Date: Tue, 7 Apr 2009 06:20:37 +0800
From: Wu Fengguang <fengguang.wu@intel.com>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Kernel Testers List <kernel-testers@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       "Lin, Ming M" <ming.m.lin@intel.com>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Nick Piggin <npiggin@suse.de>, Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [Bug #12809] iozone regression with 2.6.29-rc6
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On Tue, Apr 07, 2009 at 06:15:09AM +0800, Wu Fengguang wrote:
> On Tue, Apr 07, 2009 at 03:05:38AM +0800, Rafael J. Wysocki wrote:
> > This message has been generated automatically as a part of a report
> > of recent regressions.
> > 
> > The following bug entry is on the current list of known regressions
> > from 2.6.28.  Please verify if it still should be listed and let me know
> > (either way).
> > 
> > 
> > Bug-Entry	: http://bugzilla.kernel.org/show_bug.cgi?id=12809
> > Subject		: iozone regression with 2.6.29-rc6
> > Submitter	: Lin Ming <ming.m.lin@intel.com>
> > Date		: 2009-02-27 9:13 (39 days old)
> > First-Bad-Commit: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=1cf6e7d83bf334cc5916137862c920a97aabc018
> > References	: http://marc.info/?l=linux-kernel&m=123572630504360&w=4
> > 		  http://lkml.org/lkml/2009/3/14/265
> > Handled-By	: Wu Fengguang <fengguang.wu@intel.com>
> > 
> 
> This bug could be closed.
> 
> The performance regression is triggered by commit 1cf6e7d83bf3(mm:
> task dirty accounting fix). Which has been reverted in 2.6.29.

Sorry for the mistake, commit 1cf6e7d83bf3 was _not_ reverted.
So 2.6.29 is expected to have this regression.. 

Thanks,
Fengguang

> For 2.6.30, commit 1cf6e7d83bf33(mm: task dirty accounting fix) and
> 1b5e62b42b55(writeback: double the dirty thresholds) were just merged
> together. The latter one restores the iozone performance. (However
> might deteriorate some writeback slowness bugs..)
> 
> Thanks,
> Fengguang
> 
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