> Perhaps you simply don't have enough garbage available for the collector
> to collect?  If you ask for 5 GiB, your system has 3 GiB free, and there
> is only 1 GiB of garbage, the best the collector can do is collect all
> the garbage (1 GiB) and leave you with just 4 GiB of free space.

Sorry for the sparse details, I forgot to mention that if I run `guix gc -F8GB`,
then I get 5-6GB back, so it _can_ remove that much garbage indeed! ;)
-- 
Pierre Neidhardt