Frosty

A thread-per-core runtime with io_uring.

lib.rs:

Tokio-uring provides a safe io-uring interface for the Tokio runtime. The library requires Linux kernel 5.10 or later.

Getting started

Using tokio-uring requires starting a tokio-uring runtime. This runtime internally manages the main Tokio runtime and a io-uring driver.

use frosty::fs::File;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    frosty::start(async {
        // Open a file
        let file = File::open("hello.txt").await?;

        let buf = vec![0; 4096];
        // Read some data, the buffer is passed by ownership and
        // submitted to the kernel. When the operation completes,
        // we get the buffer back.
        let (res, buf) = file.read_at(buf, 0).await;
        let n = res?;

        // Display the contents
        println!("{:?}", &buf[..n]);

        Ok(())
    })
}

Under the hood, frosty::start starts a current-thread Runtime. For concurrency, spawn multiple threads, each with a tokio-uring runtime. The tokio-uring resource types are optimized for single-threaded usage and most are !Sync.

Submit-based operations

Unlike Tokio proper, io-uring is based on submission based operations. Ownership of resources are passed to the kernel, which then performs the operation. When the operation completes, ownership is passed back to the caller. Because of this difference, the tokio-uring APIs diverge.

For example, in the above example, reading from a File requires passing ownership of the buffer.

Closing resources

With io-uring, closing a resource (e.g. a file) is an asynchronous operation. Because Rust does not support asynchronous drop yet, resource types provide an explicit close() function. If the close() function is not called, the resource will still be closed on drop, but the operation will happen in the background. There is no guarantee as to when the implicit close-on-drop operation happens, so it is recommended to explicitly call close().