Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759430AbYGJSAt (ORCPT ); Thu, 10 Jul 2008 14:00:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753138AbYGJSAl (ORCPT ); Thu, 10 Jul 2008 14:00:41 -0400 Received: from terminus.zytor.com ([198.137.202.10]:55996 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752721AbYGJSAl (ORCPT ); Thu, 10 Jul 2008 14:00:41 -0400 Message-ID: <48764CB4.8080207@zytor.com> Date: Thu, 10 Jul 2008 13:53:56 -0400 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Christoph Lameter CC: Jeremy Fitzhardinge , "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> In-Reply-To: <48763CA6.9030802@linux-foundation.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: 838 Lines: 20 Christoph Lameter wrote: > > There will be no additional overhead since the memory already mapped 1-1 using 2MB TLBs and we want to use the same for the percpu areas. This is similar to the vmemmap solution. > THAT sounds strange. If you're using dedicated virtual maps (which is what you're responding to here) then you will *always* have additional TLB pressure. Furthermore, if you use 2 MB pages, you: a) can only allocate full 2 MB pages, which is expensive for the static users and difficult for the dynamic users; b) increase pressure in the relatively small 2 MB TLB. -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/