Paper/Spigot-Server-Patches/0529-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 d9580eb998801edd34c610ced3f82f9627c6685b..537a22b72aa2c90f0102b035843e09c54e5ae39f 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;
@@ -118,6 +121,32 @@ 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());
+            synchronized (chunkHolder.neighborPriorities) {
+                if (!chunkHolder.neighborPriorities.isEmpty()) {
+                    PaperFileIOThread.LOGGER.log(Level.ERROR, indentStr + "Neighbors Requested Priority: ");
+                    for (Long2ObjectMap.Entry<Integer> entry : chunkHolder.neighborPriorities.long2ObjectEntrySet()) {
+                        ChunkCoordIntPair r = new ChunkCoordIntPair(entry.getLongKey());
+                        PaperFileIOThread.LOGGER.log(Level.ERROR, indentStr + " (" + r.x + "," + r.z + "): " + entry.getValue());
+                    }
+                }
+            }
+
+            synchronized (chunkHolder.neighbors) {
+                if (!chunkHolder.neighbors.isEmpty()) {
+                    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;
+                        PaperFileIOThread.LOGGER.log(Level.ERROR, indentStr + "  " + nx + "," + nz + " in " + chunkHolder.getWorld().getWorld().getName() + ":");
+                        dumpChunkInfo(neighbor, nx, nz, indent + 1);
+                    }
+                }
+            }
         }
     }
 
diff --git a/src/main/java/net/minecraft/server/ChunkMapDistance.java b/src/main/java/net/minecraft/server/ChunkMapDistance.java
index 586a20fe5c77c2ad5fa26f337a94a16e21d8b5e2..58407f488bbd8bda8781959d7c9da5d09f2a3cc4 100644
--- a/src/main/java/net/minecraft/server/ChunkMapDistance.java
+++ b/src/main/java/net/minecraft/server/ChunkMapDistance.java
@@ -154,7 +154,7 @@ public abstract class ChunkMapDistance {
         Ticket<?> ticket1 = (Ticket) arraysetsorted.a(ticket); // CraftBukkit - decompile error
 
         ticket1.a(this.currentTick);
-        if (ticket.b() < j) {
+        if (ticket.b() < j || (ticket.getTicketType() == TicketType.PRIORITY && (30 - ticket.priority) < j)) { // Paper - check priority tickets too
             this.e.b(i, ticket.b(), true);
         }
 
@@ -182,6 +182,54 @@ public abstract class ChunkMapDistance {
         this.addTicketAtLevel(tickettype, chunkcoordintpair, i, t0);
     }
 
+    // Paper start
+    public boolean markUrgent(ChunkCoordIntPair coords) {
+        return this.markHighPriority(coords, 30);
+    }
+    public boolean markHighPriority(ChunkCoordIntPair coords, int priority) {
+        priority = Math.min(30, Math.max(1, priority));
+        long pair = coords.pair();
+        int currentPriority = getChunkPriority(coords);
+        if (currentPriority > priority) {
+            return false;
+        }
+        Ticket<Integer> ticket = new Ticket<Integer>(TicketType.PRIORITY, 31, 0);
+        ticket.priority = priority;
+        this.removeTicket(pair, ticket);
+        return this.addTicket(pair, ticket);
+    }
+    public int getChunkPriority(ChunkCoordIntPair coords) {
+        int priority = 0;
+        ArraySetSorted<Ticket<?>> tickets = this.tickets.get(coords.pair());
+        if (tickets == null) {
+            return priority;
+        }
+        for (Ticket<?> ticket : tickets) {
+            if (ticket.getTicketType() == TicketType.PRIORITY && ticket.priority > 0) {
+                return ticket.priority;
+            }
+        }
+        return priority;
+    }
+
+    public void refreshUrgentTicket(ChunkCoordIntPair coords) {
+        ArraySetSorted<Ticket<?>> tickets = this.tickets.get(coords.pair());
+        if (tickets == null) {
+            markUrgent(coords);
+            return;
+        }
+        for (Ticket<?> ticket : tickets) {
+            if (ticket.getTicketType() == TicketType.PRIORITY) {
+                ticket.setCurrentTick(this.currentTick);
+                return;
+            }
+        }
+
+    }
+    public void clearPriorityTickets(ChunkCoordIntPair coords) {
+        this.removeTicket(coords.pair(), new Ticket<Integer>(TicketType.PRIORITY, 31, 0));
+    }
+    // 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
@@ -397,7 +445,8 @@ public abstract class ChunkMapDistance {
 
