There are a few methods to control CPU allocation and the available CPU cycles for KVM machines-using cgroups and the libvirt-provided CPU pinning and affinity functions, we are going to explore in this recipe. CPU affinity is a scheduler property that connects a process to a given set of CPUs on the host OS.
When provisioning virtual machines with libvirt, the default behavior is to provision the guests on any available CPU cores. In some cases, Non-Uniform Memory Access (NUMA) is a good example of when we need to designate a core per KVM instance (as we are going to see in the next recipe), that it's better to assign the virtual machine to a specified CPU core. Since each KVM virtual machine is a kernel process (
qemu-system-x86_64 more specifically in our examples), we can do this using tools such as
taskset or the
virsh command. We can also use the cgroups CPU subsystem to manage CPU cycle allocation, which provides more granular control over CPU resource utilization...