Commit aae17ebb authored by Leonardo Bras's avatar Leonardo Bras Committed by Tejun Heo
Browse files

workqueue: Avoid using isolated cpus' timers on queue_delayed_work 



When __queue_delayed_work() is called, it chooses a cpu for handling the
timer interrupt. As of today, it will pick either the cpu passed as
parameter or the last cpu used for this.

This is not good if a system does use CPU isolation, because it can take
away some valuable cpu time to:
1 - deal with the timer interrupt,
2 - schedule-out the desired task,
3 - queue work on a random workqueue, and
4 - schedule the desired task back to the cpu.

So to fix this, during __queue_delayed_work(), if cpu isolation is in
place, pick a random non-isolated cpu to handle the timer interrupt.

As an optimization, if the current cpu is not isolated, use it instead
of looking for another candidate.

Signed-off-by: default avatarLeonardo Bras <leobras@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 07daa99b

kernel/workqueue.c

+11 −3
Original line number Diff line number Diff line
@@ -2362,10 +2362,18 @@ static void __queue_delayed_work(int cpu, struct workqueue_struct *wq, 
	dwork->cpu = cpu;

	timer->expires = jiffies + delay;



	if (unlikely(cpu != WORK_CPU_UNBOUND))

	if (housekeeping_enabled(HK_TYPE_TIMER)) {

		/* If the current cpu is a housekeeping cpu, use it. */

		cpu = smp_processor_id();

		if (!housekeeping_test_cpu(cpu, HK_TYPE_TIMER))

			cpu = housekeeping_any_cpu(HK_TYPE_TIMER);

		add_timer_on(timer, cpu);

	else

	} else {

		if (likely(cpu == WORK_CPU_UNBOUND))

			add_timer(timer);

		else

			add_timer_on(timer, cpu);

	}

}



/**