Re: scheduler vs hardware? (was Re: another i7 (linux) bug?)
From: Ingo Molnar
Date: Sat Jan 23 2010 - 04:43:37 EST
* Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Fri, 2010-01-22 at 08:19 +0100, Mike Galbraith wrote:
> > > if I run a cpu intensive process with the lowest priority (19
> > > from man nice) I obtain much better performance that with the
> > > highest priority available (-20 from man nice).
> > >
> > > For example the same file is processed by lame in 8.7 seconds
> > > at the lowest priority, and in 12 seconds at the highest
> > > priority. Before posting a bug I wold like to understand if
> > > this is a problem related to the i7 mobile (my processor is a
> > > i7 Q720).
> > >
> > > As far as I tested on the same laptop series (dell studio 15),
> > > with the same kernel this problem does not exists.
> > So you only see this on the i7. That's odd. Can you try 33-rc5?
> > Posting a reliable reproducer would be nice. It'd also be nice to see
> > what all is running when you see this, and where.
> Using a sample from: http://lame.sourceforge.net/quality.php
> My laptop does:
> # time nice -n 19 lame -b 256 -V0 -h youcantdothat.wav - > /dev/null
A 'perf stat --repeat 3' run would tell us more about the underlying reasons i
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