Does --no-substitutes save bandwidth?

Does --no-substitutes save bandwidth?

[Luther]

I've installed Guix 0.2 on my Ubuntu system. As I type this, I'm using
it to install gcc. If all goes well, I hope to soon install Trisquel as
my base system with Guix as a package manager.

I'm trying to save as much bandwidth as possible, so I started the
daemon with --no-substitutes. But it occurred to me that binaries might
not be much bigger than source tarballs, even with documentation. What
do you guys think? Would --no-substitutes be generally useful for saving
bandwidth?

Luther

Re: Does --no-substitutes save bandwidth?

[Ludovic Courtès]

Luther <lutheroto@gmail.com> skribis:

> I've installed Guix 0.2 on my Ubuntu system. As I type this, I'm using
> it to install gcc. If all goes well, I hope to soon install Trisquel as
> my base system with Guix as a package manager.

Nice.  Welcome!  :-)

> I'm trying to save as much bandwidth as possible, so I started the
> daemon with --no-substitutes. But it occurred to me that binaries might
> not be much bigger than source tarballs, even with documentation. What
> do you guys think? Would --no-substitutes be generally useful for saving
> bandwidth?

Good question.

For GCC 4.8.0, the bzip2’d “Nix archive” (which is the format under
which binaries from hydra.gnu.org are served[*]) takes 25 MiB on x86_64,
whereas gcc-4.8.0.tar.bz2 takes 83 MiB.

Then one should also look at the size of the closure of the package of
interest.  Often, packages have a lot of build-time dependencies, and
their run-time dependencies are just a small subset thereof.

So if all you want is to install GNU Hello, you’ll have the choice
between downloading binaries of Hello and libc, and downloading the
source tarballs of GCC, Binutils, glibc, GMP, MPFR, MPC, etc. etc., just
to build all the chain leading to GNU Hello.

Hmm, the most accurate answer may well be “it depends”.  :-)

Thanks,
Ludo’.

[*] Can be obtained with ‘nix-store --export
    /nix/store/53fv51m204zhkyfrkkacjyhm2h1k4xad-gcc-4.8.0 | bzip2’ or
    the API in (guix nar).