Paper/patches/server/0769-Replace-player-chunk-loader-system.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <spottedleaf@spottedleaf.dev>
Date: Sun, 24 Jan 2021 20:27:32 -0800
Subject: [PATCH] Replace player chunk loader system

The old one has undebuggable problems. Rewriting seems
the most sensible option.

This new player chunk manager will also strictly rate limit
chunk sends so that netty threads do not get overloaded, whether
it be from the anti-xray logic or the compression itself.

Chunk loading is also rate limited in the same manner, so this
will result in a maximum responsiveness for change.

Config:
```
chunk-loading:
  min-load-radius: 2
  max-concurrent-sends: 2
  autoconfig-send-distance: true
  target-player-chunk-send-rate: 100.0
  global-max-chunk-send-rate: -1
  enable-frustum-priority: false
  global-max-chunk-load-rate: 300.0
  player-max-concurrent-loads: 4.0
  global-max-concurrent-loads: 500.0
```

min-load-radius - The radius of chunks around a player that
are not throttled for loading. The number of chunks
affected is actually the configured value plus one as this
config controls the chunks the client will be able to render.

max-concurrent-sends - The maximum number of chunks that
can be queued to send at any given time. Low values
are generally going to solve server-sided networking
bottlenecks like anti-xray and chunk compression. Client
side networking is unlikely to be helped (i.e this wont help
people running off McDonald's wifi).

autoconfig-send-distance - Whether to try to use the client's
view distance for the send view distance in the server. In the
case that no plugin has explicitly set the send distance and
the client view distance is less-than the server's send distance,
the client's view distance will be used. This will not affect
tick view distance or no-tick view distance.

target-player-chunk-send-rate - The maximum chunk send rate
an individual player will have. -1 means no limit

global-max-chunk-send-rate - The maximum chunk send rate for
the whole server. -1 means no limit

enable-frustum-priority - Whether chunks in front of a player
are prioritised to load/send first. Disabled by default
because the client can bug out due to the out of order
chunk sending.

global-max-chunk-load-rate - The maximum chunk load rate
for the whole server.

player-max-concurrent-loads and global-max-concurrent-loads
The maximum number of concurrent loads for the server is
determined by the number of players on the server multiplied by the
`player-max-concurrent-loads`. It is then limited to
whatever `global-max-concurrent-loads` is configured to.

diff --git a/src/main/java/co/aikar/timings/TimingsExport.java b/src/main/java/co/aikar/timings/TimingsExport.java
index cfe293881f68c8db337c3a48948362bb7b3e3522..7d44abcb4fff9717a1af55879deb7eb9c2d9e7e9 100644
--- a/src/main/java/co/aikar/timings/TimingsExport.java
+++ b/src/main/java/co/aikar/timings/TimingsExport.java
@@ -153,7 +153,7 @@ public class TimingsExport extends Thread {
                     return pair(rule, world.getWorld().getGameRuleValue(rule));
                 })),
                 pair("ticking-distance", world.getChunkSource().chunkMap.getEffectiveViewDistance()),
-                pair("notick-viewdistance", world.getChunkSource().chunkMap.getEffectiveNoTickViewDistance())
+                pair("notick-viewdistance", world.getChunkSource().chunkMap.playerChunkManager.getTargetNoTickViewDistance()) // Paper - replace old player chunk management
             ));
         }));
 
