From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933165AbXHAOFZ (ORCPT ); Wed, 1 Aug 2007 10:05:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932307AbXHAOFL (ORCPT ); Wed, 1 Aug 2007 10:05:11 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:35349 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932187AbXHAOFJ (ORCPT ); Wed, 1 Aug 2007 10:05:09 -0400 Subject: Re: CFS review From: Arjan van de Ven To: Ingo Molnar Cc: Roman Zippel , Mike Galbraith , Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org In-Reply-To: <20070801135949.GA10839@elte.hu> References: <20070711211638.GE18767@one.firstfloor.org> <20070711214649.GK14435@v2.random> <1184302024.6709.11.camel@Homer.simpson.net> <1184389456.6632.13.camel@Homer.simpson.net> <20070801112229.GA11710@elte.hu> <20070801135949.GA10839@elte.hu> Content-Type: text/plain Organization: Intel International BV Date: Wed, 01 Aug 2007 07:04:34 -0700 Message-Id: <1185977074.2754.23.camel@laptopd505.fenrus.org> Mime-Version: 1.0 X-Mailer: Evolution 2.10.3 (2.10.3-2.fc7) Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > but that's nothing new. CFS cannot conjure up time measurement methods > that do not exist. If you have a low-res clock and if you create an app > that syncs precisely to the tick of that clock via timers that run off > that exact tick then there's nothing the scheduler can do about it. It > is false to charachterise this as 'sleeper starvation' or 'rounding > error' like you did. No amount of rounding logic can create a > high-resolution clock out of thin air. CFS is only as fair as your clock is good.