sched_fair.c 109.5 KB
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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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 */

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#include <linux/latencytop.h>
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#include <linux/sched.h>
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#include <linux/cpumask.h>
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/*
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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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#ifndef CONFIG_64BIT
	smp_wmb();
	cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
#endif
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}

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/*
 * Enqueue an entity into the rb-tree:
 */
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static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
	struct rb_node *parent = NULL;
	struct sched_entity *entry;
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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
658
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
659 660 661 662
{
	/*
	 * We are starting a new run period:
	 */
663
	se->exec_start = rq_of(cfs_rq)->clock_task;
664 665 666 667 668 669
}

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

670 671 672 673 674 675 676 677 678 679 680 681 682
#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

683 684 685 686
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
687 688
	if (!parent_entity(se))
		inc_cpu_load(rq_of(cfs_rq), se->load.weight);
689
	if (entity_is_task(se)) {
690
		add_cfs_task_weight(cfs_rq, se->load.weight);
691 692
		list_add(&se->group_node, &cfs_rq->tasks);
	}
693 694 695 696 697 698 699
	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);
700 701
	if (!parent_entity(se))
		dec_cpu_load(rq_of(cfs_rq), se->load.weight);
702
	if (entity_is_task(se)) {
703
		add_cfs_task_weight(cfs_rq, -se->load.weight);
704 705
		list_del_init(&se->group_node);
	}
706 707 708
	cfs_rq->nr_running--;
}

709 710
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726
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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{
728
	u64 period = sysctl_sched_shares_window;
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	u64 now, delta;
730
	unsigned long load = cfs_rq->load.weight;
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732
	if (cfs_rq->tg == &root_task_group)
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		return;

735
	now = rq_of(cfs_rq)->clock_task;
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	delta = now - cfs_rq->load_stamp;

738 739 740 741 742
	/* 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;
743
		delta = period - 1;
744 745
	}

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	cfs_rq->load_stamp = now;
747
	cfs_rq->load_unacc_exec_time = 0;
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	cfs_rq->load_period += delta;
749 750 751 752
	if (load) {
		cfs_rq->load_last = now;
		cfs_rq->load_avg += delta * load;
	}
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754 755 756 757 758
	/* 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;
	}
769

770 771
	if (!cfs_rq->curr && !cfs_rq->nr_running && !cfs_rq->load_avg)
		list_del_leaf_cfs_rq(cfs_rq);
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}

774
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
775 776 777
{
	long load_weight, load, shares;

778
	load = cfs_rq->load.weight;
779 780 781

	load_weight = atomic_read(&tg->load_weight);
	load_weight += load;
782
	load_weight -= cfs_rq->load_contribution;
783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799

	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);
800
		update_cfs_shares(cfs_rq);
801 802 803 804 805 806 807
	}
}
# else /* CONFIG_SMP */
static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
{
}

808
static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg)
809 810 811 812 813 814 815 816
{
	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)
{
820 821 822 823
	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);
825
	}
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	update_load_set(&se->load, weight);

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

833
static void update_cfs_shares(struct cfs_rq *cfs_rq)
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{
	struct task_group *tg;
	struct sched_entity *se;
837
	long shares;
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838 839 840 841 842

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
	if (!se)
		return;
843 844 845 846
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
847
	shares = calc_cfs_shares(cfs_rq, tg);
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	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
852
static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
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853 854 855
{
}

856
static inline void update_cfs_shares(struct cfs_rq *cfs_rq)
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{
}
859 860 861 862

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

865
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
866 867
{
#ifdef CONFIG_SCHEDSTATS
868 869 870 871 872
	struct task_struct *tsk = NULL;

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

873 874
	if (se->statistics.sleep_start) {
		u64 delta = rq_of(cfs_rq)->clock - se->statistics.sleep_start;
875 876 877 878

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

879 880
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
881

882 883
		se->statistics.sleep_start = 0;
		se->statistics.sum_sleep_runtime += delta;
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Arjan van de Ven 已提交
884

885
		if (tsk) {
886
			account_scheduler_latency(tsk, delta >> 10, 1);
887 888
			trace_sched_stat_sleep(tsk, delta);
		}
889
	}
890 891
	if (se->statistics.block_start) {
		u64 delta = rq_of(cfs_rq)->clock - se->statistics.block_start;
892 893 894 895

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

896 897
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
898

899 900
		se->statistics.block_start = 0;
		se->statistics.sum_sleep_runtime += delta;
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901

902
		if (tsk) {
903
			if (tsk->in_iowait) {
904 905
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
906
				trace_sched_stat_iowait(tsk, delta);
907 908
			}

909 910 911 912 913 914 915 916 917 918 919
			/*
			 * 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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920
		}
921 922 923 924
	}
#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
}

938 939 940
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
941
	u64 vruntime = cfs_rq->min_vruntime;
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943 944 945 946 947 948
	/*
	 * 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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949
	if (initial && sched_feat(START_DEBIT))
950
		vruntime += sched_vslice(cfs_rq, se);
951

952
	/* sleeps up to a single latency don't count. */
953
	if (!initial) {
954
		unsigned long thresh = sysctl_sched_latency;
955

956 957 958 959 960 961
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
962

963
		vruntime -= thresh;
964 965
	}

966 967 968
	/* ensure we never gain time by being placed backwards. */
	vruntime = max_vruntime(se->vruntime, vruntime);

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	se->vruntime = vruntime;
970 971
}

972
static void
973
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
974
{
975 976 977 978
	/*
	 * Update the normalized vruntime before updating min_vruntime
	 * through callig update_curr().
	 */
979
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
980 981
		se->vruntime += cfs_rq->min_vruntime;

982
	/*
983
	 * Update run-time statistics of the 'current'.
984
	 */
985
	update_curr(cfs_rq);
986
	update_cfs_load(cfs_rq, 0);
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987
	account_entity_enqueue(cfs_rq, se);
988
	update_cfs_shares(cfs_rq);
989

990
	if (flags & ENQUEUE_WAKEUP) {
991
		place_entity(cfs_rq, se, 0);
992
		enqueue_sleeper(cfs_rq, se);
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993
	}
994

995
	update_stats_enqueue(cfs_rq, se);
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996
	check_spread(cfs_rq, se);
997 998
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
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999
	se->on_rq = 1;
1000 1001 1002

	if (cfs_rq->nr_running == 1)
		list_add_leaf_cfs_rq(cfs_rq);
1003 1004
}

1005
static void __clear_buddies_last(struct sched_entity *se)
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1006
{
1007 1008 1009 1010 1011 1012 1013 1014
	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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1016 1017 1018 1019 1020 1021 1022 1023 1024
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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}

1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037
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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1038 1039
static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
1040 1041 1042 1043 1044
	if (cfs_rq->last == se)
		__clear_buddies_last(se);

	if (cfs_rq->next == se)
		__clear_buddies_next(se);
1045 1046 1047

	if (cfs_rq->skip == se)
		__clear_buddies_skip(se);
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1048 1049
}

1050
static void
1051
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1052
{
1053 1054 1055 1056 1057
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);

1058
	update_stats_dequeue(cfs_rq, se);
1059
	if (flags & DEQUEUE_SLEEP) {
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1060
#ifdef CONFIG_SCHEDSTATS
1061 1062 1063 1064
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
1065
				se->statistics.sleep_start = rq_of(cfs_rq)->clock;
1066
			if (tsk->state & TASK_UNINTERRUPTIBLE)
1067
				se->statistics.block_start = rq_of(cfs_rq)->clock;
1068
		}
1069
#endif
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1070 1071
	}

