So, I tried comparing old profiler with HotShot (2.2's new C based profiler). I ran a simple twisted web server that serves from memory. Running with Python 2.2 I got 350 hits/second. time command says it takes 11 CPU seconds, and with time the hits/sec is a bit lower. Running with old profiler: ~70 hits/second, profiler said it took 2-3 CPU seconds to run (don't ask me why) Running with HotShot: 290 hits/second, it said it took 15 CPU seconds (11 of which were in doSelect on its own). Conclusions: HotShot is much much much much much much much better than old profiler We need to optimize doSelect something wicked HotShot still has bugs (it would fail occasionally) I have a command-line interface to hotshot at http://itamarst.org/software/