Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756649AbYGJUZ2 (ORCPT ); Thu, 10 Jul 2008 16:25:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751455AbYGJUZT (ORCPT ); Thu, 10 Jul 2008 16:25:19 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:56150 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750952AbYGJUZS (ORCPT ); Thu, 10 Jul 2008 16:25:18 -0400 Date: Thu, 10 Jul 2008 22:24:53 +0200 From: Ingo Molnar To: "Eric W. Biederman" Cc: Mike Travis , "H. Peter Anvin" , Christoph Lameter , Jeremy Fitzhardinge , Andrew Morton , Jack Steiner , linux-kernel@vger.kernel.org, Arjan van de Ven Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses Message-ID: <20080710202453.GA7534@elte.hu> References: <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1272 Lines: 35 * Eric W. Biederman wrote: > 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. /me willing to test & babysit any test-patch in that area ... this is a big problem and it's getting worse quadratically ;-) Ingo -- 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/