sched_fair.c 102.6 KB
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/*
 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
 *
 *  Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 *  Interactivity improvements by Mike Galbraith
 *  (C) 2007 Mike Galbraith <efault@gmx.de>
 *
 *  Various enhancements by Dmitry Adamushko.
 *  (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
 *
 *  Group scheduling enhancements by Srivatsa Vaddagiri
 *  Copyright IBM Corporation, 2007
 *  Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
 *
 *  Scaled math optimizations by Thomas Gleixner
 *  Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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 *
 *  Adaptive scheduling granularity, math enhancements by Peter Zijlstra
 *  Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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 */

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

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/*
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 * Minimal preemption granularity for CPU-bound tasks:
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 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds)
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 */
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unsigned int sysctl_sched_min_granularity = 750000ULL;
unsigned int normalized_sysctl_sched_min_granularity = 750000ULL;
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/*
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 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
 */
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static unsigned int sched_nr_latency = 8;
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/*
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 * After fork, child runs first. If set to 0 (default) then
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 * parent will (try to) run first.
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 */
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unsigned int sysctl_sched_child_runs_first __read_mostly;
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/*
 * sys_sched_yield() compat mode
 *
 * This option switches the agressive yield implementation of the
 * old scheduler back on.
 */
unsigned int __read_mostly sysctl_sched_compat_yield;

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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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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];
}

/* 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;
}

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

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

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

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

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#endif	/* CONFIG_FAIR_GROUP_SCHED */

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

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

	return min_vruntime;
}

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

	return min_vruntime;
}

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

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

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

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

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

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

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

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/*
 * Enqueue an entity into the rb-tree:
 */
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static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
	struct rb_node *parent = NULL;
	struct sched_entity *entry;
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	s64 key = entity_key(cfs_rq, se);
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	int leftmost = 1;

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

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

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

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

static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
{
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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_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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#ifdef CONFIG_SCHED_DEBUG
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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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/*
 * 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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}

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

	if (unlikely(!curr))
		return;

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

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

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

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

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

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

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

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

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#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

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static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
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	if (!parent_entity(se))
		inc_cpu_load(rq_of(cfs_rq), se->load.weight);
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	if (entity_is_task(se)) {
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		add_cfs_task_weight(cfs_rq, se->load.weight);
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		list_add(&se->group_node, &cfs_rq->tasks);
	}
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	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);
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	if (!parent_entity(se))
		dec_cpu_load(rq_of(cfs_rq), se->load.weight);
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	if (entity_is_task(se)) {
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		add_cfs_task_weight(cfs_rq, -se->load.weight);
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		list_del_init(&se->group_node);
	}
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	cfs_rq->nr_running--;
}

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#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
static void update_cfs_load(struct cfs_rq *cfs_rq)
{
	u64 period = sched_avg_period();
	u64 now, delta;

	if (!cfs_rq)
		return;

	now = rq_of(cfs_rq)->clock;
	delta = now - cfs_rq->load_stamp;

	cfs_rq->load_stamp = now;
	cfs_rq->load_period += delta;
	cfs_rq->load_avg += delta * cfs_rq->load.weight;

	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;
	}
}

static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
	if (se->on_rq)
		account_entity_dequeue(cfs_rq, se);

	update_load_set(&se->load, weight);

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

static void update_cfs_shares(struct cfs_rq *cfs_rq)
{
	struct task_group *tg;
	struct sched_entity *se;
	long load_weight, load, shares;

	if (!cfs_rq)
		return;

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
	if (!se)
		return;

	load = cfs_rq->load.weight;

	load_weight = atomic_read(&tg->load_weight);
	load_weight -= cfs_rq->load_contribution;
	load_weight += load;

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

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

	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
static inline void update_cfs_load(struct cfs_rq *cfs_rq)
{
}

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

731
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
732 733
{
#ifdef CONFIG_SCHEDSTATS
734 735 736 737 738
	struct task_struct *tsk = NULL;

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

739 740
	if (se->statistics.sleep_start) {
		u64 delta = rq_of(cfs_rq)->clock - se->statistics.sleep_start;
741 742 743 744

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

745 746
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
747

748 749
		se->statistics.sleep_start = 0;
		se->statistics.sum_sleep_runtime += delta;
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751
		if (tsk) {
752
			account_scheduler_latency(tsk, delta >> 10, 1);
753 754
			trace_sched_stat_sleep(tsk, delta);
		}
755
	}
756 757
	if (se->statistics.block_start) {
		u64 delta = rq_of(cfs_rq)->clock - se->statistics.block_start;
758 759 760 761

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

762 763
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
764

765 766
		se->statistics.block_start = 0;
		se->statistics.sum_sleep_runtime += delta;
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768
		if (tsk) {
769
			if (tsk->in_iowait) {
770 771
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
772
				trace_sched_stat_iowait(tsk, delta);
773 774
			}

775 776 777 778 779 780 781 782 783 784 785
			/*
			 * 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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		}
787 788 789 790
	}
#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
}

804 805 806
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
807
	u64 vruntime = cfs_rq->min_vruntime;
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809 810 811 812 813 814
	/*
	 * 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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	if (initial && sched_feat(START_DEBIT))
816
		vruntime += sched_vslice(cfs_rq, se);
817

818
	/* sleeps up to a single latency don't count. */
819
	if (!initial) {
820
		unsigned long thresh = sysctl_sched_latency;
821

822 823 824 825 826 827
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
828

829
		vruntime -= thresh;
830 831
	}

832 833 834
	/* ensure we never gain time by being placed backwards. */
	vruntime = max_vruntime(se->vruntime, vruntime);

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	se->vruntime = vruntime;
836 837
}

838
static void
839
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
840
{
841 842 843 844
	/*
	 * Update the normalized vruntime before updating min_vruntime
	 * through callig update_curr().
	 */
845
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
846 847
		se->vruntime += cfs_rq->min_vruntime;

848
	/*
849
	 * Update run-time statistics of the 'current'.
850
	 */
851
	update_curr(cfs_rq);
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	update_cfs_load(cfs_rq);
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	account_entity_enqueue(cfs_rq, se);
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	update_cfs_shares(cfs_rq);
855

856
	if (flags & ENQUEUE_WAKEUP) {
857
		place_entity(cfs_rq, se, 0);
858
		enqueue_sleeper(cfs_rq, se);
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	}
860

861
	update_stats_enqueue(cfs_rq, se);
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	check_spread(cfs_rq, se);
863 864
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
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	se->on_rq = 1;
866 867
}

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static void __clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
870
	if (!se || cfs_rq->last == se)
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		cfs_rq->last = NULL;

873
	if (!se || cfs_rq->next == se)
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		cfs_rq->next = NULL;
}

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static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	for_each_sched_entity(se)
		__clear_buddies(cfs_rq_of(se), se);
}

883
static void
884
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
885
{
886 887 888 889 890
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);

891
	update_stats_dequeue(cfs_rq, se);
892
	if (flags & DEQUEUE_SLEEP) {
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#ifdef CONFIG_SCHEDSTATS
894 895 896 897
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
898
				se->statistics.sleep_start = rq_of(cfs_rq)->clock;
899
			if (tsk->state & TASK_UNINTERRUPTIBLE)
900
				se->statistics.block_start = rq_of(cfs_rq)->clock;
901
		}
902
#endif
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	}

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	clear_buddies(cfs_rq, se);
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907
	if (se != cfs_rq->curr)
908
		__dequeue_entity(cfs_rq, se);
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	se->on_rq = 0;
	update_cfs_load(cfs_rq);
911
	account_entity_dequeue(cfs_rq, se);
912
	update_min_vruntime(cfs_rq);
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	update_cfs_shares(cfs_rq);
914 915 916 917 918 919

