From: Andreas Dilger Subject: Re: [PATCH, RFC] ext4: Use preallocation when reading from the inode table Date: Tue, 23 Sep 2008 05:50:45 -0600 Message-ID: <20080923115045.GI10950@webber.adilger.int> References: <20080923101613.58768083@lxorguk.ukuu.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7BIT Cc: "Theodore Ts'o" , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org To: Alan Cox Return-path: Received: from sca-es-mail-1.Sun.COM ([192.18.43.132]:53153 "EHLO sca-es-mail-1.sun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750838AbYIWLvS (ORCPT ); Tue, 23 Sep 2008 07:51:18 -0400 In-reply-to: <20080923101613.58768083@lxorguk.ukuu.org.uk> Content-disposition: inline Sender: linux-ext4-owner@vger.kernel.org List-ID: On Sep 23, 2008 10:16 +0100, Alan Cox wrote: > On Mon, 22 Sep 2008 20:35:23 -0400 > "Theodore Ts'o" wrote: > > With modern hard drives, reading 64k takes roughly the same time as > > reading a 4k block. So request adjacent inode table blocks to reduce > > the time it takes when iterating over directories (especially when doing > > this in htree sort order) in a cold cache case. With this patch, the > > time it takes to run "git status" on a kernel tree after flushing the > > caches via "echo 3 > /proc/sys/vm/drop_caches", is reduced by 21%. > > > > Signed-off-by: "Theodore Ts'o" > > Acked-by: Alan Cox > > I'm actually suprised that 16 is the magic tuning number you've used and > a bigger one isn't even more of a win I was going to suggest making this at least a #defined constant instead of hard coding the values there. Making it a mount option and/or /proc value would allow further testing. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc.