We are using Ubuntu server in AWS running linux-image-3.8.0-19-generic when an instance has moderate network load (around 30mbit) we start to see :

[31333817.179933] xennet: skb rides the rocket: 19 slots [31334587.454365] xennet: skb rides the rocket: 21 slots [31334772.157791] xennet: skb rides the rocket: 20 slots [31335254.431489] xennet: skb rides the rocket: 19 slots [31336785.643018] xennet: skb rides the rocket: 19 slots [31337438.686311] xennet: skb rides the rocket: 21 slots

This ...