                         });
                     }, i, () -> {
-                        return j;
+                        PlayerChunk chunk = chunkMap.getUpdatingChunk(i); // Paper
+                        return chunk != null && chunk.getCurrentPriority() < j ? chunk.getCurrentPriority() : j; // Paper
                     }));
                 } else {
                     ChunkMapDistance.this.k.a(ChunkTaskQueueSorter.a(() -> { // CraftBukkit - decompile error
diff --git a/src/main/java/net/minecraft/server/ChunkProviderServer.java b/src/main/java/net/minecraft/server/ChunkProviderServer.java
index 0a99b347d8497f097ef1da6560a5d0adc1374f25..e57e4c739b86646ef148c1f8e06ca160dbc778a1 100644
--- a/src/main/java/net/minecraft/server/ChunkProviderServer.java
+++ b/src/main/java/net/minecraft/server/ChunkProviderServer.java
@@ -431,6 +431,16 @@ 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 chunkMapDistance.markUrgent(coords);
+    }
+    public boolean markHighPriority(ChunkCoordIntPair coords, int priority) {
+        return chunkMapDistance.markHighPriority(coords, priority);
+    }
+    public void clearPriorityTickets(ChunkCoordIntPair coords) {
+        this.chunkMapDistance.clearPriorityTickets(coords);
+    }
     // Paper end
 
     @Nullable
@@ -469,14 +479,22 @@ public class ChunkProviderServer extends IChunkProvider {
 
             if (!completablefuture.isDone()) { // Paper
                 // Paper start - async chunk io/loading
+                ChunkCoordIntPair pair = new ChunkCoordIntPair(x, z);
+                this.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
                 com.destroystokyo.paper.io.SyncLoadFinder.logSyncLoad(this.world, x, z); // Paper - sync load info
                 this.world.timings.syncChunkLoad.startTiming(); // Paper
-            this.serverThreadQueue.awaitTasks(completablefuture::isDone);
+                // Paper start - keep priority ticket refreshed
+                this.serverThreadQueue.awaitTasks(() -> {
+                    this.chunkMapDistance.refreshUrgentTicket(pair);
+                    return completablefuture.isDone();
+                });
+                // PAper end
                 com.destroystokyo.paper.io.chunk.ChunkTaskManager.popChunkWait(); // Paper - async chunk debug
                 this.world.timings.syncChunkLoad.stopTiming(); // Paper
+                this.clearPriorityTickets(pair); // Paper
             } // Paper
             ichunkaccess = (IChunkAccess) ((Either) completablefuture.join()).map((ichunkaccess1) -> {
                 return ichunkaccess1;
@@ -529,6 +547,7 @@ public class ChunkProviderServer extends IChunkProvider {
         if (flag && !currentlyUnloading) {
             // CraftBukkit end
             this.chunkMapDistance.a(TicketType.UNKNOWN, chunkcoordintpair, l, chunkcoordintpair);
+            if (isUrgent) this.markUrgent(chunkcoordintpair); // Paper
             if (this.a(playerchunk, l)) {
                 GameProfilerFiller gameprofilerfiller = this.world.getMethodProfiler();
 
