From owner-freebsd-amd64@FreeBSD.ORG Mon Feb 2 02:06:36 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 81FF816A4CE for ; Mon, 2 Feb 2004 02:06:36 -0800 (PST) Received: from dragon.nuxi.com (trang.nuxi.com [66.93.134.19]) by mx1.FreeBSD.org (Postfix) with ESMTP id B3FD243D58 for ; Mon, 2 Feb 2004 02:06:33 -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 i12A6WA0025275; Mon, 2 Feb 2004 02:06:33 -0800 (PST) (envelope-from obrien@dragon.nuxi.com) Received: (from obrien@localhost) by dragon.nuxi.com (8.12.10/8.12.10/Submit) id i12A6WVJ025274; Mon, 2 Feb 2004 02:06:32 -0800 (PST) (envelope-from obrien) Date: Mon, 2 Feb 2004 02:06:32 -0800 From: "David O'Brien" To: "Haapanen, Tom" Message-ID: <20040202100632.GA25194@dragon.nuxi.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: amd64@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 10:06:36 -0000 On Sun, Feb 01, 2004 at 09:45:29PM -0500, Haapanen, Tom wrote: > David O'Brien wrote: > > 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). > > But isn't that (the 50-50 CPU memory access split) assuming that there is no > CPU-awareness in memory allocation? Yes. > Suppose that I have process/thread X running on CPU 1, and the OS kernel is > clever enough to allocate physical pages located on CPU 1's memory bank > whenever thread X requests new memory. In that scenario, wouldn't it be > reasonable to assume that more than 50% of memory accesses are local? Yes. However, this part of this thread started with the assumption that the OS was not NUMA aware. (unless I misread eariler emails) > Of course, having processes and/or threads that have CPU affinity would help > a whole lot, too. > > Is this ... > (a) an incorrect assumption; or > (b) impractical to implement, given virtual memory etc.? Not impractical -- Linux for AMD64 has NUMA support. -- -- David (obrien@FreeBSD.org)