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.

1 files changed, 40 insertions, 0 deletions

diff --git a/patches/server/0249-Optimize-MappedRegistry.patch b/patches/server/0249-Optimize-MappedRegistry.patch
new file mode 100644
index 0000000000..70684ff905
--- /dev/null
+++ b/patches/server/0249-Optimize-MappedRegistry.patch
@@ -0,0 +1,40 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Aikar <[email protected]>
+Date: Sun, 26 Aug 2018 20:49:50 -0400
+Subject: [PATCH] Optimize MappedRegistry
+
+Use larger initial sizes to increase bucket capacity on the BiMap
+
+BiMap.get was seen to be using a good bit of CPU time.
+
+diff --git a/src/main/java/net/minecraft/core/MappedRegistry.java b/src/main/java/net/minecraft/core/MappedRegistry.java
+index db530be96664fc45c881f7438c739109a0aace75..3ef5d440fd3ce209110543bfd36569e846a5b749 100644
+--- a/src/main/java/net/minecraft/core/MappedRegistry.java
++++ b/src/main/java/net/minecraft/core/MappedRegistry.java
+@@ -37,13 +37,11 @@ import org.slf4j.Logger;
+ public class MappedRegistry<T> extends WritableRegistry<T> {
+     private static final Logger LOGGER = LogUtils.getLogger();
+     private final ObjectList<Holder.Reference<T>> byId = new ObjectArrayList<>(256);
+-    private final Object2IntMap<T> toId = Util.make(new Object2IntOpenCustomHashMap<>(Util.identityStrategy()), (object2IntOpenCustomHashMap) -> {
+-        object2IntOpenCustomHashMap.defaultReturnValue(-1);
+-    });
+-    private final Map<ResourceLocation, Holder.Reference<T>> byLocation = new HashMap<>();
+-    private final Map<ResourceKey<T>, Holder.Reference<T>> byKey = new HashMap<>();
+-    private final Map<T, Holder.Reference<T>> byValue = new IdentityHashMap<>();
+-    private final Map<T, Lifecycle> lifecycles = new IdentityHashMap<>();
++    private final it.unimi.dsi.fastutil.objects.Reference2IntOpenHashMap<T> toId = new it.unimi.dsi.fastutil.objects.Reference2IntOpenHashMap<T>(2048);// Paper - use bigger expected size to reduce collisions and direct intent for FastUtil to be identity map
++    private final Map<ResourceLocation, Holder.Reference<T>> byLocation = new HashMap<>(2048); // Paper - use bigger expected size to reduce collisions
++    private final Map<ResourceKey<T>, Holder.Reference<T>> byKey = new HashMap<>(2048); // Paper - use bigger expected size to reduce collisions
++    private final Map<T, Holder.Reference<T>> byValue = new IdentityHashMap<>(2048); // Paper - use bigger expected size to reduce collisions
++    private final Map<T, Lifecycle> lifecycles = new IdentityHashMap<>(2048); // Paper - use bigger expected size to reduce collisions
+     private Lifecycle elementsLifecycle;
+     private volatile Map<TagKey<T>, HolderSet.Named<T>> tags = new IdentityHashMap<>();
+     private boolean frozen;
+@@ -63,6 +61,7 @@ public class MappedRegistry<T> extends WritableRegistry<T> {
+             this.intrusiveHolderCache = new IdentityHashMap<>();
+         }
+ 
++        this.toId.defaultReturnValue(-1); // Paper
+     }
+ 
+     private List<Holder.Reference<T>> holdersInOrder() {