From 6b6c3587bc8544032b96c53c9fd5bcb0cb738625 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Tue, 2 Oct 2018 21:55:30 -0400
Subject: [PATCH] Optimize some light chunk access

light calculations repeatedly looks up the same chunk while going
down on the Y access. Pass the chunk to it to skip many round trips
to the map lookup process.

while the gains arent as big since we have last access cache, it
should hopefully avoid many callstacks of depth and improve inlining,
as well as avoids entering a synchronized code block.

The avoiding of entering synchronized section is the main goal here.
---
 ...h-entity-loss-due-to-unloaded-chunks.patch |  2 +-
 .../Optimize-Light-Recalculations.patch       | 40 ++++++++++++++++++-
 2 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/Spigot-Server-Patches/Fix-issues-with-entity-loss-due-to-unloaded-chunks.patch b/Spigot-Server-Patches/Fix-issues-with-entity-loss-due-to-unloaded-chunks.patch
index 5503554a94..ed1c7a5055 100644
--- a/Spigot-Server-Patches/Fix-issues-with-entity-loss-due-to-unloaded-chunks.patch
+++ b/Spigot-Server-Patches/Fix-issues-with-entity-loss-due-to-unloaded-chunks.patch
@@ -18,7 +18,7 @@ This change ensures the chunks are always loaded when entities are
 added to the world, or a valid entity moves between chunks.
 
 diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
-index 763401835d..3379b68acb 100644
+index 4179ba7cd8..d659ffe9ba 100644
 --- a/src/main/java/net/minecraft/server/World.java
 +++ b/src/main/java/net/minecraft/server/World.java
 @@ -0,0 +0,0 @@ public abstract class World implements IEntityAccess, GeneratorAccess, IIBlockAc
diff --git a/Spigot-Server-Patches/Optimize-Light-Recalculations.patch b/Spigot-Server-Patches/Optimize-Light-Recalculations.patch
index 5c49e9965d..b34241b51a 100644
--- a/Spigot-Server-Patches/Optimize-Light-Recalculations.patch
+++ b/Spigot-Server-Patches/Optimize-Light-Recalculations.patch
@@ -10,10 +10,22 @@ do not impact light calculations.
 So the only way light should change, is if the block itself
 changes from 1 block to another.
 
+Also optimizes to not repeatedly look up the same chunk for
+light lookups.
+
 diff --git a/src/main/java/net/minecraft/server/Chunk.java b/src/main/java/net/minecraft/server/Chunk.java
-index 53aab97866..e4bda70bb9 100644
+index 9162151e2a..651bb23be9 100644
 --- a/src/main/java/net/minecraft/server/Chunk.java
 +++ b/src/main/java/net/minecraft/server/Chunk.java
+@@ -0,0 +0,0 @@ public class Chunk implements IChunkAccess {
+     private void a(int i, int j, int k, int l) {
+         if (l > k && this.areNeighborsLoaded(1)) { // Paper
+             for (int i1 = k; i1 < l; ++i1) {
+-                this.world.c(EnumSkyBlock.SKY, new BlockPosition(i, i1, j));
++                this.world.updateBrightness(EnumSkyBlock.SKY, new BlockPosition(i, i1, j), this); // Paper
+             }
+ 
+             this.x = true;
 @@ -0,0 +0,0 @@ public class Chunk implements IChunkAccess {
              } else {
                  if (flag1) {
@@ -24,7 +36,7 @@ index 53aab97866..e4bda70bb9 100644
                      int i1 = iblockdata.b(this.world, blockposition);
                      int j1 = iblockdata1.b(this.world, blockposition);
 diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
-index 13f69f1b82..763401835d 100644
+index 13f69f1b82..4179ba7cd8 100644
 --- a/src/main/java/net/minecraft/server/World.java
 +++ b/src/main/java/net/minecraft/server/World.java
 @@ -0,0 +0,0 @@ public abstract class World implements IEntityAccess, GeneratorAccess, IIBlockAc
@@ -36,4 +48,28 @@ index 13f69f1b82..763401835d 100644
                      this.methodProfiler.a("checkLight");
                      chunk.runOrQueueLightUpdate(() -> this.r(blockposition)); // Paper - Queue light update
                      this.methodProfiler.e();
+@@ -0,0 +0,0 @@ public abstract class World implements IEntityAccess, GeneratorAccess, IIBlockAc
+         }
+ 
+         if (this.worldProvider.g()) {
+-            for (i1 = k; i1 <= l; ++i1) {
+-                this.c(EnumSkyBlock.SKY, new BlockPosition(i, i1, j));
++            Chunk chunk = getChunkIfLoaded(i >> 4, j >> 4); // Paper
++            for (i1 = k; chunk != null && i1 <= l; ++i1) { // Paper
++                this.updateBrightness(EnumSkyBlock.SKY, new BlockPosition(i, i1, j), chunk); // Paper
+             }
+         }
+ 
+@@ -0,0 +0,0 @@ public abstract class World implements IEntityAccess, GeneratorAccess, IIBlockAc
+     public boolean c(EnumSkyBlock enumskyblock, BlockPosition blockposition) {
+         // CraftBukkit start - Use neighbor cache instead of looking up
+         Chunk chunk = this.getChunkIfLoaded(blockposition.getX() >> 4, blockposition.getZ() >> 4);
++        // Paper start - optimize light updates where chunk is known
++        return updateBrightness(enumskyblock, blockposition, chunk);
++    }
++    public boolean updateBrightness(EnumSkyBlock enumskyblock, BlockPosition blockposition, Chunk chunk) {
++        // Paper end
+         if (chunk == null || !chunk.areNeighborsLoaded(1) /*!this.areChunksLoaded(blockposition, 17, false)*/) {
+             // CraftBukkit end
+             return false;
 --
\ No newline at end of file