From: Adrian Hunter Subject: Re: [PATCH 1/2] HACK: ext3: mount fast even when recovering Date: Wed, 15 Jul 2009 18:35:38 +0300 Message-ID: <4A5DF74A.8090607@nokia.com> References: <20090714140548.26116.2919.sendpatchset@ahunter-tower> <20090714140554.26116.54779.sendpatchset@ahunter-tower> <20090714143449.cae624c8.akpm@linux-foundation.org> <4A5CFCBD.70305@redhat.com> <20090714223649.GJ10131@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: Eric Sandeen , Andrew Morton , "sct@redhat.com" , "adilger@sun.com" , "linux-ext4@vger.kernel.org" , "Bityutskiy Artem (Nokia-D/Helsinki)" To: Theodore Tso Return-path: Received: from smtp.nokia.com ([192.100.122.230]:25863 "EHLO mgw-mx03.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755518AbZGOPga (ORCPT ); Wed, 15 Jul 2009 11:36:30 -0400 In-Reply-To: <20090714223649.GJ10131@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: Theodore Tso wrote: > On Tue, Jul 14, 2009 at 04:46:37PM -0500, Eric Sandeen wrote: >> (whoa, can barriers make something faster? who woulda thunk it) > > I sent this reply in response to the first Adrian's first e-mail, that > had bogus e-mail addresses for akpm and sct, so resending it here: Sorry about that. > Have you actually benchmarked these patches, ideally with a fixed > filesystem image so the two runs are done requiring exactly the same > number of blocks to recover? We implement ordered I/O in terms of > doing a flush, so it would be surprising to see that a significant > difference in times. Also, it would be useful to do a blktrace before > and after your patches, again with a fixed filesystem image so the > experiment can be carefully controlled. Yes the I/O is no faster. The hacks just make the file system available for reading while recovery I/O is ongoing. Attempts to write are likely to block (even buffered I/O must wait for locked buffers). I will send some examples.