testserver/Spigot-Server-Patches/0528-Implement-Chunk-Priority-Urgency-System-for-Chunks.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 11 Apr 2020 03:56:07 -0400
Subject: [PATCH] Implement Chunk Priority / Urgency System for Chunks

Mark chunks that are blocking main thread for world generation as urgent

Implements a general priority system so that chunks that are sorted in
the generator queues can prioritize certain chunks over another.

Urgent chunks will jump to the front of the line, ensuring that a
sync chunk load on an ungenerated chunk does not lag the server for
a long period of time if the servers generator queues are filled with
lots of chunks already.

This massively reduces the lag spikes from sync chunk gens.

Then we further prioritize loading order so nearby chunks have higher
priority than distant chunks, reducing the pressure a high no tick
view distance holds on you.

Chunks in front of the player have higher priority, to help with
fast traveling players keep up with their movement.

diff --git a/src/main/java/com/destroystokyo/paper/io/chunk/ChunkTaskManager.java b/src/main/java/com/destroystokyo/paper/io/chunk/ChunkTaskManager.java
index b5c2e1f4a2b5fdcaa6bb01f4b3b6847cd5b73ae8..6209b33d8497ec56bbde507e523db0649c66f590 100644
--- a/src/main/java/com/destroystokyo/paper/io/chunk/ChunkTaskManager.java
+++ b/src/main/java/com/destroystokyo/paper/io/chunk/ChunkTaskManager.java
@@ -4,7 +4,10 @@ import com.destroystokyo.paper.io.PaperFileIOThread;
 import com.destroystokyo.paper.io.IOUtil;
 import com.destroystokyo.paper.io.PrioritizedTaskQueue;
 import com.destroystokyo.paper.io.QueueExecutorThread;
+import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
+import net.minecraft.server.ChunkCoordIntPair;
 import net.minecraft.server.ChunkRegionLoader;
+import net.minecraft.server.ChunkStatus;
 import net.minecraft.server.IAsyncTaskHandler;
 import net.minecraft.server.IChunkAccess;
 import net.minecraft.server.MinecraftServer;
@@ -106,7 +109,7 @@ public final class ChunkTaskManager {
     }
 
     static void dumpChunkInfo(Set<PlayerChunk> seenChunks, PlayerChunk chunkHolder, int x, int z) {
-        dumpChunkInfo(seenChunks, chunkHolder, x, z, 0, 1);
+        dumpChunkInfo(seenChunks, chunkHolder, x, z, 0, 4);
     }
 
     static void dumpChunkInfo(Set<PlayerChunk> seenChunks, PlayerChunk chunkHolder, int x, int z, int indent, int maxDepth) {
@@ -127,6 +130,30 @@ public final class ChunkTaskManager {
             PaperFileIOThread.LOGGER.log(Level.ERROR, indentStr + "Chunk Status - " + ((chunk == null) ? "null chunk" : chunk.getChunkStatus().toString()));
             PaperFileIOThread.LOGGER.log(Level.ERROR, indentStr + "Chunk Ticket Status - "  + PlayerChunk.getChunkStatus(chunkHolder.getTicketLevel()));
             PaperFileIOThread.LOGGER.log(Level.ERROR, indentStr + "Chunk Holder Status - " + ((holderStatus == null) ? "null" : holderStatus.toString()));
+            PaperFileIOThread.LOGGER.log(Level.ERROR, indentStr + "Chunk Holder Priority - " + chunkHolder.getCurrentPriority());
+
+            if (!chunkHolder.neighbors.isEmpty()) {
+                if (indent >= maxDepth) {
+                    PaperFileIOThread.LOGGER.log(Level.ERROR, indentStr + "Chunk Neighbors: (Can't show, too deeply nested)");
+                    return;
+                }
+                PaperFileIOThread.LOGGER.log(Level.ERROR, indentStr + "Chunk Neighbors: ");
+                for (PlayerChunk neighbor : chunkHolder.neighbors.keySet()) {
+                    ChunkStatus status = neighbor.getChunkHolderStatus();
+                    if (status != null && status.isAtLeastStatus(PlayerChunk.getChunkStatus(neighbor.getTicketLevel()))) {
+                        continue;
+                    }
+                    int nx = neighbor.location.x;
+                    int nz = neighbor.location.z;
+                    if (seenChunks.contains(neighbor)) {
+                        PaperFileIOThread.LOGGER.log(Level.ERROR, indentStr + "  " + nx + "," + nz + " in " + chunkHolder.getWorld().getWorld().getName() + " (CIRCULAR)");
+                        continue;
+                    }
+                    PaperFileIOThread.LOGGER.log(Level.ERROR, indentStr + "  " + nx + "," + nz + " in " + chunkHolder.getWorld().getWorld().getName() + ":");
+                    dumpChunkInfo(seenChunks, neighbor, nx, nz, indent + 1, maxDepth);
+                }
+            }
+
         }
     }
 
diff --git a/src/main/java/net/minecraft/server/ChunkCoordIntPair.java b/src/main/java/net/minecraft/server/ChunkCoordIntPair.java
index f617636a22167b06ac8073aa25efd8c7099155f0..0f40793f004639822b9d40521cd21ec50391ba3b 100644
--- a/src/main/java/net/minecraft/server/ChunkCoordIntPair.java
+++ b/src/main/java/net/minecraft/server/ChunkCoordIntPair.java
@@ -110,6 +110,7 @@ public class ChunkCoordIntPair {
         return "[" + this.x + ", " + this.z + "]";
     }
 
+    public final BlockPosition asPosition() { return l(); } // Paper - OBFHELPER
     public BlockPosition l() {
         return new BlockPosition(this.x << 4, 0, this.z << 4);
     }
diff --git a/src/main/java/net/minecraft/server/ChunkMapDistance.java b/src/main/java/net/minecraft/server/ChunkMapDistance.java
index 7702fbefa598bce7e6a2d287f7ec36b78a62bff8..02d07d3ff5c3b824047402ff1f58aa338a46c254 100644
--- a/src/main/java/net/minecraft/server/ChunkMapDistance.java
+++ b/src/main/java/net/minecraft/server/ChunkMapDistance.java
@@ -23,6 +23,7 @@ import java.util.concurrent.Executor;
 import javax.annotation.Nullable;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.spigotmc.AsyncCatcher; // Paper
 
 public abstract class ChunkMapDistance {
 
@@ -84,6 +85,7 @@ public abstract class ChunkMapDistance {
     }
 
     private static int a(ArraySetSorted<Ticket<?>> arraysetsorted) {
+        AsyncCatcher.catchOp("ChunkMapDistance::getHighestTicketLevel"); // Paper
         return !arraysetsorted.isEmpty() ? ((Ticket) arraysetsorted.b()).b() : PlayerChunkMap.GOLDEN_TICKET + 1;
     }
 
@@ -97,6 +99,7 @@ public abstract class ChunkMapDistance {
 
     public boolean a(PlayerChunkMap playerchunkmap) {
         //this.f.a(); // Paper - no longer used
+        AsyncCatcher.catchOp("DistanceManagerTick");
         this.g.a();
         int i = Integer.MAX_VALUE - this.e.a(Integer.MAX_VALUE);
         boolean flag = i != 0;
@@ -107,11 +110,13 @@ public abstract class ChunkMapDistance {
 
