Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759567AbYGJSCa (ORCPT ); Thu, 10 Jul 2008 14:02:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753330AbYGJSCX (ORCPT ); Thu, 10 Jul 2008 14:02:23 -0400 Received: from terminus.zytor.com ([198.137.202.10]:56009 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753138AbYGJSCW (ORCPT ); Thu, 10 Jul 2008 14:02:22 -0400 Message-ID: <48764D19.9000407@zytor.com> Date: Thu, 10 Jul 2008 13:55:37 -0400 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Jeremy Fitzhardinge CC: Christoph Lameter , "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> <48764C7C.5010309@goop.org> In-Reply-To: <48764C7C.5010309@goop.org> 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: 729 Lines: 19 Jeremy Fitzhardinge wrote: > >> 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. > That's easy enough to fix -- synthesizing a GDT entry is trivial enough -- but since it currently works, and since the offsets on 32 bits can reach the full address space anyway, there is no reason to change. -hpa -- 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/