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Paper/patches/server/0714-Execute-chunk-tasks-mid-tick.patch
Spottedleaf 01a13871de
Rewrite chunk system (#8177) 
Patch documentation to come

Issues with the old system that are fixed now:
- World generation does not scale with cpu cores effectively.
- Relies on the main thread for scheduling and maintaining chunk state, dropping chunk load/generate rates at lower tps.
- Unreliable prioritisation of chunk gen/load calls that block the main thread.
- Shutdown logic is utterly unreliable, as it has to wait for all chunks to unload - is it guaranteed that the chunk system is in a state on shutdown that it can reliably do this? Watchdog shutdown also typically failed due to thread checks, which is now resolved.
- Saving of data is not unified (i.e can save chunk data without saving entity data, poses problems for desync if shutdown is really abnormal.
- Entities are not loaded with chunks. This caused quite a bit of headache for Chunk#getEntities API, but now the new chunk system loads entities with chunks so that they are ready whenever the chunk loads in. Effectively brings the behavior back to 1.16 era, but still storing entities in their own separate regionfiles.

The above list is not complete. The patch documentation will complete it.

New chunk system hard relies on starlight and dataconverter, and most importantly the new concurrent utilities in ConcurrentUtil.

Some of the old async chunk i/o interface (i.e the old file io thread reroutes _some_ calls to the new file io thread) is kept for plugin compat reasons. It will be removed in the next major version of minecraft.

The old legacy chunk system patches have been moved to the removed folder in case we need them again.
2022-09-26 01:02:51 -07:00

