From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753399AbWKCRgJ (ORCPT ); Fri, 3 Nov 2006 12:36:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753402AbWKCRgJ (ORCPT ); Fri, 3 Nov 2006 12:36:09 -0500 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:23453 "EHLO ebiederm.dsl.xmission.com") by vger.kernel.org with ESMTP id S1753399AbWKCRgH (ORCPT ); Fri, 3 Nov 2006 12:36:07 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: tim.c.chen@linux.intel.com Cc: Adrian Bunk , linux-kernel@vger.kernel.org, ak@suse.de, discuss@x86-64.org Subject: Re: 2.6.19-rc1: x86_64 slowdown in lmbench's fork References: <1162485897.10806.72.camel@localhost.localdomain> <1162492453.10806.75.camel@localhost.localdomain> <20061103021145.GD13381@stusta.de> <1162570216.10806.79.camel@localhost.localdomain> Date: Fri, 03 Nov 2006 10:35:36 -0700 In-Reply-To: <1162570216.10806.79.camel@localhost.localdomain> (Tim Chen's message of "Fri, 03 Nov 2006 08:10:16 -0800") Message-ID: User-Agent: Gnus/5.110004 (No Gnus v0.4) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Tim Chen writes: > On Fri, 2006-11-03 at 03:11 +0100, Adrian Bunk wrote: > >> >> What's your CONFIG_NR_CPUS setting that you are seeing such a big >> regression? >> > > CONFIG_NR_CPUS is set to 8. Ugh. This simply changes NR_IRQS from 256 to 512. Changing the size of data from 1K to 2K. So unless there is some other array that is sized by NR_IRQs in the context switch path which could account for this in other ways. It looks like you just got unlucky. The only hypothesis that I can seem to come up with is that maybe you are getting an extra tlb now that you didn't use to. I think the per cpu area is covered by huge pages but maybe not. Eric