From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: 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>
Subject: Re: [PATCH v3] sched/core: Use empty mask to reset cpumasks in sched_setaffinity()
Date: Tue, 3 Oct 2023 12:06:02 +0200 [thread overview]
Message-ID: <20231003100602.GF27267@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20230804023218.75544-1-longman@redhat.com>
On Thu, Aug 03, 2023 at 10:32:18PM -0400, Waiman Long wrote:
> Since commit 8f9ea86fdf99 ("sched: Always preserve the user requested
> cpumask"), user provided CPU affinity via sched_setaffinity(2) is
> perserved even if the task is being moved to a different cpuset. However,
> that affinity is also being inherited by any subsequently created child
> processes which may not want or be aware of that affinity.
>
> One way to solve this problem is to provide a way to back off from
> that user provided CPU affinity. This patch implements such a scheme
> by using an empty cpumask to signal a reset of the cpumasks to the
> default as allowed by the current cpuset.
So I still don't like this much, the normal state is all bits set:
$ grep allowed /proc/self/status
Cpus_allowed: ff,ffffffff
The all clear bitmask just feels weird for this.
next prev parent reply other threads:[~2023-10-03 10:06 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-04 2:32 [PATCH v3] sched/core: Use empty mask to reset cpumasks in sched_setaffinity() Waiman Long
2023-08-18 18:47 ` Waiman Long
2023-10-03 9:17 ` Ingo Molnar
2023-10-03 18:32 ` Waiman Long
2023-10-03 10:06 ` Peter Zijlstra [this message]
2023-10-03 18:58 ` Waiman Long
2023-10-03 21:48 ` Peter Zijlstra
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