[Python-Dev] Re: "immortal" objects and how they would help per-interpreter GIL

I've just updated the original Immortal Instances PR with a bunch of tricks that I used to achieve as much performance parity as possible: https://github.com/python/cpython/pull/19474 . You can see the details along with some benchmarks in the PR itself. This should address a bunch of the original performance concerns. Furthermore, it opens up the possibility of iterating on top of this to keep improving perf (i.e immortal intern strings, immortal heap types, less gc cycles from moving long lived objects to the perm gen, etc.).