From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Waiman Long <longman@redhat.com>, Ingo Molnar <mingo@redhat.com>,
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>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Valentin Schneider <vschneid@redhat.com>,
linux-kernel@vger.kernel.org, Phil Auld <pauld@redhat.com>,
Brent Rowsell <browsell@redhat.com>,
Peter Hunt <pehunt@redhat.com>,
Florian Weimer <fweimer@redhat.com>
Subject: Re: [PATCH v4] sched/core: Use zero length to reset cpumasks in sched_setaffinity()
Date: Wed, 4 Oct 2023 11:43:30 +0200 [thread overview]
Message-ID: <20231004094330.GL1539@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <ZR0vHXDeGi+iVogR@gmail.com>
On Wed, Oct 04, 2023 at 11:23:41AM +0200, Ingo Molnar wrote:
> > if (user_mask) {
> > - cpumask_copy(user_mask, in_mask);
> > + /*
> > + * All-set user cpumask resets affinity and drops the explicit
> > + * user mask.
> > + */
> > + cpumask_and(user_mask, in_mask, cpu_possible_mask);
> > + if (cpumask_equal(user_mask, cpu_possible_mask)) {
> > + kfree(user_mask);
> > + user_mask = NULL;
> > + }
>
> Question: is there any observable behavioral difference between current
> (old) all-set cpumask calls and the patched (new) one?
Very little I think -- the main difference is that we no longer carry
the ->user_cpus_ptr mask around, and that saves a little masking.
next prev parent reply other threads:[~2023-10-04 9:44 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-03 20:57 [PATCH v4] sched/core: Use zero length to reset cpumasks in sched_setaffinity() Waiman Long
2023-10-04 8:36 ` Peter Zijlstra
2023-10-04 9:23 ` Ingo Molnar
2023-10-04 9:43 ` Peter Zijlstra [this message]
2023-10-04 10:06 ` Ingo Molnar
2023-10-04 12:19 ` Waiman Long
2023-10-04 12:34 ` Florian Weimer
2023-10-04 12:41 ` Waiman Long
2023-10-04 12:55 ` Florian Weimer
2023-10-04 16:23 ` Waiman Long
2023-10-04 13:52 ` Peter Zijlstra
2023-10-04 13:54 ` Peter Zijlstra
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