sched_fair.c 40.2 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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/*
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 * Targeted preemption latency for CPU-bound tasks:
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 * (default: 20ms * (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 = 20000000ULL;
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/*
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 * Minimal preemption granularity for CPU-bound tasks:
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 * (default: 4 msec * (1 + ilog(ncpus)), units: nanoseconds)
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 */
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unsigned int sysctl_sched_min_granularity = 4000000ULL;
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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 = 5;
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/*
 * After fork, child runs first. (default) If set to 0 then
 * parent will (try to) run first.
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 */
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const_debug unsigned int sysctl_sched_child_runs_first = 1;
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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: 5 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 = 5000000UL;
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const_debug unsigned int sysctl_sched_migration_cost = 500000UL;

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static const struct sched_class fair_sched_class;

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

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

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

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

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

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

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

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

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

	return 0;
}

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

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

	for_each_sched_entity(se)
		depth++;

	return depth;
}

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

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

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

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

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

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

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#else	/* CONFIG_FAIR_GROUP_SCHED */
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
	return container_of(cfs_rq, struct rq, cfs);
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}

#define entity_is_task(se)	1

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

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

	return &rq->cfs;
}

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

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

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

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

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

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

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#endif	/* CONFIG_FAIR_GROUP_SCHED */

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

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

	return min_vruntime;
}

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

	return min_vruntime;
}

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static inline 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);

		if (vruntime == cfs_rq->min_vruntime)
			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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	if (cfs_rq->next == se)
		cfs_rq->next = NULL;

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	rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
}

static inline struct rb_node *first_fair(struct cfs_rq *cfs_rq)
{
	return cfs_rq->rb_leftmost;
}

static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
{
	return rb_entry(first_fair(cfs_rq), struct sched_entity, run_node);
}

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static inline struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
{
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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
int sched_nr_latency_handler(struct ctl_table *table, int write,
		struct file *filp, void __user *buffer, size_t *lenp,
		loff_t *ppos)
{
	int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);

	if (ret || !write)
		return ret;

	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
					sysctl_sched_min_granularity);

	return 0;
}
#endif
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/*
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 * delta *= P[w / rw]
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 */
static inline unsigned long
calc_delta_weight(unsigned long delta, struct sched_entity *se)
{
	for_each_sched_entity(se) {
		delta = calc_delta_mine(delta,
				se->load.weight, &cfs_rq_of(se)->load);
	}

	return delta;
}

/*
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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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	unsigned long nr_running = cfs_rq->nr_running;

	if (unlikely(!se->on_rq))
		nr_running++;

	return calc_delta_weight(__sched_period(nr_running), se);
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}

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/*
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 * We calculate the vruntime slice of a to be inserted task
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 *
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 * vs = s/w
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 */
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static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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	return calc_delta_fair(sched_slice(cfs_rq, se), se);
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}

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

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static void update_curr(struct cfs_rq *cfs_rq)
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{
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	struct sched_entity *curr = cfs_rq->curr;
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	u64 now = rq_of(cfs_rq)->clock;
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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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	__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);

		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->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->wait_max, max(se->wait_max,
			rq_of(cfs_rq)->clock - se->wait_start));
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	schedstat_set(se->wait_count, se->wait_count + 1);
	schedstat_set(se->wait_sum, se->wait_sum +
			rq_of(cfs_rq)->clock - se->wait_start);
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	schedstat_set(se->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;
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}

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

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#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
static void
add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight)
{
	cfs_rq->task_weight += weight;
}
#else
static inline void
add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight)
{
}
#endif

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static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_add(&cfs_rq->load, se->load.weight);
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	if (!parent_entity(se))
		inc_cpu_load(rq_of(cfs_rq), se->load.weight);
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	if (entity_is_task(se)) {
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		add_cfs_task_weight(cfs_rq, se->load.weight);
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		list_add(&se->group_node, &cfs_rq->tasks);
	}
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	cfs_rq->nr_running++;
	se->on_rq = 1;
}

static void
account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	update_load_sub(&cfs_rq->load, se->load.weight);
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	if (!parent_entity(se))
		dec_cpu_load(rq_of(cfs_rq), se->load.weight);
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	if (entity_is_task(se)) {
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		add_cfs_task_weight(cfs_rq, -se->load.weight);
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		list_del_init(&se->group_node);
	}
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	cfs_rq->nr_running--;
	se->on_rq = 0;
}

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static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
#ifdef CONFIG_SCHEDSTATS
	if (se->sleep_start) {
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		u64 delta = rq_of(cfs_rq)->clock - se->sleep_start;
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		struct task_struct *tsk = task_of(se);
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		if ((s64)delta < 0)
			delta = 0;

		if (unlikely(delta > se->sleep_max))
			se->sleep_max = delta;

		se->sleep_start = 0;
		se->sum_sleep_runtime += delta;
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		account_scheduler_latency(tsk, delta >> 10, 1);
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	}
	if (se->block_start) {
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		u64 delta = rq_of(cfs_rq)->clock - se->block_start;
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		struct task_struct *tsk = task_of(se);
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		if ((s64)delta < 0)
			delta = 0;

		if (unlikely(delta > se->block_max))
			se->block_max = delta;

		se->block_start = 0;
		se->sum_sleep_runtime += delta;
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		/*
		 * 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)) {
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			profile_hits(SLEEP_PROFILING, (void *)get_wchan(tsk),
				     delta >> 20);
		}
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		account_scheduler_latency(tsk, delta >> 10, 0);
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	}
#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
}

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static void
place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
{
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	u64 vruntime = cfs_rq->min_vruntime;
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	/*
	 * 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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Peter Zijlstra 已提交
678
	if (initial && sched_feat(START_DEBIT))
679
		vruntime += sched_vslice(cfs_rq, se);
680

I
Ingo Molnar 已提交
681
	if (!initial) {
682
		/* sleeps upto a single latency don't count. */
683 684 685 686 687 688 689 690 691 692 693
		if (sched_feat(NEW_FAIR_SLEEPERS)) {
			unsigned long thresh = sysctl_sched_latency;

			/*
			 * convert the sleeper threshold into virtual time
			 */
			if (sched_feat(NORMALIZED_SLEEPER))
				thresh = calc_delta_fair(thresh, se);

			vruntime -= thresh;
		}
694

695 696
		/* ensure we never gain time by being placed backwards. */
		vruntime = max_vruntime(se->vruntime, vruntime);
697 698
	}

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Peter Zijlstra 已提交
699
	se->vruntime = vruntime;
700 701
}

702
static void
703
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
704 705
{
	/*
706
	 * Update run-time statistics of the 'current'.
707
	 */
708
	update_curr(cfs_rq);
P
Peter Zijlstra 已提交
709
	account_entity_enqueue(cfs_rq, se);
710

I
Ingo Molnar 已提交
711
	if (wakeup) {
712
		place_entity(cfs_rq, se, 0);
713
		enqueue_sleeper(cfs_rq, se);
I
Ingo Molnar 已提交
714
	}
715

716
	update_stats_enqueue(cfs_rq, se);
P
Peter Zijlstra 已提交
717
	check_spread(cfs_rq, se);
718 719
	if (se != cfs_rq->curr)
		__enqueue_entity(cfs_rq, se);
720 721 722
}

static void
723
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
724
{
725 726 727 728 729
	/*
	 * Update run-time statistics of the 'current'.
	 */
	update_curr(cfs_rq);

730
	update_stats_dequeue(cfs_rq, se);
731
	if (sleep) {
P
Peter Zijlstra 已提交
732
#ifdef CONFIG_SCHEDSTATS
733 734 735 736
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
737
				se->sleep_start = rq_of(cfs_rq)->clock;
738
			if (tsk->state & TASK_UNINTERRUPTIBLE)
739
				se->block_start = rq_of(cfs_rq)->clock;
740
		}
741
#endif
P
Peter Zijlstra 已提交
742 743
	}

744
	if (se != cfs_rq->curr)
745 746
		__dequeue_entity(cfs_rq, se);
	account_entity_dequeue(cfs_rq, se);
747
	update_min_vruntime(cfs_rq);
748 749 750 751 752
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
753
static void
I
Ingo Molnar 已提交
754
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
755
{
756 757
	unsigned long ideal_runtime, delta_exec;

P
Peter Zijlstra 已提交
758
	ideal_runtime = sched_slice(cfs_rq, curr);
759
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
I
Ingo Molnar 已提交
760
	if (delta_exec > ideal_runtime)
761 762 763
		resched_task(rq_of(cfs_rq)->curr);
}

764
static void
765
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
766
{
767 768 769 770 771 772 773 774 775 776 777
	/* '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);
	}

778
	update_stats_curr_start(cfs_rq, se);
779
	cfs_rq->curr = se;
I
Ingo Molnar 已提交
780 781 782 783 784 785
#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):
	 */
786
	if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
I
Ingo Molnar 已提交
787 788 789 790
		se->slice_max = max(se->slice_max,
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
791
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
792 793
}

