The commit 28d28e053db6b69d91c2dfd579207cd8ccbc39e7 caused a performance regression on Windows which is currently blocking the Python 3.10.0 final release: bpo-45116.

Moroever, this issue introduced a incompatible C API change which is not documented in What's New in Python 3.10, and it doesn't provide any solution for projects broken by these changes. So far, the following projects are known to be broken by the change:

* Cython
* greenlet (fixed)
* dipy
* yappi
* smartcols

Would it be possible to:

* Bare minimum: document the change in What's in Python 3.10?

* Provide a solution to broken project? If possible, solution working on old and new Python versions. Maybe a compatibility functions can added to https://github.com/pythoncapi/pythoncapi_compat if needed.

* Maybe revert the change in Python 3.10 since a full solution may require additional work.

By the way, I'm also disappointed that nothing was done to enhance the situation for 4 months (since the first known projects were reported here in May).

I raise the priority to release blocker to make more people aware of the situation.