
4220 4221 4222
{
}

4223
static inline void update_h_load(long cpu)
P
Peter Zijlstra 已提交
4224 4225 4226
{
}

4227
static unsigned long task_h_load(struct task_struct *p)
4228
{
4229
	return p->se.avg.load_avg_contrib;
4230
}
P
Peter Zijlstra 已提交
4231
#endif
4232 4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248

/********** 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;
4249
	unsigned long this_has_capacity;
4250
	unsigned int  this_idle_cpus;
4251 4252

	/* Statistics of the busiest group */
4253
	unsigned int  busiest_idle_cpus;
4254 4255 4256
	unsigned long max_load;
	unsigned long busiest_load_per_task;
	unsigned long busiest_nr_running;
4257
	unsigned long busiest_group_capacity;
4258
	unsigned long busiest_has_capacity;
4259
	unsigned int  busiest_group_weight;
4260 4261 4262 4263 4264 4265 4266 4267 4268 4269 4270 4271 4272

	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;
4273 4274
	unsigned long idle_cpus;
	unsigned long group_weight;
4275
	int group_imb; /* Is there an imbalance in the group ? */
4276
	int group_has_capacity; /* Is there extra capacity in the group? */
4277 4278 4279 4280 4281 4282 4283 4284 4285 4286 4287 4288 4289 4290 4291 4292 4293 4294 4295 4296 4297 4298 4299 4300 4301 4302 4303 4304
};

/**
 * 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;
}

4305
static unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
4306
{
4307
	return SCHED_POWER_SCALE;
4308 4309 4310 4311 4312 4313 4314
}

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

4315
static unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
4316
{
4317
	unsigned long weight = sd->span_weight;
4318 4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329
	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);
}

4330
static unsigned long scale_rt_power(int cpu)
4331 4332
{
	struct rq *rq = cpu_rq(cpu);
4333
	u64 total, available, age_stamp, avg;
4334

4335 4336 4337 4338 4339 4340 4341
	/*
	 * 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);

4342
	total = sched_avg_period() + (rq_clock(rq) - age_stamp);
4343

4344
	if (unlikely(total < avg)) {
4345 4346 4347
		/* Ensures that power won't end up being negative */
		available = 0;
	} else {
4348
		available = total - avg;
4349
	}
4350

4351 4352
	if (unlikely((s64)total < SCHED_POWER_SCALE))
		total = SCHED_POWER_SCALE;
4353

4354
	total >>= SCHED_POWER_SHIFT;
4355 4356 4357 4358 4359 4360

	return div_u64(available, total);
}

static void update_cpu_power(struct sched_domain *sd, int cpu)
{
4361
	unsigned long weight = sd->span_weight;
4362
	unsigned long power = SCHED_POWER_SCALE;
4363 4364 4365 4366 4367 4368 4369 4370
	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);

4371
		power >>= SCHED_POWER_SHIFT;
4372 4373
	}

4374
	sdg->sgp->power_orig = power;
4375 4376 4377 4378 4379 4380

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

4381
	power >>= SCHED_POWER_SHIFT;
4382

4383
	power *= scale_rt_power(cpu);
4384
	power >>= SCHED_POWER_SHIFT;
4385 4386 4387 4388

	if (!power)
		power = 1;

4389
	cpu_rq(cpu)->cpu_power = power;
4390
	sdg->sgp->power = power;
4391 4392
}

4393
void update_group_power(struct sched_domain *sd, int cpu)
4394 4395 4396 4397
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
	unsigned long power;
4398 4399 4400 4401 4402
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
	sdg->sgp->next_update = jiffies + interval;
4403 4404 4405 4406 4407 4408 4409 4410

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

	power = 0;

P
Peter Zijlstra 已提交
4411 4412 4413 4414 4415 4416 4417 4418 4419 4420 4421 4422 4423 4424 4425 4426 4427 4428 4429 4430
	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);
	}
4431

4432
	sdg->sgp->power_orig = sdg->sgp->power = power;
4433 4434
}

4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445
/*
 * 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)
{
	/*
4446
	 * Only siblings can have significantly less than SCHED_POWER_SCALE
4447
	 */
P
Peter Zijlstra 已提交
4448
	if (!(sd->flags & SD_SHARE_CPUPOWER))
4449 4450 4451 4452 4453
		return 0;

	/*
	 * If ~90% of the cpu_power is still there, we're good.
	 */
4454
	if (group->sgp->power * 32 > group->sgp->power_orig * 29)
4455 4456 4457 4458 4459
		return 1;

	return 0;
}

4460 4461
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
4462
 * @env: The load balancing environment.
4463 4464 4465 4466 4467 4468
 * @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.
 */
4469 4470
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
4471
			int local_group, int *balance, struct sg_lb_stats *sgs)
4472
{
4473 4474
	unsigned long nr_running, max_nr_running, min_nr_running;
	unsigned long load, max_cpu_load, min_cpu_load;
4475
	unsigned int balance_cpu = -1, first_idle_cpu = 0;
4476
	unsigned long avg_load_per_task = 0;
4477
	int i;
4478

4479
	if (local_group)
P
Peter Zijlstra 已提交
4480
		balance_cpu = group_balance_cpu(group);
4481 4482 4483 4484