794 795 796
static struct sched_entity *
pick_next(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
797 798
	struct rq *rq = rq_of(cfs_rq);
	u64 pair_slice = rq->clock - cfs_rq->pair_start;
799

800
	if (!cfs_rq->next || pair_slice > sysctl_sched_min_granularity) {
801
		cfs_rq->pair_start = rq->clock;
802
		return se;
803
	}
804 805 806 807

	return cfs_rq->next;
}

808
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
809
{
D
Dmitry Adamushko 已提交
810
	struct sched_entity *se = NULL;
811

D
Dmitry Adamushko 已提交
812 813
	if (first_fair(cfs_rq)) {
		se = __pick_next_entity(cfs_rq);
814
		se = pick_next(cfs_rq, se);
D
Dmitry Adamushko 已提交
815 816
		set_next_entity(cfs_rq, se);
	}
817 818 819 820

	return se;
}

821
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
822 823 824 825 826 827
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
828
		update_curr(cfs_rq);
829

P
Peter Zijlstra 已提交
830
	check_spread(cfs_rq, prev);
831
	if (prev->on_rq) {
832
		update_stats_wait_start(cfs_rq, prev);
833 834 835
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
	}
836
	cfs_rq->curr = NULL;
837 838
}

P
Peter Zijlstra 已提交
839 840
static void
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
841 842
{
	/*
843
	 * Update run-time statistics of the 'current'.
844
	 */
845
	update_curr(cfs_rq);
846

P
Peter Zijlstra 已提交
847 848 849 850 851
#ifdef CONFIG_SCHED_HRTICK
	/*
	 * queued ticks are scheduled to match the slice, so don't bother
	 * validating it and just reschedule.
	 */
852 853 854 855
	if (queued) {
		resched_task(rq_of(cfs_rq)->curr);
		return;
	}
P
Peter Zijlstra 已提交
856 857 858 859 860 861 862 863
	/*
	 * 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

864
	if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
I
Ingo Molnar 已提交
865
		check_preempt_tick(cfs_rq, curr);
866 867 868 869 870 871
}

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

P
Peter Zijlstra 已提交
872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894
#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.
		 */
895
		if (rq->curr != p)
896
			delta = max_t(s64, 10000LL, delta);
P
Peter Zijlstra 已提交
897

898
		hrtick_start(rq, delta);
P
Peter Zijlstra 已提交
899 900
	}
}
901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916

/*
 * 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);
}
917
#else /* !CONFIG_SCHED_HRTICK */
P
Peter Zijlstra 已提交
918 919 920 921
static inline void
hrtick_start_fair(struct rq *rq, struct task_struct *p)
{
}
922 923 924 925

static inline void hrtick_update(struct rq *rq)
{
}
P
Peter Zijlstra 已提交
926 927
#endif

928 929 930 931 932
/*
 * 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:
 */
933
static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
934 935
{
	struct cfs_rq *cfs_rq;
936
	struct sched_entity *se = &p->se;
937 938

	for_each_sched_entity(se) {
939
		if (se->on_rq)
940 941
			break;
		cfs_rq = cfs_rq_of(se);
942
		enqueue_entity(cfs_rq, se, wakeup);
943
		wakeup = 1;
944
	}
P
Peter Zijlstra 已提交
945

946
	hrtick_update(rq);
947 948 949 950 951 952 953
}

/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
954
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
955 956
{
	struct cfs_rq *cfs_rq;
957
	struct sched_entity *se = &p->se;
958 959 960

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
961
		dequeue_entity(cfs_rq, se, sleep);
962
		/* Don't dequeue parent if it has other entities besides us */
963
		if (cfs_rq->load.weight)
964
			break;
965
		sleep = 1;
966
	}
P
Peter Zijlstra 已提交
967

968
	hrtick_update(rq);
969 970 971
}

/*
972 973 974
 * 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.
975
 */
976
static void yield_task_fair(struct rq *rq)
977
{
978 979 980
	struct task_struct *curr = rq->curr;
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
	struct sched_entity *rightmost, *se = &curr->se;
981 982

	/*
983 984 985 986 987
	 * Are we the only task in the tree?
	 */
	if (unlikely(cfs_rq->nr_running == 1))
		return;

988
	if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {
989
		update_rq_clock(rq);
990
		/*
991
		 * Update run-time statistics of the 'current'.
992
		 */
D
Dmitry Adamushko 已提交
993
		update_curr(cfs_rq);
994 995 996 997 998

		return;
	}
	/*
	 * Find the rightmost entry in the rbtree:
999
	 */
D
Dmitry Adamushko 已提交
1000
	rightmost = __pick_last_entity(cfs_rq);
1001 1002 1003
	/*
	 * Already in the rightmost position?
	 */
1004
	if (unlikely(!rightmost || rightmost->vruntime < se->vruntime))
1005 1006 1007 1008
		return;

