PaperMC/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/PacketPlayOutLightUpdate.java b/src/main/java/net/minecraft/network/protocol/game/PacketPlayOutLightUpdate.java
index 247d969e7d1aa59d9650fce1032aaa09db3903e5..9050ff7180f63c1f5756570446c4d0a8cc767779 100644
--- a/src/main/java/net/minecraft/network/protocol/game/PacketPlayOutLightUpdate.java
+++ b/src/main/java/net/minecraft/network/protocol/game/PacketPlayOutLightUpdate.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.SectionPosition;
 import net.minecraft.network.PacketDataSerializer;
 import net.minecraft.network.protocol.Packet;
+import net.minecraft.server.MCUtil;
+import net.minecraft.server.level.EntityPlayer;
 import net.minecraft.world.level.ChunkCoordIntPair;
 import net.minecraft.world.level.EnumSkyBlock;
 import net.minecraft.world.level.chunk.NibbleArray;
@@ -24,14 +28,43 @@ public class PacketPlayOutLightUpdate implements Packet<PacketListenerPlayOut> {
     private List<byte[]> h;
     private boolean i;
 
+    // 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(EntityPlayer player) {
+        remainingSends.incrementAndGet();
+    }
+
+    @Override
+    public void onPacketDispatchFinish(EntityPlayer 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 PacketPlayOutLightUpdate() {}
 
     public PacketPlayOutLightUpdate(ChunkCoordIntPair chunkcoordintpair, LightEngine lightengine, boolean flag) {
         this.a = chunkcoordintpair.x;
         this.b = chunkcoordintpair.z;
         this.i = flag;
-        this.g = Lists.newArrayList();
-        this.h = Lists.newArrayList();
+        this.g = Lists.newArrayList();cleaner1 = MCUtil.registerListCleaner(this, this.g, NibbleArray::releaseBytes); // Paper
+        this.h = Lists.newArrayList();cleaner2 = MCUtil.registerListCleaner(this, this.h, NibbleArray::releaseBytes); // Paper
 
         for (int i = 0; i < 18; ++i) {
             NibbleArray nibblearray = lightengine.a(EnumSkyBlock.SKY).a(SectionPosition.a(chunkcoordintpair, -1 + i));
@@ -42,7 +75,7 @@ public class PacketPlayOutLightUpdate implements Packet<PacketListenerPlayOut> {
                     this.e |= 1 << i;
                 } else {
                     this.c |= 1 << i;
-                    this.g.add(nibblearray.asBytes().clone());
+                    this.g.add(nibblearray.getCloneIfSet()); // Paper
                 }
             }
 
@@ -51,7 +84,7 @@ public class PacketPlayOutLightUpdate implements Packet<PacketListenerPlayOut> {
                     this.f |= 1 << i;
                 } else {
                     this.d |= 1 << i;
-                    this.h.add(nibblearray1.asBytes().clone());
+                    this.h.add(nibblearray1.getCloneIfSet()); // Paper
                 }
             }
         }
@@ -64,8 +97,8 @@ public class PacketPlayOutLightUpdate implements Packet<PacketListenerPlayOut> {
         this.i = flag;
         this.c = i;
         this.d = j;
-        this.g = Lists.newArrayList();
-        this.h = Lists.newArrayList();
+        this.g = Lists.newArrayList();cleaner1 = MCUtil.registerListCleaner(this, this.g, NibbleArray::releaseBytes); // Paper
+        this.h = Lists.newArrayList();cleaner2 = MCUtil.registerListCleaner(this, this.h, NibbleArray::releaseBytes); // Paper
 
