brotliの圧縮率と圧縮時間の検証 (gzip, zopfliと比較)

前投稿でzopfliの圧縮率と圧縮時間を再検討した事もあり、良い機会なので運用中サイト群の完全HTTPS化を頑張ってみようかと。 効果を確認するために事前検討で以下のスクリプトを走らせてみました。検証ではbrotli-0.60, zopfli-1.01を利用しています。

file = ARGV[0]

def calc(label, cmd, file)
  t = Time.now
  `#{cmd}`
  t = Time.now - t
  size = File.size(file)
  puts "#{label}: #{sprintf("%.6f", t)} sec, #{size} bytes"
end

puts "original: #{File.size(file)} bytes"
(1..10).each {|level|
  calc("brotli #{level}", "brotli --force --quality #{level} --input #{file} --output #{file}.br", "#{file}.br")
}
((1..9).to_a + [10,15,20,25,30]).each {|level|
  calc("zopfli #{level}", "zopfli --i#{level} #{file}", "#{file}.gz")
}
(1..9).each {|level|
  calc("gzip   #{level}", "gzip -#{level} -c -f #{file} > #{file}.gz", "#{file}.gz")
}

ギリギリまで冗長性を削除しているHTMLをテストに利用してみたところ、gzip-18%、zopfli-16%となり素晴らしい結果でした。

$ ruby test.rb test.html
original: 15652 bytes
brotli 1: 0.002033 sec, 5047 bytes
brotli 2: 0.001699 sec, 5009 bytes
brotli 3: 0.001784 sec, 4980 bytes
brotli 4: 0.002044 sec, 4747 bytes
brotli 5: 0.002624 sec, 4172 bytes
brotli 6: 0.003607 sec, 4162 bytes
brotli 7: 0.004323 sec, 4107 bytes
brotli 8: 0.004056 sec, 4100 bytes
brotli 9: 0.005396 sec, 4087 bytes
brotli 10: 0.043826 sec, 3881 bytes
zopfli 1: 0.252186 sec, 4612 bytes
zopfli 2: 0.273344 sec, 4606 bytes
zopfli 3: 0.306744 sec, 4603 bytes
zopfli 4: 0.265884 sec, 4603 bytes
zopfli 5: 0.327768 sec, 4603 bytes
zopfli 6: 0.302046 sec, 4603 bytes
zopfli 7: 0.322396 sec, 4603 bytes
zopfli 8: 0.310021 sec, 4603 bytes
zopfli 9: 0.340069 sec, 4605 bytes
zopfli 10: 0.338060 sec, 4605 bytes
zopfli 15: 0.383038 sec, 4603 bytes
zopfli 20: 0.392550 sec, 4603 bytes
zopfli 25: 0.360510 sec, 4603 bytes
zopfli 30: 0.277653 sec, 4603 bytes
gzip   1: 0.002162 sec, 5122 bytes
gzip   2: 0.001989 sec, 5033 bytes
gzip   3: 0.001755 sec, 4981 bytes
gzip   4: 0.001775 sec, 4791 bytes
gzip   5: 0.001814 sec, 4739 bytes
gzip   6: 0.002046 sec, 4734 bytes
gzip   7: 0.002149 sec, 4732 bytes
gzip   8: 0.003049 sec, 4729 bytes
gzip   9: 0.002149 sec, 4729 bytes

前回利用したJSONファイルも確認してみた。これもギリギリまで冗長性は排除していますが、gzip-18%、zopfli-13%と素晴らしい結果でした。

$ ruby test.rb test.json
original: 438146 bytes
brotli 1: 0.008709 sec, 143812 bytes
brotli 2: 0.010706 sec, 142193 bytes
brotli 3: 0.012212 sec, 139530 bytes
brotli 4: 0.014156 sec, 138066 bytes
brotli 5: 0.026652 sec, 125302 bytes
brotli 6: 0.034410 sec, 123004 bytes
brotli 7: 0.043270 sec, 120508 bytes
brotli 8: 0.052716 sec, 119024 bytes
brotli 9: 0.070479 sec, 118026 bytes
brotli 10: 1.337605 sec, 104952 bytes
zopfli 1: 1.116614 sec, 120899 bytes
zopfli 2: 1.178194 sec, 120623 bytes
zopfli 3: 1.271736 sec, 120548 bytes
zopfli 4: 1.345818 sec, 120485 bytes
zopfli 5: 1.492534 sec, 120455 bytes
zopfli 6: 1.529910 sec, 120438 bytes
zopfli 7: 1.594525 sec, 120432 bytes
zopfli 8: 1.665754 sec, 120408 bytes
zopfli 9: 1.750016 sec, 120398 bytes
zopfli 10: 1.884538 sec, 120392 bytes
zopfli 15: 2.519045 sec, 120390 bytes
zopfli 20: 3.101787 sec, 120390 bytes
zopfli 25: 2.980007 sec, 120390 bytes
zopfli 30: 3.701557 sec, 120387 bytes
gzip   1: 0.013838 sec, 170265 bytes
gzip   2: 0.039754 sec, 161152 bytes
gzip   3: 0.034746 sec, 151130 bytes
gzip   4: 0.015178 sec, 144631 bytes
gzip   5: 0.019380 sec, 134481 bytes
gzip   6: 0.030051 sec, 130714 bytes
gzip   7: 0.040470 sec, 129113 bytes
gzip   8: 0.066297 sec, 127468 bytes
gzip   9: 0.066368 sec, 127468 bytes

brotliのqualityは、応答性を求めるなら4、ほどほどの圧縮時間で良ければ9、圧縮時間を問わなければ10を利用するのが良さそうです。