	/*
	 * Minimally necessary key value to be last in the tree:
D
Dmitry Adamushko 已提交
1009 1010
	 * Upon rescheduling, sched_class::put_prev_task() will place
	 * 'current' within the tree based on its new key value.
1011
	 */
1012
	se->vruntime = rightmost->vruntime + 1;
1013 1014
}

1015 1016 1017 1018 1019
/*
 * wake_idle() will wake a task on an idle cpu if task->cpu is
 * not idle and an idle cpu is available.  The span of cpus to
 * search starts with cpus closest then further out as needed,
 * so we always favor a closer, idle cpu.
1020 1021
 * Domains may include CPUs that are not usable for migration,
 * hence we need to mask them out (cpu_active_map)
1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040
 *
 * Returns the CPU we should wake onto.
 */
#if defined(ARCH_HAS_SCHED_WAKE_IDLE)
static int wake_idle(int cpu, struct task_struct *p)
{
	cpumask_t tmp;
	struct sched_domain *sd;
	int i;

	/*
	 * If it is idle, then it is the best cpu to run this task.
	 *
	 * This cpu is also the best, if it has more than one task already.
	 * Siblings must be also busy(in most cases) as they didn't already
	 * pickup the extra load from this cpu and hence we need not check
	 * sibling runqueue info. This will avoid the checks and cache miss
	 * penalities associated with that.
	 */
1041
	if (idle_cpu(cpu) || cpu_rq(cpu)->cfs.nr_running > 1)
1042 1043 1044
		return cpu;

	for_each_domain(cpu, sd) {
1045 1046 1047
		if ((sd->flags & SD_WAKE_IDLE)
		    || ((sd->flags & SD_WAKE_IDLE_FAR)
			&& !task_hot(p, task_rq(p)->clock, sd))) {
1048
			cpus_and(tmp, sd->span, p->cpus_allowed);
1049
			cpus_and(tmp, tmp, cpu_active_map);
1050
			for_each_cpu_mask_nr(i, tmp) {
1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064
				if (idle_cpu(i)) {
					if (i != task_cpu(p)) {
						schedstat_inc(p,
						       se.nr_wakeups_idle);
					}
					return i;
				}
			}
		} else {
			break;
		}
	}
	return cpu;
}
1065
#else /* !ARCH_HAS_SCHED_WAKE_IDLE*/
1066 1067 1068 1069 1070 1071 1072
static inline int wake_idle(int cpu, struct task_struct *p)
{
	return cpu;
}
#endif

#ifdef CONFIG_SMP
1073

1074
#ifdef CONFIG_FAIR_GROUP_SCHED
1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095
/*
 * 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.
 *
 * The problem is that perfectly aligning the shares is rather expensive, hence
 * we try to avoid doing that too often - see update_shares(), which ratelimits
 * this change.
 *
 * We compensate this by not only taking the current delta into account, but
 * also considering the delta between when the shares were last adjusted and
 * now.
 *
 * We still saw a performance dip, some tracing learned us that between
 * cgroup:/ and cgroup:/foo balancing the number of affine wakeups increased
 * significantly. Therefore try to bias the error in direction of failing
 * the affine wakeup.
 *
 */
1096 1097
static long effective_load(struct task_group *tg, int cpu,
		long wl, long wg)
1098
{
P
Peter Zijlstra 已提交
1099
	struct sched_entity *se = tg->se[cpu];
1100 1101 1102 1103

	if (!tg->parent)
		return wl;

1104 1105 1106 1107 1108 1109 1110
	/*
	 * By not taking the decrease of shares on the other cpu into
	 * account our error leans towards reducing the affine wakeups.
	 */
	if (!wl && sched_feat(ASYM_EFF_LOAD))
		return wl;

P
Peter Zijlstra 已提交
1111
	for_each_sched_entity(se) {
1112
		long S, rw, s, a, b;
1113 1114 1115 1116 1117 1118 1119 1120 1121
		long more_w;

		/*
		 * Instead of using this increment, also add the difference
		 * between when the shares were last updated and now.
		 */
		more_w = se->my_q->load.weight - se->my_q->rq_weight;
		wl += more_w;
		wg += more_w;
P
Peter Zijlstra 已提交
1122 1123 1124

		S = se->my_q->tg->shares;
		s = se->my_q->shares;
1125
		rw = se->my_q->rq_weight;
1126

