AMD Opteron 6282 SE and NUMA

[rschmitz]

Hello,

Here's my question, and I will get into discussion after:  How many NUMA nodes are on the Opteron 6282 SE, and how many Cores per node?

We're trying to fine tune some small performance problems with some of our Guest VM's on ESX 5.1 w vCenter in regards to vCPU's and NUMA nodes.  According to the vSphere 5.1 Performance Best Practices Guide (Pages 21 and 42), it gives examples of what's recommended on Opteron-based systems and how many vCPU's to allocate out.  My guess is the Opteron 6282 SE has two NUMA nodes with 8 cores on each, but I want to make sure it's not four NUMA nodes with 4 cores on each.  This will help me adjust the vCPU's in the VM guests to allocate the proper number of cores.

Here's a snippet from the Best Practices Guide:

Size your virtual machines so they align with physical NUMA boundaries. For example, if you have a host

system with six cores per NUMA node, size your virtual machines with a multiple of six vCPUs (i.e., 6

vCPUs, 12 vCPUs, 18 vCPUs, 24 vCPUs, and so on).

   When creating a virtual machine you have the option to specify the number of virtual sockets and the

number of cores per virtual socket. In general, we recommend leaving this at the default value of 1 core

per socket (with the number of virtual sockets therefore equal to the number of vCPUs).

If the number of cores per virtual socket on a vNUMA-enabled virtual machine is set to any value other

than the default of 1, and that value doesn't align with the underlying physical host topology,

performance might be slightly reduced. Therefore if a virtual machine is to be configured with a

non-default number of cores per virtual socket, for best performance that number should be an integer

multiple or integer divisor of the physical NUMA node size.

In some cases, setting the number of cores per virtual socket to the number of cores per physical NUMA

node shows a performance improvement.

NOTE Some multi-core processors have NUMA node sizes that are different than the number of cores

per socket. For example, some 12-core processors have two six-core NUMA nodes per processor.

Currently, we have NUMA enabled in the BIOS, but are configuring our VM Guests as multi-core sockets, which is what we're looking to change.  We have 3 VM Host machines with a 6282 SE, but we also have a 4th Host that has one of the Opteron 6300 Processors in it, also a 16-core.

AMD Opteron Specs:  http://products.amd.com/en-us/OpteronCPUDetail.aspx?id=756&f1=AMD+Opteron%e2%84%a2+6200+Series+Proce...

Very Helpful VMware Blog:  Does corespersocket Affect Performance? | VMware vSphere Blog - VMware Blogs

Any help would be appreciated.

Rory Schmitz