From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: NONPLAYT <76615486+NONPLAYT@users.noreply.github.com>
Date: Mon, 3 Mar 2025 19:57:47 +0300
Subject: [PATCH] Leaf: Optimize Connection.flushQueue

Original author - Taiyou06
Original patch - https://github.com/Winds-Studio/Leaf/pull/235

diff --git a/net/minecraft/network/Connection.java b/net/minecraft/network/Connection.java
index 5b46036868b6c9d082e35591e58735e16adaae62..a7f5c08726cce94c6a6c2a69028ad016a1bef30a 100644
--- a/net/minecraft/network/Connection.java
+++ b/net/minecraft/network/Connection.java
@@ -85,7 +85,11 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     private static final ProtocolInfo<ServerHandshakePacketListener> INITIAL_PROTOCOL = HandshakeProtocols.SERVERBOUND;
     private final PacketFlow receiving;
     private volatile boolean sendLoginDisconnect = true;
-    private final Queue<WrappedConsumer> pendingActions = Queues.newConcurrentLinkedQueue(); // Paper - Optimize network
+    // DivineMC start - Optimize Connection.flushQueue
+    private final Queue<WrappedConsumer> pendingActions = org.bxteam.divinemc.DivineConfig.connectionFlushQueueRewrite
+        ? new java.util.ArrayDeque<>()
+        : Queues.newConcurrentLinkedQueue(); // Paper - Optimize network
+    // DivineMC end - Optimize Connection.flushQueue
     public Channel channel;
     public SocketAddress address;
     // Spigot start
@@ -542,10 +546,16 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
         if (io.papermc.paper.util.MCUtil.isMainThread()) {
             return this.processQueue();
         } else if (this.isPending) {
-            // Should only happen during login/status stages
-            synchronized (this.pendingActions) {
-                return this.processQueue();
+            // DivineMC start - Leaf: Optimize Connection.flushQueue
+            if (org.bxteam.divinemc.DivineConfig.connectionFlushQueueRewrite) {
+                this.channel.eventLoop().execute(this::processQueue);
+                return false;
+            } else {
+                synchronized (this.pendingActions) {
+                    return this.processQueue();
+                }
             }
+            // DivineMC end - Leaf: Optimize Connection.flushQueue
         }
         return false;
     }
@@ -555,33 +565,52 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
             return true;
         }
 
-        // If we are on main, we are safe here in that nothing else should be processing queue off main anymore
-        // But if we are not on main due to login/status, the parent is synchronized on packetQueue
-        final java.util.Iterator<WrappedConsumer> iterator = this.pendingActions.iterator();
-        while (iterator.hasNext()) {
-            final WrappedConsumer queued = iterator.next(); // poll -> peek
+        // DivineMC start - Leaf: Optimize Connection.flushQueue
+        if (org.bxteam.divinemc.DivineConfig.connectionFlushQueueRewrite) {
+            WrappedConsumer queued;
+            while ((queued = this.pendingActions.poll()) != null) {
+                if (queued instanceof PacketSendAction packetSendAction) {
+                    final Packet<?> packet = packetSendAction.packet;
+                    if (!packet.isReady()) {
+                        this.pendingActions.add(queued);
+                        return false;
+                    }
+                }
 
-            // Fix NPE (Spigot bug caused by handleDisconnection())
-            if (queued == null) {
-                return true;
+                if (queued.tryMarkConsumed()) {
+                    queued.accept(this);
+                }
             }
+        } else {
+            // If we are on main, we are safe here in that nothing else should be processing queue off main anymore
+            // But if we are not on main due to login/status, the parent is synchronized on packetQueue
+            final java.util.Iterator<WrappedConsumer> iterator = this.pendingActions.iterator();
+            while (iterator.hasNext()) {
+                final WrappedConsumer queued = iterator.next(); // poll -> peek
+
+                // Fix NPE (Spigot bug caused by handleDisconnection())
+                if (queued == null) {
+                    return true;
+                }
 
-            if (queued.isConsumed()) {
-                continue;
-            }
+                if (queued.isConsumed()) {
+                    continue;
+                }
 
-            if (queued instanceof PacketSendAction packetSendAction) {
-                final Packet<?> packet = packetSendAction.packet;
-                if (!packet.isReady()) {
-                    return false;
+                if (queued instanceof PacketSendAction packetSendAction) {
+                    final Packet<?> packet = packetSendAction.packet;
+                    if (!packet.isReady()) {
+                        return false;
+                    }
                 }
-            }
 
-            iterator.remove();
-            if (queued.tryMarkConsumed()) {
-                queued.accept(this);
+                iterator.remove();
+                if (queued.tryMarkConsumed()) {
+                    queued.accept(this);
+                }
             }
         }
+        // DivineMC end - Leaf: Optimize Connection.flushQueue
         return true;
     }
     // Paper end - Optimize network
@@ -914,15 +943,40 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     // Paper start - Optimize network
     public void clearPacketQueue() {
         final net.minecraft.server.level.ServerPlayer player = getPlayer();
-        for (final Consumer<Connection> queuedAction : this.pendingActions) {
-            if (queuedAction instanceof PacketSendAction packetSendAction) {
-                final Packet<?> packet = packetSendAction.packet;
-                if (packet.hasFinishListener()) {
-                    packet.onPacketDispatchFinish(player, null);
+
+        // DivineMC start - Leaf: Optimize Connection.flushQueue
+        if (org.bxteam.divinemc.DivineConfig.connectionFlushQueueRewrite) {
+            if (this.channel != null && !this.channel.eventLoop().inEventLoop()) {
+                this.channel.eventLoop().execute(this::clearPacketQueue);
+                return;
+            }
+
+            java.util.List<Consumer<Connection>> queueSnapshot = new java.util.ArrayList<>(this.pendingActions);
+
+            for (Consumer<Connection> queuedAction : queueSnapshot) {
+                if (queuedAction instanceof PacketSendAction packetSendAction) {
+                    final Packet<?> packet = packetSendAction.packet;
+                    if (packet.hasFinishListener()) {
+                        packet.onPacketDispatchFinish(player, null);
+                    }
+                }
+            }
+
+            this.pendingActions.clear();
+        } else {
+            synchronized (this.pendingActions) {
+                for (final Consumer<Connection> queuedAction : this.pendingActions) {
+                    if (queuedAction instanceof PacketSendAction packetSendAction) {
+                        final Packet<?> packet = packetSendAction.packet;
+                        if (packet.hasFinishListener()) {
+                            packet.onPacketDispatchFinish(player, null);
+                        }
+                    }
                 }
+                this.pendingActions.clear();
             }
         }
-        this.pendingActions.clear();
+        // DivineMC end - Leaf: Optimize Connection.flushQueue
     }
 
     private static class InnerUtil { // Attempt to hide these methods from ProtocolLib, so it doesn't accidently pick them up.