[Bug 1488620] Re: [FFe] Add LZ4 support to initramfs-tools

[Balint Reczey]

** Description changed:

+ Feature Freeze Justification
+ ============================
+ 
+ Initramfs-tools uses gzip compression by default which served us well
+ for quite some time but LZ4 offers way faster decompression while
+ making a only slightly bigger initramfs files.
+ 
+ Having lz4 supported by initramfs-tools would allow users to opt-in for
+ faster boot in Bionic from day 1.
+ 
+ On my old laptop the initramfs extraction time decreased from ~1.2s to ~0.24s:
+ (with lz4)
+ kernel: [    0.285692] Unpacking initramfs...
+ kernel: [    0.518806] Freeing initrd memory: 65148K
+ kernel: [    0.289731] Unpacking initramfs...
+ kernel: [    0.522823] Freeing initrd memory: 65148K
+ (with gzip)
+ kernel: [    0.273748] Unpacking initramfs...
+ kernel: [    1.490066] Freeing initrd memory: 57140K
+ kernel: [    0.281729] Unpacking initramfs...
+ kernel: [    1.498493] Freeing initrd memory: 57140K
+ 
+ Discussion on ubuntu-devel:
+ https://lists.ubuntu.com/archives/ubuntu-devel/2018-March/040258.html
+ 
+ IMO the attached patch is minimally intrusive and it is safe to make
+ this change even at this late hour of the release cycle.
+ 
+ 
+ Original Bug Text
+ =================
+ 
  I found that I could enable LZ4 compression for initramfs on my vivid
  machine by installing liblz4-tool package, adding one line to
  mkinitramfs and installing a kernel compiled with CONFIG_CRYPTO_LZ4=y.
  
  Please include support for (legacy) LZ4.
  
  Attached patch includes changes made to the latest version (initramfs-
  tools_0.120ubuntu3).

** Description changed:

  Feature Freeze Justification
  ============================
  
  Initramfs-tools uses gzip compression by default which served us well
  for quite some time but LZ4 offers way faster decompression while
  making a only slightly bigger initramfs files.
  
  Having lz4 supported by initramfs-tools would allow users to opt-in for
  faster boot in Bionic from day 1.
  
  On my old laptop the initramfs extraction time decreased from ~1.2s to ~0.24s:
  (with lz4)
  kernel: [    0.285692] Unpacking initramfs...
  kernel: [    0.518806] Freeing initrd memory: 65148K
  kernel: [    0.289731] Unpacking initramfs...
  kernel: [    0.522823] Freeing initrd memory: 65148K
  (with gzip)
  kernel: [    0.273748] Unpacking initramfs...
  kernel: [    1.490066] Freeing initrd memory: 57140K
  kernel: [    0.281729] Unpacking initramfs...
  kernel: [    1.498493] Freeing initrd memory: 57140K
  
  Discussion on ubuntu-devel:
  https://lists.ubuntu.com/archives/ubuntu-devel/2018-March/040258.html
  
  IMO the attached patch is minimally intrusive and it is safe to make
  this change even at this late hour of the release cycle.
  
+ I have uploaded the package to this PPA for testing the build:
+ https://launchpad.net/~rbalint/+archive/ubuntu/scratch
+ 
+ I'm also using the updated package on my system.
  
  Original Bug Text
  =================
  
  I found that I could enable LZ4 compression for initramfs on my vivid
  machine by installing liblz4-tool package, adding one line to
  mkinitramfs and installing a kernel compiled with CONFIG_CRYPTO_LZ4=y.
  
  Please include support for (legacy) LZ4.
  
  Attached patch includes changes made to the latest version (initramfs-
  tools_0.120ubuntu3).

** Changed in: initramfs-tools (Ubuntu)
       Status: Triaged => New

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https://bugs.launchpad.net/bugs/1488620

Title:
  [FFe] Add LZ4 support to initramfs-tools

Status in initramfs-tools package in Ubuntu:
  New

Bug description:
  Feature Freeze Justification
  ============================

  Initramfs-tools uses gzip compression by default which served us well
  for quite some time but LZ4 offers way faster decompression while
  making a only slightly bigger initramfs files.

  Having lz4 supported by initramfs-tools would allow users to opt-in
  for faster boot in Bionic from day 1.

  On my old laptop the initramfs extraction time decreased from ~1.2s to ~0.24s:
  (with lz4)
  kernel: [    0.285692] Unpacking initramfs...
  kernel: [    0.518806] Freeing initrd memory: 65148K
  kernel: [    0.289731] Unpacking initramfs...
  kernel: [    0.522823] Freeing initrd memory: 65148K
  (with gzip)
  kernel: [    0.273748] Unpacking initramfs...
  kernel: [    1.490066] Freeing initrd memory: 57140K
  kernel: [    0.281729] Unpacking initramfs...
  kernel: [    1.498493] Freeing initrd memory: 57140K

  Discussion on ubuntu-devel:
  https://lists.ubuntu.com/archives/ubuntu-devel/2018-March/040258.html

  IMO the attached patch is minimally intrusive and it is safe to make
  this change even at this late hour of the release cycle.

  I have uploaded the package to this PPA for testing the build:
  https://launchpad.net/~rbalint/+archive/ubuntu/scratch

  I'm also using the updated package on my system.

  Original Bug Text
  =================

  I found that I could enable LZ4 compression for initramfs on my vivid
  machine by installing liblz4-tool package, adding one line to
  mkinitramfs and installing a kernel compiled with CONFIG_CRYPTO_LZ4=y.

  Please include support for (legacy) LZ4.

  Attached patch includes changes made to the latest version (initramfs-
  tools_0.120ubuntu3).

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