Paper/Spigot-Server-Patches/0537-Optimize-Light-Engine.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Thu, 4 Jun 2020 22:43:29 -0400
Subject: [PATCH] Optimize Light Engine

Massive update to light to improve performance and chunk loading/generation.

1) Massive bit packing/unpacking optimizations and inlining.
  A lot of performance has to do with constant packing and unpacking of bits.
  We now inline a most bit operations, and re-use base x/y/z bits in many places.
  This helps with cpu level processing to just do all the math at once instead
  of having to jump in and out of function calls.

  This much logic also is likely over the JVM Inline limit for JIT too.
2) Applied a few of JellySquid's Phosphor mod optimizations such as
  - ensuring we don't notify neighbor chunks when neighbor chunk doesn't need to be notified
  - reduce hasLight checks in initializing light, and prob some more, they are tagged JellySquid where phosphor influence was used.
3) Optimize hot path accesses to getting updating chunk to have less branching
4) Optimize getBlock accesses to have less branching, and less unpacking
5) Have a separate urgent bucket for chunk light tasks. These tasks will always cut in line over non blocking light tasks.
6) Retain chunk priority while light tasks are enqueued. So if a task comes in at high priority but the queue is full
   of tasks already at a lower priority, before the task was simply added to the end. Now it can cut in line to the front.
   this applies for both urgent and non urgent tasks.
7) Buffer non urgent tasks even if queueUpdate is called multiple times to improve efficiency.
8) Fix NPE risk that crashes server in getting nibble data

diff --git a/src/main/java/net/minecraft/server/Block.java b/src/main/java/net/minecraft/server/Block.java
index d051a54aa04326f84e211cd68ddd2bb209230770..bd7a92599b4182739aafef9eeaaf8665d2f9f954 100644
--- a/src/main/java/net/minecraft/server/Block.java
+++ b/src/main/java/net/minecraft/server/Block.java
@@ -309,7 +309,7 @@ public class Block implements IMaterial {
         return false;
     }
 
-    @Deprecated
+    public final boolean canOcclude(IBlockData blockData) { return n(blockData); } @Deprecated // Paper - OBFHELPER
     public final boolean n(IBlockData iblockdata) {
         return this.j;
     }
diff --git a/src/main/java/net/minecraft/server/ChunkProviderServer.java b/src/main/java/net/minecraft/server/ChunkProviderServer.java
index 340d6e992786e8877243ccb472b462e88ec1e6fb..d07fcc0c51679104506d81acfdee6f391f30c0a0 100644
--- a/src/main/java/net/minecraft/server/ChunkProviderServer.java
+++ b/src/main/java/net/minecraft/server/ChunkProviderServer.java
@@ -1089,12 +1089,13 @@ public class ChunkProviderServer extends IChunkProvider {
             if (ChunkProviderServer.this.tickDistanceManager()) {
                 return true;
             } else {
-                ChunkProviderServer.this.lightEngine.queueUpdate();
+                //ChunkProviderServer.this.lightEngine.queueUpdate(); // Paper - move down
                 return super.executeNext() || execChunkTask; // Paper
             }
         } finally {
             playerChunkMap.chunkLoadConversionCallbackExecutor.run(); // Paper - Add chunk load conversion callback executor to prevent deadlock due to recursion in the chunk task queue sorter
             playerChunkMap.callbackExecutor.run();
+            ChunkProviderServer.this.lightEngine.queueUpdate(); // Paper - always run, this is rate limited now
         }
         // CraftBukkit end
         }
diff --git a/src/main/java/net/minecraft/server/IBlockData.java b/src/main/java/net/minecraft/server/IBlockData.java
index 296b41bf36ee1ace5bd9db2b810bf926b5f5278f..b39554faf235b6f81c86542673dfb4508d4c3e5a 100644
--- a/src/main/java/net/minecraft/server/IBlockData.java
+++ b/src/main/java/net/minecraft/server/IBlockData.java
@@ -24,6 +24,7 @@ public class IBlockData extends BlockDataAbstract<Block, IBlockData> implements
     private final boolean e;
     private final boolean isAir; // Paper
     private final boolean isTicking; // Paper
+    private final boolean canOcclude; // Paper
 
     public IBlockData(Block block, ImmutableMap<IBlockState<?>, Comparable<?>> immutablemap) {
         super(block, immutablemap);
@@ -31,6 +32,7 @@ public class IBlockData extends BlockDataAbstract<Block, IBlockData> implements
         this.e = block.o(this);
         this.isAir = this.getBlock().isAir(this); // Paper
         this.isTicking = this.getBlock().isTicking(this); // Paper
+        this.canOcclude = this.getBlock().canOcclude(this); // Paper
     }
 
     public void c() {
@@ -83,7 +85,7 @@ public class IBlockData extends BlockDataAbstract<Block, IBlockData> implements
         return this.c == null || this.c.h;
     }
 
-    public boolean g() {
+    public final boolean g() { // Paper
         return this.e;
     }
 
@@ -151,8 +153,8 @@ public class IBlockData extends BlockDataAbstract<Block, IBlockData> implements
         return this.c != null ? this.c.c : this.getBlock().k(this, iblockaccess, blockposition);
     }
 
-    public boolean o() {
-        return this.c != null ? this.c.b : this.getBlock().n(this);
+    public final boolean o() { // Paper
+        return canOcclude; // Paper
     }
 
     public VoxelShape getShape(IBlockAccess iblockaccess, BlockPosition blockposition) {
diff --git a/src/main/java/net/minecraft/server/LightEngineBlock.java b/src/main/java/net/minecraft/server/LightEngineBlock.java
index 07fadc21ee12138b52cc77c50da536fec5b032f5..86868bedc65948b00edc8a7b6f219b85cc8c6374 100644
--- a/src/main/java/net/minecraft/server/LightEngineBlock.java
+++ b/src/main/java/net/minecraft/server/LightEngineBlock.java
@@ -13,9 +13,11 @@ public final class LightEngineBlock extends LightEngineLayer<LightEngineStorageB
     }
 
     private int d(long i) {
-        int j = BlockPosition.b(i);
-        int k = BlockPosition.c(i);
-        int l = BlockPosition.d(i);
+        // Paper start - inline math
+        int j = (int) (i >> 38);
+        int k = (int) ((i << 52) >> 52);
+        int l = (int) ((i << 26) >> 38);
+        // Paper end
         IBlockAccess iblockaccess = this.a.c(j >> 4, l >> 4);
 
         return iblockaccess != null ? iblockaccess.h(this.f.d(j, k, l)) : 0;
@@ -30,25 +32,33 @@ public final class LightEngineBlock extends LightEngineLayer<LightEngineStorageB
         } else if (k >= 15) {
             return k;
         } else {
-            int l = Integer.signum(BlockPosition.b(j) - BlockPosition.b(i));
-            int i1 = Integer.signum(BlockPosition.c(j) - BlockPosition.c(i));
-            int j1 = Integer.signum(BlockPosition.d(j) - BlockPosition.d(i));
+            // Paper start - reuse math - credit to JellySquid for idea
+            int jx = (int) (j >> 38);
+            int jy = (int) ((j << 52) >> 52);
+            int jz = (int) ((j << 26) >> 38);
+            int ix = (int) (i >> 38);
+            int iy = (int) ((i << 52) >> 52);
+            int iz = (int) ((i << 26) >> 38);
+            int l = Integer.signum(jx - ix);
+            int i1 = Integer.signum(jy - iy);
+            int j1 = Integer.signum(jz - iz);
+            // Paper end
             EnumDirection enumdirection = EnumDirection.a(l, i1, j1);
 
             if (enumdirection == null) {
                 return 15;
             } else {
                 //MutableInt mutableint = new MutableInt(); // Paper - share mutableint, single threaded
-                IBlockData iblockdata = this.a(j, mutableint);
-
-                if (mutableint.getValue() >= 15) {
+                IBlockData iblockdata = this.getBlockOptimized(jx, jy, jz, mutableint); // Paper
+                int blockedLight = mutableint.getValue(); // Paper
+                if (blockedLight >= 15) { // Paper
                     return 15;
                 } else {
-                    IBlockData iblockdata1 = this.a(i, (MutableInt) null);
+                    IBlockData iblockdata1 = this.getBlockOptimized(ix, iy, iz); // Paper
                     VoxelShape voxelshape = this.a(iblockdata1, i, enumdirection);
                     VoxelShape voxelshape1 = this.a(iblockdata, j, enumdirection.opposite());
 
