This is splitting one concern from bug 9807 - specifically to avoid parsing pyconfig.h and Makefile in the sysconfig module by autogenerating an extension module (e.g. _sysconfig.c) at build time and using that to get the variables from those two files.

See issue 9807

And also issue 10764. This issue affects alternative implementations of Python.

"avoid parsing pyconfig.h and Makefile in the sysconfig module by autogenerating an extension module"

This feature will be appreciated by small devices embeding Python: on such device, headers and Makefile are not copied to not waste disk space.

To me, it is also an horrible thing to parse pyconfig.h and Makefile at startup, because these files are non trivial to parse and it should be done only once. Because these files are created one, we should parse them once, when Python is compiled. So an "autogenerating an extension module" is an excellent idea. It will speed up Python startup.

I wouldn’t call this a performance issue.  From #4359, you can see that the two main reasons are first to avoid breakage on platforms that put pyconfig.h and Makefile in another package than the interpreter, and most importantly than the code is hard to maintain.  Resource usage diminution will just be a nice side-effect.