( while :; do date ; /usr/bin/time heroku run false ; sleep 1; done ) 2>&1 | ruby parse_bench.rb

parse_bench.rb

#!/usr/bin/env ruby

samples = []

STDIN.lines.each do |line|
  next if line =~ /^stty/
  next if line =~ /^Running/
  if line =~ /real.*user.*sys/
    real,_,user,_,sys = line.strip.split(/\s+/)
    samples << [Float(real),Float(user),Float(sys)]
  end

end

def percentile(values, percentile)
  values_sorted = values.sort
  k = (percentile*(values_sorted.length-1)+1).floor - 1
  f = (percentile*(values_sorted.length-1)+1).modulo(1)

  return values_sorted[k] + (f * (values_sorted[k+1] - values_sorted[k]))
end

puts percentile(samples.map{|s|s[0]}, 0.95)
puts "#{samples.length} samples"