PaperMC/patches/server/0453-Stop-copy-on-write-operations-for-updating-light-dat.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <spottedleaf@spottedleaf.dev>
Date: Mon, 27 Apr 2020 04:05:38 -0700
Subject: [PATCH] Stop copy-on-write operations for updating light data

Causes huge memory allocations + gc issues

diff --git a/src/main/java/net/minecraft/world/level/lighting/BlockLightSectionStorage.java b/src/main/java/net/minecraft/world/level/lighting/BlockLightSectionStorage.java
index 573cdb0897978eef8f5fc906ed4928293f4b2ab9..314b46f0becd088d26956b45981217b128d539cb 100644
--- a/src/main/java/net/minecraft/world/level/lighting/BlockLightSectionStorage.java
+++ b/src/main/java/net/minecraft/world/level/lighting/BlockLightSectionStorage.java
@@ -9,7 +9,7 @@ import net.minecraft.world.level.chunk.LightChunkGetter;
 
 public class BlockLightSectionStorage extends LayerLightSectionStorage<BlockLightSectionStorage.BlockDataLayerStorageMap> {
     protected BlockLightSectionStorage(LightChunkGetter chunkProvider) {
-        super(LightLayer.BLOCK, chunkProvider, new BlockLightSectionStorage.BlockDataLayerStorageMap(new Long2ObjectOpenHashMap<>()));
+        super(LightLayer.BLOCK, chunkProvider, new BlockLightSectionStorage.BlockDataLayerStorageMap(new com.destroystokyo.paper.util.map.QueuedChangesMapLong2Object<>(), false)); // Paper - avoid copying light data
     }
 
     @Override
@@ -20,13 +20,13 @@ public class BlockLightSectionStorage extends LayerLightSectionStorage<BlockLigh
     }
 
     protected static final class BlockDataLayerStorageMap extends DataLayerStorageMap<BlockLightSectionStorage.BlockDataLayerStorageMap> {
-        public BlockDataLayerStorageMap(Long2ObjectOpenHashMap<DataLayer> arrays) {
-            super(arrays);
+        public BlockDataLayerStorageMap(com.destroystokyo.paper.util.map.QueuedChangesMapLong2Object<DataLayer> long2objectopenhashmap, boolean isVisible) { // Paper - avoid copying light data
+            super(long2objectopenhashmap, isVisible); // Paper - avoid copying light data
         }
 
         @Override
         public BlockLightSectionStorage.BlockDataLayerStorageMap copy() {
-            return new BlockLightSectionStorage.BlockDataLayerStorageMap(this.map.clone());
+            return new BlockDataLayerStorageMap(this.data, true); // Paper - avoid copying light data
         }
     }
 }
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 67ff66e232592203cf8dad605ad01eabc4dded89..f357a3473682c2d37a20fb862522c67b9979402a 100644
--- a/src/main/java/net/minecraft/world/level/lighting/DataLayerStorageMap.java
+++ b/src/main/java/net/minecraft/world/level/lighting/DataLayerStorageMap.java
@@ -9,10 +9,23 @@ public abstract class DataLayerStorageMap<M extends DataLayerStorageMap<M>> {
     private final long[] lastSectionKeys = new long[2];
     private final DataLayer[] lastSections = new DataLayer[2];
     private boolean cacheEnabled;
-    protected final Long2ObjectOpenHashMap<DataLayer> map;
+    protected final com.destroystokyo.paper.util.map.QueuedChangesMapLong2Object<DataLayer> data; // Paper - avoid copying light data
+    protected final boolean isVisible; // Paper - avoid copying light data
+    java.util.function.Function<Long, DataLayer> lookup; // Paper - faster branchless lookup
 
-    protected DataLayerStorageMap(Long2ObjectOpenHashMap<DataLayer> arrays) {
-        this.map = arrays;
+    // Paper start - avoid copying light data
+    protected DataLayerStorageMap(com.destroystokyo.paper.util.map.QueuedChangesMapLong2Object<DataLayer> data, boolean isVisible) {
+        if (isVisible) {
+            data.performUpdatesLockMap();
+        }
+        this.data = data;
+        this.isVisible = isVisible;
+        if (isVisible) {
+            lookup = data::getVisibleAsync;
+        } else {
+            lookup = data::getUpdating;
+        }
+        // Paper end - avoid copying light data
         this.clearCache();
         this.cacheEnabled = true;
     }
@@ -20,16 +33,17 @@ public abstract class DataLayerStorageMap<M extends DataLayerStorageMap<M>> {
     public abstract M copy();
 
     public void copyDataLayer(long pos) {
-        this.map.put(pos, this.map.get(pos).copy());
+        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
         this.clearCache();
     }
 
     public boolean hasLayer(long chunkPos) {
-        return this.map.containsKey(chunkPos);
+        return lookup.apply(chunkPos) != null; // Paper - avoid copying light data
     }
 
