how much time does Ruby spend in executing a function

benchmark_findAllPrime.rb

def howmanyPrime(number)
  dd = 3
  dr = 2
  output = []

  for dd in 3..number
    for dr in 2..(number-1)
      if dd%dr == 0
        break
      elsif dr+1 == dd 
          output.push(dd)
          next
      end
    end
  end
  return output
end

# 測時間_1
a = Time.now
p howmanyPrime(100000)
b = Time.now
puts "#{(b-a)*1000} mils"

# 測時間_2
require 'benchmark'
Benchmark.bm do |x|
  x.report do
    p howmanyPrime(100000)
  end
end