Re: [PATCH] feat: add zstd support to image conversions

["Roberto A. Foglietta" <roberto.foglietta@gmail.com>]

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Il Lun 23 Gen 2023, 20:22 Jan Kiszka <jan.kiszka@siemens.com> ha scritto:

> On 23.01.23 15:00, Michael Adler wrote:
> > This patch enables ISAR to build zstd compressed images.
> >
>
> I was briefly thinking you had solved the dpkg vs. zstd issue - just a
> dream :)
>

Hi Jan.

I think you are speaking about zstd compression for the debian package that
is 1% bigger but 13x times faster in expanding. [1]

Ubuntu and Arch adopted zstd but not debian which is still using xz and as
far as I have seen neither in parallel using option -T.

I think you should ask them to produce all package with

export XZ_DEFAULTS='-T 8'

and enabling dpkg to set internally

XZ_DEFAULTS='-T 0'

unless it is differently set. What Do you think about changing ISAR to use
zstd or xz -T without repackaging everything at fetch time?

It would be a solution: fetch, repackage with zstd and the downloads remain
for a long time like a permanent cache and also the benefits.

The counter effect is that those debian packages and those produced by ISAR
will be not anymore compatible with a standard debian and this could be a
nasty surprise in some cases for some users.

The alternative is to repackage everything with xz parallel. Usually a
modern laptop has 8 pipes but I have the sensation that with -T 0 it counts
just the cores because on my machine spawn 4 not 8.

Best regards, R-

[1]
https://archlinux.org/news/now-using-zstandard-instead-of-xz-for-package-compression/

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