reNixos/viola/systemd/slices/user-slice.nix

{...}: {
  systemd = {
    slices = {
      user = {
        sliceConfig = {
          ManagedOOMSwap = "kill";
          ManagedOOMMemoryPressure = "kill";
          ManagedOOMMemoryPressureLimit = "40%";
          ManagedOOMMemoryPressureDurationSec = 0;
        };
      };
    };
  };
}