WoW, SimpleDelegator is REALLY slow...

delegation_bm.rb

require 'benchmark'
require 'active_support/core_ext/module/delegation'

# 6! = 720
METHODS = %w[a b c d e f].permutation.map(&:join)

class Decoratee
  METHODS.each do |m|
    define_method m do
      m
    end
  end
end

class SimpleDecorator
  def initialize(object)
    @object = object
  end

  protected

  attr_reader :object

  class << self
    def auto_delegate(*methods)
      delegate(*methods, to: :object)
    end
  end
end

class Decorated < SimpleDecorator
  def abcdef
    object.abcdef
  end
end

class DelegatedDecorated < SimpleDecorator
  auto_delegate :abcdef
end

class Delegated < SimpleDelegator
  def xpto
    abcdef
  end

  def xptz
    __getobj__.abcdef
  end
end

class Missing
  def initialize(obj)
    @obj = obj
  end

  def responds_to?(method)
    @obj.responds_to?(method)
  end

  def method_missing(method, *args)
    @obj.send(method, *args)
  end
end

class SmartMissing
  def initialize(obj)
    @obj = obj
  end

  def respond_to_missing?(method)
    @obj.respond_to?(method)
  end

  def method_missing(method, *args)
    if respond_to_missing?(method)
      self.class.class_eval <<~RUBY
        def #{method}(*args)
          @obj.#{method}(*args)
        end
      RUBY
    end
    @obj.send(method, *args)
  end
end

TESTS = 10_000_000

decoratee = Decoratee.new

decorated = Decorated.new(decoratee)
delegated_decorated = DelegatedDecorated.new(decoratee)
delegated = Delegated.new(decoratee)
missing = Missing.new(decoratee)
smartmissing = SmartMissing.new(decoratee)

Benchmark.bm do |x|
  x.report('Baseline:                               ') { TESTS.times { decoratee.abcdef } }
  x.report('SimpleDecorator - method                ') { TESTS.times { decorated.abcdef } }
  x.report('SimpleDecorator - delegation:           ') { TESTS.times { delegated_decorated.abcdef } }
  x.report('SimpleDelegator - method:               ') { TESTS.times { delegated.xptz } }
  x.report('SimpleDelegator - method w/ delegation: ') { TESTS.times { delegated.xpto } }
  x.report('SimpleDelegator - delegation:           ') { TESTS.times { delegated.abcdef } }
  x.report('MethodMissing - simple mm:              ') { TESTS.times { missing.abcdef } }
  x.report('MethodMissing - smart mm:               ') { TESTS.times { smartmissing.abcdef } }
end

results.txt

       user     system      total        real
Baseline:                                 0.875386   0.000259   0.875645 (  0.875677)
SimpleDecorator - method                  1.311704   0.000217   1.311921 (  1.311985)
SimpleDecorator - delegation:             2.043516   0.000587   2.044103 (  2.044270)
SimpleDelegator - method:                 1.371788   0.000402   1.372190 (  1.372431)
SimpleDelegator - method w/ delegation:   3.280072   0.000998   3.281070 (  3.281436)
SimpleDelegator - delegation:             3.125444   0.001395   3.126839 (  3.127281)
MethodMissing - simple mm:                2.132746   0.000728   2.133474 (  2.133660)
MethodMissing - smart mm:                 1.555830   0.000233   1.556063 (  1.556142)