Managing CPU and memory resources in KVM

Changing the amount of allocated memory or the number of CPUs can be done either by editing the XML definition for the VM or using the libvirt toolset. In this recipe, we are going to look at examples of changing both the memory and the CPU count for a KVM instance.

Getting ready

For this recipe, we are going to need the following:

• A running KVM instance with 1 GB of memory, 1 CPU allocated, and console access
• The libvirt package
• A guest OS with at least 4 GB of available memory and minimum of 4 CPUs

How to do it...

To inspect and update the memory and CPU resources assigned to a virtual machine follow the process outlined here:

1. Get memory statistics for the running instance:

root@kvm:~# virsh dommemstat kvm1
actual 1048576
swap_in 0
rss 333644

root@kvm:~#

2. Update the available memory for the VM to 2 GB:

root@kvm:~# virsh setmem kvm1 --size 1049000

root@kvm:~#

3. Stop the running instance:

root@kvm:~# virsh destroy kvm1
Domain kvm1 destroyed

root@kvm:~#

4. Set the...