sched_fair.c 31.3 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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 * Targeted preemption latency for CPU-bound tasks:
 * (default: 20ms, units: nanoseconds)
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 *
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 * NOTE: this latency value is not the same as the concept of
 * 'timeslice length' - timeslices in CFS are of variable length.
 * (to see the precise effective timeslice length of your workload,
 *  run vmstat and monitor the context-switches field)
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 *
 * On SMP systems the value of this is multiplied by the log2 of the
 * number of CPUs. (i.e. factor 2x on 2-way systems, 3x on 4-way
 * systems, 4x on 8-way systems, 5x on 16-way systems, etc.)
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 * Targeted preemption latency for CPU-bound tasks:
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 */
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unsigned int sysctl_sched_latency __read_mostly = 20000000ULL;

/*
 * Minimal preemption granularity for CPU-bound tasks:
 * (default: 2 msec, units: nanoseconds)
 */
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unsigned int sysctl_sched_min_granularity __read_mostly = 2000000ULL;
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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_BATCH wake-up granularity.
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 * (default: 25 msec, 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_batch_wakeup_granularity __read_mostly = 25000000UL;
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/*
 * SCHED_OTHER wake-up granularity.
 * (default: 1 msec, units: nanoseconds)
 *
 * 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 __read_mostly = 1000000UL;
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unsigned int sysctl_sched_stat_granularity __read_mostly;

/*
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 * Initialized in sched_init_granularity() [to 5 times the base granularity]:
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 */
unsigned int sysctl_sched_runtime_limit __read_mostly;

/*
 * Debugging: various feature bits
 */
enum {
	SCHED_FEAT_FAIR_SLEEPERS	= 1,
	SCHED_FEAT_SLEEPER_AVG		= 2,
	SCHED_FEAT_SLEEPER_LOAD_AVG	= 4,
	SCHED_FEAT_PRECISE_CPU_LOAD	= 8,
	SCHED_FEAT_START_DEBIT		= 16,
	SCHED_FEAT_SKIP_INITIAL		= 32,
};

unsigned int sysctl_sched_features __read_mostly =
		SCHED_FEAT_FAIR_SLEEPERS	*1 |
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		SCHED_FEAT_SLEEPER_AVG		*0 |
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		SCHED_FEAT_SLEEPER_LOAD_AVG	*1 |
		SCHED_FEAT_PRECISE_CPU_LOAD	*1 |
		SCHED_FEAT_START_DEBIT		*1 |
		SCHED_FEAT_SKIP_INITIAL		*0;

extern struct sched_class fair_sched_class;

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

#ifdef CONFIG_FAIR_GROUP_SCHED

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

/* currently running entity (if any) on this cfs_rq */
static inline struct sched_entity *cfs_rq_curr(struct cfs_rq *cfs_rq)
{
	return cfs_rq->curr;
}

/* An entity is a task if it doesn't "own" a runqueue */
#define entity_is_task(se)	(!se->my_q)

static inline void
set_cfs_rq_curr(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	cfs_rq->curr = se;
}

#else	/* CONFIG_FAIR_GROUP_SCHED */

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

static inline struct sched_entity *cfs_rq_curr(struct cfs_rq *cfs_rq)
{
	struct rq *rq = rq_of(cfs_rq);

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

	return &rq->curr->se;
}

#define entity_is_task(se)	1

static inline void
set_cfs_rq_curr(struct cfs_rq *cfs_rq, struct sched_entity *se) { }

#endif	/* CONFIG_FAIR_GROUP_SCHED */

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


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

/*
 * Enqueue an entity into the rb-tree:
 */
static inline void
__enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
	struct rb_node *parent = NULL;
	struct sched_entity *entry;
	s64 key = se->fair_key;
	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.
		 */
		if (key - entry->fair_key < 0) {
			link = &parent->rb_left;
		} else {
			link = &parent->rb_right;
			leftmost = 0;
		}
	}

