From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261668AbUKSWlO (ORCPT ); Fri, 19 Nov 2004 17:41:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261669AbUKSWeA (ORCPT ); Fri, 19 Nov 2004 17:34:00 -0500 Received: from omx1-ext.sgi.com ([192.48.179.11]:22919 "EHLO omx1.americas.sgi.com") by vger.kernel.org with ESMTP id S261668AbUKSWdM (ORCPT ); Fri, 19 Nov 2004 17:33:12 -0500 Date: Thu, 18 Nov 2004 10:39:44 -0600 From: Jack Steiner To: linux-kernel@vger.kernel.org Cc: linux-ia64@vger.kernel.org Subject: Re: Externalize SLIT table Message-ID: <20041118163944.GA28955@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org (Resend of mail sent Nov 10, 2004 - as far as I can tell, it went nowhere) On Wed, Nov 10, 2004 at 04:05:43PM +1100, Mark Goodwin wrote: > > On Tue, 9 Nov 2004, Matthew Dobson wrote: > >On Tue, 2004-11-09 at 12:34, Mark Goodwin wrote: > >>Once again however, it depends on the definition of distance. For nodes, > >>we've established it's the ACPI SLIT (relative distance to memory). For > >>cpus, should it be distance to memory? Distance to cache? Registers? Or > >>what? > >> > >That's the real issue. We need to agree upon a meaningful definition of > >CPU-to-CPU "distance". As Jesse mentioned in a follow-up, we can all > >agree on what Node-to-Node "distance" means, but there doesn't appear to > >be much consensus on what CPU "distance" means. > > How about we define cpu-distance to be "relative distance to the > lowest level cache on another CPU". On a system that has nodes with > multiple sockets (each supporting multiple cores or HT "CPUs" sharing > some level of cache), when the scheduler needs to migrate a task it would > first choose a CPU sharing the same cache, then a CPU on the same node, > then an off-node CPU (i.e. falling back to node distance). I think I like your definition better than the one I originally proposed (cpu distance was distance between the local memories of the cpus). But how do we determine the distance between the caches. > > Of course, I have no idea if that's anything like an optimal or desirable > task migration policy. Probably depends on cache-trashiness of the task > being migrated. > > -- Mark -- Thanks Jack Steiner (steiner@sgi.com) 651-683-5302 Principal Engineer SGI - Silicon Graphics, Inc.