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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 13:45:20 +0100	[thread overview]
Message-ID: <87a6r95067.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <87mtva4l6o.fsf@nanos.tec.linutronix.de>

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.

Thanks,

        tglx


  reply	other threads:[~2021-03-11 12:46 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 [this message]
2021-03-11 14:20                   ` Thomas Gleixner
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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