dci_benchmark.rb

require 'rubygems'
require 'benchmark/ips'

class ExampleClass
  def foo; 42; end
end

module ExampleMixin
  def foo; 43; end
end

Benchmark.ips do |bm|
  bm.report("without dci") { ExampleClass.new.foo }
  bm.report("with extend dci") do
    obj = ExampleClass.new
    obj.extend(ExampleMixin)
    obj.foo
  end
  bm.report("with include dci") do
    obj = ExampleClass.new
    obj.include(ExampleMixin)
    obj.foo
  end
end

results.txt

# ruby 1.9.3p327 (2012-11-10 revision 37606) [x86_64-darwin12.2.0]

             #iterations/sec
without dci  3938758.7 (±1.9%) i/s -   19754280 in   5.017387s
  with dci    537904.0 (±8.0%) i/s -    2683515 in   5.024073s