Allocating virtual machine resources with virt-manager

I plan to host Windows 10 on Fedora 34 KVM. Both Windows and Fedora will be used as desk-top computers.

When creating a new virtual machine, virt-manager says how much of a resource is “available on the host” (screen shot below) e.g.

  • Memory: Up to 3223 MiB available on the host
  • CPUs: Up to 2 available

I want the host and guest to have about the same amount of performance.
Would splitting the difference work?: Half the capacity for guest and half for host?
Can the resource parameters be changed later?


Maybe? It is more a matter of how much each OS needs. That number you are seeing is how much memory you have available at that moment. How much physical memory do you have in that machine? Running a windows VM with less than 3GB of RAM is not ideal in my experience.

Yes. It can be changed at any time. You can also specify a base and maximum amount in the settings after you create the VM.

CPU usage is shared so you probably want to increase that to 2.

That being said, you seem to pretty tight on systems to support running a Windows VM for any kind of real-world application usage.

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The screen shot is just an example I found online. My PC has

  • Intel i5 2.50GHz CPU
  • 8GB RAM
  • 120GB SSD

If you are using the default zram settings for Fedora you should be able to run a 4GB Windows VM without too much trouble depending on how many cores your i5 has.

Intel 5i has two Cores.

Only 2 cores? if that limited then likely only 1 can be used full time for the VM, although you can try 2.

On fedora the output of “cat /proc/cpuinfo” will give you detailed info about each usable processor core on the cpu.

IIRC the i5 with 2 cores is seen as 4 processors with hyperthreading.