cd1b48bc35
This allows you to use the Linux kernel's built-in compressed memory as swap space functionality. It is recommended to enable only for kernel 3.14 (which is when zram came out of the staging drivers area) or higher.
138 lines
3.9 KiB
Nix
138 lines
3.9 KiB
Nix
{ config, lib, pkgs, ... }:
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with lib;
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let
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cfg = config.zramSwap;
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devices = map (nr: "zram${toString nr}") (range 0 (cfg.numDevices - 1));
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modprobe = "${config.system.sbin.modprobe}/sbin/modprobe";
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in
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{
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###### interface
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options = {
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zramSwap = {
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enable = mkOption {
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default = false;
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type = types.bool;
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description = ''
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Enable in-memory compressed swap space provided by the zram kernel
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module. It is recommended to enable only for kernel 3.14 or higher.
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'';
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};
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numDevices = mkOption {
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default = 4;
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type = types.int;
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description = ''
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Number of zram swap devices to create. It should be equal to the
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number of CPU cores your system has.
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'';
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};
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memoryPercent = mkOption {
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default = 50;
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type = types.int;
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description = ''
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Maximum amount of memory that can be used by the zram swap devices
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(as a percentage of your total memory). Defaults to 1/2 of your total
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RAM.
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'';
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};
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priority = mkOption {
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default = 5;
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type = types.int;
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description = ''
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Priority of the zram swap devices. It should be a number higher than
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the priority of your disk-based swap devices (so that the system will
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fill the zram swap devices before falling back to disk swap).
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'';
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};
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};
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};
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config = mkIf cfg.enable {
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system.requiredKernelConfig = with config.lib.kernelConfig; [
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(isModule "ZRAM")
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];
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# Disabling this for the moment, as it would create and mkswap devices twice,
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# once in stage 2 boot, and again when the zram-reloader service starts.
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# boot.kernelModules = [ "zram" ];
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boot.extraModprobeConfig = ''
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options zram num_devices=${toString cfg.numDevices}
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'';
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services.udev.extraRules = ''
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KERNEL=="zram[0-9]*", ENV{SYSTEMD_WANTS}="zram-init-%k.service", TAG+="systemd"
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'';
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systemd.services =
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let
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createZramInitService = dev:
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nameValuePair "zram-init-${dev}" {
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description = "Init swap on zram-based device ${dev}";
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bindsTo = [ "dev-${dev}.swap" ];
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after = [ "dev-${dev}.device" "zram-reloader.service" ];
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requires = [ "dev-${dev}.device" "zram-reloader.service" ];
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before = [ "dev-${dev}.swap" ];
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requiredBy = [ "dev-${dev}.swap" ];
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serviceConfig = {
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Type = "oneshot";
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RemainAfterExit = true;
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ExecStop = "${pkgs.stdenv.shell} -c 'echo 1 > /sys/class/block/${dev}/reset'";
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};
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script = ''
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set -u
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set -o pipefail
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PATH=${pkgs.procps}/bin:${pkgs.gnugrep}/bin:${pkgs.gnused}/bin
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# Calculate memory to use for zram
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totalmem=$(free | grep -e "^Mem:" | sed -e 's/^Mem: *//' -e 's/ *.*//')
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mem=$(((totalmem * ${toString cfg.memoryPercent} / 100 / ${toString cfg.numDevices}) * 1024))
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echo $mem > /sys/class/block/${dev}/disksize
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${pkgs.utillinux}/sbin/mkswap /dev/${dev}
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'';
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restartIfChanged = false;
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};
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in listToAttrs ((map createZramInitService devices) ++ [(nameValuePair "zram-reloader"
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{
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description = "Reload zram kernel module when number of devices changes";
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serviceConfig = {
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Type = "oneshot";
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RemainAfterExit = true;
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ExecStartPre = "${modprobe} -r zram";
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ExecStart = "${modprobe} zram";
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ExecStop = "${modprobe} -r zram";
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};
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restartTriggers = [ cfg.numDevices ];
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restartIfChanged = true;
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})]);
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swapDevices =
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let
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useZramSwap = dev:
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{
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device = "/dev/${dev}";
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priority = cfg.priority;
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};
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in map useZramSwap devices;
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};
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}
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