-                    return VoxelShapes.b(voxelshape, voxelshape1) ? 15 : k + Math.max(1, mutableint.getValue());
+                    return VoxelShapes.b(voxelshape, voxelshape1) ? 15 : k + Math.max(1, blockedLight); // Paper
                 }
             }
         }
@@ -56,14 +66,19 @@ public final class LightEngineBlock extends LightEngineLayer<LightEngineStorageB
 
     @Override
     protected void a(long i, int j, boolean flag) {
-        long k = SectionPosition.e(i);
+        // Paper start - reuse unpacking, credit to JellySquid (Didn't do full optimization though)
+        int x = (int) (i >> 38);
+        int y = (int) ((i << 52) >> 52);
+        int z = (int) ((i << 26) >> 38);
+        long k = SectionPosition.asLong(x >> 4, y >> 4, z >> 4);
+        // Paper end
         EnumDirection[] aenumdirection = LightEngineBlock.e;
         int l = aenumdirection.length;
 
         for (int i1 = 0; i1 < l; ++i1) {
             EnumDirection enumdirection = aenumdirection[i1];
-            long j1 = BlockPosition.a(i, enumdirection);
-            long k1 = SectionPosition.e(j1);
+            long j1 = BlockPosition.asLong(x + enumdirection.getAdjacentX(), y + enumdirection.getAdjacentY(), z + enumdirection.getAdjacentZ()); // Paper
+            long k1 = SectionPosition.asLong((x + enumdirection.getAdjacentX()) >> 4, (y + enumdirection.getAdjacentY()) >> 4, (z + enumdirection.getAdjacentZ()) >> 4); // Paper
 
             if (k == k1 || ((LightEngineStorageBlock) this.c).g(k1)) {
                 this.b(i, j1, j, flag);
@@ -88,27 +103,36 @@ public final class LightEngineBlock extends LightEngineLayer<LightEngineStorageB
             }
         }
 
-        long j1 = SectionPosition.e(i);
-        NibbleArray nibblearray = ((LightEngineStorageBlock) this.c).a(j1, true);
+        // Paper start
+        int baseX = (int) (i >> 38);
+        int baseY = (int) ((i << 52) >> 52);
+        int baseZ = (int) ((i << 26) >> 38);
+        long j1 = (((long) (baseX >> 4) & 4194303L) << 42) | (((long) (baseY >> 4) & 1048575L)) | (((long) (baseZ >> 4) & 4194303L) << 20);
+        NibbleArray nibblearray = this.c.updating.getUpdatingOptimized(j1);
+        // Paper end
         EnumDirection[] aenumdirection = LightEngineBlock.e;
         int k1 = aenumdirection.length;
 
         for (int l1 = 0; l1 < k1; ++l1) {
             EnumDirection enumdirection = aenumdirection[l1];
-            long i2 = BlockPosition.a(i, enumdirection);
-
-            if (i2 != j) {
-                long j2 = SectionPosition.e(i2);
+            // Paper start
+            int newX = baseX + enumdirection.getAdjacentX();
+            int newY = baseY + enumdirection.getAdjacentY();
+            int newZ = baseZ + enumdirection.getAdjacentZ();
+            if (newX != baseX || newY != baseY || newZ != baseZ) {
+                long i2 = BlockPosition.asLong(newX, newY, newZ);
+                long j2 = SectionPosition.blockPosAsSectionLong(newX, newY, newZ);
+                // Paper end
                 NibbleArray nibblearray1;
 
                 if (j1 == j2) {
                     nibblearray1 = nibblearray;
                 } else {
-                    nibblearray1 = ((LightEngineStorageBlock) this.c).a(j2, true);
+                    nibblearray1 = ((LightEngineStorageBlock) this.c).updating.getUpdatingOptimized(j2); // Paper
                 }
 
                 if (nibblearray1 != null) {
-                    int k2 = this.b(i2, i, this.a(nibblearray1, i2));
+                    int k2 = this.b(i2, i, this.getNibbleLightInverse(nibblearray1, newX, newY, newZ)); // Paper
 
                     if (l > k2) {
                         l = k2;
diff --git a/src/main/java/net/minecraft/server/LightEngineGraphSection.java b/src/main/java/net/minecraft/server/LightEngineGraphSection.java
index 2eb37fb5796d423a70fa7321899a19b6625bbecc..13d067f48647dea63ef1bf3a2a3e0868074ba75f 100644
--- a/src/main/java/net/minecraft/server/LightEngineGraphSection.java
+++ b/src/main/java/net/minecraft/server/LightEngineGraphSection.java
@@ -13,14 +13,20 @@ public abstract class LightEngineGraphSection extends LightEngineGraph {
 
     @Override
     protected void a(long i, int j, boolean flag) {
+        // Paper start
+        int x = (int) (i >> 42);
+        int y = (int) (i << 44 >> 44);
+        int z = (int) (i << 22 >> 42);
+        // Paper end
         for (int k = -1; k <= 1; ++k) {
             for (int l = -1; l <= 1; ++l) {
                 for (int i1 = -1; i1 <= 1; ++i1) {
-                    long j1 = SectionPosition.a(i, k, l, i1);
+                    if (k == 0 && l == 0 && i1 == 0) continue; // Paper
+                    long j1 = (((long) (x + k) & 4194303L) << 42) | (((long) (y + l) & 1048575L)) | (((long) (z + i1) & 4194303L) << 20); // Paper
 
-                    if (j1 != i) {
+                    //if (j1 != i) { // Paper - checked above
                         this.b(i, j1, j, flag);
-                    }
+                    //} // Paper
                 }
             }
         }
@@ -31,10 +37,15 @@ public abstract class LightEngineGraphSection extends LightEngineGraph {
     protected int a(long i, long j, int k) {
         int l = k;
 
+        // Paper start
+        int x = (int) (i >> 42);
+        int y = (int) (i << 44 >> 44);
+        int z = (int) (i << 22 >> 42);
+        // Paper end
         for (int i1 = -1; i1 <= 1; ++i1) {
             for (int j1 = -1; j1 <= 1; ++j1) {
                 for (int k1 = -1; k1 <= 1; ++k1) {
-                    long l1 = SectionPosition.a(i, i1, j1, k1);
+                    long l1 = (((long) (x + i1) & 4194303L) << 42) | (((long) (y + j1) & 1048575L)) | (((long) (z + k1) & 4194303L) << 20); // Paper
 
                     if (l1 == i) {
                         l1 = Long.MAX_VALUE;
diff --git a/src/main/java/net/minecraft/server/LightEngineLayer.java b/src/main/java/net/minecraft/server/LightEngineLayer.java
index f72ff8495bcf704c15040676b95c51fecb72b73a..faa432779ec70c2c6b5fe7fe3523f171e26d3a5f 100644
--- a/src/main/java/net/minecraft/server/LightEngineLayer.java
+++ b/src/main/java/net/minecraft/server/LightEngineLayer.java
@@ -11,9 +11,9 @@ public abstract class LightEngineLayer<M extends LightEngineStorageArray<M>, S e
     protected final EnumSkyBlock b;
     protected final S c;
     private boolean f;
-    protected final BlockPosition.MutableBlockPosition d = new BlockPosition.MutableBlockPosition();
+    protected final BlockPosition.MutableBlockPosition d = new BlockPosition.MutableBlockPosition(); protected final BlockPosition.MutableBlockPosition pos = d; // Paper
     private final long[] g = new long[2];
-    private final IBlockAccess[] h = new IBlockAccess[2];
+    private final IChunkAccess[] h = new IChunkAccess[2]; // Paper
 
     public LightEngineLayer(ILightAccess ilightaccess, EnumSkyBlock enumskyblock, S s0) {
         super(16, 256, 8192);
@@ -33,7 +33,7 @@ public abstract class LightEngineLayer<M extends LightEngineStorageArray<M>, S e
     }
 