@@ -541,8 +560,13 @@ 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.clearPriorityTickets(chunkcoordintpair));
+        }
+        return future;
+        // Paper end
     }
 
     private boolean a(@Nullable PlayerChunk playerchunk, int i) {
diff --git a/src/main/java/net/minecraft/server/EntityPlayer.java b/src/main/java/net/minecraft/server/EntityPlayer.java
index 07a6fc3d88e7d44bfab7f3d6a0eef7dc132ab422..d60f659b368500e3a8c3305f99e60ffc643e2fbd 100644
--- a/src/main/java/net/minecraft/server/EntityPlayer.java
+++ b/src/main/java/net/minecraft/server/EntityPlayer.java
@@ -441,6 +441,7 @@ 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() && this.ticksLived % 20 == 0) ((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 d129c7f54d9f65fff6f512d8ff5f1c3866632603..9b9536fba4a62c0153b921e678e6a9683bf2e37f 100644
--- a/src/main/java/net/minecraft/server/MCUtil.java
+++ b/src/main/java/net/minecraft/server/MCUtil.java
@@ -658,6 +658,7 @@ 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..46462298c7d02fcf31bb8da502a3ee5d98fe7905 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 +68,92 @@ public class PlayerChunk {
         return null;
     }
     // Paper end - no-tick view distance
+    // Paper start - Chunk gen/load priority system
+    volatile int neighborPriority = -1;
+    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<>();
+
+    public int getPreferredPriority() {
+        int priority = neighborPriority; // if we have a neighbor priority, use it
+        int priorityBoost = chunkMap.chunkDistanceManager.getChunkPriority(location);
+        int basePriority = ticketLevel - priorityBoost;
+
+        if (priority == -1 || priority > basePriority) {
+            if (priorityBoost > 0) {
+                //System.out.println(location + " boost " + (basePriority) + " = " + ticketLevel + " - " + priorityBoost);
+            }
+            priority = basePriority;
+            if (ticketLevel >= 34 && priorityBoost == 0) {
+                priority += 5;
+            }
+        }
+
+
+        return Math.max(1, Math.min(PlayerChunkMap.GOLDEN_TICKET, priority));
+    }
+    public void onNeighborRequest(PlayerChunk neighbor, ChunkStatus status) {
+        int priority = getCurrentPriority() + 1;
+        if (!neighborPriorities.containsKey(neighbor.location.pair()) && (neighbor.neighborPriority == -1 || neighbor.neighborPriority > priority)) {
+            this.neighbors.put(neighbor, status);
+            neighbor.setNeighborPriority(this, Math.max(1, priority));
+        }
+    }
+
+    private void setNeighborPriority(PlayerChunk requester, int priority) {
+        if (priority < neighborPriority || neighborPriority == -1) {
+            synchronized (neighborPriorities) {
+                if (priority < neighborPriority || neighborPriority == -1) {
+                    neighborPriority = priority;
+                    neighborPriorities.put(requester.location.pair(), Integer.valueOf(priority));
+                }
+            }
+        }
+    }
+
+    public void onNeighborsDone() {
+        java.util.List<PlayerChunk> neighbors = new java.util.ArrayList<>(this.neighbors.keySet());
+        this.neighbors.clear();
+        for (PlayerChunk neighbor : neighbors) {
+            synchronized (neighbor.neighborPriorities) {
+                neighbor.neighborPriorities.remove(location.pair());
+                neighbor.recalcNeighborPriority();
+            }
+        }
+    }
+
+    private void recalcNeighborPriority() {
+        neighborPriority = -1;
+        if (!neighborPriorities.isEmpty()) {
+            synchronized (neighborPriorities) {
+                for (Integer neighbor : neighborPriorities.values()) {
+                    if (neighbor < neighborPriority || neighborPriority == -1) {
+                        neighborPriority = neighbor;
+                    }
+                }
+            }
+        }
+    }
+
+    public final double getDistanceFromPointInFront(EntityPlayer player, int dist) {
+        int inFront = dist * 16;
+        final float yaw = MCUtil.normalizeYaw(player.yaw);
+        double rads = Math.toRadians(yaw);
+        final double x = player.locX() + inFront * Math.cos(rads);
+        final double z = player.locZ() + inFront * Math.sin(rads);
+        return getDistance(x, z);
+    }
+
+    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);
+    }
+    // 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 +252,12 @@ public class PlayerChunk {
         }
         return null;
     }
+    public static ChunkStatus getNextStatus(ChunkStatus status) {
+        if (status == ChunkStatus.FULL) {
+            return status;
+        }
+        return CHUNK_STATUSES.get(status.getStatusIndex() + 1);
+    }
     // Paper end
 
     public CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> getStatusFutureUnchecked(ChunkStatus chunkstatus) {
@@ -418,6 +511,7 @@ public class PlayerChunk {
         return this.n;
     }
 
