Automatically defer heavily shared objects in free-threading.

[Fidget-Spinner]

Feature or enhancement

Proposal:

@corona10 asked if it would be possible to automatically apply deferred refcounting on objects if we notice they're heavily shared in the interpreter through some heuristic. The problem in #134762 (comment) is that we need to defer basically anything shared as it would perform badly in a microbenchmark otherwise.

I think it should be possible. We could rely on biased refcounting to give us a rough estimate on when something is shared, once it's past a certain threshold, we automatically defer the object. Does anyone have a better heuristic to suggest?

Also I'm not going to take this up, as I have too much work on my plate already, so let me know if you'd like to work on it, I can collaborate and provide guidance.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-134821: Automatically enable deferred reference counting on shared objects #134880

[ZeroIntensity]

I'd be happy to try this.

[corona10]

I will happily track the issue or try to help.