One of the issues is that OS schedulers are complex, and actually much more expensive than context switch itself. You can mitigate this with user-mode schedulin

One of the issues is that OS schedulers are complex, and actually much more expensive than context switch itself. You can mitigate this with user-mode scheduling of kernel threads: https://www.youtube.com/watch?v=KXuZi9aeGTw https://www.youtube.com/watch?v=KXuZi9aeGTw