	/*
	 * 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.
	 */
920
	if (!(flags & DEQUEUE_SLEEP))
921
		se->vruntime -= cfs_rq->min_vruntime;
922 923 924 925 926
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
927
static void
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check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
929
{
930 931
	unsigned long ideal_runtime, delta_exec;

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	ideal_runtime = sched_slice(cfs_rq, curr);
933
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
934
	if (delta_exec > ideal_runtime) {
935
		resched_task(rq_of(cfs_rq)->curr);
936 937 938 939 940
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960
		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) {
		struct sched_entity *se = __pick_next_entity(cfs_rq);
		s64 delta = curr->vruntime - se->vruntime;

		if (delta > ideal_runtime)
			resched_task(rq_of(cfs_rq)->curr);
961
	}
962 963
}

964
static void
965
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
966
{
967 968 969 970 971 972 973 974 975 976 977
	/* '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);
	}

978
	update_stats_curr_start(cfs_rq, se);
979
	cfs_rq->curr = se;
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#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):
	 */
986
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
987
		se->statistics.slice_max = max(se->statistics.slice_max,
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			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
991
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
992 993
}

994 995 996
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

997
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
998
{
999
	struct sched_entity *se = __pick_next_entity(cfs_rq);
1000
	struct sched_entity *left = se;
1001

1002 1003
	if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
		se = cfs_rq->next;
1004

1005 1006 1007 1008 1009 1010 1011
	/*
	 * 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;

	clear_buddies(cfs_rq, se);
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	return se;
1014 1015
}

1016
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
1017 1018 1019 1020 1021 1022
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
1023
		update_curr(cfs_rq);
1024

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	check_spread(cfs_rq, prev);
1026
	if (prev->on_rq) {
1027
		update_stats_wait_start(cfs_rq, prev);
1028 1029 1030
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
	}
1031
	cfs_rq->curr = NULL;
1032 1033
}

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static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
1036 1037
{
	/*
1038
	 * Update run-time statistics of the 'current'.
1039
	 */
1040
	update_curr(cfs_rq);
1041

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#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
1047 1048 1049 1050
	if (queued) {
		resched_task(rq_of(cfs_rq)->curr);
		return;
	}
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1051 1052 1053 1054 1055 1056 1057 1058
	/*
	 * 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

1059
	if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
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		check_preempt_tick(cfs_rq, curr);
1061 1062 1063 1064 1065 1066
}

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

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#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.
		 */
1090
		if (rq->curr != p)
1091
			delta = max_t(s64, 10000LL, delta);
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1093
		hrtick_start(rq, delta);
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1094 1095
	}
}
1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111

/*
 * 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);
}
1112
#else /* !CONFIG_SCHED_HRTICK */
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1113 1114 1115 1116
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
1117 1118 1119 1120

static inline void hrtick_update(struct rq *rq)
{
}
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1121 1122
#endif

1123 1124 1125 1126 1127
/*
 * 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:
 */
1128
static void
1129
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
1130 1131
{
	struct cfs_rq *cfs_rq;
1132
	struct sched_entity *se = &p->se;
1133 1134

	for_each_sched_entity(se) {
1135
		if (se->on_rq)
1136 1137
			break;
		cfs_rq = cfs_rq_of(se);
1138 1139
		enqueue_entity(cfs_rq, se, flags);
		flags = ENQUEUE_WAKEUP;
1140
	}
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1142 1143 1144 1145 1146 1147 1148
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

		update_cfs_load(cfs_rq);
		update_cfs_shares(cfs_rq);
	}

1149
	hrtick_update(rq);
1150 1151 1152 1153 1154 1155 1156
}

/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
1157
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
1158 1159
{
	struct cfs_rq *cfs_rq;
1160
	struct sched_entity *se = &p->se;
1161 1162 1163

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
1164
		dequeue_entity(cfs_rq, se, flags);
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1166
		/* Don't dequeue parent if it has other entities besides us */
1167
		if (cfs_rq->load.weight)
1168
			break;
1169
		flags |= DEQUEUE_SLEEP;
1170
	}
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1172 1173 1174 1175 1176 1177 1178
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

		update_cfs_load(cfs_rq);
		update_cfs_shares(cfs_rq);
	}

1179
	hrtick_update(rq);
1180 1181 1182
}

/*
1183 1184 1185
 * sched_yield() support is very simple - we dequeue and enqueue.
 *
 * If compat_yield is turned on then we requeue to the end of the tree.
1186
 */
1187
static void yield_task_fair(struct rq *rq)
1188
{
1189 1190 1191
	struct task_struct *curr = rq->curr;
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
	struct sched_entity *rightmost, *se = &curr->se;
1192 1193

	/*
1194 1195 1196 1197 1198
	 * Are we the only task in the tree?
	 */
	if (unlikely(cfs_rq->nr_running == 1))
		return;

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	clear_buddies(cfs_rq, se);

1201
	if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {
1202
		update_rq_clock(rq);
1203
		/*
1204
		 * Update run-time statistics of the 'current'.
1205
		 */
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		update_curr(cfs_rq);
1207 1208 1209 1210 1211

		return;
	}
	/*
	 * Find the rightmost entry in the rbtree:
1212
	 */
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1213
	rightmost = __pick_last_entity(cfs_rq);
1214 1215 1216
	/*
	 * Already in the rightmost position?
	 */
1217
	if (unlikely(!rightmost || entity_before(rightmost, se)))
1218 1219 1220 1221
		return;

	/*
	 * Minimally necessary key value to be last in the tree:
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1222 1223
	 * Upon rescheduling, sched_class::put_prev_task() will place
	 * 'current' within the tree based on its new key value.
1224
	 */
1225
	se->vruntime = rightmost->vruntime + 1;
1226 1227
}

1228
#ifdef CONFIG_SMP
1229

1230 1231 1232 1233 1234 1235 1236 1237
static void task_waking_fair(struct rq *rq, struct task_struct *p)
{
	struct sched_entity *se = &p->se;
	struct cfs_rq *cfs_rq = cfs_rq_of(se);

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

1238
#ifdef CONFIG_FAIR_GROUP_SCHED
1239 1240 1241 1242 1243 1244 1245
/*
 * 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.
 */
P
Peter Zijlstra 已提交
1246
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
1247
{
P
Peter Zijlstra 已提交
1248
	struct sched_entity *se = tg->se[cpu];
1249 1250 1251 1252

	if (!tg->parent)
		return wl;

P
Peter Zijlstra 已提交
1253
	for_each_sched_entity(se) {
1254
		long S, rw, s, a, b;
P
Peter Zijlstra 已提交
1255 1256

		S = se->my_q->tg->shares;
P
Peter Zijlstra 已提交
1257 1258
		s = se->load.weight;
		rw = se->my_q->load.weight;
1259

1260 1261
		a = S*(rw + wl);
		b = S*rw + s*wg;
P
Peter Zijlstra 已提交
1262

1263 1264 1265 1266 1267
		wl = s*(a-b);

		if (likely(b))
			wl /= b;

1268 1269 1270 1271 1272 1273 1274
		/*
		 * Assume the group is already running and will
		 * thus already be accounted for in the weight.
		 *
		 * That is, moving shares between CPUs, does not
		 * alter the group weight.
		 */
P
Peter Zijlstra 已提交
1275 1276
		wg = 0;
	}
1277

