Paper/patches/server/0478-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 :)

1.17 update note: ClientboundLightUpdatePacket has has made changes which necessitate updating this patch

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 24d5a44cb81ec5f10bfcce002a193f4566de88fc..d8be2ad889f46491e50404916fb4ae0de5f42098 100644
--- a/src/main/java/net/minecraft/network/protocol/game/ClientboundLightUpdatePacket.java
+++ b/src/main/java/net/minecraft/network/protocol/game/ClientboundLightUpdatePacket.java
@@ -2,11 +2,14 @@ package net.minecraft.network.protocol.game;
 
 import com.google.common.collect.Lists;
 import java.util.BitSet;
+import io.netty.channel.ChannelFuture; // Paper
 import java.util.List;
 import javax.annotation.Nullable;
 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;
@@ -22,6 +25,35 @@ public class ClientboundLightUpdatePacket implements Packet<ClientGamePacketList
     private final List<byte[]> skyUpdates;
     private final List<byte[]> blockUpdates;
     private final 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(ChunkPos chunkPos, LevelLightEngine lightProvider, @Nullable BitSet bitSet, @Nullable BitSet bitSet2, boolean nonEdge) {
         this.x = chunkPos.x;
@@ -31,8 +63,8 @@ public class ClientboundLightUpdatePacket implements Packet<ClientGamePacketList
         this.blockYMask = new BitSet();
         this.emptySkyYMask = new BitSet();
         this.emptyBlockYMask = new BitSet();
-        this.skyUpdates = Lists.newArrayList();
-        this.blockUpdates = Lists.newArrayList();
+        this.skyUpdates = Lists.newArrayList();this.cleaner1 = MCUtil.registerListCleaner(this, this.skyUpdates, DataLayer::releaseBytes); // Paper
+        this.blockUpdates = Lists.newArrayList();this.cleaner2 = MCUtil.registerListCleaner(this, this.blockUpdates, DataLayer::releaseBytes); // Paper
 
         for(int i = 0; i < lightProvider.getLightSectionCount(); ++i) {
             if (bitSet == null || bitSet.get(i)) {
@@ -53,7 +85,7 @@ public class ClientboundLightUpdatePacket implements Packet<ClientGamePacketList
                 bitSet2.set(i);
             } else {
                 bitSet.set(i);
-                list.add((byte[])dataLayer.getData().clone());
+                list.add((byte[])dataLayer.getCloneIfSet()); // Paper
             }
         }
 
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 88a2a5c3d588c15989f7cf6df9d2afc3d2ed8ae9..25570730f376665ca6477263d3b3f94d725ecd21 100644
--- a/src/main/java/net/minecraft/world/level/chunk/DataLayer.java
+++ b/src/main/java/net/minecraft/world/level/chunk/DataLayer.java
@@ -12,11 +12,65 @@ public class DataLayer {
     private static final int NIBBLE_SIZE = 4;
     @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 com.destroystokyo.paper.util.pooled.PooledObjects<byte[]> BYTE_2048 = new com.destroystokyo.paper.util.pooled.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 = net.minecraft.server.MCUtil.registerCleaner(this, this.data, DataLayer::releaseBytes);
+        } else {
+            cleaner = net.minecraft.server.MCUtil.once(() -> DataLayer.releaseBytes(this.data));
+        }
+    }
     public DataLayer() {}
 
     public DataLayer(byte[] bytes) {
+        // Paper start
+        this(bytes, false);
+    }
+    public DataLayer(byte[] bytes, boolean isSafe) {
         this.data = bytes;
+        if (!isSafe) this.data = getCloneIfSet(); // Paper - clone for safety
+        registerCleaner();
+        // Paper end
         if (bytes.length != 2048) {
             throw (IllegalArgumentException) Util.pauseInIde((Throwable) (new IllegalArgumentException("ChunkNibbleArrays should be 2048 bytes not: " + bytes.length)));
         }
@@ -50,7 +104,8 @@ 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);
@@ -72,13 +127,33 @@ 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;
     }
 
