libuv VS tokio-uring

I wound up on a different team with pre-existing Python code so temporarily shelved my use of Go for a bit, and we used Sanic (an async Python framework built on top of the excellent uvloop & libuv that also powers Node.js) to build some APIs for live channel management & operations. We hand-wrote our OpenAPI and used it to generate documentation and a CLI, which was an improvement over what was there (or not) before. Other teams used the OpenAPI document to generate SDKs to interact with our service.

In the source code of the Node.js opensource project, lib folder contains JavaScript code, mostly wrappers over C++ and function definitions. On the contrary, src folder contains C++ implementations of the functions, which pulls dependencies from the V8 project, the libuv project, the zlib project, the llhttp project, and many more - which are all placed at the deps folder.

Libuv, the C library that gives Node.js its asynchronous, non-blocking I/O capability is responsible for managing the thread pool. Node.js gives you the capability of using additional threads for computationally expensive and long-lasting operations to avoid blocking the event loop.

Node.js is written in C, C++, and JavaScript. The core components of Node.js - the V8 engine and the libuv library - are written in C++ and C, respectively, since these languages provide low-level access to system resources, making them well-suited for building high-performance and efficient applications. JavaScript is mainly used to write the application logic.

x8 apparently https://github.com/libuv/libuv/pull/3952

Notably upgrades to libuv 1.45 which has io_uring support. Faster file system access! Awhh yeah, it's on.

Remarkable what a mild & unintrusive PR adding io_uring was. https://github.com/libuv/libuv/pull/3952

Well, the single-threaded nature ultimately leads to its biggest downfall. Node.js utilizes a synchronous event loop engineered using Libuv that takes in code from the call stack and executes it.

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.