fair.c 166.4 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

I
Ingo Molnar 已提交
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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Peter Zijlstra 已提交
739 740
	if (!delta_exec)
		return;
741

I
Ingo Molnar 已提交
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
/*
821 822 823
 * Approximate time to scan a full NUMA task in ms. The task scan period is
 * calculated based on the tasks virtual memory size and
 * numa_balancing_scan_size.
824
 */
825 826 827
unsigned int sysctl_numa_balancing_scan_period_min = 1000;
unsigned int sysctl_numa_balancing_scan_period_max = 60000;
unsigned int sysctl_numa_balancing_scan_period_reset = 60000;
828 829 830

/* Portion of address space to scan in MB */
unsigned int sysctl_numa_balancing_scan_size = 256;
831

832 833 834
/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
unsigned int sysctl_numa_balancing_scan_delay = 1000;

835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879
static unsigned int task_nr_scan_windows(struct task_struct *p)
{
	unsigned long rss = 0;
	unsigned long nr_scan_pages;

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

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

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

static unsigned int task_scan_min(struct task_struct *p)
{
	unsigned int scan, floor;
	unsigned int windows = 1;

	if (sysctl_numa_balancing_scan_size < MAX_SCAN_WINDOW)
		windows = MAX_SCAN_WINDOW / sysctl_numa_balancing_scan_size;
	floor = 1000 / windows;

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

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

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

880 881
static void task_numa_placement(struct task_struct *p)
{
882 883
	int seq, nid, max_nid = -1;
	unsigned long max_faults = 0;
884

885 886 887
	if (!p->mm)	/* for example, ksmd faulting in a user's mm */
		return;
	seq = ACCESS_ONCE(p->mm->numa_scan_seq);
888 889 890
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
891
	p->numa_scan_period_max = task_scan_max(p);
892

893 894
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
895 896 897
		unsigned long faults;

		/* Decay existing window and copy faults since last scan */
898
		p->numa_faults[nid] >>= 1;
899 900 901 902
		p->numa_faults[nid] += p->numa_faults_buffer[nid];
		p->numa_faults_buffer[nid] = 0;

		faults = p->numa_faults[nid];
903 904 905 906 907 908 909 910 911
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
	}

	/* Update the tasks preferred node if necessary */
	if (max_faults && max_nid != p->numa_preferred_nid)
		p->numa_preferred_nid = max_nid;
912 913 914 915 916
}

/*
 * Got a PROT_NONE fault for a page on @node.
 */
917
void task_numa_fault(int node, int pages, bool migrated)
918 919 920
{
	struct task_struct *p = current;

921
	if (!numabalancing_enabled)
922 923
		return;

924 925 926 927
	/* Allocate buffer to track faults on a per-node basis */
	if (unlikely(!p->numa_faults)) {
		int size = sizeof(*p->numa_faults) * nr_node_ids;

928 929
		/* numa_faults and numa_faults_buffer share the allocation */
		p->numa_faults = kzalloc(size * 2, GFP_KERNEL|__GFP_NOWARN);
930 931
		if (!p->numa_faults)
			return;
932 933 934

		BUG_ON(p->numa_faults_buffer);
		p->numa_faults_buffer = p->numa_faults + nr_node_ids;
935
	}
936

937
	/*
938 939
	 * If pages are properly placed (did not migrate) then scan slower.
	 * This is reset periodically in case of phase changes
940
	 */
941 942 943 944 945 946 947 948
	if (!migrated) {
		/* Initialise if necessary */
		if (!p->numa_scan_period_max)
			p->numa_scan_period_max = task_scan_max(p);

		p->numa_scan_period = min(p->numa_scan_period_max,
			p->numa_scan_period + 10);
	}
949

950
	task_numa_placement(p);
951

952
	p->numa_faults_buffer[node] += pages;
953 954
}

955 956 957 958 959 960
static void reset_ptenuma_scan(struct task_struct *p)
{
	ACCESS_ONCE(p->mm->numa_scan_seq)++;
	p->mm->numa_scan_offset = 0;
}

961 962 963 964 965 966 967 968 969
/*
 * 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;
970
	struct vm_area_struct *vma;
971
	unsigned long start, end;
972
	unsigned long nr_pte_updates = 0;
973
	long pages;
974 975 976 977 978 979 980 981 982 983 984 985 986 987 988

	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;

989 990 991 992 993 994 995
	if (!mm->numa_next_reset || !mm->numa_next_scan) {
		mm->numa_next_scan = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
		mm->numa_next_reset = now +
			msecs_to_jiffies(sysctl_numa_balancing_scan_period_reset);
	}

996 997 998 999 1000 1001 1002 1003
	/*
	 * 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)) {
1004
		p->numa_scan_period = task_scan_min(p);
1005 1006 1007 1008
		next_scan = now + msecs_to_jiffies(sysctl_numa_balancing_scan_period_reset);
		xchg(&mm->numa_next_reset, next_scan);
	}

1009 1010 1011 1012 1013 1014 1015
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

1016 1017 1018 1019
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
		p->numa_scan_period = task_scan_min(p);
	}
1020

1021
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
1022 1023 1024
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

1025 1026 1027 1028 1029 1030
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

1031 1032 1033 1034 1035
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
	if (!pages)
		return;
1036

1037
	down_read(&mm->mmap_sem);
1038
	vma = find_vma(mm, start);
1039 1040
	if (!vma) {
		reset_ptenuma_scan(p);
1041
		start = 0;
1042 1043
		vma = mm->mmap;
	}
1044
	for (; vma; vma = vma->vm_next) {
1045 1046 1047 1048
		if (!vma_migratable(vma))
			continue;

		/* Skip small VMAs. They are not likely to be of relevance */
1049
		if (vma->vm_end - vma->vm_start < HPAGE_SIZE)
1050 1051
			continue;

1052 1053 1054 1055
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
1056 1057 1058 1059 1060 1061 1062 1063 1064
			nr_pte_updates += change_prot_numa(vma, start, end);

			/*
			 * Scan sysctl_numa_balancing_scan_size but ensure that
			 * at least one PTE is updated so that unused virtual
			 * address space is quickly skipped.
			 */
			if (nr_pte_updates)
				pages -= (end - start) >> PAGE_SHIFT;
1065

1066 1067 1068 1069
			start = end;
			if (pages <= 0)
				goto out;
		} while (end != vma->vm_end);
1070
	}
1071

1072
out:
1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084
	/*
	 * If the whole process was scanned without updates then no NUMA
	 * hinting faults are being recorded and scan rate should be lower.
	 */
	if (mm->numa_scan_offset == 0 && !nr_pte_updates) {
		p->numa_scan_period = min(p->numa_scan_period_max,
			p->numa_scan_period << 1);

		next_scan = now + msecs_to_jiffies(p->numa_scan_period);
		mm->numa_next_scan = next_scan;
	}

1085
	/*
P
Peter Zijlstra 已提交
1086 1087 1088 1089
	 * 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.
1090 1091
	 */
	if (vma)
1092
		mm->numa_scan_offset = start;
1093 1094 1095
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121
}

/*
 * 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) {
1122
		if (!curr->node_stamp)
1123
			curr->numa_scan_period = task_scan_min(curr);
1124
		curr->node_stamp += period;
1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137

		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 */

1138 1139 1140 1141
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
1142
	if (!parent_entity(se))
1143
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
1144 1145
#ifdef CONFIG_SMP
	if (entity_is_task(se))
1146
		list_add(&se->group_node, &rq_of(cfs_rq)->cfs_tasks);
1147
#endif
1148 1149 1150 1151 1152 1153 1154
	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);
1155
	if (!parent_entity(se))
1156
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
1157
	if (entity_is_task(se))
1158
		list_del_init(&se->group_node);
1159 1160 1161
	cfs_rq->nr_running--;
}

1162 1163
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
1164 1165 1166 1167 1168 1169 1170 1171 1172
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().
	 */
1173
	tg_weight = atomic_long_read(&tg->load_avg);
1174
	tg_weight -= cfs_rq->tg_load_contrib;
1175 1176 1177 1178 1179
	tg_weight += cfs_rq->load.weight;

	return tg_weight;
}

1180
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1181
{
1182
	long tg_weight, load, shares;
1183

1184
	tg_weight = calc_tg_weight(tg, cfs_rq);
1185
	load = cfs_rq->load.weight;
1186 1187

	shares = (tg->shares * load);
1188 1189
	if (tg_weight)
		shares /= tg_weight;
1190 1191 1192 1193 1194 1195 1196 1197 1198

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

	return shares;
}
# else /* CONFIG_SMP */
1199
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1200 1201 1202 1203
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
P
Peter Zijlstra 已提交
1204 1205 1206
static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
1207 1208 1209 1210
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
P
Peter Zijlstra 已提交
1211
		account_entity_dequeue(cfs_rq, se);
1212
	}
P
Peter Zijlstra 已提交
1213 1214 1215 1216 1217 1218 1219

	update_load_set(&se->load, weight);

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

1220 1221
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

1222
static void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
1223 1224 1225
{
	struct task_group *tg;
	struct sched_entity *se;
1226
	long shares;
P
Peter Zijlstra 已提交
1227 1228 1229

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
1230
	if (!se || throttled_hierarchy(cfs_rq))
P
Peter Zijlstra 已提交
1231
		return;
1232 1233 1234 1235
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
1236
	shares = calc_cfs_shares(cfs_rq, tg);
P
Peter Zijlstra 已提交
1237 1238 1239 1240

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
1241
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
P
Peter Zijlstra 已提交
1242 1243 1244 1245
{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

1246
#ifdef CONFIG_SMP
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 1273 1274
/*
 * 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,
};

1275 1276 1277 1278 1279 1280
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300
	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;
1301 1302
	}

1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333
	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];
1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367
}

/*
 * 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)
{
1368 1369
	u64 delta, periods;
	u32 runnable_contrib;
1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402
	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;
1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422
		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;
1423 1424 1425 1426 1427 1428 1429 1430 1431 1432
	}

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

	return decayed;
}

1433
/* Synchronize an entity's decay with its parenting cfs_rq.*/
1434
static inline u64 __synchronize_entity_decay(struct sched_entity *se)
1435 1436 1437 1438 1439 1440
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 decays = atomic64_read(&cfs_rq->decay_counter);

	decays -= se->avg.decay_count;
	if (!decays)
1441
		return 0;
1442 1443 1444

	se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
	se->avg.decay_count = 0;
1445 1446

	return decays;
1447 1448
}

1449 1450 1451 1452 1453
#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;
1454
	long tg_contrib;
1455 1456 1457 1458

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

1459 1460
	if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) {
		atomic_long_add(tg_contrib, &tg->load_avg);
1461 1462 1463
		cfs_rq->tg_load_contrib += tg_contrib;
	}
}
1464

1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485
/*
 * 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;
	}
}

1486 1487 1488 1489
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;
1490 1491
	int runnable_avg;

1492 1493 1494
	u64 contrib;

	contrib = cfs_rq->tg_load_contrib * tg->shares;
1495 1496
	se->avg.load_avg_contrib = div_u64(contrib,
				     atomic_long_read(&tg->load_avg) + 1);
1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525

	/*
	 * 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;
	}
1526
}
1527 1528 1529
#else
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
						 int force_update) {}
1530 1531
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
						  struct cfs_rq *cfs_rq) {}
1532
static inline void __update_group_entity_contrib(struct sched_entity *se) {}
1533 1534
#endif

1535 1536 1537 1538 1539 1540 1541 1542 1543 1544
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);
}

1545 1546 1547 1548 1549
/* 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;

1550 1551 1552
	if (entity_is_task(se)) {
		__update_task_entity_contrib(se);
	} else {
1553
		__update_tg_runnable_avg(&se->avg, group_cfs_rq(se));
1554 1555
		__update_group_entity_contrib(se);
	}
1556 1557 1558 1559

	return se->avg.load_avg_contrib - old_contrib;
}

1560 1561 1562 1563 1564 1565 1566 1567 1568
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;
}

1569 1570
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);

1571
/* Update a sched_entity's runnable average */
1572 1573
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq)
1574
{
1575 1576
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	long contrib_delta;
1577
	u64 now;
1578

1579 1580 1581 1582 1583 1584 1585 1586 1587 1588
	/*
	 * 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))
1589 1590 1591
		return;

	contrib_delta = __update_entity_load_avg_contrib(se);
1592 1593 1594 1595

	if (!update_cfs_rq)
		return;

