sched_fair.c 107.8 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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/*
 * The exponential sliding  window over which load is averaged for shares
 * distribution.
 * (default: 10msec)
 */
unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL;

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static const struct sched_class fair_sched_class;

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/**************************************************************
 * CFS operations on generic schedulable entities:
 */

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#ifdef CONFIG_FAIR_GROUP_SCHED
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/* cpu runqueue to which this cfs_rq is attached */
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
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	return cfs_rq->rq;
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}

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/* An entity is a task if it doesn't "own" a runqueue */
#define entity_is_task(se)	(!se->my_q)
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static inline struct task_struct *task_of(struct sched_entity *se)
{
#ifdef CONFIG_SCHED_DEBUG
	WARN_ON_ONCE(!entity_is_task(se));
#endif
	return container_of(se, struct task_struct, se);
}

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/* Walk up scheduling entities hierarchy */
#define for_each_sched_entity(se) \
		for (; se; se = se->parent)

static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
{
	return p->se.cfs_rq;
}

/* runqueue on which this entity is (to be) queued */
static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
{
	return se->cfs_rq;
}

/* runqueue "owned" by this group */
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
{
	return grp->my_q;
}

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

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static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (!cfs_rq->on_list) {
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		/*
		 * Ensure we either appear before our parent (if already
		 * enqueued) or force our parent to appear after us when it is
		 * enqueued.  The fact that we always enqueue bottom-up
		 * reduces this to two cases.
		 */
		if (cfs_rq->tg->parent &&
		    cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) {
			list_add_rcu(&cfs_rq->leaf_cfs_rq_list,
				&rq_of(cfs_rq)->leaf_cfs_rq_list);
		} else {
			list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list,
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				&rq_of(cfs_rq)->leaf_cfs_rq_list);
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		}
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		cfs_rq->on_list = 1;
	}
}

static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
	if (cfs_rq->on_list) {
		list_del_rcu(&cfs_rq->leaf_cfs_rq_list);
		cfs_rq->on_list = 0;
	}
}

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/* Iterate thr' all leaf cfs_rq's on a runqueue */
#define for_each_leaf_cfs_rq(rq, cfs_rq) \
	list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)

/* Do the two (enqueued) entities belong to the same group ? */
static inline int
is_same_group(struct sched_entity *se, struct sched_entity *pse)
{
	if (se->cfs_rq == pse->cfs_rq)
		return 1;

	return 0;
}

static inline struct sched_entity *parent_entity(struct sched_entity *se)
{
	return se->parent;
}

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/* return depth at which a sched entity is present in the hierarchy */
static inline int depth_se(struct sched_entity *se)
{
	int depth = 0;

	for_each_sched_entity(se)
		depth++;

	return depth;
}

static void
find_matching_se(struct sched_entity **se, struct sched_entity **pse)
{
	int se_depth, pse_depth;

	/*
	 * preemption test can be made between sibling entities who are in the
	 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
	 * both tasks until we find their ancestors who are siblings of common
	 * parent.
	 */

	/* First walk up until both entities are at same depth */
	se_depth = depth_se(*se);
	pse_depth = depth_se(*pse);

	while (se_depth > pse_depth) {
		se_depth--;
		*se = parent_entity(*se);
	}

	while (pse_depth > se_depth) {
		pse_depth--;
		*pse = parent_entity(*pse);
	}

	while (!is_same_group(*se, *pse)) {
		*se = parent_entity(*se);
		*pse = parent_entity(*pse);
	}
}

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#else	/* !CONFIG_FAIR_GROUP_SCHED */

static inline struct task_struct *task_of(struct sched_entity *se)
{
	return container_of(se, struct task_struct, se);
}
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
	return container_of(cfs_rq, struct rq, cfs);
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}

#define entity_is_task(se)	1

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#define for_each_sched_entity(se) \
		for (; se; se = NULL)
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static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
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{
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	return &task_rq(p)->cfs;
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}

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static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
{
	struct task_struct *p = task_of(se);
	struct rq *rq = task_rq(p);

	return &rq->cfs;
}

/* runqueue "owned" by this group */
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
{
	return NULL;
}

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

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static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
}

static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq)
{
}

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

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

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

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

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#endif	/* CONFIG_FAIR_GROUP_SCHED */

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

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

	return min_vruntime;
}

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

	return min_vruntime;
}

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

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

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

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

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

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

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

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

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

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

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

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

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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static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update);
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static void update_cfs_shares(struct cfs_rq *cfs_rq, long weight_delta);

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/*
 * Update the current task's runtime statistics. Skip current tasks that
 * are not in our scheduling class.
 */
static inline void
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__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
	      unsigned long delta_exec)
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{
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	unsigned long delta_exec_weighted;
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	schedstat_set(curr->statistics.exec_max,
		      max((u64)delta_exec, curr->statistics.exec_max));
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	curr->sum_exec_runtime += delta_exec;
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	schedstat_add(cfs_rq, exec_clock, delta_exec);
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	delta_exec_weighted = calc_delta_fair(delta_exec, curr);
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	curr->vruntime += delta_exec_weighted;
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	update_min_vruntime(cfs_rq);
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#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
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	cfs_rq->load_unacc_exec_time += delta_exec;
#endif
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}

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

	if (unlikely(!curr))
		return;

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

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

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

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

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

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

/*
 * We are picking a new current task - update its stats:
 */
static inline void
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update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
	/*
	 * We are starting a new run period:
	 */
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	se->exec_start = rq_of(cfs_rq)->clock_task;
657 658 659 660 661 662
}

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

663 664 665 666 667 668 669 670 671 672 673 674 675
#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

676 677 678 679
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
680 681
	if (!parent_entity(se))
		inc_cpu_load(rq_of(cfs_rq), se->load.weight);
682
	if (entity_is_task(se)) {
683
		add_cfs_task_weight(cfs_rq, se->load.weight);
684 685
		list_add(&se->group_node, &cfs_rq->tasks);
	}
686 687 688 689 690 691 692
	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);
693 694
	if (!parent_entity(se))
		dec_cpu_load(rq_of(cfs_rq), se->load.weight);
695
	if (entity_is_task(se)) {
696
		add_cfs_task_weight(cfs_rq, -se->load.weight);
697 698
		list_del_init(&se->group_node);
	}
699 700 701
	cfs_rq->nr_running--;
}

702 703
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
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static void update_cfs_rq_load_contribution(struct cfs_rq *cfs_rq,
					    int global_update)
{
	struct task_group *tg = cfs_rq->tg;
	long load_avg;

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

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

static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
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{
721
	u64 period = sysctl_sched_shares_window;
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	u64 now, delta;
723
	unsigned long load = cfs_rq->load.weight;
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	if (!cfs_rq)
		return;

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

731 732 733 734 735 736 737
	/* truncate load history at 4 idle periods */
	if (cfs_rq->load_stamp > cfs_rq->load_last &&
	    now - cfs_rq->load_last > 4 * period) {
		cfs_rq->load_period = 0;
		cfs_rq->load_avg = 0;
	}

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	cfs_rq->load_stamp = now;
739
	cfs_rq->load_unacc_exec_time = 0;
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	cfs_rq->load_period += delta;
741 742 743 744
	if (load) {
		cfs_rq->load_last = now;
		cfs_rq->load_avg += delta * load;
	}
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746 747 748 749 750
	/* consider updating load contribution on each fold or truncate */
	if (global_update || cfs_rq->load_period > period
	    || !cfs_rq->load_period)
		update_cfs_rq_load_contribution(cfs_rq, global_update);

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	while (cfs_rq->load_period > period) {
		/*
		 * Inline assembly required to prevent the compiler
		 * optimising this loop into a divmod call.
		 * See __iter_div_u64_rem() for another example of this.
		 */
		asm("" : "+rm" (cfs_rq->load_period));
		cfs_rq->load_period /= 2;
		cfs_rq->load_avg /= 2;
	}
761

