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

[Darren Wu]

I have 4Mbps (512KBytes/s) 'broad'band and i7-6500U CPU. I wanna cry.

On Sat, Mar 16, 2019, 13:38 Adam Fontenot via arch-general <
arch-general at archlinux.org> wrote:

> Hi,
>
> It's now been about half a year since support for zstd landed in our
> packaging tools. I've been quietly using it for all my locally built
> packages since then with no issues. I think it would be worthwhile to
> have a discussion about whether to use zstd for officially built
> packages. Here is a brief summary of negatives and positives:
>
> Negatives:
>  * Changing things takes time and might break someone's workflow.
>  * Zstd -19 results in slightly larger files than xz -6 (default).
>
> Positives:
>  * Change would be invisible to most users.
>  * Would keep Arch Linux on top of the latest in packaging tech.
>  * Updating would be much faster for most users.
>
> To expand on that last point: for reasonably fast connections, the
> additional time required to decompress xz compressed packages means
> that updating can actually take more time than it would for packages
> that are not compressed at all! Because zstd is designed to have very
> fast decompression, for a wide range of modern broadband connections
> zstd -19 is the fastest algorithm to download and decompress. For
> example, check out this compression test (with the Mozilla dataset):
> https://quixdb.github.io/squash-benchmark/unstable/
>
> Or look at my local test with the most recent Firefox package:
>
> Tool      Compression time  Size   Time to DL (100 Mbps) + decompress
> xz -6     5m 53s            49 MB  0m 21s
> zstd -19  6m 0s             53 MB  0m 6s
>
> So while xz and zstd compress in about the same amount of time and
> result in files of similar size, from the user's standpoint zstd
> results in much faster updates. Multiply this by a few hundred packages
> and you have a pretty substantial effect.
>
> I look forward to discussing this with you all.
>
> Cheers,
> Adam
>