CODEWITHSUNDEEP
cpuvmwareesxinuma
CHENJIAN
CHENJIAN

Reputation: 1940

Which factor determines the numbers of Numa nodes?

SITUATION

I am running a Virtual Machine(CentOS7) based on ESXi 6.5.

No matter how I change the number of vCPUs or the number of sockets, there is always ONE NUMA NODE on the VM. By reading the blog NUMA And vNUMA – Back To The Basic, I find that the numbers of NUMA node are no difference between assigning cores or sockets.

I also find some advanced settings on the documentation of ESXi 6.5, but I do NOT know to use the following arguments appropriately.

WANT

What I want is that there are two NUMA nodes, or I can control the numbers of NUMA nodes.

QUESTION

  1. Which factor determines the numbers of Numa nodes?
  2. How to modify the numbers of Numa nodes(Detailed steps, please)?

Upvotes: 0

Views: 2750

Answers (1)

Hadi Brais
Hadi Brais

Reputation: 23719

Which factor determines the numbers of Numa nodes?

From the perspective of the hardware, the physical layout of processors (cores) and main memory modules is what determines the number of NUMA nodes in a system. A NUMA node consists of a collection of cores, some other logic and memory units, and a collection of memory modules that can be accessed by these cores with a much smaller latency compared to the other memory modules.

But from the perspective of the OS, if the OS is not NUMA-aware, by default in most (all?) systems, the BIOS will configure the system so that the physical address space is interleaved across the physical NUMA nodes. So from that perspective, the whole system would like a single NUMA node, even though there are multiple NUMA nodes physically. Even for a NUMA-aware OS, it's usually possible to enable node interleaving from BIOS or the OS. Doing that makes the whole system to be treated as a single NUMA node. In addition if the OS is running on a VM, the VM itself must be configured to enable NUMA.

How to modify the numbers of Numa nodes(Detailed steps, please)?

You'll have to ensure that ESXi 6.5 is configured to expose a virtual NUMA topology to guest operating systems. So you most probably have a configuration issue. See this and this.

Upvotes: 3

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