1127 1128
		a = S*(rw + wl);
		b = S*rw + s*wg;
P
Peter Zijlstra 已提交
1129

1130 1131 1132 1133 1134
		wl = s*(a-b);

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

1135 1136 1137 1138 1139 1140 1141
		/*
		 * Assume the group is already running and will
		 * thus already be accounted for in the weight.
		 *
		 * That is, moving shares between CPUs, does not
		 * alter the group weight.
		 */
P
Peter Zijlstra 已提交
1142 1143
		wg = 0;
	}
1144

P
Peter Zijlstra 已提交
1145
	return wl;
1146
}
P
Peter Zijlstra 已提交
1147

1148
#else
P
Peter Zijlstra 已提交
1149

1150 1151
static inline unsigned long effective_load(struct task_group *tg, int cpu,
		unsigned long wl, unsigned long wg)
P
Peter Zijlstra 已提交
1152
{
1153
	return wl;
1154
}
P
Peter Zijlstra 已提交
1155

1156 1157
#endif

1158
static int
1159
wake_affine(struct sched_domain *this_sd, struct rq *this_rq,
I
Ingo Molnar 已提交
1160 1161
	    struct task_struct *p, int prev_cpu, int this_cpu, int sync,
	    int idx, unsigned long load, unsigned long this_load,
1162 1163
	    unsigned int imbalance)
{
I
Ingo Molnar 已提交
1164
	struct task_struct *curr = this_rq->curr;
1165
	struct task_group *tg;
1166 1167
	unsigned long tl = this_load;
	unsigned long tl_per_task;
1168
	unsigned long weight;
1169
	int balanced;
1170

1171
	if (!(this_sd->flags & SD_WAKE_AFFINE) || !sched_feat(AFFINE_WAKEUPS))
1172 1173
		return 0;

M
Mike Galbraith 已提交
1174 1175 1176
	if (sync && (curr->se.avg_overlap > sysctl_sched_migration_cost ||
			p->se.avg_overlap > sysctl_sched_migration_cost))
		sync = 0;
1177

1178 1179 1180 1181 1182
	/*
	 * If sync wakeup then subtract the (maximum possible)
	 * effect of the currently running task from the load
	 * of the current CPU:
	 */
1183 1184 1185 1186 1187 1188 1189
	if (sync) {
		tg = task_group(current);
		weight = current->se.load.weight;

		tl += effective_load(tg, this_cpu, -weight, -weight);
		load += effective_load(tg, prev_cpu, 0, -weight);
	}
1190

1191 1192
	tg = task_group(p);
	weight = p->se.load.weight;
1193

1194 1195
	balanced = 100*(tl + effective_load(tg, this_cpu, weight, weight)) <=
		imbalance*(load + effective_load(tg, prev_cpu, 0, weight));
1196

1197
	/*
I
Ingo Molnar 已提交
1198 1199 1200
	 * If the currently running task will sleep within
	 * a reasonable amount of time then attract this newly
	 * woken task:
1201
	 */
1202 1203
	if (sync && balanced)
		return 1;
1204 1205 1206 1207

	schedstat_inc(p, se.nr_wakeups_affine_attempts);
	tl_per_task = cpu_avg_load_per_task(this_cpu);

1208 1209
	if (balanced || (tl <= load && tl + target_load(prev_cpu, idx) <=
			tl_per_task)) {
1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222
		/*
		 * This domain has SD_WAKE_AFFINE and
		 * p is cache cold in this domain, and
		 * there is no bad imbalance.
		 */
		schedstat_inc(this_sd, ttwu_move_affine);
		schedstat_inc(p, se.nr_wakeups_affine);

		return 1;
	}
	return 0;
}

1223 1224 1225
static int select_task_rq_fair(struct task_struct *p, int sync)
{
	struct sched_domain *sd, *this_sd = NULL;
1226
	int prev_cpu, this_cpu, new_cpu;
1227
	unsigned long load, this_load;
1228
	struct rq *this_rq;
1229 1230
	unsigned int imbalance;
	int idx;
1231

1232 1233
	prev_cpu	= task_cpu(p);
	this_cpu	= smp_processor_id();
I
Ingo Molnar 已提交
1234
	this_rq		= cpu_rq(this_cpu);
1235
	new_cpu		= prev_cpu;
1236

1237 1238
	if (prev_cpu == this_cpu)
		goto out;
1239 1240 1241 1242
	/*
	 * 'this_sd' is the first domain that both
	 * this_cpu and prev_cpu are present in:
	 */
1243
	for_each_domain(this_cpu, sd) {
1244
		if (cpu_isset(prev_cpu, sd->span)) {
1245 1246 1247 1248 1249 1250
			this_sd = sd;
			break;
		}
	}

	if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
1251
		goto out;
1252 1253 1254 1255

