Paper/patches/server/0995-Optimise-chunk-tick-iteration.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Sat, 23 Sep 2023 21:36:36 -0700
Subject: [PATCH] Optimise chunk tick iteration

When per-player mob spawning is enabled we do not need to randomly
shuffle the chunk list. Additionally, we can use the NearbyPlayers
class to quickly retrieve nearby players instead of possible
searching all players on the server.

diff --git a/src/main/java/io/papermc/paper/util/player/NearbyPlayers.java b/src/main/java/io/papermc/paper/util/player/NearbyPlayers.java
index c3ce8a42dddd76b7189ad5685b23f9d9f8ccadb3..f164256d59b761264876ca0c85f812d101bfd5de 100644
--- a/src/main/java/io/papermc/paper/util/player/NearbyPlayers.java
+++ b/src/main/java/io/papermc/paper/util/player/NearbyPlayers.java
@@ -17,7 +17,8 @@ public final class NearbyPlayers {
         GENERAL_SMALL,
         GENERAL_REALLY_SMALL,
         TICK_VIEW_DISTANCE,
-        VIEW_DISTANCE;
+        VIEW_DISTANCE, // Paper - optimise chunk iteration
+        SPAWN_RANGE, // Paper - optimise chunk iteration
     }
 
     private static final NearbyMapType[] MOB_TYPES = NearbyMapType.values();
@@ -26,10 +27,12 @@ public final class NearbyPlayers {
     private static final int GENERAL_AREA_VIEW_DISTANCE = 33;
     private static final int GENERAL_SMALL_VIEW_DISTANCE = 10;
     private static final int GENERAL_REALLY_SMALL_VIEW_DISTANCE = 3;
+    private static final int SPAWN_RANGE_VIEW_DISTANCE = net.minecraft.server.level.DistanceManager.MOB_SPAWN_RANGE; // Paper - optimise chunk iteration
 
     public static final int GENERAL_AREA_VIEW_DISTANCE_BLOCKS = (GENERAL_AREA_VIEW_DISTANCE << 4);
     public static final int GENERAL_SMALL_AREA_VIEW_DISTANCE_BLOCKS = (GENERAL_SMALL_VIEW_DISTANCE << 4);
     public static final int GENERAL_REALLY_SMALL_AREA_VIEW_DISTANCE_BLOCKS = (GENERAL_REALLY_SMALL_VIEW_DISTANCE << 4);
+    public static final int SPAWN_RANGE_VIEW_DISTANCE_BLOCKS = (SPAWN_RANGE_VIEW_DISTANCE << 4); // Paper - optimise chunk iteration
 
     private final ServerLevel world;
     private final Reference2ReferenceOpenHashMap<ServerPlayer, TrackedPlayer[]> players = new Reference2ReferenceOpenHashMap<>();
@@ -80,6 +83,7 @@ public final class NearbyPlayers {
         players[NearbyMapType.GENERAL_REALLY_SMALL.ordinal()].update(chunk.x, chunk.z, GENERAL_REALLY_SMALL_VIEW_DISTANCE);
         players[NearbyMapType.TICK_VIEW_DISTANCE.ordinal()].update(chunk.x, chunk.z, ChunkSystem.getTickViewDistance(player));
         players[NearbyMapType.VIEW_DISTANCE.ordinal()].update(chunk.x, chunk.z, ChunkSystem.getLoadViewDistance(player));
+        players[NearbyMapType.SPAWN_RANGE.ordinal()].update(chunk.x, chunk.z, SPAWN_RANGE_VIEW_DISTANCE); // Paper - optimise chunk iteration
     }
 
     public TrackedChunk getChunk(final ChunkPos pos) {
diff --git a/src/main/java/net/minecraft/server/level/ChunkHolder.java b/src/main/java/net/minecraft/server/level/ChunkHolder.java
index 2b998bdbe49bf8211b755e0eb7c1bf13ac280eab..627a88ec8c3b215b19b55a6d461c8754b4fcd1e8 100644
--- a/src/main/java/net/minecraft/server/level/ChunkHolder.java
+++ b/src/main/java/net/minecraft/server/level/ChunkHolder.java
@@ -79,11 +79,19 @@ public class ChunkHolder {
 
