Supporting LZ4 as initramfs compressor

[Dimitri John Ledkov]

On Thu, 30 May 2019 at 11:35, Dimitri John Ledkov <xnox at ubuntu.com> wrote:
>
> I see a lot of code in livecd-rootfs that tries hard to use lzma
> compression for the initaller (first-boot) initrd.
> On the classic, subsequent initrds get rebuild as gzip, and on core
> lzma persists.
> I do wonder what compression we should use by default for the
> installer media, Ubuntu Core, cloud images.
>
> Is the rationale for lzma installer initrds still valid? And what was
> it? Smallest size initrd?
>

Note subiquity dropped using lzma for the installer image to improve boot speed.
https://bugs.launchpad.net/subiquity/+bug/1750873

Which I find confusing from the spreadsheet graphs....
gzip is fast at kernel, but not initrd
lzma fast at initrd, but not kernel

As if lz4 kernel & xz initrd would yield the fastest boot time? That
sounds counter-intuitive. Unless for initrd, only the compressed size
matters and initrd decompression time does not matter?

Measurements until break=bottom is reached would be nice.

-- 
Regards,

Dimitri.