fair.c 170.1 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
I
Ingo Molnar 已提交
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):
	 */
I
Ingo Molnar 已提交
738
	delta_exec = (unsigned long)(now - curr->exec_start);
P
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);
}

880 881 882 883 884 885 886 887 888
/*
 * Once a preferred node is selected the scheduler balancer will prefer moving
 * a task to that node for sysctl_numa_balancing_settle_count number of PTE
 * scans. This will give the process the chance to accumulate more faults on
 * the preferred node but still allow the scheduler to move the task again if
 * the nodes CPUs are overloaded.
 */
unsigned int sysctl_numa_balancing_settle_count __read_mostly = 3;

889 890 891 892 893 894 895 896 897 898 899 900 901 902
static inline int task_faults_idx(int nid, int priv)
{
	return 2 * nid + priv;
}

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

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

903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927
static unsigned long weighted_cpuload(const int cpu);


static int
find_idlest_cpu_node(int this_cpu, int nid)
{
	unsigned long load, min_load = ULONG_MAX;
	int i, idlest_cpu = this_cpu;

	BUG_ON(cpu_to_node(this_cpu) == nid);

	rcu_read_lock();
	for_each_cpu(i, cpumask_of_node(nid)) {
		load = weighted_cpuload(i);

		if (load < min_load) {
			min_load = load;
			idlest_cpu = i;
		}
	}
	rcu_read_unlock();

	return idlest_cpu;
}

928 929
static void task_numa_placement(struct task_struct *p)
{
930 931
	int seq, nid, max_nid = -1;
	unsigned long max_faults = 0;
932

933 934 935
	if (!p->mm)	/* for example, ksmd faulting in a user's mm */
		return;
	seq = ACCESS_ONCE(p->mm->numa_scan_seq);
936 937 938
	if (p->numa_scan_seq == seq)
		return;
	p->numa_scan_seq = seq;
939
	p->numa_migrate_seq++;
940
	p->numa_scan_period_max = task_scan_max(p);
941

942 943
	/* Find the node with the highest number of faults */
	for_each_online_node(nid) {
944
		unsigned long faults;
945
		int priv, i;
946

947 948
		for (priv = 0; priv < 2; priv++) {
			i = task_faults_idx(nid, priv);
949

950 951 952 953 954 955 956 957
			/* Decay existing window, copy faults since last scan */
			p->numa_faults[i] >>= 1;
			p->numa_faults[i] += p->numa_faults_buffer[i];
			p->numa_faults_buffer[i] = 0;
		}

		/* Find maximum private faults */
		faults = p->numa_faults[task_faults_idx(nid, 1)];
958 959 960 961 962 963
		if (faults > max_faults) {
			max_faults = faults;
			max_nid = nid;
		}
	}

964 965 966 967 968 969
	/*
	 * Record the preferred node as the node with the most faults,
	 * requeue the task to be running on the idlest CPU on the
	 * preferred node and reset the scanning rate to recheck
	 * the working set placement.
	 */
970
	if (max_faults && max_nid != p->numa_preferred_nid) {
971 972 973 974 975 976 977 978 979 980 981 982 983
		int preferred_cpu;

		/*
		 * If the task is not on the preferred node then find the most
		 * idle CPU to migrate to.
		 */
		preferred_cpu = task_cpu(p);
		if (cpu_to_node(preferred_cpu) != max_nid) {
			preferred_cpu = find_idlest_cpu_node(preferred_cpu,
							     max_nid);
		}

		/* Update the preferred nid and migrate task if possible */
984
		p->numa_preferred_nid = max_nid;
985
		p->numa_migrate_seq = 0;
986
		migrate_task_to(p, preferred_cpu);
987
	}
988 989 990 991 992
}

/*
 * Got a PROT_NONE fault for a page on @node.
 */
993
void task_numa_fault(int last_nid, int node, int pages, bool migrated)
994 995
{
	struct task_struct *p = current;
996
	int priv;
997

998
	if (!numabalancing_enabled)
999 1000
		return;

1001 1002 1003
	/* For now, do not attempt to detect private/shared accesses */
	priv = 1;

1004 1005
	/* Allocate buffer to track faults on a per-node basis */
	if (unlikely(!p->numa_faults)) {
1006
		int size = sizeof(*p->numa_faults) * 2 * nr_node_ids;
1007

1008 1009
		/* numa_faults and numa_faults_buffer share the allocation */
		p->numa_faults = kzalloc(size * 2, GFP_KERNEL|__GFP_NOWARN);
1010 1011
		if (!p->numa_faults)
			return;
1012 1013

		BUG_ON(p->numa_faults_buffer);
1014
		p->numa_faults_buffer = p->numa_faults + (2 * nr_node_ids);
1015
	}
1016

1017
	/*
1018 1019
	 * If pages are properly placed (did not migrate) then scan slower.
	 * This is reset periodically in case of phase changes
1020
	 */
1021 1022 1023 1024 1025 1026 1027 1028
	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);
	}
1029

1030
	task_numa_placement(p);
1031

1032
	p->numa_faults_buffer[task_faults_idx(node, priv)] += pages;
1033 1034
}

1035 1036 1037 1038 1039 1040
static void reset_ptenuma_scan(struct task_struct *p)
{
	ACCESS_ONCE(p->mm->numa_scan_seq)++;
	p->mm->numa_scan_offset = 0;
}

1041 1042 1043 1044 1045 1046 1047 1048 1049
/*
 * 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;
1050
	struct vm_area_struct *vma;
1051
	unsigned long start, end;
1052
	unsigned long nr_pte_updates = 0;
1053
	long pages;
1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068

	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;

1069 1070 1071 1072 1073 1074 1075
	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);
	}

1076 1077 1078 1079 1080 1081 1082 1083
	/*
	 * 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)) {
1084
		p->numa_scan_period = task_scan_min(p);
1085 1086 1087 1088
		next_scan = now + msecs_to_jiffies(sysctl_numa_balancing_scan_period_reset);
		xchg(&mm->numa_next_reset, next_scan);
	}

1089 1090 1091 1092 1093 1094 1095
	/*
	 * Enforce maximal scan/migration frequency..
	 */
	migrate = mm->numa_next_scan;
	if (time_before(now, migrate))
		return;

1096 1097 1098 1099
	if (p->numa_scan_period == 0) {
		p->numa_scan_period_max = task_scan_max(p);
		p->numa_scan_period = task_scan_min(p);
	}
1100

1101
	next_scan = now + msecs_to_jiffies(p->numa_scan_period);
1102 1103 1104
	if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
		return;

1105 1106 1107 1108 1109 1110
	/*
	 * Delay this task enough that another task of this mm will likely win
	 * the next time around.
	 */
	p->node_stamp += 2 * TICK_NSEC;

1111 1112 1113 1114 1115
	start = mm->numa_scan_offset;
	pages = sysctl_numa_balancing_scan_size;
	pages <<= 20 - PAGE_SHIFT; /* MB in pages */
	if (!pages)
		return;
1116

1117
	down_read(&mm->mmap_sem);
1118
	vma = find_vma(mm, start);
1119 1120
	if (!vma) {
		reset_ptenuma_scan(p);
1121
		start = 0;
1122 1123
		vma = mm->mmap;
	}
1124
	for (; vma; vma = vma->vm_next) {
1125 1126 1127 1128
		if (!vma_migratable(vma))
			continue;

		/* Skip small VMAs. They are not likely to be of relevance */
1129
		if (vma->vm_end - vma->vm_start < HPAGE_SIZE)
1130 1131
			continue;

1132 1133 1134 1135
		do {
			start = max(start, vma->vm_start);
			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
			end = min(end, vma->vm_end);
1136 1137 1138 1139 1140 1141 1142 1143 1144
			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;
1145

1146 1147 1148 1149
			start = end;
			if (pages <= 0)
				goto out;
		} while (end != vma->vm_end);
1150
	}
1151

1152
out:
1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164
	/*
	 * 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;
	}

1165
	/*
P
Peter Zijlstra 已提交
1166 1167 1168 1169
	 * 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.
1170 1171
	 */
	if (vma)
1172
		mm->numa_scan_offset = start;
1173 1174 1175
	else
		reset_ptenuma_scan(p);
	up_read(&mm->mmap_sem);
1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201
}

/*
 * 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) {
1202
		if (!curr->node_stamp)
1203
			curr->numa_scan_period = task_scan_min(curr);
1204
		curr->node_stamp += period;
1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217

		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 */

1218 1219 1220 1221
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
1222
	if (!parent_entity(se))
1223
		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
1224 1225
#ifdef CONFIG_SMP
	if (entity_is_task(se))
1226
		list_add(&se->group_node, &rq_of(cfs_rq)->cfs_tasks);
1227
#endif
1228 1229 1230 1231 1232 1233 1234
	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);
1235
	if (!parent_entity(se))
1236
		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
1237
	if (entity_is_task(se))
1238
		list_del_init(&se->group_node);
1239 1240 1241
	cfs_rq->nr_running--;
}

1242 1243
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
1244 1245 1246 1247 1248 1249 1250 1251 1252
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().
	 */
1253
	tg_weight = atomic_long_read(&tg->load_avg);
1254
	tg_weight -= cfs_rq->tg_load_contrib;
1255 1256 1257 1258 1259
	tg_weight += cfs_rq->load.weight;

	return tg_weight;
}

1260
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1261
{
1262
	long tg_weight, load, shares;
1263

1264
	tg_weight = calc_tg_weight(tg, cfs_rq);
1265
	load = cfs_rq->load.weight;
1266 1267

	shares = (tg->shares * load);
1268 1269
	if (tg_weight)
		shares /= tg_weight;
1270 1271 1272 1273 1274 1275 1276 1277 1278

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

	return shares;
}
# else /* CONFIG_SMP */
1279
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
1280 1281 1282 1283
{
	return tg->shares;
}
# endif /* CONFIG_SMP */
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static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
1287 1288 1289 1290
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
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		account_entity_dequeue(cfs_rq, se);
1292
	}
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	update_load_set(&se->load, weight);

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

1300 1301
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

1302
static void update_cfs_shares(struct cfs_rq *cfs_rq)
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{
	struct task_group *tg;
	struct sched_entity *se;
1306
	long shares;
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	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
1310
	if (!se || throttled_hierarchy(cfs_rq))
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		return;
1312 1313 1314 1315
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
1316
	shares = calc_cfs_shares(cfs_rq, tg);
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	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
1321
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
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{
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

1326
#ifdef CONFIG_SMP
1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354
/*
 * 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,
};

1355 1356 1357 1358 1359 1360
/*
 * Approximate:
 *   val * y^n,    where y^32 ~= 0.5 (~1 scheduling period)
 */
static __always_inline u64 decay_load(u64 val, u64 n)
{
1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380
	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;
1381 1382
	}

1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413
	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];
1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447
}

/*
 * 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)
{
1448 1449
	u64 delta, periods;
	u32 runnable_contrib;
1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482
	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;
1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502
		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;
1503 1504 1505 1506 1507 1508 1509 1510 1511 1512
	}

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

	return decayed;
}

1513
/* Synchronize an entity's decay with its parenting cfs_rq.*/
1514
static inline u64 __synchronize_entity_decay(struct sched_entity *se)
1515 1516 1517 1518 1519 1520
{
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	u64 decays = atomic64_read(&cfs_rq->decay_counter);

	decays -= se->avg.decay_count;
	if (!decays)
1521
		return 0;
1522 1523 1524

	se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
	se->avg.decay_count = 0;
1525 1526

	return decays;
1527 1528
}

1529 1530 1531 1532 1533
#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;
1534
	long tg_contrib;
1535 1536 1537 1538

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

1539 1540
	if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) {
		atomic_long_add(tg_contrib, &tg->load_avg);
1541 1542 1543
		cfs_rq->tg_load_contrib += tg_contrib;
	}
}
1544

1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565
/*
 * 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;
	}
}

1566 1567 1568 1569
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;
1570 1571
	int runnable_avg;

1572 1573 1574
	u64 contrib;

	contrib = cfs_rq->tg_load_contrib * tg->shares;
1575 1576
	se->avg.load_avg_contrib = div_u64(contrib,
				     atomic_long_read(&tg->load_avg) + 1);
1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605

	/*
	 * 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;
	}
1606
}
1607 1608 1609
#else
static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq,
						 int force_update) {}
1610 1611
static inline void __update_tg_runnable_avg(struct sched_avg *sa,
						  struct cfs_rq *cfs_rq) {}
1612
static inline void __update_group_entity_contrib(struct sched_entity *se) {}
1613 1614
#endif

1615 1616 1617 1618 1619 1620 1621 1622 1623 1624
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);
}

1625 1626 1627 1628 1629
/* 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;

1630 1631 1632
	if (entity_is_task(se)) {
		__update_task_entity_contrib(se);
	} else {
1633
		__update_tg_runnable_avg(&se->avg, group_cfs_rq(se));
1634 1635
		__update_group_entity_contrib(se);
	}
1636 1637 1638 1639

	return se->avg.load_avg_contrib - old_contrib;
}

1640 1641 1642 1643 1644 1645 1646 1647 1648
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;
}

1649 1650
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);

1651
/* Update a sched_entity's runnable average */
1652 1653
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq)
1654
{
1655 1656
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
	long contrib_delta;
1657
	u64 now;
1658

1659 1660 1661 1662 1663 1664 1665 1666 1667 1668
	/*
	 * 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))
1669 1670 1671
		return;

	contrib_delta = __update_entity_load_avg_contrib(se);
1672 1673 1674 1675

	if (!update_cfs_rq)
		return;

