From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Subject: Re: [PATCH v3 4/6] add a new scheduler hook for context switch
Date: Wed, 30 May 2012 13:40:51 +0200
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To: Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devel-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, "Eric W. Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>, handai.szj-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, Andrew.Phillips-xheW4WVAX9Y@public.gmane.org, Serge Hallyn <serge.hallyn-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>

On Wed, 2012-05-30 at 13:20 +0200, Peter Zijlstra wrote:
> 
> $ perf stat -e cycles --repeat 100 perf bench sched messaging -p -g 100
> 
>     48,826,146,710 cycles  #    2.470 GHz  ( +-  0.17% )
>        2.149005270 seconds time elapsed    ( +-  0.12% ) 

A repeat count of 250 dropped it down to:

        2.144582157 seconds time elapsed    ( +-  0.08% )

Also, if you're poking at the context switch path, something like:

$ taskset 1 perf stat -e cycles --repeat 10 perf bench sched pipe -l 100000

gives a good number and is usually more stable than hackbench.