From: Thomas Gleixner <tglx@linutronix.de>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
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>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Oleg Nesterov <oleg@redhat.com>,
Matt Fleming <matt@codeblueprint.co.uk>
Subject: Re: [PATCH] signal: Allow RT tasks to cache one sigqueue struct
Date: Thu, 11 Mar 2021 15:20:00 +0100 [thread overview]
Message-ID: <877dmd4vsf.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <87a6r95067.fsf@nanos.tec.linutronix.de>
On Thu, Mar 11 2021 at 13:45, Thomas Gleixner wrote:
> On Thu, Mar 11 2021 at 00:56, Thomas Gleixner wrote:
>> Rant aside, there is no massive benefit of doing that caching in
>> general, but there is not much of a downside either and for particular
>> use cases it's useful even outside of PREEMPT_RT.
>>
>> IMO, having it there unconditionally is better than yet another special
>> cased hackery.
>
> Just did some micro instrumentation to measure the time spent in
> __sigqueue_alloc/free() with and without the caching.
>
> Unsurprisingly that results in a time reduction of ~67% saving about 3us
> per alloc/free pair. Not hugely relevant for a kernel build but for
> anything which is signal heavy it'll make an difference.
That's all fastpath allocations and nothing which hit the slow path,
which would be way worse.
Thanks,
tglx
next prev parent reply other threads:[~2021-03-11 14:20 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-03 14:20 [PATCH] signal: Allow RT tasks to cache one sigqueue struct Sebastian Andrzej Siewior
2021-03-03 15:37 ` Oleg Nesterov
2021-03-04 21:10 ` Thomas Gleixner
2021-03-05 10:57 ` Oleg Nesterov
2021-03-04 21:14 ` Thomas Gleixner
2021-03-03 22:09 ` Eric W. Biederman
2021-03-04 8:11 ` Sebastian Andrzej Siewior
2021-03-04 15:02 ` Thomas Gleixner
2021-03-04 19:04 ` Eric W. Biederman
2021-03-04 20:58 ` Thomas Gleixner
2021-03-10 18:54 ` Thomas Gleixner
2021-03-10 21:57 ` Eric W. Biederman
2021-03-10 23:56 ` Thomas Gleixner
2021-03-11 12:45 ` Thomas Gleixner
2021-03-11 14:20 ` Thomas Gleixner [this message]
2021-03-11 16:32 ` Eric W. Biederman
2021-03-04 19:01 ` Eric W. Biederman
[not found] <draft-874khk5yed.fsf@nanos.tec.linutronix.de>
2021-03-10 8:57 ` Thomas Gleixner
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