From: Andreas Dilger Subject: Re: [PATCH] ext4: start seraching for the right extent from the goal group. Date: Fri, 02 May 2008 11:53:19 -0700 Message-ID: <20080502185319.GG2950@webber.adilger.int> References: <1209554186-6251-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <48186CFB.8050206@redhat.com> <20080501153747.GA7005@skywalker> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7BIT Cc: Eric Sandeen , linux-ext4@vger.kernel.org, cmm@us.ibm.com, tytso@mit.edu To: "Aneesh Kumar K.V" Return-path: Received: from sca-es-mail-1.Sun.COM ([192.18.43.132]:62361 "EHLO sca-es-mail-1.sun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756751AbYEBSxX (ORCPT ); Fri, 2 May 2008 14:53:23 -0400 Received: from fe-sfbay-10.sun.com ([192.18.43.129]) by sca-es-mail-1.sun.com (8.13.7+Sun/8.12.9) with ESMTP id m42IrMtU002431 for ; Fri, 2 May 2008 11:53:22 -0700 (PDT) Received: from conversion-daemon.fe-sfbay-10.sun.com by fe-sfbay-10.sun.com (Sun Java System Messaging Server 6.2-8.04 (built Feb 28 2007)) id <0K0900M018C2O800@fe-sfbay-10.sun.com> (original mail from adilger@sun.com) for linux-ext4@vger.kernel.org; Fri, 02 May 2008 11:53:22 -0700 (PDT) In-reply-to: <20080501153747.GA7005@skywalker> Content-disposition: inline Sender: linux-ext4-owner@vger.kernel.org List-ID: On May 01, 2008 21:07 +0530, Aneesh Kumar K.V wrote: > On Wed, Apr 30, 2008 at 07:58:35AM -0500, Eric Sandeen wrote: > > Aneesh Kumar K.V wrote: > > > With mballoc we search for the best extent using different > > > criteria. We should always use the goal group when we are > > > starting with a new criteria. > > > > Aneesh, is there any testcase etc that will demonstrate the resulting > > difference in layout? > > > > It's not clear to me from this changelog (without looking at a lot more > > context) exactly what you're changing and why... > > I don't have any specific test case. With mballoc depending on the > request size we follow different criteria to allocate blocks. For > example if the size is stripe size multiple we use criteria 1 and start > searching for the right blocks from block group starting with goal > group. If we don't find right count of blocks, we use criteria 2 and start > searching from the group block 0. I guess with criteria 2 also, we should start > searching from the goal group so that when we find the right count of > blocks we find them close to the goal group. This makes sense to me. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc.