Toying with KVM


a few weeks ago I installed ubuntu 13.04 on a separate partition, and decided to try KVM.

(a friend from red hat told me that KVM is better than Xen, …)

Now KVM support PCI passthrough too, and I was wondering if it’s working, and if it’s easier to setup than Xen.

KVM is really easy to setup, and virtual machine manager makes it easy to configure the VM.

I was even able to run my Xen Win7 installation with KVM, so no need to reinstall anything !

what I did is only :

blacklist radeon

install KVM (sudo apt-get install kvm, virt-manager)

with lvm, I create a new partition and copied my Xen guest disk with dd.

on the other hand, it’s not usable for me, and I will install Xen soon.

KVM has some performance issue :

  1. if you pass more than 1 CPU to the guest, you have to set the “topology” (otherwise Win7 limit to 2 CPU on 2 sockets).
  2. There are some issue with irq in the guest. when I run teamspeak in the VM, it uses a usb sound card (and I use PCI passthrough on the USB controller), I have 1 CPU at 50% in interrupt. with Xen I’m below 5% CPU utilization when running teamspeak.
  3. when playing “Chivalry” (based on UT3 engine), I have 60FPS on Xen, and only 15-20 with KVM.

Chivalry is one of my favorite game, so I will stay on Xen.


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