From aae17ebb53cd3da37f5dfbde937acd091eb4340c Mon Sep 17 00:00:00 2001 From: Leonardo Bras Date: Mon, 29 Jan 2024 22:00:46 -0300 Subject: [PATCH] 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 Signed-off-by: Tejun Heo --- kernel/workqueue.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 903be39bd2d1..9221a4c57ae1 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -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); + } } /**