> The entire point of the article is that it is not just for IO

I went through the list of operations supported by `io_uring_enter`. Almost all of them are for IO, the remainder (NOP, timeout, madvise) are useful for supporting IO, though madvise might have some non-IO uses as well. While io_uring could form the basis of a generic async syscall interface in the future, in its current state it most certainly is not.

The article mostly talks about io_uring enabling completion based IO instead of readiness based IO.

AFAIK kqueue also supports completion based IO using aio_read/aio_write together with sigevent.