	/*
	 * Check for affine wakeup and passive balancing possibilities.
	 */
1256
	if (!this_sd)
1257
		goto out;
1258

1259 1260 1261 1262
	idx = this_sd->wake_idx;

	imbalance = 100 + (this_sd->imbalance_pct - 100) / 2;

1263
	load = source_load(prev_cpu, idx);
1264 1265
	this_load = target_load(this_cpu, idx);

1266
	if (wake_affine(this_sd, this_rq, p, prev_cpu, this_cpu, sync, idx,
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Ingo Molnar 已提交
1267 1268 1269
				     load, this_load, imbalance))
		return this_cpu;

1270 1271 1272 1273 1274 1275 1276 1277
	/*
	 * Start passive balancing when half the imbalance_pct
	 * limit is reached.
	 */
	if (this_sd->flags & SD_WAKE_BALANCE) {
		if (imbalance*this_load <= 100*load) {
			schedstat_inc(this_sd, ttwu_move_balance);
			schedstat_inc(p, se.nr_wakeups_passive);
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Ingo Molnar 已提交
1278
			return this_cpu;
1279 1280 1281
		}
	}

1282
out:
1283 1284 1285 1286
	return wake_idle(new_cpu, p);
}
#endif /* CONFIG_SMP */

1287 1288 1289 1290 1291
static unsigned long wakeup_gran(struct sched_entity *se)
{
	unsigned long gran = sysctl_sched_wakeup_granularity;

	/*
1292 1293
	 * More easily preempt - nice tasks, while not making it harder for
	 * + nice tasks.
1294
	 */
1295 1296
	if (!sched_feat(ASYM_GRAN) || se->load.weight > NICE_0_LOAD)
		gran = calc_delta_fair(sysctl_sched_wakeup_granularity, se);
1297 1298 1299 1300

	return gran;
}

1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329
/*
 * 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;

	gran = wakeup_gran(curr);
	if (vdiff > gran)
		return 1;

	return 0;
}

1330 1331 1332
/*
 * Preempt the current task with a newly woken task if needed:
 */
1333
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
1334 1335
{
	struct task_struct *curr = rq->curr;
1336
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
1337
	struct sched_entity *se = &curr->se, *pse = &p->se;
1338 1339

	if (unlikely(rt_prio(p->prio))) {
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Ingo Molnar 已提交
1340
		update_rq_clock(rq);
1341
		update_curr(cfs_rq);
1342 1343 1344
		resched_task(curr);
		return;
	}
1345

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1346 1347 1348
	if (unlikely(se == pse))
		return;

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1349 1350
	cfs_rq_of(pse)->next = pse;

1351 1352 1353 1354 1355 1356 1357
	/*
	 * We can come here with TIF_NEED_RESCHED already set from new task
	 * wake up path.
	 */
	if (test_tsk_need_resched(curr))
		return;

1358 1359 1360 1361 1362 1363
	/*
	 * Batch tasks do not preempt (their preemption is driven by
	 * the tick):
	 */
	if (unlikely(p->policy == SCHED_BATCH))
		return;
1364

1365 1366
	if (!sched_feat(WAKEUP_PREEMPT))
		return;
1367

1368 1369 1370
	if (sched_feat(WAKEUP_OVERLAP) && (sync ||
			(se->avg_overlap < sysctl_sched_migration_cost &&
			 pse->avg_overlap < sysctl_sched_migration_cost))) {
1371 1372 1373 1374
		resched_task(curr);
		return;
	}

1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387
	find_matching_se(&se, &pse);

	while (se) {
		BUG_ON(!pse);

		if (wakeup_preempt_entity(se, pse) == 1) {
			resched_task(curr);
			break;
		}

		se = parent_entity(se);
		pse = parent_entity(pse);
	}
1388 1389
}

1390
static struct task_struct *pick_next_task_fair(struct rq *rq)
1391
{
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1392
	struct task_struct *p;
1393 1394 1395 1396 1397 1398 1399
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

	if (unlikely(!cfs_rq->nr_running))
		return NULL;

	do {
1400
		se = pick_next_entity(cfs_rq);
1401 1402 1403
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

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1404 1405 1406 1407
	p = task_of(se);
	hrtick_start_fair(rq, p);

	return p;
1408 1409 1410 1411 1412
}

/*
 * Account for a descheduled task:
 */
1413
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
1414 1415 1416 1417 1418 1419
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
1420
		put_prev_entity(cfs_rq, se);
1421 1422 1423
	}
}