1596 1597
	if (se->on_rq)
		cfs_rq->runnable_load_avg += contrib_delta;
1598 1599 1600 1601 1602 1603 1604 1605
	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.
 */
1606
static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
1607
{
1608
	u64 now = cfs_rq_clock_task(cfs_rq) >> 20;
1609 1610 1611
	u64 decays;

	decays = now - cfs_rq->last_decay;
1612
	if (!decays && !force_update)
1613 1614
		return;

1615 1616 1617
	if (atomic_long_read(&cfs_rq->removed_load)) {
		unsigned long removed_load;
		removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
1618 1619
		subtract_blocked_load_contrib(cfs_rq, removed_load);
	}
1620

1621 1622 1623 1624 1625 1626
	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;
	}
1627 1628

	__update_cfs_rq_tg_load_contrib(cfs_rq, force_update);
1629
}
1630 1631 1632

static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
{
1633
	__update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable);
1634
	__update_tg_runnable_avg(&rq->avg, &rq->cfs);
1635
}
1636 1637 1638

/* 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,
1639 1640
						  struct sched_entity *se,
						  int wakeup)
1641
{
1642 1643 1644 1645
	/*
	 * 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.
1646 1647 1648 1649
	 *
	 * 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.
1650 1651
	 */
	if (unlikely(se->avg.decay_count <= 0)) {
1652
		se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq));
1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667
		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;
		}
1668 1669
		wakeup = 0;
	} else {
1670 1671 1672 1673 1674 1675 1676
		/*
		 * 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;
1677 1678
	}

1679 1680
	/* migrated tasks did not contribute to our blocked load */
	if (wakeup) {
1681
		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
1682 1683
		update_entity_load_avg(se, 0);
	}
1684

1685
	cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
1686 1687
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !wakeup);
1688 1689
}

1690 1691 1692 1693 1694
/*
 * 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.
 */
1695
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
1696 1697
						  struct sched_entity *se,
						  int sleep)
1698
{
1699
	update_entity_load_avg(se, 1);
1700 1701
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !sleep);
1702

1703
	cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
1704 1705 1706 1707
	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 */
1708
}
1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729

/*
 * 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);
}

1730
#else
1731 1732
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq) {}
1733
static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
1734
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
1735 1736
					   struct sched_entity *se,
					   int wakeup) {}
1737
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
1738 1739
					   struct sched_entity *se,
					   int sleep) {}
1740 1741
static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
					      int force_update) {}
1742 1743
#endif

1744
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
1745 1746
{
#ifdef CONFIG_SCHEDSTATS
1747 1748 1749 1750 1751
	struct task_struct *tsk = NULL;

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

1752
	if (se->statistics.sleep_start) {
1753
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
1754 1755 1756 1757

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

1758 1759
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
1760

1761
		se->statistics.sleep_start = 0;
1762
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
1763

1764
		if (tsk) {
1765
			account_scheduler_latency(tsk, delta >> 10, 1);
1766 1767
			trace_sched_stat_sleep(tsk, delta);
		}
1768
	}
1769
	if (se->statistics.block_start) {
1770
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
1771 1772 1773 1774

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

1775 1776
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
1777

1778
		se->statistics.block_start = 0;
1779
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
1780

1781
		if (tsk) {
1782
			if (tsk->in_iowait) {
1783 1784
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
1785
				trace_sched_stat_iowait(tsk, delta);
1786 1787
			}

1788 1789
			trace_sched_stat_blocked(tsk, delta);

1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800
			/*
			 * 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
1801
		}
1802 1803 1804 1805
	}
#endif
}

P
Peter Zijlstra 已提交
1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818
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
}

1819 1820 1821
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
1822
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
1823

1824 1825 1826 1827 1828 1829
	/*
	 * 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
1830
	if (initial && sched_feat(START_DEBIT))
1831
		vruntime += sched_vslice(cfs_rq, se);
1832

1833
	/* sleeps up to a single latency don't count. */
1834
	if (!initial) {
1835
		unsigned long thresh = sysctl_sched_latency;
1836

1837 1838 1839 1840 1841 1842
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
1843

1844
		vruntime -= thresh;
1845 1846
	}

1847
	/* ensure we never gain time by being placed backwards. */
1848
	se->vruntime = max_vruntime(se->vruntime, vruntime);
1849 1850
}

1851 1852
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

1853
static void
1854
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1855
{
1856 1857
	/*
	 * Update the normalized vruntime before updating min_vruntime
1858
	 * through calling update_curr().
1859
	 */
1860
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
1861 1862
		se->vruntime += cfs_rq->min_vruntime;

1863
	/*
1864
	 * Update run-time statistics of the 'current'.
1865
	 */
1866
	update_curr(cfs_rq);
1867
	enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
1868 1869
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
1870

1871
	if (flags & ENQUEUE_WAKEUP) {
1872
		place_entity(cfs_rq, se, 0);
1873
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
1874
	}
1875

1876
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
1877
	check_spread(cfs_rq, se);
1878 1879
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
1880
	se->on_rq = 1;
1881

1882
	if (cfs_rq->nr_running == 1) {
1883
		list_add_leaf_cfs_rq(cfs_rq);
1884 1885
		check_enqueue_throttle(cfs_rq);
	}
1886 1887
}

1888
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
1889
{
1890 1891 1892 1893 1894 1895 1896 1897
	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
1898

1899 1900 1901 1902 1903 1904 1905 1906 1907
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
1908 1909
}

1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
		if (cfs_rq->skip == se)
			cfs_rq->skip = NULL;
		else
			break;
	}
}

P
Peter Zijlstra 已提交
1921 1922
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
1923 1924 1925 1926 1927
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
1928 1929 1930

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
1931 1932
}

1933
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
1934

1935
static void
1936
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1937
{
1938 1939 1940 1941
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
1942
	dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);
1943

1944
	update_stats_dequeue(cfs_rq, se);
1945
	if (flags & DEQUEUE_SLEEP) {
P
Peter Zijlstra 已提交
1946
#ifdef CONFIG_SCHEDSTATS
1947 1948 1949 1950
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
1951
				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
1952
			if (tsk->state & TASK_UNINTERRUPTIBLE)
1953
				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
1954
		}
1955
#endif
P
Peter Zijlstra 已提交
1956 1957
	}

P
Peter Zijlstra 已提交
1958
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
1959

1960
	if (se != cfs_rq->curr)
1961
		__dequeue_entity(cfs_rq, se);
1962
	se->on_rq = 0;
1963
	account_entity_dequeue(cfs_rq, se);
1964 1965 1966 1967 1968 1969

	/*
	 * 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.
	 */
1970
	if (!(flags & DEQUEUE_SLEEP))
1971
		se->vruntime -= cfs_rq->min_vruntime;
1972

1973 1974 1975
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

1976
	update_min_vruntime(cfs_rq);
1977
	update_cfs_shares(cfs_rq);
1978 1979 1980 1981 1982
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
1983
static void
I
Ingo Molnar 已提交
1984
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
1985
{
1986
	unsigned long ideal_runtime, delta_exec;
1987 1988
	struct sched_entity *se;
	s64 delta;
1989

P
Peter Zijlstra 已提交
1990
	ideal_runtime = sched_slice(cfs_rq, curr);
1991
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
1992
	if (delta_exec > ideal_runtime) {
1993
		resched_task(rq_of(cfs_rq)->curr);
1994 1995 1996 1997 1998
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
		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;

2010 2011
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
2012

2013 2014
	if (delta < 0)
		return;
2015

2016 2017
	if (delta > ideal_runtime)
		resched_task(rq_of(cfs_rq)->curr);
2018 2019
}

2020
static void
2021
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
2022
{
2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033
	/* '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);
	}

2034
	update_stats_curr_start(cfs_rq, se);
2035
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
2036 2037 2038 2039 2040 2041
#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):
	 */
2042
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
2043
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
2044 2045 2046
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
2047
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
2048 2049
}

2050 2051 2052
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

2053 2054 2055 2056 2057 2058 2059
/*
 * 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
 */
2060
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
2061
{
2062
	struct sched_entity *se = __pick_first_entity(cfs_rq);
2063
	struct sched_entity *left = se;
2064

2065 2066 2067 2068 2069 2070 2071 2072 2073
	/*
	 * 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;
	}
2074

2075 2076 2077 2078 2079 2080
	/*
	 * 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;

2081 2082 2083 2084 2085 2086
	/*
	 * 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;

2087
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
2088 2089

	return se;
2090 2091
}

2092 2093
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq);

2094
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
2095 2096 2097 2098 2099 2100
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
2101
		update_curr(cfs_rq);
2102

2103 2104 2105
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

P
Peter Zijlstra 已提交
2106
	check_spread(cfs_rq, prev);
2107
	if (prev->on_rq) {
2108
		update_stats_wait_start(cfs_rq, prev);
2109 2110
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
2111
		/* in !on_rq case, update occurred at dequeue */
2112
		update_entity_load_avg(prev, 1);
2113
	}
2114
	cfs_rq->curr = NULL;
2115 2116
}

P
Peter Zijlstra 已提交
2117 2118
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
2119 2120
{
	/*
2121
	 * Update run-time statistics of the 'current'.
2122
	 */
2123
	update_curr(cfs_rq);
2124

2125 2126 2127
	/*
	 * Ensure that runnable average is periodically updated.
	 */
2128
	update_entity_load_avg(curr, 1);
2129
	update_cfs_rq_blocked_load(cfs_rq, 1);
2130
	update_cfs_shares(cfs_rq);
2131

P
Peter Zijlstra 已提交
2132 2133 2134 2135 2136
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
2137 2138 2139 2140
	if (queued) {
		resched_task(rq_of(cfs_rq)->curr);
		return;
	}
P
Peter Zijlstra 已提交
2141 2142 2143 2144 2145 2146 2147 2148
	/*
	 * 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
2149
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
2150
		check_preempt_tick(cfs_rq, curr);
2151 2152
}

2153 2154 2155 2156 2157 2158

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

#ifdef CONFIG_CFS_BANDWIDTH
2159 2160

#ifdef HAVE_JUMP_LABEL
2161
static struct static_key __cfs_bandwidth_used;
2162 2163 2164

static inline bool cfs_bandwidth_used(void)
{
2165
	return static_key_false(&__cfs_bandwidth_used);
2166 2167 2168 2169 2170 2171
}

void account_cfs_bandwidth_used(int enabled, int was_enabled)
{
	/* only need to count groups transitioning between enabled/!enabled */
	if (enabled && !was_enabled)
2172
		static_key_slow_inc(&__cfs_bandwidth_used);
2173
	else if (!enabled && was_enabled)
2174
		static_key_slow_dec(&__cfs_bandwidth_used);
2175 2176 2177 2178 2179 2180 2181 2182 2183 2184
}
#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 */

2185 2186 2187 2188 2189 2190 2191 2192
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
2193 2194 2195 2196 2197 2198

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

P
Paul Turner 已提交
2199 2200 2201 2202 2203 2204 2205
/*
 * 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
 */
2206
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217
{
	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);
}

2218 2219 2220 2221 2222
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

2223 2224 2225 2226 2227 2228
/* 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;

2229
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
2230 2231
}

2232 2233
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2234 2235 2236
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
2237
	u64 amount = 0, min_amount, expires;
2238 2239 2240 2241 2242 2243 2244

	/* 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;
2245
	else {
P
Paul Turner 已提交
2246 2247 2248 2249 2250 2251 2252 2253
		/*
		 * 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);
2254
			__start_cfs_bandwidth(cfs_b);
P
Paul Turner 已提交
2255
		}
2256 2257 2258 2259 2260 2261

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
2262
	}
P
Paul Turner 已提交
2263
	expires = cfs_b->runtime_expires;
2264 2265 2266
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
2267 2268 2269 2270 2271 2272 2273
	/*
	 * 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;
2274 2275

	return cfs_rq->runtime_remaining > 0;
2276 2277
}

P
Paul Turner 已提交
2278 2279 2280 2281 2282
/*
 * 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)
2283
{
P
Paul Turner 已提交
2284 2285 2286
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
2287
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
2288 2289
		return;

P
Paul Turner 已提交
2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314
	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) */
2315
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
2316 2317 2318
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
2319 2320
		return;

2321 2322 2323 2324 2325 2326
	/*
	 * 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);
2327 2328
}

2329 2330
static __always_inline
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec)
2331
{
2332
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
2333 2334 2335 2336 2337
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

2338 2339
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
2340
	return cfs_bandwidth_used() && cfs_rq->throttled;
2341 2342
}

2343 2344 2345
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
2346
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374
}