     // Paper start
     public void onChunkAdd() {
-
+        // Paper start - optimise chunk tick iteration
+        if (this.needsBroadcastChanges()) {
+            this.chunkMap.needsChangeBroadcasting.add(this);
+        }
+        // Paper end - optimise chunk tick iteration
     }
 
     public void onChunkRemove() {
-
+        // Paper start - optimise chunk tick iteration
+        if (this.needsBroadcastChanges()) {
+            this.chunkMap.needsChangeBroadcasting.remove(this);
+        }
+        // Paper end - optimise chunk tick iteration
     }
     // Paper end
 
@@ -230,7 +238,7 @@ public class ChunkHolder {
 
             if (i < 0 || i >= this.changedBlocksPerSection.length) return; // CraftBukkit - SPIGOT-6086, SPIGOT-6296
             if (this.changedBlocksPerSection[i] == null) {
-                this.hasChangedSections = true;
+                this.hasChangedSections = true; this.addToBroadcastMap(); // Paper - optimise chunk tick iteration
                 this.changedBlocksPerSection[i] = new ShortOpenHashSet();
             }
 
@@ -254,6 +262,7 @@ public class ChunkHolder {
                     int k = this.lightEngine.getMaxLightSection();
 
                     if (y >= j && y <= k) {
+                        this.addToBroadcastMap(); // Paper - optimise chunk tick iteration
                         int l = y - j;
 
                         if (lightType == LightLayer.SKY) {
@@ -268,8 +277,19 @@ public class ChunkHolder {
         }
     }
 
+    // Paper start - optimise chunk tick iteration
+    public final boolean needsBroadcastChanges() {
+        return this.hasChangedSections || !this.skyChangedLightSectionFilter.isEmpty() || !this.blockChangedLightSectionFilter.isEmpty();
+    }
+
+    private void addToBroadcastMap() {
+        io.papermc.paper.util.TickThread.ensureTickThread(this.chunkMap.level, this.pos, "Asynchronous ChunkHolder update is not allowed");
+        this.chunkMap.needsChangeBroadcasting.add(this);
+    }
+    // Paper end - optimise chunk tick iteration
+
     public void broadcastChanges(LevelChunk chunk) {
-        if (this.hasChangedSections || !this.skyChangedLightSectionFilter.isEmpty() || !this.blockChangedLightSectionFilter.isEmpty()) {
+        if (this.needsBroadcastChanges()) { // Paper - optimise chunk tick iteration; moved into above, other logic needs to call
             Level world = chunk.getLevel();
             List list;
 
diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index ce808a48478be3b310d33f4b28364f70f4cd3236..1b2b510cf5ea1799c1f5dec990cec52671e900a9 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -191,6 +191,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
             this.playerEntityTrackerTrackMaps[i].remove(player);
         }
         // Paper end - use distance map to optimise tracker
+        this.playerMobSpawnMap.remove(player); // Paper - optimise chunk tick iteration
     }
 
     void updateMaps(ServerPlayer player) {
@@ -240,6 +241,10 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     }
     public final io.papermc.paper.util.player.NearbyPlayers nearbyPlayers;
     // Paper end
+    // Paper start - optimise chunk tick iteration
+    public final it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<ChunkHolder> needsChangeBroadcasting = new it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<>();
+    public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerMobSpawnMap = new com.destroystokyo.paper.util.misc.PlayerAreaMap(this.pooledLinkedPlayerHashSets);
+    // Paper end - optimise chunk tick iteration
 
     public ChunkMap(ServerLevel world, LevelStorageSource.LevelStorageAccess session, DataFixer dataFixer, StructureTemplateManager structureTemplateManager, Executor executor, BlockableEventLoop<Runnable> mainThreadExecutor, LightChunkGetter chunkProvider, ChunkGenerator chunkGenerator, ChunkProgressListener worldGenerationProgressListener, ChunkStatusUpdateListener chunkStatusChangeListener, Supplier<DimensionDataStorage> persistentStateManagerFactory, int viewDistance, boolean dsync) {
         super(session.getDimensionPath(world.dimension()).resolve("region"), dataFixer, dsync);
@@ -409,7 +414,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     }
     // Paper end - Optional per player mob spawns
 
