From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755817AbZDTNLH (ORCPT ); Mon, 20 Apr 2009 09:11:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754302AbZDTNKy (ORCPT ); Mon, 20 Apr 2009 09:10:54 -0400 Received: from relay1.sgi.com ([192.48.179.29]:51446 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752519AbZDTNKx (ORCPT ); Mon, 20 Apr 2009 09:10:53 -0400 Date: Mon, 20 Apr 2009 08:10:49 -0500 From: Jack Steiner To: Andi Kleen Cc: mingo@elte.hu, tglx@linutronix.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH] - Memoryless nodes Message-ID: <20090420131049.GA11839@sgi.com> References: <20090417142242.GA23743@sgi.com> <87hc0mqqtd.fsf@basil.nowhere.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87hc0mqqtd.fsf@basil.nowhere.org> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Apr 18, 2009 at 11:00:46AM +0200, Andi Kleen wrote: > Jack Steiner writes: > > > Add support for nodes that have cpus but no memory. > > The current code was failing to add these nodes > > to the nodes_present_map. > > That was intentional because a node is defined as an area of memory > and an area of memory without memory didn't seem to make sense. > I still don't think it does. Instead the CPUs are assigned > to nearby nodes. Back then the generic code also couldn't deal > with them at all, so you might well run into more problems. Nodes can also be viewed as a collection of cpus and memory that are located "close together" - ie., same PXM in the SRAT. Normally nodes will have both memory & cpus but in theory either cpus or memory could be missing. I have run a number of tests of nodes with cpus only and so far have not seen any issues. I certainly won't rule out problems but have not seen them yet. If there are any corner cases that you are aware of, let me know & I can do some more targeted testing. (Note: this is not a bizarre end case that I'm trying to fix. UV actually has blades with cpus and no memory available to the OS.) --- jack