         // Paper start
         if (!this.pendingChunkUpdates.isEmpty()) {
+            this.pollingPendingChunkUpdates = true;
             while(!this.pendingChunkUpdates.isEmpty()) {
                 PlayerChunk remove = this.pendingChunkUpdates.remove();
                 remove.isUpdateQueued = false;
                 remove.a(playerchunkmap);
             }
+            this.pollingPendingChunkUpdates = false;
             // Paper end
             return true;
         } else {
@@ -147,8 +152,10 @@ public abstract class ChunkMapDistance {
             return flag;
         }
     }
+    boolean pollingPendingChunkUpdates = false; // Paper
 
     private boolean addTicket(long i, Ticket<?> ticket) { // CraftBukkit - void -> boolean
+        AsyncCatcher.catchOp("ChunkMapDistance::addTicket"); // Paper
         ArraySetSorted<Ticket<?>> arraysetsorted = this.e(i);
         int j = a(arraysetsorted);
         Ticket<?> ticket1 = (Ticket) arraysetsorted.a(ticket); // CraftBukkit - decompile error
@@ -162,7 +169,9 @@ public abstract class ChunkMapDistance {
     }
 
     private boolean removeTicket(long i, Ticket<?> ticket) { // CraftBukkit - void -> boolean
+        AsyncCatcher.catchOp("ChunkMapDistance::removeTicket"); // Paper
         ArraySetSorted<Ticket<?>> arraysetsorted = this.e(i);
+        int oldLevel = a(arraysetsorted); // Paper
 
         boolean removed = false; // CraftBukkit
         if (arraysetsorted.remove(ticket)) {
@@ -172,8 +181,8 @@ public abstract class ChunkMapDistance {
         if (arraysetsorted.isEmpty()) {
             this.tickets.remove(i);
         }
-
-        this.e.b(i, a(arraysetsorted), false);
+        int newLevel = a(arraysetsorted); // Paper
+        if (newLevel > oldLevel) this.e.b(i, newLevel, false); // Paper
         return removed; // CraftBukkit
     }
 
@@ -182,6 +191,116 @@ public abstract class ChunkMapDistance {
         this.addTicketAtLevel(tickettype, chunkcoordintpair, i, t0);
     }
 
+    // Paper start
+    public static final int PRIORITY_TICKET_LEVEL = PlayerChunkMap.GOLDEN_TICKET;
+    public static final int URGENT_PRIORITY = 29;
+    public boolean delayDistanceManagerTick = false;
+    public boolean markUrgent(ChunkCoordIntPair coords) {
+        return addPriorityTicket(coords, TicketType.URGENT, URGENT_PRIORITY);
+    }
+    public boolean markHighPriority(ChunkCoordIntPair coords, int priority) {
+        priority = Math.min(URGENT_PRIORITY - 1, Math.max(1, priority));
+        return addPriorityTicket(coords, TicketType.PRIORITY, priority);
+    }
+
+    public void markAreaHighPriority(ChunkCoordIntPair center, int priority, int radius) {
+        delayDistanceManagerTick = true;
+        MCUtil.getSpiralOutChunks(center.asPosition(), radius).forEach(coords -> {
+            addPriorityTicket(coords, TicketType.PRIORITY, priority);
+        });
+        delayDistanceManagerTick = false;
+        chunkMap.world.getChunkProvider().tickDistanceManager();
+    }
+
+    public void clearAreaPriorityTickets(ChunkCoordIntPair center, int radius) {
+        delayDistanceManagerTick = true;
+        MCUtil.getSpiralOutChunks(center.asPosition(), radius).forEach(coords -> {
+            this.removeTicket(coords.pair(), new Ticket<ChunkCoordIntPair>(TicketType.PRIORITY, PRIORITY_TICKET_LEVEL, coords));
+        });
+        delayDistanceManagerTick = false;
+        chunkMap.world.getChunkProvider().tickDistanceManager();
+    }
+
+    private boolean addPriorityTicket(ChunkCoordIntPair coords, TicketType<ChunkCoordIntPair> ticketType, int priority) {
+        AsyncCatcher.catchOp("ChunkMapDistance::addPriorityTicket");
+        long pair = coords.pair();
+        PlayerChunk chunk = chunkMap.getUpdatingChunk(pair);
+        if (chunk != null && chunk.isFullChunkReady()) {
+            return false;
+        }
+        if (chunk != null && chunk.getTicketLevel() > 33 && chunkMap.playerViewDistanceNoTickMap.getObjectsInRange(pair) != null) {
+            Ticket<?> ticket = new Ticket<>(TicketType.PLAYER, 33, coords);
+            addTicket(pair, ticket);
+        }
+        if (getChunkPriority(coords) >= priority) {
+            return false;
+        }
+
+        boolean success;
+        if (!(success = updatePriorityTicket(coords, ticketType, priority))) {
+            Ticket<ChunkCoordIntPair> ticket = new Ticket<ChunkCoordIntPair>(ticketType, PRIORITY_TICKET_LEVEL, coords);
+            ticket.priority = priority;
+            success = this.addTicket(pair, ticket);
+        } else {
+            if (chunk == null) {
+                chunk = chunkMap.getUpdatingChunk(pair);
+            }
+            chunkMap.queueHolderUpdate(chunk);
+        }
+
+        //chunkMap.world.getWorld().spawnParticle(priority <= 15 ? org.bukkit.Particle.EXPLOSION_HUGE : org.bukkit.Particle.EXPLOSION_NORMAL, chunkMap.world.getWorld().getPlayers(), null, coords.x << 4, 70, coords.z << 4, 2, 0, 0, 0, 1, null, true);
+
+        chunkMap.world.getChunkProvider().tickDistanceManager();
+
+        return success;
+    }
+
+    private boolean updatePriorityTicket(ChunkCoordIntPair coords, TicketType<ChunkCoordIntPair> type, int priority) {
+        ArraySetSorted<Ticket<?>> tickets = this.tickets.get(coords.pair());
+        if (tickets == null) {
+            return false;
+        }
+        for (Ticket<?> ticket : tickets) {
+            if (ticket.getTicketType() == type) {
+                // We only support increasing, not decreasing, too complicated
+                ticket.setCurrentTick(this.currentTick);
+                ticket.priority = Math.max(ticket.priority, priority);
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    public int getChunkPriority(ChunkCoordIntPair coords) {
+        AsyncCatcher.catchOp("ChunkMapDistance::getChunkPriority");
+        ArraySetSorted<Ticket<?>> tickets = this.tickets.get(coords.pair());
+        if (tickets == null) {
+            return 0;
+        }
+        for (Ticket<?> ticket : tickets) {
+            if (ticket.getTicketType() == TicketType.URGENT) {
+                return URGENT_PRIORITY;
+            }
+        }
+        for (Ticket<?> ticket : tickets) {
+            if (ticket.getTicketType() == TicketType.PRIORITY && ticket.priority > 0) {
+                return ticket.priority;
+            }
+        }
+        return 0;
+    }
+
+    public void clearPriorityTickets(ChunkCoordIntPair coords) {
+        AsyncCatcher.catchOp("ChunkMapDistance::clearPriority");
+        this.removeTicket(coords.pair(), new Ticket<ChunkCoordIntPair>(TicketType.PRIORITY, PRIORITY_TICKET_LEVEL, coords));
+    }
+
+    public void clearUrgent(ChunkCoordIntPair coords) {
+        AsyncCatcher.catchOp("ChunkMapDistance::clearUrgent");
+        this.removeTicket(coords.pair(), new Ticket<ChunkCoordIntPair>(TicketType.URGENT, PRIORITY_TICKET_LEVEL, coords));
+    }
+    // Paper end
     public <T> boolean addTicketAtLevel(TicketType<T> ticketType, ChunkCoordIntPair chunkcoordintpair, int level, T identifier) {
         return this.addTicket(chunkcoordintpair.pair(), new Ticket<>(ticketType, level, identifier));
         // CraftBukkit end
@@ -384,24 +503,29 @@ public abstract class ChunkMapDistance {
                 Ticket<?> ticket = new Ticket<>(TicketType.PLAYER, 33, new ChunkCoordIntPair(i)); // Paper - no-tick view distance
 
