Merge pull request #2029 from Spottedleaf/optimize-datawatcher

Optimize DataWatcher

Spigot-Server-Patches/0079-Use-Optimized-Collections.patch

@@ -1,4 +1,4 @@
-From 7ec6ae32dc53d6401706f46533d05f47cb554b30 Mon Sep 17 00:00:00 2001
+From b82a8f1e62534de6c4f4bfceeda56a580ca0eaa6 Mon Sep 17 00:00:00 2001
 From: Aikar <aikar@aikar.co>
 Date: Wed, 30 Mar 2016 02:13:24 -0400
 Subject: [PATCH] Use Optimized Collections
@@ -13,7 +13,7 @@ These collections are super fast as seen
 http://java-performance.info/hashmap-overview-jdk-fastutil-goldman-sachs-hppc-koloboke-trove-january-2015/
 
 diff --git a/src/main/java/net/minecraft/server/DataWatcher.java b/src/main/java/net/minecraft/server/DataWatcher.java
-index 79a240cd1..6c259effb 100644
+index 79a240cd1d..f224043d8e 100644
 --- a/src/main/java/net/minecraft/server/DataWatcher.java
 +++ b/src/main/java/net/minecraft/server/DataWatcher.java
 @@ -12,6 +12,7 @@ import java.util.Map;
@@ -29,7 +29,7 @@ index 79a240cd1..6c259effb 100644
      private static final Map<Class<? extends Entity>, Integer> b = Maps.newHashMap();
      private final Entity c;
 -    private final Map<Integer, DataWatcher.Item<?>> d = Maps.newHashMap();
-+    private final Map<Integer, DataWatcher.Item<?>> d = new Int2ObjectOpenHashMap<>(); // Paper
++    private final Int2ObjectOpenHashMap<DataWatcher.Item<?>> d = new Int2ObjectOpenHashMap<>(); // Paper
      private final ReadWriteLock e = new ReentrantReadWriteLock();
      private boolean f = true;
      private boolean g;

