benchmark_object_access.rb

require "benchmark"

puts RUBY_DESCRIPTION

class A
  attr_accessor :x
end

class B
  def y
    "Hello!"
  end
end

TIMES = 1_000_000

Benchmark.bm(7) do |x|
  a = A.new
  a.x = B.new

  x.report("a.x.y:") do
    1.upto(TIMES) { a.x.y }
  end

  x.report("b.y:") do
    b = a.x
    1.upto(TIMES) { b.y }
  end

  x.report("c:") do
    c = a.x.y
    1.upto(TIMES) { c }
  end
end

output

> ruby benchmark_object_access.rb
ruby 1.9.3p327 (2012-11-10 revision 37606) [x86_64-darwin11.4.2]
              user     system      total        real
a.x.y:    0.310000   0.000000   0.310000 (  0.308913)
b.y:      0.220000   0.000000   0.220000 (  0.230498)
c:        0.080000   0.000000   0.080000 (  0.074294)