An interesting thing happened last week when I upgraded qemu-kvm from version 0.12.5 (Debian Squeeze) to 1.1.2 (Debian Wheezy). After a reboot (shutdown and start) of all my VM’s, they are using less CPU in total! I noticed this from the stats Collectd is collecting for me.
I’m running about 5 Debian Linux VM’s on my low power home server (Intel G620, 8G DDR3, DH67CF). Most of the time the VM’s are idle. As you can see in the graph below the CPU usage dropped. In particular the System CPU usage. The Wait-IO usage is mostly from Collectd, saving all the stats.
Looking a bit further I also noticed that the Local Timer Interrupts and Rescheduling Interrupts are halved.
They’ve done a nice job at Qemu-KVM!