Paper/patches/server/0736-Optimise-chunk-tick-iteration.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <spottedleaf@spottedleaf.dev>
Date: Thu, 7 May 2020 05:48:54 -0700
Subject: [PATCH] Optimise chunk tick iteration

Use a dedicated list of entity ticking chunks to reduce the cost

diff --git a/src/main/java/net/minecraft/server/level/ChunkHolder.java b/src/main/java/net/minecraft/server/level/ChunkHolder.java
index b75b3c4d274252a3a5c53059b9702728eeada389..8bea90cb57f38f33e8b3162e24e353993a98ebbf 100644
--- a/src/main/java/net/minecraft/server/level/ChunkHolder.java
+++ b/src/main/java/net/minecraft/server/level/ChunkHolder.java
@@ -86,11 +86,21 @@ public class ChunkHolder {
         long key = net.minecraft.server.MCUtil.getCoordinateKey(this.pos);
         this.playersInMobSpawnRange = this.chunkMap.playerMobSpawnMap.getObjectsInRange(key);
         this.playersInChunkTickRange = this.chunkMap.playerChunkTickRangeMap.getObjectsInRange(key);
+        // Paper start - optimise chunk tick iteration
+        if (this.needsBroadcastChanges()) {
+            this.chunkMap.needsChangeBroadcasting.add(this);
+        }
+        // Paper end - optimise chunk tick iteration
     }
 
     void onChunkRemove() {
         this.playersInMobSpawnRange = null;
         this.playersInChunkTickRange = null;
+        // Paper start - optimise chunk tick iteration
+        if (this.needsBroadcastChanges()) {
+            this.chunkMap.needsChangeBroadcasting.remove(this);
+        }
+        // Paper end - optimise chunk tick iteration
     }
     // Paper end - optimise anyPlayerCloseEnoughForSpawning
     long lastAutoSaveTime; // Paper - incremental autosave
@@ -253,7 +263,7 @@ public class ChunkHolder {
 
             if (i < 0 || i >= this.changedBlocksPerSection.length) return; // CraftBukkit - SPIGOT-6086, SPIGOT-6296
             if (this.changedBlocksPerSection[i] == null) {
-                this.hasChangedSections = true;
+                this.hasChangedSections = true; this.addToBroadcastMap(); // Paper - optimise chunk tick iteration
                 this.changedBlocksPerSection[i] = new ShortOpenHashSet();
             }
 
@@ -276,6 +286,7 @@ public class ChunkHolder {
                     int k = this.lightEngine.getMaxLightSection();
 
                     if (y >= j && y <= k) {
+                    this.addToBroadcastMap(); // Paper - optimise chunk tick iteration
                         int l = y - j;
 
                         if (lightType == LightLayer.SKY) {
@@ -290,8 +301,19 @@ public class ChunkHolder {
         }
     }
 
+    // Paper start - optimise chunk tick iteration
+    public final boolean needsBroadcastChanges() {
+        return this.hasChangedSections || !this.skyChangedLightSectionFilter.isEmpty() || !this.blockChangedLightSectionFilter.isEmpty();
+    }
+
+    private void addToBroadcastMap() {
+        org.spigotmc.AsyncCatcher.catchOp("ChunkHolder update");
+        this.chunkMap.needsChangeBroadcasting.add(this);
+    }
+    // Paper end - optimise chunk tick iteration
+
     public void broadcastChanges(LevelChunk chunk) {
-        if (this.hasChangedSections || !this.skyChangedLightSectionFilter.isEmpty() || !this.blockChangedLightSectionFilter.isEmpty()) {
+        if (this.needsBroadcastChanges()) { // Paper - moved into above, other logic needs to call
             Level world = chunk.getLevel();
             int i = 0;
 
diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index d9d9f2c6bf56a89ba92856caadf9f52bc9f5d931..0110a63e96a22bc179f5e2451d5c67927fd10ee5 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -163,6 +163,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
     private final Queue<Runnable> unloadQueue;
     int viewDistance;
     public final com.destroystokyo.paper.util.misc.PlayerAreaMap playerMobDistanceMap; // Paper
+    public final ReferenceOpenHashSet<ChunkHolder> needsChangeBroadcasting = new ReferenceOpenHashSet<>();
 