         for (int k = 0; k < 18; ++k) {
             NibbleArray nibblearray;
@@ -73,7 +106,7 @@ public class PacketPlayOutLightUpdate implements Packet<PacketListenerPlayOut> {
             if ((this.c & 1 << k) != 0) {
                 nibblearray = lightengine.a(EnumSkyBlock.SKY).a(SectionPosition.a(chunkcoordintpair, -1 + k));
                 if (nibblearray != null && !nibblearray.c()) {
-                    this.g.add(nibblearray.asBytes().clone());
+                    this.g.add(nibblearray.getCloneIfSet()); // Paper
                 } else {
                     this.c &= ~(1 << k);
                     if (nibblearray != null) {
@@ -85,7 +118,7 @@ public class PacketPlayOutLightUpdate implements Packet<PacketListenerPlayOut> {
             if ((this.d & 1 << k) != 0) {
                 nibblearray = lightengine.a(EnumSkyBlock.BLOCK).a(SectionPosition.a(chunkcoordintpair, -1 + k));
                 if (nibblearray != null && !nibblearray.c()) {
-                    this.h.add(nibblearray.asBytes().clone());
+                    this.h.add(nibblearray.getCloneIfSet()); // Paper
                 } else {
                     this.d &= ~(1 << k);
                     if (nibblearray != null) {
diff --git a/src/main/java/net/minecraft/world/level/chunk/NibbleArray.java b/src/main/java/net/minecraft/world/level/chunk/NibbleArray.java
index 86b4db483787c5fd10461f7d7e90a772ee049599..b82420e9a5d42a4383d24921614fe613c640edb9 100644
--- a/src/main/java/net/minecraft/world/level/chunk/NibbleArray.java
+++ b/src/main/java/net/minecraft/world/level/chunk/NibbleArray.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.SystemUtils;
+import net.minecraft.server.MCUtil;
 
 public class NibbleArray {
 
-    @Nullable
-    protected byte[] a;
+    // 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 NibbleArray markPoolSafe(byte[] bytes) {
+        if (bytes != EMPTY_NIBBLE) this.a = bytes;
+        return markPoolSafe();
+    }
+    public NibbleArray markPoolSafe() {
+        poolSafe = true;
+        return this;
+    }
+    public byte[] getIfSet() {
+        return this.a != null ? this.a : EMPTY_NIBBLE;
+    }
+    public byte[] getCloneIfSet() {
+        if (a == null) {
+            return EMPTY_NIBBLE;
+        }
+        byte[] ret = BYTE_2048.acquire();
+        System.arraycopy(getIfSet(), 0, ret, 0, 2048);
+        return ret;
+    }
+
+    public NibbleArray cloneAndSet(byte[] bytes) {
+        if (bytes != null && bytes != EMPTY_NIBBLE) {
+            this.a = BYTE_2048.acquire();
+            System.arraycopy(bytes, 0, this.a, 0, 2048);
+        }
+        return this;
+    }
+    boolean poolSafe = false;
+    public java.lang.Runnable cleaner;
+    private void registerCleaner() {
+        if (!poolSafe) {
+            cleaner = MCUtil.registerCleaner(this, this.a, NibbleArray::releaseBytes);
+        } else {
+            cleaner = MCUtil.once(() -> NibbleArray.releaseBytes(this.a));
+        }
+    }
+    // Paper end
+    @Nullable protected byte[] a;
+
 
     public NibbleArray() {}
 
     public NibbleArray(byte[] abyte) {
+        // Paper start
+        this(abyte, false);
+    }
+    public NibbleArray(byte[] abyte, boolean isSafe) {
         this.a = abyte;
+        if (!isSafe) this.a = getCloneIfSet(); // Paper - clone for safety
+        registerCleaner();
+        // Paper end
         if (abyte.length != 2048) {
             throw (IllegalArgumentException) SystemUtils.c((Throwable) (new IllegalArgumentException("ChunkNibbleArrays should be 2048 bytes not: " + abyte.length)));
         }
@@ -46,7 +106,8 @@ public class NibbleArray {
 
     public void a(int i, int j) { // PAIL: private -> public
         if (this.a == null) {
-            this.a = new byte[2048];
+            this.a = BYTE_2048.acquire(); // Paper
+            registerCleaner();// Paper
         }
 
         int k = this.d(i);
@@ -68,14 +129,36 @@ public class NibbleArray {
     public byte[] asBytes() {
         if (this.a == null) {
             this.a = 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.a = this.a.clone();
+                cleaner.run(); // release the previously pooled value
+                this.cleaner = null;
+            }
+        }
+        // Paper end
+
+        return this.a;
+    }
+
+    @Nonnull
+    public byte[] asBytesPoolSafe() {
+        if (this.a == null) {
+            this.a = BYTE_2048.acquire(); // Paper
+            registerCleaner(); // Paper
         }
 
