L4Linux performance vs hardware virtualization

Hi Folks, L4Linux.org mentioned: "Compared to monolithic Linux, there is a small performance tradeoff because of the µ-kernel architecture. However, the initial L4Linux has been somewhat optimized, and on L4/x86 it has a very acceptable slowdown of less than 4 % for any relevant load. " Any place can find more detail about the test? And I'm very curious the L4Linux performance vs "using hardware virtualization on top of L4", have you made any comparison before? -- Thank you! Bob