Bug#1003427: COMPRESS=zstd and COMPRESS=lz4 hard-coded to bad COMPRESSLEVELs

["Trent W. Buck" <trentbuck@gmail.com>]

Ben Hutchings wrote:
> On Mon, 2022-01-10 at 11:04 +1100, Trent W. Buck wrote:
> > Package: initramfs-tools
> > Version: 0.140
> > Severity: wishlist
> > 
> > This is a vote for https://salsa.debian.org/kernel-team/initramfs-tools/-/merge_requests/52
> > I did this investigation 2 months ago, but AFAICT I forgot to push it to bugs.debian.org.
> > https://github.com/cyberitsolutions/bootstrap2020/blob/main/doc/NNNNN-ramdisk-compression.rst
> > 
> > Are pigz and xz *REALLY* the best choices for rd compression?
> > Surely lz4 and zstd are better tradeoffs?
> [...]
> 
> You'll be pleased to hear that in master, zstd with compression level 9
> is now the default.  The -T0 option is still unconditional though...
> 
> I have no idea whether the lz4 options should be changed.  I'm not sure
> it's actually a good choice for anyone.

FTR my two use cases are:

  1. Build a test Debian Live image and run qemu on it, just once.
     Build should be quick and ideally not make my laptop heat up.
     Output size doesn't matter at all.

  2. Build a prod Debian Live image and then upload it to a server
     where 1000 desktops will netboot it daily.

I'm using tar2squashfs --comp=lz4 for case #1, so
using lz4 at other layers was intuitive.

Based on the actual measurements, however, I think pigz is a better
bet than lz4 unless/until lz4 gets a -T0 option. ;-)