attr_* more fast than defined method

gistfile1.rb

require "benchmark"

CYCLES = 1_000_000

class SomeModel
  attr_accessor :attr_names
  
  def method_name
    @method_name
  end
end

Benchmark.bmbm do |x|
  c = SomeModel.new
  x.report("attr")   { CYCLES.times{ c.attr_names  } }
  x.report("method") { CYCLES.times{ c.method_name } }
end

# Result
# Rehearsal ------------------------------------------
# attr     0.190000   0.000000   0.190000 (  0.220931)
# method   0.310000   0.000000   0.310000 (  0.372111)
# --------------------------------- total: 0.500000sec
# 
#              user     system      total        real
# attr     0.190000   0.000000   0.190000 (  0.271583)
# method   0.310000   0.000000   0.310000 (  0.423103)