Multi-threaded chunk saving (not really)

sources/src/main/java/io/akarin/api/internal/Akari.java

@@ -96,9 +96,9 @@ public abstract class Akari {
      */
     public final static Timing worldTiming = getTiming("Akarin - Full World Tick");
     
-    public final static Timing entityCallbackTiming = getTiming("Akarin - Entity Callback");
+    public final static Timing entityCallbackTiming = getTiming("Akarin - Entity Parallell Await");
     
-    public final static Timing callbackTiming = getTiming("Akarin - Callback");
+    public final static Timing callbackTiming = getTiming("Akarin - Callback Queue");
     
     private static Timing getTiming(String name) {
         try {

sources/src/main/java/io/akarin/server/core/AkarinGlobalConfig.java

@@ -172,7 +172,7 @@ public class AkarinGlobalConfig {
     
     public static long timeUpdateInterval;
     private static void timeUpdateInterval() {
-        timeUpdateInterval = getSeconds(getString("core.tick-rate.world-time-update-interval", "1s")) * 10;
+        timeUpdateInterval = getSeconds(getString("core.tick-rate.world-time-update-interval", "1s")) * 10 * 2;
     }
     
     public static long keepAliveSendInterval;
@@ -267,7 +267,7 @@ public class AkarinGlobalConfig {
     
     public static long playersInfoUpdateInterval;
     private static void playersInfoUpdateInterval() {
-        playersInfoUpdateInterval = getSeconds(getString("core.tick-rate.players-info-update-interval", "30s")) * 10;
+        playersInfoUpdateInterval = getSeconds(getString("core.tick-rate.players-info-update-interval", "30s")) * 10 * 2;
     }
     
     public static long versionUpdateInterval;
@@ -284,4 +284,9 @@ public class AkarinGlobalConfig {
     private static void forceHardcoreDifficulty() {
         forceHardcoreDifficulty = getBoolean("alternative.force-difficulty-on-hardcore", true);
     }
+    
+    public static int fileIOThreads;
+    private static void fileIOThreads() {
+        fileIOThreads = getInt("core.chunk-save-threads", 2);
+    }
 }

sources/src/main/java/io/akarin/server/mixin/core/MixinFileIOThread.java

@@ -0,0 +1,56 @@
+package io.akarin.server.mixin.core;
+
+import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Overwrite;
+import org.spongepowered.asm.mixin.Shadow;
+
+import com.destroystokyo.paper.PaperConfig;
+import com.google.common.util.concurrent.ThreadFactoryBuilder;
+
+import io.akarin.server.core.AkarinGlobalConfig;
+import net.minecraft.server.FileIOThread;
+import net.minecraft.server.IAsyncChunkSaver;
+
+@Mixin(value = FileIOThread.class, remap = false)
+public abstract class MixinFileIOThread {
+    private final Executor executor = Executors.newFixedThreadPool(AkarinGlobalConfig.fileIOThreads, new ThreadFactoryBuilder().setNameFormat("Akarin File IO Thread - %1$d").setPriority(1).build());
+    private final AtomicInteger queuedChunkCounter = new AtomicInteger(0);
+    
+    @Shadow(aliases = "e") private volatile boolean isAwaitFinish;
+    
+    @Overwrite // OBFHELPER: saveChunk
+    public void a(IAsyncChunkSaver iasyncchunksaver) {
+        queuedChunkCounter.incrementAndGet();
+        executor.execute(() -> writeChunk(iasyncchunksaver));
+    }
+    
+    /**
+     * Process a chunk, re-add to the queue if unsuccessful
+     */
+    private void writeChunk(IAsyncChunkSaver iasyncchunksaver)  {
+        if (!iasyncchunksaver.a()) { // PAIL: WriteNextIO() -> Returns if the write was unsuccessful
+            queuedChunkCounter.decrementAndGet();
+            
+            if (PaperConfig.enableFileIOThreadSleep) {
+                try {
+                    Thread.sleep(isAwaitFinish ? 0L : 2L);
+                } catch (InterruptedException ex) {
+                    ex.printStackTrace();
+                }
+            }
+        } else {
+            writeChunk(iasyncchunksaver);
+        }
+    }
+    
+    @Overwrite // OBFHELPER: waitForFinish
+    public void b() throws InterruptedException {
+        isAwaitFinish = true;
+        while (queuedChunkCounter.get() != 0) Thread.sleep(9L);
+        isAwaitFinish = false;
+    }
+}

