PaperMC/Remapped-Spigot-Server-Patches/0477-Optimize-NibbleArray-to-use-pooled-buffers.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Wed, 6 May 2020 23:30:30 -0400
Subject: [PATCH] Optimize NibbleArray to use pooled buffers

Massively reduces memory allocation of 2048 byte buffers by using
an object pool for these.

Uses lots of advanced new capabilities of the Paper codebase :)

diff --git a/src/main/java/net/minecraft/network/protocol/game/ClientboundLightUpdatePacket.java b/src/main/java/net/minecraft/network/protocol/game/ClientboundLightUpdatePacket.java
index bc1b4cc2e0a4181bde5ac05ce0a20a651cb0c4c3..902f14e2e5ac5aa11b545a68ac69e9b0282df7f4 100644
--- a/src/main/java/net/minecraft/network/protocol/game/ClientboundLightUpdatePacket.java
+++ b/src/main/java/net/minecraft/network/protocol/game/ClientboundLightUpdatePacket.java
@@ -1,12 +1,16 @@
 package net.minecraft.network.protocol.game;
 
 import com.google.common.collect.Lists;
+import io.netty.channel.ChannelFuture; // Paper
+
 import java.io.IOException;
 import java.util.Iterator;
 import java.util.List;
 import net.minecraft.core.SectionPos;
 import net.minecraft.network.FriendlyByteBuf;
 import net.minecraft.network.protocol.Packet;
+import net.minecraft.server.MCUtil;
+import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.world.level.ChunkPos;
 import net.minecraft.world.level.LightLayer;
 import net.minecraft.world.level.chunk.DataLayer;
@@ -24,14 +28,43 @@ public class ClientboundLightUpdatePacket implements Packet<ClientGamePacketList
     private List<byte[]> blockUpdates;
     private boolean trustEdges;
 
+    // Paper start
+    java.lang.Runnable cleaner1;
+    java.lang.Runnable cleaner2;
+    java.util.concurrent.atomic.AtomicInteger remainingSends = new java.util.concurrent.atomic.AtomicInteger(0);
+
+    @Override
+    public void onPacketDispatch(ServerPlayer player) {
+        remainingSends.incrementAndGet();
+    }
+
+    @Override
+    public void onPacketDispatchFinish(ServerPlayer player, ChannelFuture future) {
+        if (remainingSends.decrementAndGet() <= 0) {
+            // incase of any race conditions, schedule this delayed
+            MCUtil.scheduleTask(5, () -> {
+                if (remainingSends.get() == 0) {
+                    cleaner1.run();
+                    cleaner2.run();
+                }
+            }, "Light Packet Release");
+        }
+    }
+
+    @Override
+    public boolean hasFinishListener() {
+        return true;
+    }
+
+    // Paper end
     public ClientboundLightUpdatePacket() {}
 
     public ClientboundLightUpdatePacket(ChunkPos chunkcoordintpair, LevelLightEngine lightengine, boolean flag) {
         this.x = chunkcoordintpair.x;
         this.z = chunkcoordintpair.z;
         this.trustEdges = flag;
-        this.skyUpdates = Lists.newArrayList();
-        this.blockUpdates = Lists.newArrayList();
+        this.skyUpdates = Lists.newArrayList();cleaner1 = MCUtil.registerListCleaner(this, this.skyUpdates, DataLayer::releaseBytes); // Paper
+        this.blockUpdates = Lists.newArrayList();cleaner2 = MCUtil.registerListCleaner(this, this.blockUpdates, DataLayer::releaseBytes); // Paper
 
         for (int i = 0; i < 18; ++i) {
             DataLayer nibblearray = lightengine.getLayerListener(LightLayer.SKY).getDataLayerData(SectionPos.of(chunkcoordintpair, -1 + i));
@@ -42,7 +75,7 @@ public class ClientboundLightUpdatePacket implements Packet<ClientGamePacketList
                     this.emptySkyYMask |= 1 << i;
                 } else {
                     this.skyYMask |= 1 << i;
-                    this.skyUpdates.add(nibblearray.getData().clone());
+                    this.skyUpdates.add(nibblearray.getCloneIfSet()); // Paper
                 }
             }
 
