While looking for something in the vSphere 8.0 API Reference, I stumbled onto a new VM configuration setting in vSphere 8 called exposeVnumaOnCpuHotadd which looks quite interesting and has the following description:
Capability to expose virtual NUMA when CPU hotadd is enabled. If set to true, ESXi will consider exposing virtual NUMA to the VM when CPU hotadd is enabled. If set to false, ESXi will enforce the VM to have single virtual NUMA node when CPU hotadd is enabled. If unset, the VM continue to follow the behavior in last poweron.
This actually reminded me of question that we got during one of our vSphere 8 Meet the Experts (MTE) sessions at VMware Explore Barcelona and whether there were any new enhancements to vNUMA when CPU hot-add is enabled, which I was not aware of any at the time. The vNUMA and CPU Hot-Add issue is detailed in this blog post by no other than my buddy Frank Denneman and here is a quick summary of the issue:
CPU Hot-Add is not compatible with vNUMA, if hot-add is enabled the virtual NUMA topology is not exposed to the guest OS and this may impact application performance.