Paper/patches/server/0578-Entity-load-save-limit-per-chunk.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jason Penilla <11360596+jpenilla@users.noreply.github.com>
Date: Wed, 18 Nov 2020 20:52:25 -0800
Subject: [PATCH] Entity load/save limit per chunk

Adds a config option to limit the number of entities saved and loaded
to a chunk. The default values of -1 disable the limit. Although
defaults are only included for certain entites, this allows setting
limits for any entity type.

diff --git a/src/main/java/net/minecraft/world/entity/EntityType.java b/src/main/java/net/minecraft/world/entity/EntityType.java
index 9d16fc698b0771bcb3c95f5fb017879c37ebb39b..823f3b3093cffb49ccdcbcfbe6d348009a553ad7 100644
--- a/src/main/java/net/minecraft/world/entity/EntityType.java
+++ b/src/main/java/net/minecraft/world/entity/EntityType.java
@@ -631,9 +631,20 @@ public class EntityType<T extends Entity> implements FeatureElement, EntityTypeT
         final Spliterator<? extends Tag> spliterator = entityNbtList.spliterator();
 
         return StreamSupport.stream(new Spliterator<Entity>() {
+            final java.util.Map<EntityType<?>, Integer> loadedEntityCounts = new java.util.HashMap<>(); // Paper
             public boolean tryAdvance(Consumer<? super Entity> consumer) {
                 return spliterator.tryAdvance((nbtbase) -> {
                     EntityType.loadEntityRecursive((CompoundTag) nbtbase, world, (entity) -> {
+                        // Paper start
+                        final EntityType<?> entityType = entity.getType();
+                        final int saveLimit = world.paperConfig().chunks.entityPerChunkSaveLimit.getOrDefault(entityType, -1);
+                        if (saveLimit > -1) {
+                            if (this.loadedEntityCounts.getOrDefault(entityType, 0) >= saveLimit) {
+                                return null;
+                            }
+                            this.loadedEntityCounts.merge(entityType, 1, Integer::sum);
+                        }
+                        // Paper end
                         consumer.accept(entity);
                         return entity;
                     });
diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/EntityStorage.java b/src/main/java/net/minecraft/world/level/chunk/storage/EntityStorage.java
index 0ec0be22f7292d57c40da6f1f4575bdebf8dbd09..060e064625969610539dbf969ce773b877a7c579 100644
--- a/src/main/java/net/minecraft/world/level/chunk/storage/EntityStorage.java
+++ b/src/main/java/net/minecraft/world/level/chunk/storage/EntityStorage.java
@@ -110,7 +110,18 @@ public class EntityStorage implements EntityPersistentStorage<Entity> {
         }
 
         ListTag listTag = new ListTag();
+        final java.util.Map<net.minecraft.world.entity.EntityType<?>, Integer> savedEntityCounts = new java.util.HashMap<>(); // Paper
         entities.forEach((entity) -> { // diff here: use entities parameter
+            // Paper start
+            final EntityType<?> entityType = entity.getType();
+            final int saveLimit = level.paperConfig().chunks.entityPerChunkSaveLimit.getOrDefault(entityType, -1);
+            if (saveLimit > -1) {
+                if (savedEntityCounts.getOrDefault(entityType, 0) >= saveLimit) {
+                    return;
+                }
+                savedEntityCounts.merge(entityType, 1, Integer::sum);
+            }
+            // Paper end
             CompoundTag compoundTag = new CompoundTag();
             if (entity.save(compoundTag)) {
                 listTag.add(compoundTag);