Relax memory ordering of shared refcount atomics
Nobody has claimed this yet.
- Dominant language
- Python
- Stars
- 77.2k
- Forks
- 35.9k
- PR merge metrics
- PR metrics pending
Description
Feature or enhancement
Proposal:
In the free-threaded build, all operations on ob_ref_shared use sequentially consistent atomics. Full ordering is stronger than the biased reference counting protocol requires, and on ARM64 the ordered instructions are measurably slower under contention. Instead, we could (and I think should) match what C++ shared_ptr implementations do which is relaxed increfs and acquire/release decrefs ^1 ^2 ^3 ^4.
Has this already been discussed elsewhere?
No response given
Links to previous discussion of this feature:
No response
Linked PRs
- gh-156135
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by locating the free-threaded implementation of ob_ref_shared and reviewing the linked gh-156135 work. Compare the current atomic ordering with the proposal and its cited shared_ptr implementations; done means the ordering change is correct and the contention performance effect is verified.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- backend, performance
- Issue type
- Feature
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100