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1072
	clear_buddies(cfs_rq, se);
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1073

1074
	if (se != cfs_rq->curr)
1075
		__dequeue_entity(cfs_rq, se);
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1076
	se->on_rq = 0;
1077
	update_cfs_load(cfs_rq, 0);
1078
	account_entity_dequeue(cfs_rq, se);
1079 1080 1081 1082 1083 1084

	/*
	 * 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.
	 */
1085
	if (!(flags & DEQUEUE_SLEEP))
1086
		se->vruntime -= cfs_rq->min_vruntime;
1087 1088 1089

	update_min_vruntime(cfs_rq);
	update_cfs_shares(cfs_rq);
1090 1091 1092 1093 1094
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
1095
static void
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1096
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
1097
{
1098 1099
	unsigned long ideal_runtime, delta_exec;

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	ideal_runtime = sched_slice(cfs_rq, curr);
1101
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
1102
	if (delta_exec > ideal_runtime) {
1103
		resched_task(rq_of(cfs_rq)->curr);
1104 1105 1106 1107 1108
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123
		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) {
1124
		struct sched_entity *se = __pick_first_entity(cfs_rq);
1125 1126
		s64 delta = curr->vruntime - se->vruntime;

1127 1128 1129
		if (delta < 0)
			return;

1130 1131
		if (delta > ideal_runtime)
			resched_task(rq_of(cfs_rq)->curr);
1132
	}
1133 1134
}

1135
static void
1136
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
1137
{
1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148
	/* '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);
	}

1149
	update_stats_curr_start(cfs_rq, se);
1150
	cfs_rq->curr = se;
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1151 1152 1153 1154 1155 1156
#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):
	 */
1157
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
1158
		se->statistics.slice_max = max(se->statistics.slice_max,
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1159 1160 1161
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
1162
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
1163 1164
}

1165 1166 1167
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

1168 1169 1170 1171 1172 1173 1174
/*
 * 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
 */
1175
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
1176
{
1177
	struct sched_entity *se = __pick_first_entity(cfs_rq);
1178
	struct sched_entity *left = se;
1179

1180 1181 1182 1183 1184 1185 1186 1187 1188
	/*
	 * 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;
	}
1189

1190 1191 1192 1193 1194 1195
	/*
	 * 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;

1196 1197 1198 1199 1200 1201
	/*
	 * 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;

1202
	clear_buddies(cfs_rq, se);
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	return se;
1205 1206
}

1207
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
1208 1209 1210 1211 1212 1213
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
1214
		update_curr(cfs_rq);
1215

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1216
	check_spread(cfs_rq, prev);
1217
	if (prev->on_rq) {
1218
		update_stats_wait_start(cfs_rq, prev);
1219 1220 1221
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
	}
1222
	cfs_rq->curr = NULL;
1223 1224
}

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1225 1226
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
1227 1228
{
	/*
1229
	 * Update run-time statistics of the 'current'.
1230
	 */
1231
	update_curr(cfs_rq);
1232

1233 1234 1235 1236 1237
	/*
	 * Update share accounting for long-running entities.
	 */
	update_entity_shares_tick(cfs_rq);

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1238 1239 1240 1241 1242
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
1243 1244 1245 1246
	if (queued) {
		resched_task(rq_of(cfs_rq)->curr);
		return;
	}
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1247 1248 1249 1250 1251 1252 1253 1254
	/*
	 * 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

1255
	if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
I
Ingo Molnar 已提交
1256
		check_preempt_tick(cfs_rq, curr);
1257 1258 1259 1260 1261 1262
}

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

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1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285
#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.
		 */
1286
		if (rq->curr != p)
1287
			delta = max_t(s64, 10000LL, delta);
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Peter Zijlstra 已提交
1288

1289
		hrtick_start(rq, delta);
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Peter Zijlstra 已提交
1290 1291
	}
}
1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307

/*
 * 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);
}
1308
#else /* !CONFIG_SCHED_HRTICK */
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1309 1310 1311 1312
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
1313 1314 1315 1316

static inline void hrtick_update(struct rq *rq)
{
}
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1317 1318
#endif

1319 1320 1321 1322 1323
/*
 * 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:
 */
1324
static void
1325
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
1326 1327
{
	struct cfs_rq *cfs_rq;
1328
	struct sched_entity *se = &p->se;
1329 1330

	for_each_sched_entity(se) {
1331
		if (se->on_rq)
1332 1333
			break;
		cfs_rq = cfs_rq_of(se);
1334 1335
		enqueue_entity(cfs_rq, se, flags);
		flags = ENQUEUE_WAKEUP;
1336
	}
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1337

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1338 1339 1340
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

1341
		update_cfs_load(cfs_rq, 0);
1342
		update_cfs_shares(cfs_rq);
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Peter Zijlstra 已提交
1343 1344
	}

1345
	hrtick_update(rq);
1346 1347
}

1348 1349
static void set_next_buddy(struct sched_entity *se);

1350 1351 1352 1353 1354
/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
1355
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
1356 1357
{
	struct cfs_rq *cfs_rq;
1358
	struct sched_entity *se = &p->se;
1359
	int task_sleep = flags & DEQUEUE_SLEEP;
1360 1361 1362

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
1363
		dequeue_entity(cfs_rq, se, flags);
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1364

1365
		/* Don't dequeue parent if it has other entities besides us */
1366 1367 1368 1369 1370 1371 1372
		if (cfs_rq->load.weight) {
			/*
			 * Bias pick_next to pick a task from this cfs_rq, as
			 * p is sleeping when it is within its sched_slice.
			 */
			if (task_sleep && parent_entity(se))
				set_next_buddy(parent_entity(se));
1373
			break;
1374
		}
1375
		flags |= DEQUEUE_SLEEP;
1376
	}
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1377

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1378 1379 1380
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

1381
		update_cfs_load(cfs_rq, 0);
1382
		update_cfs_shares(cfs_rq);
P
Peter Zijlstra 已提交
1383 1384
	}

1385
	hrtick_update(rq);
1386 1387
}

1388
#ifdef CONFIG_SMP
1389

1390
static void task_waking_fair(struct task_struct *p)
1391 1392 1393
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);
1394 1395 1396 1397
	u64 min_vruntime;

#ifndef CONFIG_64BIT
	u64 min_vruntime_copy;
1398

1399 1400 1401 1402 1403 1404 1405 1406
	do {
		min_vruntime_copy = cfs_rq->min_vruntime_copy;
		smp_rmb();
		min_vruntime = cfs_rq->min_vruntime;
	} while (min_vruntime != min_vruntime_copy);
#else
	min_vruntime = cfs_rq->min_vruntime;
#endif
1407

1408
	se->vruntime -= min_vruntime;
1409 1410
}

1411
#ifdef CONFIG_FAIR_GROUP_SCHED
1412 1413 1414 1415 1416 1417 1418
/*
 * 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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Peter Zijlstra 已提交
1419
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
1420
{
P
Peter Zijlstra 已提交
1421
	struct sched_entity *se = tg->se[cpu];
1422 1423 1424 1425

	if (!tg->parent)
		return wl;

P
Peter Zijlstra 已提交
1426
	for_each_sched_entity(se) {
1427
		long lw, w;
P
Peter Zijlstra 已提交
1428

1429 1430
		tg = se->my_q->tg;
		w = se->my_q->load.weight;
1431

1432 1433 1434 1435
		/* use this cpu's instantaneous contribution */
		lw = atomic_read(&tg->load_weight);
		lw -= se->my_q->load_contribution;
		lw += w + wg;
P
Peter Zijlstra 已提交
1436

