From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: How git affects kernel.org performance Date: Mon, 08 Jan 2007 08:43:01 -0500 Message-ID: <45A24A65.1070706@garzik.org> References: <1166297434.26330.34.camel@localhost.localdomain> <1166304080.13548.8.camel@nigel.suspend2.net> <459152B1.9040106@zytor.com> <1168140954.2153.1.camel@nigel.suspend2.net> <45A08269.4050504@zytor.com> <45A083F2.5000000@zytor.com> <20070107085526.GR24090@1wt.eu> <20070107011542.3496bc76.akpm@osdl.org> <20070108030555.GA7289@in.ibm.com> <20070108125819.GA32756@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-From: git-owner@vger.kernel.org Mon Jan 08 14:43:22 2007 Return-path: Envelope-to: gcvg-git@gmane.org Received: from vger.kernel.org ([209.132.176.167]) by lo.gmane.org with esmtp (Exim 4.50) id 1H3umW-0007eI-EV for gcvg-git@gmane.org; Mon, 08 Jan 2007 14:43:20 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161291AbXAHNnQ (ORCPT ); Mon, 8 Jan 2007 08:43:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161296AbXAHNnQ (ORCPT ); Mon, 8 Jan 2007 08:43:16 -0500 Received: from srv5.dvmed.net ([207.36.208.214]:54682 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161291AbXAHNnP (ORCPT ); Mon, 8 Jan 2007 08:43:15 -0500 Received: from cpe-065-190-194-075.nc.res.rr.com ([65.190.194.75] helo=[10.10.10.10]) by mail.dvmed.net with esmtpsa (Exim 4.63 #1 (Red Hat Linux)) id 1H3umE-0000IN-UR; Mon, 08 Jan 2007 13:43:03 +0000 User-Agent: Thunderbird 1.5.0.9 (X11/20061219) To: Theodore Tso , Suparna Bhattacharya , Andrew Morton , Willy Tarreau , Linus Torvalds , "H. Peter Anvin" , git@vger.kernel.org, nigel@nigel.suspend2.net, "J.H." , Randy Dunlap , Pavel Machek , kernel list , webmaster@kernel.org, "linux-ext4@vger.kernel.org" In-Reply-To: <20070108125819.GA32756@thunk.org> X-Spam-Score: -4.3 (----) X-Spam-Report: SpamAssassin version 3.1.7 on srv5.dvmed.net summary: Content analysis details: (-4.3 points, 5.0 required) Sender: git-owner@vger.kernel.org Precedence: bulk X-Mailing-List: git@vger.kernel.org Archived-At: Theodore Tso wrote: > The fastest and probably most important thing to add is some readahead > smarts to directories --- both to the htree and non-htree cases. If > you're using some kind of b-tree structure, such as XFS does for > directories, preallocation doesn't help you much. Delayed allocation > can save you if your delayed allocator knows how to structure disk > blocks so that a btree-traversal is efficient, but I'm guessing the > biggest reason why we are losing is because we don't have sufficient > readahead. This also has the advantage that it will help without > needing to doing a backup/restore to improve layout. Something I just thought of: ATA and SCSI hard disks do their own read-ahead. Seeking all over the place to pick up bits of directory will hurt even more with the disk reading and throwing away data (albeit in its internal elevator and cache). Jeff