n00b question - how to add more CPU cores to a VM?

[alpha754293]

I am running Proxmox VE 7.3-3 on a HP Z420 workstation (Intel Xeon E5-2690 (8-core, 16 thread).
When I originally set up my Windows 10 VM, I only gave it 4 CPU cores.

Now I want to increase to that 8 CPU cores.

I stopped the VM, when to hardware, double clicked on "processors", changed it from 1 socket, 4 cores to 1 socket, 8 cores) and then started the VM.

However, the Windows Task Manager, once the VM is booted up, still only shows 4 "Common KVM processor".

I tried to enable CPU Hotplugging and that didn't seem to make a difference neither.

Can someone please educate me on what I am doing wrong here? I would have thought or assumed that increasing the number of CPU cores shouldn't take more steps than this, but I am not sure that I understand why it appears to not have an effect on the VM.

Your help is greatly appreciated.

Thank you.

*edit*
Sidebar: If I create a new Windows 10 VM with the 1 sockets/8 cores, then that shows up correctly in Windows Task Manager. I'm not really sure why I couldn't change it from 1 socket/4 cores to 1 socket/8 cores. Thank you.

*edit #2*
I created a new VM originally with 8 CPU cores. Once I got it all set up and running, then I shut it down, changed it from 8 cores to 4 cores, started it again and Windows Task Manager confirmed the change. Shut it down again, changed it back to 8 CPU cores, started it back up again, and Windows Task Manager is still only showing 4 CPU cores.

Any ideas as to why Proxmox is doing that?

This issue does not appear to be happening with my Windows 7 guests/VMs, so I am not really sure that I understand why this is happening on my Windows 10 guests/VMs.

Again, any help, insights, etc. would be greatly appreciated.

Thank you.

 

[Dunuin]

That usually should work. Make sure to really stop that VM. Changes to the number of cores will only be applied when starting the VM after it stopped (stuff that isn't applied yet will be shown orage in the webUI). A restart from the guest won't be enough.

 

[alpha754293]

That usually should work. Make sure to really stop that VM. Changes to the number of cores will only be applied when starting the VM after it stopped (stuff that isn't applied yet will be shown orage in the webUI). A restart from the guest won't be enough.

Yeah, I did that.

More specifically, in Windows, I would shutdown Windows (which, I am guessing, has the same effect as stopping the VM, in the end), making the changes, and then starting said VM back up again.

I think that the weirder/crazier thing is that the Intel Xeon E5-2690 has 8 physical cores, and with HyperThreading enabled, 16-threads (16 logical cores).

Therefore; if I create a VM initially with only 4 cores, and then increase it to 8, there shouldn't be any problems with that, but that does not appear to be the case.

My Windows 10 VM that I originally created with 4 cores, I have changed the setting now to 8 cores (1 socket) and when I boot it up, and check the Windows Task Manager, it still shows only 4 "Common KVM processors". (see attached screenshot)

Thanks.

 

[dasriqk]

I am running Proxmox VE 7.3-3 on a HP Z420 workstation (Intel Xeon E5-2690 (8-core, 16 thread).
When I originally set up my Windows 10 VM, I only gave it 4 CPU cores.

Now I want to increase to that 8 CPU cores.

I stopped the VM, when to hardware, double clicked on "processors", changed it from 1 socket, 4 cores to 1 socket, 8 cores) and then started the VM.

However, the Windows Task Manager, once the VM is booted up, still only shows 4 "Common KVM processor".

I tried to enable CPU Hotplugging and that didn't seem to make a difference neither.

Can someone please educate me on what I am doing wrong here? I would have thought or assumed that increasing the number of CPU cores shouldn't take more steps than this, but I am not sure that I understand why it appears to not have an effect on the VM.

Your help is greatly appreciated.

Thank you.

*edit*
Sidebar: If I create a new Windows 10 VM with the 1 sockets/8 cores, then that shows up correctly in Windows Task Manager. I'm not really sure why I couldn't change it from 1 socket/4 cores to 1 socket/8 cores. Thank you.

*edit #2*
I created a new VM originally with 8 CPU cores. Once I got it all set up and running, then I shut it down, changed it from 8 cores to 4 cores, started it again and Windows Task Manager confirmed the change. Shut it down again, changed it back to 8 CPU cores, started it back up again, and Windows Task Manager is still only showing 4 CPU cores.

Any ideas as to why Proxmox is doing that?

This issue does not appear to be happening with my Windows 7 guests/VMs, so I am not really sure that I understand why this is happening on my Windows 10 guests/VMs.

Again, any help, insights, etc. would be greatly appreciated.

Thank you.

Hi! After editing the processor options and increasing the cores to 8, you need to enable the advanced options and increase the vCPU to 8. This will reflect the increased cores in windows.

I hope it works for you, regards.

 

[alpha754293]

Hi! After editing the processor options and increasing the cores to 8, you need to enable the advanced options and increase the vCPU to 8. This will reflect the increased cores in windows.

I hope it works for you, regards.

I will have to try that.

That's interesting that increasing the number of CPUs doesn't automatically change/update the number of vCPUs that's assigned to the VM.

 

[vinhquangth]

Hello pro,
I have Dell R550 with 2 CPU (24 cores). I want to create 3 VM on this. Can I set 2 socket for VM1, 1 socket for VM2, 1 socket for VM3?
The best way to set sockets and cores to VMs?

many thanks!

 

[leesteken]

I have Dell R550 with 2 CPU (24 cores). I want to create 3 VM on this. Can I set 2 socket for VM1, 1 socket for VM2, 1 socket for VM3?

Yes, whatever you want. You probably want to enable NUMA since you have more than one physical socket.

The best way to set sockets and cores to VMs?

Read the manual about it first?