From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261212AbTD1RFj (ORCPT ); Mon, 28 Apr 2003 13:05:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261210AbTD1RFi (ORCPT ); Mon, 28 Apr 2003 13:05:38 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.103]:46583 "EHLO e3.ny.us.ibm.com") by vger.kernel.org with ESMTP id S261212AbTD1RFh (ORCPT ); Mon, 28 Apr 2003 13:05:37 -0400 Message-ID: <3EAD61FB.30907@us.ibm.com> Date: Mon, 28 Apr 2003 10:16:43 -0700 From: Dave Hansen User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.0.0) Gecko/20020623 Debian/1.0.0-0.woody.1 X-Accept-Language: en MIME-Version: 1.0 To: Carl-Daniel Hailfinger CC: Andi Kleen , Henti Smith , linux-kernel@vger.kernel.org, lse-tech@lists.sourceforge.net, Riley Williams Subject: Re: [Lse-tech] Re: maximum possible memory limit .. References: <20030424200524.5030a86b.bain@tcsn.co.za> <3EAD27B2.9010807@gmx.net> <20030428141023.GC4525@Wotan.suse.de> <3EAD5AC1.7090003@us.ibm.com> <3EAD5D90.7010101@gmx.net> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Carl-Daniel Hailfinger wrote: > Cool. Sorry to be pestering about the 64-bit limits, but can we really > use 2^64 bytes of memory on ia64/ppc64/x86-64 etc.? (AFAIK, 64-bit > arches don't suffer from a small ZONE_LOWMEM.) First of all, I'm not sure any of the 64-bit arches even fully support 64-bit physical addresses. If I remember correctly the first hammers support 40 bits, with more to be added later. Power4 is in close to the same boat, but I know they go up to 256GB today (I seem to recall something about 44-bit being the limit, though). Don't forget that highmem starts to be needed before the 4G boundary. The kernel has only 1GB of virtual space (look for PAGE_OFFSET, which defines it), which means that you start needing to pull all of the highmem trickery before you get to the actual limits. Nobody knows how far it will go. It's fairly safe to say that, at this rate, Linux will keep up with whatever hardware anyone produces. Unless, of course, someone gets even more perverse than PAE. :) -- Dave Hansen haveblue@us.ibm.com