nixos/profiles/systems/zramSwap.nix

   1 { pkgs, lib, config, ... }:
   2 {
   3 zramSwap = {
   4   enable = true;
   5   algorithm = lib.mkDefault "zstd";
   6   memoryPercent = lib.mkDefault 50;
   7   # Linux supports multithreaded compression for 1 device since 3.15.
   8   # See https://lkml.org/lkml/2014/2/28/404 for details.
   9   swapDevices = lib.mkDefault 1;
  10 };
  11
  12 boot.kernel.sysctl = {
  13   # Increase cache pressure, which increases the tendency of the kernel to
  14   # reclaim memory used for caching of directory and inode objects. You will use
  15   # less memory over a longer period of time. The performance hit is negated by
  16   # the downside of swapping sooner.
  17   "vm.vfs_cache_pressure" = lib.mkDefault 500;
  18
  19   # Increasing how aggressively the kernel will swap memory pages since we are
  20   # using ZRAM first.
  21   "vm.swappiness" = lib.mkDefault 100;
  22
  23   # Background processes will start writing right away when it hits the 1% limit
  24   "vm.dirty_background_ratio" = lib.mkDefault 1;
  25
  26   # The system won’t force synchronous I/O until it gets to 50% dirty_ratio.
  27   "vm.dirty_ratio" = lib.mkDefault 50;
  28 };
  29 }