singleton_speed.rb

require 'benchmark'

class Foo
  def bar; end
end

singleton = (100_000 * 20).times.map do |i|
  foo = Foo.new
  foo.singleton_class
  foo
end

no_singleton = (100_000 * 20).times.map do |i|
  foo = Foo.new
  #foo.singleton_class
  foo
end

GC.disable

p :no_singleton => Benchmark.realtime { no_singleton.each { |foo| foo.bar } }
p :singleton => Benchmark.realtime { singleton.each { |foo| foo.bar } }