	/* Tally up the load of all CPUs in the group */
	max_cpu_load = 0;
	min_cpu_load = ~0UL;
4485
	max_nr_running = 0;
4486
	min_nr_running = ~0UL;
4487

4488
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
4489 4490
		struct rq *rq = cpu_rq(i);

4491 4492
		nr_running = rq->nr_running;

4493 4494
		/* Bias balancing toward cpus of our domain */
		if (local_group) {
P
Peter Zijlstra 已提交
4495 4496
			if (idle_cpu(i) && !first_idle_cpu &&
					cpumask_test_cpu(i, sched_group_mask(group))) {
4497
				first_idle_cpu = 1;
4498 4499
				balance_cpu = i;
			}
4500 4501

			load = target_load(i, load_idx);
4502 4503
		} else {
			load = source_load(i, load_idx);
4504
			if (load > max_cpu_load)
4505 4506 4507
				max_cpu_load = load;
			if (min_cpu_load > load)
				min_cpu_load = load;
4508 4509 4510 4511 4512

			if (nr_running > max_nr_running)
				max_nr_running = nr_running;
			if (min_nr_running > nr_running)
				min_nr_running = nr_running;
4513 4514 4515
		}

		sgs->group_load += load;
4516
		sgs->sum_nr_running += nr_running;
4517
		sgs->sum_weighted_load += weighted_cpuload(i);
4518 4519
		if (idle_cpu(i))
			sgs->idle_cpus++;
4520 4521 4522 4523 4524 4525 4526 4527
	}

	/*
	 * 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.
	 */
4528
	if (local_group) {
4529
		if (env->idle != CPU_NEWLY_IDLE) {
4530
			if (balance_cpu != env->dst_cpu) {
4531 4532 4533
				*balance = 0;
				return;
			}
4534
			update_group_power(env->sd, env->dst_cpu);
4535
		} else if (time_after_eq(jiffies, group->sgp->next_update))
4536
			update_group_power(env->sd, env->dst_cpu);
4537 4538 4539
	}

	/* Adjust by relative CPU power of the group */
4540
	sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / group->sgp->power;
4541 4542 4543

	/*
	 * Consider the group unbalanced when the imbalance is larger
P
Peter Zijlstra 已提交
4544
	 * than the average weight of a task.
4545 4546 4547 4548 4549 4550
	 *
	 * 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?
	 */
4551 4552
	if (sgs->sum_nr_running)
		avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
4553

4554 4555
	if ((max_cpu_load - min_cpu_load) >= avg_load_per_task &&
	    (max_nr_running - min_nr_running) > 1)
4556 4557
		sgs->group_imb = 1;

4558
	sgs->group_capacity = DIV_ROUND_CLOSEST(group->sgp->power,
4559
						SCHED_POWER_SCALE);
4560
	if (!sgs->group_capacity)
4561
		sgs->group_capacity = fix_small_capacity(env->sd, group);
4562
	sgs->group_weight = group->group_weight;
4563 4564 4565

	if (sgs->group_capacity > sgs->sum_nr_running)
		sgs->group_has_capacity = 1;
4566 4567
}

4568 4569
/**
 * update_sd_pick_busiest - return 1 on busiest group
4570
 * @env: The load balancing environment.
4571 4572
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
4573
 * @sgs: sched_group statistics
4574 4575 4576 4577
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
 */
4578
static bool update_sd_pick_busiest(struct lb_env *env,
4579 4580
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
4581
				   struct sg_lb_stats *sgs)
4582 4583 4584 4585 4586 4587 4588 4589 4590 4591 4592 4593 4594 4595 4596
{
	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.
	 */
4597 4598
	if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
	    env->dst_cpu < group_first_cpu(sg)) {
4599 4600 4601 4602 4603 4604 4605 4606 4607 4608
		if (!sds->busiest)
			return true;

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

	return false;
}

4609
/**
4610
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
4611
 * @env: The load balancing environment.
4612 4613 4614
 * @balance: Should we balance.
 * @sds: variable to hold the statistics for this sched_domain.
 */
4615
static inline void update_sd_lb_stats(struct lb_env *env,
4616
					int *balance, struct sd_lb_stats *sds)
4617
{
4618 4619
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
4620 4621 4622 4623 4624 4625
	struct sg_lb_stats sgs;
	int load_idx, prefer_sibling = 0;

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

4626
	load_idx = get_sd_load_idx(env->sd, env->idle);
4627 4628 4629 4630

	do {
		int local_group;

4631
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
4632
		memset(&sgs, 0, sizeof(sgs));
4633
		update_sg_lb_stats(env, sg, load_idx, local_group, balance, &sgs);
4634

P
Peter Zijlstra 已提交
4635
		if (local_group && !(*balance))
4636 4637 4638
			return;

		sds->total_load += sgs.group_load;
4639
		sds->total_pwr += sg->sgp->power;
4640 4641 4642

