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

If you can point to a practical example of a program doing it this way and seeing a performance benefit, I would be curious to see it. I did some googling and didn't really even find any articles mentioning this as possibility.

kqueue is widely considered to be readiness based, just like epoll, not completion based.

What you wrote sounds like an interesting hack, but I'm not sure it counts for much if it is impractical to use.