/*
 * 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) {
2375
		/* adjust cfs_rq_clock_task() */
2376
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
2377
					     cfs_rq->throttled_clock_task;
2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388
	}
#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)];

2389 2390
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
2391
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
2392 2393 2394 2395 2396
	cfs_rq->throttle_count++;

	return 0;
}

2397
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
2398 2399 2400 2401 2402 2403 2404 2405
{
	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))];

2406
	/* freeze hierarchy runnable averages while throttled */
2407 2408 2409
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429

	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;
2430
	cfs_rq->throttled_clock = rq_clock(rq);
2431 2432 2433 2434 2435
	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);
}

2436
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
2437 2438 2439 2440 2441 2442 2443
{
	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;

2444
	se = cfs_rq->tg->se[cpu_of(rq)];
2445 2446

	cfs_rq->throttled = 0;
2447 2448 2449

	update_rq_clock(rq);

2450
	raw_spin_lock(&cfs_b->lock);
2451
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
2452 2453 2454
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

2455 2456 2457
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520
	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;
}

2521 2522 2523 2524 2525 2526 2527 2528
/*
 * 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)
{
2529 2530
	u64 runtime, runtime_expires;
	int idle = 1, throttled;
2531 2532 2533 2534 2535 2536

	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;

2537 2538 2539
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
	/* idle depends on !throttled (for the case of a large deficit) */
	idle = cfs_b->idle && !throttled;
2540
	cfs_b->nr_periods += overrun;
2541

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Paul Turner 已提交
2542 2543 2544 2545 2546 2547
	/* if we're going inactive then everything else can be deferred */
	if (idle)
		goto out_unlock;

	__refill_cfs_bandwidth_runtime(cfs_b);

2548 2549 2550 2551 2552 2553
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
		goto out_unlock;
	}

2554 2555 2556
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580
	/*
	 * 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);
	}
2581

2582 2583 2584 2585 2586 2587 2588 2589 2590
	/* 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;
2591 2592 2593 2594 2595 2596 2597
out_unlock:
	if (idle)
		cfs_b->timer_active = 0;
	raw_spin_unlock(&cfs_b->lock);

	return idle;
}
2598

2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662
/* 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)
{
2663 2664 2665
	if (!cfs_bandwidth_used())
		return;

2666
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
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
		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);
}

2704 2705 2706 2707 2708 2709 2710
/*
 * 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)
{
2711 2712 2713
	if (!cfs_bandwidth_used())
		return;

2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730
	/* 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)
{
2731 2732 2733
	if (!cfs_bandwidth_used())
		return;

2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745
	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);
}
2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826

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);
}

2827
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847
{
	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 */
2848 2849
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
2850
	return rq_clock_task(rq_of(cfs_rq));
2851 2852 2853 2854
}

static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
				     unsigned long delta_exec) {}
2855 2856
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
2857
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2858 2859 2860 2861 2862

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873

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;
}
2874 2875 2876 2877 2878

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) {}
2879 2880
#endif

2881 2882 2883 2884 2885
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) {}
2886
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
2887 2888 2889

#endif /* CONFIG_CFS_BANDWIDTH */

2890 2891 2892 2893
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
2894 2895 2896 2897 2898 2899 2900 2901
#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);

2902
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916
		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.
		 */
2917
		if (rq->curr != p)
2918
			delta = max_t(s64, 10000LL, delta);
P
Peter Zijlstra 已提交
2919

2920
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
2921 2922
	}
}
2923 2924 2925 2926 2927 2928 2929 2930 2931 2932

/*
 * 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;

2933
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
2934 2935 2936 2937 2938
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
2939
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
2940 2941 2942 2943
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
2944 2945 2946 2947

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
2948 2949
#endif

2950 2951 2952 2953 2954
/*
 * 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:
 */
2955
static void
2956
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
2957 2958
{
	struct cfs_rq *cfs_rq;
2959
	struct sched_entity *se = &p->se;
2960 2961

	for_each_sched_entity(se) {
2962
		if (se->on_rq)
2963 2964
			break;
		cfs_rq = cfs_rq_of(se);
2965
		enqueue_entity(cfs_rq, se, flags);
2966 2967 2968 2969 2970 2971 2972 2973 2974

		/*
		 * 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;
2975
		cfs_rq->h_nr_running++;
2976

2977
		flags = ENQUEUE_WAKEUP;
2978
	}
P
Peter Zijlstra 已提交
2979

P
Peter Zijlstra 已提交
2980
	for_each_sched_entity(se) {
2981
		cfs_rq = cfs_rq_of(se);
2982
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
2983

2984 2985 2986
		if (cfs_rq_throttled(cfs_rq))
			break;

2987
		update_cfs_shares(cfs_rq);
2988
		update_entity_load_avg(se, 1);
P
Peter Zijlstra 已提交
2989 2990
	}

2991 2992
	if (!se) {
		update_rq_runnable_avg(rq, rq->nr_running);
2993
		inc_nr_running(rq);
2994
	}
2995
	hrtick_update(rq);
2996 2997
}

2998 2999
static void set_next_buddy(struct sched_entity *se);

3000 3001 3002 3003 3004
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
3005
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
3006 3007
{
	struct cfs_rq *cfs_rq;
3008
	struct sched_entity *se = &p->se;
3009
	int task_sleep = flags & DEQUEUE_SLEEP;
3010 3011 3012

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
3013
		dequeue_entity(cfs_rq, se, flags);
3014 3015 3016 3017 3018 3019 3020 3021 3022

		/*
		 * 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;
3023
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
3024

3025
		/* Don't dequeue parent if it has other entities besides us */
3026 3027 3028 3029 3030 3031 3032
		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));
3033 3034 3035

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
3036
			break;
3037
		}
3038
		flags |= DEQUEUE_SLEEP;
3039
	}
P
Peter Zijlstra 已提交
3040

P
Peter Zijlstra 已提交
3041
	for_each_sched_entity(se) {
3042
		cfs_rq = cfs_rq_of(se);
3043
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
3044

3045 3046 3047
		if (cfs_rq_throttled(cfs_rq))
			break;

3048
		update_cfs_shares(cfs_rq);
3049
		update_entity_load_avg(se, 1);
P
Peter Zijlstra 已提交
3050 3051
	}

3052
	if (!se) {
3053
		dec_nr_running(rq);
3054 3055
		update_rq_runnable_avg(rq, 1);
	}
3056
	hrtick_update(rq);
3057 3058
}

3059
#ifdef CONFIG_SMP
3060 3061 3062
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
3063
	return cpu_rq(cpu)->cfs.runnable_load_avg;
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 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107
}

/*
 * 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);
3108
	unsigned long load_avg = rq->cfs.runnable_load_avg;
3109 3110

	if (nr_running)
3111
		return load_avg / nr_running;
3112 3113 3114 3115

	return 0;
}

3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132
static void record_wakee(struct task_struct *p)
{
	/*
	 * Rough decay (wiping) for cost saving, don't worry
	 * about the boundary, really active task won't care
	 * about the loss.
	 */
	if (jiffies > current->wakee_flip_decay_ts + HZ) {
		current->wakee_flips = 0;
		current->wakee_flip_decay_ts = jiffies;
	}

	if (current->last_wakee != p) {
		current->last_wakee = p;
		current->wakee_flips++;
	}
}
3133

3134
static void task_waking_fair(struct task_struct *p)
3135 3136 3137
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
3138 3139 3140 3141
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
3142

3143 3144 3145 3146 3147 3148 3149 3150
	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
3151

3152
	se->vruntime -= min_vruntime;
3153
	record_wakee(p);
3154 3155
}

3156
#ifdef CONFIG_FAIR_GROUP_SCHED
3157 3158 3159 3160 3161 3162
/*
 * 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.
3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205
 *
 * 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.
3206
 */
P
Peter Zijlstra 已提交
3207
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
3208
{
P
Peter Zijlstra 已提交
3209
	struct sched_entity *se = tg->se[cpu];
3210

3211
	if (!tg->parent)	/* the trivial, non-cgroup case */
3212 3213
		return wl;

P
Peter Zijlstra 已提交
3214
	for_each_sched_entity(se) {
3215
		long w, W;
P
Peter Zijlstra 已提交
3216

3217
		tg = se->my_q->tg;
3218

3219 3220 3221 3222
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
3223

3224 3225 3226 3227
		/*
		 * w = rw_i + @wl
		 */
		w = se->my_q->load.weight + wl;
3228

3229 3230 3231 3232 3233
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
			wl = (w * tg->shares) / W;
3234 3235
		else
			wl = tg->shares;
3236

3237 3238 3239 3240 3241
		/*
		 * 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().
		 */
3242 3243
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
3244 3245 3246 3247

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
3248
		wl -= se->load.weight;
3249 3250 3251 3252 3253 3254 3255 3256

		/*
		 * 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
3257 3258
		wg = 0;
	}
3259

P
Peter Zijlstra 已提交
3260
	return wl;
3261 3262
}
#else
P
Peter Zijlstra 已提交
3263

3264 3265
static inline unsigned long effective_load(struct task_group *tg, int cpu,
		unsigned long wl, unsigned long wg)
P
Peter Zijlstra 已提交
3266
{
3267
	return wl;
3268
}
P
Peter Zijlstra 已提交
3269

3270 3271
#endif

3272 3273
static int wake_wide(struct task_struct *p)
{
3274
	int factor = this_cpu_read(sd_llc_size);
3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293

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

	return 0;
}

3294
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
3295
{
3296
	s64 this_load, load;
3297
	int idx, this_cpu, prev_cpu;
3298
	unsigned long tl_per_task;
3299
	struct task_group *tg;
3300
	unsigned long weight;
3301
	int balanced;
3302

3303 3304 3305 3306 3307 3308 3309
	/*
	 * If we wake multiple tasks be careful to not bounce
	 * ourselves around too much.
	 */
	if (wake_wide(p))
		return 0;

3310 3311 3312 3313 3314
	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);
3315

3316 3317 3318 3319 3320
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
3321 3322 3323 3324
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

3325
		this_load += effective_load(tg, this_cpu, -weight, -weight);
3326 3327
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
3328

3329 3330
	tg = task_group(p);
	weight = p->se.load.weight;
3331

3332 3333
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
3334 3335 3336
	 * 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.
3337 3338 3339 3340
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
3341 3342
	if (this_load > 0) {
		s64 this_eff_load, prev_eff_load;
3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355

		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;
3356

3357
	/*
I
Ingo Molnar 已提交
3358 3359 3360
	 * If the currently running task will sleep within
	 * a reasonable amount of time then attract this newly
	 * woken task:
3361
	 */
3362 3363
	if (sync && balanced)
		return 1;
3364

3365
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
3366 3367
	tl_per_task = cpu_avg_load_per_task(this_cpu);

3368 3369 3370
	if (balanced ||
	    (this_load <= load &&
	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
3371 3372 3373 3374 3375
		/*
		 * This domain has SD_WAKE_AFFINE and
		 * p is cache cold in this domain, and
		 * there is no bad imbalance.
		 */
3376
		schedstat_inc(sd, ttwu_move_affine);
3377
		schedstat_inc(p, se.statistics.nr_wakeups_affine);
3378 3379 3380 3381 3382 3383

		return 1;
	}
	return 0;
}

3384 3385 3386 3387 3388
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
3389
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
3390
		  int this_cpu, int load_idx)
3391
{
3392
	struct sched_group *idlest = NULL, *group = sd->groups;
3393 3394
	unsigned long min_load = ULONG_MAX, this_load = 0;
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
3395

3396 3397 3398 3399
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
3400

3401 3402
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
3403
					tsk_cpus_allowed(p)))
3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422
			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 */
3423
		avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;
3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445 3446 3447 3448

		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 */
3449
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
3450 3451 3452 3453 3454
		load = weighted_cpuload(i);

		if (load < min_load || (load == min_load && i == this_cpu)) {
			min_load = load;
			idlest = i;
3455 3456 3457
		}
	}

3458 3459
	return idlest;
}
3460

3461 3462 3463
/*
 * Try and locate an idle CPU in the sched_domain.
 */
3464
static int select_idle_sibling(struct task_struct *p, int target)
3465
{
3466
	struct sched_domain *sd;
3467
	struct sched_group *sg;
3468
	int i = task_cpu(p);
3469

3470 3471
	if (idle_cpu(target))
		return target;
3472 3473

	/*
3474
	 * If the prevous cpu is cache affine and idle, don't be stupid.
3475
	 */
3476 3477
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
3478 3479