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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Mon, 6 Apr 2020 04:20:44 -0700
Subject: [PATCH] Execute chunk tasks mid-tick
This will help the server load chunks if tick times are high.
diff --git a/src/main/java/co/aikar/timings/MinecraftTimings.java b/src/main/java/co/aikar/timings/MinecraftTimings.java
index 23e564b05ba438924180c91f9b19a60731eedd1b..5ec241d49ff5e3a161a39006f05823a5de847c5e 100644
--- a/src/main/java/co/aikar/timings/MinecraftTimings.java
+++ b/src/main/java/co/aikar/timings/MinecraftTimings.java
@@ -46,6 +46,8 @@ public final class MinecraftTimings {
public static final Timing antiXrayUpdateTimer = Timings.ofSafe("anti-xray - update");
public static final Timing antiXrayObfuscateTimer = Timings.ofSafe("anti-xray - obfuscate");
+ public static final Timing midTickChunkTasks = Timings.ofSafe("Mid Tick Chunk Tasks");
+
private static final Map<Class<?>, String> taskNameCache = new MapMaker().weakKeys().makeMap();
private MinecraftTimings() {}
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index 79c4ee2dd842fcf29eb91a69e536960c814c1a0d..207c1fb92493757de90f1a583a66ae4ad18b0e3f 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -1298,6 +1298,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
private boolean pollTaskInternal() {
if (super.pollTask()) {
+ this.executeMidTickTasks(); // Paper - execute chunk tasks mid tick
return true;
} else {
if (this.haveTime()) {
@@ -2669,4 +2670,74 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
}
}
// Paper end
+
+ // Paper start - execute chunk tasks mid tick
+ static final long CHUNK_TASK_QUEUE_BACKOFF_MIN_TIME = 25L * 1000L; // 25us
+ static final long MAX_CHUNK_EXEC_TIME = 1000L; // 1us
+
+ static final long TASK_EXECUTION_FAILURE_BACKOFF = 5L * 1000L; // 5us
+
+ private static long lastMidTickExecute;
+ private static long lastMidTickExecuteFailure;
+
+ private boolean tickMidTickTasks() {
+ // give all worlds a fair chance at by targetting them all.
+ // if we execute too many tasks, that's fine - we have logic to correctly handle overuse of allocated time.
+ boolean executed = false;
+ for (ServerLevel world : this.getAllLevels()) {
+ long currTime = System.nanoTime();
+ if (currTime - world.lastMidTickExecuteFailure <= TASK_EXECUTION_FAILURE_BACKOFF) {
+ continue;
+ }
+ if (!world.getChunkSource().pollTask()) {
+ // we need to back off if this fails
+ world.lastMidTickExecuteFailure = currTime;
+ } else {
+ executed = true;
+ }
+ }
+
+ return executed;
+ }
+
+ public final void executeMidTickTasks() {
+ org.spigotmc.AsyncCatcher.catchOp("mid tick chunk task execution");
+ long startTime = System.nanoTime();
+ if ((startTime - lastMidTickExecute) <= CHUNK_TASK_QUEUE_BACKOFF_MIN_TIME || (startTime - lastMidTickExecuteFailure) <= TASK_EXECUTION_FAILURE_BACKOFF) {
+ // it's shown to be bad to constantly hit the queue (chunk loads slow to a crawl), even if no tasks are executed.
+ // so, backoff to prevent this
+ return;
+ }
+
+ co.aikar.timings.MinecraftTimings.midTickChunkTasks.startTiming();
+ try {
+ for (;;) {
+ boolean moreTasks = this.tickMidTickTasks();
+ long currTime = System.nanoTime();
+ long diff = currTime - startTime;
+
+ if (!moreTasks || diff >= MAX_CHUNK_EXEC_TIME) {
+ if (!moreTasks) {
+ lastMidTickExecuteFailure = currTime;
+ }
+
+ // note: negative values reduce the time
+ long overuse = diff - MAX_CHUNK_EXEC_TIME;
+ if (overuse >= (10L * 1000L * 1000L)) { // 10ms
+ // make sure something like a GC or dumb plugin doesn't screw us over...
+ overuse = 10L * 1000L * 1000L; // 10ms
+ }
+
+ double overuseCount = (double)overuse/(double)MAX_CHUNK_EXEC_TIME;
+ long extraSleep = (long)Math.round(overuseCount*CHUNK_TASK_QUEUE_BACKOFF_MIN_TIME);
+
+ lastMidTickExecute = currTime + extraSleep;
+ return;
+ }
+ }
+ } finally {
+ co.aikar.timings.MinecraftTimings.midTickChunkTasks.stopTiming();
+ }
+ }
+ // Paper end - execute chunk tasks mid tick
}
diff --git a/src/main/java/net/minecraft/server/level/ServerChunkCache.java b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
index cfcb3ba96569f3eb24d1035d770c50085f60b772..89ecb5c6c25246d0c71b14cc089386d4c4b83093 100644
--- a/src/main/java/net/minecraft/server/level/ServerChunkCache.java
+++ b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
@@ -748,6 +748,7 @@ public class ServerChunkCache extends ChunkSource {
iterator1 = shuffled.iterator();
}
+ int chunksTicked = 0; // Paper
try {
while (iterator1.hasNext()) {
LevelChunk chunk1 = iterator1.next();
@@ -765,6 +766,7 @@ public class ServerChunkCache extends ChunkSource {
if (true || this.level.shouldTickBlocksAt(chunkcoordintpair.toLong())) { // Paper - the chunk is known ticking
this.level.tickChunk(chunk1, k);
+ if ((chunksTicked++ & 1) == 0) net.minecraft.server.MinecraftServer.getServer().executeMidTickTasks(); // Paper
}
}
// Paper start - optimise chunk tick iteration
diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
index 4fa19370e05600391e60b9b416f343834362cbac..b4b7aa2f7d602fe996ebc320ab9641866b672abe 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -212,6 +212,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
private final StructureManager structureManager;
private final StructureCheck structureCheck;
private final boolean tickTime;
+ public long lastMidTickExecuteFailure; // Paper - execute chunk tasks mid tick
// CraftBukkit start
public final LevelStorageSource.LevelStorageAccess convertable;
@@ -1024,6 +1025,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
if (fluid1.is(fluid)) {
fluid1.tick(this, pos);
}
+ MinecraftServer.getServer().executeMidTickTasks(); // Paper - exec chunk tasks during world tick
}
@@ -1033,6 +1035,7 @@ public class ServerLevel extends Level implements WorldGenLevel {
if (iblockdata.is(block)) {
iblockdata.tick(this, pos, this.random);
}
+ MinecraftServer.getServer().executeMidTickTasks(); // Paper - exec chunk tasks during world tick
}
diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
index e30414e1a5e7907c59917c5cd182bca65bc65825..4a3cfc66fdbff749f098a384c16a2c7cfc72e294 100644
--- a/src/main/java/net/minecraft/world/level/Level.java
+++ b/src/main/java/net/minecraft/world/level/Level.java
@@ -804,6 +804,11 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
// Spigot end
} else if (this.shouldTickBlocksAt(tickingblockentity.getPos())) {
tickingblockentity.tick();
+ // Paper start - execute chunk tasks during tick
+ if ((this.tileTickPosition & 7) == 0) {
+ MinecraftServer.getServer().executeMidTickTasks();
+ }
+ // Paper end - execute chunk tasks during tick
}
}
this.blockEntityTickers.removeAll(toRemove);
@@ -818,6 +823,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
public <T extends Entity> void guardEntityTick(Consumer<T> tickConsumer, T entity) {
try {
tickConsumer.accept(entity);
+ MinecraftServer.getServer().executeMidTickTasks(); // Paper - execute chunk tasks mid tick
} catch (Throwable throwable) {
if (throwable instanceof ThreadDeath) throw throwable; // Paper
// Paper start - Prevent tile entity and entity crashes
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