Hi younger self! l...@gnu.org (Ludovic Courtès) skribis:
> As of right now (v0.9.0-2007-g66a30a3), ‘graft-derivation’ works either by: > > 1. Fetching substitute info about the things being built so that it > can determine its references, which in turns allows it to determine > whether they need to be grafted. > > 2. Building stuff, as a last resort, so that it can determine its > references. > > Case #1 is hopefully going to be the most common. > > The problem with #1 is that when building a profile, we do one > ‘package-derivation’ call for each package in the profile, which > translates in one ‘graft-derivation’ call for each relevant package¹, > which translates into one ‘references/substitutes’ call for each. > > Concretely, what this means is this: > > $ guix package -u > substitute: updating list of substitutes from 'http://mirror.guixsd.org'... > 100.0% > substitute: updating list of substitutes from 'http://mirror.guixsd.org'... > 100.0% > substitute: updating list of substitutes from 'http://mirror.guixsd.org'... > 100.0% > substitute: updating list of substitutes from 'http://mirror.guixsd.org'... > 100.0% > substitute: updating list of substitutes from 'http://mirror.guixsd.org'... > 100.0% > substitute: updating list of substitutes from 'http://mirror.guixsd.org'... > 100.0% > substitute: updating list of substitutes from 'http://mirror.guixsd.org'... > 100.0% > […] > The following files would be downloaded: > > Each of the initial “updating list” message corresponds to an HTTP > request for a single narinfo file, which can take around 1 second. This is finally fixed with commit 710854304b1ab29332edcb76f3de532e0724c197, as discussed earlier this week¹. \o/ The solution is simpler and more orthogonal than what was envisioned earlier in this thread, which is nice. I also potentially addresses other uses of “dynamic dependencies” elsewhere in the code base, such as ‘remote-eval’ calls in ‘guix deploy’. Feedback welcome! Ludo’. ¹ https://lists.gnu.org/archive/html/guix-devel/2020-03/msg00337.html
