From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1767181AbXEBSmX (ORCPT ); Wed, 2 May 2007 14:42:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1767188AbXEBSmX (ORCPT ); Wed, 2 May 2007 14:42:23 -0400 Received: from mga01.intel.com ([192.55.52.88]:57303 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1767181AbXEBSmW (ORCPT ); Wed, 2 May 2007 14:42:22 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.14,481,1170662400"; d="scan'208";a="240832852" Subject: Re: [patch] CFS scheduler, -v8 From: "Li, Tong N" To: tingy@cs.umass.edu CC: Ingo Molnar , linux-kernel@vger.kernel.org In-Reply-To: <4637FE0A.7090405@cs.umass.edu> References: <20070501212223.GA29867@elte.hu> <4637FE0A.7090405@cs.umass.edu> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Wed, 2 May 2007 11:42:20 -0700 Message-ID: <1178131340.25170.24.camel@tongli.jf.intel.com> MIME-Version: 1.0 X-Mailer: Evolution 2.8.3 (2.8.3-2.fc6) X-OriginalArrivalTime: 02 May 2007 18:42:21.0370 (UTC) FILETIME=[9E4159A0:01C78CE9] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > Based on my understanding, adopting something like EEVDF in CFS should > not be very difficult given their similarities, although I do not have > any idea on how this impacts the load balancing for SMP. Does this worth > a try? > > Sorry for such a long email :-) Thanks for the excellent explanation. I think EEVDF and many algs alike assume global ordering of all tasks in the system (based on virtual time), whereas CFS does so locally on each processor and relies on load balancing to achieve fairness across processors. It'd achieve strong fairness locally, but I'm not sure about its global fairness properties in an MP environment. If ideally the total load weight on each processor is always the same, then local fairness would imply global fairness, but this is a bin packing problem and is intractable ... tong