diff --git a/src/main/java/com/destroystokyo/paper/PaperConfig.java b/src/main/java/com/destroystokyo/paper/PaperConfig.java
index bc4081483a228aa275511d28231d615fe0f36d4e..be132f9d683767002a3e7f5641cb3cc3db74464c 100644
--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
@@ -522,4 +522,26 @@ public class PaperConfig {
         itemValidationBookAuthorLength = getInt("settings.item-validation.book.author", itemValidationBookAuthorLength);
         itemValidationBookPageLength = getInt("settings.item-validation.book.page", itemValidationBookPageLength);
     }
+
+    public static int playerMinChunkLoadRadius;
+    public static boolean playerAutoConfigureSendViewDistance;
+    public static int playerMaxConcurrentChunkSends;
+    public static double playerTargetChunkSendRate;
+    public static double globalMaxChunkSendRate;
+    public static boolean playerFrustumPrioritisation;
+    public static double globalMaxChunkLoadRate;
+    public static double playerMaxConcurrentChunkLoads;
+    public static double globalMaxConcurrentChunkLoads;
+
+    private static void newPlayerChunkManagement() {
+        playerMinChunkLoadRadius = getInt("settings.chunk-loading.min-load-radius", 2);
+        playerMaxConcurrentChunkSends = getInt("settings.chunk-loading.max-concurrent-sends", 2);
+        playerAutoConfigureSendViewDistance = getBoolean("settings.chunk-loading.autoconfig-send-distance", true);
+        playerTargetChunkSendRate = getDouble("settings.chunk-loading.target-player-chunk-send-rate", 100.0);
+        globalMaxChunkSendRate = getDouble("settings.chunk-loading.global-max-chunk-send-rate", -1.0);
+        playerFrustumPrioritisation = getBoolean("settings.chunk-loading.enable-frustum-priority", false);
+        globalMaxChunkLoadRate = getDouble("settings.chunk-loading.global-max-chunk-load-rate", 300.0);
+        playerMaxConcurrentChunkLoads = getDouble("settings.chunk-loading.player-max-concurrent-loads", 4.0);
+        globalMaxConcurrentChunkLoads = getDouble("settings.chunk-loading.global-max-concurrent-loads", 500.0);
+    }
 }
diff --git a/src/main/java/io/papermc/paper/chunk/PlayerChunkLoader.java b/src/main/java/io/papermc/paper/chunk/PlayerChunkLoader.java
new file mode 100644
index 0000000000000000000000000000000000000000..b3da5ec6701448a4b273c86aff9c64e3d75e5885
--- /dev/null
+++ b/src/main/java/io/papermc/paper/chunk/PlayerChunkLoader.java
@@ -0,0 +1,989 @@
+package io.papermc.paper.chunk;
+
+import com.destroystokyo.paper.PaperConfig;
+import com.destroystokyo.paper.util.misc.PlayerAreaMap;
+import com.destroystokyo.paper.util.misc.PooledLinkedHashSets;
+import io.papermc.paper.util.CoordinateUtils;
+import io.papermc.paper.util.IntervalledCounter;
+import io.papermc.paper.util.TickThread;
+import it.unimi.dsi.fastutil.longs.LongOpenHashSet;
+import it.unimi.dsi.fastutil.objects.Reference2IntOpenHashMap;
+import it.unimi.dsi.fastutil.objects.Reference2ObjectLinkedOpenHashMap;
+import it.unimi.dsi.fastutil.objects.ReferenceLinkedOpenHashSet;
+import net.minecraft.network.protocol.Packet;
+import net.minecraft.network.protocol.game.ClientboundSetChunkCacheCenterPacket;
+import net.minecraft.network.protocol.game.ClientboundSetChunkCacheRadiusPacket;
+import net.minecraft.server.MCUtil;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ChunkHolder;
+import net.minecraft.server.level.ChunkMap;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.server.level.TicketType;
+import net.minecraft.util.Mth;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.LevelChunk;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.TreeSet;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public final class PlayerChunkLoader {
+
+    public static final int MIN_VIEW_DISTANCE = 2;
+    public static final int MAX_VIEW_DISTANCE = 32;
+
+    public static final int TICK_TICKET_LEVEL = 31;
+    public static final int LOADED_TICKET_LEVEL = 33;
+
+    protected final ChunkMap chunkMap;
+    protected final Reference2ObjectLinkedOpenHashMap<ServerPlayer, PlayerLoaderData> playerMap = new Reference2ObjectLinkedOpenHashMap<>(512, 0.7f);
+    protected final ReferenceLinkedOpenHashSet<PlayerLoaderData> chunkSendQueue = new ReferenceLinkedOpenHashSet<>(512, 0.7f);
+
+    protected final TreeSet<PlayerLoaderData> chunkLoadQueue = new TreeSet<>((final PlayerLoaderData p1, final PlayerLoaderData p2) -> {
+        if (p1 == p2) {
+            return 0;
+        }
+
+        final ChunkPriorityHolder holder1 = p1.loadQueue.peekFirst();
+        final ChunkPriorityHolder holder2 = p2.loadQueue.peekFirst();
+
+        final int priorityCompare = Double.compare(holder1 == null ? Double.MAX_VALUE : holder1.priority, holder2 == null ? Double.MAX_VALUE : holder2.priority);
+
+        if (priorityCompare != 0) {
+            return priorityCompare;
+        }
+
+        final int idCompare = Integer.compare(p1.player.getId(), p2.player.getId());
+
+        if (idCompare != 0) {
+            return idCompare;
+        }
+
+        // last resort
+        return Integer.compare(System.identityHashCode(p1), System.identityHashCode(p2));
+    });
+
+    protected final TreeSet<PlayerLoaderData> chunkSendWaitQueue = new TreeSet<>((final PlayerLoaderData p1, final PlayerLoaderData p2) -> {
+        if (p1 == p2) {
+            return 0;
+        }
+
+        final int timeCompare = Long.compare(p1.nextChunkSendTarget, p2.nextChunkSendTarget);
+        if (timeCompare != 0) {
+            return timeCompare;
+        }
+
+        final int idCompare = Integer.compare(p1.player.getId(), p2.player.getId());
+
+        if (idCompare != 0) {
+            return idCompare;
+        }
+
+        // last resort
+        return Integer.compare(System.identityHashCode(p1), System.identityHashCode(p2));
+    });
+
+
+    // no throttling is applied below this VD for loading
+
+    /**
+     * The chunks to be sent to players, provided they're send-ready. Send-ready means the chunk and its 1 radius neighbours are loaded.
+     */
+    public final PlayerAreaMap broadcastMap;
+
+    /**
+     * The chunks to be brought up to send-ready status. Send-ready means the chunk and its 1 radius neighbours are loaded.
+     */
+    public final PlayerAreaMap loadMap;
+
+    /**
+     * Areamap used only to remove tickets for send-ready chunks. View distance is always + 1 of load view distance. Thus,
+     * this map is always representing the chunks we are actually going to load.
+     */
+    public final PlayerAreaMap loadTicketCleanup;
+
+    /**
+     * The chunks to brought to ticking level. Each chunk must have 2 radius neighbours loaded before this can happen.
+     */
+    public final PlayerAreaMap tickMap;
+
+    /**
+     * -1 if defaulting to [load distance], else always in [2, load distance]
+     */
+    protected int rawSendDistance = -1;
+
+    /**
+     * -1 if defaulting to [tick view distance + 1], else always in [tick view distance + 1, 32 + 1]
+     */
+    protected int rawLoadDistance = -1;
+
+    /**
+     * Never -1, always in [2, 32]
+     */
+    protected int rawTickDistance = -1;
+
+    // methods to bridge for API
+
+    public int getTargetViewDistance() {
+        return this.getTickDistance();
+    }
+
+    public void setTargetViewDistance(final int distance) {
+        this.setTickDistance(distance);
+    }
+
+    public int getTargetNoTickViewDistance() {
+        return this.getLoadDistance() - 1;
+    }
+
+    public void setTargetNoTickViewDistance(final int distance) {
+        this.setLoadDistance(distance == -1 ? -1 : distance + 1);
+    }
+
+    public int getTargetSendDistance() {
+        return this.rawSendDistance == -1 ? this.getLoadDistance() : this.rawSendDistance;
+    }
+
+    public void setTargetSendDistance(final int distance) {
+        this.setSendDistance(distance);
+    }
+
+    // internal methods
+
+    public int getSendDistance() {
+        final int loadDistance = this.getLoadDistance();
+        return this.rawSendDistance == -1 ? loadDistance : Math.min(this.rawSendDistance, loadDistance);
+    }
+
+    public void setSendDistance(final int distance) {
+        if (distance != -1 && (distance < MIN_VIEW_DISTANCE || distance > MAX_VIEW_DISTANCE + 1)) {
+            throw new IllegalArgumentException(Integer.toString(distance));
+        }
+        this.rawSendDistance = distance;
+    }
+
+    public int getLoadDistance() {
+        final int tickDistance = this.getTickDistance();
+        return this.rawLoadDistance == -1 ? tickDistance + 1 : Math.max(tickDistance + 1, this.rawLoadDistance);
+    }
+
+    public void setLoadDistance(final int distance) {
+        if (distance != -1 && (distance < MIN_VIEW_DISTANCE || distance > MAX_VIEW_DISTANCE + 1)) {
+            throw new IllegalArgumentException(Integer.toString(distance));
+        }
+        this.rawLoadDistance = distance;
+    }
+
+    public int getTickDistance() {
+        return this.rawTickDistance;
+    }
+
+    public void setTickDistance(final int distance) {
+        if (distance < MIN_VIEW_DISTANCE || distance > MAX_VIEW_DISTANCE) {
+            throw new IllegalArgumentException(Integer.toString(distance));
+        }
+        this.rawTickDistance = distance;
+    }
+
+    /*
+      Players have 3 different types of view distance:
+      1. Sending view distance
+      2. Loading view distance
+      3. Ticking view distance
+
+      But for configuration purposes (and API) there are:
+      1. No-tick view distance
+      2. Tick view distance
+      3. Broadcast view distance
+
+      These aren't always the same as the types we represent internally.
+
+      Loading view distance is always max(no-tick + 1, tick + 1)
+      - no-tick has 1 added because clients need an extra radius to render chunks
+      - tick has 1 added because it needs an extra radius of chunks to load before they can be marked ticking
+
+      Loading view distance is defined as the radius of chunks that will be brought to send-ready status, which means
+      it loads chunks in radius load-view-distance + 1.
+
+      The maximum value for send view distance is the load view distance. API can set it lower.
+     */
+
+    public PlayerChunkLoader(final ChunkMap chunkMap, final PooledLinkedHashSets<ServerPlayer> pooledHashSets) {
+        this.chunkMap = chunkMap;
+        this.broadcastMap = new PlayerAreaMap(pooledHashSets,
+                (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
+                 com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
+                    if (player.needsChunkCenterUpdate) {
+                        player.needsChunkCenterUpdate = false;
+                        player.connection.send(new ClientboundSetChunkCacheCenterPacket(currPosX, currPosZ));
+                    }
+                    PlayerChunkLoader.this.onChunkEnter(player, rangeX, rangeZ);
+                },
+                (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
+                 com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
+                    PlayerChunkLoader.this.onChunkLeave(player, rangeX, rangeZ);
+                });
+        this.loadMap = new PlayerAreaMap(pooledHashSets,
+                null,
+                (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
+                 com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
+                    if (newState != null) {
+                        return;
+                    }
+                    PlayerChunkLoader.this.isTargetedForPlayerLoad.remove(CoordinateUtils.getChunkKey(rangeX, rangeZ));
+                });
+        this.loadTicketCleanup = new PlayerAreaMap(pooledHashSets,
+                null,
+                (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
+                 com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
+                    if (newState != null) {
+                        return;
+                    }
+                    ChunkPos chunkPos = new ChunkPos(rangeX, rangeZ);
+                    PlayerChunkLoader.this.chunkMap.level.getChunkSource().removeTicketAtLevel(TicketType.PLAYER, chunkPos, LOADED_TICKET_LEVEL, chunkPos);
+                    if (PlayerChunkLoader.this.chunkTicketTracker.remove(chunkPos.toLong())) {
+                        --PlayerChunkLoader.this.concurrentChunkLoads;
+                    }
+                });
+        this.tickMap = new PlayerAreaMap(pooledHashSets,
+                (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
+                 com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
+                    if (newState.size() != 1) {
+                        return;
+                    }
+                    LevelChunk chunk = PlayerChunkLoader.this.chunkMap.level.getChunkSource().getChunkAtIfLoadedMainThreadNoCache(rangeX, rangeZ);
+                    if (chunk == null || !chunk.areNeighboursLoaded(2)) {
+                        return;
+                    }
+
+                    ChunkPos chunkPos = new ChunkPos(rangeX, rangeZ);
+                    PlayerChunkLoader.this.chunkMap.level.getChunkSource().addTicketAtLevel(TicketType.PLAYER, chunkPos, TICK_TICKET_LEVEL, chunkPos);
+                },
+                (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
+                 com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
+                    if (newState != null) {
+                        return;
+                    }
+                    ChunkPos chunkPos = new ChunkPos(rangeX, rangeZ);
+                    PlayerChunkLoader.this.chunkMap.level.getChunkSource().removeTicketAtLevel(TicketType.PLAYER, chunkPos, TICK_TICKET_LEVEL, chunkPos);
+                });
+    }
+
+    protected final LongOpenHashSet isTargetedForPlayerLoad = new LongOpenHashSet();
+    protected final LongOpenHashSet chunkTicketTracker = new LongOpenHashSet();
+
+    // rets whether the chunk is at a loaded stage that is ready to be sent to players
+    public boolean isChunkPlayerLoaded(final int chunkX, final int chunkZ) {
+        final long key = CoordinateUtils.getChunkKey(chunkX, chunkZ);
+        final ChunkHolder chunk = this.chunkMap.getVisibleChunkIfPresent(key);
+
+        if (chunk == null) {
+            return false;
+        }
+
+        return chunk.getSendingChunk() != null && this.isTargetedForPlayerLoad.contains(key);
+    }
+
+    public boolean isChunkSent(final ServerPlayer player, final int chunkX, final int chunkZ) {
+        final PlayerLoaderData data = this.playerMap.get(player);
+        if (data == null) {
+            return false;
+        }
+
+        return data.hasSentChunk(chunkX, chunkZ);
+    }
+
+    protected int getMaxConcurrentChunkSends() {
+        return PaperConfig.playerMaxConcurrentChunkSends;
+    }
+
+    protected int getMaxChunkLoads() {
+        double config = PaperConfig.playerMaxConcurrentChunkLoads;
+        double max = PaperConfig.globalMaxConcurrentChunkLoads;
+        return (int)Math.ceil(Math.min(config * MinecraftServer.getServer().getPlayerCount(), max <= 1.0 ? Double.MAX_VALUE : max));
+    }
+
+    protected long getTargetSendPerPlayerAddend() {
+        return PaperConfig.playerTargetChunkSendRate <= 1.0 ? 0L : (long)Math.round(1.0e9 / PaperConfig.playerTargetChunkSendRate);
+    }
+
+    protected long getMaxSendAddend() {
+        return PaperConfig.globalMaxChunkSendRate <= 1.0 ? 0L : (long)Math.round(1.0e9 / PaperConfig.globalMaxChunkSendRate);
+    }
+
+    public void onChunkPlayerTickReady(final int chunkX, final int chunkZ) {
+        final ChunkPos chunkPos = new ChunkPos(chunkX, chunkZ);
+        this.chunkMap.level.getChunkSource().addTicketAtLevel(TicketType.PLAYER, chunkPos, TICK_TICKET_LEVEL, chunkPos);
+    }
+
+    public void onChunkSendReady(final int chunkX, final int chunkZ) {
