Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261243AbVAMRK7 (ORCPT ); Thu, 13 Jan 2005 12:10:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261263AbVAMRKA (ORCPT ); Thu, 13 Jan 2005 12:10:00 -0500 Received: from c-24-1-16-159.client.comcast.net ([24.1.16.159]:28888 "EHLO leaper.linuxtx.org") by vger.kernel.org with ESMTP id S261249AbVAMRHu (ORCPT ); Thu, 13 Jan 2005 12:07:50 -0500 Date: Thu, 13 Jan 2005 11:07:33 -0600 From: "Justin M. Forbes" To: Raphael Jacquot Cc: sander@humilis.net, Kernel Mailing List , "Sergey S. Kostyliov" Subject: Re: NUMA or not on dual Opteron Message-ID: <20050113170733.GA14524@linuxtx.org> References: <200501121824.44327.rathamahata@ehouse.ru> <20050113094537.GB2547@favonius> <41E6472B.5020701@imag.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <41E6472B.5020701@imag.fr> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1634 Lines: 34 On Thu, Jan 13, 2005 at 11:02:19AM +0100, Raphael Jacquot wrote: > >I was under the impression that NUMA is useful on > 2-way systems only. > >Is this true, and if not, under what circumstances is NUMA useful on > >2-way Opteron systems? > > > >In other words: why should one want NUMA to be enabled or disabled for > >dual Opteron? > > > >Thanks in advance. > > > > Numa needs to be enabled on bi-opteron systems because each processor > controls part of the memory. unlike the intel memory architecture, where > processors share the same bus to access memory. > Numa in opteron systems is thus required to allow sharing of memory . This is somewhat true. There are 2 types of dual opteron boards. Those in the $200 US range only have one memory bank, which is attached to CPU0. They operate as a single node, and may perform better with numa turned off. Those in the $400+ range tend to have one bank per CPU and will certainly perform better with numa on. They do usually have a bios option to interleave the nodes which would show up as a single node, and probably perform better with numa turned off, but a better solution is to turn off the node interleave in bios and run the kernel with numa support. Basically if you have 2 CPUs and only one memory bank, maybe turning numa off will give better performance, but if you have one memory bank per CPU numa should be on. Justin - 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/