bignum_bm.rb

require 'benchmark'

#ruby2.1.0
#x64

fixnum_max = 4611686018427387903
bignum_min = fixnum_max + 1

#Fixnum
Benchmark.bm do |b|
  b.report do
    (0..fixnum_max).step(100000000000) {|n|}
  end
end
  
#Bignum

Benchmark.bm do |b|
  b.report do
    (bignum_min..(bignum_min + fixnum_max)).step(100000000000) {|n|}
  end
end

#      user     system      total        real
#  2.100000   0.010000   2.110000 (  2.201473)
#      user     system      total        real
# 11.400000   0.060000  11.460000 ( 12.068350)