P
Peter Zijlstra 已提交
1278
	return wl;
1279
}
P
Peter Zijlstra 已提交
1280

1281
#else
P
Peter Zijlstra 已提交
1282

1283 1284
static inline unsigned long effective_load(struct task_group *tg, int cpu,
		unsigned long wl, unsigned long wg)
P
Peter Zijlstra 已提交
1285
{
1286
	return wl;
1287
}
P
Peter Zijlstra 已提交
1288

1289 1290
#endif

1291
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
1292
{
1293 1294
	unsigned long this_load, load;
	int idx, this_cpu, prev_cpu;
1295
	unsigned long tl_per_task;
1296
	struct task_group *tg;
1297
	unsigned long weight;
1298
	int balanced;
1299

1300 1301 1302 1303 1304
	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);
1305

1306 1307 1308 1309 1310
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
1311
	rcu_read_lock();
1312 1313 1314 1315
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

1316
		this_load += effective_load(tg, this_cpu, -weight, -weight);
1317 1318
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
1319

1320 1321
	tg = task_group(p);
	weight = p->se.load.weight;
1322

1323 1324
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
1325 1326 1327
	 * 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.
1328 1329 1330 1331
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346
	if (this_load) {
		unsigned long this_eff_load, prev_eff_load;

		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;
1347
	rcu_read_unlock();
1348

1349
	/*
I
Ingo Molnar 已提交
1350 1351 1352
	 * If the currently running task will sleep within
	 * a reasonable amount of time then attract this newly
	 * woken task:
1353
	 */
1354 1355
	if (sync && balanced)
		return 1;
1356

1357
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
1358 1359
	tl_per_task = cpu_avg_load_per_task(this_cpu);

1360 1361 1362
	if (balanced ||
	    (this_load <= load &&
	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
1363 1364 1365 1366 1367
		/*
		 * This domain has SD_WAKE_AFFINE and
		 * p is cache cold in this domain, and
		 * there is no bad imbalance.
		 */
1368
		schedstat_inc(sd, ttwu_move_affine);
1369
		schedstat_inc(p, se.statistics.nr_wakeups_affine);
1370 1371 1372 1373 1374 1375

		return 1;
	}
	return 0;
}

1376 1377 1378 1379 1380
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
1381
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
1382
		  int this_cpu, int load_idx)
1383
{
1384
	struct sched_group *idlest = NULL, *group = sd->groups;
1385 1386
	unsigned long min_load = ULONG_MAX, this_load = 0;
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
1387

1388 1389 1390 1391
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
1392

1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446
		/* Skip over this group if it has no CPUs allowed */
		if (!cpumask_intersects(sched_group_cpus(group),
					&p->cpus_allowed))
			continue;

		local_group = cpumask_test_cpu(this_cpu,
					       sched_group_cpus(group));

		/* Tally up the load of all CPUs in the group */
		avg_load = 0;

		for_each_cpu(i, sched_group_cpus(group)) {
			/* Bias balancing toward cpus of our domain */
			if (local_group)
				load = source_load(i, load_idx);
			else
				load = target_load(i, load_idx);

			avg_load += load;
		}

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

		if (local_group) {
			this_load = avg_load;
		} else if (avg_load < min_load) {
			min_load = avg_load;
			idlest = group;
		}
	} while (group = group->next, group != sd->groups);

	if (!idlest || 100*this_load < imbalance*min_load)
		return NULL;
	return idlest;
}

/*
 * find_idlest_cpu - find the idlest cpu among the cpus in group.
 */
static int
find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
{
	unsigned long load, min_load = ULONG_MAX;
	int idlest = -1;
	int i;

	/* Traverse only the allowed CPUs */
	for_each_cpu_and(i, sched_group_cpus(group), &p->cpus_allowed) {
		load = weighted_cpuload(i);

		if (load < min_load || (load == min_load && i == this_cpu)) {
			min_load = load;
			idlest = i;
1447 1448 1449
		}
	}

1450 1451
	return idlest;
}
1452

1453 1454 1455
/*
 * Try and locate an idle CPU in the sched_domain.
 */
1456
static int select_idle_sibling(struct task_struct *p, int target)
1457 1458 1459
{
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
1460
	struct sched_domain *sd;
1461 1462 1463
	int i;

	/*
1464 1465
	 * If the task is going to be woken-up on this cpu and if it is
	 * already idle, then it is the right target.
1466
	 */
1467 1468 1469 1470 1471 1472 1473 1474
	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))
1475
		return prev_cpu;
1476 1477

	/*
1478
	 * Otherwise, iterate the domains and find an elegible idle cpu.
1479
	 */
1480 1481
	for_each_domain(target, sd) {
		if (!(sd->flags & SD_SHARE_PKG_RESOURCES))
1482
			break;
1483 1484 1485 1486 1487 1488

		for_each_cpu_and(i, sched_domain_span(sd), &p->cpus_allowed) {
			if (idle_cpu(i)) {
				target = i;
				break;
			}
1489
		}
1490 1491 1492 1493 1494 1495 1496 1497

		/*
		 * 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;
1498 1499 1500 1501 1502
	}

	return target;
}

1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513
/*
 * 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.
 */
1514 1515
static int
select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_flags)
1516
{
1517
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
1518 1519 1520
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
	int new_cpu = cpu;
1521
	int want_affine = 0;
1522
	int want_sd = 1;
1523
	int sync = wake_flags & WF_SYNC;
1524

1525
	if (sd_flag & SD_BALANCE_WAKE) {
1526
		if (cpumask_test_cpu(cpu, &p->cpus_allowed))
1527 1528 1529
			want_affine = 1;
		new_cpu = prev_cpu;
	}
1530 1531

	for_each_domain(cpu, tmp) {
1532 1533 1534
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

1535
		/*
1536 1537
		 * If power savings logic is enabled for a domain, see if we
		 * are not overloaded, if so, don't balance wider.
1538
		 */
P
Peter Zijlstra 已提交
1539
		if (tmp->flags & (SD_POWERSAVINGS_BALANCE|SD_PREFER_LOCAL)) {
1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551
			unsigned long power = 0;
			unsigned long nr_running = 0;
			unsigned long capacity;
			int i;

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

			capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);

P
Peter Zijlstra 已提交
1552 1553 1554 1555
			if (tmp->flags & SD_POWERSAVINGS_BALANCE)
				nr_running /= 2;

			if (nr_running < capacity)
1556
				want_sd = 0;
1557
		}
1558

1559
		/*
1560 1561
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
1562
		 */
1563 1564 1565 1566
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
			want_affine = 0;
1567 1568
		}

1569 1570 1571
		if (!want_sd && !want_affine)
			break;

1572
		if (!(tmp->flags & sd_flag))
1573 1574
			continue;

1575 1576 1577 1578
		if (want_sd)
			sd = tmp;
	}

1579
	if (affine_sd) {
1580 1581 1582 1583
		if (cpu == prev_cpu || wake_affine(affine_sd, p, sync))
			return select_idle_sibling(p, cpu);
		else
			return select_idle_sibling(p, prev_cpu);
1584
	}
1585

1586
	while (sd) {
1587
		int load_idx = sd->forkexec_idx;
1588
		struct sched_group *group;
1589
		int weight;
1590

1591
		if (!(sd->flags & sd_flag)) {
1592 1593 1594
			sd = sd->child;
			continue;
		}
1595

1596 1597
		if (sd_flag & SD_BALANCE_WAKE)
			load_idx = sd->wake_idx;
1598

1599
		group = find_idlest_group(sd, p, cpu, load_idx);
1600 1601 1602 1603
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
1604

1605
		new_cpu = find_idlest_cpu(group, p, cpu);
1606 1607 1608 1609
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
1610
		}
1611 1612 1613