1437
		wl += w;
1438

1439 1440 1441 1442
		if (lw > 0 && wl < lw)
			wl = (wl * tg->shares) / lw;
		else
			wl = tg->shares;
1443

1444 1445 1446 1447
		/* zero point is MIN_SHARES */
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
		wl -= se->load.weight;
P
Peter Zijlstra 已提交
1448 1449
		wg = 0;
	}
1450

P
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1451
	return wl;
1452
}
P
Peter Zijlstra 已提交
1453

1454
#else
P
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1455

1456 1457
static inline unsigned long effective_load(struct task_group *tg, int cpu,
		unsigned long wl, unsigned long wg)
P
Peter Zijlstra 已提交
1458
{
1459
	return wl;
1460
}
P
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1461

1462 1463
#endif

1464
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
1465
{
1466
	s64 this_load, load;
1467
	int idx, this_cpu, prev_cpu;
1468
	unsigned long tl_per_task;
1469
	struct task_group *tg;
1470
	unsigned long weight;
1471
	int balanced;
1472

1473 1474 1475 1476 1477
	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);
1478

1479 1480 1481 1482 1483
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
1484
	rcu_read_lock();
1485 1486 1487 1488
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

1489
		this_load += effective_load(tg, this_cpu, -weight, -weight);
1490 1491
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
1492

1493 1494
	tg = task_group(p);
	weight = p->se.load.weight;
1495

1496 1497
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
1498 1499 1500
	 * 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.
1501 1502 1503 1504
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
1505 1506
	if (this_load > 0) {
		s64 this_eff_load, prev_eff_load;
1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519

		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;
1520
	rcu_read_unlock();
1521

1522
	/*
I
Ingo Molnar 已提交
1523 1524 1525
	 * If the currently running task will sleep within
	 * a reasonable amount of time then attract this newly
	 * woken task:
1526
	 */
1527 1528
	if (sync && balanced)
		return 1;
1529

1530
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
1531 1532
	tl_per_task = cpu_avg_load_per_task(this_cpu);

1533 1534 1535
	if (balanced ||
	    (this_load <= load &&
	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
1536 1537 1538 1539 1540
		/*
		 * This domain has SD_WAKE_AFFINE and
		 * p is cache cold in this domain, and
		 * there is no bad imbalance.
		 */
1541
		schedstat_inc(sd, ttwu_move_affine);
1542
		schedstat_inc(p, se.statistics.nr_wakeups_affine);
1543 1544 1545 1546 1547 1548

		return 1;
	}
	return 0;
}

1549 1550 1551 1552 1553
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
1554
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
1555
		  int this_cpu, int load_idx)
1556
{
1557
	struct sched_group *idlest = NULL, *group = sd->groups;
1558 1559
	unsigned long min_load = ULONG_MAX, this_load = 0;
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
1560

1561 1562 1563 1564
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
1565

1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587
		/* 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 */
1588
		avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power;
1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619

		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;
1620 1621 1622
		}
	}

1623 1624
	return idlest;
}
1625

1626 1627 1628
/*
 * Try and locate an idle CPU in the sched_domain.
 */
1629
static int select_idle_sibling(struct task_struct *p, int target)
1630 1631 1632
{
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
1633
	struct sched_domain *sd;
1634 1635 1636
	int i;

	/*
1637 1638
	 * If the task is going to be woken-up on this cpu and if it is
	 * already idle, then it is the right target.
1639
	 */
1640 1641 1642 1643 1644 1645 1646 1647
	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))
1648
		return prev_cpu;
1649 1650

	/*
1651
	 * Otherwise, iterate the domains and find an elegible idle cpu.
1652
	 */
1653
	rcu_read_lock();
1654 1655
	for_each_domain(target, sd) {
		if (!(sd->flags & SD_SHARE_PKG_RESOURCES))
1656
			break;
1657 1658 1659 1660 1661 1662

		for_each_cpu_and(i, sched_domain_span(sd), &p->cpus_allowed) {
			if (idle_cpu(i)) {
				target = i;
				break;
			}
1663
		}
1664 1665 1666 1667 1668 1669 1670 1671

		/*
		 * 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;
1672
	}
1673
	rcu_read_unlock();
1674 1675 1676 1677

	return target;
}

1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688
/*
 * 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.
 */
1689
static int
1690
select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
1691
{
1692
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
1693 1694 1695
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
	int new_cpu = cpu;
1696
	int want_affine = 0;
1697
	int want_sd = 1;
1698
	int sync = wake_flags & WF_SYNC;
1699

1700
	if (sd_flag & SD_BALANCE_WAKE) {
1701
		if (cpumask_test_cpu(cpu, &p->cpus_allowed))
1702 1703 1704
			want_affine = 1;
		new_cpu = prev_cpu;
	}
1705

1706
	rcu_read_lock();
1707
	for_each_domain(cpu, tmp) {
1708 1709 1710
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

1711
		/*
1712 1713
		 * If power savings logic is enabled for a domain, see if we
		 * are not overloaded, if so, don't balance wider.
1714
		 */
P
Peter Zijlstra 已提交
1715
		if (tmp->flags & (SD_POWERSAVINGS_BALANCE|SD_PREFER_LOCAL)) {
1716 1717 1718 1719 1720 1721 1722 1723 1724 1725
			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;
			}

1726
			capacity = DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE);
1727

P
Peter Zijlstra 已提交
1728 1729 1730 1731
			if (tmp->flags & SD_POWERSAVINGS_BALANCE)
				nr_running /= 2;

			if (nr_running < capacity)
1732
				want_sd = 0;
1733
		}
1734

1735
		/*
1736 1737
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
1738
		 */
1739 1740 1741 1742
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
			want_affine = 0;
1743 1744
		}

1745 1746 1747
		if (!want_sd && !want_affine)
			break;

1748
		if (!(tmp->flags & sd_flag))
1749 1750
			continue;

1751 1752 1753 1754
		if (want_sd)
			sd = tmp;
	}

1755
	if (affine_sd) {
1756
		if (cpu == prev_cpu || wake_affine(affine_sd, p, sync))
1757 1758 1759 1760
			prev_cpu = cpu;

		new_cpu = select_idle_sibling(p, prev_cpu);
		goto unlock;
1761
	}
1762

1763
	while (sd) {
1764
		int load_idx = sd->forkexec_idx;
1765
		struct sched_group *group;
1766
		int weight;
1767

1768
		if (!(sd->flags & sd_flag)) {
1769 1770 1771
			sd = sd->child;
			continue;
		}
1772

1773 1774
		if (sd_flag & SD_BALANCE_WAKE)
			load_idx = sd->wake_idx;
1775

1776
		group = find_idlest_group(sd, p, cpu, load_idx);
1777 1778 1779 1780
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
1781

1782
		new_cpu = find_idlest_cpu(group, p, cpu);
1783 1784 1785 1786
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
1787
		}
1788 1789 1790

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
1791
		weight = sd->span_weight;
1792 1793
		sd = NULL;
		for_each_domain(cpu, tmp) {
1794
			if (weight <= tmp->span_weight)
1795
				break;
1796
			if (tmp->flags & sd_flag)
1797 1798 1799
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
1800
	}
1801 1802
unlock:
	rcu_read_unlock();
1803

1804
	return new_cpu;
1805 1806 1807
}
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
1808 1809
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
1810 1811 1812 1813
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
1814 1815
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
1816 1817 1818 1819 1820 1821 1822 1823 1824
	 *
	 * 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.
1825
	 */
1826
	return calc_delta_fair(gran, se);
1827 1828
}

