Paper-Old/Spigot-Server-Patches/0461-Speed-up-processing-of-chunk-loads-and-generation.patch

From f711da2a5ed987d6abead3d3964343cc90f7a1ef Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Thu, 9 Apr 2020 00:09:26 -0400
Subject: [PATCH] Speed up processing of chunk loads and generation

Credit to Spotted for the idea

A lot of the new chunk system requires constant back and forth the main thread
to handle priority scheduling and ensuring conflicting tasks do not run at the
same time.

The issue is, these queues are only checked at either:

A) Sync Chunk Loads
B) End of Tick while sleeping

This results in generating chunks sitting waiting for a full tick to
complete before it will even start the next unit of work to do.

Additionally, this also delays loading of chunks until this same timing.

We will now periodically poll the chunk task queues throughout the tick,
looking for work to do.
We do this in a fair method that considers all worlds, not just the one being
ticked, so that each world can get 1 task procesed each before the next pass.

We also cap the throughput of these task processes to 1 per world per 0.1ms or
200 max per tick, to ensure that high volume of tasks do not overload the current
tick time.

In a view distance of 15, chunk loading performance was visually faster on the client.

Flying at high speed in spectator mode was able to keep up with chunk loading (as long as they are already generated)

diff --git a/src/main/java/co/aikar/timings/MinecraftTimings.java b/src/main/java/co/aikar/timings/MinecraftTimings.java
index 69e26a8267..434833d50e 100644
--- a/src/main/java/co/aikar/timings/MinecraftTimings.java
+++ b/src/main/java/co/aikar/timings/MinecraftTimings.java
@@ -13,6 +13,7 @@ import java.util.Map;
 public final class MinecraftTimings {
 
     public static final Timing serverOversleep = Timings.ofSafe("Server Oversleep");
+    public static final Timing midTickChunkTasks = Timings.ofSafe("Mid Tick Chunk Tasks");
     public static final Timing playerListTimer = Timings.ofSafe("Player List");
     public static final Timing commandFunctionsTimer = Timings.ofSafe("Command Functions");
     public static final Timing connectionTimer = Timings.ofSafe("Connection Handler");
diff --git a/src/main/java/net/minecraft/server/ChunkProviderServer.java b/src/main/java/net/minecraft/server/ChunkProviderServer.java
index e627440c41..bacfc4cba6 100644
--- a/src/main/java/net/minecraft/server/ChunkProviderServer.java
+++ b/src/main/java/net/minecraft/server/ChunkProviderServer.java
@@ -602,6 +602,7 @@ public class ChunkProviderServer extends IChunkProvider {
         this.world.getMethodProfiler().enter("purge");
         this.world.timings.doChunkMap.startTiming(); // Spigot
         this.chunkMapDistance.purgeTickets();
+        this.world.getMinecraftServer().midTickLoadChunks(); // Paper
         this.tickDistanceManager();
         this.world.timings.doChunkMap.stopTiming(); // Spigot
         this.world.getMethodProfiler().exitEnter("chunks");
@@ -611,6 +612,7 @@ public class ChunkProviderServer extends IChunkProvider {
         this.world.timings.doChunkUnload.startTiming(); // Spigot
         this.world.getMethodProfiler().exitEnter("unload");
         this.playerChunkMap.unloadChunks(booleansupplier);
+        this.world.getMinecraftServer().midTickLoadChunks(); // Paper
         this.world.timings.doChunkUnload.stopTiming(); // Spigot
         this.world.getMethodProfiler().exit();
         this.clearCache();
@@ -669,7 +671,7 @@ public class ChunkProviderServer extends IChunkProvider {
                 entityPlayer.playerNaturallySpawnedEvent.callEvent();
             };
             // Paper end
-            this.playerChunkMap.forEachVisibleChunk((playerchunk) -> { // Paper - safe iterator incase chunk loads, also no wrapping
+            final int[] chunksTicked = {0}; this.playerChunkMap.forEachVisibleChunk((playerchunk) -> { // Paper - safe iterator incase chunk loads, also no wrapping
                 Optional<Chunk> optional = ((Either) playerchunk.b().getNow(PlayerChunk.UNLOADED_CHUNK)).left();
 
                 if (optional.isPresent()) {
@@ -752,6 +754,7 @@ public class ChunkProviderServer extends IChunkProvider {
                         this.world.timings.chunkTicks.startTiming(); // Spigot // Paper
                         this.world.a(chunk, k);
                         this.world.timings.chunkTicks.stopTiming(); // Spigot // Paper
+                        if (chunksTicked[0]++ % 10 == 0) this.world.getMinecraftServer().midTickLoadChunks(); // Paper
                     }
                 }
             });
@@ -893,6 +896,38 @@ public class ChunkProviderServer extends IChunkProvider {
             super.executeTask(runnable);
         }
 
