←back to thread

Io_uring, kTLS and Rust for zero syscall HTTPS server

(blog.habets.se)
495 points guntars | 1 comments | 22 Aug 25 03:51 UTC | HN request time: 0s | source
Show context
Seattle3503 ◴[22 Aug 25 05:44 UTC] No.44981374[source]▶
> For example when submitting a write operation, the memory location of those bytes must not be deallocated or overwritten.

> The io-uring crate doesn’t help much with this. The API doesn’t allow the borrow checker to protect you at compile time, and I don’t see it doing any runtime checks either.

I've seen comments like this before[1], and I get the impression that building a a safe async Rust library around io_uring is actually quite difficult. Which is sort of a bummer.

IIRC Alice from the tokio team also suggested there hasn't been much interest in pushing through these difficulties more recently, as the current performance is "good enough".

[1] https://boats.gitlab.io/blog/post/io-uring/

replies(7): >>44981390 #>>44981469 #>>44981966 #>>44982846 #>>44983850 #>>44983930 #>>44989979 #
JoshTriplett ◴[22 Aug 25 05:48 UTC] No.44981390[source]▶
I think the right way to build a safe interface around io_uring would be to use ring-owned buffers, ask the ring for a buffer when you want one, and give the buffer back to the ring when initiating a write.
replies(2): >>44981470 #>>44982162 #
Tuna-Fish ◴[22 Aug 25 08:31 UTC] No.44982162[source]▶
This works perfectly well, and allows using the type system to handle safety. But it also really limits how you handle memory, and makes it impossible to do things like filling out parts of existing objects, so a lot of people are reluctant to take the plunge.
replies(1): >>44984196 #
1. johncolanduoni ◴[22 Aug 25 13:07 UTC] No.44984196[source]▶
That’s annoying for people writing bespoke low-level networking code, but for a high-level HTTP library it’s a rounding error in the overall complexity on display. I think the bigger barrier for Tokio is that the interplay between having an epoll instance and a io_uring instance on the same pool is problematic and can erase performance gains. If done greenfield you could implement the “normal” APIs with ‘IORING_OP_POLL_ADD’, but not all of the exposed ‘mio’ surface area can work this way - only the oneshot API.