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
1614
		weight = sd->span_weight;
1615 1616
		sd = NULL;
		for_each_domain(cpu, tmp) {
1617
			if (weight <= tmp->span_weight)
1618
				break;
1619
			if (tmp->flags & sd_flag)
1620 1621 1622
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
1623 1624
	}

1625
	return new_cpu;
1626 1627 1628
}
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
1629 1630
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
1631 1632 1633 1634
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
1635 1636
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
1637 1638 1639 1640 1641 1642 1643 1644 1645
	 *
	 * 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.
1646
	 */
M
Mike Galbraith 已提交
1647 1648
	if (unlikely(se->load.weight != NICE_0_LOAD))
		gran = calc_delta_fair(gran, se);
1649 1650 1651 1652

	return gran;
}

1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674
/*
 * 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
1675
	gran = wakeup_gran(curr, se);
1676 1677 1678 1679 1680 1681
	if (vdiff > gran)
		return 1;

	return 0;
}

1682 1683
static void set_last_buddy(struct sched_entity *se)
{
1684 1685 1686 1687
	if (likely(task_of(se)->policy != SCHED_IDLE)) {
		for_each_sched_entity(se)
			cfs_rq_of(se)->last = se;
	}
1688 1689 1690 1691
}

static void set_next_buddy(struct sched_entity *se)
{
1692 1693 1694 1695
	if (likely(task_of(se)->policy != SCHED_IDLE)) {
		for_each_sched_entity(se)
			cfs_rq_of(se)->next = se;
	}
1696 1697
}

1698 1699 1700
/*
 * Preempt the current task with a newly woken task if needed:
 */
1701
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
1702 1703
{
	struct task_struct *curr = rq->curr;
1704
	struct sched_entity *se = &curr->se, *pse = &p->se;
1705
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
1706
	int scale = cfs_rq->nr_running >= sched_nr_latency;
1707

1708 1709
	if (unlikely(rt_prio(p->prio)))
		goto preempt;
1710

P
Peter Zijlstra 已提交
1711 1712 1713
	if (unlikely(p->sched_class != &fair_sched_class))
		return;

I
Ingo Molnar 已提交
1714 1715 1716
	if (unlikely(se == pse))
		return;

1717
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK))
M
Mike Galbraith 已提交
1718
		set_next_buddy(pse);
P
Peter Zijlstra 已提交
1719

1720 1721 1722 1723 1724 1725 1726
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
	 */
	if (test_tsk_need_resched(curr))
		return;

1727
	/*
1728
	 * Batch and idle tasks do not preempt (their preemption is driven by
1729 1730
	 * the tick):
	 */
1731
	if (unlikely(p->policy != SCHED_NORMAL))
1732
		return;
1733

1734
	/* Idle tasks are by definition preempted by everybody. */
1735 1736
	if (unlikely(curr->policy == SCHED_IDLE))
		goto preempt;
1737

1738 1739 1740
	if (!sched_feat(WAKEUP_PREEMPT))
		return;

1741
	update_curr(cfs_rq);
1742
	find_matching_se(&se, &pse);
1743
	BUG_ON(!pse);
1744 1745
	if (wakeup_preempt_entity(se, pse) == 1)
		goto preempt;
1746

1747
	return;
1748

1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764
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);
1765 1766
}

1767
static struct task_struct *pick_next_task_fair(struct rq *rq)
1768
{
P
Peter Zijlstra 已提交
1769
	struct task_struct *p;
1770 1771 1772
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

1773
	if (!cfs_rq->nr_running)
1774 1775 1776
		return NULL;

	do {
1777
		se = pick_next_entity(cfs_rq);
1778
		set_next_entity(cfs_rq, se);
1779 1780 1781
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
1782 1783 1784 1785
	p = task_of(se);
	hrtick_start_fair(rq, p);

	return p;
1786 1787 1788 1789 1790
}

/*
 * Account for a descheduled task:
 */
1791
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
1792 1793 1794 1795 1796 1797
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
1798
		put_prev_entity(cfs_rq, se);
1799 1800 1801
	}
}

1802
#ifdef CONFIG_SMP
1803 1804 1805 1806
/**************************************************
 * Fair scheduling class load-balancing methods:
 */

1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817
/*
 * 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);
1818 1819 1820 1821

	/* re-arm NEWIDLE balancing when moving tasks */
	src_rq->avg_idle = this_rq->avg_idle = 2*sysctl_sched_migration_cost;
	this_rq->idle_stamp = 0;
1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839
}

/*
 * 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)) {
1840
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
1841 1842 1843 1844 1845
		return 0;
	}
	*all_pinned = 0;

	if (task_running(rq, p)) {
1846
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
1847 1848 1849 1850 1851 1852 1853 1854 1855
		return 0;
	}

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

1856
	tsk_cache_hot = task_hot(p, rq->clock_task, sd);
1857 1858 1859 1860 1861
	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]);
1862
			schedstat_inc(p, se.statistics.nr_forced_migrations);
1863 1864 1865 1866 1867 1868
		}
#endif
		return 1;
	}

	if (tsk_cache_hot) {
1869
		schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
1870 1871 1872 1873 1874
		return 0;
	}
	return 1;
}

1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910
/*
 * 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;
}

1911 1912 1913 1914
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,
1915
	      int *this_best_prio, struct cfs_rq *busiest_cfs_rq)
1916 1917 1918
{
	int loops = 0, pulled = 0, pinned = 0;
	long rem_load_move = max_load_move;
1919
	struct task_struct *p, *n;
1920 1921 1922 1923 1924 1925

	if (max_load_move == 0)
		goto out;

	pinned = 1;

1926 1927 1928
	list_for_each_entry_safe(p, n, &busiest_cfs_rq->tasks, se.group_node) {
		if (loops++ > sysctl_sched_nr_migrate)
			break;
1929

1930 1931 1932
		if ((p->se.load.weight >> 1) > rem_load_move ||
		    !can_migrate_task(p, busiest, this_cpu, sd, idle, &pinned))
			continue;
1933

1934 1935 1936
		pull_task(busiest, p, this_rq, this_cpu);
		pulled++;
		rem_load_move -= p->se.load.weight;
1937 1938

#ifdef CONFIG_PREEMPT
1939 1940 1941 1942 1943 1944 1945
		/*
		 * 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;
1946 1947
#endif

1948 1949 1950 1951 1952 1953 1954
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
		if (rem_load_move <= 0)
			break;

1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971
		if (p->prio < *this_best_prio)
			*this_best_prio = p->prio;
	}
out:
	/*
	 * Right now, this is one of only two places pull_task() is called,
	 * so we can safely collect pull_task() stats here rather than
	 * inside pull_task().
	 */
	schedstat_add(sd, lb_gained[idle], pulled);

	if (all_pinned)
		*all_pinned = pinned;

	return max_load_move - rem_load_move;
}

P
Peter Zijlstra 已提交
1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 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 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031
#ifdef CONFIG_FAIR_GROUP_SCHED
static unsigned long
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
		  unsigned long max_load_move,
		  struct sched_domain *sd, enum cpu_idle_type idle,
		  int *all_pinned, int *this_best_prio)
{
	long rem_load_move = max_load_move;
	int busiest_cpu = cpu_of(busiest);
	struct task_group *tg;

	rcu_read_lock();
	update_h_load(busiest_cpu);

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

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

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

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

		if (!moved_load)
			continue;

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

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

	return max_load_move - rem_load_move;
}
#else
static unsigned long
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
		  unsigned long max_load_move,
		  struct sched_domain *sd, enum cpu_idle_type idle,
		  int *all_pinned, int *this_best_prio)
{
	return balance_tasks(this_rq, this_cpu, busiest,
			max_load_move, sd, idle, all_pinned,
			this_best_prio, &busiest->cfs);
}
#endif