1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850
/*
 * 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
1851
	gran = wakeup_gran(curr, se);
1852 1853 1854 1855 1856 1857
	if (vdiff > gran)
		return 1;

	return 0;
}

1858 1859
static void set_last_buddy(struct sched_entity *se)
{
1860 1861 1862 1863 1864
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->last = se;
1865 1866 1867 1868
}

static void set_next_buddy(struct sched_entity *se)
{
1869 1870 1871 1872 1873
	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
		return;

	for_each_sched_entity(se)
		cfs_rq_of(se)->next = se;
1874 1875
}

1876 1877
static void set_skip_buddy(struct sched_entity *se)
{
1878 1879
	for_each_sched_entity(se)
		cfs_rq_of(se)->skip = se;
1880 1881
}

1882 1883 1884
/*
 * Preempt the current task with a newly woken task if needed:
 */
1885
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
1886 1887
{
	struct task_struct *curr = rq->curr;
1888
	struct sched_entity *se = &curr->se, *pse = &p->se;
1889
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
1890
	int scale = cfs_rq->nr_running >= sched_nr_latency;
1891
	int next_buddy_marked = 0;
1892

I
Ingo Molnar 已提交
1893 1894 1895
	if (unlikely(se == pse))
		return;

1896
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) {
M
Mike Galbraith 已提交
1897
		set_next_buddy(pse);
1898 1899
		next_buddy_marked = 1;
	}
P
Peter Zijlstra 已提交
1900

1901 1902 1903 1904 1905 1906 1907
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
	 */
	if (test_tsk_need_resched(curr))
		return;

1908 1909 1910 1911 1912
	/* Idle tasks are by definition preempted by non-idle tasks. */
	if (unlikely(curr->policy == SCHED_IDLE) &&
	    likely(p->policy != SCHED_IDLE))
		goto preempt;

1913
	/*
1914 1915
	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
	 * is driven by the tick):
1916
	 */
1917
	if (unlikely(p->policy != SCHED_NORMAL))
1918
		return;
1919 1920


1921 1922 1923
	if (!sched_feat(WAKEUP_PREEMPT))
		return;

1924
	update_curr(cfs_rq);
1925
	find_matching_se(&se, &pse);
1926
	BUG_ON(!pse);
1927 1928 1929 1930 1931 1932 1933
	if (wakeup_preempt_entity(se, pse) == 1) {
		/*
		 * Bias pick_next to pick the sched entity that is
		 * triggering this preemption.
		 */
		if (!next_buddy_marked)
			set_next_buddy(pse);
1934
		goto preempt;
1935
	}
1936

1937
	return;
1938

1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954
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);
1955 1956
}

1957
static struct task_struct *pick_next_task_fair(struct rq *rq)
1958
{
P
Peter Zijlstra 已提交
1959
	struct task_struct *p;
1960 1961 1962
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

1963
	if (!cfs_rq->nr_running)
1964 1965 1966
		return NULL;

	do {
1967
		se = pick_next_entity(cfs_rq);
1968
		set_next_entity(cfs_rq, se);
1969 1970 1971
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
1972 1973 1974 1975
	p = task_of(se);
	hrtick_start_fair(rq, p);

	return p;
1976 1977 1978 1979 1980
}

/*
 * Account for a descheduled task:
 */
1981
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
1982 1983 1984 1985 1986 1987
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
1988
		put_prev_entity(cfs_rq, se);
1989 1990 1991
	}
}

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021
/*
 * 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);
}

2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036
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);

	yield_task_fair(rq);

	return true;
}

2037
#ifdef CONFIG_SMP
2038 2039 2040 2041
/**************************************************
 * Fair scheduling class load-balancing methods:
 */

2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070
/*
 * 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)) {
2071
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
2072 2073 2074 2075 2076
		return 0;
	}
	*all_pinned = 0;

	if (task_running(rq, p)) {
2077
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
2078 2079 2080 2081 2082 2083 2084 2085 2086
		return 0;
	}

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

2087
	tsk_cache_hot = task_hot(p, rq->clock_task, sd);
2088 2089 2090 2091 2092
	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]);
2093
			schedstat_inc(p, se.statistics.nr_forced_migrations);
2094 2095 2096 2097 2098 2099
		}
#endif
		return 1;
	}

	if (tsk_cache_hot) {
2100
		schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
2101 2102 2103 2104 2105
		return 0;
	}
	return 1;
}

2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141
/*
 * 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;
}

2142 2143 2144 2145
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,
2146
	      struct cfs_rq *busiest_cfs_rq)
2147
{
K
Ken Chen 已提交
2148
	int loops = 0, pulled = 0;
2149
	long rem_load_move = max_load_move;
2150
	struct task_struct *p, *n;
2151 2152 2153 2154

	if (max_load_move == 0)
		goto out;

2155 2156 2157
	list_for_each_entry_safe(p, n, &busiest_cfs_rq->tasks, se.group_node) {
		if (loops++ > sysctl_sched_nr_migrate)
			break;
2158

2159
		if ((p->se.load.weight >> 1) > rem_load_move ||
K
Ken Chen 已提交
2160 2161
		    !can_migrate_task(p, busiest, this_cpu, sd, idle,
				      all_pinned))
2162
			continue;
2163

2164 2165 2166
		pull_task(busiest, p, this_rq, this_cpu);
		pulled++;
		rem_load_move -= p->se.load.weight;
2167 2168

#ifdef CONFIG_PREEMPT
2169 2170 2171 2172 2173 2174 2175
		/*
		 * 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;
2176 2177
#endif

2178 2179 2180 2181 2182 2183
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
		if (rem_load_move <= 0)
			break;
2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195
	}
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);

	return max_load_move - rem_load_move;
}

P
Peter Zijlstra 已提交
2196
#ifdef CONFIG_FAIR_GROUP_SCHED
2197 2198 2199
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
2200
static int update_shares_cpu(struct task_group *tg, int cpu)
2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214
{
	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);
2215
	update_cfs_load(cfs_rq, 1);
2216 2217 2218 2219 2220

	/*
	 * We need to update shares after updating tg->load_weight in
	 * order to adjust the weight of groups with long running tasks.
	 */
2221
	update_cfs_shares(cfs_rq);
2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233

	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();
2234 2235
	for_each_leaf_cfs_rq(rq, cfs_rq)
		update_shares_cpu(cfs_rq->tg, cpu);
2236 2237 2238
	rcu_read_unlock();
}

P
Peter Zijlstra 已提交
2239 2240 2241 2242
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,
2243
		  int *all_pinned)
P
Peter Zijlstra 已提交
2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267
{
	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,
2268
				rem_load, sd, idle, all_pinned,
P
Peter Zijlstra 已提交
2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285
				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
2286 2287 2288 2289
static inline void update_shares(int cpu)
{
}

P
Peter Zijlstra 已提交
2290 2291 2292 2293
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,
2294
		  int *all_pinned)
P
Peter Zijlstra 已提交
2295 2296 2297
{
	return balance_tasks(this_rq, this_cpu, busiest,
			max_load_move, sd, idle, all_pinned,
2298
			&busiest->cfs);
P
Peter Zijlstra 已提交
2299 2300 2301
}
#endif