     @Nullable
-    private IBlockAccess a(int i, int j) {
+    private IChunkAccess a(int i, int j) { // Paper
         long k = ChunkCoordIntPair.pair(i, j);
 
         for (int l = 0; l < 2; ++l) {
@@ -42,7 +42,7 @@ public abstract class LightEngineLayer<M extends LightEngineStorageArray<M>, S e
             }
         }
 
-        IBlockAccess iblockaccess = this.a.c(i, j);
+        IChunkAccess iblockaccess = (IChunkAccess) this.a.c(i, j); // Paper
 
         for (int i1 = 1; i1 > 0; --i1) {
             this.g[i1] = this.g[i1 - 1];
@@ -59,37 +59,64 @@ public abstract class LightEngineLayer<M extends LightEngineStorageArray<M>, S e
         Arrays.fill(this.h, (Object) null);
     }
 
-    protected IBlockData a(long i, @Nullable MutableInt mutableint) {
-        if (i == Long.MAX_VALUE) {
-            if (mutableint != null) {
-                mutableint.setValue(0);
-            }
-
-            return Blocks.AIR.getBlockData();
+    // Paper start - unused, optimized versions below, comment out to detect changes
+//    protected IBlockData a(long i, @Nullable MutableInt mutableint) {
+//        if (i == Long.MAX_VALUE) {
+//            if (mutableint != null) {
+//                mutableint.setValue(0);
+//            }
+//
+//            return Blocks.AIR.getBlockData();
+//        } else {
+//            int j = SectionPosition.a(BlockPosition.b(i));
+//            int k = SectionPosition.a(BlockPosition.d(i));
+//            IBlockAccess iblockaccess = this.a(j, k);
+//
+//            if (iblockaccess == null) {
+//                if (mutableint != null) {
+//                    mutableint.setValue(16);
+//                }
+//
+//                return Blocks.BEDROCK.getBlockData();
+//            } else {
+//                this.d.g(i);
+//                IBlockData iblockdata = iblockaccess.getType(this.d);
+//                boolean flag = iblockdata.o() && iblockdata.g();
+//
+//                if (mutableint != null) {
+//                    mutableint.setValue(iblockdata.b(this.a.getWorld(), (BlockPosition) this.d));
+//                }
+//
+//                return flag ? iblockdata : Blocks.AIR.getBlockData();
+//            }
+//        }
+//    }
+    // optimized method with less branching for when scenarios arent needed.
+    // avoid using mutable version if can
+    protected final IBlockData getBlockOptimized(int x, int y, int z, MutableInt mutableint) {
+        IChunkAccess iblockaccess = this.a(x >> 4, z >> 4);
+
+        if (iblockaccess == null) {
+            mutableint.setValue(16);
+            return Blocks.BEDROCK.getBlockData();
         } else {
-            int j = SectionPosition.a(BlockPosition.b(i));
-            int k = SectionPosition.a(BlockPosition.d(i));
-            IBlockAccess iblockaccess = this.a(j, k);
-
-            if (iblockaccess == null) {
-                if (mutableint != null) {
-                    mutableint.setValue(16);
-                }
-
-                return Blocks.BEDROCK.getBlockData();
-            } else {
-                this.d.g(i);
-                IBlockData iblockdata = iblockaccess.getType(this.d);
-                boolean flag = iblockdata.o() && iblockdata.g();
-
-                if (mutableint != null) {
-                    mutableint.setValue(iblockdata.b(this.a.getWorld(), (BlockPosition) this.d));
-                }
+            this.pos.setValues(x, y, z);
+            IBlockData iblockdata = iblockaccess.getType(x, y, z);
+            mutableint.setValue(iblockdata.b(this.a.getWorld(), this.pos));
+            return iblockdata.o() && iblockdata.g() ? iblockdata : Blocks.AIR.getBlockData();
+        }
+    }
+    protected final IBlockData getBlockOptimized(int x, int y, int z) {
+        IChunkAccess iblockaccess = this.a(x >> 4, z >> 4);
 
-                return flag ? iblockdata : Blocks.AIR.getBlockData();
-            }
+        if (iblockaccess == null) {
+            return Blocks.BEDROCK.getBlockData();
+        } else {
+            IBlockData iblockdata = iblockaccess.getType(x, y, z);
+            return iblockdata.o() && iblockdata.g() ? iblockdata : Blocks.AIR.getBlockData();
         }
     }
+    // Paper end
 
     protected VoxelShape a(IBlockData iblockdata, long i, EnumDirection enumdirection) {
         return iblockdata.o() ? iblockdata.a(this.a.getWorld(), this.d.g(i), enumdirection) : VoxelShapes.a();
@@ -124,8 +151,9 @@ public abstract class LightEngineLayer<M extends LightEngineStorageArray<M>, S e
         return i == Long.MAX_VALUE ? 0 : 15 - this.c.i(i);
     }
 
+    protected int getNibbleLightInverse(NibbleArray nibblearray, int x, int y, int z) { return 15 - nibblearray.a(x & 15, y & 15, z & 15); } // Paper - x/y/z version of below
     protected int a(NibbleArray nibblearray, long i) {
-        return 15 - nibblearray.a(SectionPosition.b(BlockPosition.b(i)), SectionPosition.b(BlockPosition.c(i)), SectionPosition.b(BlockPosition.d(i)));
+        return 15 - nibblearray.a((int) (i >> 38) & 15, (int) ((i << 52) >> 52) & 15, (int) ((i << 26) >> 38) & 15); // Paper
     }
 
     @Override
diff --git a/src/main/java/net/minecraft/server/LightEngineSky.java b/src/main/java/net/minecraft/server/LightEngineSky.java
index f0b57784006752e031800a12a1a3c1a5945c636b..3d508fdb0ea86fbe78891113776a1cb312df8dce 100644
--- a/src/main/java/net/minecraft/server/LightEngineSky.java
+++ b/src/main/java/net/minecraft/server/LightEngineSky.java
@@ -29,21 +29,25 @@ public final class LightEngineSky extends LightEngineLayer<LightEngineStorageSky
                 return k;
             } else {
                 //MutableInt mutableint = new MutableInt(); // Paper - share mutableint, single threaded
-                IBlockData iblockdata = this.a(j, mutableint);
-
-                if (mutableint.getValue() >= 15) {
+                // Paper start - use x/y/z and optimized block lookup
+                int jx = (int) (j >> 38);
+                int jy = (int) ((j << 52) >> 52);
+                int jz = (int) ((j << 26) >> 38);
+                IBlockData iblockdata = this.getBlockOptimized(jx, jy, jz, mutableint);
+                int blockedLight = mutableint.getValue();
+                if (blockedLight >= 15) {
+                    // Paper end
                     return 15;
                 } else {
-                    int l = BlockPosition.b(i);
-                    int i1 = BlockPosition.c(i);
-                    int j1 = BlockPosition.d(i);
-                    int k1 = BlockPosition.b(j);
-                    int l1 = BlockPosition.c(j);
-                    int i2 = BlockPosition.d(j);
-                    boolean flag = l == k1 && j1 == i2;
-                    int j2 = Integer.signum(k1 - l);
-                    int k2 = Integer.signum(l1 - i1);
-                    int l2 = Integer.signum(i2 - j1);
+                    // Paper start - inline math
+                    int ix = (int) (i >> 38);
+                    int iy = (int) ((i << 52) >> 52);
+                    int iz = (int) ((i << 26) >> 38);
+                    boolean flag = ix == jx && iz == jz;
+                    int j2 = Integer.signum(jx - ix);
+                    int k2 = Integer.signum(jy - iy);
+                    int l2 = Integer.signum(jz - iz);
+                    // Paper end
                     EnumDirection enumdirection;
 
                     if (i == Long.MAX_VALUE) {
@@ -52,7 +56,7 @@ public final class LightEngineSky extends LightEngineLayer<LightEngineStorageSky
                         enumdirection = EnumDirection.a(j2, k2, l2);
                     }
 