     @Nullable
-    public DataLayer getLayer(long chunkPos) {
+    public final DataLayer getLayer(long chunkPos) { // Paper - final
         if (this.cacheEnabled) {
             for(int i = 0; i < 2; ++i) {
                 if (chunkPos == this.lastSectionKeys[i]) {
@@ -38,7 +52,7 @@ public abstract class DataLayerStorageMap<M extends DataLayerStorageMap<M>> {
             }
         }
 
-        DataLayer dataLayer = this.map.get(chunkPos);
+        DataLayer dataLayer = lookup.apply(chunkPos); // Paper - avoid copying light data
         if (dataLayer == null) {
             return null;
         } else {
@@ -58,11 +72,13 @@ public abstract class DataLayerStorageMap<M extends DataLayerStorageMap<M>> {
 
     @Nullable
     public DataLayer removeLayer(long chunkPos) {
-        return this.map.remove(chunkPos);
+        if (this.isVisible) { throw new IllegalStateException("writing to visible data"); } // Paper - avoid copying light data
+        return (DataLayer) this.data.queueRemove(chunkPos); // Paper - avoid copying light data
     }
 
     public void setLayer(long pos, DataLayer data) {
-        this.map.put(pos, data);
+        if (this.isVisible) { throw new IllegalStateException("writing to visible data"); } // Paper - avoid copying light data
+        this.data.queueUpdate(pos, data); // Paper - avoid copying light data
     }
 
     public void 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 99a758341d4b31cb1703fdce0a257f65ed602ca0..4f7b63f2cc8a69fa8efb3a84f6abc3d3dcf05b49 100644
--- a/src/main/java/net/minecraft/world/level/lighting/LayerLightSectionStorage.java
+++ b/src/main/java/net/minecraft/world/level/lighting/LayerLightSectionStorage.java
@@ -28,7 +28,7 @@ public abstract class LayerLightSectionStorage<M extends DataLayerStorageMap<M>>
     protected final LongSet dataSectionSet = new LongOpenHashSet();
     protected final LongSet toMarkNoData = new LongOpenHashSet();
     protected final LongSet toMarkData = new LongOpenHashSet();
-    protected volatile M visibleSectionData;
+    protected volatile M e_visible; protected final Object visibleUpdateLock = new Object(); // Paper - diff on change, should be "visible" - force compile fail on usage change
     protected final M updatingSectionData;
     protected final LongSet changedSections = new LongOpenHashSet();
     protected final LongSet sectionsAffectedByLightUpdates = new LongOpenHashSet();
@@ -43,8 +43,8 @@ public abstract class LayerLightSectionStorage<M extends DataLayerStorageMap<M>>
         this.layer = lightType;
         this.chunkSource = chunkProvider;
         this.updatingSectionData = lightData;
-        this.visibleSectionData = lightData.copy();
-        this.visibleSectionData.disableCache();
+        this.e_visible = lightData.copy(); // Paper - avoid copying light dat
+        this.e_visible.disableCache(); // Paper - avoid copying light dat
     }
 
     protected boolean storingLightForSection(long sectionPos) {
@@ -53,7 +53,15 @@ public abstract class LayerLightSectionStorage<M extends DataLayerStorageMap<M>>
 
     @Nullable
     protected DataLayer getDataLayer(long sectionPos, boolean cached) {
-        return this.getDataLayer((M)(cached ? this.updatingSectionData : this.visibleSectionData), sectionPos);
+        // Paper start - avoid copying light data
+        if (cached) {
+            return this.getDataLayer(this.updatingSectionData, sectionPos);
+        } else {
+            synchronized (this.visibleUpdateLock) {
+                return this.getDataLayer(this.e_visible, sectionPos);
+            }
+        }
+        // Paper end - avoid copying light data
     }
 
