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

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Message-Id: <1256739779.7503.59.camel@marge.simson.net>
Date:	Wed, 28 Oct 2009 15:22:59 +0100
From:	Mike Galbraith <efault@....de>
To:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
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 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.

	-Mike

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