-                    IBlockData iblockdata1 = this.a(i, (MutableInt) null);
+                    IBlockData iblockdata1 = i == Long.MAX_VALUE ? Blocks.AIR.getBlockData() : this.getBlockOptimized(ix, iy, iz); // Paper
                     VoxelShape voxelshape;
 
                     if (enumdirection != null) {
@@ -82,9 +86,9 @@ public final class LightEngineSky extends LightEngineLayer<LightEngineStorageSky
                         }
                     }
 
-                    boolean flag1 = i == Long.MAX_VALUE || flag && i1 > l1;
+                    boolean flag1 = i == Long.MAX_VALUE || flag && iy > jy; // Paper rename vars to iy > jy
 
-                    return flag1 && k == 0 && mutableint.getValue() == 0 ? 0 : k + Math.max(1, mutableint.getValue());
+                    return flag1 && k == 0 && blockedLight == 0 ? 0 : k + Math.max(1, blockedLight); // Paper
                 }
             }
         }
@@ -92,8 +96,13 @@ public final class LightEngineSky extends LightEngineLayer<LightEngineStorageSky
 
     @Override
     protected void a(long i, int j, boolean flag) {
-        long k = SectionPosition.e(i);
-        int l = BlockPosition.c(i);
+        // Paper start
+        int baseX = (int) (i >> 38);
+        int baseY = (int) ((i << 52) >> 52);
+        int baseZ = (int) ((i << 26) >> 38);
+        long k = SectionPosition.blockPosAsSectionLong(baseX, baseY, baseZ);
+        int l = baseY;
+        // Paper end
         int i1 = SectionPosition.b(l);
         int j1 = SectionPosition.a(l);
         int k1;
@@ -103,22 +112,28 @@ public final class LightEngineSky extends LightEngineLayer<LightEngineStorageSky
         } else {
             int l1;
 
-            for (l1 = 0; !((LightEngineStorageSky) this.c).g(SectionPosition.a(k, 0, -l1 - 1, 0)) && ((LightEngineStorageSky) this.c).a(j1 - l1 - 1); ++l1) {
+            // Paper start - cache and optimize base values
+            int secX = baseX >> 4;
+            int secY = baseY >> 4;
+            int secZ = baseZ >> 4;
+            for (l1 = 0; !((LightEngineStorageSky) this.c).g(SectionPosition.asLong(secX, secY + -l1 - 1, secZ)) && ((LightEngineStorageSky) this.c).a(j1 - l1 - 1); ++l1) {
+                // Paper end
                 ;
             }
 
             k1 = l1;
         }
 
-        long i2 = BlockPosition.a(i, 0, -1 - k1 * 16, 0);
-        long j2 = SectionPosition.e(i2);
+        int newBaseY = baseY + -1 - k1 * 16; // Paper
+        long i2 = BlockPosition.asLong(baseX, newBaseY, baseZ); // Paper
+        long j2 = SectionPosition.blockPosAsSectionLong(baseX, newBaseY, baseZ); // Paper
 
         if (k == j2 || ((LightEngineStorageSky) this.c).g(j2)) {
             this.b(i, i2, j, flag);
         }
 
-        long k2 = BlockPosition.a(i, EnumDirection.UP);
-        long l2 = SectionPosition.e(k2);
+        long k2 = BlockPosition.asLong(baseX, baseY + 1, baseZ); // Paper
+        long l2 = SectionPosition.blockPosAsSectionLong(baseX, baseY + 1, baseZ); // Paper
 
         if (k == l2 || ((LightEngineStorageSky) this.c).g(l2)) {
             this.b(i, k2, j, flag);
@@ -133,8 +148,8 @@ public final class LightEngineSky extends LightEngineLayer<LightEngineStorageSky
             int k3 = 0;
 
             while (true) {
-                long l3 = BlockPosition.a(i, enumdirection.getAdjacentX(), -k3, enumdirection.getAdjacentZ());
-                long i4 = SectionPosition.e(l3);
+                long l3 = BlockPosition.asLong(baseX + enumdirection.getAdjacentX(), baseY - k3, baseZ + enumdirection.getAdjacentZ()); // Paper
+                long i4 = SectionPosition.blockPosAsSectionLong(baseX + enumdirection.getAdjacentX(), baseY - k3, baseZ + enumdirection.getAdjacentZ()); // Paper
 
                 if (k == i4) {
                     this.b(i, l3, j, flag);
@@ -172,26 +187,36 @@ public final class LightEngineSky extends LightEngineLayer<LightEngineStorageSky
             }
         }
 
-        long j1 = SectionPosition.e(i);
-        NibbleArray nibblearray = ((LightEngineStorageSky) this.c).a(j1, true);
+        // Paper start
+        int baseX = (int) (i >> 38);
+        int baseY = (int) ((i << 52) >> 52);
+        int baseZ = (int) ((i << 26) >> 38);
+        long j1 = (((long) (baseX >> 4) & 4194303L) << 42) | (((long) (baseY >> 4) & 1048575L)) | (((long) (baseZ >> 4) & 4194303L) << 20);
+        NibbleArray nibblearray = this.c.updating.getUpdatingOptimized(j1);
+        // Paper end
         EnumDirection[] aenumdirection = LightEngineSky.e;
         int k1 = aenumdirection.length;
 
         for (int l1 = 0; l1 < k1; ++l1) {
             EnumDirection enumdirection = aenumdirection[l1];
-            long i2 = BlockPosition.a(i, enumdirection);
-            long j2 = SectionPosition.e(i2);
+            // Paper start
+            int newX = baseX + enumdirection.getAdjacentX();
+            int newY = baseY + enumdirection.getAdjacentY();
+            int newZ = baseZ + enumdirection.getAdjacentZ();
+            long i2 = BlockPosition.asLong(newX, newY, newZ);
+            long j2 = SectionPosition.blockPosAsSectionLong(newX, newY, newZ);
+            // Paper end
             NibbleArray nibblearray1;
 
             if (j1 == j2) {
                 nibblearray1 = nibblearray;
             } else {
-                nibblearray1 = ((LightEngineStorageSky) this.c).a(j2, true);
+                nibblearray1 = ((LightEngineStorageSky) this.c).updating.getUpdatingOptimized(j2); // Paper
             }
 
             if (nibblearray1 != null) {
                 if (i2 != j) {
-                    int k2 = this.b(i2, i, this.a(nibblearray1, i2));
+                    int k2 = this.b(i2, i, this.getNibbleLightInverse(nibblearray1, newX, newY, newZ)); // Paper
 
                     if (l > k2) {
                         l = k2;
@@ -206,7 +231,7 @@ public final class LightEngineSky extends LightEngineLayer<LightEngineStorageSky
                     j2 = SectionPosition.a(j2, EnumDirection.UP);
                 }
 
-                NibbleArray nibblearray2 = ((LightEngineStorageSky) this.c).a(j2, true);
+                NibbleArray nibblearray2 = this.c.updating.getUpdatingOptimized(j2); // Paper
 
                 if (i2 != j) {
                     int l2;
diff --git a/src/main/java/net/minecraft/server/LightEngineStorage.java b/src/main/java/net/minecraft/server/LightEngineStorage.java
index b0b7544592981bcff22c8acee7230a211918ef28..84a2589ef0bbb2c5d8b5d4808277916a2323447f 100644
--- a/src/main/java/net/minecraft/server/LightEngineStorage.java
+++ b/src/main/java/net/minecraft/server/LightEngineStorage.java
@@ -20,42 +20,42 @@ public abstract class LightEngineStorage<M extends LightEngineStorageArray<M>> e
     protected final LongSet c = new LongOpenHashSet();
     protected final LongSet d = new LongOpenHashSet();
     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 f; // Paper - diff on change, should be "updating"
+    protected final M f; protected final M updating; // Paper - diff on change, should be "updating"
     protected final LongSet g = new LongOpenHashSet();
-    protected final LongSet h = new LongOpenHashSet();
+    protected final LongSet h = new LongOpenHashSet(); LongSet dirty = h; // Paper - OBFHELPER
     protected final Long2ObjectMap<NibbleArray> i = Long2ObjectMaps.synchronize(new Long2ObjectOpenHashMap());
     private final LongSet n = new LongOpenHashSet();
     private final LongSet o = new LongOpenHashSet();
     protected volatile boolean j;
 
     protected LightEngineStorage(EnumSkyBlock enumskyblock, ILightAccess ilightaccess, M m0) {
-        super(3, 16, 256);
+        super(3, 256, 256); // Paper - bump expected size of level sets to improve collisions and reduce rehashing (seen a lot of it)
         this.l = enumskyblock;
         this.m = ilightaccess;
-        this.f = m0;
+        this.f = m0; updating = m0; // Paper
         this.e_visible = m0.b(); // Paper - avoid copying light data
         this.e_visible.d(); // Paper - avoid copying light data
     }
 