sources/src/main/java/io/akarin/server/mixin/core/MixinTimingHandler.java

@@ -37,8 +37,8 @@ public abstract class MixinTimingHandler {
     
     @SuppressWarnings({"rawtypes", "unchecked"})
     @Inject(method = "startTiming", at = @At("HEAD"), cancellable = true)
-    public void onStartTiming(CallbackInfoReturnable ci) {
-        if (!Akari.isPrimaryThread(false)) ci.setReturnValue(this); // Avoid modify any field
+    public void onStartTiming(CallbackInfoReturnable cir) {
+        if (!Akari.isPrimaryThread(false)) cir.setReturnValue(this); // Avoid modify any field
     }
     
     @Overwrite

sources/src/main/java/net/minecraft/server/FileIOThread.java

@@ -0,0 +1,81 @@
+package net.minecraft.server;
+
+import java.util.List;
+
+/**
+ * Akarin Changes Note
+ * 1) Multi-threaded chunk saving (performance)
+ */
+public class FileIOThread implements Runnable {
+
+    private static final FileIOThread a = new FileIOThread();
+    private final List<IAsyncChunkSaver> b = /*Collections.synchronizedList(Lists.newArrayList())*/ null; // Akarin - I don't think any plugin rely on this
+    private volatile long c;
+    private volatile long d;
+    private volatile boolean e;
+
+    private FileIOThread() {
+        // Thread thread = new Thread(this, "File IO Thread"); // Akarin
+
+        // thread.setPriority(1); // Akarin
+        // thread.start(); // Akarin
+    }
+
+    public static FileIOThread a() {
+        return FileIOThread.a;
+    }
+
+    public void run() {
+        while (true) {
+            this.c();
+        }
+    }
+
+    private void c() {
+        for (int i = 0; i < this.b.size(); ++i) {
+            IAsyncChunkSaver iasyncchunksaver = (IAsyncChunkSaver) this.b.get(i);
+            boolean flag = iasyncchunksaver.a();
+
+            if (!flag) {
+                this.b.remove(i--);
+                ++this.d;
+            }
+
+            // Paper start - Add toggle
+            if (com.destroystokyo.paper.PaperConfig.enableFileIOThreadSleep) {
+                try {
+                    Thread.sleep(this.e ? 0L : 2L);
+                } catch (InterruptedException interruptedexception) {
+                    interruptedexception.printStackTrace();
+                }
+            }
+            // Paper end
+        }
+
+        if (this.b.isEmpty()) {
+            try {
+                Thread.sleep(25L);
+            } catch (InterruptedException interruptedexception1) {
+                interruptedexception1.printStackTrace();
+            }
+        }
+
+    }
+
+    public void a(IAsyncChunkSaver iasyncchunksaver) {
+        if (!this.b.contains(iasyncchunksaver)) {
+            ++this.c;
+            this.b.add(iasyncchunksaver);
+        }
+    }
+
+    public void b() throws InterruptedException {
+        this.e = true;
+
+        while (this.c != this.d) {
+            Thread.sleep(10L);
+        }
+
+        this.e = false;
+    }
+}

sources/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java

@@ -1157,9 +1157,9 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
 
         getHandle().playerConnection.sendPacket(new PacketPlayOutPlayerInfo(PacketPlayOutPlayerInfo.EnumPlayerInfoAction.ADD_PLAYER, other));
 
+        tracker.entriesLock.lock(); // Akarin
         EntityTrackerEntry entry = tracker.trackedEntities.get(other.getId());
         if (entry != null && !entry.trackedPlayers.contains(getHandle())) {
-            tracker.entriesLock.lock(); // Akarin
             entry.updatePlayer(getHandle());
             tracker.entriesLock.unlock(); // Akarin
         }

sources/src/main/resources/mixins.akarin.core.json

@@ -19,6 +19,7 @@
         "core.MixinCommandKick",
         "core.MixinCraftServer",
         "core.MixinWorldServer",
+        "core.MixinFileIOThread",
         "core.MixinWorldManager",
         "core.MixinCommandBanIp",
         "core.MixinChunkSection",