		/*
		 * In case the child domain prefers tasks go to siblings
4643
		 * first, lower the sg capacity to one so that we'll try
4644 4645 4646 4647 4648 4649
		 * 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).
4650
		 */
4651
		if (prefer_sibling && !local_group && sds->this_has_capacity)
4652 4653 4654 4655
			sgs.group_capacity = min(sgs.group_capacity, 1UL);

		if (local_group) {
			sds->this_load = sgs.avg_load;
4656
			sds->this = sg;
4657 4658
			sds->this_nr_running = sgs.sum_nr_running;
			sds->this_load_per_task = sgs.sum_weighted_load;
4659
			sds->this_has_capacity = sgs.group_has_capacity;
4660
			sds->this_idle_cpus = sgs.idle_cpus;
4661
		} else if (update_sd_pick_busiest(env, sds, sg, &sgs)) {
4662
			sds->max_load = sgs.avg_load;
4663
			sds->busiest = sg;
4664
			sds->busiest_nr_running = sgs.sum_nr_running;
4665
			sds->busiest_idle_cpus = sgs.idle_cpus;
4666
			sds->busiest_group_capacity = sgs.group_capacity;
4667
			sds->busiest_load_per_task = sgs.sum_weighted_load;
4668
			sds->busiest_has_capacity = sgs.group_has_capacity;
4669
			sds->busiest_group_weight = sgs.group_weight;
4670 4671 4672
			sds->group_imb = sgs.group_imb;
		}

4673
		sg = sg->next;
4674
	} while (sg != env->sd->groups);
4675 4676 4677 4678 4679 4680 4681 4682 4683 4684 4685 4686 4687 4688 4689 4690 4691 4692 4693
}

/**
 * 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.
 *
4694 4695 4696
 * Returns 1 when packing is required and a task should be moved to
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
4697
 * @env: The load balancing environment.
4698 4699
 * @sds: Statistics of the sched_domain which is to be packed
 */
4700
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
4701 4702 4703
{
	int busiest_cpu;

4704
	if (!(env->sd->flags & SD_ASYM_PACKING))
4705 4706 4707 4708 4709 4710
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
4711
	if (env->dst_cpu > busiest_cpu)
4712 4713
		return 0;

4714 4715 4716
	env->imbalance = DIV_ROUND_CLOSEST(
		sds->max_load * sds->busiest->sgp->power, SCHED_POWER_SCALE);

4717
	return 1;
4718 4719 4720 4721 4722 4723
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
4724
 * @env: The load balancing environment.
4725 4726
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
4727 4728
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
4729 4730 4731
{
	unsigned long tmp, pwr_now = 0, pwr_move = 0;
	unsigned int imbn = 2;
4732
	unsigned long scaled_busy_load_per_task;
4733 4734 4735 4736 4737 4738

	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;
4739
	} else {
4740
		sds->this_load_per_task =
4741 4742
			cpu_avg_load_per_task(env->dst_cpu);
	}
4743

4744
	scaled_busy_load_per_task = sds->busiest_load_per_task
4745
					 * SCHED_POWER_SCALE;
4746
	scaled_busy_load_per_task /= sds->busiest->sgp->power;
4747 4748 4749

	if (sds->max_load - sds->this_load + scaled_busy_load_per_task >=
			(scaled_busy_load_per_task * imbn)) {
4750
		env->imbalance = sds->busiest_load_per_task;
4751 4752 4753 4754 4755 4756 4757 4758 4759
		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.
	 */

4760
	pwr_now += sds->busiest->sgp->power *
4761
			min(sds->busiest_load_per_task, sds->max_load);
4762
	pwr_now += sds->this->sgp->power *
4763
			min(sds->this_load_per_task, sds->this_load);
4764
	pwr_now /= SCHED_POWER_SCALE;
4765 4766

	/* Amount of load we'd subtract */
4767
	tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
4768
		sds->busiest->sgp->power;
4769
	if (sds->max_load > tmp)
4770
		pwr_move += sds->busiest->sgp->power *
4771 4772 4773
			min(sds->busiest_load_per_task, sds->max_load - tmp);

	/* Amount of load we'd add */
4774
	if (sds->max_load * sds->busiest->sgp->power <
4775
		sds->busiest_load_per_task * SCHED_POWER_SCALE)
4776 4777
		tmp = (sds->max_load * sds->busiest->sgp->power) /
			sds->this->sgp->power;
4778
	else
4779
		tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
4780 4781
			sds->this->sgp->power;
	pwr_move += sds->this->sgp->power *
4782
			min(sds->this_load_per_task, sds->this_load + tmp);
4783
	pwr_move /= SCHED_POWER_SCALE;
4784 4785 4786

	/* Move if we gain throughput */
	if (pwr_move > pwr_now)
4787
		env->imbalance = sds->busiest_load_per_task;
4788 4789 4790 4791 4792
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
4793
 * @env: load balance environment
4794 4795
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
4796
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
4797
{
4798 4799 4800 4801 4802 4803 4804 4805
	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);
	}

4806 4807 4808 4809 4810 4811
	/*
	 * 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) {
4812 4813
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
4814 4815
	}

4816 4817 4818 4819 4820 4821 4822
	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);

4823
		load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
4824

4825
		load_above_capacity /= sds->busiest->sgp->power;
4826 4827 4828 4829 4830 4831 4832 4833 4834 4835 4836 4837 4838
	}

