Re: VirtualBox, Proxmox, QEMU and CPU Vs vCPUs

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Author: Ryan Petris via PLUG-discuss
Date:  
To: PLUG-discuss
CC: Ryan Petris
Subject: Re: VirtualBox, Proxmox, QEMU and CPU Vs vCPUs
I think the option you're looking for is called "affinity":

https://pve.proxmox.com/pve-docs/pve-admin-guide.html#qm_cpu_resource_limits

> With the *affinity* option, you can specify the physical CPU cores that are used to run the VM’s vCPUs. Peripheral VM processes, such as those for I/O, are not affected by this setting. Note that the *CPU affinity is not a security feature*.


That said, I'm wondering why you're wanting to do this, specifically what you think you're going to gain over just allowing the kernel to schedule things the way it normally does.

For instance, it's not going to lock that core specifically for use to that VM; other processes can still use that core. You'd literally have to set the affinity of every single process on your system to specific cores which would be an extreme pain. You still wouldn't have much control over which cores receive interrupts and whatnot so even then you still wouldn't have complete control.

Just let the scheduler do its thing, otherwise you're likely going to end up with weird issues that no one can help with or explain.

On Tue, Jul 2, 2024, at 1:51 PM, Snyder, Alexander J via PLUG-discuss wrote:
> I have a VM running with QEMU on Debian, v is a TrueNAS. Although they give you a GUI to select options, it is my understanding that it's just pure QEMU running on the backend.
>
> In this VM, I have vCPUs configured.
>
> --
> Thanks,
> Alexander
>
> Sent from my Google Pixel 7 Pro
>
> On Tue, Jul 2, 2024, 13:43 Keith Smith via PLUG-discuss <> wrote:
>> Hi,
>>
>> I've started to skim the Ubuntu docs on QEMU. It talks about vCPUs.
>> I've run both VirtualBox and Proxmox. Seems both VirtualBox and Proxmox
>> only allow for CPU allocation at the CPU level.
>>
>> I'd really like to be able allocate vCPUs.
>>
>> Do I understand this correctly?
>>
>> Thanks!!
>> Keith
>>
>>
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