linux-kernel - hackbench regression with kernel 2.6.32-rc1

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Message-Id: <1255079943.25078.23.camel@ymzhang>
Date:	Fri, 09 Oct 2009 17:19:03 +0800
From:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: hackbench regression with kernel 2.6.32-rc1

Comparing with 2.6.31's results, hackbench has some regression on a couple of
machines woth kernel 2.6.32-rc1.
I run it with commandline:
./hackbench 100 process 2000

1) On 4*4 core tigerton: 70%;
2) On 2*4 core stoakley: 7%.

I located below 2 patches.
commit 29cd8bae396583a2ee9a3340db8c5102acf9f6fd
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date:   Thu Sep 17 09:01:14 2009 +0200

    sched: Fix SD_POWERSAVING_BALANCE|SD_PREFER_LOCAL vs SD_WAKE_AFFINE

and 

commit de69a80be32445b0a71e8e3b757e584d7beb90f7
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date:   Thu Sep 17 09:01:20 2009 +0200

    sched: Stop buddies from hogging the system

1) On 4*4 core tigerton: if I revert patch 29cd8b, the regression becomes
less than 55%; If I revert the 2 patches, all regression disappears.
2) On 2*4 core stakley: If I revert the 2 patches, comparing with 2.6.31,
I get about 8% improvement instead of regression.

Sorry for reporting the regression later as there is a long national holiday.

Yanmin

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