Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755129AbZKIMiV (ORCPT ); Mon, 9 Nov 2009 07:38:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754705AbZKIMiU (ORCPT ); Mon, 9 Nov 2009 07:38:20 -0500 Received: from one.firstfloor.org ([213.235.205.2]:48609 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754228AbZKIMiU (ORCPT ); Mon, 9 Nov 2009 07:38:20 -0500 Date: Mon, 9 Nov 2009 13:38:24 +0100 From: Andi Kleen To: Andre Przywara Cc: Andi Kleen , Linux-kernel Subject: Re: x86/NUMA: Reason for ignoring too small NUMA nodes? Message-ID: <20091109123824.GE26740@basil.fritz.box> References: <4AF80AA3.9020400@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4AF80AA3.9020400@amd.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1269 Lines: 25 On Mon, Nov 09, 2009 at 01:27:15PM +0100, Andre Przywara wrote: > while experimenting with a system with a memory-less NUMA node I stumbled > upon code in the Linux kernel which ignores nodes containing less than a > certain amount of RAM, obviously to fix systems with a buggy BIOS. > Can you elaborate on this? What kind of incorrect entry have you seen? > To correctly map the memory less node I did a patch to accept at least > nodes with exactly zero bytes of memory (read: no SRAT memory entry), was > this special condition also present in the buggy machines? It was a misparsed numa node, not zero. I don't remember if the bug was in Linux or in the BIOS. This was a sanity check to catch all such cases. I haven't seen misparsed nodes for quite some time, so in theory it could be removed I guess. Zero size node were back then not supported in the VM. I still think the concept doesn't make too much sense: a memory range without memory (and it bitrots all the time even today, see recent patches) -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/