762 763
	if (!cfs_rq->curr && !cfs_rq->nr_running && !cfs_rq->load_avg)
		list_del_leaf_cfs_rq(cfs_rq);
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}

766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810
static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg,
				long weight_delta)
{
	long load_weight, load, shares;

	load = cfs_rq->load.weight + weight_delta;

	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;

	return shares;
}

static void update_entity_shares_tick(struct cfs_rq *cfs_rq)
{
	if (cfs_rq->load_unacc_exec_time > sysctl_sched_shares_window) {
		update_cfs_load(cfs_rq, 0);
		update_cfs_shares(cfs_rq, 0);
	}
}
# else /* CONFIG_SMP */
static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
{
}

static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg,
				long weight_delta)
{
	return tg->shares;
}

static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq)
{
}
# endif /* CONFIG_SMP */
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static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
			    unsigned long weight)
{
814 815 816 817
	if (se->on_rq) {
		/* commit outstanding execution time */
		if (cfs_rq->curr == se)
			update_curr(cfs_rq);
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		account_entity_dequeue(cfs_rq, se);
819
	}
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	update_load_set(&se->load, weight);

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

827
static void update_cfs_shares(struct cfs_rq *cfs_rq, long weight_delta)
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{
	struct task_group *tg;
	struct sched_entity *se;
831
	long shares;
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	if (!cfs_rq)
		return;

	tg = cfs_rq->tg;
	se = tg->se[cpu_of(rq_of(cfs_rq))];
	if (!se)
		return;
840 841 842 843 844
#ifndef CONFIG_SMP
	if (likely(se->load.weight == tg->shares))
		return;
#endif
	shares = calc_cfs_shares(cfs_rq, tg, weight_delta);
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	reweight_entity(cfs_rq_of(se), se, shares);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
849
static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update)
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{
}

853
static inline void update_cfs_shares(struct cfs_rq *cfs_rq, long weight_delta)
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{
}
856 857 858 859

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

862
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
863 864
{
#ifdef CONFIG_SCHEDSTATS
865 866 867 868 869
	struct task_struct *tsk = NULL;

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

870 871
	if (se->statistics.sleep_start) {
		u64 delta = rq_of(cfs_rq)->clock - se->statistics.sleep_start;
872 873 874 875

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

876 877
		if (unlikely(delta > se->statistics.sleep_max))
			se->statistics.sleep_max = delta;
878

879 880
		se->statistics.sleep_start = 0;
		se->statistics.sum_sleep_runtime += delta;
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882
		if (tsk) {
883
			account_scheduler_latency(tsk, delta >> 10, 1);
884 885
			trace_sched_stat_sleep(tsk, delta);
		}
886
	}
887 888
	if (se->statistics.block_start) {
		u64 delta = rq_of(cfs_rq)->clock - se->statistics.block_start;
889 890 891 892

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

893 894
		if (unlikely(delta > se->statistics.block_max))
			se->statistics.block_max = delta;
895

896 897
		se->statistics.block_start = 0;
		se->statistics.sum_sleep_runtime += delta;
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899
		if (tsk) {
900
			if (tsk->in_iowait) {
901 902
				se->statistics.iowait_sum += delta;
				se->statistics.iowait_count++;
903
				trace_sched_stat_iowait(tsk, delta);
904 905
			}

906 907 908 909 910 911 912 913 914 915 916
			/*
			 * 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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		}
918 919 920 921
	}
#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
}

935 936 937
static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
938
	u64 vruntime = cfs_rq->min_vruntime;
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940 941 942 943 944 945
	/*
	 * 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))
947
		vruntime += sched_vslice(cfs_rq, se);
948

949
	/* sleeps up to a single latency don't count. */
950
	if (!initial) {
951
		unsigned long thresh = sysctl_sched_latency;
952

953 954 955 956 957 958
		/*
		 * Halve their sleep time's effect, to allow
		 * for a gentler effect of sleepers:
		 */
		if (sched_feat(GENTLE_FAIR_SLEEPERS))
			thresh >>= 1;
959

960
		vruntime -= thresh;
961 962
	}

963 964 965
	/* ensure we never gain time by being placed backwards. */
	vruntime = max_vruntime(se->vruntime, vruntime);

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	se->vruntime = vruntime;
967 968
}

969
static void
970
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
971
{
972 973 974 975
	/*
	 * Update the normalized vruntime before updating min_vruntime
	 * through callig update_curr().
	 */
976
	if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING))
977 978
		se->vruntime += cfs_rq->min_vruntime;

979
	/*
980
	 * Update run-time statistics of the 'current'.
981
	 */
982
	update_curr(cfs_rq);
983
	update_cfs_load(cfs_rq, 0);
984
	update_cfs_shares(cfs_rq, se->load.weight);
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	account_entity_enqueue(cfs_rq, se);
986

987
	if (flags & ENQUEUE_WAKEUP) {
988
		place_entity(cfs_rq, se, 0);
989
		enqueue_sleeper(cfs_rq, se);
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	}
991

992
	update_stats_enqueue(cfs_rq, se);
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	check_spread(cfs_rq, se);
994 995
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
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	se->on_rq = 1;
997 998 999

	if (cfs_rq->nr_running == 1)
		list_add_leaf_cfs_rq(cfs_rq);
1000 1001
}

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static void __clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
1004
	if (!se || cfs_rq->last == se)
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		cfs_rq->last = NULL;

1007
	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);
}

1017
static void
1018
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
1019
{
1020 1021 1022 1023 1024
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);

1025
	update_stats_dequeue(cfs_rq, se);
1026
	if (flags & DEQUEUE_SLEEP) {
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#ifdef CONFIG_SCHEDSTATS
1028 1029 1030 1031
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
1032
				se->statistics.sleep_start = rq_of(cfs_rq)->clock;
1033
			if (tsk->state & TASK_UNINTERRUPTIBLE)
1034
				se->statistics.block_start = rq_of(cfs_rq)->clock;
1035
		}
1036
#endif
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	}

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	clear_buddies(cfs_rq, se);
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1041
	if (se != cfs_rq->curr)
1042
		__dequeue_entity(cfs_rq, se);
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	se->on_rq = 0;
1044
	update_cfs_load(cfs_rq, 0);
1045
	account_entity_dequeue(cfs_rq, se);
1046
	update_min_vruntime(cfs_rq);
1047
	update_cfs_shares(cfs_rq, 0);
1048 1049 1050 1051 1052 1053

	/*
	 * 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.
	 */
1054
	if (!(flags & DEQUEUE_SLEEP))
1055
		se->vruntime -= cfs_rq->min_vruntime;
1056 1057 1058 1059 1060
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
1061
static void
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check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
1063
{
1064 1065
	unsigned long ideal_runtime, delta_exec;

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	ideal_runtime = sched_slice(cfs_rq, curr);
1067
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
1068
	if (delta_exec > ideal_runtime) {
1069
		resched_task(rq_of(cfs_rq)->curr);
1070 1071 1072 1073 1074
		/*
		 * The current task ran long enough, ensure it doesn't get
		 * re-elected due to buddy favours.
		 */
		clear_buddies(cfs_rq, curr);
1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092
		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;

1093 1094 1095
		if (delta < 0)
			return;

1096 1097
		if (delta > ideal_runtime)
			resched_task(rq_of(cfs_rq)->curr);
1098
	}
1099 1100
}

1101
static void
1102
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
1103
{
1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114
	/* '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);
	}

1115
	update_stats_curr_start(cfs_rq, se);
1116
	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):
	 */
1123
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
1124
		se->statistics.slice_max = max(se->statistics.slice_max,
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			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
1128
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
1129 1130
}

1131 1132 1133
static int
wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);