-    protected boolean g(long i) {
-        return this.a(i, true) != null;
+    protected final boolean g(long i) { // Paper - final to help inlining
+        return this.updating.getUpdatingOptimized(i) != null; // Paper - inline to avoid branching
     }
 
     @Nullable
     protected NibbleArray a(long i, boolean flag) {
         // Paper start - avoid copying light data
         if (flag) {
-            return this.a(this.f, i);
+            return this.updating.getUpdatingOptimized(i);
         } else {
             synchronized (this.visibleUpdateLock) {
-                return this.a(this.e_visible, i);
+                return this.e_visible.lookup.apply(i);
             }
         }
         // Paper end - avoid copying light data
     }
 
     @Nullable
-    protected NibbleArray a(M m0, long i) {
+    protected final NibbleArray a(M m0, long i) { // Paper
         return m0.c(i);
     }
 
@@ -69,27 +69,56 @@ public abstract class LightEngineStorage<M extends LightEngineStorageArray<M>> e
     protected abstract int d(long i);
 
     protected int i(long i) {
-        long j = SectionPosition.e(i);
-        NibbleArray nibblearray = this.a(j, true);
+        // Paper start - reuse and inline math, use Optimized Updating path
+        final int x = (int) (i >> 38);
+        final int y = (int) ((i << 52) >> 52);
+        final int z = (int) ((i << 26) >> 38);
+        NibbleArray nibblearray = this.updating.getUpdatingOptimized((((long) (x >> 4) & 4194303L) << 42) | (((long) (y >> 4) & 1048575L)) | (((long) (z >> 4) & 4194303L) << 20));
+        //  BUG: Sometimes returns null and crashes, try to recover, but to prevent crash just return no light.
+        if (nibblearray == null) {
+            nibblearray = this.e_visible.lookup.apply((((long) (x >> 4) & 4194303L) << 42) | (((long) (y >> 4) & 1048575L)) | (((long) (z >> 4) & 4194303L) << 20));
+        }
+        if (nibblearray == null) {
+            System.err.println("Null nibble, preventing crash " + BlockPosition.fromLong(i));
+            return 0;
+        }
 
-        return nibblearray.a(SectionPosition.b(BlockPosition.b(i)), SectionPosition.b(BlockPosition.c(i)), SectionPosition.b(BlockPosition.d(i)));
+        return nibblearray.a(x & 15, y & 15, z & 15); // Paper - inline operations
+        // Paper end
     }
 
     protected void b(long i, int j) {
-        long k = SectionPosition.e(i);
+        // Paper start - cache part of the math done in loop below
+        int x = (int) (i >> 38);
+        int y = (int) ((i << 52) >> 52);
+        int z = (int) ((i << 26) >> 38);
+        long k = SectionPosition.asLong(x >> 4, y >> 4, z >> 4);
+        // Paper end
 
         if (this.g.add(k)) {
             this.f.a(k);
         }
 
         NibbleArray nibblearray = this.a(k, true);
-
-        nibblearray.a(SectionPosition.b(BlockPosition.b(i)), SectionPosition.b(BlockPosition.c(i)), SectionPosition.b(BlockPosition.d(i)), j);
-
-        for (int l = -1; l <= 1; ++l) {
-            for (int i1 = -1; i1 <= 1; ++i1) {
-                for (int j1 = -1; j1 <= 1; ++j1) {
-                    this.h.add(SectionPosition.e(BlockPosition.a(i, i1, j1, l)));
+        nibblearray.a(x & 15, y & 15, z & 15, j); // Paper - use already calculated x/y/z
+
+        // Paper start - credit to JellySquid for a major optimization here:
+        /*
+         * An extremely important optimization is made here in regards to adding items to the pending notification set. The
+         * original implementation attempts to add the coordinate of every chunk which contains a neighboring block position
+         * even though a huge number of loop iterations will simply map to block positions within the same updating chunk.
+         *
+         * Our implementation here avoids this by pre-calculating the min/max chunk coordinates so we can iterate over only
+         * the relevant chunk positions once. This reduces what would always be 27 iterations to just 1-8 iterations.
+         *
+         * @reason Use faster implementation
+         * @author JellySquid
+         */
+        for (int z2 = (z - 1) >> 4; z2 <= (z + 1) >> 4; ++z2) {
+            for (int x2 = (x - 1) >> 4; x2 <= (x + 1) >> 4; ++x2) {
+                for (int y2 = (y - 1) >> 4; y2 <= (y + 1) >> 4; ++y2) {
+                    this.dirty.add(SectionPosition.asLong(x2, y2, z2));
+                    // Paper end
                 }
             }
         }
@@ -121,17 +150,23 @@ public abstract class LightEngineStorage<M extends LightEngineStorageArray<M>> e
         }
 
         if (k >= 2 && j != 2) {
-            if (this.o.contains(i)) {
-                this.o.remove(i);
-            } else {
+            if (!this.o.remove(i)) { // Paper - remove useless contains - credit to JellySquid
+                //this.o.remove(i); // Paper
+            //} else { // Pape
                 this.f.a(i, this.j(i));
                 this.g.add(i);
                 this.k(i);
 
-                for (int l = -1; l <= 1; ++l) {
-                    for (int i1 = -1; i1 <= 1; ++i1) {
-                        for (int j1 = -1; j1 <= 1; ++j1) {
-                            this.h.add(SectionPosition.e(BlockPosition.a(i, i1, j1, l)));
+                // Paper start - reuse x/y/z and only notify valid chunks - Credit to JellySquid (See above method for notes)
+                int x = (int) (i >> 38);
+                int y = (int) ((i << 52) >> 52);
+                int z = (int) ((i << 26) >> 38);
+
+                for (int z2 = (z - 1) >> 4; z2 <= (z + 1) >> 4; ++z2) {
+                    for (int x2 = (x - 1) >> 4; x2 <= (x + 1) >> 4; ++x2) {
+                        for (int y2 = (y - 1) >> 4; y2 <= (y + 1) >> 4; ++y2) {
+                            this.dirty.add(SectionPosition.asLong(x2, y2, z2));
+                            // Paper end
                         }
                     }
                 }
@@ -157,9 +192,9 @@ public abstract class LightEngineStorage<M extends LightEngineStorageArray<M>> e
                 return SectionPosition.e(j) == i;
             });
         } else {
-            int j = SectionPosition.c(SectionPosition.b(i));
-            int k = SectionPosition.c(SectionPosition.c(i));
-            int l = SectionPosition.c(SectionPosition.d(i));
+            int j = (int) (i >> 42) << 4; // Paper - inline
+            int k = (int) (i << 44 >> 44) << 4; // Paper - inline
+            int l = (int) (i << 22 >> 42) << 4; // Paper - inline
 
             for (int i1 = 0; i1 < 16; ++i1) {
                 for (int j1 = 0; j1 < 16; ++j1) {
@@ -186,7 +221,7 @@ public abstract class LightEngineStorage<M extends LightEngineStorageArray<M>> e
             NibbleArray nibblearray;
 
             while (longiterator.hasNext()) {
-                i = (Long) longiterator.next();
+                i = longiterator.nextLong(); // Paper
                 this.a(lightenginelayer, i);
                 NibbleArray nibblearray1 = (NibbleArray) this.i.remove(i);
 
