Re: When substitute download + decompression is CPU-bound

[Jonathan Brielmaier]

Super interesting findings!

On 14.12.20 23:20, Ludovic Courtès wrote:
>    2. Use Zstd like all the cool kids since it seems to have a much
>       higher decompression speed: <https://facebook.github.io/zstd/>.
>       630 MB/s on ungoogled-chromium on my laptop.  Woow.

Not only decompression speed is fast, compression is as well:

size    file                    time for compression (lower is better)
335M    uc.nar

104M    uc.nar.gz
                  8
71M     uc.nar.lz.level9        120
74M     uc.nar.lz.level6
         80
82M     uc.nar.lz.level3         30
89M     uc.nar.lz
.level1  16
97M     uc.nar.zst                1

So I am bought by zstd, as user and as substitution server care taker :)

For mobile users and users without internet flatrates the increased nar
size is a problem.
Although I think the problem here is not bewtween gzip, lzip and zstd.
It's the fact that we completely download the new package even if's just
some 100 lines of diffoscope diff[0]. And most of them is due to the
change /gnu/store name...

[0] diffoscope --max-diff-block-lines 0
/gnu/store/zvcn2r352wxnmq7jayz5myg23gh9s17q-icedove-78.5.1
/gnu/store/dzjym6y7b9z4apgvvydj9lf0kbaa8qbv-icedove-78.5.1
lines: 783
size: 64k