1134
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
1135
{
1136
	struct sched_entity *se = __pick_next_entity(cfs_rq);
1137
	struct sched_entity *left = se;
1138

1139 1140
	if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
		se = cfs_rq->next;
1141

1142 1143 1144 1145 1146 1147 1148
	/*
	 * 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;
1151 1152
}

1153
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
1154 1155 1156 1157 1158 1159
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
1160
		update_curr(cfs_rq);
1161

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	check_spread(cfs_rq, prev);
1163
	if (prev->on_rq) {
1164
		update_stats_wait_start(cfs_rq, prev);
1165 1166 1167
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
	}
1168
	cfs_rq->curr = NULL;
1169 1170
}

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static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
1173 1174
{
	/*
1175
	 * Update run-time statistics of the 'current'.
1176
	 */
1177
	update_curr(cfs_rq);
1178

1179 1180 1181 1182 1183
	/*
	 * Update share accounting for long-running entities.
	 */
	update_entity_shares_tick(cfs_rq);

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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.
	 */
1189 1190 1191 1192
	if (queued) {
		resched_task(rq_of(cfs_rq)->curr);
		return;
	}
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	/*
	 * 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

1201
	if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
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		check_preempt_tick(cfs_rq, curr);
1203 1204 1205 1206 1207 1208
}

/**************************************************
 * 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.
		 */
1232
		if (rq->curr != p)
1233
			delta = max_t(s64, 10000LL, delta);
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Peter Zijlstra 已提交
1234

1235
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
1236 1237
	}
}
1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253

/*
 * 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);
}
1254
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
1255 1256 1257 1258
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
1259 1260 1261 1262

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
1263 1264
#endif

1265 1266 1267 1268 1269
/*
 * 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:
 */
1270
static void
1271
enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
1272 1273
{
	struct cfs_rq *cfs_rq;
1274
	struct sched_entity *se = &p->se;
1275 1276

	for_each_sched_entity(se) {
1277
		if (se->on_rq)
1278 1279
			break;
		cfs_rq = cfs_rq_of(se);
1280 1281
		enqueue_entity(cfs_rq, se, flags);
		flags = ENQUEUE_WAKEUP;
1282
	}
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1283

P
Peter Zijlstra 已提交
1284 1285 1286
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

1287
		update_cfs_load(cfs_rq, 0);
1288
		update_cfs_shares(cfs_rq, 0);
P
Peter Zijlstra 已提交
1289 1290
	}

1291
	hrtick_update(rq);
1292 1293 1294 1295 1296 1297 1298
}

/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
1299
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
1300 1301
{
	struct cfs_rq *cfs_rq;
1302
	struct sched_entity *se = &p->se;
1303 1304 1305

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
1306
		dequeue_entity(cfs_rq, se, flags);
P
Peter Zijlstra 已提交
1307

1308
		/* Don't dequeue parent if it has other entities besides us */
1309
		if (cfs_rq->load.weight)
1310
			break;
1311
		flags |= DEQUEUE_SLEEP;
1312
	}
P
Peter Zijlstra 已提交
1313

P
Peter Zijlstra 已提交
1314 1315 1316
	for_each_sched_entity(se) {
		struct cfs_rq *cfs_rq = cfs_rq_of(se);

1317
		update_cfs_load(cfs_rq, 0);
1318
		update_cfs_shares(cfs_rq, 0);
P
Peter Zijlstra 已提交
1319 1320
	}

1321
	hrtick_update(rq);
1322 1323 1324
}

/*
1325 1326 1327
 * 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.
1328
 */
1329
static void yield_task_fair(struct rq *rq)
1330
{
1331 1332 1333
	struct task_struct *curr = rq->curr;
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
	struct sched_entity *rightmost, *se = &curr->se;
1334 1335

	/*
1336 1337 1338 1339 1340
	 * Are we the only task in the tree?
	 */
	if (unlikely(cfs_rq->nr_running == 1))
		return;

P
Peter Zijlstra 已提交
1341 1342
	clear_buddies(cfs_rq, se);

1343
	if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {
1344
		update_rq_clock(rq);
1345
		/*
1346
		 * Update run-time statistics of the 'current'.
1347
		 */
D
Dmitry Adamushko 已提交
1348
		update_curr(cfs_rq);
1349 1350 1351 1352 1353

		return;
	}
	/*
	 * Find the rightmost entry in the rbtree:
1354
	 */
D
Dmitry Adamushko 已提交
1355
	rightmost = __pick_last_entity(cfs_rq);
1356 1357 1358
	/*
	 * Already in the rightmost position?
	 */
1359
	if (unlikely(!rightmost || entity_before(rightmost, se)))
1360 1361 1362 1363
		return;

	/*
	 * Minimally necessary key value to be last in the tree:
D
Dmitry Adamushko 已提交
1364 1365
	 * Upon rescheduling, sched_class::put_prev_task() will place
	 * 'current' within the tree based on its new key value.
1366
	 */
1367
	se->vruntime = rightmost->vruntime + 1;
1368 1369
}

1370
#ifdef CONFIG_SMP
1371

1372 1373 1374 1375 1376 1377 1378 1379
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;
}

1380
#ifdef CONFIG_FAIR_GROUP_SCHED
1381 1382 1383 1384 1385 1386 1387
/*
 * 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
1388
static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
1389
{
P
Peter Zijlstra 已提交
1390
	struct sched_entity *se = tg->se[cpu];
1391 1392 1393 1394

	if (!tg->parent)
		return wl;

P
Peter Zijlstra 已提交
1395
	for_each_sched_entity(se) {
1396
		long lw, w;
P
Peter Zijlstra 已提交
1397

1398 1399
		tg = se->my_q->tg;
		w = se->my_q->load.weight;
1400

1401 1402 1403 1404
		/* use this cpu's instantaneous contribution */
		lw = atomic_read(&tg->load_weight);
		lw -= se->my_q->load_contribution;
		lw += w + wg;
P
Peter Zijlstra 已提交
1405

1406
		wl += w;
1407

1408 1409 1410 1411
		if (lw > 0 && wl < lw)
			wl = (wl * tg->shares) / lw;
		else
			wl = tg->shares;
1412

1413 1414 1415 1416
		/* zero point is MIN_SHARES */
		if (wl < MIN_SHARES)
			wl = MIN_SHARES;
		wl -= se->load.weight;
P
Peter Zijlstra 已提交
1417 1418
		wg = 0;
	}
1419

P
Peter Zijlstra 已提交
1420
	return wl;
1421
}
P
Peter Zijlstra 已提交
1422

1423
#else
P
Peter Zijlstra 已提交
1424

1425 1426
static inline unsigned long effective_load(struct task_group *tg, int cpu,
		unsigned long wl, unsigned long wg)
P
Peter Zijlstra 已提交
1427
{
1428
	return wl;
1429
}
P
Peter Zijlstra 已提交
1430

1431 1432
#endif

1433
static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
1434
{
1435 1436
	unsigned long this_load, load;
	int idx, this_cpu, prev_cpu;
1437
	unsigned long tl_per_task;
1438
	struct task_group *tg;
1439
	unsigned long weight;
1440
	int balanced;
1441

1442 1443 1444 1445 1446
	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);
1447

1448 1449 1450 1451 1452
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
1453
	rcu_read_lock();
1454 1455 1456 1457
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

1458
		this_load += effective_load(tg, this_cpu, -weight, -weight);
1459 1460
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
1461

1462 1463
	tg = task_group(p);
	weight = p->se.load.weight;
1464

1465 1466
	/*
	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
1467 1468 1469
	 * 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.
1470 1471 1472 1473
	 *
	 * Otherwise check if either cpus are near enough in load to allow this
	 * task to be woken on this_cpu.
	 */
1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488
	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;
1489
	rcu_read_unlock();
1490

