output

$ ruby serialization.rb 
Sizes:
marshal: 44
msgpack: 35
json: 46
Rehearsal -------------------------------------------
marshal   0.840000   0.030000   0.870000 (  0.878109)
msgpack   0.420000   0.060000   0.480000 (  0.467086)
json      1.310000   0.130000   1.440000 (  1.444504)
---------------------------------- total: 2.790000sec

              user     system      total        real
marshal   0.850000   0.030000   0.880000 (  0.872736)
msgpack   0.290000   0.030000   0.320000 (  0.319910)
json      1.230000   0.110000   1.340000 (  1.338845)

serialization.rb

require 'rubygems'
require 'benchmark'
require 'msgpack'
require 'json'

Benchmark.bmbm do |x|

  object = {:id => 'asdf;lkjr2l;kjdsokj23', :hit => {:a => 'b'}}

  puts "Sizes:",
    "marshal: #{Marshal.dump(object).length}",
    "msgpack: #{object.to_msgpack.length}",
    "json: #{object.to_json.length}"

  x.report('marshal') do
    100_000.times do
      Marshal.load(Marshal.dump(object))
    end
  end

  x.report('msgpack') do
    100_000.times do
      MessagePack.unpack(object.to_msgpack)
    end
  end

  x.report('json') do
    100_000.times do
      JSON.parse(object.to_json)
    end
  end

end