+    @javax.annotation.Nonnull
+    public byte[] asBytesPoolSafe() {
+        if (this.data == null) {
+            this.data = BYTE_2048.acquire(); // Paper
+            registerCleaner(); // Paper
+        }
+
+        return this.data;
+    }
+    // Paper end
     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 1f95ac18990822a64f0bb2af947693c4b88cdf73..e1330caba0574c94e5343ea1e444b511edf07b05 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
@@ -481,11 +481,11 @@ 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 f357a3473682c2d37a20fb862522c67b9979402a..52682471adc13dffc0383fc4abacbd3397f3bb10 100644
--- a/src/main/java/net/minecraft/world/level/lighting/DataLayerStorageMap.java
+++ b/src/main/java/net/minecraft/world/level/lighting/DataLayerStorageMap.java
@@ -34,7 +34,9 @@ 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) net.minecraft.server.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 0a65818e68605a3fa944c2de808ebc069f3f8007..cdc7d890841818f615aa09b6068cf98c3936e9a7 100644
--- a/src/main/java/net/minecraft/world/level/lighting/FlatDataLayer.java
+++ b/src/main/java/net/minecraft/world/level/lighting/FlatDataLayer.java
@@ -11,7 +11,7 @@ public class FlatDataLayer extends DataLayer {
 
     public FlatDataLayer(DataLayer chunkNibbleArray, int offset) {
         super(128);
-        System.arraycopy(chunkNibbleArray.getData(), offset * 128, this.data, 0, 128);
+        System.arraycopy(chunkNibbleArray.getIfSet(), offset * 128, this.data, 0, 128); // Paper
     }
 
     @Override
@@ -21,7 +21,7 @@ public class FlatDataLayer extends DataLayer {
 
     @Override
     public byte[] getData() {
-        byte[] bs = new byte[2048];
+        byte[] bs = BYTE_2048.acquire(); // Paper
 
         for(int i = 0; i < 16; ++i) {
             System.arraycopy(this.data, 0, bs, 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 cc9eb8273d5157fb649d84a3ec589b0b923b5bc9..fd1cdb6e2023713f947b9497c605cf6f4bae8994 100644
--- a/src/main/java/net/minecraft/world/level/lighting/LayerLightSectionStorage.java
+++ b/src/main/java/net/minecraft/world/level/lighting/LayerLightSectionStorage.java
@@ -162,7 +162,7 @@ public abstract class LayerLightSectionStorage<M extends DataLayerStorageMap<M>>
 
     protected DataLayer createDataLayer(long sectionPos) {
         DataLayer dataLayer = this.queuedSections.get(sectionPos);
-        return dataLayer != null ? dataLayer : new DataLayer();
+        return dataLayer != null ? dataLayer : new DataLayer().markPoolSafe(); // Paper
     }
 
     protected void clearQueuedSectionBlocks(LayerLightEngine<?, ?> storage, long sectionPos) {
@@ -321,12 +321,12 @@ public abstract class LayerLightSectionStorage<M extends DataLayerStorageMap<M>>
 
     protected void queueSectionData(long sectionPos, @Nullable DataLayer array, boolean bl) {
         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 (!bl) {
                 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 f6df52403a1068a0779e4ff8c2ce5dc06176e061..7dc194b4f04b2d59dcb100b0a3b2ca0132f832cf 100644
--- a/src/main/java/net/minecraft/world/level/lighting/SkyLightSectionStorage.java
+++ b/src/main/java/net/minecraft/world/level/lighting/SkyLightSectionStorage.java
@@ -161,9 +161,9 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
                     l = SectionPos.offset(l, Direction.UP);
                 }
 
-                return new DataLayer((new FlatDataLayer(dataLayer2, 0)).getData());
+                return new DataLayer().markPoolSafe(new FlatDataLayer(dataLayer2, 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)
             }
         }
     }
@@ -182,7 +182,7 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
                                 this.updatingSectionData.copyDataLayer(l);
                             }
 
-                            Arrays.fill(this.getDataLayer(l, true).getData(), (byte)-1);
+                            Arrays.fill(this.getDataLayer(l, true).asBytesPoolSafe(), (byte)-1); // Paper
                             int j = SectionPos.sectionToBlockCoord(SectionPos.x(l));
                             int k = SectionPos.sectionToBlockCoord(SectionPos.y(l));
                             int m = SectionPos.sectionToBlockCoord(SectionPos.z(l));
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftChunk.java b/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
index 4dd7cea1eec5ec55a3700ce9786da8a513e72a28..91145e3dff181ab3a8da3fc30378e672fa58e713 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
@@ -286,14 +286,14 @@ public class CraftChunk implements Chunk {
                     sectionSkyLights[i] = CraftChunk.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] = CraftChunk.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
                 }
             }
         }