Ruby 2.0 starts applications in less than half the time taken by 1.9.3. We'll see the techniques I used to diagnose (and fix) the problem, which can be used for any performance problem in MRI or a C extension. The same principles apply to fixing performance problems in Ruby code.
(As delivered at Pivotal Labs in San Francisco, 2013-04-02.)
For a recording of the complete in-person presentation, see http://bostonrb.org/presentations/profiling-ruby (a slightly different version.)