1676 1677
	if (se->on_rq)
		cfs_rq->runnable_load_avg += contrib_delta;
1678 1679 1680 1681 1682 1683 1684 1685
	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.
 */
1686
static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
1687
{
1688
	u64 now = cfs_rq_clock_task(cfs_rq) >> 20;
1689 1690 1691
	u64 decays;

	decays = now - cfs_rq->last_decay;
1692
	if (!decays && !force_update)
1693 1694
		return;

1695 1696 1697
	if (atomic_long_read(&cfs_rq->removed_load)) {
		unsigned long removed_load;
		removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0);
1698 1699
		subtract_blocked_load_contrib(cfs_rq, removed_load);
	}
1700

1701 1702 1703 1704 1705 1706
	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;
	}
1707 1708

	__update_cfs_rq_tg_load_contrib(cfs_rq, force_update);
1709
}
1710 1711 1712

static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
{
1713
	__update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable);
1714
	__update_tg_runnable_avg(&rq->avg, &rq->cfs);
1715
}
1716 1717 1718

/* 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,
1719 1720
						  struct sched_entity *se,
						  int wakeup)
1721
{
1722 1723 1724 1725
	/*
	 * 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.
1726 1727 1728 1729
	 *
	 * 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.
1730 1731
	 */
	if (unlikely(se->avg.decay_count <= 0)) {
1732
		se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq));
1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747
		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;
		}
1748 1749
		wakeup = 0;
	} else {
1750 1751 1752 1753 1754 1755 1756
		/*
		 * 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;
1757 1758
	}

1759 1760
	/* migrated tasks did not contribute to our blocked load */
	if (wakeup) {
1761
		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
1762 1763
		update_entity_load_avg(se, 0);
	}
1764

1765
	cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
1766 1767
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !wakeup);
1768 1769
}

1770 1771 1772 1773 1774
/*
 * 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.
 */
1775
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
1776 1777
						  struct sched_entity *se,
						  int sleep)
1778
{
1779
	update_entity_load_avg(se, 1);
1780 1781
	/* we force update consideration on load-balancer moves */
	update_cfs_rq_blocked_load(cfs_rq, !sleep);
1782

1783
	cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
1784 1785 1786 1787
	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 */
1788
}
1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809

/*
 * 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);
}

1810
#else
1811 1812
static inline void update_entity_load_avg(struct sched_entity *se,
					  int update_cfs_rq) {}
1813
static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {}
1814
static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
1815 1816
					   struct sched_entity *se,
					   int wakeup) {}
1817
static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
1818 1819
					   struct sched_entity *se,
					   int sleep) {}
1820 1821
static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
					      int force_update) {}
1822 1823
#endif

1824
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
1825 1826
{
#ifdef CONFIG_SCHEDSTATS
1827 1828 1829 1830 1831
	struct task_struct *tsk = NULL;

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

1832
	if (se->statistics.sleep_start) {
1833
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start;
1834 1835 1836 1837

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

1838 1839
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
1840

1841
		se->statistics.sleep_start = 0;
1842
		se->statistics.sum_sleep_runtime += delta;
A
Arjan van de Ven 已提交
1843

1844
		if (tsk) {
1845
			account_scheduler_latency(tsk, delta >> 10, 1);
1846 1847
			trace_sched_stat_sleep(tsk, delta);
		}
1848
	}
1849
	if (se->statistics.block_start) {
1850
		u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start;
1851 1852 1853 1854

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

1855 1856
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
1857

1858
		se->statistics.block_start = 0;
1859
		se->statistics.sum_sleep_runtime += delta;
I
Ingo Molnar 已提交
1860

1861
		if (tsk) {
1862
			if (tsk->in_iowait) {
1863 1864
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
1865
				trace_sched_stat_iowait(tsk, delta);
1866 1867
			}

1868 1869
			trace_sched_stat_blocked(tsk, delta);

1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880
			/*
			 * 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
1881
		}
1882 1883 1884 1885
	}
#endif
}

P
Peter Zijlstra 已提交
1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898
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
}

1899 1900 1901
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
1902
	u64 vruntime = cfs_rq->min_vruntime;
P
Peter Zijlstra 已提交
1903

1904 1905 1906 1907 1908 1909
	/*
	 * 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
1910
	if (initial && sched_feat(START_DEBIT))
1911
		vruntime += sched_vslice(cfs_rq, se);
1912

1913
	/* sleeps up to a single latency don't count. */
1914
	if (!initial) {
1915
		unsigned long thresh = sysctl_sched_latency;
1916

1917 1918 1919 1920 1921 1922
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
1923

1924
		vruntime -= thresh;
1925 1926
	}

1927
	/* ensure we never gain time by being placed backwards. */
1928
	se->vruntime = max_vruntime(se->vruntime, vruntime);
1929 1930
}

1931 1932
static void check_enqueue_throttle(struct cfs_rq *cfs_rq);

1933
static void
1934
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1935
{
1936 1937
	/*
	 * Update the normalized vruntime before updating min_vruntime
1938
	 * through calling update_curr().
1939
	 */
1940
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
1941 1942
		se->vruntime += cfs_rq->min_vruntime;

1943
	/*
1944
	 * Update run-time statistics of the 'current'.
1945
	 */
1946
	update_curr(cfs_rq);
1947
	enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
1948 1949
	account_entity_enqueue(cfs_rq, se);
	update_cfs_shares(cfs_rq);
1950

1951
	if (flags & ENQUEUE_WAKEUP) {
1952
		place_entity(cfs_rq, se, 0);
1953
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
1954
	}
1955

1956
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
1957
	check_spread(cfs_rq, se);
1958 1959
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
P
Peter Zijlstra 已提交
1960
	se->on_rq = 1;
1961

1962
	if (cfs_rq->nr_running == 1) {
1963
		list_add_leaf_cfs_rq(cfs_rq);
1964 1965
		check_enqueue_throttle(cfs_rq);
	}
1966 1967
}

1968
static void __clear_buddies_last(struct sched_entity *se)
P
Peter Zijlstra 已提交
1969
{
1970 1971 1972 1973 1974 1975 1976 1977
	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
1978

1979 1980 1981 1982 1983 1984 1985 1986 1987
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
1988 1989
}

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000
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
2001 2002
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
2003 2004 2005 2006 2007
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
2008 2009 2010

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
P
Peter Zijlstra 已提交
2011 2012
}

2013
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq);
2014

2015
static void
2016
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
2017
{
2018 2019 2020 2021
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);
2022
	dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);
2023

2024
	update_stats_dequeue(cfs_rq, se);
2025
	if (flags & DEQUEUE_SLEEP) {
P
Peter Zijlstra 已提交
2026
#ifdef CONFIG_SCHEDSTATS
2027 2028 2029 2030
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
2031
				se->statistics.sleep_start = rq_clock(rq_of(cfs_rq));
2032
			if (tsk->state & TASK_UNINTERRUPTIBLE)
2033
				se->statistics.block_start = rq_clock(rq_of(cfs_rq));
2034
		}
2035
#endif
P
Peter Zijlstra 已提交
2036 2037
	}

P
Peter Zijlstra 已提交
2038
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
2039

2040
	if (se != cfs_rq->curr)
2041
		__dequeue_entity(cfs_rq, se);
2042
	se->on_rq = 0;
2043
	account_entity_dequeue(cfs_rq, se);
2044 2045 2046 2047 2048 2049

	/*
	 * 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.
	 */
2050
	if (!(flags & DEQUEUE_SLEEP))
2051
		se->vruntime -= cfs_rq->min_vruntime;
2052

2053 2054 2055
	/* return excess runtime on last dequeue */
	return_cfs_rq_runtime(cfs_rq);

2056
	update_min_vruntime(cfs_rq);
2057
	update_cfs_shares(cfs_rq);
2058 2059 2060 2061 2062
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
2063
static void
I
Ingo Molnar 已提交
2064
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
2065
{
2066
	unsigned long ideal_runtime, delta_exec;
2067 2068
	struct sched_entity *se;
	s64 delta;
2069

P
Peter Zijlstra 已提交
2070
	ideal_runtime = sched_slice(cfs_rq, curr);
2071
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
2072
	if (delta_exec > ideal_runtime) {
2073
		resched_task(rq_of(cfs_rq)->curr);
2074 2075 2076 2077 2078
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089
		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;

2090 2091
	se = __pick_first_entity(cfs_rq);
	delta = curr->vruntime - se->vruntime;
2092

2093 2094
	if (delta < 0)
		return;
2095

2096 2097
	if (delta > ideal_runtime)
		resched_task(rq_of(cfs_rq)->curr);
2098 2099
}

2100
static void
2101
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
2102
{
2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113
	/* '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);
	}

2114
	update_stats_curr_start(cfs_rq, se);
2115
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
2116 2117 2118 2119 2120 2121
#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):
	 */
2122
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
2123
		se->statistics.slice_max = max(se->statistics.slice_max,
I
Ingo Molnar 已提交
2124 2125 2126
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
2127
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
2128 2129
}

2130 2131 2132
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

2133 2134 2135 2136 2137 2138 2139
/*
 * 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
 */
2140
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
2141
{
2142
	struct sched_entity *se = __pick_first_entity(cfs_rq);
2143
	struct sched_entity *left = se;
2144

2145 2146 2147 2148 2149 2150 2151 2152 2153
	/*
	 * 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;
	}
2154

2155 2156 2157 2158 2159 2160
	/*
	 * 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;

2161 2162 2163 2164 2165 2166
	/*
	 * 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;

2167
	clear_buddies(cfs_rq, se);
P
Peter Zijlstra 已提交
2168 2169

	return se;
2170 2171
}

2172 2173
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq);

2174
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
2175 2176 2177 2178 2179 2180
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
2181
		update_curr(cfs_rq);
2182

2183 2184 2185
	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

P
Peter Zijlstra 已提交
2186
	check_spread(cfs_rq, prev);
2187
	if (prev->on_rq) {
2188
		update_stats_wait_start(cfs_rq, prev);
2189 2190
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
2191
		/* in !on_rq case, update occurred at dequeue */
2192
		update_entity_load_avg(prev, 1);
2193
	}
2194
	cfs_rq->curr = NULL;
2195 2196
}

P
Peter Zijlstra 已提交
2197 2198
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
2199 2200
{
	/*
2201
	 * Update run-time statistics of the 'current'.
2202
	 */
2203
	update_curr(cfs_rq);
2204

2205 2206 2207
	/*
	 * Ensure that runnable average is periodically updated.
	 */
2208
	update_entity_load_avg(curr, 1);
2209
	update_cfs_rq_blocked_load(cfs_rq, 1);
2210
	update_cfs_shares(cfs_rq);
2211

P
Peter Zijlstra 已提交
2212 2213 2214 2215 2216
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
2217 2218 2219 2220
	if (queued) {
		resched_task(rq_of(cfs_rq)->curr);
		return;
	}
P
Peter Zijlstra 已提交
2221 2222 2223 2224 2225 2226 2227 2228
	/*
	 * 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
2229
	if (cfs_rq->nr_running > 1)
I
Ingo Molnar 已提交
2230
		check_preempt_tick(cfs_rq, curr);
2231 2232
}

2233 2234 2235 2236 2237 2238

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

#ifdef CONFIG_CFS_BANDWIDTH
2239 2240

#ifdef HAVE_JUMP_LABEL
2241
static struct static_key __cfs_bandwidth_used;
2242 2243 2244

static inline bool cfs_bandwidth_used(void)
{
2245
	return static_key_false(&__cfs_bandwidth_used);
2246 2247 2248 2249 2250 2251
}

void account_cfs_bandwidth_used(int enabled, int was_enabled)
{
	/* only need to count groups transitioning between enabled/!enabled */
	if (enabled && !was_enabled)
2252
		static_key_slow_inc(&__cfs_bandwidth_used);
2253
	else if (!enabled && was_enabled)
2254
		static_key_slow_dec(&__cfs_bandwidth_used);
2255 2256 2257 2258 2259 2260 2261 2262 2263 2264
}
#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 */

2265 2266 2267 2268 2269 2270 2271 2272
/*
 * default period for cfs group bandwidth.
 * default: 0.1s, units: nanoseconds
 */
static inline u64 default_cfs_period(void)
{
	return 100000000ULL;
}
2273 2274 2275 2276 2277 2278

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

P
Paul Turner 已提交
2279 2280 2281 2282 2283 2284 2285
/*
 * 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
 */
2286
void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
P
Paul Turner 已提交
2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297
{
	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);
}

2298 2299 2300 2301 2302
static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg)
{
	return &tg->cfs_bandwidth;
}

2303 2304 2305 2306 2307 2308
/* 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;

2309
	return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time;
2310 2311
}

2312 2313
/* returns 0 on failure to allocate runtime */
static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)
2314 2315 2316
{
	struct task_group *tg = cfs_rq->tg;
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
P
Paul Turner 已提交
2317
	u64 amount = 0, min_amount, expires;
2318 2319 2320 2321 2322 2323 2324