+        final PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> playersInSendRange = this.broadcastMap.getObjectsInRange(chunkX, chunkZ);
+
+        if (playersInSendRange == null) {
+            return;
+        }
+
+        final Object[] rawData = playersInSendRange.getBackingSet();
+        for (int i = 0, len = rawData.length; i < len; ++i) {
+            final Object raw = rawData[i];
+
+            if (!(raw instanceof ServerPlayer)) {
+                continue;
+            }
+            this.onChunkEnter((ServerPlayer)raw, chunkX, chunkZ);
+        }
+
+        // now let's try and queue mid tick logic again
+    }
+
+    public void onChunkEnter(final ServerPlayer player, final int chunkX, final int chunkZ) {
+        final PlayerLoaderData data = this.playerMap.get(player);
+
+        if (data == null) {
+            return;
+        }
+
+        if (data.hasSentChunk(chunkX, chunkZ) || !this.isChunkPlayerLoaded(chunkX, chunkZ)) {
+            // if we don't have player tickets, then the load logic will pick this up and queue to send
+            return;
+        }
+
+        final long playerPos = this.broadcastMap.getLastCoordinate(player);
+        final int playerChunkX = CoordinateUtils.getChunkX(playerPos);
+        final int playerChunkZ = CoordinateUtils.getChunkZ(playerPos);
+        final int manhattanDistance = Math.abs(playerChunkX - chunkX) + Math.abs(playerChunkZ - chunkZ);
+
+        final ChunkPriorityHolder holder = new ChunkPriorityHolder(chunkX, chunkZ, manhattanDistance, 0.0);
+        data.sendQueue.add(holder);
+    }
+
+    public void onChunkLoad(final int chunkX, final int chunkZ) {
+        if (this.chunkTicketTracker.remove(CoordinateUtils.getChunkKey(chunkX, chunkZ))) {
+            --this.concurrentChunkLoads;
+        }
+    }
+
+    public void onChunkLeave(final ServerPlayer player, final int chunkX, final int chunkZ) {
+        final PlayerLoaderData data = this.playerMap.get(player);
+
+        if (data == null) {
+            return;
+        }
+
+        data.unloadChunk(chunkX, chunkZ);
+    }
+
+    public void addPlayer(final ServerPlayer player) {
+        TickThread.ensureTickThread("Cannot add player async");
+        if (!player.isRealPlayer) {
+            return;
+        }
+        final PlayerLoaderData data = new PlayerLoaderData(player, this);
+        if (this.playerMap.putIfAbsent(player, data) == null) {
+            data.update();
+        }
+    }
+
+    public void removePlayer(final ServerPlayer player) {
+        TickThread.ensureTickThread("Cannot remove player async");
+        if (!player.isRealPlayer) {
+            return;
+        }
+
+        final PlayerLoaderData loaderData = this.playerMap.remove(player);
+        if (loaderData == null) {
+            return;
+        }
+        loaderData.remove();
+        this.chunkLoadQueue.remove(loaderData);
+        this.chunkSendQueue.remove(loaderData);
+        this.chunkSendWaitQueue.remove(loaderData);
+        synchronized (this.sendingChunkCounts) {
+            final int count = this.sendingChunkCounts.removeInt(loaderData);
+            if (count != 0) {
+                concurrentChunkSends.getAndAdd(-count);
+            }
+        }
+    }
+
+    public void updatePlayer(final ServerPlayer player) {
+        TickThread.ensureTickThread("Cannot update player async");
+        if (!player.isRealPlayer) {
+            return;
+        }
+        final PlayerLoaderData loaderData = this.playerMap.get(player);
+        if (loaderData != null) {
+            loaderData.update();
+        }
+    }
+
+    public PlayerLoaderData getData(final ServerPlayer player) {
+        return this.playerMap.get(player);
+    }
+
+    public void tick() {
+        TickThread.ensureTickThread("Cannot tick async");
+        for (final PlayerLoaderData data : this.playerMap.values()) {
+            data.update();
+        }
+        this.tickMidTick();
+    }
+
+    protected static final AtomicInteger concurrentChunkSends = new AtomicInteger();
+    protected final Reference2IntOpenHashMap<PlayerLoaderData> sendingChunkCounts = new Reference2IntOpenHashMap<>();
+    private static long nextChunkSend;
+    private void trySendChunks() {
+        final long time = System.nanoTime();
+        if (time < nextChunkSend) {
+            return;
+        }
+        // drain entries from wait queue
+        while (!this.chunkSendWaitQueue.isEmpty()) {
+            final PlayerLoaderData data = this.chunkSendWaitQueue.first();
+
+            if (data.nextChunkSendTarget > time) {
+                break;
+            }
+
+            this.chunkSendWaitQueue.pollFirst();
+
+            this.chunkSendQueue.add(data);
+        }
+
+        if (this.chunkSendQueue.isEmpty()) {
+            return;
+        }
+
+        final int maxSends = this.getMaxConcurrentChunkSends();
+        final long nextPlayerDeadline = this.getTargetSendPerPlayerAddend() + time;
+        for (;;) {
+            if (this.chunkSendQueue.isEmpty()) {
+                break;
+            }
+            final int currSends = concurrentChunkSends.get();
+            if (currSends >= maxSends) {
+                break;
+            }
+
+            if (!concurrentChunkSends.compareAndSet(currSends, currSends + 1)) {
+                continue;
+            }
+
+            // send chunk
+
+            final PlayerLoaderData data = this.chunkSendQueue.removeFirst();
+
+            final ChunkPriorityHolder queuedSend = data.sendQueue.pollFirst();
+            if (queuedSend == null) {
+                concurrentChunkSends.getAndDecrement(); // we never sent, so decrease
+                // stop iterating over players who have nothing to send
+                if (this.chunkSendQueue.isEmpty()) {
+                    // nothing left
+                    break;
+                }
+                continue;
+            }
+
+            if (!this.isChunkPlayerLoaded(queuedSend.chunkX, queuedSend.chunkZ)) {
+                throw new IllegalStateException();
+            }
+
+            data.nextChunkSendTarget = nextPlayerDeadline;
+            this.chunkSendWaitQueue.add(data);
+
+            synchronized (this.sendingChunkCounts) {
+                this.sendingChunkCounts.addTo(data, 1);
+            }
+
+            data.sendChunk(queuedSend.chunkX, queuedSend.chunkZ, () -> {
+                synchronized (this.sendingChunkCounts) {
+                    final int count = this.sendingChunkCounts.getInt(data);
+                    if (count == 0) {
+                        // disconnected, so we don't need to decrement: it will be decremented for us
+                        return;
+                    }
+                    if (count == 1) {
+                        this.sendingChunkCounts.removeInt(data);
+                    } else {
+                        this.sendingChunkCounts.put(data, count - 1);
+                    }
+                }
+
+                concurrentChunkSends.getAndDecrement();
+            });
+
+            nextChunkSend = this.getMaxSendAddend() + time;
+            if (time < nextChunkSend) {
+                break;
+            }
+        }
+    }
+
+    protected int concurrentChunkLoads;
+    // this interval prevents bursting a lot of chunk loads
+    protected static final IntervalledCounter TICKET_ADDITION_COUNTER_SHORT = new IntervalledCounter((long)(1.0e6 * 50.0)); // 50ms
+    // this interval ensures the rate is kept between ticks correctly
+    protected static final IntervalledCounter TICKET_ADDITION_COUNTER_LONG = new IntervalledCounter((long)(1.0e6 * 1000.0)); // 1000ms
+    private void tryLoadChunks() {
+        if (this.chunkLoadQueue.isEmpty()) {
+            return;
+        }
+
+        final int maxLoads = this.getMaxChunkLoads();
+        final long time = System.nanoTime();
+        boolean updatedCounters = false;
+        for (;;) {
+            final PlayerLoaderData data = this.chunkLoadQueue.pollFirst();
+
+            final ChunkPriorityHolder queuedLoad = data.loadQueue.peekFirst();
+            if (queuedLoad == null) {
+                if (this.chunkLoadQueue.isEmpty()) {
+                    break;
+                }
+                continue;
+            }
+
+            if (!updatedCounters) {
+                updatedCounters = true;
+                TICKET_ADDITION_COUNTER_SHORT.updateCurrentTime(time);
+                TICKET_ADDITION_COUNTER_LONG.updateCurrentTime(time);
+            }
+
+            if (this.isChunkPlayerLoaded(queuedLoad.chunkX, queuedLoad.chunkZ)) {
+                // already loaded!
+                data.loadQueue.pollFirst(); // already loaded so we just skip
+                this.chunkLoadQueue.add(data);
+
+                // ensure the chunk is queued to send
+                this.onChunkSendReady(queuedLoad.chunkX, queuedLoad.chunkZ);
+                continue;
+            }
+
+            final long chunkKey = CoordinateUtils.getChunkKey(queuedLoad.chunkX, queuedLoad.chunkZ);
+
+            final double priority = queuedLoad.priority;
+            // while we do need to rate limit chunk loads, the logic for sending chunks requires that tickets are present.
+            // when chunks are loaded (i.e spawn) but do not have this player's tickets, they have to wait behind the
+            // load queue. To avoid this problem, we check early here if tickets are required to load the chunk - if they
+            // aren't required, it bypasses the limiter system.
+            boolean unloadedTargetChunk = false;
+            unloaded_check:
+            for (int dz = -1; dz <= 1; ++dz) {
+                for (int dx = -1; dx <= 1; ++dx) {
+                    final int offX = queuedLoad.chunkX + dx;
+                    final int offZ = queuedLoad.chunkZ + dz;
+                    if (this.chunkMap.level.getChunkSource().getChunkAtIfLoadedMainThreadNoCache(offX, offZ) == null) {
+                        unloadedTargetChunk = true;
+                        break unloaded_check;
+                    }
+                }
+            }
+            if (unloadedTargetChunk && priority > 0.0) {
+                // priority > 0.0 implies rate limited chunks
+
+                final int currentChunkLoads = this.concurrentChunkLoads;
+                if (currentChunkLoads >= maxLoads || (TICKET_ADDITION_COUNTER_SHORT.getRate() >= PaperConfig.globalMaxChunkLoadRate || TICKET_ADDITION_COUNTER_LONG.getRate() >= PaperConfig.globalMaxChunkLoadRate)) {
+                    // don't poll, we didn't load it
+                    this.chunkLoadQueue.add(data);
+                    break;
+                }
+            }
+
+            // can only poll after we decide to load
+            data.loadQueue.pollFirst();
+
+            // now that we've polled we can re-add to load queue
+            this.chunkLoadQueue.add(data);
+
+            // add necessary tickets to load chunk up to send-ready
+            for (int dz = -1; dz <= 1; ++dz) {
+                for (int dx = -1; dx <= 1; ++dx) {
+                    final int offX = queuedLoad.chunkX + dx;
+                    final int offZ = queuedLoad.chunkZ + dz;
+                    final ChunkPos chunkPos = new ChunkPos(offX, offZ);
+
+                    this.chunkMap.level.getChunkSource().addTicketAtLevel(TicketType.PLAYER, chunkPos, LOADED_TICKET_LEVEL, chunkPos);
+                    if (this.chunkMap.level.getChunkSource().getChunkAtIfLoadedMainThreadNoCache(offX, offZ) != null) {
+                        continue;
+                    }
+
+                    if (priority > 0.0 && this.chunkTicketTracker.add(CoordinateUtils.getChunkKey(offX, offZ))) {
+                        // won't reach here if unloadedTargetChunk is false
+                        ++this.concurrentChunkLoads;
+                        TICKET_ADDITION_COUNTER_SHORT.addTime(time);
+                        TICKET_ADDITION_COUNTER_LONG.addTime(time);
+                    }
+                }
+            }
+
+            // mark that we've added tickets here
+            this.isTargetedForPlayerLoad.add(chunkKey);
+
+            // it's possible all we needed was the player tickets to queue up the send.
+            if (this.isChunkPlayerLoaded(queuedLoad.chunkX, queuedLoad.chunkZ)) {
+                // yup, all we needed.
+                this.onChunkSendReady(queuedLoad.chunkX, queuedLoad.chunkZ);
+            }
+        }
+    }
+
+    public void tickMidTick() {
+        // try to send more chunks
+        this.trySendChunks();
+
+        // try to queue more chunks to load
+        this.tryLoadChunks();
+    }
+
+    static final class ChunkPriorityHolder {
+        public final int chunkX;
+        public final int chunkZ;
+        public final int manhattanDistanceToPlayer;
+        public final double priority;
+
+        public ChunkPriorityHolder(final int chunkX, final int chunkZ, final int manhattanDistanceToPlayer, final double priority) {
+            this.chunkX = chunkX;
+            this.chunkZ = chunkZ;
+            this.manhattanDistanceToPlayer = manhattanDistanceToPlayer;
+            this.priority = priority;
+        }
+    }
+
+    public static final class PlayerLoaderData {
+
+        protected static final float FOV = 110.0f;
+        protected static final double PRIORITISED_DISTANCE = 12.0 * 16.0;
+
+        // Player max sprint speed is approximately 8m/s
+        protected static final double LOOK_PRIORITY_SPEED_THRESHOLD = (10.0/20.0) * (10.0/20.0);
+        protected static final double LOOK_PRIORITY_YAW_DELTA_RECALC_THRESHOLD = 3.0f;
+
+        protected double lastLocX = Double.NEGATIVE_INFINITY;
+        protected double lastLocZ = Double.NEGATIVE_INFINITY;
+
+        protected int lastChunkX;
+        protected int lastChunkZ;
+
+        // this is corrected so that 0 is along the positive x-axis
+        protected float lastYaw = Float.NEGATIVE_INFINITY;
+
+        protected int lastSendDistance = Integer.MIN_VALUE;
+        protected int lastLoadDistance = Integer.MIN_VALUE;
+        protected int lastTickDistance = Integer.MIN_VALUE;
+        protected boolean usingLookingPriority;
+
+        protected final ServerPlayer player;
+        protected final PlayerChunkLoader loader;
+
+        // warning: modifications of this field must be aware that the loadQueue inside PlayerChunkLoader uses this field
+        // in a comparator!
+        protected final ArrayDeque<ChunkPriorityHolder> loadQueue = new ArrayDeque<>();
+        protected final LongOpenHashSet sentChunks = new LongOpenHashSet();
+
+        protected final TreeSet<ChunkPriorityHolder> sendQueue = new TreeSet<>((final ChunkPriorityHolder p1, final ChunkPriorityHolder p2) -> {
+            final int distanceCompare = Integer.compare(p1.manhattanDistanceToPlayer, p2.manhattanDistanceToPlayer);
+            if (distanceCompare != 0) {
+                return distanceCompare;
+            }
+
+            final int coordinateXCompare = Integer.compare(p1.chunkX, p2.chunkX);
+            if (coordinateXCompare != 0) {
+                return coordinateXCompare;
+            }
+
+            return Integer.compare(p1.chunkZ, p2.chunkZ);
+        });
+
+        protected int sendViewDistance = -1;
+        protected int loadViewDistance = -1;
+        protected int tickViewDistance = -1;
+
+        protected long nextChunkSendTarget;
+
+        public PlayerLoaderData(final ServerPlayer player, final PlayerChunkLoader loader) {
+            this.player = player;
+            this.loader = loader;
+        }
+
+        // these view distance methods are for api
+        public int getTargetSendViewDistance() {
+            final int tickViewDistance = this.tickViewDistance == -1 ? this.loader.getTickDistance() : this.tickViewDistance;