@@ -51,7 +84,7 @@ public class ClientboundLightUpdatePacket implements Packet<ClientGamePacketList
                     this.emptyBlockYMask |= 1 << i;
                 } else {
                     this.blockYMask |= 1 << i;
-                    this.blockUpdates.add(nibblearray1.getData().clone());
+                    this.blockUpdates.add(nibblearray1.getCloneIfSet()); // Paper
                 }
             }
         }
@@ -64,8 +97,8 @@ public class ClientboundLightUpdatePacket implements Packet<ClientGamePacketList
         this.trustEdges = flag;
         this.skyYMask = skyLightMask;
         this.blockYMask = blockLightMask;
-        this.skyUpdates = Lists.newArrayList();
-        this.blockUpdates = Lists.newArrayList();
+        this.skyUpdates = Lists.newArrayList();cleaner1 = MCUtil.registerListCleaner(this, this.skyUpdates, DataLayer::releaseBytes); // Paper
+        this.blockUpdates = Lists.newArrayList();cleaner2 = MCUtil.registerListCleaner(this, this.blockUpdates, DataLayer::releaseBytes); // Paper
 
         for (int k = 0; k < 18; ++k) {
             DataLayer nibblearray;
@@ -73,7 +106,7 @@ public class ClientboundLightUpdatePacket implements Packet<ClientGamePacketList
             if ((this.skyYMask & 1 << k) != 0) {
                 nibblearray = lightProvider.getLayerListener(LightLayer.SKY).getDataLayerData(SectionPos.of(pos, -1 + k));
                 if (nibblearray != null && !nibblearray.isEmpty()) {
-                    this.skyUpdates.add(nibblearray.getData().clone());
+                    this.skyUpdates.add(nibblearray.getCloneIfSet()); // Paper
                 } else {
                     this.skyYMask &= ~(1 << k);
                     if (nibblearray != null) {
@@ -85,7 +118,7 @@ public class ClientboundLightUpdatePacket implements Packet<ClientGamePacketList
             if ((this.blockYMask & 1 << k) != 0) {
                 nibblearray = lightProvider.getLayerListener(LightLayer.BLOCK).getDataLayerData(SectionPos.of(pos, -1 + k));
                 if (nibblearray != null && !nibblearray.isEmpty()) {
-                    this.blockUpdates.add(nibblearray.getData().clone());
+                    this.blockUpdates.add(nibblearray.getCloneIfSet()); // Paper
                 } else {
                     this.blockYMask &= ~(1 << k);
                     if (nibblearray != null) {
diff --git a/src/main/java/net/minecraft/world/level/chunk/DataLayer.java b/src/main/java/net/minecraft/world/level/chunk/DataLayer.java
index 2b798f4e556302f6f79d54182a309f4716a84f04..83e9d8bff9a31fe13a0e22445cd6eecb7abe8561 100644
--- a/src/main/java/net/minecraft/world/level/chunk/DataLayer.java
+++ b/src/main/java/net/minecraft/world/level/chunk/DataLayer.java
@@ -1,18 +1,78 @@
 // mc-dev import
 package net.minecraft.world.level.chunk;
 
+import com.destroystokyo.paper.util.pooled.PooledObjects; // Paper
+
+import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import net.minecraft.Util;
+import net.minecraft.server.MCUtil;
 