-    private static double euclideanDistanceSquared(ChunkPos pos, Entity entity) {
+    public static double euclideanDistanceSquared(ChunkPos pos, Entity entity) { // Paper - optimise chunk iteration; public
         double d0 = (double) SectionPos.sectionToBlockCoord(pos.x, 8);
         double d1 = (double) SectionPos.sectionToBlockCoord(pos.z, 8);
         double d2 = d0 - entity.getX();
diff --git a/src/main/java/net/minecraft/server/level/DistanceManager.java b/src/main/java/net/minecraft/server/level/DistanceManager.java
index c80a625f7289e3bb33c6851d2072957e153ca1fb..7c425ac50c83757b66a2178bc19d4c920b82f12f 100644
--- a/src/main/java/net/minecraft/server/level/DistanceManager.java
+++ b/src/main/java/net/minecraft/server/level/DistanceManager.java
@@ -50,7 +50,7 @@ public abstract class DistanceManager {
     private static final int INITIAL_TICKET_LIST_CAPACITY = 4;
     final Long2ObjectMap<ObjectSet<ServerPlayer>> playersPerChunk = new Long2ObjectOpenHashMap();
     // Paper - rewrite chunk system
-    private final DistanceManager.FixedPlayerDistanceChunkTracker naturalSpawnChunkCounter = new DistanceManager.FixedPlayerDistanceChunkTracker(8);
+    public static final int MOB_SPAWN_RANGE = 8; //private final DistanceManager.FixedPlayerDistanceChunkTracker naturalSpawnChunkCounter = new DistanceManager.FixedPlayerDistanceChunkTracker(8); // Paper - optimise chunk tick iteration
     // Paper - rewrite chunk system
     private final ChunkMap chunkMap; // Paper
 
@@ -135,7 +135,7 @@ public abstract class DistanceManager {
         long i = chunkcoordintpair.toLong();
 
         // Paper - no longer used
-        this.naturalSpawnChunkCounter.update(i, 0, true);
+        //this.naturalSpawnChunkCounter.update(i, 0, true); // Paper - optimise chunk tick iteration
         //this.playerTicketManager.update(i, 0, true); // Paper - no longer used
         //this.tickingTicketsTracker.addTicket(TicketType.PLAYER, chunkcoordintpair, this.getPlayerTicketLevel(), chunkcoordintpair); // Paper - no longer used
     }
@@ -149,7 +149,7 @@ public abstract class DistanceManager {
         if (objectset != null) objectset.remove(player); // Paper - some state corruption happens here, don't crash, clean up gracefully
         if (objectset == null || objectset.isEmpty()) { // Paper
             this.playersPerChunk.remove(i);
-            this.naturalSpawnChunkCounter.update(i, Integer.MAX_VALUE, false);
+            //this.naturalSpawnChunkCounter.update(i, Integer.MAX_VALUE, false); // Paper - optimise chunk tick iteration
             //this.playerTicketManager.update(i, Integer.MAX_VALUE, false); // Paper - no longer used
             //this.tickingTicketsTracker.removeTicket(TicketType.PLAYER, chunkcoordintpair, this.getPlayerTicketLevel(), chunkcoordintpair); // Paper - no longer used
         }
@@ -191,13 +191,11 @@ public abstract class DistanceManager {
     }
 
     public int getNaturalSpawnChunkCount() {
-        this.naturalSpawnChunkCounter.runAllUpdates();
-        return this.naturalSpawnChunkCounter.chunks.size();
+        return this.chunkMap.playerMobSpawnMap.size(); // Paper - optimise chunk tick iteration
     }
 
     public boolean hasPlayersNearby(long chunkPos) {
-        this.naturalSpawnChunkCounter.runAllUpdates();
-        return this.naturalSpawnChunkCounter.chunks.containsKey(chunkPos);
+        return this.chunkMap.playerMobSpawnMap.getObjectsInRange(chunkPos) != null; // Paper - optimise chunk tick iteration
     }
 