	/*
3480
	 * Otherwise, iterate the domains and find an elegible idle cpu.
3481
	 */
3482
	sd = rcu_dereference(per_cpu(sd_llc, target));
3483
	for_each_lower_domain(sd) {
3484 3485 3486 3487 3488 3489 3490
		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)) {
3491
				if (i == target || !idle_cpu(i))
3492 3493
					goto next;
			}
3494

3495 3496 3497 3498 3499 3500 3501 3502
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
3503 3504 3505
	return target;
}

3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516
/*
 * 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.
 */
3517
static int
3518
select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
3519
{
3520
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
3521 3522 3523
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
	int new_cpu = cpu;
3524
	int want_affine = 0;
3525
	int sync = wake_flags & WF_SYNC;
3526

3527
	if (p->nr_cpus_allowed == 1)
3528 3529
		return prev_cpu;

3530
	if (sd_flag & SD_BALANCE_WAKE) {
3531
		if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
3532 3533 3534
			want_affine = 1;
		new_cpu = prev_cpu;
	}
3535

3536
	rcu_read_lock();
3537
	for_each_domain(cpu, tmp) {
3538 3539 3540
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

3541
		/*
3542 3543
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
3544
		 */
3545 3546 3547
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
3548
			break;
3549
		}
3550

3551
		if (tmp->flags & sd_flag)
3552 3553 3554
			sd = tmp;
	}

3555
	if (affine_sd) {
3556
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
3557 3558 3559 3560
			prev_cpu = cpu;

		new_cpu = select_idle_sibling(p, prev_cpu);
		goto unlock;
3561
	}
3562

3563
	while (sd) {
3564
		int load_idx = sd->forkexec_idx;
3565
		struct sched_group *group;
3566
		int weight;
3567

3568
		if (!(sd->flags & sd_flag)) {
3569 3570 3571
			sd = sd->child;
			continue;
		}
3572

3573 3574
		if (sd_flag & SD_BALANCE_WAKE)
			load_idx = sd->wake_idx;
3575

3576
		group = find_idlest_group(sd, p, cpu, load_idx);
3577 3578 3579 3580
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
3581

3582
		new_cpu = find_idlest_cpu(group, p, cpu);
3583 3584 3585 3586
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
3587
		}
3588 3589 3590

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
3591
		weight = sd->span_weight;
3592 3593
		sd = NULL;
		for_each_domain(cpu, tmp) {
3594
			if (weight <= tmp->span_weight)
3595
				break;
3596
			if (tmp->flags & sd_flag)
3597 3598 3599
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
3600
	}
3601 3602
unlock:
	rcu_read_unlock();
3603

3604
	return new_cpu;
3605
}
3606 3607 3608 3609 3610 3611 3612 3613 3614 3615

/*
 * 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)
{
3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626
	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);
3627 3628
		atomic_long_add(se->avg.load_avg_contrib,
						&cfs_rq->removed_load);
3629
	}
3630
}
3631 3632
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
3633 3634
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
3635 3636 3637 3638
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
3639 3640
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
3641 3642 3643 3644 3645 3646 3647 3648 3649
	 *
	 * 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.
3650
	 */
3651
	return calc_delta_fair(gran, se);
3652 3653
}

3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675
/*
 * 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
3676
	gran = wakeup_gran(curr, se);
3677 3678 3679 3680 3681 3682
	if (vdiff > gran)
		return 1;

	return 0;
}

3683 3684
static void set_last_buddy(struct sched_entity *se)
{
3685 3686 3687 3688 3689
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
3690 3691 3692 3693
}

static void set_next_buddy(struct sched_entity *se)
{
3694 3695 3696 3697 3698
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
3699 3700
}

3701 3702
static void set_skip_buddy(struct sched_entity *se)
{
3703 3704
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
3705 3706
}

3707 3708 3709
/*
 * Preempt the current task with a newly woken task if needed:
 */
3710
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
3711 3712
{
	struct task_struct *curr = rq->curr;
3713
	struct sched_entity *se = &curr->se, *pse = &p->se;
3714
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
3715
	int scale = cfs_rq->nr_running >= sched_nr_latency;
3716
	int next_buddy_marked = 0;
3717

I
Ingo Molnar 已提交
3718 3719 3720
	if (unlikely(se == pse))
		return;

3721
	/*
3722
	 * This is possible from callers such as move_task(), in which we
3723 3724 3725 3726 3727 3728 3729
	 * 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;

3730
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
3731
		set_next_buddy(pse);
3732 3733
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
3734

3735 3736 3737
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
3738 3739 3740 3741 3742 3743
	 *
	 * 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.
3744 3745 3746 3747
	 */
	if (test_tsk_need_resched(curr))
		return;

3748 3749 3750 3751 3752
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

3753
	/*
3754 3755
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
3756
	 */
3757
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
3758
		return;
3759

3760
	find_matching_se(&se, &pse);
3761
	update_curr(cfs_rq_of(se));
3762
	BUG_ON(!pse);
3763 3764 3765 3766 3767 3768 3769
	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);
3770
		goto preempt;
3771
	}
3772

3773
	return;
3774

3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790
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);
3791 3792
}

3793
static struct task_struct *pick_next_task_fair(struct rq *rq)
3794
{
P
Peter Zijlstra 已提交
3795
	struct task_struct *p;
3796 3797 3798
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

3799
	if (!cfs_rq->nr_running)
3800 3801 3802
		return NULL;

	do {
3803
		se = pick_next_entity(cfs_rq);
3804
		set_next_entity(cfs_rq, se);
3805 3806 3807
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
3808
	p = task_of(se);
3809 3810
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
3811 3812

	return p;
3813 3814 3815 3816 3817
}

/*
 * Account for a descheduled task:
 */
3818
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
3819 3820 3821 3822 3823 3824
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
3825
		put_prev_entity(cfs_rq, se);
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
/*
 * 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);
3854 3855 3856 3857 3858 3859
		/*
		 * 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;
3860 3861 3862 3863 3864
	}

	set_skip_buddy(se);
}

3865 3866 3867 3868
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

3869 3870
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
3871 3872 3873 3874 3875 3876 3877 3878 3879 3880
		return false;

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

	yield_task_fair(rq);

	return true;
}

3881
#ifdef CONFIG_SMP
3882
/**************************************************
P
Peter Zijlstra 已提交
3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 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 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996 3997 3998
 * 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.]
 */ 
3999

4000 4001
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

4002
#define LBF_ALL_PINNED	0x01
4003
#define LBF_NEED_BREAK	0x02
4004 4005
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
4006 4007 4008 4009 4010

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
4011
	int			src_cpu;
4012 4013 4014 4015

	int			dst_cpu;
	struct rq		*dst_rq;

4016 4017
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
4018
	enum cpu_idle_type	idle;
4019
	long			imbalance;
4020 4021 4022
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

4023
	unsigned int		flags;
4024 4025 4026 4027

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
4028 4029
};

4030
/*
4031
 * move_task - move a task from one runqueue to another runqueue.
4032 4033
 * Both runqueues must be locked.
 */
4034
static void move_task(struct task_struct *p, struct lb_env *env)
4035
{
4036 4037 4038 4039
	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);
4040 4041
}

4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073
/*
 * 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;
}

4074 4075 4076 4077
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
4078
int can_migrate_task(struct task_struct *p, struct lb_env *env)
4079 4080 4081 4082
{
	int tsk_cache_hot = 0;
	/*
	 * We do not migrate tasks that are:
4083
	 * 1) throttled_lb_pair, or
4084
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
4085 4086
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
4087
	 */
4088 4089 4090
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

4091
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
4092
		int cpu;
4093

4094
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
4095

4096 4097
		env->flags |= LBF_SOME_PINNED;

4098 4099 4100 4101 4102 4103 4104 4105
		/*
		 * 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.
		 */
4106
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
4107 4108
			return 0;

4109 4110 4111
		/* 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))) {
4112
				env->flags |= LBF_DST_PINNED;
4113 4114 4115
				env->new_dst_cpu = cpu;
				break;
			}
4116
		}
4117

4118 4119
		return 0;
	}
4120 4121

	/* Record that we found atleast one task that could run on dst_cpu */
4122
	env->flags &= ~LBF_ALL_PINNED;
4123

4124
	if (task_running(env->src_rq, p)) {
4125
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
4126 4127 4128 4129 4130 4131 4132 4133 4134
		return 0;
	}

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

4135
	tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd);
4136
	if (!tsk_cache_hot ||
4137
		env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
Z
Zhang Hang 已提交
4138

4139
		if (tsk_cache_hot) {
4140
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
4141
			schedstat_inc(p, se.statistics.nr_forced_migrations);
4142
		}
Z
Zhang Hang 已提交
4143

4144 4145 4146
		return 1;
	}

Z
Zhang Hang 已提交
4147 4148
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
4149 4150
}

4151 4152 4153 4154 4155 4156 4157
/*
 * 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.
 */
4158
static int move_one_task(struct lb_env *env)
4159 4160 4161
{
	struct task_struct *p, *n;

4162 4163 4164
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
4165

4166 4167 4168 4169 4170 4171 4172 4173
		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;
4174 4175 4176 4177
	}
	return 0;
}

4178 4179
static unsigned long task_h_load(struct task_struct *p);

4180 4181
static const unsigned int sched_nr_migrate_break = 32;

4182
/*
4183
 * move_tasks tries to move up to imbalance weighted load from busiest to
4184 4185 4186 4187 4188 4189
 * 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)
4190
{
4191 4192
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
4193 4194
	unsigned long load;
	int pulled = 0;
4195

4196
	if (env->imbalance <= 0)
4197
		return 0;
4198

4199 4200
	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
4201

4202 4203
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
4204
		if (env->loop > env->loop_max)
4205
			break;
4206 4207

		/* take a breather every nr_migrate tasks */
4208
		if (env->loop > env->loop_break) {
4209
			env->loop_break += sched_nr_migrate_break;
4210
			env->flags |= LBF_NEED_BREAK;
4211
			break;
4212
		}
4213

4214
		if (!can_migrate_task(p, env))
4215 4216 4217
			goto next;

		load = task_h_load(p);
4218

4219
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
4220 4221
			goto next;

4222
		if ((load / 2) > env->imbalance)
4223
			goto next;
4224

4225
		move_task(p, env);
4226
		pulled++;
4227
		env->imbalance -= load;
4228 4229

#ifdef CONFIG_PREEMPT
4230 4231 4232 4233 4234
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
		 * kernels will stop after the first task is pulled to minimize
		 * the critical section.
		 */
4235
		if (env->idle == CPU_NEWLY_IDLE)
4236
			break;
4237 4238
#endif

4239 4240 4241 4242
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
4243
		if (env->imbalance <= 0)
4244
			break;
4245 4246 4247

		continue;
next:
4248
		list_move_tail(&p->se.group_node, tasks);
4249
	}
4250

4251
	/*
4252 4253 4254
	 * 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().
4255
	 */
4256
	schedstat_add(env->sd, lb_gained[env->idle], pulled);
4257

4258
	return pulled;
4259 4260
}

P
Peter Zijlstra 已提交
4261
#ifdef CONFIG_FAIR_GROUP_SCHED
4262 4263 4264
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
4265
static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
4266
{
4267 4268
	struct sched_entity *se = tg->se[cpu];
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
4269

4270 4271 4272
	/* throttled entities do not contribute to load */
	if (throttled_hierarchy(cfs_rq))
		return;
4273

4274
	update_cfs_rq_blocked_load(cfs_rq, 1);
4275

4276 4277 4278 4279 4280 4281 4282 4283 4284 4285 4286 4287 4288 4289
	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 {
4290
		struct rq *rq = rq_of(cfs_rq);
4291 4292
		update_rq_runnable_avg(rq, rq->nr_running);
	}
4293 4294
}

4295
static void update_blocked_averages(int cpu)
4296 4297
{
	struct rq *rq = cpu_rq(cpu);
4298 4299
	struct cfs_rq *cfs_rq;
	unsigned long flags;
4300

4301 4302
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
4303 4304 4305 4306
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
4307
	for_each_leaf_cfs_rq(rq, cfs_rq) {
4308 4309 4310 4311 4312 4313
		/*
		 * 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);
4314
	}
4315 4316

	raw_spin_unlock_irqrestore(&rq->lock, flags);
4317 4318
}

4319
/*
4320
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
4321 4322 4323
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
4324
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
4325
{
4326 4327
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
4328
	unsigned long now = jiffies;
4329
	unsigned long load;
4330

