You realize that the guest OS _does_ things right? It's not just overhead. You can't just remove the Linux network stack, you have to replace it with something.

You realize that the guest OS _does_ things right? It's not just overhead. You can't just remove the Linux network stack, you have to replace it with something. (And the Linux network stack is pretty damned good at what it does.) The intrinsic overhead of the OS (i.e. costs of mode switching) is much smaller than you might think. It's true that some programs don't really want an OS getting in their way, but a modern operating system provide decent facilities for getting _out_ of the way (e.g. O_DIRECT for block I/O, pinning tasks to cores) and that's usually what those things use.