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, 34 insertions, 0 deletions

diff --git a/patches/server/0180-Disable-Explicit-Network-Manager-Flushing.patch b/patches/server/0180-Disable-Explicit-Network-Manager-Flushing.patch
new file mode 100644
index 0000000000..9ddb02e579
--- /dev/null
+++ b/patches/server/0180-Disable-Explicit-Network-Manager-Flushing.patch
@@ -0,0 +1,34 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Aikar <[email protected]>
+Date: Sun, 11 Mar 2018 14:13:33 -0400
+Subject: [PATCH] Disable Explicit Network Manager Flushing
+
+This seems completely pointless, as packet dispatch uses .writeAndFlush.
+
+Things seem to work fine without explicit flushing, but incase issues arise,
+provide a System property to re-enable it using improved logic of doing the
+flushing on the netty event loop, so it won't do the flush on the main thread.
+
+Renable flushing by passing -Dpaper.explicit-flush=true
+
+diff --git a/src/main/java/net/minecraft/network/Connection.java b/src/main/java/net/minecraft/network/Connection.java
+index 9f4d21b3316c1faebc043fda711b0a9d0411dfff..7d85817a0a041c2fa257396d1508488bfc7da55b 100644
+--- a/src/main/java/net/minecraft/network/Connection.java
++++ b/src/main/java/net/minecraft/network/Connection.java
+@@ -114,6 +114,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
+     // Paper start - NetworkClient implementation
+     public int protocolVersion;
+     public java.net.InetSocketAddress virtualHost;
++    private static boolean enableExplicitFlush = Boolean.getBoolean("paper.explicit-flush");
+     // Paper end
+ 
+     public Connection(PacketFlow side) {
+@@ -309,7 +310,7 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
+         }
+ 
+         if (this.channel != null) {
+-            this.channel.flush();
++            if (enableExplicitFlush) this.channel.eventLoop().execute(() -> this.channel.flush()); // Paper - we don't need to explicit flush here, but allow opt in incase issues are found to a better version
+         }
+ 
+         if (this.tickCount++ % 20 == 0) {