Spigot-Server-Patches/0393-Elide-lock-in-DataWatcher.patch

@@ -0,0 +1,140 @@
+From 8cb44a97224fca86ef23ca29a80cbadb9d4ea1d3 Mon Sep 17 00:00:00 2001
+From: Spottedleaf <Spottedleaf@users.noreply.github.com>
+Date: Sat, 11 May 2019 08:19:27 -0700
+Subject: [PATCH] Elide lock in DataWatcher
+
+The lock in DataWatcher is used to prevent concurrent modifications
+to the 'd' field (entries in MCP). However any modifications to
+this map only occur on initialization of an Entity in its
+constructor. This modification is write-locked.
+
+Every other access is through a readlock, which allows
+the threads to pass if there is no thread holding the
+writelock.
+
+Since the writelock is only obtained in the constructor
+of the Entity, the further readlocks are actually
+useless (which get obtained on set, get, etc calls).
+
+diff --git a/src/main/java/net/minecraft/server/DataWatcher.java b/src/main/java/net/minecraft/server/DataWatcher.java
+index f224043d8e..bbea8ef726 100644
+--- a/src/main/java/net/minecraft/server/DataWatcher.java
++++ b/src/main/java/net/minecraft/server/DataWatcher.java
+@@ -23,7 +23,7 @@ public class DataWatcher {
+     private static final Map<Class<? extends Entity>, Integer> b = Maps.newHashMap();
+     private final Entity c;
+     private final Int2ObjectOpenHashMap<DataWatcher.Item<?>> d = new Int2ObjectOpenHashMap<>(); // Paper
+-    private final ReadWriteLock e = new ReentrantReadWriteLock();
++    //private final ReadWriteLock e = new ReentrantReadWriteLock(); // Paper - not required
+     private boolean f = true;
+     private boolean g;
+ 
+@@ -88,30 +88,14 @@ public class DataWatcher {
+     private <T> void registerObject(DataWatcherObject<T> datawatcherobject, T t0) {
+         DataWatcher.Item<T> datawatcher_item = new DataWatcher.Item<>(datawatcherobject, t0);
+ 
+-        this.e.writeLock().lock();
++        //this.e.writeLock().lock(); // Paper - not required
+         this.d.put(datawatcherobject.a(), datawatcher_item);
+         this.f = false;
+-        this.e.writeLock().unlock();
++        //this.e.writeLock().unlock(); // Paper - not required
+     }
+ 
+     private <T> DataWatcher.Item<T> b(DataWatcherObject<T> datawatcherobject) {
+-        this.e.readLock().lock();
+-
+-        DataWatcher.Item datawatcher_item;
+-
+-        try {
+-            datawatcher_item = (DataWatcher.Item) this.d.get(datawatcherobject.a());
+-        } catch (Throwable throwable) {
+-            CrashReport crashreport = CrashReport.a(throwable, "Getting synched entity data");
+-            CrashReportSystemDetails crashreportsystemdetails = crashreport.a("Synched entity data");
+-
+-            crashreportsystemdetails.a("Data ID", (Object) datawatcherobject);
+-            throw new ReportedException(crashreport);
+-        } finally {
+-            this.e.readLock().unlock();
+-        }
+-
+-        return datawatcher_item;
++        return (DataWatcher.Item<T>)this.d.get(datawatcherobject.a()); // Paper - avoid lock and try catch, get() does not fail
+     }
+ 
+     public <T> T get(DataWatcherObject<T> datawatcherobject) {
+@@ -158,7 +142,7 @@ public class DataWatcher {
+         List<DataWatcher.Item<?>> list = null;
+ 
+         if (this.g) {
+-            this.e.readLock().lock();
++            //this.e.readLock().lock(); // Paper - not required
+             Iterator iterator = this.d.values().iterator();
+ 
+             while (iterator.hasNext()) {
+@@ -174,7 +158,7 @@ public class DataWatcher {
+                 }
+             }
+ 
+-            this.e.readLock().unlock();
++            //this.e.readLock().unlock(); // Paper - not required
+         }
+ 
+         this.g = false;
+@@ -182,7 +166,7 @@ public class DataWatcher {
+     }
+ 
+     public void a(PacketDataSerializer packetdataserializer) throws IOException {
+-        this.e.readLock().lock();
++        //this.e.readLock().lock(); // Paper - not required
+         Iterator iterator = this.d.values().iterator();
+ 
+         while (iterator.hasNext()) {
+@@ -191,7 +175,7 @@ public class DataWatcher {
+             a(packetdataserializer, datawatcher_item);
+         }
+ 
+-        this.e.readLock().unlock();
++        //this.e.readLock().unlock(); // Paper - not required
+         packetdataserializer.writeByte(255);
+     }
+ 
+@@ -199,7 +183,7 @@ public class DataWatcher {
+     public List<DataWatcher.Item<?>> c() {
+         List<DataWatcher.Item<?>> list = null;
+ 
+-        this.e.readLock().lock();
++        //this.e.readLock().lock(); // Paper - not required
+ 
+         DataWatcher.Item datawatcher_item;
+ 
+@@ -210,7 +194,7 @@ public class DataWatcher {
+             }
+         }
+ 
+-        this.e.readLock().unlock();
++        //this.e.readLock().unlock(); // Paper - not required
+         return list;
+     }
+ 
+@@ -261,7 +245,7 @@ public class DataWatcher {
+ 
+     public void e() {
+         this.g = false;
+-        this.e.readLock().lock();
++        //this.e.readLock().lock(); // Paper - not required
+         Iterator iterator = this.d.values().iterator();
+ 
+         while (iterator.hasNext()) {
+@@ -270,7 +254,7 @@ public class DataWatcher {
+             datawatcher_item.a(false);
+         }
+ 
+-        this.e.readLock().unlock();
++        //this.e.readLock().unlock(); // Paper - not required
+     }
+ 
+     public static class Item<T> {
+-- 
+2.21.0
+