VM only uses 50% of CPU

[DANILO MONTAGNA]

Hi,

I have a proxmox 7.3.4 host with 4 sockets with 16 cores each (AMD Opteron 6282 SE), total 64 cores

I created a Windows VM on proxmox and allocate 64 cores to this VM to use all cpus available (only 1 vm per host)

when I run a cpu stress test on VM, only 50% of the all cores is at 100%, meaning only 50% all cpu is being used..

Why I cant use 64 cores at 100% ? proxmox is limiting the windows VM to only use 50% of all cpu available on Task Manager...

I have no cpu limit setting on vm hardware, CPU type is 'host' and NUMA is enabled... I tried also with CPU type "kvm64", with NUMA disabled etc.. and VM only use 50% of all CPU whatever set I change...

any help?

 

[apoc]

I created a Windows VM on proxmox and allocate 64 cores to this VM to use all cpus available (only 1 vm per host)

Dont do that. Virtualization is not bare metal!
Scheduling overhead is to be considered. Additionally keep the host in mind which always needs cycles too.
My suggestion: only assign 56 and see if it gets better