All good questions, but none of these seem possible in today's POSIX APIs either. (Most, I feel, probably are best just implemented as "options" to the syscall

All good questions, but none of these seem possible in today's POSIX APIs either. (Most, I feel, probably are best just implemented as "options" to the syscall in either the sync or async view of the world.) The point was more to have async operations be possible, whereas today, they're not. > It sounded at first like you were describing vectored i/o but I assume you want something more abstract than that, kinda like a more generalized blk-multiqueue? Asynchronous I/O, not so much vectored (though vectored is similar, but I want to stay away from that term as most of the APIs (e.g., readv writev) I've seen for that aren't actually asynchronous and are just more efficient user-to-kernel bindings).