** Description changed:

  Use `lz4 -9 -l` compression for initramfs by default as discussed on
  ubuntu-devel.
  
  This would also pull the lz4 package into main
  
  https://lists.ubuntu.com/archives/ubuntu-devel/2019-June/040726.html
+ 
+ [Regression Potential]
+ 
+ We are trying to optimize for total boot speed, but performing a micro-
+ optimization upon time to create/unpack kernel/initrd is an insufficient
+ benchmark for total boot speed. This is because it ignores time to load
+ the kernel/initrd, and whether the firmware/bootloader were able to
+ stream decompress it whilst loading it. I.e. it is argued that in the
+ real world, subsecond decompression gains are irrelevant if UEFI
+ firmware, tftp boot, etc. take a lot longer than that to read extra 10s
+ of MBs of boot material.
+ 
+ [TODO]
+ Measure pure i/o load speed with stopwatch, to figure out MB/s speed of 
loading initrds/kernel off FAT32, EXT4, TFTP, HTTP.
+ Re-evaluate if we should provide different compression mechanisms:
+ - ie. gzip instead of lz4 for most cases (revert)
+ - ie. xz for painful i/o cases (e.g. netboot)

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https://bugs.launchpad.net/bugs/1831736

Title:
  [MIR] lz4 by default

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