It would be great if Cython could support the "nogil" Python fork. (A fork of CPython 3.9 that runs without the global interpreter lock.) I'm currently maintaining patches to Cython for compatibility. If the Cython maintainers are OK with it, I'll submit PRs for compatibility.

There are two pieces, both pretty small:

• The configuration in Cython/Utility/ModuleSetupCode.c
• Making MemoryView reference counting thread-safe without the GIL

Making Cython compatible with "nogil" Python will make it easier to install Python packages that depend on Cython. In particular, because source distributions (sdist) often include pre-Cythonized files.