From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Tue, 23 Oct 2018 23:14:38 -0400
Subject: [PATCH] Improve Server Thread Pool and Thread Priorities

Use a simple executor since Fork join is a much more complex pool
type and we are not using its capabilities.

Set thread priorities so main thread has above normal priority over
server threads

Allow usage of a single thread executor by not using ForkJoin so single core CPU's.

diff --git a/src/main/java/net/minecraft/Util.java b/src/main/java/net/minecraft/Util.java
index 7b36274718b7cce24ac00530697f145648d52590..cec5ad5052c8cf6059e9b117117846bdb217748f 100644
--- a/src/main/java/net/minecraft/Util.java
+++ b/src/main/java/net/minecraft/Util.java
@@ -45,7 +45,7 @@ import java.util.stream.Stream;
 import javax.annotation.Nullable;
 import net.minecraft.resources.ResourceLocation;
 import net.minecraft.server.Bootstrap;
-import net.minecraft.util.Mth;
+import net.minecraft.server.ServerWorkerThread;
 import net.minecraft.util.datafix.DataFixers;
 import net.minecraft.world.level.block.state.properties.Property;
 import org.apache.logging.log4j.LogManager;
@@ -54,8 +54,8 @@ import org.apache.logging.log4j.Logger;
 public class Util {
 
     private static final AtomicInteger WORKER_COUNT = new AtomicInteger(1);
-    private static final ExecutorService BOOTSTRAP_EXECUTOR = makeExecutor("Bootstrap");
-    private static final ExecutorService BACKGROUND_EXECUTOR = makeExecutor("Main");
+    private static final ExecutorService BOOTSTRAP_EXECUTOR = a("Bootstrap", -2); // Paper - add -2 priority
+    private static final ExecutorService BACKGROUND_EXECUTOR = a("Main", -1); // Paper - add -1 priority
     private static final ExecutorService IO_POOL = makeIoExecutor();
     public static LongSupplier timeSource = System::nanoTime;
     public static final UUID NIL_UUID = new UUID(0L, 0L); public static final UUID getNullUUID() {return NIL_UUID;} // Paper OBFHELPER
@@ -85,30 +85,34 @@ public class Util {
         return Instant.now().toEpochMilli();
     }
 
-    private static ExecutorService makeExecutor(String name) {
-        int i = Mth.clamp(Runtime.getRuntime().availableProcessors() - 1, 1, 7);
-        Object object;
+    private static ExecutorService a(String s, int priorityModifier) { // Paper - add priority
+        // Paper start - use simpler thread pool that allows 1 thread
+        int i = Math.min(8, Math.max(Runtime.getRuntime().availableProcessors() - 2, 1));
+        i = Integer.getInteger("Paper.WorkerThreadCount", i);
+        ExecutorService object;
 
         if (i <= 0) {
             object = MoreExecutors.newDirectExecutorService();
         } else {
-            object = new ForkJoinPool(i, (forkjoinpool) -> {
-                ForkJoinWorkerThread forkjoinworkerthread = new ForkJoinWorkerThread(forkjoinpool) {
+            object = new java.util.concurrent.ThreadPoolExecutor(i, i,0L, TimeUnit.MILLISECONDS, new java.util.concurrent.LinkedBlockingQueue<Runnable>(), target -> new ServerWorkerThread(target, s, priorityModifier));
+        }
+        /*
                     protected void onTermination(Throwable throwable) {
                         if (throwable != null) {
-                            Util.LOGGER.warn("{} died", this.getName(), throwable);
+                            SystemUtils.LOGGER.warn("{} died", this.getName(), throwable);
                         } else {
-                            Util.LOGGER.debug("{} shutdown", this.getName());
+                            SystemUtils.LOGGER.debug("{} shutdown", this.getName());
                         }
 
                         super.onTermination(throwable);
                     }
                 };
 
-                forkjoinworkerthread.setName("Worker-" + name + "-" + Util.WORKER_COUNT.getAndIncrement());
+                forkjoinworkerthread.setName("Worker-" + s + "-" + SystemUtils.c.getAndIncrement());
                 return forkjoinworkerthread;
-            }, Util::onThreadException, true);
+            }, SystemUtils::a, true);
         }
+        }*/ // Paper end
 
         return (ExecutorService) object;
     }
@@ -157,6 +161,7 @@ public class Util {
         });
     }
 
+    public static void onThreadError(Thread thread, Throwable throwable) { onThreadException(thread, throwable); } // Paper - OBFHELPER
     private static void onThreadException(Thread thread, Throwable throwable) {
         pauseInIde(throwable);
         if (throwable instanceof CompletionException) {
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index 5a76ca77b974ff6fe862c9e05a88b507a34b44be..5faa8f3cc251b6687e33e40009db98d2aee48f2c 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -284,6 +284,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
         S s0 = serverFactory.apply(thread); // CraftBukkit - decompile error
 
         atomicreference.set(s0);
+        thread.setPriority(Thread.NORM_PRIORITY+2); // Paper - boost priority
         thread.start();
         return s0;
     }
diff --git a/src/main/java/net/minecraft/server/ServerWorkerThread.java b/src/main/java/net/minecraft/server/ServerWorkerThread.java
new file mode 100644
index 0000000000000000000000000000000000000000..4313e21463c16ea9a3edc81763d40702f9d3930b
--- /dev/null
+++ b/src/main/java/net/minecraft/server/ServerWorkerThread.java
@@ -0,0 +1,14 @@
+package net.minecraft.server;
+
+import java.util.concurrent.atomic.AtomicInteger;
+import net.minecraft.Util;
+
+public class ServerWorkerThread extends Thread {
+    private static final AtomicInteger threadId = new AtomicInteger(1);
+    public ServerWorkerThread(Runnable target, String poolName, int prioritityModifier) {
+        super(target, "Worker-" + poolName + "-" + threadId.getAndIncrement());
+        setPriority(Thread.NORM_PRIORITY+prioritityModifier); // Deprioritize over main
+        this.setDaemon(true);
+        this.setUncaughtExceptionHandler(Util::onThreadError);
+    }
+}