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

Ilpo Järvinen
2008-09-17T13:36:31Z

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...

--
i.