4331
	if (cfs_rq->last_h_load_update == now)
4332 4333
		return;

4334 4335 4336 4337 4338 4339 4340
	cfs_rq->h_load_next = NULL;
	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
		cfs_rq->h_load_next = se;
		if (cfs_rq->last_h_load_update == now)
			break;
	}
4341

4342
	if (!se) {
4343
		cfs_rq->h_load = cfs_rq->runnable_load_avg;
4344 4345 4346 4347 4348 4349 4350 4351 4352 4353 4354
		cfs_rq->last_h_load_update = now;
	}

	while ((se = cfs_rq->h_load_next) != NULL) {
		load = cfs_rq->h_load;
		load = div64_ul(load * se->avg.load_avg_contrib,
				cfs_rq->runnable_load_avg + 1);
		cfs_rq = group_cfs_rq(se);
		cfs_rq->h_load = load;
		cfs_rq->last_h_load_update = now;
	}
4355 4356
}

4357
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
4358
{
4359
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
4360

4361
	update_cfs_rq_h_load(cfs_rq);
4362 4363
	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
4364 4365
}
#else
4366
static inline void update_blocked_averages(int cpu)
4367 4368 4369
{
}

4370
static unsigned long task_h_load(struct task_struct *p)
4371
{
4372
	return p->se.avg.load_avg_contrib;
4373
}
P
Peter Zijlstra 已提交
4374
#endif
4375 4376 4377 4378 4379 4380 4381 4382 4383

/********** Helpers for find_busiest_group ************************/
/*
 * sg_lb_stats - stats of a sched_group required for load_balancing
 */
struct sg_lb_stats {
	unsigned long avg_load; /*Avg load across the CPUs of the group */
	unsigned long group_load; /* Total load over the CPUs of the group */
	unsigned long sum_weighted_load; /* Weighted load of group's tasks */
J
Joonsoo Kim 已提交
4384
	unsigned long load_per_task;
4385
	unsigned long group_power;
4386 4387 4388 4389
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int group_capacity;
	unsigned int idle_cpus;
	unsigned int group_weight;
4390
	int group_imb; /* Is there an imbalance in the group ? */
4391
	int group_has_capacity; /* Is there extra capacity in the group? */
4392 4393
};

J
Joonsoo Kim 已提交
4394 4395 4396 4397 4398 4399 4400 4401 4402 4403 4404 4405
/*
 * sd_lb_stats - Structure to store the statistics of a sched_domain
 *		 during load balancing.
 */
struct sd_lb_stats {
	struct sched_group *busiest;	/* Busiest group in this sd */
	struct sched_group *local;	/* Local group in this sd */
	unsigned long total_load;	/* Total load of all groups in sd */
	unsigned long total_pwr;	/* Total power of all groups in sd */
	unsigned long avg_load;	/* Average load across all groups in sd */

	struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
4406
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
4407 4408
};

4409 4410 4411 4412 4413 4414 4415 4416 4417 4418 4419 4420 4421 4422 4423 4424 4425 4426 4427
static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
{
	/*
	 * Skimp on the clearing to avoid duplicate work. We can avoid clearing
	 * local_stat because update_sg_lb_stats() does a full clear/assignment.
	 * We must however clear busiest_stat::avg_load because
	 * update_sd_pick_busiest() reads this before assignment.
	 */
	*sds = (struct sd_lb_stats){
		.busiest = NULL,
		.local = NULL,
		.total_load = 0UL,
		.total_pwr = 0UL,
		.busiest_stat = {
			.avg_load = 0UL,
		},
	};
}

4428 4429 4430 4431
/**
 * 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.
4432 4433
 *
 * Return: The load index.
4434 4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445 4446 4447 4448 4449 4450 4451 4452 4453 4454 4455
 */
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;
}

4456
static unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
4457
{
4458
	return SCHED_POWER_SCALE;
4459 4460 4461 4462 4463 4464 4465
}

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

4466
static unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
4467
{
4468
	unsigned long weight = sd->span_weight;
4469 4470 4471 4472 4473 4474 4475 4476 4477 4478 4479 4480
	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);
}

4481
static unsigned long scale_rt_power(int cpu)
4482 4483
{
	struct rq *rq = cpu_rq(cpu);
4484
	u64 total, available, age_stamp, avg;
4485

4486 4487 4488 4489 4490 4491 4492
	/*
	 * 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);

4493
	total = sched_avg_period() + (rq_clock(rq) - age_stamp);
4494

4495
	if (unlikely(total < avg)) {
4496 4497 4498
		/* Ensures that power won't end up being negative */
		available = 0;
	} else {
4499
		available = total - avg;
4500
	}
4501

4502 4503
	if (unlikely((s64)total < SCHED_POWER_SCALE))
		total = SCHED_POWER_SCALE;
4504

4505
	total >>= SCHED_POWER_SHIFT;
4506 4507 4508 4509 4510 4511

	return div_u64(available, total);
}

static void update_cpu_power(struct sched_domain *sd, int cpu)
{
4512
	unsigned long weight = sd->span_weight;
4513
	unsigned long power = SCHED_POWER_SCALE;
4514 4515 4516 4517 4518 4519 4520 4521
	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);

4522
		power >>= SCHED_POWER_SHIFT;
4523 4524
	}

4525
	sdg->sgp->power_orig = power;
4526 4527 4528 4529 4530 4531

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

4532
	power >>= SCHED_POWER_SHIFT;
4533

4534
	power *= scale_rt_power(cpu);
4535
	power >>= SCHED_POWER_SHIFT;
4536 4537 4538 4539

	if (!power)
		power = 1;

4540
	cpu_rq(cpu)->cpu_power = power;
4541
	sdg->sgp->power = power;
4542 4543
}

4544
void update_group_power(struct sched_domain *sd, int cpu)
4545 4546 4547
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
4548
	unsigned long power, power_orig;
4549 4550 4551 4552 4553
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
	sdg->sgp->next_update = jiffies + interval;
4554 4555 4556 4557 4558 4559

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

4560
	power_orig = power = 0;
4561

P
Peter Zijlstra 已提交
4562 4563 4564 4565 4566 4567
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

4568 4569 4570 4571 4572 4573
		for_each_cpu(cpu, sched_group_cpus(sdg)) {
			struct sched_group *sg = cpu_rq(cpu)->sd->groups;

			power_orig += sg->sgp->power_orig;
			power += sg->sgp->power;
		}
P
Peter Zijlstra 已提交
4574 4575 4576 4577 4578 4579 4580 4581
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
4582
			power_orig += group->sgp->power_orig;
P
Peter Zijlstra 已提交
4583 4584 4585 4586
			power += group->sgp->power;
			group = group->next;
		} while (group != child->groups);
	}
4587

4588 4589
	sdg->sgp->power_orig = power_orig;
	sdg->sgp->power = power;
4590 4591
}

4592 4593 4594 4595 4596 4597 4598 4599 4600 4601 4602
/*
 * 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)
{
	/*
4603
	 * Only siblings can have significantly less than SCHED_POWER_SCALE
4604
	 */
P
Peter Zijlstra 已提交
4605
	if (!(sd->flags & SD_SHARE_CPUPOWER))
4606 4607 4608 4609 4610
		return 0;

	/*
	 * If ~90% of the cpu_power is still there, we're good.
	 */
4611
	if (group->sgp->power * 32 > group->sgp->power_orig * 29)
4612 4613 4614 4615 4616
		return 1;

	return 0;
}

4617 4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632
/*
 * Group imbalance indicates (and tries to solve) the problem where balancing
 * groups is inadequate due to tsk_cpus_allowed() constraints.
 *
 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a
 * cpumask covering 1 cpu of the first group and 3 cpus of the second group.
 * Something like:
 *
 * 	{ 0 1 2 3 } { 4 5 6 7 }
 * 	        *     * * *
 *
 * If we were to balance group-wise we'd place two tasks in the first group and
 * two tasks in the second group. Clearly this is undesired as it will overload
 * cpu 3 and leave one of the cpus in the second group unused.
 *
 * The current solution to this issue is detecting the skew in the first group
4633 4634
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
4635 4636 4637
 *
 * When this is so detected; this group becomes a candidate for busiest; see
 * update_sd_pick_busiest(). And calculcate_imbalance() and
4638
 * find_busiest_group() avoid some of the usual balance conditions to allow it
4639 4640 4641 4642 4643 4644 4645
 * to create an effective group imbalance.
 *
 * This is a somewhat tricky proposition since the next run might not find the
 * group imbalance and decide the groups need to be balanced again. A most
 * subtle and fragile situation.
 */

4646
static inline int sg_imbalanced(struct sched_group *group)
4647
{
4648
	return group->sgp->imbalance;
4649 4650
}

4651 4652 4653
/*
 * Compute the group capacity.
 *
4654 4655 4656
 * Avoid the issue where N*frac(smt_power) >= 1 creates 'phantom' cores by
 * first dividing out the smt factor and computing the actual number of cores
 * and limit power unit capacity with that.
4657 4658 4659
 */
static inline int sg_capacity(struct lb_env *env, struct sched_group *group)
{
4660 4661 4662 4663 4664 4665
	unsigned int capacity, smt, cpus;
	unsigned int power, power_orig;

	power = group->sgp->power;
	power_orig = group->sgp->power_orig;
	cpus = group->group_weight;
4666

4667 4668 4669
	/* smt := ceil(cpus / power), assumes: 1 < smt_power < 2 */
	smt = DIV_ROUND_UP(SCHED_POWER_SCALE * cpus, power_orig);
	capacity = cpus / smt; /* cores */
4670

4671
	capacity = min_t(unsigned, capacity, DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE));
4672 4673 4674 4675 4676 4677
	if (!capacity)
		capacity = fix_small_capacity(env->sd, group);

	return capacity;
}

4678 4679
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
4680
 * @env: The load balancing environment.
4681 4682 4683 4684 4685
 * @group: sched_group whose statistics are to be updated.
 * @load_idx: Load index of sched_domain of this_cpu for load calc.
 * @local_group: Does group contain this_cpu.
 * @sgs: variable to hold the statistics for this group.
 */
4686 4687
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
4688
			int local_group, struct sg_lb_stats *sgs)
4689
{
4690 4691
	unsigned long nr_running;
	unsigned long load;
4692
	int i;
4693

4694 4695
	memset(sgs, 0, sizeof(*sgs));

4696
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
4697 4698
		struct rq *rq = cpu_rq(i);

4699 4700
		nr_running = rq->nr_running;

4701
		/* Bias balancing toward cpus of our domain */
4702
		if (local_group)
4703
			load = target_load(i, load_idx);
4704
		else
4705 4706 4707
			load = source_load(i, load_idx);

		sgs->group_load += load;
4708
		sgs->sum_nr_running += nr_running;
4709
		sgs->sum_weighted_load += weighted_cpuload(i);
4710 4711
		if (idle_cpu(i))
			sgs->idle_cpus++;
4712 4713 4714
	}

	/* Adjust by relative CPU power of the group */
4715 4716
	sgs->group_power = group->sgp->power;
	sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / sgs->group_power;
4717

4718
	if (sgs->sum_nr_running)
4719
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
4720

4721
	sgs->group_weight = group->group_weight;
4722

4723 4724 4725
	sgs->group_imb = sg_imbalanced(group);
	sgs->group_capacity = sg_capacity(env, group);

4726 4727
	if (sgs->group_capacity > sgs->sum_nr_running)
		sgs->group_has_capacity = 1;
4728 4729
}

4730 4731
/**
 * update_sd_pick_busiest - return 1 on busiest group
4732
 * @env: The load balancing environment.
4733 4734
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
4735
 * @sgs: sched_group statistics
4736 4737 4738
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
4739 4740 4741
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
4742
 */
4743
static bool update_sd_pick_busiest(struct lb_env *env,
4744 4745
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
4746
				   struct sg_lb_stats *sgs)
4747
{
J
Joonsoo Kim 已提交
4748
	if (sgs->avg_load <= sds->busiest_stat.avg_load)
4749 4750 4751 4752 4753 4754 4755 4756 4757 4758 4759 4760 4761
		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.
	 */
4762 4763
	if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
	    env->dst_cpu < group_first_cpu(sg)) {
4764 4765 4766 4767 4768 4769 4770 4771 4772 4773
		if (!sds->busiest)
			return true;

