Paper/patches/server/0779-Optimise-nearby-player-lookups.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <spottedleaf@spottedleaf.dev>
Date: Thu, 27 Aug 2020 16:22:52 -0700
Subject: [PATCH] Optimise nearby player lookups

Use a distance map to map out close players.
Note that it's important that we cache the distance map value per chunk
since the penalty of a map lookup could outweigh the benefits of
searching less players (as it basically did in the outside range patch).

diff --git a/src/main/java/net/minecraft/server/level/ChunkHolder.java b/src/main/java/net/minecraft/server/level/ChunkHolder.java
index bb411853cb9e0120bcaa82e878724ee17167057b..7f663523b8c43b356763d6d5249e1aec416de37c 100644
--- a/src/main/java/net/minecraft/server/level/ChunkHolder.java
+++ b/src/main/java/net/minecraft/server/level/ChunkHolder.java
@@ -83,6 +83,12 @@ public class ChunkHolder {
         long key = net.minecraft.server.MCUtil.getCoordinateKey(this.pos);
         this.playersInMobSpawnRange = this.chunkMap.playerMobSpawnMap.getObjectsInRange(key);
         this.playersInChunkTickRange = this.chunkMap.playerChunkTickRangeMap.getObjectsInRange(key);
+        // Paper start - optimise checkDespawn
+        LevelChunk chunk = this.getFullChunkUnchecked();
+        if (chunk != null) {
+            chunk.updateGeneralAreaCache();
+        }
+        // Paper end - optimise checkDespawn
     }
     // Paper end - optimise anyPlayerCloseEnoughForSpawning
     long lastAutoSaveTime; // Paper - incremental autosave
diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index 9ab37d95b0dbd13dfe31b34b2a91c2a7bc7f6e64..27e9bd7dabb5f827b8baf126565d1efb9eb2c2ef 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -159,6 +159,13 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     int viewDistance;
     public final com.destroystokyo.paper.util.PlayerMobDistanceMap playerMobDistanceMap; // Paper
 
+    // Paper start - optimise checkDespawn
+    public static final int GENERAL_AREA_MAP_SQUARE_RADIUS = 40;
+    public static final double GENERAL_AREA_MAP_ACCEPTABLE_SEARCH_RANGE = 16.0 * (GENERAL_AREA_MAP_SQUARE_RADIUS - 1);
+    public static final double GENERAL_AREA_MAP_ACCEPTABLE_SEARCH_RANGE_SQUARED = GENERAL_AREA_MAP_ACCEPTABLE_SEARCH_RANGE * GENERAL_AREA_MAP_ACCEPTABLE_SEARCH_RANGE;
+    public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerGeneralAreaMap;
+    // Paper end - optimise checkDespawn
+
     // CraftBukkit start - recursion-safe executor for Chunk loadCallback() and unloadCallback()
     public final CallbackExecutor callbackExecutor = new CallbackExecutor();
     public static final class CallbackExecutor implements java.util.concurrent.Executor, Runnable {
@@ -239,6 +246,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         this.playerChunkTickRangeMap.update(player, chunkX, chunkZ, DistanceManager.MOB_SPAWN_RANGE);
         this.playerChunkTickRangeMap.add(player, chunkX, chunkZ, DistanceManager.MOB_SPAWN_RANGE);
         // Paper end - optimise ChunkMap#anyPlayerCloseEnoughForSpawning
+        this.playerGeneralAreaMap.add(player, chunkX, chunkZ, GENERAL_AREA_MAP_SQUARE_RADIUS); // Paper - optimise checkDespawn
     }
 
     void removePlayerFromDistanceMaps(ServerPlayer player) {
@@ -251,6 +259,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         this.playerMobSpawnMap.remove(player);
         this.playerChunkTickRangeMap.remove(player);
         // Paper end - optimise ChunkMap#anyPlayerCloseEnoughForSpawning
+        this.playerGeneralAreaMap.remove(player); // Paper - optimise checkDespawns
     }
 