	/* 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;
2325
	else {
P
Paul Turner 已提交
2326 2327 2328 2329 2330 2331 2332 2333
		/*
		 * 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);
2334
			__start_cfs_bandwidth(cfs_b);
P
Paul Turner 已提交
2335
		}
2336 2337 2338 2339 2340 2341

		if (cfs_b->runtime > 0) {
			amount = min(cfs_b->runtime, min_amount);
			cfs_b->runtime -= amount;
			cfs_b->idle = 0;
		}
2342
	}
P
Paul Turner 已提交
2343
	expires = cfs_b->runtime_expires;
2344 2345 2346
	raw_spin_unlock(&cfs_b->lock);

	cfs_rq->runtime_remaining += amount;
P
Paul Turner 已提交
2347 2348 2349 2350 2351 2352 2353
	/*
	 * 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;
2354 2355

	return cfs_rq->runtime_remaining > 0;
2356 2357
}

P
Paul Turner 已提交
2358 2359 2360 2361 2362
/*
 * 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)
2363
{
P
Paul Turner 已提交
2364 2365 2366
	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	/* if the deadline is ahead of our clock, nothing to do */
2367
	if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0))
2368 2369
		return;

P
Paul Turner 已提交
2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394
	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) */
2395
	cfs_rq->runtime_remaining -= delta_exec;
P
Paul Turner 已提交
2396 2397 2398
	expire_cfs_rq_runtime(cfs_rq);

	if (likely(cfs_rq->runtime_remaining > 0))
2399 2400
		return;

2401 2402 2403 2404 2405 2406
	/*
	 * 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);
2407 2408
}

2409 2410
static __always_inline
void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec)
2411
{
2412
	if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled)
2413 2414 2415 2416 2417
		return;

	__account_cfs_rq_runtime(cfs_rq, delta_exec);
}

2418 2419
static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
2420
	return cfs_bandwidth_used() && cfs_rq->throttled;
2421 2422
}

2423 2424 2425
/* check whether cfs_rq, or any parent, is throttled */
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)
{
2426
	return cfs_bandwidth_used() && cfs_rq->throttle_count;
2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454
}

/*
 * 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) {
2455
		/* adjust cfs_rq_clock_task() */
2456
		cfs_rq->throttled_clock_task_time += rq_clock_task(rq) -
2457
					     cfs_rq->throttled_clock_task;
2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468
	}
#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)];

2469 2470
	/* group is entering throttled state, stop time */
	if (!cfs_rq->throttle_count)
2471
		cfs_rq->throttled_clock_task = rq_clock_task(rq);
2472 2473 2474 2475 2476
	cfs_rq->throttle_count++;

	return 0;
}

2477
static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
2478 2479 2480 2481 2482 2483 2484 2485
{
	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))];

2486
	/* freeze hierarchy runnable averages while throttled */
2487 2488 2489
	rcu_read_lock();
	walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq);
	rcu_read_unlock();
2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509

	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;
2510
	cfs_rq->throttled_clock = rq_clock(rq);
2511 2512 2513 2514 2515
	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);
}

2516
void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
2517 2518 2519 2520 2521 2522 2523
{
	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;

2524
	se = cfs_rq->tg->se[cpu_of(rq)];
2525 2526

	cfs_rq->throttled = 0;
2527 2528 2529

	update_rq_clock(rq);

2530
	raw_spin_lock(&cfs_b->lock);
2531
	cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock;
2532 2533 2534
	list_del_rcu(&cfs_rq->throttled_list);
	raw_spin_unlock(&cfs_b->lock);

2535 2536 2537
	/* update hierarchical throttle state */
	walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq);

2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600
	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;
}

2601 2602 2603 2604 2605 2606 2607 2608
/*
 * 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)
{
2609 2610
	u64 runtime, runtime_expires;
	int idle = 1, throttled;
2611 2612 2613 2614 2615 2616

	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;

2617 2618 2619
	throttled = !list_empty(&cfs_b->throttled_cfs_rq);
	/* idle depends on !throttled (for the case of a large deficit) */
	idle = cfs_b->idle && !throttled;
2620
	cfs_b->nr_periods += overrun;
2621

P
Paul Turner 已提交
2622 2623 2624 2625 2626 2627
	/* if we're going inactive then everything else can be deferred */
	if (idle)
		goto out_unlock;

	__refill_cfs_bandwidth_runtime(cfs_b);

2628 2629 2630 2631 2632 2633
	if (!throttled) {
		/* mark as potentially idle for the upcoming period */
		cfs_b->idle = 1;
		goto out_unlock;
	}

2634 2635 2636
	/* account preceding periods in which throttling occurred */
	cfs_b->nr_throttled += overrun;

2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660
	/*
	 * 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);
	}
2661

2662 2663 2664 2665 2666 2667 2668 2669 2670
	/* 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;
2671 2672 2673 2674 2675 2676 2677
out_unlock:
	if (idle)
		cfs_b->timer_active = 0;
	raw_spin_unlock(&cfs_b->lock);

	return idle;
}
2678

2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742
/* 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)
{
2743 2744 2745
	if (!cfs_bandwidth_used())
		return;

2746
	if (!cfs_rq->runtime_enabled || cfs_rq->nr_running)
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
		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);
}

2784 2785 2786 2787 2788 2789 2790
/*
 * 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)
{
2791 2792 2793
	if (!cfs_bandwidth_used())
		return;

2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810
	/* 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)
{
2811 2812 2813
	if (!cfs_bandwidth_used())
		return;

2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825
	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);
}
2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906

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);
}

2907
static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq)
2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927
{
	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 */
2928 2929
static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq)
{
2930
	return rq_clock_task(rq_of(cfs_rq));
2931 2932 2933 2934
}

static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
				     unsigned long delta_exec) {}
2935 2936
static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {}
2937
static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {}
2938 2939 2940 2941 2942

static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)
{
	return 0;
}
2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953

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;
}
2954 2955 2956 2957 2958

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) {}
2959 2960
#endif

2961 2962 2963 2964 2965
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) {}
2966
static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {}
2967 2968 2969

#endif /* CONFIG_CFS_BANDWIDTH */

2970 2971 2972 2973
/**************************************************
 * CFS operations on tasks:
 */

P
Peter Zijlstra 已提交
2974 2975 2976 2977 2978 2979 2980 2981
#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);

2982
	if (cfs_rq->nr_running > 1) {
P
Peter Zijlstra 已提交
2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996
		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.
		 */
2997
		if (rq->curr != p)
2998
			delta = max_t(s64, 10000LL, delta);
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Peter Zijlstra 已提交
2999

3000
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
3001 3002
	}
}
3003 3004 3005 3006 3007 3008 3009 3010 3011 3012

/*
 * 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;

3013
	if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class)
3014 3015 3016 3017 3018
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
3019
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
3020 3021 3022 3023
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
3024 3025 3026 3027

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
3028 3029
#endif

3030 3031 3032 3033 3034
/*
 * 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:
 */
3035
static void
3036
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
3037 3038
{
	struct cfs_rq *cfs_rq;
3039
	struct sched_entity *se = &p->se;
3040 3041

	for_each_sched_entity(se) {
3042
		if (se->on_rq)
3043 3044
			break;
		cfs_rq = cfs_rq_of(se);
3045
		enqueue_entity(cfs_rq, se, flags);
3046 3047 3048 3049 3050 3051 3052 3053 3054

		/*
		 * 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;
3055
		cfs_rq->h_nr_running++;
3056

3057
		flags = ENQUEUE_WAKEUP;
3058
	}
P
Peter Zijlstra 已提交
3059

P
Peter Zijlstra 已提交
3060
	for_each_sched_entity(se) {
3061
		cfs_rq = cfs_rq_of(se);
3062
		cfs_rq->h_nr_running++;
P
Peter Zijlstra 已提交
3063

3064 3065 3066
		if (cfs_rq_throttled(cfs_rq))
			break;

3067
		update_cfs_shares(cfs_rq);
3068
		update_entity_load_avg(se, 1);
P
Peter Zijlstra 已提交
3069 3070
	}

3071 3072
	if (!se) {
		update_rq_runnable_avg(rq, rq->nr_running);
3073
		inc_nr_running(rq);
3074
	}
3075
	hrtick_update(rq);
3076 3077
}

3078 3079
static void set_next_buddy(struct sched_entity *se);

3080 3081 3082 3083 3084
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
3085
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
3086 3087
{
	struct cfs_rq *cfs_rq;
3088
	struct sched_entity *se = &p->se;
3089
	int task_sleep = flags & DEQUEUE_SLEEP;
3090 3091 3092

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
3093
		dequeue_entity(cfs_rq, se, flags);
3094 3095 3096 3097 3098 3099 3100 3101 3102

		/*
		 * 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;
3103
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
3104

3105
		/* Don't dequeue parent if it has other entities besides us */
3106 3107 3108 3109 3110 3111 3112
		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));
3113 3114 3115

			/* avoid re-evaluating load for this entity */
			se = parent_entity(se);
3116
			break;
3117
		}
3118
		flags |= DEQUEUE_SLEEP;
3119
	}
P
Peter Zijlstra 已提交
3120

P
Peter Zijlstra 已提交
3121
	for_each_sched_entity(se) {
3122
		cfs_rq = cfs_rq_of(se);
3123
		cfs_rq->h_nr_running--;
P
Peter Zijlstra 已提交
3124

3125 3126 3127
		if (cfs_rq_throttled(cfs_rq))
			break;

3128
		update_cfs_shares(cfs_rq);
3129
		update_entity_load_avg(se, 1);
P
Peter Zijlstra 已提交
3130 3131
	}

3132
	if (!se) {
3133
		dec_nr_running(rq);
3134 3135
		update_rq_runnable_avg(rq, 1);
	}
3136
	hrtick_update(rq);
3137 3138
}

3139
#ifdef CONFIG_SMP
3140 3141 3142
/* Used instead of source_load when we know the type == 0 */
static unsigned long weighted_cpuload(const int cpu)
{
3143
	return cpu_rq(cpu)->cfs.runnable_load_avg;
3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187
}

/*
 * 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);
3188
	unsigned long load_avg = rq->cfs.runnable_load_avg;
3189 3190

	if (nr_running)
3191
		return load_avg / nr_running;
3192 3193 3194 3195

	return 0;
}

3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212
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++;
	}
}
3213

3214
static void task_waking_fair(struct task_struct *p)
3215 3216 3217
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
3218 3219 3220 3221
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
3222

3223 3224 3225 3226 3227 3228 3229 3230
	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
3231

3232
	se->vruntime -= min_vruntime;
3233
	record_wakee(p);
3234 3235
}

3236
#ifdef CONFIG_FAIR_GROUP_SCHED
3237 3238 3239 3240 3241 3242
/*
 * 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.
3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285
 *
 * 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.
3286
 */
P
Peter Zijlstra 已提交
3287
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
3288
{
P
Peter Zijlstra 已提交
3289
	struct sched_entity *se = tg->se[cpu];
3290

3291
	if (!tg->parent)	/* the trivial, non-cgroup case */
3292 3293
		return wl;

P
Peter Zijlstra 已提交
3294
	for_each_sched_entity(se) {
3295
		long w, W;
P
Peter Zijlstra 已提交
3296

3297
		tg = se->my_q->tg;
3298

3299 3300 3301 3302
		/*
		 * W = @wg + \Sum rw_j
		 */
		W = wg + calc_tg_weight(tg, se->my_q);
P
Peter Zijlstra 已提交
3303

3304 3305 3306 3307
		/*
		 * w = rw_i + @wl
		 */
		w = se->my_q->load.weight + wl;
3308

3309 3310 3311 3312 3313
		/*
		 * wl = S * s'_i; see (2)
		 */
		if (W > 0 && w < W)
			wl = (w * tg->shares) / W;
3314 3315
		else
			wl = tg->shares;
3316

3317 3318 3319 3320 3321
		/*
		 * 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().
		 */
3322 3323
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
3324 3325 3326 3327

		/*
		 * wl = dw_i = S * (s'_i - s_i); see (3)
		 */
3328
		wl -= se->load.weight;
3329 3330 3331 3332 3333 3334 3335 3336

		/*
		 * 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
3337 3338
		wg = 0;
	}
3339

P
Peter Zijlstra 已提交
3340
	return wl;
3341 3342
}
#else
P
Peter Zijlstra 已提交
3343

3344 3345
static inline unsigned long effective_load(struct task_group *tg, int cpu,
		unsigned long wl, unsigned long wg)
P
Peter Zijlstra 已提交
3346
{
3347
	return wl;
3348
}
P
Peter Zijlstra 已提交
3349

3350 3351
#endif

3352 3353
static int wake_wide(struct task_struct *p)
{
3354
	int factor = this_cpu_read(sd_llc_size);
3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373

	/*
	 * 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;
}

3374
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
3375
{
3376
	s64 this_load, load;
3377
	int idx, this_cpu, prev_cpu;
3378
	unsigned long tl_per_task;
3379
	struct task_group *tg;
3380
	unsigned long weight;
3381
	int balanced;
3382

3383 3384 3385 3386 3387 3388 3389
	/*
	 * If we wake multiple tasks be careful to not bounce
	 * ourselves around too much.
	 */
	if (wake_wide(p))
		return 0;

3390 3391 3392 3393 3394
	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);
3395

3396 3397 3398 3399 3400
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
3401 3402 3403 3404
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

3405
		this_load += effective_load(tg, this_cpu, -weight, -weight);
3406 3407
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
3408

3409 3410
	tg = task_group(p);
	weight = p->se.load.weight;
3411

3412 3413
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
3414 3415 3416
	 * 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.
3417 3418 3419 3420
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
3421 3422
	if (this_load > 0) {
		s64 this_eff_load, prev_eff_load;
3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435

		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;
3436

3437
	/*
I
Ingo Molnar 已提交
3438 3439 3440
	 * If the currently running task will sleep within
	 * a reasonable amount of time then attract this newly
	 * woken task:
3441
	 */
3442 3443
	if (sync && balanced)
		return 1;
3444

