As a short Follow-Up to
justindpettit wrote a nice Blog post about recent performance improvements in OVS:
What does this mean for a simple KVM/ OpenStack setup? For me it shows that the Linux bridge is still superior when only doing Layer 2 forwarding. OVS might be as fast but takes a whole lot more CPU power which is taken away from your VMs. And it seems to be even worse for old versions of OVS in LTS distris.