Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759424AbZCZOut (ORCPT ); Thu, 26 Mar 2009 10:50:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759209AbZCZOtM (ORCPT ); Thu, 26 Mar 2009 10:49:12 -0400 Received: from casper.infradead.org ([85.118.1.10]:44191 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759215AbZCZOtK (ORCPT ); Thu, 26 Mar 2009 10:49:10 -0400 Date: Thu, 26 Mar 2009 07:49:55 -0700 From: Arjan van de Ven To: Jens Axboe Cc: Ingo Molnar , Jan Kara , Linus Torvalds , Theodore Tso , Andrew Morton , Alan Cox , Peter Zijlstra , Nick Piggin , David Rees , Jesper Krogh , Linux Kernel Mailing List , Oleg Nesterov , Roland McGrath Subject: Re: ext3 IO latency measurements (was: Linux 2.6.29) Message-ID: <20090326074955.54add4d3@infradead.org> In-Reply-To: <20090326143618.GD27476@kernel.dk> References: <20090325150041.GM32307@mit.edu> <20090325185824.GO32307@mit.edu> <20090325215137.GQ32307@mit.edu> <20090325235041.GA11024@duck.suse.cz> <20090326090630.GA9369@elte.hu> <20090326110815.GT27476@kernel.dk> <20090326072707.5a98242d@infradead.org> <20090326143618.GD27476@kernel.dk> Organization: Intel X-Mailer: Claws Mail 3.7.0 (GTK+ 2.14.7; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1473 Lines: 39 On Thu, 26 Mar 2009 15:36:18 +0100 Jens Axboe wrote: > On Thu, Mar 26 2009, Arjan van de Ven wrote: > > On Thu, 26 Mar 2009 12:08:15 +0100 > > Jens Axboe wrote: > > > > > > Did you capture the trace of the long delays in the read test > > > case? It can be two things, at least. One is that each little > > > read takes much longer than it should, the other is that we get > > > stuck waiting on a dirty page and hence that slows down the reads > > > a lot. > > > > > > > would be interesting to run latencytop during such runs... > > Things just drown in the noise in there sometimes, is my experience... > And disappear. Perhaps I'm just not very good at reading the output, > but it was never very useful for me. I know, not a very useful > complaint, I'll try and use it again and come up with something more > productive :-) > > But in this case, I bet it's also the atime updates. If Ingo turned > those off, the read results would likely be a lot better (and > consistent). latencytop does identify those for sure. > -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org -- 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/