XCP-ng
    • Categories
    • Recent
    • Tags
    • Popular
    • Users
    • Groups
    • Register
    • Login

    Assign all the CPU cores to a single VM

    Scheduled Pinned Locked Moved Compute
    5 Posts 2 Posters 483 Views 2 Watching
    Loading More Posts
    • Oldest to Newest
    • Newest to Oldest
    • Most Votes
    Reply
    • Reply as topic
    Log in to reply
    This topic has been deleted. Only users with topic management privileges can see it.
    • D Offline
      dredknight
      last edited by

      What is the maximum amount of cores that can be assigned to a VM?

      I know the max limit known is 32 but can I make it more?

      For example - if we buy 2 x CPUs that have 32 cores like AMD EPYC. Is there a way to override the limit so i can assign all the 64 cores to the VM? or even better all the 128 threads to the VM ?

      1 Reply Last reply Reply Quote 0
      • olivierlambertO Offline
        olivierlambert Vates 🪐 Co-Founder CEO
        last edited by olivierlambert

        Hi,

        The main limit is that you can't assign more vCPUs than physical cores on a machine (for obvious security reasons since Spectre/Meltdown)

        The other one is that after 64 cores, there's no official support. However, it might work OK on Linux, for Windows I have no idea.

        D 1 Reply Last reply Reply Quote 1
        • D Offline
          dredknight @olivierlambert
          last edited by

          alright i managed to put my hands on such host.

          out of 128 cores (including hyperthreading) i managed to create a Debian 11 vm with 108 cores. if i go higher i get an error.

          I assume the error is due to some threads being exclusive for the hypervisor. Its possible that is the actual limit too though.

          Not that important though just got curious how far i can push it.

          1 Reply Last reply Reply Quote 0
          • olivierlambertO Offline
            olivierlambert Vates 🪐 Co-Founder CEO
            last edited by

            What kind of error do you have?

            D 1 Reply Last reply Reply Quote 0
            • D Offline
              dredknight @olivierlambert
              last edited by

              @olivierlambert its looks like it was not from XCP but from the cloud provider managing it (Cloudstack). as soon as max restrictions were removed i could assign all 128 threads as vCPUs to a single VM.

              1 Reply Last reply Reply Quote 0
              • D dredknight marked this topic as a question on
              • D dredknight marked this topic as a regular topic on
              • First post
                Last post