Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755263AbYGIWcL (ORCPT ); Wed, 9 Jul 2008 18:32:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752311AbYGIWb6 (ORCPT ); Wed, 9 Jul 2008 18:31:58 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:40680 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751801AbYGIWb5 (ORCPT ); Wed, 9 Jul 2008 18:31:57 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Christoph Lameter Cc: Jeremy Fitzhardinge , Ingo Molnar , Mike Travis , Andrew Morton , "H. Peter Anvin" , 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> Date: Wed, 09 Jul 2008 15:22:44 -0700 In-Reply-To: <48752CCD.30507@linux-foundation.org> (Christoph Lameter's message of "Wed, 09 Jul 2008 16:25:33 -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 * -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% * [score: 0.0088] * -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: 855 Lines: 19 Christoph Lameter writes: > Note also that the 32 bit offset size limits the offset that can be added to the > segment register. You either need to place the per cpu area either in the last > 2G of the address space or in the first 2G. The zero based approach removes that > limitation. Good point. Which means that fundamentally we need to come up with a special linker segment or some other way to guarantee that the offsets we use for per cpu variables is within 2G of the segment register. Which means that my idea of using the technique we use on x86_32 will not work. 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/