Bridging the gap between software and hardware techniques for I/O virtualization

Abstract

The paravirtualized I/O driver domain model, used in Xen, provides severl advantages including device driver isolation in a safe execution environment, support for guest VM transparent services including live migration, and hardware independence for guests. However, these advantages currently come at the cost of high CPU overhead which can lead to low throughput for high bandwidth links such as 10 gigabit Ethernet. Direct I/O has been proposed as the solution to this performance problem but at the cost of removing the benefits of the driver domain model. In this paper we show how to significantly narrow the performance gap by improving the performance of the driver domain model. In particular, we reduce execution costs for conventional NICs by 56% on the receive path, and we achieve close to direct I/O performance for network devices supporting multiple hardware receive queues. These results make the Xen driver domain model an attractive solution for I/O virtualization for a wider range of scenarios.