	/*
	 * 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);
4839 4840

	/* How much load to actually move to equalise the imbalance */
4841
	env->imbalance = min(max_pull * sds->busiest->sgp->power,
4842
		(sds->avg_load - sds->this_load) * sds->this->sgp->power)
4843
			/ SCHED_POWER_SCALE;
4844 4845 4846

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
4847
	 * there is no guarantee that any tasks will be moved so we'll have
4848 4849 4850
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
4851 4852
	if (env->imbalance < sds->busiest_load_per_task)
		return fix_small_imbalance(env, sds);
4853 4854

}
4855

4856 4857 4858 4859 4860 4861 4862 4863 4864 4865 4866 4867
/******* 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.
 *
4868
 * @env: The load balancing environment.
4869 4870 4871 4872 4873 4874 4875 4876 4877
 * @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 *
4878
find_busiest_group(struct lb_env *env, int *balance)
4879 4880 4881 4882 4883 4884 4885 4886 4887
{
	struct sd_lb_stats sds;

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

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
4888
	update_sd_lb_stats(env, balance, &sds);
4889

4890 4891 4892
	/*
	 * this_cpu is not the appropriate cpu to perform load balancing at
	 * this level.
4893
	 */
P
Peter Zijlstra 已提交
4894
	if (!(*balance))
4895 4896
		goto ret;

4897 4898
	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(env, &sds))
4899 4900
		return sds.busiest;

4901
	/* There is no busy sibling group to pull tasks from */
4902 4903 4904
	if (!sds.busiest || sds.busiest_nr_running == 0)
		goto out_balanced;

4905
	sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
4906

P
Peter Zijlstra 已提交
4907 4908 4909 4910 4911 4912 4913 4914
	/*
	 * 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;

4915
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
4916
	if (env->idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
4917 4918 4919
			!sds.busiest_has_capacity)
		goto force_balance;

4920 4921 4922 4923
	/*
	 * If the local group is more busy than the selected busiest group
	 * don't try and pull any tasks.
	 */
4924 4925 4926
	if (sds.this_load >= sds.max_load)
		goto out_balanced;

4927 4928 4929 4930
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
4931 4932 4933
	if (sds.this_load >= sds.avg_load)
		goto out_balanced;

4934
	if (env->idle == CPU_IDLE) {
4935 4936 4937 4938 4939 4940
		/*
		 * 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.
		 */
4941
		if ((sds.this_idle_cpus <= sds.busiest_idle_cpus + 1) &&
4942 4943
		    sds.busiest_nr_running <= sds.busiest_group_weight)
			goto out_balanced;
4944 4945 4946 4947 4948
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
4949
		if (100 * sds.max_load <= env->sd->imbalance_pct * sds.this_load)
4950
			goto out_balanced;
4951
	}
4952

4953
force_balance:
4954
	/* Looks like there is an imbalance. Compute it */
4955
	calculate_imbalance(env, &sds);
4956 4957 4958 4959
	return sds.busiest;

out_balanced:
ret:
4960
	env->imbalance = 0;
4961 4962 4963 4964 4965 4966
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
4967
static struct rq *find_busiest_queue(struct lb_env *env,
4968
				     struct sched_group *group)
4969 4970 4971 4972 4973 4974 4975
{
	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);
4976 4977
		unsigned long capacity = DIV_ROUND_CLOSEST(power,
							   SCHED_POWER_SCALE);
4978 4979
		unsigned long wl;

4980
		if (!capacity)
4981
			capacity = fix_small_capacity(env->sd, group);
4982

4983
		if (!cpumask_test_cpu(i, env->cpus))
4984 4985 4986
			continue;

		rq = cpu_rq(i);
4987
		wl = weighted_cpuload(i);
4988

4989 4990 4991 4992
		/*
		 * When comparing with imbalance, use weighted_cpuload()
		 * which is not scaled with the cpu power.
		 */
4993
		if (capacity && rq->nr_running == 1 && wl > env->imbalance)
4994 4995
			continue;

4996 4997 4998 4999 5000 5001
		/*
		 * 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.
		 */
5002
		wl = (wl * SCHED_POWER_SCALE) / power;
5003

5004 5005 5006 5007 5008 5009 5010 5011 5012 5013 5014 5015 5016 5017 5018 5019
		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. */
5020
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
5021

5022
static int need_active_balance(struct lb_env *env)
5023
{
5024 5025 5026
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
5027 5028 5029 5030 5031 5032

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
5033
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
5034
			return 1;
5035 5036 5037 5038 5039
	}

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

5040 5041
static int active_load_balance_cpu_stop(void *data);

5042 5043 5044 5045 5046 5047 5048 5049
/*
 * 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)
{
5050
	int ld_moved, cur_ld_moved, active_balance = 0;
5051 5052 5053
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
5054
	struct cpumask *cpus = __get_cpu_var(load_balance_mask);
5055

5056 5057
	struct lb_env env = {
		.sd		= sd,
5058 5059
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
5060
		.dst_grpmask    = sched_group_cpus(sd->groups),
5061
		.idle		= idle,
5062
		.loop_break	= sched_nr_migrate_break,
5063
		.cpus		= cpus,
5064 5065
	};

5066 5067 5068 5069
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
5070
	if (idle == CPU_NEWLY_IDLE)
5071 5072
		env.dst_grpmask = NULL;

