From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756514AbZEGOtv (ORCPT ); Thu, 7 May 2009 10:49:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755328AbZEGOtl (ORCPT ); Thu, 7 May 2009 10:49:41 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:35906 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753623AbZEGOtk (ORCPT ); Thu, 7 May 2009 10:49:40 -0400 Date: Thu, 7 May 2009 16:49:04 +0200 From: Ingo Molnar To: "H. Peter Anvin" Cc: Pavel Machek , Rik van Riel , "linux-kernel@vger.kernel.org" , linux-mm@kvack.org, mingo@redhat.com, akpm@linux-foundation.org Subject: Re: [PATCH] x86: 46 bit PAE support Message-ID: <20090507144904.GA2344@elte.hu> References: <20090505172856.6820db22@cuia.bos.redhat.com> <4A00ED83.1030700@zytor.com> <4A0180AB.20108@redhat.com> <20090507120103.GA1497@ucw.cz> <20090507141642.GJ481@elte.hu> <4A02EFD2.40707@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A02EFD2.40707@zytor.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * H. Peter Anvin wrote: > Ingo Molnar wrote: > > > > Yes, struct page is ~64 bytes, and 64*64 == 4096. > > > > Alas, it's not a problem: my suggestion wasnt to simulate 64 TB of > > RAM. My suggestion was to create a sparse physical memory map (in a > > virtual machine) that spreads ~1GB of RAM all around the 64 TB > > physical address space. That will test whether the kernel is able to > > map and work with such physical addresses. (which will cover most of > > the issues) > > > > A good look at /debug/x86/dump_pagetables with such a system booted > > up would be nice as well - to make sure every virtual memory range > > is in its proper area, and that there's enough free space around > > them. > > > > We're working on simulating this at Intel. We should hopefully be > able to test this next week. Wow, very nice! It would be nice to do it on a KVM basis and submit the weird-memory-layout submission to the KVM tree. It would be helpful with the reproduction of weird, memory layout dependent bugs too for example. Plus we could create a test facility that randomizes the physical memory layout (with a given fragmentation level). Ingo