1491
	/*
I
Ingo Molnar 已提交
1492 1493 1494
	 * If the currently running task will sleep within
	 * a reasonable amount of time then attract this newly
	 * woken task:
1495
	 */
1496 1497
	if (sync && balanced)
		return 1;
1498

1499
	schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts);
1500 1501
	tl_per_task = cpu_avg_load_per_task(this_cpu);

1502 1503 1504
	if (balanced ||
	    (this_load <= load &&
	     this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
1505 1506 1507 1508 1509
		/*
		 * This domain has SD_WAKE_AFFINE and
		 * p is cache cold in this domain, and
		 * there is no bad imbalance.
		 */
1510
		schedstat_inc(sd, ttwu_move_affine);
1511
		schedstat_inc(p, se.statistics.nr_wakeups_affine);
1512 1513 1514 1515 1516 1517

		return 1;
	}
	return 0;
}

1518 1519 1520 1521 1522
/*
 * find_idlest_group finds and returns the least busy CPU group within the
 * domain.
 */
static struct sched_group *
P
Peter Zijlstra 已提交
1523
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
1524
		  int this_cpu, int load_idx)
1525
{
1526
	struct sched_group *idlest = NULL, *group = sd->groups;
1527 1528
	unsigned long min_load = ULONG_MAX, this_load = 0;
	int imbalance = 100 + (sd->imbalance_pct-100)/2;
1529

1530 1531 1532 1533
	do {
		unsigned long load, avg_load;
		int local_group;
		int i;
1534

1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588
		/* 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;
1589 1590 1591
		}
	}

1592 1593
	return idlest;
}
1594

1595 1596 1597
/*
 * Try and locate an idle CPU in the sched_domain.
 */
1598
static int select_idle_sibling(struct task_struct *p, int target)
1599 1600 1601
{
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
1602
	struct sched_domain *sd;
1603 1604 1605
	int i;

	/*
1606 1607
	 * If the task is going to be woken-up on this cpu and if it is
	 * already idle, then it is the right target.
1608
	 */
1609 1610 1611 1612 1613 1614 1615 1616
	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))
1617
		return prev_cpu;
1618 1619

	/*
1620
	 * Otherwise, iterate the domains and find an elegible idle cpu.
1621
	 */
1622 1623
	for_each_domain(target, sd) {
		if (!(sd->flags & SD_SHARE_PKG_RESOURCES))
1624
			break;
1625 1626 1627 1628 1629 1630

		for_each_cpu_and(i, sched_domain_span(sd), &p->cpus_allowed) {
			if (idle_cpu(i)) {
				target = i;
				break;
			}
1631
		}
1632 1633 1634 1635 1636 1637 1638 1639

		/*
		 * 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;
1640 1641 1642 1643 1644
	}

	return target;
}

1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655
/*
 * 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.
 */
1656 1657
static int
select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_flags)
1658
{
1659
	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
1660 1661 1662
	int cpu = smp_processor_id();
	int prev_cpu = task_cpu(p);
	int new_cpu = cpu;
1663
	int want_affine = 0;
1664
	int want_sd = 1;
1665
	int sync = wake_flags & WF_SYNC;
1666

1667
	if (sd_flag & SD_BALANCE_WAKE) {
1668
		if (cpumask_test_cpu(cpu, &p->cpus_allowed))
1669 1670 1671
			want_affine = 1;
		new_cpu = prev_cpu;
	}
1672 1673

	for_each_domain(cpu, tmp) {
1674 1675 1676
		if (!(tmp->flags & SD_LOAD_BALANCE))
			continue;

1677
		/*
1678 1679
		 * If power savings logic is enabled for a domain, see if we
		 * are not overloaded, if so, don't balance wider.
1680
		 */
P
Peter Zijlstra 已提交
1681
		if (tmp->flags & (SD_POWERSAVINGS_BALANCE|SD_PREFER_LOCAL)) {
1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693
			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
1694 1695 1696 1697
			if (tmp->flags & SD_POWERSAVINGS_BALANCE)
				nr_running /= 2;

			if (nr_running < capacity)
1698
				want_sd = 0;
1699
		}
1700

1701
		/*
1702 1703
		 * If both cpu and prev_cpu are part of this domain,
		 * cpu is a valid SD_WAKE_AFFINE target.
1704
		 */
1705 1706 1707 1708
		if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
			affine_sd = tmp;
			want_affine = 0;
1709 1710
		}

1711 1712 1713
		if (!want_sd && !want_affine)
			break;

1714
		if (!(tmp->flags & sd_flag))
1715 1716
			continue;

1717 1718 1719 1720
		if (want_sd)
			sd = tmp;
	}

1721
	if (affine_sd) {
1722 1723 1724 1725
		if (cpu == prev_cpu || wake_affine(affine_sd, p, sync))
			return select_idle_sibling(p, cpu);
		else
			return select_idle_sibling(p, prev_cpu);
1726
	}
1727

1728
	while (sd) {
1729
		int load_idx = sd->forkexec_idx;
1730
		struct sched_group *group;
1731
		int weight;
1732

1733
		if (!(sd->flags & sd_flag)) {
1734 1735 1736
			sd = sd->child;
			continue;
		}
1737

1738 1739
		if (sd_flag & SD_BALANCE_WAKE)
			load_idx = sd->wake_idx;
1740

1741
		group = find_idlest_group(sd, p, cpu, load_idx);
1742 1743 1744 1745
		if (!group) {
			sd = sd->child;
			continue;
		}
I
Ingo Molnar 已提交
1746

1747
		new_cpu = find_idlest_cpu(group, p, cpu);
1748 1749 1750 1751
		if (new_cpu == -1 || new_cpu == cpu) {
			/* Now try balancing at a lower domain level of cpu */
			sd = sd->child;
			continue;
1752
		}
1753 1754 1755

		/* Now try balancing at a lower domain level of new_cpu */
		cpu = new_cpu;
1756
		weight = sd->span_weight;
1757 1758
		sd = NULL;
		for_each_domain(cpu, tmp) {
1759
			if (weight <= tmp->span_weight)
1760
				break;
1761
			if (tmp->flags & sd_flag)
1762 1763 1764
				sd = tmp;
		}
		/* while loop will break here if sd == NULL */
1765 1766
	}

1767
	return new_cpu;
1768 1769 1770
}
#endif /* CONFIG_SMP */

P
Peter Zijlstra 已提交
1771 1772
static unsigned long
wakeup_gran(struct sched_entity *curr, struct sched_entity *se)
1773 1774 1775 1776
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
P
Peter Zijlstra 已提交
1777 1778
	 * Since its curr running now, convert the gran from real-time
	 * to virtual-time in his units.
M
Mike Galbraith 已提交
1779 1780 1781 1782 1783 1784 1785 1786 1787
	 *
	 * 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.
1788
	 */
M
Mike Galbraith 已提交
1789 1790
	if (unlikely(se->load.weight != NICE_0_LOAD))
		gran = calc_delta_fair(gran, se);
1791 1792 1793 1794

	return gran;
}

1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816
/*
 * 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
1817
	gran = wakeup_gran(curr, se);
1818 1819 1820 1821 1822 1823
	if (vdiff > gran)
		return 1;

	return 0;
}

1824 1825
static void set_last_buddy(struct sched_entity *se)
{
1826 1827 1828 1829
	if (likely(task_of(se)->policy != SCHED_IDLE)) {
		for_each_sched_entity(se)
			cfs_rq_of(se)->last = se;
	}
1830 1831 1832 1833
}

static void set_next_buddy(struct sched_entity *se)
{
1834 1835 1836 1837
	if (likely(task_of(se)->policy != SCHED_IDLE)) {
		for_each_sched_entity(se)
			cfs_rq_of(se)->next = se;
	}
1838 1839
}