5073 5074 5075 5076 5077
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
5078
	group = find_busiest_group(&env, balance);
5079 5080 5081 5082 5083 5084 5085 5086 5087

	if (*balance == 0)
		goto out_balanced;

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

5088
	busiest = find_busiest_queue(&env, group);
5089 5090 5091 5092 5093
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

5094
	BUG_ON(busiest == env.dst_rq);
5095

5096
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
5097 5098 5099 5100 5101 5102 5103 5104 5105

	ld_moved = 0;
	if (busiest->nr_running > 1) {
		/*
		 * Attempt to move tasks. If find_busiest_group has found
		 * an imbalance but busiest->nr_running <= 1, the group is
		 * still unbalanced. ld_moved simply stays zero, so it is
		 * correctly treated as an imbalance.
		 */
5106
		env.flags |= LBF_ALL_PINNED;
5107 5108 5109
		env.src_cpu   = busiest->cpu;
		env.src_rq    = busiest;
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
5110

5111
		update_h_load(env.src_cpu);
5112
more_balance:
5113
		local_irq_save(flags);
5114
		double_rq_lock(env.dst_rq, busiest);
5115 5116 5117 5118 5119 5120 5121

		/*
		 * 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;
5122
		double_rq_unlock(env.dst_rq, busiest);
5123 5124 5125 5126 5127
		local_irq_restore(flags);

		/*
		 * some other cpu did the load balance for us.
		 */
5128 5129 5130
		if (cur_ld_moved && env.dst_cpu != smp_processor_id())
			resched_cpu(env.dst_cpu);

5131 5132 5133 5134 5135
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

5136 5137 5138 5139 5140 5141 5142 5143 5144 5145 5146 5147 5148 5149 5150 5151 5152 5153 5154
		/*
		 * 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.
		 */
5155
		if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) {
5156

5157
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
5158 5159 5160 5161
			env.dst_cpu	 = env.new_dst_cpu;
			env.flags	&= ~LBF_SOME_PINNED;
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
5162 5163 5164 5165

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

5166 5167 5168 5169 5170 5171
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
5172 5173

		/* All tasks on this runqueue were pinned by CPU affinity */
5174
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
5175
			cpumask_clear_cpu(cpu_of(busiest), cpus);
5176 5177 5178
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
5179
				goto redo;
5180
			}
5181 5182 5183 5184 5185 5186
			goto out_balanced;
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
5187 5188 5189 5190 5191 5192 5193 5194
		/*
		 * 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++;
5195

5196
		if (need_active_balance(&env)) {
5197 5198
			raw_spin_lock_irqsave(&busiest->lock, flags);

5199 5200 5201
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
5202 5203
			 */
			if (!cpumask_test_cpu(this_cpu,
5204
					tsk_cpus_allowed(busiest->curr))) {
5205 5206
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
5207
				env.flags |= LBF_ALL_PINNED;
5208 5209 5210
				goto out_one_pinned;
			}

5211 5212 5213 5214 5215
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
5216 5217 5218 5219 5220 5221
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
5222

5223
			if (active_balance) {
5224 5225 5226
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
5227
			}
5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238 5239 5240 5241 5242 5243 5244 5245 5246 5247 5248 5249 5250 5251 5252 5253 5254 5255 5256 5257 5258 5259 5260

			/*
			 * 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 */
5261
	if (((env.flags & LBF_ALL_PINNED) &&
5262
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
5263 5264 5265
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

5266
	ld_moved = 0;
5267 5268 5269 5270 5271 5272 5273 5274
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.
 */
5275
void idle_balance(int this_cpu, struct rq *this_rq)
5276 5277 5278 5279 5280
{
	struct sched_domain *sd;
	int pulled_task = 0;
	unsigned long next_balance = jiffies + HZ;

5281
	this_rq->idle_stamp = rq_clock(this_rq);
5282 5283 5284 5285

	if (this_rq->avg_idle < sysctl_sched_migration_cost)
		return;

5286 5287 5288 5289 5290
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

5291
	update_blocked_averages(this_cpu);
5292
	rcu_read_lock();
5293 5294
	for_each_domain(this_cpu, sd) {
		unsigned long interval;
5295
		int balance = 1;
5296 5297 5298 5299

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

5300
		if (sd->flags & SD_BALANCE_NEWIDLE) {
5301
			/* If we've pulled tasks over stop searching: */
5302 5303 5304
			pulled_task = load_balance(this_cpu, this_rq,
						   sd, CPU_NEWLY_IDLE, &balance);
		}
5305 5306 5307 5308

		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
5309 5310
		if (pulled_task) {
			this_rq->idle_stamp = 0;
5311
			break;
N
Nikhil Rao 已提交
5312
		}
5313
	}
5314
	rcu_read_unlock();
5315 5316 5317

	raw_spin_lock(&this_rq->lock);

5318 5319 5320 5321 5322 5323 5324 5325 5326 5327
	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;
	}
}

/*
5328 5329 5330 5331
 * 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.
5332
 */
5333
static int active_load_balance_cpu_stop(void *data)
5334
{
5335 5336
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
5337
	int target_cpu = busiest_rq->push_cpu;
5338
	struct rq *target_rq = cpu_rq(target_cpu);
5339
	struct sched_domain *sd;
5340 5341 5342 5343 5344 5345 5346