1424
#ifdef CONFIG_SMP
1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435
/**************************************************
 * Fair scheduling class load-balancing methods:
 */

/*
 * Load-balancing iterator. Note: while the runqueue stays locked
 * during the whole iteration, the current task might be
 * dequeued so the iterator has to be dequeue-safe. Here we
 * achieve that by always pre-iterating before returning
 * the current task:
 */
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Alexey Dobriyan 已提交
1436
static struct task_struct *
1437
__load_balance_iterator(struct cfs_rq *cfs_rq, struct list_head *next)
1438
{
D
Dhaval Giani 已提交
1439 1440
	struct task_struct *p = NULL;
	struct sched_entity *se;
1441

1442 1443 1444
	if (next == &cfs_rq->tasks)
		return NULL;

1445 1446 1447
	se = list_entry(next, struct sched_entity, group_node);
	p = task_of(se);
	cfs_rq->balance_iterator = next->next;
1448

1449 1450 1451 1452 1453 1454 1455
	return p;
}

static struct task_struct *load_balance_start_fair(void *arg)
{
	struct cfs_rq *cfs_rq = arg;

1456
	return __load_balance_iterator(cfs_rq, cfs_rq->tasks.next);
1457 1458 1459 1460 1461 1462
}

static struct task_struct *load_balance_next_fair(void *arg)
{
	struct cfs_rq *cfs_rq = arg;

1463
	return __load_balance_iterator(cfs_rq, cfs_rq->balance_iterator);
1464 1465
}

1466 1467 1468 1469 1470
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,
		struct cfs_rq *cfs_rq)
1471
{
1472
	struct rq_iterator cfs_rq_iterator;
1473

1474 1475 1476
	cfs_rq_iterator.start = load_balance_start_fair;
	cfs_rq_iterator.next = load_balance_next_fair;
	cfs_rq_iterator.arg = cfs_rq;
1477

1478 1479 1480
	return balance_tasks(this_rq, this_cpu, busiest,
			max_load_move, sd, idle, all_pinned,
			this_best_prio, &cfs_rq_iterator);
1481 1482
}

1483
#ifdef CONFIG_FAIR_GROUP_SCHED
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Peter Williams 已提交
1484
static unsigned long
1485
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
1486
		  unsigned long max_load_move,
1487 1488
		  struct sched_domain *sd, enum cpu_idle_type idle,
		  int *all_pinned, int *this_best_prio)
1489 1490
{
	long rem_load_move = max_load_move;
1491 1492
	int busiest_cpu = cpu_of(busiest);
	struct task_group *tg;
1493

1494
	rcu_read_lock();
1495
	update_h_load(busiest_cpu);
1496

1497
	list_for_each_entry_rcu(tg, &task_groups, list) {
1498
		struct cfs_rq *busiest_cfs_rq = tg->cfs_rq[busiest_cpu];
1499 1500
		unsigned long busiest_h_load = busiest_cfs_rq->h_load;
		unsigned long busiest_weight = busiest_cfs_rq->load.weight;
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Srivatsa Vaddagiri 已提交
1501
		u64 rem_load, moved_load;
1502

1503 1504 1505
		/*
		 * empty group
		 */
1506
		if (!busiest_cfs_rq->task_weight)
1507 1508
			continue;

S
Srivatsa Vaddagiri 已提交
1509 1510
		rem_load = (u64)rem_load_move * busiest_weight;
		rem_load = div_u64(rem_load, busiest_h_load + 1);
1511

1512
		moved_load = __load_balance_fair(this_rq, this_cpu, busiest,
1513
				rem_load, sd, idle, all_pinned, this_best_prio,
1514
				tg->cfs_rq[busiest_cpu]);
1515

1516
		if (!moved_load)
1517 1518
			continue;

1519
		moved_load *= busiest_h_load;
S
Srivatsa Vaddagiri 已提交
1520
		moved_load = div_u64(moved_load, busiest_weight + 1);
1521

1522 1523
		rem_load_move -= moved_load;
		if (rem_load_move < 0)
1524 1525
			break;
	}
1526
	rcu_read_unlock();
1527

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Peter Williams 已提交
1528
	return max_load_move - rem_load_move;
1529
}
1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541
#else
static unsigned long
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
		  unsigned long max_load_move,
		  struct sched_domain *sd, enum cpu_idle_type idle,
		  int *all_pinned, int *this_best_prio)
{
	return __load_balance_fair(this_rq, this_cpu, busiest,
			max_load_move, sd, idle, all_pinned,
			this_best_prio, &busiest->cfs);
}
#endif
1542

