PaperMC/Spigot-Server-Patches/0428-Don-t-update-entity-trackers-for-worlds-without-play.patch

From 1b01715133963b2fda50c547261b419386e12cc3 Mon Sep 17 00:00:00 2001
From: Shane Freeder <theboyetronic@gmail.com>
Date: Sun, 24 Mar 2019 18:52:31 +0000
Subject: [PATCH] Don't update entity trackers for worlds without players

PlayerList#moveToWorld already untracks the player from the player list,
meaning that we do not need to worry about this untracking players
who've left the world, The server also untracks a player during
disconnect, handing yet another case.

If we don't need to untrack players who've left the world, it should be
reasonably save to do this, as we're not going to be performing any
server->client updates here, which is what this code is intended to do,
and all players should be untracked.

diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index ce39ea09e8..b93fccf919 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -1113,7 +1113,7 @@ public abstract class MinecraftServer implements IAsyncTaskHandler, IMojangStati
 
                 this.methodProfiler.exit();
                 this.methodProfiler.enter("tracker");
-                worldserver.getTracker().updatePlayers();
+                if (playerList.players.size() > 0) worldserver.getTracker().updatePlayers(); // Paper - No players, why spend time tracking them? (See patch)
                 this.methodProfiler.exit();
                 this.methodProfiler.exit();
                 worldserver.explosionDensityCache.clear(); // Paper - Optimize explosions
-- 
2.21.0