1840 1841 1842
/*
 * Preempt the current task with a newly woken task if needed:
 */
1843
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
1844 1845
{
	struct task_struct *curr = rq->curr;
1846
	struct sched_entity *se = &curr->se, *pse = &p->se;
1847
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
1848
	int scale = cfs_rq->nr_running >= sched_nr_latency;
1849

I
Ingo Molnar 已提交
1850 1851 1852
	if (unlikely(se == pse))
		return;

1853
	if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK))
M
Mike Galbraith 已提交
1854
		set_next_buddy(pse);
P
Peter Zijlstra 已提交
1855

1856 1857 1858 1859 1860 1861 1862
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
	 */
	if (test_tsk_need_resched(curr))
		return;

1863
	/*
1864
	 * Batch and idle tasks do not preempt (their preemption is driven by
1865 1866
	 * the tick):
	 */
1867
	if (unlikely(p->policy != SCHED_NORMAL))
1868
		return;
1869

1870
	/* Idle tasks are by definition preempted by everybody. */
1871 1872
	if (unlikely(curr->policy == SCHED_IDLE))
		goto preempt;
1873

1874 1875 1876
	if (!sched_feat(WAKEUP_PREEMPT))
		return;

1877
	update_curr(cfs_rq);
1878
	find_matching_se(&se, &pse);
1879
	BUG_ON(!pse);
1880 1881
	if (wakeup_preempt_entity(se, pse) == 1)
		goto preempt;
1882

1883
	return;
1884

1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900
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);
1901 1902
}

1903
static struct task_struct *pick_next_task_fair(struct rq *rq)
1904
{
P
Peter Zijlstra 已提交
1905
	struct task_struct *p;
1906 1907 1908
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

1909
	if (!cfs_rq->nr_running)
1910 1911 1912
		return NULL;

	do {
1913
		se = pick_next_entity(cfs_rq);
1914
		set_next_entity(cfs_rq, se);
1915 1916 1917
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

P
Peter Zijlstra 已提交
1918 1919 1920 1921
	p = task_of(se);
	hrtick_start_fair(rq, p);

	return p;
1922 1923 1924 1925 1926
}

/*
 * Account for a descheduled task:
 */
1927
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
1928 1929 1930 1931 1932 1933
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
1934
		put_prev_entity(cfs_rq, se);
1935 1936 1937
	}
}

1938
#ifdef CONFIG_SMP
1939 1940 1941 1942
/**************************************************
 * Fair scheduling class load-balancing methods:
 */

1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971
/*
 * pull_task - move a task from a remote runqueue to the local runqueue.
 * Both runqueues must be locked.
 */
static void pull_task(struct rq *src_rq, struct task_struct *p,
		      struct rq *this_rq, int this_cpu)
{
	deactivate_task(src_rq, p, 0);
	set_task_cpu(p, this_cpu);
	activate_task(this_rq, p, 0);
	check_preempt_curr(this_rq, p, 0);
}

/*
 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
 */
static
int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
		     struct sched_domain *sd, enum cpu_idle_type idle,
		     int *all_pinned)
{
	int tsk_cache_hot = 0;
	/*
	 * We do not migrate tasks that are:
	 * 1) running (obviously), or
	 * 2) cannot be migrated to this CPU due to cpus_allowed, or
	 * 3) are cache-hot on their current CPU.
	 */
	if (!cpumask_test_cpu(this_cpu, &p->cpus_allowed)) {
1972
		schedstat_inc(p, se.statistics.nr_failed_migrations_affine);
1973 1974 1975 1976 1977
		return 0;
	}
	*all_pinned = 0;

	if (task_running(rq, p)) {
1978
		schedstat_inc(p, se.statistics.nr_failed_migrations_running);
1979 1980 1981 1982 1983 1984 1985 1986 1987
		return 0;
	}

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

1988
	tsk_cache_hot = task_hot(p, rq->clock_task, sd);
1989 1990 1991 1992 1993
	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]);
1994
			schedstat_inc(p, se.statistics.nr_forced_migrations);
1995 1996 1997 1998 1999 2000
		}
#endif
		return 1;
	}

	if (tsk_cache_hot) {
2001
		schedstat_inc(p, se.statistics.nr_failed_migrations_hot);
2002 2003 2004 2005 2006
		return 0;
	}
	return 1;
}

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 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042
/*
 * 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;
}

2043 2044 2045 2046
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,
2047
	      int *this_best_prio, struct cfs_rq *busiest_cfs_rq)
2048 2049 2050
{
	int loops = 0, pulled = 0, pinned = 0;
	long rem_load_move = max_load_move;
2051
	struct task_struct *p, *n;
2052 2053 2054 2055 2056 2057

	if (max_load_move == 0)
		goto out;

	pinned = 1;

2058 2059 2060
	list_for_each_entry_safe(p, n, &busiest_cfs_rq->tasks, se.group_node) {
		if (loops++ > sysctl_sched_nr_migrate)
			break;
2061

2062 2063 2064
		if ((p->se.load.weight >> 1) > rem_load_move ||
		    !can_migrate_task(p, busiest, this_cpu, sd, idle, &pinned))
			continue;
2065

2066 2067 2068
		pull_task(busiest, p, this_rq, this_cpu);
		pulled++;
		rem_load_move -= p->se.load.weight;
2069 2070

#ifdef CONFIG_PREEMPT
2071 2072 2073 2074 2075 2076 2077
		/*
		 * 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;
2078 2079
#endif

2080 2081 2082 2083 2084 2085 2086
		/*
		 * We only want to steal up to the prescribed amount of
		 * weighted load.
		 */
		if (rem_load_move <= 0)
			break;

2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103
		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
2104
#ifdef CONFIG_FAIR_GROUP_SCHED
2105 2106 2107
/*
 * update tg->load_weight by folding this cpu's load_avg
 */
2108
static int update_shares_cpu(struct task_group *tg, int cpu)
2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122
{
	struct cfs_rq *cfs_rq;
	unsigned long flags;
	struct rq *rq;

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

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

	raw_spin_lock_irqsave(&rq->lock, flags);

	update_rq_clock(rq);
2123
	update_cfs_load(cfs_rq, 1);
2124 2125 2126 2127 2128

	/*
	 * We need to update shares after updating tg->load_weight in
	 * order to adjust the weight of groups with long running tasks.
	 */
2129
	update_cfs_shares(cfs_rq, 0);
2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141

	raw_spin_unlock_irqrestore(&rq->lock, flags);

	return 0;
}

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

	rcu_read_lock();
2142 2143
	for_each_leaf_cfs_rq(rq, cfs_rq)
		update_shares_cpu(cfs_rq->tg, cpu);
2144 2145 2146
	rcu_read_unlock();
}

P
Peter Zijlstra 已提交
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
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
2194 2195 2196 2197
static inline void update_shares(int cpu)
{
}

P
Peter Zijlstra 已提交
2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209
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

2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221
/*
 * 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)
{
2222
	unsigned long total_load_moved = 0, load_moved;
2223 2224 2225
	int this_best_prio = this_rq->curr->prio;

	do {
2226
		load_moved = load_balance_fair(this_rq, this_cpu, busiest,
2227 2228
				max_load_move - total_load_moved,
				sd, idle, all_pinned, &this_best_prio);
2229 2230

		total_load_moved += load_moved;
2231 2232 2233 2234 2235 2236 2237 2238 2239

#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;
2240 2241 2242 2243

		if (raw_spin_is_contended(&this_rq->lock) ||
				raw_spin_is_contended(&busiest->lock))
			break;
2244
#endif
2245
	} while (load_moved && max_load_move > total_load_moved);
2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265

	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;
2266
	unsigned long this_has_capacity;
2267
	unsigned int  this_idle_cpus;
2268 2269

