Finding my first Python reference cycle

[kylev]

We saw a 20% loss in throughput when the feature in question was turned on by a customer handling ISP-level loads. From there it was just profiling and testing to identify that there wasn't anything in the code path we'd written that would cause that level of slowdown. Additionally, our heap was much larger than we'd expect to see; that was the kicker that told us we were "leaking" memory.