use to get a feeling about expensive requires in your application.

snippet.rb

module Kernel
  # make an alias of the original require
  alias_method :original_require, :require
  $require_times = {}

  # rewrite require
  def require name
    start_time = Time.now
    original_require name
    time_took = Time.now - start_time
    $require_times[name] ||= time_took
    # puts ("%.6f sec.  -- #{name}" % time_took)
  end

  def slowest_requires(num = 10)
    slowest_keys = $require_times.keys.sort{ |x,y| $require_times[y] <=> $require_times[x] }[0..num-1]
    slowest_keys.map do |k|
      [k, $require_times[k]]
    end
  end

  def pp_slowest_requiries(num=10)
    res = slowest_requires(num)
    res.each do |ar|
      puts "%.6f sec.  - #{ar[0]}" % ar[1]
    end
  end
end

require "time"
pp_slowest_requiries