	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;
5347 5348 5349

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
5350
		goto out_unlock;
5351 5352 5353 5354 5355 5356 5357 5358 5359 5360 5361 5362

	/*
	 * 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. */
5363
	rcu_read_lock();
5364 5365 5366 5367 5368 5369 5370
	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)) {
5371 5372
		struct lb_env env = {
			.sd		= sd,
5373 5374 5375 5376
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
5377 5378 5379
			.idle		= CPU_IDLE,
		};

5380 5381
		schedstat_inc(sd, alb_count);

5382
		if (move_one_task(&env))
5383 5384 5385 5386
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
5387
	rcu_read_unlock();
5388
	double_unlock_balance(busiest_rq, target_rq);
5389 5390 5391 5392
out_unlock:
	busiest_rq->active_balance = 0;
	raw_spin_unlock_irq(&busiest_rq->lock);
	return 0;
5393 5394
}

5395
#ifdef CONFIG_NO_HZ_COMMON
5396 5397 5398 5399 5400 5401
/*
 * 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.
 */
5402
static struct {
5403
	cpumask_var_t idle_cpus_mask;
5404
	atomic_t nr_cpus;
5405 5406
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
5407

5408
static inline int find_new_ilb(int call_cpu)
5409
{
5410
	int ilb = cpumask_first(nohz.idle_cpus_mask);
5411

5412 5413 5414 5415
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
5416 5417
}

5418 5419 5420 5421 5422 5423 5424 5425 5426 5427 5428
/*
 * 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++;

5429
	ilb_cpu = find_new_ilb(cpu);
5430

5431 5432
	if (ilb_cpu >= nr_cpu_ids)
		return;
5433

5434
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
5435 5436 5437 5438 5439 5440 5441 5442
		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);
5443 5444 5445
	return;
}

5446
static inline void nohz_balance_exit_idle(int cpu)
5447 5448 5449 5450 5451 5452 5453 5454
{
	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));
	}
}

5455 5456 5457 5458 5459
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;

	rcu_read_lock();
N
Nathan Zimmer 已提交
5460
	sd = rcu_dereference_check_sched_domain(this_rq()->sd);
V
Vincent Guittot 已提交
5461 5462 5463 5464 5465 5466

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

	for (; sd; sd = sd->parent)
5467
		atomic_inc(&sd->groups->sgp->nr_busy_cpus);
V
Vincent Guittot 已提交
5468
unlock:
5469 5470 5471 5472 5473 5474 5475 5476
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;

	rcu_read_lock();
N
Nathan Zimmer 已提交
5477
	sd = rcu_dereference_check_sched_domain(this_rq()->sd);
V
Vincent Guittot 已提交
5478 5479 5480 5481 5482 5483

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

	for (; sd; sd = sd->parent)
5484
		atomic_dec(&sd->groups->sgp->nr_busy_cpus);
V
Vincent Guittot 已提交
5485
unlock:
5486 5487 5488
	rcu_read_unlock();
}

5489
/*
5490
 * This routine will record that the cpu is going idle with tick stopped.
5491
 * This info will be used in performing idle load balancing in the future.
5492
 */
5493
void nohz_balance_enter_idle(int cpu)
5494
{
5495 5496 5497 5498 5499 5500
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

5501 5502
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
5503

5504 5505 5506
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
5507
}
5508 5509 5510 5511 5512 5513

static int __cpuinit sched_ilb_notifier(struct notifier_block *nfb,
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
5514
		nohz_balance_exit_idle(smp_processor_id());
5515 5516 5517 5518 5519
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
5520 5521 5522 5523
#endif

static DEFINE_SPINLOCK(balancing);

5524 5525 5526 5527
/*
 * 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.
 */
5528
void update_max_interval(void)
5529 5530 5531 5532
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

5533 5534 5535 5536
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
5537
 * Balancing parameters are set up in init_sched_domains.
5538 5539 5540 5541 5542 5543
 */
static void rebalance_domains(int cpu, enum cpu_idle_type idle)
{
	int balance = 1;
	struct rq *rq = cpu_rq(cpu);
	unsigned long interval;
5544
	struct sched_domain *sd;
5545 5546 5547 5548 5549
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
	int need_serialize;

5550
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
5551

5552
	rcu_read_lock();
5553 5554 5555 5556 5557 5558 5559 5560 5561 5562
	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);
5563
		interval = clamp(interval, 1UL, max_load_balance_interval);
5564 5565 5566 5567 5568 5569 5570 5571 5572 5573 5574

		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)) {
				/*
5575 5576 5577
				 * The LBF_SOME_PINNED logic could have changed
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
5578
				 */
5579
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
5580 5581 5582 5583 5584 5585 5586 5587 5588 5589 5590 5591 5592 5593 5594 5595 5596 5597 5598
			}
			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;
	}
5599
	rcu_read_unlock();
5600 5601 5602 5603 5604 5605 5606 5607 5608 5609

	/*
	 * 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;
}

5610
#ifdef CONFIG_NO_HZ_COMMON
5611
/*
5612
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
5613 5614
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
5615 5616 5617 5618 5619 5620
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;