3445
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
3446 3447
	tl_per_task = cpu_avg_load_per_task(this_cpu);

3448 3449 3450
	if (balanced ||
	    (this_load <= load &&
	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
3451 3452 3453 3454 3455
		/*
		 * This domain has SD_WAKE_AFFINE and
		 * p is cache cold in this domain, and
		 * there is no bad imbalance.
		 */
3456
		schedstat_inc(sd, ttwu_move_affine);
3457
		schedstat_inc(p, se.statistics.nr_wakeups_affine);
3458 3459 3460 3461 3462 3463

		return 1;
	}
	return 0;
}

3464 3465 3466 3467 3468
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
3469
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
3470
		  int this_cpu, int load_idx)
3471
{
3472
	struct sched_group *idlest = NULL, *group = sd->groups;
3473 3474
	unsigned long min_load = ULONG_MAX, this_load = 0;
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
3475

3476 3477 3478 3479
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
3480

3481 3482
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
3483
					tsk_cpus_allowed(p)))
3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500 3501 3502
			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 */
3503
		avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;
3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528

		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 */
3529
	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
3530 3531 3532 3533 3534
		load = weighted_cpuload(i);

		if (load < min_load || (load == min_load && i == this_cpu)) {
			min_load = load;
			idlest = i;
3535 3536 3537
		}
	}

3538 3539
	return idlest;
}
3540

3541 3542 3543
/*
 * Try and locate an idle CPU in the sched_domain.
 */
3544
static int select_idle_sibling(struct task_struct *p, int target)
3545
{
3546
	struct sched_domain *sd;
3547
	struct sched_group *sg;
3548
	int i = task_cpu(p);
3549

3550 3551
	if (idle_cpu(target))
		return target;
3552 3553

	/*
3554
	 * If the prevous cpu is cache affine and idle, don't be stupid.
3555
	 */
3556 3557
	if (i != target && cpus_share_cache(i, target) && idle_cpu(i))
		return i;
3558 3559

	/*
3560
	 * Otherwise, iterate the domains and find an elegible idle cpu.
3561
	 */
3562
	sd = rcu_dereference(per_cpu(sd_llc, target));
3563
	for_each_lower_domain(sd) {
3564 3565 3566 3567 3568 3569 3570
		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)) {
3571
				if (i == target || !idle_cpu(i))
3572 3573
					goto next;
			}
3574

3575 3576 3577 3578 3579 3580 3581 3582
			target = cpumask_first_and(sched_group_cpus(sg),
					tsk_cpus_allowed(p));
			goto done;
next:
			sg = sg->next;
		} while (sg != sd->groups);
	}
done:
3583 3584 3585
	return target;
}

3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596
/*
 * 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.
 */
3597
static int
3598
select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
3599
{
3600
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
3601 3602 3603
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
	int new_cpu = cpu;
3604
	int want_affine = 0;
3605
	int sync = wake_flags & WF_SYNC;
3606

3607
	if (p->nr_cpus_allowed == 1)
3608 3609
		return prev_cpu;

3610
	if (sd_flag & SD_BALANCE_WAKE) {
3611
		if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
3612 3613 3614
			want_affine = 1;
		new_cpu = prev_cpu;
	}
3615

3616
	rcu_read_lock();
3617
	for_each_domain(cpu, tmp) {
3618 3619 3620
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

3621
		/*
3622 3623
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
3624
		 */
3625 3626 3627
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
3628
			break;
3629
		}
3630

3631
		if (tmp->flags & sd_flag)
3632 3633 3634
			sd = tmp;
	}

3635
	if (affine_sd) {
3636
		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
3637 3638 3639 3640
			prev_cpu = cpu;

		new_cpu = select_idle_sibling(p, prev_cpu);
		goto unlock;
3641
	}
3642

3643
	while (sd) {
3644
		int load_idx = sd->forkexec_idx;
3645
		struct sched_group *group;
3646
		int weight;
3647

3648
		if (!(sd->flags & sd_flag)) {
3649 3650 3651
			sd = sd->child;
			continue;
		}
3652

3653 3654
		if (sd_flag & SD_BALANCE_WAKE)
			load_idx = sd->wake_idx;
3655

3656
		group = find_idlest_group(sd, p, cpu, load_idx);
3657 3658 3659 3660
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
3661

3662
		new_cpu = find_idlest_cpu(group, p, cpu);
3663 3664 3665 3666
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
3667
		}
3668 3669 3670

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
3671
		weight = sd->span_weight;
3672 3673
		sd = NULL;
		for_each_domain(cpu, tmp) {
3674
			if (weight <= tmp->span_weight)
3675
				break;
3676
			if (tmp->flags & sd_flag)
3677 3678 3679
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
3680
	}
3681 3682
unlock:
	rcu_read_unlock();
3683

3684
	return new_cpu;
3685
}
3686 3687 3688 3689 3690 3691 3692 3693 3694 3695

/*
 * 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)
{
3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706
	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);
3707 3708
		atomic_long_add(se->avg.load_avg_contrib,
						&cfs_rq->removed_load);
3709
	}
3710
}
3711 3712
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
3713 3714
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
3715 3716 3717 3718
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
3719 3720
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
3721 3722 3723 3724 3725 3726 3727 3728 3729
	 *
	 * 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.
3730
	 */
3731
	return calc_delta_fair(gran, se);
3732 3733
}

3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754 3755
/*
 * 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
3756
	gran = wakeup_gran(curr, se);
3757 3758 3759 3760 3761 3762
	if (vdiff > gran)
		return 1;

	return 0;
}

3763 3764
static void set_last_buddy(struct sched_entity *se)
{
3765 3766 3767 3768 3769
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
3770 3771 3772 3773
}

static void set_next_buddy(struct sched_entity *se)
{
3774 3775 3776 3777 3778
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
3779 3780
}

3781 3782
static void set_skip_buddy(struct sched_entity *se)
{
3783 3784
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
3785 3786
}

3787 3788 3789
/*
 * Preempt the current task with a newly woken task if needed:
 */
3790
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
3791 3792
{
	struct task_struct *curr = rq->curr;
3793
	struct sched_entity *se = &curr->se, *pse = &p->se;
3794
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
3795
	int scale = cfs_rq->nr_running >= sched_nr_latency;
3796
	int next_buddy_marked = 0;
3797

I
Ingo Molnar 已提交
3798 3799 3800
	if (unlikely(se == pse))
		return;

3801
	/*
3802
	 * This is possible from callers such as move_task(), in which we
3803 3804 3805 3806 3807 3808 3809
	 * 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;

3810
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
3811
		set_next_buddy(pse);
3812 3813
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
3814

3815 3816 3817
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
3818 3819 3820 3821 3822 3823
	 *
	 * 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.
3824 3825 3826 3827
	 */
	if (test_tsk_need_resched(curr))
		return;

3828 3829 3830 3831 3832
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

3833
	/*
3834 3835
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
3836
	 */
3837
	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
3838
		return;
3839

3840
	find_matching_se(&se, &pse);
3841
	update_curr(cfs_rq_of(se));
3842
	BUG_ON(!pse);
3843 3844 3845 3846 3847 3848 3849
	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);
3850
		goto preempt;
3851
	}
3852

3853
	return;
3854

3855 3856 3857 3858 3859 3860 3861 3862 3863 3864 3865 3866 3867 3868 3869 3870
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);
3871 3872
}

3873
static struct task_struct *pick_next_task_fair(struct rq *rq)
3874
{
P
Peter Zijlstra 已提交
3875
	struct task_struct *p;
3876 3877 3878
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

3879
	if (!cfs_rq->nr_running)
3880 3881 3882
		return NULL;

	do {
3883
		se = pick_next_entity(cfs_rq);
3884
		set_next_entity(cfs_rq, se);
3885 3886 3887
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
3888
	p = task_of(se);
3889 3890
	if (hrtick_enabled(rq))
		hrtick_start_fair(rq, p);
P
Peter Zijlstra 已提交
3891 3892

	return p;
3893 3894 3895 3896 3897
}

/*
 * Account for a descheduled task:
 */
3898
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
3899 3900 3901 3902 3903 3904
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
3905
		put_prev_entity(cfs_rq, se);
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
/*
 * 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);
3934 3935 3936 3937 3938 3939
		/*
		 * 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;
3940 3941 3942 3943 3944
	}

	set_skip_buddy(se);
}

3945 3946 3947 3948
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

3949 3950
	/* throttled hierarchies are not runnable */
	if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se)))
3951 3952 3953 3954 3955 3956 3957 3958 3959 3960
		return false;

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

	yield_task_fair(rq);

	return true;
}

3961
#ifdef CONFIG_SMP
3962
/**************************************************
P
Peter Zijlstra 已提交
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 3999 4000 4001 4002 4003 4004 4005 4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 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 4074 4075 4076 4077 4078
 * 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.]
 */ 
4079

4080 4081
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

4082
#define LBF_ALL_PINNED	0x01
4083
#define LBF_NEED_BREAK	0x02
4084 4085
#define LBF_DST_PINNED  0x04
#define LBF_SOME_PINNED	0x08
4086 4087 4088 4089 4090

struct lb_env {
	struct sched_domain	*sd;

	struct rq		*src_rq;
4091
	int			src_cpu;
4092 4093 4094 4095

	int			dst_cpu;
	struct rq		*dst_rq;

4096 4097
	struct cpumask		*dst_grpmask;
	int			new_dst_cpu;
4098
	enum cpu_idle_type	idle;
4099
	long			imbalance;
4100 4101 4102
	/* The set of CPUs under consideration for load-balancing */
	struct cpumask		*cpus;

4103
	unsigned int		flags;
4104 4105 4106 4107

	unsigned int		loop;
	unsigned int		loop_break;
	unsigned int		loop_max;
4108 4109
};

4110
/*
4111
 * move_task - move a task from one runqueue to another runqueue.
4112 4113
 * Both runqueues must be locked.
 */
4114
static void move_task(struct task_struct *p, struct lb_env *env)
4115
{
4116 4117 4118 4119
	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);
4120 4121
}

4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153
/*
 * 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;
}

4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170 4171 4172
#ifdef CONFIG_NUMA_BALANCING
/* Returns true if the destination node has incurred more faults */
static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
{
	int src_nid, dst_nid;

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

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

	if (src_nid == dst_nid ||
	    p->numa_migrate_seq >= sysctl_numa_balancing_settle_count)
		return false;

	if (dst_nid == p->numa_preferred_nid ||
4173
	    task_faults(p, dst_nid) > task_faults(p, src_nid))
4174 4175 4176 4177
		return true;

	return false;
}
4178 4179 4180 4181 4182 4183 4184 4185 4186 4187 4188 4189 4190 4191 4192 4193 4194 4195 4196


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

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

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

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

	if (src_nid == dst_nid ||
	    p->numa_migrate_seq >= sysctl_numa_balancing_settle_count)
		return false;

4197
	if (task_faults(p, dst_nid) < task_faults(p, src_nid))
4198 4199 4200 4201 4202
		return true;

	return false;
}

4203 4204 4205 4206 4207 4208
#else
static inline bool migrate_improves_locality(struct task_struct *p,
					     struct lb_env *env)
{
	return false;
}
4209 4210 4211 4212 4213 4214

static inline bool migrate_degrades_locality(struct task_struct *p,
					     struct lb_env *env)
{
	return false;
}
4215 4216
#endif

4217 4218 4219 4220
/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
4221
int can_migrate_task(struct task_struct *p, struct lb_env *env)
4222 4223 4224 4225
{
	int tsk_cache_hot = 0;
	/*
	 * We do not migrate tasks that are:
4226
	 * 1) throttled_lb_pair, or
4227
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
4228 4229
	 * 3) running (obviously), or
	 * 4) are cache-hot on their current CPU.
4230
	 */
4231 4232 4233
	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
		return 0;

4234
	if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) {
4235
		int cpu;
4236

4237
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
4238

4239 4240
		env->flags |= LBF_SOME_PINNED;

4241 4242 4243 4244 4245 4246 4247 4248
		/*
		 * 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.
		 */
4249
		if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED))
4250 4251
			return 0;

4252 4253 4254
		/* 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))) {
4255
				env->flags |= LBF_DST_PINNED;
4256 4257 4258
				env->new_dst_cpu = cpu;
				break;
			}
4259
		}
4260

4261 4262
		return 0;
	}
4263 4264

	/* Record that we found atleast one task that could run on dst_cpu */
4265
	env->flags &= ~LBF_ALL_PINNED;
4266

4267
	if (task_running(env->src_rq, p)) {
4268
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
4269 4270 4271 4272 4273
		return 0;
	}

	/*
	 * Aggressive migration if:
4274 4275 4276
	 * 1) destination numa is preferred
	 * 2) task is cache cold, or
	 * 3) too many balance attempts have failed.
4277
	 */
4278
	tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd);
4279 4280
	if (!tsk_cache_hot)
		tsk_cache_hot = migrate_degrades_locality(p, env);
4281 4282 4283 4284 4285 4286 4287 4288 4289 4290 4291

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

4292
	if (!tsk_cache_hot ||
4293
		env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
Z
Zhang Hang 已提交
4294

4295
		if (tsk_cache_hot) {
4296
			schedstat_inc(env->sd, lb_hot_gained[env->idle]);
4297
			schedstat_inc(p, se.statistics.nr_forced_migrations);
4298
		}
Z
Zhang Hang 已提交
4299

4300 4301 4302
		return 1;
	}

Z
Zhang Hang 已提交
4303 4304
	schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
	return 0;
4305 4306
}

