From 26a1e69e6b0a7f8ab454751fa9e48d06b6b491eb Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sun, 22 Jan 2017 18:07:56 -0500
Subject: [PATCH] Cap Entity Collisions

Limit a single entity to colliding a max of configurable times per tick.
This will alleviate issues where living entities are hoarded in 1x1 pens

This is not tied to the maxEntityCramming rule. Cramming will still apply
just as it does in Vanilla, but entity pushing logic will be capped.

You can set this to 0 to disable collisions.

diff --git a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
index 70af657f5..af953dda4 100644
--- a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
@@ -410,4 +410,10 @@ public class PaperWorldConfig {
     private void armorStandEntityLookups() {
         armorStandEntityLookups = getBoolean("armor-stands-do-collision-entity-lookups", true);
     }
+
+    public int maxCollisionsPerEntity;
+    private void maxEntityCollision() {
+        maxCollisionsPerEntity = getInt( "max-entity-collisions", this.spigotConfig.getInt("max-entity-collisions", 8) );
+        log( "Max Entity Collisions: " + maxCollisionsPerEntity );
+    }
 }
diff --git a/src/main/java/net/minecraft/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index 147f00fe8..d34ec4ff1 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -169,6 +169,7 @@ public abstract class Entity implements ICommandListener {
     public final boolean defaultActivationState;
     public long activatedTick = Integer.MIN_VALUE;
     public boolean fromMobSpawner;
+    protected int numCollisions = 0; // Paper
     public void inactiveTick() { }
     // Spigot end
 
diff --git a/src/main/java/net/minecraft/server/EntityLiving.java b/src/main/java/net/minecraft/server/EntityLiving.java
index 194d55c30..b18fc969a 100644
--- a/src/main/java/net/minecraft/server/EntityLiving.java
+++ b/src/main/java/net/minecraft/server/EntityLiving.java
@@ -2182,8 +2182,11 @@ public abstract class EntityLiving extends Entity {
                 }
             }
 
-            for (j = 0; j < list.size(); ++j) {
+            numCollisions = Math.max(0, numCollisions - world.paperConfig.maxCollisionsPerEntity); // Paper
+            for (j = 0; j < list.size() && numCollisions < world.paperConfig.maxCollisionsPerEntity; ++j) { // Paper
                 Entity entity = (Entity) list.get(j);
+                entity.numCollisions++; // Paper
+                numCollisions++; // Paper
 
                 this.C(entity);
             }
-- 
2.13.1