@@ -204,48 +239,56 @@ public abstract class LightEngineStorage<M extends LightEngineStorageArray<M>> e
             longiterator = this.o.iterator();
 
             while (longiterator.hasNext()) {
-                i = (Long) longiterator.next();
+                i = longiterator.nextLong(); // Paper
                 this.l(i);
             }
 
             this.o.clear();
             this.j = false;
-            ObjectIterator objectiterator = this.i.long2ObjectEntrySet().iterator();
+            ObjectIterator<Long2ObjectMap.Entry<NibbleArray>> objectiterator = Long2ObjectMaps.fastIterator(this.i); // Paper
 
             Entry entry;
             long j;
 
+            NibbleArray test = null; // Paper
+            LongSet propagating = new LongOpenHashSet(); // Paper - credit JellySquid for idea to move this up
             while (objectiterator.hasNext()) {
                 entry = (Entry) objectiterator.next();
                 j = entry.getLongKey();
-                if (this.g(j)) {
+                if ((test = this.updating.getUpdatingOptimized(j)) != null) { // Paper - dont look up nibble twice
                     nibblearray = (NibbleArray) entry.getValue();
-                    if (this.f.c(j) != nibblearray) {
+                    if (test != nibblearray) { // Paper
                         this.a(lightenginelayer, j);
                         this.f.a(j, nibblearray);
                         this.g.add(j);
                     }
+                    if (!flag1) propagating.add(j); // Paper
+                    objectiterator.remove(); // Paper
                 }
             }
 
             this.f.c();
-            if (!flag1) {
-                longiterator = this.i.keySet().iterator();
+            if (!flag1) {// Paper - diff on change, change propagating add a few lines up
+                longiterator = propagating.iterator(); // Paper
 
                 while (longiterator.hasNext()) {
-                    i = (Long) longiterator.next();
-                    if (this.g(i)) {
-                        int k = SectionPosition.c(SectionPosition.b(i));
-                        int l = SectionPosition.c(SectionPosition.c(i));
-                        int i1 = SectionPosition.c(SectionPosition.d(i));
+                    // Paper start
+                    i = longiterator.nextLong();
+                    if (true) { // don't check hasLight, this iterator is filtered already
+                        int baseX = (int) (i >> 42);
+                        int baseY = (int) (i << 44 >> 44);
+                        int baseZ = (int) (i << 22 >> 42);
+                        int k = baseX << 4;
+                        int l = baseY << 4;
+                        int i1 = baseZ << 4;
+                        // Paper end
                         EnumDirection[] aenumdirection = LightEngineStorage.k;
                         int j1 = aenumdirection.length;
 
                         for (int k1 = 0; k1 < j1; ++k1) {
                             EnumDirection enumdirection = aenumdirection[k1];
-                            long l1 = SectionPosition.a(i, enumdirection);
-
-                            if (!this.i.containsKey(l1) && this.g(l1)) {
+                            long l1 = SectionPosition.asLong(baseX + enumdirection.getAdjacentX(), baseY + enumdirection.getAdjacentY(), baseZ + enumdirection.getAdjacentZ()); // Paper - avoid unpacking
+                            if (!propagating.contains(l1) && this.g(l1)) { // Paper - use propagating
                                 for (int i2 = 0; i2 < 16; ++i2) {
                                     for (int j2 = 0; j2 < 16; ++j2) {
                                         long k2;
@@ -287,6 +330,8 @@ public abstract class LightEngineStorage<M extends LightEngineStorageArray<M>> e
                 }
             }
 
+            // Paper start - moved above - Credit JellySquid for idea
+            /*
             objectiterator = this.i.long2ObjectEntrySet().iterator();
 
             while (objectiterator.hasNext()) {
@@ -295,7 +340,8 @@ public abstract class LightEngineStorage<M extends LightEngineStorageArray<M>> e
                 if (this.g(j)) {
                     objectiterator.remove();
                 }
-            }
+            }*/
+            // Paper end
 
         }
     }
diff --git a/src/main/java/net/minecraft/server/LightEngineStorageArray.java b/src/main/java/net/minecraft/server/LightEngineStorageArray.java
index 37c44a89f28c44915fcae5a7e2c4797b1c123723..53c204455c3800b4fe399ce6261b0495eea4d003 100644
--- a/src/main/java/net/minecraft/server/LightEngineStorageArray.java
+++ b/src/main/java/net/minecraft/server/LightEngineStorageArray.java
@@ -43,6 +43,25 @@ public abstract class LightEngineStorageArray<M extends LightEngineStorageArray<
         return lookup.apply(i) != null; // Paper - avoid copying light data
     }
 
+    // Paper start - less branching as we know we are using cache and updating
+    public final NibbleArray getUpdatingOptimized(long i) { // Paper - final
+        if (this.b[0] == i) return this.c[0];
+        if (this.b[1] == i) return this.c[1];
+
+        NibbleArray nibblearray = this.data.getUpdating(i); // Paper - avoid copying light data
+        if (nibblearray == null) {
+            return null;
+        } else {
+            this.b[1] = this.b[0];
+            this.c[1] = this.c[0];
+
+            this.b[0] = i;
+            this.c[0] = nibblearray;
+            return nibblearray;
+        }
+    }
+    // Paper end
+
     @Nullable
     public final NibbleArray c(long i) { // Paper - final
         if (this.d) {
diff --git a/src/main/java/net/minecraft/server/LightEngineStorageBlock.java b/src/main/java/net/minecraft/server/LightEngineStorageBlock.java
index 292d8c742d3be41ba8ad7fb7f1251dc7f790b62b..ae6a5d2f660a53885b5b0c61ce39cf75a7dd99be 100644
--- a/src/main/java/net/minecraft/server/LightEngineStorageBlock.java
+++ b/src/main/java/net/minecraft/server/LightEngineStorageBlock.java
@@ -10,10 +10,15 @@ public class LightEngineStorageBlock extends LightEngineStorage<LightEngineStora
 
     @Override
     protected int d(long i) {
-        long j = SectionPosition.e(i);
+        // Paper start
+        int baseX = (int) (i >> 38);
+        int baseY = (int) ((i << 52) >> 52);
+        int baseZ = (int) ((i << 26) >> 38);
+        long j = (((long) (baseX >> 4) & 4194303L) << 42) | (((long) (baseY >> 4) & 1048575L)) | (((long) (baseZ >> 4) & 4194303L) << 20);
+        // Paper end
         NibbleArray nibblearray = this.a(j, false);
 
-        return nibblearray == null ? 0 : nibblearray.a(SectionPosition.b(BlockPosition.b(i)), SectionPosition.b(BlockPosition.c(i)), SectionPosition.b(BlockPosition.d(i)));
+        return nibblearray == null ? 0 : nibblearray.a(baseX & 15, baseY & 15, baseZ & 15); // Paper
     }
 
     public static final class a extends LightEngineStorageArray<LightEngineStorageBlock.a> {
diff --git a/src/main/java/net/minecraft/server/LightEngineStorageSky.java b/src/main/java/net/minecraft/server/LightEngineStorageSky.java
index 097f58e9ac3f4096d3b9dad75b6ebe76021fa92c..5ccd81bd0d49052fe84d4f34e29774f0cc2dd732 100644
--- a/src/main/java/net/minecraft/server/LightEngineStorageSky.java
+++ b/src/main/java/net/minecraft/server/LightEngineStorageSky.java
@@ -22,7 +22,12 @@ public class LightEngineStorageSky extends LightEngineStorage<LightEngineStorage
 
