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
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