nixos/profiles/systems/zramSwap.nix

   1 { pkgs, lib, config, ... }:
   2 with lib;
   3 {
   4 zramSwap = {
   5   enable = true;
   6   algorithm = mkDefault "zstd";
   7   # There is little point creating a zram greater
   8   # than twice the size of memory.
   9   memoryPercent = mkDefault 150;
  10   # Linux supports multithreaded compression for 1 device since 3.15.
  11   # See https://lkml.org/lkml/2014/2/28/404 for details.
  12   swapDevices = mkDefault 1;
  13 };
  14
  15 boot.kernel.sysctl = {
  16   # Increase cache pressure, which increases the tendency of the kernel to
  17   # reclaim memory used for caching of directory and inode objects. You will use
  18   # less memory over a longer period of time. The performance hit is negated by
  19   # the downside of swapping sooner.
  20   "vm.vfs_cache_pressure" = mkDefault 500;
  21
  22   # Increasing how aggressively the kernel will swap memory pages since we are
  23   # using ZRAM first.
  24   "vm.swappiness" = mkDefault 100;
  25
  26   # Background processes will start writing right away when it hits the 1% limit
  27   "vm.dirty_background_ratio" = mkDefault 1;
  28
  29   # The system won’t force synchronous I/O until it gets to 50% dirty_ratio.
  30   "vm.dirty_ratio" = mkDefault 50;
  31 };
  32 }