io_uring support

[dvc94ch]

Mostly for tech porn reasons, it's new and shiny. Apparently it's also faster. Not sure if it fits in async-io, because it works very different from epoll from what I understand by reading withoutboats blog.

[ghost]

I think io_uring would fit in async-io. We can keep using epoll and then only use io_uring inside AsyncRead and AsyncWrite implementations. So epoll would still be the primary mechanism for checking if a FD is readable or writable, while io_uring would be an optimization for fast reads and writes.

[dvc94ch]

Getting async file reads and writes, random numbers and stdin/stdout would be cool... These things require a thread pool using epoll.

[tinywombat765]

Has there any progress or further work on this?

[notgull]

Is there still an interest in this? I feel like we could do this pretty easily now using the io_uring crate.

[sehz]

Would prefer to using: https://docs.rs/rustix/latest/rustix/io_uring/index.html. Benefits:

• Safe system call
• I/O Safety

[notgull]

Would prefer to using: https://docs.rs/rustix/latest/rustix/io_uring/index.html. Benefits:

* Safe system call

* I/O Safety

I feel like the io_uring crate provides a more comprehensive API that makes it easier to not dip your hands in unions. Since io_uring deals in raw pointers anyhow, I doubt that I/O safety will matter much as well.

[notgull]

I tried integrating io_uring into async-io, but when it comes to the syscalls that async-io uses (for polling for reads and writes), epoll ends up being faster.

However it might be more useful for higher level crates, like async-net and async-fs (rel: smol-rs/async-fs#24). In this case we can just call the operations themselves rather than needing to go through polling.

Of course, setting all of this up would be a lot of work I don't have time for. So unless someone sponsors me to do this, I'll wait for someone else to put in the elbow grease.

[gaykitty]

I did something similar for my grad project and came to the same conclusion. Using io_uring while trying to emulate the APIs of something as low level as async-io has no benefit.