2006 USENIX Annual Technical Conference Abstract
Pp. 1528 of the Proceedings
Awarded Best Paper!
Optimizing Network Virtualization in Xen
Aravind Menon, EPFL; Alan L. Cox, Rice University; Willy Zwaenepoel, EPFL
In this paper, we propose and evaluate three techniques
for optimizing network performance in the Xen virtualized
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
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 offload functionality in
the virtual interface, even when such functionality is not supported
in the underlying physical interface. Second, we optimize
the implementation of the data transfer path
between guest and driver domains. The optimization
avoids expensive data remapping 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 effectively utilize advanced virtual
memory features such as superpages and global page
The overall impact of these optimizations is an
improvement 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.
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