From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932134AbWFFJfA (ORCPT ); Tue, 6 Jun 2006 05:35:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932137AbWFFJfA (ORCPT ); Tue, 6 Jun 2006 05:35:00 -0400 Received: from faui03.informatik.uni-erlangen.de ([131.188.30.103]:52937 "EHLO faui03.informatik.uni-erlangen.de") by vger.kernel.org with ESMTP id S932134AbWFFJe7 (ORCPT ); Tue, 6 Jun 2006 05:34:59 -0400 Date: Tue, 6 Jun 2006 11:34:56 +0200 From: Thomas Glanzmann To: LKML Subject: AMD64: 64 bit kernel 32 bit userland - some pending questions Message-ID: <20060606093456.GL4552@cip.informatik.uni-erlangen.de> Mail-Followup-To: Thomas Glanzmann , LKML MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hello everyone, I would like to use an AMD64 Opteron System with a 64 bit Linux Kernel, but a 32 bit userland (Debian Sarge). I have a few questions about this: - Is it possible to give the userland 3Gbyte virtual address space (default for 2.4 and 2.6). But give the Kernel a 64 bit virtual address space so that I get more than 1 Gbyte physical Memory into LOWMEM - say I want 8 Gbyte - without using HIGHMEM at all? If this scenario is possible I would get cheap memory access at the benefit of a well tested userland. I don't have applications that need more than 2 Gbyte virtual address space. - What is the easiest way to build a 64 bit kernel on a 32 bit Debian sarge. Are there crosscompiler packages available? Are there any guides on this? - If the above scenario works out like I imagine it, does this add some additional overhead I am not aware of when I switch for example from 32 bit userland to 64 bit kernel space which would override the performance gain I get from the huge LOWMEM virtuall address space? Thomas