Re: XFS filesystem performance drop in kernels 2.6.16+

[David Chinner <dgc@sgi.com>]

On Thu, Nov 09, 2006 at 12:08:35PM -0600, Russell Cattelan wrote:
> On Thu, 2006-11-09 at 20:30 +0300, Igor A. Valcov wrote:
> > Hello,
> > 
> > For one of our projects we have a test program that measures file
> > system performance by writing up to 1000 files simultaneously. After
> > installing kernel v2.6.16 we noticed that XFS performance dropped by a
> > factor of 5 (tests that took around 4 minutes on kernel 2.6.15 now
> > take around 20 minutes to complete). We then checked all kernels
> > starting from 2.6.16 up to 2.6.19-rc5 with the same unpleasant result.
> > The funny thing about all this is that we chose XFS for that
> > particular project specifically because it was about 5 times faster
> > with the tests than the other file systems. Now they all take about
> > the same time.
> > 
> > I also noticed that I/O barriers were introduced in v2.6.16 and
> > thought they may be the cause, but mounting the file system with
> > 'nobarrier' doesn't seem to affect the performance in any way.
> > 
> > Any thoughts on the matter are appreciated.
> I would try verifying the problem on a non ide disk just
> to confirm the write barrier theory.
> 
> Also file a bug.
> http://oss/sgi.com/bugzilla
> include test case and hard description if possible.

and cc xfs@oss.sgi.com on XFS bug reports ;)

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group