The async runtime is almost always built on top of non-blocking I/O APIs, and the extra layer of abstraction adds overhead. You're rarely calling epoll in your

The async runtime is almost always built on top of non-blocking I/O APIs, and the extra layer of abstraction adds overhead. You're rarely calling epoll in your async code, but rather your runtime is handling all of that for you. That is, unless you're using io_uring, POSIX AIO, etc., in which case your async code might not have the extra layer of abstraction on top of the system APIs.