Optimizing network virtualization in xen

In this paper, we propose and evaluate three techniques for optimizing network performance in the Xen virtual-ized environment. Our techniques retain the basic Xen architecture of locating device drivers in a privileged ‘driver ’ domain with access to I/O devices, and providing network access to unprivileged ‘guest ’ domains through virtualized network interfaces. First, we redefine the virtual network interfaces of guest domains to incorporate high-level network offfload features available in most modern network cards. We demonstrate the performance benefits of high-level of-fload functionality in the virtual interface, even when such functionality is not supported in the underlying physical interface. Second, we optimize the implemen-tation of the data transfer path between guest and driver domains. The optimization avoids expensive data remap-ping operations on the transmit path, and replaces page remapping by data copying on the receive path. Finally, we provide support for guest operating systems to effec-tively utilize advanced virtual memory features such as superpages and global page mappings. The overall impact of these optimizations is an im-provement in transmit performance of guest domains by a factor of 4.4. The receive performance of the driver domain is improved by 35 % and reaches within 7 % of native Linux performance. The receive performance in guest domains improves by 18%, but still trails the native Linux performance by 61%. We analyse the performance improvements in detail, and quantify the contribution of each optimization to the overall performance.