Can I set the nice level for Nix build processes?

Help
1

I have found these two settings: NixOS Search - Loading...

{
  nix.daemonNiceLevel = 19;
  nix.daemonIONiceLevel = 7;
}

But that doesn’t actually make the builds themselves use these nice values from what I’ve observed.
It appears to affect only the nix-daemon process itself.

Is there a way to also set nice for all build processes Nix daemon spawns?

2

if the nix daemon is spawning the build, in theory the sub process should inherit the parents nice value… unless its spawning the builder in such a way that it’s not honouring this.

it also may/may not - be effected by autogroup … I’ll look into this later when i get a min to try it out.

autogroup is enabled by default on nix/OS …so it maybe a contributing factor?

3

Maybe I was checking this incorrectly but when I looked at htop the only process with nice value of 19 was nix-daemon.