 public class DataLayer {
 
-    @Nullable
-    protected byte[] data;
+    // Paper start
+    public static byte[] EMPTY_NIBBLE = new byte[2048];
+    private static final int nibbleBucketSizeMultiplier = Integer.getInteger("Paper.nibbleBucketSize", 3072);
+    private static final int maxPoolSize = Integer.getInteger("Paper.maxNibblePoolSize", (int) Math.min(6, Math.max(1, Runtime.getRuntime().maxMemory() / 1024 / 1024 / 1024)) * (nibbleBucketSizeMultiplier * 8));
+    public static final PooledObjects<byte[]> BYTE_2048 = new PooledObjects<>(() -> new byte[2048], maxPoolSize);
+    public static void releaseBytes(byte[] bytes) {
+        if (bytes != null && bytes != EMPTY_NIBBLE && bytes.length == 2048) {
+            System.arraycopy(EMPTY_NIBBLE, 0, bytes, 0, 2048);
+            BYTE_2048.release(bytes);
+        }
+    }
+
+    public DataLayer markPoolSafe(byte[] bytes) {
+        if (bytes != EMPTY_NIBBLE) this.data = bytes;
+        return markPoolSafe();
+    }
+    public DataLayer markPoolSafe() {
+        poolSafe = true;
+        return this;
+    }
+    public byte[] getIfSet() {
+        return this.data != null ? this.data : EMPTY_NIBBLE;
+    }
+    public byte[] getCloneIfSet() {
+        if (data == null) {
+            return EMPTY_NIBBLE;
+        }
+        byte[] ret = BYTE_2048.acquire();
+        System.arraycopy(getIfSet(), 0, ret, 0, 2048);
+        return ret;
+    }
+
+    public DataLayer cloneAndSet(byte[] bytes) {
+        if (bytes != null && bytes != EMPTY_NIBBLE) {
+            this.data = BYTE_2048.acquire();
+            System.arraycopy(bytes, 0, this.data, 0, 2048);
+        }
+        return this;
+    }
+    boolean poolSafe = false;
+    public java.lang.Runnable cleaner;
+    private void registerCleaner() {
+        if (!poolSafe) {
+            cleaner = MCUtil.registerCleaner(this, this.data, DataLayer::releaseBytes);
+        } else {
+            cleaner = MCUtil.once(() -> DataLayer.releaseBytes(this.data));
+        }
+    }
+    // Paper end
+    @Nullable protected byte[] data;
+
 
     public DataLayer() {}
 
     public DataLayer(byte[] abyte) {
+        // Paper start
+        this(abyte, false);
+    }
+    public DataLayer(byte[] abyte, boolean isSafe) {
         this.data = abyte;
+        if (!isSafe) this.data = getCloneIfSet(); // Paper - clone for safety
+        registerCleaner();
+        // Paper end
         if (abyte.length != 2048) {
             throw (IllegalArgumentException) Util.pauseInIde((Throwable) (new IllegalArgumentException("ChunkNibbleArrays should be 2048 bytes not: " + abyte.length)));
         }
@@ -46,7 +106,8 @@ public class DataLayer {
 
     public void set(int index, int value) { // PAIL: private -> public
         if (this.data == null) {
-            this.data = new byte[2048];
+            this.data = BYTE_2048.acquire(); // Paper
+            registerCleaner();// Paper
         }
 
         int k = this.getPosition(index);
@@ -68,14 +129,36 @@ public class DataLayer {
     public byte[] getData() {
         if (this.data == null) {
             this.data = new byte[2048];
+        } else { // Paper start
+            // Accessor may need this object past garbage collection so need to clone it and return pooled value
+            // If we know its safe for pre GC access, use asBytesPoolSafe(). If you just need read, use getIfSet()
+            Runnable cleaner = this.cleaner;
+            if (cleaner != null) {
+                this.data = this.data.clone();
+                cleaner.run(); // release the previously pooled value
+                this.cleaner = null;
+            }
+        }
+        // Paper end
+
+        return this.data;
+    }
+
+    @Nonnull
+    public byte[] asBytesPoolSafe() {
+        if (this.data == null) {
+            this.data = BYTE_2048.acquire(); // Paper
+            registerCleaner(); // Paper
         }
 
+        //noinspection ConstantConditions
         return this.data;
     }
+    // Paper end
 
     public DataLayer copy() { return this.copy(); } // Paper - OBFHELPER
     public DataLayer copy() {
-        return this.data == null ? new DataLayer() : new DataLayer((byte[]) this.data.clone());
+        return this.data == null ? new DataLayer() : new DataLayer(this.data); // Paper - clone in ctor
     }
 
     public String toString() {
diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
index 6c28a611b9b79c3322ab07883972c07b3bfc3073..1e58958c3d7b10da5a5f22fc9591d9183e53e3cc 100644
--- a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
+++ b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
@@ -435,11 +435,11 @@ public class ChunkSerializer {
                 }
 
                 if (nibblearray != null && !nibblearray.isEmpty()) {
-                    nbttagcompound2.putByteArray("BlockLight", nibblearray.getData());
+                    nbttagcompound2.putByteArray("BlockLight", nibblearray.asBytesPoolSafe().clone()); // Paper
                 }
 