+            final int loadViewDistance = Math.max(tickViewDistance + 1, this.loadViewDistance == -1 ? this.loader.getLoadDistance() : this.loadViewDistance);
+            final int clientViewDistance = this.getClientViewDistance();
+            final int sendViewDistance = Math.min(loadViewDistance, this.sendViewDistance == -1 ? (!PaperConfig.playerAutoConfigureSendViewDistance || clientViewDistance == -1 ? this.loader.getSendDistance() : clientViewDistance + 1) : this.sendViewDistance);
+            return sendViewDistance;
+        }
+
+        public void setTargetSendViewDistance(final int distance) {
+            if (distance != -1 && (distance < MIN_VIEW_DISTANCE || distance > MAX_VIEW_DISTANCE + 1)) {
+                throw new IllegalArgumentException(Integer.toString(distance));
+            }
+            this.sendViewDistance = distance;
+        }
+
+        public int getTargetNoTickViewDistance() {
+            return (this.loadViewDistance == -1 ? this.getLoadDistance() : this.loadViewDistance) - 1;
+        }
+
+        public void setTargetNoTickViewDistance(final int distance) {
+            if (distance != -1 && (distance < MIN_VIEW_DISTANCE || distance > MAX_VIEW_DISTANCE)) {
+                throw new IllegalArgumentException(Integer.toString(distance));
+            }
+            this.loadViewDistance = distance == -1 ? -1 : distance + 1;
+        }
+
+        public int getTargetTickViewDistance() {
+            return this.tickViewDistance == -1 ? this.loader.getTickDistance() : this.tickViewDistance;
+        }
+
+        public void setTargetTickViewDistance(final int distance) {
+            if (distance < MIN_VIEW_DISTANCE || distance > MAX_VIEW_DISTANCE) {
+                throw new IllegalArgumentException(Integer.toString(distance));
+            }
+            this.tickViewDistance = distance;
+        }
+
+        protected int getLoadDistance() {
+            final int tickViewDistance = this.tickViewDistance == -1 ? this.loader.getTickDistance() : this.tickViewDistance;
+
+            return Math.max(tickViewDistance + 1, this.loadViewDistance == -1 ? this.loader.getLoadDistance() : this.loadViewDistance);
+        }
+
+        public boolean hasSentChunk(final int chunkX, final int chunkZ) {
+            return this.sentChunks.contains(CoordinateUtils.getChunkKey(chunkX, chunkZ));
+        }
+
+        public void sendChunk(final int chunkX, final int chunkZ, final Runnable onChunkSend) {
+            if (this.sentChunks.add(CoordinateUtils.getChunkKey(chunkX, chunkZ))) {
+                this.player.getLevel().getChunkSource().chunkMap.updateChunkTracking(this.player,
+                        new ChunkPos(chunkX, chunkZ), new Packet[2], false, true); // unloaded, loaded
+                this.player.connection.connection.execute(onChunkSend);
+            } else {
+                throw new IllegalStateException();
+            }
+        }
+
+        public void unloadChunk(final int chunkX, final int chunkZ) {
+            if (this.sentChunks.remove(CoordinateUtils.getChunkKey(chunkX, chunkZ))) {
+                this.player.getLevel().getChunkSource().chunkMap.updateChunkTracking(this.player,
+                        new ChunkPos(chunkX, chunkZ), null, true, false); // unloaded, loaded
+            }
+        }
+
+        protected static boolean triangleIntersects(final double p1x, final double p1z, // triangle point
+                                                    final double p2x, final double p2z, // triangle point
+                                                    final double p3x, final double p3z, // triangle point
+
+                                                    final double targetX, final double targetZ) { // point
+            // from barycentric coordinates:
+            // targetX = a*p1x + b*p2x + c*p3x
+            // targetZ = a*p1z + b*p2z + c*p3z
+            // 1.0     = a*1.0 + b*1.0 + c*1.0
+            // where a, b, c >= 0.0
+            // so, if any of a, b, c are less-than zero then there is no intersection.
+
+            // d = ((p2z - p3z)(p1x - p3x) + (p3x - p2x)(p1z - p3z))
+            // a = ((p2z - p3z)(targetX - p3x) + (p3x - p2x)(targetZ - p3z)) / d
+            // b = ((p3z - p1z)(targetX - p3x) + (p1x - p3x)(targetZ - p3z)) / d
+            // c = 1.0 - a - b
+
+            final double d = (p2z - p3z)*(p1x - p3x) + (p3x - p2x)*(p1z - p3z);
+            final double a = ((p2z - p3z)*(targetX - p3x) + (p3x - p2x)*(targetZ - p3z)) / d;
+
+            if (a < 0.0 || a > 1.0) {
+                return false;
+            }
+
+            final double b = ((p3z - p1z)*(targetX - p3x) + (p1x - p3x)*(targetZ - p3z)) / d;
+            if (b < 0.0 || b > 1.0) {
+                return false;
+            }
+
+            final double c = 1.0 - a - b;
+
+            return c >= 0.0 && c <= 1.0;
+        }
+
+        public void remove() {
+            this.loader.broadcastMap.remove(this.player);
+            this.loader.loadMap.remove(this.player);
+            this.loader.loadTicketCleanup.remove(this.player);
+            this.loader.tickMap.remove(this.player);
+        }
+
+        protected int getClientViewDistance() {
+            return this.player.clientViewDistance == null ? -1 : this.player.clientViewDistance.intValue();
+        }
+
+        public void update() {
+            final int tickViewDistance = this.tickViewDistance == -1 ? this.loader.getTickDistance() : this.tickViewDistance;
+            // load view cannot be less-than tick view + 1
+            final int loadViewDistance = Math.max(tickViewDistance + 1, this.loadViewDistance == -1 ? this.loader.getLoadDistance() : this.loadViewDistance);
+            // send view cannot be greater-than load view
+            final int clientViewDistance = this.getClientViewDistance();
+            final int sendViewDistance = Math.min(loadViewDistance, this.sendViewDistance == -1 ? (!PaperConfig.playerAutoConfigureSendViewDistance || clientViewDistance == -1 ? this.loader.getSendDistance() : clientViewDistance + 1) : this.sendViewDistance);
+
+            final double posX = this.player.getX();
+            final double posZ = this.player.getZ();
+            final float yaw = MCUtil.normalizeYaw(this.player.yRot + 90.0f); // mc yaw 0 is along the positive z axis, but obviously this is really dumb - offset so we are at positive x-axis
+
+            // in general, we really only want to prioritise chunks in front if we know we're moving pretty fast into them.
+            final boolean useLookPriority = PaperConfig.playerFrustumPrioritisation && (this.player.getDeltaMovement().horizontalDistanceSqr() > LOOK_PRIORITY_SPEED_THRESHOLD ||
+                    this.player.getAbilities().flying);
+
+            // make sure we're in the send queue
+            this.loader.chunkSendWaitQueue.add(this);
+
+            if (
+                // has view distance stayed the same?
+                    sendViewDistance == this.lastSendDistance
+                            && loadViewDistance == this.lastLoadDistance
+                            && tickViewDistance == this.lastTickDistance
+
+                            && (this.usingLookingPriority ? (
+                                    // has our block stayed the same (this also accounts for chunk change)?
+                                    Mth.floor(this.lastLocX) == Mth.floor(posX)
+                                    && Mth.floor(this.lastLocZ) == Mth.floor(posZ)
+                            ) : (
+                                    // has our chunk stayed the same
+                                    (Mth.floor(this.lastLocX) >> 4) == (Mth.floor(posX) >> 4)
+                                    && (Mth.floor(this.lastLocZ) >> 4) == (Mth.floor(posZ) >> 4)
+                            ))
+
+                            // has our decision about look priority changed?
+                            && this.usingLookingPriority == useLookPriority
+
+                            // if we are currently using look priority, has our yaw stayed within recalc threshold?
+                            && (!this.usingLookingPriority || Math.abs(yaw - this.lastYaw) <= LOOK_PRIORITY_YAW_DELTA_RECALC_THRESHOLD)
+            ) {
+                // nothing we care about changed, so we're not re-calculating
+                return;
+            }
+
+            final int centerChunkX = Mth.floor(posX) >> 4;
+            final int centerChunkZ = Mth.floor(posZ) >> 4;
+
+            this.player.needsChunkCenterUpdate = true;
+            this.loader.broadcastMap.addOrUpdate(this.player, centerChunkX, centerChunkZ, sendViewDistance);
+            this.player.needsChunkCenterUpdate = false;
+            this.loader.loadMap.addOrUpdate(this.player, centerChunkX, centerChunkZ, loadViewDistance);
+            this.loader.loadTicketCleanup.addOrUpdate(this.player, centerChunkX, centerChunkZ, loadViewDistance + 1);
+            this.loader.tickMap.addOrUpdate(this.player, centerChunkX, centerChunkZ, tickViewDistance);
+
+            if (sendViewDistance != this.lastSendDistance) {
+                // update the view radius for client
+                // note that this should be after the map calls because the client wont expect unload calls not in its VD
+                // and it's possible we decreased VD here
+                this.player.connection.send(new ClientboundSetChunkCacheRadiusPacket(sendViewDistance - 1)); // client already expects the 1 radius neighbours, so subtract 1.
+            }
+
+            this.lastLocX = posX;
+            this.lastLocZ = posZ;
+            this.lastYaw = yaw;
+            this.lastSendDistance = sendViewDistance;
+            this.lastLoadDistance = loadViewDistance;
+            this.lastTickDistance = tickViewDistance;
+            this.usingLookingPriority = useLookPriority;
+
+            this.lastChunkX = centerChunkX;
+            this.lastChunkZ = centerChunkZ;
+
+            // points for player "view" triangle:
+
+            // obviously, the player pos is a vertex
+            final double p1x = posX;
+            final double p1z = posZ;
+
+            // to the left of the looking direction
+            final double p2x = PRIORITISED_DISTANCE * Math.cos(Math.toRadians(yaw + (double)(FOV / 2.0))) // calculate rotated vector
+                    + p1x; // offset vector
+            final double p2z = PRIORITISED_DISTANCE * Math.sin(Math.toRadians(yaw + (double)(FOV / 2.0))) // calculate rotated vector
+                    + p1z; // offset vector
+
+            // to the right of the looking direction
+            final double p3x = PRIORITISED_DISTANCE * Math.cos(Math.toRadians(yaw - (double)(FOV / 2.0))) // calculate rotated vector
+                    + p1x; // offset vector
+            final double p3z = PRIORITISED_DISTANCE * Math.sin(Math.toRadians(yaw - (double)(FOV / 2.0))) // calculate rotated vector
+                    + p1z; // offset vector
+
+            // now that we have all of our points, we can recalculate the load queue
+
+            final List<ChunkPriorityHolder> loadQueue = new ArrayList<>();
+
+            // clear send queue, we are re-sorting
+            this.sendQueue.clear();
+
+            final int searchViewDistance = Math.max(loadViewDistance, sendViewDistance);
+
+            for (int dx = -searchViewDistance; dx <= searchViewDistance; ++dx) {
+                for (int dz = -searchViewDistance; dz <= searchViewDistance; ++dz) {
+                    final int chunkX = dx + centerChunkX;
+                    final int chunkZ = dz + centerChunkZ;
+                    final int squareDistance = Math.max(Math.abs(dx), Math.abs(dz));
+
+                    if (this.hasSentChunk(chunkX, chunkZ)) {
+                        // already sent (which means it is also loaded)
+                        continue;
+                    }
+
+                    final boolean loadChunk = squareDistance <= loadViewDistance;
+                    final boolean sendChunk = squareDistance <= sendViewDistance;
+
+                    final boolean prioritised = useLookPriority && triangleIntersects(
+                            // prioritisation triangle
+                            p1x, p1z, p2x, p2z, p3x, p3z,
+
+                            // center of chunk
+                            (double)((chunkX << 4) | 8), (double)((chunkZ << 4) | 8)
+                    );
+
+
+                    final int manhattanDistance = (Math.abs(dx) + Math.abs(dz));
+
+                    final double priority;
+
+                    if (squareDistance <= PaperConfig.playerMinChunkLoadRadius) {
+                        // priority should be negative, and we also want to order it from center outwards
+                        // so we want (0,0) to be the smallest, and (minLoadedRadius,minLoadedRadius) to be the greatest
+                        priority = -((2 * PaperConfig.playerMinChunkLoadRadius + 1) - (dx + dz));
+                    } else {
+                        if (prioritised) {
+                            // we don't prioritise these chunks above others because we also want to make sure some chunks
+                            // will be loaded if the player changes direction
+                            priority = (double)manhattanDistance / 6.0;
+                        } else {
+                            priority = (double)manhattanDistance;
+                        }
+                    }
+
+                    final ChunkPriorityHolder holder = new ChunkPriorityHolder(chunkX, chunkZ, manhattanDistance, priority);
+
+                    if (!this.loader.isChunkPlayerLoaded(chunkX, chunkZ)) {
+                        if (loadChunk) {
+                            loadQueue.add(holder);
+                        }
+                    } else {
+                        // loaded but not sent: so queue it!
+                        if (sendChunk) {
+                            this.sendQueue.add(holder);
+                        }
+                    }
+                }
+            }
+
+            loadQueue.sort((final ChunkPriorityHolder p1, final ChunkPriorityHolder p2) -> {
+                return Double.compare(p1.priority, p2.priority);
+            });
+
+            // we're modifying loadQueue, must remove
+            this.loader.chunkLoadQueue.remove(this);
+
+            this.loadQueue.clear();
+            this.loadQueue.addAll(loadQueue);
+
+            // must re-add
+            this.loader.chunkLoadQueue.add(this);
+        }
+    }
+}
diff --git a/src/main/java/net/minecraft/network/Connection.java b/src/main/java/net/minecraft/network/Connection.java
index 103657ad936f1a75ffbb92ca5eafb816e977e363..23757f466da571aec35a373112dcbba0d1f46dcb 100644
--- a/src/main/java/net/minecraft/network/Connection.java
+++ b/src/main/java/net/minecraft/network/Connection.java
@@ -93,6 +93,28 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     public boolean queueImmunity = false;
     public ConnectionProtocol protocol;
     // Paper end
+    // Paper start - add pending task queue
+    private final Queue<Runnable> pendingTasks = new java.util.concurrent.ConcurrentLinkedQueue<>();
+    public void execute(final Runnable run) {
+        if (this.channel == null || !this.channel.isRegistered()) {
+            run.run();
+            return;
+        }
+        final boolean queue = !this.queue.isEmpty();
+        if (!queue) {
+            this.channel.eventLoop().execute(run);
+        } else {
+            this.pendingTasks.add(run);
+            if (this.queue.isEmpty()) {
+                // something flushed async, dump tasks now
+                Runnable r;
+                while ((r = this.pendingTasks.poll()) != null) {
+                    this.channel.eventLoop().execute(r);
+                }
+            }
+        }
+    }
+    // Paper end - add pending task queue
 
