Re: 02/02: gnu: next: Compress the executable.

[Maxim Cournoyer]

Hi Pierre,

The problem where using Btrfs compression wasn't effective for
/gnu/store (or anything else) was caused by the init RAM disk not
honoring options on the root file system.

I could notice about this when running just 'mount', and the options I
gave in my config.scm were missing.

Since this was fixed with commit
900ef20b1da66ad71145082c883dc12f31fafa54, retesting compsize gives
better results :-).

Here are the results when using the zstd compression (default level, 3)
on the /gnu/store of this relatively new machine:

--8<---------------cut here---------------start------------->8---
sudo compsize /gnu/store
Password: 
Processed 1166359 files, 379224 regular extents (1025522 refs), 543008 inline.
Type       Perc     Disk Usage   Uncompressed Referenced  
TOTAL       65%       30G          46G         107G       
none       100%       23G          23G          52G       
zstd        29%      6.8G          22G          55G
--8<---------------cut here---------------end--------------->8---

We see that there's 23 GiB that aren't compressed.  I attribute those to
already compressed files in the store, that Btrfs doesn't consider worth
compressing.

For the compressible files, Zstd achieves an impressive 29% compression
ratio, while overall the compression ration is 65%.

The last column shows how much space a traditional file system would
need to store the content referenced.

Maxim