Hi, On 24-03-19, Robin Broda via arch-dev-public wrote:
So, TL;DR, the benefits of `zstd -c -T0 -18 -` over `xz -c -z -` are: - Massive speed gain in compression - Massive speed gain in decompression - Stable, reproducible multithreading The speed gain in decompression substantially increases pacman's package installation speed.
Interesting results, thanks! Just one detail: your results for -19, -20 and -21 are identical because apparently zstd needs an additional flag (--ultra) to "unlock" the higher compression levels: zstd -c -T0 -20 - Warning : compression level higher than max, reduced to 19 Also, I see you did not test zstd with a small number of cores: can you add e.g. -T1, -T2 and -T4 to the comparison? It would give a more realistic idea of what to expect when building on a typical machine, as opposed to dragon ;) In my tests, using less threads also decreased memory usage when compressing (35% less memory when switching from -T2 to -T1). For decompression, it seems that both xz and zstd run single-threaded, so there's not much to think about (zstd is just incredibly fast). In any case, I support this change! Baptiste