MUmuizelaar·Dec 13, 2024
An older non concurrent cycle collector is here: https://github.com/fitzgen/bacon-rajan-cc
In Garbage collected smart pointers in Rust via concurrent cycle collectionfitzgen
bacon-rajan-cc
Rust2017–2024
fitzgen / bacon-rajan-cc
bacon-rajan-cc
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| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| 2017 | 2017-01-01 00:00:00 UTC | 2018-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2018 | 2018-01-01 00:00:00 UTC | 2019-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2019 | 2019-01-01 00:00:00 UTC | 2020-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2020 | 2020-01-01 00:00:00 UTC | 2021-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2021 | 2021-01-01 00:00:00 UTC | 2022-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2022 | 2022-01-01 00:00:00 UTC | 2023-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2023 | 2023-01-01 00:00:00 UTC | 2024-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2024 | 2024-01-01 00:00:00 UTC | 2025-01-01 00:00:00 UTC | 2 | 0 | 2 |
What Hacker News says
4 sources> One way to look at reference counting is as a sort of eager, optimized form of garbage collection that works in the case that you have strictly acyclic data (or can tolerate leaking cycles).
It's interesting to note that python operates with the refcounting + tracing hybrid described (and I know of production deployments where they force the tracing collector to e.g. only run once every N requests because python's never got that fast either).
perl, meanwhile, is pure refcounting but has weak references so you can make data acyclic from a refcounting POV at the cost of having to pay attention to which parts of the cyclic structure you keep references to (and for cyclic object graphs there are some tricks you can pull to move the weak link around so you don't have to pay such attention, but that would be a whole comment on its own).
koka
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does refcounting in theory but tries to lift as much of it to compile time as possible in practice, plus if you do e.g. 'y = x + 1' and x has only a single reference to it and is guaranteed to not be used afterwards, it re-uses the storage for y and so can do in-place mutation.
nim, meanwhile, offers something called ORC, which is automatic reference counting plus an implementation of Bacon+Rajan's Recycler algorithm which is designed to collect -only- cycles in an otherwise refcounting based system and as such is really rather fast at doing so.
Coming back to Rust: There's a stop the world Recycler implementation (rather than concurrent as intended both by the original paper and the author's future plans if the itch returns) here - https://github.com/fitzgen/bacon-rajan-cc - released as the bacon-rajan-ccc crate from this fork - https://github.com/mbartlett21/bacon-rajan-cc - and the README for those contains an Alternative section linking to other experiments in the same area.
(I've yet to play with any of the rust versions but love Recycler sufficiently as a concept that I suspect if/when I encounter a situation where it might help I'll be going back and doing so)
If you're having trouble finding the Recycler papers, I stashed a copy of each under https://trout.me.uk/gc/ (and if you're a similar sort of strange to me, you might also enjoy the ones stashed under https://trout.me.uk/lisp/ ;)
Thanks for the recommendation, with some brief poking around it does seem promising! It looks like the algorithm is this? https://github.com/fitzgen/bacon-rajan-cc
The link to the paper seems dead unfortunately from this blog post https://nim-lang.org/blog/2020/12/08/introducing-orc.html
I could see how it works as a drop in replacement for Rc
In Steel – An embeddable and extensible Scheme dialectThe paper describes the design and implementation of a Garbage Collector in Rust:
"We show that our Immix implementation has almost identical performance on micro benchmarks, compared to its implementation in C, and outperforms the popular BDW collector on the gcbench micro benchmark. We find that Rust’s safety features do not create significant barriers to implementing a high performance collector.
Though memory managers are usually considered low-level, our high performance implementation relies on very little unsafe code, with the vast majority of the implementation benefiting from Rust’s safety."
Partial source for the authors' implementation is contained in the paper's appendices rather than in a repository, other implementations mentioned in the paper:
A reference counted type with cycle collection for Rust: https://github.com/fitzg
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en/bacon-rajan-cc
A simple tracing (mark and sweep) garbage collector for Rust: https://github.com/Manishearth/rust-gc