Paper/nms-patches/PlayerChunk.patch

--- a/net/minecraft/server/PlayerChunk.java
+++ b/net/minecraft/server/PlayerChunk.java
@@ -8,32 +8,48 @@
 import javax.annotation.Nullable;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+// CraftBukkit Start
+import org.bukkit.craftbukkit.chunkio.ChunkIOExecutor;
+// CraftBukkit end
 
 public class PlayerChunk {
 
     private static final Logger a = LogManager.getLogger();
     private final PlayerChunkMap playerChunkMap;
-    private final List<EntityPlayer> c = Lists.newArrayList();
+    public final List<EntityPlayer> c = Lists.newArrayList(); // CraftBukkit - public
     private final ChunkCoordIntPair location;
     private final short[] dirtyBlocks = new short[64];
     @Nullable
-    private Chunk chunk;
+    public Chunk chunk; // CraftBukkit - public
     private int dirtyCount;
     private int h;
     private long i;
     private boolean done;
 
+    // CraftBukkit start - add fields
+    private boolean loadInProgress = false;
+    private Runnable loadedRunnable = new Runnable() {
+        public void run() {
+            loadInProgress = false;
+            PlayerChunk.this.chunk = PlayerChunk.this.playerChunkMap.getWorld().getChunkProviderServer().getOrLoadChunkAt(location.x, location.z);
+        }
+    };
+    // CraftBukkit end
+
     public PlayerChunk(PlayerChunkMap playerchunkmap, int i, int j) {
         this.playerChunkMap = playerchunkmap;
         this.location = new ChunkCoordIntPair(i, j);
-        this.chunk = playerchunkmap.getWorld().getChunkProviderServer().getOrLoadChunkAt(i, j);
+        // CraftBukkit start
+        loadInProgress = true;
+        this.chunk = playerchunkmap.getWorld().getChunkProviderServer().getChunkAt(i, j, loadedRunnable, false);
+        // CraftBukkit end
     }
 
     public ChunkCoordIntPair a() {
         return this.location;
     }
 
-    public void a(EntityPlayer entityplayer) {
+    public void a(final EntityPlayer entityplayer) { // CraftBukkit - added final to argument
         if (this.c.contains(entityplayer)) {
             PlayerChunk.a.debug("Failed to add player. {} already is in chunk {}, {}", entityplayer, Integer.valueOf(this.location.x), Integer.valueOf(this.location.z));
         } else {
@@ -42,15 +58,32 @@
             }
 
             this.c.add(entityplayer);
+            // CraftBukkit start - use async chunk io
+            // if (this.done) {
+            //     this.sendChunk(entityplayer);
+            // }
             if (this.done) {
                 this.sendChunk(entityplayer);
             }
+            // CraftBukkit end
 
         }
     }
 
     public void b(EntityPlayer entityplayer) {
         if (this.c.contains(entityplayer)) {
+            // CraftBukkit start - If we haven't loaded yet don't load the chunk just so we can clean it up
+            if (!this.done) {
+                this.c.remove(entityplayer);
+
+                if (this.c.isEmpty()) {
+                    ChunkIOExecutor.dropQueuedChunkLoad(this.playerChunkMap.getWorld(), this.location.x, this.location.z, this.loadedRunnable);
+                    this.playerChunkMap.b(this);
+                }
+
+                return;
+            }
+            // CraftBukkit end
             if (this.done) {
                 entityplayer.playerConnection.sendPacket(new PacketPlayOutUnloadChunk(this.location.x, this.location.z));
             }
@@ -67,11 +100,18 @@
         if (this.chunk != null) {
             return true;
         } else {
+            /* CraftBukkit start
             if (flag) {
                 this.chunk = this.playerChunkMap.getWorld().getChunkProviderServer().getChunkAt(this.location.x, this.location.z);
             } else {
                 this.chunk = this.playerChunkMap.getWorld().getChunkProviderServer().getOrLoadChunkAt(this.location.x, this.location.z);
             }
+            */
+            if (!loadInProgress) {
+                loadInProgress = true;
+                this.chunk = playerChunkMap.getWorld().getChunkProviderServer().getChunkAt(this.location.x, this.location.z, loadedRunnable, flag);
+            }
+            // CraftBukkit end
 
             return this.chunk != null;
         }