alt Hacker NewsIn order to make this work, libc would have to:
- Start some sort of async executor thread to service the io_uring requests/responses
- Make it so every call to "normal" syscalls causes the calling thread to sleep until the result is available (that's 1 syscall)
- When the executor thread gets a result, have it wake up the original thread (that's another syscall)
So you're basically turning 1 syscall into 2 in order to emulate the legacy syscalls.
io_uring only makes sense if you're already async. Emulating sync on top of async is nearly always a terrible idea.
You don't need to start spawning new threads to use io_uring as a backend for synchronous IO APIs. You just need to set up the rings once, then when the program does an fwrite or whatever, that gets implemented as sending a submission queue entry followed by a single io_uring_enter syscall that informs the kernel there's something in the submission queue, and using the arguments indicating that the calling process wants to block until there's something in the completion queue.