Paper-Old/Spigot-Server-Patches/0071-Optimize-Entity-and-Tile-Entity-Removal.patch

From 0faf299cfd4aa28f0aec544159cc14bc475c08ef Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Fri, 16 Oct 2015 22:14:48 -0500
Subject: [PATCH] Optimize Entity and Tile Entity Removal

Java's implementation of List.removeAll is extremely slow. This is
currently causing lots of TPS loss when lots of chunk unload activity
occurs, as the process iterates the removal list for every entry in the
source list, resulting in O(n^2) performance.

This change will switch the process to instead iterate over the
removal list, and marking a boolean that its removed.

Then, we then iterate the source list and use a compaction technique
that skips any object marked for removal.

After all live objects are compacted down, we do a range
removal to clear out any removed objects at the end of the current list.

This gives us O(n) performance and a much cheaper overall operation.

Compaction technique was originally used by CyberTiger in a different
implementation.

Finally, we remove MOST single .remove() calls, and run a 2nd compaction
after ticking in order to remove the singles.

This also fixes a bug with Tick Position in the Tick limiter, where
previously .removeAll would shift entity index order but the tick
position was never moved to its new location.

diff --git a/src/main/java/net/minecraft/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index 68126c4..868064d 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -32,7 +32,12 @@ import org.bukkit.event.entity.EntityPortalEvent;
 import org.bukkit.plugin.PluginManager;
 // CraftBukkit end
 
-public abstract class Entity implements ICommandListener {
+// PaperSpigot start - Optimized entity and tileentity removal
+public abstract class Entity implements ICommandListener, org.github.paperspigot.OptimizedRemoveAll.Marker {
+    private boolean needsRemoved = false;
+    public boolean isToBeRemoved() { return needsRemoved; }
+    public void markToBeRemoved() { needsRemoved = true; }
+    // PaperSpigot end
 
     // CraftBukkit start
     private static final int CURRENT_LEVEL = 2;
diff --git a/src/main/java/net/minecraft/server/TileEntity.java b/src/main/java/net/minecraft/server/TileEntity.java
index 3fc6450..a69a3c9 100644
--- a/src/main/java/net/minecraft/server/TileEntity.java
+++ b/src/main/java/net/minecraft/server/TileEntity.java
@@ -9,7 +9,12 @@ import org.apache.logging.log4j.Logger;
 import org.spigotmc.CustomTimingsHandler; // Spigot
 import org.bukkit.inventory.InventoryHolder; // CraftBukkit
 
-public abstract class TileEntity {
+// PaperSpigot start - Optimized entity and tileentity removal
+public abstract class TileEntity implements org.github.paperspigot.OptimizedRemoveAll.Marker {
+    private boolean needsRemoved = false;
+    public boolean isToBeRemoved() { return needsRemoved; }
+    public void markToBeRemoved() { needsRemoved = true; }
+    // PaperSpigot end
 
     public CustomTimingsHandler tickTimer = org.bukkit.craftbukkit.SpigotTimings.getTileEntityTimings(this); // Spigot
     private static final Logger a = LogManager.getLogger();
diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
index a9c627e..eb5fe7f 100644
--- a/src/main/java/net/minecraft/server/World.java
+++ b/src/main/java/net/minecraft/server/World.java
@@ -1393,7 +1393,7 @@ public abstract class World implements IBlockAccess {
         }
 
         this.methodProfiler.c("remove");
-        this.entityList.removeAll(this.g);
+        tickPosition = org.github.paperspigot.OptimizedRemoveAll.removeAll(this.entityList, this.g, tickPosition); // PaperSpigot
 
         int j;
         int k;
@@ -1462,13 +1462,15 @@ public abstract class World implements IBlockAccess {
                 }
 
                 guardEntityList = false; // Spigot
-                this.entityList.remove(this.tickPosition--); // CraftBukkit - Use field for loop variable
+                if (entity instanceof EntityPlayer) this.entityList.remove(this.tickPosition--); // CraftBukkit - Use field for loop variable // PaperSpigot
+                else entity.markToBeRemoved(); // PaperSpigot
                 guardEntityList = true; // Spigot
                 this.b(entity);
             }
 
             this.methodProfiler.b();
         }
+        tickPosition = org.github.paperspigot.OptimizedRemoveAll.removeAll(this.entityList, null, tickPosition); // PaperSpigot
         guardEntityList = false; // Spigot
 
         timings.entityTick.stopTiming(); // Spigot
@@ -1477,7 +1479,7 @@ public abstract class World implements IBlockAccess {
         this.M = true;
         // CraftBukkit start - From below, clean up tile entities before ticking them
         if (!this.c.isEmpty()) {
-            this.tileEntityList.removeAll(this.c);
+            tileTickPosition = org.github.paperspigot.OptimizedRemoveAll.removeAll(this.tileEntityList, this.c, tileTickPosition); // PaperSpigot
             //this.h.removeAll(this.c); // PaperSpigot - Remove unused list
             this.c.clear();
         }
@@ -1526,13 +1528,15 @@ public abstract class World implements IBlockAccess {
 
