Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760860AbYGJRxX (ORCPT ); Thu, 10 Jul 2008 13:53:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757827AbYGJRxO (ORCPT ); Thu, 10 Jul 2008 13:53:14 -0400 Received: from gw.goop.org ([64.81.55.164]:58053 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754181AbYGJRxN (ORCPT ); Thu, 10 Jul 2008 13:53:13 -0400 Message-ID: <48764C7C.5010309@goop.org> Date: Thu, 10 Jul 2008 10:53:00 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Christoph Lameter CC: "H. Peter Anvin" , "Eric W. Biederman" , Ingo Molnar , Mike Travis , Andrew Morton , 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> <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> <487639ED.7000502@zytor.com> <48763CA6.9030802@linux-foundation.org> <487647EF.5010609@goop.org> <48764A01.1070402@linux-foundation.org> In-Reply-To: <48764A01.1070402@linux-foundation.org> 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: 962 Lines: 26 Christoph Lameter wrote: >> The nice thing about the non-zero-based scheme i386 uses is that setting >> gs-base to zero means that percpu variables accesses get directly to the >> prototype percpu data area, which simplifies boot time setup (which is >> doubly awkward on 32-bit because you need to generate a GDT entry rather >> than just load an MSR as you do in 64-bit). >> > > Great but it causes trouble in other ways as discussed. What other trouble? It works fine. > Its best to consistently access > per cpu variables using the segment registers. > It is, but initially the segment base is 0, so just using a percpu variable does something sensible from the start with no special setup. 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/