4307 4308 4309 4310 4311 4312 4313
/*
 * 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.
 */
4314
static int move_one_task(struct lb_env *env)
4315 4316 4317
{
	struct task_struct *p, *n;

4318 4319 4320
	list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
		if (!can_migrate_task(p, env))
			continue;
4321

4322 4323 4324 4325 4326 4327 4328 4329
		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;
4330 4331 4332 4333
	}
	return 0;
}

4334 4335
static unsigned long task_h_load(struct task_struct *p);

4336 4337
static const unsigned int sched_nr_migrate_break = 32;

4338
/*
4339
 * move_tasks tries to move up to imbalance weighted load from busiest to
4340 4341 4342 4343 4344 4345
 * 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)
4346
{
4347 4348
	struct list_head *tasks = &env->src_rq->cfs_tasks;
	struct task_struct *p;
4349 4350
	unsigned long load;
	int pulled = 0;
4351

4352
	if (env->imbalance <= 0)
4353
		return 0;
4354

4355 4356
	while (!list_empty(tasks)) {
		p = list_first_entry(tasks, struct task_struct, se.group_node);
4357

4358 4359
		env->loop++;
		/* We've more or less seen every task there is, call it quits */
4360
		if (env->loop > env->loop_max)
4361
			break;
4362 4363

		/* take a breather every nr_migrate tasks */
4364
		if (env->loop > env->loop_break) {
4365
			env->loop_break += sched_nr_migrate_break;
4366
			env->flags |= LBF_NEED_BREAK;
4367
			break;
4368
		}
4369

4370
		if (!can_migrate_task(p, env))
4371 4372 4373
			goto next;

		load = task_h_load(p);
4374

4375
		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
4376 4377
			goto next;

4378
		if ((load / 2) > env->imbalance)
4379
			goto next;
4380

4381
		move_task(p, env);
4382
		pulled++;
4383
		env->imbalance -= load;
4384 4385

#ifdef CONFIG_PREEMPT
4386 4387 4388 4389 4390
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
		 * kernels will stop after the first task is pulled to minimize
		 * the critical section.
		 */
4391
		if (env->idle == CPU_NEWLY_IDLE)
4392
			break;
4393 4394
#endif

4395 4396 4397 4398
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
4399
		if (env->imbalance <= 0)
4400
			break;
4401 4402 4403

		continue;
next:
4404
		list_move_tail(&p->se.group_node, tasks);
4405
	}
4406

4407
	/*
4408 4409 4410
	 * 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().
4411
	 */
4412
	schedstat_add(env->sd, lb_gained[env->idle], pulled);
4413

4414
	return pulled;
4415 4416
}

P
Peter Zijlstra 已提交
4417
#ifdef CONFIG_FAIR_GROUP_SCHED
4418 4419 4420
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
4421
static void __update_blocked_averages_cpu(struct task_group *tg, int cpu)
4422
{
4423 4424
	struct sched_entity *se = tg->se[cpu];
	struct cfs_rq *cfs_rq = tg->cfs_rq[cpu];
4425

4426 4427 4428
	/* throttled entities do not contribute to load */
	if (throttled_hierarchy(cfs_rq))
		return;
4429

4430
	update_cfs_rq_blocked_load(cfs_rq, 1);
4431

4432 4433 4434 4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445
	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 {
4446
		struct rq *rq = rq_of(cfs_rq);
4447 4448
		update_rq_runnable_avg(rq, rq->nr_running);
	}
4449 4450
}

4451
static void update_blocked_averages(int cpu)
4452 4453
{
	struct rq *rq = cpu_rq(cpu);
4454 4455
	struct cfs_rq *cfs_rq;
	unsigned long flags;
4456

4457 4458
	raw_spin_lock_irqsave(&rq->lock, flags);
	update_rq_clock(rq);
4459 4460 4461 4462
	/*
	 * Iterates the task_group tree in a bottom up fashion, see
	 * list_add_leaf_cfs_rq() for details.
	 */
4463
	for_each_leaf_cfs_rq(rq, cfs_rq) {
4464 4465 4466 4467 4468 4469
		/*
		 * 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);
4470
	}
4471 4472

	raw_spin_unlock_irqrestore(&rq->lock, flags);
4473 4474
}

4475
/*
4476
 * Compute the hierarchical load factor for cfs_rq and all its ascendants.
4477 4478 4479
 * This needs to be done in a top-down fashion because the load of a child
 * group is a fraction of its parents load.
 */
4480
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
4481
{
4482 4483
	struct rq *rq = rq_of(cfs_rq);
	struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
4484
	unsigned long now = jiffies;
4485
	unsigned long load;
4486

4487
	if (cfs_rq->last_h_load_update == now)
4488 4489
		return;

4490 4491 4492 4493 4494 4495 4496
	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;
	}
4497

4498
	if (!se) {
4499
		cfs_rq->h_load = cfs_rq->runnable_load_avg;
4500 4501 4502 4503 4504 4505 4506 4507 4508 4509 4510
		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;
	}
4511 4512
}

4513
static unsigned long task_h_load(struct task_struct *p)
P
Peter Zijlstra 已提交
4514
{
4515
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
P
Peter Zijlstra 已提交
4516

4517
	update_cfs_rq_h_load(cfs_rq);
4518 4519
	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
4520 4521
}
#else
4522
static inline void update_blocked_averages(int cpu)
4523 4524 4525
{
}

4526
static unsigned long task_h_load(struct task_struct *p)
4527
{
4528
	return p->se.avg.load_avg_contrib;
4529
}
P
Peter Zijlstra 已提交
4530
#endif
4531 4532 4533 4534 4535 4536 4537 4538 4539

/********** 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
4540
	unsigned long load_per_task;
4541
	unsigned long group_power;
4542 4543 4544 4545
	unsigned int sum_nr_running; /* Nr tasks running in the group */
	unsigned int group_capacity;
	unsigned int idle_cpus;
	unsigned int group_weight;
4546
	int group_imb; /* Is there an imbalance in the group ? */
4547
	int group_has_capacity; /* Is there extra capacity in the group? */
4548 4549
};

J
Joonsoo Kim 已提交
4550 4551 4552 4553 4554 4555 4556 4557 4558 4559 4560 4561
/*
 * 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 */
4562
	struct sg_lb_stats local_stat;	/* Statistics of the local group */
J
Joonsoo Kim 已提交
4563 4564
};

4565 4566 4567 4568 4569 4570 4571 4572 4573 4574 4575 4576 4577 4578 4579 4580 4581 4582 4583
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,
		},
	};
}

4584 4585 4586 4587
/**
 * 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.
4588 4589
 *
 * Return: The load index.
4590 4591 4592 4593 4594 4595 4596 4597 4598 4599 4600 4601 4602 4603 4604 4605 4606 4607 4608 4609 4610 4611
 */
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;
}

4612
static unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
4613
{
4614
	return SCHED_POWER_SCALE;
4615 4616 4617 4618 4619 4620 4621
}

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

4622
static unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
4623
{
4624
	unsigned long weight = sd->span_weight;
4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636
	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);
}

4637
static unsigned long scale_rt_power(int cpu)
4638 4639
{
	struct rq *rq = cpu_rq(cpu);
4640
	u64 total, available, age_stamp, avg;
4641

4642 4643 4644 4645 4646 4647 4648
	/*
	 * 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);

4649
	total = sched_avg_period() + (rq_clock(rq) - age_stamp);
4650

4651
	if (unlikely(total < avg)) {
4652 4653 4654
		/* Ensures that power won't end up being negative */
		available = 0;
	} else {
4655
		available = total - avg;
4656
	}
4657

4658 4659
	if (unlikely((s64)total < SCHED_POWER_SCALE))
		total = SCHED_POWER_SCALE;
4660

4661
	total >>= SCHED_POWER_SHIFT;
4662 4663 4664 4665 4666 4667

	return div_u64(available, total);
}

static void update_cpu_power(struct sched_domain *sd, int cpu)
{
4668
	unsigned long weight = sd->span_weight;
4669
	unsigned long power = SCHED_POWER_SCALE;
4670 4671 4672 4673 4674 4675 4676 4677
	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);

4678
		power >>= SCHED_POWER_SHIFT;
4679 4680
	}

4681
	sdg->sgp->power_orig = power;
4682 4683 4684 4685 4686 4687

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

4688
	power >>= SCHED_POWER_SHIFT;
4689

4690
	power *= scale_rt_power(cpu);
4691
	power >>= SCHED_POWER_SHIFT;
4692 4693 4694 4695

	if (!power)
		power = 1;

4696
	cpu_rq(cpu)->cpu_power = power;
4697
	sdg->sgp->power = power;
4698 4699
}

4700
void update_group_power(struct sched_domain *sd, int cpu)
4701 4702 4703
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
4704
	unsigned long power, power_orig;
4705 4706 4707 4708 4709
	unsigned long interval;

	interval = msecs_to_jiffies(sd->balance_interval);
	interval = clamp(interval, 1UL, max_load_balance_interval);
	sdg->sgp->next_update = jiffies + interval;
4710 4711 4712 4713 4714 4715

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

4716
	power_orig = power = 0;
4717

P
Peter Zijlstra 已提交
4718 4719 4720 4721 4722 4723
	if (child->flags & SD_OVERLAP) {
		/*
		 * SD_OVERLAP domains cannot assume that child groups
		 * span the current group.
		 */

4724 4725 4726 4727 4728 4729
		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
4730 4731 4732 4733 4734 4735 4736 4737
	} else  {
		/*
		 * !SD_OVERLAP domains can assume that child groups
		 * span the current group.
		 */ 

		group = child->groups;
		do {
4738
			power_orig += group->sgp->power_orig;
P
Peter Zijlstra 已提交
4739 4740 4741 4742
			power += group->sgp->power;
			group = group->next;
		} while (group != child->groups);
	}
4743

4744 4745
	sdg->sgp->power_orig = power_orig;
	sdg->sgp->power = power;
4746 4747
}

4748 4749 4750 4751 4752 4753 4754 4755 4756 4757 4758
/*
 * 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)
{
	/*
4759
	 * Only siblings can have significantly less than SCHED_POWER_SCALE
4760
	 */
P
Peter Zijlstra 已提交
4761
	if (!(sd->flags & SD_SHARE_CPUPOWER))
4762 4763 4764 4765 4766
		return 0;

	/*
	 * If ~90% of the cpu_power is still there, we're good.
	 */
4767
	if (group->sgp->power * 32 > group->sgp->power_orig * 29)
4768 4769 4770 4771 4772
		return 1;

	return 0;
}

4773 4774 4775 4776 4777 4778 4779 4780 4781 4782 4783 4784 4785 4786 4787 4788
/*
 * 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
4789 4790
 * by noticing the lower domain failed to reach balance and had difficulty
 * moving tasks due to affinity constraints.
4791 4792 4793
 *
 * When this is so detected; this group becomes a candidate for busiest; see
 * update_sd_pick_busiest(). And calculcate_imbalance() and
4794
 * find_busiest_group() avoid some of the usual balance conditions to allow it
4795 4796 4797 4798 4799 4800 4801
 * 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.
 */

4802
static inline int sg_imbalanced(struct sched_group *group)
4803
{
4804
	return group->sgp->imbalance;
4805 4806
}

4807 4808 4809
/*
 * Compute the group capacity.
 *
4810 4811 4812
 * 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.
4813 4814 4815
 */
static inline int sg_capacity(struct lb_env *env, struct sched_group *group)
{
4816 4817 4818 4819 4820 4821
	unsigned int capacity, smt, cpus;
	unsigned int power, power_orig;

	power = group->sgp->power;
	power_orig = group->sgp->power_orig;
	cpus = group->group_weight;
4822

4823 4824 4825
	/* smt := ceil(cpus / power), assumes: 1 < smt_power < 2 */
	smt = DIV_ROUND_UP(SCHED_POWER_SCALE * cpus, power_orig);
	capacity = cpus / smt; /* cores */
4826

4827
	capacity = min_t(unsigned, capacity, DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE));
4828 4829 4830 4831 4832 4833
	if (!capacity)
		capacity = fix_small_capacity(env->sd, group);

	return capacity;
}

4834 4835
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
4836
 * @env: The load balancing environment.
4837 4838 4839 4840 4841
 * @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.
 */
4842 4843
static inline void update_sg_lb_stats(struct lb_env *env,
			struct sched_group *group, int load_idx,
4844
			int local_group, struct sg_lb_stats *sgs)
4845
{
4846 4847
	unsigned long nr_running;
	unsigned long load;
4848
	int i;
4849

4850 4851
	memset(sgs, 0, sizeof(*sgs));

4852
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
4853 4854
		struct rq *rq = cpu_rq(i);

4855 4856
		nr_running = rq->nr_running;

4857
		/* Bias balancing toward cpus of our domain */
4858
		if (local_group)
4859
			load = target_load(i, load_idx);
4860
		else
4861 4862 4863
			load = source_load(i, load_idx);

		sgs->group_load += load;
4864
		sgs->sum_nr_running += nr_running;
4865
		sgs->sum_weighted_load += weighted_cpuload(i);
4866 4867
		if (idle_cpu(i))
			sgs->idle_cpus++;
4868 4869 4870
	}

	/* Adjust by relative CPU power of the group */
4871 4872
	sgs->group_power = group->sgp->power;
	sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / sgs->group_power;
4873

4874
	if (sgs->sum_nr_running)
4875
		sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
4876