                 if (nibblearray1 != null && !nibblearray1.isEmpty()) {
-                    nbttagcompound2.putByteArray("SkyLight", nibblearray1.getData());
+                    nbttagcompound2.putByteArray("SkyLight", nibblearray1.asBytesPoolSafe().clone()); // Paper
                 }
 
                 nbttaglist.add(nbttagcompound2);
diff --git a/src/main/java/net/minecraft/world/level/lighting/DataLayerStorageMap.java b/src/main/java/net/minecraft/world/level/lighting/DataLayerStorageMap.java
index 4c9041f1c1cb4b3ec114fbd0c5d4db50a6f2526d..54cca3b376e5ce02936edc8b9c17e67e17f07147 100644
--- a/src/main/java/net/minecraft/world/level/lighting/DataLayerStorageMap.java
+++ b/src/main/java/net/minecraft/world/level/lighting/DataLayerStorageMap.java
@@ -2,6 +2,7 @@ package net.minecraft.world.level.lighting;
 
 import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
 import javax.annotation.Nullable;
+import net.minecraft.server.MCUtil;
 import net.minecraft.world.level.chunk.DataLayer;
 
 public abstract class DataLayerStorageMap<M extends DataLayerStorageMap<M>> {
@@ -34,7 +35,9 @@ public abstract class DataLayerStorageMap<M extends DataLayerStorageMap<M>> {
 
     public void copyDataLayer(long pos) {
         if (this.isVisible) { throw new IllegalStateException("writing to visible data"); } // Paper - avoid copying light data
-        this.data.queueUpdate(pos, ((DataLayer) this.data.getUpdating(pos)).copy()); // Paper - avoid copying light data
+        DataLayer updating = this.data.getUpdating(pos); // Paper - pool nibbles
+        this.data.queueUpdate(pos, new DataLayer().markPoolSafe(updating.getCloneIfSet())); // Paper - avoid copying light data - pool safe clone
+        if (updating.cleaner != null) MCUtil.scheduleTask(2, updating.cleaner, "Light Engine Release"); // Paper - delay clean incase anything holding ref was still using it
         this.clearCache();
     }
 
diff --git a/src/main/java/net/minecraft/world/level/lighting/FlatDataLayer.java b/src/main/java/net/minecraft/world/level/lighting/FlatDataLayer.java
index 9b95ae0ff193d7f52650f406c70e76e3f7e07e1c..c0d356ac4d54b952fe9ddaf5125b07177ac44d1f 100644
--- a/src/main/java/net/minecraft/world/level/lighting/FlatDataLayer.java
+++ b/src/main/java/net/minecraft/world/level/lighting/FlatDataLayer.java
@@ -10,7 +10,7 @@ public class FlatDataLayer extends DataLayer {
 
     public FlatDataLayer(DataLayer nibblearray, int i) {
         super(128);
-        System.arraycopy(nibblearray.getData(), i * 128, this.data, 0, 128);
+        System.arraycopy(nibblearray.getIfSet(), i * 128, this.data, 0, 128); // Paper
     }
 
     @Override
@@ -20,7 +20,7 @@ public class FlatDataLayer extends DataLayer {
 
     @Override
     public byte[] getData() {
-        byte[] abyte = new byte[2048];
+        byte[] abyte = BYTE_2048.acquire(); // Paper
 
         for (int i = 0; i < 16; ++i) {
             System.arraycopy(this.data, 0, abyte, i * 128, 128);
diff --git a/src/main/java/net/minecraft/world/level/lighting/LayerLightSectionStorage.java b/src/main/java/net/minecraft/world/level/lighting/LayerLightSectionStorage.java
index 177dae992d13674bb285a60b8427df9ea843dc99..5757bcfded35f112d52a7c81586850ba50e0d8dd 100644
--- a/src/main/java/net/minecraft/world/level/lighting/LayerLightSectionStorage.java
+++ b/src/main/java/net/minecraft/world/level/lighting/LayerLightSectionStorage.java
@@ -156,7 +156,7 @@ public abstract class LayerLightSectionStorage<M extends DataLayerStorageMap<M>>
     protected DataLayer createDataLayer(long sectionPos) {
         DataLayer nibblearray = (DataLayer) this.queuedSections.get(sectionPos);
 