     @Override
     protected int d(long i) {
-        long j = SectionPosition.e(i);
+        // Paper start
+        int baseX = (int) (i >> 38);
+        int baseY = (int) ((i << 52) >> 52);
+        int baseZ = (int) ((i << 26) >> 38);
+        long j = (((long) (baseX >> 4) & 4194303L) << 42) | (((long) (baseY >> 4) & 1048575L)) | (((long) (baseZ >> 4) & 4194303L) << 20);
+        // Paper end
         int k = SectionPosition.c(j);
         synchronized (this.visibleUpdateLock) { // Paper - avoid copying light data
         LightEngineStorageSky.a lightenginestoragesky_a = (LightEngineStorageSky.a) this.e_visible; // Paper - avoid copying light data - must be after lock acquire
@@ -43,7 +48,7 @@ public class LightEngineStorageSky extends LightEngineStorage<LightEngineStorage
                 }
             }
 
-            return nibblearray.a(SectionPosition.b(BlockPosition.b(i)), SectionPosition.b(BlockPosition.c(i)), SectionPosition.b(BlockPosition.d(i)));
+            return nibblearray.a(baseX & 15, (int) ((i << 52) >> 52) & 15, (int) baseZ & 15); // Paper - y changed above
         } else {
             return 15;
         }
@@ -162,7 +167,7 @@ public class LightEngineStorageSky extends LightEngineStorage<LightEngineStorage
             if (k != ((LightEngineStorageSky.a) this.f).b && SectionPosition.c(j) < k) {
                 NibbleArray nibblearray1;
 
-                while ((nibblearray1 = this.a(j, true)) == null) {
+                while ((nibblearray1 = this.updating.getUpdatingOptimized(j)) == null) { // Paper
                     j = SectionPosition.a(j, EnumDirection.UP);
                 }
 
@@ -186,7 +191,10 @@ public class LightEngineStorageSky extends LightEngineStorage<LightEngineStorage
                 longiterator = this.m.iterator();
 
                 while (longiterator.hasNext()) {
-                    i = (Long) longiterator.next();
+                    i = longiterator.nextLong(); // Paper
+                    int baseX = (int) (i >> 42) << 4; // Paper
+                    int baseY = (int) (i << 44 >> 44) << 4; // Paper
+                    int baseZ = (int) (i << 22 >> 42) << 4; // Paper
                     j = this.c(i);
                     if (j != 2 && !this.n.contains(i) && this.l.add(i)) {
                         int l;
@@ -197,10 +205,10 @@ public class LightEngineStorageSky extends LightEngineStorage<LightEngineStorage
                                 ((LightEngineStorageSky.a) this.f).a(i);
                             }
 
-                            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));
+                            Arrays.fill(this.updating.getUpdatingOptimized(i).asBytesPoolSafe(), (byte) -1); // Paper - use optimized
+                            k = baseX; // Paper
+                            l = baseY; // Paper
+                            int i1 = baseZ; // Paper
                             EnumDirection[] aenumdirection = LightEngineStorageSky.k;
                             int j1 = aenumdirection.length;
 
@@ -209,7 +217,7 @@ public class LightEngineStorageSky extends LightEngineStorage<LightEngineStorage
                             for (int l1 = 0; l1 < j1; ++l1) {
                                 EnumDirection enumdirection = aenumdirection[l1];
 
-                                k1 = SectionPosition.a(i, enumdirection);
+                                k1 = SectionPosition.asLong(baseX + enumdirection.getAdjacentX(), baseY + enumdirection.getAdjacentY(), baseZ + enumdirection.getAdjacentZ()); // Paper
                                 if ((this.n.contains(k1) || !this.l.contains(k1) && !this.m.contains(k1)) && this.g(k1)) {
                                     for (int i2 = 0; i2 < 16; ++i2) {
                                         for (int j2 = 0; j2 < 16; ++j2) {
@@ -242,16 +250,16 @@ public class LightEngineStorageSky extends LightEngineStorage<LightEngineStorage
 
                             for (int i3 = 0; i3 < 16; ++i3) {
                                 for (j1 = 0; j1 < 16; ++j1) {
-                                    long j3 = BlockPosition.a(SectionPosition.c(SectionPosition.b(i)) + i3, SectionPosition.c(SectionPosition.c(i)), SectionPosition.c(SectionPosition.d(i)) + j1);
+                                    long j3 = BlockPosition.a(baseX + i3, baseY, baseZ + j1); // Paper
 
-                                    k1 = BlockPosition.a(SectionPosition.c(SectionPosition.b(i)) + i3, SectionPosition.c(SectionPosition.c(i)) - 1, SectionPosition.c(SectionPosition.d(i)) + j1);
+                                    k1 = BlockPosition.a(baseX + i3, baseY - 1, baseZ + j1); // Paper
                                     lightenginelayer.a(j3, k1, lightenginelayer.b(j3, k1, 0), true);
                                 }
                             }
                         } else {
                             for (k = 0; k < 16; ++k) {
                                 for (l = 0; l < 16; ++l) {
-                                    long k3 = BlockPosition.a(SectionPosition.c(SectionPosition.b(i)) + k, SectionPosition.c(SectionPosition.c(i)) + 16 - 1, SectionPosition.c(SectionPosition.d(i)) + l);
+                                    long k3 = BlockPosition.a(baseX + k, baseY + 16 - 1, baseZ + l); // Paper
 
                                     lightenginelayer.a(Long.MAX_VALUE, k3, 0, true);
                                 }
@@ -266,11 +274,14 @@ public class LightEngineStorageSky extends LightEngineStorage<LightEngineStorage
                 longiterator = this.n.iterator();
 
                 while (longiterator.hasNext()) {
-                    i = (Long) longiterator.next();
+                    i = longiterator.nextLong(); // Paper
+                    int baseX = (int) (i >> 42) << 4; // Paper
+                    int baseY = (int) (i << 44 >> 44) << 4; // Paper
+                    int baseZ = (int) (i << 22 >> 42) << 4; // Paper
                     if (this.l.remove(i) && this.g(i)) {
                         for (j = 0; j < 16; ++j) {
                             for (k = 0; k < 16; ++k) {
-                                long l3 = BlockPosition.a(SectionPosition.c(SectionPosition.b(i)) + j, SectionPosition.c(SectionPosition.c(i)) + 16 - 1, SectionPosition.c(SectionPosition.d(i)) + k);
+                                long l3 = BlockPosition.a(baseX + j, baseY + 16 - 1, baseZ + k); // Paper
 
                                 lightenginelayer.a(Long.MAX_VALUE, l3, 15, false);
                             }
diff --git a/src/main/java/net/minecraft/server/LightEngineThreaded.java b/src/main/java/net/minecraft/server/LightEngineThreaded.java
index 8776799de033f02b0f87e9ea7e4a4ce912e94dd4..72cc711d6c2645aed44f208ee44f8702d64c5af8 100644
--- a/src/main/java/net/minecraft/server/LightEngineThreaded.java
+++ b/src/main/java/net/minecraft/server/LightEngineThreaded.java
@@ -15,8 +15,70 @@ public class LightEngineThreaded extends LightEngine implements AutoCloseable {
 
