Remove lazy dictionary tracking

[markshannon]

Feature or enhancement

Proposal:

In order to reduce the overhead of cycle GC detection for objects that cannot be part of cycles, we lazily untrack tuples and dictionary that only refer to objects that cannot be part of a cycle.

This is fine for tuples, but dictionaries are mutable, so we need to check every time a dictionary is modified whether it needs to be tracked.

Since most objects no longer have a __dict__ dictionary, the complexity and overhead of this lazy tracking is not worth the small benefit in the cycle GC.

This was originally implemented in #126502, but is largely orthogonal to the main purpose of that PR, so should be implemented separately.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• GH-127010: Don't lazily track and untrack dicts #127027

[nascheme]

This sounds like a good idea to me.