From: Aaron Tomlin <atomlin@redhat.com>
To: Phil Auld <pauld@redhat.com>
Cc: frederic@kernel.org, tglx@linutronix.de, mingo@kernel.org,
mingo@redhat.com, atomlin@atomlin.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too
Date: Wed, 16 Feb 2022 14:34:12 +0000 [thread overview]
Message-ID: <20220216143412.dwxjlkq4w2zeweld@ava.usersys.com> (raw)
In-Reply-To: <YfxVpEO+UJTC+a9e@lorien.usersys.redhat.com>
On Thu 2022-02-03 17:22 -0500, Phil Auld wrote:
> As I said earlier, I don't think you want to call quiet_vmstat()
> unconditionally. And I don't think this will catch the cases you are
> trying to fix. Once the tick is stopped tick_nohz_stop_tick should not be
> getting called again until it's been restarted.
Phil,
Sorry about the delay. If I understand correctly, I see a scenario by which
tick_nohz_stop_tick() can be called on transition/or exit from idle (e.g.
default_idle_call()):
1. The idle/or scheduling-clock was previously
stopped
2. It is considered safe for the scheduling-clock
tick to remain "stopped"/or omitted; no need to
reprogram and enable a periodic tick
(e.g. no queued/or expired pending timer)
...
do_idle
cpuidle_idle_call
{
...
.-- default_idle_call
| arch_cpu_idle
| goto exit_idle
|
| exit_idle:
| __current_set_polling()
|
| }
| tick_nohz_idle_exit()
| {
|
| tick_stopped = ts->tick_stopped
|
| if (tick_stopped)
| tick_nohz_idle_update_tick(ts, now)
| if (tick_nohz_full_cpu(smp_processor_id()))
| __tick_nohz_full_update_tick(ts, now)
| {
| int cpu = smp_processor_id()
|
| if (can_stop_full_tick(cpu, ts))
| tick_nohz_stop_sched_tick(ts, cpu)
| if (tick_nohz_next_event(ts, cpu))
'-- tick_nohz_stop_tick(ts, cpu)
}
}
If I understand correctly, __tick_nohz_full_update_tick() can return with
no changes to the current tick (e.g. expire time == KTIME_MAX), no?
Kind regards,
--
Aaron Tomlin
next prev parent reply other threads:[~2022-02-16 14:34 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-03 21:43 [RFC PATCH] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too Aaron Tomlin
2022-02-03 22:22 ` Phil Auld
2022-02-16 14:34 ` Aaron Tomlin [this message]
2022-02-16 21:20 ` Phil Auld
2022-02-17 12:57 ` Frederic Weisbecker
2022-02-17 14:45 ` Aaron Tomlin
2022-02-17 12:47 ` Frederic Weisbecker
2022-02-17 14:26 ` Aaron Tomlin
2022-02-17 16:32 ` Frederic Weisbecker
2022-02-18 12:54 ` Aaron Tomlin
2022-02-19 15:46 ` Aaron Tomlin
2022-02-24 12:27 ` Marcelo Tosatti
2022-02-24 12:30 ` Marcelo Tosatti
2022-02-24 13:01 ` Aaron Tomlin
2022-02-24 12:37 ` Marcelo Tosatti
2022-02-24 13:00 ` Aaron Tomlin
2022-02-24 13:14 ` Marcelo Tosatti
2022-02-24 13:28 ` Aaron Tomlin
2022-02-24 13:40 ` Marcelo Tosatti
2022-02-24 13:44 ` Aaron Tomlin
2022-03-31 14:33 ` Aaron Tomlin
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