Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031044AbWKPBfv (ORCPT ); Wed, 15 Nov 2006 20:35:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1031047AbWKPBfv (ORCPT ); Wed, 15 Nov 2006 20:35:51 -0500 Received: from omx1-ext.sgi.com ([192.48.179.11]:61067 "EHLO omx1.sgi.com") by vger.kernel.org with ESMTP id S1031044AbWKPBfu (ORCPT ); Wed, 15 Nov 2006 20:35:50 -0500 Date: Wed, 15 Nov 2006 19:35:34 -0600 From: Jack Steiner To: Christoph Lameter Cc: Christian Krafft , linux-mm@kvack.org, Martin Bligh , linux-kernel@vger.kernel.org Subject: Re: [patch 2/2] enables booting a NUMA system where some nodes have no memory Message-ID: <20061116013534.GB1066@sgi.com> References: <20061115193049.3457b44c@localhost> <20061115193437.25cdc371@localhost> <20061115215845.GB20526@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1626 Lines: 41 On Wed, Nov 15, 2006 at 02:40:36PM -0800, Christoph Lameter wrote: > On Wed, 15 Nov 2006, Jack Steiner wrote: > > > A lot of the core infrastructure is currently missing that is required > > to describe IO nodes as regular nodes, but in principle, I don't > > see anything wrong with nodes w/o memory. > > Every processor has a local node on which it runs. The kernel places > memory used by the processor on the local node. Even if we allow > nodes without memory: We still need to associate a "local" node to the > processor. If that is across some NUMA interlink then it is going to be > slower but it will work. True. > > AFAIK It seems to be better to explicitly associate a memory node with a > processor during bootup in arch code. > > Various kernel optimizations rely on local memory. Would we create > a special case here of a pglist_data structure without a zones structure? > > It seems that the contents of pglist_data are targeted to a memory node. > If we do not have a pglist_data structure then the node would not exist > for the kernel. > > What would the benefit or difference be of having nodes without memory? I doubt that there is a demand for systems with memoryless nodes. However, if the DIMM(s) on a node fails, I think the system may perform better with the cpus on the node enabled than it will if they have to be disabled. -- jack - 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/