Hyperthreading Mitigation - Threads or Cores?

[webza]

I followed this article for a HP DL380p Gen8:

VMware Knowledge Base

It states to enable VMKernel.Boot.hyperthreadingMitigation to "true" and that in doing do, vSphere/ESXi will only display 1 logical processer per core.

This particular processor has 12 cores, making 24 threads with HT enabled.

Just to help me understand, can I still count on having all 24 CPU threads available in planning or only 12 with the option set to "true"?

Thanks in advance.

[daphnissov]

Regardless of that setting or not, you should never do capacity planning where you treat a hyper thread as a physical core. All sizings and calculations should be based on physical cores only.

[webza]

Thanks, but I've always used the "Logical processors" count in planning, and it's served me well with other servers. The logical processors available takes hyperthreading into consideration, as I'm sure you're aware.

My question is specific to the amount of logical processors available. Is it 12 or 24, based on my question and the "true" setting? It shows 12, but changing to "false" shows 24.

The setting is creating the confusion for me on the actual logical count available, which is the specific answer I'm looking to address.

[daphnissov]

Per the KB you referenced, setting the value to "true" should show you 12 logical processors as it effectively disables hyperthreading.