Re: PROBLEM: Heavy iowait on 2.6 kernels

[Nick Piggin]

Guy Van Sanden wrote:
> I recently discovered why my new Gentoo server slows to a crawl on a
> intermediate load on the 2.6 kernel series.  The reason seems to be an
> unusual amount of iowait.
> I can reproduce this on two systems, one with a KT400 and and one with
> Sis735 chipset.
>
> iostat -c 1 (or vmstat) while running something like bonnie produces
> iowaits of 99%.
> Any 2.6 kernel responds the same (regardless of the patchset), even
> vanilla. (2.6.5-mm, 2.6.6-mm, 2.6.6-vanilla and 2.6.5-gentoo-r1).
> Any 2.4-series kernel is fine.

Hi, can you try booting with elevator=deadline, please?
Then include a vmstat 1 output for a 2.6 and a 2.4 kernel.

I don't think 2.4 kernels will show iowait, so some real
performance measurements would be helpful.

Thanks

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