                 if (flag1) {
-                    ChunkMapDistance.this.j.a(ChunkTaskQueueSorter.a(() -> { // CraftBukkit - decompile error
-                        ChunkMapDistance.this.m.execute(() -> {
-                            if (this.c(this.c(i))) {
+                    // Paper start - smarter ticket delay based on frustum and distance
+                    scheduleChunkLoad(i, MinecraftServer.currentTick, j, (priority) -> {
+                        ChunkMapDistance.this.j.a(ChunkTaskQueueSorter.a(() -> { // CraftBukkit - decompile error
+                            if (priority < 5 && this.c(this.c(i))) {
+                                // Skip throttle for near chunks
+                                ChunkMapDistance.this.addTicket(i, ticket);
+                                ChunkMapDistance.this.l.add(i);
+                            } else if (this.c(this.c(i))) { // Copy c(c()) stuff below
+                                // Paper end
                                 ChunkMapDistance.this.addTicket(i, ticket);
                                 ChunkMapDistance.this.l.add(i);
                             } else {
                                 ChunkMapDistance.this.k.a(ChunkTaskQueueSorter.a(() -> { // CraftBukkit - decompile error
                                 }, i, false));
                             }
-
-                        });
                     }, i, () -> {
-                        return j;
-                    }));
+                        return Math.min(PlayerChunkMap.GOLDEN_TICKET, (priority <= 6 ? 20 : 30) + priority); // Paper - delay new ticket adds to avoid spamming the queue
+                    })); }); // Paper
                 } else {
                     ChunkMapDistance.this.k.a(ChunkTaskQueueSorter.a(() -> { // CraftBukkit - decompile error
                         ChunkMapDistance.this.m.execute(() -> {
                             ChunkMapDistance.this.removeTicket(i, ticket);
+                            ChunkMapDistance.this.clearPriorityTickets(new ChunkCoordIntPair(i)); // Paper
                         });
                     }, i, true));
                 }
@@ -409,6 +533,99 @@ public abstract class ChunkMapDistance {
 
         }
 
+        // Paper start - smart scheduling of player tickets
+        public void scheduleChunkLoad(long i, long startTick, int initialDistance, java.util.function.Consumer<Integer> task) {
+            long elapsed = MinecraftServer.currentTick - startTick;
+            ChunkCoordIntPair chunkPos = new ChunkCoordIntPair(i);
+            PlayerChunk updatingChunk = chunkMap.getUpdatingChunk(i);
+            if ((updatingChunk != null && updatingChunk.isFullChunkReady()) || !this.c(this.c(i)) || getChunkPriority(chunkPos) > 0) { // Copied from above
+                // no longer needed
+                task.accept(1);
+                return;
+            }
+
+            int desireDelay = 0;
+            double minDist = Double.MAX_VALUE;
+            com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<EntityPlayer> players = chunkMap.playerViewDistanceNoTickMap.getObjectsInRange(i);
+            if (elapsed == 0 && initialDistance <= 4) {
+                // Aim for no delay on initial 6 chunk radius tickets save on performance of the below code to only > 6
+                minDist = initialDistance;
+            } else if (players != null) {
+                Object[] backingSet = players.getBackingSet();
+
+                BlockPosition blockPos = chunkPos.asPosition();
+
+                boolean isFront = false;
+                BlockPosition.PooledBlockPosition pos = BlockPosition.PooledBlockPosition.acquire();
+                for (int index = 0, len = backingSet.length; index < len; ++index) {
+                    if (!(backingSet[index] instanceof EntityPlayer)) {
+                        continue;
+                    }
+                    EntityPlayer player = (EntityPlayer) backingSet[index];
+
+                    ChunkCoordIntPair pointInFront = player.getChunkInFront(5);
+                    pos.setValues(pointInFront.x << 4, 0, pointInFront.z << 4);
+                    double frontDist = MCUtil.distanceSq(pos, blockPos);
+
+                    pos.setValues(player.locX(), 0, player.locZ());
+                    double center = MCUtil.distanceSq(pos, blockPos);
+
+                    double dist = Math.min(frontDist, center);
+                    if (!isFront) {
+
+                        ChunkCoordIntPair pointInBack = player.getChunkInFront(-5);
+                        pos.setValues(pointInBack.x << 4, 0, pointInBack.z << 4);
+                        double backDist = MCUtil.distanceSq(pos, blockPos);
+                        if (frontDist < backDist) {
+                            isFront = true;
+                        }
+                    }
+                    if (dist < minDist) {
+                        minDist = dist;
+                    }
+                }
+                pos.close();
+                if (minDist == Double.MAX_VALUE) {
+                    minDist = 15;
+                } else {
+                    minDist = Math.sqrt(minDist) / 16;
+                }
+                if (minDist > 4) {
+                    int desiredTimeDelayMax = isFront ?
+                        (minDist < 10 ? 10 : 15) : // Front
+                        (minDist < 10 ? 15 : 30); // Back
+                    desireDelay += (desiredTimeDelayMax * 20) * (minDist / 32);
+                }
+            } else {
+                minDist = initialDistance;
+                desireDelay = 1;
+            }
+            long delay = desireDelay - elapsed;
+            if (delay <= 0 && minDist > 4 && minDist < Double.MAX_VALUE) {
+                boolean hasAnyNeighbor = false;
+                for (int x = -1; x <= 1; x++) {
+                    for (int z = -1; z <= 1; z++) {
+                        if (x == 0 && z == 0) continue;
+                        long pair = new ChunkCoordIntPair(chunkPos.x + x, chunkPos.z + z).pair();
+                        PlayerChunk neighbor = chunkMap.getUpdatingChunk(pair);
+                        ChunkStatus current = neighbor != null ? neighbor.getChunkHolderStatus() : null;
+                        if (current != null && current.isAtLeastStatus(ChunkStatus.LIGHT)) {
+                            hasAnyNeighbor = true;
+                        }
+                    }
+                }
+                if (!hasAnyNeighbor) {
+                    delay += 10;
+                }
+            }
+            if (delay <= 0) {
+                task.accept((int) minDist);
+            } else {
+                MCUtil.scheduleTask((int) Math.min(delay, minDist >= 10 ? 40 : (minDist < 6 ? 10 : 20)), () -> scheduleChunkLoad(i, startTick, initialDistance, task), "Player Ticket Delayer");
+            }
+        }
+        // Paper end
+
         @Override
         public void a() {
             super.a();
diff --git a/src/main/java/net/minecraft/server/ChunkProviderServer.java b/src/main/java/net/minecraft/server/ChunkProviderServer.java
index 7a275bf3260f9fbefc41883c5ebdc1eb2196daf0..340d6e992786e8877243ccb472b462e88ec1e6fb 100644
--- a/src/main/java/net/minecraft/server/ChunkProviderServer.java
+++ b/src/main/java/net/minecraft/server/ChunkProviderServer.java
@@ -432,6 +432,26 @@ public class ChunkProviderServer extends IChunkProvider {
     public <T> void removeTicketAtLevel(TicketType<T> ticketType, ChunkCoordIntPair chunkPos, int ticketLevel, T identifier) {
         this.chunkMapDistance.removeTicketAtLevel(ticketType, chunkPos, ticketLevel, identifier);
     }
+
+    public boolean markUrgent(ChunkCoordIntPair coords) {
+        return this.chunkMapDistance.markUrgent(coords);
+    }
+
+    public boolean markHighPriority(ChunkCoordIntPair coords, int priority) {
+        return this.chunkMapDistance.markHighPriority(coords, priority);
+    }
+
+    public void markAreaHighPriority(ChunkCoordIntPair center, int priority, int radius) {
+        this.chunkMapDistance.markAreaHighPriority(center, priority, radius);
+    }
+
+    public void clearAreaPriorityTickets(ChunkCoordIntPair center, int radius) {
+        this.chunkMapDistance.clearAreaPriorityTickets(center, radius);
+    }
+
+    public void clearPriorityTickets(ChunkCoordIntPair coords) {
+        this.chunkMapDistance.clearPriorityTickets(coords);
+    }
     // Paper end
 