-        return nibblearray != null ? nibblearray : new DataLayer();
+        return nibblearray != null ? nibblearray : new DataLayer().markPoolSafe(); // Paper
     }
 
     protected void clearQueuedSectionBlocks(LayerLightEngine<?, ?> storage, long sectionPos) {
@@ -338,12 +338,12 @@ public abstract class LayerLightSectionStorage<M extends DataLayerStorageMap<M>>
 
     protected void queueSectionData(long sectionPos, @Nullable DataLayer array, boolean flag) {
         if (array != null) {
-            this.queuedSections.put(sectionPos, array);
+            DataLayer remove = this.queuedSections.put(sectionPos, array); if (remove != null && remove.cleaner != null) remove.cleaner.run(); // Paper - clean up when removed
             if (!flag) {
                 this.untrustedSections.add(sectionPos);
             }
         } else {
-            this.queuedSections.remove(sectionPos);
+            DataLayer remove = this.queuedSections.remove(sectionPos); if (remove != null && remove.cleaner != null) remove.cleaner.run(); // Paper - clean up when removed
         }
 
     }
diff --git a/src/main/java/net/minecraft/world/level/lighting/SkyLightSectionStorage.java b/src/main/java/net/minecraft/world/level/lighting/SkyLightSectionStorage.java
index 410fcfa8c01b7e3d3e3829ebdb92a11badff16ea..88f168f9d4c29cfc93500227bf8a60de4b6e4d8a 100644
--- a/src/main/java/net/minecraft/world/level/lighting/SkyLightSectionStorage.java
+++ b/src/main/java/net/minecraft/world/level/lighting/SkyLightSectionStorage.java
@@ -172,9 +172,9 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
                     j = SectionPos.offset(j, Direction.UP);
                 }
 
-                return new DataLayer((new FlatDataLayer(nibblearray1, 0)).getData());
+                return new DataLayer().markPoolSafe(new FlatDataLayer(nibblearray1, 0).getData()); // Paper - mark pool use as safe (no auto cleaner)
             } else {
-                return new DataLayer();
+                return new DataLayer().markPoolSafe(); // Paper - mark pool use as safe (no auto cleaner)
             }
         }
     }
@@ -203,7 +203,7 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
                                 ((SkyLightSectionStorage.SkyDataLayerStorageMap) this.updatingSectionData).copyDataLayer(i);
                             }
 
-                            Arrays.fill(this.getDataLayer(i, true).getData(), (byte) -1);
+                            Arrays.fill(this.getDataLayer(i, true).asBytesPoolSafe(), (byte) -1); // Paper
                             k = SectionPos.sectionToBlockCoord(SectionPos.x(i));
                             l = SectionPos.sectionToBlockCoord(SectionPos.y(i));
                             int i1 = SectionPos.sectionToBlockCoord(SectionPos.z(i));
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftChunk.java b/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
index 0f45f4b2486e910d11fd94b260bcd68e49eae31e..77584a2552c0d59d4308342253ad42edaa794c97 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
@@ -298,14 +298,14 @@ public class CraftChunk implements Chunk {
                     sectionSkyLights[i] = emptyLight;
                 } else {
                     sectionSkyLights[i] = new byte[2048];
-                    System.arraycopy(skyLightArray.getData(), 0, sectionSkyLights[i], 0, 2048);
+                    System.arraycopy(skyLightArray.getIfSet(), 0, sectionSkyLights[i], 0, 2048); // Paper
                 }
                 DataLayer emitLightArray = lightengine.getLayerListener(LightLayer.BLOCK).getDataLayerData(SectionPos.of(x, i, z));
                 if (emitLightArray == null) {
                     sectionEmitLights[i] = emptyLight;
                 } else {
                     sectionEmitLights[i] = new byte[2048];
-                    System.arraycopy(emitLightArray.getData(), 0, sectionEmitLights[i], 0, 2048);
+                    System.arraycopy(emitLightArray.getIfSet(), 0, sectionEmitLights[i], 0, 2048); // Paper
                 }
             }
         }