linux-kernel - Re: Scheduler accounting inflated for io bound processes.

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Message-ID: <1372262508.8776.83.camel@marge.simpson.net>
Date:	Wed, 26 Jun 2013 18:01:48 +0200
From:	Mike Galbraith <bitbucket@...ine.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Dave Chiluk <chiluk@...onical.com>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: Scheduler accounting inflated for io bound processes.

On Wed, 2013-06-26 at 17:50 +0200, Ingo Molnar wrote: 
> * Peter Zijlstra <peterz@...radead.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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