2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043
/*
 * 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)
{
2044
	unsigned long total_load_moved = 0, load_moved;
2045 2046 2047
	int this_best_prio = this_rq->curr->prio;

	do {
2048
		load_moved = load_balance_fair(this_rq, this_cpu, busiest,
2049 2050
				max_load_move - total_load_moved,
				sd, idle, all_pinned, &this_best_prio);
2051 2052

		total_load_moved += load_moved;
2053 2054 2055 2056 2057 2058 2059 2060 2061

#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;
2062 2063 2064 2065

		if (raw_spin_is_contended(&this_rq->lock) ||
				raw_spin_is_contended(&busiest->lock))
			break;
2066
#endif
2067
	} while (load_moved && max_load_move > total_load_moved);
2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087

	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;
2088
	unsigned long this_has_capacity;
2089 2090 2091 2092 2093

	/* Statistics of the busiest group */
	unsigned long max_load;
	unsigned long busiest_load_per_task;
	unsigned long busiest_nr_running;
2094
	unsigned long busiest_group_capacity;
2095
	unsigned long busiest_has_capacity;
2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117

	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;
	int group_imb; /* Is there an imbalance in the group ? */
2118
	int group_has_capacity; /* Is there extra capacity in the group? */
2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309
};

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

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

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

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

	return load_idx;
}


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

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

	if (!sds->power_savings_balance)
		return;

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

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

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

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

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

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

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

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

	return 1;

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

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

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


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

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

unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
{
2310
	unsigned long weight = sd->span_weight;
2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328
	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);
2329 2330 2331 2332 2333 2334 2335

	if (unlikely(total < rq->rt_avg)) {
		/* Ensures that power won't end up being negative */
		available = 0;
	} else {
		available = total - rq->rt_avg;
	}
2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346

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

	total >>= SCHED_LOAD_SHIFT;

	return div_u64(available, total);
}

static void update_cpu_power(struct sched_domain *sd, int cpu)
{
2347
	unsigned long weight = sd->span_weight;
2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359
	unsigned long power = SCHED_LOAD_SCALE;
	struct sched_group *sdg = sd->groups;

	if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
		if (sched_feat(ARCH_POWER))
			power *= arch_scale_smt_power(sd, cpu);
		else
			power *= default_scale_smt_power(sd, cpu);

		power >>= SCHED_LOAD_SHIFT;
	}

2360 2361 2362 2363 2364 2365 2366 2367 2368
	sdg->cpu_power_orig = power;

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

	power >>= SCHED_LOAD_SHIFT;

2369 2370 2371 2372 2373 2374
	power *= scale_rt_power(cpu);
	power >>= SCHED_LOAD_SHIFT;

	if (!power)
		power = 1;

2375
	cpu_rq(cpu)->cpu_power = power;
2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400
	sdg->cpu_power = power;
}

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

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

	power = 0;

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

	sdg->cpu_power = power;
}

2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419
/*
 * Try and fix up capacity for tiny siblings, this is needed when
 * things like SD_ASYM_PACKING need f_b_g to select another sibling
 * which on its own isn't powerful enough.
 *
 * See update_sd_pick_busiest() and check_asym_packing().
 */
static inline int
fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
{
	/*
	 * Only siblings can have significantly less than SCHED_LOAD_SCALE
	 */
	if (sd->level != SD_LV_SIBLING)
		return 0;

	/*
	 * If ~90% of the cpu_power is still there, we're good.
	 */
M
Michael Neuling 已提交
2420
	if (group->cpu_power * 32 > group->cpu_power_orig * 29)
2421 2422 2423 2424 2425
		return 1;

	return 0;
}

2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444
/**
 * 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.
 * @sd_idle: Idle status of the sched_domain containing group.
 * @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,
			enum cpu_idle_type idle, int load_idx, int *sd_idle,
			int local_group, const struct cpumask *cpus,
			int *balance, struct sg_lb_stats *sgs)
{
2445
	unsigned long load, max_cpu_load, min_cpu_load, max_nr_running;
2446 2447
	int i;
	unsigned int balance_cpu = -1, first_idle_cpu = 0;
2448
	unsigned long avg_load_per_task = 0;
2449

2450
	if (local_group)
2451 2452 2453 2454 2455
		balance_cpu = group_first_cpu(group);

	/* Tally up the load of all CPUs in the group */
	max_cpu_load = 0;
	min_cpu_load = ~0UL;
2456
	max_nr_running = 0;
2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473

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

		if (*sd_idle && rq->nr_running)
			*sd_idle = 0;

		/* 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);
2474
			if (load > max_cpu_load) {
2475
				max_cpu_load = load;
2476 2477
				max_nr_running = rq->nr_running;
			}
2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493
			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);

	}

	/*
	 * 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.
	 */
2494 2495 2496 2497 2498 2499
	if (idle != CPU_NEWLY_IDLE && local_group) {
		if (balance_cpu != this_cpu) {
			*balance = 0;
			return;
		}
		update_group_power(sd, this_cpu);
2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513
	}

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

	/*
	 * Consider the group unbalanced when the imbalance is larger
	 * than the average weight of two tasks.
	 *
	 * APZ: with cgroup the avg task weight can vary wildly and
	 *      might not be a suitable number - should we keep a
	 *      normalized nr_running number somewhere that negates
	 *      the hierarchy?
	 */
2514 2515
	if (sgs->sum_nr_running)
		avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
2516

2517
	if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task && max_nr_running > 1)
2518 2519
		sgs->group_imb = 1;

2520
	sgs->group_capacity = DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE);
2521 2522
	if (!sgs->group_capacity)
		sgs->group_capacity = fix_small_capacity(sd, group);
2523 2524 2525

	if (sgs->group_capacity > sgs->sum_nr_running)
		sgs->group_has_capacity = 1;
2526 2527
}

2528 2529 2530 2531 2532
/**
 * 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
2533 2534
 * @sgs: sched_group statistics
 * @this_cpu: the current cpu
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
 *
 * 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;
}

2571 2572 2573 2574 2575
/**
 * 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
2576
 * @sd_idle: Idle status of the sched_domain containing sg.
2577 2578 2579 2580 2581 2582 2583 2584 2585 2586
 * @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,
			enum cpu_idle_type idle, int *sd_idle,
			const struct cpumask *cpus, int *balance,
			struct sd_lb_stats *sds)
{
	struct sched_domain *child = sd->child;
2587
	struct sched_group *sg = sd->groups;
2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599
	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;

2600
		local_group = cpumask_test_cpu(this_cpu, sched_group_cpus(sg));
2601
		memset(&sgs, 0, sizeof(sgs));
2602
		update_sg_lb_stats(sd, sg, this_cpu, idle, load_idx, sd_idle,
2603 2604
				local_group, cpus, balance, &sgs);

P
Peter Zijlstra 已提交
2605
		if (local_group && !(*balance))
2606 2607 2608
			return;

		sds->total_load += sgs.group_load;
2609
		sds->total_pwr += sg->cpu_power;
2610 2611 2612

