bug#65345: guix-pull --list-generations is slow

bug#65345: guix-pull --list-generations is slow

[Olivier Dion]

Hi,

Calling `guix-pull --list-generations' is very slow on my system with 37
generations.

$ time guix pull --list-generations > /dev/null
real    0m58.702s
user    1m8.418s
sys     0m1.527s

Also, it takes a lot of CPU (100% of a core).

$ guix describe:
  guix 7b2b0a5
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: 7b2b0a5e1d635fb0e3d2d3e9141ac27c2db644b5

From a search in pull.scm, I think that the culprit is in the
`channel-news-for-commit' procedure.

Thanks,

old
-- 
Olivier Dion
EfficiOS Inc.
https://www.efficios.com

bug#65345: guix-pull --list-generations is slow

[Simon Tournier]

Hi,

On Wed, 16 Aug 2023 at 15:29, Olivier Dion <odion@efficios.com> wrote:

> $ time guix pull --list-generations > /dev/null
> real    0m58.702s
> user    1m8.418s
> sys     0m1.527s

On my poor laptop, it’s the same (14 Generations):

        $ time guix pull --list-generations >/dev/null

        real	1m2.201s
        user	1m0.021s
        sys	0m2.482s

And note before it was worse. ;-)

        $ time guix pull --list-generations --details > /dev/null

        real	1m57.606s
        user	2m6.575s
        sys	0m5.608s


> From a search in pull.scm, I think that the culprit is in the
> `channel-news-for-commit' procedure.

Well, as pointers, we discussed some part of this issue in:

    https://issues.guix.gnu.org/53909
    https://issues.guix.gnu.org/54000

And as I said in these past discussions, because the default behaviour
is very slow for me, I barely use these options.  I do not know if it
can be optimized or if another option for bypassing the news part should
be added.


Cheers,
simon