nixos/profiles/zramSwap.nix

   1 { lib, ... }:
   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 }