Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756131AbZJBQXt (ORCPT ); Fri, 2 Oct 2009 12:23:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754524AbZJBQXs (ORCPT ); Fri, 2 Oct 2009 12:23:48 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:48724 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754502AbZJBQXs (ORCPT ); Fri, 2 Oct 2009 12:23:48 -0400 Date: Fri, 2 Oct 2009 18:22:40 +0200 From: Ingo Molnar To: Linus Torvalds Cc: Jens Axboe , Mike Galbraith , Vivek Goyal , Ulrich Lukas , linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, dm-devel@redhat.com, nauman@google.com, dpshah@google.com, lizf@cn.fujitsu.com, mikew@google.com, fchecconi@gmail.com, paolo.valente@unimore.it, ryov@valinux.co.jp, fernando@oss.ntt.co.jp, jmoyer@redhat.com, dhaval@linux.vnet.ibm.com, balbir@linux.vnet.ibm.com, righi.andrea@gmail.com, m-ikeda@ds.jp.nec.com, agk@redhat.com, akpm@linux-foundation.org, peterz@infradead.org, jmarchan@redhat.com, riel@redhat.com Subject: Re: IO scheduler based IO controller V10 Message-ID: <20091002162240.GA12546@elte.hu> References: <1254340730.7695.32.camel@marge.simson.net> <1254341139.7695.36.camel@marge.simson.net> <20090930202447.GA28236@redhat.com> <1254382405.7595.9.camel@marge.simson.net> <20091001185816.GU14918@kernel.dk> <1254464628.7158.101.camel@marge.simson.net> <20091002080417.GG14918@kernel.dk> <20091002092409.GA19529@elte.hu> <20091002092839.GA26962@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1226 Lines: 32 * Linus Torvalds wrote: > On Fri, 2 Oct 2009, Jens Axboe wrote: > > > > It's really not that simple, if we go and do easy latency bits, then > > throughput drops 30% or more. > > Well, if we're talking 500-950% improvement vs 30% deprovement, I > think it's pretty clear, though. Even the server people do care about > latencies. > > Often they care quite a bit, in fact. The other thing is that latency is basically a given property in any system - as an app writer you have to live with it, there's not much you can do to improve it. Bandwidth on the other hand is a lot more engineerable, as it tends to be about batching things and you can batch in user-space too. Batching is often easier to do than getting good latencies. Then there's also the fact that the range of apps that care about bandwidth is a lot smaller than the range of apps which care about latencies. The default should help more apps - i.e. latencies. Ingo -- 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/