	/*
	 * Maintain a cache of leftmost tree entries (it is frequently
	 * used):
	 */
	if (leftmost)
		cfs_rq->rb_leftmost = &se->run_node;

	rb_link_node(&se->run_node, parent, link);
	rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
	update_load_add(&cfs_rq->load, se->load.weight);
	cfs_rq->nr_running++;
	se->on_rq = 1;
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	schedstat_add(cfs_rq, wait_runtime, se->wait_runtime);
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}

static inline void
__dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	if (cfs_rq->rb_leftmost == &se->run_node)
		cfs_rq->rb_leftmost = rb_next(&se->run_node);
	rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
	update_load_sub(&cfs_rq->load, se->load.weight);
	cfs_rq->nr_running--;
	se->on_rq = 0;
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	schedstat_add(cfs_rq, wait_runtime, -se->wait_runtime);
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}

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);
}

/**************************************************************
 * Scheduling class statistics methods:
 */

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/*
 * Calculate the preemption granularity needed to schedule every
 * runnable task once per sysctl_sched_latency amount of time.
 * (down to a sensible low limit on granularity)
 *
 * For example, if there are 2 tasks running and latency is 10 msecs,
 * we switch tasks every 5 msecs. If we have 3 tasks running, we have
 * to switch tasks every 3.33 msecs to get a 10 msecs observed latency
 * for each task. We do finer and finer scheduling up to until we
 * reach the minimum granularity value.
 *
 * To achieve this we use the following dynamic-granularity rule:
 *
 *    gran = lat/nr - lat/nr/nr
 *
 * This comes out of the following equations:
 *
 *    kA1 + gran = kB1
 *    kB2 + gran = kA2
 *    kA2 = kA1
 *    kB2 = kB1 - d + d/nr
 *    lat = d * nr
 *
 * Where 'k' is key, 'A' is task A (waiting), 'B' is task B (running),
 * '1' is start of time, '2' is end of time, 'd' is delay between
 * 1 and 2 (during which task B was running), 'nr' is number of tasks
 * running, 'lat' is the the period of each task. ('lat' is the
 * sched_latency that we aim for.)
 */
static long
sched_granularity(struct cfs_rq *cfs_rq)
{
	unsigned int gran = sysctl_sched_latency;
	unsigned int nr = cfs_rq->nr_running;

	if (nr > 1) {
		gran = gran/nr - gran/nr/nr;
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		gran = max(gran, sysctl_sched_min_granularity);
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	}

	return gran;
}

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/*
 * We rescale the rescheduling granularity of tasks according to their
 * nice level, but only linearly, not exponentially:
 */
static long
niced_granularity(struct sched_entity *curr, unsigned long granularity)
{
	u64 tmp;

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	if (likely(curr->load.weight == NICE_0_LOAD))
		return granularity;
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	/*
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	 * Positive nice levels get the same granularity as nice-0:
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	 */
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	if (likely(curr->load.weight < NICE_0_LOAD)) {
		tmp = curr->load.weight * (u64)granularity;
		return (long) (tmp >> NICE_0_SHIFT);
	}
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	/*
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	 * Negative nice level tasks get linearly finer
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	 * granularity:
	 */
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	tmp = curr->load.inv_weight * (u64)granularity;
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	/*
	 * It will always fit into 'long':
	 */
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	return (long) (tmp >> (WMULT_SHIFT-NICE_0_SHIFT));
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}

static inline void
limit_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
	long limit = sysctl_sched_runtime_limit;

