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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: Leonardo Bras <leobras@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Leonardo Bras 2024-01-29 22:00:46 -03:00 committed by Tejun Heo
parent 07daa99b7f
commit aae17ebb53
1 changed files with 11 additions and 3 deletions
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14
kernel/workqueue.c
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@ -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
add_timer(timer);
} else {
if (likely(cpu == WORK_CPU_UNBOUND))
add_timer(timer);
else
add_timer_on(timer, cpu);
}
}
/**