linux-ext4 - Re: defrag deployment status (was Re: [PATCH] ext4: allow defrag (EXT4_IOC_MOVE

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Message-ID: <4B9518DA.8010201@davidnewall.com>
Date:	Tue, 09 Mar 2010 02:03:46 +1030
From:	David Newall <davidn@...idnewall.com>
To:	Christian Borntraeger <borntraeger@...ibm.com>
CC:	Jeff Garzik <jeff@...zik.org>, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org, Akira Fujita <a-fujita@...jp.nec.com>
Subject: Re: defrag deployment status (was Re: [PATCH] ext4: allow defrag
 (EXT4_IOC_MOVE_EXT) in 32bit compat mode)

Christian Borntraeger wrote:
> Some bigger things are missing in the e4defrag tool:
> ...
> - overall layout considerations (e.g. putting files close to its directory or
>   use the atime to move often used files to the beginning of a disk etc.)

Shouldn't oft-used files be placed closer to the middle?  If you place 
them at the beginning of the file, it's only possible for the head-stack 
to be close to the file from the inner direction.  Place them in the 
middle and it's possible for the head-stack to be close from the outer 
direction, too, which sounds like a doubling of probability.  It seems 
that it's the least frequently used files that should be placed at one 
end of the disk or the other.
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