From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: NUMA and SMP Date: Mon, 15 Jan 2007 11:21:37 -0600 Message-ID: <45ABB821.4090402@linux.vnet.ibm.com> References: <280848580701140355l7ed6a198l21aa3b36fc8bddbd@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <280848580701140355l7ed6a198l21aa3b36fc8bddbd@mail.gmail.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: David Pilger Cc: xen-devel , Ryan Harper List-Id: xen-devel@lists.xenproject.org David Pilger wrote: > Hi all, > > 1. Does desktop computers, such as intel dual core really benefit from > NUMA? No. NUMA standards Non-Uniform Memory Architecture. It's basically a system where you have nodes (which are essentially independent computers) that are connected via a high speed bus. Each node has it's own memory but through the magic of NUMA, every node can access the other nodes memory as if it's own. Most NUMA systems (if not all) are very high end servers. > 2. Does it have a real effect on the performance of Xen? On a NUMA system, absolutely. If you have a domain running on a particular node, you want to make sure that it's using memory that's in it's node if at all possible. Accessing memory on a local node is considerably faster than access memory on other nodes. Prior to Ryan's NUMA work, Xen would just blindly allocate memory to a domain without taking into account memory locality. > 3. Can't we let the guest OS manage NUMA instead of Xen? what is the > difference? and why is it implemented in Xen? If a guest OS spans multiple nodes, then you would want it to be NUMA aware. However, you always want Xen to, at least, be NUMA aware so that it allocates memory appropriately. Regards, Anthony Liguori > Thanks, > David.