From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Mon, 1 Feb 2021 15:35:14 -0800
Subject: [PATCH] Fix chunks refusing to unload at low TPS

The full chunk future is appended to the chunk save future, but
when moving to unloaded ticket level it is not being completed with
the empty chunk access, so the chunk save must wait for the full
chunk future to complete. We can simply schedule to the immediate
executor to get this effect, rather than the main mailbox.

diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index 5eeabc64d5067361c27b68e4268de3596c29787e..66dd1759bb38ebcba49e5858121bfa2bad1ae2f3 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -1220,9 +1220,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
 
                 return chunk;
             });
-        }, (runnable) -> {
-            this.mainThreadMailbox.tell(ChunkTaskPriorityQueueSorter.message(playerchunk, runnable));
-        });
+        }, this.mainThreadExecutor); // Paper - queue to execute immediately so this doesn't delay chunk unloading
     }
 
     public int getTickingGenerated() {