     void updateMaps(ServerPlayer player) {
@@ -266,6 +275,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         }
         // Paper end - use distance map to optimise entity tracker
         this.playerChunkTickRangeMap.update(player, chunkX, chunkZ, DistanceManager.MOB_SPAWN_RANGE); // Paper - optimise ChunkMap#anyPlayerCloseEnoughForSpawning
+        this.playerGeneralAreaMap.update(player, chunkX, chunkZ, GENERAL_AREA_MAP_SQUARE_RADIUS); // Paper - optimise checkDespawn
     }
     // Paper end
     // Paper start
@@ -421,6 +431,23 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
                 }
             });
         // Paper end - optimise ChunkMap#anyPlayerCloseEnoughForSpawning
+        // Paper start - optimise checkDespawn
+        this.playerGeneralAreaMap = new com.destroystokyo.paper.util.misc.PlayerAreaMap(this.pooledLinkedPlayerHashSets,
+            (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
+             com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
+                LevelChunk chunk = ChunkMap.this.level.getChunkSource().getChunkAtIfCachedImmediately(rangeX, rangeZ);
+                if (chunk != null) {
+                    chunk.updateGeneralAreaCache(newState);
+                }
+            },
+            (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
+             com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
+                LevelChunk chunk = ChunkMap.this.level.getChunkSource().getChunkAtIfCachedImmediately(rangeX, rangeZ);
+                if (chunk != null) {
+                    chunk.updateGeneralAreaCache(newState);
+                }
+            });
+        // Paper end - optimise checkDespawn
     }
 
     protected ChunkGenerator generator() {
diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
index 17b01c1592ec2481d1ff444ff12dbc3790e09368..3ce8055f0fb8c5b605356e4e85ee1dbdcc73ba0e 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -396,6 +396,83 @@ public class ServerLevel extends Level implements WorldGenLevel {
         return this.getServer().getPlayerList().getPlayer(uuid);
     }
     // Paper end
+    // Paper start - optimise checkDespawn
+    public final List<ServerPlayer> playersAffectingSpawning = new java.util.ArrayList<>();
+    // Paper end - optimise checkDespawn
+    // Paper start - optimise get nearest players for entity AI
+    @Override
+    public final ServerPlayer getNearestPlayer(net.minecraft.world.entity.ai.targeting.TargetingConditions condition, @Nullable LivingEntity source,
+                                               double centerX, double centerY, double centerZ) {
+        com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> nearby;
+        nearby = this.getChunkSource().chunkMap.playerGeneralAreaMap.getObjectsInRange(Mth.floor(centerX) >> 4, Mth.floor(centerZ) >> 4);
+
+        if (nearby == null) {
+            return null;
+        }
+
+        Object[] backingSet = nearby.getBackingSet();
+
+        double closestDistanceSquared = Double.MAX_VALUE;
+        ServerPlayer closest = null;
+
+        for (int i = 0, len = backingSet.length; i < len; ++i) {
+            Object _player = backingSet[i];
+            if (!(_player instanceof ServerPlayer)) {
+                continue;
+            }
+            ServerPlayer player = (ServerPlayer)_player;
+
+            double distanceSquared = player.distanceToSqr(centerX, centerY, centerZ);
+            if (distanceSquared < closestDistanceSquared && condition.test(source, player)) {
+                closest = player;
+                closestDistanceSquared = distanceSquared;
+            }
+        }
+
+        return closest;
+    }
+
+    @Override
+    public Player getNearestPlayer(net.minecraft.world.entity.ai.targeting.TargetingConditions pathfindertargetcondition, LivingEntity entityliving) {
+        return this.getNearestPlayer(pathfindertargetcondition, entityliving, entityliving.getX(), entityliving.getY(), entityliving.getZ());
+    }
+
+    @Override
+    public Player getNearestPlayer(net.minecraft.world.entity.ai.targeting.TargetingConditions pathfindertargetcondition,
+                                   double d0, double d1, double d2) {
+        return this.getNearestPlayer(pathfindertargetcondition, null, d0, d1, d2);
+    }
+
+    @Override
+    public List<Player> getNearbyPlayers(net.minecraft.world.entity.ai.targeting.TargetingConditions condition, LivingEntity source, AABB axisalignedbb) {
+        com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> nearby;
+        double centerX = (axisalignedbb.maxX + axisalignedbb.minX) * 0.5;
+        double centerZ = (axisalignedbb.maxZ + axisalignedbb.minZ) * 0.5;
+        nearby = this.getChunkSource().chunkMap.playerGeneralAreaMap.getObjectsInRange(Mth.floor(centerX) >> 4, Mth.floor(centerZ) >> 4);
+
+        List<Player> ret = new java.util.ArrayList<>();
+
+        if (nearby == null) {
+            return ret;
+        }
+
+        Object[] backingSet = nearby.getBackingSet();
+
+        for (int i = 0, len = backingSet.length; i < len; ++i) {
+            Object _player = backingSet[i];
+            if (!(_player instanceof ServerPlayer)) {
+                continue;
+            }
+            ServerPlayer player = (ServerPlayer)_player;
+
+            if (axisalignedbb.contains(player.getX(), player.getY(), player.getZ()) && condition.test(source, player)) {
+                ret.add(player);
+            }
+        }
+
+        return ret;
+    }
+    // Paper end - optimise get nearest players for entity AI
 
