Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit c249f255 authored by Dave Kleikamp's avatar Dave Kleikamp Committed by Ingo Molnar
Browse files

sched/rt: Minimize rq->lock contention in do_sched_rt_period_timer() 



With CONFIG_RT_GROUP_SCHED=y, do_sched_rt_period_timer() sequentially
takes each CPU's rq->lock. On a large, busy system, the cumulative time it
takes to acquire each lock can be excessive, even triggering a watchdog
timeout.

If rt_rq->rt_time and rt_rq->rt_nr_running are both zero, this function does
nothing while holding the lock, so don't bother taking it at all.

Signed-off-by: default avatarDave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/a767637b-df85-912f-ba69-c90ee00a3fb6@oracle.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 896bbb25

kernel/sched/rt.c

+11 −0
Original line number Diff line number Diff line
@@ -840,6 +840,17 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun) 
		int enqueue = 0;

		struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);

		struct rq *rq = rq_of_rt_rq(rt_rq);

		int skip;



		/*

		 * When span == cpu_online_mask, taking each rq->lock

		 * can be time-consuming. Try to avoid it when possible.

		 */

		raw_spin_lock(&rt_rq->rt_runtime_lock);

		skip = !rt_rq->rt_time && !rt_rq->rt_nr_running;

		raw_spin_unlock(&rt_rq->rt_runtime_lock);

		if (skip)

			continue;



		raw_spin_lock(&rq->lock);

		if (rt_rq->rt_time) {