nixos/zram: use zram-generator
This commit is contained in:
Nick Cao
parent
73b9fb8afa
commit
3d26221082
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@ -1,45 +1,27 @@
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{ 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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# don't set swapDevices as mkDefault, so we can detect user had read our warning
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# (see below) and made an action (or not)
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devicesCount = if cfg.swapDevices != null then cfg.swapDevices else cfg.numDevices;
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devices = map (nr: "zram${toString nr}") (range 0 (devicesCount - 1));
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modprobe = "${pkgs.kmod}/bin/modprobe";
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warnings =
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assert cfg.swapDevices != null -> cfg.numDevices >= cfg.swapDevices;
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flatten [
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(optional (cfg.numDevices > 1 && cfg.swapDevices == null) ''
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Using several small zram devices as swap is no better than using one large.
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Set either zramSwap.numDevices = 1 or explicitly set zramSwap.swapDevices.
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Previously multiple zram devices were used to enable multithreaded
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compression. Linux supports multithreaded compression for 1 device
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since 3.15. See https://lkml.org/lkml/2014/2/28/404 for details.
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'')
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];
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devices = map (nr: "zram${toString nr}") (lib.range 0 (cfg.swapDevices - 1));
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in
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{
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imports = [
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(lib.mkRemovedOptionModule [ "zramSwap" "numDevices" ] "Using ZRAM devices as general purpose ephemeral block devices is no longer supported")
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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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enable = lib.mkOption {
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default = false;
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type = types.bool;
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type = lib.types.bool;
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description = lib.mdDoc ''
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Enable in-memory compressed devices and swap space provided by the zram
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kernel module.
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@ -49,29 +31,18 @@ in
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'';
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};
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numDevices = mkOption {
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default = 1;
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type = types.int;
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description = lib.mdDoc ''
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Number of zram devices to create. See also
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`zramSwap.swapDevices`
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'';
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};
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swapDevices = mkOption {
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default = null;
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swapDevices = lib.mkOption {
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default = 0;
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example = 1;
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type = with types; nullOr int;
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type = lib.types.int;
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description = lib.mdDoc ''
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Number of zram devices to be used as swap. Must be
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`<= zramSwap.numDevices`.
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Default is same as `zramSwap.numDevices`, recommended is 1.
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Number of zram devices to be used as swap, recommended is 1.
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'';
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};
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memoryPercent = mkOption {
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memoryPercent = lib.mkOption {
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default = 50;
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type = types.int;
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type = lib.types.int;
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description = lib.mdDoc ''
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Maximum total amount of memory that can be stored in 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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@ -80,9 +51,9 @@ in
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'';
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};
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memoryMax = mkOption {
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memoryMax = lib.mkOption {
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default = null;
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type = with types; nullOr int;
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type = with lib.types; nullOr int;
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description = lib.mdDoc ''
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Maximum total amount of memory (in bytes) that can be stored in the zram
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swap devices.
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@ -90,9 +61,9 @@ in
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'';
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};
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priority = mkOption {
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priority = lib.mkOption {
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default = 5;
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type = types.int;
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type = lib.types.int;
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description = lib.mdDoc ''
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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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@ -100,10 +71,10 @@ in
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'';
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};
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algorithm = mkOption {
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algorithm = lib.mkOption {
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default = "zstd";
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example = "lz4";
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type = with types; either (enum [ "lzo" "lz4" "zstd" ]) str;
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type = with lib.types; either (enum [ "lzo" "lz4" "zstd" ]) str;
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description = lib.mdDoc ''
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Compression algorithm. `lzo` has good compression,
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but is slow. `lz4` has bad compression, but is fast.
