[arch-general] [arch-announce] Moving to Zstandard images by default on mkinitcpio

mpan archml-y1vf3axu at mpan.pl
Sat Feb 20 20:25:21 UTC 2021

> I benchmarked it on my mkinitcpio image, and zstd with mkinitcpio's […]
   Though you have benchmarked a wrong thing. It’s decompression time 
that matters here, not compression. The image is compressed to make it 
load faster during boot and that’s the important metric here.

   I did my own benchmarks, though. On my decade-old system lz4 is still 
faster than zstd during decompression: 0.117415s (s=0.005948) vs 
0.229915s (s=0.027075s). However, looking deeper, the time spent in 
syscalls suggests a different thing. lz4, having a bigger file, spent 
0.049630s (s=0.007560s), while zstd 0.038125s (s=0.011196). That is not 
enough to claim they are different or zstd is better than lz4. But you 
can see in which direction it goes, in particular if one assumes a 
faster CPU+RAM.

   Methodology: image compressed using lz4 and zstd (same options as 
Geert Hendrickx has used). Copied to 50 files to create a batch, flushed 
to disk. Decompression of each file into /dev/null timed separately with 
caches dropped between each batch. Each batch ran 4 times for the total 
sample size of 200 for each group.

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