             if (tileentity.x()) {
                 tilesThisCycle--;
-                this.tileEntityList.remove(tileTickPosition--);
+                tileentity.markToBeRemoved(); // PaperSpigot
+                //this.tileEntityList.remove(tileTickPosition--);
                 //this.h.remove(tileentity); // PaperSpigot - Remove unused list
                 if (this.isLoaded(tileentity.getPosition())) {
                     this.getChunkAtWorldCoords(tileentity.getPosition()).e(tileentity.getPosition());
                 }
             }
         }
+        tileTickPosition = org.github.paperspigot.OptimizedRemoveAll.removeAll(this.tileEntityList, null, tileTickPosition); // PaperSpigot
 
         timings.tileEntityTick.stopTiming(); // Spigot
         timings.tileEntityPending.startTiming(); // Spigot
@@ -2636,6 +2640,7 @@ public abstract class World implements IBlockAccess {
 
         while (iterator.hasNext()) {
             Entity entity = (Entity) iterator.next();
+            if (entity.isToBeRemoved()) { continue; } // PaperSpigot
 
             if (oclass.isAssignableFrom(entity.getClass()) && predicate.apply((T) entity)) { // CraftBukkit - fix decompile error
                 arraylist.add(entity);
@@ -2705,6 +2710,7 @@ public abstract class World implements IBlockAccess {
 
         while (iterator.hasNext()) {
             Entity entity = (Entity) iterator.next();
+            if (entity.isToBeRemoved()) { continue; } // PaperSpigot
             // CraftBukkit start - Split out persistent check, don't apply it to special persistent mobs
             if (entity instanceof EntityInsentient) {
                 EntityInsentient entityinsentient = (EntityInsentient) entity;
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
index 4402d57..dbde8ab 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
@@ -647,7 +647,7 @@ public class CraftWorld implements World {
                 Entity bukkitEntity = mcEnt.getBukkitEntity();
 
                 // Assuming that bukkitEntity isn't null
-                if (bukkitEntity != null) {
+                if (bukkitEntity != null && !mcEnt.isToBeRemoved()) { // PaperSpigot
                     list.add(bukkitEntity);
                 }
             }
@@ -665,7 +665,7 @@ public class CraftWorld implements World {
                 Entity bukkitEntity = mcEnt.getBukkitEntity();
 
                 // Assuming that bukkitEntity isn't null
-                if (bukkitEntity != null && bukkitEntity instanceof LivingEntity) {
+                if (bukkitEntity != null && bukkitEntity instanceof LivingEntity && !mcEnt.isToBeRemoved()) { // PaperSpigot
                     list.add((LivingEntity) bukkitEntity);
                 }
             }
@@ -688,7 +688,7 @@ public class CraftWorld implements World {
             if (entity instanceof net.minecraft.server.Entity) {
                 Entity bukkitEntity = ((net.minecraft.server.Entity) entity).getBukkitEntity();
 
-                if (bukkitEntity == null) {
+                if (bukkitEntity == null || ((net.minecraft.server.Entity) entity).isToBeRemoved()) { // PaperSpigot
                     continue;
                 }
 
@@ -710,7 +710,7 @@ public class CraftWorld implements World {
             if (entity instanceof net.minecraft.server.Entity) {
                 Entity bukkitEntity = ((net.minecraft.server.Entity) entity).getBukkitEntity();
 
-                if (bukkitEntity == null) {
+                if (bukkitEntity == null || ((net.minecraft.server.Entity) entity).isToBeRemoved()) { // PaperSpigot
                     continue;
                 }
 
diff --git a/src/main/java/org/github/paperspigot/OptimizedRemoveAll.java b/src/main/java/org/github/paperspigot/OptimizedRemoveAll.java
new file mode 100644
index 0000000..0095c25
--- /dev/null
+++ b/src/main/java/org/github/paperspigot/OptimizedRemoveAll.java
@@ -0,0 +1,50 @@
+package org.github.paperspigot;
+
+import java.util.List;
+
+/**
+ * Improved algorithim for bulk removing entries from a list
+ * <p>
+ * WARNING: This system only works on Identity Based lists,
+ * unlike traditional .removeAll() that operates on object equality.
+ */
+public final class OptimizedRemoveAll {
+    private OptimizedRemoveAll() {
+    }
+
+    public interface Marker {
+        boolean isToBeRemoved();
+
+        void markToBeRemoved();
+    }
+
+    /**
+     * More effecient removeAll method
+     *
+     * @param tickPosition Previous Tick Position
+     * @return New Tick Position
+     */
+    public static <E extends Marker> int removeAll(List<E> list, List<E> removal, int tickPosition) {
+        if (removal != null && !removal.isEmpty()) {
+            int removalSize = removal.size();
+            for (int i = 0; i < removalSize; i++) {
+                removal.get(i).markToBeRemoved();
+            }
+        }
+
+        int size = list.size();
+        int insertAt = 0;
+        for (int i = 0; i < size; i++) {
+            E el = list.get(i);
+            if (i == tickPosition) {
+                tickPosition = insertAt;
+            }
+            if (el != null && !el.isToBeRemoved()) {
+                list.set(insertAt++, el);
+            }
+        }
+        list.subList(insertAt, size).clear();
+        return tickPosition;
+    }
+
+}
-- 
2.6.1.windows.1