sched_fair.c 108.1 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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/*
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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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static 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;
}

/* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on
 * another cpu ('this_cpu')
 */
static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
{
	return cfs_rq->tg->cfs_rq[this_cpu];
}

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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;
	}
}

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;
}

static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
{
	return &cpu_rq(this_cpu)->cfs;
}

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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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/**************************************************************
 * Scheduling class tree data structure manipulation methods:
 */

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

	return min_vruntime;
}

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

	return min_vruntime;
}

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

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static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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	return se->vruntime - cfs_rq->min_vruntime;
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}

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

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

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

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

	cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
}

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/*
 * 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;
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	s64 key = entity_key(cfs_rq, se);
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	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 (key < entity_key(cfs_rq, 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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static 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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static 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.
 *
 * When there are too many tasks (sysctl_sched_nr_latency) we have to stretch
 * 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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static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update);
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static void update_cfs_shares(struct cfs_rq *cfs_rq);
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/*
 * Update the current task's runtime statistics. Skip current tasks that
 * are not in our scheduling class.
 */
static inline void
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__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
	      unsigned long delta_exec)
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{
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	unsigned long delta_exec_weighted;
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	schedstat_set(curr->statistics.exec_max,
		      max((u64)delta_exec, curr->statistics.exec_max));
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	curr->sum_exec_runtime += delta_exec;
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	schedstat_add(cfs_rq, exec_clock, delta_exec);
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	delta_exec_weighted = calc_delta_fair(delta_exec, curr);
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	curr->vruntime += delta_exec_weighted;
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	update_min_vruntime(cfs_rq);
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#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
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	cfs_rq->load_unacc_exec_time += delta_exec;
#endif
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}

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static void update_curr(struct cfs_rq *cfs_rq)
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{
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	struct sched_entity *curr = cfs_rq->curr;
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	u64 now = rq_of(cfs_rq)->clock_task;
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	unsigned long delta_exec;

	if (unlikely(!curr))
		return;

	/*
	 * Get the amount of time the current task was running
	 * since the last time we changed load (this cannot
	 * overflow on 32 bits):
	 */
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	delta_exec = (unsigned long)(now - curr->exec_start);
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	if (!delta_exec)
		return;
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	__update_curr(cfs_rq, curr, delta_exec);
	curr->exec_start = now;
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	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

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		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
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		cpuacct_charge(curtask, delta_exec);
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		account_group_exec_runtime(curtask, delta_exec);
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	}
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}

static inline void
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update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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	schedstat_set(se->statistics.wait_start, rq_of(cfs_rq)->clock);
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}

/*
 * Task is being enqueued - update stats:
 */
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static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
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	if (se != cfs_rq->curr)
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		update_stats_wait_start(cfs_rq, se);
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}

static void
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update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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	schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
			rq_of(cfs_rq)->clock - se->statistics.wait_start));
	schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
	schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
			rq_of(cfs_rq)->clock - se->statistics.wait_start);
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#ifdef CONFIG_SCHEDSTATS
	if (entity_is_task(se)) {
		trace_sched_stat_wait(task_of(se),
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			rq_of(cfs_rq)->clock - se->statistics.wait_start);
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	}
#endif
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	schedstat_set(se->statistics.wait_start, 0);
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}

static inline void
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update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
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	if (se != cfs_rq->curr)
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		update_stats_wait_end(cfs_rq, se);
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}

/*
 * We are picking a new current task - update its stats:
 */
static inline void
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update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
	/*
	 * We are starting a new run period:
	 */
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	se->exec_start = rq_of(cfs_rq)->clock_task;
659 660 661 662 663 664
}

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

665 666 667 668 669 670 671 672 673 674 675 676 677
#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
static void
add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight)
{
	cfs_rq->task_weight += weight;
}
#else
static inline void
add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight)
{
}
#endif

678 679 680 681
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
682 683
	if (!parent_entity(se))
		inc_cpu_load(rq_of(cfs_rq), se->load.weight);
684
	if (entity_is_task(se)) {
685
		add_cfs_task_weight(cfs_rq, se->load.weight);
686 687
		list_add(&se->group_node, &cfs_rq->tasks);
	}
688 689 690 691 692 693 694
	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);
695 696
	if (!parent_entity(se))
		dec_cpu_load(rq_of(cfs_rq), se->load.weight);
697
	if (entity_is_task(se)) {
698
		add_cfs_task_weight(cfs_rq, -se->load.weight);
699 700
		list_del_init(&se->group_node);
	}
701 702 703
	cfs_rq->nr_running--;
}

704 705
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721
static void update_cfs_rq_load_contribution(struct cfs_rq *cfs_rq,
					    int global_update)
{
	struct task_group *tg = cfs_rq->tg;
	long load_avg;

	load_avg = div64_u64(cfs_rq->load_avg, cfs_rq->load_period+1);
	load_avg -= cfs_rq->load_contribution;

	if (global_update || abs(load_avg) > cfs_rq->load_contribution / 8) {
		atomic_add(load_avg, &tg->load_weight);
		cfs_rq->load_contribution += load_avg;
	}
}

static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
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{
723
	u64 period = sysctl_sched_shares_window;
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	u64 now, delta;
725
	unsigned long load = cfs_rq->load.weight;
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727
	if (cfs_rq->tg == &root_task_group)
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		return;

730
	now = rq_of(cfs_rq)->clock_task;
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	delta = now - cfs_rq->load_stamp;

733 734 735 736 737
	/* truncate load history at 4 idle periods */
	if (cfs_rq->load_stamp > cfs_rq->load_last &&
	    now - cfs_rq->load_last > 4 * period) {
		cfs_rq->load_period = 0;
		cfs_rq->load_avg = 0;
738
		delta = period - 1;
739 740
	}

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	cfs_rq->load_stamp = now;
742
	cfs_rq->load_unacc_exec_time = 0;
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	cfs_rq->load_period += delta;
744 745 746 747
	if (load) {
		cfs_rq->load_last = now;
		cfs_rq->load_avg += delta * load;
	}
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749 750 751 752 753
	/* consider updating load contribution on each fold or truncate */
	if (global_update || cfs_rq->load_period > period
	    || !cfs_rq->load_period)
		update_cfs_rq_load_contribution(cfs_rq, global_update);

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	while (cfs_rq->load_period > period) {
		/*
		 * Inline assembly required to prevent the compiler
		 * optimising this loop into a divmod call.
		 * See __iter_div_u64_rem() for another example of this.
		 */
		asm("" : "+rm" (cfs_rq->load_period));
		cfs_rq->load_period /= 2;
		cfs_rq->load_avg /= 2;
	}
764

765 766
	if (!cfs_rq->curr && !cfs_rq->nr_running && !cfs_rq->load_avg)
		list_del_leaf_cfs_rq(cfs_rq);
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}

769
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
770 771 772
{
	long load_weight, load, shares;

773
	load = cfs_rq->load.weight;
774 775 776

	load_weight = atomic_read(&tg->load_weight);
	load_weight += load;
777
	load_weight -= cfs_rq->load_contribution;
778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794

	shares = (tg->shares * load);
	if (load_weight)
		shares /= load_weight;

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

	return shares;
}

static void update_entity_shares_tick(struct cfs_rq *cfs_rq)
{
	if (cfs_rq->load_unacc_exec_time > sysctl_sched_shares_window) {
		update_cfs_load(cfs_rq, 0);
795
		update_cfs_shares(cfs_rq);
796 797 798 799 800 801 802
	}
}
# else /* CONFIG_SMP */
static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
{
}

803
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
804 805 806 807 808 809 810 811
{
	return tg->shares;
}

static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
{
}
# endif /* CONFIG_SMP */
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static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
815 816 817 818
	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);
820
	}
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	update_load_set(&se->load, weight);

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

828
static void update_cfs_shares(struct cfs_rq *cfs_rq)
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{
	struct task_group *tg;
	struct sched_entity *se;
832
	long shares;
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	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
	if (!se)
		return;
838 839 840 841
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
842
	shares = calc_cfs_shares(cfs_rq, tg);
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	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
847
static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
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848 849 850
{
}

851
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
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{
}
854 855 856 857

static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
{
}
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#endif /* CONFIG_FAIR_GROUP_SCHED */

860
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
861 862
{
#ifdef CONFIG_SCHEDSTATS
863 864 865 866 867
	struct task_struct *tsk = NULL;

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

868 869
	if (se->statistics.sleep_start) {
		u64 delta = rq_of(cfs_rq)->clock - se->statistics.sleep_start;
870 871 872 873

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

874 875
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
876

877 878
		se->statistics.sleep_start = 0;
		se->statistics.sum_sleep_runtime += delta;
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Arjan van de Ven 已提交
879

880
		if (tsk) {
881
			account_scheduler_latency(tsk, delta >> 10, 1);
882 883
			trace_sched_stat_sleep(tsk, delta);
		}
884
	}
885 886
	if (se->statistics.block_start) {
		u64 delta = rq_of(cfs_rq)->clock - se->statistics.block_start;
887 888 889 890

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

891 892
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
893

894 895
		se->statistics.block_start = 0;
		se->statistics.sum_sleep_runtime += delta;
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896

897
		if (tsk) {
898
			if (tsk->in_iowait) {
899 900
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
901
				trace_sched_stat_iowait(tsk, delta);
902 903
			}

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

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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
}

933 934 935
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
936
	u64 vruntime = cfs_rq->min_vruntime;
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938 939 940 941 942 943
	/*
	 * 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.
	 */
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944
	if (initial && sched_feat(START_DEBIT))
945
		vruntime += sched_vslice(cfs_rq, se);
946

947
	/* sleeps up to a single latency don't count. */
948
	if (!initial) {
949
		unsigned long thresh = sysctl_sched_latency;
950

951 952 953 954 955 956
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
957

958
		vruntime -= thresh;
959 960
	}

961 962 963
	/* ensure we never gain time by being placed backwards. */
	vruntime = max_vruntime(se->vruntime, vruntime);

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964
	se->vruntime = vruntime;
965 966
}

967
static void
968
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
969
{
970 971 972 973
	/*
	 * Update the normalized vruntime before updating min_vruntime
	 * through callig update_curr().
	 */
974
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
975 976
		se->vruntime += cfs_rq->min_vruntime;

977
	/*
978
	 * Update run-time statistics of the 'current'.
979
	 */
980
	update_curr(cfs_rq);
981
	update_cfs_load(cfs_rq, 0);
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982
	account_entity_enqueue(cfs_rq, se);
983
	update_cfs_shares(cfs_rq);
984

985
	if (flags & ENQUEUE_WAKEUP) {
986
		place_entity(cfs_rq, se, 0);
987
		enqueue_sleeper(cfs_rq, se);
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988
	}
989

990
	update_stats_enqueue(cfs_rq, se);
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991
	check_spread(cfs_rq, se);
992 993
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
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	se->on_rq = 1;
995 996 997

	if (cfs_rq->nr_running == 1)
		list_add_leaf_cfs_rq(cfs_rq);
998 999
}

1000
static void __clear_buddies_last(struct sched_entity *se)
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1001
{
1002 1003 1004 1005 1006 1007 1008 1009
	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;
	}
}
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1010

1011 1012 1013 1014 1015 1016 1017 1018 1019
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;
	}
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1020 1021
}

1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032
static void __clear_buddies_skip(struct sched_entity *se)
{
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);
		if (cfs_rq->skip == se)
			cfs_rq->skip = NULL;
		else
			break;
	}
}

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1033 1034
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
1035 1036 1037 1038 1039
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
1040 1041 1042

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
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1043 1044
}

1045
static void
1046
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1047
{
1048 1049 1050 1051 1052
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);

