Re: cfq-iosched: a regression

[Jens Axboe]

On 2011-08-16 04:47, Shaohua Li wrote:
> We have a kernel build regression since 3.1-rc1, which is about 10%
> regression. The kernel source is in an ext3 filesystem.
> Alex Shi bisect it to commit:
> commit a07405b7802691d29ab3b23bdc76ee6d006aad0b
> Author: Justin TerAvest <teravest@xxxxxxxxxx>
> Date:   Sun Jul 10 22:09:19 2011 +0200
> 
>     cfq: Remove special treatment for metadata rqs.
> 
> Apparently this is caused by lack metadata preemption, where ext3/ext4
> do use READ_META. I didn't see a way to fix the issue, so suggest
> reverting the patch.
> 
> Reported-by: Alex Shi<alex.shi@xxxxxxxxx>
> Reported-by: Shaohua Li<shaohua.li@xxxxxxxxx>

I had a gut feeling on that meta data, it's hard to know exactly where
it helps at this point. I'll revert the commit and then we can diagnose
this on the side.

-- 
Jens Axboe

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