	/* Statistics of the busiest group */
2270
	unsigned int  busiest_idle_cpus;
2271 2272 2273
	unsigned long max_load;
	unsigned long busiest_load_per_task;
	unsigned long busiest_nr_running;
2274
	unsigned long busiest_group_capacity;
2275
	unsigned long busiest_has_capacity;
2276
	unsigned int  busiest_group_weight;
2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297

	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;
2298 2299
	unsigned long idle_cpus;
	unsigned long group_weight;
2300
	int group_imb; /* Is there an imbalance in the group ? */
2301
	int group_has_capacity; /* Is there extra capacity in the group? */
2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492
};

/**
 * 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)
{
2493
	unsigned long weight = sd->span_weight;
2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511
	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);
2512 2513 2514 2515 2516 2517 2518

	if (unlikely(total < rq->rt_avg)) {
		/* Ensures that power won't end up being negative */
		available = 0;
	} else {
		available = total - rq->rt_avg;
	}
2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529

	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)
{
2530
	unsigned long weight = sd->span_weight;
2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542
	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;
	}

2543 2544 2545 2546 2547 2548 2549 2550 2551
	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;

2552 2553 2554 2555 2556 2557
	power *= scale_rt_power(cpu);
	power >>= SCHED_LOAD_SHIFT;

	if (!power)
		power = 1;

2558
	cpu_rq(cpu)->cpu_power = power;
2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583
	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;
}

2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602
/*
 * 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
2603
	if (group->cpu_power * 32 > group->cpu_power_orig * 29)
2604 2605 2606 2607 2608
		return 1;

	return 0;
}

2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627
/**
 * 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)
{
2628
	unsigned long load, max_cpu_load, min_cpu_load, max_nr_running;
2629 2630
	int i;
	unsigned int balance_cpu = -1, first_idle_cpu = 0;
2631
	unsigned long avg_load_per_task = 0;
2632

2633
	if (local_group)
2634 2635 2636 2637 2638
		balance_cpu = group_first_cpu(group);

	/* Tally up the load of all CPUs in the group */
	max_cpu_load = 0;
	min_cpu_load = ~0UL;
2639
	max_nr_running = 0;
2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656

	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);
2657
			if (load > max_cpu_load) {
2658
				max_cpu_load = load;
2659 2660
				max_nr_running = rq->nr_running;
			}
2661 2662 2663 2664 2665 2666 2667
			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);
2668 2669
		if (idle_cpu(i))
			sgs->idle_cpus++;
2670 2671 2672 2673 2674 2675 2676 2677
	}

	/*
	 * 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.
	 */
2678 2679 2680 2681 2682 2683
	if (idle != CPU_NEWLY_IDLE && local_group) {
		if (balance_cpu != this_cpu) {
			*balance = 0;
			return;
		}
		update_group_power(sd, this_cpu);
2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697
	}

	/* 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?
	 */
2698 2699
	if (sgs->sum_nr_running)
		avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
2700

2701
	if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task && max_nr_running > 1)
2702 2703
		sgs->group_imb = 1;

2704
	sgs->group_capacity = DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE);
2705 2706
	if (!sgs->group_capacity)
		sgs->group_capacity = fix_small_capacity(sd, group);
2707
	sgs->group_weight = group->group_weight;
2708 2709 2710

	if (sgs->group_capacity > sgs->sum_nr_running)
		sgs->group_has_capacity = 1;
2711 2712
}

2713 2714 2715 2716 2717
/**
 * 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
2718 2719
 * @sgs: sched_group statistics
 * @this_cpu: the current cpu
2720 2721 2722 2723 2724 2725 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
 *
 * 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;
}

2756 2757 2758 2759 2760
/**
 * 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
2761
 * @sd_idle: Idle status of the sched_domain containing sg.
2762 2763 2764 2765 2766 2767 2768 2769 2770 2771
 * @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;
2772
	struct sched_group *sg = sd->groups;
2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784
	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;

2785
		local_group = cpumask_test_cpu(this_cpu, sched_group_cpus(sg));
2786
		memset(&sgs, 0, sizeof(sgs));
2787
		update_sg_lb_stats(sd, sg, this_cpu, idle, load_idx, sd_idle,
2788 2789
				local_group, cpus, balance, &sgs);

P
Peter Zijlstra 已提交
2790
		if (local_group && !(*balance))
2791 2792 2793
			return;

		sds->total_load += sgs.group_load;
2794
		sds->total_pwr += sg->cpu_power;
2795 2796 2797

		/*
		 * In case the child domain prefers tasks go to siblings
2798
		 * first, lower the sg capacity to one so that we'll try
2799 2800 2801 2802 2803 2804
		 * 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).
2805
		 */
2806
		if (prefer_sibling && !local_group && sds->this_has_capacity)
2807 2808 2809 2810
			sgs.group_capacity = min(sgs.group_capacity, 1UL);

		if (local_group) {
			sds->this_load = sgs.avg_load;
2811
			sds->this = sg;
2812 2813
			sds->this_nr_running = sgs.sum_nr_running;
			sds->this_load_per_task = sgs.sum_weighted_load;
2814
			sds->this_has_capacity = sgs.group_has_capacity;
2815
			sds->this_idle_cpus = sgs.idle_cpus;
2816
		} else if (update_sd_pick_busiest(sd, sds, sg, &sgs, this_cpu)) {
2817
			sds->max_load = sgs.avg_load;
2818
			sds->busiest = sg;
2819
			sds->busiest_nr_running = sgs.sum_nr_running;
2820
			sds->busiest_idle_cpus = sgs.idle_cpus;
2821
			sds->busiest_group_capacity = sgs.group_capacity;
2822
			sds->busiest_load_per_task = sgs.sum_weighted_load;
2823
			sds->busiest_has_capacity = sgs.group_has_capacity;
2824
			sds->busiest_group_weight = sgs.group_weight;
2825 2826 2827
			sds->group_imb = sgs.group_imb;
		}

2828 2829 2830 2831 2832
		update_sd_power_savings_stats(sg, sds, local_group, &sgs);
		sg = sg->next;
	} while (sg != sd->groups);
}

M
Michael Neuling 已提交
2833
int __weak arch_sd_sibling_asym_packing(void)
2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854
{
       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.
 *
2855 2856 2857
 * Returns 1 when packing is required and a task should be moved to
 * this CPU.  The amount of the imbalance is returned in *imbalance.
 *
2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881
 * @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;
2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896
}

/**
 * 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;
2897
	unsigned long scaled_busy_load_per_task;
2898 2899 2900 2901 2902 2903 2904 2905 2906 2907

	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);

2908 2909 2910 2911 2912 2913
	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)) {
2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963
		*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)
{
2964 2965 2966 2967 2968 2969 2970 2971
	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);
	}

2972 2973 2974 2975 2976 2977 2978 2979 2980 2981
	/*
	 * 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);
	}

2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004
	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);
3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020

	/* 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);

}
3021

3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 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
/******* 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.
3073 3074 3075 3076 3077
	 *
	 * 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.
3078
	 */
P
Peter Zijlstra 已提交
3079
	if (!(*balance))
3080 3081
		goto ret;

3082 3083 3084 3085
	if ((idle == CPU_IDLE || idle == CPU_NEWLY_IDLE) &&
	    check_asym_packing(sd, &sds, this_cpu, imbalance))
		return sds.busiest;

3086 3087 3088
	if (!sds.busiest || sds.busiest_nr_running == 0)
		goto out_balanced;

3089 3090 3091 3092 3093
	/*  SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
	if (idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
			!sds.busiest_has_capacity)
		goto force_balance;

3094 3095 3096 3097 3098 3099 3100 3101
	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;