     // Add env and gen to constructor, WorldData -> WorldDataServer
     public ServerLevel(MinecraftServer minecraftserver, Executor executor, LevelStorageSource.LevelStorageAccess convertable_conversionsession, ServerLevelData iworlddataserver, ResourceKey<Level> resourcekey, DimensionType dimensionmanager, ChunkProgressListener worldloadlistener, ChunkGenerator chunkgenerator, boolean flag, long i, List<CustomSpawner> list, boolean flag1, org.bukkit.World.Environment env, org.bukkit.generator.ChunkGenerator gen, org.bukkit.generator.BiomeProvider biomeProvider) {
@@ -484,6 +561,14 @@ public class ServerLevel extends Level implements WorldGenLevel {
     }
 
     public void tick(BooleanSupplier shouldKeepTicking) {
+        // Paper start - optimise checkDespawn
+        this.playersAffectingSpawning.clear();
+        for (ServerPlayer player : this.players) {
+            if (net.minecraft.world.entity.EntitySelector.affectsSpawning.test(player)) {
+                this.playersAffectingSpawning.add(player);
+            }
+        }
+        // Paper end - optimise checkDespawn
         ProfilerFiller gameprofilerfiller = this.getProfiler();
 
         this.handlingTick = true;
diff --git a/src/main/java/net/minecraft/world/entity/Mob.java b/src/main/java/net/minecraft/world/entity/Mob.java
index 697c2663c4deeb8f2ad603c979ab0884ac027930..0b46066d35d9bb38d98a9d6e5ca8dbdc0ba1dc5a 100644
--- a/src/main/java/net/minecraft/world/entity/Mob.java
+++ b/src/main/java/net/minecraft/world/entity/Mob.java
@@ -792,7 +792,12 @@ public abstract class Mob extends LivingEntity {
         if (this.level.getDifficulty() == Difficulty.PEACEFUL && this.shouldDespawnInPeaceful()) {
             this.discard();
         } else if (!this.isPersistenceRequired() && !this.requiresCustomPersistence()) {
-            Player entityhuman = this.level.findNearbyPlayer(this, -1.0D, EntitySelector.affectsSpawning); // Paper
+            // Paper start - optimise checkDespawn
+            Player entityhuman = this.level.findNearbyPlayer(this, level.paperConfig.hardDespawnDistances.getInt(this.getType().getCategory()) + 1, EntitySelector.affectsSpawning); // Paper
+            if (entityhuman == null) {
+                entityhuman = ((ServerLevel)this.level).playersAffectingSpawning.isEmpty() ? null : ((ServerLevel)this.level).playersAffectingSpawning.get(0);
+            }
+            // Paper end - optimise checkDespawn
 
