Implemented Martin's suggestion to clear the free lists during the garbage collection of the highest generation.
diff --git a/Include/methodobject.h b/Include/methodobject.h
index 810a69c..6e160b6 100644
--- a/Include/methodobject.h
+++ b/Include/methodobject.h
@@ -85,6 +85,8 @@
     PyObject    *m_module; /* The __module__ attribute, can be anything */
 } PyCFunctionObject;
 
+PyAPI_FUNC(int) PyCFunction_ClearFreeList(void);
+
 #ifdef __cplusplus
 }
 #endif