linux-kernel - Re: [PATCH] perf: add 'perf bench syscall'

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Message-ID: <CALCETrUo10+BYrWU__E1hC6+ri8q2x1WmGkYkK+uiffCnY7ZTA@mail.gmail.com>
Date:	Mon, 20 Jun 2016 12:16:22 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Rik van Riel <riel@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>, clark@...hat.com,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] perf: add 'perf bench syscall'

On Mon, Jun 20, 2016 at 11:00 AM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:

>
> From: Josh Poimboeuf <jpoimboe@...hat.com>
> Subject: [PATCH] perf: add 'perf bench syscall'
>
> Add a basic 'perf bench syscall' benchmark which does a getppid() system
> call in a tight loop.
>

My one suggestion would be to use a different syscall than getppid(),
as getppid() can have unusual performance characteristics on kernels
with pid namespaces enabled.  I'm a fan of prctl(-1, 0, 0, 0, 0).