	/*
	 * Niced tasks have the same history dynamic range as
	 * non-niced tasks:
	 */
	if (unlikely(se->wait_runtime > limit)) {
		se->wait_runtime = limit;
		schedstat_inc(se, wait_runtime_overruns);
		schedstat_inc(cfs_rq, wait_runtime_overruns);
	}
	if (unlikely(se->wait_runtime < -limit)) {
		se->wait_runtime = -limit;
		schedstat_inc(se, wait_runtime_underruns);
		schedstat_inc(cfs_rq, wait_runtime_underruns);
	}
}

static inline void
__add_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se, long delta)
{
	se->wait_runtime += delta;
	schedstat_add(se, sum_wait_runtime, delta);
	limit_wait_runtime(cfs_rq, se);
}

static void
add_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se, long delta)
{
	schedstat_add(cfs_rq, wait_runtime, -se->wait_runtime);
	__add_wait_runtime(cfs_rq, se, delta);
	schedstat_add(cfs_rq, wait_runtime, se->wait_runtime);
}

/*
 * 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)
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{
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	unsigned long delta, delta_exec, delta_fair, delta_mine;
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	struct load_weight *lw = &cfs_rq->load;
	unsigned long load = lw->weight;

	delta_exec = curr->delta_exec;
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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;
	cfs_rq->exec_clock += delta_exec;

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	if (unlikely(!load))
		return;

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	delta_fair = calc_delta_fair(delta_exec, lw);
	delta_mine = calc_delta_mine(delta_exec, curr->load.weight, lw);

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	if (cfs_rq->sleeper_bonus > sysctl_sched_min_granularity) {
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		delta = min((u64)delta_mine, cfs_rq->sleeper_bonus);
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		delta = min(delta, (unsigned long)(
			(long)sysctl_sched_runtime_limit - curr->wait_runtime));
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		cfs_rq->sleeper_bonus -= delta;
		delta_mine -= delta;
	}

	cfs_rq->fair_clock += delta_fair;
	/*
	 * We executed delta_exec amount of time on the CPU,
	 * but we were only entitled to delta_mine amount of
	 * time during that period (if nr_running == 1 then
	 * the two values are equal)
	 * [Note: delta_mine - delta_exec is negative]:
	 */
	add_wait_runtime(cfs_rq, curr, delta_mine - delta_exec);
}

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static void update_curr(struct cfs_rq *cfs_rq)
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{
	struct sched_entity *curr = cfs_rq_curr(cfs_rq);
	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)(rq_of(cfs_rq)->clock - curr->exec_start);
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	curr->delta_exec += delta_exec;

	if (unlikely(curr->delta_exec > sysctl_sched_stat_granularity)) {
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		__update_curr(cfs_rq, curr);
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		curr->delta_exec = 0;
	}
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	curr->exec_start = rq_of(cfs_rq)->clock;
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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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{
	se->wait_start_fair = cfs_rq->fair_clock;
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	schedstat_set(se->wait_start, rq_of(cfs_rq)->clock);
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}

/*
 * We calculate fair deltas here, so protect against the random effects
 * of a multiplication overflow by capping it to the runtime limit:
 */
#if BITS_PER_LONG == 32
static inline unsigned long
calc_weighted(unsigned long delta, unsigned long weight, int shift)
{
	u64 tmp = (u64)delta * weight >> shift;

	if (unlikely(tmp > sysctl_sched_runtime_limit*2))
		return sysctl_sched_runtime_limit*2;
	return tmp;
}
#else
static inline unsigned long
calc_weighted(unsigned long delta, unsigned long weight, int shift)
{
	return delta * weight >> shift;
}
#endif

/*
 * 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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{
	s64 key;

	/*
	 * Are we enqueueing a waiting task? (for current tasks
	 * a dequeue/enqueue event is a NOP)
	 */
	if (se != cfs_rq_curr(cfs_rq))
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		update_stats_wait_start(cfs_rq, se);
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	/*
	 * Update the key:
	 */
	key = cfs_rq->fair_clock;

