Paper/Spigot-Server-Patches/0532-Unload-leaked-Cached-Chunks.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Mon, 25 May 2020 11:02:42 -0400
Subject: [PATCH] Unload leaked Cached Chunks

Due to some complexity in mojangs complicated chain of juggling
whether or not a chunk should be unloaded when the last ticket is
removed, many chunks are remaining around in the cache.

These chunks are never being targetted for unload because they are
vastly out of view distance range and have no reason to be looked at.

This is a huge issue for performance because we have to iterate these
chunks EVERY TICK... This is what's been leading to high SELF time in
Ticking Chunks timings/profiler results.

We will now detect these chunks in that iteration, and automatically
add it to the unload queue when the chunk is found without any tickets.

diff --git a/src/main/java/net/minecraft/server/ChunkProviderServer.java b/src/main/java/net/minecraft/server/ChunkProviderServer.java
index 54e89c9cc6c47ff2c4f4dd5d4c22a391f8a3d6e0..1209fbf1c906511954bc61ffb1a8882498855ba4 100644
--- a/src/main/java/net/minecraft/server/ChunkProviderServer.java
+++ b/src/main/java/net/minecraft/server/ChunkProviderServer.java
@@ -560,6 +560,7 @@ public class ChunkProviderServer extends IChunkProvider {
             }
         }
         // Paper start
+        if (playerchunk != null) playerchunk.lastActivity = world.getTime(); // Paper
         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));
@@ -812,6 +813,7 @@ public class ChunkProviderServer extends IChunkProvider {
             this.world.timings.countNaturalMobs.stopTiming(); // Paper - timings
             this.world.getMethodProfiler().exit();
             // Paper - replaced by above
+            final long time = world.getTime(); // Paper
             final int[] chunksTicked = {0}; this.playerChunkMap.forEachVisibleChunk((playerchunk) -> { // Paper - safe iterator incase chunk loads, also no wrapping
                 Optional<Chunk> optional = ((Either) playerchunk.b().getNow(PlayerChunk.UNLOADED_CHUNK)).left();
 
@@ -897,7 +899,7 @@ public class ChunkProviderServer extends IChunkProvider {
                         this.world.timings.chunkTicks.stopTiming(); // Spigot // Paper
                         if (chunksTicked[0]++ % 10 == 0) this.world.getMinecraftServer().midTickLoadChunks(); // Paper
                     }
-                }
+                } else { checkInactiveChunk(playerchunk, time); } // Paper - check inaccessible chunks
             });
             this.world.getMethodProfiler().enter("customSpawners");
             if (flag1) {
@@ -913,6 +915,37 @@ public class ChunkProviderServer extends IChunkProvider {
         this.playerChunkMap.g();
     }
 
+    // Paper start - remove inaccessible chunks leaked
+    private void checkInactiveChunk(PlayerChunk playerchunk, long time) {
+        int ticketLevel = playerchunk.getTicketLevel();
+        if (ticketLevel > 33 && ticketLevel == playerchunk.oldTicketLevel &&
+            (playerchunk.lastActivity == 0 || time - playerchunk.lastActivity > 20*180) &&
+            playerchunk.location.pair() % 20 == 0 && playerChunkMap.unloadQueue.size() < 100 &&
+            PlayerChunk.getChunkState(ticketLevel) == PlayerChunk.State.INACCESSIBLE
+        ) {
+            ChunkStatus chunkHolderStatus = playerchunk.getChunkHolderStatus();
+            ChunkStatus desiredStatus = PlayerChunk.getChunkStatus(ticketLevel);
+            if (chunkHolderStatus != null && !chunkHolderStatus.isAtLeastStatus(desiredStatus)) {
+                return;
+            }
+            if (playerchunk.lastActivity == 0) {
+                playerchunk.lastActivity = time;
+                return;
+            }
+            playerchunk.lastActivity = time;
+            Chunk chunk = playerchunk.getChunk();
+            if ((chunk != null && chunk.isAnyNeighborsLoaded()) || !playerchunk.neighborPriorities.isEmpty()) {
+                return;
+            }
+            long key = playerchunk.location.pair();
+            ArraySetSorted<Ticket<?>> tickets = playerChunkMap.chunkDistanceManager.tickets.get(key);
+            if (tickets == null || tickets.isEmpty()) {
+                playerChunkMap.unloadQueue.add(key);
+            }
+        }
+    }
+    // Paper end
+
     @Override
     public String getName() {
         return "ServerChunkCache: " + this.h();
diff --git a/src/main/java/net/minecraft/server/PlayerChunk.java b/src/main/java/net/minecraft/server/PlayerChunk.java
index b8fe42e8123e972b1ec97b048c35d90118076e66..ecac7b72759a3884020b9c19c58d3db3338e0fc3 100644
--- a/src/main/java/net/minecraft/server/PlayerChunk.java
+++ b/src/main/java/net/minecraft/server/PlayerChunk.java
@@ -44,6 +44,7 @@ public class PlayerChunk {
 
     long lastAutoSaveTime; // Paper - incremental autosave
     long inactiveTimeStart; // Paper - incremental autosave
+    long lastActivity; // Paper - fix chunk leak
 
