From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966007AbXDBWh6 (ORCPT ); Mon, 2 Apr 2007 18:37:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S966002AbXDBWh6 (ORCPT ); Mon, 2 Apr 2007 18:37:58 -0400 Received: from netops-testserver-3-out.sgi.com ([192.48.171.28]:40460 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965966AbXDBWh5 (ORCPT ); Mon, 2 Apr 2007 18:37:57 -0400 Date: Mon, 2 Apr 2007 15:37:56 -0700 (PDT) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Andi Kleen cc: Dave Hansen , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Martin Bligh , linux-mm@kvack.org, KAMEZAWA Hiroyuki Subject: Re: [PATCH 1/4] x86_64: Switch to SPARSE_VIRTUAL In-Reply-To: <200704030031.24898.ak@suse.de> Message-ID: References: <20070401071024.23757.4113.sendpatchset@schroedinger.engr.sgi.com> <1175550968.22373.122.camel@localhost.localdomain> <200704030031.24898.ak@suse.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 3 Apr 2007, Andi Kleen wrote: > If it works I would be inclined to replaced old sparsemem with Christoph's > new one on x86-64. Perhaps that could cut down the bewildering sparsemem > ifdef jungle that is there currently. > > But I presume it won't work on 32bit because of the limited address space? Not in general but it will work in non PAE mode. 4GB need 2^(32-21+4) = 16MB pages. This would require the mapping on 4 4MB pages. For 64GB you'd need 256M which would be a quarter of low mem. Probably takes up too much of low mem. > > But, without some cold, hard, data, we mere mortals without the 1024-way > > machines can only guess. ;) > > Yep. > > -Andi (who would be scared of a 1024 way x86 machine) - Christoph (who does not believe that Andi has to wait long for something bigger)