[bug#29928] [PATCH 0/5] Optimize profile hooks

[ludo@gnu.org (Ludovic Courtès)]

Hi,

iyzsong@member.fsf.org (宋文武) skribis:

> ludo@gnu.org (Ludovic Courtès) writes:

[...]

>>> One drawback is 'guix package --dry-run' no longer report the derivations of
>>> profile hooks, and the derivation of profile it reports is not the real one.
>>> Addition files will be built when the profiles hooks are run.
>>
>> FWIW I’m not entirely convinced by the approach.
>
> Well.. these patches modify package hooks to:
>
> 1. build all manifest inputs first.
>
> 2. filter manifest inputs to get interested ones.
>
> 3. run hook with its interested inputs.
>
> I think reducing the inputs of hook from the whole manifest to its
> interested ones is the only way to avoid unneeded reruns.

Agreed.

>> As discussed earlier, I’d like to experiment with a notion of “build
>> rounds”: the first round would build a profile without any hooks, the
>> second round would, depending on what the profile contains, rebuild it
>> with certain hooks.
>
> I think "build rounds" would improve the UI/UX, and by changing inputs
> from manifest inputs to a built profile, it would simply the current
> implementations of profile hooks, but it won't avoid unneeded reruns
> compare to the filtered interested inputs way.
>
> Is my understanding correct?

A “build round” is something that computes derivations based on the
output of previously-built derivations.  So it’s just another way to
structure steps 1/2/3 above; it should not reduce expressivity.

Build rounds would allow us to ensure that ‘build-derivations’ is not
called right in the middle of Guix, and is instead always under the
control of the “top level”.

Ludo’.