How to enable HT Hyper Threading inside guest OS?

[WillL]

Hi,

Our software license is based on core, eg 8 core license allows 8 core 16 thread CPUs.

Our physical hosts have HT enabled but I can't figure out how to setup Windows 2012 VM to see HT? I want to allocate 16 vCPU, and in Windows VM shows up as 8 core 16 logical processor. So far it's always 16 core 16 logical processor. I've tried all three HT Sharing options.

C:\> WMIC CPU Get DeviceID,NumberOfCores,NumberOfLogicalProcessors,SocketDesignation

DeviceID  NumberOfCores  NumberOfLogicalProcessors  SocketDesignation

CPU0      8              8                          CPU socket #0

CPU1      8              8                          CPU socket #1

Thanks in advance!

Will

[PaulLab3]

IMO you cant do this.

ESXi shows CPUs to VM which are pCPU for guestOS.

[RAJ_RAJ]

Hi ,

HT is featured comes with Physical CPU  and it is enabled on the H/W bios level . I haven't see an option to enable HT from GOS  because it should be on the H/W platform level (CPU / BIOS)

VM you have option enable / disable HT

Hyperthreaded Core Sharing: Any (default setting)

Using this setting the VM shares HT-enabled cores with other VMs.

Hyperthreaded Core Sharing: None

This setting is equal to “Hyperthreading disabled”.
The VM’s vCPU has exclusive access to a core whenever it is scheduled. The vCPU will not share the core with another vCPU.

Hyperthreaded Core Sharing: Internal

This setting applies only for VM’s with two or more vCPUs.
The result is, that two vCPUs from the same virtual machine can share one physical core, but it will never share the core with the vCPU from another VM.

[johnw230873]

someone has to ask it, Why??

Yep can say I've heard of it either normally if it is a license issue then you change the socket / core ratio in the config of the VM.

[WillL]

won't help in this case of core based license, different story if socket based license.

[WillL]

Obviously HT Sharing option None would give best possible performance, but waste same amount of logical cores.Hard to tell between Any and Internal which would give better performance?

[WillL]

I think you are right, it's not possible. ESXi would need to guarantee to schedule 8 core 16 threads every time to the 16 vCPU Guest OS, for that reason it won't let Guest OS see HT.

[aranguiz82]

Please check this KB article, in ESX 5.X the license version is an important information.

I hope that help you.

https://kb.vmware.com/selfservice/search.do?cmd=displayKC&docType=kc&docTypeID=DT_KB_1_1&externalId=...‌

Regards.