     public String getDebugStatus() {
diff --git a/src/main/java/net/minecraft/server/level/ServerChunkCache.java b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
index dfecd5531862109cd89cfd8a041a8beef70c1a6a..65a20974428ae1c0be2022d997234a16dc281292 100644
--- a/src/main/java/net/minecraft/server/level/ServerChunkCache.java
+++ b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
@@ -516,18 +516,10 @@ public class ServerChunkCache extends ChunkSource {
 
             gameprofilerfiller.push("pollingChunks");
             gameprofilerfiller.push("filteringLoadedChunks");
-            List<ServerChunkCache.ChunkAndHolder> list = Lists.newArrayListWithCapacity(this.chunkMap.size());
-            Iterator iterator = this.chunkMap.getChunks().iterator();
+            // Paper - optimise chunk tick iteration
             if (this.level.getServer().tickRateManager().runsNormally()) this.level.timings.chunkTicks.startTiming(); // Paper
 
-            while (iterator.hasNext()) {
-                ChunkHolder playerchunk = (ChunkHolder) iterator.next();
-                LevelChunk chunk = playerchunk.getTickingChunk();
-
-                if (chunk != null) {
-                    list.add(new ServerChunkCache.ChunkAndHolder(chunk, playerchunk));
-                }
-            }
+            // Paper - optimise chunk tick iteration
 
             if (this.level.getServer().tickRateManager().runsNormally()) {
                 gameprofilerfiller.popPush("naturalSpawnCount");
@@ -562,38 +554,109 @@ public class ServerChunkCache extends ChunkSource {
                 gameprofilerfiller.popPush("spawnAndTick");
                 boolean flag = this.level.getGameRules().getBoolean(GameRules.RULE_DOMOBSPAWNING) && !this.level.players().isEmpty(); // CraftBukkit
 
-                Util.shuffle(list, this.level.random);
-                // Paper start - call player naturally spawn event
-                int chunkRange = level.spigotConfig.mobSpawnRange;
-                chunkRange = (chunkRange > level.spigotConfig.viewDistance) ? (byte) level.spigotConfig.viewDistance : chunkRange;
-                chunkRange = Math.min(chunkRange, 8);
-                for (ServerPlayer entityPlayer : this.level.players()) {
-                    entityPlayer.playerNaturallySpawnedEvent = new com.destroystokyo.paper.event.entity.PlayerNaturallySpawnCreaturesEvent(entityPlayer.getBukkitEntity(), (byte) chunkRange);
-                    entityPlayer.playerNaturallySpawnedEvent.callEvent();
+                // Paper start - optimise chunk tick iteration
+                ChunkMap playerChunkMap = this.chunkMap;
+                for (ServerPlayer player : this.level.players) {
+                    if (!player.affectsSpawning || player.isSpectator()) {
+                        playerChunkMap.playerMobSpawnMap.remove(player);
+                        player.playerNaturallySpawnedEvent = null;
+                        player.lastEntitySpawnRadiusSquared = -1.0;
+                        continue;
+                    }
+
+                    int viewDistance = io.papermc.paper.chunk.system.ChunkSystem.getTickViewDistance(player);
+
+                    // copied and modified from isOutisdeRange
+                    int chunkRange = (int)level.spigotConfig.mobSpawnRange;
+                    chunkRange = (chunkRange > viewDistance) ? viewDistance : chunkRange;
+                    chunkRange = (chunkRange > DistanceManager.MOB_SPAWN_RANGE) ? DistanceManager.MOB_SPAWN_RANGE : chunkRange;
+
+                    com.destroystokyo.paper.event.entity.PlayerNaturallySpawnCreaturesEvent event = new com.destroystokyo.paper.event.entity.PlayerNaturallySpawnCreaturesEvent(player.getBukkitEntity(), (byte)chunkRange);
+                    event.callEvent();
+                    if (event.isCancelled() || event.getSpawnRadius() < 0) {
+                        playerChunkMap.playerMobSpawnMap.remove(player);
+                        player.playerNaturallySpawnedEvent = null;
+                        player.lastEntitySpawnRadiusSquared = -1.0;
+                        continue;
+                    }
+
+                    int range = Math.min(event.getSpawnRadius(), DistanceManager.MOB_SPAWN_RANGE); // limit to max spawn range
+                    int chunkX = io.papermc.paper.util.CoordinateUtils.getChunkCoordinate(player.getX());
+                    int chunkZ = io.papermc.paper.util.CoordinateUtils.getChunkCoordinate(player.getZ());
+
+                    playerChunkMap.playerMobSpawnMap.addOrUpdate(player, chunkX, chunkZ, range);
+                    player.lastEntitySpawnRadiusSquared = (double)((range << 4) * (range << 4)); // used in anyPlayerCloseEnoughForSpawning
+                    player.playerNaturallySpawnedEvent = event;
                 }
-                // Paper end
+                // Paper end - optimise chunk tick iteration
                 int l = this.level.getGameRules().getInt(GameRules.RULE_RANDOMTICKING);
                 boolean flag1 = this.level.ticksPerSpawnCategory.getLong(org.bukkit.entity.SpawnCategory.ANIMAL) != 0L && this.level.getLevelData().getGameTime() % this.level.ticksPerSpawnCategory.getLong(org.bukkit.entity.SpawnCategory.ANIMAL) == 0L; // CraftBukkit
-                Iterator iterator1 = list.iterator();
+                // Paper - optimise chunk tick iteration
 
