Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757639AbYGJVc3 (ORCPT ); Thu, 10 Jul 2008 17:32:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752699AbYGJVcF (ORCPT ); Thu, 10 Jul 2008 17:32:05 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:52250 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751731AbYGJVcD (ORCPT ); Thu, 10 Jul 2008 17:32:03 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Christoph Lameter Cc: "H. Peter Anvin" , Mike Travis , Jeremy Fitzhardinge , Arjan van de Ven , Ingo Molnar , Andrew Morton , Jack Steiner , linux-kernel@vger.kernel.org, Rusty Russell References: <20080709165129.292635000@polaris-admin.engr.sgi.com> <20080709200757.GD14009@elte.hu> <48751B57.8030605@goop.org> <20080709133958.612635f0@infradead.org> <4875231F.1020506@zytor.com> <487524A0.6020304@goop.org> <487529AE.3060505@zytor.com> <48753A71.2030006@zytor.com> <48763732.7020805@sgi.com> <487641D6.5060206@goop.org> <487649B2.3000405@sgi.com> <48764E8A.5010400@zytor.com> <4876766F.4030605@linux-foundation.org> <48767804.8080007@zytor.com> <48767A28.7070900@linux-foundation.org> Date: Thu, 10 Jul 2008 14:26:17 -0700 In-Reply-To: <48767A28.7070900@linux-foundation.org> (Christoph Lameter's message of "Thu, 10 Jul 2008 16:07:52 -0500") 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; sa01 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Christoph Lameter 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 * -0.7 BAYES_20 BODY: Bayesian spam probability is 5 to 20% * [score: 0.0956] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa01 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: 976 Lines: 26 Christoph Lameter writes: > H. Peter Anvin wrote: > >> And how much is that, especially on *small* systems? > > i386? > > i386 uses 4K mappings. There are just a few cpus supported, there is scarcity of > ZONE_NORMAL memory so the per cpu areas really cannot get that big. See the > cpu_alloc patchsets for i386. i386 is fundamentally resource constrained. However x86_32 should support a strict superset of the machines the x86_64 kernel supports. Because it is resource constrained in the lowmem zone you should not be able to bring up all of the cpus on a huge cpu box. But you should still be able to boot and run the kernel. So for percpu data we have effectively same size constraints. 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/