[arch-general] Suggestion: switch to zstd -19 for compressing packages over xz

[Ralph Corderoy]

Hi Dan,

> > I hope your local authorities decide to give you real broadband in
> > the near future, however. :-)
>
> My situation is similar to Darren's:  My primary connection to the
> internet is through my cell phone carrier and a mobile WiFi hot spot.

I'm UK mainland, get about 580 KiB/s download, and pay per byte during
the day, which is why I try and get most package updates during the
toll-free midnight hours, but sometimes I need a new package and can't
delay.

> My vote, whether it has any weight or not, is for higher compression
> ratios at the expense of CPU cycles when decompressing; i.e., xz
> rather than zstd.

I'd also favour fewer bytes, but would suggest replacing xz with lzip as
xz has quite a few flaws in its file format.

    Xz format inadequate for long-term archiving
    https://www.nongnu.org/lzip/xz_inadequate.html

https://www.nongnu.org/lzip/lzip_benchmark.html#xz compares the two in
various ways, and explains how xz's -9 allocates double the dictionary
memory than lzma's and lzip's -9 and thus initially looks better unless
the playing field is levelled.

-- 
Cheers, Ralph.