I have a basic question I am hoping to get answered. Its a n00bish question but I can't find a direct answer... When assigning CPU to a VM does it immediately take it away from the Non VM side for example....   I have plex and its heavy on my cpu. I have an 9 core 16thread Ryzan 1700x. If I were to assign 4 cores to a VM. does that immediately take that away from whats available for plex leaving Plex with just 4 cores when the VM is running or is it that the VM can use UP to 4 cores. I ask because I see that the ram immediately gets used.

thanks.

When testing, I have run 2 VM's with the same cores assigned and also run a Docker container with the same cores assigned as a VM had assigned. So, it doesn't seem like the CPU's are locked to the VM.

 

You can test dynamically assign CPU's so that no cores are fixed to a VM. Basically, edit the XML and turn the section like this;

<vcpu placement='static'>2</vcpu>
  <cputune>
    <vcpupin vcpu='0' cpuset='2'/>
    <vcpupin vcpu='1' cpuset='3'/>
  </cputune>

 

into something like this.

 

<vcpu placement='static'>2</vcpu>

 

This makes for a VM with 2 cores assigned but it spreads the load out over all the hardware CPU cores available instead of the fixed cores you assign.