PaperMC/patches/server/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 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/network/protocol/game/ClientboundLightUpdatePacket.java
+++ b/src/main/java/net/minecraft/network/protocol/game/ClientboundLightUpdatePacket.java
@@ -0,0 +0,0 @@ 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;
@@ -0,0 +0,0 @@ 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;
@@ -0,0 +0,0 @@ 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)) {
@@ -0,0 +0,0 @@ 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 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/level/chunk/DataLayer.java
+++ b/src/main/java/net/minecraft/world/level/chunk/DataLayer.java
@@ -0,0 +0,0 @@ public final 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("DataLayer should be 2048 bytes not: " + bytes.length)));
         }
@@ -0,0 +0,0 @@ public final class DataLayer {
 
     private void set(int index, int value) {
         if (this.data == null) {
-            this.data = new byte[2048];
+            this.data = BYTE_2048.acquire(); // Paper
+            registerCleaner();// Paper
         }
 
         int k = DataLayer.getByteIndex(index);
@@ -0,0 +0,0 @@ public final 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 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 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
@@ -0,0 +0,0 @@ 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 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/level/lighting/DataLayerStorageMap.java
+++ b/src/main/java/net/minecraft/world/level/lighting/DataLayerStorageMap.java
@@ -0,0 +0,0 @@ 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/LayerLightSectionStorage.java b/src/main/java/net/minecraft/world/level/lighting/LayerLightSectionStorage.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/level/lighting/LayerLightSectionStorage.java
+++ b/src/main/java/net/minecraft/world/level/lighting/LayerLightSectionStorage.java
@@ -0,0 +0,0 @@ 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) {
@@ -0,0 +0,0 @@ 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 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/world/level/lighting/SkyLightSectionStorage.java
+++ b/src/main/java/net/minecraft/world/level/lighting/SkyLightSectionStorage.java
@@ -0,0 +0,0 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
 
                 return repeatFirstLayer(dataLayer2);
             } else {
-                return new DataLayer();
+                return new DataLayer().markPoolSafe(); // Paper - mark pool use as safe (no auto cleaner)
             }
         }
     }
 
     private static DataLayer repeatFirstLayer(DataLayer source) {
         if (source.isEmpty()) {
-            return new DataLayer();
+            return new DataLayer().markPoolSafe(); // Paper - mark pool use as safe (no auto cleaner)
         } else {
             byte[] bs = source.getData();
             byte[] cs = new byte[2048];
@@ -0,0 +0,0 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
                 System.arraycopy(bs, 0, cs, i * 128, 128);
             }
 
-            return new DataLayer(cs);
+            return new DataLayer(cs).markPoolSafe(cs); // Paper - mark pool use as safe (no auto cleaner)
         }
     }
 
@@ -0,0 +0,0 @@ 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 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
@@ -0,0 +0,0 @@ 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
                 }
             }
         }