Using rails-perftest with Rails 4.1 and Ruby 2.1

Question

In Railscasts 411 Performance Testing http://railscasts.com/episodes/411-performance-testing Ryan forces the garbage collector in our version of Ruby. He used Ruby 1.9.3. Is it still required for Ruby 2.1.1, with its new garbage collector? if so, follow the same instructions? Without it, perftest memory does not generate any data.