Comment by vmp

The next default compressor might be lrzip [1] by Con Kolivas; I've only see it a couple of times in the wild so far but for certain files it can increase the compression ratio quite a bit.

[1] https://github.com/ckolivas/lrzip

  # 151M    linux-4.14-rc6.tar.gz
  # GZIP decompression
  ~$ time gzip -dk linux-4.14-rc6.tar.gz

  real    0m4.518s
  user    0m3.328s
  sys     0m13.422s

  # 787M    linux-4.14-rc6.tar
  # LRZIP compression
  ~$ time lrzip -v linux-4.14-rc6.tar
  [...]
  linux-4.14-rc6.tar - Compression Ratio: 7.718. Average Compression Speed: 13.789MB/s.
  Total time: 00:00:56.37

  real    0m56.533s
  user    5m35.484s
  sys     0m9.422s

  # 137M    linux-4.14-rc6.tar.lrz
  # LRZIP decompression
  ~$ time lrzip -dv linux-4.14-rc6.tar.lrz
  [...]
  100%     786.16 /    786.16 MB
  Average DeCompression Speed: 131.000MB/s
  Output filename is: linux-4.14-rc6.tar: [OK] - 824350720 bytes
  Total time: 00:00:06.35

  real    0m6.524s
  user    0m8.031s
  sys     0m1.766s

  # Results
  ~$ du -hs linux* | sort -h
  137M    linux-4.14-rc6.tar.lrz
  151M    linux-4.14-rc6.tar.gz
  787M    linux-4.14-rc6.tar

tested on WSL (Ubuntu BASH for Windows 10)

edit:

  ~$ time xz -vk linux-4.14-rc6.tar
  linux-4.14-rc6.tar (1/1)
    100 %        98.9 MiB / 786.2 MiB = 0.126   3.0 MiB/s       4:25

  real    4m25.189s
  user    4m23.828s
  sys     0m1.094s
  
  ~$ du -hs linux* | sort -h
  99M     linux-4.14-rc6.tar.xz
  137M    linux-4.14-rc6.tar.lrz
  151M    linux-4.14-rc6.tar.gz
  787M    linux-4.14-rc6.tar

It looks like XZ still has the best compression ratio but also took the longest (real)time.