+        //noinspection ConstantConditions
         return this.a;
     }
+    // Paper end
 
     public NibbleArray copy() { return this.b(); } // Paper - OBFHELPER
     public NibbleArray b() {
-        return this.a == null ? new NibbleArray() : new NibbleArray((byte[]) this.a.clone());
+        return this.a == null ? new NibbleArray() : new NibbleArray(this.a); // Paper - clone in ctor
     }
 
     public String toString() {
diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkRegionLoader.java b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkRegionLoader.java
index e16e046d165330326ed220c9c440a637007f3137..91bcbf7156dd90b00e2d53bb6bff4abc44ecb721 100644
--- a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkRegionLoader.java
+++ b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkRegionLoader.java
@@ -435,11 +435,11 @@ public class ChunkRegionLoader {
                 }
 
                 if (nibblearray != null && !nibblearray.c()) {
-                    nbttagcompound2.setByteArray("BlockLight", nibblearray.asBytes());
+                    nbttagcompound2.setByteArray("BlockLight", nibblearray.asBytesPoolSafe().clone()); // Paper
                 }
 
                 if (nibblearray1 != null && !nibblearray1.c()) {
-                    nbttagcompound2.setByteArray("SkyLight", nibblearray1.asBytes());
+                    nbttagcompound2.setByteArray("SkyLight", nibblearray1.asBytesPoolSafe().clone()); // Paper
                 }
 
                 nbttaglist.add(nbttagcompound2);
diff --git a/src/main/java/net/minecraft/world/level/lighting/LightEngineStorage.java b/src/main/java/net/minecraft/world/level/lighting/LightEngineStorage.java
index 5b1ff4ff87591dd4ff0b79e4ac6ff0494fc3d0f8..9ba9efb181b9607f25b7c921e69e4c59b182d429 100644
--- a/src/main/java/net/minecraft/world/level/lighting/LightEngineStorage.java
+++ b/src/main/java/net/minecraft/world/level/lighting/LightEngineStorage.java
@@ -156,7 +156,7 @@ public abstract class LightEngineStorage<M extends LightEngineStorageArray<M>> e
     protected NibbleArray j(long i) {
         NibbleArray nibblearray = (NibbleArray) this.i.get(i);
 
-        return nibblearray != null ? nibblearray : new NibbleArray();
+        return nibblearray != null ? nibblearray : new NibbleArray().markPoolSafe(); // Paper
     }
 
     protected void a(LightEngineLayer<?, ?> lightenginelayer, long i) {
@@ -338,12 +338,12 @@ public abstract class LightEngineStorage<M extends LightEngineStorageArray<M>> e
 
     protected void a(long i, @Nullable NibbleArray nibblearray, boolean flag) {
         if (nibblearray != null) {
-            this.i.put(i, nibblearray);
+            NibbleArray remove = this.i.put(i, nibblearray); if (remove != null && remove.cleaner != null) remove.cleaner.run(); // Paper - clean up when removed
             if (!flag) {
                 this.n.add(i);
             }
         } else {
-            this.i.remove(i);
+            NibbleArray remove = this.i.remove(i); 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/LightEngineStorageArray.java b/src/main/java/net/minecraft/world/level/lighting/LightEngineStorageArray.java
index ed7864c552054fc47c6010a094230ce4aebf1c54..da78d4c4b5f8af4648ac82d63c21f6a2a5b73ecb 100644
--- a/src/main/java/net/minecraft/world/level/lighting/LightEngineStorageArray.java
+++ b/src/main/java/net/minecraft/world/level/lighting/LightEngineStorageArray.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.NibbleArray;
 
 public abstract class LightEngineStorageArray<M extends LightEngineStorageArray<M>> {
@@ -34,7 +35,9 @@ public abstract class LightEngineStorageArray<M extends LightEngineStorageArray<
 
     public void a(long i) {
         if (this.isVisible) { throw new IllegalStateException("writing to visible data"); } // Paper - avoid copying light data
-        this.data.queueUpdate(i, ((NibbleArray) this.data.getUpdating(i)).b()); // Paper - avoid copying light data
+        NibbleArray updating = this.data.getUpdating(i); // Paper - pool nibbles
+        this.data.queueUpdate(i, new NibbleArray().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.c();
     }
 
