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, 21 insertions, 0 deletions

diff --git a/patches/server/0724-Don-t-read-neighbour-chunk-data-off-disk-when-conver.patch b/patches/server/0724-Don-t-read-neighbour-chunk-data-off-disk-when-conver.patch
new file mode 100644
index 0000000000..112bd2a090
--- /dev/null
+++ b/patches/server/0724-Don-t-read-neighbour-chunk-data-off-disk-when-conver.patch
@@ -0,0 +1,21 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Spottedleaf <[email protected]>
+Date: Sun, 11 Apr 2021 02:58:48 -0700
+Subject: [PATCH] Don't read neighbour chunk data off disk when converting
+ chunks
+
+Lighting is purged on update anyways, so let's not add more
+into the conversion process
+
+diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkStorage.java b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkStorage.java
+index 84ad2f6dfe33d747453365656c1a0114ea6d2a54..6e9af1401918995e3c268eea7d4a74af94707242 100644
+--- a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkStorage.java
++++ b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkStorage.java
+@@ -51,6 +51,7 @@ public class ChunkStorage implements AutoCloseable {
+ 
+     // CraftBukkit start
+     private boolean check(ServerChunkCache cps, int x, int z) {
++        if (true) return true; // Paper - this isn't even needed anymore, light is purged updating to 1.14+, why are we holding up the conversion process reading chunk data off disk - return true, we need to set light populated to true so the converter recognizes the chunk as being "full"
+         ChunkPos pos = new ChunkPos(x, z);
+         if (cps != null) {
+             //com.google.common.base.Preconditions.checkState(org.bukkit.Bukkit.isPrimaryThread(), "primary thread"); // Paper - this function is now MT-Safe