The model is very similar to how epoll works. The executor does not poll futures in a loop. Between polls, the executor waits for a readiness notification. If

The model is very similar to how epoll works. The executor does not poll futures in a loop. Between polls, the executor waits for a readiness notification. If `Future::poll` returns Pending, once it becomes ready to do more work, it notifies the executor, the executor then schedules the future to be polled again.