     @Nullable
@@ -343,9 +351,11 @@ public abstract class LayerLightSectionStorage<M extends DataLayerStorageMap<M>>
 
     protected void swapSectionMap() {
         if (!this.changedSections.isEmpty()) {
+            synchronized (this.visibleUpdateLock) { // Paper - avoid copying light data
             M dataLayerStorageMap = this.updatingSectionData.copy();
             dataLayerStorageMap.disableCache();
-            this.visibleSectionData = dataLayerStorageMap;
+            this.e_visible = dataLayerStorageMap; // Paper - avoid copying light data
+            } // Paper - avoid copying light data
             this.changedSections.clear();
         }
 
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 1f6ed4309f0f5e06cd2981864feaa6ea16df0350..9797254e981d08d3934f7ca8f369dd78a6ef1a48 100644
--- a/src/main/java/net/minecraft/world/level/lighting/SkyLightSectionStorage.java
+++ b/src/main/java/net/minecraft/world/level/lighting/SkyLightSectionStorage.java
@@ -21,7 +21,7 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
     private volatile boolean hasSourceInconsistencies;
 
     protected SkyLightSectionStorage(LightChunkGetter chunkProvider) {
-        super(LightLayer.SKY, chunkProvider, new SkyLightSectionStorage.SkyDataLayerStorageMap(new Long2ObjectOpenHashMap<>(), new Long2IntOpenHashMap(), Integer.MAX_VALUE));
+        super(LightLayer.SKY, chunkProvider, new SkyLightSectionStorage.SkyDataLayerStorageMap(new com.destroystokyo.paper.util.map.QueuedChangesMapLong2Object<>(), new com.destroystokyo.paper.util.map.QueuedChangesMapLong2Int(), Integer.MAX_VALUE, false)); // Paper - avoid copying light data
     }
 
     @Override
@@ -32,8 +32,9 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
     protected int getLightValue(long blockPos, boolean cached) {
         long l = SectionPos.blockToSection(blockPos);
         int i = SectionPos.y(l);
-        SkyLightSectionStorage.SkyDataLayerStorageMap skyDataLayerStorageMap = cached ? this.updatingSectionData : this.visibleSectionData;
-        int j = skyDataLayerStorageMap.topSections.get(SectionPos.getZeroNode(l));
+        synchronized (this.visibleUpdateLock) { // Paper - avoid copying light data
+        SkyLightSectionStorage.SkyDataLayerStorageMap skyDataLayerStorageMap = (SkyLightSectionStorage.SkyDataLayerStorageMap) this.e_visible; // Paper - avoid copying light data - must be after lock acquire
+        int j = skyDataLayerStorageMap.otherData.getVisibleAsync(SectionPos.getZeroNode(l)); // Paper - avoid copying light data
         if (j != skyDataLayerStorageMap.currentLowestY && i < j) {
             DataLayer dataLayer = this.getDataLayer(skyDataLayerStorageMap, l);
             if (dataLayer == null) {
@@ -52,6 +53,7 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
         } else {
             return cached && !this.lightOnInSection(l) ? 0 : 15;
         }
+        } // Paper - avoid copying light data
     }
 
     @Override
@@ -59,13 +61,13 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
         int i = SectionPos.y(sectionPos);
         if ((this.updatingSectionData).currentLowestY > i) {
             (this.updatingSectionData).currentLowestY = i;
-            (this.updatingSectionData).topSections.defaultReturnValue((this.updatingSectionData).currentLowestY);
+            (this.updatingSectionData).otherData.queueDefaultReturnValue((this.updatingSectionData).currentLowestY); // Paper - avoid copying light data
         }
 
         long l = SectionPos.getZeroNode(sectionPos);
-        int j = (this.updatingSectionData).topSections.get(l);
+        int j = (this.updatingSectionData).otherData.getUpdating(l); // Paper - avoid copying light data
         if (j < i + 1) {
-            (this.updatingSectionData).topSections.put(l, i + 1);
+            (this.updatingSectionData).otherData.queueUpdate(l, i + 1); // Paper - avoid copying light data
             if (this.columnsWithSkySources.contains(l)) {
                 this.queueAddSource(sectionPos);
                 if (j > (this.updatingSectionData).currentLowestY) {
@@ -102,19 +104,19 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
         }
 