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

	return false;
}

4774
/**
4775
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
4776
 * @env: The load balancing environment.
4777 4778 4779
 * @balance: Should we balance.
 * @sds: variable to hold the statistics for this sched_domain.
 */
4780
static inline void update_sd_lb_stats(struct lb_env *env,
4781
					struct sd_lb_stats *sds)
4782
{
4783 4784
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
4785
	struct sg_lb_stats tmp_sgs;
4786 4787 4788 4789 4790
	int load_idx, prefer_sibling = 0;

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

4791
	load_idx = get_sd_load_idx(env->sd, env->idle);
4792 4793

	do {
J
Joonsoo Kim 已提交
4794
		struct sg_lb_stats *sgs = &tmp_sgs;
4795 4796
		int local_group;

4797
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
4798 4799 4800
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
4801 4802 4803 4804

			if (env->idle != CPU_NEWLY_IDLE ||
			    time_after_eq(jiffies, sg->sgp->next_update))
				update_group_power(env->sd, env->dst_cpu);
J
Joonsoo Kim 已提交
4805
		}
4806

J
Joonsoo Kim 已提交
4807
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs);
4808

4809 4810 4811
		if (local_group)
			goto next_group;

4812 4813
		/*
		 * In case the child domain prefers tasks go to siblings
4814
		 * first, lower the sg capacity to one so that we'll try
4815 4816 4817 4818 4819 4820
		 * 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).
4821
		 */
4822 4823
		if (prefer_sibling && sds->local &&
		    sds->local_stat.group_has_capacity)
4824
			sgs->group_capacity = min(sgs->group_capacity, 1U);
4825

4826
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
4827
			sds->busiest = sg;
J
Joonsoo Kim 已提交
4828
			sds->busiest_stat = *sgs;
4829 4830
		}

4831 4832 4833 4834 4835
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
		sds->total_pwr += sgs->group_power;

4836
		sg = sg->next;
4837
	} while (sg != env->sd->groups);
4838 4839 4840 4841 4842 4843 4844 4845 4846 4847 4848 4849 4850 4851 4852 4853 4854 4855 4856
}

/**
 * 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.
 *
4857
 * Return: 1 when packing is required and a task should be moved to
4858 4859
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
4860
 * @env: The load balancing environment.
4861 4862
 * @sds: Statistics of the sched_domain which is to be packed
 */
4863
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
4864 4865 4866
{
	int busiest_cpu;

4867
	if (!(env->sd->flags & SD_ASYM_PACKING))
4868 4869 4870 4871 4872 4873
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
4874
	if (env->dst_cpu > busiest_cpu)
4875 4876
		return 0;

4877
	env->imbalance = DIV_ROUND_CLOSEST(
4878 4879
		sds->busiest_stat.avg_load * sds->busiest_stat.group_power,
		SCHED_POWER_SCALE);
4880

4881
	return 1;
4882 4883 4884 4885 4886 4887
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
4888
 * @env: The load balancing environment.
4889 4890
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
4891 4892
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
4893 4894 4895
{
	unsigned long tmp, pwr_now = 0, pwr_move = 0;
	unsigned int imbn = 2;
4896
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
4897
	struct sg_lb_stats *local, *busiest;
4898

J
Joonsoo Kim 已提交
4899 4900
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
4901

J
Joonsoo Kim 已提交
4902 4903 4904 4905
	if (!local->sum_nr_running)
		local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
	else if (busiest->load_per_task > local->load_per_task)
		imbn = 1;
4906

J
Joonsoo Kim 已提交
4907 4908
	scaled_busy_load_per_task =
		(busiest->load_per_task * SCHED_POWER_SCALE) /
4909
		busiest->group_power;
J
Joonsoo Kim 已提交
4910

4911 4912
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
4913
		env->imbalance = busiest->load_per_task;
4914 4915 4916 4917 4918 4919 4920 4921 4922
		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.
	 */

4923
	pwr_now += busiest->group_power *
J
Joonsoo Kim 已提交
4924
			min(busiest->load_per_task, busiest->avg_load);
4925
	pwr_now += local->group_power *
J
Joonsoo Kim 已提交
4926
			min(local->load_per_task, local->avg_load);
4927
	pwr_now /= SCHED_POWER_SCALE;
4928 4929

	/* Amount of load we'd subtract */
J
Joonsoo Kim 已提交
4930
	tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
4931
		busiest->group_power;
J
Joonsoo Kim 已提交
4932
	if (busiest->avg_load > tmp) {
4933
		pwr_move += busiest->group_power *
J
Joonsoo Kim 已提交
4934 4935 4936
			    min(busiest->load_per_task,
				busiest->avg_load - tmp);
	}
4937 4938

	/* Amount of load we'd add */
4939
	if (busiest->avg_load * busiest->group_power <
J
Joonsoo Kim 已提交
4940
	    busiest->load_per_task * SCHED_POWER_SCALE) {
4941 4942
		tmp = (busiest->avg_load * busiest->group_power) /
		      local->group_power;
J
Joonsoo Kim 已提交
4943 4944
	} else {
		tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
4945
		      local->group_power;
J
Joonsoo Kim 已提交
4946
	}
4947 4948
	pwr_move += local->group_power *
		    min(local->load_per_task, local->avg_load + tmp);
4949
	pwr_move /= SCHED_POWER_SCALE;
4950 4951 4952

	/* Move if we gain throughput */
	if (pwr_move > pwr_now)
J
Joonsoo Kim 已提交
4953
		env->imbalance = busiest->load_per_task;
4954 4955 4956 4957 4958
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
4959
 * @env: load balance environment
4960 4961
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
4962
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
4963
{
4964
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
4965 4966 4967 4968
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
4969

J
Joonsoo Kim 已提交
4970
	if (busiest->group_imb) {
4971 4972 4973 4974
		/*
		 * In the group_imb case we cannot rely on group-wide averages
		 * to ensure cpu-load equilibrium, look at wider averages. XXX
		 */
J
Joonsoo Kim 已提交
4975 4976
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
4977 4978
	}

4979 4980 4981 4982 4983
	/*
	 * 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..)
	 */
4984 4985
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
4986 4987
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
4988 4989
	}

J
Joonsoo Kim 已提交
4990
	if (!busiest->group_imb) {
4991 4992
		/*
		 * Don't want to pull so many tasks that a group would go idle.
4993 4994
		 * Except of course for the group_imb case, since then we might
		 * have to drop below capacity to reach cpu-load equilibrium.
4995
		 */
J
Joonsoo Kim 已提交
4996 4997
		load_above_capacity =
			(busiest->sum_nr_running - busiest->group_capacity);
4998

4999
		load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
5000
		load_above_capacity /= busiest->group_power;
5001 5002 5003 5004 5005 5006 5007 5008 5009 5010
	}

	/*
	 * 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.
	 */
5011
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
5012 5013

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
5014
	env->imbalance = min(
5015 5016
		max_pull * busiest->group_power,
		(sds->avg_load - local->avg_load) * local->group_power
J
Joonsoo Kim 已提交
5017
	) / SCHED_POWER_SCALE;
5018 5019 5020

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
5021
	 * there is no guarantee that any tasks will be moved so we'll have
5022 5023 5024
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
5025
	if (env->imbalance < busiest->load_per_task)
5026
		return fix_small_imbalance(env, sds);
5027
}
5028

5029 5030 5031 5032 5033 5034 5035 5036 5037 5038 5039 5040
/******* 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.
 *
5041
 * @env: The load balancing environment.
5042
 *
5043
 * Return:	- The busiest group if imbalance exists.
5044 5045 5046 5047
 *		- If no imbalance and user has opted for power-savings balance,
 *		   return the least loaded group whose CPUs can be
 *		   put to idle by rebalancing its tasks onto our group.
 */
J
Joonsoo Kim 已提交
5048
static struct sched_group *find_busiest_group(struct lb_env *env)
5049
{
J
Joonsoo Kim 已提交
5050
	struct sg_lb_stats *local, *busiest;
5051 5052
	struct sd_lb_stats sds;

5053
	init_sd_lb_stats(&sds);
5054 5055 5056 5057 5058

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
5059
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
5060 5061
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
5062

5063 5064
	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(env, &sds))
5065 5066
		return sds.busiest;

5067
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
5068
	if (!sds.busiest || busiest->sum_nr_running == 0)
5069 5070
		goto out_balanced;

5071
	sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
5072

P
Peter Zijlstra 已提交
5073 5074
	/*
	 * If the busiest group is imbalanced the below checks don't
5075
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
5076 5077
	 * isn't true due to cpus_allowed constraints and the like.
	 */
J
Joonsoo Kim 已提交
5078
	if (busiest->group_imb)
P
Peter Zijlstra 已提交
5079 5080
		goto force_balance;

5081
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
J
Joonsoo Kim 已提交
5082 5083
	if (env->idle == CPU_NEWLY_IDLE && local->group_has_capacity &&
	    !busiest->group_has_capacity)
5084 5085
		goto force_balance;

5086 5087 5088 5089
	/*
	 * If the local group is more busy than the selected busiest group
	 * don't try and pull any tasks.
	 */
J
Joonsoo Kim 已提交
5090
	if (local->avg_load >= busiest->avg_load)
5091 5092
		goto out_balanced;

5093 5094 5095 5096
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
5097
	if (local->avg_load >= sds.avg_load)
5098 5099
		goto out_balanced;

5100
	if (env->idle == CPU_IDLE) {
5101 5102 5103 5104 5105 5106
		/*
		 * This cpu is idle. If the busiest group load doesn't
		 * have more tasks than the number of available cpu's and
		 * there is no imbalance between this and busiest group
		 * wrt to idle cpu's, it is balanced.
		 */
J
Joonsoo Kim 已提交
5107 5108
		if ((local->idle_cpus < busiest->idle_cpus) &&
		    busiest->sum_nr_running <= busiest->group_weight)
5109
			goto out_balanced;
5110 5111 5112 5113 5114
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
5115 5116
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
5117
			goto out_balanced;
5118
	}
5119

5120
force_balance:
5121
	/* Looks like there is an imbalance. Compute it */
5122
	calculate_imbalance(env, &sds);
5123 5124 5125
	return sds.busiest;

out_balanced:
5126
	env->imbalance = 0;
5127 5128 5129 5130 5131 5132
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
5133
static struct rq *find_busiest_queue(struct lb_env *env,
5134
				     struct sched_group *group)
5135 5136
{
	struct rq *busiest = NULL, *rq;
5137
	unsigned long busiest_load = 0, busiest_power = 1;
5138 5139
	int i;

5140
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
5141
		unsigned long power = power_of(i);
5142 5143
		unsigned long capacity = DIV_ROUND_CLOSEST(power,
							   SCHED_POWER_SCALE);
5144 5145
		unsigned long wl;

5146
		if (!capacity)
5147
			capacity = fix_small_capacity(env->sd, group);
5148

5149
		rq = cpu_rq(i);
5150
		wl = weighted_cpuload(i);
5151

5152 5153 5154 5155
		/*
		 * When comparing with imbalance, use weighted_cpuload()
		 * which is not scaled with the cpu power.
		 */
5156
		if (capacity && rq->nr_running == 1 && wl > env->imbalance)
5157 5158
			continue;

5159 5160 5161 5162 5163
		/*
		 * 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.
5164 5165 5166 5167 5168
		 *
		 * Thus we're looking for max(wl_i / power_i), crosswise
		 * multiplication to rid ourselves of the division works out
		 * to: wl_i * power_j > wl_j * power_i;  where j is our
		 * previous maximum.
5169
		 */
5170 5171 5172
		if (wl * busiest_power > busiest_load * power) {
			busiest_load = wl;
			busiest_power = power;
5173 5174 5175 5176 5177 5178 5179 5180 5181 5182 5183 5184 5185 5186
			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. */
5187
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
5188

5189
static int need_active_balance(struct lb_env *env)
5190
{
5191 5192 5193
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
5194 5195 5196 5197 5198 5199

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
5200
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
5201
			return 1;
5202 5203 5204 5205 5206
	}

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

5207 5208
static int active_load_balance_cpu_stop(void *data);

5209 5210 5211 5212 5213 5214 5215 5216 5217 5218 5219 5220 5221 5222 5223 5224 5225 5226 5227 5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238 5239
static int should_we_balance(struct lb_env *env)
{
	struct sched_group *sg = env->sd->groups;
	struct cpumask *sg_cpus, *sg_mask;
	int cpu, balance_cpu = -1;

