From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Mon, 25 May 2020 11:02:42 -0400
Subject: [PATCH] Unload leaked Cached Chunks

Due to some complexity in mojangs complicated chain of juggling
whether or not a chunk should be unloaded when the last ticket is
removed, many chunks are remaining around in the cache.

These chunks are never being targetted for unload because they are
vastly out of view distance range and have no reason to be looked at.

This is a huge issue for performance because we have to iterate these
chunks EVERY TICK... This is what's been leading to high SELF time in
Ticking Chunks timings/profiler results.

We will now detect these chunks in that iteration, and automatically
add it to the unload queue when the chunk is found without any tickets.

diff --git a/src/main/java/net/minecraft/server/ChunkProviderServer.java b/src/main/java/net/minecraft/server/ChunkProviderServer.java
index 54e89c9cc6c47ff2c4f4dd5d4c22a391f8a3d6e0..899a49974acf60eb7a160a4b55d1ab389249d3b0 100644
--- a/src/main/java/net/minecraft/server/ChunkProviderServer.java
+++ b/src/main/java/net/minecraft/server/ChunkProviderServer.java
@@ -898,6 +898,29 @@ public class ChunkProviderServer extends IChunkProvider {
                         if (chunksTicked[0]++ % 10 == 0) this.world.getMinecraftServer().midTickLoadChunks(); // Paper
                     }
                 }
+                // Paper start - remove inaccessible chunks leaked
+                else if (playerchunk.getTicketLevel() == playerchunk.oldTicketLevel &&
+                    playerChunkMap.unloadQueue.size() < 100 &&
+                    (playerchunk.lastActivity == 0 || world.getTime() - playerchunk.lastActivity > 20*15) &&
+                    PlayerChunk.getChunkState(playerchunk.getTicketLevel()) == PlayerChunk.State.INACCESSIBLE
+                ) {
+                    ChunkStatus chunkHolderStatus = playerchunk.getChunkHolderStatus();
+                    ChunkStatus desiredStatus = PlayerChunk.getChunkStatus(playerchunk.getTicketLevel());
+                    if (chunkHolderStatus != null && !chunkHolderStatus.isAtLeastStatus(desiredStatus)) {
+                        return;
+                    }
+                    playerchunk.lastActivity = world.getTime();
+                    Chunk chunk = playerchunk.getChunk();
+                    if ((chunk != null && chunk.isAnyNeighborsLoaded()) || !playerchunk.neighborPriorities.isEmpty()) {
+                        return;
+                    }
+                    long key = playerchunk.location.pair();
+                    ArraySetSorted<Ticket<?>> tickets = playerChunkMap.chunkDistanceManager.tickets.get(key);
+                    if (tickets == null || tickets.isEmpty()) {
+                        playerChunkMap.unloadQueue.add(key);
+                    }
+                    // Paper end
+                }
             });
             this.world.getMethodProfiler().enter("customSpawners");
             if (flag1) {
diff --git a/src/main/java/net/minecraft/server/PlayerChunk.java b/src/main/java/net/minecraft/server/PlayerChunk.java
index b8fe42e8123e972b1ec97b048c35d90118076e66..ecac7b72759a3884020b9c19c58d3db3338e0fc3 100644
--- a/src/main/java/net/minecraft/server/PlayerChunk.java
+++ b/src/main/java/net/minecraft/server/PlayerChunk.java
@@ -44,6 +44,7 @@ public class PlayerChunk {
 
     long lastAutoSaveTime; // Paper - incremental autosave
     long inactiveTimeStart; // Paper - incremental autosave
+    long lastActivity; // Paper - fix chunk leak
 
     // Paper start - optimise isOutsideOfRange
     // cached here to avoid a map lookup
@@ -562,6 +563,7 @@ public class PlayerChunk {
     protected void a(PlayerChunkMap playerchunkmap) {
         ChunkStatus chunkstatus = getChunkStatus(this.oldTicketLevel);
         ChunkStatus chunkstatus1 = getChunkStatus(this.ticketLevel);
+        if (oldTicketLevel != ticketLevel) lastActivity = chunkMap.world.getTime(); // Paper - chunk leak
         boolean flag = this.oldTicketLevel <= PlayerChunkMap.GOLDEN_TICKET;
         boolean flag1 = this.ticketLevel <= PlayerChunkMap.GOLDEN_TICKET; // Paper - diff on change: (flag1 = new ticket level is in loadable range)
         PlayerChunk.State playerchunk_state = getChunkState(this.oldTicketLevel);
diff --git a/src/main/java/net/minecraft/server/PlayerChunkMap.java b/src/main/java/net/minecraft/server/PlayerChunkMap.java
index 2b09437642ec846d025b226692f2290f9bb5b556..f0bb519450d5ff2a5c8f7364fa8d8ecac03a6c59 100644
--- a/src/main/java/net/minecraft/server/PlayerChunkMap.java
+++ b/src/main/java/net/minecraft/server/PlayerChunkMap.java
@@ -639,6 +639,7 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
                         }
                     }));
                 }
+                playerchunk.lastActivity = world.getTime(); // