"async" and threads are not the only options for concurrent IO. I've never saw anyone discuss using poll(2) style concurrency here which is interesting but als

"async" and threads are not the only options for concurrent IO. I've never saw anyone discuss using poll(2) style concurrency here which is interesting but also kind of sad. With the mio crate for example, it uses the operating systems "select/poll" interface. On Linix this is epoll(7), but other OSes have their own interface. "poll" style concurrency is a lot less complicated for me. The general idea is to register IO handles such as sockets into a data structure and pass it into the kernel. The kernel will emit events whenever a handle is ready to do something. There is the option to go to sleep and block until one of the handles are ready but it's not required. "async" is an abstraction on top of this. The async runtime is handling the event loop and other stuff for you which is very useful but also a little bit complicated. I am not in any way against "async" style concurrency but I think a lot of libraries could avoid pulling in a runtime and still be concurrent.