noclone.diff

diff --git a/src/main/java/net/minecraft/server/MCUtil.java b/src/main/java/net/minecraft/server/MCUtil.java
index b9d5844520..9980e4c277 100644
--- a/src/main/java/net/minecraft/server/MCUtil.java
+++ b/src/main/java/net/minecraft/server/MCUtil.java
@@ -500,7 +500,7 @@ public final class MCUtil {
 
             WorldServer world = ((org.bukkit.craftbukkit.CraftWorld)bukkitWorld).getHandle();
             PlayerChunkMap chunkMap = world.getChunkProvider().playerChunkMap;
-            Long2ObjectLinkedOpenHashMap<PlayerChunk> visibleChunks = chunkMap.visibleChunks;
+            Long2ObjectLinkedOpenHashMap<PlayerChunk> visibleChunks = chunkMap.getVisibleChunks();
             ChunkMapDistance chunkMapDistance = chunkMap.getChunkMapDistanceManager();
             List<PlayerChunk> allChunks = new ArrayList<>(visibleChunks.values());
             List<EntityPlayer> players = world.players;
diff --git a/src/main/java/net/minecraft/server/PlayerChunkMap.java b/src/main/java/net/minecraft/server/PlayerChunkMap.java
index e1e4ea793a..a5da664296 100644
--- a/src/main/java/net/minecraft/server/PlayerChunkMap.java
+++ b/src/main/java/net/minecraft/server/PlayerChunkMap.java
@@ -56,7 +56,8 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
     private static final Logger LOGGER = LogManager.getLogger();
     public static final int GOLDEN_TICKET = 33 + ChunkStatus.b();
     public final Long2ObjectLinkedOpenHashMap<PlayerChunk> updatingChunks = new Long2ObjectLinkedOpenHashMap();
-    public volatile Long2ObjectLinkedOpenHashMap<PlayerChunk> visibleChunks;
+    public final Long2ObjectLinkedOpenHashMap<PlayerChunk> visibleChunks = new Long2ObjectLinkedOpenHashMap(); // Paper - remove copying, make mt safe
+    public transient Long2ObjectLinkedOpenHashMap<PlayerChunk> visibleChunksClone; // Paper - remove copying, make mt safe
     private final Long2ObjectLinkedOpenHashMap<PlayerChunk> pendingUnload;
     final LongSet loadedChunks; // Paper - private -> package
     public final WorldServer world;
@@ -170,7 +171,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
 
     public PlayerChunkMap(WorldServer worldserver, File file, DataFixer datafixer, DefinedStructureManager definedstructuremanager, Executor executor, IAsyncTaskHandler<Runnable> iasynctaskhandler, ILightAccess ilightaccess, ChunkGenerator<?> chunkgenerator, WorldLoadListener worldloadlistener, Supplier<WorldPersistentData> supplier, int i) {
         super(new File(worldserver.getWorldProvider().getDimensionManager().a(file), "region"), datafixer);
-        this.visibleChunks = this.updatingChunks.clone();
+        //this.visibleChunks = this.updatingChunks.clone(); // Paper - no more cloning
         this.pendingUnload = new Long2ObjectLinkedOpenHashMap();
         this.loadedChunks = new LongOpenHashSet();
         this.unloadQueue = new LongOpenHashSet();
@@ -262,8 +263,31 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
         return (PlayerChunk) this.updatingChunks.get(i);
     }
 
+    // Paper start - remove cloning of visible chunks unless accessed as a collection async
+    public Long2ObjectLinkedOpenHashMap<PlayerChunk> getVisibleChunks() {
+        if (Thread.currentThread() == this.world.serverThread) {
+            return this.visibleChunks;
+        } else {
+            synchronized (this.visibleChunks) {
+                new Throwable("Async getVisibleChunks").printStackTrace();
+                if (this.visibleChunksClone == null) {
+                    this.visibleChunksClone = this.visibleChunks.clone();
+                }
+                return this.visibleChunksClone;
+            }
+        }
+    }
+    // Paper end
+
     @Nullable
     public PlayerChunk getVisibleChunk(long i) { // Paper - protected -> public
+        // Paper start - mt safe get
+        if (Thread.currentThread() != this.world.serverThread) {
+            synchronized (this.visibleChunks) {
+                return (PlayerChunk) this.visibleChunks.get(i);
+            }
+        }
+        // Paper end
         return (PlayerChunk) this.visibleChunks.get(i);
     }
 