2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313
/*
 * 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)
{
2314
	unsigned long total_load_moved = 0, load_moved;
2315 2316

	do {
2317
		load_moved = load_balance_fair(this_rq, this_cpu, busiest,
2318
				max_load_move - total_load_moved,
2319
				sd, idle, all_pinned);
2320 2321

		total_load_moved += load_moved;
2322 2323 2324 2325 2326 2327 2328 2329 2330

#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;
2331 2332 2333 2334

		if (raw_spin_is_contended(&this_rq->lock) ||
				raw_spin_is_contended(&busiest->lock))
			break;
2335
#endif
2336
	} while (load_moved && max_load_move > total_load_moved);
2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356

	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;
2357
	unsigned long this_has_capacity;
2358
	unsigned int  this_idle_cpus;
2359 2360

	/* Statistics of the busiest group */
2361
	unsigned int  busiest_idle_cpus;
2362 2363 2364
	unsigned long max_load;
	unsigned long busiest_load_per_task;
	unsigned long busiest_nr_running;
2365
	unsigned long busiest_group_capacity;
2366
	unsigned long busiest_has_capacity;
2367
	unsigned int  busiest_group_weight;
2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388

	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;
2389 2390
	unsigned long idle_cpus;
	unsigned long group_weight;
2391
	int group_imb; /* Is there an imbalance in the group ? */
2392
	int group_has_capacity; /* Is there extra capacity in the group? */
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 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573
};

/**
 * 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)
{
2574
	return SCHED_POWER_SCALE;
2575 2576 2577 2578 2579 2580 2581 2582 2583
}

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)
{
2584
	unsigned long weight = sd->span_weight;
2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602
	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);
2603 2604 2605 2606 2607 2608 2609

	if (unlikely(total < rq->rt_avg)) {
		/* Ensures that power won't end up being negative */
		available = 0;
	} else {
		available = total - rq->rt_avg;
	}
2610

2611 2612
	if (unlikely((s64)total < SCHED_POWER_SCALE))
		total = SCHED_POWER_SCALE;
2613

2614
	total >>= SCHED_POWER_SHIFT;
2615 2616 2617 2618 2619 2620

	return div_u64(available, total);
}

static void update_cpu_power(struct sched_domain *sd, int cpu)
{
2621
	unsigned long weight = sd->span_weight;
2622
	unsigned long power = SCHED_POWER_SCALE;
2623 2624 2625 2626 2627 2628 2629 2630
	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);

2631
		power >>= SCHED_POWER_SHIFT;
2632 2633
	}

2634
	sdg->sgp->power_orig = power;
2635 2636 2637 2638 2639 2640

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

2641
	power >>= SCHED_POWER_SHIFT;
2642

2643
	power *= scale_rt_power(cpu);
2644
	power >>= SCHED_POWER_SHIFT;
2645 2646 2647 2648

	if (!power)
		power = 1;

2649
	cpu_rq(cpu)->cpu_power = power;
2650
	sdg->sgp->power = power;
2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667
}

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 {
2668
		power += group->sgp->power;
2669 2670 2671
		group = group->next;
	} while (group != child->groups);

2672
	sdg->sgp->power = power;
2673 2674
}

2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685
/*
 * 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)
{
	/*
2686
	 * Only siblings can have significantly less than SCHED_POWER_SCALE
2687
	 */
P
Peter Zijlstra 已提交
2688
	if (!(sd->flags & SD_SHARE_CPUPOWER))
2689 2690 2691 2692 2693
		return 0;

	/*
	 * If ~90% of the cpu_power is still there, we're good.
	 */
2694
	if (group->sgp->power * 32 > group->sgp->power_orig * 29)
2695 2696 2697 2698 2699
		return 1;

	return 0;
}

2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713
/**
 * 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,
2714
			enum cpu_idle_type idle, int load_idx,
2715 2716 2717
			int local_group, const struct cpumask *cpus,
			int *balance, struct sg_lb_stats *sgs)
{
2718
	unsigned long load, max_cpu_load, min_cpu_load, max_nr_running;
2719 2720
	int i;
	unsigned int balance_cpu = -1, first_idle_cpu = 0;
2721
	unsigned long avg_load_per_task = 0;
2722

2723
	if (local_group)
2724 2725 2726 2727 2728
		balance_cpu = group_first_cpu(group);

	/* Tally up the load of all CPUs in the group */
	max_cpu_load = 0;
	min_cpu_load = ~0UL;
2729
	max_nr_running = 0;
2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743

	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);
2744
			if (load > max_cpu_load) {
2745
				max_cpu_load = load;
2746 2747
				max_nr_running = rq->nr_running;
			}
2748 2749 2750 2751 2752 2753 2754
			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);
2755 2756
		if (idle_cpu(i))
			sgs->idle_cpus++;
2757 2758 2759 2760 2761 2762 2763 2764
	}

	/*
	 * 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.
	 */
2765 2766 2767 2768 2769 2770
	if (idle != CPU_NEWLY_IDLE && local_group) {
		if (balance_cpu != this_cpu) {
			*balance = 0;
			return;
		}
		update_group_power(sd, this_cpu);
2771 2772 2773
	}

	/* Adjust by relative CPU power of the group */
2774
	sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / group->sgp->power;
2775 2776 2777

	/*
	 * Consider the group unbalanced when the imbalance is larger
P
Peter Zijlstra 已提交
2778
	 * than the average weight of a task.
2779 2780 2781 2782 2783 2784
	 *
	 * 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?
	 */
2785 2786
	if (sgs->sum_nr_running)
		avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
2787

P
Peter Zijlstra 已提交
2788
	if ((max_cpu_load - min_cpu_load) >= avg_load_per_task && max_nr_running > 1)
2789 2790
		sgs->group_imb = 1;

2791
	sgs->group_capacity = DIV_ROUND_CLOSEST(group->sgp->power,
2792
						SCHED_POWER_SCALE);
2793 2794
	if (!sgs->group_capacity)
		sgs->group_capacity = fix_small_capacity(sd, group);
2795
	sgs->group_weight = group->group_weight;
2796 2797 2798

	if (sgs->group_capacity > sgs->sum_nr_running)
		sgs->group_has_capacity = 1;
2799 2800
}

2801 2802 2803 2804 2805
/**
 * 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
2806 2807
 * @sgs: sched_group statistics
 * @this_cpu: the current cpu
2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843
 *
 * 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;
}

2844 2845 2846 2847 2848 2849 2850 2851 2852 2853
/**
 * 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,
2854 2855
			enum cpu_idle_type idle, const struct cpumask *cpus,
			int *balance, struct sd_lb_stats *sds)
2856 2857
{
	struct sched_domain *child = sd->child;
2858
	struct sched_group *sg = sd->groups;
2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870
	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;

2871
		local_group = cpumask_test_cpu(this_cpu, sched_group_cpus(sg));
2872
		memset(&sgs, 0, sizeof(sgs));
2873
		update_sg_lb_stats(sd, sg, this_cpu, idle, load_idx,
2874 2875
				local_group, cpus, balance, &sgs);

P
Peter Zijlstra 已提交
2876
		if (local_group && !(*balance))
2877 2878 2879
			return;

		sds->total_load += sgs.group_load;
2880
		sds->total_pwr += sg->sgp->power;
2881 2882 2883

