Post #2353291
2026-05-06 12:46 UTC
@Mehrad@fosstodon.org To be clear, setting the cores flag `-c` is for limiting the resources, not for granting more, each derivation is built with the cores set to all the available ones.
It's for situations where you may want to spread the load between a few derivations. For example, if you are building `gcc@12` and `gcc@13`, you may want to do `guix build -c 25 -M 2 ...`, given you have enough cores available.
I'm assuming that GCC caps the builds at 24 cores (I don't recall if that's true).
Replies (1)
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@futurile@mastodon.social 2026-05-06 16:19
@shepherd@fosstodon.org @Mehrad@fosstodon.org Yeah it makes sense when you _know_ what it's doing, but it's slightly counter-intuitive. The --max-jobs is for how many builds the guix daemon will do in parallel. If you are building lots of small libraries then it makes sense to use it. If you are building one big thing, then it won't help. The --cores assigns the number of cores PER BUILD. So if you have 4 builds (--max-jobs 4), and you set --cores 2, then it will use 8 in total.