		/*
		 * In case the child domain prefers tasks go to siblings
2613
		 * first, lower the sg capacity to one so that we'll try
2614 2615 2616 2617 2618 2619
		 * 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).
2620
		 */
2621
		if (prefer_sibling && !local_group && sds->this_has_capacity)
2622 2623 2624 2625
			sgs.group_capacity = min(sgs.group_capacity, 1UL);

		if (local_group) {
			sds->this_load = sgs.avg_load;
2626
			sds->this = sg;
2627 2628
			sds->this_nr_running = sgs.sum_nr_running;
			sds->this_load_per_task = sgs.sum_weighted_load;
2629
			sds->this_has_capacity = sgs.group_has_capacity;
2630
		} else if (update_sd_pick_busiest(sd, sds, sg, &sgs, this_cpu)) {
2631
			sds->max_load = sgs.avg_load;
2632
			sds->busiest = sg;
2633
			sds->busiest_nr_running = sgs.sum_nr_running;
2634
			sds->busiest_group_capacity = sgs.group_capacity;
2635
			sds->busiest_load_per_task = sgs.sum_weighted_load;
2636
			sds->busiest_has_capacity = sgs.group_has_capacity;
2637 2638 2639
			sds->group_imb = sgs.group_imb;
		}

2640 2641 2642 2643 2644
		update_sd_power_savings_stats(sg, sds, local_group, &sgs);
		sg = sg->next;
	} while (sg != sd->groups);
}

M
Michael Neuling 已提交
2645
int __weak arch_sd_sibling_asym_packing(void)
2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666
{
       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.
 *
2667 2668 2669
 * Returns 1 when packing is required and a task should be moved to
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693
 * @sd: The sched_domain whose packing is to be checked.
 * @sds: Statistics of the sched_domain which is to be packed
 * @this_cpu: The cpu at whose sched_domain we're performing load-balance.
 * @imbalance: returns amount of imbalanced due to packing.
 */
static int check_asym_packing(struct sched_domain *sd,
			      struct sd_lb_stats *sds,
			      int this_cpu, unsigned long *imbalance)
{
	int busiest_cpu;

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

	if (!sds->busiest)
		return 0;

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

	*imbalance = DIV_ROUND_CLOSEST(sds->max_load * sds->busiest->cpu_power,
				       SCHED_LOAD_SCALE);
	return 1;
2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708
}

/**
 * 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;
2709
	unsigned long scaled_busy_load_per_task;
2710 2711 2712 2713 2714 2715 2716 2717 2718 2719

	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);

2720 2721 2722 2723 2724 2725
	scaled_busy_load_per_task = sds->busiest_load_per_task
						 * SCHED_LOAD_SCALE;
	scaled_busy_load_per_task /= sds->busiest->cpu_power;

	if (sds->max_load - sds->this_load + scaled_busy_load_per_task >=
			(scaled_busy_load_per_task * imbn)) {
2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775
		*imbalance = sds->busiest_load_per_task;
		return;
	}

	/*
	 * OK, we don't have enough imbalance to justify moving tasks,
	 * however we may be able to increase total CPU power used by
	 * moving them.
	 */

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

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

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

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

/**
 * calculate_imbalance - Calculate the amount of imbalance present within the
 *			 groups of a given sched_domain during load balance.
 * @sds: statistics of the sched_domain whose imbalance is to be calculated.
 * @this_cpu: Cpu for which currently load balance is being performed.
 * @imbalance: The variable to store the imbalance.
 */
static inline void calculate_imbalance(struct sd_lb_stats *sds, int this_cpu,
		unsigned long *imbalance)
{
2776 2777 2778 2779 2780 2781 2782 2783
	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);
	}

2784 2785 2786 2787 2788 2789 2790 2791 2792 2793
	/*
	 * 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);
	}

2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816
	if (!sds->group_imb) {
		/*
		 * Don't want to pull so many tasks that a group would go idle.
		 */
		load_above_capacity = (sds->busiest_nr_running -
						sds->busiest_group_capacity);

		load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_LOAD_SCALE);

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

	/*
	 * We're trying to get all the cpus to the average_load, so we don't
	 * want to push ourselves above the average load, nor do we wish to
	 * reduce the max loaded cpu below the average load. At the same time,
	 * we also don't want to reduce the group load below the group capacity
	 * (so that we can implement power-savings policies etc). Thus we look
	 * for the minimum possible imbalance.
	 * Be careful of negative numbers as they'll appear as very large values
	 * with unsigned longs.
	 */
	max_pull = min(sds->max_load - sds->avg_load, load_above_capacity);
2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832

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

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

}
2833

2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884
/******* 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.
 * @sd_idle: The idleness of sd
 * @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,
		   int *sd_idle, const struct cpumask *cpus, int *balance)
{
	struct sd_lb_stats sds;

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

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

	/* Cases where imbalance does not exist from POV of this_cpu */
	/* 1) this_cpu is not the appropriate cpu to perform load balancing
	 *    at this level.
	 * 2) There is no busy sibling group to pull from.
	 * 3) This group is the busiest group.
	 * 4) This group is more busy than the avg busieness at this
	 *    sched_domain.
	 * 5) The imbalance is within the specified limit.
2885 2886 2887 2888 2889
	 *
	 * Note: when doing newidle balance, if the local group has excess
	 * capacity (i.e. nr_running < group_capacity) and the busiest group
	 * does not have any capacity, we force a load balance to pull tasks
	 * to the local group. In this case, we skip past checks 3, 4 and 5.
2890
	 */
P
Peter Zijlstra 已提交
2891
	if (!(*balance))
2892 2893
		goto ret;

2894 2895 2896 2897
	if ((idle == CPU_IDLE || idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(sd, &sds, this_cpu, imbalance))
		return sds.busiest;

2898 2899 2900
	if (!sds.busiest || sds.busiest_nr_running == 0)
		goto out_balanced;

2901 2902 2903 2904 2905
	/*  SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
	if (idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
			!sds.busiest_has_capacity)
		goto force_balance;

2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916
	if (sds.this_load >= sds.max_load)
		goto out_balanced;

	sds.avg_load = (SCHED_LOAD_SCALE * sds.total_load) / sds.total_pwr;

	if (sds.this_load >= sds.avg_load)
		goto out_balanced;

	if (100 * sds.max_load <= sd->imbalance_pct * sds.this_load)
		goto out_balanced;

2917
force_balance:
2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937
	/* 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 *
2938 2939 2940
find_busiest_queue(struct sched_domain *sd, struct sched_group *group,
		   enum cpu_idle_type idle, unsigned long imbalance,
		   const struct cpumask *cpus)
2941 2942 2943 2944 2945 2946 2947 2948 2949 2950
{
	struct rq *busiest = NULL, *rq;
	unsigned long max_load = 0;
	int i;

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

2951 2952 2953
		if (!capacity)
			capacity = fix_small_capacity(sd, group);

2954 2955 2956 2957
		if (!cpumask_test_cpu(i, cpus))
			continue;

		rq = cpu_rq(i);
2958
		wl = weighted_cpuload(i);
2959

2960 2961 2962 2963
		/*
		 * When comparing with imbalance, use weighted_cpuload()
		 * which is not scaled with the cpu power.
		 */
2964 2965 2966
		if (capacity && rq->nr_running == 1 && wl > imbalance)
			continue;

2967 2968 2969 2970 2971 2972 2973 2974
		/*
		 * For the load comparisons with the other cpu's, consider
		 * the weighted_cpuload() scaled with the cpu power, so that
		 * the load can be moved away from the cpu that is potentially
		 * running at a lower capacity.
		 */
		wl = (wl * SCHED_LOAD_SCALE) / power;

2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992
		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);

2993 2994
static int need_active_balance(struct sched_domain *sd, int sd_idle, int idle,
			       int busiest_cpu, int this_cpu)
2995 2996
{
	if (idle == CPU_NEWLY_IDLE) {
2997 2998 2999 3000 3001 3002 3003 3004 3005

		/*
		 * 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;

3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035
		/*
		 * 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 (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
		    !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
			return 0;

		if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP)
			return 0;
	}

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

3036 3037
static int active_load_balance_cpu_stop(void *data);

