bug#41702: `guix environment` performance issues

[Ludovic Courtès]

Hi,

Lars-Dominik Braun <ldb@leibniz-psychology.org> skribis:

> grafting is still a performance issue imo. Compare for example:

Agreed.  The fix in 58bb833365db4e8934a386497d5b00a063cfd27d is
incomplete: we’re still potentially doing things several times.

> $ time guix environment --ad-hoc  --search-paths r-learnr
> guix environment --ad-hoc --search-paths r-learnr  5,90s user 0,09s system 
> 210% cpu 2,844 total
> $ time guix environment --ad-hoc  --search-paths r-learnr --no-grafts
> guix environment --ad-hoc --search-paths r-learnr --no-grafts  2,03s user 
> 0,08s system 164% cpu 1,277 total

Here’s what I get over a local socket:

--8<---------------cut here---------------start------------->8---
ludo@ribbon ~/src/guix$ time guix environment --ad-hoc  --search-paths r-learnr 
--no-grafts
export 
PATH="/gnu/store/wkhd1fnmg1q30g21bfn5jprz24m041w6-profile/bin${PATH:+:}$PATH"

real    0m1.790s
user    0m1.928s
sys     0m0.102s
ludo@ribbon ~/src/guix$ time guix environment --ad-hoc  --search-paths r-learnr
export 
PATH="/gnu/store/pwzrpzdbli2561f2yq70kljywn93h5w6-profile/bin${PATH:+:}$PATH"

real    0m3.820s
user    0m4.954s
sys     0m0.105s
--8<---------------cut here---------------end--------------->8---

Ludo’.