		/*
		 * In case the child domain prefers tasks go to siblings
2884
		 * first, lower the sg capacity to one so that we'll try
2885 2886 2887 2888 2889 2890
		 * 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).
2891
		 */
2892
		if (prefer_sibling && !local_group && sds->this_has_capacity)
2893 2894 2895 2896
			sgs.group_capacity = min(sgs.group_capacity, 1UL);

		if (local_group) {
			sds->this_load = sgs.avg_load;
2897
			sds->this = sg;
2898 2899
			sds->this_nr_running = sgs.sum_nr_running;
			sds->this_load_per_task = sgs.sum_weighted_load;
2900
			sds->this_has_capacity = sgs.group_has_capacity;
2901
			sds->this_idle_cpus = sgs.idle_cpus;
2902
		} else if (update_sd_pick_busiest(sd, sds, sg, &sgs, this_cpu)) {
2903
			sds->max_load = sgs.avg_load;
2904
			sds->busiest = sg;
2905
			sds->busiest_nr_running = sgs.sum_nr_running;
2906
			sds->busiest_idle_cpus = sgs.idle_cpus;
2907
			sds->busiest_group_capacity = sgs.group_capacity;
2908
			sds->busiest_load_per_task = sgs.sum_weighted_load;
2909
			sds->busiest_has_capacity = sgs.group_has_capacity;
2910
			sds->busiest_group_weight = sgs.group_weight;
2911 2912 2913
			sds->group_imb = sgs.group_imb;
		}

2914 2915 2916 2917 2918
		update_sd_power_savings_stats(sg, sds, local_group, &sgs);
		sg = sg->next;
	} while (sg != sd->groups);
}

M
Michael Neuling 已提交
2919
int __weak arch_sd_sibling_asym_packing(void)
2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940
{
       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.
 *
2941 2942 2943
 * Returns 1 when packing is required and a task should be moved to
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964
 * @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;

2965
	*imbalance = DIV_ROUND_CLOSEST(sds->max_load * sds->busiest->sgp->power,
2966
				       SCHED_POWER_SCALE);
2967
	return 1;
2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982
}

/**
 * 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;
2983
	unsigned long scaled_busy_load_per_task;
2984 2985 2986 2987 2988 2989 2990 2991 2992 2993

	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);

2994
	scaled_busy_load_per_task = sds->busiest_load_per_task
2995
					 * SCHED_POWER_SCALE;
2996
	scaled_busy_load_per_task /= sds->busiest->sgp->power;
2997 2998 2999

	if (sds->max_load - sds->this_load + scaled_busy_load_per_task >=
			(scaled_busy_load_per_task * imbn)) {
3000 3001 3002 3003 3004 3005 3006 3007 3008 3009
		*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.
	 */

3010
	pwr_now += sds->busiest->sgp->power *
3011
			min(sds->busiest_load_per_task, sds->max_load);
3012
	pwr_now += sds->this->sgp->power *
3013
			min(sds->this_load_per_task, sds->this_load);
3014
	pwr_now /= SCHED_POWER_SCALE;
3015 3016

	/* Amount of load we'd subtract */
3017
	tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
3018
		sds->busiest->sgp->power;
3019
	if (sds->max_load > tmp)
3020
		pwr_move += sds->busiest->sgp->power *
3021 3022 3023
			min(sds->busiest_load_per_task, sds->max_load - tmp);

	/* Amount of load we'd add */
3024
	if (sds->max_load * sds->busiest->sgp->power <
3025
		sds->busiest_load_per_task * SCHED_POWER_SCALE)
3026 3027
		tmp = (sds->max_load * sds->busiest->sgp->power) /
			sds->this->sgp->power;
3028
	else
3029
		tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
3030 3031
			sds->this->sgp->power;
	pwr_move += sds->this->sgp->power *
3032
			min(sds->this_load_per_task, sds->this_load + tmp);
3033
	pwr_move /= SCHED_POWER_SCALE;
3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049

	/* 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)
{
3050 3051 3052 3053 3054 3055 3056 3057
	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);
	}

3058 3059 3060 3061 3062 3063 3064 3065 3066 3067
	/*
	 * 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);
	}

3068 3069 3070 3071 3072 3073 3074
	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);

3075
		load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
3076

3077
		load_above_capacity /= sds->busiest->sgp->power;
3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090
	}

	/*
	 * 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);
3091 3092

	/* How much load to actually move to equalise the imbalance */
3093 3094
	*imbalance = min(max_pull * sds->busiest->sgp->power,
		(sds->avg_load - sds->this_load) * sds->this->sgp->power)
3095
			/ SCHED_POWER_SCALE;
3096 3097 3098

	/*
	 * if *imbalance is less than the average load per runnable task
L
Lucas De Marchi 已提交
3099
	 * there is no guarantee that any tasks will be moved so we'll have
3100 3101 3102 3103 3104 3105 3106
	 * 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);

}
3107

3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136
/******* 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,
3137
		   const struct cpumask *cpus, int *balance)
3138 3139 3140 3141 3142 3143 3144 3145 3146
{
	struct sd_lb_stats sds;

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

	/*
	 * Compute the various statistics relavent for load balancing at
	 * this level.
	 */
3147
	update_sd_lb_stats(sd, this_cpu, idle, cpus, balance, &sds);
3148

3149 3150 3151
	/*
	 * this_cpu is not the appropriate cpu to perform load balancing at
	 * this level.
3152
	 */
P
Peter Zijlstra 已提交
3153
	if (!(*balance))
3154 3155
		goto ret;

3156 3157 3158 3159
	if ((idle == CPU_IDLE || idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(sd, &sds, this_cpu, imbalance))
		return sds.busiest;

3160
	/* There is no busy sibling group to pull tasks from */
3161 3162 3163
	if (!sds.busiest || sds.busiest_nr_running == 0)
		goto out_balanced;

3164
	sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
3165

P
Peter Zijlstra 已提交
3166 3167 3168 3169 3170 3171 3172 3173
	/*
	 * If the busiest group is imbalanced the below checks don't
	 * work because they assumes all things are equal, which typically
	 * isn't true due to cpus_allowed constraints and the like.
	 */
	if (sds.group_imb)
		goto force_balance;

3174
	/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
3175 3176 3177 3178
	if (idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
			!sds.busiest_has_capacity)
		goto force_balance;

3179 3180 3181 3182
	/*
	 * If the local group is more busy than the selected busiest group
	 * don't try and pull any tasks.
	 */
3183 3184 3185
	if (sds.this_load >= sds.max_load)
		goto out_balanced;

3186 3187 3188 3189
	/*
	 * Don't pull any tasks if this group is already above the domain
	 * average load.
	 */
3190 3191 3192
	if (sds.this_load >= sds.avg_load)
		goto out_balanced;

3193
	if (idle == CPU_IDLE) {
3194 3195 3196 3197 3198 3199
		/*
		 * 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.
		 */
3200
		if ((sds.this_idle_cpus <= sds.busiest_idle_cpus + 1) &&
3201 3202
		    sds.busiest_nr_running <= sds.busiest_group_weight)
			goto out_balanced;
3203 3204 3205 3206 3207 3208 3209
	} 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;
3210
	}
3211

3212
force_balance:
3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232
	/* 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 *
3233 3234 3235
find_busiest_queue(struct sched_domain *sd, struct sched_group *group,
		   enum cpu_idle_type idle, unsigned long imbalance,
		   const struct cpumask *cpus)
3236 3237 3238 3239 3240 3241 3242
{
	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);
3243 3244
		unsigned long capacity = DIV_ROUND_CLOSEST(power,
							   SCHED_POWER_SCALE);
3245 3246
		unsigned long wl;

3247 3248 3249
		if (!capacity)
			capacity = fix_small_capacity(sd, group);

3250 3251 3252 3253
		if (!cpumask_test_cpu(i, cpus))
			continue;

		rq = cpu_rq(i);
3254
		wl = weighted_cpuload(i);
3255

3256 3257 3258 3259
		/*
		 * When comparing with imbalance, use weighted_cpuload()
		 * which is not scaled with the cpu power.
		 */
3260 3261 3262
		if (capacity && rq->nr_running == 1 && wl > imbalance)
			continue;

