[Bug 1932329] Re: Benchmark if we can compress kernel modules

[Dimitri John Ledkov]

** Also affects: initramfs-tools (Ubuntu)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1932329

Title:
  Benchmark if we can compress kernel modules

Status in initramfs-tools package in Ubuntu:
  New
Status in linux package in Ubuntu:
  In Progress

Bug description:
  Symbol: MODULE_COMPRESS_ZSTD [=n]
  Type  : bool

  = Impacts to measure and observe =

  == Disk space ==

  * Inspect linux-modules-* and linux-modules-extra* deb package
  Installed-Size and Download-Size changes, i.e.

  $ apt show linux-modules-5.8.0-53-generic linux-modules-
  extra-5.8.0-53-generic  | grep -e Package: -e Size:

  Package: linux-modules-5.8.0-53-generic
  Installed-Size: 81.5 MB
  Download-Size: 15.5 MB

  Package: linux-modules-extra-5.8.0-53-generic
  Installed-Size: 215 MB
  Download-Size: 41.5 MB

  In theory, there should not be a significant change in the Download-
  size. It is desired that there is a significant reduction in
  Installed-Size. Modules take up about 300MB and normally one has upto
  three kernel version installed, resulting in about of 1GB of disk
  space that one constantly pays for.

  == Boot Speed ==

  In theory, boot speed may either improve or regress. It depends if
  disk IO is slower than decompression speed, meaning loading compressed
  modules is faster.

  Also one has to observe the changes in the initrd size. zstd(zstd)
  compression may result in slight growth, which shouldn't impact boot
  speed too much.

  = Outcomes =

  If installed size savings can be achieved without regressing bootspeed
  we should enable CONFIG_MODULE_COMPRESS_ZSTD=y by default.

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