require "benchmark"
Benchmark.bm do |x|
  5.times do
    x.report do
      o = Object.new
      10000.times do
        def o.method; end
      end
    end
  end
end

      user     system      total        real
  0.080000   0.000000   0.080000 (  0.083388)
  0.040000   0.010000   0.050000 (  0.054322)
  0.040000   0.000000   0.040000 (  0.038894)
  0.040000   0.000000   0.040000 (  0.038702)
  0.040000   0.000000   0.040000 (  0.038113)

      user     system      total        real
  0.070000   0.000000   0.070000 (  0.084311)
  0.050000   0.000000   0.050000 (  0.044328)
  0.030000   0.000000   0.030000 (  0.039399)
  0.040000   0.010000   0.050000 (  0.039387)
  0.040000   0.000000   0.040000 (  0.066599)

require "benchmark"
Benchmark.bm do |x|
  5.times do
    x.report do
        o = Object.new
        class << o
          10000.times do
          def method; end
        end
      end
    end
  end
end

      user     system      total        real
  0.080000   0.000000   0.080000 (  0.109011)
  0.040000   0.010000   0.050000 (  0.039272)
  0.040000   0.000000   0.040000 (  0.038535)
  0.040000   0.000000   0.040000 (  0.040846)
  0.030000   0.010000   0.040000 (  0.051187)

      user     system      total        real
  0.050000   0.000000   0.050000 (  0.063544)
  0.030000   0.000000   0.030000 (  0.036843)
  0.040000   0.000000   0.040000 (  0.036338)
  0.040000   0.000000   0.040000 (  0.037811)
  0.030000   0.000000   0.030000 (  0.036806)