Installing ruby-prof

First install ruby-prof 0.6.1:

   1  git clone git://github.com/jeremy/ruby-prof.git
   2  cd ruby-prof/
   3  rake gem
   4  sudo gem install pkg/ruby-prof-0.6.1.gem

Note that version 0.6.0 doesn’t work, at least not with Rails 2.1.1. With 0.6.0 I got this message:

   1  `gem install ruby-prof` to use the profiler

Setting up a new environment for profiling

Create config/environments/profiling.rb:

   1  config.cache_classes = true
   2  config.action_controller.consider_all_requests_local = false
   3  config.action_controller.perform_caching             = true
   4  config.action_view.cache_template_loading            = true
   5  
   6  #config.log_level = :debug

Add the new environment to database.yml. You might want to reuse the development database.

Creating a profiling script

Next we’ll create a script that simply fetches the homepage, save the following code in profiling/homepage.rb:

   1  get '/'
   2  say "GET / => #{path}"

Run the script

Now run the script 100 times:

   1  RAILS_ENV=profiling ./script/performance/request -n 100 profiling/homepage.rb

Profiling plain Ruby applications

You can also profile a block of code by calling RubyProf from your code:

   1  require 'ruby-prof'
   2  
   3  # Profile the code
   4  RubyProf.start
   5  ...
   6  [code to profile]
   7  ...
   8  result = RubyProf.stop
   9  
  10  # Print a flat profile to text
  11  printer = RubyProf::FlatPrinter.new(result)
  12  printer.print(STDOUT, 0)

You can easily benchmark your Ruby code like this:

   1  require 'benchmark'
   2  seconds = Benchmark.realtime do
   3  	sleep 1
   4  end
   5  print "#{seconds} elapsed..."

The output should be close to 1 second.