Re: Staging branch [substitute availability]

[Mathieu Othacehe <othacehe@gnu.org>]

Hello Leo,

> ------
> master branch
> aarch64: 66% 
> x86_64: 93% 
> i686: 85%
> armhf: 51%
>
> staging branch
> aarch64: 44% 
> x86_64: 80% 
> i686: 60%
> armhf: 30%
> ------

Thanks for the figures. I can comment on some stuff. Until recently it
was hard to monitor the build farm status because there were a lot of
contention at the main guix-daemon level.

Since the introduction of the "wip-offload" branch on Cuirass, the
situation has much improved. The workers are constantly building. For
now we are building three specifications:

* guix-modular-master
* guix-master
* staging

for x86_64, i686 and aarch64. If you look at the "Pending builds" chart
here[1], you will see that the CI is barely catching up. That's because
the "aarch64" emulated builds are incredibly slow, and monopolizing all
the build resources.

I deliberately chose to put armhf aside until I have a clearer view of
the situation.

Now, how to move on?

First, I still need to connect the four overdrives machine to the new
Cuirass remote building mechanism, and I would need some help for that
(asked on guix-sysadmins). But, I'm not sure it will much improve the
situation.

Longer term, we need to figure out a better solution. It's now
obvious that we do not have the computation power to build all our
branches for 5 different architectures, relying heavily on emulation for
armhf and aarch64. Anyone knows how Nix deals with that?

I guess that other major distributions provide only cross-compiled
packages for those architectures, but I don't think it's an option for
us, Ludo?

Thanks,

Mathieu

[1]: https://ci.guix.gnu.org/metrics