bench.rb

require "benchmark"
$:.unshift "."

HASH = { :d => :d, 'e' => :e, 2 => 2 } 

TESTS = 100_000
Benchmark.bmbm do |results|
  results.report("Hash#[:sym]") { TESTS.times { HASH[:d] } }
  results.report("Hash#[:str]") { TESTS.times { HASH['e'] } }
  results.report("Hash#[:fix]") { TESTS.times { HASH[2] } }
end

patched ruby

methodmissing:ruby lourens$ ./ruby hash_bench.rb
Rehearsal -----------------------------------------------
Hash#[:sym]   0.020000   0.000000   0.020000 (  0.014036)
Hash#[:str]   0.030000   0.000000   0.030000 (  0.029462)
Hash#[:fix]   0.010000   0.000000   0.010000 (  0.012764)
-------------------------------------- total: 0.060000sec

                  user     system      total        real
Hash#[:sym]   0.010000   0.000000   0.010000 (  0.013941)
Hash#[:str]   0.030000   0.000000   0.030000 (  0.030123)
Hash#[:fix]   0.020000   0.000000   0.020000 (  0.013026)

sys ruby

methodmissing:ruby lourens$ ruby hash_bench.rb
Rehearsal -----------------------------------------------
Hash#[:sym]   0.020000   0.000000   0.020000 (  0.024361)
Hash#[:str]   0.040000   0.000000   0.040000 (  0.034907)
Hash#[:fix]   0.020000   0.000000   0.020000 (  0.025307)
-------------------------------------- total: 0.080000sec

                  user     system      total        real
Hash#[:sym]   0.030000   0.000000   0.030000 (  0.026289)
Hash#[:str]   0.040000   0.000000   0.040000 (  0.035867)
Hash#[:fix]   0.020000   0.000000   0.020000 (  0.025469)