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.

[docbobo]

FYI: My kernel log says: "compressor zstd not available, using default lzo" That's on 6.12.4-asahi...

[sioodmy]

FYI: My kernel log says: "compressor zstd not available, using default lzo" That's on 6.12.4-asahi...

same for me

[sioodmy]

@docbobo I found a solution https://github.com/sioodmy/dotfiles/commit/c391b65bd39f3aab11865920b1afeab8aae30459

[waltmck]

I'm still seeing compressor zstd not available, using default lzo on 6.12.12-asahi.

@docbobo I found a solution sioodmy/dotfiles@c391b65

This is not a solution, you are switching from zswap to zram (these aren't the same thing). zstd is probably faster than lzo for most memory-intensive workloads at this point given how fast Apple Silicon is, so it would be very nice to have this in the kernel.

[waltmck]

zstd is included in #341, which should close this issue if merged.