linux-ext4 - [PATCH 0/2] ext3 HACKs

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Date:	Tue, 14 Jul 2009 17:02:53 +0300
From:	Adrian Hunter <adrian.hunter@...ia.com>
To:	Andrew.Morton.akpm@...ux-foundation.org,
	Andreas.Dilger.adilger@....com, Stephen.Tweedie.sct@...hat.com
Cc:	Artem Bityutskiy <artem.bityutskiy@...ia.com>,
	linux-ext4@...r.kernel.org, Adrian Hunter <adrian.hunter@...ia.com>
Subject: [PATCH 0/2] ext3 HACKs

Hi

We are using linux 2.6.28 and we have a situation where ext3
can take 30-60 seconds to mount.

The cause is the underlying device has extremely poor random
write speed (several orders of magnitude slower than sequential
write speed), and journal recovery can involve many small random
writes.

To alleviate this situation somewhat, I have two moderately ugly
hacks:
	HACK 1: ext3: mount fast even when recovering
	HACK 2: do I/O read requests while ext3 journal recovers

HACK 1 uses a I/O barrier in place of waiting for recovery I/O to be
flushed.

HACK 2 crudely throws I/O read requests to the front of the dispatch
queue until the I/O barrier from HACK 1 is reached.

If you can spare a moment to glance at these hacks and notice
any obvious flaws, or suggest a better alternative, it would be
greatly appreciated.

Regards
Adrian Hunter

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