	/*
	 * In the newly idle case, we will allow all the cpu's
	 * to do the newly idle load balance.
	 */
	if (env->idle == CPU_NEWLY_IDLE)
		return 1;

	sg_cpus = sched_group_cpus(sg);
	sg_mask = sched_group_mask(sg);
	/* Try to find first idle cpu */
	for_each_cpu_and(cpu, sg_cpus, env->cpus) {
		if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu))
			continue;

		balance_cpu = cpu;
		break;
	}

	if (balance_cpu == -1)
		balance_cpu = group_balance_cpu(sg);

	/*
	 * First idle cpu or the first cpu(busiest) in this sched group
	 * is eligible for doing load balancing at this and above domains.
	 */
5240
	return balance_cpu == env->dst_cpu;
5241 5242
}

5243 5244 5245 5246 5247 5248
/*
 * 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,
5249
			int *continue_balancing)
5250
{
5251
	int ld_moved, cur_ld_moved, active_balance = 0;
5252
	struct sched_domain *sd_parent = sd->parent;
5253 5254 5255
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
5256
	struct cpumask *cpus = __get_cpu_var(load_balance_mask);
5257

5258 5259
	struct lb_env env = {
		.sd		= sd,
5260 5261
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
5262
		.dst_grpmask    = sched_group_cpus(sd->groups),
5263
		.idle		= idle,
5264
		.loop_break	= sched_nr_migrate_break,
5265
		.cpus		= cpus,
5266 5267
	};

5268 5269 5270 5271
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
5272
	if (idle == CPU_NEWLY_IDLE)
5273 5274
		env.dst_grpmask = NULL;

5275 5276 5277 5278 5279
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
5280 5281
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
5282
		goto out_balanced;
5283
	}
5284

5285
	group = find_busiest_group(&env);
5286 5287 5288 5289 5290
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

5291
	busiest = find_busiest_queue(&env, group);
5292 5293 5294 5295 5296
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

5297
	BUG_ON(busiest == env.dst_rq);
5298

5299
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
5300 5301 5302 5303 5304 5305 5306 5307 5308

	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.
		 */
5309
		env.flags |= LBF_ALL_PINNED;
5310 5311 5312
		env.src_cpu   = busiest->cpu;
		env.src_rq    = busiest;
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
5313

5314
more_balance:
5315
		local_irq_save(flags);
5316
		double_rq_lock(env.dst_rq, busiest);
5317 5318 5319 5320 5321 5322 5323

		/*
		 * 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;
5324
		double_rq_unlock(env.dst_rq, busiest);
5325 5326 5327 5328 5329
		local_irq_restore(flags);

		/*
		 * some other cpu did the load balance for us.
		 */
5330 5331 5332
		if (cur_ld_moved && env.dst_cpu != smp_processor_id())
			resched_cpu(env.dst_cpu);

5333 5334 5335 5336 5337
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

5338 5339 5340 5341 5342 5343 5344 5345 5346 5347 5348 5349 5350 5351 5352 5353 5354 5355 5356
		/*
		 * 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.
		 */
5357
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
5358

5359 5360 5361
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

5362
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
5363
			env.dst_cpu	 = env.new_dst_cpu;
5364
			env.flags	&= ~LBF_DST_PINNED;
5365 5366
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
5367

5368 5369 5370 5371 5372 5373
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
5374

5375 5376 5377 5378 5379 5380 5381 5382 5383 5384 5385 5386
		/*
		 * We failed to reach balance because of affinity.
		 */
		if (sd_parent) {
			int *group_imbalance = &sd_parent->groups->sgp->imbalance;

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

5387
		/* All tasks on this runqueue were pinned by CPU affinity */
5388
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
5389
			cpumask_clear_cpu(cpu_of(busiest), cpus);
5390 5391 5392
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
5393
				goto redo;
5394
			}
5395 5396 5397 5398 5399 5400
			goto out_balanced;
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
5401 5402 5403 5404 5405 5406 5407 5408
		/*
		 * 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++;
5409

5410
		if (need_active_balance(&env)) {
5411 5412
			raw_spin_lock_irqsave(&busiest->lock, flags);

5413 5414 5415
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
5416 5417
			 */
			if (!cpumask_test_cpu(this_cpu,
5418
					tsk_cpus_allowed(busiest->curr))) {
5419 5420
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
5421
				env.flags |= LBF_ALL_PINNED;
5422 5423 5424
				goto out_one_pinned;
			}

5425 5426 5427 5428 5429
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
5430 5431 5432 5433 5434 5435
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
5436

5437
			if (active_balance) {
5438 5439 5440
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
5441
			}
5442 5443 5444 5445 5446 5447 5448 5449 5450 5451 5452 5453 5454 5455 5456 5457 5458 5459 5460 5461 5462 5463 5464 5465 5466 5467 5468 5469 5470 5471 5472 5473 5474

			/*
			 * 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 */
5475
	if (((env.flags & LBF_ALL_PINNED) &&
5476
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
5477 5478 5479
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

5480
	ld_moved = 0;
5481 5482 5483 5484 5485 5486 5487 5488
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.
 */
5489
void idle_balance(int this_cpu, struct rq *this_rq)
5490 5491 5492 5493
{
	struct sched_domain *sd;
	int pulled_task = 0;
	unsigned long next_balance = jiffies + HZ;
5494
	u64 curr_cost = 0;
5495

5496
	this_rq->idle_stamp = rq_clock(this_rq);
5497 5498 5499 5500

	if (this_rq->avg_idle < sysctl_sched_migration_cost)
		return;

5501 5502 5503 5504 5505
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

5506
	update_blocked_averages(this_cpu);
5507
	rcu_read_lock();
5508 5509
	for_each_domain(this_cpu, sd) {
		unsigned long interval;
5510
		int continue_balancing = 1;
5511
		u64 t0, domain_cost;
5512 5513 5514 5515

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

5516 5517 5518
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost)
			break;

5519
		if (sd->flags & SD_BALANCE_NEWIDLE) {
5520 5521
			t0 = sched_clock_cpu(this_cpu);

5522
			/* If we've pulled tasks over stop searching: */
5523
			pulled_task = load_balance(this_cpu, this_rq,
5524 5525
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
5526 5527 5528 5529 5530 5531

			domain_cost = sched_clock_cpu(this_cpu) - t0;
			if (domain_cost > sd->max_newidle_lb_cost)
				sd->max_newidle_lb_cost = domain_cost;

			curr_cost += domain_cost;
5532
		}
5533 5534 5535 5536

		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
5537 5538
		if (pulled_task) {
			this_rq->idle_stamp = 0;
5539
			break;
N
Nikhil Rao 已提交
5540
		}
5541
	}
5542
	rcu_read_unlock();
5543 5544 5545

	raw_spin_lock(&this_rq->lock);

5546 5547 5548 5549 5550 5551 5552
	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;
	}
5553 5554 5555

	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;
5556 5557 5558
}

/*
5559 5560 5561 5562
 * 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.
5563
 */
5564
static int active_load_balance_cpu_stop(void *data)
5565
{
5566 5567
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
5568
	int target_cpu = busiest_rq->push_cpu;
5569
	struct rq *target_rq = cpu_rq(target_cpu);
5570
	struct sched_domain *sd;
5571 5572 5573 5574 5575 5576 5577

	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;
5578 5579 5580

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
5581
		goto out_unlock;
5582 5583 5584 5585 5586 5587 5588 5589 5590 5591 5592 5593

	/*
	 * 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. */
5594
	rcu_read_lock();
5595 5596 5597 5598 5599 5600 5601
	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)) {
5602 5603
		struct lb_env env = {
			.sd		= sd,
5604 5605 5606 5607
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
5608 5609 5610
			.idle		= CPU_IDLE,
		};

5611 5612
		schedstat_inc(sd, alb_count);

5613
		if (move_one_task(&env))
5614 5615 5616 5617
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
5618
	rcu_read_unlock();
5619
	double_unlock_balance(busiest_rq, target_rq);
5620 5621 5622 5623
out_unlock:
	busiest_rq->active_balance = 0;
	raw_spin_unlock_irq(&busiest_rq->lock);
	return 0;
5624 5625
}

5626
#ifdef CONFIG_NO_HZ_COMMON
5627 5628 5629 5630 5631 5632
/*
 * 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.
 */
5633
static struct {
5634
	cpumask_var_t idle_cpus_mask;
5635
	atomic_t nr_cpus;
5636 5637
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
5638

5639
static inline int find_new_ilb(int call_cpu)
5640
{
5641
	int ilb = cpumask_first(nohz.idle_cpus_mask);
5642

5643 5644 5645 5646
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
5647 5648
}

5649 5650 5651 5652 5653 5654 5655 5656 5657 5658 5659
/*
 * 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++;

5660
	ilb_cpu = find_new_ilb(cpu);
5661

5662 5663
	if (ilb_cpu >= nr_cpu_ids)
		return;
5664

5665
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
5666 5667 5668 5669 5670 5671 5672 5673
		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);
5674 5675 5676
	return;
}

5677
static inline void nohz_balance_exit_idle(int cpu)
5678 5679 5680 5681 5682 5683 5684 5685
{
	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));
	}
}

5686 5687 5688 5689 5690
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;

	rcu_read_lock();
N
Nathan Zimmer 已提交
5691
	sd = rcu_dereference_check_sched_domain(this_rq()->sd);
V
Vincent Guittot 已提交
5692 5693 5694 5695 5696 5697

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

	for (; sd; sd = sd->parent)
5698
		atomic_inc(&sd->groups->sgp->nr_busy_cpus);
V
Vincent Guittot 已提交
5699
unlock:
5700 5701 5702 5703 5704 5705 5706 5707
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;

	rcu_read_lock();
N
Nathan Zimmer 已提交
5708
	sd = rcu_dereference_check_sched_domain(this_rq()->sd);
V
Vincent Guittot 已提交
5709 5710 5711 5712 5713 5714

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

	for (; sd; sd = sd->parent)
5715
		atomic_dec(&sd->groups->sgp->nr_busy_cpus);
V
Vincent Guittot 已提交
5716
unlock:
5717 5718 5719
	rcu_read_unlock();
}

5720
/*
5721
 * This routine will record that the cpu is going idle with tick stopped.
5722
 * This info will be used in performing idle load balancing in the future.
5723
 */
5724
void nohz_balance_enter_idle(int cpu)
5725
{
5726 5727 5728 5729 5730 5731
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

5732 5733
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
5734

5735 5736 5737
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
5738
}
5739

5740
static int sched_ilb_notifier(struct notifier_block *nfb,
5741 5742 5743 5744
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
5745
		nohz_balance_exit_idle(smp_processor_id());
5746 5747 5748 5749 5750
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
5751 5752 5753 5754
#endif

static DEFINE_SPINLOCK(balancing);

5755 5756 5757 5758
/*
 * 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.
 */
5759
void update_max_interval(void)
5760 5761 5762 5763
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

5764 5765 5766 5767
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
5768
 * Balancing parameters are set up in init_sched_domains.
5769 5770 5771
 */
static void rebalance_domains(int cpu, enum cpu_idle_type idle)
{
5772
	int continue_balancing = 1;
5773 5774
	struct rq *rq = cpu_rq(cpu);
	unsigned long interval;
5775
	struct sched_domain *sd;
5776 5777 5778
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
5779 5780
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
5781

5782
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
5783

5784
	rcu_read_lock();
5785
	for_each_domain(cpu, sd) {
5786 5787 5788 5789 5790 5791 5792 5793 5794 5795 5796 5797
		/*
		 * Decay the newidle max times here because this is a regular
		 * visit to all the domains. Decay ~1% per second.
		 */
		if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
			sd->max_newidle_lb_cost =
				(sd->max_newidle_lb_cost * 253) / 256;
			sd->next_decay_max_lb_cost = jiffies + HZ;
			need_decay = 1;
		}
		max_cost += sd->max_newidle_lb_cost;

5798 5799 5800
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

5801 5802 5803 5804 5805 5806 5807 5808 5809 5810 5811
		/*
		 * Stop the load balance at this level. There is another
		 * CPU in our sched group which is doing load balancing more
		 * actively.
		 */
		if (!continue_balancing) {
			if (need_decay)
				continue;
			break;
		}

5812 5813 5814 5815 5816 5817
		interval = sd->balance_interval;
		if (idle != CPU_IDLE)
			interval *= sd->busy_factor;

		/* scale ms to jiffies */
		interval = msecs_to_jiffies(interval);
5818
		interval = clamp(interval, 1UL, max_load_balance_interval);
5819 5820 5821 5822 5823 5824 5825 5826 5827

		need_serialize = sd->flags & SD_SERIALIZE;

