linux-kernel - Re: hackbench regression with kernel 2.6.32-rc1

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Message-Id: <1256777448.16282.21.camel@ymzhang>
Date:	Thu, 29 Oct 2009 08:50:47 +0800
From:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
To:	Mike Galbraith <efault@....de>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: hackbench regression with kernel 2.6.32-rc1

On Wed, 2009-10-28 at 15:22 +0100, Mike Galbraith wrote:
> On Wed, 2009-10-28 at 17:29 +0800, Zhang, Yanmin wrote:
> > 	-Mike
> > I'm investigating 5% tbench regression on Nehalem machine. perf_counter shows
> > select_task_rq_fair consumes about 5% cpu time with 2.6.32-rc1 while it consumes
> > less than 0.5% with 2.6.31.
> > 
> > Patch c88d5910890 has comments to explain it, but I still can't understand why
> > to add complicated balance logic when selecting task rq.
> > 
> > I will check which section in function select_task_rq_fair consumes so much time.
> 
> Turn off SD_WAKE_BALANCE as it was called in rc1.  See commit 182a85f.
I run testing against 2.6.32-rc1 which already includes the patch.


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