From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938793AbXG1CsG (ORCPT ); Fri, 27 Jul 2007 22:48:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761261AbXG1Cry (ORCPT ); Fri, 27 Jul 2007 22:47:54 -0400 Received: from mx1.redhat.com ([66.187.233.31]:33979 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761096AbXG1Cry (ORCPT ); Fri, 27 Jul 2007 22:47:54 -0400 Message-ID: <46AAAE39.4070905@redhat.com> Date: Fri, 27 Jul 2007 22:47:21 -0400 From: Rik van Riel Organization: Red Hat, Inc User-Agent: Thunderbird 1.5.0.7 (X11/20061008) MIME-Version: 1.0 To: tim.c.chen@linux.intel.com CC: mingo@elte.hu, linux-kernel@vger.kernel.org Subject: Re: Volanomark slows by 80% under CFS References: <1185573687.19777.44.camel@localhost.localdomain> In-Reply-To: <1185573687.19777.44.camel@localhost.localdomain> 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 Tim Chen wrote: > Ingo, > > Volanomark slows by 80% with CFS scheduler on 2.6.23-rc1. > Benchmark was run on a 2 socket Core2 machine. > > The change in scheduler treatment of sched_yield > could play a part in changing Volanomark behavior. > In CFS, sched_yield is implemented > by dequeueing and requeueing a process . The time a process > has spent running probably reduced the the cpu time due it > by only a bit. The process could get re-queued pretty close > to head of the queue, and may get scheduled again pretty > quickly if there is still a lot of cpu time due. I wonder if this explains the 30% drop in top performance seen with the MySQL sysbench benchmark when the scheduler changed to CFS... See http://people.freebsd.org/~jeff/sysbench.png -- 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.