From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id D6F136B003D for ; Thu, 7 May 2009 10:16:41 -0400 (EDT) Date: Thu, 7 May 2009 16:16:42 +0200 From: Ingo Molnar Subject: Re: [PATCH] x86: 46 bit PAE support Message-ID: <20090507141642.GJ481@elte.hu> References: <20090505172856.6820db22@cuia.bos.redhat.com> <4A00ED83.1030700@zytor.com> <4A0180AB.20108@redhat.com> <20090507120103.GA1497@ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090507120103.GA1497@ucw.cz> Sender: owner-linux-mm@kvack.org To: Pavel Machek Cc: Rik van Riel , "H. Peter Anvin" , "linux-kernel@vger.kernel.org" , linux-mm@kvack.org, mingo@redhat.com, akpm@linux-foundation.org List-ID: * Pavel Machek wrote: > On Wed 2009-05-06 08:20:59, Rik van Riel wrote: > > H. Peter Anvin wrote: > >> Rik van Riel wrote: > >>> Testing: booted it on an x86-64 system with 6GB RAM. Did you really think > >>> I had access to a system with 64TB of RAM? :) > >> > >> No, but it would be good if we could test it under Qemu or KVM with an > >> appropriately set up sparse memory map. > > > > I don't have a system with 1TB either, which is how much space > > the memmap[] would take... > > Do we really have 1 byte overhead per 64 bytes of RAM? > Pavel 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. Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org