minecraft: make more responsive

services/minecraft.nix

@@ -35,7 +35,38 @@
         let
           heap_size = "4000M";
         in
-        "-Xmx${heap_size} -Xms${heap_size} -XX:+UseZGC -XX:+ZGenerational";
+        lib.concatStringsSep " " [
+          # Memory
+          "-Xmx${heap_size}"
+          "-Xms${heap_size}"
+          # GC
+          "-XX:+UseZGC"
+          "-XX:+ZGenerational"
+          # Base JVM optimizations (brucethemoose/Minecraft-Performance-Flags-Benchmarks)
+          "-XX:+UnlockExperimentalVMOptions"
+          "-XX:+UnlockDiagnosticVMOptions"
+          "-XX:+AlwaysActAsServerClassMachine"
+          "-XX:+AlwaysPreTouch"
+          "-XX:+DisableExplicitGC"
+          "-XX:+UseNUMA"
+          "-XX:+PerfDisableSharedMem"
+          "-XX:+UseFastUnorderedTimeStamps"
+          "-XX:+UseCriticalJavaThreadPriority"
+          "-XX:ThreadPriorityPolicy=1"
+          "-XX:AllocatePrefetchStyle=3"
+          "-XX:-DontCompileHugeMethods"
+          "-XX:MaxNodeLimit=240000"
+          "-XX:NodeLimitFudgeFactor=8000"
+          "-XX:ReservedCodeCacheSize=400M"
+          "-XX:NonNMethodCodeHeapSize=12M"
+          "-XX:ProfiledCodeHeapSize=194M"
+          "-XX:NonProfiledCodeHeapSize=194M"
+          "-XX:NmethodSweepActivity=1"
+          "-XX:+UseVectorCmov"
+          # Large pages (requires vm.nr_hugepages sysctl)
+          "-XX:+UseLargePages"
+          "-XX:LargePageSizeInBytes=2m"
+        ];
 
       serverProperties = {
         server-port = service_configs.ports.minecraft;
@@ -116,6 +147,14 @@
     };
   };
 
+  systemd.services.minecraft-server-main = {
+    serviceConfig = {
+      Nice = -5;
+      IOSchedulingPriority = 0;
+      LimitMEMLOCK = "infinity"; # Required for large pages
+    };
+  };
+
   services.caddy.virtualHosts = lib.mkIf (config.services.caddy.enable) {
     "map.${service_configs.https.domain}".extraConfig = ''
       root * ${service_configs.minecraft.parent_dir}/${service_configs.minecraft.server_name}/squaremap/web