3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121
	/*
	 * In the CPU_NEWLY_IDLE, use imbalance_pct to be conservative.
	 * And to check for busy balance use !idle_cpu instead of
	 * CPU_NOT_IDLE. This is because HT siblings will use CPU_NOT_IDLE
	 * even when they are idle.
	 */
	if (idle == CPU_NEWLY_IDLE || !idle_cpu(this_cpu)) {
		if (100 * sds.max_load <= sd->imbalance_pct * sds.this_load)
			goto out_balanced;
	} else {
		/*
		 * This cpu is idle. If the busiest group load doesn't
		 * have more tasks than the number of available cpu's and
		 * there is no imbalance between this and busiest group
		 * wrt to idle cpu's, it is balanced.
		 */
		if ((sds.this_idle_cpus  <= sds.busiest_idle_cpus + 1) &&
		    sds.busiest_nr_running <= sds.busiest_group_weight)
			goto out_balanced;
	}
3122

3123
force_balance:
3124 3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143
	/* 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 *
3144 3145 3146
find_busiest_queue(struct sched_domain *sd, struct sched_group *group,
		   enum cpu_idle_type idle, unsigned long imbalance,
		   const struct cpumask *cpus)
3147 3148 3149 3150 3151 3152 3153 3154 3155 3156
{
	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;

3157 3158 3159
		if (!capacity)
			capacity = fix_small_capacity(sd, group);

3160 3161 3162 3163
		if (!cpumask_test_cpu(i, cpus))
			continue;

		rq = cpu_rq(i);
3164
		wl = weighted_cpuload(i);
3165

3166 3167 3168 3169
		/*
		 * When comparing with imbalance, use weighted_cpuload()
		 * which is not scaled with the cpu power.
		 */
3170 3171 3172
		if (capacity && rq->nr_running == 1 && wl > imbalance)
			continue;

3173 3174 3175 3176 3177 3178 3179 3180
		/*
		 * 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;

3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198
		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);

3199 3200
static int need_active_balance(struct sched_domain *sd, int sd_idle, int idle,
			       int busiest_cpu, int this_cpu)
3201 3202
{
	if (idle == CPU_NEWLY_IDLE) {
3203 3204 3205 3206 3207 3208 3209 3210 3211

		/*
		 * 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;

3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241
		/*
		 * 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);
}

3242 3243
static int active_load_balance_cpu_stop(void *data);

3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284
/*
 * 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;
	}

3285
	busiest = find_busiest_queue(sd, group, idle, imbalance, cpus);
3286 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 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326
	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]);
3327 3328 3329 3330 3331 3332 3333 3334
		/*
		 * 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++;
3335

3336 3337
		if (need_active_balance(sd, sd_idle, idle, cpu_of(busiest),
					this_cpu)) {
3338 3339
			raw_spin_lock_irqsave(&busiest->lock, flags);

3340 3341 3342
			/* don't kick the active_load_balance_cpu_stop,
			 * if the curr task on busiest cpu can't be
			 * moved to this_cpu
3343 3344 3345 3346 3347 3348 3349 3350 3351
			 */
			if (!cpumask_test_cpu(this_cpu,
					      &busiest->curr->cpus_allowed)) {
				raw_spin_unlock_irqrestore(&busiest->lock,
							    flags);
				all_pinned = 1;
				goto out_one_pinned;
			}

3352 3353 3354 3355 3356
			/*
			 * ->active_balance synchronizes accesses to
			 * ->active_balance_work.  Once set, it's cleared
			 * only after active load balance is finished.
			 */
3357 3358 3359 3360 3361 3362
			if (!busiest->active_balance) {
				busiest->active_balance = 1;
				busiest->push_cpu = this_cpu;
				active_balance = 1;
			}
			raw_spin_unlock_irqrestore(&busiest->lock, flags);
3363

3364
			if (active_balance)
3365 3366 3367
				stop_one_cpu_nowait(cpu_of(busiest),
					active_load_balance_cpu_stop, busiest,
					&busiest->active_balance_work);
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 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432

			/*
			 * 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;

3433 3434 3435 3436 3437
	/*
	 * Drop the rq->lock, but keep IRQ/preempt disabled.
	 */
	raw_spin_unlock(&this_rq->lock);

P
Paul Turner 已提交
3438
	update_shares(this_cpu);
3439 3440
	for_each_domain(this_cpu, sd) {
		unsigned long interval;
3441
		int balance = 1;
3442 3443 3444 3445

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

3446
		if (sd->flags & SD_BALANCE_NEWIDLE) {
3447
			/* If we've pulled tasks over stop searching: */
3448 3449 3450
			pulled_task = load_balance(this_cpu, this_rq,
						   sd, CPU_NEWLY_IDLE, &balance);
		}
3451 3452 3453 3454

		interval = msecs_to_jiffies(sd->balance_interval);
		if (time_after(next_balance, sd->last_balance + interval))
			next_balance = sd->last_balance + interval;
N
Nikhil Rao 已提交
3455 3456
		if (pulled_task) {
			this_rq->idle_stamp = 0;
3457
			break;
N
Nikhil Rao 已提交
3458
		}
3459
	}
3460 3461 3462

	raw_spin_lock(&this_rq->lock);

3463 3464 3465 3466 3467 3468 3469 3470 3471 3472
	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;
	}
}

/*
3473 3474 3475 3476
 * 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.
3477
 */
3478
static int active_load_balance_cpu_stop(void *data)
3479
{
3480 3481
	struct rq *busiest_rq = data;
	int busiest_cpu = cpu_of(busiest_rq);
3482
	int target_cpu = busiest_rq->push_cpu;
3483
	struct rq *target_rq = cpu_rq(target_cpu);
3484
	struct sched_domain *sd;
3485 3486 3487 3488 3489 3490 3491

	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;
3492 3493 3494

	/* Is there any task to move? */
	if (busiest_rq->nr_running <= 1)
3495
		goto out_unlock;
3496 3497 3498 3499 3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523

	/*
	 * 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);
3524 3525 3526 3527
out_unlock:
	busiest_rq->active_balance = 0;
	raw_spin_unlock_irq(&busiest_rq->lock);
	return 0;
3528 3529 3530
}

#ifdef CONFIG_NO_HZ
3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546 3547 3548 3549 3550 3551 3552 3553 3554 3555 3556

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.
 */
3557 3558
static struct {
	atomic_t load_balancer;
3559 3560 3561 3562 3563 3564
	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;
3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617

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)
{
3618
	cpumask_and(nohz.grp_idle_mask, nohz.idle_cpus_mask,
3619 3620 3621 3622 3623 3624
					sched_group_cpus(ilb_group));

	/*
	 * A sched_group is semi-idle when it has atleast one busy cpu
	 * and atleast one idle cpu.
	 */
3625
	if (cpumask_empty(nohz.grp_idle_mask))
3626 3627
		return 0;

3628
	if (cpumask_equal(nohz.grp_idle_mask, sched_group_cpus(ilb_group)))
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
		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
	 */
3661
	if (cpumask_weight(nohz.idle_cpus_mask) < 2)
3662 3663 3664 3665 3666 3667 3668
		goto out_done;

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

		do {
			if (is_semi_idle_group(ilb_group))
3669
				return cpumask_first(nohz.grp_idle_mask);
3670 3671 3672 3673 3674 3675 3676

			ilb_group = ilb_group->next;

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

out_done:
3677
	return nr_cpu_ids;
3678 3679 3680 3681
}
#else /*  (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */
static inline int find_new_ilb(int call_cpu)
{
3682
	return nr_cpu_ids;
3683 3684 3685
}
#endif

3686 3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714
/*
 * 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;
}

3715 3716 3717
/*
 * 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
3718
 * load balancing on behalf of all those cpus.
3719
 *
3720 3721 3722
 * 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.
3723
 *
3724 3725 3726
 * 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).
3727
 */
3728
void select_nohz_load_balancer(int stop_tick)
3729 3730 3731 3732 3733 3734
{
	int cpu = smp_processor_id();

	if (stop_tick) {
		if (!cpu_active(cpu)) {
			if (atomic_read(&nohz.load_balancer) != cpu)
3735
				return;
3736 3737 3738 3739 3740