diff --git a/src/main/java/net/minecraft/world/level/lighting/LightEngineStorageSky.java b/src/main/java/net/minecraft/world/level/lighting/LightEngineStorageSky.java
index 64d37f4c6a8167f47c80953a388ea6635490563a..488403a6765598317faedc2d600ae82238e99e39 100644
--- a/src/main/java/net/minecraft/world/level/lighting/LightEngineStorageSky.java
+++ b/src/main/java/net/minecraft/world/level/lighting/LightEngineStorageSky.java
@@ -172,9 +172,9 @@ public class LightEngineStorageSky extends LightEngineStorage<LightEngineStorage
                     j = SectionPosition.a(j, EnumDirection.UP);
                 }
 
-                return new NibbleArray((new NibbleArrayFlat(nibblearray1, 0)).asBytes());
+                return new NibbleArray().markPoolSafe(new NibbleArrayFlat(nibblearray1, 0).asBytes()); // Paper - mark pool use as safe (no auto cleaner)
             } else {
-                return new NibbleArray();
+                return new NibbleArray().markPoolSafe(); // Paper - mark pool use as safe (no auto cleaner)
             }
         }
     }
@@ -203,7 +203,7 @@ public class LightEngineStorageSky extends LightEngineStorage<LightEngineStorage
                                 ((LightEngineStorageSky.a) this.f).a(i);
                             }
 
-                            Arrays.fill(this.a(i, true).asBytes(), (byte) -1);
+                            Arrays.fill(this.a(i, true).asBytesPoolSafe(), (byte) -1); // Paper
                             k = SectionPosition.c(SectionPosition.b(i));
                             l = SectionPosition.c(SectionPosition.c(i));
                             int i1 = SectionPosition.c(SectionPosition.d(i));
diff --git a/src/main/java/net/minecraft/world/level/lighting/NibbleArrayFlat.java b/src/main/java/net/minecraft/world/level/lighting/NibbleArrayFlat.java
index dc059d5f332fdf561c7e410ce9959154de25006a..883a0d94cc0aa9d7cd8ab1ce320af86a9eacd1b8 100644
--- a/src/main/java/net/minecraft/world/level/lighting/NibbleArrayFlat.java
+++ b/src/main/java/net/minecraft/world/level/lighting/NibbleArrayFlat.java
@@ -10,7 +10,7 @@ public class NibbleArrayFlat extends NibbleArray {
 
     public NibbleArrayFlat(NibbleArray nibblearray, int i) {
         super(128);
-        System.arraycopy(nibblearray.asBytes(), i * 128, this.a, 0, 128);
+        System.arraycopy(nibblearray.getIfSet(), i * 128, this.a, 0, 128); // Paper
     }
 
     @Override
@@ -20,7 +20,7 @@ public class NibbleArrayFlat extends NibbleArray {
 
     @Override
     public byte[] asBytes() {
-        byte[] abyte = new byte[2048];
+        byte[] abyte = BYTE_2048.acquire(); // Paper
 
         for (int i = 0; i < 16; ++i) {
             System.arraycopy(this.a, 0, abyte, i * 128, 128);
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftChunk.java b/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
index 8ade81a693286cdf65f8c0eeca2121a217c90350..98ab124b4dca9387b4793cef68a33c67aed64e21 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
@@ -299,14 +299,14 @@ public class CraftChunk implements Chunk {
                     sectionSkyLights[i] = emptyLight;
                 } else {
                     sectionSkyLights[i] = new byte[2048];
-                    System.arraycopy(skyLightArray.asBytes(), 0, sectionSkyLights[i], 0, 2048);
+                    System.arraycopy(skyLightArray.getIfSet(), 0, sectionSkyLights[i], 0, 2048); // Paper
                 }
                 NibbleArray emitLightArray = lightengine.a(EnumSkyBlock.BLOCK).a(SectionPosition.a(x, i, z));
                 if (emitLightArray == null) {
                     sectionEmitLights[i] = emptyLight;
                 } else {
                     sectionEmitLights[i] = new byte[2048];
-                    System.arraycopy(emitLightArray.asBytes(), 0, sectionEmitLights[i], 0, 2048);
+                    System.arraycopy(emitLightArray.getIfSet(), 0, sectionEmitLights[i], 0, 2048); // Paper
                 }
             }
         }