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SubjectRe: 2.6.30-rc deadline scheduler performance regression for iozone over NFS
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.



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