     // Paper start - optimise isOutsideOfRange
     // cached here to avoid a map lookup
@@ -562,6 +563,7 @@ public class PlayerChunk {
     protected void a(PlayerChunkMap playerchunkmap) {
         ChunkStatus chunkstatus = getChunkStatus(this.oldTicketLevel);
         ChunkStatus chunkstatus1 = getChunkStatus(this.ticketLevel);
+        if (oldTicketLevel != ticketLevel) lastActivity = chunkMap.world.getTime(); // Paper - chunk leak
         boolean flag = this.oldTicketLevel <= PlayerChunkMap.GOLDEN_TICKET;
         boolean flag1 = this.ticketLevel <= PlayerChunkMap.GOLDEN_TICKET; // Paper - diff on change: (flag1 = new ticket level is in loadable range)
         PlayerChunk.State playerchunk_state = getChunkState(this.oldTicketLevel);
diff --git a/src/main/java/net/minecraft/server/PlayerChunkMap.java b/src/main/java/net/minecraft/server/PlayerChunkMap.java
index 2b09437642ec846d025b226692f2290f9bb5b556..b7d8a7487e303c2c44160ec1093987b3e0d175bc 100644
--- a/src/main/java/net/minecraft/server/PlayerChunkMap.java
+++ b/src/main/java/net/minecraft/server/PlayerChunkMap.java
@@ -639,6 +639,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
                         }
                     }));
                 }
+                playerchunk.lastActivity = world.getTime(); // Paper - chunk leak
 
                 ChunkStatus chunkstatus = (ChunkStatus) intfunction.apply(j1);
                 CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> completablefuture = playerchunk.a(chunkstatus, this);
@@ -646,6 +647,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
                 if (requestingNeighbor != null && requestingNeighbor != playerchunk && !completablefuture.isDone()) {
                     requestingNeighbor.onNeighborRequest(playerchunk, chunkstatus);
                     completablefuture.thenAccept(either -> {
+                        playerchunk.lastActivity = world.getTime(); // Paper - chunk leak
                         requestingNeighbor.onNeighborDone(playerchunk, chunkstatus, either.left().orElse(null));
                     });
                 }
@@ -871,6 +873,8 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
         while (longiterator.hasNext()) { // Spigot
             long j = longiterator.nextLong();
             longiterator.remove(); // Spigot
+            ArraySetSorted<Ticket<?>> tickets = chunkDistanceManager.tickets.get(j); // Paper - chunk leak
+            if (tickets != null && !tickets.isEmpty()) continue; // Paper - ticket got added, don't remove
             PlayerChunk playerchunk = (PlayerChunk) this.updatingChunks.remove(j);
 
             if (playerchunk != null) {
diff --git a/src/main/java/net/minecraft/server/StructureGenerator.java b/src/main/java/net/minecraft/server/StructureGenerator.java
index acfe732af5b9f63fc2f6b78499defabe2e73ee45..25b19346fc1c702cc37275d0ec16abbbfacfb418 100644
--- a/src/main/java/net/minecraft/server/StructureGenerator.java
+++ b/src/main/java/net/minecraft/server/StructureGenerator.java
@@ -160,7 +160,7 @@ public abstract class StructureGenerator<C extends WorldGenFeatureConfiguration>
         while (longiterator.hasNext()) {
             long k = longiterator.nextLong();
             IChunkAccess ichunkaccess1 = generatoraccess.getChunkAt(ChunkCoordIntPair.getX(k), ChunkCoordIntPair.getZ(k), ChunkStatus.STRUCTURE_STARTS, false); // CraftBukkit - don't load chunks
-            StructureStart structurestart = ichunkaccess1.a(this.b());
+            StructureStart structurestart = ichunkaccess1 != null ? ichunkaccess1.a(this.b()) : null; // Paper - make sure not null
 
             if (structurestart != null) {
                 list.add(structurestart);