From: Leonardo Bras <leobras@redhat.com>
To: Tejun Heo <tj@kernel.org>, Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Leonardo Bras <leobras@redhat.com>,
linux-kernel@vger.kernel.org, Junyao Zhao <junzhao@redhat.com>
Subject: [PATCH v2 1/1] wq: Avoid using isolated cpus' timers on queue_delayed_work
Date: Mon, 29 Jan 2024 22:00:46 -0300 [thread overview]
Message-ID: <20240130010046.2730139-2-leobras@redhat.com> (raw)
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
next reply other threads:[~2024-01-30 1:01 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-30 1:00 Leonardo Bras [this message]
2024-01-30 1:22 ` [PATCH v2 1/1] wq: Avoid using isolated cpus' timers on queue_delayed_work Tejun Heo
2024-01-30 2:58 ` Leonardo Bras
2024-04-02 10:58 ` Oleg Nesterov
2024-04-03 19:12 ` Tejun Heo
2024-04-03 20:38 ` Oleg Nesterov
2024-04-05 14:04 ` Oleg Nesterov
2024-04-05 15:38 ` Tejun Heo
2024-04-05 22:03 ` Frederic Weisbecker
2024-04-05 21:52 ` Nohz_full on boot CPU is broken (was: Re: [PATCH v2 1/1] wq: Avoid using isolated cpus' timers on queue_delayed_work) Frederic Weisbecker
2024-04-07 13:09 ` Oleg Nesterov
2024-04-07 13:52 ` Oleg Nesterov
2024-04-09 12:05 ` Frederic Weisbecker
2024-04-09 12:04 ` Frederic Weisbecker
2024-04-09 13:07 ` Oleg Nesterov
2024-04-09 13:59 ` Frederic Weisbecker
2024-04-10 4:26 ` Nicholas Piggin
2024-04-10 13:55 ` Oleg Nesterov
2024-04-11 13:41 ` Oleg Nesterov
2024-04-11 14:39 ` [PATCH] sched/isolation: fix boot crash when the boot CPU is nohz_full Oleg Nesterov
2024-04-11 16:59 ` Oleg Nesterov
2024-04-13 14:17 ` [PATCH] sched/isolation: fix boot crash when maxcpus < first-housekeeping-cpu Oleg Nesterov
2024-04-18 14:54 ` Phil Auld
2024-04-18 15:40 ` Frederic Weisbecker
2024-04-24 20:05 ` [tip: sched/urgent] sched/isolation: Fix boot crash when maxcpus < first housekeeping CPU tip-bot2 for Oleg Nesterov
2024-04-28 8:13 ` Ingo Molnar
2024-04-28 13:16 ` Oleg Nesterov
2024-04-28 8:24 ` tip-bot2 for Oleg Nesterov
2024-04-15 21:37 ` [PATCH] sched/isolation: fix boot crash when the boot CPU is nohz_full Frederic Weisbecker
2024-04-18 14:50 ` Phil Auld
2024-04-22 18:50 ` Oleg Nesterov
2024-04-24 14:42 ` Phil Auld
2024-04-24 20:05 ` [tip: sched/urgent] sched/isolation: {revent " tip-bot2 for Oleg Nesterov
2024-04-24 20:41 ` Phil Auld
2024-04-28 8:14 ` Ingo Molnar
2024-04-29 11:50 ` Phil Auld
2024-04-28 8:24 ` [tip: sched/urgent] sched/isolation: Prevent " tip-bot2 for Oleg Nesterov
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