Add memory flags to minecraft server

lib/fudo/default.nix

@@ -28,6 +28,7 @@ with lib; {
     ./local-network.nix
     ./mail.nix
     ./mail-container.nix
+    ./minecraft-clj.nix
     ./minecraft-server.nix
     ./netinfo-email.nix
     ./node-exporter.nix

lib/fudo/minecraft-clj.nix

@@ -0,0 +1,113 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+let
+  cfg = config.fudo.minecraft-clj;
+
+  papermcWithPlugins = pkgs.buildEnv {
+    name = "papermcWithPlugins";
+    paths = with pkgs; [ papermc witchcraft-plugin-current ];
+  };
+
+  highMemFlags = [
+    "-XX:G1NewSizePercent=40"
+    "-XX:G1MaxNewSizePercent=50"
+    "-XX:G1HeapRegionSize=16M"
+    "-XX:G1ReservePercent=15"
+    "-XX:InitiatingHeapOccupancyPercent=20"
+  ];
+
+  commonFlags = [
+    "-XX:+UseG1GC"
+    "-XX:+ParallelRefProcEnabled"
+    "-XX:MaxGCPauseMillis=200"
+    "-XX:+UnlockExperimentalVMOptions"
+    "-XX:+DisableExplicitGC"
+    "-XX:+AlwaysPreTouch"
+    "-XX:G1NewSizePercent=30"
+    "-XX:G1MaxNewSizePercent=40"
+    "-XX:G1HeapRegionSize=8M"
+    "-XX:G1ReservePercent=20"
+    "-XX:G1HeapWastePercent=5"
+    "-XX:G1MixedGCCountTarget=4"
+    "-XX:InitiatingHeapOccupancyPercent=15"
+    "-XX:G1MixedGCLiveThresholdPercent=90"
+    "-XX:G1RSetUpdatingPauseTimePercent=5"
+    "-XX:SurvivorRatio=32"
+    "-XX:+PerfDisableSharedMem"
+    "-XX:MaxTenuringThreshold=1"
+    "-Dusing.aikars.flags=https://mcflags.emc.gs"
+    "-Daikars.new.flags=true"
+  ];
+
+in {
+  options.fudo.minecraft-clj = with types; {
+    enable = mkEnableOption "Enable Minecraft server with Clojure repl.";
+
+    data-dir = mkOption {
+      type = str;
+      description = "Path at which to store Minecraft data.";
+    };
+
+    allocated-memory = mkOption {
+      type = int;
+      description = "Memory to allocate to Minecraft, in GB.";
+      default = 4;
+    };
+
+    user = mkOption {
+      type = str;
+      description = "User as which to run the minecraft server.";
+      default = "minecraft-clj";
+    };
+
+    group = mkOption {
+      type = str;
+      description = "Group as which to run the minecraft server.";
+      default = "minecraft-clj";
+    };
+  };
+
+  config = {
+    users = {
+      users."${cfg.user}" = {
+        isNormalUser = false;
+        home = cfg.data-dir;
+        group = cfg.group;
+        createHome = true;
+      };
+      groups."${cfg.group}" = { members = [ cfg.user ]; };
+    };
+
+    systemd.services.minecraft-clj = {
+      description = "Minecraft server with Clojure REPL.";
+      wantedBy = [ "multi-user.target" ];
+      after = [ "network-online.target" ];
+      serviceConfig = {
+        User = cfg.user;
+        Group = cfg.group;
+        ExecStart = let
+          mem = "${cfg.allocated-memory}G";
+          memFlags = [ "-Xms${mem}" "-Xmx${mem}" ];
+          flags = commonFlags ++ memFlags
+            ++ (optionals (cfg.allocated-memory >= 12) highMemFlags);
+          flagStr = concatStringsSep " " flags;
+        in "${pkgs.papermc}/bin/minecraft-server ${flagStr}";
+
+        Restart = "always";
+        NoNewPrivileges = true;
+        PrivateTmp = true;
+        PrivateDevices = true;
+        ProtectSystem = "strict";
+        ProtectHome = true;
+        ProtectControlGroups = true;
+        ProtectKernelModules = true;
+        ProtectKernalTunables = true;
+        RestrictAddressFamilies = [ "AF_INET" "AF_INET6" ];
+        RestrictRealtime = true;
+        RestrictNamespaces = true;
+        MemoryDenyWriteExecute = true;
+      };
+    };
+  };
+}

lib/fudo/minecraft-server.nix

@@ -45,6 +45,12 @@ in {
       type = types.bool;
       default = false;
     };
+
+    allocated-memory = mkOption {
+      type = types.int;
+      description = "Memory (in GB) to allocate to the Minecraft server.";
+      default = 2;
+    };
   };
 
   config = mkIf cfg.enable {
@@ -63,6 +69,34 @@ in {
         gamemode = cfg.game-mode;
         allow-cheats = true;
       };
+      jvmOpts = [
+        "-Xms${toString cfg.allocated-memory}G"
+        "-Xmx${toString cfg.allocated-memory}G"
+        "-XX:+UseG1GC"
+        "-XX:+ParallelRefProcEnabled"
+        "-XX:MaxGCPauseMillis=200"
+        "-XX:+UnlockExperimentalVMOptions"
+        "-XX:+DisableExplicitGC"
+        "-XX:+AlwaysPreTouch"
+        "-XX:G1NewSizePercent=30"
+        "-XX:G1MaxNewSizePercent=40"
+        "-XX:G1HeapRegionSize=8M"
+        "-XX:G1ReservePercent=20"
+        "-XX:G1HeapWastePercent=5"
+        "-XX:G1MixedGCCountTarget=4"
+        "-XX:InitiatingHeapOccupancyPercent=15"
+        "-XX:G1MixedGCLiveThresholdPercent=90"
+        "-XX:G1RSetUpdatingPauseTimePercent=5"
+        "-XX:SurvivorRatio=32"
+        "-XX:+PerfDisableSharedMem"
+        "-XX:MaxTenuringThreshold=1"
+      ] ++ (optionals (cfg.allocated-memory >= 12) [
+        "-XX:G1NewSizePercent=40"
+        "-XX:G1MaxNewSizePercent=50"
+        "-XX:G1HeapRegionSize=16M"
+        "-XX:G1ReservePercent=15"
+        "-XX:InitiatingHeapOccupancyPercent=20"
+      ]);
     };
   };
 }