[arch-dev-public] RFC: (devtools) Changing default compression method to zstd

Evangelos Foutras evangelos at foutrelis.com
Mon Mar 25 02:46:44 UTC 2019

On Mon, 25 Mar 2019 at 02:47, Robin Broda via arch-dev-public
<arch-dev-public at archlinux.org> wrote:
> What's unclear to me is the difference between zstd -T0 and zstdmt, however.

zstdmt is an alias/shortcut for "zstd -T0".

> I do think that at -19+, memory usage becomes a bigger issue.
> The difference between -18 and -19 on cuda is almost a gigabyte!

The large memory usage comes from running it with 24 cores. It is fair
to assume that boxes with high core counts can spare an extra 1G of

Compressing cuda using 4 cores shows:

-18: 613 MiB RSS / 4:18 elapsed time
-19: 746 MiB RSS / 5:24 elapsed time

(With 8 threads, memory usage is 1014 MiB with -18 and 1270 MiB with -19.)

Memory usage is fine in my opinion. Compression time is a bigger
concern (increased by 25%) for what seems to be 0.25% smaller package
size for cuda (and about 0.5% for chromium). But for most packages the
time difference would be a few seconds and the space savings, however
tiny, would apply to the whole archive. So I still believe -19 is
preferable since decompression speed is the same for both levels.

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