From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Sat, 25 Jan 2020 17:04:35 -0800
Subject: [PATCH] Optimise getChunkAt calls for loaded chunks

bypass the need to get a player chunk, then get the either,
then unwrap it...

diff --git a/src/main/java/net/minecraft/server/ChunkProviderServer.java b/src/main/java/net/minecraft/server/ChunkProviderServer.java
index 633f12098973857eca04acd2839bb4d453860f1e..e467cd8123dafc46a8c894f1ffa9440de0d45340 100644
--- a/src/main/java/net/minecraft/server/ChunkProviderServer.java
+++ b/src/main/java/net/minecraft/server/ChunkProviderServer.java
@@ -446,6 +446,12 @@ public class ChunkProviderServer extends IChunkProvider {
                 return this.getChunkAt(i, j, chunkstatus, flag);
             }, this.serverThreadQueue).join();
         } else {
+            // Paper start - optimise for loaded chunks
+            Chunk ifLoaded = this.getChunkAtIfLoadedMainThread(i, j);
+            if (ifLoaded != null) {
+                return ifLoaded;
+            }
+            // Paper end
             GameProfilerFiller gameprofilerfiller = this.world.getMethodProfiler();
 
             gameprofilerfiller.c("getChunk");
@@ -496,39 +502,7 @@ public class ChunkProviderServer extends IChunkProvider {
         if (Thread.currentThread() != this.serverThread) {
             return null;
         } else {
-            this.world.getMethodProfiler().c("getChunkNow");
-            long k = ChunkCoordIntPair.pair(i, j);
-
-            for (int l = 0; l < 4; ++l) {
-                if (k == this.cachePos[l] && this.cacheStatus[l] == ChunkStatus.FULL) {
-                    IChunkAccess ichunkaccess = this.cacheChunk[l];
-
-                    return ichunkaccess instanceof Chunk ? (Chunk) ichunkaccess : null;
-                }
-            }
-
-            PlayerChunk playerchunk = this.getChunk(k);
-
-            if (playerchunk == null) {
-                return null;
-            } else {
-                Either<IChunkAccess, PlayerChunk.Failure> either = (Either) playerchunk.b(ChunkStatus.FULL).getNow(null); // CraftBukkit - decompile error
-
-                if (either == null) {
-                    return null;
-                } else {
-                    IChunkAccess ichunkaccess1 = (IChunkAccess) either.left().orElse(null); // CraftBukkit - decompile error
-
-                    if (ichunkaccess1 != null) {
-                        this.a(k, ichunkaccess1, ChunkStatus.FULL);
-                        if (ichunkaccess1 instanceof Chunk) {
-                            return (Chunk) ichunkaccess1;
-                        }
-                    }
-
-                    return null;
-                }
-            }
+            return this.getChunkAtIfLoadedMainThread(i, j); // Paper - optimise for loaded chunks
         }
     }
 
diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
index d7ac4c86d170a8d7d816f86ac691c3b5129a20ba..adacff593ee20804b5ddb2df55b66bc6c162dc70 100644
--- a/src/main/java/net/minecraft/server/World.java
+++ b/src/main/java/net/minecraft/server/World.java
@@ -266,6 +266,14 @@ public abstract class World implements GeneratorAccess, AutoCloseable {
 
     @Override
     public Chunk getChunkAt(int i, int j) {
+        // Paper start - optimise this for loaded chunks
+        if (Thread.currentThread() == this.serverThread) {
+            Chunk ifLoaded = ((WorldServer) this).getChunkProvider().getChunkAtIfLoadedMainThread(i, j);
+            if (ifLoaded != null) {
+                return ifLoaded;
+            }
+        }
+        // Paper end
         return (Chunk) this.getChunkAt(i, j, ChunkStatus.FULL);
     }