foo.rb

require 'benchmark'

module Foo
end

times = 1_000_000

Benchmark.bm 30 do |r|
  r.report 'extend' do
    times.times do
      o = Object.new
      o.extend Foo
    end
  end
  GC.start
  r.report 'singleton_class include' do
    times.times do
      o = Object.new
      o.singleton_class.include Foo
    end
  end
  GC.start
  r.report 'singleton_class prepend' do
    times.times do
      o = Object.new
      o.singleton_class.include Foo
    end
  end
end