+    private void setPriority(int i) { d(i); } // Paper - OBFHELPER
     private void d(int i) {
         this.n = i;
     }
@@ -507,6 +601,7 @@ public class PlayerChunk {
                     Chunk fullChunk = either.left().get();
                     PlayerChunk.this.isFullChunkReady = true;
                     fullChunk.playerChunk = PlayerChunk.this;
+                    this.chunkMap.chunkDistanceManager.clearPriorityTickets(location);
 
 
                 }
@@ -581,8 +676,30 @@ 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
+        int priority = getPreferredPriority();
+        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);
+        }
+        this.w.a(this.location, this::getCurrentPriority, priority, this::setPriority); // use preferred priority
+        this.neighbors.forEach((neighbor, neighborDesired) -> {
+            ChunkStatus neighborCurrent = neighbor.getChunkHolderStatus();
+            if (neighborCurrent == null || !neighborCurrent.isAtLeastStatus(neighborDesired)) {
+                if (neighbor.getCurrentPriority() > priority + 1 && neighbor.neighborPriority > priority + 1) {
+                    neighbor.setNeighborPriority(this, priority + 1);
+                    // Pending chunk update will run this same code here for the neighbor to update their priority
+                    // And since we are in the poll loop when this method runs, it should happen immediately after this.
+                    chunkMap.chunkDistanceManager.pendingChunkUpdates.add(neighbor);
+                }
+            }
+        });
+        // 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.
@@ -669,6 +786,7 @@ 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 e772095e1c44842f743661a326c2a9a8a677ab02..5621416660d2722f26582fcecd5b61a164cd1530 100644
--- a/src/main/java/net/minecraft/server/PlayerChunkMap.java
+++ b/src/main/java/net/minecraft/server/PlayerChunkMap.java
@@ -352,6 +352,7 @@ 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;
                 }
@@ -370,7 +371,8 @@ 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,
@@ -387,6 +389,62 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
             });
         // Paper end - no-tick view distance
     }
+    // Paper start - Chunk Prioritization
+    private static final int[][] neighborMatrix = {{-1, 0}, {0, -1}, {0, 1}, {1, 0}};
+    public void checkHighPriorityChunks(EntityPlayer player) {
+        MCUtil.getSpiralOutChunks(new BlockPosition(player), Math.min(7, getLoadViewDistance())).forEach(coord -> {
+            PlayerChunk chunk = getUpdatingChunk(coord.pair());
+            if (chunk == null || chunk.isFullChunkReady() || chunk.getTicketLevel() >= 34 ||
+                !world.getWorldBorder().isInBounds(coord)
+            ) {
+                return;
+            }
+
+            double dist = chunk.getDistance(player);
+            // Prioritize immediate
+            if (dist <= 5) {
+                chunkDistanceManager.markHighPriority(coord, (int) (29 - dist));
+                return;
+            }
+            boolean hasNeighbor = false;
+            for (int[] matrix : neighborMatrix) {
+                long neighborKey = MCUtil.getCoordinateKey(coord.x + matrix[0], coord.x + matrix[1]);
+                PlayerChunk neighbor = getUpdatingChunk(neighborKey);
+                if (neighbor != null && neighbor.isFullChunkReady()) {
+                    hasNeighbor = true;
+                    break;
+                }
+            }
+            if (!hasNeighbor) {
+                return;
+            }
+            // Prioritize Frustum near
+            double distFront1 = chunk.getDistanceFromPointInFront(player, 2);
+            if (distFront1 <= (4*4)) {
+                if (distFront1 <= (2 * 2)) {
+                    chunkDistanceManager.markHighPriority(coord, 24);
+                } else {
+                    chunkDistanceManager.markHighPriority(coord, 22);
+                }
+                return;
+            }
+            // Prioritize Frustum far
+            double distFront2 = chunk.getDistanceFromPointInFront(player, 4);
+            if (distFront2 <= (3*3)) {
+                if (distFront2 <= (2 * 2)) {
+                    chunkDistanceManager.markHighPriority(coord, 23);
+                } else {
+                    chunkDistanceManager.markHighPriority(coord, 20);
+                }
+                return;
+            }
+            // Prioritize nearby chunks
+            if (dist <= (5*5)) {
+                chunkDistanceManager.markHighPriority(coord, (int) (16 - Math.sqrt(dist*(4D/5D))));
+            }
+        });
+    }
+    // Paper end
 