@@ -444,8 +468,9 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
     // Paper end
 
     protected void save(boolean flag) {
+        Long2ObjectLinkedOpenHashMap<PlayerChunk> visibleChunks = this.getVisibleChunks(); // Paper remove clone of visible Chunks unless saving off main thread (watchdog kill)
         if (flag) {
-            List<PlayerChunk> list = (List) this.visibleChunks.values().stream().filter(PlayerChunk::hasBeenLoaded).peek(PlayerChunk::m).collect(Collectors.toList());
+            List<PlayerChunk> list = (List) visibleChunks.values().stream().filter(PlayerChunk::hasBeenLoaded).peek(PlayerChunk::m).collect(Collectors.toList()); // Paper - remove cloning of visible chunks
             MutableBoolean mutableboolean = new MutableBoolean();
 
             do {
@@ -473,7 +498,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
 //            this.i(); // Paper - nuke IOWorker
             PlayerChunkMap.LOGGER.info("ThreadedAnvilChunkStorage ({}): All chunks are saved", this.w.getName());
         } else {
-            this.visibleChunks.values().stream().filter(PlayerChunk::hasBeenLoaded).forEach((playerchunk) -> {
+            visibleChunks.values().stream().filter(PlayerChunk::hasBeenLoaded).forEach((playerchunk) -> {
                 IChunkAccess ichunkaccess = (IChunkAccess) playerchunk.getChunkSave().getNow(null); // CraftBukkit - decompile error
 
                 if (ichunkaccess instanceof ProtoChunkExtension || ichunkaccess instanceof Chunk) {
@@ -643,7 +668,14 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
         if (!this.updatingChunksModified) {
             return false;
         } else {
-            this.visibleChunks = this.updatingChunks.clone();
+            // Paper start - stop cloning visibleChunks
+            synchronized (this.visibleChunks) {
+                this.visibleChunks.clear();
+                this.visibleChunks.putAll(this.updatingChunks);
+                this.visibleChunksClone = null;
+            }
+            // Paper end
+
             this.updatingChunksModified = false;
             return true;
         }
@@ -1104,12 +1136,12 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
     }
 
     protected Iterable<PlayerChunk> f() {
-        return Iterables.unmodifiableIterable(this.visibleChunks.values());
+        return Iterables.unmodifiableIterable(this.getVisibleChunks().values()); // Paper
     }
 
     void a(Writer writer) throws IOException {
         CSVWriter csvwriter = CSVWriter.a().a("x").a("z").a("level").a("in_memory").a("status").a("full_status").a("accessible_ready").a("ticking_ready").a("entity_ticking_ready").a("ticket").a("spawning").a("entity_count").a("block_entity_count").a(writer);
-        ObjectBidirectionalIterator objectbidirectionaliterator = this.visibleChunks.long2ObjectEntrySet().iterator();
+        ObjectBidirectionalIterator objectbidirectionaliterator = this.getVisibleChunks().long2ObjectEntrySet().iterator(); // Paper
 
         while (objectbidirectionaliterator.hasNext()) {
             Entry<PlayerChunk> entry = (Entry) objectbidirectionaliterator.next();
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
index 051506fce8..f2727429b0 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
@@ -290,6 +290,7 @@ public class CraftWorld implements World {
         return ret;
     }
     public int getTileEntityCount() {
+        org.spigotmc.AsyncCatcher.catchOp("getTileEntityCount");
         // We don't use the full world tile entity list, so we must iterate chunks
         Long2ObjectLinkedOpenHashMap<PlayerChunk> chunks = world.getChunkProvider().playerChunkMap.visibleChunks;
         int size = 0;
@@ -306,6 +307,7 @@ public class CraftWorld implements World {
         return world.tileEntityListTick.size();
     }
     public int getChunkCount() {
+        org.spigotmc.AsyncCatcher.catchOp("getChunkCount");
         int ret = 0;
 
         for (PlayerChunk chunkHolder : world.getChunkProvider().playerChunkMap.visibleChunks.values()) {
@@ -432,6 +434,7 @@ public class CraftWorld implements World {
 
     @Override
     public Chunk[] getLoadedChunks() {
+        org.spigotmc.AsyncCatcher.catchOp("getLoadedChunks");
         Long2ObjectLinkedOpenHashMap<PlayerChunk> chunks = world.getChunkProvider().playerChunkMap.visibleChunks;
         return chunks.values().stream().map(PlayerChunk::getFullChunk).filter(Objects::nonNull).map(net.minecraft.server.Chunk::getBukkitChunk).toArray(Chunk[]::new);
     }