incrementing.rb

require 'benchmark'

counter = 0

bm = Benchmark.measure do
  500_000_000.times do
    counter += 1
  end
end

puts counter
puts bm

output

--(jadams@jibbajabba)-(12/pts/13)-(1812/19-Apr-13)--
--($:~/ruby/benchmarking)ruby-head@benchmarking-- 
$ ruby incrementing.rb 
500000000
 31.800000   0.000000  31.800000 ( 31.913337)
--(jadams@jibbajabba)-(13/pts/13)-(1821/19-Apr-13)--
--($:~/ruby/benchmarking)ruby-head@benchmarking-- 
$ . .rvmrc 
Using /home/jadams/.rvm/gems/jruby-1.7.3 with gemset benchmarking
--(jadams@jibbajabba)-(14/pts/13)-(1821/19-Apr-13)--
--($:~/ruby/benchmarking)jruby-1.7.3@benchmarking-- 
$ ruby incrementing.rb 
500000000
 24.160000   0.220000  24.380000 ( 21.346000)