linux-ext4 - Re: Large directories and poor order correlation

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Message-ID: <8239molspy.fsf@mid.bfk.de>
Date:	Tue, 15 Mar 2011 07:59:21 +0000
From:	Florian Weimer <fweimer@....de>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	Phillip Susi <psusi@....rr.com>,
	"linux-ext4\@vger.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: Large directories and poor order correlation

* Eric Sandeen:

> No, because htree (dir_index) dirs returns names in hash-value
> order, not inode number order.  i.e. "at random."
>
> As you say, sorting by inode number will work much better...

The dpkg folks tested this and it turns out that you get better
results if you open the file and use FIBMAP to get the first block
number, and sort by that.  You could sort by inode number before the
open/fstat calls, but it does not seem to help much.

-- 
Florian Weimer                <fweimer@....de>
BFK edv-consulting GmbH       http://www.bfk.de/
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