tachyonix

An asynchronous, multi-producer, single-consumer (MPSC) bounded channel that operates at tachyonic speeds.

This library is an offshot of Asynchronix, an ongoing effort at a high performance asynchronous computation framework for system simulation.

No laws of physics were broken in the making of this library.

Overview

This is a no-frills async channel which only claim to fame is to be extremely fast (see benchmarks). Its performance mainly results from its focus on the MPSC use-case and from a number of careful optimizations, among which:

• aggressively optimized notification primitives for full-queue and empty-queue events (the latter is courtesy of diatomic-waker, a fast, spinlock-free alternative to atomic-waker),
• no allocation after the senders are created, even for blocked sender/receiver notifications,
• no spinlocks[^spinlocks] and conservative use of Mutexes (only used for blocked senders),
• underlying queue optimized for the single receiver use-case.

[^spinlocks]: some MPMC channels use spinlocks, such as crossbeam-channel and async-channel where they are required to linearize the underlying queue.

Usage

Add this to your Cargo.toml:

[dependencies]
tachyonix = "0.1.1"

Example

use tachyonix;
use futures_executor::{block_on, ThreadPool};

let pool = ThreadPool::new().unwrap();

let (mut s, mut r) = tachyonix::channel(3);

block_on( async move {
    pool.spawn_ok( async move {
        assert_eq!(s.send("Hello").await, Ok(()));
    });
    
    assert_eq!(r.recv().await, Ok("Hello"));
});

Limitations

The original raison d'être of this library was to provide a less idiosyncratic sibling to the channels developed for Asynchronix that could be easily benchmarked against other channel implementations. The experiment turned out better than anticipated so a slightly more fleshed out version was released for public consumption in the hope that others may find it useful. However, its API surface is intentionally kept small and it does not aspire to become much more than it is today.

Note also that, just like the bounded channel of the futures crate but unlike most other channels, sending requires mutable access to a Sender.

Safety

Despite the focus on performance, implementation quality and correctness are a very high priority. The library comes with a decent battery of tests, in particular for all low-level (unsafe) concurrency primitives which are extensively tested with Loom. As amazing as they are, however, Loom and MIRI cannot formally prove the absence of data races so soundness issues are possible. You should therefore exercise caution before using it in mission-critical software until it receives more testing in the wild.

Benchmarks

Benchmarks overview

A custom benchmarking suite was implemented that can test a number of popular MPSC and MPMS channels with several executors (Tokio, async-std, smolscale and Asynchronix).

It contains at the moment 2 benchmarks:

• pinball: an upgraded version of the classical pin-pong benchmark where messages ("balls") perform a random walk between 13 vertices ("pins") of a fully connected graph; it is parametrized by the total number of balls within the graph,
• funnel: the most common MPSC benchmark where messages are sent in a tight loop from 13 senders to a unique receiver; it is parametrized by the channel capacity.

Each benchmark executes 61 instances of an elementary bench rig, which ensures that all executor threads are busy at nearly all times. The pinball benchmark is a relatively good proxy for performance in situations where channel receivers are often starved but senders are never blocked (i.e. the channel capacity is always sufficient). The funnel benchmark is less objective and more difficult to interpret as it is sensitive not only to the absolute speed of enqueue, dequeue and notifications, but can also be affected by their relative speed.

More information about these benchmarks can be found in the bench repo.

Benchmark results

The benchmarks were run on EC2 instances of comparable performance but different micro-architectures (Intel Ice Lake, AMD Zen 3, ARM Graviton 2). The reported performance is the mean number of messages per microsecond after averaging over 10 benchmark runs.

The reported results were obtained with Tokio, which in practice was found significantly faster than either async-std or smolscale. Asynchronix is faster yet, but probably less relevant as a baseline as it is not meant for general-purpose async programming.

EC2 c6i.2xlarge

EC2 c6a.2xlarge

EC2 c6g.2xlarge

License

This software is licensed under the Apache License, Version 2.0 or the MIT license, at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.