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Re: [Xen-devel] Re: NUMA and SMP

  • To: "Anthony Liguori" <aliguori@xxxxxxxxxxxxxxxxxx>
  • From: "ron minnich" <rminnich@xxxxxxxxx>
  • Date: Tue, 16 Jan 2007 07:51:07 -0700
  • Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, David Pilger <pilger.david@xxxxxxxxx>, Ryan Harper <ryanh@xxxxxxxxxx>
  • Delivery-date: Tue, 16 Jan 2007 06:50:40 -0800
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On 1/15/07, Anthony Liguori <aliguori@xxxxxxxxxxxxxxxxxx> wrote:

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.

no, at this point, most NUMA servers are probably Alienware desktops
for gamers :-) Especially now that Dell is selling them. Opteron
brought NUMA into the mainstream in a big way. And desktop unit sales
trump all supercomputer sales :-) Us poor supercomputer types are,
once again, in the noise where dollar volume is concerned.

And, Linux has known for some time how to exploit the NUMA-ness of
these Opteron systems. There is even an ACPI table entry, SRAT, to
describe the NUMA-ness of a machine.

> 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.

Right, but it's not even close to a  factor of two on a desktop
machine like dual opteron. It's still worth being NUMA aware, however.



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