David M Beazley (http://www.dabeaz.com)
On February 11, 2010, I launched a single large EC2 instance running a custom HTTP server written entirely in Python. That server launched a pool 512 execution threads running inside a version of the interpreter modified to record thread and GIL traces. I then used Twitter and my blog to ask Python programmers to launch an all out assault on the server with the hope of bringing it to a crushing death.
The visualization on this page shows the behavior of the server several hours after the initial onslaught. You will notice that although the server is getting a lot of traffic, much of the initial pounding has passed. There is not nearly as much GIL contention.
Tests were conducted on the following system: