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SubjectRe: 2.6.30-rc deadline scheduler performance regression for iozone over NFS
On Fri, May 08 2009, Andrew Morton wrote:
> On Thu, 23 Apr 2009 10:01:58 -0400
> Jeff Moyer <jmoyer@redhat.com> wrote:
>
> > Hi,
> >
> > I've been working on CFQ improvements for interleaved I/Os between
> > processes, and noticed a regression in performance when using the
> > deadline I/O scheduler. The test uses a server configured with a cciss
> > array and 1Gb/s ethernet.
> >
> > The iozone command line was:
> > iozone -s 2000000 -r 64 -f /mnt/test/testfile -i 1 -w
> >
> > The numbers in the nfsd's row represent the number of nfsd "threads".
> > These numbers (in MB/s) represent the average of 5 runs.
> >
> > v2.6.29
> >
> > nfsd's | 1 | 2 | 4 | 8
> > --------+---------------+-------+------
> > deadline| 43207 | 67436 | 96289 | 107590
> >
> > 2.6.30-rc1
> >
> > nfsd's | 1 | 2 | 4 | 8
> > --------+---------------+-------+------
> > deadline| 43732 | 68059 | 76659 | 83231
> >
> > 2.6.30-rc3.block-for-linus
> >
> > nfsd's | 1 | 2 | 4 | 8
> > --------+---------------+-------+------
> > deadline| 46102 | 71151 | 83120 | 82330
> >
> >
> > Notice the drop for 4 and 8 threads. It may be worth noting that the
> > default number of NFSD threads is 8.
> >
>
> I guess we should ask Rafael to add this to the post-2.6.29 regression
> list.

I agree. It'd be nice to bisect this one down, I'm guessing some mm
change has caused this writeout regression.

--
Jens Axboe



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