I'm reopening this bug even though it's been long closed and even though the attached patch is no longer relevant.

We recently found a degenerative performance problem with entrypoints and threads.  As the number of threads increases, it becomes increasingly horrible to extract entrypoints.  

https://github.com/takluyver/entrypoints

The problem is that entrypoints uses glob.iglob() to find the .{dist,egg}-info directory.  iglob() uses regexps on a fairly simple pattern.  GIL contention can cause entrypoint discovery with 16 threads to take ~10 seconds for all threads to complete.

We have some test cases that I'll try to attach later, but since my bugs archeology found this bug, I decided to reopen it rather than start with a new bug.