bug#49439: grafts cause “guix environment” to get killed with OOM

[Ludovic Courtès]

Hello!

Ludovic Courtès <ludo@gnu.org> skribis:

> I added counters and ‘pk’ calls in ‘map/accumulate-builds’ & co. to see
> what happens.  AFAICS, a cutoff as in the attached patch does the job.
> It’s a basic heuristic to avoid unbounded growth, at the expense of
> possibly reduced accumulation.  For example, here’s the effect on my
> user profile with 300+ packages:

Pushed as fa81971cbae85b39183ccf8f51e8d96ac88fb4ac.

I saw your message on IRC, Sarah; note that because grafts are “dynamic
dependencies” (they depend on previous build results), we cannot know in
advance which grafts we’re going to build, so there’s necessarily at
least a second phase during which grafts get built.  See
<https://guix.gnu.org/en/blog/2020/grafts-continued/> for background.

Thanks!

Ludo’.