Optimizing ‘guix package’

[Ludovic Courtès]

Mark H Weaver <address@hidden> skribis:

> * Although I can now run union-build in 2 minutes, another full minute
>   is spent in 'display-search-paths',

Commit 27c6845 optimizes that (50%!).

The problem is that currently this is an inherently inefficient
operation: search path information is not stored in the manifest, so
‘search-path-environment-variables’ has to look up the package
corresponding to each manifest entry to find out what the search path
variables are.  That involves traversing the module tree, which does a
lot of I/O (this is OKish on an SSD, but much less on a real hard disk.)

Perhaps eventually we could store search path info in manifest entries.

Ludo’.