     @Nullable
@@ -470,6 +490,8 @@ public class ChunkProviderServer extends IChunkProvider {
 
             if (!completablefuture.isDone()) { // Paper
                 // Paper start - async chunk io/loading
+                ChunkCoordIntPair pair = new ChunkCoordIntPair(x, z);
+                this.chunkMapDistance.markUrgent(pair);
                 this.world.asyncChunkTaskManager.raisePriority(x, z, com.destroystokyo.paper.io.PrioritizedTaskQueue.HIGHEST_PRIORITY);
                 com.destroystokyo.paper.io.chunk.ChunkTaskManager.pushChunkWait(this.world, x, z);
                 // Paper end
@@ -478,6 +500,8 @@ public class ChunkProviderServer extends IChunkProvider {
             this.serverThreadQueue.awaitTasks(completablefuture::isDone);
                 com.destroystokyo.paper.io.chunk.ChunkTaskManager.popChunkWait(); // Paper - async chunk debug
                 this.world.timings.syncChunkLoad.stopTiming(); // Paper
+                this.chunkMapDistance.clearPriorityTickets(pair); // Paper
+                this.chunkMapDistance.clearUrgent(pair); // Paper
             } // Paper
             ichunkaccess = (IChunkAccess) ((Either) completablefuture.join()).map((ichunkaccess1) -> {
                 return ichunkaccess1;
@@ -527,9 +551,10 @@ public class ChunkProviderServer extends IChunkProvider {
             PlayerChunk.State currentChunkState = PlayerChunk.getChunkState(playerchunk.getTicketLevel());
             currentlyUnloading = (oldChunkState.isAtLeast(PlayerChunk.State.BORDER) && !currentChunkState.isAtLeast(PlayerChunk.State.BORDER));
         }
-        if (flag && !currentlyUnloading) {
+        if (flag) { // Paper - don't care about unloading state
             // CraftBukkit end
             this.chunkMapDistance.a(TicketType.UNKNOWN, chunkcoordintpair, l, chunkcoordintpair);
+            if (isUrgent) this.chunkMapDistance.markUrgent(chunkcoordintpair); // Paper
             if (this.a(playerchunk, l)) {
                 GameProfilerFiller gameprofilerfiller = this.world.getMethodProfiler();
 
@@ -542,8 +567,13 @@ public class ChunkProviderServer extends IChunkProvider {
                 }
             }
         }
-
-        return this.a(playerchunk, l) ? PlayerChunk.UNLOADED_CHUNK_ACCESS_FUTURE : playerchunk.a(chunkstatus, this.playerChunkMap);
+        // Paper start
+        CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> future = this.a(playerchunk, l) ? PlayerChunk.UNLOADED_CHUNK_ACCESS_FUTURE : playerchunk.a(chunkstatus, this.playerChunkMap);
+        if (isUrgent) {
+            future.thenAccept(either -> this.chunkMapDistance.clearUrgent(chunkcoordintpair));
+        }
+        return future;
+        // Paper end
     }
 
     private boolean a(@Nullable PlayerChunk playerchunk, int i) {
@@ -593,7 +623,8 @@ public class ChunkProviderServer extends IChunkProvider {
         return this.serverThreadQueue.executeNext();
     }
 
-    private boolean tickDistanceManager() {
+    public boolean tickDistanceManager() { // Paper - public
+        if (chunkMapDistance.delayDistanceManagerTick) return false; // Paper
         boolean flag = this.chunkMapDistance.a(this.playerChunkMap);
         boolean flag1 = this.playerChunkMap.b();
 
diff --git a/src/main/java/net/minecraft/server/EntityPlayer.java b/src/main/java/net/minecraft/server/EntityPlayer.java
index 07a6fc3d88e7d44bfab7f3d6a0eef7dc132ab422..4ed4ad6bc3b4ab6702ca500dc26e889dca6ed2d7 100644
--- a/src/main/java/net/minecraft/server/EntityPlayer.java
+++ b/src/main/java/net/minecraft/server/EntityPlayer.java
@@ -55,6 +55,7 @@ public class EntityPlayer extends EntityHuman implements ICrafting {
     private int lastArmorScored = Integer.MIN_VALUE;
     private int lastExpLevelScored = Integer.MIN_VALUE;
     private int lastExpTotalScored = Integer.MIN_VALUE;
+    public long lastHighPriorityChecked; // Paper
     private float lastHealthSent = -1.0E8F;
     private int lastFoodSent = -99999999;
     private boolean lastSentSaturationZero = true;
@@ -132,6 +133,21 @@ public class EntityPlayer extends EntityHuman implements ICrafting {
         this.maxHealthCache = this.getMaxHealth();
         this.cachedSingleMobDistanceMap = new com.destroystokyo.paper.util.PooledHashSets.PooledObjectLinkedOpenHashSet<>(this); // Paper
     }
+    // Paper start
+    public BlockPosition getPointInFront(double inFront) {
+        double rads = Math.toRadians(MCUtil.normalizeYaw(this.yaw+90)); // MC rotates yaw 90 for some odd reason
+        final double x = locX() + inFront * Math.cos(rads);
+        final double z = locZ() + inFront * Math.sin(rads);
+        return new BlockPosition(x, locY(), z);
+    }
+
+    public ChunkCoordIntPair getChunkInFront(double inFront) {
+        double rads = Math.toRadians(MCUtil.normalizeYaw(this.yaw+90)); // MC rotates yaw 90 for some odd reason
+        final double x = locX() + (inFront * 16) * Math.cos(rads);
+        final double z = locZ() + (inFront * 16) * Math.sin(rads);
+        return new ChunkCoordIntPair(MathHelper.floor(x) >> 4, MathHelper.floor(z) >> 4);
+    }
+    // Paper end
 
     // Yes, this doesn't match Vanilla, but it's the best we can do for now.
     // If this is an issue, PRs are welcome
@@ -441,6 +457,7 @@ public class EntityPlayer extends EntityHuman implements ICrafting {
             if (valid && (!this.isSpectator() || this.world.isLoaded(new BlockPosition(this)))) { // Paper - don't tick dead players that are not in the world currently (pending respawn)
                 super.tick();
             }
+            if (valid && isAlive()) ((WorldServer)world).getChunkProvider().playerChunkMap.checkHighPriorityChunks(this); // Paper
 
             for (int i = 0; i < this.inventory.getSize(); ++i) {
                 ItemStack itemstack = this.inventory.getItem(i);
diff --git a/src/main/java/net/minecraft/server/MCUtil.java b/src/main/java/net/minecraft/server/MCUtil.java
index ce0bf608b71cf492fc31e89a360ecd83fa5c23a6..87d58002116f361d8255d79fc0dbd1200f442168 100644
--- a/src/main/java/net/minecraft/server/MCUtil.java
+++ b/src/main/java/net/minecraft/server/MCUtil.java
@@ -666,6 +666,7 @@ public final class MCUtil {
                 chunkData.addProperty("x", playerChunk.location.x);
                 chunkData.addProperty("z", playerChunk.location.z);
                 chunkData.addProperty("ticket-level", playerChunk.getTicketLevel());
+                chunkData.addProperty("priority", playerChunk.getCurrentPriority());
                 chunkData.addProperty("state", PlayerChunk.getChunkState(playerChunk.getTicketLevel()).toString());
                 chunkData.addProperty("queued-for-unload", chunkMap.unloadQueue.contains(playerChunk.location.pair()));
                 chunkData.addProperty("status", status == null ? "unloaded" : status.toString());
diff --git a/src/main/java/net/minecraft/server/PlayerChunk.java b/src/main/java/net/minecraft/server/PlayerChunk.java
index aeca6b2b9d5d73aeb6dc639b5cad2f2533a2de44..04dcb79c6033f1dec62c5df49937a4ef067a2cb8 100644
--- a/src/main/java/net/minecraft/server/PlayerChunk.java
+++ b/src/main/java/net/minecraft/server/PlayerChunk.java
@@ -26,8 +26,8 @@ public class PlayerChunk {
     private CompletableFuture<IChunkAccess> chunkSave;
     public int oldTicketLevel;
     private int ticketLevel;
-    private int n;
-    final ChunkCoordIntPair location; // Paper - private -> package
+    volatile int n; public final int getCurrentPriority() { return n; } // Paper - OBFHELPER - make volatile since this is concurrently accessed
+    public final ChunkCoordIntPair location; // Paper - private -> public
     private final short[] dirtyBlocks;
     private int dirtyCount;
     private int r;
@@ -40,6 +40,7 @@ public class PlayerChunk {
     private boolean hasBeenLoaded;
 