	/*
	 * Optimize the common nice 0 case:
	 */
	if (likely(se->load.weight == NICE_0_LOAD)) {
		key -= se->wait_runtime;
	} else {
		u64 tmp;

		if (se->wait_runtime < 0) {
			tmp = -se->wait_runtime;
			key += (tmp * se->load.inv_weight) >>
					(WMULT_SHIFT - NICE_0_SHIFT);
		} else {
			tmp = se->wait_runtime;
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			key -= (tmp * se->load.inv_weight) >>
					(WMULT_SHIFT - NICE_0_SHIFT);
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		}
	}

	se->fair_key = key;
}

/*
 * Note: must be called with a freshly updated rq->fair_clock.
 */
static inline void
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__update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
	unsigned long delta_fair = se->delta_fair_run;

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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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	if (unlikely(se->load.weight != NICE_0_LOAD))
		delta_fair = calc_weighted(delta_fair, se->load.weight,
							NICE_0_SHIFT);

	add_wait_runtime(cfs_rq, se, delta_fair);
}

static void
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update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
	unsigned long delta_fair;

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	if (unlikely(!se->wait_start_fair))
		return;

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	delta_fair = (unsigned long)min((u64)(2*sysctl_sched_runtime_limit),
			(u64)(cfs_rq->fair_clock - se->wait_start_fair));

	se->delta_fair_run += delta_fair;
	if (unlikely(abs(se->delta_fair_run) >=
				sysctl_sched_stat_granularity)) {
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		__update_stats_wait_end(cfs_rq, se);
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		se->delta_fair_run = 0;
	}

	se->wait_start_fair = 0;
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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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{
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	update_curr(cfs_rq);
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	/*
	 * Mark the end of the wait period if dequeueing a
	 * waiting task:
	 */
	if (se != cfs_rq_curr(cfs_rq))
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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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}

/*
 * We are descheduling a task - update its stats:
 */
static inline void
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update_stats_curr_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
	se->exec_start = 0;
}

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

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static void __enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
	unsigned long load = cfs_rq->load.weight, delta_fair;
	long prev_runtime;

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	/*
	 * Do not boost sleepers if there's too much bonus 'in flight'
	 * already:
	 */
	if (unlikely(cfs_rq->sleeper_bonus > sysctl_sched_runtime_limit))
		return;

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	if (sysctl_sched_features & SCHED_FEAT_SLEEPER_LOAD_AVG)
		load = rq_of(cfs_rq)->cpu_load[2];

	delta_fair = se->delta_fair_sleep;

	/*
	 * Fix up delta_fair with the effect of us running
	 * during the whole sleep period:
	 */
	if (sysctl_sched_features & SCHED_FEAT_SLEEPER_AVG)
		delta_fair = div64_likely32((u64)delta_fair * load,
						load + se->load.weight);

	if (unlikely(se->load.weight != NICE_0_LOAD))
		delta_fair = calc_weighted(delta_fair, se->load.weight,
							NICE_0_SHIFT);

	prev_runtime = se->wait_runtime;
	__add_wait_runtime(cfs_rq, se, delta_fair);
	delta_fair = se->wait_runtime - prev_runtime;

	/*
	 * Track the amount of bonus we've given to sleepers:
	 */
	cfs_rq->sleeper_bonus += delta_fair;
}

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static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
	struct task_struct *tsk = task_of(se);
	unsigned long delta_fair;

	if ((entity_is_task(se) && tsk->policy == SCHED_BATCH) ||
			 !(sysctl_sched_features & SCHED_FEAT_FAIR_SLEEPERS))
		return;

	delta_fair = (unsigned long)min((u64)(2*sysctl_sched_runtime_limit),
		(u64)(cfs_rq->fair_clock - se->sleep_start_fair));

	se->delta_fair_sleep += delta_fair;
	if (unlikely(abs(se->delta_fair_sleep) >=
				sysctl_sched_stat_granularity)) {
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		__enqueue_sleeper(cfs_rq, se);
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		se->delta_fair_sleep = 0;
	}

	se->sleep_start_fair = 0;

