bench.rb

require 'benchmark/ips'

Benchmark.ips do |x|
  x.config(:time => 5, :warmup => 5)
  x.report("times") { 6.times {|x| } }
  x.report("range iteration") { (0..5).each {|x| } }
  x.report("upto") { 0.upto(5) {|x| } }
  x.report("for") do
    for x in 0..5
    end
  end
end

results.txt

# jruby-1.7.19
chris@luna /var/www/repos $ ruby bench.rb
Calculating -------------------------------------
               times   116.501k i/100ms
     range iteration   125.917k i/100ms
                upto   132.437k i/100ms
                 for   146.393k i/100ms
-------------------------------------------------
               times      2.933M (± 4.5%) i/s -     14.679M
     range iteration      2.883M (± 6.5%) i/s -     14.355M
                upto      2.817M (± 5.4%) i/s -     14.038M
                 for      3.943M (± 6.1%) i/s -     19.617M

# jruby-head
chris@luna /var/www/repos $ ruby bench.rb
Calculating -------------------------------------
               times    84.885k i/100ms
     range iteration    99.954k i/100ms
                upto    96.530k i/100ms
                 for    92.034k i/100ms
-------------------------------------------------
               times      2.685M (± 4.6%) i/s -     13.412M
     range iteration      2.581M (± 5.3%) i/s -     12.894M
                upto      2.767M (± 4.7%) i/s -     13.804M
                 for      2.219M (± 2.8%) i/s -     11.136M