nixos-config/modules/programs/gamemode/default.nix

{ ... }:

{
  config.programs.gamemode = {
    enable = true;
    enableRenice = true;
    settings = {
      general = {
        reaper_freq = 5;
        desiredgov = "performance";
        igpu_desiredgov = "powersave";
        igpu_power_threshold = 0.3;

        softrealtime = "on";
        renice = 0;
        ioprio = 0;
        inhibit_screensaver = 1;
      };
    };
  };
}