     private final PlayerChunkMap chunkMap; // Paper
+    public WorldServer getWorld() { return chunkMap.world; } // Paper
 
     long lastAutoSaveTime; // Paper - incremental autosave
     long inactiveTimeStart; // Paper - incremental autosave
@@ -67,6 +68,124 @@ public class PlayerChunk {
         return null;
     }
     // Paper end - no-tick view distance
+    // Paper start - Chunk gen/load priority system
+    volatile int neighborPriority = -1;
+    volatile int priorityBoost = 0;
+    public final java.util.concurrent.ConcurrentHashMap<PlayerChunk, ChunkStatus> neighbors = new java.util.concurrent.ConcurrentHashMap<>();
+    public final it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap<Integer> neighborPriorities = new it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap<>();
+
+    private int getDemandedPriority() {
+        int priority = neighborPriority; // if we have a neighbor priority, use it
+        int myPriority = getMyPriority();
+
+        if (priority == -1 || (ticketLevel <= 33 && priority > myPriority)) {
+            priority = myPriority;
+        }
+
+        return Math.max(1, Math.min(Math.max(ticketLevel, PlayerChunkMap.GOLDEN_TICKET), priority));
+    }
+
+    private int getMyPriority() {
+        if (priorityBoost == ChunkMapDistance.URGENT_PRIORITY) {
+            return 2; // Urgent - ticket level isn't always 31 so 33-30 = 3, but allow 1 more tasks to go below this for dependents
+        }
+        int basePriority = ticketLevel - priorityBoost;
+        if (ticketLevel >= 33 && priorityBoost == 0 && (neighborPriority >= 34 || neighborPriorities.isEmpty())) {
+            basePriority += 5;
+        }
+        return basePriority;
+    }
+
+    private int getNeighborsPriority() {
+        return neighborPriorities.isEmpty() ? getMyPriority() : getDemandedPriority();
+    }
+
+    public void onNeighborRequest(PlayerChunk neighbor, ChunkStatus status) {
+        neighbor.setNeighborPriority(this, getNeighborsPriority());
+        this.neighbors.compute(neighbor, (playerChunk, currentWantedStatus) -> {
+            if (currentWantedStatus == null || !currentWantedStatus.isAtLeastStatus(status)) {
+                //System.out.println(this + " request " + neighbor + " at " + status + " currently " + currentWantedStatus);
+                return status;
+            } else {
+                //System.out.println(this + " requested " + neighbor + " at " + status + " but thats lower than other wanted status " + currentWantedStatus);
+                return currentWantedStatus;
+            }
+        });
+
+    }
+
+    public void onNeighborDone(PlayerChunk neighbor, ChunkStatus chunkstatus, IChunkAccess chunk) {
+        this.neighbors.compute(neighbor, (playerChunk, wantedStatus) -> {
+            if (wantedStatus != null && chunkstatus.isAtLeastStatus(wantedStatus)) {
+                //System.out.println(this + " neighbor done at " + neighbor + " for status " + chunkstatus + " wanted " + wantedStatus);
+                neighbor.removeNeighborPriority(this);
+                return null;
+            } else {
+                //System.out.println(this + " neighbor finished our previous request at " + neighbor + " for status " + chunkstatus + " but we now want instead " + wantedStatus);
+                return wantedStatus;
+            }
+        });
+    }
+
+    private void removeNeighborPriority(PlayerChunk requester) {
+        synchronized (neighborPriorities) {
+            neighborPriorities.remove(requester.location.pair());
+            recalcNeighborPriority();
+        }
+        checkPriority();
+    }
+
+
+    private void setNeighborPriority(PlayerChunk requester, int priority) {
+        synchronized (neighborPriorities) {
+            neighborPriorities.put(requester.location.pair(), Integer.valueOf(priority));
+            recalcNeighborPriority();
+        }
+        checkPriority();
+    }
+
+    private void recalcNeighborPriority() {
+        neighborPriority = -1;
+        if (!neighborPriorities.isEmpty()) {
+            synchronized (neighborPriorities) {
+                for (Integer neighbor : neighborPriorities.values()) {
+                    if (neighbor < neighborPriority || neighborPriority == -1) {
+                        neighborPriority = neighbor;
+                    }
+                }
+            }
+        }
+    }
+    private void checkPriority() {
+        if (getCurrentPriority() != getDemandedPriority()) this.chunkMap.queueHolderUpdate(this);
+    }
+
+    public final double getDistance(EntityPlayer player) {
+        return getDistance(player.locX(), player.locZ());
+    }
+    public final double getDistance(double blockX, double blockZ) {
+        int cx = MCUtil.fastFloor(blockX) >> 4;
+        int cz = MCUtil.fastFloor(blockZ) >> 4;
+        final double x = location.x - cx;
+        final double z = location.z - cz;
+        return (x * x) + (z * z);
+    }
+
+    public final double getDistanceFrom(BlockPosition pos) {
+        return getDistance(pos.getX(), pos.getZ());
+    }
+
+    @Override
+    public String toString() {
+        return "PlayerChunk{" +
+            "location=" + location +
+            ", ticketLevel=" + ticketLevel + "/" + getChunkStatus(this.ticketLevel) +
+            ", chunkHolderStatus=" + getChunkHolderStatus() +
+            ", neighborPriority=" + getNeighborsPriority() +
+            ", priority=(" + ticketLevel + " - " + priorityBoost +" vs N " + neighborPriority + ") = " + getDemandedPriority() + " A " + getCurrentPriority() +
+            '}';
+    }
+    // Paper end
 
     public PlayerChunk(ChunkCoordIntPair chunkcoordintpair, int i, LightEngine lightengine, PlayerChunk.c playerchunk_c, PlayerChunk.d playerchunk_d) {
         this.statusFutures = new AtomicReferenceArray(PlayerChunk.CHUNK_STATUSES.size());
@@ -165,6 +284,15 @@ public class PlayerChunk {
         }
         return null;
     }
+    public static ChunkStatus getNextStatus(ChunkStatus status) {
+        if (status == ChunkStatus.FULL) {
+            return status;
+        }
+        return CHUNK_STATUSES.get(status.getStatusIndex() + 1);
+    }
+    public CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> getStatusFutureUncheckedMain(ChunkStatus chunkstatus) {
+        return MCUtil.ensureMain(getStatusFutureUnchecked(chunkstatus));
+    }
     // Paper end
 
     public CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> getStatusFutureUnchecked(ChunkStatus chunkstatus) {
@@ -418,6 +546,7 @@ public class PlayerChunk {
         return this.n;
     }
 