             if (entityhuman != null) {
                 double d0 = entityhuman.distanceToSqr((Entity) this);
diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
index 02a240a3925008152ea93059db47122e7f1a40d9..c2220d5157d3065a256cd17410760c6aedf24987 100644
--- a/src/main/java/net/minecraft/world/level/Level.java
+++ b/src/main/java/net/minecraft/world/level/Level.java
@@ -244,6 +244,69 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
         return ret;
     }
     // Paper end
+    // Paper start - optimise checkDespawn
+    public final List<net.minecraft.server.level.ServerPlayer> getNearbyPlayers(@Nullable Entity source, double sourceX, double sourceY,
+                                                                                double sourceZ, double maxRange, @Nullable Predicate<Entity> predicate) {
+        LevelChunk chunk;
+        if (maxRange < 0.0 || maxRange >= net.minecraft.server.level.ChunkMap.GENERAL_AREA_MAP_ACCEPTABLE_SEARCH_RANGE ||
+            (chunk = (LevelChunk)this.getChunkIfLoadedImmediately(Mth.floor(sourceX) >> 4, Mth.floor(sourceZ) >> 4)) == null) {
+            return this.getNearbyPlayersSlow(source, sourceX, sourceY, sourceZ, maxRange, predicate);
+        }
+
+        List<net.minecraft.server.level.ServerPlayer> ret = new java.util.ArrayList<>();
+        chunk.getNearestPlayers(sourceX, sourceY, sourceZ, predicate, maxRange, ret);
+        return ret;
+    }
+
+    private List<net.minecraft.server.level.ServerPlayer> getNearbyPlayersSlow(@Nullable Entity source, double sourceX, double sourceY,
+                                                                               double sourceZ, double maxRange, @Nullable Predicate<Entity> predicate) {
+        List<net.minecraft.server.level.ServerPlayer> ret = new java.util.ArrayList<>();
+        double maxRangeSquared = maxRange * maxRange;
+
+        for (net.minecraft.server.level.ServerPlayer player : (List<net.minecraft.server.level.ServerPlayer>)this.players()) {
+            if ((maxRange < 0.0 || player.distanceToSqr(sourceX, sourceY, sourceZ) < maxRangeSquared)) {
+                if (predicate == null || predicate.test(player)) {
+                    ret.add(player);
+                }
+            }
+        }
+
+        return ret;
+    }
+
+    private net.minecraft.server.level.ServerPlayer getNearestPlayerSlow(@Nullable Entity source, double sourceX, double sourceY,
+                                                                         double sourceZ, double maxRange, @Nullable Predicate<Entity> predicate) {
+        net.minecraft.server.level.ServerPlayer closest = null;
+        double closestRangeSquared = maxRange < 0.0 ? Double.MAX_VALUE : maxRange * maxRange;
+
+        for (net.minecraft.server.level.ServerPlayer player : (List<net.minecraft.server.level.ServerPlayer>)this.players()) {
+            double distanceSquared = player.distanceToSqr(sourceX, sourceY, sourceZ);
+            if (distanceSquared < closestRangeSquared && (predicate == null || predicate.test(player))) {
+                closest = player;
+                closestRangeSquared = distanceSquared;
+            }
+        }
+
+        return closest;
+    }
+
+
+    public final net.minecraft.server.level.ServerPlayer getNearestPlayer(@Nullable Entity source, double sourceX, double sourceY,
+                                                                          double sourceZ, double maxRange, @Nullable Predicate<Entity> predicate) {
+        LevelChunk chunk;
+        if (maxRange < 0.0 || maxRange >= net.minecraft.server.level.ChunkMap.GENERAL_AREA_MAP_ACCEPTABLE_SEARCH_RANGE ||
+            (chunk = (LevelChunk)this.getChunkIfLoadedImmediately(Mth.floor(sourceX) >> 4, Mth.floor(sourceZ) >> 4)) == null) {
+            return this.getNearestPlayerSlow(source, sourceX, sourceY, sourceZ, maxRange, predicate);
+        }
+
+        return chunk.findNearestPlayer(sourceX, sourceY, sourceZ, maxRange, predicate);
+    }
+
+    @Override
+    public @Nullable Player getNearestPlayer(double d0, double d1, double d2, double d3, @Nullable Predicate<Entity> predicate) {
+        return this.getNearestPlayer(null, d0, d1, d2, d3, predicate);
+    }
+    // Paper end - optimise checkDespawn
 
