From: Theodore Tso Subject: Re: Question on block group allocation Date: Mon, 27 Apr 2009 06:42:21 -0400 Message-ID: <20090427104221.GB9059@mit.edu> References: <6601abe90904230941x5cdd590ck2d51410326df2fc5@mail.gmail.com> <20090423190817.GN3209@webber.adilger.int> <6601abe90904231502y393155dbrf8913b728c704320@mail.gmail.com> <20090427021411.GA9059@mit.edu> <6601abe90904262229w602e17d8s51ceae05c2895ce5@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andreas Dilger , ext4 development To: Curt Wohlgemuth Return-path: Received: from thunk.org ([69.25.196.29]:56548 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752079AbZD0Km3 (ORCPT ); Mon, 27 Apr 2009 06:42:29 -0400 Content-Disposition: inline In-Reply-To: <6601abe90904262229w602e17d8s51ceae05c2895ce5@mail.gmail.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Sun, Apr 26, 2009 at 11:29:39PM -0600, Curt Wohlgemuth wrote: > > The random read throughput on the 10GB file went from ~16 MB/s to ~22 > MB/s after Andreas' patch; the total fragmentation of the file was > much lower than before his patch. > > However, the number of extents went up by quite a bit (I don't have > the debugfs output in front of me at the moment, sorry). It seemed > that no extent crossed a block group; I didn't have time to see if > Andreas' patch disabled flex BGs or not, as to what was going on. Try running e2fsck with the "-E fragcheck" option, and then capture e2fsck's stdout. It will help with the grunt work of doing the analysis, in terms of displaying the details of all of the files which are discontiguous. - Ted