1053
	update_stats_dequeue(cfs_rq, se);
1054
	if (flags & DEQUEUE_SLEEP) {
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1055
#ifdef CONFIG_SCHEDSTATS
1056 1057 1058 1059
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
1060
				se->statistics.sleep_start = rq_of(cfs_rq)->clock;
1061
			if (tsk->state & TASK_UNINTERRUPTIBLE)
1062
				se->statistics.block_start = rq_of(cfs_rq)->clock;
1063
		}
1064
#endif
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1065 1066
	}

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1067
	clear_buddies(cfs_rq, se);
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1068

1069
	if (se != cfs_rq->curr)
1070
		__dequeue_entity(cfs_rq, se);
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1071
	se->on_rq = 0;
1072
	update_cfs_load(cfs_rq, 0);
1073
	account_entity_dequeue(cfs_rq, se);
1074
	update_min_vruntime(cfs_rq);
1075
	update_cfs_shares(cfs_rq);
1076 1077 1078 1079 1080 1081

	/*
	 * 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.
	 */
1082
	if (!(flags & DEQUEUE_SLEEP))
1083
		se->vruntime -= cfs_rq->min_vruntime;
1084 1085 1086 1087 1088
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
1089
static void
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1090
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
1091
{
1092 1093
	unsigned long ideal_runtime, delta_exec;

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1094
	ideal_runtime = sched_slice(cfs_rq, curr);
1095
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
1096
	if (delta_exec > ideal_runtime) {
1097
		resched_task(rq_of(cfs_rq)->curr);
1098 1099 1100 1101 1102
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117
		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 (!sched_feat(WAKEUP_PREEMPT))
		return;

	if (delta_exec < sysctl_sched_min_granularity)
		return;

	if (cfs_rq->nr_running > 1) {
1118
		struct sched_entity *se = __pick_first_entity(cfs_rq);
1119 1120
		s64 delta = curr->vruntime - se->vruntime;

1121 1122 1123
		if (delta < 0)
			return;

1124 1125
		if (delta > ideal_runtime)
			resched_task(rq_of(cfs_rq)->curr);
1126
	}
1127 1128
}

1129
static void
1130
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
1131
{
1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142
	/* '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);
	}

1143
	update_stats_curr_start(cfs_rq, se);
1144
	cfs_rq->curr = se;
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1145 1146 1147 1148 1149 1150
#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):
	 */
1151
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
1152
		se->statistics.slice_max = max(se->statistics.slice_max,
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1153 1154 1155
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
1156
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
1157 1158
}

1159 1160 1161
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

1162 1163 1164 1165 1166 1167 1168
/*
 * 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
 */
1169
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
1170
{
1171
	struct sched_entity *se = __pick_first_entity(cfs_rq);
1172
	struct sched_entity *left = se;
1173

1174 1175 1176 1177 1178 1179 1180 1181 1182
	/*
	 * 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;
	}
1183

1184 1185 1186 1187 1188 1189
	/*
	 * 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;

1190 1191 1192 1193 1194 1195
	/*
	 * 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;

1196
	clear_buddies(cfs_rq, se);
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	return se;
1199 1200
}

1201
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
1202 1203 1204 1205 1206 1207
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
1208
		update_curr(cfs_rq);
1209

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1210
	check_spread(cfs_rq, prev);
1211
	if (prev->on_rq) {
1212
		update_stats_wait_start(cfs_rq, prev);
1213 1214 1215
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
	}
1216
	cfs_rq->curr = NULL;
1217 1218
}

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1219 1220
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
1221 1222
{
	/*
1223
	 * Update run-time statistics of the 'current'.
1224
	 */
1225
	update_curr(cfs_rq);
1226

1227 1228 1229 1230 1231
	/*
	 * Update share accounting for long-running entities.
	 */
	update_entity_shares_tick(cfs_rq);

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1232 1233 1234 1235 1236
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
1237 1238 1239 1240
	if (queued) {
		resched_task(rq_of(cfs_rq)->curr);
		return;
	}
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1241 1242 1243 1244 1245 1246 1247 1248
	/*
	 * 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

1249
	if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
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1250
		check_preempt_tick(cfs_rq, curr);
1251 1252 1253 1254 1255 1256
}

/**************************************************
 * CFS operations on tasks:
 */

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1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279
#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);

	if (hrtick_enabled(rq) && cfs_rq->nr_running > 1) {
		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.
		 */
1280
		if (rq->curr != p)
1281
			delta = max_t(s64, 10000LL, delta);
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1282

1283
		hrtick_start(rq, delta);
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1284 1285
	}
}
1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301

/*
 * 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;

	if (curr->sched_class != &fair_sched_class)
		return;

	if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency)
		hrtick_start_fair(rq, curr);
}
1302
#else /* !CONFIG_SCHED_HRTICK */
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1303 1304 1305 1306
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
1307 1308 1309 1310

static inline void hrtick_update(struct rq *rq)
{
}
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1311 1312
#endif

1313 1314 1315 1316 1317
/*
 * 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:
 */
1318
static void
1319
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
1320 1321
{
	struct cfs_rq *cfs_rq;
1322
	struct sched_entity *se = &p->se;
1323 1324

	for_each_sched_entity(se) {
1325
		if (se->on_rq)
1326 1327
			break;
		cfs_rq = cfs_rq_of(se);
1328 1329
		enqueue_entity(cfs_rq, se, flags);
		flags = ENQUEUE_WAKEUP;
1330
	}
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1331

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1332 1333 1334
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

1335
		update_cfs_load(cfs_rq, 0);
1336
		update_cfs_shares(cfs_rq);
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1337 1338
	}

1339
	hrtick_update(rq);
1340 1341 1342 1343 1344 1345 1346
}

/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
1347
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
1348 1349
{
	struct cfs_rq *cfs_rq;
1350
	struct sched_entity *se = &p->se;
1351 1352 1353

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
1354
		dequeue_entity(cfs_rq, se, flags);
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1355

1356
		/* Don't dequeue parent if it has other entities besides us */
1357
		if (cfs_rq->load.weight)
1358
			break;
1359
		flags |= DEQUEUE_SLEEP;
1360
	}
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1361

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1362 1363 1364
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

1365
		update_cfs_load(cfs_rq, 0);
1366
		update_cfs_shares(cfs_rq);
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1367 1368
	}

1369
	hrtick_update(rq);
1370 1371
}

1372
#ifdef CONFIG_SMP
1373

1374 1375 1376 1377 1378 1379 1380 1381
static void task_waking_fair(struct rq *rq, struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

	se->vruntime -= cfs_rq->min_vruntime;
}

1382
#ifdef CONFIG_FAIR_GROUP_SCHED
1383 1384 1385 1386 1387 1388 1389
/*
 * 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.
 */
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1390
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
1391
{
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1392
	struct sched_entity *se = tg->se[cpu];
1393 1394 1395 1396

	if (!tg->parent)
		return wl;

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1397
	for_each_sched_entity(se) {
1398
		long lw, w;
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1399

1400 1401
		tg = se->my_q->tg;
		w = se->my_q->load.weight;
1402

1403 1404 1405 1406
		/* use this cpu's instantaneous contribution */
		lw = atomic_read(&tg->load_weight);
		lw -= se->my_q->load_contribution;
		lw += w + wg;
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1407

1408
		wl += w;
1409

1410 1411 1412 1413
		if (lw > 0 && wl < lw)
			wl = (wl * tg->shares) / lw;
		else
			wl = tg->shares;
1414

1415 1416 1417 1418
		/* zero point is MIN_SHARES */
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
		wl -= se->load.weight;
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1419 1420
		wg = 0;
	}
1421

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1422
	return wl;
1423
}
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1424

1425
#else
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1426

1427 1428
static inline unsigned long effective_load(struct task_group *tg, int cpu,
		unsigned long wl, unsigned long wg)
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1429
{
1430
	return wl;
1431
}
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1432

1433 1434
#endif

1435
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
1436
{
1437
	s64 this_load, load;
1438
	int idx, this_cpu, prev_cpu;
1439
	unsigned long tl_per_task;
1440
	struct task_group *tg;
1441
	unsigned long weight;
1442
	int balanced;
1443

1444 1445 1446 1447 1448
	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);
1449

1450 1451 1452 1453 1454
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
1455
	rcu_read_lock();
1456 1457 1458 1459
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

1460
		this_load += effective_load(tg, this_cpu, -weight, -weight);
1461 1462
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
1463

1464 1465
	tg = task_group(p);
	weight = p->se.load.weight;
1466

1467 1468
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
1469 1470 1471
	 * 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.
1472 1473 1474 1475
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
1476 1477
	if (this_load > 0) {
		s64 this_eff_load, prev_eff_load;
1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490

		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;
1491
	rcu_read_unlock();
1492

1493
	/*
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Ingo Molnar 已提交
1494 1495 1496
	 * If the currently running task will sleep within
	 * a reasonable amount of time then attract this newly
	 * woken task:
1497
	 */
1498 1499
	if (sync && balanced)
		return 1;
1500

1501
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
1502 1503
	tl_per_task = cpu_avg_load_per_task(this_cpu);

1504 1505 1506
	if (balanced ||
	    (this_load <= load &&
	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
1507 1508 1509 1510 1511
		/*
		 * This domain has SD_WAKE_AFFINE and
		 * p is cache cold in this domain, and
		 * there is no bad imbalance.
		 */
1512
		schedstat_inc(sd, ttwu_move_affine);
1513
		schedstat_inc(p, se.statistics.nr_wakeups_affine);
1514 1515 1516 1517 1518 1519

		return 1;
	}
	return 0;
}

1520 1521 1522 1523 1524
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
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Peter Zijlstra 已提交
1525
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
1526
		  int this_cpu, int load_idx)
1527
{
1528
	struct sched_group *idlest = NULL, *group = sd->groups;
1529 1530
	unsigned long min_load = ULONG_MAX, this_load = 0;
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
1531

1532 1533 1534 1535
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
1536

1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
					&p->cpus_allowed))
			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 */
		avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;

		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 */
	for_each_cpu_and(i, sched_group_cpus(group), &p->cpus_allowed) {
		load = weighted_cpuload(i);

		if (load < min_load || (load == min_load && i == this_cpu)) {
			min_load = load;
			idlest = i;
1591 1592 1593
		}
	}

1594 1595
	return idlest;
}
1596

1597 1598 1599
/*
 * Try and locate an idle CPU in the sched_domain.
 */
1600
static int select_idle_sibling(struct task_struct *p, int target)
1601 1602 1603
{
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
1604
	struct sched_domain *sd;
1605 1606 1607
	int i;

	/*
1608 1609
	 * If the task is going to be woken-up on this cpu and if it is
	 * already idle, then it is the right target.
1610
	 */
1611 1612 1613 1614 1615 1616 1617 1618
	if (target == cpu && idle_cpu(cpu))
		return cpu;

	/*
	 * If the task is going to be woken-up on the cpu where it previously
	 * ran and if it is currently idle, then it the right target.
	 */
	if (target == prev_cpu && idle_cpu(prev_cpu))
1619
		return prev_cpu;
1620 1621

	/*
1622
	 * Otherwise, iterate the domains and find an elegible idle cpu.
1623
	 */
1624 1625
	for_each_domain(target, sd) {
		if (!(sd->flags & SD_SHARE_PKG_RESOURCES))
1626
			break;
1627 1628 1629 1630 1631 1632

		for_each_cpu_and(i, sched_domain_span(sd), &p->cpus_allowed) {
			if (idle_cpu(i)) {
				target = i;
				break;
			}
1633
		}
1634 1635 1636 1637 1638 1639 1640 1641

		/*
		 * Lets stop looking for an idle sibling when we reached
		 * the domain that spans the current cpu and prev_cpu.
		 */
		if (cpumask_test_cpu(cpu, sched_domain_span(sd)) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(sd)))
			break;
1642 1643 1644 1645 1646
	}

	return target;
}

1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657
/*
 * 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.
 */
1658 1659
static int
select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_flags)
1660
{
1661
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
1662 1663 1664
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
	int new_cpu = cpu;
1665
	int want_affine = 0;
1666
	int want_sd = 1;
1667
	int sync = wake_flags & WF_SYNC;
1668

1669
	if (sd_flag & SD_BALANCE_WAKE) {
1670
		if (cpumask_test_cpu(cpu, &p->cpus_allowed))
1671 1672 1673
			want_affine = 1;
		new_cpu = prev_cpu;
	}
1674 1675

	for_each_domain(cpu, tmp) {
1676 1677 1678
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

1679
		/*
1680 1681
		 * If power savings logic is enabled for a domain, see if we
		 * are not overloaded, if so, don't balance wider.
1682
		 */
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Peter Zijlstra 已提交
1683
		if (tmp->flags & (SD_POWERSAVINGS_BALANCE|SD_PREFER_LOCAL)) {
1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695
			unsigned long power = 0;
			unsigned long nr_running = 0;
			unsigned long capacity;
			int i;

			for_each_cpu(i, sched_domain_span(tmp)) {
				power += power_of(i);
				nr_running += cpu_rq(i)->cfs.nr_running;
			}

			capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);

P
Peter Zijlstra 已提交
1696 1697 1698 1699
			if (tmp->flags & SD_POWERSAVINGS_BALANCE)
				nr_running /= 2;

			if (nr_running < capacity)
1700
				want_sd = 0;
1701
		}
1702

1703
		/*
1704 1705
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
1706
		 */
1707 1708 1709 1710
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
			want_affine = 0;
1711 1712
		}

1713 1714 1715
		if (!want_sd && !want_affine)
			break;

1716
		if (!(tmp->flags & sd_flag))
1717 1718
			continue;

1719 1720 1721 1722
		if (want_sd)
			sd = tmp;
	}

1723
	if (affine_sd) {
1724 1725 1726 1727
		if (cpu == prev_cpu || wake_affine(affine_sd, p, sync))
			return select_idle_sibling(p, cpu);
		else
			return select_idle_sibling(p, prev_cpu);
1728
	}
1729

1730
	while (sd) {
1731
		int load_idx = sd->forkexec_idx;
1732
		struct sched_group *group;
1733
		int weight;
1734

1735
		if (!(sd->flags & sd_flag)) {
1736 1737 1738
			sd = sd->child;
			continue;
		}
1739

1740 1741
		if (sd_flag & SD_BALANCE_WAKE)
			load_idx = sd->wake_idx;
1742

1743
		group = find_idlest_group(sd, p, cpu, load_idx);
1744 1745 1746 1747
		if (!group) {
			sd = sd->child;
			continue;
		}
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Ingo Molnar 已提交
1748

1749
		new_cpu = find_idlest_cpu(group, p, cpu);
1750 1751 1752 1753
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
1754
		}
1755 1756 1757

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
1758
		weight = sd->span_weight;
1759 1760
		sd = NULL;
		for_each_domain(cpu, tmp) {
1761
			if (weight <= tmp->span_weight)
1762
				break;
1763
			if (tmp->flags & sd_flag)
1764 1765 1766
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
1767 1768
	}

1769
	return new_cpu;
1770 1771 1772
}
#endif /* CONFIG_SMP */

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Peter Zijlstra 已提交
1773 1774
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
1775 1776 1777 1778
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
1779 1780
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
1781 1782 1783 1784 1785 1786 1787 1788 1789
	 *
	 * 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.
1790
	 */
M
Mike Galbraith 已提交
1791 1792
	if (unlikely(se->load.weight != NICE_0_LOAD))
		gran = calc_delta_fair(gran, se);
1793 1794 1795 1796

	return gran;
}

1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818
/*
 * 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
1819
	gran = wakeup_gran(curr, se);
1820 1821 1822 1823 1824 1825
	if (vdiff > gran)
		return 1;

	return 0;
}

1826 1827
static void set_last_buddy(struct sched_entity *se)
{
1828 1829 1830 1831
	if (likely(task_of(se)->policy != SCHED_IDLE)) {
		for_each_sched_entity(se)
			cfs_rq_of(se)->last = se;
	}
1832 1833 1834 1835
}

static void set_next_buddy(struct sched_entity *se)
{
1836 1837 1838 1839
	if (likely(task_of(se)->policy != SCHED_IDLE)) {
		for_each_sched_entity(se)
			cfs_rq_of(se)->next = se;
	}
1840 1841
}

1842 1843 1844 1845 1846 1847 1848 1849
static void set_skip_buddy(struct sched_entity *se)
{
	if (likely(task_of(se)->policy != SCHED_IDLE)) {
		for_each_sched_entity(se)
			cfs_rq_of(se)->skip = se;
	}
}

1850 1851 1852
/*
 * Preempt the current task with a newly woken task if needed:
 */
1853
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
1854 1855
{
	struct task_struct *curr = rq->curr;
1856
	struct sched_entity *se = &curr->se, *pse = &p->se;
1857
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
1858
	int scale = cfs_rq->nr_running >= sched_nr_latency;
1859

I
Ingo Molnar 已提交
1860 1861 1862
	if (unlikely(se == pse))
		return;

1863
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK))
M
Mike Galbraith 已提交
1864
		set_next_buddy(pse);
P
Peter Zijlstra 已提交
1865

1866 1867 1868 1869 1870 1871 1872
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
	 */
	if (test_tsk_need_resched(curr))
		return;

1873
	/*
1874
	 * Batch and idle tasks do not preempt (their preemption is driven by
1875 1876
	 * the tick):
	 */
1877
	if (unlikely(p->policy != SCHED_NORMAL))
1878
		return;
1879

1880
	/* Idle tasks are by definition preempted by everybody. */
1881 1882
	if (unlikely(curr->policy == SCHED_IDLE))
		goto preempt;
1883

1884 1885 1886
	if (!sched_feat(WAKEUP_PREEMPT))
		return;

1887
	update_curr(cfs_rq);
1888
	find_matching_se(&se, &pse);
1889
	BUG_ON(!pse);
1890 1891
	if (wakeup_preempt_entity(se, pse) == 1)
		goto preempt;
1892

1893
	return;
1894

1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910
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);
1911 1912
}

1913
static struct task_struct *pick_next_task_fair(struct rq *rq)
1914
{
P
Peter Zijlstra 已提交
1915
	struct task_struct *p;
1916 1917 1918
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

1919
	if (!cfs_rq->nr_running)
1920 1921 1922
		return NULL;

	do {
1923
		se = pick_next_entity(cfs_rq);
1924
		set_next_entity(cfs_rq, se);
1925 1926 1927
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
1928 1929 1930 1931
	p = task_of(se);
	hrtick_start_fair(rq, p);

	return p;
1932 1933 1934 1935 1936
}

/*
 * Account for a descheduled task:
 */
1937
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
1938 1939 1940 1941 1942 1943
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
1944
		put_prev_entity(cfs_rq, se);
1945 1946 1947
	}
}

1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977
/*
 * 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);
	}

	set_skip_buddy(se);
}

1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996
static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt)
{
	struct sched_entity *se = &p->se;

	if (!se->on_rq)
		return false;

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

	/* Make p's CPU reschedule; pick_next_entity takes care of fairness. */
	if (preempt)
		resched_task(rq->curr);

	yield_task_fair(rq);

	return true;
}

1997
#ifdef CONFIG_SMP
1998 1999 2000 2001
/**************************************************
 * Fair scheduling class load-balancing methods:
 */

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030
/*
 * pull_task - move a task from a remote runqueue to the local runqueue.
 * Both runqueues must be locked.
 */
static void pull_task(struct rq *src_rq, struct task_struct *p,
		      struct rq *this_rq, int this_cpu)
{
	deactivate_task(src_rq, p, 0);
	set_task_cpu(p, this_cpu);
	activate_task(this_rq, p, 0);
	check_preempt_curr(this_rq, p, 0);
}

/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
		     struct sched_domain *sd, enum cpu_idle_type idle,
		     int *all_pinned)
{
	int tsk_cache_hot = 0;
	/*
	 * We do not migrate tasks that are:
	 * 1) running (obviously), or
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
	 * 3) are cache-hot on their current CPU.
	 */
	if (!cpumask_test_cpu(this_cpu, &p->cpus_allowed)) {
2031
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
2032 2033 2034 2035 2036
		return 0;
	}
	*all_pinned = 0;

	if (task_running(rq, p)) {
2037
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
2038 2039 2040 2041 2042 2043 2044 2045 2046
		return 0;
	}

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

2047
	tsk_cache_hot = task_hot(p, rq->clock_task, sd);
2048 2049 2050 2051 2052
	if (!tsk_cache_hot ||
		sd->nr_balance_failed > sd->cache_nice_tries) {
#ifdef CONFIG_SCHEDSTATS
		if (tsk_cache_hot) {
			schedstat_inc(sd, lb_hot_gained[idle]);
2053
			schedstat_inc(p, se.statistics.nr_forced_migrations);
2054 2055 2056 2057 2058 2059
		}
#endif
		return 1;
	}

	if (tsk_cache_hot) {
2060
		schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
2061 2062 2063 2064 2065
		return 0;
	}
	return 1;
}

2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101
/*
 * 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.
 */
static int
move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
	      struct sched_domain *sd, enum cpu_idle_type idle)
{
	struct task_struct *p, *n;
	struct cfs_rq *cfs_rq;
	int pinned = 0;

	for_each_leaf_cfs_rq(busiest, cfs_rq) {
		list_for_each_entry_safe(p, n, &cfs_rq->tasks, se.group_node) {

			if (!can_migrate_task(p, busiest, this_cpu,
						sd, idle, &pinned))
				continue;

			pull_task(busiest, p, this_rq, this_cpu);
			/*
			 * Right now, this is only the second place pull_task()
			 * is called, so we can safely collect pull_task()
			 * stats here rather than inside pull_task().
			 */
			schedstat_inc(sd, lb_gained[idle]);
			return 1;
		}
	}

	return 0;
}

2102 2103 2104 2105
static unsigned long
balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
	      unsigned long max_load_move, struct sched_domain *sd,
	      enum cpu_idle_type idle, int *all_pinned,
2106
	      int *this_best_prio, struct cfs_rq *busiest_cfs_rq)
2107 2108 2109
{
	int loops = 0, pulled = 0, pinned = 0;
	long rem_load_move = max_load_move;
2110
	struct task_struct *p, *n;
2111 2112 2113 2114 2115 2116

	if (max_load_move == 0)
		goto out;

	pinned = 1;

2117 2118 2119
	list_for_each_entry_safe(p, n, &busiest_cfs_rq->tasks, se.group_node) {
		if (loops++ > sysctl_sched_nr_migrate)
			break;
2120

2121 2122 2123
		if ((p->se.load.weight >> 1) > rem_load_move ||
		    !can_migrate_task(p, busiest, this_cpu, sd, idle, &pinned))
			continue;
2124

2125 2126 2127
		pull_task(busiest, p, this_rq, this_cpu);
		pulled++;
		rem_load_move -= p->se.load.weight;
2128 2129

#ifdef CONFIG_PREEMPT
2130 2131 2132 2133 2134 2135 2136
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
		 * kernels will stop after the first task is pulled to minimize
		 * the critical section.
		 */
		if (idle == CPU_NEWLY_IDLE)
			break;
2137 2138
#endif

2139 2140 2141 2142 2143 2144 2145
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
		if (rem_load_move <= 0)
			break;

2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162
		if (p->prio < *this_best_prio)
			*this_best_prio = p->prio;
	}
out:
	/*
	 * Right now, this is one of only two places pull_task() is called,
	 * so we can safely collect pull_task() stats here rather than
	 * inside pull_task().
	 */
	schedstat_add(sd, lb_gained[idle], pulled);

	if (all_pinned)
		*all_pinned = pinned;

	return max_load_move - rem_load_move;
}

P
Peter Zijlstra 已提交
2163
#ifdef CONFIG_FAIR_GROUP_SCHED
2164 2165 2166
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
2167
static int update_shares_cpu(struct task_group *tg, int cpu)
2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181
{
	struct cfs_rq *cfs_rq;
	unsigned long flags;
	struct rq *rq;

	if (!tg->se[cpu])
		return 0;

	rq = cpu_rq(cpu);
	cfs_rq = tg->cfs_rq[cpu];

	raw_spin_lock_irqsave(&rq->lock, flags);

	update_rq_clock(rq);
2182
	update_cfs_load(cfs_rq, 1);
2183 2184 2185 2186 2187

	/*
	 * We need to update shares after updating tg->load_weight in
	 * order to adjust the weight of groups with long running tasks.
	 */
2188
	update_cfs_shares(cfs_rq);
2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200

	raw_spin_unlock_irqrestore(&rq->lock, flags);

	return 0;
}

static void update_shares(int cpu)
{
	struct cfs_rq *cfs_rq;
	struct rq *rq = cpu_rq(cpu);

	rcu_read_lock();
2201 2202
	for_each_leaf_cfs_rq(rq, cfs_rq)
		update_shares_cpu(cfs_rq->tg, cpu);
2203 2204 2205
	rcu_read_unlock();
}

P
Peter Zijlstra 已提交
2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252
static unsigned long
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
		  unsigned long max_load_move,
		  struct sched_domain *sd, enum cpu_idle_type idle,
		  int *all_pinned, int *this_best_prio)
{
	long rem_load_move = max_load_move;
	int busiest_cpu = cpu_of(busiest);
	struct task_group *tg;

	rcu_read_lock();
	update_h_load(busiest_cpu);

	list_for_each_entry_rcu(tg, &task_groups, list) {
		struct cfs_rq *busiest_cfs_rq = tg->cfs_rq[busiest_cpu];
		unsigned long busiest_h_load = busiest_cfs_rq->h_load;
		unsigned long busiest_weight = busiest_cfs_rq->load.weight;
		u64 rem_load, moved_load;

		/*
		 * empty group
		 */
		if (!busiest_cfs_rq->task_weight)
			continue;

		rem_load = (u64)rem_load_move * busiest_weight;
		rem_load = div_u64(rem_load, busiest_h_load + 1);

		moved_load = balance_tasks(this_rq, this_cpu, busiest,
				rem_load, sd, idle, all_pinned, this_best_prio,
				busiest_cfs_rq);

		if (!moved_load)
			continue;

		moved_load *= busiest_h_load;
		moved_load = div_u64(moved_load, busiest_weight + 1);

		rem_load_move -= moved_load;
		if (rem_load_move < 0)
			break;
	}
	rcu_read_unlock();

	return max_load_move - rem_load_move;
}
#else
2253 2254 2255 2256
static inline void update_shares(int cpu)
{
}

P
Peter Zijlstra 已提交
2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268
static unsigned long
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
		  unsigned long max_load_move,
		  struct sched_domain *sd, enum cpu_idle_type idle,
		  int *all_pinned, int *this_best_prio)
{
	return balance_tasks(this_rq, this_cpu, busiest,
			max_load_move, sd, idle, all_pinned,
			this_best_prio, &busiest->cfs);
}
#endif

2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280
/*
 * move_tasks tries to move up to max_load_move weighted load from busiest to
 * 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 rq *this_rq, int this_cpu, struct rq *busiest,
		      unsigned long max_load_move,
		      struct sched_domain *sd, enum cpu_idle_type idle,
		      int *all_pinned)
{
2281
	unsigned long total_load_moved = 0, load_moved;
2282 2283 2284
	int this_best_prio = this_rq->curr->prio;

	do {
2285
		load_moved = load_balance_fair(this_rq, this_cpu, busiest,
2286 2287
				max_load_move - total_load_moved,
				sd, idle, all_pinned, &this_best_prio);
2288 2289

		total_load_moved += load_moved;
2290 2291 2292 2293 2294 2295 2296 2297 2298

#ifdef CONFIG_PREEMPT
		/*
		 * NEWIDLE balancing is a source of latency, so preemptible
		 * kernels will stop after the first task is pulled to minimize
		 * the critical section.
		 */
		if (idle == CPU_NEWLY_IDLE && this_rq->nr_running)
			break;
2299 2300 2301 2302

		if (raw_spin_is_contended(&this_rq->lock) ||
				raw_spin_is_contended(&busiest->lock))
			break;
2303
#endif
2304
	} while (load_moved && max_load_move > total_load_moved);
2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324

	return total_load_moved > 0;
}

/********** Helpers for find_busiest_group ************************/
/*
 * sd_lb_stats - Structure to store the statistics of a sched_domain
 * 		during load balancing.
 */
struct sd_lb_stats {
	struct sched_group *busiest; /* Busiest group in this sd */
	struct sched_group *this;  /* Local group in this sd */
	unsigned long total_load;  /* Total load of all groups in sd */
	unsigned long total_pwr;   /*	Total power of all groups in sd */
	unsigned long avg_load;	   /* Average load across all groups in sd */

	/** Statistics of this group */
	unsigned long this_load;
	unsigned long this_load_per_task;
	unsigned long this_nr_running;
2325
	unsigned long this_has_capacity;
2326
	unsigned int  this_idle_cpus;
2327 2328

	/* Statistics of the busiest group */
2329
	unsigned int  busiest_idle_cpus;
2330 2331 2332
	unsigned long max_load;
	unsigned long busiest_load_per_task;
	unsigned long busiest_nr_running;
2333
	unsigned long busiest_group_capacity;
2334
	unsigned long busiest_has_capacity;
2335
	unsigned int  busiest_group_weight;
2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356

	int group_imb; /* Is there imbalance in this sd */
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
	int power_savings_balance; /* Is powersave balance needed for this sd */
	struct sched_group *group_min; /* Least loaded group in sd */
	struct sched_group *group_leader; /* Group which relieves group_min */
	unsigned long min_load_per_task; /* load_per_task in group_min */
	unsigned long leader_nr_running; /* Nr running of group_leader */
	unsigned long min_nr_running; /* Nr running of group_min */
#endif
};

/*
 * sg_lb_stats - stats of a sched_group required for load_balancing
 */
struct sg_lb_stats {
	unsigned long avg_load; /*Avg load across the CPUs of the group */
	unsigned long group_load; /* Total load over the CPUs of the group */
	unsigned long sum_nr_running; /* Nr tasks running in the group */
	unsigned long sum_weighted_load; /* Weighted load of group's tasks */
	unsigned long group_capacity;
2357 2358
	unsigned long idle_cpus;
	unsigned long group_weight;
2359
	int group_imb; /* Is there an imbalance in the group ? */
2360
	int group_has_capacity; /* Is there extra capacity in the group? */
2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 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 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551
};

/**
 * group_first_cpu - Returns the first cpu in the cpumask of a sched_group.
 * @group: The group whose first cpu is to be returned.
 */
static inline unsigned int group_first_cpu(struct sched_group *group)
{
	return cpumask_first(sched_group_cpus(group));
}

/**
 * get_sd_load_idx - Obtain the load index for a given sched domain.
 * @sd: The sched_domain whose load_idx is to be obtained.
 * @idle: The Idle status of the CPU for whose sd load_icx is obtained.
 */
static inline int get_sd_load_idx(struct sched_domain *sd,
					enum cpu_idle_type idle)
{
	int load_idx;

	switch (idle) {
	case CPU_NOT_IDLE:
		load_idx = sd->busy_idx;
		break;

	case CPU_NEWLY_IDLE:
		load_idx = sd->newidle_idx;
		break;
	default:
		load_idx = sd->idle_idx;
		break;
	}

	return load_idx;
}


#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
/**
 * init_sd_power_savings_stats - Initialize power savings statistics for
 * the given sched_domain, during load balancing.
 *
 * @sd: Sched domain whose power-savings statistics are to be initialized.
 * @sds: Variable containing the statistics for sd.
 * @idle: Idle status of the CPU at which we're performing load-balancing.
 */
static inline void init_sd_power_savings_stats(struct sched_domain *sd,
	struct sd_lb_stats *sds, enum cpu_idle_type idle)
{
	/*
	 * Busy processors will not participate in power savings
	 * balance.
	 */
	if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
		sds->power_savings_balance = 0;
	else {
		sds->power_savings_balance = 1;
		sds->min_nr_running = ULONG_MAX;
		sds->leader_nr_running = 0;
	}
}

/**
 * update_sd_power_savings_stats - Update the power saving stats for a
 * sched_domain while performing load balancing.
 *
 * @group: sched_group belonging to the sched_domain under consideration.
 * @sds: Variable containing the statistics of the sched_domain
 * @local_group: Does group contain the CPU for which we're performing
 * 		load balancing ?
 * @sgs: Variable containing the statistics of the group.
 */
static inline void update_sd_power_savings_stats(struct sched_group *group,
	struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
{

	if (!sds->power_savings_balance)
		return;

	/*
	 * If the local group is idle or completely loaded
	 * no need to do power savings balance at this domain
	 */
	if (local_group && (sds->this_nr_running >= sgs->group_capacity ||
				!sds->this_nr_running))
		sds->power_savings_balance = 0;

	/*
	 * If a group is already running at full capacity or idle,
	 * don't include that group in power savings calculations
	 */
	if (!sds->power_savings_balance ||
		sgs->sum_nr_running >= sgs->group_capacity ||
		!sgs->sum_nr_running)
		return;

	/*
	 * Calculate the group which has the least non-idle load.
	 * This is the group from where we need to pick up the load
	 * for saving power
	 */
	if ((sgs->sum_nr_running < sds->min_nr_running) ||
	    (sgs->sum_nr_running == sds->min_nr_running &&
	     group_first_cpu(group) > group_first_cpu(sds->group_min))) {
		sds->group_min = group;
		sds->min_nr_running = sgs->sum_nr_running;
		sds->min_load_per_task = sgs->sum_weighted_load /
						sgs->sum_nr_running;
	}

	/*
	 * Calculate the group which is almost near its
	 * capacity but still has some space to pick up some load
	 * from other group and save more power
	 */
	if (sgs->sum_nr_running + 1 > sgs->group_capacity)
		return;

	if (sgs->sum_nr_running > sds->leader_nr_running ||
	    (sgs->sum_nr_running == sds->leader_nr_running &&
	     group_first_cpu(group) < group_first_cpu(sds->group_leader))) {
		sds->group_leader = group;
		sds->leader_nr_running = sgs->sum_nr_running;
	}
}

/**
 * check_power_save_busiest_group - see if there is potential for some power-savings balance
 * @sds: Variable containing the statistics of the sched_domain
 *	under consideration.
 * @this_cpu: Cpu at which we're currently performing load-balancing.
 * @imbalance: Variable to store the imbalance.
 *
 * Description:
 * Check if we have potential to perform some power-savings balance.
 * If yes, set the busiest group to be the least loaded group in the
 * sched_domain, so that it's CPUs can be put to idle.
 *
 * Returns 1 if there is potential to perform power-savings balance.
 * Else returns 0.
 */
static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
					int this_cpu, unsigned long *imbalance)
{
	if (!sds->power_savings_balance)
		return 0;

	if (sds->this != sds->group_leader ||
			sds->group_leader == sds->group_min)
		return 0;

	*imbalance = sds->min_load_per_task;
	sds->busiest = sds->group_min;

	return 1;

}
#else /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
static inline void init_sd_power_savings_stats(struct sched_domain *sd,
	struct sd_lb_stats *sds, enum cpu_idle_type idle)
{
	return;
}

static inline void update_sd_power_savings_stats(struct sched_group *group,
	struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
{
	return;
}

static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
					int this_cpu, unsigned long *imbalance)
{
	return 0;
}
#endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */


