linux-kernel - Re: readahead on directories

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Message-ID: <20100421004434.GA27420@shareable.org>
Date:	Wed, 21 Apr 2010 01:44:34 +0100
From:	Jamie Lokier <jamie@...reable.org>
To:	Phillip Susi <psusi@....rr.com>
Cc:	linux-fsdevel@...r.kernel.org,
	Linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: readahead on directories

Phillip Susi wrote:
> I have been trying to improve boot times with ureadahead and have
> identified a period of time of almost zero IO throughput caused by calls
> to open() blocking during name lookup while fetching directory blocks.
> At first I thought this could simply be fixed by calling readahead() on
> the directories first before open()ing all of the normal files for
> readahead.
> 
> Unfortunately it seems that readahead() fails when called on a
> directory.  I was wondering if I could get some help understanding why
> this is, and how it could be fixed.

readahead() doesn't make much sense on a directory - the offset and
size aren't meaningful.

But does plain opendir/readdir/closedir solve the problem?

-- Jamie
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