Thursday, 30 May 2019

Re: Supporting LZ4 as initramfs compressor

On Thu, 30 May 2019 at 11:35, Dimitri John Ledkov <> 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.

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.



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