From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932664AbXDRHJq (ORCPT ); Wed, 18 Apr 2007 03:09:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932753AbXDRHJq (ORCPT ); Wed, 18 Apr 2007 03:09:46 -0400 Received: from waste.org ([66.93.16.53]:53483 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932664AbXDRHJq (ORCPT ); Wed, 18 Apr 2007 03:09:46 -0400 Date: Wed, 18 Apr 2007 01:55:34 -0500 From: Matt Mackall To: Nick Piggin Cc: William Lee Irwin III , Peter Williams , Mike Galbraith , Con Kolivas , Ingo Molnar , ck list , Bill Huey , linux-kernel@vger.kernel.org, Linus Torvalds , Andrew Morton , Arjan van de Ven , Thomas Gleixner Subject: Re: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS] Message-ID: <20070418065534.GT11115@waste.org> References: <20070417060955.GO8915@holomorphy.com> <20070417061503.GC1057@wotan.suse.de> <20070417062621.GL2986@holomorphy.com> <20070417070155.GF1057@wotan.suse.de> <20070417213954.GE11166@waste.org> <20070418031511.GA18452@wotan.suse.de> <20070418043831.GR11115@waste.org> <20070418050024.GF18452@wotan.suse.de> <20070418055525.GS11115@waste.org> <20070418063711.GH18452@wotan.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070418063711.GH18452@wotan.suse.de> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 18, 2007 at 08:37:11AM +0200, Nick Piggin wrote: > I don't know how that supports your argument for unfairness, I never had such an argument. I like fairness. My argument is that -you- don't have an argument for making fairness a -requirement-. > processes are special only because that's how we've always done > scheduling. I'm not precluding other groupings for fairness, though. If you make one form of fairness a -requirement- for all acceptable algorithms, your -are- precluding most other forms of fairness. If you refuse to define what "fairness" means when specifying your requirement, what's the point of requiring it? > What do you mean optimal? If your criteria is fairness, then of course > it is optimal. If your criteria is throughput, then it probably isn't. I don't know what optimal behavior is. And neither do you. It may or may not be fair. It very likely includes small deviations from fair. > > [2] It's trivial to construct two or more perfectly reasonable and > > desirable definitions of fairness that are mutually incompatible. > > Probably not if you use common sense, and in the context of a replacement > for the 2.6 scheduler. Ok, trivial example. You cannot allocate equal CPU time to processes/tasks and simultaneously allocate equal time to thread groups. Is it common sense that a heavily-threaded app should be able to get hugely more CPU than a well-written app? No. I don't want Joe's stupid Java app to make my compile crawl. On the other hand, if my heavily threaded app is, say, a voicemail server serving 30 customers, I probably want it to get 30x the CPU of my gzip job. -- Mathematics is the supreme nostalgia of our time.