Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753548Ab2EZUnT (ORCPT ); Sat, 26 May 2012 16:43:19 -0400 Received: from mail-wg0-f44.google.com ([74.125.82.44]:48634 "EHLO mail-wg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750981Ab2EZUnS (ORCPT ); Sat, 26 May 2012 16:43:18 -0400 MIME-Version: 1.0 In-Reply-To: <4FC112AB.1040605@redhat.com> References: <1337965359-29725-1-git-send-email-aarcange@redhat.com> <4FC112AB.1040605@redhat.com> From: Linus Torvalds Date: Sat, 26 May 2012 13:42:56 -0700 X-Google-Sender-Auth: YKmZmsotaLjD8IWmD1YvMt3wMMo Message-ID: Subject: Re: [PATCH 00/35] AutoNUMA alpha14 To: Rik van Riel Cc: Andrea Arcangeli , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Hillf Danton , Dan Smith , Peter Zijlstra , Andrew Morton , Thomas Gleixner , Ingo Molnar , Paul Turner , Suresh Siddha , Mike Galbraith , "Paul E. McKenney" , Lai Jiangshan , Bharata B Rao , Lee Schermerhorn , Johannes Weiner , Srivatsa Vaddagiri , Christoph Lameter Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1888 Lines: 43 On Sat, May 26, 2012 at 10:28 AM, Rik van Riel wrote: > > It would be good to get everybody's ideas out there on this > topic, because this is the fundamental factor in deciding > between Peter's approach to NUMA and Andrea's approach. > > Ingo? Andrew? Linus? Paul? I'm a *firm* believer that if it cannot be done automatically "well enough", the absolute last thing we should ever do is worry about the crazy people who think they can tweak it to perfection with complex interfaces. You can't do it, except for trivial loads (often benchmarks), and for very specific machines. So I think very strongly that we should entirely dismiss all the people who want to do manual placement and claim that they know what their loads do. They're either full of sh*t (most likely), or they have a very specific benchmark and platform that they are tuning for that is totally irrelevant to everybody else. What we *should* try to aim for is a system that doesn't do horribly badly right out of the box. IOW, no tuning what-so-ever (at most a kind of "yes, I want you to try to do the NUMA thing" flag to just enable it at all), and try to not suck. Seriously. "Try to avoid sucking" is *way* superior to "We can let the user tweak things to their hearts content". Because users won't get it right. Give the anal people a knob they can tweak, and tell them it does something fancy. And never actually wire the damn thing up. They'll be really happy with their OCD tweaking, and do lots of nice graphs that just show how the error bars are so big that you can find any damn pattern you want in random noise. 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/