Yeah, I hate touching posixmodule.c for the same reason. It'd be nice to split it up into separate platform files, but nobody is volunteering for that.

If you focus on the performance, then yeah, this change probably isn't worth it. OTOH, the number of Windows platforms keep increasing (e.g. ARM, phone/tablet/various sandboxes, etc.) and the fewer dependencies we have the more likely Python will Just Work in them. (And the more value that a split up posixmodule.c will have... guess it'll have to happen eventually.)