                 int chunksTicked = 0; // Paper
-                while (iterator1.hasNext()) {
-                    ServerChunkCache.ChunkAndHolder chunkproviderserver_a = (ServerChunkCache.ChunkAndHolder) iterator1.next();
-                    LevelChunk chunk1 = chunkproviderserver_a.chunk;
+                // Paper start - optimise chunk tick iteration
+                io.papermc.paper.util.player.NearbyPlayers nearbyPlayers = this.chunkMap.getNearbyPlayers(); // Paper - optimise chunk tick iteration
+                Iterator<LevelChunk> chunkIterator;
+                if (this.level.paperConfig().entities.spawning.perPlayerMobSpawns) {
+                    chunkIterator = this.tickingChunks.iterator();
+                } else {
+                    chunkIterator = this.tickingChunks.unsafeIterator();
+                    List<LevelChunk> shuffled = Lists.newArrayListWithCapacity(this.tickingChunks.size());
+                    while (chunkIterator.hasNext()) {
+                        shuffled.add(chunkIterator.next());
+                    }
+                    Util.shuffle(shuffled, this.level.random);
+                    chunkIterator = shuffled.iterator();
+                }
+                try {
+                // Paper end - optimise chunk tick iteration
+                while (chunkIterator.hasNext()) {
+                    LevelChunk chunk1 = chunkIterator.next();
+                    // Paper end - optimise chunk tick iteration
                     ChunkPos chunkcoordintpair = chunk1.getPos();
 
-                    if (this.level.isNaturalSpawningAllowed(chunkcoordintpair) && this.chunkMap.anyPlayerCloseEnoughForSpawning(chunkcoordintpair)) {
+                    // Paper start - optimise chunk tick iteration
+                    com.destroystokyo.paper.util.maplist.ReferenceList<ServerPlayer> playersNearby
+                        = nearbyPlayers.getPlayers(chunkcoordintpair, io.papermc.paper.util.player.NearbyPlayers.NearbyMapType.SPAWN_RANGE);
+                    if (playersNearby == null) {
+                        continue;
+                    }
+                    Object[] rawData = playersNearby.getRawData();
+                    boolean spawn = false;
+                    boolean tick = false;
+                    for (int itr = 0, len = playersNearby.size(); itr < len; ++itr) {
+                        ServerPlayer player = (ServerPlayer)rawData[itr];
+                        if (player.isSpectator()) {
+                            continue;
+                        }
+
+                        double distance = ChunkMap.euclideanDistanceSquared(chunkcoordintpair, player);
+                        spawn |= player.lastEntitySpawnRadiusSquared >= distance;
+                        tick |= ((double)io.papermc.paper.util.player.NearbyPlayers.SPAWN_RANGE_VIEW_DISTANCE_BLOCKS) * ((double)io.papermc.paper.util.player.NearbyPlayers.SPAWN_RANGE_VIEW_DISTANCE_BLOCKS) >= distance;
+                        if (spawn & tick) {
+                            break;
+                        }
+                    }
+                    if (tick && chunk1.chunkStatus.isOrAfter(net.minecraft.server.level.FullChunkStatus.ENTITY_TICKING)) {
+                        // Paper end - optimise chunk tick iteration
                         chunk1.incrementInhabitedTime(j);
-                        if (flag && (this.spawnEnemies || this.spawnFriendlies) && this.level.getWorldBorder().isWithinBounds(chunkcoordintpair) && this.chunkMap.anyPlayerCloseEnoughForSpawning(chunkcoordintpair, true)) { // Spigot
+                        if (spawn && flag && (this.spawnEnemies || this.spawnFriendlies) && this.level.getWorldBorder().isWithinBounds(chunkcoordintpair)) { // Spigot // Paper - optimise chunk tick iteration
                             NaturalSpawner.spawnForChunk(this.level, chunk1, spawnercreature_d, this.spawnFriendlies, this.spawnEnemies, flag1);
                         }
 
