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Commit 11697830 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: fix ideal_runtime calculations for reniced tasks 



fix ideal_runtime:

  - do not scale it using niced_granularity()
    it is against sum_exec_delta, so its wall-time, not fair-time.

  - move the whole check into __check_preempt_curr_fair()
    so that wakeup preemption can also benefit from the new logic.

this also results in code size reduction:

   text    data     bss     dec     hex filename
  13391     228    1204   14823    39e7 sched.o.before
  13369     228    1204   14801    39d1 sched.o.after

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 4a55b450

kernel/sched_fair.c

+22 −16
Original line number Diff line number Diff line
@@ -678,11 +678,31 @@ __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;

	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;



	/*

	 * Take scheduling granularity into account - do not

	 * preempt the current task unless the best task has

	 * a larger than sched_granularity fairness advantage:

	 *

	 * scale granularity as key space is in fair_clock.

	 */

	if (__delta > niced_granularity(curr, granularity))

		resched_task(rq_of(cfs_rq)->curr);
@@ -731,7 +751,6 @@ static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev) 


static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)

{

	unsigned long gran, ideal_runtime, delta_exec;

	struct sched_entity *next;



	/*
@@ -748,21 +767,8 @@ static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) 
	if (next == curr)

		return;



	gran = sched_granularity(cfs_rq);

	ideal_runtime = niced_granularity(curr,

		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)

		gran = 0;



	__check_preempt_curr_fair(cfs_rq, next, curr, gran);

	__check_preempt_curr_fair(cfs_rq, next, curr,

			sched_granularity(cfs_rq));

}



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