			/*
			 * If we are going offline and still the leader,
			 * give up!
			 */
3741 3742
			if (atomic_cmpxchg(&nohz.load_balancer, cpu,
					   nr_cpu_ids) != cpu)
3743 3744
				BUG();

3745
			return;
3746 3747
		}

3748
		cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
3749

3750 3751 3752 3753
		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);
3754

3755
		if (atomic_read(&nohz.load_balancer) >= nr_cpu_ids) {
3756 3757
			int new_ilb;

3758 3759 3760 3761 3762
			/* make me the ilb owner */
			if (atomic_cmpxchg(&nohz.load_balancer, nr_cpu_ids,
					   cpu) != nr_cpu_ids)
				return;

3763 3764 3765 3766 3767 3768
			/*
			 * 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) {
3769
				atomic_set(&nohz.load_balancer, nr_cpu_ids);
3770
				resched_cpu(new_ilb);
3771
				return;
3772
			}
3773
			return;
3774 3775
		}
	} else {
3776 3777
		if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
			return;
3778

3779
		cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
3780 3781

		if (atomic_read(&nohz.load_balancer) == cpu)
3782 3783
			if (atomic_cmpxchg(&nohz.load_balancer, cpu,
					   nr_cpu_ids) != cpu)
3784 3785
				BUG();
	}
3786
	return;
3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804 3805 3806 3807 3808
}
#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
3809 3810
	update_shares(cpu);

3811 3812 3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831 3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861 3862 3863 3864 3865 3866 3867 3868 3869
	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;
}

3870
#ifdef CONFIG_NO_HZ
3871
/*
3872
 * In CONFIG_NO_HZ case, the idle balance kickee will do the
3873 3874
 * rebalancing for all the cpus for whom scheduler ticks are stopped.
 */
3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898
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);
3899
		update_rq_clock(this_rq);
3900 3901 3902 3903 3904 3905 3906 3907 3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933
		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
3934
	if (rq->idle_at_tick)
3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965
		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).
 */
3966 3967 3968 3969 3970 3971 3972 3973 3974 3975
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);

	/*
3976
	 * If this cpu has a pending nohz_balance_kick, then do the
3977 3978 3979
	 * balancing on behalf of the other idle cpus whose ticks are
	 * stopped.
	 */
3980
	nohz_idle_balance(this_cpu, idle);
3981 3982 3983 3984
}

static inline int on_null_domain(int cpu)
{
3985
	return !rcu_dereference_sched(cpu_rq(cpu)->sd);
3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996
}

/*
 * 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);
3997 3998 3999 4000
#ifdef CONFIG_NO_HZ
	else if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
		nohz_balancer_kick(cpu);
#endif
4001 4002
}

4003 4004 4005 4006 4007 4008 4009 4010 4011 4012
static void rq_online_fair(struct rq *rq)
{
	update_sysctl();
}

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

4013 4014 4015 4016 4017 4018 4019 4020 4021
#else	/* CONFIG_SMP */

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

4022
#endif /* CONFIG_SMP */
4023

4024 4025 4026
/*
 * scheduler tick hitting a task of our scheduling class:
 */
P
Peter Zijlstra 已提交
4027
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
4028 4029 4030 4031 4032 4033
{
	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
4034
		entity_tick(cfs_rq, se, queued);
4035 4036 4037 4038
	}
}

/*
P
Peter Zijlstra 已提交
4039 4040 4041
 * called on fork with the child task as argument from the parent's context
 *  - child not yet on the tasklist
 *  - preemption disabled
4042
 */
P
Peter Zijlstra 已提交
4043
static void task_fork_fair(struct task_struct *p)
4044
{
P
Peter Zijlstra 已提交
4045
	struct cfs_rq *cfs_rq = task_cfs_rq(current);
4046
	struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
4047
	int this_cpu = smp_processor_id();
P
Peter Zijlstra 已提交
4048 4049 4050
	struct rq *rq = this_rq();
	unsigned long flags;

4051
	raw_spin_lock_irqsave(&rq->lock, flags);
4052

4053 4054
	update_rq_clock(rq);

4055 4056
	if (unlikely(task_cpu(p) != this_cpu)) {
		rcu_read_lock();
P
Peter Zijlstra 已提交
4057
		__set_task_cpu(p, this_cpu);
4058 4059
		rcu_read_unlock();
	}
4060

4061
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
4062

4063 4064
	if (curr)
		se->vruntime = curr->vruntime;
4065
	place_entity(cfs_rq, se, 1);
4066

P
Peter Zijlstra 已提交
4067
	if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
D
Dmitry Adamushko 已提交
4068
		/*
4069 4070 4071
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
4072
		swap(curr->vruntime, se->vruntime);
4073
		resched_task(rq->curr);
4074
	}
4075

4076 4077
	se->vruntime -= cfs_rq->min_vruntime;

4078
	raw_spin_unlock_irqrestore(&rq->lock, flags);
4079 4080
}

4081 4082 4083 4084 4085 4086 4087 4088 4089 4090 4091 4092 4093 4094 4095 4096
/*
 * 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
4097
		check_preempt_curr(rq, p, 0);
4098 4099 4100 4101 4102 4103 4104 4105 4106 4107 4108 4109 4110 4111 4112 4113
}

/*
 * 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
4114
		check_preempt_curr(rq, p, 0);
4115 4116
}

4117 4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129
/* 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
4130
#ifdef CONFIG_FAIR_GROUP_SCHED
4131
static void task_move_group_fair(struct task_struct *p, int on_rq)
P
Peter Zijlstra 已提交
4132
{
4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144 4145 4146 4147 4148
	/*
	 * 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));
4149
	if (!on_rq)
4150
		p->se.vruntime += cfs_rq_of(&p->se)->min_vruntime;
P
Peter Zijlstra 已提交
4151 4152 4153
}
#endif

4154
static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168
{
	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;
}

4169 4170 4171
/*
 * All the scheduling class methods:
 */
4172 4173
static const struct sched_class fair_sched_class = {
	.next			= &idle_sched_class,
4174 4175 4176 4177
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,

I
Ingo Molnar 已提交
4178
	.check_preempt_curr	= check_preempt_wakeup,
4179 4180 4181 4182

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

4183
#ifdef CONFIG_SMP
L
Li Zefan 已提交
4184 4185
	.select_task_rq		= select_task_rq_fair,

4186 4187
	.rq_online		= rq_online_fair,
	.rq_offline		= rq_offline_fair,
4188 4189

	.task_waking		= task_waking_fair,
4190
#endif
4191

4192
	.set_curr_task          = set_curr_task_fair,
4193
	.task_tick		= task_tick_fair,
P
Peter Zijlstra 已提交
4194
	.task_fork		= task_fork_fair,
4195 4196 4197

	.prio_changed		= prio_changed_fair,
	.switched_to		= switched_to_fair,
P
Peter Zijlstra 已提交
4198

4199 4200
	.get_rr_interval	= get_rr_interval_fair,

P
Peter Zijlstra 已提交
4201
#ifdef CONFIG_FAIR_GROUP_SCHED
4202
	.task_move_group	= task_move_group_fair,
P
Peter Zijlstra 已提交
4203
#endif
4204 4205 4206
};

#ifdef CONFIG_SCHED_DEBUG
4207
static void print_cfs_stats(struct seq_file *m, int cpu)
4208 4209 4210
{
	struct cfs_rq *cfs_rq;

4211
	rcu_read_lock();
4212
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
4213
		print_cfs_rq(m, cpu, cfs_rq);
4214
	rcu_read_unlock();
4215 4216
}
#endif