max-jobs and parallel-builds

[Phil <phil@beadling.co.uk>]

Hi all,

Does guix-daemon option max-jobs
(https://guix.gnu.org/manual/en/guix.html#Invoking-guix_002ddaemon) dictate:

1. how many instances of "guix build" can be executed from the console in
tandem, or

2. how many steps/phases within a build can run in tandem, or

3. how many processes a command as part of the package description can
run (eg if I "invoke" a command like "make -j8" is it throttled?), or

4. How many guixbuildNN users it can use to perform an action - and if
this is the case what does this mean in terms of practical throughput?

Or is it something else?

Also when setting up an offload server
(https://guix.gnu.org/manual/en/guix.html#Daemon-Offload-Setup), it
looks to me like the machines.scm setting parallel-build dictates how
many builds will be potentially offloaded to each server - however how
does this interplay if at all with the setting of max-jobs on the
offload server?  For example if I restrict max-jobs on my offload server
to 1, but set the parallel-build on my main server to 4 - who wins?
Will the offload server build 1 or 4 builds in parallel?

Or do they not overlap at all because they mean slightly different things?

Thanks,
Phil.

From the docs - perhaps the distinction is "builds" and "build jobs" but
I'm not 100% clear:

parallel-builds (default: 1)

    The number of builds that may run in parallel on the machine.


--max-jobs=n
-M n

    Allow at most n build jobs in parallel. The default value is 1. Setting it to 0 means that no builds will be performed locally; instead, the daemon will offload builds (see Daemon Offload Setup), or simply fail.