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Improve synchronization on chunk gen to not block main - Fixes #1550 

Chunk Generation was occuring while inside of the progressCache lock
this caused the progressCache to stay blocked for a long period of time
which then blocked main when main needed to clean the expiring map.

We now maintain a separate map for pending scheduler entries, that
we can join on if a 2nd request comes in while one is starting.

This strategy keeps the lock only for a fraction of time but
maintains thread safety.

So now the chunk is generated without holding a lock and wont
block the main thread on the expiring map as we will insert it
once ready.
This commit is contained in:
Aikar 2018-10-08 00:45:04 -04:00
parent 2a2d9fb508
commit 1f5866fcf8
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GPG Key ID: 401ADFC9891FAAFE
1 changed files with 55 additions and 6 deletions
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61
Spigot-Server-Patches/0375-Async-Chunk-Loading-and-Generation.patch
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@ -1,4 +1,4 @@
From a10d0f7e8c1c88b4cd66e8e6bddca04e69369ec1 Mon Sep 17 00:00:00 2001
From be56cc5d2ee5ab579c019b798637538ff0544d52 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 21 Jul 2018 16:55:04 -0400
Subject: [PATCH] Async Chunk Loading and Generation
@ -599,10 +599,10 @@ index bdfc7d81ff..a5c4564d60 100644
public IBlockData getType(int i, int j, int k) {
return this.blockIds.a(i, j, k);
diff --git a/src/main/java/net/minecraft/server/ChunkTaskScheduler.java b/src/main/java/net/minecraft/server/ChunkTaskScheduler.java
index 34019bd1b3..d7b9ca3ee7 100644
index 34019bd1b3..fc9091c801 100644
--- a/src/main/java/net/minecraft/server/ChunkTaskScheduler.java
+++ b/src/main/java/net/minecraft/server/ChunkTaskScheduler.java
@@ -20,7 +20,7 @@ public class ChunkTaskScheduler extends Scheduler<ChunkCoordIntPair, ChunkStatus
@@ -20,13 +20,14 @@ public class ChunkTaskScheduler extends Scheduler<ChunkCoordIntPair, ChunkStatus
private final ChunkGenerator<?> d;
private final IChunkLoader e;
private final IAsyncTaskHandler f;
@ -611,15 +611,64 @@ index 34019bd1b3..d7b9ca3ee7 100644
protected boolean a(Scheduler.a scheduler_a) {
ProtoChunk protochunk = (ProtoChunk) scheduler_a.a();
@@ -50,7 +50,7 @@ public class ChunkTaskScheduler extends Scheduler<ChunkCoordIntPair, ChunkStatus
return !protochunk.ab_() /*&& !protochunk.h()*/; // Paper
}
};
+ private final Long2ObjectMap<java.util.concurrent.CompletableFuture<Scheduler.a>> pendingSchedulers = new it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap<>(); // Paper
public ChunkTaskScheduler(int i, World world, ChunkGenerator<?> chunkgenerator, IChunkLoader ichunkloader, IAsyncTaskHandler iasynctaskhandler) {
super("WorldGen", i, ChunkStatus.FINALIZED, () -> {
@@ -50,8 +51,28 @@ public class ChunkTaskScheduler extends Scheduler<ChunkCoordIntPair, ChunkStatus
protected Scheduler.a a(ChunkCoordIntPair chunkcoordintpair, boolean flag) {
IChunkLoader ichunkloader = this.e;
- synchronized (this.e) {
+ synchronized (progressCache) { // Paper - synchronize on progress cache instead
return flag ? (Scheduler.a) this.progressCache.computeIfAbsent(chunkcoordintpair.a(), (i) -> {
- return flag ? (Scheduler.a) this.progressCache.computeIfAbsent(chunkcoordintpair.a(), (i) -> {
+ // Paper start - refactor a lot of this - avoid generating a chunk while holding lock on expiring map
+ java.util.concurrent.CompletableFuture<Scheduler.a> pending = null;
+ boolean created = false;
+ long key = chunkcoordintpair.a();
+ synchronized (pendingSchedulers) {
+ Scheduler.a existing = this.progressCache.get(key);
+ if (existing != null) {
+ return existing;
+ }
+ pending = this.pendingSchedulers.get(key);
+ if (pending == null) {
+ if (!flag) {
+ return null;
+ }
+ created = true;
+ pending = new java.util.concurrent.CompletableFuture<>();
+ pendingSchedulers.put(key, pending);
+ }
+ }
+ if (created) {
+ java.util.function.Function<Long, Scheduler.a> get = (i) -> {
+ // Paper end
ProtoChunk protochunk;
try {
@@ -70,8 +91,18 @@ public class ChunkTaskScheduler extends Scheduler<ChunkCoordIntPair, ChunkStatus
} else {
return new Scheduler.a(chunkcoordintpair, new ProtoChunk(chunkcoordintpair, ChunkConverter.a, this.getWorld()), ChunkStatus.EMPTY); // Paper - Anti-Xray
}
- }) : (Scheduler.a) this.progressCache.get(chunkcoordintpair.a());
+ // Paper start
+ };
+ Scheduler.a scheduler = get.apply(key);
+ progressCache.put(key, scheduler);
+ pending.complete(scheduler);
+ synchronized (pendingSchedulers) {
+ pendingSchedulers.remove(key);
+ }
+ return scheduler;
}
+ return pending.join();
+ // Paper end
}
protected ProtoChunk a(ChunkCoordIntPair chunkcoordintpair, ChunkStatus chunkstatus, Map<ChunkCoordIntPair, ProtoChunk> map) {
diff --git a/src/main/java/net/minecraft/server/DataPaletteBlock.java b/src/main/java/net/minecraft/server/DataPaletteBlock.java
index 71a3636be6..ff0fe25417 100644
--- a/src/main/java/net/minecraft/server/DataPaletteBlock.java