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

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

unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
{
2552
	unsigned long weight = sd->span_weight;
2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570
	unsigned long smt_gain = sd->smt_gain;

	smt_gain /= weight;

	return smt_gain;
}

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

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

	total = sched_avg_period() + (rq->clock - rq->age_stamp);
2571 2572 2573 2574 2575 2576 2577

	if (unlikely(total < rq->rt_avg)) {
		/* Ensures that power won't end up being negative */
		available = 0;
	} else {
		available = total - rq->rt_avg;
	}
2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588

	if (unlikely((s64)total < SCHED_LOAD_SCALE))
		total = SCHED_LOAD_SCALE;

	total >>= SCHED_LOAD_SHIFT;

	return div_u64(available, total);
}

static void update_cpu_power(struct sched_domain *sd, int cpu)
{
2589
	unsigned long weight = sd->span_weight;
2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601
	unsigned long power = SCHED_LOAD_SCALE;
	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);

		power >>= SCHED_LOAD_SHIFT;
	}

2602 2603 2604 2605 2606 2607 2608 2609 2610
	sdg->cpu_power_orig = power;

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

	power >>= SCHED_LOAD_SHIFT;

2611 2612 2613 2614 2615 2616
	power *= scale_rt_power(cpu);
	power >>= SCHED_LOAD_SHIFT;

	if (!power)
		power = 1;

2617
	cpu_rq(cpu)->cpu_power = power;
2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642
	sdg->cpu_power = power;
}

static void update_group_power(struct sched_domain *sd, int cpu)
{
	struct sched_domain *child = sd->child;
	struct sched_group *group, *sdg = sd->groups;
	unsigned long power;

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

	power = 0;

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

	sdg->cpu_power = power;
}

2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661
/*
 * 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)
{
	/*
	 * Only siblings can have significantly less than SCHED_LOAD_SCALE
	 */
	if (sd->level != SD_LV_SIBLING)
		return 0;

	/*
	 * If ~90% of the cpu_power is still there, we're good.
	 */
M
Michael Neuling 已提交
2662
	if (group->cpu_power * 32 > group->cpu_power_orig * 29)
2663 2664 2665 2666 2667
		return 1;

	return 0;
}

2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681
/**
 * update_sg_lb_stats - Update sched_group's statistics for load balancing.
 * @sd: The sched_domain whose statistics are to be updated.
 * @group: sched_group whose statistics are to be updated.
 * @this_cpu: Cpu for which load balance is currently performed.
 * @idle: Idle status of this_cpu
 * @load_idx: Load index of sched_domain of this_cpu for load calc.
 * @local_group: Does group contain this_cpu.
 * @cpus: Set of cpus considered for load balancing.
 * @balance: Should we balance.
 * @sgs: variable to hold the statistics for this group.
 */
static inline void update_sg_lb_stats(struct sched_domain *sd,
			struct sched_group *group, int this_cpu,
2682
			enum cpu_idle_type idle, int load_idx,
2683 2684 2685
			int local_group, const struct cpumask *cpus,
			int *balance, struct sg_lb_stats *sgs)
{
2686
	unsigned long load, max_cpu_load, min_cpu_load, max_nr_running;
2687 2688
	int i;
	unsigned int balance_cpu = -1, first_idle_cpu = 0;
2689
	unsigned long avg_load_per_task = 0;
2690

2691
	if (local_group)
2692 2693 2694 2695 2696
		balance_cpu = group_first_cpu(group);

	/* Tally up the load of all CPUs in the group */
	max_cpu_load = 0;
	min_cpu_load = ~0UL;
2697
	max_nr_running = 0;
2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711

	for_each_cpu_and(i, sched_group_cpus(group), cpus) {
		struct rq *rq = cpu_rq(i);

		/* Bias balancing toward cpus of our domain */
		if (local_group) {
			if (idle_cpu(i) && !first_idle_cpu) {
				first_idle_cpu = 1;
				balance_cpu = i;
			}

			load = target_load(i, load_idx);
		} else {
			load = source_load(i, load_idx);
2712
			if (load > max_cpu_load) {
2713
				max_cpu_load = load;
2714 2715
				max_nr_running = rq->nr_running;
			}
2716 2717 2718 2719 2720 2721 2722
			if (min_cpu_load > load)
				min_cpu_load = load;
		}

		sgs->group_load += load;
		sgs->sum_nr_running += rq->nr_running;
		sgs->sum_weighted_load += weighted_cpuload(i);
2723 2724
		if (idle_cpu(i))
			sgs->idle_cpus++;
2725 2726 2727 2728 2729 2730 2731 2732
	}

	/*
	 * First idle cpu or the first cpu(busiest) in this sched group
	 * is eligible for doing load balancing at this and above
	 * domains. In the newly idle case, we will allow all the cpu's
	 * to do the newly idle load balance.
	 */
2733 2734 2735 2736 2737 2738
	if (idle != CPU_NEWLY_IDLE && local_group) {
		if (balance_cpu != this_cpu) {
			*balance = 0;
			return;
		}
		update_group_power(sd, this_cpu);
2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752
	}

	/* Adjust by relative CPU power of the group */
	sgs->avg_load = (sgs->group_load * SCHED_LOAD_SCALE) / group->cpu_power;

	/*
	 * Consider the group unbalanced when the imbalance is larger
	 * than the average weight of two tasks.
	 *
	 * APZ: with cgroup the avg task weight can vary wildly and
	 *      might not be a suitable number - should we keep a
	 *      normalized nr_running number somewhere that negates
	 *      the hierarchy?
	 */
2753 2754
	if (sgs->sum_nr_running)
		avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
2755

2756
	if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task && max_nr_running > 1)
2757 2758
		sgs->group_imb = 1;

2759
	sgs->group_capacity = DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE);
2760 2761
	if (!sgs->group_capacity)
		sgs->group_capacity = fix_small_capacity(sd, group);
2762
	sgs->group_weight = group->group_weight;
2763 2764 2765

	if (sgs->group_capacity > sgs->sum_nr_running)
		sgs->group_has_capacity = 1;
2766 2767
}

2768 2769 2770 2771 2772
/**
 * update_sd_pick_busiest - return 1 on busiest group
 * @sd: sched_domain whose statistics are to be checked
 * @sds: sched_domain statistics
 * @sg: sched_group candidate to be checked for being the busiest
2773 2774
 * @sgs: sched_group statistics
 * @this_cpu: the current cpu
2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810
 *
 * Determine if @sg is a busier group than the previously selected
 * busiest group.
 */
static bool update_sd_pick_busiest(struct sched_domain *sd,
				   struct sd_lb_stats *sds,
				   struct sched_group *sg,
				   struct sg_lb_stats *sgs,
				   int this_cpu)
{
	if (sgs->avg_load <= sds->max_load)
		return false;

	if (sgs->sum_nr_running > sgs->group_capacity)
		return true;

	if (sgs->group_imb)
		return true;

	/*
	 * ASYM_PACKING needs to move all the work to the lowest
	 * numbered CPUs in the group, therefore mark all groups
	 * higher than ourself as busy.
	 */
	if ((sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running &&
	    this_cpu < group_first_cpu(sg)) {
		if (!sds->busiest)
			return true;

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

	return false;
}

2811 2812 2813 2814 2815 2816 2817 2818 2819 2820
/**
 * update_sd_lb_stats - Update sched_group's statistics for load balancing.
 * @sd: sched_domain whose statistics are to be updated.
 * @this_cpu: Cpu for which load balance is currently performed.
 * @idle: Idle status of this_cpu
 * @cpus: Set of cpus considered for load balancing.
 * @balance: Should we balance.
 * @sds: variable to hold the statistics for this sched_domain.
 */
static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
2821 2822
			enum cpu_idle_type idle, const struct cpumask *cpus,
			int *balance, struct sd_lb_stats *sds)
2823 2824
{
	struct sched_domain *child = sd->child;
2825
	struct sched_group *sg = sd->groups;
2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837
	struct sg_lb_stats sgs;
	int load_idx, prefer_sibling = 0;

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

	init_sd_power_savings_stats(sd, sds, idle);
	load_idx = get_sd_load_idx(sd, idle);

	do {
		int local_group;

2838
		local_group = cpumask_test_cpu(this_cpu, sched_group_cpus(sg));
2839
		memset(&sgs, 0, sizeof(sgs));
2840
		update_sg_lb_stats(sd, sg, this_cpu, idle, load_idx,
2841 2842
				local_group, cpus, balance, &sgs);

P
Peter Zijlstra 已提交
2843
		if (local_group && !(*balance))
2844 2845 2846
			return;

		sds->total_load += sgs.group_load;
2847
		sds->total_pwr += sg->cpu_power;
2848 2849 2850

		/*
		 * In case the child domain prefers tasks go to siblings
2851
		 * first, lower the sg capacity to one so that we'll try
2852 2853 2854 2855 2856 2857
		 * 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).
2858
		 */
2859
		if (prefer_sibling && !local_group && sds->this_has_capacity)
2860 2861 2862 2863
			sgs.group_capacity = min(sgs.group_capacity, 1UL);

		if (local_group) {
			sds->this_load = sgs.avg_load;
2864
			sds->this = sg;
2865 2866
			sds->this_nr_running = sgs.sum_nr_running;
			sds->this_load_per_task = sgs.sum_weighted_load;
2867
			sds->this_has_capacity = sgs.group_has_capacity;
2868
			sds->this_idle_cpus = sgs.idle_cpus;
2869
		} else if (update_sd_pick_busiest(sd, sds, sg, &sgs, this_cpu)) {
2870
			sds->max_load = sgs.avg_load;
2871
			sds->busiest = sg;
2872
			sds->busiest_nr_running = sgs.sum_nr_running;
2873
			sds->busiest_idle_cpus = sgs.idle_cpus;
2874
			sds->busiest_group_capacity = sgs.group_capacity;
2875
			sds->busiest_load_per_task = sgs.sum_weighted_load;
2876
			sds->busiest_has_capacity = sgs.group_has_capacity;
2877
			sds->busiest_group_weight = sgs.group_weight;
2878 2879 2880
			sds->group_imb = sgs.group_imb;
		}

2881 2882 2883 2884 2885
		update_sd_power_savings_stats(sg, sds, local_group, &sgs);
		sg = sg->next;
	} while (sg != sd->groups);
}

M
Michael Neuling 已提交
2886
int __weak arch_sd_sibling_asym_packing(void)
2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907
{
       return 0*SD_ASYM_PACKING;
}

/**
 * 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.
 *
2908 2909 2910
 * Returns 1 when packing is required and a task should be moved to
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934
 * @sd: The sched_domain whose packing is to be checked.
 * @sds: Statistics of the sched_domain which is to be packed
 * @this_cpu: The cpu at whose sched_domain we're performing load-balance.
 * @imbalance: returns amount of imbalanced due to packing.
 */
static int check_asym_packing(struct sched_domain *sd,
			      struct sd_lb_stats *sds,
			      int this_cpu, unsigned long *imbalance)
{
	int busiest_cpu;

	if (!(sd->flags & SD_ASYM_PACKING))
		return 0;

	if (!sds->busiest)
		return 0;

	busiest_cpu = group_first_cpu(sds->busiest);
	if (this_cpu > busiest_cpu)
		return 0;

	*imbalance = DIV_ROUND_CLOSEST(sds->max_load * sds->busiest->cpu_power,
				       SCHED_LOAD_SCALE);
	return 1;
2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949
}

