On Mon, 25 Mar 2019 at 02:47, Robin Broda via arch-dev-public <arch-dev-public@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 RAM. 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.