The Windows7 buildbot now runs the test suite with the "largefile" resource disabled and no longer timed out on test_mmap.  So that immediate problem is now resolved.  Before closing the issue, it would be good to discuss whether we should do the same for some of the other Windows buildbots (perhaps allow "largefile" only on the buildbot with the most capacity?) and/or disabling "largefile" on all Windows CI tests (if not done already).