/**
 * fix_small_imbalance - Calculate the minor imbalance that exists
 *			amongst the groups of a sched_domain, during
 *			load balancing.
 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
 * @this_cpu: The cpu at whose sched_domain we're performing load-balance.
 * @imbalance: Variable to store the imbalance.
 */
static inline void fix_small_imbalance(struct sd_lb_stats *sds,
				int this_cpu, unsigned long *imbalance)
{
	unsigned long tmp, pwr_now = 0, pwr_move = 0;
	unsigned int imbn = 2;
2950
	unsigned long scaled_busy_load_per_task;
2951 2952 2953 2954 2955 2956 2957 2958 2959 2960

	if (sds->this_nr_running) {
		sds->this_load_per_task /= sds->this_nr_running;
		if (sds->busiest_load_per_task >
				sds->this_load_per_task)
			imbn = 1;
	} else
		sds->this_load_per_task =
			cpu_avg_load_per_task(this_cpu);

2961 2962 2963 2964 2965 2966
	scaled_busy_load_per_task = sds->busiest_load_per_task
						 * SCHED_LOAD_SCALE;
	scaled_busy_load_per_task /= sds->busiest->cpu_power;

	if (sds->max_load - sds->this_load + scaled_busy_load_per_task >=
			(scaled_busy_load_per_task * imbn)) {
2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016
		*imbalance = sds->busiest_load_per_task;
		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.
	 */

	pwr_now += sds->busiest->cpu_power *
			min(sds->busiest_load_per_task, sds->max_load);
	pwr_now += sds->this->cpu_power *
			min(sds->this_load_per_task, sds->this_load);
	pwr_now /= SCHED_LOAD_SCALE;

	/* Amount of load we'd subtract */
	tmp = (sds->busiest_load_per_task * SCHED_LOAD_SCALE) /
		sds->busiest->cpu_power;
	if (sds->max_load > tmp)
		pwr_move += sds->busiest->cpu_power *
			min(sds->busiest_load_per_task, sds->max_load - tmp);

	/* Amount of load we'd add */
	if (sds->max_load * sds->busiest->cpu_power <
		sds->busiest_load_per_task * SCHED_LOAD_SCALE)
		tmp = (sds->max_load * sds->busiest->cpu_power) /
			sds->this->cpu_power;
	else
		tmp = (sds->busiest_load_per_task * SCHED_LOAD_SCALE) /
			sds->this->cpu_power;
	pwr_move += sds->this->cpu_power *
			min(sds->this_load_per_task, sds->this_load + tmp);
	pwr_move /= SCHED_LOAD_SCALE;

	/* Move if we gain throughput */
	if (pwr_move > pwr_now)
		*imbalance = sds->busiest_load_per_task;
}

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 * @this_cpu: Cpu for which currently load balance is being performed.
 * @imbalance: The variable to store the imbalance.
 */
static inline void calculate_imbalance(struct sd_lb_stats *sds, int this_cpu,
		unsigned long *imbalance)
{
3017 3018 3019 3020 3021 3022 3023 3024
	unsigned long max_pull, load_above_capacity = ~0UL;

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

3025 3026 3027 3028 3029 3030 3031 3032 3033 3034
	/*
	 * In the presence of smp nice balancing, certain scenarios can have
	 * max load less than avg load(as we skip the groups at or below
	 * its cpu_power, while calculating max_load..)
	 */
	if (sds->max_load < sds->avg_load) {
		*imbalance = 0;
		return fix_small_imbalance(sds, this_cpu, imbalance);
	}

3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057
	if (!sds->group_imb) {
		/*
		 * Don't want to pull so many tasks that a group would go idle.
		 */
		load_above_capacity = (sds->busiest_nr_running -
						sds->busiest_group_capacity);

		load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_LOAD_SCALE);

		load_above_capacity /= sds->busiest->cpu_power;
	}

	/*
	 * We're trying to get all the cpus to the average_load, so we don't
	 * want to push ourselves above the average load, nor do we wish to
	 * reduce the max loaded cpu below the average load. At the same time,
	 * we also don't want to reduce the group load below the group capacity
	 * (so that we can implement power-savings policies etc). Thus we look
	 * for the minimum possible imbalance.
	 * Be careful of negative numbers as they'll appear as very large values
	 * with unsigned longs.
	 */
	max_pull = min(sds->max_load - sds->avg_load, load_above_capacity);
3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073

	/* How much load to actually move to equalise the imbalance */
	*imbalance = min(max_pull * sds->busiest->cpu_power,
		(sds->avg_load - sds->this_load) * sds->this->cpu_power)
			/ SCHED_LOAD_SCALE;

	/*
	 * if *imbalance is less than the average load per runnable task
	 * there is no gaurantee that any tasks will be moved so we'll have
	 * a think about bumping its value to force at least one task to be
	 * moved
	 */
	if (*imbalance < sds->busiest_load_per_task)
		return fix_small_imbalance(sds, this_cpu, imbalance);

}
3074

3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103
/******* 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.
 *
 * @sd: The sched_domain whose busiest group is to be returned.
 * @this_cpu: The cpu for which load balancing is currently being performed.
 * @imbalance: Variable which stores amount of weighted load which should
 *		be moved to restore balance/put a group to idle.
 * @idle: The idle status of this_cpu.
 * @cpus: The set of CPUs under consideration for load-balancing.
 * @balance: Pointer to a variable indicating if this_cpu
 *	is the appropriate cpu to perform load balancing at this_level.
 *
 * Returns:	- the busiest group if imbalance exists.
 *		- If no imbalance and user has opted for power-savings balance,
 *		   return the least loaded group whose CPUs can be
 *		   put to idle by rebalancing its tasks onto our group.
 */
static struct sched_group *
find_busiest_group(struct sched_domain *sd, int this_cpu,
		   unsigned long *imbalance, enum cpu_idle_type idle,
3104
		   const struct cpumask *cpus, int *balance)
3105 3106 3107 3108 3109 3110 3111 3112 3113
{
	struct sd_lb_stats sds;

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

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
3114
	update_sd_lb_stats(sd, this_cpu, idle, cpus, balance, &sds);
3115

3116 3117 3118
	/*
	 * this_cpu is not the appropriate cpu to perform load balancing at
	 * this level.
3119
	 */
P
Peter Zijlstra 已提交
3120
	if (!(*balance))
3121 3122
		goto ret;

3123 3124 3125 3126
	if ((idle == CPU_IDLE || idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(sd, &sds, this_cpu, imbalance))
		return sds.busiest;

3127
	/* There is no busy sibling group to pull tasks from */
3128 3129 3130
	if (!sds.busiest || sds.busiest_nr_running == 0)
		goto out_balanced;

3131
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
3132 3133 3134 3135
	if (idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
			!sds.busiest_has_capacity)
		goto force_balance;

3136 3137 3138 3139
	/*
	 * If the local group is more busy than the selected busiest group
	 * don't try and pull any tasks.
	 */
3140 3141 3142
	if (sds.this_load >= sds.max_load)
		goto out_balanced;

3143 3144 3145 3146
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
3147 3148 3149 3150
	sds.avg_load = (SCHED_LOAD_SCALE * sds.total_load) / sds.total_pwr;
	if (sds.this_load >= sds.avg_load)
		goto out_balanced;

3151
	if (idle == CPU_IDLE) {
3152 3153 3154 3155 3156 3157
		/*
		 * 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.
		 */
3158
		if ((sds.this_idle_cpus <= sds.busiest_idle_cpus + 1) &&
3159 3160
		    sds.busiest_nr_running <= sds.busiest_group_weight)
			goto out_balanced;
3161 3162 3163 3164 3165 3166 3167
	} else {
		/*
		 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
		 * imbalance_pct to be conservative.
		 */
		if (100 * sds.max_load <= sd->imbalance_pct * sds.this_load)
			goto out_balanced;
3168
	}
3169

3170
force_balance:
3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190
	/* Looks like there is an imbalance. Compute it */
	calculate_imbalance(&sds, this_cpu, imbalance);
	return sds.busiest;

out_balanced:
	/*
	 * There is no obvious imbalance. But check if we can do some balancing
	 * to save power.
	 */
	if (check_power_save_busiest_group(&sds, this_cpu, imbalance))
		return sds.busiest;
ret:
	*imbalance = 0;
	return NULL;
}

/*
 * find_busiest_queue - find the busiest runqueue among the cpus in group.
 */
static struct rq *
3191 3192 3193
find_busiest_queue(struct sched_domain *sd, struct sched_group *group,
		   enum cpu_idle_type idle, unsigned long imbalance,
		   const struct cpumask *cpus)
3194 3195 3196 3197 3198 3199 3200 3201 3202 3203
{
	struct rq *busiest = NULL, *rq;
	unsigned long max_load = 0;
	int i;

	for_each_cpu(i, sched_group_cpus(group)) {
		unsigned long power = power_of(i);
		unsigned long capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
		unsigned long wl;

3204 3205 3206
		if (!capacity)
			capacity = fix_small_capacity(sd, group);

3207 3208 3209 3210
		if (!cpumask_test_cpu(i, cpus))
			continue;

		rq = cpu_rq(i);
3211
		wl = weighted_cpuload(i);
3212

3213 3214 3215 3216
		/*
		 * When comparing with imbalance, use weighted_cpuload()
		 * which is not scaled with the cpu power.
		 */
3217 3218 3219
		if (capacity && rq->nr_running == 1 && wl > imbalance)
			continue;

3220 3221 3222 3223 3224 3225 3226 3227
		/*
		 * 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.
		 */
		wl = (wl * SCHED_LOAD_SCALE) / power;

3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245
		if (wl > max_load) {
			max_load = wl;
			busiest = rq;
		}
	}

	return busiest;
}

/*
 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
 * so long as it is large enough.
 */
#define MAX_PINNED_INTERVAL	512

/* Working cpumask for load_balance and load_balance_newidle. */
static DEFINE_PER_CPU(cpumask_var_t, load_balance_tmpmask);

3246
static int need_active_balance(struct sched_domain *sd, int idle,
3247
			       int busiest_cpu, int this_cpu)
3248 3249
{
	if (idle == CPU_NEWLY_IDLE) {
3250 3251 3252 3253 3254 3255 3256 3257 3258

		/*
		 * ASYM_PACKING needs to force migrate tasks from busy but
		 * higher numbered CPUs in order to pack all tasks in the
		 * lowest numbered CPUs.
		 */
		if ((sd->flags & SD_ASYM_PACKING) && busiest_cpu > this_cpu)
			return 1;

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
		/*
		 * The only task running in a non-idle cpu can be moved to this
		 * cpu in an attempt to completely freeup the other CPU
		 * package.
		 *
		 * The package power saving logic comes from
		 * find_busiest_group(). If there are no imbalance, then
		 * f_b_g() will return NULL. However when sched_mc={1,2} then
		 * f_b_g() will select a group from which a running task may be
		 * pulled to this cpu in order to make the other package idle.
		 * If there is no opportunity to make a package idle and if
		 * there are no imbalance, then f_b_g() will return NULL and no
		 * action will be taken in load_balance_newidle().
		 *
		 * Under normal task pull operation due to imbalance, there
		 * will be more than one task in the source run queue and
		 * move_tasks() will succeed.  ld_moved will be true and this
		 * active balance code will not be triggered.
		 */
		if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP)
			return 0;
	}

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

3285 3286
static int active_load_balance_cpu_stop(void *data);

3287 3288 3289 3290 3291 3292 3293 3294
/*
 * Check this_cpu to ensure it is balanced within domain. Attempt to move
 * tasks if there is an imbalance.
 */
static int load_balance(int this_cpu, struct rq *this_rq,
			struct sched_domain *sd, enum cpu_idle_type idle,
			int *balance)
{
3295
	int ld_moved, all_pinned = 0, active_balance = 0;
3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306
	struct sched_group *group;
	unsigned long imbalance;
	struct rq *busiest;
	unsigned long flags;
	struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);

	cpumask_copy(cpus, cpu_active_mask);

	schedstat_inc(sd, lb_count[idle]);

redo:
3307
	group = find_busiest_group(sd, this_cpu, &imbalance, idle,
3308 3309 3310 3311 3312 3313 3314 3315 3316 3317
				   cpus, balance);

	if (*balance == 0)
		goto out_balanced;