     public void updatePlayerMobTypeMap(Entity entity) {
         if (!this.world.paperConfig.perPlayerMobSpawns) {
@@ -516,6 +574,7 @@ 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) {
@@ -533,6 +592,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
                 }
 
                 ChunkStatus chunkstatus = (ChunkStatus) intfunction.apply(j1);
+                if (requestingNeighbor != null && requestingNeighbor != playerchunk) requestingNeighbor.onNeighborRequest(playerchunk, chunkstatus); // Paper
                 CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> completablefuture = playerchunk.a(chunkstatus, this);
 
                 list.add(completablefuture);
@@ -997,14 +1057,22 @@ 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
     }
@@ -1041,6 +1109,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
                 return CompletableFuture.completedFuture(Either.right(playerchunk_failure));
             });
         }, (runnable) -> {
+            playerchunk.onNeighborsDone(); // Paper
             this.mailboxWorldGen.a(ChunkTaskQueueSorter.a(playerchunk, runnable)); // CraftBukkit - decompile error
         });
     }
@@ -1133,7 +1202,7 @@ 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, playerchunk::getCurrentPriority)); // CraftBukkit - decompile error // Paper - use priority not ticket level....
         });
     }
 
diff --git a/src/main/java/net/minecraft/server/Ticket.java b/src/main/java/net/minecraft/server/Ticket.java
index 7a8397815a5b7f79f3e3a0348aeedf63fe879f8f..a7cd67b0d5e49a4492dc14ec80e442a0f32671d3 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;
@@ -56,6 +57,7 @@ public final class Ticket<T> implements Comparable<Ticket<?>> {
         return this.b;
     }
 
+    protected final void setCurrentTick(long i) { a(i); } // Paper - OBFHELPER
     protected void a(long i) {
         this.d = i;
     }
diff --git a/src/main/java/net/minecraft/server/TicketType.java b/src/main/java/net/minecraft/server/TicketType.java
index 8055f5998213ab1c6c10d03d88d2b14d220a5e40..4913205c15a2b6d5ea058890b02090b494e9c177 100644
--- a/src/main/java/net/minecraft/server/TicketType.java
+++ b/src/main/java/net/minecraft/server/TicketType.java
@@ -23,6 +23,7 @@ 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<Integer> PRIORITY = a("priority", Integer::compareTo, 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 bbfbfeed12890c9d20d78a9661ab172c901f008c..589926d6029ca2a4aeb4f2c7903a5f9517deebef 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
@@ -2472,10 +2472,15 @@ public class CraftWorld implements World {
             }
         }
 
-        return this.world.getChunkProvider().getChunkAtAsynchronously(x, z, gen, urgent).thenComposeAsync((either) -> {
+        CompletableFuture<Chunk> future = 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());
         }, MinecraftServer.getServer());
+        if (urgent) {
+            world.asyncChunkTaskManager.raisePriority(x, z, com.destroystokyo.paper.io.PrioritizedTaskQueue.HIGHEST_PRIORITY);
+        }
+        return future;
+
     }
     // Paper end