Yuslow

Yuslow [waɪ ju sləʊ] is a lightweight profiler for Ruby designed to debug slow parts of your system.

gem install yuslow

Require the gem in the file which you would like to investigate.

require 'yuslow'

then add

Yuslow.investigate do
  a_very_slow_method
end

or

investigation = Yuslow.investigation

investigation.start
a_very_slow_method
investigation.finish

to your code. Execute the code and you will see output in $stdout with the following tree structure. It will help you understand which branch and method of your code has poor performance.

Thread[1]:
  Object#very_slow elapsed 1000 ms
    Object#not_my_fault elapsed 1000 ms
      Object#not_me elapsed 0 ms
      Object#root_cause elapsed 1000 ms
        Kernel#sleep elapsed 1000 ms