3263 3264 3265 3266 3267 3268
		/*
		 * 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.
		 */
3269
		wl = (wl * SCHED_POWER_SCALE) / power;
3270

3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288
		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);

3289
static int need_active_balance(struct sched_domain *sd, int idle,
3290
			       int busiest_cpu, int this_cpu)
3291 3292
{
	if (idle == CPU_NEWLY_IDLE) {
3293 3294 3295 3296 3297 3298 3299 3300 3301

		/*
		 * 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;

3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327
		/*
		 * 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);
}

3328 3329
static int active_load_balance_cpu_stop(void *data);

3330 3331 3332 3333 3334 3335 3336 3337
/*
 * 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)
{
3338
	int ld_moved, all_pinned = 0, active_balance = 0;
3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349
	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:
3350
	group = find_busiest_group(sd, this_cpu, &imbalance, idle,
3351 3352 3353 3354 3355 3356 3357 3358 3359 3360
				   cpus, balance);

	if (*balance == 0)
		goto out_balanced;

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

3361
	busiest = find_busiest_queue(sd, group, idle, imbalance, cpus);
3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378
	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.
		 */
K
Ken Chen 已提交
3379
		all_pinned = 1;
3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403
		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]);
3404 3405 3406 3407 3408 3409 3410 3411
		/*
		 * 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++;
3412

3413
		if (need_active_balance(sd, idle, cpu_of(busiest), this_cpu)) {
3414 3415
			raw_spin_lock_irqsave(&busiest->lock, flags);

3416 3417 3418
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
3419 3420 3421 3422 3423 3424 3425 3426 3427
			 */
			if (!cpumask_test_cpu(this_cpu,
					      &busiest->curr->cpus_allowed)) {
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
				all_pinned = 1;
				goto out_one_pinned;
			}

3428 3429 3430 3431 3432
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
3433 3434 3435 3436 3437 3438
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
3439

3440
			if (active_balance)
3441 3442 3443
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480

			/*
			 * 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;

3481
	ld_moved = 0;
3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500
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;

3501 3502 3503 3504 3505
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

P
Paul Turner 已提交
3506
	update_shares(this_cpu);
3507
	rcu_read_lock();
3508 3509
	for_each_domain(this_cpu, sd) {
		unsigned long interval;
3510
		int balance = 1;
3511 3512 3513 3514

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

3515
		if (sd->flags & SD_BALANCE_NEWIDLE) {
3516
			/* If we've pulled tasks over stop searching: */
3517 3518 3519
			pulled_task = load_balance(this_cpu, this_rq,
						   sd, CPU_NEWLY_IDLE, &balance);
		}
3520 3521 3522 3523

		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
3524 3525
		if (pulled_task) {
			this_rq->idle_stamp = 0;
3526
			break;
N
Nikhil Rao 已提交
3527
		}
3528
	}
3529
	rcu_read_unlock();
3530 3531 3532

	raw_spin_lock(&this_rq->lock);

3533 3534 3535 3536 3537 3538 3539 3540 3541 3542
	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;
	}
}

/*
3543 3544 3545 3546
 * 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.
3547
 */
3548
static int active_load_balance_cpu_stop(void *data)
3549
{
3550 3551
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
3552
	int target_cpu = busiest_rq->push_cpu;
3553
	struct rq *target_rq = cpu_rq(target_cpu);
3554
	struct sched_domain *sd;
3555 3556 3557 3558 3559 3560 3561

	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;
3562 3563 3564

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
3565
		goto out_unlock;
3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577

	/*
	 * 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. */
3578
	rcu_read_lock();
3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593
	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);
	}
3594
	rcu_read_unlock();
3595
	double_unlock_balance(busiest_rq, target_rq);
3596 3597 3598 3599
out_unlock:
	busiest_rq->active_balance = 0;
	raw_spin_unlock_irq(&busiest_rq->lock);
	return 0;
3600 3601 3602
}

#ifdef CONFIG_NO_HZ
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

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.
 */
3629 3630
static struct {
	atomic_t load_balancer;
3631 3632 3633 3634 3635 3636
	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;
3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649 3650 3651 3652 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 3685 3686 3687 3688 3689

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)
{
3690
	cpumask_and(nohz.grp_idle_mask, nohz.idle_cpus_mask,
3691 3692 3693 3694 3695 3696
					sched_group_cpus(ilb_group));

	/*
	 * A sched_group is semi-idle when it has atleast one busy cpu
	 * and atleast one idle cpu.
	 */
3697
	if (cpumask_empty(nohz.grp_idle_mask))
3698 3699
		return 0;

3700
	if (cpumask_equal(nohz.grp_idle_mask, sched_group_cpus(ilb_group)))
3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720
		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;
3721
	int ilb = nr_cpu_ids;
3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733

	/*
	 * 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
	 */
3734
	if (cpumask_weight(nohz.idle_cpus_mask) < 2)
3735 3736
		goto out_done;

3737
	rcu_read_lock();
3738 3739 3740 3741
	for_each_flag_domain(cpu, sd, SD_POWERSAVINGS_BALANCE) {
		ilb_group = sd->groups;

		do {
3742 3743 3744 3745
			if (is_semi_idle_group(ilb_group)) {
				ilb = cpumask_first(nohz.grp_idle_mask);
				goto unlock;
			}
3746 3747 3748 3749 3750

			ilb_group = ilb_group->next;

		} while (ilb_group != sd->groups);
	}
3751 3752
unlock:
	rcu_read_unlock();
3753 3754

out_done:
3755
	return ilb;
3756 3757 3758 3759
}
#else /*  (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */
static inline int find_new_ilb(int call_cpu)
{
3760
	return nr_cpu_ids;
3761 3762 3763
}
#endif

3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792
/*
 * 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;
}

3793 3794 3795
/*
 * 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
3796
 * load balancing on behalf of all those cpus.
3797
 *
3798 3799 3800
 * 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.
3801
 *
3802 3803 3804
 * 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).
3805
 */
3806
void select_nohz_load_balancer(int stop_tick)
3807 3808 3809 3810 3811 3812
{
	int cpu = smp_processor_id();

	if (stop_tick) {
		if (!cpu_active(cpu)) {
			if (atomic_read(&nohz.load_balancer) != cpu)
3813
				return;
3814 3815 3816 3817 3818

			/*
			 * If we are going offline and still the leader,
			 * give up!
			 */
3819 3820
			if (atomic_cmpxchg(&nohz.load_balancer, cpu,
					   nr_cpu_ids) != cpu)
3821 3822
				BUG();

3823
			return;
3824 3825
		}

3826
		cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
3827

3828 3829 3830 3831
		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);
3832

3833
		if (atomic_read(&nohz.load_balancer) >= nr_cpu_ids) {
3834 3835
			int new_ilb;

3836 3837 3838 3839 3840
			/* make me the ilb owner */
			if (atomic_cmpxchg(&nohz.load_balancer, nr_cpu_ids,
					   cpu) != nr_cpu_ids)
				return;

3841 3842 3843 3844 3845 3846
			/*
			 * 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) {
3847
				atomic_set(&nohz.load_balancer, nr_cpu_ids);
3848
				resched_cpu(new_ilb);
3849
				return;
3850
			}
3851
			return;
3852 3853
		}
	} else {
3854 3855
		if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
			return;
3856

