guix --container is RAM hungry

[Edouard Klein <edou@rdklein.fr>]

Dear Guixers,

I'm a huge fan of guix --container, and I created a system to use those
by default for network services. But the VPS these services run on has
only 2GB of RAM, and I just realized that a container, by default,
requires at least 200MB.

Try it:
guix shell time which -- bash -c "$(which time) -v guix shell
--container"

Then Ctrl-D, and look for this line:
	Maximum resident set size (kbytes): 291300

291MB of RAM to run bash.


By contrast, removing the --container option from above yields:
	Maximum resident set size (kbytes): 64496

64MB, still a lot, but I can live with that.

I tried various calls to unshare, but got no significant increase of
RAM.

From an outsider's point of view, the --container option is a wrapper
for unshare, and the dependency resolution is done by guix shell with
or without the --container option, so I don't understand where the RAM
explosion come from.
I mean no implication that '--container' is simple or trivial to
implement, I just wrestled with namespaces for a few weeks and I know
they're a pain, to stay polite. I'm thankful for the tool and would like
to use it more, but I can't in its current state.


Any ideas ?

Thanks in advance,

Edouard.