benchmark.rb

require 'benchmark'

n = 1_000_000

login = 'login'
time = Time.now.to_i

Benchmark.bmbm 20 do |results|
  results.report 'cycle' do
    n.times do
    end
  end

  # result: 3 array object usage
  results.report '[] + []' do
    n.times do
      [login, time] + [3, 4, 5]
    end
  end

  # result: 2 array object usage
  results.report '[].push(*[])' do
    n.times do
      [login, time].push(*[3, 4, 5])
    end
  end

  # result: 1 array object usage
  results.report '[].unshift(a, b)' do
    n.times do
      [3, 4, 5].unshift(login, time)
    end
  end
end

$ uname -a && ruby benchmark.rb
Linux Inspiron-17R 3.13.0-43-generic #72-Ubuntu SMP Mon Dec 8 19:35:44 UTC 2014 i686 i686 i686 GNU/Linux
Rehearsal --------------------------------------------------------
cycle                  0.050000   0.000000   0.050000 (  0.047094)
[] + []                0.340000   0.000000   0.340000 (  0.338438)
[].push(*[])           0.360000   0.000000   0.360000 (  0.362075)
[].unshift(a, b)       0.270000   0.000000   0.270000 (  0.281735)
----------------------------------------------- total: 1.020000sec

                           user     system      total        real
cycle                  0.050000   0.000000   0.050000 (  0.046404)
[] + []                0.340000   0.000000   0.340000 (  0.343467)
[].push(*[])           0.360000   0.000000   0.360000 (  0.357942)
[].unshift(a, b)       0.280000   0.010000   0.290000 (  0.276724)