3857
		cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
3858 3859

		if (atomic_read(&nohz.load_balancer) == cpu)
3860 3861
			if (atomic_cmpxchg(&nohz.load_balancer, cpu,
					   nr_cpu_ids) != cpu)
3862 3863
				BUG();
	}
3864
	return;
3865 3866 3867 3868 3869
}
#endif

static DEFINE_SPINLOCK(balancing);

3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880
static unsigned long __read_mostly max_load_balance_interval = HZ/10;

/*
 * Scale the max load_balance interval with the number of CPUs in the system.
 * This trades load-balance latency on larger machines for less cross talk.
 */
static void update_max_interval(void)
{
	max_load_balance_interval = HZ*num_online_cpus()/10;
}

3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897
/*
 * 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
3898 3899
	update_shares(cpu);

3900
	rcu_read_lock();
3901 3902 3903 3904 3905 3906 3907 3908 3909 3910
	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);
3911
		interval = clamp(interval, 1UL, max_load_balance_interval);
3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923

		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
3924
				 * longer idle.
3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945
				 */
				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;
	}
3946
	rcu_read_unlock();
3947 3948 3949 3950 3951 3952 3953 3954 3955 3956

	/*
	 * 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;
}

3957
#ifdef CONFIG_NO_HZ
3958
/*
3959
 * In CONFIG_NO_HZ case, the idle balance kickee will do the
3960 3961
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
3962 3963 3964 3965 3966 3967 3968 3969 3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985
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);
3986
		update_rq_clock(this_rq);
3987 3988 3989 3990 3991 3992 3993 3994 3995 3996 3997 3998 3999 4000 4001 4002 4003 4004 4005 4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020
		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
4021
	if (rq->idle_at_tick)
4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052
		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).
 */
4053 4054 4055 4056 4057 4058 4059 4060 4061 4062
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);

	/*
4063
	 * If this cpu has a pending nohz_balance_kick, then do the
4064 4065 4066
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
4067
	nohz_idle_balance(this_cpu, idle);
4068 4069 4070 4071
}

static inline int on_null_domain(int cpu)
{
4072
	return !rcu_dereference_sched(cpu_rq(cpu)->sd);
4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083
}

/*
 * 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);
4084 4085 4086 4087
#ifdef CONFIG_NO_HZ
	else if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
		nohz_balancer_kick(cpu);
#endif
4088 4089
}

4090 4091 4092 4093 4094 4095 4096 4097 4098 4099
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
}

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

4100 4101 4102 4103 4104 4105 4106 4107 4108
#else	/* CONFIG_SMP */

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

4109
#endif /* CONFIG_SMP */
4110

4111 4112 4113
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
4114
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
4115 4116 4117 4118 4119 4120
{
	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
4121
		entity_tick(cfs_rq, se, queued);
4122 4123 4124 4125
	}
}

/*
P
Peter Zijlstra 已提交
4126 4127 4128
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
4129
 */
P
Peter Zijlstra 已提交
4130
static void task_fork_fair(struct task_struct *p)
4131
{
P
Peter Zijlstra 已提交
4132
	struct cfs_rq *cfs_rq = task_cfs_rq(current);
4133
	struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
4134
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
4135 4136 4137
	struct rq *rq = this_rq();
	unsigned long flags;

4138
	raw_spin_lock_irqsave(&rq->lock, flags);
4139

4140 4141
	update_rq_clock(rq);

4142 4143
	if (unlikely(task_cpu(p) != this_cpu)) {
		rcu_read_lock();
P
Peter Zijlstra 已提交
4144
		__set_task_cpu(p, this_cpu);
4145 4146
		rcu_read_unlock();
	}
4147

4148
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
4149

4150 4151
	if (curr)
		se->vruntime = curr->vruntime;
4152
	place_entity(cfs_rq, se, 1);
4153

P
Peter Zijlstra 已提交
4154
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
4155
		/*
4156 4157 4158
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
4159
		swap(curr->vruntime, se->vruntime);
4160
		resched_task(rq->curr);
4161
	}
4162

4163 4164
	se->vruntime -= cfs_rq->min_vruntime;

4165
	raw_spin_unlock_irqrestore(&rq->lock, flags);
4166 4167
}

4168 4169 4170 4171
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
P
Peter Zijlstra 已提交
4172 4173
static void
prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio)
4174
{
P
Peter Zijlstra 已提交
4175 4176 4177
	if (!p->se.on_rq)
		return;

4178 4179 4180 4181 4182
	/*
	 * 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
4183
	if (rq->curr == p) {
4184 4185 4186
		if (p->prio > oldprio)
			resched_task(rq->curr);
	} else
4187
		check_preempt_curr(rq, p, 0);
4188 4189
}

P
Peter Zijlstra 已提交
4190 4191 4192 4193 4194 4195 4196 4197 4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208 4209 4210 4211 4212 4213
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;
	}
}

4214 4215 4216
/*
 * We switched to the sched_fair class.
 */
P
Peter Zijlstra 已提交
4217
static void switched_to_fair(struct rq *rq, struct task_struct *p)
4218
{
P
Peter Zijlstra 已提交
4219 4220 4221
	if (!p->se.on_rq)
		return;

4222 4223 4224 4225 4226
	/*
	 * 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
4227
	if (rq->curr == p)
4228 4229
		resched_task(rq->curr);
	else
4230
		check_preempt_curr(rq, p, 0);
4231 4232
}

4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245
/* 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
4246
#ifdef CONFIG_FAIR_GROUP_SCHED
4247
static void task_move_group_fair(struct task_struct *p, int on_rq)
P
Peter Zijlstra 已提交
4248
{
4249 4250 4251 4252 4253 4254 4255 4256 4257 4258 4259 4260 4261 4262 4263 4264
	/*
	 * 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));
4265
	if (!on_rq)
4266
		p->se.vruntime += cfs_rq_of(&p->se)->min_vruntime;
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}
#endif

4270
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282 4283 4284
{
	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;
}

4285 4286 4287
/*
 * All the scheduling class methods:
 */
4288 4289
static const struct sched_class fair_sched_class = {
	.next			= &idle_sched_class,
4290 4291 4292
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,
4293
	.yield_to_task		= yield_to_task_fair,
4294

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Ingo Molnar 已提交
4295
	.check_preempt_curr	= check_preempt_wakeup,
4296 4297 4298 4299

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

4300
#ifdef CONFIG_SMP
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Li Zefan 已提交
4301 4302
	.select_task_rq		= select_task_rq_fair,

4303 4304
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
4305 4306

	.task_waking		= task_waking_fair,
4307
#endif
4308

4309
	.set_curr_task          = set_curr_task_fair,
4310
	.task_tick		= task_tick_fair,
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Peter Zijlstra 已提交
4311
	.task_fork		= task_fork_fair,
4312 4313

	.prio_changed		= prio_changed_fair,
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Peter Zijlstra 已提交
4314
	.switched_from		= switched_from_fair,
4315
	.switched_to		= switched_to_fair,
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Peter Zijlstra 已提交
4316

4317 4318
	.get_rr_interval	= get_rr_interval_fair,

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Peter Zijlstra 已提交
4319
#ifdef CONFIG_FAIR_GROUP_SCHED
4320
	.task_move_group	= task_move_group_fair,
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Peter Zijlstra 已提交
4321
#endif
4322 4323 4324
};

#ifdef CONFIG_SCHED_DEBUG
4325
static void print_cfs_stats(struct seq_file *m, int cpu)
4326 4327 4328
{
	struct cfs_rq *cfs_rq;

4329
	rcu_read_lock();
4330
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
4331
		print_cfs_rq(m, cpu, cfs_rq);
4332
	rcu_read_unlock();
4333 4334
}
#endif