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

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
5828
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
5829
				/*
5830
				 * The LBF_DST_PINNED logic could have changed
5831 5832
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
5833
				 */
5834
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
5835 5836 5837 5838 5839 5840 5841 5842 5843 5844
			}
			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;
		}
5845 5846
	}
	if (need_decay) {
5847
		/*
5848 5849
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
5850
		 */
5851 5852
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
5853
	}
5854
	rcu_read_unlock();
5855 5856 5857 5858 5859 5860 5861 5862 5863 5864

	/*
	 * 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;
}

5865
#ifdef CONFIG_NO_HZ_COMMON
5866
/*
5867
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
5868 5869
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
5870 5871 5872 5873 5874 5875
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;

5876 5877 5878
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
5879 5880

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
5881
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
5882 5883 5884 5885 5886 5887 5888
			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.
		 */
5889
		if (need_resched())
5890 5891
			break;

V
Vincent Guittot 已提交
5892 5893 5894 5895 5896 5897
		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);
5898 5899 5900 5901 5902 5903 5904

		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;
5905 5906
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
5907 5908 5909
}

/*
5910 5911 5912 5913 5914 5915 5916
 * 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.
5917 5918 5919 5920
 */
static inline int nohz_kick_needed(struct rq *rq, int cpu)
{
	unsigned long now = jiffies;
5921
	struct sched_domain *sd;
5922

5923
	if (unlikely(idle_cpu(cpu)))
5924 5925
		return 0;

5926 5927 5928 5929
       /*
	* 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.
	*/
5930
	set_cpu_sd_state_busy();
5931
	nohz_balance_exit_idle(cpu);
5932 5933 5934 5935 5936 5937 5938

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
		return 0;
5939 5940

	if (time_before(now, nohz.next_balance))
5941 5942
		return 0;

5943 5944
	if (rq->nr_running >= 2)
		goto need_kick;
5945

5946
	rcu_read_lock();
5947 5948 5949 5950
	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);
5951

5952
		if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1)
5953
			goto need_kick_unlock;
5954 5955 5956 5957

		if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight
		    && (cpumask_first_and(nohz.idle_cpus_mask,
					  sched_domain_span(sd)) < cpu))
5958
			goto need_kick_unlock;
5959 5960 5961

		if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING)))
			break;
5962
	}
5963
	rcu_read_unlock();
5964
	return 0;
5965 5966 5967

need_kick_unlock:
	rcu_read_unlock();
5968 5969
need_kick:
	return 1;
5970 5971 5972 5973 5974 5975 5976 5977 5978
}
#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).
 */
5979 5980 5981 5982
static void run_rebalance_domains(struct softirq_action *h)
{
	int this_cpu = smp_processor_id();
	struct rq *this_rq = cpu_rq(this_cpu);
5983
	enum cpu_idle_type idle = this_rq->idle_balance ?
5984 5985 5986 5987 5988
						CPU_IDLE : CPU_NOT_IDLE;

	rebalance_domains(this_cpu, idle);

	/*
5989
	 * If this cpu has a pending nohz_balance_kick, then do the
5990 5991 5992
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
5993
	nohz_idle_balance(this_cpu, idle);
5994 5995 5996 5997
}

static inline int on_null_domain(int cpu)
{
5998
	return !rcu_dereference_sched(cpu_rq(cpu)->sd);
5999 6000 6001 6002 6003
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
6004
void trigger_load_balance(struct rq *rq, int cpu)
6005 6006 6007 6008 6009
{
	/* 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);
6010
#ifdef CONFIG_NO_HZ_COMMON
6011
	if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
6012 6013
		nohz_balancer_kick(cpu);
#endif
6014 6015
}

6016 6017 6018 6019 6020 6021 6022 6023
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
6024 6025 6026

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
6027 6028
}

6029
#endif /* CONFIG_SMP */
6030

6031 6032 6033
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
6034
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
6035 6036 6037 6038 6039 6040
{
	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
6041
		entity_tick(cfs_rq, se, queued);
6042
	}
6043

6044
	if (numabalancing_enabled)
6045
		task_tick_numa(rq, curr);
6046

6047
	update_rq_runnable_avg(rq, 1);
6048 6049 6050
}

/*
P
Peter Zijlstra 已提交
6051 6052 6053
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
6054
 */
P
Peter Zijlstra 已提交
6055
static void task_fork_fair(struct task_struct *p)
6056
{
6057 6058
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
6059
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
6060 6061 6062
	struct rq *rq = this_rq();
	unsigned long flags;

6063
	raw_spin_lock_irqsave(&rq->lock, flags);
6064

6065 6066
	update_rq_clock(rq);

6067 6068 6069
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

6070 6071 6072 6073 6074 6075 6076 6077 6078
	/*
	 * Not only the cpu but also the task_group of the parent might have
	 * been changed after parent->se.parent,cfs_rq were copied to
	 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those
	 * of child point to valid ones.
	 */
	rcu_read_lock();
	__set_task_cpu(p, this_cpu);
	rcu_read_unlock();
6079

6080
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
6081

6082 6083
	if (curr)
		se->vruntime = curr->vruntime;
6084
	place_entity(cfs_rq, se, 1);
6085

P
Peter Zijlstra 已提交
6086
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
6087
		/*
6088 6089 6090
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
6091
		swap(curr->vruntime, se->vruntime);
6092
		resched_task(rq->curr);
6093
	}
6094

6095 6096
	se->vruntime -= cfs_rq->min_vruntime;

6097
	raw_spin_unlock_irqrestore(&rq->lock, flags);
6098 6099
}

6100 6101 6102 6103
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
6104 6105
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
6106
{
P
Peter Zijlstra 已提交
6107 6108 6109
	if (!p->se.on_rq)
		return;

6110 6111 6112 6113 6114
	/*
	 * 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
6115
	if (rq->curr == p) {
6116 6117 6118
		if (p->prio > oldprio)
			resched_task(rq->curr);
	} else
6119
		check_preempt_curr(rq, p, 0);
6120 6121
}

P
Peter Zijlstra 已提交
6122 6123 6124 6125 6126 6127 6128 6129 6130 6131 6132 6133 6134 6135 6136 6137 6138 6139 6140 6141 6142 6143
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;
	}
6144

6145
#ifdef CONFIG_SMP
6146 6147 6148 6149 6150
	/*
	* 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.
	*/
6151 6152 6153
	if (se->avg.decay_count) {
		__synchronize_entity_decay(se);
		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
6154 6155
	}
#endif
P
Peter Zijlstra 已提交
6156 6157
}

6158 6159 6160
/*
 * We switched to the sched_fair class.
 */
P
Peter Zijlstra 已提交
6161
static void switched_to_fair(struct rq *rq, struct task_struct *p)
6162
{
P
Peter Zijlstra 已提交
6163 6164 6165
	if (!p->se.on_rq)
		return;

6166 6167 6168 6169 6170
	/*
	 * 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
6171
	if (rq->curr == p)
6172 6173
		resched_task(rq->curr);
	else
6174
		check_preempt_curr(rq, p, 0);
6175 6176
}

6177 6178 6179 6180 6181 6182 6183 6184 6185
/* 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;

6186 6187 6188 6189 6190 6191 6192
	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);
	}
6193 6194
}

6195 6196 6197 6198 6199 6200 6201
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
6202
#ifdef CONFIG_SMP
6203
	atomic64_set(&cfs_rq->decay_counter, 1);
6204
	atomic_long_set(&cfs_rq->removed_load, 0);
6205
#endif
6206 6207
}

P
Peter Zijlstra 已提交
6208
#ifdef CONFIG_FAIR_GROUP_SCHED
6209
static void task_move_group_fair(struct task_struct *p, int on_rq)
P
Peter Zijlstra 已提交
6210
{
6211
	struct cfs_rq *cfs_rq;
6212 6213 6214 6215 6216 6217 6218 6219 6220 6221 6222 6223 6224
	/*
	 * 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.
	 */
6225 6226 6227 6228 6229 6230
	/*
	 * 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().
6231 6232
	 * - Moving a task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
6233 6234 6235 6236
	 *
	 * To prevent boost or penalty in the new cfs_rq caused by delta
	 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
	 */
6237
	if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING))
6238 6239
		on_rq = 1;

6240 6241 6242
	if (!on_rq)
		p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
	set_task_rq(p, task_cpu(p));
6243 6244 6245 6246 6247 6248 6249 6250 6251 6252 6253 6254 6255
	if (!on_rq) {
		cfs_rq = cfs_rq_of(&p->se);
		p->se.vruntime += cfs_rq->min_vruntime;
#ifdef CONFIG_SMP
		/*
		 * migrate_task_rq_fair() will have removed our previous
		 * contribution, but we must synchronize for ongoing future
		 * decay.
		 */
		p->se.avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
		cfs_rq->blocked_load_avg += p->se.avg.load_avg_contrib;
#endif
	}
P
Peter Zijlstra 已提交
6256
}
6257 6258 6259 6260 6261 6262 6263 6264 6265 6266 6267 6268 6269 6270 6271 6272 6273 6274 6275 6276 6277 6278 6279 6280 6281 6282 6283 6284 6285 6286 6287 6288 6289 6290 6291 6292 6293 6294 6295 6296 6297 6298 6299 6300 6301 6302 6303 6304 6305 6306 6307 6308 6309 6310 6311 6312 6313 6314 6315 6316 6317 6318 6319 6320 6321 6322 6323 6324 6325 6326 6327 6328 6329 6330 6331 6332 6333 6334 6335 6336 6337 6338 6339 6340 6341 6342 6343 6344 6345 6346 6347 6348 6349 6350 6351 6352 6353 6354 6355 6356 6357 6358 6359 6360 6361 6362 6363 6364 6365 6366 6367 6368 6369 6370 6371 6372 6373 6374 6375 6376 6377 6378 6379 6380 6381 6382 6383 6384 6385

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);
6386 6387 6388

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
6389
		for_each_sched_entity(se)
6390 6391 6392 6393 6394 6395 6396 6397 6398 6399 6400 6401 6402 6403 6404 6405 6406 6407 6408 6409 6410
			update_cfs_shares(group_cfs_rq(se));
		raw_spin_unlock_irqrestore(&rq->lock, flags);
	}

done:
	mutex_unlock(&shares_mutex);
	return 0;
}
#else /* CONFIG_FAIR_GROUP_SCHED */

void free_fair_sched_group(struct task_group *tg) { }

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
{
	return 1;
}

void unregister_fair_sched_group(struct task_group *tg, int cpu) { }

#endif /* CONFIG_FAIR_GROUP_SCHED */

P
Peter Zijlstra 已提交
6411

6412
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
6413 6414 6415 6416 6417 6418 6419 6420 6421
{
	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)
6422
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
6423 6424 6425 6426

	return rr_interval;
}

6427 6428 6429
/*
 * All the scheduling class methods:
 */
6430
const struct sched_class fair_sched_class = {
6431
	.next			= &idle_sched_class,
6432 6433 6434
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
6435
	.yield_to_task		= yield_to_task_fair,
6436

I
Ingo Molnar 已提交
6437
	.check_preempt_curr	= check_preempt_wakeup,
6438 6439 6440 6441

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

6442
#ifdef CONFIG_SMP
L
Li Zefan 已提交
6443
	.select_task_rq		= select_task_rq_fair,
6444
	.migrate_task_rq	= migrate_task_rq_fair,
6445

6446 6447
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
6448 6449

	.task_waking		= task_waking_fair,
6450
#endif
6451

6452
	.set_curr_task          = set_curr_task_fair,
6453
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
6454
	.task_fork		= task_fork_fair,
6455 6456

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
6457
	.switched_from		= switched_from_fair,
6458
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
6459

6460 6461
	.get_rr_interval	= get_rr_interval_fair,

P
Peter Zijlstra 已提交
6462
#ifdef CONFIG_FAIR_GROUP_SCHED
6463
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
6464
#endif
6465 6466 6467
};

#ifdef CONFIG_SCHED_DEBUG
6468
void print_cfs_stats(struct seq_file *m, int cpu)
6469 6470 6471
{
	struct cfs_rq *cfs_rq;

6472
	rcu_read_lock();
6473
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
6474
		print_cfs_rq(m, cpu, cfs_rq);
6475
	rcu_read_unlock();
6476 6477
}
#endif
6478 6479 6480 6481 6482 6483

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

6484
#ifdef CONFIG_NO_HZ_COMMON
6485
	nohz.next_balance = jiffies;
6486
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
6487
	cpu_notifier(sched_ilb_notifier, 0);
6488 6489 6490 6491
#endif
#endif /* SMP */

}