From: Frederic Weisbecker <frederic@kernel.org>
To: Marco Crivellari <marco.crivellari@suse.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
K Prateek Nayak <kprateek.nayak@amd.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
Anna-Maria Behnsen <anna-maria@linutronix.de>,
Thomas Gleixner <tglx@kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
Randy Dunlap <rdunlap@infradead.org>,
Shuah Khan <skhan@linuxfoundation.org>,
Michal Hocko <mhocko@suse.com>,
Aaron Tomlin <atomlin@atomlin.com>,
Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH v3 1/5] tick/nohz: Re-evaluate the tick on return to user space
Date: Sat, 14 Nov 2026 21:43:47 +0100 [thread overview]
Message-ID: <avjIA1bSaAmNcRcR@pavilion.home> (raw)
In-Reply-To: <20261112163813.524336-2-marco.crivellari@suse.com>
Le Thu, Nov 12, 2026 at 05:38:09PM +0100, Marco Crivellari a écrit :
> On nohz_full CPUs the tick is re-evaluated on IRQ exit and on idle exit.
>
> This is not enough on return to user space. If the tick is left running in
> the kernel, for example because a tick dependency was cleared
> (tick_nohz_dep_clear*() don't kick the CPU) or a timer that kept it
> running was cancelled, it fires at least once in userspace before
> tick_nohz_irq_exit() stops it.
>
> Stop it from context tracking right before resuming userspace. When the
> tick is already stopped, the common case, this costs a few flag tests on
> each return to userspace.
>
> Suggested-by: Frederic Weisbecker <frederic@kernel.org>
> Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
--
Frederic Weisbecker
SUSE Labs
next prev parent reply other threads:[~2026-11-14 20:43 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-12 16:38 [PATCH v3 0/5] Stop the idle tick on polling idle on nohz_full CPUs Marco Crivellari
2026-11-12 16:38 ` [PATCH v3 1/5] tick/nohz: Re-evaluate the tick on return to user space Marco Crivellari
2026-11-14 20:43 ` Frederic Weisbecker [this message]
2026-11-12 16:38 ` [PATCH v3 2/5] sched/idle: Don't handle polling idle as dynticks idle Marco Crivellari
2026-11-12 16:38 ` [PATCH v3 3/5] tick/nohz: Remove tick_nohz_idle_restart_tick() Marco Crivellari
2026-11-12 16:38 ` [PATCH v3 4/5] tick/nohz: Reset got_idle_tick when entering dynticks idle Marco Crivellari
2026-11-12 16:38 ` [PATCH v3 5/5] Documentation: no_hz: Add tick stop in polling idle Marco Crivellari
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=avjIA1bSaAmNcRcR@pavilion.home \
--to=frederic@kernel.org \
--cc=anna-maria@linutronix.de \
--cc=atomlin@atomlin.com \
--cc=bsegall@google.com \
--cc=corbet@lwn.net \
--cc=dietmar.eggemann@arm.com \
--cc=juri.lelli@redhat.com \
--cc=kprateek.nayak@amd.com \
--cc=linux-kernel@vger.kernel.org \
--cc=marco.crivellari@suse.com \
--cc=mgorman@suse.de \
--cc=mhocko@suse.com \
--cc=mingo@kernel.org \
--cc=mtosatti@redhat.com \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=rdunlap@infradead.org \
--cc=rostedt@goodmis.org \
--cc=skhan@linuxfoundation.org \
--cc=tglx@kernel.org \
--cc=vincent.guittot@linaro.org \
--cc=vschneid@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.