4877
	sgs->group_weight = group->group_weight;
4878

4879 4880 4881
	sgs->group_imb = sg_imbalanced(group);
	sgs->group_capacity = sg_capacity(env, group);

4882 4883
	if (sgs->group_capacity > sgs->sum_nr_running)
		sgs->group_has_capacity = 1;
4884 4885
}

4886 4887
/**
 * update_sd_pick_busiest - return 1 on busiest group
4888
 * @env: The load balancing environment.
4889 4890
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
4891
 * @sgs: sched_group statistics
4892 4893 4894
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
4895 4896 4897
 *
 * Return: %true if @sg is a busier group than the previously selected
 * busiest group. %false otherwise.
4898
 */
4899
static bool update_sd_pick_busiest(struct lb_env *env,
4900 4901
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
4902
				   struct sg_lb_stats *sgs)
4903
{
J
Joonsoo Kim 已提交
4904
	if (sgs->avg_load <= sds->busiest_stat.avg_load)
4905 4906 4907 4908 4909 4910 4911 4912 4913 4914 4915 4916 4917
		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.
	 */
4918 4919
	if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
	    env->dst_cpu < group_first_cpu(sg)) {
4920 4921 4922 4923 4924 4925 4926 4927 4928 4929
		if (!sds->busiest)
			return true;

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

	return false;
}

4930
/**
4931
 * update_sd_lb_stats - Update sched_domain's statistics for load balancing.
4932
 * @env: The load balancing environment.
4933 4934 4935
 * @balance: Should we balance.
 * @sds: variable to hold the statistics for this sched_domain.
 */
4936
static inline void update_sd_lb_stats(struct lb_env *env,
4937
					struct sd_lb_stats *sds)
4938
{
4939 4940
	struct sched_domain *child = env->sd->child;
	struct sched_group *sg = env->sd->groups;
J
Joonsoo Kim 已提交
4941
	struct sg_lb_stats tmp_sgs;
4942 4943 4944 4945 4946
	int load_idx, prefer_sibling = 0;

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

4947
	load_idx = get_sd_load_idx(env->sd, env->idle);
4948 4949

	do {
J
Joonsoo Kim 已提交
4950
		struct sg_lb_stats *sgs = &tmp_sgs;
4951 4952
		int local_group;

4953
		local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
J
Joonsoo Kim 已提交
4954 4955 4956
		if (local_group) {
			sds->local = sg;
			sgs = &sds->local_stat;
4957 4958 4959 4960

			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
4961
		}
4962

J
Joonsoo Kim 已提交
4963
		update_sg_lb_stats(env, sg, load_idx, local_group, sgs);
4964

4965 4966 4967
		if (local_group)
			goto next_group;

4968 4969
		/*
		 * In case the child domain prefers tasks go to siblings
4970
		 * first, lower the sg capacity to one so that we'll try
4971 4972 4973 4974 4975 4976
		 * 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).
4977
		 */
4978 4979
		if (prefer_sibling && sds->local &&
		    sds->local_stat.group_has_capacity)
4980
			sgs->group_capacity = min(sgs->group_capacity, 1U);
4981

4982
		if (update_sd_pick_busiest(env, sds, sg, sgs)) {
4983
			sds->busiest = sg;
J
Joonsoo Kim 已提交
4984
			sds->busiest_stat = *sgs;
4985 4986
		}

4987 4988 4989 4990 4991
next_group:
		/* Now, start updating sd_lb_stats */
		sds->total_load += sgs->group_load;
		sds->total_pwr += sgs->group_power;

4992
		sg = sg->next;
4993
	} while (sg != env->sd->groups);
4994 4995 4996 4997 4998 4999 5000 5001 5002 5003 5004 5005 5006 5007 5008 5009 5010 5011 5012
}

/**
 * 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.
 *
5013
 * Return: 1 when packing is required and a task should be moved to
5014 5015
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
5016
 * @env: The load balancing environment.
5017 5018
 * @sds: Statistics of the sched_domain which is to be packed
 */
5019
static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
5020 5021 5022
{
	int busiest_cpu;

5023
	if (!(env->sd->flags & SD_ASYM_PACKING))
5024 5025 5026 5027 5028 5029
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
5030
	if (env->dst_cpu > busiest_cpu)
5031 5032
		return 0;

5033
	env->imbalance = DIV_ROUND_CLOSEST(
5034 5035
		sds->busiest_stat.avg_load * sds->busiest_stat.group_power,
		SCHED_POWER_SCALE);
5036

5037
	return 1;
5038 5039 5040 5041 5042 5043
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
5044
 * @env: The load balancing environment.
5045 5046
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 */
5047 5048
static inline
void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
5049 5050 5051
{
	unsigned long tmp, pwr_now = 0, pwr_move = 0;
	unsigned int imbn = 2;
5052
	unsigned long scaled_busy_load_per_task;
J
Joonsoo Kim 已提交
5053
	struct sg_lb_stats *local, *busiest;
5054

J
Joonsoo Kim 已提交
5055 5056
	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
5057

J
Joonsoo Kim 已提交
5058 5059 5060 5061
	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;
5062

J
Joonsoo Kim 已提交
5063 5064
	scaled_busy_load_per_task =
		(busiest->load_per_task * SCHED_POWER_SCALE) /
5065
		busiest->group_power;
J
Joonsoo Kim 已提交
5066

5067 5068
	if (busiest->avg_load + scaled_busy_load_per_task >=
	    local->avg_load + (scaled_busy_load_per_task * imbn)) {
J
Joonsoo Kim 已提交
5069
		env->imbalance = busiest->load_per_task;
5070 5071 5072 5073 5074 5075 5076 5077 5078
		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.
	 */

5079
	pwr_now += busiest->group_power *
J
Joonsoo Kim 已提交
5080
			min(busiest->load_per_task, busiest->avg_load);
5081
	pwr_now += local->group_power *
J
Joonsoo Kim 已提交
5082
			min(local->load_per_task, local->avg_load);
5083
	pwr_now /= SCHED_POWER_SCALE;
5084 5085

	/* Amount of load we'd subtract */
J
Joonsoo Kim 已提交
5086
	tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
5087
		busiest->group_power;
J
Joonsoo Kim 已提交
5088
	if (busiest->avg_load > tmp) {
5089
		pwr_move += busiest->group_power *
J
Joonsoo Kim 已提交
5090 5091 5092
			    min(busiest->load_per_task,
				busiest->avg_load - tmp);
	}
5093 5094

	/* Amount of load we'd add */
5095
	if (busiest->avg_load * busiest->group_power <
J
Joonsoo Kim 已提交
5096
	    busiest->load_per_task * SCHED_POWER_SCALE) {
5097 5098
		tmp = (busiest->avg_load * busiest->group_power) /
		      local->group_power;
J
Joonsoo Kim 已提交
5099 5100
	} else {
		tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
5101
		      local->group_power;
J
Joonsoo Kim 已提交
5102
	}
5103 5104
	pwr_move += local->group_power *
		    min(local->load_per_task, local->avg_load + tmp);
5105
	pwr_move /= SCHED_POWER_SCALE;
5106 5107 5108

	/* Move if we gain throughput */
	if (pwr_move > pwr_now)
J
Joonsoo Kim 已提交
5109
		env->imbalance = busiest->load_per_task;
5110 5111 5112 5113 5114
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
5115
 * @env: load balance environment
5116 5117
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 */
5118
static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
5119
{
5120
	unsigned long max_pull, load_above_capacity = ~0UL;
J
Joonsoo Kim 已提交
5121 5122 5123 5124
	struct sg_lb_stats *local, *busiest;

	local = &sds->local_stat;
	busiest = &sds->busiest_stat;
5125

J
Joonsoo Kim 已提交
5126
	if (busiest->group_imb) {
5127 5128 5129 5130
		/*
		 * 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
5131 5132
		busiest->load_per_task =
			min(busiest->load_per_task, sds->avg_load);
5133 5134
	}

5135 5136 5137 5138 5139
	/*
	 * 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..)
	 */
5140 5141
	if (busiest->avg_load <= sds->avg_load ||
	    local->avg_load >= sds->avg_load) {
5142 5143
		env->imbalance = 0;
		return fix_small_imbalance(env, sds);
5144 5145
	}

J
Joonsoo Kim 已提交
5146
	if (!busiest->group_imb) {
5147 5148
		/*
		 * Don't want to pull so many tasks that a group would go idle.
5149 5150
		 * Except of course for the group_imb case, since then we might
		 * have to drop below capacity to reach cpu-load equilibrium.
5151
		 */
J
Joonsoo Kim 已提交
5152 5153
		load_above_capacity =
			(busiest->sum_nr_running - busiest->group_capacity);
5154

5155
		load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
5156
		load_above_capacity /= busiest->group_power;
5157 5158 5159 5160 5161 5162 5163 5164 5165 5166
	}

	/*
	 * 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.
	 */
5167
	max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity);
5168 5169

	/* How much load to actually move to equalise the imbalance */
J
Joonsoo Kim 已提交
5170
	env->imbalance = min(
5171 5172
		max_pull * busiest->group_power,
		(sds->avg_load - local->avg_load) * local->group_power
J
Joonsoo Kim 已提交
5173
	) / SCHED_POWER_SCALE;
5174 5175 5176

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
5177
	 * there is no guarantee that any tasks will be moved so we'll have
5178 5179 5180
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
J
Joonsoo Kim 已提交
5181
	if (env->imbalance < busiest->load_per_task)
5182
		return fix_small_imbalance(env, sds);
5183
}
5184

5185 5186 5187 5188 5189 5190 5191 5192 5193 5194 5195 5196
/******* 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.
 *
5197
 * @env: The load balancing environment.
5198
 *
5199
 * Return:	- The busiest group if imbalance exists.
5200 5201 5202 5203
 *		- 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
5204
static struct sched_group *find_busiest_group(struct lb_env *env)
5205
{
J
Joonsoo Kim 已提交
5206
	struct sg_lb_stats *local, *busiest;
5207 5208
	struct sd_lb_stats sds;

5209
	init_sd_lb_stats(&sds);
5210 5211 5212 5213 5214

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
5215
	update_sd_lb_stats(env, &sds);
J
Joonsoo Kim 已提交
5216 5217
	local = &sds.local_stat;
	busiest = &sds.busiest_stat;
5218

5219 5220
	if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(env, &sds))
5221 5222
		return sds.busiest;

5223
	/* There is no busy sibling group to pull tasks from */
J
Joonsoo Kim 已提交
5224
	if (!sds.busiest || busiest->sum_nr_running == 0)
5225 5226
		goto out_balanced;

5227
	sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
5228

P
Peter Zijlstra 已提交
5229 5230
	/*
	 * If the busiest group is imbalanced the below checks don't
5231
	 * work because they assume all things are equal, which typically
P
Peter Zijlstra 已提交
5232 5233
	 * isn't true due to cpus_allowed constraints and the like.
	 */
J
Joonsoo Kim 已提交
5234
	if (busiest->group_imb)
P
Peter Zijlstra 已提交
5235 5236
		goto force_balance;

5237
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
J
Joonsoo Kim 已提交
5238 5239
	if (env->idle == CPU_NEWLY_IDLE && local->group_has_capacity &&
	    !busiest->group_has_capacity)
5240 5241
		goto force_balance;

5242 5243 5244 5245
	/*
	 * 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
5246
	if (local->avg_load >= busiest->avg_load)
5247 5248
		goto out_balanced;

5249 5250 5251 5252
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
J
Joonsoo Kim 已提交
5253
	if (local->avg_load >= sds.avg_load)
5254 5255
		goto out_balanced;

5256
	if (env->idle == CPU_IDLE) {
5257 5258 5259 5260 5261 5262
		/*
		 * 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
5263 5264
		if ((local->idle_cpus < busiest->idle_cpus) &&
		    busiest->sum_nr_running <= busiest->group_weight)
5265
			goto out_balanced;
5266 5267 5268 5269 5270
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
J
Joonsoo Kim 已提交
5271 5272
		if (100 * busiest->avg_load <=
				env->sd->imbalance_pct * local->avg_load)
5273
			goto out_balanced;
5274
	}
5275

5276
force_balance:
5277
	/* Looks like there is an imbalance. Compute it */
5278
	calculate_imbalance(env, &sds);
5279 5280 5281
	return sds.busiest;

out_balanced:
5282
	env->imbalance = 0;
5283 5284 5285 5286 5287 5288
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
5289
static struct rq *find_busiest_queue(struct lb_env *env,
5290
				     struct sched_group *group)
5291 5292
{
	struct rq *busiest = NULL, *rq;
5293
	unsigned long busiest_load = 0, busiest_power = 1;
5294 5295
	int i;

5296
	for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
5297
		unsigned long power = power_of(i);
5298 5299
		unsigned long capacity = DIV_ROUND_CLOSEST(power,
							   SCHED_POWER_SCALE);
5300 5301
		unsigned long wl;

5302
		if (!capacity)
5303
			capacity = fix_small_capacity(env->sd, group);
5304

5305
		rq = cpu_rq(i);
5306
		wl = weighted_cpuload(i);
5307

5308 5309 5310 5311
		/*
		 * When comparing with imbalance, use weighted_cpuload()
		 * which is not scaled with the cpu power.
		 */
5312
		if (capacity && rq->nr_running == 1 && wl > env->imbalance)
5313 5314
			continue;

5315 5316 5317 5318 5319
		/*
		 * 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.
5320 5321 5322 5323 5324
		 *
		 * 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.
5325
		 */
5326 5327 5328
		if (wl * busiest_power > busiest_load * power) {
			busiest_load = wl;
			busiest_power = power;
5329 5330 5331 5332 5333 5334 5335 5336 5337 5338 5339 5340 5341 5342
			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. */
5343
DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
5344

