Real-Time Ring Buffer

A wait-free single-producer single-consumer (SPSC) ring buffer for Rust.

• Crate: https://crates.io/crates/rtrb
• Documentation: https://docs.rs/rtrb

This crate can be used without the standard library (#![no_std]) by disabling the std feature (which is enabled by default), but the alloc crate is needed nevertheless.

Usage

Add this to your Cargo.toml:

[dependencies]
rtrb = "0.3"

Breaking Changes

For a list of breaking changes and for instructions how to upgrade between released versions, have a look at the changelog.

Performance

Measuring the performance of a data structure for inter-thread communication can be quite brittle and the results depend on many factors. A few performance comparisons between competing crates are shown in issue #39, but like all benchmarks, they are deeply flawed and to be taken with a grain of salt. You should make your own measurements that are relevant to your usage patterns. Feel free to share your own results by commenting on that issue.

Development

Creating the HTML docs (which will be available in target/doc/rtrb/index.html):

cargo doc

Running the tests:

cargo test

Testing the benchmarks (without actually benchmarking):

cargo test --benches

Running the benchmarks (using the criterion crate; results will be available in target/criterion/report/index.html):

cargo bench

Creating flame graphs for the benchmarks; first a few preparations:

cargo install flamegraph
echo -1 | sudo tee /proc/sys/kernel/perf_event_paranoid
export CARGO_PROFILE_BENCH_DEBUG=true

Then, creating the flame graph (which will be saved to flamegraph.svg), providing a benchmark (e.g. two_threads), a desired runtime and optionally a benchmark function (e.g. large):

cargo flamegraph --bench two_threads -- --bench --profile-time 10 large

To measure code coverage, nightly Rust is required, as well as a few additional dependencies:

rustup toolchain install nightly
rustup component add llvm-tools-preview
cargo install grcov

Test coverage data can be obtained and analyzed with these commands:

cargo clean
RUSTFLAGS="-Z instrument-coverage" RUSTDOCFLAGS="-Z instrument-coverage -Z unstable-options --persist-doctests target/debug/doctestbins" LLVM_PROFILE_FILE="coverage/%p-%m.profraw" cargo +nightly test
grcov coverage --source-dir . --binary-path target/debug --output-type html --output-path coverage

The last command creates an HTML report in coverage/index.html.

Testing with Miri also needs nightly Rust:

cargo +nightly miri test

This Miri flag should also be tried:

MIRIFLAGS="-Zmiri-preemption-rate=0" cargo +nightly miri test

Running the tests with ThreadSanitizer requires nightly Rust as well:

RUSTFLAGS="-Z sanitizer=thread" cargo +nightly test --tests -Z build-std --target x86_64-unknown-linux-gnu

You might have to adapt the --target option to your system (see e.g. rustup show).

Minimum Supported rustc Version

This crate's minimum supported rustc version (MSRV) is 1.38.0. The MSRV is not expected to be updated frequently, but if it is, there will be (at least) a minor version bump.

Origin Story

The initial code has been ripped off of https://github.com/crossbeam-rs/crossbeam/pull/338, with permission of the PR author.

It has been isolated from the rest of crossbeam with git-filter-repo:

git-filter-repo --subdirectory-filter crossbeam-queue --path src/spsc.rs --path tests/spsc.rs --refs refs/heads/spsc

Alternatives

If you don't like this crate, no problem, there are several alternatives for you to choose from. There are many varieties of ring buffers available, here we limit the selection to wait-free SPSC implementations:

• ach-spsc (using const generics)
• heapless (for embedded systems, see heapless::spsc)
• jack (FFI bindings for JACK, see jack::Ringbuffer)
• magnetic (see magnetic::spsc module)
• npnc (see npnc::bounded::spsc module)
• ringbuf (supports const generics and heap allocation)
• ringbuffer-spsc (using const generics)
• shmem-ipc (see shmem_ipc::sharedring and shmem_ipc::ringbuf modules)

There are also implementations in other languages:

• boost::lockfree::spsc_queue (C++)
• folly::ProducerConsumerQueue (C++)
• JACK ring buffer (C)
• PortAudio ring buffer (C)
• readerwriterqueue (C++)
• ringbuf.js (JavaScript, using SharedArrayBuffer)
• SPSCQueue (C++)

If you know more alternatives for this list, please open an issue.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Note that this crate contains a copy of the file cache_padded.rs from https://github.com/crossbeam-rs/crossbeam.

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.