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Commit 85dac906 authored by Paul Turner's avatar Paul Turner Committed by Ingo Molnar
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sched: Add support for throttling group entities 



Now that consumption is tracked (via update_curr()) we add support to throttle
group entities (and their corresponding cfs_rqs) in the case where this is no
run-time remaining.

Throttled entities are dequeued to prevent scheduling, additionally we mark
them as throttled (using cfs_rq->throttled) to prevent them from becoming
re-enqueued until they are unthrottled.  A list of a task_group's throttled
entities are maintained on the cfs_bandwidth structure.

Note: While the machinery for throttling is added in this patch the act of
throttling an entity exceeding its bandwidth is deferred until later within
the series.

Signed-off-by: default avatarPaul Turner <pjt@google.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.480608533@google.com


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent a9cf55b2

kernel/sched.c

+7 −0
Original line number Diff line number Diff line
@@ -260,6 +260,8 @@ struct cfs_bandwidth { 


	int idle, timer_active;

	struct hrtimer period_timer;

	struct list_head throttled_cfs_rq;



#endif

};
@@ -399,6 +401,9 @@ struct cfs_rq { 
	int runtime_enabled;

	u64 runtime_expires;

	s64 runtime_remaining;



	int throttled;

	struct list_head throttled_list;

#endif

#endif

};
@@ -441,6 +446,7 @@ static void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) 
	cfs_b->quota = RUNTIME_INF;

	cfs_b->period = ns_to_ktime(default_cfs_period());



	INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq);

	hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);

	cfs_b->period_timer.function = sched_cfs_period_timer;

}
@@ -448,6 +454,7 @@ static void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) 
static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)

{

	cfs_rq->runtime_enabled = 0;

	INIT_LIST_HEAD(&cfs_rq->throttled_list);

}



/* requires cfs_b->lock, may release to reprogram timer */

kernel/sched_fair.c

+85 −4
Original line number Diff line number Diff line
@@ -1291,7 +1291,8 @@ static void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b) 
	cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period);

}



static void assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)

/* returns 0 on failure to allocate runtime */

static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq)

{

	struct task_group *tg = cfs_rq->tg;

	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg);
@@ -1332,6 +1333,8 @@ static void assign_cfs_rq_runtime(struct cfs_rq *cfs_rq) 
	 */

	if ((s64)(expires - cfs_rq->runtime_expires) > 0)

		cfs_rq->runtime_expires = expires;



	return cfs_rq->runtime_remaining > 0;

}



/*
@@ -1378,7 +1381,12 @@ static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, 
	if (likely(cfs_rq->runtime_remaining > 0))

		return;



	assign_cfs_rq_runtime(cfs_rq);

	/*

	 * if we're unable to extend our runtime we resched so that the active

	 * hierarchy can be throttled

	 */

	if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr))

		resched_task(rq_of(cfs_rq)->curr);

}



static __always_inline void account_cfs_rq_runtime(struct cfs_rq *cfs_rq,
@@ -1390,6 +1398,47 @@ static __always_inline void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, 
	__account_cfs_rq_runtime(cfs_rq, delta_exec);

}



static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)

{

	return cfs_rq->throttled;

}



static __used void throttle_cfs_rq(struct cfs_rq *cfs_rq)

{

	struct rq *rq = rq_of(cfs_rq);

	struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);

	struct sched_entity *se;

	long task_delta, dequeue = 1;



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



	/* account load preceding throttle */

	update_cfs_load(cfs_rq, 0);



	task_delta = cfs_rq->h_nr_running;

	for_each_sched_entity(se) {

		struct cfs_rq *qcfs_rq = cfs_rq_of(se);

		/* throttled entity or throttle-on-deactivate */

		if (!se->on_rq)

			break;



		if (dequeue)

			dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP);

		qcfs_rq->h_nr_running -= task_delta;



		if (qcfs_rq->load.weight)

			dequeue = 0;

	}



	if (!se)

		rq->nr_running -= task_delta;



	cfs_rq->throttled = 1;

	raw_spin_lock(&cfs_b->lock);

	list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq);

	raw_spin_unlock(&cfs_b->lock);

}



/*

 * Responsible for refilling a task_group's bandwidth and unthrottling its

 * cfs_rqs as appropriate. If there has been no activity within the last
@@ -1425,6 +1474,11 @@ static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun) 
#else

static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq,

				     unsigned long delta_exec) {}



static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq)

{

	return 0;

}

#endif



/**************************************************
@@ -1503,7 +1557,17 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) 
			break;

		cfs_rq = cfs_rq_of(se);

		enqueue_entity(cfs_rq, se, flags);



		/*

		 * end evaluation on encountering a throttled cfs_rq

		 *

		 * note: in the case of encountering a throttled cfs_rq we will

		 * post the final h_nr_running increment below.

		*/

		if (cfs_rq_throttled(cfs_rq))

			break;

		cfs_rq->h_nr_running++;



		flags = ENQUEUE_WAKEUP;

	}
@@ -1511,10 +1575,14 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) 
		cfs_rq = cfs_rq_of(se);

		cfs_rq->h_nr_running++;



		if (cfs_rq_throttled(cfs_rq))

			break;



		update_cfs_load(cfs_rq, 0);

		update_cfs_shares(cfs_rq);

	}



	if (!se)

		inc_nr_running(rq);

	hrtick_update(rq);

}
@@ -1535,6 +1603,15 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) 
	for_each_sched_entity(se) {

		cfs_rq = cfs_rq_of(se);

		dequeue_entity(cfs_rq, se, flags);



		/*

		 * end evaluation on encountering a throttled cfs_rq

		 *

		 * note: in the case of encountering a throttled cfs_rq we will

		 * post the final h_nr_running decrement below.

		*/

		if (cfs_rq_throttled(cfs_rq))

			break;

		cfs_rq->h_nr_running--;



		/* Don't dequeue parent if it has other entities besides us */
@@ -1557,10 +1634,14 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) 
		cfs_rq = cfs_rq_of(se);

		cfs_rq->h_nr_running--;



		if (cfs_rq_throttled(cfs_rq))

			break;



		update_cfs_load(cfs_rq, 0);

		update_cfs_shares(cfs_rq);

	}



	if (!se)

		dec_nr_running(rq);

	hrtick_update(rq);

}