How to create a NUMA topology in single system environment

Question

I want to know if it possible to create a NUMA topology(2 NUMA nodes is also fine) in a single system environment (I'm using virtualbox ubuntu 18.04).

When I run $numactl -H, I see the following

available: 1 nodes (0)
node 0 cpus: 0 1 2 3
node 0 size: 1992 MB
node 0 free: 477 MB
node distances:
node   0 
  0:  10 

I was wondering if it is really possible to create two NUMA nodes (just for simulating distributed environment) in a system having 4 cores. Or do I need to have more than four cores for doing so?

Answer 1

In virtualization the number of total cores you can assign to all VMs is near infinite. But the number of cores you can assign to each individual VM cannot exceed the total number of logical cores on the host.

So, to put it concisely: Yes, you can create as many NUMA cores as your host can handle.

Hypervisors use a scheduler to queue each VM's CPU instructions to the host's CPU. The more VMs you set up just means there's a longer queue heading through the hypervisor's scheduler into the host's CPU, which means things slow down, but they don't fail. CPUs and modern system architectures are designed to handle queues, and this is actually one reason why virtualization is such a useful and powerful thing: It keeps the queue on the host more full more of the time, more efficiently using the hosts's resources.