Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757656AbZC3DbG (ORCPT ); Sun, 29 Mar 2009 23:31:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754425AbZC3Day (ORCPT ); Sun, 29 Mar 2009 23:30:54 -0400 Received: from THUNK.ORG ([69.25.196.29]:34017 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754084AbZC3Dax (ORCPT ); Sun, 29 Mar 2009 23:30:53 -0400 Date: Sun, 29 Mar 2009 23:28:27 -0400 From: Theodore Tso To: Trenton Adams Cc: Mark Lord , Stefan Richter , Jeff Garzik , Linus Torvalds , Matthew Garrett , Alan Cox , Andrew Morton , David Rees , Jesper Krogh , Linux Kernel Mailing List Subject: Re: Linux 2.6.29 Message-ID: <20090330032827.GD13356@mit.edu> Mail-Followup-To: Theodore Tso , Trenton Adams , Mark Lord , Stefan Richter , Jeff Garzik , Linus Torvalds , Matthew Garrett , Alan Cox , Andrew Morton , David Rees , Jesper Krogh , Linux Kernel Mailing List References: <49CD7B10.7010601@garzik.org> <49CD891A.7030103@rtr.ca> <49CD9047.4060500@garzik.org> <49CE2633.2000903@s5r6.in-berlin.de> <49CE3186.8090903@garzik.org> <49CE35AE.1080702@s5r6.in-berlin.de> <49CE3F74.6090103@rtr.ca> <20090329231451.GR26138@disturbed> <20090330003948.GA13356@mit.edu> <9b1675090903291829u7a69df36m65b6698290773859@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9b1675090903291829u7a69df36m65b6698290773859@mail.gmail.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@mit.edu X-SA-Exim-Scanned: No (on thunker.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1902 Lines: 36 On Sun, Mar 29, 2009 at 07:29:09PM -0600, Trenton Adams wrote: > I am slightly confused by the "data=ordered" thing that everyone is > mentioning of late. In theory, it made sense to me before I tried it. > I switched to mounting my ext3 as ext4, and I'm still seeing > seriously delayed fsyncs. Theodore, I used a modified version of your > fsync-tester.c to bench 1M writes, while doing a dd, and I'm still > getting *almost* as bad of "fsync" performance as I was on ext3. On > ext3, the fsync would usually not finish until the dd was complete. How much memory do you have? On my 4gig X61 laptop, using a 5400 rpm laptop drive, I see typical times of 1 to 1.5 seconds, with a few outliers at 4-5 seconds. With ext3, the fsync times immediately jumped up to 6-8 seconds, with the outliers in the 13-15 second range. (This is with a filesystem formated as ext3, and mounted as either ext3 or ext4; if the filesystem is formatted using "mke2fs -t ext4", what you see is a very smooth 1.2-1.5 seconds fsync latency, indirect blocks for very big files end up being quite inefficient.) So I'm seeing a definite difference --- but also please remember that "dd if=/dev/zero of=bigzero.img" really is an unfair, worst-case scenario, since you are dirtying memory as fast as your CPU will dirty pages. Normally, even if you are running distcc, the rate at which you can dirty pages will be throttled at your local network speed. You might want to try more normal workloads and see whether you are seeing distinct fsync latency differences with ext4. Even with the worst-case dd if=/dev/zero, I'm seeing major differences in my testing. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/