From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: NONPLAYT <76615486+NONPLAYT@users.noreply.github.com>
Date: Fri, 11 Jul 2025 20:39:54 +0300
Subject: [PATCH] Paper PR: Optimise non-flush packet sending

Original project: https://github.com/PaperMC/Paper
Original license: GPLv3
Paper pull request: https://github.com/PaperMC/Paper/pull/10172

Places like entity tracking make heavy use of packet sending,
and internally netty will use some very expensive thread wakeup
calls when scheduling.

Thanks to various hacks in ProtocolLib as well as other
plugins, we cannot simply use a queue of packets to group
send on execute. We have to call execute for each packet.

Tux's suggestion here is exactly what was needed - tag
the Runnable indicating it should not make a wakeup call.

Big thanks to Tux for making this possible as I had given
up on this optimisation before he came along.

Locally this patch drops the entity tracker tick by a full 1.5x.

diff --git a/net/minecraft/network/Connection.java b/net/minecraft/network/Connection.java
index e28d859b457ca0e24bc6dc9d6cd4a97f12ae0671..5b31eed8f91b45b46521da5169d8003dfd5ec669 100644
--- a/net/minecraft/network/Connection.java
+++ b/net/minecraft/network/Connection.java
@@ -150,6 +150,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     // Paper start - Optimize network
     public boolean isPending = true;
     public boolean queueImmunity;
+    private io.netty.channel.SingleThreadEventLoop eventLoop; // Paper - Optimise non-flush packet sending
     // Paper end - Optimize network
 
     public Connection(PacketFlow receiving) {
@@ -160,6 +161,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     public void channelActive(ChannelHandlerContext ctx) throws Exception {
         super.channelActive(ctx);
         this.channel = ctx.channel();
+        this.eventLoop = (io.netty.channel.SingleThreadEventLoop) this.channel.eventLoop(); // Paper - Optimise non-flush packet sending
         this.address = this.channel.remoteAddress();
         this.preparing = false; // Spigot
         if (this.delayedDisconnect != null) {
@@ -472,7 +474,13 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
         if (this.channel.eventLoop().inEventLoop()) {
             this.doSendPacket(packet, sendListener, flush);
         } else {
-            this.channel.eventLoop().execute(() -> this.doSendPacket(packet, sendListener, flush));
+            // Paper start - Optimise non-flush packet sending
+            if (!flush && org.bxteam.divinemc.config.DivineConfig.NetworkCategory.optimizeNonFlushPacketSending) {
+                this.eventLoop.lazyExecute(() -> this.doSendPacket(packet, sendListener, flush));
+            } else {
+                this.channel.eventLoop().execute(() -> this.doSendPacket(packet, sendListener, flush));
+            }
+            // Paper end - Optimise non-flush packet sending
         }
     }