When starting with some compute benchmarks, the multi-threaded-happy C-Ray test profile did the best when using KVM virtualization. The KVM guest instance was handling this multi-threaded ray-tracing test at 91% the speed of the host while VirtualBox on the Sandy Bridge CPU was running at 85% the speed and the Xen DomU guest at 68% the speed.
POV-Ray 3.6.1 is a single-threaded ray-tracing test and KVM continued to perform the best among the three tested Linux virtualization methods. KVM was nearly as fast as the bare metal configuration when using the Linux 3.0 kernel on the Sandy Bridge notebook. VirtualBox came in slightly behind KVM and in a distant last place was Xen.
Smallpt is multi-threaded and here the trend continued: KVM was the fastest means of Linux virtualization, then VirtualBox, and Xen lagging behind.