5621 5622 5623
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
5624 5625

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
5626
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
5627 5628 5629 5630 5631 5632 5633
			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.
		 */
5634
		if (need_resched())
5635 5636
			break;

V
Vincent Guittot 已提交
5637 5638 5639 5640 5641 5642
		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);
5643 5644 5645 5646 5647 5648 5649

		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;
5650 5651
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
5652 5653 5654
}

/*
5655 5656 5657 5658 5659 5660 5661
 * 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.
5662 5663 5664 5665
 */
static inline int nohz_kick_needed(struct rq *rq, int cpu)
{
	unsigned long now = jiffies;
5666
	struct sched_domain *sd;
5667

5668
	if (unlikely(idle_cpu(cpu)))
5669 5670
		return 0;

5671 5672 5673 5674
       /*
	* 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.
	*/
5675
	set_cpu_sd_state_busy();
5676
	nohz_balance_exit_idle(cpu);
5677 5678 5679 5680 5681 5682 5683

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
		return 0;
5684 5685

	if (time_before(now, nohz.next_balance))
5686 5687
		return 0;

5688 5689
	if (rq->nr_running >= 2)
		goto need_kick;
5690

5691
	rcu_read_lock();
5692 5693 5694 5695
	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);
5696

5697
		if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1)
5698
			goto need_kick_unlock;
5699 5700 5701 5702

		if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight
		    && (cpumask_first_and(nohz.idle_cpus_mask,
					  sched_domain_span(sd)) < cpu))
5703
			goto need_kick_unlock;
5704 5705 5706

		if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING)))
			break;
5707
	}
5708
	rcu_read_unlock();
5709
	return 0;
5710 5711 5712

need_kick_unlock:
	rcu_read_unlock();
5713 5714
need_kick:
	return 1;
5715 5716 5717 5718 5719 5720 5721 5722 5723
}
#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).
 */
5724 5725 5726 5727
static void run_rebalance_domains(struct softirq_action *h)
{
	int this_cpu = smp_processor_id();
	struct rq *this_rq = cpu_rq(this_cpu);
5728
	enum cpu_idle_type idle = this_rq->idle_balance ?
5729 5730 5731 5732 5733
						CPU_IDLE : CPU_NOT_IDLE;

	rebalance_domains(this_cpu, idle);

	/*
5734
	 * If this cpu has a pending nohz_balance_kick, then do the
5735 5736 5737
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
5738
	nohz_idle_balance(this_cpu, idle);
5739 5740 5741 5742
}

static inline int on_null_domain(int cpu)
{
5743
	return !rcu_dereference_sched(cpu_rq(cpu)->sd);
5744 5745 5746 5747 5748
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
5749
void trigger_load_balance(struct rq *rq, int cpu)
5750 5751 5752 5753 5754
{
	/* 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);
5755
#ifdef CONFIG_NO_HZ_COMMON
5756
	if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
5757 5758
		nohz_balancer_kick(cpu);
#endif
5759 5760
}

5761 5762 5763 5764 5765 5766 5767 5768
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
5769 5770 5771

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
5772 5773
}

5774
#endif /* CONFIG_SMP */
5775

5776 5777 5778
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
5779
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
5780 5781 5782 5783 5784 5785
{
	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
5786
		entity_tick(cfs_rq, se, queued);
5787
	}
5788

5789 5790
	if (sched_feat_numa(NUMA))
		task_tick_numa(rq, curr);
5791

5792
	update_rq_runnable_avg(rq, 1);
5793 5794 5795
}

/*
P
Peter Zijlstra 已提交
5796 5797 5798
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
5799
 */
P
Peter Zijlstra 已提交
5800
static void task_fork_fair(struct task_struct *p)
5801
{
5802 5803
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
5804
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
5805 5806 5807
	struct rq *rq = this_rq();
	unsigned long flags;

5808
	raw_spin_lock_irqsave(&rq->lock, flags);
5809

5810 5811
	update_rq_clock(rq);

5812 5813 5814
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

5815 5816
	if (unlikely(task_cpu(p) != this_cpu)) {
		rcu_read_lock();
P
Peter Zijlstra 已提交
5817
		__set_task_cpu(p, this_cpu);
5818 5819
		rcu_read_unlock();
	}
5820

5821
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
5822

5823 5824
	if (curr)
		se->vruntime = curr->vruntime;
5825
	place_entity(cfs_rq, se, 1);
5826

P
Peter Zijlstra 已提交
5827
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
5828
		/*
5829 5830 5831
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
5832
		swap(curr->vruntime, se->vruntime);
5833
		resched_task(rq->curr);
5834
	}
5835

5836 5837
	se->vruntime -= cfs_rq->min_vruntime;

5838
	raw_spin_unlock_irqrestore(&rq->lock, flags);
5839 5840
}

5841 5842 5843 5844
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
5845 5846
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
5847
{
P
Peter Zijlstra 已提交
5848 5849 5850
	if (!p->se.on_rq)
		return;

5851 5852 5853 5854 5855
	/*
	 * 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
5856
	if (rq->curr == p) {
5857 5858 5859
		if (p->prio > oldprio)
			resched_task(rq->curr);
	} else
5860
		check_preempt_curr(rq, p, 0);
5861 5862
}