5345
static int need_active_balance(struct lb_env *env)
5346
{
5347 5348 5349
	struct sched_domain *sd = env->sd;

	if (env->idle == CPU_NEWLY_IDLE) {
5350 5351 5352 5353 5354 5355

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
5356
		if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu)
5357
			return 1;
5358 5359 5360 5361 5362
	}

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

5363 5364
static int active_load_balance_cpu_stop(void *data);

5365 5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379 5380 5381 5382 5383 5384 5385 5386 5387 5388 5389 5390 5391 5392 5393 5394 5395
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.
	 */
5396
	return balance_cpu == env->dst_cpu;
5397 5398
}

5399 5400 5401 5402 5403 5404
/*
 * 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,
5405
			int *continue_balancing)
5406
{
5407
	int ld_moved, cur_ld_moved, active_balance = 0;
5408
	struct sched_domain *sd_parent = sd->parent;
5409 5410 5411
	struct sched_group *group;
	struct rq *busiest;
	unsigned long flags;
5412
	struct cpumask *cpus = __get_cpu_var(load_balance_mask);
5413

5414 5415
	struct lb_env env = {
		.sd		= sd,
5416 5417
		.dst_cpu	= this_cpu,
		.dst_rq		= this_rq,
5418
		.dst_grpmask    = sched_group_cpus(sd->groups),
5419
		.idle		= idle,
5420
		.loop_break	= sched_nr_migrate_break,
5421
		.cpus		= cpus,
5422 5423
	};

5424 5425 5426 5427
	/*
	 * For NEWLY_IDLE load_balancing, we don't need to consider
	 * other cpus in our group
	 */
5428
	if (idle == CPU_NEWLY_IDLE)
5429 5430
		env.dst_grpmask = NULL;

5431 5432 5433 5434 5435
	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
5436 5437
	if (!should_we_balance(&env)) {
		*continue_balancing = 0;
5438
		goto out_balanced;
5439
	}
5440

5441
	group = find_busiest_group(&env);
5442 5443 5444 5445 5446
	if (!group) {
		schedstat_inc(sd, lb_nobusyg[idle]);
		goto out_balanced;
	}

5447
	busiest = find_busiest_queue(&env, group);
5448 5449 5450 5451 5452
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

5453
	BUG_ON(busiest == env.dst_rq);
5454

5455
	schedstat_add(sd, lb_imbalance[idle], env.imbalance);
5456 5457 5458 5459 5460 5461 5462 5463 5464

	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.
		 */
5465
		env.flags |= LBF_ALL_PINNED;
5466 5467 5468
		env.src_cpu   = busiest->cpu;
		env.src_rq    = busiest;
		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);
5469

5470
more_balance:
5471
		local_irq_save(flags);
5472
		double_rq_lock(env.dst_rq, busiest);
5473 5474 5475 5476 5477 5478 5479

		/*
		 * 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;
5480
		double_rq_unlock(env.dst_rq, busiest);
5481 5482 5483 5484 5485
		local_irq_restore(flags);

		/*
		 * some other cpu did the load balance for us.
		 */
5486 5487 5488
		if (cur_ld_moved && env.dst_cpu != smp_processor_id())
			resched_cpu(env.dst_cpu);

5489 5490 5491 5492 5493
		if (env.flags & LBF_NEED_BREAK) {
			env.flags &= ~LBF_NEED_BREAK;
			goto more_balance;
		}

5494 5495 5496 5497 5498 5499 5500 5501 5502 5503 5504 5505 5506 5507 5508 5509 5510 5511 5512
		/*
		 * 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.
		 */
5513
		if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
5514

5515 5516 5517
			/* Prevent to re-select dst_cpu via env's cpus */
			cpumask_clear_cpu(env.dst_cpu, env.cpus);

5518
			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
5519
			env.dst_cpu	 = env.new_dst_cpu;
5520
			env.flags	&= ~LBF_DST_PINNED;
5521 5522
			env.loop	 = 0;
			env.loop_break	 = sched_nr_migrate_break;
5523

5524 5525 5526 5527 5528 5529
			/*
			 * Go back to "more_balance" rather than "redo" since we
			 * need to continue with same src_cpu.
			 */
			goto more_balance;
		}
5530

5531 5532 5533 5534 5535 5536 5537 5538 5539 5540 5541 5542
		/*
		 * 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;
		}

5543
		/* All tasks on this runqueue were pinned by CPU affinity */
5544
		if (unlikely(env.flags & LBF_ALL_PINNED)) {
5545
			cpumask_clear_cpu(cpu_of(busiest), cpus);
5546 5547 5548
			if (!cpumask_empty(cpus)) {
				env.loop = 0;
				env.loop_break = sched_nr_migrate_break;
5549
				goto redo;
5550
			}
5551 5552 5553 5554 5555 5556
			goto out_balanced;
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
5557 5558 5559 5560 5561 5562 5563 5564
		/*
		 * 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++;
5565

5566
		if (need_active_balance(&env)) {
5567 5568
			raw_spin_lock_irqsave(&busiest->lock, flags);

5569 5570 5571
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
5572 5573
			 */
			if (!cpumask_test_cpu(this_cpu,
5574
					tsk_cpus_allowed(busiest->curr))) {
5575 5576
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
5577
				env.flags |= LBF_ALL_PINNED;
5578 5579 5580
				goto out_one_pinned;
			}

5581 5582 5583 5584 5585
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
5586 5587 5588 5589 5590 5591
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
5592

5593
			if (active_balance) {
5594 5595 5596
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
5597
			}
5598 5599 5600 5601 5602 5603 5604 5605 5606 5607 5608 5609 5610 5611 5612 5613 5614 5615 5616 5617 5618 5619 5620 5621 5622 5623 5624 5625 5626 5627 5628 5629 5630

			/*
			 * 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 */
5631
	if (((env.flags & LBF_ALL_PINNED) &&
5632
			sd->balance_interval < MAX_PINNED_INTERVAL) ||
5633 5634 5635
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

5636
	ld_moved = 0;
5637 5638 5639 5640 5641 5642 5643 5644
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.
 */
5645
void idle_balance(int this_cpu, struct rq *this_rq)
5646 5647 5648 5649
{
	struct sched_domain *sd;
	int pulled_task = 0;
	unsigned long next_balance = jiffies + HZ;
5650
	u64 curr_cost = 0;
5651

5652
	this_rq->idle_stamp = rq_clock(this_rq);
5653 5654 5655 5656

	if (this_rq->avg_idle < sysctl_sched_migration_cost)
		return;

5657 5658 5659 5660 5661
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

5662
	update_blocked_averages(this_cpu);
5663
	rcu_read_lock();
5664 5665
	for_each_domain(this_cpu, sd) {
		unsigned long interval;
5666
		int continue_balancing = 1;
5667
		u64 t0, domain_cost;
5668 5669 5670 5671

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

5672 5673 5674
		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost)
			break;

5675
		if (sd->flags & SD_BALANCE_NEWIDLE) {
5676 5677
			t0 = sched_clock_cpu(this_cpu);

5678
			/* If we've pulled tasks over stop searching: */
5679
			pulled_task = load_balance(this_cpu, this_rq,
5680 5681
						   sd, CPU_NEWLY_IDLE,
						   &continue_balancing);
5682 5683 5684 5685 5686 5687

			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;
5688
		}
5689 5690 5691 5692

		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
5693 5694
		if (pulled_task) {
			this_rq->idle_stamp = 0;
5695
			break;
N
Nikhil Rao 已提交
5696
		}
5697
	}
5698
	rcu_read_unlock();
5699 5700 5701

	raw_spin_lock(&this_rq->lock);

5702 5703 5704 5705 5706 5707 5708
	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;
	}
5709 5710 5711

	if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;
5712 5713 5714
}

/*
5715 5716 5717 5718
 * 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.
5719
 */
5720
static int active_load_balance_cpu_stop(void *data)
5721
{
5722 5723
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
5724
	int target_cpu = busiest_rq->push_cpu;
5725
	struct rq *target_rq = cpu_rq(target_cpu);
5726
	struct sched_domain *sd;
5727 5728 5729 5730 5731 5732 5733

	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;
5734 5735 5736

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
5737
		goto out_unlock;
5738 5739 5740 5741 5742 5743 5744 5745 5746 5747 5748 5749

	/*
	 * 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. */
5750
	rcu_read_lock();
5751 5752 5753 5754 5755 5756 5757
	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)) {
5758 5759
		struct lb_env env = {
			.sd		= sd,
5760 5761 5762 5763
			.dst_cpu	= target_cpu,
			.dst_rq		= target_rq,
			.src_cpu	= busiest_rq->cpu,
			.src_rq		= busiest_rq,
5764 5765 5766
			.idle		= CPU_IDLE,
		};

5767 5768
		schedstat_inc(sd, alb_count);

5769
		if (move_one_task(&env))
5770 5771 5772 5773
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
5774
	rcu_read_unlock();
5775
	double_unlock_balance(busiest_rq, target_rq);
5776 5777 5778 5779
out_unlock:
	busiest_rq->active_balance = 0;
	raw_spin_unlock_irq(&busiest_rq->lock);
	return 0;
5780 5781
}

5782
#ifdef CONFIG_NO_HZ_COMMON
5783 5784 5785 5786 5787 5788
/*
 * 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.
 */
5789
static struct {
5790
	cpumask_var_t idle_cpus_mask;
5791
	atomic_t nr_cpus;
5792 5793
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
5794

5795
static inline int find_new_ilb(int call_cpu)
5796
{
5797
	int ilb = cpumask_first(nohz.idle_cpus_mask);
5798

5799 5800 5801 5802
	if (ilb < nr_cpu_ids && idle_cpu(ilb))
		return ilb;

	return nr_cpu_ids;
5803 5804
}

5805 5806 5807 5808 5809 5810 5811 5812 5813 5814 5815
/*
 * 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++;

5816
	ilb_cpu = find_new_ilb(cpu);
5817

5818 5819
	if (ilb_cpu >= nr_cpu_ids)
		return;
5820

5821
	if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu)))
5822 5823 5824 5825 5826 5827 5828 5829
		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);
5830 5831 5832
	return;
}

5833
static inline void nohz_balance_exit_idle(int cpu)
5834 5835 5836 5837 5838 5839 5840 5841
{
	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));
	}
}

5842 5843 5844 5845 5846
static inline void set_cpu_sd_state_busy(void)
{
	struct sched_domain *sd;

	rcu_read_lock();
N
Nathan Zimmer 已提交
5847
	sd = rcu_dereference_check_sched_domain(this_rq()->sd);
V
Vincent Guittot 已提交
5848 5849 5850 5851 5852 5853

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

	for (; sd; sd = sd->parent)
5854
		atomic_inc(&sd->groups->sgp->nr_busy_cpus);
V
Vincent Guittot 已提交
5855
unlock:
5856 5857 5858 5859 5860 5861 5862 5863
	rcu_read_unlock();
}

void set_cpu_sd_state_idle(void)
{
	struct sched_domain *sd;

	rcu_read_lock();
N
Nathan Zimmer 已提交
5864
	sd = rcu_dereference_check_sched_domain(this_rq()->sd);
V
Vincent Guittot 已提交
5865 5866 5867 5868 5869 5870

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

	for (; sd; sd = sd->parent)
5871
		atomic_dec(&sd->groups->sgp->nr_busy_cpus);
V
Vincent Guittot 已提交
5872
unlock:
5873 5874 5875
	rcu_read_unlock();
}

5876
/*
5877
 * This routine will record that the cpu is going idle with tick stopped.
5878
 * This info will be used in performing idle load balancing in the future.
5879
 */
5880
void nohz_balance_enter_idle(int cpu)
5881
{
5882 5883 5884 5885 5886 5887
	/*
	 * If this cpu is going down, then nothing needs to be done.
	 */
	if (!cpu_active(cpu))
		return;

5888 5889
	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
		return;
5890

5891 5892 5893
	cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
	atomic_inc(&nohz.nr_cpus);
	set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu));
5894
}
5895

5896
static int sched_ilb_notifier(struct notifier_block *nfb,
5897 5898 5899 5900
					unsigned long action, void *hcpu)
{
	switch (action & ~CPU_TASKS_FROZEN) {
	case CPU_DYING:
5901
		nohz_balance_exit_idle(smp_processor_id());
5902 5903 5904 5905 5906
		return NOTIFY_OK;
	default:
		return NOTIFY_DONE;
	}
}
5907 5908 5909 5910
#endif

static DEFINE_SPINLOCK(balancing);

5911 5912 5913 5914
/*
 * 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.
 */
5915
void update_max_interval(void)
5916 5917 5918 5919
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

5920 5921 5922 5923
/*
 * It checks each scheduling domain to see if it is due to be balanced,
 * and initiates a balancing operation if so.
 *
5924
 * Balancing parameters are set up in init_sched_domains.
5925 5926 5927
 */
static void rebalance_domains(int cpu, enum cpu_idle_type idle)
{
5928
	int continue_balancing = 1;
5929 5930
	struct rq *rq = cpu_rq(cpu);
	unsigned long interval;
5931
	struct sched_domain *sd;
5932 5933 5934
	/* Earliest time when we have to do rebalance again */
	unsigned long next_balance = jiffies + 60*HZ;
	int update_next_balance = 0;
5935 5936
	int need_serialize, need_decay = 0;
	u64 max_cost = 0;
5937