1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565
static int
move_one_task_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
		   struct sched_domain *sd, enum cpu_idle_type idle)
{
	struct cfs_rq *busy_cfs_rq;
	struct rq_iterator cfs_rq_iterator;

	cfs_rq_iterator.start = load_balance_start_fair;
	cfs_rq_iterator.next = load_balance_next_fair;

	for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
		/*
		 * pass busy_cfs_rq argument into
		 * load_balance_[start|next]_fair iterators
		 */
		cfs_rq_iterator.arg = busy_cfs_rq;
		if (iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
				       &cfs_rq_iterator))
		    return 1;
	}

	return 0;
}
1566
#endif /* CONFIG_SMP */
1567

1568 1569 1570
/*
 * scheduler tick hitting a task of our scheduling class:
 */
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Peter Zijlstra 已提交
1571
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
1572 1573 1574 1575 1576 1577
{
	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
1578
		entity_tick(cfs_rq, se, queued);
1579 1580 1581
	}
}

1582
#define swap(a, b) do { typeof(a) tmp = (a); (a) = (b); (b) = tmp; } while (0)
1583

1584 1585 1586 1587 1588 1589 1590
/*
 * Share the fairness runtime between parent and child, thus the
 * total amount of pressure for CPU stays equal - new tasks
 * get a chance to run but frequent forkers are not allowed to
 * monopolize the CPU. Note: the parent runqueue is locked,
 * the child is not running yet.
 */
1591
static void task_new_fair(struct rq *rq, struct task_struct *p)
1592 1593
{
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
1594
	struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
1595
	int this_cpu = smp_processor_id();
1596 1597 1598

	sched_info_queued(p);

1599
	update_curr(cfs_rq);
1600
	place_entity(cfs_rq, se, 1);
1601

1602
	/* 'curr' will be NULL if the child belongs to a different group */
1603
	if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
1604
			curr && curr->vruntime < se->vruntime) {
D
Dmitry Adamushko 已提交
1605
		/*
1606 1607 1608
		 * Upon rescheduling, sched_class::put_prev_task() will place
		 * 'current' within the tree based on its new key value.
		 */
1609
		swap(curr->vruntime, se->vruntime);
1610
		resched_task(rq->curr);
1611
	}
1612

1613
	enqueue_task_fair(rq, p, 0);
1614 1615
}

1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631
/*
 * 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
1632
		check_preempt_curr(rq, p, 0);
1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648
}

/*
 * 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
1649
		check_preempt_curr(rq, p, 0);
1650 1651
}

1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664
/* 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);
}

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Peter Zijlstra 已提交
1665 1666 1667 1668 1669 1670 1671 1672 1673 1674
#ifdef CONFIG_FAIR_GROUP_SCHED
static void moved_group_fair(struct task_struct *p)
{
	struct cfs_rq *cfs_rq = task_cfs_rq(p);

	update_curr(cfs_rq);
	place_entity(cfs_rq, &p->se, 1);
}
#endif

1675 1676 1677
/*
 * All the scheduling class methods:
 */
1678 1679
static const struct sched_class fair_sched_class = {
	.next			= &idle_sched_class,
1680 1681 1682 1683
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,

I
Ingo Molnar 已提交
1684
	.check_preempt_curr	= check_preempt_wakeup,
1685 1686 1687 1688

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

1689
#ifdef CONFIG_SMP
L
Li Zefan 已提交
1690 1691
	.select_task_rq		= select_task_rq_fair,

1692
	.load_balance		= load_balance_fair,
1693
	.move_one_task		= move_one_task_fair,
1694
#endif
1695

1696
	.set_curr_task          = set_curr_task_fair,
1697 1698
	.task_tick		= task_tick_fair,
	.task_new		= task_new_fair,
1699 1700 1701

	.prio_changed		= prio_changed_fair,
	.switched_to		= switched_to_fair,
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Peter Zijlstra 已提交
1702 1703 1704 1705

#ifdef CONFIG_FAIR_GROUP_SCHED
	.moved_group		= moved_group_fair,
#endif
1706 1707 1708
};

#ifdef CONFIG_SCHED_DEBUG
1709
static void print_cfs_stats(struct seq_file *m, int cpu)
1710 1711 1712
{
	struct cfs_rq *cfs_rq;

1713
	rcu_read_lock();
1714
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
1715
		print_cfs_rq(m, cpu, cfs_rq);
1716
	rcu_read_unlock();
1717 1718
}
#endif