ruby-prof is a fast code profiler for Ruby. Its features include:

* Speed - it is a C extension and therefore many times faster than the
  standard Ruby profiler.
* Modes - Ruby prof can measure a number of different parameters,
  including call times, memory usage and object allocations.
* Reports - can generate text and cross-referenced html reports
  o Flat Profiles - similar to the reports generated by the standard
    Ruby profiler
  o Graph profiles - similar to GProf, these show how long a method
    runs, which methods call it and which methods it calls.
  o Call tree profiles - outputs results in the calltree format
    suitable for the KCacheGrind profiling tool.
* Threads - supports profiling multiple threads simultaneously
* Recursive calls - supports profiling recursive method calls