5938
	update_blocked_averages(cpu);
P
Peter Zijlstra 已提交
5939

5940
	rcu_read_lock();
5941
	for_each_domain(cpu, sd) {
5942 5943 5944 5945 5946 5947 5948 5949 5950 5951 5952 5953
		/*
		 * 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;

5954 5955 5956
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

5957 5958 5959 5960 5961 5962 5963 5964 5965 5966 5967
		/*
		 * 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;
		}

5968 5969 5970 5971 5972 5973
		interval = sd->balance_interval;
		if (idle != CPU_IDLE)
			interval *= sd->busy_factor;

		/* scale ms to jiffies */
		interval = msecs_to_jiffies(interval);
5974
		interval = clamp(interval, 1UL, max_load_balance_interval);
5975 5976 5977 5978 5979 5980 5981 5982 5983

		need_serialize = sd->flags & SD_SERIALIZE;

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

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
5984
			if (load_balance(cpu, rq, sd, idle, &continue_balancing)) {
5985
				/*
5986
				 * The LBF_DST_PINNED logic could have changed
5987 5988
				 * env->dst_cpu, so we can't know our idle
				 * state even if we migrated tasks. Update it.
5989
				 */
5990
				idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
5991 5992 5993 5994 5995 5996 5997 5998 5999 6000
			}
			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;
		}
6001 6002
	}
	if (need_decay) {
6003
		/*
6004 6005
		 * Ensure the rq-wide value also decays but keep it at a
		 * reasonable floor to avoid funnies with rq->avg_idle.
6006
		 */
6007 6008
		rq->max_idle_balance_cost =
			max((u64)sysctl_sched_migration_cost, max_cost);
6009
	}
6010
	rcu_read_unlock();
6011 6012 6013 6014 6015 6016 6017 6018 6019 6020

	/*
	 * 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;
}

6021
#ifdef CONFIG_NO_HZ_COMMON
6022
/*
6023
 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the
6024 6025
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
6026 6027 6028 6029 6030 6031
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;

6032 6033 6034
	if (idle != CPU_IDLE ||
	    !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)))
		goto end;
6035 6036

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
6037
		if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
6038 6039 6040 6041 6042 6043 6044
			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.
		 */
6045
		if (need_resched())
6046 6047
			break;

V
Vincent Guittot 已提交
6048 6049 6050 6051 6052 6053
		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);
6054 6055 6056 6057 6058 6059 6060

		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;
6061 6062
end:
	clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu));
6063 6064 6065
}

/*
6066 6067 6068 6069 6070 6071 6072
 * 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.
6073 6074 6075 6076
 */
static inline int nohz_kick_needed(struct rq *rq, int cpu)
{
	unsigned long now = jiffies;
6077
	struct sched_domain *sd;
6078

6079
	if (unlikely(idle_cpu(cpu)))
6080 6081
		return 0;

6082 6083 6084 6085
       /*
	* 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.
	*/
6086
	set_cpu_sd_state_busy();
6087
	nohz_balance_exit_idle(cpu);
6088 6089 6090 6091 6092 6093 6094

	/*
	 * None are in tickless mode and hence no need for NOHZ idle load
	 * balancing.
	 */
	if (likely(!atomic_read(&nohz.nr_cpus)))
		return 0;
6095 6096

	if (time_before(now, nohz.next_balance))
6097 6098
		return 0;

6099 6100
	if (rq->nr_running >= 2)
		goto need_kick;
6101

6102
	rcu_read_lock();
6103 6104 6105 6106
	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);
6107

6108
		if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1)
6109
			goto need_kick_unlock;
6110 6111 6112 6113

		if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight
		    && (cpumask_first_and(nohz.idle_cpus_mask,
					  sched_domain_span(sd)) < cpu))
6114
			goto need_kick_unlock;
6115 6116 6117

		if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING)))
			break;
6118
	}
6119
	rcu_read_unlock();
6120
	return 0;
6121 6122 6123

need_kick_unlock:
	rcu_read_unlock();
6124 6125
need_kick:
	return 1;
6126 6127 6128 6129 6130 6131 6132 6133 6134
}
#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).
 */
6135 6136 6137 6138
static void run_rebalance_domains(struct softirq_action *h)
{
	int this_cpu = smp_processor_id();
	struct rq *this_rq = cpu_rq(this_cpu);
6139
	enum cpu_idle_type idle = this_rq->idle_balance ?
6140 6141 6142 6143 6144
						CPU_IDLE : CPU_NOT_IDLE;

	rebalance_domains(this_cpu, idle);

	/*
6145
	 * If this cpu has a pending nohz_balance_kick, then do the
6146 6147 6148
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
6149
	nohz_idle_balance(this_cpu, idle);
6150 6151 6152 6153
}

static inline int on_null_domain(int cpu)
{
6154
	return !rcu_dereference_sched(cpu_rq(cpu)->sd);
6155 6156 6157 6158 6159
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
6160
void trigger_load_balance(struct rq *rq, int cpu)
6161 6162 6163 6164 6165
{
	/* 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);
6166
#ifdef CONFIG_NO_HZ_COMMON
6167
	if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
6168 6169
		nohz_balancer_kick(cpu);
#endif
6170 6171
}

6172 6173 6174 6175 6176 6177 6178 6179
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
6180 6181 6182

	/* Ensure any throttled groups are reachable by pick_next_task */
	unthrottle_offline_cfs_rqs(rq);
6183 6184
}

6185
#endif /* CONFIG_SMP */
6186

6187 6188 6189
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
6190
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
6191 6192 6193 6194 6195 6196
{
	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
6197
		entity_tick(cfs_rq, se, queued);
6198
	}
6199

6200
	if (numabalancing_enabled)
6201
		task_tick_numa(rq, curr);
6202

6203
	update_rq_runnable_avg(rq, 1);
6204 6205 6206
}

/*
P
Peter Zijlstra 已提交
6207 6208 6209
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
6210
 */
P
Peter Zijlstra 已提交
6211
static void task_fork_fair(struct task_struct *p)
6212
{
6213 6214
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se, *curr;
6215
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
6216 6217 6218
	struct rq *rq = this_rq();
	unsigned long flags;

6219
	raw_spin_lock_irqsave(&rq->lock, flags);
6220

6221 6222
	update_rq_clock(rq);

6223 6224 6225
	cfs_rq = task_cfs_rq(current);
	curr = cfs_rq->curr;

6226 6227 6228 6229 6230 6231 6232 6233 6234
	/*
	 * 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();
6235

6236
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
6237

6238 6239
	if (curr)
		se->vruntime = curr->vruntime;
6240
	place_entity(cfs_rq, se, 1);
6241

P
Peter Zijlstra 已提交
6242
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
6243
		/*
6244 6245 6246
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
6247
		swap(curr->vruntime, se->vruntime);
6248
		resched_task(rq->curr);
6249
	}
6250

6251 6252
	se->vruntime -= cfs_rq->min_vruntime;

6253
	raw_spin_unlock_irqrestore(&rq->lock, flags);
6254 6255
}

6256 6257 6258 6259
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
6260 6261
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
6262
{
P
Peter Zijlstra 已提交
6263 6264 6265
	if (!p->se.on_rq)
		return;

6266 6267 6268 6269 6270
	/*
	 * 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
6271
	if (rq->curr == p) {
6272 6273 6274
		if (p->prio > oldprio)
			resched_task(rq->curr);
	} else
6275
		check_preempt_curr(rq, p, 0);
6276 6277
}

P
Peter Zijlstra 已提交
6278 6279 6280 6281 6282 6283 6284 6285 6286 6287 6288 6289 6290 6291 6292 6293 6294 6295 6296 6297 6298 6299
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;
	}
6300

6301
#ifdef CONFIG_SMP
6302 6303 6304 6305 6306
	/*
	* 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.
	*/
6307 6308 6309
	if (se->avg.decay_count) {
		__synchronize_entity_decay(se);
		subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib);
6310 6311
	}
#endif
P
Peter Zijlstra 已提交
6312 6313
}

6314 6315 6316
/*
 * We switched to the sched_fair class.
 */
P
Peter Zijlstra 已提交
6317
static void switched_to_fair(struct rq *rq, struct task_struct *p)
6318
{
P
Peter Zijlstra 已提交
6319 6320 6321
	if (!p->se.on_rq)
		return;

6322 6323 6324 6325 6326
	/*
	 * 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
6327
	if (rq->curr == p)
6328 6329
		resched_task(rq->curr);
	else
6330
		check_preempt_curr(rq, p, 0);
6331 6332
}

6333 6334 6335 6336 6337 6338 6339 6340 6341
/* 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;

6342 6343 6344 6345 6346 6347 6348
	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);
	}
6349 6350
}

6351 6352 6353 6354 6355 6356 6357
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
6358
#ifdef CONFIG_SMP
6359
	atomic64_set(&cfs_rq->decay_counter, 1);
6360
	atomic_long_set(&cfs_rq->removed_load, 0);
6361
#endif
6362 6363
}

P
Peter Zijlstra 已提交
6364
#ifdef CONFIG_FAIR_GROUP_SCHED
6365
static void task_move_group_fair(struct task_struct *p, int on_rq)
P
Peter Zijlstra 已提交
6366
{
6367
	struct cfs_rq *cfs_rq;
6368 6369 6370 6371 6372 6373 6374 6375 6376 6377 6378 6379 6380
	/*
	 * 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.
	 */
6381 6382 6383 6384 6385 6386
	/*
	 * 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().
6387 6388
	 * - Moving a task which has been woken up by try_to_wake_up() and
	 *   waiting for actually being woken up by sched_ttwu_pending().
6389 6390 6391 6392
	 *
	 * To prevent boost or penalty in the new cfs_rq caused by delta
	 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment.
	 */
6393
	if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING))
6394 6395
		on_rq = 1;

6396 6397 6398
	if (!on_rq)
		p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
	set_task_rq(p, task_cpu(p));
6399 6400 6401 6402 6403 6404 6405 6406 6407 6408 6409 6410 6411
	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
6412
}
6413 6414 6415 6416 6417 6418 6419 6420 6421 6422 6423 6424 6425 6426 6427 6428 6429 6430 6431 6432 6433 6434 6435 6436 6437 6438 6439 6440 6441 6442 6443 6444 6445 6446 6447 6448 6449 6450 6451 6452 6453 6454 6455 6456 6457 6458 6459 6460 6461 6462 6463 6464 6465 6466 6467 6468 6469 6470 6471 6472 6473 6474 6475 6476 6477 6478 6479 6480 6481 6482 6483 6484 6485 6486 6487 6488 6489 6490 6491 6492 6493 6494 6495 6496 6497 6498 6499 6500 6501 6502 6503 6504 6505 6506 6507 6508 6509 6510 6511 6512 6513 6514 6515 6516 6517 6518 6519 6520 6521 6522 6523 6524 6525 6526 6527 6528 6529 6530 6531 6532 6533 6534 6535 6536 6537 6538 6539 6540 6541

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);
6542 6543 6544

		/* Possible calls to update_curr() need rq clock */
		update_rq_clock(rq);
6545
		for_each_sched_entity(se)
6546 6547 6548 6549 6550 6551 6552 6553 6554 6555 6556 6557 6558 6559 6560 6561 6562 6563 6564 6565 6566
			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
6567

6568
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
6569 6570 6571 6572 6573 6574 6575 6576 6577
{
	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)
6578
		rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se));
6579 6580 6581 6582

	return rr_interval;
}

6583 6584 6585
/*
 * All the scheduling class methods:
 */
6586
const struct sched_class fair_sched_class = {
6587
	.next			= &idle_sched_class,
6588 6589 6590
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
6591
	.yield_to_task		= yield_to_task_fair,
6592

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Ingo Molnar 已提交
6593
	.check_preempt_curr	= check_preempt_wakeup,
6594 6595 6596 6597

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

6598
#ifdef CONFIG_SMP
L
Li Zefan 已提交
6599
	.select_task_rq		= select_task_rq_fair,
6600
	.migrate_task_rq	= migrate_task_rq_fair,
6601

6602 6603
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
6604 6605

	.task_waking		= task_waking_fair,
6606
#endif
6607

6608
	.set_curr_task          = set_curr_task_fair,
6609
	.task_tick		= task_tick_fair,
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Peter Zijlstra 已提交
6610
	.task_fork		= task_fork_fair,
6611 6612

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
6613
	.switched_from		= switched_from_fair,
6614
	.switched_to		= switched_to_fair,
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Peter Zijlstra 已提交
6615

6616 6617
	.get_rr_interval	= get_rr_interval_fair,

P
Peter Zijlstra 已提交
6618
#ifdef CONFIG_FAIR_GROUP_SCHED
6619
	.task_move_group	= task_move_group_fair,
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Peter Zijlstra 已提交
6620
#endif
6621 6622 6623
};

#ifdef CONFIG_SCHED_DEBUG
6624
void print_cfs_stats(struct seq_file *m, int cpu)
6625 6626 6627
{
	struct cfs_rq *cfs_rq;

6628
	rcu_read_lock();
6629
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
6630
		print_cfs_rq(m, cpu, cfs_rq);
6631
	rcu_read_unlock();
6632 6633
}
#endif
6634 6635 6636 6637 6638 6639

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

6640
#ifdef CONFIG_NO_HZ_COMMON
6641
	nohz.next_balance = jiffies;
6642
	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
6643
	cpu_notifier(sched_ilb_notifier, 0);
6644 6645 6646 6647
#endif
#endif /* SMP */

}