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@ -116,9 +87,7 @@ in
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};
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config = mkIf cfg.enable {
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inherit warnings;
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config = lib.mkIf cfg.enable {
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system.requiredKernelConfig = with config.lib.kernelConfig; [
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(isModule "ZRAM")
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@ -128,78 +97,25 @@ in
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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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systemd.packages = [ pkgs.zram-generator ];
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systemd.services."systemd-zram-setup@".path = [ pkgs.util-linux ]; # for mkswap
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boot.kernelParams = ["zram.num_devices=${toString cfg.numDevices}"];
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services.udev.extraRules = ''
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KERNEL=="zram[0-9]*", ENV{SYSTEMD_WANTS}="zram-init-%k.service", TAG+="systemd"
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'';
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systemd.services =
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let
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createZramInitService = dev:
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nameValuePair "zram-init-${dev}" {
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description = "Init swap on zram-based device ${dev}";
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after = [ "dev-${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-${dev}.swap" ];
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unitConfig.DefaultDependencies = false; # needed to prevent a cycle
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serviceConfig = {
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Type = "oneshot";
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RemainAfterExit = true;
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ExecStop = "${pkgs.runtimeShell} -c 'echo 1 > /sys/class/block/${dev}/reset'";
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};
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script = ''
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set -euo pipefail
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# Calculate memory to use for zram
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mem=$(${pkgs.gawk}/bin/awk '/MemTotal: / {
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value=int($2*${toString cfg.memoryPercent}/100.0/${toString devicesCount}*1024);
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${lib.optionalString (cfg.memoryMax != null) ''
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memory_max=int(${toString cfg.memoryMax}/${toString devicesCount});
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if (value > memory_max) { value = memory_max }
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''}
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print value
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}' /proc/meminfo)
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${pkgs.util-linux}/sbin/zramctl --size $mem --algorithm ${cfg.algorithm} /dev/${dev}
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${pkgs.util-linux}/sbin/mkswap /dev/${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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wants = [ "systemd-udevd.service" ];
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after = [ "systemd-udevd.service" ];
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unitConfig.DefaultDependencies = false; # needed to prevent a cycle
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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 = "-${modprobe} -r zram";
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};
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restartTriggers = [
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cfg.numDevices
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cfg.algorithm
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cfg.memoryPercent
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];
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restartIfChanged = true;
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})]);
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swapDevices =
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let
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useZramSwap = dev:
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{
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device = "/dev/${dev}";
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priority = cfg.priority;
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};
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in map useZramSwap devices;
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environment.etc."systemd/zram-generator.conf".source =
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(pkgs.formats.ini { }).generate "zram-generator.conf" (lib.listToAttrs
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(builtins.map
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(dev: {
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name = dev;
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value =
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let
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size = "${toString cfg.memoryPercent} / 100 * ram";
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in
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{
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zram-size = if cfg.memoryMax != null then "min(${size}, ${toString cfg.memoryMax} / 1024 / 1024)" else size;
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compression-algorithm = cfg.algorithm;
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swap-priority = cfg.priority;
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};
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})
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devices));
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};
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@ -1,18 +1,24 @@
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import ./make-test-python.nix {
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name = "zram-generator";
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nodes.machine = { pkgs, ... }: {
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environment.etc."systemd/zram-generator.conf".text = ''
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[zram0]
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zram-size = ram / 2
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'';
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systemd.packages = [ pkgs.zram-generator ];
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systemd.services."systemd-zram-setup@".path = [ pkgs.util-linux ]; # for mkswap
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nodes.machine = { ... }: {
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zramSwap = {
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enable = true;
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priority = 10;
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algorithm = "lz4";
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swapDevices = 2;
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memoryPercent = 30;
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memoryMax = 10 * 1024 * 1024;
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};
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};
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testScript = ''
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machine.wait_for_unit("systemd-zram-setup@zram0.service")
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assert "zram0" in machine.succeed("zramctl -n")
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assert "zram0" in machine.succeed("swapon --show --noheadings")
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machine.wait_for_unit("systemd-zram-setup@zram1.service")
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zram = machine.succeed("zramctl --noheadings --raw")
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swap = machine.succeed("swapon --show --noheadings")
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for i in range(2):
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assert f"/dev/zram{i} lz4 10M" in zram
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assert f"/dev/zram{i} partition 10M" in swap
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'';
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}
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