     // Paper start - allow controlled flushing
     volatile boolean canFlush = true;
@@ -399,6 +421,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
         return false;
     }
     private boolean processQueue() {
+        try { // Paper - add pending task queue
         if (this.queue.isEmpty()) return true;
         // Paper start - make only one flush call per sendPacketQueue() call
         final boolean needsFlush = this.canFlush;
@@ -430,6 +453,12 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
             }
         }
         return true;
+        } finally { // Paper start - add pending task queue
+            Runnable r;
+            while ((r = this.pendingTasks.poll()) != null) {
+                this.channel.eventLoop().execute(r);
+            }
+        } // Paper end - add pending task queue
     }
     // Paper end
 
diff --git a/src/main/java/net/minecraft/server/MCUtil.java b/src/main/java/net/minecraft/server/MCUtil.java
index ee668b989d661e1db1bdfe05b94d7cdadeae6923..a7ae331258b9d09795fcd20e6e633d4fa8bfb7fa 100644
--- a/src/main/java/net/minecraft/server/MCUtil.java
+++ b/src/main/java/net/minecraft/server/MCUtil.java
@@ -637,7 +637,7 @@ public final class MCUtil {
 
             worldData.addProperty("name", world.getWorld().getName());
             worldData.addProperty("view-distance", world.getChunkSource().chunkMap.getEffectiveViewDistance());
-            worldData.addProperty("no-view-distance", world.getChunkSource().chunkMap.getRawNoTickViewDistance());
+            worldData.addProperty("no-view-distance", world.getChunkSource().chunkMap.playerChunkManager.getTargetNoTickViewDistance()); // Paper - replace old player chunk management
             worldData.addProperty("keep-spawn-loaded", world.keepSpawnInMemory);
             worldData.addProperty("keep-spawn-loaded-range", world.paperConfig.keepLoadedRange);
             worldData.addProperty("visible-chunk-count", visibleChunks.size());
diff --git a/src/main/java/net/minecraft/server/level/ChunkHolder.java b/src/main/java/net/minecraft/server/level/ChunkHolder.java
index 54822e418e319db551bfea3218d00faf0e043f43..de0c6316c9b75a2ecc7d6abf7bcca24e25de0ac0 100644
--- a/src/main/java/net/minecraft/server/level/ChunkHolder.java
+++ b/src/main/java/net/minecraft/server/level/ChunkHolder.java
@@ -491,7 +491,7 @@ public class ChunkHolder {
         // Paper start - per player view distance
         // there can be potential desync with player's last mapped section and the view distance map, so use the
         // view distance map here.
-        com.destroystokyo.paper.util.misc.PlayerAreaMap viewDistanceMap = this.chunkMap.playerViewDistanceBroadcastMap;
+        com.destroystokyo.paper.util.misc.PlayerAreaMap viewDistanceMap = this.chunkMap.playerChunkManager.broadcastMap; // Paper - replace old player chunk manager
         com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> players = viewDistanceMap.getObjectsInRange(this.pos);
         if (players == null) {
             return;
@@ -508,6 +508,7 @@ public class ChunkHolder {
 
                 int viewDistance = viewDistanceMap.getLastViewDistance(player);
                 long lastPosition = viewDistanceMap.getLastCoordinate(player);
+                if (!this.chunkMap.playerChunkManager.isChunkSent(player, this.pos.x, this.pos.z)) continue; // Paper - replace player chunk management
 
                 int distX = Math.abs(net.minecraft.server.MCUtil.getCoordinateX(lastPosition) - this.pos.x);
                 int distZ = Math.abs(net.minecraft.server.MCUtil.getCoordinateZ(lastPosition) - this.pos.z);
@@ -524,6 +525,7 @@ public class ChunkHolder {
                     continue;
                 }
                 ServerPlayer player = (ServerPlayer)temp;
+                if (!this.chunkMap.playerChunkManager.isChunkSent(player, this.pos.x, this.pos.z)) continue; // Paper - replace player chunk management
                 player.connection.send(packet);
             }
         }
diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index 58cf34b714ba98f35bdbe3895078ae4f87a0360e..e343c0ad21da97c4b830c626b3d59e03fa60e494 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -187,22 +187,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     final CallbackExecutor chunkLoadConversionCallbackExecutor = new CallbackExecutor(); // Paper
     // Paper start - distance maps
     private final com.destroystokyo.paper.util.misc.PooledLinkedHashSets<ServerPlayer> pooledLinkedPlayerHashSets = new com.destroystokyo.paper.util.misc.PooledLinkedHashSets<>();
-    // Paper start - no-tick view distance
-    int noTickViewDistance;
-    public final int getRawNoTickViewDistance() {
-        return this.noTickViewDistance;
-    }
-    public final int getEffectiveNoTickViewDistance() {
-        return this.noTickViewDistance == -1 ? this.getEffectiveViewDistance() : this.noTickViewDistance;
-    }
-    public final int getLoadViewDistance() {
-        return Math.max(this.getEffectiveViewDistance(), this.getEffectiveNoTickViewDistance());
-    }
-
-    public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerViewDistanceBroadcastMap;
-    public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerViewDistanceTickMap;
-    public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerViewDistanceNoTickMap;
-    // Paper end - no-tick view distance
+    public final io.papermc.paper.chunk.PlayerChunkLoader playerChunkManager = new io.papermc.paper.chunk.PlayerChunkLoader(this, this.pooledLinkedPlayerHashSets); // Paper - replace chunk loader
     // Paper start - use distance map to optimise tracker
     public static boolean isLegacyTrackingEntity(Entity entity) {
         return entity.isLegacyTrackingEntity;
@@ -241,7 +226,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
             com.destroystokyo.paper.util.misc.PlayerAreaMap trackMap = this.playerEntityTrackerTrackMaps[i];
             int trackRange = this.entityTrackerTrackRanges[i];
 
-            trackMap.add(player, chunkX, chunkZ, Math.min(trackRange, this.getEffectiveViewDistance()));
+            trackMap.add(player, chunkX, chunkZ, Math.min(trackRange, player.getBukkitEntity().getViewDistance())); // Paper - per player view distances
         }
         // Paper end - use distance map to optimise entity tracker
         // Paper start - optimise PlayerChunkMap#isOutsideRange
@@ -250,19 +235,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         // Paper start - optimise PlayerChunkMap#isOutsideRange
         this.playerChunkTickRangeMap.add(player, chunkX, chunkZ, DistanceManager.MOB_SPAWN_RANGE);
         // Paper end - optimise PlayerChunkMap#isOutsideRange
-        // Paper start - no-tick view distance
-        int effectiveTickViewDistance = this.getEffectiveViewDistance();
-        int effectiveNoTickViewDistance = Math.max(this.getEffectiveNoTickViewDistance(), effectiveTickViewDistance);
-
-        if (!this.skipPlayer(player)) {
-            this.playerViewDistanceTickMap.add(player, chunkX, chunkZ, effectiveTickViewDistance);
-            this.playerViewDistanceNoTickMap.add(player, chunkX, chunkZ, effectiveNoTickViewDistance + 2); // clients need chunk 1 neighbour, and we need another 1 for sending those extra neighbours (as we require neighbours to send)
-        }
-
-        player.needsChunkCenterUpdate = true;
-        this.playerViewDistanceBroadcastMap.add(player, chunkX, chunkZ, effectiveNoTickViewDistance + 1); // clients need an extra neighbour to render the full view distance configured
-        player.needsChunkCenterUpdate = false;
-        // Paper end - no-tick view distance
+        this.playerChunkManager.addPlayer(player); // Paper - replace chunk loader
     }
 
     void removePlayerFromDistanceMaps(ServerPlayer player) {
@@ -275,11 +248,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         this.playerMobSpawnMap.remove(player);
         this.playerChunkTickRangeMap.remove(player);
         // Paper end - optimise PlayerChunkMap#isOutsideRange
-        // Paper start - no-tick view distance
-        this.playerViewDistanceBroadcastMap.remove(player);
-        this.playerViewDistanceTickMap.remove(player);
-        this.playerViewDistanceNoTickMap.remove(player);
-        // Paper end - no-tick view distance
+        this.playerChunkManager.removePlayer(player); // Paper - replace chunk loader
     }
 
     void updateMaps(ServerPlayer player) {
@@ -291,25 +260,13 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
             com.destroystokyo.paper.util.misc.PlayerAreaMap trackMap = this.playerEntityTrackerTrackMaps[i];
             int trackRange = this.entityTrackerTrackRanges[i];
 