3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078
/*
 * 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)
{
	int ld_moved, all_pinned = 0, active_balance = 0, sd_idle = 0;
	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);

	/*
	 * When power savings policy is enabled for the parent domain, idle
	 * sibling can pick up load irrespective of busy siblings. In this case,
	 * let the state of idle sibling percolate up as CPU_IDLE, instead of
	 * portraying it as CPU_NOT_IDLE.
	 */
	if (idle != CPU_NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER &&
	    !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
		sd_idle = 1;

	schedstat_inc(sd, lb_count[idle]);

redo:
	group = find_busiest_group(sd, this_cpu, &imbalance, idle, &sd_idle,
				   cpus, balance);

	if (*balance == 0)
		goto out_balanced;

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

3079
	busiest = find_busiest_queue(sd, group, idle, imbalance, cpus);
3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120
	if (!busiest) {
		schedstat_inc(sd, lb_nobusyq[idle]);
		goto out_balanced;
	}

	BUG_ON(busiest == this_rq);

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

	ld_moved = 0;
	if (busiest->nr_running > 1) {
		/*
		 * Attempt to move tasks. If find_busiest_group has found
		 * an imbalance but busiest->nr_running <= 1, the group is
		 * still unbalanced. ld_moved simply stays zero, so it is
		 * correctly treated as an imbalance.
		 */
		local_irq_save(flags);
		double_rq_lock(this_rq, busiest);
		ld_moved = move_tasks(this_rq, this_cpu, busiest,
				      imbalance, sd, idle, &all_pinned);
		double_rq_unlock(this_rq, busiest);
		local_irq_restore(flags);

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

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

	if (!ld_moved) {
		schedstat_inc(sd, lb_failed[idle]);
3121 3122 3123 3124 3125 3126 3127 3128
		/*
		 * 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++;
3129

3130 3131
		if (need_active_balance(sd, sd_idle, idle, cpu_of(busiest),
					this_cpu)) {
3132 3133
			raw_spin_lock_irqsave(&busiest->lock, flags);

3134 3135 3136
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
3137 3138 3139 3140 3141 3142 3143 3144 3145
			 */
			if (!cpumask_test_cpu(this_cpu,
					      &busiest->curr->cpus_allowed)) {
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
				all_pinned = 1;
				goto out_one_pinned;
			}

3146 3147 3148 3149 3150
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
3151 3152 3153 3154 3155 3156
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
3157

3158
			if (active_balance)
3159 3160 3161
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226

			/*
			 * 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;
	}

	if (!ld_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
	    !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
		ld_moved = -1;

	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;

	if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
	    !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
		ld_moved = -1;
	else
		ld_moved = 0;
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;

3227 3228 3229 3230 3231
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

3232 3233
	for_each_domain(this_cpu, sd) {
		unsigned long interval;
3234
		int balance = 1;
3235 3236 3237 3238

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

3239
		if (sd->flags & SD_BALANCE_NEWIDLE) {
3240
			/* If we've pulled tasks over stop searching: */
3241 3242 3243
			pulled_task = load_balance(this_cpu, this_rq,
						   sd, CPU_NEWLY_IDLE, &balance);
		}
3244 3245 3246 3247

		interval = msecs_to_jiffies(sd->balance_interval);
		if (time_after(next_balance, sd->last_balance + interval))
			next_balance = sd->last_balance + interval;
3248
		if (pulled_task)
3249 3250
			break;
	}
3251 3252 3253

	raw_spin_lock(&this_rq->lock);

3254 3255 3256 3257 3258 3259 3260 3261 3262 3263
	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;
	}
}

/*
3264 3265 3266 3267
 * 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.
3268
 */
3269
static int active_load_balance_cpu_stop(void *data)
3270
{
3271 3272
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
3273
	int target_cpu = busiest_rq->push_cpu;
3274
	struct rq *target_rq = cpu_rq(target_cpu);
3275
	struct sched_domain *sd;
3276 3277 3278 3279 3280 3281 3282

	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;
3283 3284 3285

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
3286
		goto out_unlock;
3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314

	/*
	 * This condition is "impossible", if it occurs
	 * we need to fix it. Originally reported by
	 * Bjorn Helgaas on a 128-cpu setup.
	 */
	BUG_ON(busiest_rq == target_rq);

	/* move a task from busiest_rq to target_rq */
	double_lock_balance(busiest_rq, target_rq);

	/* Search for an sd spanning us and the target CPU. */
	for_each_domain(target_cpu, sd) {
		if ((sd->flags & SD_LOAD_BALANCE) &&
		    cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
				break;
	}

	if (likely(sd)) {
		schedstat_inc(sd, alb_count);

		if (move_one_task(target_rq, target_cpu, busiest_rq,
				  sd, CPU_IDLE))
			schedstat_inc(sd, alb_pushed);
		else
			schedstat_inc(sd, alb_failed);
	}
	double_unlock_balance(busiest_rq, target_rq);
3315 3316 3317 3318
out_unlock:
	busiest_rq->active_balance = 0;
	raw_spin_unlock_irq(&busiest_rq->lock);
	return 0;
3319 3320 3321
}

#ifdef CONFIG_NO_HZ
3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347

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.
 */
3348 3349
static struct {
	atomic_t load_balancer;
3350 3351 3352 3353 3354 3355
	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;
3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408

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)
{
3409
	cpumask_and(nohz.grp_idle_mask, nohz.idle_cpus_mask,
3410 3411 3412 3413 3414 3415
					sched_group_cpus(ilb_group));

	/*
	 * A sched_group is semi-idle when it has atleast one busy cpu
	 * and atleast one idle cpu.
	 */
3416
	if (cpumask_empty(nohz.grp_idle_mask))
3417 3418
		return 0;

3419
	if (cpumask_equal(nohz.grp_idle_mask, sched_group_cpus(ilb_group)))
3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451
		return 0;

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

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

	/*
	 * Optimize for the case when we have no idle CPUs or only one
	 * idle CPU. Don't walk the sched_domain hierarchy in such cases
	 */
3452
	if (cpumask_weight(nohz.idle_cpus_mask) < 2)
3453 3454 3455 3456 3457 3458 3459
		goto out_done;

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

		do {
			if (is_semi_idle_group(ilb_group))
3460
				return cpumask_first(nohz.grp_idle_mask);
3461 3462 3463 3464 3465 3466 3467

			ilb_group = ilb_group->next;

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

out_done:
3468
	return nr_cpu_ids;
3469 3470 3471 3472
}
#else /*  (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */
static inline int find_new_ilb(int call_cpu)
{
3473
	return nr_cpu_ids;
3474 3475 3476
}
#endif

3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500 3501 3502 3503 3504 3505
/*
 * 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;
}

3506 3507 3508
/*
 * 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
3509
 * load balancing on behalf of all those cpus.
3510
 *
3511 3512 3513
 * 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.
3514
 *
3515 3516 3517
 * 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).
3518
 */
3519
void select_nohz_load_balancer(int stop_tick)
3520 3521 3522 3523 3524 3525
{
	int cpu = smp_processor_id();

	if (stop_tick) {
		if (!cpu_active(cpu)) {
			if (atomic_read(&nohz.load_balancer) != cpu)
3526
				return;
3527 3528 3529 3530 3531

			/*
			 * If we are going offline and still the leader,
			 * give up!
			 */
3532 3533
			if (atomic_cmpxchg(&nohz.load_balancer, cpu,
					   nr_cpu_ids) != cpu)
3534 3535
				BUG();

3536
			return;
3537 3538
		}

3539
		cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
3540

3541 3542 3543 3544
		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);
3545