#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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		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;
	}
	if (se->block_start) {
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		u64 delta = rq_of(cfs_rq)->clock - se->block_start;
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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)) {
			profile_hits(SLEEP_PROFILING, (void *)get_wchan(tsk),
				     delta >> 20);
		}
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	}
#endif
}

static void
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enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
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{
	/*
	 * Update the fair clock.
	 */
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	update_curr(cfs_rq);
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	if (wakeup)
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		enqueue_sleeper(cfs_rq, se);
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	update_stats_enqueue(cfs_rq, se);
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	__enqueue_entity(cfs_rq, se);
}

static void
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dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
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{
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	update_stats_dequeue(cfs_rq, se);
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	if (sleep) {
		se->sleep_start_fair = cfs_rq->fair_clock;
#ifdef CONFIG_SCHEDSTATS
		if (entity_is_task(se)) {
			struct task_struct *tsk = task_of(se);

			if (tsk->state & TASK_INTERRUPTIBLE)
682
				se->sleep_start = rq_of(cfs_rq)->clock;
683
			if (tsk->state & TASK_UNINTERRUPTIBLE)
684
				se->block_start = rq_of(cfs_rq)->clock;
685 686 687 688 689 690 691 692 693
		}
#endif
	}
	__dequeue_entity(cfs_rq, se);
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
694
static void
695 696 697 698
__check_preempt_curr_fair(struct cfs_rq *cfs_rq, struct sched_entity *se,
			  struct sched_entity *curr, unsigned long granularity)
{
	s64 __delta = curr->fair_key - se->fair_key;
699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716
	unsigned long ideal_runtime, delta_exec;

	/*
	 * ideal_runtime is compared against sum_exec_runtime, which is
	 * walltime, hence do not scale.
	 */
	ideal_runtime = max(sysctl_sched_latency / cfs_rq->nr_running,
			(unsigned long)sysctl_sched_min_granularity);

	/*
	 * If we executed more than what the latency constraint suggests,
	 * reduce the rescheduling granularity. This way the total latency
	 * of how much a task is not scheduled converges to
	 * sysctl_sched_latency:
	 */
	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
	if (delta_exec > ideal_runtime)
		granularity = 0;
717 718 719 720 721

	/*
	 * Take scheduling granularity into account - do not
	 * preempt the current task unless the best task has
	 * a larger than sched_granularity fairness advantage:
722 723
	 *
	 * scale granularity as key space is in fair_clock.
724
	 */
725
	if (__delta > niced_granularity(curr, granularity))
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		resched_task(rq_of(cfs_rq)->curr);
}

static inline void
730
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
731 732 733 734 735 736 737 738
{
	/*
	 * 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. (note, here we rely on pick_next_task() having
	 * done a put_prev_task_fair() shortly before this, which
	 * updated rq->fair_clock - used by update_stats_wait_end())
	 */
739
	update_stats_wait_end(cfs_rq, se);
740
	update_stats_curr_start(cfs_rq, se);
741
	set_cfs_rq_curr(cfs_rq, 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):
	 */
	if (rq_of(cfs_rq)->ls.load.weight >= 2*se->load.weight) {
		se->slice_max = max(se->slice_max,
			se->sum_exec_runtime - se->prev_sum_exec_runtime);
	}
#endif
753
	se->prev_sum_exec_runtime = se->sum_exec_runtime;
754 755
}

756
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
757 758 759
{
	struct sched_entity *se = __pick_next_entity(cfs_rq);

760
	set_next_entity(cfs_rq, se);
761 762 763 764

	return se;
}

765
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
766 767 768 769 770 771
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
772
		update_curr(cfs_rq);
773

