Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756213AbZCZWsk (ORCPT ); Thu, 26 Mar 2009 18:48:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754261AbZCZWsb (ORCPT ); Thu, 26 Mar 2009 18:48:31 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:49481 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753984AbZCZWsb (ORCPT ); Thu, 26 Mar 2009 18:48:31 -0400 Date: Thu, 26 Mar 2009 15:39:53 -0700 (PDT) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Jan Kara cc: Ingo Molnar , Theodore Tso , Andrew Morton , Alan Cox , Arjan van de Ven , Peter Zijlstra , Nick Piggin , Jens Axboe , David Rees , Jesper Krogh , Linux Kernel Mailing List , Oleg Nesterov , Roland McGrath Subject: Re: ext3 IO latency measurements (was: Linux 2.6.29) In-Reply-To: <20090326181106.GC17159@duck.suse.cz> Message-ID: References: <20090324041249.1133efb6.akpm@linux-foundation.org> <20090325123744.GK23439@duck.suse.cz> <20090325150041.GM32307@mit.edu> <20090325185824.GO32307@mit.edu> <20090325215137.GQ32307@mit.edu> <20090325235041.GA11024@duck.suse.cz> <20090326090630.GA9369@elte.hu> <20090326181106.GC17159@duck.suse.cz> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1116 Lines: 27 On Thu, 26 Mar 2009, Jan Kara wrote: > > Reads are measurably better with the patch - the test with cat you > describe below took ~0.5s per file without the patch and always less than > 0.02s with the patch. So it seems to help something. That would seem to be a _huge_ improvement. Reads are the biggest issue for starting a new process (eg starting firefox while under load), and if cat'ing that small file improved by that much, then I bet there's a huge practical implication for a lot of desktop uses. The fundamental fsync() latency problem we sadly can't help much with, the way ext3 seems to work. But I do suspect that the whole "don't synchronize with the journal for normal write-outs" may end up helping even fsync just a bit, if only because I suspect it will improve writeout throughput too and thus avoid one particular bottleneck. Linus -- 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/