-                        if (this.level.shouldTickBlocksAt(chunkcoordintpair.toLong())) {
+                        if (true || this.level.shouldTickBlocksAt(chunkcoordintpair.toLong())) { // Paper - optimise chunk tick iteration
                             this.level.tickChunk(chunk1, l);
                             if ((chunksTicked++ & 1) == 0) net.minecraft.server.MinecraftServer.getServer().executeMidTickTasks(); // Paper
                         }
                     }
                 }
+                // Paper start - optimise chunk tick iteration
+                } finally {
+                    if (chunkIterator instanceof io.papermc.paper.util.maplist.IteratorSafeOrderedReferenceSet.Iterator safeIterator) {
+                        safeIterator.finishedIterating();
+                    }
+                }
+                // Paper end - optimise chunk tick iteration
                 this.level.timings.chunkTicks.stopTiming(); // Paper
 
                 gameprofilerfiller.popPush("customSpawners");
@@ -605,11 +668,23 @@ public class ServerChunkCache extends ChunkSource {
             }
 
             gameprofilerfiller.popPush("broadcast");
-            list.forEach((chunkproviderserver_a1) -> {
+            // Paper - optimise chunk tick iteration
                 this.level.timings.broadcastChunkUpdates.startTiming(); // Paper - timing
-                chunkproviderserver_a1.holder.broadcastChanges(chunkproviderserver_a1.chunk);
+            // Paper start - optimise chunk tick iteration
+            if (!this.chunkMap.needsChangeBroadcasting.isEmpty()) {
+                it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<ChunkHolder> copy = this.chunkMap.needsChangeBroadcasting.clone();
+                this.chunkMap.needsChangeBroadcasting.clear();
+                for (ChunkHolder holder : copy) {
+                    holder.broadcastChanges(holder.getFullChunkNowUnchecked()); // LevelChunks are NEVER unloaded
+                    if (holder.needsBroadcastChanges()) {
+                        // I DON'T want to KNOW what DUMB plugins might be doing.
+                        this.chunkMap.needsChangeBroadcasting.add(holder);
+                    }
+                }
+            }
+            // Paper end - optimise chunk tick iteration
                 this.level.timings.broadcastChunkUpdates.stopTiming(); // Paper - timing
-            });
+            // Paper - optimise chunk tick iteration
             gameprofilerfiller.pop();
             gameprofilerfiller.pop();
         }
diff --git a/src/main/java/net/minecraft/server/level/ServerPlayer.java b/src/main/java/net/minecraft/server/level/ServerPlayer.java
index 6ae35f3adce280e8be8e7e2f3bc4a0896ef6df83..84974c72dd3838ea118cc60c284709911cd7630b 100644
--- a/src/main/java/net/minecraft/server/level/ServerPlayer.java
+++ b/src/main/java/net/minecraft/server/level/ServerPlayer.java
@@ -325,6 +325,9 @@ public class ServerPlayer extends Player {
         });
     }
     // Paper end - replace player chunk loader
+    // Paper start - optimise chunk tick iteration
+    public double lastEntitySpawnRadiusSquared = -1.0;
+    // Paper end - optimise chunk tick iteration
 
     public ServerPlayer(MinecraftServer server, ServerLevel world, GameProfile profile, ClientInformation clientOptions) {
         super(world, world.getSharedSpawnPos(), world.getSharedSpawnAngle(), profile);