Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757561AbYGJUWR (ORCPT ); Thu, 10 Jul 2008 16:22:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752834AbYGJUWF (ORCPT ); Thu, 10 Jul 2008 16:22:05 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:44927 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752773AbYGJUWD (ORCPT ); Thu, 10 Jul 2008 16:22:03 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Mike Travis Cc: "H. Peter Anvin" , Christoph Lameter , Jeremy Fitzhardinge , Ingo Molnar , Andrew Morton , Jack Steiner , linux-kernel@vger.kernel.org, Arjan van de Ven References: <20080709165129.292635000@polaris-admin.engr.sgi.com> <20080709200757.GD14009@elte.hu> <48751B57.8030605@goop.org> <48751CF9.4020901@linux-foundation.org> <4875209D.8010603@goop.org> <48752CCD.30507@linux-foundation.org> <48753C99.5050408@goop.org> <487555A8.2050007@zytor.com> <487556A5.5090907@goop.org> <4876194E.4080205@linux-foundation.org> <48761C06.3020003@zytor.com> <48762A3B.5050104@linux-foundation.org> <48762DD2.5090802@zytor.com> <487637A1.4080403@linux-foundation.org> <48764C21.4020601@zytor.com> <4876608B.10408@sgi.com> Date: Thu, 10 Jul 2008 13:17:54 -0700 In-Reply-To: <4876608B.10408@sgi.com> (Mike Travis's message of "Thu, 10 Jul 2008 12:18:35 -0700") Message-ID: User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-SA-Exim-Connect-IP: 24.130.11.59 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-DCC: XMission; sa02 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Mike Travis X-Spam-Relay-Country: X-Spam-Report: * -1.8 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 T_TM2_M_HEADER_IN_MSG BODY: T_TM2_M_HEADER_IN_MSG * -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% * [score: 0.0051] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa02 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 XM_SPF_Neutral SPF-Neutral Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses X-SA-Exim-Version: 4.2 (built Thu, 03 Mar 2005 10:44:12 +0100) X-SA-Exim-Scanned: Yes (on mgr1.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1041 Lines: 26 Mike Travis writes: > The biggest growth came from moving all the xxx[NR_CPUS] arrays into > the per cpu area. So you free up a huge amount of unused memory when > the NR_CPUS count starts getting into the ozone layer. 4k now, 16k > real soon now, ??? future? Hmm. Do you know how big a role kernel_stat plays. It is a per cpu structure that is sized via NR_IRQS. NR_IRQS is by NR_CPUS. So ultimately the amount of memory take up is NR_CPUS*NR_CPUS*32 or so. I have a patch I wrote long ago, that addresses that specific nasty configuration by moving the per cpu irq counters into pointer available from struct irq_desc. The next step which I did not get to (but is interesting from a scaling perspective) was to start dynamically allocating the irq structures. Eric -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/