Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757405AbZJBJ2i (ORCPT ); Fri, 2 Oct 2009 05:28:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757385AbZJBJ2h (ORCPT ); Fri, 2 Oct 2009 05:28:37 -0400 Received: from brick.kernel.dk ([93.163.65.50]:41141 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757360AbZJBJ2g (ORCPT ); Fri, 2 Oct 2009 05:28:36 -0400 Date: Fri, 2 Oct 2009 11:28:39 +0200 From: Jens Axboe To: Ingo Molnar Cc: 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, torvalds@linux-foundation.org, riel@redhat.com Subject: Re: IO scheduler based IO controller V10 Message-ID: <20091002092839.GA26962@kernel.dk> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091002092409.GA19529@elte.hu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1423 Lines: 36 On Fri, Oct 02 2009, Ingo Molnar wrote: > > * Jens Axboe wrote: > > > It's not hard to make the latency good, the hard bit is making sure we > > also perform well for all other scenarios. > > Looking at the numbers from Mike: > > | dd competing against perf stat -- konsole -e exec timings, 5 back to > | back runs > | Avg > | before 9.15 14.51 9.39 15.06 9.90 11.6 > | after [+patch] 1.76 1.54 1.93 1.88 1.56 1.7 > > _PLEASE_ make read latencies this good - the numbers are _vastly_ > better. We'll worry about the 'other' things _after_ we've reached good > latencies. > > I thought this principle was a well established basic rule of Linux IO > scheduling. Why do we have to have a 'latency vs. bandwidth' discussion > again and again? I thought latency won hands down. It's really not that simple, if we go and do easy latency bits, then throughput drops 30% or more. You can't say it's black and white latency vs throughput issue, that's just not how the real world works. The server folks would be most unpleased. -- Jens Axboe -- 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/