linux-kernel - Re: scheduler vs hardware? (was Re: another i7 (linux) bug?)

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Date:	Fri, 22 Jan 2010 21:15:00 +0100
From:	Luca Zini <luca.zini@...il.com>
To:	Mike Galbraith <efault@....de>
Cc:	aagaande@...il.com, rdelcueto@...mail.com, mingo@...e.hu,
	a.p.zijlstra@...llo.nl,
	"linux-kernel" <linux-kernel@...r.kernel.org>,
	Alex Chiang <achiang@...com>
Subject: Re: scheduler vs hardware? (was Re: another i7  (linux) bug?)

vanilla 33-rc5 runs ok:
with nice set to -20
real    0m8.649s
user    0m8.600s
sys     0m0.030s


with nice set to 19:
real    0m8.658s
user    0m8.600s
sys     0m0.040s

thank you!
	Luca


On Friday 22 January 2010 08:19:18 am 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.
> 
> 	-Mike
> 
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