linux-kernel - Re: [RESEND] [PATCH] readahead:add blk_run_backing

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Message-ID: <20090715205220.GL31657@tpkurt2.suse.de>
Date:	Wed, 15 Jul 2009 22:52:20 +0200
From:	Kurt Garloff <garloff@...e.de>
To:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [RESEND] [PATCH] readahead:add blk_run_backing_dev

Hi,

On Wed, Jul 08, 2009 at 04:40:08PM +0400, Vladislav Bolkhovitin wrote:
> I've also long ago noticed that reading data from block devices is slower 
> than from files from mounted on those block devices file systems. Can 
> anybody explain it?

Brainstorming:
- block size (reads on the block dev might be done with smaller size)
- readahead (do we use the same RA algo for block devs)
- page cache might be better optimized than buffer cache?

Just guesses from someone that has not looked into that area of the
kernel for a while, so take it with a grain of salt.

Cheers,
-- 
Kurt Garloff, VP OPS Partner Engineering -- Novell Inc.

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