+    private void setPriority(int i) { d(i); } // Paper - OBFHELPER
     private void d(int i) {
         this.n = i;
     }
@@ -436,7 +565,7 @@ public class PlayerChunk {
         // CraftBukkit start
         // ChunkUnloadEvent: Called before the chunk is unloaded: isChunkLoaded is still true and chunk can still be modified by plugins.
         if (playerchunk_state.isAtLeast(PlayerChunk.State.BORDER) && !playerchunk_state1.isAtLeast(PlayerChunk.State.BORDER)) {
-            this.getStatusFutureUnchecked(ChunkStatus.FULL).thenAccept((either) -> {
+            this.getStatusFutureUncheckedMain(ChunkStatus.FULL).thenAccept((either) -> { // Paper - ensure main
                 Chunk chunk = (Chunk)either.left().orElse(null);
                 if (chunk != null) {
                     playerchunkmap.callbackExecutor.execute(() -> {
@@ -501,12 +630,13 @@ public class PlayerChunk {
         if (!flag2 && flag3) {
             // Paper start - cache ticking ready status
             int expectCreateCount = ++this.fullChunkCreateCount;
-            this.fullChunkFuture = playerchunkmap.b(this); this.fullChunkFuture.thenAccept((either) -> {
+            this.fullChunkFuture = playerchunkmap.b(this); MCUtil.ensureMain(this.fullChunkFuture).thenAccept((either) -> { // Paper - ensure main
                 if (either.left().isPresent() && PlayerChunk.this.fullChunkCreateCount == expectCreateCount) {
                     // note: Here is a very good place to add callbacks to logic waiting on this.
                     Chunk fullChunk = either.left().get();
                     PlayerChunk.this.isFullChunkReady = true;
                     fullChunk.playerChunk = PlayerChunk.this;
+                    this.chunkMap.chunkDistanceManager.clearPriorityTickets(location);
 
 
                 }
@@ -531,7 +661,7 @@ public class PlayerChunk {
 
         if (!flag4 && flag5) {
             // Paper start - cache ticking ready status
-            this.tickingFuture = playerchunkmap.a(this); this.tickingFuture.thenAccept((either) -> {
+            this.tickingFuture = playerchunkmap.a(this); MCUtil.ensureMain(this.tickingFuture).thenAccept((either) -> { // Paper - ensure main
                 if (either.left().isPresent()) {
                     // note: Here is a very good place to add callbacks to logic waiting on this.
                     Chunk tickingChunk = either.left().get();
@@ -562,7 +692,7 @@ public class PlayerChunk {
             }
 
             // Paper start - cache ticking ready status
-            this.entityTickingFuture = playerchunkmap.b(this.location); this.entityTickingFuture.thenAccept((either) -> {
+            this.entityTickingFuture = playerchunkmap.b(this.location); MCUtil.ensureMain(this.entityTickingFuture).thenAccept((either) -> { // Paper ensureMain
                 if (either.left().isPresent()) {
                     // note: Here is a very good place to add callbacks to logic waiting on this.
                     Chunk entityTickingChunk = either.left().get();
@@ -581,13 +711,29 @@ public class PlayerChunk {
             this.entityTickingFuture.complete(PlayerChunk.UNLOADED_CHUNK); this.isEntityTickingReady = false; // Paper - cache chunk ticking stage
             this.entityTickingFuture = PlayerChunk.UNLOADED_CHUNK_FUTURE;
         }
-
-        this.w.a(this.location, this::k, this.ticketLevel, this::d);
+        // Paper start - raise IO/load priority if priority changes, use our preferred priority
+        priorityBoost = chunkMap.chunkDistanceManager.getChunkPriority(location);
+        int priority = getDemandedPriority();
+        if (getCurrentPriority() > priority) {
+            int ioPriority = com.destroystokyo.paper.io.PrioritizedTaskQueue.NORMAL_PRIORITY;
+            if (priority <= 10) {
+                ioPriority = com.destroystokyo.paper.io.PrioritizedTaskQueue.HIGHEST_PRIORITY;
+            } else if (priority <= 20) {
+                ioPriority = com.destroystokyo.paper.io.PrioritizedTaskQueue.HIGH_PRIORITY;
+            }
+            chunkMap.world.asyncChunkTaskManager.raisePriority(location.x, location.z, ioPriority);
+        }
+        if (getCurrentPriority() != priority) {
+            this.w.a(this.location, this::getCurrentPriority, priority, this::setPriority); // use preferred priority
+            int neighborsPriority = getNeighborsPriority();
+            this.neighbors.forEach((neighbor, neighborDesired) -> neighbor.setNeighborPriority(this, neighborsPriority));
+        }
+        // Paper end
         this.oldTicketLevel = this.ticketLevel;
         // CraftBukkit start
         // ChunkLoadEvent: Called after the chunk is loaded: isChunkLoaded returns true and chunk is ready to be modified by plugins.
         if (!playerchunk_state.isAtLeast(PlayerChunk.State.BORDER) && playerchunk_state1.isAtLeast(PlayerChunk.State.BORDER)) {
-            this.getStatusFutureUnchecked(ChunkStatus.FULL).thenAccept((either) -> {
+            this.getStatusFutureUncheckedMain(ChunkStatus.FULL).thenAccept((either) -> { // Paper - ensure main
                 Chunk chunk = (Chunk)either.left().orElse(null);
                 if (chunk != null) {
                     playerchunkmap.callbackExecutor.execute(() -> {
@@ -669,6 +815,7 @@ public class PlayerChunk {
 
     public interface c {
 
+        default void changePriority(ChunkCoordIntPair chunkcoordintpair, IntSupplier intsupplier, int i, IntConsumer intconsumer) { a(chunkcoordintpair, intsupplier, i, intconsumer); } // Paper - OBFHELPER
         void a(ChunkCoordIntPair chunkcoordintpair, IntSupplier intsupplier, int i, IntConsumer intconsumer);
     }
 
diff --git a/src/main/java/net/minecraft/server/PlayerChunkMap.java b/src/main/java/net/minecraft/server/PlayerChunkMap.java
index 0aa14bfca6e1845eb6e9f5bd4e0e36335fa7f532..6c0dbad8e06b02b32dcff518cc2a5f7c8c1c316c 100644
--- a/src/main/java/net/minecraft/server/PlayerChunkMap.java
+++ b/src/main/java/net/minecraft/server/PlayerChunkMap.java
@@ -50,6 +50,7 @@ import org.apache.commons.lang3.mutable.MutableBoolean;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.bukkit.entity.Player; // CraftBukkit
+import org.spigotmc.AsyncCatcher;
 
 public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
 
@@ -123,6 +124,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
 
         @Override
         public void execute(Runnable runnable) {
+            AsyncCatcher.catchOp("Callback Executor execute");
             if (queued == null) {
                 queued = new java.util.ArrayDeque<>();
             }
@@ -131,6 +133,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
 