     protected Level(WritableLevelData worlddatamutable, ResourceKey<Level> resourcekey, final DimensionType dimensionmanager, Supplier<ProfilerFiller> supplier, boolean flag, boolean flag1, long i, org.bukkit.generator.ChunkGenerator gen, org.bukkit.generator.BiomeProvider biomeProvider, org.bukkit.World.Environment env, java.util.concurrent.Executor executor) { // Paper - Async-Anti-Xray - Pass executor
         this.spigotConfig = new org.spigotmc.SpigotWorldConfig(((net.minecraft.world.level.storage.PrimaryLevelData) worlddatamutable).getLevelName()); // Spigot
diff --git a/src/main/java/net/minecraft/world/level/NaturalSpawner.java b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
index 928025438af179711c42381fc3eaeac74cd20c59..c48d0773e7f1af4bc247d777eccc8a42c7e17601 100644
--- a/src/main/java/net/minecraft/world/level/NaturalSpawner.java
+++ b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
@@ -275,7 +275,7 @@ public final class NaturalSpawner {
                             blockposition_mutableblockposition.set(l, i, i1);
                             double d0 = (double) l + 0.5D;
                             double d1 = (double) i1 + 0.5D;
-                            Player entityhuman = world.getNearestPlayer(d0, (double) i, d1, -1.0D, false);
+                            Player entityhuman = (chunk instanceof LevelChunk) ? ((LevelChunk)chunk).findNearestPlayer(d0, i, d1, 576.0D, net.minecraft.world.entity.EntitySelector.NO_SPECTATORS) : world.getNearestPlayer(d0, (double) i, d1, -1.0D, false); // Paper - use chunk's player cache to optimize search in range
 
                             if (entityhuman != null) {
                                 double d2 = entityhuman.distanceToSqr(d0, (double) i, d1);
@@ -348,7 +348,7 @@ public final class NaturalSpawner {
     }
 
     private static boolean isRightDistanceToPlayerAndSpawnPoint(ServerLevel world, ChunkAccess chunk, BlockPos.MutableBlockPos pos, double squaredDistance) {
-        return squaredDistance <= 576.0D ? false : (world.getSharedSpawnPos().closerThan((Position) (new Vec3((double) pos.getX() + 0.5D, (double) pos.getY(), (double) pos.getZ() + 0.5D)), 24.0D) ? false : Objects.equals(new ChunkPos(pos), chunk.getPos()) || world.isPositionEntityTicking((BlockPos) pos));
+        return squaredDistance <= 576.0D ? false : (world.getSharedSpawnPos().closerThan((Position) (new Vec3((double) pos.getX() + 0.5D, (double) pos.getY(), (double) pos.getZ() + 0.5D)), 24.0D) ? false : Objects.equals(new ChunkPos(pos), chunk.getPos()) || world.isPositionEntityTicking((BlockPos) pos)); // Paper - diff on change, copy into caller
     }
 
