_warnings.c was initially created to help with startup performance. It turned out to be a tricky bit of code to get right to continue to support the Python version of the module.

But now that we live in a world where we have startup benchmarks instead of hunches and we freeze code like importlib, maybe it's time to re-evaluate whether warnings.py is such a bad thing to have as part of the startup process? I would be curious to know what the performance impact is if we made _warnings the frozen version of warnings.py instead of the C code and measured the startup performance.