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

3318
	busiest = find_busiest_queue(sd, group, idle, imbalance, cpus);
3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

	BUG_ON(busiest == this_rq);

	schedstat_add(sd, lb_imbalance[idle], imbalance);

	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.
		 */
		local_irq_save(flags);
		double_rq_lock(this_rq, busiest);
		ld_moved = move_tasks(this_rq, this_cpu, busiest,
				      imbalance, sd, idle, &all_pinned);
		double_rq_unlock(this_rq, busiest);
		local_irq_restore(flags);

		/*
		 * some other cpu did the load balance for us.
		 */
		if (ld_moved && this_cpu != smp_processor_id())
			resched_cpu(this_cpu);

		/* All tasks on this runqueue were pinned by CPU affinity */
		if (unlikely(all_pinned)) {
			cpumask_clear_cpu(cpu_of(busiest), cpus);
			if (!cpumask_empty(cpus))
				goto redo;
			goto out_balanced;
		}
	}

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
3360 3361 3362 3363 3364 3365 3366 3367
		/*
		 * 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++;
3368

3369
		if (need_active_balance(sd, idle, cpu_of(busiest), this_cpu)) {
3370 3371
			raw_spin_lock_irqsave(&busiest->lock, flags);

3372 3373 3374
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
3375 3376 3377 3378 3379 3380 3381 3382 3383
			 */
			if (!cpumask_test_cpu(this_cpu,
					      &busiest->curr->cpus_allowed)) {
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
				all_pinned = 1;
				goto out_one_pinned;
			}

3384 3385 3386 3387 3388
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
3389 3390 3391 3392 3393 3394
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
3395

3396
			if (active_balance)
3397 3398 3399
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436

			/*
			 * 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 */
	if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) ||
			(sd->balance_interval < sd->max_interval))
		sd->balance_interval *= 2;

3437
	ld_moved = 0;
3438 3439 3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456
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.
 */
static void idle_balance(int this_cpu, struct rq *this_rq)
{
	struct sched_domain *sd;
	int pulled_task = 0;
	unsigned long next_balance = jiffies + HZ;

	this_rq->idle_stamp = this_rq->clock;

	if (this_rq->avg_idle < sysctl_sched_migration_cost)
		return;

3457 3458 3459 3460 3461
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

P
Paul Turner 已提交
3462
	update_shares(this_cpu);
3463 3464
	for_each_domain(this_cpu, sd) {
		unsigned long interval;
3465
		int balance = 1;
3466 3467 3468 3469

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

3470
		if (sd->flags & SD_BALANCE_NEWIDLE) {
3471
			/* If we've pulled tasks over stop searching: */
3472 3473 3474
			pulled_task = load_balance(this_cpu, this_rq,
						   sd, CPU_NEWLY_IDLE, &balance);
		}
3475 3476 3477 3478

		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
3479 3480
		if (pulled_task) {
			this_rq->idle_stamp = 0;
3481
			break;
N
Nikhil Rao 已提交
3482
		}
3483
	}
3484 3485 3486

	raw_spin_lock(&this_rq->lock);

3487 3488 3489 3490 3491 3492 3493 3494 3495 3496
	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;
	}
}

/*
3497 3498 3499 3500
 * 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.
3501
 */
3502
static int active_load_balance_cpu_stop(void *data)
3503
{
3504 3505
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
3506
	int target_cpu = busiest_rq->push_cpu;
3507
	struct rq *target_rq = cpu_rq(target_cpu);
3508
	struct sched_domain *sd;
3509 3510 3511 3512 3513 3514 3515

	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;
3516 3517 3518

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
3519
		goto out_unlock;
3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546 3547

	/*
	 * 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. */
	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)) {
		schedstat_inc(sd, alb_count);

		if (move_one_task(target_rq, target_cpu, busiest_rq,
				  sd, CPU_IDLE))
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
	double_unlock_balance(busiest_rq, target_rq);
3548 3549 3550 3551
out_unlock:
	busiest_rq->active_balance = 0;
	raw_spin_unlock_irq(&busiest_rq->lock);
	return 0;
3552 3553 3554
}

#ifdef CONFIG_NO_HZ
3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580

static DEFINE_PER_CPU(struct call_single_data, remote_sched_softirq_cb);

static void trigger_sched_softirq(void *data)
{
	raise_softirq_irqoff(SCHED_SOFTIRQ);
}

static inline void init_sched_softirq_csd(struct call_single_data *csd)
{
	csd->func = trigger_sched_softirq;
	csd->info = NULL;
	csd->flags = 0;
	csd->priv = 0;
}

/*
 * idle load balancing details
 * - One of the idle CPUs nominates itself as idle load_balancer, while
 *   entering idle.
 * - This idle load balancer CPU will also go into tickless mode when
 *   it is idle, just like all other idle CPUs
 * - 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.
 */
3581 3582
static struct {
	atomic_t load_balancer;
3583 3584 3585 3586 3587 3588
	atomic_t first_pick_cpu;
	atomic_t second_pick_cpu;
	cpumask_var_t idle_cpus_mask;
	cpumask_var_t grp_idle_mask;
	unsigned long next_balance;     /* in jiffy units */
} nohz ____cacheline_aligned;
3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641

int get_nohz_load_balancer(void)
{
	return atomic_read(&nohz.load_balancer);
}

#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
/**
 * lowest_flag_domain - Return lowest sched_domain containing flag.
 * @cpu:	The cpu whose lowest level of sched domain is to
 *		be returned.
 * @flag:	The flag to check for the lowest sched_domain
 *		for the given cpu.
 *
 * Returns the lowest sched_domain of a cpu which contains the given flag.
 */
static inline struct sched_domain *lowest_flag_domain(int cpu, int flag)
{
	struct sched_domain *sd;

	for_each_domain(cpu, sd)
		if (sd && (sd->flags & flag))
			break;

	return sd;
}

/**
 * for_each_flag_domain - Iterates over sched_domains containing the flag.
 * @cpu:	The cpu whose domains we're iterating over.
 * @sd:		variable holding the value of the power_savings_sd
 *		for cpu.
 * @flag:	The flag to filter the sched_domains to be iterated.
 *
 * Iterates over all the scheduler domains for a given cpu that has the 'flag'
 * set, starting from the lowest sched_domain to the highest.
 */
#define for_each_flag_domain(cpu, sd, flag) \
	for (sd = lowest_flag_domain(cpu, flag); \
		(sd && (sd->flags & flag)); sd = sd->parent)

/**
 * is_semi_idle_group - Checks if the given sched_group is semi-idle.
 * @ilb_group:	group to be checked for semi-idleness
 *
 * Returns:	1 if the group is semi-idle. 0 otherwise.
 *
 * We define a sched_group to be semi idle if it has atleast one idle-CPU
 * and atleast one non-idle CPU. This helper function checks if the given
 * sched_group is semi-idle or not.
 */
static inline int is_semi_idle_group(struct sched_group *ilb_group)
{
3642
	cpumask_and(nohz.grp_idle_mask, nohz.idle_cpus_mask,
3643 3644 3645 3646 3647 3648
					sched_group_cpus(ilb_group));

	/*
	 * A sched_group is semi-idle when it has atleast one busy cpu
	 * and atleast one idle cpu.
	 */
3649
	if (cpumask_empty(nohz.grp_idle_mask))
3650 3651
		return 0;

3652
	if (cpumask_equal(nohz.grp_idle_mask, sched_group_cpus(ilb_group)))
3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684
		return 0;

	return 1;
}
/**
 * find_new_ilb - Finds the optimum idle load balancer for nomination.
 * @cpu:	The cpu which is nominating a new idle_load_balancer.
 *
 * Returns:	Returns the id of the idle load balancer if it exists,
 *		Else, returns >= nr_cpu_ids.
 *
 * This algorithm picks the idle load balancer such that it belongs to a
 * semi-idle powersavings sched_domain. The idea is to try and avoid
 * completely idle packages/cores just for the purpose of idle load balancing
 * when there are other idle cpu's which are better suited for that job.
 */
static int find_new_ilb(int cpu)
{
	struct sched_domain *sd;
	struct sched_group *ilb_group;

	/*
	 * Have idle load balancer selection from semi-idle packages only
	 * when power-aware load balancing is enabled
	 */
	if (!(sched_smt_power_savings || sched_mc_power_savings))
		goto out_done;

	/*
	 * Optimize for the case when we have no idle CPUs or only one
	 * idle CPU. Don't walk the sched_domain hierarchy in such cases
	 */
3685
	if (cpumask_weight(nohz.idle_cpus_mask) < 2)
3686 3687 3688 3689 3690 3691 3692
		goto out_done;

	for_each_flag_domain(cpu, sd, SD_POWERSAVINGS_BALANCE) {
		ilb_group = sd->groups;

		do {
			if (is_semi_idle_group(ilb_group))
3693
				return cpumask_first(nohz.grp_idle_mask);
3694 3695 3696 3697 3698 3699 3700

			ilb_group = ilb_group->next;

		} while (ilb_group != sd->groups);
	}

out_done:
3701
	return nr_cpu_ids;
3702 3703 3704 3705
}
#else /*  (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */
static inline int find_new_ilb(int call_cpu)
{
3706
	return nr_cpu_ids;
3707 3708 3709
}
#endif

3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738
/*
 * 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++;

	ilb_cpu = get_nohz_load_balancer();

	if (ilb_cpu >= nr_cpu_ids) {
		ilb_cpu = cpumask_first(nohz.idle_cpus_mask);
		if (ilb_cpu >= nr_cpu_ids)
			return;
	}

	if (!cpu_rq(ilb_cpu)->nohz_balance_kick) {
		struct call_single_data *cp;

		cpu_rq(ilb_cpu)->nohz_balance_kick = 1;
		cp = &per_cpu(remote_sched_softirq_cb, cpu);
		__smp_call_function_single(ilb_cpu, cp, 0);
	}
	return;
}

3739 3740 3741
/*
 * This routine will try to nominate the ilb (idle load balancing)
 * owner among the cpus whose ticks are stopped. ilb owner will do the idle
3742
 * load balancing on behalf of all those cpus.
3743
 *
3744 3745 3746
 * When the ilb owner becomes busy, we will not have new ilb owner until some
 * idle CPU wakes up and goes back to idle or some busy CPU tries to kick
 * idle load balancing by kicking one of the idle CPUs.
3747
 *
3748 3749 3750
 * Ticks are stopped for the ilb owner as well, with busy CPU kicking this
 * ilb owner CPU in future (when there is a need for idle load balancing on
 * behalf of all idle CPUs).
3751
 */
3752
void select_nohz_load_balancer(int stop_tick)
3753 3754 3755 3756 3757 3758
{
	int cpu = smp_processor_id();

	if (stop_tick) {
		if (!cpu_active(cpu)) {
			if (atomic_read(&nohz.load_balancer) != cpu)
3759
				return;
3760 3761 3762 3763 3764

			/*
			 * If we are going offline and still the leader,
			 * give up!
			 */
3765 3766
			if (atomic_cmpxchg(&nohz.load_balancer, cpu,
					   nr_cpu_ids) != cpu)
3767 3768
				BUG();

3769
			return;
3770 3771
		}

3772
		cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
3773

3774 3775 3776 3777
		if (atomic_read(&nohz.first_pick_cpu) == cpu)
			atomic_cmpxchg(&nohz.first_pick_cpu, cpu, nr_cpu_ids);
		if (atomic_read(&nohz.second_pick_cpu) == cpu)
			atomic_cmpxchg(&nohz.second_pick_cpu, cpu, nr_cpu_ids);
3778

3779
		if (atomic_read(&nohz.load_balancer) >= nr_cpu_ids) {
3780 3781
			int new_ilb;

