FWIW, PEP 554 is part of a larger project that I've been working on (slowly) for several years now. [1]  The concrete objective is to leverage subinterpreters as the mechanism by which we can achieve multi-core parallelism in Python code.  Moving the GIL (and some other parts of _PyRuntimeState, as Victor indicated) down to per-interpreter state is essential to that.

However, I don't thing making _PyRuntime a per-interpreter thing is right.  The runtime holds the set of interpreters, as well as any state state shared by the interpreters.

Also, to be clear, the status quo is not a problem for me, so make sure I'm not used as the justification for the change (thoughtful as that is of Victor). :)


[1] https://github.com/ericsnowcurrently/multi-core-python