From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: MrPowerGamerBR <git@mrpowergamerbr.com>
Date: Sun, 26 Nov 2023 13:02:16 -0300
Subject: [PATCH] PaperPR: Fix MC-117075: Block Entities Unload Lag Spike

Original license: GPLv3
Original project: https://github.com/SparklyPower/SparklyPaper
Paper pull request: https://github.com/PaperMC/Paper/pull/9970

We replaced the `blockEntityTickers` list with a custom list based on fastutil's `ObjectArrayList` with a small yet huge change for us: A method that allows us to remove a list of indexes from the list.

This is WAY FASTER than using `removeAll` with a list of entries to be removed, because we don't need to calculate the identity of each block entity to be removed, and we can jump directly to where the search should begin, giving a performance boost for small removals (because we don't need to loop thru the entire list to find what element should be removed) and a performance boost for big removals (no need to calculate the identity of each block entity).

diff --git a/net/minecraft/world/level/Level.java b/net/minecraft/world/level/Level.java
index f145453f70a219c1be33b241309ae2ab22a8004b..22da84734462d09a55bc599db4374e1e4f4d6bd2 100644
--- a/net/minecraft/world/level/Level.java
+++ b/net/minecraft/world/level/Level.java
@@ -104,7 +104,7 @@ public abstract class Level implements LevelAccessor, UUIDLookup<Entity>, AutoCl
     public static final int TICKS_PER_DAY = 24000;
     public static final int MAX_ENTITY_SPAWN_Y = 20000000;
     public static final int MIN_ENTITY_SPAWN_Y = -20000000;
-    public final List<TickingBlockEntity> blockEntityTickers = Lists.newArrayList();
+    public final org.dreeam.leaf.util.list.BlockEntityTickersList blockEntityTickers = new org.dreeam.leaf.util.list.BlockEntityTickersList(); // SparklyPaper - optimize block entity removals
     protected final NeighborUpdater neighborUpdater;
     private final List<TickingBlockEntity> pendingBlockEntityTickers = Lists.newArrayList();
     private boolean tickingBlockEntities;
@@ -1506,13 +1506,11 @@ public abstract class Level implements LevelAccessor, UUIDLookup<Entity>, AutoCl
         boolean runsNormally = this.tickRateManager().runsNormally();
 
         int tickedEntities = 0; // Paper - rewrite chunk system
-        var toRemove = new it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet<TickingBlockEntity>(); // Paper - Fix MC-117075; use removeAll
-        toRemove.add(null); // Paper - Fix MC-117075
         for (this.tileTickPosition = 0; this.tileTickPosition < this.blockEntityTickers.size(); this.tileTickPosition++) { // Paper - Disable tick limiters
             TickingBlockEntity tickingBlockEntity = this.blockEntityTickers.get(this.tileTickPosition);
             // Spigot end
             if (tickingBlockEntity.isRemoved()) {
-                toRemove.add(tickingBlockEntity); // Paper - Fix MC-117075; use removeAll
+                this.blockEntityTickers.markAsRemoved(this.tileTickPosition); // toRemove.add(tickingBlockEntity); // Paper - Fix MC-117075; use removeAll // SparklyPaper - optimize block entity removals
             } else if (runsNormally && this.shouldTickBlocksAt(tickingBlockEntity.getPos())) {
                 tickingBlockEntity.tick();
                 // Paper start - rewrite chunk system
@@ -1522,7 +1520,7 @@ public abstract class Level implements LevelAccessor, UUIDLookup<Entity>, AutoCl
                 // Paper end - rewrite chunk system
             }
         }
-        this.blockEntityTickers.removeAll(toRemove); // Paper - Fix MC-117075
+        this.blockEntityTickers.removeMarkedEntries(); // SparklyPaper - optimize block entity removals
 
         this.tickingBlockEntities = false;
         this.spigotConfig.currentPrimedTnt = 0; // Spigot