From owner-freebsd-amd64@FreeBSD.ORG Sun Feb 1 16:53:30 2004 Return-Path: Delivered-To: freebsd-amd64@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 21EE816A4CE for ; Sun, 1 Feb 2004 16:53:30 -0800 (PST) Received: from dragon.nuxi.com (trang.nuxi.com [66.93.134.19]) by mx1.FreeBSD.org (Postfix) with ESMTP id E4AE043D2D for ; Sun, 1 Feb 2004 16:53:28 -0800 (PST) (envelope-from obrien@dragon.nuxi.com) Received: from dragon.nuxi.com (obrien@localhost [127.0.0.1]) by dragon.nuxi.com (8.12.10/8.12.9) with ESMTP id i120rSA0094939; Sun, 1 Feb 2004 16:53:28 -0800 (PST) (envelope-from obrien@dragon.nuxi.com) Received: (from obrien@localhost) by dragon.nuxi.com (8.12.10/8.12.10/Submit) id i120rQte094934; Sun, 1 Feb 2004 16:53:26 -0800 (PST) (envelope-from obrien) Date: Sun, 1 Feb 2004 16:53:26 -0800 From: "David O'Brien" To: Andreas Braukmann Message-ID: <20040202005326.GB60117@dragon.nuxi.com> References: <1071900000.1075679494@cage.int.unixxinu.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1071900000.1075679494@cage.int.unixxinu.de> User-Agent: Mutt/1.4.1i X-Operating-System: FreeBSD 5.2-CURRENT Organization: The NUXI BSD Group X-Pgp-Rsa-Fingerprint: B7 4D 3E E9 11 39 5F A3 90 76 5D 69 58 D9 98 7A X-Pgp-Rsa-Keyid: 1024/34F9F9D5 cc: amd64@freebsd.org Subject: Re: Dual processor, AMD 64 machine freezing. X-BeenThere: freebsd-amd64@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: obrien@freebsd.org List-Id: Porting FreeBSD to the AMD64 platform List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 02 Feb 2004 00:53:30 -0000 On Mon, Feb 02, 2004 at 12:51:34AM +0100, Andreas Braukmann wrote: > > P.S. For best performance, I think you really want to run 4x 512 MB. > > Running with two DIMMs means either you only get 64-bit memory access (not > > 128-bit) or else you need to put both DIMMs into the CPU1 memory slots > > (which means CPU2 will have to access those through hypertransport). > > Thats theory. ;-) > Since the allocators don't know about the numa-like architecture > memory would be accessed through hyptertransport (statistically) > more or less "half of the time". (CPU0 ---> HT ---> MEM1 ; > CPU1 ---> HT ---> MEM0) Its not theory, its fact -- even w/o a NUMA aware OS. Statistically, 1/2 the accesses by a CPU are to local memory, 1/2 to distant memory. If you put all them memory on a single CPU then you've got two processors trying to access memory, saturating the memory controller on the single CPU with memory -- thus giving you less BW. Your diagram above leaves out the memory controller (and its request buffer). -- -- David (obrien@FreeBSD.org) P.S. I work at AMD