Backtrace:
    Kernel(ThreadScalability)#len (method_missing_cv) at kernel/core/kernel.rb:648
         ThreadScalability#reverse_string {} at bench_threaded_reverse.rb:21
                       Integer(Fixnum)#times at kernel/core/integer.rb:33
            ThreadScalability#reverse_string at bench_threaded_reverse.rb:19
           ThreadScalability#reverse_strings at bench_threaded_reverse.rb:60
                ThreadScalability#do_test {} at bench_threaded_reverse.rb:46
                        Thread#initialize {} at kernel/core/thread.rb:83