gistfile1.txt

% cat tmp/define_method_test.rb 
class Foo
  def foo
    :foo
  end
  define_method(:bar) { :foo }
end

def time(method_name, count, &block)
  start = Time.now
  count.times &block
  stop = Time.now
  puts "#{method_name}[#{count}] : #{stop - start}"
end

foo = Foo.new

[1, 10, 100, 1000, 10000, 100000].each do |i|
  time("foo", i) { foo.foo }
  time("bar", i) { foo.bar }
end

% ruby -v tmp/define_method_test.rb
ruby 1.9.2p290 (2011-07-09) [x86_64-darwin11.1.0]
foo[1] : 1.9e-05
bar[1] : 1.1e-05
foo[10] : 3.0e-06
bar[10] : 4.0e-06
foo[100] : 1.6e-05
bar[100] : 2.5e-05
foo[1000] : 0.00015
bar[1000] : 0.000246
foo[10000] : 0.001503
bar[10000] : 0.00245
foo[100000] : 0.015126
bar[100000] : 0.030158