Messages in this thread Patch in this message | | | From | Leonardo Bras <> | Subject | [PATCH v2 1/1] wq: Avoid using isolated cpus' timers on queue_delayed_work | Date | Mon, 29 Jan 2024 22:00:46 -0300 |
| |
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> --- Changes since v1: - Make sure the CPU is isolated for any value of "cpu"
Changes since RFC: - Do not use the same cpu from the timer for queueing the work. - If the current cpu is not isolated, use it's timer instead of looking for another candidate.
kernel/workqueue.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 76e60faed8923..8dd7c01b326a4 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1958,10 +1958,18 @@ 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); + } } /** -- 2.43.0
| |