     // CraftBukkit start - recursion-safe executor for Chunk loadCallback() and unloadCallback()
     public final CallbackExecutor callbackExecutor = new CallbackExecutor();
diff --git a/src/main/java/net/minecraft/server/level/ServerChunkCache.java b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
index ce88da358c8a89564a911e6c818e906e845006ff..438406936633b9c67d21b26527c3d1654118c744 100644
--- a/src/main/java/net/minecraft/server/level/ServerChunkCache.java
+++ b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
@@ -47,6 +47,7 @@ import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemp
 import net.minecraft.world.level.storage.DimensionDataStorage;
 import net.minecraft.world.level.storage.LevelData;
 import net.minecraft.world.level.storage.LevelStorageSource;
+import it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet; // Paper
 
 public class ServerChunkCache extends ChunkSource {
 
@@ -987,34 +988,42 @@ public class ServerChunkCache extends ChunkSource {
 
             this.lastSpawnState = spawnercreature_d;
             gameprofilerfiller.popPush("filteringLoadedChunks");
-            List<ServerChunkCache.ChunkAndHolder> list = Lists.newArrayListWithCapacity(l);
-            Iterator iterator = this.chunkMap.getChunks().iterator();
+            // Paper - moved down
             this.level.timings.chunkTicks.startTiming(); // Paper
 
-            while (iterator.hasNext()) {
-                ChunkHolder playerchunk = (ChunkHolder) iterator.next();
-                LevelChunk chunk = playerchunk.getTickingChunk();
-
-                if (chunk != null) {
-                    list.add(new ServerChunkCache.ChunkAndHolder(chunk, playerchunk));
-                }
-            }
+            // Paper - moved down
 
             gameprofilerfiller.popPush("spawnAndTick");
             boolean flag2 = this.level.getGameRules().getBoolean(GameRules.RULE_DOMOBSPAWNING) && !this.level.players().isEmpty(); // CraftBukkit
 
-            Collections.shuffle(list);
+            // Paper - only shuffle if per-player mob spawning is disabled
             // Paper - moved natural spawn event up
-            Iterator iterator1 = list.iterator();
+            // Paper start - optimise chunk tick iteration
+            Iterator<LevelChunk> iterator1;
+            if (this.level.paperConfig().entities.spawning.perPlayerMobSpawns) {
+                iterator1 = this.entityTickingChunks.iterator();
+            } else {
+                iterator1 = this.entityTickingChunks.unsafeIterator();
+                List<LevelChunk> shuffled = Lists.newArrayListWithCapacity(this.entityTickingChunks.size());
+                while (iterator1.hasNext()) {
+                    shuffled.add(iterator1.next());
+                }
+                Collections.shuffle(shuffled);
+                iterator1 = shuffled.iterator();
+            }
 
+            try {
             while (iterator1.hasNext()) {
-                ServerChunkCache.ChunkAndHolder chunkproviderserver_a = (ServerChunkCache.ChunkAndHolder) iterator1.next();
-                LevelChunk chunk1 = chunkproviderserver_a.chunk;
+                LevelChunk chunk1 = iterator1.next();
+                ChunkHolder holder = chunk1.playerChunk;
+                if (holder != null) {
+                    // Paper - move down
+                // Paper end - optimise chunk tick iteration
                 ChunkPos chunkcoordintpair = chunk1.getPos();
 
