Message-ID: <1372262508.8776.83.camel@marge.simpson.net>
Subject: Re: Scheduler accounting inflated for io bound processes.
From: Mike Galbraith <bitbucket@online.de>
To: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>, Dave Chiluk <chiluk@canonical.com>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org
Date: Wed, 26 Jun 2013 18:01:48 +0200
In-Reply-To: <20130626155048.GA7399@gmail.com>
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On Wed, 2013-06-26 at 17:50 +0200, Ingo Molnar wrote: 
> * Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > On Wed, Jun 26, 2013 at 11:37:13AM +0200, Ingo Molnar wrote:
> > > Would be very nice to randomize the sampling rate, by randomizing the 
> > > intervals within a 1% range or so - perf tooling will probably recognize 
> > > the different weights.
> > 
> > You're suggesting adding noise to the regular kernel tick?
> 
> No, to the perf interval (which I assumed Mike was using to profile this?)

Yeah, perf top -F 250 exhibits the same inaccuracy as 250 Hz tick cpu
accounting.  (sufficient sample jitter should cure it, but I think I'd
prefer to just live with it)

-Mike

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