Much like physical CPUs in host machines, virtual CPUs (vCPUs) are critical to virtual machine (VM) performance. Optimizing vCPUs can have a significant impact on the resource efficiency of your VMs.

The general steps to optimize your vCPU include the following:

• Adjust how many host CPUs are assigned to the VM. You can do this by using the command line or the web console.
• Ensure that the vCPU model is aligned with the CPU model of the host. For example, to set the testguest1 VM to use the CPU model of the host:

  # virt-xml testguest1 --edit --cpu host-model

• Manage kernel same-page merging (KSM).
• If your host machine uses Non-Uniform Memory Access (NUMA), you can also configure NUMA for its VMs. This maps the host’s CPU and memory processes onto the CPU and memory processes of the VM as closely as possible. In effect, NUMA tuning provides the vCPU with a more streamlined access to the system memory allocated to the VM, which can improve the vCPU processing effectiveness.