774
	update_stats_curr_end(cfs_rq, prev);
775 776

	if (prev->on_rq)
777
		update_stats_wait_start(cfs_rq, prev);
778 779 780 781 782 783
	set_cfs_rq_curr(cfs_rq, NULL);
}

static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
{
	struct sched_entity *next;
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	/*
	 * Dequeue and enqueue the task to update its
	 * position within the tree:
	 */
789
	dequeue_entity(cfs_rq, curr, 0);
790
	enqueue_entity(cfs_rq, curr, 0);
791 792 793 794 795 796 797 798

	/*
	 * Reschedule if another task tops the current one.
	 */
	next = __pick_next_entity(cfs_rq);
	if (next == curr)
		return;

799 800
	__check_preempt_curr_fair(cfs_rq, next, curr,
			sched_granularity(cfs_rq));
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}

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

#ifdef CONFIG_FAIR_GROUP_SCHED

/* 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)
{
	/* A later patch will take group into account */
	return &cpu_rq(this_cpu)->cfs;
}

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

/* Do the two (enqueued) tasks belong to the same group ? */
static inline int is_same_group(struct task_struct *curr, struct task_struct *p)
{
	if (curr->se.cfs_rq == p->se.cfs_rq)
		return 1;

	return 0;
}

#else	/* CONFIG_FAIR_GROUP_SCHED */

#define for_each_sched_entity(se) \
		for (; se; se = NULL)

static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
{
	return &task_rq(p)->cfs;
}

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 task_struct *curr, struct task_struct *p)
{
	return 1;
}

#endif	/* CONFIG_FAIR_GROUP_SCHED */

/*
 * 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:
 */
896
static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
897 898 899 900 901 902 903 904
{
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se;

	for_each_sched_entity(se) {
		if (se->on_rq)
			break;
		cfs_rq = cfs_rq_of(se);
905
		enqueue_entity(cfs_rq, se, wakeup);
906 907 908 909 910 911 912 913
	}
}

/*
 * The dequeue_task method is called before nr_running is
 * decreased. We remove the task from the rbtree and
 * update the fair scheduling stats:
 */
914
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
915 916 917 918 919 920
{
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &p->se;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
921
		dequeue_entity(cfs_rq, se, sleep);
922 923 924 925 926 927 928
		/* Don't dequeue parent if it has other entities besides us */
		if (cfs_rq->load.weight)
			break;
	}
}

/*
929 930 931
 * 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.
932 933 934 935
 */
static void yield_task_fair(struct rq *rq, struct task_struct *p)
{
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
936 937 938
	struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
	struct sched_entity *rightmost, *se = &p->se;
	struct rb_node *parent;
939 940

	/*
941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958
	 * Are we the only task in the tree?
	 */
	if (unlikely(cfs_rq->nr_running == 1))
		return;

	if (likely(!sysctl_sched_compat_yield)) {
		__update_rq_clock(rq);
		/*
		 * Dequeue and enqueue the task to update its
		 * position within the tree:
		 */
		dequeue_entity(cfs_rq, &p->se, 0);
		enqueue_entity(cfs_rq, &p->se, 0);

		return;
	}
	/*
	 * Find the rightmost entry in the rbtree:
959
	 */
960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984
	do {
		parent = *link;
		link = &parent->rb_right;
	} while (*link);

	rightmost = rb_entry(parent, struct sched_entity, run_node);
	/*
	 * Already in the rightmost position?
	 */
	if (unlikely(rightmost == se))
		return;

	/*
	 * Minimally necessary key value to be last in the tree:
	 */
	se->fair_key = rightmost->fair_key + 1;

	if (cfs_rq->rb_leftmost == &se->run_node)
		cfs_rq->rb_leftmost = rb_next(&se->run_node);
	/*
	 * Relink the task to the rightmost position:
	 */
	rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
	rb_link_node(&se->run_node, parent, link);
	rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
985 986 987 988 989 990 991 992 993 994 995 996
}