     private static Boolean isValidSpawnPostitionForType(ServerLevel world, MobCategory group, StructureFeatureManager structureAccessor, ChunkGenerator chunkGenerator, MobSpawnSettings.SpawnerData spawnEntry, BlockPos.MutableBlockPos pos, double squaredDistance) { // Paper
diff --git a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
index f73b3bb9b92fab3ca73d8561672797c1fd3e318b..c30204c5daac422eb009a447c1eb4fbc94a84318 100644
--- a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
+++ b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
@@ -235,6 +235,93 @@ public class LevelChunk extends ChunkAccess {
         }
     }
     // Paper end
+    // Paper start - optimise checkDespawn
+    private boolean playerGeneralAreaCacheSet;
+    private com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<net.minecraft.server.level.ServerPlayer> playerGeneralAreaCache;
+
+    public com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<net.minecraft.server.level.ServerPlayer> getPlayerGeneralAreaCache() {
+        if (!this.playerGeneralAreaCacheSet) {
+            this.updateGeneralAreaCache();
+        }
+        return this.playerGeneralAreaCache;
+    }
+
+    public void updateGeneralAreaCache() {
+        this.updateGeneralAreaCache(((ServerLevel)this.level).getChunkSource().chunkMap.playerGeneralAreaMap.getObjectsInRange(this.coordinateKey));
+    }
+
+    public void updateGeneralAreaCache(com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<net.minecraft.server.level.ServerPlayer> value) {
+        this.playerGeneralAreaCacheSet = true;
+        this.playerGeneralAreaCache = value;
+    }
+
+    public net.minecraft.server.level.ServerPlayer findNearestPlayer(double sourceX, double sourceY, double sourceZ,
+                                                                     double maxRange, java.util.function.Predicate<Entity> predicate) {
+        if (!this.playerGeneralAreaCacheSet) {
+            this.updateGeneralAreaCache();
+        }
+
+        com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<net.minecraft.server.level.ServerPlayer> nearby = this.playerGeneralAreaCache;
+
+        if (nearby == null) {
+            return null;
+        }
+
+        Object[] backingSet = nearby.getBackingSet();
+        double closestDistance = maxRange < 0.0 ? Double.MAX_VALUE : maxRange * maxRange;
+        net.minecraft.server.level.ServerPlayer closest = null;
+        for (int i = 0, len = backingSet.length; i < len; ++i) {
+            Object _player = backingSet[i];
+            if (!(_player instanceof net.minecraft.server.level.ServerPlayer)) {
+                continue;
+            }
+            net.minecraft.server.level.ServerPlayer player = (net.minecraft.server.level.ServerPlayer)_player;
+
+            double distance = player.distanceToSqr(sourceX, sourceY, sourceZ);
+            if (distance < closestDistance && predicate.test(player)) {
+                closest = player;
+                closestDistance = distance;
+            }
+        }
+
+        return closest;
+    }
+
+    public void getNearestPlayers(double sourceX, double sourceY, double sourceZ, java.util.function.Predicate<Entity> predicate,
+                                  double range, java.util.List<net.minecraft.server.level.ServerPlayer> ret) {
+        if (!this.playerGeneralAreaCacheSet) {
+            this.updateGeneralAreaCache();
+        }
+
+        com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<net.minecraft.server.level.ServerPlayer> nearby = this.playerGeneralAreaCache;
+
+        if (nearby == null) {
+            return;
+        }
+
+        double rangeSquared = range * range;
+
+        Object[] backingSet = nearby.getBackingSet();
+        for (int i = 0, len = backingSet.length; i < len; ++i) {
+            Object _player = backingSet[i];
+            if (!(_player instanceof net.minecraft.server.level.ServerPlayer)) {
+                continue;
+            }
+            net.minecraft.server.level.ServerPlayer player = (net.minecraft.server.level.ServerPlayer)_player;
+
+            if (range >= 0.0) {
+                double distanceSquared = player.distanceToSqr(sourceX, sourceY, sourceZ);
+                if (distanceSquared > rangeSquared) {
+                    continue;
+                }
+            }
+
+            if (predicate == null || predicate.test(player)) {
+                ret.add(player);
+            }
+        }
+    }
+    // Paper end - optimise checkDespawn
 
     public LevelChunk(ServerLevel world, ProtoChunk protoChunk, @Nullable LevelChunk.PostLoadProcessor entityLoader) {
         this(world, protoChunk.getPos(), protoChunk.getUpgradeData(), protoChunk.unpackBlockTicks(), protoChunk.unpackFluidTicks(), protoChunk.getInhabitedTime(), protoChunk.getSections(), entityLoader, protoChunk.getBlendingData());