3546
		if (atomic_read(&nohz.load_balancer) >= nr_cpu_ids) {
3547 3548
			int new_ilb;

3549 3550 3551 3552 3553
			/* make me the ilb owner */
			if (atomic_cmpxchg(&nohz.load_balancer, nr_cpu_ids,
					   cpu) != nr_cpu_ids)
				return;

3554 3555 3556 3557 3558 3559
			/*
			 * 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) {
3560
				atomic_set(&nohz.load_balancer, nr_cpu_ids);
3561
				resched_cpu(new_ilb);
3562
				return;
3563
			}
3564
			return;
3565 3566
		}
	} else {
3567 3568
		if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
			return;
3569

3570
		cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
3571 3572

		if (atomic_read(&nohz.load_balancer) == cpu)
3573 3574
			if (atomic_cmpxchg(&nohz.load_balancer, cpu,
					   nr_cpu_ids) != cpu)
3575 3576
				BUG();
	}
3577
	return;
3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 3599
}
#endif

static DEFINE_SPINLOCK(balancing);

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

P
Peter Zijlstra 已提交
3600 3601
	update_shares(cpu);

3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649 3650 3651 3652 3653 3654 3655 3656 3657 3658 3659 3660
	for_each_domain(cpu, sd) {
		if (!(sd->flags & SD_LOAD_BALANCE))
			continue;

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

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

		need_serialize = sd->flags & SD_SERIALIZE;

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

		if (time_after_eq(jiffies, sd->last_balance + interval)) {
			if (load_balance(cpu, rq, sd, idle, &balance)) {
				/*
				 * We've pulled tasks over so either we're no
				 * longer idle, or one of our SMT siblings is
				 * not idle.
				 */
				idle = CPU_NOT_IDLE;
			}
			sd->last_balance = jiffies;
		}
		if (need_serialize)
			spin_unlock(&balancing);
out:
		if (time_after(next_balance, sd->last_balance + interval)) {
			next_balance = sd->last_balance + interval;
			update_next_balance = 1;
		}

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

	/*
	 * next_balance will be updated only when there is a need.
	 * When the cpu is attached to null domain for ex, it will not be
	 * updated.
	 */
	if (likely(update_next_balance))
		rq->next_balance = next_balance;
}

3661
#ifdef CONFIG_NO_HZ
3662
/*
3663
 * In CONFIG_NO_HZ case, the idle balance kickee will do the
3664 3665
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
3666 3667 3668 3669 3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689
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);
3690
		update_rq_clock(this_rq);
3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722 3723 3724
		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
3725
	if (rq->idle_at_tick)
3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754 3755 3756
		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).
 */
3757 3758 3759 3760 3761 3762 3763 3764 3765 3766
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);

	/*
3767
	 * If this cpu has a pending nohz_balance_kick, then do the
3768 3769 3770
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
3771
	nohz_idle_balance(this_cpu, idle);
3772 3773 3774 3775
}

static inline int on_null_domain(int cpu)
{
3776
	return !rcu_dereference_sched(cpu_rq(cpu)->sd);
3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787
}

/*
 * 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);
3788 3789 3790 3791
#ifdef CONFIG_NO_HZ
	else if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
		nohz_balancer_kick(cpu);
#endif
3792 3793
}

3794 3795 3796 3797 3798 3799 3800 3801 3802 3803
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
}

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

3804 3805 3806 3807 3808 3809 3810 3811 3812
#else	/* CONFIG_SMP */

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

3813
#endif /* CONFIG_SMP */
3814

3815 3816 3817
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
3818
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
3819 3820 3821 3822 3823 3824
{
	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
3825
		entity_tick(cfs_rq, se, queued);
3826 3827 3828 3829
	}
}

/*
P
Peter Zijlstra 已提交
3830 3831 3832
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
3833
 */
P
Peter Zijlstra 已提交
3834
static void task_fork_fair(struct task_struct *p)
3835
{
P
Peter Zijlstra 已提交
3836
	struct cfs_rq *cfs_rq = task_cfs_rq(current);
3837
	struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
3838
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
3839 3840 3841
	struct rq *rq = this_rq();
	unsigned long flags;

3842
	raw_spin_lock_irqsave(&rq->lock, flags);
3843

3844 3845
	update_rq_clock(rq);

3846 3847
	if (unlikely(task_cpu(p) != this_cpu)) {
		rcu_read_lock();
P
Peter Zijlstra 已提交
3848
		__set_task_cpu(p, this_cpu);
3849 3850
		rcu_read_unlock();
	}
3851

3852
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
3853

3854 3855
	if (curr)
		se->vruntime = curr->vruntime;
3856
	place_entity(cfs_rq, se, 1);
3857

P
Peter Zijlstra 已提交
3858
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
3859
		/*
3860 3861 3862
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
3863
		swap(curr->vruntime, se->vruntime);
3864
		resched_task(rq->curr);
3865
	}
3866

3867 3868
	se->vruntime -= cfs_rq->min_vruntime;

3869
	raw_spin_unlock_irqrestore(&rq->lock, flags);
3870 3871
}

3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887
/*
 * Priority of the task has changed. Check to see if we preempt
 * the current task.
 */
static void prio_changed_fair(struct rq *rq, struct task_struct *p,
			      int oldprio, int running)
{
	/*
	 * 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
	 */
	if (running) {
		if (p->prio > oldprio)
			resched_task(rq->curr);
	} else
3888
		check_preempt_curr(rq, p, 0);
3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904
}

/*
 * We switched to the sched_fair class.
 */
static void switched_to_fair(struct rq *rq, struct task_struct *p,
			     int running)
{
	/*
	 * 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.
	 */
	if (running)
		resched_task(rq->curr);
	else
3905
		check_preempt_curr(rq, p, 0);
3906 3907
}

3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920
/* 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
3921
#ifdef CONFIG_FAIR_GROUP_SCHED
3922
static void task_move_group_fair(struct task_struct *p, int on_rq)
P
Peter Zijlstra 已提交
3923
{
3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939
	/*
	 * 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));
3940
	if (!on_rq)
3941
		p->se.vruntime += cfs_rq_of(&p->se)->min_vruntime;
P
Peter Zijlstra 已提交
3942 3943 3944
}
#endif

3945
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
3946 3947 3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959
{
	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;
}

3960 3961 3962
/*
 * All the scheduling class methods:
 */
3963 3964
static const struct sched_class fair_sched_class = {
	.next			= &idle_sched_class,
3965 3966 3967 3968
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,

I
Ingo Molnar 已提交
3969
	.check_preempt_curr	= check_preempt_wakeup,
3970 3971 3972 3973

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

3974
#ifdef CONFIG_SMP
L
Li Zefan 已提交
3975 3976
	.select_task_rq		= select_task_rq_fair,

3977 3978
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
3979 3980

	.task_waking		= task_waking_fair,
3981
#endif
3982

3983
	.set_curr_task          = set_curr_task_fair,
3984
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
3985
	.task_fork		= task_fork_fair,
3986 3987 3988

	.prio_changed		= prio_changed_fair,
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
3989

3990 3991
	.get_rr_interval	= get_rr_interval_fair,

P
Peter Zijlstra 已提交
3992
#ifdef CONFIG_FAIR_GROUP_SCHED
3993
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
3994
#endif
3995 3996 3997
};

#ifdef CONFIG_SCHED_DEBUG
3998
static void print_cfs_stats(struct seq_file *m, int cpu)
3999 4000 4001
{
	struct cfs_rq *cfs_rq;

4002
	rcu_read_lock();
4003
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
4004
		print_cfs_rq(m, cpu, cfs_rq);
4005
	rcu_read_unlock();
4006 4007
}
#endif