/*
 * Preempt the current task with a newly woken task if needed:
 */
static void check_preempt_curr_fair(struct rq *rq, struct task_struct *p)
{
	struct task_struct *curr = rq->curr;
	struct cfs_rq *cfs_rq = task_cfs_rq(curr);
	unsigned long gran;

	if (unlikely(rt_prio(p->prio))) {
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		update_rq_clock(rq);
998
		update_curr(cfs_rq);
999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013
		resched_task(curr);
		return;
	}

	gran = sysctl_sched_wakeup_granularity;
	/*
	 * Batch tasks prefer throughput over latency:
	 */
	if (unlikely(p->policy == SCHED_BATCH))
		gran = sysctl_sched_batch_wakeup_granularity;

	if (is_same_group(curr, p))
		__check_preempt_curr_fair(cfs_rq, &p->se, &curr->se, gran);
}

1014
static struct task_struct *pick_next_task_fair(struct rq *rq)
1015 1016 1017 1018 1019 1020 1021 1022
{
	struct cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;

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

	do {
1023
		se = pick_next_entity(cfs_rq);
1024 1025 1026 1027 1028 1029 1030 1031 1032
		cfs_rq = group_cfs_rq(se);
	} while (cfs_rq);

	return task_of(se);
}

/*
 * Account for a descheduled task:
 */
1033
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
1034 1035 1036 1037 1038 1039
{
	struct sched_entity *se = &prev->se;
	struct cfs_rq *cfs_rq;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
1040
		put_prev_entity(cfs_rq, se);
1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082
	}
}

/**************************************************
 * 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:
 */
static inline struct task_struct *
__load_balance_iterator(struct cfs_rq *cfs_rq, struct rb_node *curr)
{
	struct task_struct *p;

	if (!curr)
		return NULL;

	p = rb_entry(curr, struct task_struct, se.run_node);
	cfs_rq->rb_load_balance_curr = rb_next(curr);

	return p;
}

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

	return __load_balance_iterator(cfs_rq, first_fair(cfs_rq));
}

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

	return __load_balance_iterator(cfs_rq, cfs_rq->rb_load_balance_curr);
}

1083
#ifdef CONFIG_FAIR_GROUP_SCHED
1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096
static int cfs_rq_best_prio(struct cfs_rq *cfs_rq)
{
	struct sched_entity *curr;
	struct task_struct *p;

	if (!cfs_rq->nr_running)
		return MAX_PRIO;

	curr = __pick_next_entity(cfs_rq);
	p = task_of(curr);

	return p->prio;
}
1097
#endif
1098

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static unsigned long
1100
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
1101 1102 1103
		  unsigned long max_nr_move, unsigned long max_load_move,
		  struct sched_domain *sd, enum cpu_idle_type idle,
		  int *all_pinned, int *this_best_prio)
1104 1105 1106 1107 1108 1109 1110 1111 1112 1113
{
	struct cfs_rq *busy_cfs_rq;
	unsigned long load_moved, total_nr_moved = 0, nr_moved;
	long rem_load_move = max_load_move;
	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) {
1114
#ifdef CONFIG_FAIR_GROUP_SCHED
1115
		struct cfs_rq *this_cfs_rq;
1116
		long imbalance;
1117 1118 1119 1120
		unsigned long maxload;

		this_cfs_rq = cpu_cfs_rq(busy_cfs_rq, this_cpu);

1121
		imbalance = busy_cfs_rq->load.weight - this_cfs_rq->load.weight;
1122 1123 1124 1125 1126 1127 1128 1129
		/* Don't pull if this_cfs_rq has more load than busy_cfs_rq */
		if (imbalance <= 0)
			continue;

		/* Don't pull more than imbalance/2 */
		imbalance /= 2;
		maxload = min(rem_load_move, imbalance);

