Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756421AbZJBO0L (ORCPT ); Fri, 2 Oct 2009 10:26:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754727AbZJBO0L (ORCPT ); Fri, 2 Oct 2009 10:26:11 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:48144 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754703AbZJBO0K (ORCPT ); Fri, 2 Oct 2009 10:26:10 -0400 Date: Fri, 2 Oct 2009 07:24:41 -0700 (PDT) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Jens Axboe cc: Ingo Molnar , 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 In-Reply-To: <20091002092839.GA26962@kernel.dk> Message-ID: References: <1254034500.7933.6.camel@marge.simson.net> <20090927164235.GA23126@kernel.dk> <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> User-Agent: Alpine 2.01 (LFD 1184 2008-12-16) 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: 1248 Lines: 33 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. And Mike's patch didn't look big or complicated. > You can't say it's black and white latency vs throughput issue, Umm. Almost 1000% vs 30%. Forget latency vs throughput. That's pretty damn black-and-white _regardless_ of what you're measuring. Plus you probably made up the 30% - have you tested the patch? And quite frankly, we get a _lot_ of complaints about latency. A LOT. It's just harder to measure, so people seldom attach numbers to it. But that again means that when people _are_ able to attach numbers to it, we should take those numbers _more_ seriously rather than less. So the 30% you threw out as a number is pretty much worthless. 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/