P
Peter Zijlstra 已提交
5863 5864 5865 5866 5867 5868 5869 5870 5871 5872 5873 5874 5875 5876 5877 5878 5879 5880 5881 5882 5883 5884
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;
	}
5885

5886
#ifdef CONFIG_SMP
5887 5888 5889 5890 5891 5892 5893 5894 5895 5896 5897 5898
	/*
	* 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
5899 5900
}

5901 5902 5903
/*
 * We switched to the sched_fair class.
 */
P
Peter Zijlstra 已提交
5904
static void switched_to_fair(struct rq *rq, struct task_struct *p)
5905
{
P
Peter Zijlstra 已提交
5906 5907 5908
	if (!p->se.on_rq)
		return;

5909 5910 5911 5912 5913
	/*
	 * 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
5914
	if (rq->curr == p)
5915 5916
		resched_task(rq->curr);
	else
5917
		check_preempt_curr(rq, p, 0);
5918 5919
}

5920 5921 5922 5923 5924 5925 5926 5927 5928
/* 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;

5929 5930 5931 5932 5933 5934 5935
	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);
	}
5936 5937
}

5938 5939 5940 5941 5942 5943 5944
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
5945
#ifdef CONFIG_SMP
5946
	atomic64_set(&cfs_rq->decay_counter, 1);
5947
	atomic_long_set(&cfs_rq->removed_load, 0);
5948
#endif
5949 5950
}

P
Peter Zijlstra 已提交
5951
#ifdef CONFIG_FAIR_GROUP_SCHED
5952
static void task_move_group_fair(struct task_struct *p, int on_rq)
P
Peter Zijlstra 已提交
5953
{
5954
	struct cfs_rq *cfs_rq;
5955 5956 5957 5958 5959 5960 5961 5962 5963 5964 5965 5966 5967
	/*
	 * 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.
	 */
5968 5969 5970 5971 5972 5973
	/*
	 * 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().
5974 5975
	 * - Moving a task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
5976 5977 5978 5979
	 *
	 * To prevent boost or penalty in the new cfs_rq caused by delta
	 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
	 */
5980
	if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING))
5981 5982
		on_rq = 1;

5983 5984 5985
	if (!on_rq)
		p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
	set_task_rq(p, task_cpu(p));
5986 5987 5988 5989 5990 5991 5992 5993 5994 5995 5996 5997 5998
	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
	}
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}
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 6069 6070 6071 6072 6073 6074 6075 6076 6077 6078 6079 6080 6081 6082 6083 6084 6085 6086 6087 6088 6089 6090 6091 6092 6093 6094 6095 6096 6097 6098 6099 6100 6101 6102 6103 6104 6105 6106 6107 6108 6109 6110 6111 6112 6113 6114 6115 6116 6117 6118 6119 6120 6121 6122 6123 6124 6125 6126 6127 6128

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);
6129 6130 6131

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
6132
		for_each_sched_entity(se)
6133 6134 6135 6136 6137 6138 6139 6140 6141 6142 6143 6144 6145 6146 6147 6148 6149 6150 6151 6152 6153
			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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6155
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
6156 6157 6158 6159 6160 6161 6162 6163 6164
{
	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)
6165
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
6166 6167 6168 6169

	return rr_interval;
}

6170 6171 6172
/*
 * All the scheduling class methods:
 */
6173
const struct sched_class fair_sched_class = {
6174
	.next			= &idle_sched_class,
6175 6176 6177
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
6178
	.yield_to_task		= yield_to_task_fair,
6179

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Ingo Molnar 已提交
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	.check_preempt_curr	= check_preempt_wakeup,
6181 6182 6183 6184

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

6185
#ifdef CONFIG_SMP
L
Li Zefan 已提交
6186
	.select_task_rq		= select_task_rq_fair,
6187
	.migrate_task_rq	= migrate_task_rq_fair,
6188

6189 6190
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
6191 6192

	.task_waking		= task_waking_fair,
6193
#endif
6194

6195
	.set_curr_task          = set_curr_task_fair,
6196
	.task_tick		= task_tick_fair,
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Peter Zijlstra 已提交
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	.task_fork		= task_fork_fair,
6198 6199

	.prio_changed		= prio_changed_fair,
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	.switched_from		= switched_from_fair,
6201
	.switched_to		= switched_to_fair,
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6203 6204
	.get_rr_interval	= get_rr_interval_fair,

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#ifdef CONFIG_FAIR_GROUP_SCHED
6206
	.task_move_group	= task_move_group_fair,
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#endif
6208 6209 6210
};

#ifdef CONFIG_SCHED_DEBUG
6211
void print_cfs_stats(struct seq_file *m, int cpu)
6212 6213 6214
{
	struct cfs_rq *cfs_rq;

6215
	rcu_read_lock();
6216
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
6217
		print_cfs_rq(m, cpu, cfs_rq);
6218
	rcu_read_unlock();
6219 6220
}
#endif
6221 6222 6223 6224 6225 6226

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

6227
#ifdef CONFIG_NO_HZ_COMMON
6228
	nohz.next_balance = jiffies;
6229
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
6230
	cpu_notifier(sched_ilb_notifier, 0);
6231 6232 6233 6234
#endif
#endif /* SMP */

}