-            trackMap.update(player, chunkX, chunkZ, Math.min(trackRange, this.getEffectiveViewDistance()));
+            trackMap.update(player, chunkX, chunkZ, Math.min(trackRange, player.getBukkitEntity().getViewDistance())); // Paper - per player view distances
         }
         // Paper end - use distance map to optimise entity tracker
         // Paper start - optimise PlayerChunkMap#isOutsideRange
         this.playerChunkTickRangeMap.update(player, chunkX, chunkZ, DistanceManager.MOB_SPAWN_RANGE);
         // Paper end - optimise PlayerChunkMap#isOutsideRange
-        // Paper start - no-tick view distance
-        int effectiveTickViewDistance = this.getEffectiveViewDistance();
-        int effectiveNoTickViewDistance = Math.max(this.getEffectiveNoTickViewDistance(), effectiveTickViewDistance);
-
-        if (!this.skipPlayer(player)) {
-            this.playerViewDistanceTickMap.update(player, chunkX, chunkZ, effectiveTickViewDistance);
-            this.playerViewDistanceNoTickMap.update(player, chunkX, chunkZ, effectiveNoTickViewDistance + 2); // clients need chunk 1 neighbour, and we need another 1 for sending those extra neighbours (as we require neighbours to send)
-        }
-
-        player.needsChunkCenterUpdate = true;
-        this.playerViewDistanceBroadcastMap.update(player, chunkX, chunkZ, effectiveNoTickViewDistance + 1); // clients need an extra neighbour to render the full view distance configured
-        player.needsChunkCenterUpdate = false;
-        // Paper end - no-tick view distance
+        this.playerChunkManager.updatePlayer(player); // Paper - replace chunk loader
     }
     // Paper end
     // Paper start
@@ -394,43 +351,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         this.regionManagers.add(this.dataRegionManager);
         // Paper end
         // Paper start - no-tick view distance
-        this.setNoTickViewDistance(this.level.paperConfig.noTickViewDistance);
-        this.playerViewDistanceTickMap = 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) -> {
-                if (newState.size() != 1) {
-                    return;
-                }
-                LevelChunk chunk = ChunkMap.this.level.getChunkSource().getChunkAtIfLoadedMainThreadNoCache(rangeX, rangeZ);
-                if (chunk == null || !chunk.areNeighboursLoaded(2)) {
-                    return;
-                }
-
-                ChunkPos chunkPos = new ChunkPos(rangeX, rangeZ);
-                ChunkMap.this.level.getChunkSource().addTicketAtLevel(TicketType.PLAYER, chunkPos, 31, chunkPos); // entity ticking level, TODO check on update
-            },
-            (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
-             com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
-                if (newState != null) {
-                    return;
-                }
-                ChunkPos chunkPos = new ChunkPos(rangeX, rangeZ);
-                ChunkMap.this.level.getChunkSource().removeTicketAtLevel(TicketType.PLAYER, chunkPos, 31, chunkPos); // entity ticking level, TODO check on update
-            });
-        this.playerViewDistanceNoTickMap = new com.destroystokyo.paper.util.misc.PlayerAreaMap(this.pooledLinkedPlayerHashSets);
-        this.playerViewDistanceBroadcastMap = 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) -> {
-                if (player.needsChunkCenterUpdate) {
-                    player.needsChunkCenterUpdate = false;
-                    player.connection.send(new ClientboundSetChunkCacheCenterPacket(currPosX, currPosZ));
-                }
-                ChunkMap.this.updateChunkTracking(player, new ChunkPos(rangeX, rangeZ), new Packet[2], false, true); // unloaded, loaded
-            },
-            (ServerPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
-             com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> newState) -> {
-                ChunkMap.this.updateChunkTracking(player, new ChunkPos(rangeX, rangeZ), null, true, false); // unloaded, loaded
-            });
+        this.setNoTickViewDistance(this.level.paperConfig.noTickViewDistance); // Paper - replace chunk loading system
         // Paper end - no-tick view distance
         this.playerMobDistanceMap = this.level.paperConfig.perPlayerMobSpawns ? new com.destroystokyo.paper.util.PlayerMobDistanceMap() : null; // Paper
         // Paper start - use distance map to optimise entity tracker
@@ -537,6 +458,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     }
 
     public void checkHighPriorityChunks(ServerPlayer player) {
+        if (true) return; // Paper - replace player chunk loader
         int currentTick = MinecraftServer.currentTick;
         if (currentTick - player.lastHighPriorityChecked < 20 || !player.isRealPlayer) { // weed out fake players
             return;
@@ -544,7 +466,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         player.lastHighPriorityChecked = currentTick;
         it.unimi.dsi.fastutil.longs.Long2IntOpenHashMap priorities = new it.unimi.dsi.fastutil.longs.Long2IntOpenHashMap();
 
-        int viewDistance = getEffectiveNoTickViewDistance();
+        int viewDistance = 10;//int viewDistance = getEffectiveNoTickViewDistance(); // Paper - replace player chunk loader
         net.minecraft.core.BlockPos.MutableBlockPos pos = new net.minecraft.core.BlockPos.MutableBlockPos();
 
         // Prioritize circular near
@@ -610,7 +532,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     }
 
     private boolean shouldSkipPrioritization(ChunkPos coord) {
-        if (playerViewDistanceNoTickMap.getObjectsInRange(coord.toLong()) == null) return true;
+        if (true) return true; // Paper - replace player chunk loader - unused outside paper player loader logic
         ChunkHolder chunk = getUpdatingChunkIfPresent(coord.toLong());
         return chunk != null && (chunk.isFullChunkReady());
     }
@@ -1548,7 +1470,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
             int k = this.viewDistance;
 
             this.viewDistance = j;
-            this.setNoTickViewDistance(this.getRawNoTickViewDistance()); // Paper - no-tick view distance - propagate changes to no-tick, which does the actual chunk loading/sending
+            this.playerChunkManager.setTickDistance(Mth.clamp(viewDistance, 2, 32)); // Paper - replace player loader system
         }
 
     }
@@ -1556,26 +1478,11 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     // Paper start - no-tick view distance
     public final void setNoTickViewDistance(int viewDistance) {
         viewDistance = viewDistance == -1 ? -1 : Mth.clamp(viewDistance, 2, 32);
-
-        this.noTickViewDistance = viewDistance;
-        int loadViewDistance = this.getLoadViewDistance();
-        this.distanceManager.setNoTickViewDistance(loadViewDistance + 2 + 2); // add 2 to account for the change to 31 -> 33 tickets // see notes in the distance map updating for the other + 2
-
-        if (this.level != null && this.level.players != null) { // this can be called from constructor, where these aren't set
-            for (ServerPlayer player : this.level.players) {
-                net.minecraft.server.network.ServerGamePacketListenerImpl connection = player.connection;
-                if (connection != null) {
-                    // moved in from PlayerList
-                    connection.send(new net.minecraft.network.protocol.game.ClientboundSetChunkCacheRadiusPacket(loadViewDistance));
-                }
-                this.updateMaps(player);
-                // Paper end - no-tick view distance
-            }
-        }
+        this.playerChunkManager.setLoadDistance(viewDistance == -1 ? -1 : viewDistance + 1); // Paper - replace player loader system - add 1 here, we need an extra one to send to clients for chunks in this viewDistance to render
 
     }
 
-    protected void updateChunkTracking(ServerPlayer player, ChunkPos pos, Packet<?>[] packets, boolean withinMaxWatchDistance, boolean withinViewDistance) {
+    public void updateChunkTracking(ServerPlayer player, ChunkPos pos, Packet<?>[] packets, boolean withinMaxWatchDistance, boolean withinViewDistance) { // Paper - public
         if (player.level == this.level) {
             if (withinViewDistance && !withinMaxWatchDistance) {
                 ChunkHolder playerchunk = this.getVisibleChunkIfPresent(pos.toLong());
@@ -1904,6 +1811,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         */ // Paper end - replaced by distance map
 
         this.updateMaps(player); // Paper - distance maps
+        this.playerChunkManager.updatePlayer(player); // Paper - respond to movement immediately
 
     }
 
@@ -1912,7 +1820,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
         // Paper start - per player view distance
         // there can be potential desync with player's last mapped section and the view distance map, so use the
         // view distance map here.
-        com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> inRange = this.playerViewDistanceBroadcastMap.getObjectsInRange(chunkPos);
+        com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> inRange = this.playerChunkManager.broadcastMap.getObjectsInRange(chunkPos); // Paper - replace player chunk loader system
 
         if (inRange == null) {
             return Stream.empty();
@@ -1928,8 +1836,9 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
                     continue;
                 }
                 ServerPlayer player = (ServerPlayer)temp;
-                int viewDistance = this.playerViewDistanceBroadcastMap.getLastViewDistance(player);
-                long lastPosition = this.playerViewDistanceBroadcastMap.getLastCoordinate(player);
+                if (!this.playerChunkManager.isChunkSent(player, chunkPos.x, chunkPos.z)) continue; // Paper - replace player chunk management
+                int viewDistance = this.playerChunkManager.broadcastMap.getLastViewDistance(player); // Paper - replace player chunk loader system
+                long lastPosition = this.playerChunkManager.broadcastMap.getLastCoordinate(player); // Paper - replace player chunk loader system
 
                 int distX = Math.abs(MCUtil.getCoordinateX(lastPosition) - chunkPos.x);
                 int distZ = Math.abs(MCUtil.getCoordinateZ(lastPosition) - chunkPos.z);
@@ -1944,6 +1853,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
                     continue;
                 }
                 ServerPlayer player = (ServerPlayer)temp;
+                if (!this.playerChunkManager.isChunkSent(player, chunkPos.x, chunkPos.z)) continue; // Paper - replace player chunk management
                 players.add(player);
             }
         }
@@ -2357,7 +2267,7 @@ Sections go from 0..16. Now whenever a section is not empty, it can potentially
                 double vec3d_dy = player.getY() - this.entity.getY();
                 double vec3d_dz = player.getZ() - this.entity.getZ();
                 // Paper end - remove allocation of Vec3D here
-                int i = Math.min(this.getEffectiveRange(), (ChunkMap.this.viewDistance - 1) * 16);
+                int i = Math.min(this.getEffectiveRange(), player.getBukkitEntity().getViewDistance() * 16); // Paper - per player view distance
                 boolean flag = vec3d_dx >= (double) (-i) && vec3d_dx <= (double) i && vec3d_dz >= (double) (-i) && vec3d_dz <= (double) i && this.entity.broadcastToPlayer(player); // Paper - remove allocation of Vec3D here
 