     private static final Logger LOGGER = LogManager.getLogger();
     private final ThreadedMailbox<Runnable> b;
-    private final ObjectList<Pair<LightEngineThreaded.Update, Runnable>> c = new ObjectArrayList();
-    private final PlayerChunkMap d;
+    // Paper start - add urgent queue, switch to ArrayDeque
+    private long nextNonUrgent = 0;
+    private boolean shouldPollNonUrgent() {
+        return urgent.isEmpty() && !c.isEmpty() && (this.c.size() >= this.f || System.nanoTime() > nextNonUrgent);
+    }
+
+    private boolean shouldPollUrgent() {
+        return (super.a() || !urgent.isEmpty());
+    }
+
+    private IntSupplier getChunkPrioritySupplier(ChunkCoordIntPair coords) {
+        return getChunkMap().getPrioritySupplier(coords.pair());
+    }
+    private static final int MAX_PRIORITIES = PlayerChunkMap.GOLDEN_TICKET + 2;
+    private static class LightQueueBucket extends java.util.ArrayDeque<Pair<LightEngineThreaded.Update, Runnable>> {
+        public LightQueueBucket() {
+            super(64);
+        }
+    }
+    // Retain the chunks priority level for queued light tasks
+    private static class LightQueue {
+
+        private int size = 0;
+        private int lowestPriority = MAX_PRIORITIES;
+        private final LightQueueBucket[] buckets = new LightQueueBucket[MAX_PRIORITIES];
+
+        private LightQueue() {
+            for (int i = 0; i < buckets.length; i++) {
+                buckets[i] = new LightQueueBucket();
+            }
+        }
+
+        public final void add(int priority, LightEngineThreaded.Update type, Runnable run) {
+            this.size++;
+            if (lowestPriority > priority) {
+                lowestPriority = priority;
+            }
+            this.buckets[priority].add(new Pair<>(type, run));
+        }
+
+        public final boolean isEmpty() {
+            return this.size == 0;
+        }
+
+        public final int size() {
+            return this.size;
+        }
+
+        public Pair<Update, Runnable> poll() {
+            for (; lowestPriority < MAX_PRIORITIES; lowestPriority++) {
+                Pair<Update, Runnable> entry = buckets[lowestPriority].pollFirst();
+                if (entry != null) {
+                    this.size--;
+                    return entry;
+                }
+            }
+            return null;
+        }
+    }
+
+    private final LightQueue urgent = new LightQueue();
+    private final LightQueue c = new LightQueue();
+    // Paper end
+    private final PlayerChunkMap d; private PlayerChunkMap getChunkMap() { return d; } // Paper - OBFHELPER
     private final Mailbox<ChunkTaskQueueSorter.a<Runnable>> e;
     private volatile int f = 5;
     private final AtomicBoolean g = new AtomicBoolean();
@@ -110,11 +172,14 @@ public class LightEngineThreaded extends LightEngine implements AutoCloseable {
     }
 
     private void a(int i, int j, IntSupplier intsupplier, LightEngineThreaded.Update lightenginethreaded_update, Runnable runnable) {
+        // Paper start
+        scheduleLightTask(i, j, intsupplier, lightenginethreaded_update, runnable, false);
+    }
+    private void scheduleLightTask(int i, int j, IntSupplier intsupplier, LightEngineThreaded.Update lightenginethreaded_update, Runnable runnable, boolean urgent) {
         this.e.a(ChunkTaskQueueSorter.a(() -> { // Paper - decompile error
-            this.c.add(Pair.of(lightenginethreaded_update, runnable));
-            if (this.c.size() >= this.f) {
-                this.b();
-            }
+            (urgent ? this.urgent : this.c).add(intsupplier.getAsInt(), lightenginethreaded_update, runnable);
+            if (shouldPollUrgent() || shouldPollNonUrgent()) queueUpdate();
+            // Paper end
 
         }, ChunkCoordIntPair.pair(i, j), intsupplier));
     }
@@ -134,7 +199,7 @@ public class LightEngineThreaded extends LightEngine implements AutoCloseable {
         ChunkCoordIntPair chunkcoordintpair = ichunkaccess.getPos();
 
         ichunkaccess.b(false);
-        this.a(chunkcoordintpair.x, chunkcoordintpair.z, LightEngineThreaded.Update.PRE_UPDATE, SystemUtils.a(() -> {
+        this.scheduleLightTask(chunkcoordintpair.x, chunkcoordintpair.z, getChunkPrioritySupplier(chunkcoordintpair), LightEngineThreaded.Update.PRE_UPDATE, SystemUtils.a(() -> { // Paper
             ChunkSection[] achunksection = ichunkaccess.getSections();
 
             for (int i = 0; i < 16; ++i) {
@@ -155,51 +220,58 @@ public class LightEngineThreaded extends LightEngine implements AutoCloseable {
             this.d.c(chunkcoordintpair);
         }, () -> {
             return "lightChunk " + chunkcoordintpair + " " + flag;
-        }));
+        }), true); // Paper - urgent flag
         return CompletableFuture.supplyAsync(() -> {
             ichunkaccess.b(true);
             super.b(chunkcoordintpair, false);
             return ichunkaccess;
         }, (runnable) -> {
-            this.a(chunkcoordintpair.x, chunkcoordintpair.z, LightEngineThreaded.Update.POST_UPDATE, runnable);
+            this.scheduleLightTask(chunkcoordintpair.x, chunkcoordintpair.z, getChunkPrioritySupplier(chunkcoordintpair), LightEngineThreaded.Update.POST_UPDATE, runnable, true); // Paper
+            queueUpdate(); // Paper
         });
     }
 
     public void queueUpdate() {
-        if ((!this.c.isEmpty() || super.a()) && this.g.compareAndSet(false, true)) {
+        if ((shouldPollUrgent() || shouldPollNonUrgent()) && this.g.compareAndSet(false, true)) { // Paper - level check is now in shouldPollUrgent
             this.b.a((() -> { // Paper - decompile error
-                this.b();
+                // Paper start
+                if (shouldPollUrgent()) {
+                    do {
+                        this.runQueue(true);
+                    } while (shouldPollUrgent());
+                } else if (shouldPollNonUrgent()) this.runQueue(false); // don't loop non urgent as urgent might come in
+                // Paper end
                 this.g.set(false);
+                queueUpdate(); // Paper - if we still have work to do, do it!
             }));
         }
 
     }
 
     private void b() {
-        int i = Math.min(this.c.size(), this.f);
-        ObjectListIterator<Pair<LightEngineThreaded.Update, Runnable>> objectlistiterator = this.c.iterator();
-
-        Pair pair;
-        int j;
-
-        for (j = 0; objectlistiterator.hasNext() && j < i; ++j) {
-            pair = (Pair) objectlistiterator.next();
-            if (pair.getFirst() == LightEngineThreaded.Update.PRE_UPDATE) {
-                ((Runnable) pair.getSecond()).run();
+        // Paper start - replace impl, use more effecient deque, avoid single removes (iterator.remove() which does a lot of copying)
+        runQueue(!this.urgent.isEmpty());
+    }
+    private void runQueue(boolean urgent) {
+        LightQueue col = urgent ? this.urgent : c;
+        java.util.List<Pair<LightEngineThreaded.Update, Runnable>> pre = new java.util.ArrayList<>();
+        java.util.List<Pair<LightEngineThreaded.Update, Runnable>> post = new java.util.ArrayList<>();
+        int i = Math.min(col.size(), 8); // process small batches so chunks can progress without waiting for everything
+        Pair<LightEngineThreaded.Update, Runnable> pair;
+        while (i-- > 0 && (pair = col.poll()) != null) {
+            if (pair.getFirst() == Update.PRE_UPDATE) {
+                pre.add(pair);
+            } else {
+                post.add(pair);
             }
         }
 
-        objectlistiterator.back(j);
+        pre.forEach(entry -> entry.getSecond().run());
         super.a(Integer.MAX_VALUE, true, true);
+        post.forEach(entry -> entry.getSecond().run());
 
-        for (j = 0; objectlistiterator.hasNext() && j < i; ++j) {
-            pair = (Pair) objectlistiterator.next();
-            if (pair.getFirst() == LightEngineThreaded.Update.POST_UPDATE) {
-                ((Runnable) pair.getSecond()).run();
-            }
-
-            objectlistiterator.remove();
-        }
+        if (!urgent && this.c.isEmpty()) nextNonUrgent = System.nanoTime() + (50 * 1000000);
+        // Paper end
 
     }
 
diff --git a/src/main/java/net/minecraft/server/PlayerChunkMap.java b/src/main/java/net/minecraft/server/PlayerChunkMap.java
index babac7a8513a1f7698ef2fb7263f13f8f3c9717c..e00692f0e19798798b1bc38c8c4c53be71447b21 100644
--- a/src/main/java/net/minecraft/server/PlayerChunkMap.java
+++ b/src/main/java/net/minecraft/server/PlayerChunkMap.java
@@ -629,6 +629,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
         // Paper end
     }
 
+    protected final IntSupplier getPrioritySupplier(long i) { return c(i); } // Paper - OBFHELPER
     protected IntSupplier c(long i) {
         return () -> {
             PlayerChunk playerchunk = this.getVisibleChunk(i);