Windows 11 VM issue on single-threaded Proxmox

[Tommaso]

I have an HP DL380 Gen9 server with two Intel Xeon E5‑2660 v4 processors. Inside it I’m running several Windows 11 virtual machines, but these VMs tend to perform slower than expected. When I run the CPU‑Z benchmark, the single‑core score is around 270–280, while it should normally be about 360.

I know that Windows 11 VMs often run slower, and I’ve already applied all the recommended settings: CPU set to host mode, various virtualization options enabled as suggested in multiple forums. However, it seems that the CPU inside the VM never reaches 3.2 GHz and stays stuck at around 2.5 GHz.

 

[leesteken]

However, it seems that the CPU inside the VM never reaches 3.2 GHz and stays stuck at around 2.5 GHz.

This is normal. You will always see the base speed Inside the VM but the cores will turbo as seen from/on the Proxmox host. See some older threads about this.

I have an HP DL380 Gen9 server with two Intel Xeon E5‑2660 v4 processors.

Those CPUs (Broadwell from 2016, EoL in 2022) don't have great single-thread performance compared to more modern CPUs. There are older threads that discuss this in more detail.

I know that Windows 11 VMs often run slower, and I’ve already applied all the recommended settings: CPU set to host mode

EDIT: Disable VBS in Windows or don't use the CPU type host or disable nested KVM or make sure Windows does not detect virtualization capabilities. There are older threads that discuss this in more detail.

 

[Tommaso]

THX, I'll try to find them, if you can help me by linking them I'd be grateful

 

[leesteken]

THX, I'll try to find them, if you can help me by linking them I'd be grateful

The actual clock speed is simply never shown in the VM by design. The CPUs are obviously slow(ish). And I don't use Windows (VMs) so I don't keep up with the details. Maybe some other volunteer here will make an effort to search the forum to give you the threads. I just wanted to give you some pointers.