                 // CraftBukkit start - respect vanish API
diff --git a/src/main/java/net/minecraft/server/level/DistanceManager.java b/src/main/java/net/minecraft/server/level/DistanceManager.java
index 1cc4e0a1f3d8235ef88b48e01ca8b78a263d2676..0b34536cdffab31a717b613042d7098109846586 100644
--- a/src/main/java/net/minecraft/server/level/DistanceManager.java
+++ b/src/main/java/net/minecraft/server/level/DistanceManager.java
@@ -46,7 +46,7 @@ public abstract class DistanceManager {
     public final Long2ObjectOpenHashMap<SortedArraySet<Ticket<?>>> tickets = new Long2ObjectOpenHashMap();
     private final DistanceManager.ChunkTicketTracker ticketTracker = new DistanceManager.ChunkTicketTracker();
     public static final int MOB_SPAWN_RANGE = 8; // private final ChunkMapDistance.b f = new ChunkMapDistance.b(8); // Paper - no longer used
-    private final DistanceManager.PlayerTicketTracker playerTicketManager = new DistanceManager.PlayerTicketTracker(33);
+    //private final DistanceManager.PlayerTicketTracker playerTicketManager = new DistanceManager.PlayerTicketTracker(33); // Paper - no longer used
     // Paper start use a queue, but still keep unique requirement
     public final java.util.Queue<ChunkHolder> pendingChunkUpdates = new java.util.ArrayDeque<ChunkHolder>() {
         @Override
@@ -113,7 +113,7 @@ public abstract class DistanceManager {
     public boolean runAllUpdates(ChunkMap playerchunkmap) {
         //this.f.a(); // Paper - no longer used
         org.spigotmc.AsyncCatcher.catchOp("DistanceManagerTick"); // Paper
-        this.playerTicketManager.runAllUpdates();
+        //this.playerTicketManager.runAllUpdates(); // Paper - no longer used
         int i = Integer.MAX_VALUE - this.ticketTracker.runDistanceUpdates(Integer.MAX_VALUE);
         boolean flag = i != 0;
 
@@ -313,7 +313,7 @@ public abstract class DistanceManager {
         org.spigotmc.AsyncCatcher.catchOp("ChunkMapDistance::addPriorityTicket");
         long pair = coords.toLong();
         ChunkHolder chunk = chunkMap.getUpdatingChunkIfPresent(pair);
-        boolean needsTicket = chunkMap.playerViewDistanceNoTickMap.getObjectsInRange(pair) != null && !hasPlayerTicket(coords, 33);
+        boolean needsTicket = false; // Paper - replace old loader system
 
         if (needsTicket) {
             Ticket<?> ticket = new Ticket<>(TicketType.PLAYER, 33, coords);
@@ -411,7 +411,7 @@ public abstract class DistanceManager {
             return new ObjectOpenHashSet();
         })).add(player);
         //this.f.update(i, 0, true); // Paper - no longer used
-        this.playerTicketManager.update(i, 0, true);
+        //this.playerTicketManager.update(i, 0, true); // Paper - no longer used
     }
 
     public void removePlayer(SectionPos pos, ServerPlayer player) {
@@ -423,7 +423,7 @@ public abstract class DistanceManager {
         if (objectset == null || objectset.isEmpty()) { // Paper
             this.playersPerChunk.remove(i);
             //this.f.update(i, Integer.MAX_VALUE, false); // Paper - no longer used
-            this.playerTicketManager.update(i, Integer.MAX_VALUE, false);
+            //this.playerTicketManager.update(i, Integer.MAX_VALUE, false); // Paper - no longer used
         }
 
     }
@@ -442,7 +442,7 @@ public abstract class DistanceManager {
     }
 
     protected void setNoTickViewDistance(int i) { // Paper - force abi breakage on usage change
-        this.playerTicketManager.updateViewDistance(i);
+        throw new UnsupportedOperationException("use world api"); // Paper - no longer relevant
     }
 
     public int getNaturalSpawnChunkCount() {
@@ -563,6 +563,7 @@ public abstract class DistanceManager {
         }
     }
 
+    /* Paper - replace old loader system
     private class FixedPlayerDistanceChunkTracker extends ChunkTracker {
 
         protected final Long2ByteMap chunks = new Long2ByteOpenHashMap();
@@ -858,4 +859,5 @@ public abstract class DistanceManager {
         }
         // Paper end
     }
+     */ // Paper - replace old loader system
 }
diff --git a/src/main/java/net/minecraft/server/level/ServerChunkCache.java b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
index 108f2212f8bd00247bf73ff4f3ba42830abad459..0d8a47770435c27519af4ebd78835ec787551733 100644
--- a/src/main/java/net/minecraft/server/level/ServerChunkCache.java
+++ b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
@@ -928,6 +928,7 @@ public class ServerChunkCache extends ChunkSource {
         this.level.timings.doChunkMap.stopTiming(); // Spigot
         this.level.getProfiler().popPush("chunks");
         this.level.timings.chunks.startTiming(); // Paper - timings
+        this.chunkMap.playerChunkManager.tick(); // Paper - this is mostly is to account for view distance changes
         this.tickChunks();
         this.level.timings.chunks.stopTiming(); // Paper - timings
         this.level.timings.doChunkUnload.startTiming(); // Spigot
@@ -1218,6 +1219,7 @@ public class ServerChunkCache extends ChunkSource {
         public boolean pollTask() {
         try {
             boolean execChunkTask = com.destroystokyo.paper.io.chunk.ChunkTaskManager.pollChunkWaitQueue() || ServerChunkCache.this.level.asyncChunkTaskManager.pollNextChunkTask(); // Paper
+            ServerChunkCache.this.chunkMap.playerChunkManager.tickMidTick(); // Paper
             if (ServerChunkCache.this.runDistanceManagerUpdates()) {
                 return true;
             } else {
diff --git a/src/main/java/net/minecraft/server/level/ServerPlayer.java b/src/main/java/net/minecraft/server/level/ServerPlayer.java
index f563e52c94735648670acd80169c0f7c4d6ad36a..6d2d2ba4a83d887f4d52188305a4a28c2ee2f014 100644
--- a/src/main/java/net/minecraft/server/level/ServerPlayer.java
+++ b/src/main/java/net/minecraft/server/level/ServerPlayer.java
@@ -261,7 +261,7 @@ public class ServerPlayer extends Player {
 
     public double lastEntitySpawnRadiusSquared; // Paper - optimise isOutsideRange, this field is in blocks
     public final com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> cachedSingleHashSet; // Paper
-    boolean needsChunkCenterUpdate; // Paper - no-tick view distance
+    public boolean needsChunkCenterUpdate; // Paper - no-tick view distance // Paper - public
     public org.bukkit.event.player.PlayerQuitEvent.QuitReason quitReason = null; // Paper - there are a lot of changes to do if we change all methods leading to the event
 
     public ServerPlayer(MinecraftServer server, ServerLevel world, GameProfile profile) {
diff --git a/src/main/java/net/minecraft/server/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
index 4c8f6d2d72194d313e7383b5a499c8ca1a84e1da..ad9fb50791779a5fe7d22268b71bd10d9c9ff3f0 100644
--- a/src/main/java/net/minecraft/server/players/PlayerList.java
+++ b/src/main/java/net/minecraft/server/players/PlayerList.java
@@ -267,7 +267,7 @@ public abstract class PlayerList {
         boolean flag1 = gamerules.getBoolean(GameRules.RULE_REDUCEDDEBUGINFO);
 
         // Spigot - view distance
-        playerconnection.send(new ClientboundLoginPacket(player.getId(), player.gameMode.getGameModeForPlayer(), player.gameMode.getPreviousGameModeForPlayer(), BiomeManager.obfuscateSeed(worldserver1.getSeed()), worlddata.isHardcore(), this.server.levelKeys(), this.registryHolder, worldserver1.dimensionType(), worldserver1.dimension(), this.getMaxPlayers(), worldserver1.getChunkSource().chunkMap.getLoadViewDistance(), flag1, !flag, worldserver1.isDebug(), worldserver1.isFlat())); // Paper - no-tick view distance
+        playerconnection.send(new ClientboundLoginPacket(player.getId(), player.gameMode.getGameModeForPlayer(), player.gameMode.getPreviousGameModeForPlayer(), BiomeManager.obfuscateSeed(worldserver1.getSeed()), worlddata.isHardcore(), this.server.levelKeys(), this.registryHolder, worldserver1.dimensionType(), worldserver1.dimension(), this.getMaxPlayers(), worldserver1.getChunkSource().chunkMap.playerChunkManager.getLoadDistance(), flag1, !flag, worldserver1.isDebug(), worldserver1.isFlat())); // Paper - no-tick view distance // Paper - replace old player chunk management
         player.getBukkitEntity().sendSupportedChannels(); // CraftBukkit
         playerconnection.send(new ClientboundCustomPayloadPacket(ClientboundCustomPayloadPacket.BRAND, (new FriendlyByteBuf(Unpooled.buffer())).writeUtf(this.getServer().getServerModName())));
         playerconnection.send(new ClientboundChangeDifficultyPacket(worlddata.getDifficulty(), worlddata.isDifficultyLocked()));
@@ -940,7 +940,7 @@ public abstract class PlayerList {
         // CraftBukkit start
         LevelData worlddata = worldserver1.getLevelData();
         entityplayer1.connection.send(new ClientboundRespawnPacket(worldserver1.dimensionType(), worldserver1.dimension(), BiomeManager.obfuscateSeed(worldserver1.getSeed()), entityplayer1.gameMode.getGameModeForPlayer(), entityplayer1.gameMode.getPreviousGameModeForPlayer(), worldserver1.isDebug(), worldserver1.isFlat(), flag));
-        entityplayer1.connection.send(new ClientboundSetChunkCacheRadiusPacket(worldserver1.getChunkSource().chunkMap.getLoadViewDistance())); // Spigot // Paper - no-tick view distance
+        entityplayer1.connection.send(new ClientboundSetChunkCacheRadiusPacket(worldserver1.getChunkSource().chunkMap.playerChunkManager.getLoadDistance())); // Spigot // Paper - no-tick view distance// Paper - replace old player chunk management
         entityplayer1.setLevel(worldserver1);
         entityplayer1.unsetRemoved();
         entityplayer1.connection.teleport(new Location(worldserver1.getWorld(), entityplayer1.getX(), entityplayer1.getY(), entityplayer1.getZ(), entityplayer1.getYRot(), entityplayer1.getXRot()));
@@ -1215,7 +1215,7 @@ public abstract class PlayerList {
             // Really shouldn't happen...
             backingSet = world != null ? world.players.toArray() : players.toArray();
         } else {
-            com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> nearbyPlayers = chunkMap.playerViewDistanceBroadcastMap.getObjectsInRange(MCUtil.fastFloor(x) >> 4, MCUtil.fastFloor(z) >> 4);
+            com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> nearbyPlayers = chunkMap.playerChunkManager.broadcastMap.getObjectsInRange(MCUtil.fastFloor(x) >> 4, MCUtil.fastFloor(z) >> 4); // Paper - replace old player chunk management
             if (nearbyPlayers == null) {
                 return;
             }
diff --git a/src/main/java/net/minecraft/world/item/EnderEyeItem.java b/src/main/java/net/minecraft/world/item/EnderEyeItem.java
index 7ccfe737fdf7f07b731ea0ff82e897564350705c..fe709bee0e657ff9bfc6deb6d4bd8ce4eccfcf06 100644
--- a/src/main/java/net/minecraft/world/item/EnderEyeItem.java
+++ b/src/main/java/net/minecraft/world/item/EnderEyeItem.java
@@ -60,9 +60,10 @@ public class EnderEyeItem extends Item {
 
