nixos/profiles/zswap.nix

   1 # Documentation: https://www.kernel.org/doc/html/latest/admin-guide/mm/zswap.html
   2 # Explanation: https://chrisdown.name/2026/03/24/zswap-vs-zram-when-to-use-what.html
   3 {
   4   config,
   5   lib,
   6   ...
   7 }:
   8 let
   9   cfg = config.zswap;
  10 in
  11 {
  12   options.zswap = {
  13     enable = lib.mkEnableOption "zswap compressed swap cache" // {
  14       default = true;
  15     };
  16
  17     max_pool_percent = lib.mkOption {
  18       type = lib.types.int;
  19       default = 50;
  20       description = "Maximum percentage of RAM to use for the zswap pool.";
  21     };
  22   };
  23
  24   config = lib.mkIf cfg.enable {
  25     boot = {
  26       kernelParams = [
  27         "zswap.enabled=1"
  28         "zswap.compressor=zstd"
  29         "zswap.max_pool_percent=${toString cfg.max_pool_percent}"
  30         "zswap.shrinker_enabled=1"
  31         "zswap.zpool=zsmalloc"
  32       ];
  33       initrd.kernelModules = [
  34         "zsmalloc"
  35         "zstd"
  36       ];
  37     };
  38
  39   };
  40 }