White Paper - Getting 10 Gb/s from Xen: Safe and Fast Device Access from Unprivileged Domains

A whitepaper from Solarflare Communications, Inc. was sent to me by Simon Crosby for distribution to the Xen Community. The full paper is available here; getting_10gbps_from_xen
Abstract
The networking performance available to Virtual Machines (VMs) can be low due to the inefficiencies of transferring network packets between the host domain and guests. This can limit the application-level performance of VMs on a 10 Gb/s network. To improve network performance, we have created a “virtualization aware” smart network adapter and modified Xen to allow direct, but safe, access to such adapters from guest operating systems. Networking overheads are reduced considerably, and the host domain is removed as a bottleneck, resulting in significantly improved performance.
We describe our modications to the Xen networking architecture that
allow guest kernels direct – but secure – access to the networking hardware,
whilst preserving support for migration. We also describe briefly
how the same technology is used to grant direct network access to userlevel
applications and thus provide even greater efficiency in terms of
bandwidth, latency and CPU utilisation.