From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752319AbXDICMe (ORCPT ); Sun, 8 Apr 2007 22:12:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752325AbXDICMe (ORCPT ); Sun, 8 Apr 2007 22:12:34 -0400 Received: from mx1.redhat.com ([66.187.233.31]:46819 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752312AbXDICMd (ORCPT ); Sun, 8 Apr 2007 22:12:33 -0400 Message-ID: <4619A101.5030600@redhat.com> Date: Sun, 08 Apr 2007 22:12:17 -0400 From: Rik van Riel Organization: Red Hat, Inc User-Agent: Thunderbird 1.5.0.7 (X11/20061008) MIME-Version: 1.0 To: Valdis.Kletnieks@vt.edu CC: root , linux-kernel@vger.kernel.org Subject: Re: [PATCH] Scheduler: Improving the scheduler performance. References: <1175967725.5798.13.camel@localhost> <8762.1176044803@turing-police.cc.vt.edu> In-Reply-To: <8762.1176044803@turing-police.cc.vt.edu> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Valdis.Kletnieks@vt.edu wrote: > On Sat, 07 Apr 2007 23:42:20 +0600, root said: > >> As we know that, linux scheduler use separate runqueue for every CPU of >> a multiprocessor system, which having an active and an expired array.If >> we use only one expired array, then the CPUs of a multiprocessor system >> will be able to share their expired task via the accumulated expired >> array, > > I got this far, and the first thought that popped into my head was: > > "Wow. This might actually win on a UP or small MP (2-15 CPU). But the > lock contention on a big 512-CPU machoflops box is likely going to *suck*". > > For that matter, my quick eyeballing of the code, although it doesn't *find* > any race conditions, doesn't convince me there's any protection taken to make > sure there aren't any. Is there some subtle algorithmic trick I'm missing > to ensure Nothing Bad Can Happen? Lock contention is going to be the least of your worries. Destroying CPU affinity is the big one I suspect. -- Politics is the struggle between those who want to make their country the best in the world, and those who believe it already is. Each group calls the other unpatriotic.