linux-kernel - cfq-iosched: a regression

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Date:	Tue, 16 Aug 2011 10:47:06 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	Jens Axboe <jaxboe@...ionio.com>
Cc:	teravest@...gle.com, lkml <linux-kernel@...r.kernel.org>,
	"Shi, Alex" <alex.shi@...el.com>
Subject: cfq-iosched: a regression

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@...gle.com>
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@...el.com>
Reported-by: Shaohua Li<shaohua.li@...el.com>

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