linux-kernel - Re: [Bug #11308] tbench regression on each kernel release from 2.6.22 -> 2.6.28

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Date:	Wed, 17 Sep 2008 16:36:31 +0300 (EEST)
From:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
To:	Mike Galbraith <efault@....de>
cc:	Ingo Molnar <mingo@...e.hu>,
	Christoph Lameter <cl@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	kernel-testers@...r.kernel.org
Subject: Re: [Bug #11308] tbench regression on each kernel release from	2.6.22
 -&gt; 2.6.28

On Wed, 17 Sep 2008, Mike Galbraith wrote:

> On Wed, 2008-09-17 at 14:49 +0200, Ingo Molnar wrote:
> 
> > git log --pretty=format:"%h: %s" 2069f45..847106f | grep -viE \
> > 'block|alsa|pcmcia|sound|Merge|iosched|blk|DAC960|scsi|s390|paride|pktcdvd|filter|cdrom|drm'
> > 
> > gives us:
> > 
> >  7daf705: Start using the new '%pS' infrastructure to print symbols
> >  6f0f0fd: security: remove register_security hook
> >  93cbace: security: remove dummy module fix
> >  5915eb5: security: remove dummy module
> >  b478a9f: security: remove unused sb_get_mnt_opts hook
> >  32502b8: splice: fix generic_file_splice_read() race with page invalidation
> >  8b3d356: ramfs: enable splice write
> >  a144ff0: xen: Avoid allocations causing swap activity on the resume path
> > 
> > which really only leaves that security commit your bisection fingered. 
> > Which _slightly_ raises its likelyhood of being implicated. Structure 
> > size changes can move two formerly far-apart netperf-relevant symbols on 
> > the same cacheline, which can start cache ping-pong-ing badly.
> 
> I sure hope it's something like ping-pong, it's driving me NUTS.

How about dividing the problem to smaller blocks then by restoring 
parts of the change...


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