Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756573AbYGIWdW (ORCPT ); Wed, 9 Jul 2008 18:33:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752311AbYGIWdL (ORCPT ); Wed, 9 Jul 2008 18:33:11 -0400 Received: from gw.goop.org ([64.81.55.164]:35341 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751801AbYGIWdK (ORCPT ); Wed, 9 Jul 2008 18:33:10 -0400 Message-ID: <48753C99.5050408@goop.org> Date: Wed, 09 Jul 2008 15:32:57 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: "Eric W. Biederman" CC: Christoph Lameter , Ingo Molnar , Mike Travis , Andrew Morton , "H. Peter Anvin" , Jack Steiner , linux-kernel@vger.kernel.org, Arjan van de Ven Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses 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> In-Reply-To: X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1065 Lines: 27 Eric W. Biederman wrote: > 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. No, the compiler memory model we use guarantees that everything will be within 2G of each other. The linker will spew loudly if that's not the case. J -- 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/