                     // CraftBukkit start - Use relative location for far away sounds
                     // world.b(1038, blockposition1.c(1, 0, 1), 0);
-                    int viewDistance = world.getCraftServer().getViewDistance() * 16;
+                    //int viewDistance = world.getCraftServer().getViewDistance() * 16; // Paper - apply view distance patch
                     BlockPos soundPos = blockposition1.offset(1, 0, 1);
                     for (ServerPlayer player : world.getServer().getPlayerList().players) {
+                        final int viewDistance = player.getBukkitEntity().getViewDistance(); // Paper - apply view distance patch
                         double deltaX = soundPos.getX() - player.getX();
                         double deltaZ = soundPos.getZ() - player.getZ();
                         double distanceSquared = deltaX * deltaX + deltaZ * deltaZ;
diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
index 6ca0134c76adc335bb5125831e332fd709f09de7..83062654f7a3b05ba0ddb97645d615988bbe511b 100644
--- a/src/main/java/net/minecraft/world/level/Level.java
+++ b/src/main/java/net/minecraft/world/level/Level.java
@@ -597,7 +597,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
                 this.sendBlockUpdated(blockposition, iblockdata1, iblockdata, i);
                 // Paper start - per player view distance - allow block updates for non-ticking chunks in player view distance
                 // if copied from above
-            } else if ((i & 2) != 0 && (!this.isClientSide || (i & 4) == 0) && (this.isClientSide || chunk == null || ((ServerLevel)this).getChunkSource().chunkMap.playerViewDistanceBroadcastMap.getObjectsInRange(MCUtil.getCoordinateKey(blockposition)) != null)) {
+            } else if ((i & 2) != 0 && (!this.isClientSide || (i & 4) == 0) && (this.isClientSide || chunk == null || ((ServerLevel)this).getChunkSource().chunkMap.playerChunkManager.broadcastMap.getObjectsInRange(MCUtil.getCoordinateKey(blockposition)) != null)) { // Paper - replace old player chunk management
                 ((ServerLevel)this).getChunkSource().blockChanged(blockposition);
                 // Paper end - per player view distance
             }
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 f0c43f9f636a5dd1f0dfbae604dfa1f4ff9ebd4e..9e75ee7f43722f05dd5df4ef00f7d3e271f4c6e5 100644
--- a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
+++ b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
@@ -293,11 +293,12 @@ public class LevelChunk implements ChunkAccess {
         ChunkMap chunkMap = chunkProviderServer.chunkMap;
         // this code handles the addition of ticking tickets - the distance map handles the removal
         if (!areNeighboursLoaded(bitsetBefore, 2) && areNeighboursLoaded(bitsetAfter, 2)) {
-            if (chunkMap.playerViewDistanceTickMap.getObjectsInRange(this.coordinateKey) != null) {
+            if (chunkMap.playerChunkManager.tickMap.getObjectsInRange(this.coordinateKey) != null) { // Paper - replace old player chunk loading system
                 // now we're ready for entity ticking
                 chunkProviderServer.mainThreadProcessor.execute(() -> {
                     // double check that this condition still holds.
-                    if (LevelChunk.this.areNeighboursLoaded(2) && chunkMap.playerViewDistanceTickMap.getObjectsInRange(LevelChunk.this.coordinateKey) != null) {
+                    if (LevelChunk.this.areNeighboursLoaded(2) && chunkMap.playerChunkManager.tickMap.getObjectsInRange(LevelChunk.this.coordinateKey) != null) { // Paper - replace old player chunk loading system
+                        chunkMap.playerChunkManager.onChunkPlayerTickReady(this.chunkPos.x, this.chunkPos.z); // Paper - replace old player chunk
                         chunkProviderServer.addTicketAtLevel(net.minecraft.server.level.TicketType.PLAYER, LevelChunk.this.chunkPos, 31, LevelChunk.this.chunkPos); // 31 -> entity ticking, TODO check on update
                     }
                 });
@@ -306,31 +307,18 @@ public class LevelChunk implements ChunkAccess {
 
         // this code handles the chunk sending
         if (!areNeighboursLoaded(bitsetBefore, 1) && areNeighboursLoaded(bitsetAfter, 1)) {
-            if (chunkMap.playerViewDistanceBroadcastMap.getObjectsInRange(this.coordinateKey) != null) {
-                // now we're ready to send
-                chunkMap.mainThreadMailbox.tell(ChunkTaskPriorityQueueSorter.message(chunkMap.getUpdatingChunkIfPresent(this.coordinateKey), (() -> { // Copied frm PlayerChunkMap
-                    // double check that this condition still holds.
-                    if (!LevelChunk.this.areNeighboursLoaded(1)) {
-                        return;
-                    }
-                    com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<net.minecraft.server.level.ServerPlayer> inRange = chunkMap.playerViewDistanceBroadcastMap.getObjectsInRange(LevelChunk.this.coordinateKey);
-                    if (inRange == null) {
-                        return;
-                    }
-
-                    // broadcast
-                    Object[] backingSet = inRange.getBackingSet();
-                    Packet[] chunkPackets = new Packet[2];
-                    for (int index = 0, len = backingSet.length; index < len; ++index) {
-                        Object temp = backingSet[index];
-                        if (!(temp instanceof net.minecraft.server.level.ServerPlayer)) {
-                            continue;
-                        }
-                        net.minecraft.server.level.ServerPlayer player = (net.minecraft.server.level.ServerPlayer)temp;
-                        chunkMap.playerLoadedChunk(player, chunkPackets, LevelChunk.this);
-                    }
-                })));
-            }
+            // Paper start - replace old player chunk loading system
+            chunkProviderServer.mainThreadProcessor.execute(() -> {
+                if (!LevelChunk.this.areNeighboursLoaded(1)) {
+                    return;
+                }
+                LevelChunk.this.postProcessGeneration();
+                if (!LevelChunk.this.areNeighboursLoaded(1)) {
+                    return;
+                }
+                chunkMap.playerChunkManager.onChunkSendReady(this.chunkPos.x, this.chunkPos.z);
+            });
+            // Paper end - replace old player chunk loading system
         }
         // Paper end - no-tick view distance
     }
@@ -871,6 +859,7 @@ public class LevelChunk implements ChunkAccess {
         // Paper end - neighbour cache
         org.bukkit.Server server = this.level.getCraftServer();
         this.level.getChunkSource().addLoadedChunk(this); // Paper
+        ((ServerLevel)this.level).getChunkSource().chunkMap.playerChunkManager.onChunkLoad(this.chunkPos.x, this.chunkPos.z); // Paper - rewrite player chunk management
         if (server != null) {
             /*
              * If it's a new world, the first few chunks are generated inside
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
index 5af560b0466ec5ba80489e8f3d65aa2ee298786c..883b2070fcf99cf10d44aef6dece0f7f84bfeeed 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
@@ -2041,14 +2041,14 @@ public class CraftWorld extends CraftRegionAccessor implements World {
             throw new IllegalArgumentException("View distance " + viewDistance + " is out of range of [2, 32]");
         }
         net.minecraft.server.level.ChunkMap chunkMap = getHandle().getChunkSource().chunkMap;
-        if (viewDistance != chunkMap.getEffectiveViewDistance()) {
+        if (true) { // Paper - replace old player chunk management
             chunkMap.setViewDistance(viewDistance);
         }
     }
 
     @Override
     public int getNoTickViewDistance() {
-        return getHandle().getChunkSource().chunkMap.getEffectiveNoTickViewDistance();
+        return getHandle().getChunkSource().chunkMap.playerChunkManager.getTargetNoTickViewDistance(); // Paper - replace old player chunk management
     }
 
     @Override
@@ -2057,11 +2057,22 @@ public class CraftWorld extends CraftRegionAccessor implements World {
             throw new IllegalArgumentException("View distance " + viewDistance + " is out of range of [2, 32]");
         }
         net.minecraft.server.level.ChunkMap chunkMap = getHandle().getChunkSource().chunkMap;
-        if (viewDistance != chunkMap.getRawNoTickViewDistance()) {
+        if (true) { // Paper - replace old player chunk management
             chunkMap.setNoTickViewDistance(viewDistance);
         }
     }
     // Paper end - per player view distance
+    // Paper start - add view distances
+    @Override
+    public int getSendViewDistance() {
+        return getHandle().getChunkSource().chunkMap.playerChunkManager.getTargetSendDistance();
+    }
+
+    @Override
+    public void setSendViewDistance(int viewDistance) {
+        getHandle().getChunkSource().chunkMap.playerChunkManager.setTargetSendDistance(viewDistance);
+    }
+    // Paper end - add view distances
 
     // Spigot start
     private final org.bukkit.World.Spigot spigot = new org.bukkit.World.Spigot()
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
index aa9775083aa804d72965a7af4988b14551293571..2f943a5f5135d4bb7c516e09277ddf15b8732fca 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
@@ -517,15 +517,70 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
         }
     }
 
+    // Paper start - implement view distances
+    @Override
+    public int getSendViewDistance() {
+        net.minecraft.server.level.ChunkMap chunkMap = this.getHandle().getLevel().getChunkSource().chunkMap;
+        io.papermc.paper.chunk.PlayerChunkLoader.PlayerLoaderData data = chunkMap.playerChunkManager.getData(this.getHandle());
+        if (data == null) {
+            return chunkMap.playerChunkManager.getTargetSendDistance();
+        }
+        return data.getTargetSendViewDistance();
+    }
+
+    @Override
+    public void setSendViewDistance(int viewDistance) {
+        net.minecraft.server.level.ChunkMap chunkMap = this.getHandle().getLevel().getChunkSource().chunkMap;
+        io.papermc.paper.chunk.PlayerChunkLoader.PlayerLoaderData data = chunkMap.playerChunkManager.getData(this.getHandle());
+        if (data == null) {
+            throw new IllegalStateException("Player is not attached to world");
+        }
+
+        data.setTargetSendViewDistance(viewDistance);
+    }
+
+    @Override
+    public int getNoTickViewDistance() {
+        net.minecraft.server.level.ChunkMap chunkMap = this.getHandle().getLevel().getChunkSource().chunkMap;
+        io.papermc.paper.chunk.PlayerChunkLoader.PlayerLoaderData data = chunkMap.playerChunkManager.getData(this.getHandle());
+        if (data == null) {
+            return chunkMap.playerChunkManager.getTargetNoTickViewDistance();
+        }
+        return data.getTargetNoTickViewDistance();
+    }
+
+    @Override
+    public void setNoTickViewDistance(int viewDistance) {
+        net.minecraft.server.level.ChunkMap chunkMap = this.getHandle().getLevel().getChunkSource().chunkMap;
+        io.papermc.paper.chunk.PlayerChunkLoader.PlayerLoaderData data = chunkMap.playerChunkManager.getData(this.getHandle());
+        if (data == null) {
+            throw new IllegalStateException("Player is not attached to world");
+        }
+
+        data.setTargetNoTickViewDistance(viewDistance);
+    }
+
     @Override
     public int getViewDistance() {
-        throw new NotImplementedException("Per-Player View Distance APIs need further understanding to properly implement (There are per world view distances though!)"); // TODO
+        net.minecraft.server.level.ChunkMap chunkMap = this.getHandle().getLevel().getChunkSource().chunkMap;
+        io.papermc.paper.chunk.PlayerChunkLoader.PlayerLoaderData data = chunkMap.playerChunkManager.getData(this.getHandle());
+        if (data == null) {
+            return chunkMap.playerChunkManager.getTargetViewDistance();
+        }
+        return data.getTargetTickViewDistance();
     }
 
     @Override
     public void setViewDistance(int viewDistance) {
-        throw new NotImplementedException("Per-Player View Distance APIs need further understanding to properly implement (There are per world view distances though!)"); // TODO
+        net.minecraft.server.level.ChunkMap chunkMap = this.getHandle().getLevel().getChunkSource().chunkMap;
+        io.papermc.paper.chunk.PlayerChunkLoader.PlayerLoaderData data = chunkMap.playerChunkManager.getData(this.getHandle());
+        if (data == null) {
+            throw new IllegalStateException("Player is not attached to world");
+        }
+
+        data.setTargetTickViewDistance(viewDistance);
     }
+    // Paper end - implement view distances
 
     @Override
     public <T> T getClientOption(com.destroystokyo.paper.ClientOption<T> type) {