Kernel & Performance

Kernel Package

The laptop runs the CachyOS kernel from the Chaotic-Nyx repository:

boot.kernelPackages = inputs.chaotic.legacyPackages."x86_64-linux".linuxPackages_cachyos;

An alternative Zen kernel option is commented out:

# boot.kernelPackages = pkgs.linuxKernel.packages.linux_zen;

The CachyOS kernel includes scheduler optimisations (BORE scheduler), improved desktop responsiveness, and additional hardware support. Binary packages are provided by the Chaotic-Nyx cache, avoiding local compilation.

Kernel Parameters

boot.kernelParams = [
  # Power saving
  "acpi=force"
  "pcie_aspm=force"
  "nowatchdog"
  "nmi_watchdog=0"
  "amd_pstate=active"
  "rcutree.enable_rcu_lazy=1"

  # Catppuccin Mocha TTY colours
  "vt.default_red=..."
  "vt.default_grn=..."
  "vt.default_blu=..."
];

Parameter	Effect
amd_pstate=active	Use the AMD P-State EPP driver for CPU frequency scaling
pcie_aspm=force	Force Active State Power Management on PCIe links
nowatchdog + nmi_watchdog=0	Disable hardware and NMI watchdogs (power saving)
rcutree.enable_rcu_lazy=1	Lazy RCU callbacks to reduce wakeups
acpi=force	Force ACPI even if firmware reports issues
vt.default_*	Set Catppuccin Mocha colour scheme for Linux virtual terminals

Blacklisted Modules

boot.blacklistedKernelModules = [ "sp5100_tco" ];

The sp5100_tco watchdog timer module is blacklisted as it is not needed and can cause unnecessary wakeups.

sysctl Tuning

boot.kernel.sysctl = {
  "kernel.kexec_load_disabled" = 1;
  "vm.swappiness" = 0;
  "vm.vfs_cache_pressure" = 50;
  "vm.dirty_bytes" = 268435456;          # 256 MB
  "vm.dirty_writeback_centisecs" = 1500; # 15 seconds
  "vm.dirty_background_bytes" = 67108864; # 64 MB
};

sysctl	Value	Rationale
kexec_load_disabled	1	Prevent kexec after boot (security)
vm.swappiness	0	No swap is configured
vm.vfs_cache_pressure	50	Prefer keeping VFS caches over reclaiming memory
vm.dirty_bytes	256 MB	Maximum dirty memory before synchronous writeback
vm.dirty_background_bytes	64 MB	Background writeback threshold
vm.dirty_writeback_centisecs	1500	Flush dirty pages every 15 seconds

These VM tunables reduce write frequency to the NVMe SSD, which helps with both SSD longevity and battery life.

Power Management (TLP)

TLP is configured in tlp.nix with separate profiles for AC and battery:

CPU

Setting	AC	Battery
Driver mode	active	active
Scaling governor	performance	powersave
Energy/perf policy	performance	balance_power
CPU boost	Enabled	Disabled
Platform profile	performance	low-power

GPU (Radeon)

Setting	AC	Battery
Power profile	default	low
DPM state	performance	battery
ABM level	0	0

Power States

Setting	AC	Battery
Memory sleep	deep	deep
PCIe ASPM	default	powersupersave

Disabling CPU boost on battery is an aggressive but effective measure -- it significantly reduces power consumption at the cost of peak single-thread performance.

Audio

PipeWire is the audio stack, configured in pipewire.nix:

services.pipewire = {
  enable = true;
  alsa.enable = true;
  jack.enable = true;
  pulse.enable = true;
  wireplumber.enable = true;
};

The camera is explicitly disabled in WirePlumber:

wireplumber.extraConfig."10-disable-camera" = {
  "wireplumber.profiles".main."monitor.libcamera" = "disabled";
};

Bluetooth

hardware.bluetooth = {
  enable = true;
  powerOnBoot = false;  # Don't power on at boot to save energy
};

Bluetooth hardware is available but not powered on at boot. Use bluetui to manage connections.

Graphics

hardware.graphics.enable = true;

This enables Mesa and the AMD Radeon driver stack for hardware-accelerated graphics under Wayland.