         @Override
         public void run() {
+            AsyncCatcher.catchOp("Callback Executor run");
             if (queued == null) {
                 return;
             }
@@ -375,6 +378,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
         this.playerViewDistanceTickMap = new com.destroystokyo.paper.util.misc.PlayerAreaMap(this.pooledLinkedPlayerHashSets,
             (EntityPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
              com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<EntityPlayer> newState) -> {
+                checkHighPriorityChunks(player);
                 if (newState.size() != 1) {
                     return;
                 }
@@ -393,7 +397,8 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
                 }
                 ChunkCoordIntPair chunkPos = new ChunkCoordIntPair(rangeX, rangeZ);
                 PlayerChunkMap.this.world.getChunkProvider().removeTicketAtLevel(TicketType.PLAYER, chunkPos, 31, chunkPos); // entity ticking level, TODO check on update
-            });
+                PlayerChunkMap.this.world.getChunkProvider().clearPriorityTickets(chunkPos);
+            }, (player, prevPos, newPos) -> checkHighPriorityChunks(player));
         this.playerViewDistanceNoTickMap = new com.destroystokyo.paper.util.misc.PlayerAreaMap(this.pooledLinkedPlayerHashSets);
         this.playerViewDistanceBroadcastMap = new com.destroystokyo.paper.util.misc.PlayerAreaMap(this.pooledLinkedPlayerHashSets,
             (EntityPlayer player, int rangeX, int rangeZ, int currPosX, int currPosZ, int prevPosX, int prevPosZ,
@@ -410,6 +415,101 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
             });
         // Paper end - no-tick view distance
     }
+    // Paper start - Chunk Prioritization
+    public void queueHolderUpdate(PlayerChunk playerchunk) {
+        Runnable runnable = () -> {
+            if (isUnloading(playerchunk)) {
+                return; // unloaded
+            }
+            chunkDistanceManager.pendingChunkUpdates.add(playerchunk);
+            if (!chunkDistanceManager.pollingPendingChunkUpdates) {
+                world.getChunkProvider().tickDistanceManager();
+            }
+        };
+        if (MCUtil.isMainThread()) {
+            // We can't use executor here because it will not execute tasks if its currently in the middle of executing tasks...
+            runnable.run();
+        } else {
+            executor.execute(runnable);
+        }
+    }
+
+    private boolean isUnloading(PlayerChunk playerchunk) {
+        return playerchunk == null || unloadQueue.contains(playerchunk.location.pair());
+    }
+
+    public void checkHighPriorityChunks(EntityPlayer player) {
+        int currentTick = MinecraftServer.currentTick;
+        if (currentTick - player.lastHighPriorityChecked < 20) {
+            return;
+        }
+        player.lastHighPriorityChecked = currentTick;
+
+        int viewDistance = getEffectiveNoTickViewDistance();
+        chunkDistanceManager.delayDistanceManagerTick = true;
+        BlockPosition.PooledBlockPosition pos = BlockPosition.PooledBlockPosition.acquire();
+
+        // Prioritize circular near
+        double playerChunkX = MathHelper.floor(player.locX()) >> 4;
+        double playerChunkZ = MathHelper.floor(player.locZ()) >> 4;
+        pos.setValues(player.locX(), 0, player.locZ());
+        MCUtil.getSpiralOutChunks(pos, Math.min(6, viewDistance)).forEach(coord -> {
+            if (shouldSkipPrioritization(coord)) return;
+
+            double dist = MCUtil.distance(playerChunkX, 0, playerChunkZ, coord.x, 0, coord.z);
+            // Prioritize immediate
+            if (dist <= 4 * 4) {
+                chunkDistanceManager.markHighPriority(coord, (int) (27 - Math.sqrt(dist)));
+                return;
+            }
+
+            // Prioritize nearby chunks
+            chunkDistanceManager.markHighPriority(coord, (int) (16 - Math.sqrt(dist*(2D/3D))));
+        });
+
+        // Prioritize Frustum near 3
+        ChunkCoordIntPair front3 = player.getChunkInFront(3);
+        pos.setValues(front3.x << 4, 0, front3.z << 4);
+        MCUtil.getSpiralOutChunks(pos, Math.min(5, viewDistance)).forEach(coord -> {
+            if (shouldSkipPrioritization(coord)) return;
+
+            chunkDistanceManager.markHighPriority(coord, 26);
+        });
+
+        // Prioritize Frustum near 5
+        if (viewDistance > 4) {
+            ChunkCoordIntPair front5 = player.getChunkInFront(5);
+            pos.setValues(front5.x << 4, 0, front5.z << 4);
+            MCUtil.getSpiralOutChunks(pos, 4).forEach(coord -> {
+                if (shouldSkipPrioritization(coord)) return;
+
+                chunkDistanceManager.markHighPriority(coord, 20);
+            });
+        }
+
+        // Prioritize Frustum far 7
+        if (viewDistance > 6) {
+            ChunkCoordIntPair front7 = player.getChunkInFront(7);
+            pos.setValues(front7.x << 4, 0, front7.z << 4);
+            MCUtil.getSpiralOutChunks(pos, 3).forEach(coord -> {
+                if (shouldSkipPrioritization(coord)) {
+                    return;
+                }
+                chunkDistanceManager.markHighPriority(coord, 15);
+            });
+        }
+
+        pos.close();
+        chunkDistanceManager.delayDistanceManagerTick = false;
+        world.getChunkProvider().tickDistanceManager();
+    }
+
+    private boolean shouldSkipPrioritization(ChunkCoordIntPair coord) {
+        if (playerViewDistanceNoTickMap.getObjectsInRange(coord.pair()) == null) return true;
+        PlayerChunk chunk = getUpdatingChunk(coord.pair());
+        return chunk != null && (chunk.isFullChunkReady());
+    }
+    // Paper end
 
     public void updatePlayerMobTypeMap(Entity entity) {
         if (!this.world.paperConfig.perPlayerMobSpawns) {
@@ -539,6 +639,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
         List<CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>>> list = Lists.newArrayList();
         int j = chunkcoordintpair.x;
         int k = chunkcoordintpair.z;
+        PlayerChunk requestingNeighbor = getUpdatingChunk(chunkcoordintpair.pair()); // Paper
 
         for (int l = -i; l <= i; ++l) {
             for (int i1 = -i; i1 <= i; ++i1) {
@@ -557,6 +658,14 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
 
                 ChunkStatus chunkstatus = (ChunkStatus) intfunction.apply(j1);
                 CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> completablefuture = playerchunk.a(chunkstatus, this);
+                // Paper start
+                if (requestingNeighbor != null && requestingNeighbor != playerchunk && !completablefuture.isDone()) {
+                    requestingNeighbor.onNeighborRequest(playerchunk, chunkstatus);
+                    completablefuture.thenAccept(either -> {
+                        requestingNeighbor.onNeighborDone(playerchunk, chunkstatus, either.left().orElse(null));
+                    });
+                }
+                // Paper end
 
                 list.add(completablefuture);
             }
@@ -1022,14 +1131,22 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
         };
 
         CompletableFuture<NBTTagCompound> chunkSaveFuture = this.world.asyncChunkTaskManager.getChunkSaveFuture(chunkcoordintpair.x, chunkcoordintpair.z);
+        PlayerChunk playerChunk = getUpdatingChunk(chunkcoordintpair.pair());
+        int chunkPriority = playerChunk != null ? playerChunk.getCurrentPriority() : 33;
+        int priority = com.destroystokyo.paper.io.PrioritizedTaskQueue.NORMAL_PRIORITY;
+
+        if (chunkPriority <= 10) {
+            priority = com.destroystokyo.paper.io.PrioritizedTaskQueue.HIGHEST_PRIORITY;
+        } else if (chunkPriority <= 20) {
+            priority = com.destroystokyo.paper.io.PrioritizedTaskQueue.HIGH_PRIORITY;
+        }
+        boolean isHighestPriority = priority == com.destroystokyo.paper.io.PrioritizedTaskQueue.HIGHEST_PRIORITY;
         if (chunkSaveFuture != null) {
-            this.world.asyncChunkTaskManager.scheduleChunkLoad(chunkcoordintpair.x, chunkcoordintpair.z,
-                com.destroystokyo.paper.io.PrioritizedTaskQueue.HIGH_PRIORITY, chunkHolderConsumer, false, chunkSaveFuture);
-            this.world.asyncChunkTaskManager.raisePriority(chunkcoordintpair.x, chunkcoordintpair.z, com.destroystokyo.paper.io.PrioritizedTaskQueue.HIGH_PRIORITY);
+            this.world.asyncChunkTaskManager.scheduleChunkLoad(chunkcoordintpair.x, chunkcoordintpair.z, priority, chunkHolderConsumer, isHighestPriority, chunkSaveFuture);
         } else {
-            this.world.asyncChunkTaskManager.scheduleChunkLoad(chunkcoordintpair.x, chunkcoordintpair.z,
-                com.destroystokyo.paper.io.PrioritizedTaskQueue.NORMAL_PRIORITY, chunkHolderConsumer, false);
+            this.world.asyncChunkTaskManager.scheduleChunkLoad(chunkcoordintpair.x, chunkcoordintpair.z, priority, chunkHolderConsumer, isHighestPriority);
         }
+        this.world.asyncChunkTaskManager.raisePriority(chunkcoordintpair.x, chunkcoordintpair.z, priority);
         return ret;
         // Paper end
     }
@@ -1158,7 +1275,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
             long i = playerchunk.i().pair();
 
             playerchunk.getClass();
-            mailbox.a(ChunkTaskQueueSorter.a(runnable, i, playerchunk::getTicketLevel)); // CraftBukkit - decompile error
+            mailbox.a(ChunkTaskQueueSorter.a(runnable, i, () -> 1)); // CraftBukkit - decompile error // Paper - final loads are always urgent!
         });
     }
 
