It's a runtime for running lightweight tasks (`Future`s, async functions) on top of it. What is not async about it? And of course it still needs posix threads. The executor needs to run somewhere, and the only somewhere that an OS offers is a thread.
Sure, but I didn't think anything about async functions implied running tasks. Isn't it just syntactic sugar over futures? You certainly don't need to use the tokio runtime in order to use async functions.
So, it's not clear why you'd abandon the async syntax just because you're compute bound.
