I will check those out tomorrow, but in the meantime: I don't mean to say that a microkernel-based system is necessarily worse on performance. However, I think a highly optimized monolithic system will probably always be somewhat faster than a highly optimized microkernel-based system. And note that the seL4 system is probably less mature, and that I have many criticisms of Linux in being a supposedly highly optimized system. I'm all for microkernels. I'm planning to write one myself. But there are some aspects that microkernel-based systems have to work harder on.