         int i = SectionPos.y(sectionPos);
-        if ((this.updatingSectionData).topSections.get(l) == i + 1) {
+        if ((this.updatingSectionData).otherData.getUpdating(l) == i + 1) { // Paper - avoid copying light data
             long m;
             for(m = sectionPos; !this.storingLightForSection(m) && this.hasSectionsBelow(i); m = SectionPos.offset(m, Direction.DOWN)) {
                 --i;
             }
 
             if (this.storingLightForSection(m)) {
-                (this.updatingSectionData).topSections.put(l, i + 1);
+                (this.updatingSectionData).otherData.queueUpdate(l, i + 1); // Paper - avoid copying light data
                 if (bl) {
                     this.queueAddSource(m);
                 }
             } else {
-                (this.updatingSectionData).topSections.remove(l);
+                (this.updatingSectionData).otherData.queueRemove(l); // Paper - avoid copying light data
             }
         }
 
@@ -128,7 +130,7 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
     protected void enableLightSources(long columnPos, boolean enabled) {
         this.runAllUpdates();
         if (enabled && this.columnsWithSkySources.add(columnPos)) {
-            int i = (this.updatingSectionData).topSections.get(columnPos);
+            int i = (this.updatingSectionData).otherData.getUpdating(columnPos); // Paper - avoid copying light data
             if (i != (this.updatingSectionData).currentLowestY) {
                 long l = SectionPos.asLong(SectionPos.x(columnPos), i - 1, SectionPos.z(columnPos));
                 this.queueAddSource(l);
@@ -152,7 +154,7 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
             return dataLayer;
         } else {
             long l = SectionPos.offset(sectionPos, Direction.UP);
-            int i = (this.updatingSectionData).topSections.get(SectionPos.getZeroNode(sectionPos));
+            int i = (this.updatingSectionData).otherData.getUpdating(SectionPos.getZeroNode(sectionPos)); // Paper - avoid copying light data
             if (i != (this.updatingSectionData).currentLowestY && SectionPos.y(l) < i) {
                 DataLayer dataLayer2;
                 while((dataLayer2 = this.getDataLayer(l, true)) == null) {
@@ -275,7 +277,7 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
 
     protected boolean isAboveData(long sectionPos) {
         long l = SectionPos.getZeroNode(sectionPos);
-        int i = (this.updatingSectionData).topSections.get(l);
+        int i = (this.updatingSectionData).otherData.getUpdating(l); // Paper - avoid copying light data
         return i == (this.updatingSectionData).currentLowestY || SectionPos.y(sectionPos) >= i;
     }
 
@@ -286,18 +288,21 @@ public class SkyLightSectionStorage extends LayerLightSectionStorage<SkyLightSec
 
     protected static final class SkyDataLayerStorageMap extends DataLayerStorageMap<SkyLightSectionStorage.SkyDataLayerStorageMap> {
         int currentLowestY;
-        final Long2IntOpenHashMap topSections;
-
-        public SkyDataLayerStorageMap(Long2ObjectOpenHashMap<DataLayer> arrays, Long2IntOpenHashMap columnToTopSection, int minSectionY) {
-            super(arrays);
-            this.topSections = columnToTopSection;
-            columnToTopSection.defaultReturnValue(minSectionY);
+        private final com.destroystokyo.paper.util.map.QueuedChangesMapLong2Int otherData; // Paper - avoid copying light data
+
+        // Paper start - avoid copying light data
+        public SkyDataLayerStorageMap(com.destroystokyo.paper.util.map.QueuedChangesMapLong2Object<DataLayer> arrays, com.destroystokyo.paper.util.map.QueuedChangesMapLong2Int columnToTopSection, int minSectionY, boolean isVisible) {
+            super(arrays, isVisible);
+            this.otherData = columnToTopSection;
+            otherData.queueDefaultReturnValue(minSectionY);
+            // Paper end
             this.currentLowestY = minSectionY;
         }
 
         @Override
         public SkyLightSectionStorage.SkyDataLayerStorageMap copy() {
-            return new SkyLightSectionStorage.SkyDataLayerStorageMap(this.map.clone(), this.topSections.clone(), this.currentLowestY);
+            this.otherData.performUpdatesLockMap(); // Paper - avoid copying light data
+            return new SkyLightSectionStorage.SkyDataLayerStorageMap(this.data, this.otherData, this.currentLowestY, true); // Paper - avoid copying light data
         }
     }
 }