+        // Paper start
+        private long lastChunkTask = 0;
+        public void midTickLoadChunks() {
+            MinecraftServer server = ChunkProviderServer.this.world.getMinecraftServer();
+            try (co.aikar.timings.Timing ignored = co.aikar.timings.MinecraftTimings.midTickChunkTasks.startTiming()) {
+                while (server.canSleepForTick()) {
+                    try {
+                        // always try to load chunks as long as we aren't falling behind, restrain generation/other updates only.
+                        boolean execChunkTask = com.destroystokyo.paper.io.chunk.ChunkTaskManager.pollChunkWaitQueue() || ChunkProviderServer.this.world.asyncChunkTaskManager.pollNextChunkTask(); // Paper
+                        if (ChunkProviderServer.this.tickDistanceManager() || execChunkTask) {
+                            continue;
+                        }
+                        long now = System.nanoTime();
+                        // cap to 1 task every 0.1ms per world and max 200 tasks per tick.
+                        // Anything that doesn't make it past this can load during sleep
+                        // we do not want to use this.executeNext as that also processes chunk loads and might count against task counter.
+                        // We also have already ticked the distance manager above too.
+                        if (server.chunksTasksRan < 200 && now - lastChunkTask > 100000 && super.executeNext()) {
+                            ChunkProviderServer.this.lightEngine.queueUpdate();
+                            server.chunksTasksRan++;
+                            lastChunkTask = now;
+                        }
+                        break;
+                    } finally {
+                        // from below: process pending Chunk loadCallback() and unloadCallback() after each run task
+                        playerChunkMap.callbackExecutor.run();
+                    }
+                }
+            }
+        }
+        // Paper end
+
         @Override
         protected boolean executeNext() {
         // CraftBukkit start - process pending Chunk loadCallback() and unloadCallback() after each run task
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index e35bacac71..2f424e6e8b 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -907,6 +907,7 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
                         // Paper end
                         tickSection = curTime;
                     }
+                    chunksTasksRan = 0; // Paper
                     // Spigot end
 
                     //MinecraftServer.currentTick = (int) (System.currentTimeMillis() / 50); // CraftBukkit // Paper - don't overwrite current tick time
@@ -977,7 +978,7 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
 
     }
 
-    private boolean canSleepForTick() {
+    public boolean canSleepForTick() { // Paper
         // CraftBukkit start
         return this.forceTicks || this.isEntered() || SystemUtils.getMonotonicMillis() < (this.ac ? this.ab : this.nextTick);
     }
@@ -1005,6 +1006,20 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
         });
     }
 
+    // Paper start
+    public int chunksTasksRan = 0;
+    public void midTickLoadChunks() {
+        if (!this.canSleepForTick()) {
+            return;
+        }
+
+        Iterator<WorldServer> iterator = this.getWorlds().iterator();
+        while (this.canSleepForTick() && iterator.hasNext()) {
+            iterator.next().getChunkProvider().serverThreadQueue.midTickLoadChunks();
+        }
+    }
+    // Paper end
+
     @Override
     protected TickTask postToMainThread(Runnable runnable) {
         return new TickTask(this.ticks, runnable);
diff --git a/src/main/java/net/minecraft/server/PlayerChunkMap.java b/src/main/java/net/minecraft/server/PlayerChunkMap.java
index e61ddeb1ff..92c9ab43d7 100644
--- a/src/main/java/net/minecraft/server/PlayerChunkMap.java
+++ b/src/main/java/net/minecraft/server/PlayerChunkMap.java
@@ -793,7 +793,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
         CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> ret = new CompletableFuture<>();
 
         Consumer<ChunkRegionLoader.InProgressChunkHolder> chunkHolderConsumer = (ChunkRegionLoader.InProgressChunkHolder holder) -> {
-            PlayerChunkMap.this.executor.addTask(() -> {
+            com.destroystokyo.paper.io.chunk.ChunkTaskManager.queueChunkWaitTask(() -> {
                 ret.complete(syncLoadComplete.apply(holder, null));
             });
         };
diff --git a/src/main/java/net/minecraft/server/WorldServer.java b/src/main/java/net/minecraft/server/WorldServer.java
index 969c6aadf6..4b9b79a996 100644
--- a/src/main/java/net/minecraft/server/WorldServer.java
+++ b/src/main/java/net/minecraft/server/WorldServer.java
@@ -420,6 +420,7 @@ public class WorldServer extends World {
         }
         timings.scheduledBlocks.stopTiming(); // Spigot
 
+        this.getMinecraftServer().midTickLoadChunks(); // Paper
         gameprofilerfiller.exitEnter("raid");
         this.timings.raids.startTiming(); // Paper - timings
         this.persistentRaid.a();
@@ -432,6 +433,7 @@ public class WorldServer extends World {
         timings.doSounds.startTiming(); // Spigot
         this.ad();
         timings.doSounds.stopTiming(); // Spigot
+        this.getMinecraftServer().midTickLoadChunks(); // Paper
         this.ticking = false;
         gameprofilerfiller.exitEnter("entities");
         boolean flag3 = true || !this.players.isEmpty() || !this.getForceLoadedChunks().isEmpty(); // CraftBukkit - this prevents entity cleanup, other issues on servers with no players
@@ -517,6 +519,7 @@ public class WorldServer extends World {
             timings.entityTick.stopTiming(); // Spigot
 
             this.tickingEntities = false;
+            this.getMinecraftServer().midTickLoadChunks(); // Paper
 
             try (co.aikar.timings.Timing ignored = this.timings.newEntities.startTiming()) { // Paper - timings
             while ((entity = (Entity) this.entitiesToAdd.poll()) != null) {
@@ -527,7 +530,9 @@ public class WorldServer extends World {
 
             gameprofilerfiller.exit();
             timings.tickEntities.stopTiming(); // Spigot
+            this.getMinecraftServer().midTickLoadChunks(); // Paper
             this.tickBlockEntities();
+            this.getMinecraftServer().midTickLoadChunks(); // Paper
         }
 
         gameprofilerfiller.exit();
-- 
2.25.1