Sane cpu frequency governor selection on NixOS

1

Currently the default kernel build sets CPU_FREQ_DEFAULT_GOV_PERFORMANCE=y, then nixos-generate-config.pl overrides this with its own defaults (that is ondemand or powersave).

Is there a reason we don’t just use the upstream kernel defaults?
On e.g. 5.7 upstream will default to schedutil on newer intel platforms. I don’t quite get why we have this convoluted dance of overriding defaults.

2

The current setting dates back to 2015. Maybe this should be revised, such that the governor is no longer defined automatically anywhere in nixpkgs, that is:

  • common-config.nix no longer defines a default for the option
  • nixos-generate-config no longer generates a cpufreq governor setting
  • the NixOS option defaults to null

However, it’s not entirely clear to me if that will result in sensible behaviour after reading linux/Documentation/admin-guide/pm/cpufreq.rst — which doesn’t mention what the default is. While the commit you mentioned does update the default for the config option definition, the current x86_64 defconfig (linux/arch/x86/configs/x86_64_defconfig) suggests that it will default to the userspace governor, which is no more sensible than performance IMHO.