1130 1131
		*this_best_prio = cfs_rq_best_prio(this_cfs_rq);
#else
1132
# define maxload rem_load_move
1133
#endif
1134 1135 1136 1137 1138 1139
		/* pass busy_cfs_rq argument into
		 * load_balance_[start|next]_fair iterators
		 */
		cfs_rq_iterator.arg = busy_cfs_rq;
		nr_moved = balance_tasks(this_rq, this_cpu, busiest,
				max_nr_move, maxload, sd, idle, all_pinned,
1140
				&load_moved, this_best_prio, &cfs_rq_iterator);
1141 1142 1143 1144 1145 1146 1147 1148 1149

		total_nr_moved += nr_moved;
		max_nr_move -= nr_moved;
		rem_load_move -= load_moved;

		if (max_nr_move <= 0 || rem_load_move <= 0)
			break;
	}

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	return max_load_move - rem_load_move;
1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173
}

/*
 * scheduler tick hitting a task of our scheduling class:
 */
static void task_tick_fair(struct rq *rq, struct task_struct *curr)
{
	struct cfs_rq *cfs_rq;
	struct sched_entity *se = &curr->se;

	for_each_sched_entity(se) {
		cfs_rq = cfs_rq_of(se);
		entity_tick(cfs_rq, se);
	}
}

/*
 * 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.
 */
1174
static void task_new_fair(struct rq *rq, struct task_struct *p)
1175 1176
{
	struct cfs_rq *cfs_rq = task_cfs_rq(p);
1177
	struct sched_entity *se = &p->se, *curr = cfs_rq_curr(cfs_rq);
1178 1179 1180

	sched_info_queued(p);

1181
	update_curr(cfs_rq);
1182
	update_stats_enqueue(cfs_rq, se);
1183 1184 1185 1186 1187
	/*
	 * Child runs first: we let it run before the parent
	 * until it reschedules once. We set up the key so that
	 * it will preempt the parent:
	 */
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	se->fair_key = curr->fair_key -
1189
		niced_granularity(curr, sched_granularity(cfs_rq)) - 1;
1190 1191 1192 1193 1194
	/*
	 * The first wait is dominated by the child-runs-first logic,
	 * so do not credit it with that waiting time yet:
	 */
	if (sysctl_sched_features & SCHED_FEAT_SKIP_INITIAL)
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		se->wait_start_fair = 0;
1196 1197 1198 1199 1200

	/*
	 * The statistical average of wait_runtime is about
	 * -granularity/2, so initialize the task with that:
	 */
1201
	if (sysctl_sched_features & SCHED_FEAT_START_DEBIT)
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		se->wait_runtime = -(sched_granularity(cfs_rq) / 2);
1203 1204

	__enqueue_entity(cfs_rq, se);
1205
	resched_task(rq->curr);
1206 1207 1208 1209 1210 1211 1212 1213 1214 1215
}

#ifdef CONFIG_FAIR_GROUP_SCHED
/* 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)
{
1216
	struct sched_entity *se = &rq->curr->se;
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1218 1219
	for_each_sched_entity(se)
		set_next_entity(cfs_rq_of(se), se);
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}
#else
static void set_curr_task_fair(struct rq *rq)
{
}
#endif

/*
 * All the scheduling class methods:
 */
struct sched_class fair_sched_class __read_mostly = {
	.enqueue_task		= enqueue_task_fair,
	.dequeue_task		= dequeue_task_fair,
	.yield_task		= yield_task_fair,

	.check_preempt_curr	= check_preempt_curr_fair,

	.pick_next_task		= pick_next_task_fair,
	.put_prev_task		= put_prev_task_fair,

	.load_balance		= load_balance_fair,

	.set_curr_task          = set_curr_task_fair,
	.task_tick		= task_tick_fair,
	.task_new		= task_new_fair,
};

#ifdef CONFIG_SCHED_DEBUG
1248
static void print_cfs_stats(struct seq_file *m, int cpu)
1249 1250 1251
{
	struct cfs_rq *cfs_rq;

1252
	for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
1253
		print_cfs_rq(m, cpu, cfs_rq);
1254 1255
}
#endif