From mboxrd@z Thu Jan 1 00:00:00 1970 From: tytso@mit.edu Subject: Re: About strange behaviour of ext4 allocation algorithm Date: Wed, 23 Dec 2009 07:07:51 -0500 Message-ID: <20091223120751.GA21594@thunk.org> References: <41BA663C8B2F72499F48B0EF991C188E047890DF84@RU-EXSTRCL1.ru.corp.acronis.com> <41BA663C8B2F72499F48B0EF991C188E0478A366D3@RU-EXSTRCL1.ru.corp.acronis.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andreas Dilger , "linux-ext4@vger.kernel.org" To: Vyacheslav Dubeyko Return-path: Received: from THUNK.ORG ([69.25.196.29]:50404 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752720AbZLWMH6 (ORCPT ); Wed, 23 Dec 2009 07:07:58 -0500 Content-Disposition: inline In-Reply-To: <41BA663C8B2F72499F48B0EF991C188E0478A366D3@RU-EXSTRCL1.ru.corp.acronis.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed, Dec 23, 2009 at 01:52:48PM +0300, Vyacheslav Dubeyko wrote: > > I use kernel: 2.6.29.4-167.fc11.i686.PAE #1 SMP Wed May 27 17:28:22 > EDT 2009 i686 i686 i386 GNU/Linux. Yeah, that was before a massive number of changes to the ext4 allocator. The changes to the allocators which speed up fsck described here: http://thunk.org/tytso/blog/2009/02/26/fast-ext4-fsck-times-revisited/ All went in *after* 2.6.29. That is, how the block and inode allocators worked change significantly between 2.6.29 and 2.6.31. > > If you delete your file, without reformatting the filesystem, and > > then re-run the test, does it produce the same results? If not, > > then it is likely you are seeing the problem with uninitialized > > groups that was fixed a month or two ago. > > After deletion of the file and re-run test (without reformatting the > filesystem) I have slightly different extents' tree. Index block > (depth of the tree = 1) has changed place and several extents has > another sizes. But nature of the extents' sequence is the same. The change which Andreas was referring to --- taking out the bias against opening up uninitialized block groups for allocations until absolutely necessary, which had a tendency to cause unnecessary fragmentation --- was merged into mainline between 2.6.30 and 2.6.31. Best regards, - Ted