6.13 Modifying the Number of Virtual CPUs Allocated to a Guest

You can dynamically modify the number of virtual CPUs allocated to a guest with the vm_maker --set --vcpu command.

All actions to modify the number of vCPUs allocated to a guest are performed in the KVM host.

It is possible to over-commit vCPUs such that the total number of vCPUs assigned to all guests exceeds the number of physical CPUs on the system. However, over-committing CPUs should be done only when competing workloads for oversubscribed resources are well understood and concurrent demand does not exceed physical capacity.

1. Determine the number of physical CPUs.

   # /opt/exadata_ovm/vm_maker --list --vcpu --domain db01_guest01.example.com

2. Modify the number of allocated vCPUs.
   The number of vCPUs must be a multiple of 2.

   For example, if you want to change the number of vCPUs allocated to 4 for the db01_guest01.example.com guest, you would use the following command:

   # /opt/exadata_ovm/vm_maker --set --vcpu 4 --domain db01_guest01.example.com