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Subject: Re: volanoMark regression with kernel 2.6.26-rc1
From: Mike Galbraith <efault@gmx.de>
To: vatsa@linux.vnet.ibm.com
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
       "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
       Dhaval Giani <dhaval@linux.vnet.ibm.com>,
       LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
       Aneesh Kumar KV <aneesh.kumar@linux.vnet.ibm.com>
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Date: Wed, 14 May 2008 16:50:33 +0200
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On Wed, 2008-05-14 at 19:14 +0530, Srivatsa Vaddagiri wrote:
> On Mon, May 12, 2008 at 11:20:47AM +0200, Peter Zijlstra wrote:
> > It looks like things like find_busiest_group() just think everything is
> > peachy when the imbalance is < 1 task - which with all this grouping
> > stuff is not necessarily true.
> 
> fwiw, the following hack seems to help bring down regression to ~5%
> (b/n 2.6.25 and 2.6.26-rc1 with USER_SCHED):
> 
> Also in the patch GROUP_SCALE can probably be less than what I used (and
> needs a ifdef GROUP_SCHED) ..

On my little Q6600 with git.today, it made no real difference, whether
NORMALIZED_SLEEPERS was enabled or not.  I see roughly 10-15% idle time
w/wo this patch, whereas pre-regression, it's < 2%.

	-Mike