diff --git a/src/main/java/net/minecraft/server/PlayerConnection.java b/src/main/java/net/minecraft/server/PlayerConnection.java
index d52fbda79fe1c52d3ddb53c0f1c1f521d7620702..7123e197c7ed01afd4fbf7aa0760611373039a13 100644
--- a/src/main/java/net/minecraft/server/PlayerConnection.java
+++ b/src/main/java/net/minecraft/server/PlayerConnection.java
@@ -1277,6 +1277,7 @@ public class PlayerConnection implements PacketListenerPlayIn {
         // CraftBukkit end
 
         this.A = this.e;
+        this.player.getWorldServer().getChunkProvider().markAreaHighPriority(new ChunkCoordIntPair(MathHelper.floor(d1) >> 4, MathHelper.floor(d3) >> 4), 28, 3); // Paper - load area high priority
         this.player.setLocation(d0, d1, d2, f, f1);
         this.syncPosition(); // Paper
         this.player.playerConnection.sendPacket(new PacketPlayOutPosition(d0 - d3, d1 - d4, d2 - d5, f - f2, f1 - f3, set, this.teleportAwait));
diff --git a/src/main/java/net/minecraft/server/PlayerList.java b/src/main/java/net/minecraft/server/PlayerList.java
index 6daca5c0ffd1d84f9a25cd106e8992a055dfb912..b0585346bf5125bebc482246bbb91c4b08c55816 100644
--- a/src/main/java/net/minecraft/server/PlayerList.java
+++ b/src/main/java/net/minecraft/server/PlayerList.java
@@ -174,8 +174,8 @@ public abstract class PlayerList {
         final ChunkCoordIntPair pos = new ChunkCoordIntPair(chunkX, chunkZ);
         PlayerChunkMap playerChunkMap = finalWorldserver.getChunkProvider().playerChunkMap;
         playerChunkMap.chunkDistanceManager.addTicketAtLevel(TicketType.LOGIN, pos, 31, pos.pair());
-        worldserver.getChunkProvider().tickDistanceManager();
-        worldserver.getChunkProvider().getChunkAtAsynchronously(chunkX, chunkZ, true, true).thenApply(chunk -> {
+        worldserver.getChunkProvider().markAreaHighPriority(pos, 28, 3);
+        worldserver.getChunkProvider().getChunkAtAsynchronously(chunkX, chunkZ, true, false).thenApply(chunk -> {
             PlayerChunk updatingChunk = playerChunkMap.getUpdatingChunk(pos.pair());
             if (updatingChunk != null) {
                 return updatingChunk.getEntityTickingFuture();
@@ -188,7 +188,6 @@ public abstract class PlayerList {
                     entityplayer, finalWorldserver, networkmanager, playerconnection,
                     nbttagcompound, networkmanager.getSocketAddress().toString(), lastKnownName
                 );
-                //playerChunkMap.chunkDistanceManager.removeTicketAtLevel(TicketType.LOGIN, pos, 31, pos.pair());
             };
         });
     }
@@ -764,6 +763,7 @@ public abstract class PlayerList {
         // CraftBukkit end
 
         worldserver.getChunkProvider().addTicket(TicketType.POST_TELEPORT, new ChunkCoordIntPair(location.getBlockX() >> 4, location.getBlockZ() >> 4), 1, entityplayer.getId()); // Paper
+        worldserver.getChunkProvider().markAreaHighPriority(new ChunkCoordIntPair(location.getBlockX() >> 4, location.getBlockZ() >> 4), 28, 3); // Paper - load area at high priority
         while (avoidSuffocation && !worldserver.getCubes(entityplayer1) && entityplayer1.locY() < 256.0D) {
             entityplayer1.setPosition(entityplayer1.locX(), entityplayer1.locY() + 1.0D, entityplayer1.locZ());
         }
diff --git a/src/main/java/net/minecraft/server/Ticket.java b/src/main/java/net/minecraft/server/Ticket.java
index 7a8397815a5b7f79f3e3a0348aeedf63fe879f8f..0d6e0f2ddaa85c04e626980591e9a78ac27fb42d 100644
--- a/src/main/java/net/minecraft/server/Ticket.java
+++ b/src/main/java/net/minecraft/server/Ticket.java
@@ -8,6 +8,7 @@ public final class Ticket<T> implements Comparable<Ticket<?>> {
     private final int b;
     public final T identifier; public final T getObjectReason() { return this.identifier; } // Paper - OBFHELPER
     private long d; public final long getCreationTick() { return this.d; } // Paper - OBFHELPER
+    public int priority = 0; // Paper
 
     protected Ticket(TicketType<T> tickettype, int i, T t0) {
         this.a = tickettype;
diff --git a/src/main/java/net/minecraft/server/TicketType.java b/src/main/java/net/minecraft/server/TicketType.java
index d7b9d9fd3a3b607278a3d72b0b306b0be2aa30ad..6fd852db6bcfbfbf84ec2acf6d23b08a6051165c 100644
--- a/src/main/java/net/minecraft/server/TicketType.java
+++ b/src/main/java/net/minecraft/server/TicketType.java
@@ -24,6 +24,8 @@ public class TicketType<T> {
     public static final TicketType<org.bukkit.plugin.Plugin> PLUGIN_TICKET = a("plugin_ticket", (plugin1, plugin2) -> plugin1.getClass().getName().compareTo(plugin2.getClass().getName())); // CraftBukkit
     public static final TicketType<Long> FUTURE_AWAIT = a("future_await", Long::compareTo); // Paper
     public static final TicketType<Long> ASYNC_LOAD = a("async_load", Long::compareTo); // Paper
+    public static final TicketType<ChunkCoordIntPair> PRIORITY = a("priority", Comparator.comparingLong(ChunkCoordIntPair::pair), 300); // Paper
+    public static final TicketType<ChunkCoordIntPair> URGENT = a("urgent", Comparator.comparingLong(ChunkCoordIntPair::pair), 300); // Paper
 
     public static <T> TicketType<T> a(String s, Comparator<T> comparator) {
         return new TicketType<>(s, comparator, 0L);
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
index 5f180bb77b736220c848357b2cac4d0d2b99e3df..d3c5b7d1904a6cbd65db406639ed2ba90ec9fd2a 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
@@ -2484,6 +2484,10 @@ public class CraftWorld implements World {
             return future;
         }
 
+        if (!urgent) {
+            // if not urgent, at least use a slightly boosted priority
+            world.getChunkProvider().markHighPriority(new ChunkCoordIntPair(x, z), 1);
+        }
         return this.world.getChunkProvider().getChunkAtAsynchronously(x, z, gen, urgent).thenComposeAsync((either) -> {
             net.minecraft.server.Chunk chunk = (net.minecraft.server.Chunk) either.left().orElse(null);
             return CompletableFuture.completedFuture(chunk == null ? null : chunk.getBukkitChunk());
diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
index bd4d5184b607db09c8ff2687ceaf47fb94368a28..141003ca718cc6ba113de8e4855b18252b293ef6 100644
--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java
@@ -738,6 +738,14 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
         throw new UnsupportedOperationException("Cannot set rotation of players. Consider teleporting instead.");
     }
 
+    // Paper start
+    @Override
+    public java.util.concurrent.CompletableFuture<Boolean> teleportAsync(Location loc, PlayerTeleportEvent.TeleportCause cause) {
+        getHandle().getWorldServer().getChunkProvider().markAreaHighPriority(new net.minecraft.server.ChunkCoordIntPair(net.minecraft.server.MathHelper.floor(loc.getX()) >> 4, net.minecraft.server.MathHelper.floor(loc.getZ()) >> 4), 28, 3); // Paper - load area high priority
+        return super.teleportAsync(loc, cause);
+    }
+    // Paper end
+
     @Override
     public boolean teleport(Location location, PlayerTeleportEvent.TeleportCause cause) {
         Preconditions.checkArgument(location != null, "location");