instrument_module.rb

module InstrumentModule
  def self.build(*methods)
    evil = methods.map do |method|
        %Q[
          def #{method}(*arguments, &block)
            t = Time.now
            r = super
            td = Time.now - t
            puts "*inst* " + (self.class === Class ? self.name + "." : self.class.name + "#") + "#{method}: " + td.to_s + " s"
            r
          end
        ]
      end

    name = "M#{Time.now.to_f.to_s.gsub(/\W/, "")}#{rand(10000)}"

    uber_evil = %Q(
      module #{name}
        #{evil.join("\n")}
      end
    )

    module_eval uber_evil

    eval name
  end
end

class C
  def self.m
    sleep 0.1
    :Cm
  end

  def self.n
    sleep 0.1
    :Cn
  end

  def m
    sleep 0.1
    :m
  end

  def n
    sleep 0.1
    :n
  end
end

class D < C
  extend  InstrumentModule.build(:m, :n)
  include InstrumentModule.build(:m, :n)
end

D.ancestors # => [D, InstrumentModule::M1283446573510151394, C, Object, Kernel, BasicObject]

D.m     # => :Cm
D.n     # => :Cn
D.new.m # => :m
D.new.n # => :n

# >> *inst* D.m: 0.100126 s
# >> *inst* D.n: 0.100163 s
# >> *inst* D#m: 0.100079 s
# >> *inst* D#n: 0.100104 s