Enable Zswap

[foldfree]

Marcan is recommending to use Zswap instead of Zram for devices that have under 24gb of ram because unified memory is conflicting with zram. See this reddit announcement

Below is a way to add zswap using theses settings as a reference:

./configuration.nix

  boot = {
    kernelParams = [
      "zswap.enabled=1"
      "zswap.compressor=zstd"
      "zswap.zpool=zsmalloc"
      "zswap.max_pool_percent=50"
    ];
  };

./hardware-configuration.nix

 swapDevices = [ {
    device = "/var/lib/swapfile";
    size = 16*1024;
  } ];

There might be a seamless solution via AppleSiliconsupport flake, though this is outside my area of expertise. Currently, Fedora Asahi uses LZ0 compression, but since zstd is already enabled in asahi-nixos kernel, I opted to use that instead.