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This is misdirection on the part of Cantrill. Anyone who has written servers which multiplex thousands to tens of thousands of streaming concurrent users is aware of the overhead of the user/kernel context switch. This single fact, eliminating user/kernel overhead, is why products like mcorelab can multiplex/stream 100k users while pushing millions of messages/s. The unikernel guys are pushing in this direction. The problem comes when something faults, the debugging can be a mess w/o an OS present. And the idea of running multiple unikernel "processes" on a single box is also probably a bad idea. Unikernel is a concept for running a singular, very high throughput process directly on the metal of a single server box.