output

$ ruby serialization.rb 
Sizes:
marshal: 55
msgpack: 35
json: 46
Rehearsal -----------------------------------------------------
marshal             1.590000   0.050000   1.640000 (  1.647142)
json                1.890000   0.200000   2.090000 (  2.091030)
marshal with yajl   1.590000   0.030000   1.620000 (  1.624589)
json with yajl      1.860000   0.060000   1.920000 (  1.926875)
msgpack             0.600000   0.050000   0.650000 (  0.646675)
-------------------------------------------- total: 7.920000sec

                        user     system      total        real
marshal             1.590000   0.050000   1.640000 (  1.645221)
json                1.870000   0.350000   2.220000 (  2.218516)
marshal with yajl   1.570000   0.040000   1.610000 (  1.605292)
json with yajl      1.860000   0.310000   2.170000 (  2.171474)
msgpack             0.580000   0.040000   0.620000 (  0.620065)

serialization.rb

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

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

  require 'yajl/json_gem'

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

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

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


end

This benchmark sucks.