Re: Performance improvements

["Ludovic Courtès" <ludo@gnu.org>]

Hi!

Some more improvements come from these commits:

  ac19950507 gnu: bootstrap: Cache the 'bootstrap-executable' origins.
  5166d02730 gnu: bootstrap: 'bootstrap-origin' preserves eq?-ness when no changes are made.
  d727a9343d derivations: Don't memoize 'derivation->bytevector'.
  f5fca9a82c gexp: Cache the module to derivation mappings.
  c57e417eff store: Allow objects in the cache to be inserted and search for with 'equal?'.
  f58b45350b gexp: Add 'imported+compiled-modules'.
  f726f6f802 derivations: 'build-expression->derivation' caches its module derivations.
  cf7648f882 derivations: Introduce 'imported+compiled-modules'.

This caches the module-to-derivation mapping, which wasn’t cached until
now.

Overall the goal is to have the high-level caches work nicely (the
“object cache” in particular), rendering the low-level caches (such as
the ‘add-data-to-store’ cache) potentially useless.  This is beneficial
because a cache hit on the object cache saves more CPU time than a cache
hit on a low-level cache.

Ludovic Courtès <ludo@gnu.org> skribis:

> $ time guix build libreoffice -nd
> /gnu/store/8drmbhsrayr2j5lkvrwq37rg8g06hgsw-libreoffice-6.1.5.2.drv
>
> real    0m2.142s
> user    0m2.323s
> sys     0m0.082s
> $ guix describe
> Generacio 110   Oct 14 2019 08:43:33    (nuna)
>   guix bd04fe8
>     repository URL: https://git.savannah.gnu.org/git/guix.git
>     branch: master
>     commit: bd04fe878627a14533d908ccdf5b906050d6e0a4

And now:

--8<---------------cut here---------------start------------->8---
$ time /tmp/new/bin/guix build libreoffice -nd
/gnu/store/ibzap0v1c367h0j2mdd2jmlsfx9jplfb-libreoffice-6.1.5.2.drv

real    0m1.658s
user    0m1.699s
sys     0m0.073s
$ /tmp/new/bin/guix describe
Generacio 1     Oct 28 2019 00:03:05    (nuna)
  guix 271b3c9
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: 271b3c9d16f8880f4a27b52a615cdec611322fae
--8<---------------cut here---------------end--------------->8---

Ludo’.