rio VS tokio-uring

Also, not to be too bad about a reputation fallacy, but I found the author to be flippant and disrespectful when good-faith unsoundness was pointed out in his crates: https://github.com/spacejam/rio/issues/30

In my previous post on linear types I spent quite a bit of time motivating linear types. For example the ergonomic rio io_uring library could be made sound if it could guarantee destructors are run. Or performing FFI with async C++ could be made more efficient if it could rely directly on destructors rather than having to involve an intermediate runtime for each call.

It's like cargo should have a way to mark a dependency as unsafe. That way, you could have a safe mmap crate as an unsafe dependency. Or something like rio which is deliberately unsound (but is fine if you abide by its rules through the entirety of the program)

for completeness there is also rio, but:

rio still has known soundness issues– its Completion futures block the thread when dropped (!!!), and can allow for use-after-free bugs if leaked. See https://github.com/spacejam/rio/issues/30 for details.

Here are some posts about the design. https://without.boats/blog/io-uring/ https://github.com/spacejam/rio/issues/30 https://github.com/axboe/liburing/issues/109

The author of sled[1], an embedded database in Rust which has a number of promising features, has also written parts of rio[2], an underlying pure Rust io_uring library, which is intended to become the core write path for sled. rio has support for files but also has a demo for TCP (on Linux 5.5 and later) and O_DIRECT.

I tested rio recently as I had a Brilliant but Bad Idea™ involving file access and was pleasantly surprised by the API, as I have been with sled's.

I'm excited for the experimentation in the Rust ecosystem and for such low level crates to handle the complex io_uring tasks (relatively) safely!

[1]: https://github.com/spacejam/sled

[2]: https://github.com/spacejam/rio

While Mio will probably not implement uring in its current design, there's https://github.com/tokio-rs/tokio-uring if you want to use io_uring in Rust.

It's still in development, but the Tokio team seems intent on getting good io_uring support at least!

As the README states, the Rust implementation requires a kernel newer than the one that shipped with Ubuntu 20.04 so I think it'll be a while before we'll see significant development among major libraries.

That's what the pool is for: https://github.com/tokio-rs/tokio-uring/blob/master/src/buf/fixed/pool.rs

Tokio supports io_uring (https://github.com/tokio-rs/tokio-uring), so perhaps when it's mature and battle-tested, it'd be easier to transition to it if Cloudflare aren't using it already.

- Tokio suffers from a similar problem

Eg via tokio-uring.

I strongly recommend you to look into io-uring and use async executors that take advantages of it: - tokio-uring (not recommended as it is still undergoing development) - monoio - glommio

This is my thinking as well. Specifically, I realized that if you don’t use tasks, but rather futures and join, than structured concurrency just works out (at the cost of less efficient poll). In a single-threaded/thread-per-core runtime, tasks could have the same semantics as futures. Somewhat elaborated here: https://github.com/tokio-rs/tokio-uring/issues/81

There's a new API on Linux called io_uring that has performance benefits, but most executors don't use it yet, except executors meant specifically to harness the power of io_uring like tokio-uring and Glommio

Breaking it down a bit further- Rust's async is zero-cost, and there's no way to write faster equivalent code to the language construct in Rust (and presumably other LLVM languages). Tokio introduces abstractions over OS APIs (indirectly) and provides a runtime. The runtime isn't zero cost, but it is likely to be better optimized for "standard" situations than a homebrewed solution, and its primary competition is in the form of other large async runtimes. On the other hand, Tokio's IO routines are (AFAIK) about as well written as one can get with blocking OS APIs, and the only competitors in that space are projects like tokio-uring that use APIs more well suited for asynchronous usage.