From: Peter Zijlstra <peterz@infradead.org>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Wangyang Guo <wangyang.guo@intel.com>,
K Prateek Nayak <kprateek.nayak@amd.com>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
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>,
linux-kernel@vger.kernel.org,
Shrikanth Hegde <sshegde@linux.ibm.com>,
Benjamin Lei <benjamin.lei@intel.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Tianyou Li <tianyou.li@intel.com>
Subject: Re: [PATCH v2] sched/clock: Avoid false sharing for sched_clock_irqtime
Date: Tue, 13 Jan 2026 11:36:26 +0100 [thread overview]
Message-ID: <20260113103626.GB830229@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <CAKfTPtDpdFuVo83ZbXFhTAbydq-5TxTAcf+JWeN8mK3nosJCQA@mail.gmail.com>
On Tue, Jan 13, 2026 at 11:14:54AM +0100, Vincent Guittot wrote:
> On Tue, 13 Jan 2026 at 11:08, Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > On Tue, Jan 13, 2026 at 03:48:07PM +0800, Wangyang Guo wrote:
> > > Read-mostly sched_clock_irqtime may share the same cacheline with
> > > frequently updated nohz struct. Mark it as __read_mostly to avoid
> > > false sharing issue.
> > >
> >
> > Is there a reason that thing can't be a static_key or so?
>
> We tried that but disable_sched_clock_irqtime can be called in atomic
> context with mark_tsc_unstable()
> https://lore.kernel.org/all/174161357383.14745.8770394914047302959.tip-bot2@tip-bot2/
Right, but if you note, that very same path has
clear_sched_clock_stable(), and that is a static_key too.
It's just that that punts by pushing it into a workqueue. So why not
lift that workqueue and do both keys or something?
next prev parent reply other threads:[~2026-01-13 10:36 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-13 7:48 Wangyang Guo
2026-01-13 9:01 ` Shrikanth Hegde
2026-01-13 10:07 ` Peter Zijlstra
2026-01-13 10:14 ` K Prateek Nayak
2026-01-13 10:14 ` Vincent Guittot
2026-01-13 10:36 ` Peter Zijlstra [this message]
2026-01-13 11:00 ` Vincent Guittot
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