On the performance of KVM-based virtual routers

This paper presents an extensive experimental evaluation of the layer 3 packet forwarding performance of virtual software routers based on the Linux kernel and the KVM virtual machine. The impact of various tuning and configuration options on forwarding performance is evaluated, focussing on the mechanism used for moving data to and from virtual machines, the algorithm used for scheduling the virtual router tasks, the number of used CPU cores, and the router tasks affinities. The presented results show how to properly configure the virtual router components to improve forwarding performance and the benefits of using appropriate CPU schedulers. Furthermore, some advanced architectures based on virtual router aggregation are evaluated. The presented experiments show that architectures based on router aggregation can better exploit the available CPU cores to reach performance not far from the ones obtained by non-virtualised software routers.