-                if (this.level.isNaturalSpawningAllowed(chunkcoordintpair) && this.chunkMap.anyPlayerCloseEnoughForSpawning(chunkproviderserver_a.holder, chunkcoordintpair, false)) { // Paper - optimise anyPlayerCloseEnoughForSpawning
+                if (this.level.isNaturalSpawningAllowed(chunkcoordintpair) && this.chunkMap.anyPlayerCloseEnoughForSpawning(holder, chunkcoordintpair, false)) { // Paper - optimise anyPlayerCloseEnoughForSpawning
                     chunk1.incrementInhabitedTime(j);
-                    if (flag2 && (this.spawnEnemies || this.spawnFriendlies) && this.level.getWorldBorder().isWithinBounds(chunkcoordintpair) && this.chunkMap.anyPlayerCloseEnoughForSpawning(chunkproviderserver_a.holder, chunkcoordintpair, true)) { // Spigot // Paper - optimise anyPlayerCloseEnoughForSpawning
+                    if (flag2 && (this.spawnEnemies || this.spawnFriendlies) && this.level.getWorldBorder().isWithinBounds(chunkcoordintpair) && this.chunkMap.anyPlayerCloseEnoughForSpawning(holder, chunkcoordintpair, true)) { // Spigot // Paper - optimise anyPlayerCloseEnoughForSpawning & optimise chunk tick iteration
                         NaturalSpawner.spawnForChunk(this.level, chunk1, spawnercreature_d, this.spawnFriendlies, this.spawnEnemies, flag1);
                     }
 
@@ -1022,7 +1031,16 @@ public class ServerChunkCache extends ChunkSource {
                         this.level.tickChunk(chunk1, k);
                     }
                 }
+                // Paper start - optimise chunk tick iteration
+                }
             }
+
+            } finally {
+                if (iterator1 instanceof io.papermc.paper.util.maplist.IteratorSafeOrderedReferenceSet.Iterator safeIterator) {
+                    safeIterator.finishedIterating();
+                }
+            }
+            // Paper end - optimise chunk tick iteration
             this.level.timings.chunkTicks.stopTiming(); // Paper
             gameprofilerfiller.popPush("customSpawners");
             if (flag2) {
@@ -1030,15 +1048,24 @@ public class ServerChunkCache extends ChunkSource {
                 this.level.tickCustomSpawners(this.spawnEnemies, this.spawnFriendlies);
                 } // Paper - timings
             }
-
-            gameprofilerfiller.popPush("broadcast");
-            list.forEach((chunkproviderserver_a1) -> {
-                this.level.timings.broadcastChunkUpdates.startTiming(); // Paper - timing
-                chunkproviderserver_a1.holder.broadcastChanges(chunkproviderserver_a1.chunk);
-                this.level.timings.broadcastChunkUpdates.stopTiming(); // Paper - timing
-            });
             gameprofilerfiller.pop();
+            // Paper start - use set of chunks requiring updates, rather than iterating every single one loaded
+            gameprofilerfiller.popPush("broadcast");
+            this.level.timings.broadcastChunkUpdates.startTiming(); // Paper - timing
+            if (!this.chunkMap.needsChangeBroadcasting.isEmpty()) {
+                ReferenceOpenHashSet<ChunkHolder> copy = this.chunkMap.needsChangeBroadcasting.clone();
+                this.chunkMap.needsChangeBroadcasting.clear();
+                for (ChunkHolder holder : copy) {
+                    holder.broadcastChanges(holder.getFullChunkNowUnchecked()); // LevelChunks are NEVER unloaded
+                    if (holder.needsBroadcastChanges()) {
+                        // I DON'T want to KNOW what DUMB plugins might be doing.
+                        this.chunkMap.needsChangeBroadcasting.add(holder);
+                    }
+                }
+            }
+            this.level.timings.broadcastChunkUpdates.stopTiming(); // Paper - timing
             gameprofilerfiller.pop();
+            // Paper end - use set of chunks requiring updates, rather than iterating every single one loaded
             this.chunkMap.tick();
         }
     }