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Subject: Re: hackbench regression with 2.6.26-rc2 on tulsa machine
From: Mike Galbraith <efault@gmx.de>
To: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
       LKML <linux-kernel@vger.kernel.org>
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Date: Wed, 21 May 2008 07:19:48 +0200
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On Wed, 2008-05-21 at 12:54 +0800, Zhang, Yanmin wrote:
> On Tue, 2008-05-20 at 11:22 +0200, Mike Galbraith wrote:

> > Do you still have group scheduling enabled?
> Yes.
> CONFIG_GROUP_SCHED=y
> CONFIG_FAIR_GROUP_SCHED=y
> # CONFIG_RT_GROUP_SCHED is not set
> CONFIG_USER_SCHED=y
> # CONFIG_CGROUP_SCHED is not set
> 
> >   If so, can you turn it off
> > and try again?  (when in doubt, grasp at any straw within reach;)
> I reran the test for dozeons of times.
> 1) Background processes have impact on the result and cause result to fluctuate with 8~9 seconds;
> 2) After turning off most services (background processes), the result looks stable;
> 3) I tested both 2.6.26-rc1 and 2.6.26-rc2 with CONFIG_GROUP_SCHED=n. the first one's result
> is about 30 seconds and the second one's result is about 31 seconds. So CONFIG_GROUP_SCHED is the key.

Thanks a bunch for re-testing.

	-Mike