3782 3783 3784 3785 3786
			/* make me the ilb owner */
			if (atomic_cmpxchg(&nohz.load_balancer, nr_cpu_ids,
					   cpu) != nr_cpu_ids)
				return;

3787 3788 3789 3790 3791 3792
			/*
			 * Check to see if there is a more power-efficient
			 * ilb.
			 */
			new_ilb = find_new_ilb(cpu);
			if (new_ilb < nr_cpu_ids && new_ilb != cpu) {
3793
				atomic_set(&nohz.load_balancer, nr_cpu_ids);
3794
				resched_cpu(new_ilb);
3795
				return;
3796
			}
3797
			return;
3798 3799
		}
	} else {
3800 3801
		if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
			return;
3802

3803
		cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
3804 3805

		if (atomic_read(&nohz.load_balancer) == cpu)
3806 3807
			if (atomic_cmpxchg(&nohz.load_balancer, cpu,
					   nr_cpu_ids) != cpu)
3808 3809
				BUG();
	}
3810
	return;
3811 3812 3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831 3832
}
#endif

static DEFINE_SPINLOCK(balancing);

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

P
Peter Zijlstra 已提交
3833 3834
	update_shares(cpu);

3835 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860
	for_each_domain(cpu, sd) {
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

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

		/* scale ms to jiffies */
		interval = msecs_to_jiffies(interval);
		if (unlikely(!interval))
			interval = 1;
		if (interval > HZ*NR_CPUS/10)
			interval = HZ*NR_CPUS/10;

		need_serialize = sd->flags & SD_SERIALIZE;

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

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
			if (load_balance(cpu, rq, sd, idle, &balance)) {
				/*
				 * We've pulled tasks over so either we're no
3861
				 * longer idle.
3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892
				 */
				idle = CPU_NOT_IDLE;
			}
			sd->last_balance = jiffies;
		}
		if (need_serialize)
			spin_unlock(&balancing);
out:
		if (time_after(next_balance, sd->last_balance + interval)) {
			next_balance = sd->last_balance + interval;
			update_next_balance = 1;
		}

		/*
		 * Stop the load balance at this level. There is another
		 * CPU in our sched group which is doing load balancing more
		 * actively.
		 */
		if (!balance)
			break;
	}

	/*
	 * 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;
}

3893
#ifdef CONFIG_NO_HZ
3894
/*
3895
 * In CONFIG_NO_HZ case, the idle balance kickee will do the
3896 3897
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921
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;

	if (idle != CPU_IDLE || !this_rq->nohz_balance_kick)
		return;

	for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
		if (balance_cpu == this_cpu)
			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.
		 */
		if (need_resched()) {
			this_rq->nohz_balance_kick = 0;
			break;
		}

		raw_spin_lock_irq(&this_rq->lock);
3922
		update_rq_clock(this_rq);
3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952 3953 3954 3955 3956
		update_cpu_load(this_rq);
		raw_spin_unlock_irq(&this_rq->lock);

		rebalance_domains(balance_cpu, CPU_IDLE);

		rq = cpu_rq(balance_cpu);
		if (time_after(this_rq->next_balance, rq->next_balance))
			this_rq->next_balance = rq->next_balance;
	}
	nohz.next_balance = this_rq->next_balance;
	this_rq->nohz_balance_kick = 0;
}

/*
 * Current heuristic for kicking the idle load balancer
 * - first_pick_cpu is the one of the busy CPUs. It will kick
 *   idle load balancer when it has more than one process active. This
 *   eliminates the need for idle load balancing altogether when we have
 *   only one running process in the system (common case).
 * - If there are more than one busy CPU, idle load balancer may have
 *   to run for active_load_balance to happen (i.e., two busy CPUs are
 *   SMT or core siblings and can run better if they move to different
 *   physical CPUs). So, second_pick_cpu is the second of the busy CPUs
 *   which will kick idle load balancer as soon as it has any load.
 */
static inline int nohz_kick_needed(struct rq *rq, int cpu)
{
	unsigned long now = jiffies;
	int ret;
	int first_pick_cpu, second_pick_cpu;

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

S
Suresh Siddha 已提交
3957
	if (rq->idle_at_tick)
3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988
		return 0;

	first_pick_cpu = atomic_read(&nohz.first_pick_cpu);
	second_pick_cpu = atomic_read(&nohz.second_pick_cpu);

	if (first_pick_cpu < nr_cpu_ids && first_pick_cpu != cpu &&
	    second_pick_cpu < nr_cpu_ids && second_pick_cpu != cpu)
		return 0;

	ret = atomic_cmpxchg(&nohz.first_pick_cpu, nr_cpu_ids, cpu);
	if (ret == nr_cpu_ids || ret == cpu) {
		atomic_cmpxchg(&nohz.second_pick_cpu, cpu, nr_cpu_ids);
		if (rq->nr_running > 1)
			return 1;
	} else {
		ret = atomic_cmpxchg(&nohz.second_pick_cpu, nr_cpu_ids, cpu);
		if (ret == nr_cpu_ids || ret == cpu) {
			if (rq->nr_running)
				return 1;
		}
	}
	return 0;
}
#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).
 */
3989 3990 3991 3992 3993 3994 3995 3996 3997 3998
static void run_rebalance_domains(struct softirq_action *h)
{
	int this_cpu = smp_processor_id();
	struct rq *this_rq = cpu_rq(this_cpu);
	enum cpu_idle_type idle = this_rq->idle_at_tick ?
						CPU_IDLE : CPU_NOT_IDLE;

	rebalance_domains(this_cpu, idle);

	/*
3999
	 * If this cpu has a pending nohz_balance_kick, then do the
4000 4001 4002
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
4003
	nohz_idle_balance(this_cpu, idle);
4004 4005 4006 4007
}

static inline int on_null_domain(int cpu)
{
4008
	return !rcu_dereference_sched(cpu_rq(cpu)->sd);
4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019
}

/*
 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
 */
static inline void trigger_load_balance(struct rq *rq, int cpu)
{
	/* 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);
4020 4021 4022 4023
#ifdef CONFIG_NO_HZ
	else if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
		nohz_balancer_kick(cpu);
#endif
4024 4025
}

4026 4027 4028 4029 4030 4031 4032 4033 4034 4035
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
}

static void rq_offline_fair(struct rq *rq)
{
	update_sysctl();
}

4036 4037 4038 4039 4040 4041 4042 4043 4044
#else	/* CONFIG_SMP */

/*
 * on UP we do not need to balance between CPUs:
 */
static inline void idle_balance(int cpu, struct rq *rq)
{
}

4045
#endif /* CONFIG_SMP */
4046

4047 4048 4049
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
4050
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
4051 4052 4053 4054 4055 4056
{
	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
4057
		entity_tick(cfs_rq, se, queued);
4058 4059 4060 4061
	}
}

/*
P
Peter Zijlstra 已提交
4062 4063 4064
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
4065
 */
P
Peter Zijlstra 已提交
4066
static void task_fork_fair(struct task_struct *p)
4067
{
P
Peter Zijlstra 已提交
4068
	struct cfs_rq *cfs_rq = task_cfs_rq(current);
4069
	struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
4070
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
4071 4072 4073
	struct rq *rq = this_rq();
	unsigned long flags;

4074
	raw_spin_lock_irqsave(&rq->lock, flags);
4075

4076 4077
	update_rq_clock(rq);

4078 4079
	if (unlikely(task_cpu(p) != this_cpu)) {
		rcu_read_lock();
P
Peter Zijlstra 已提交
4080
		__set_task_cpu(p, this_cpu);
4081 4082
		rcu_read_unlock();
	}
4083

4084
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
4085

4086 4087
	if (curr)
		se->vruntime = curr->vruntime;
4088
	place_entity(cfs_rq, se, 1);
4089

P
Peter Zijlstra 已提交
4090
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
4091
		/*
4092 4093 4094
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
4095
		swap(curr->vruntime, se->vruntime);
4096
		resched_task(rq->curr);
4097
	}
4098

4099 4100
	se->vruntime -= cfs_rq->min_vruntime;

4101
	raw_spin_unlock_irqrestore(&rq->lock, flags);
4102 4103
}

4104 4105 4106 4107
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
4108 4109
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
4110
{
P
Peter Zijlstra 已提交
4111 4112 4113
	if (!p->se.on_rq)
		return;

4114 4115 4116 4117 4118
	/*
	 * 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
4119
	if (rq->curr == p) {
4120 4121 4122
		if (p->prio > oldprio)
			resched_task(rq->curr);
	} else
4123
		check_preempt_curr(rq, p, 0);
4124 4125
}

P
Peter Zijlstra 已提交
4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149
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;
	}
}

4150 4151 4152
/*
 * We switched to the sched_fair class.
 */
P
Peter Zijlstra 已提交
4153
static void switched_to_fair(struct rq *rq, struct task_struct *p)
4154
{
P
Peter Zijlstra 已提交
4155 4156 4157
	if (!p->se.on_rq)
		return;

4158 4159 4160 4161 4162
	/*
	 * 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
4163
	if (rq->curr == p)
4164 4165
		resched_task(rq->curr);
	else
4166
		check_preempt_curr(rq, p, 0);
4167 4168
}

4169 4170 4171 4172 4173 4174 4175 4176 4177 4178 4179 4180 4181
/* 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;

	for_each_sched_entity(se)
		set_next_entity(cfs_rq_of(se), se);
}

P
Peter Zijlstra 已提交
4182
#ifdef CONFIG_FAIR_GROUP_SCHED
4183
static void task_move_group_fair(struct task_struct *p, int on_rq)
P
Peter Zijlstra 已提交
4184
{
4185 4186 4187 4188 4189 4190 4191 4192 4193 4194 4195 4196 4197 4198 4199 4200
	/*
	 * 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.
	 */
	if (!on_rq)
		p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime;
	set_task_rq(p, task_cpu(p));
4201
	if (!on_rq)
4202
		p->se.vruntime += cfs_rq_of(&p->se)->min_vruntime;
P
Peter Zijlstra 已提交
4203 4204 4205
}
#endif

4206
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
4207 4208 4209 4210 4211 4212 4213 4214 4215 4216 4217 4218 4219 4220
{
	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)
		rr_interval = NS_TO_JIFFIES(sched_slice(&rq->cfs, se));

	return rr_interval;
}

4221 4222 4223
/*
 * All the scheduling class methods:
 */
4224 4225
static const struct sched_class fair_sched_class = {
	.next			= &idle_sched_class,
4226 4227 4228
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
4229
	.yield_to_task		= yield_to_task_fair,
4230

I
Ingo Molnar 已提交
4231
	.check_preempt_curr	= check_preempt_wakeup,
4232 4233 4234 4235

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

4236
#ifdef CONFIG_SMP
L
Li Zefan 已提交
4237 4238
	.select_task_rq		= select_task_rq_fair,

4239 4240
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
4241 4242

	.task_waking		= task_waking_fair,
4243
#endif
4244

4245
	.set_curr_task          = set_curr_task_fair,
4246
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
4247
	.task_fork		= task_fork_fair,
4248 4249

	.prio_changed		= prio_changed_fair,
P
Peter Zijlstra 已提交
4250
	.switched_from		= switched_from_fair,
4251
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
4252

4253 4254
	.get_rr_interval	= get_rr_interval_fair,

P
Peter Zijlstra 已提交
4255
#ifdef CONFIG_FAIR_GROUP_SCHED
4256
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
4257
#endif
4258 4259 4260
};

#ifdef CONFIG_SCHED_DEBUG
4261
static void print_cfs_stats(struct seq_file *m, int cpu)
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{
	struct cfs_rq *cfs_rq;

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	rcu_read_lock();
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	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
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		print_cfs_rq(m, cpu, cfs_rq);
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	rcu_read_unlock();
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}
#endif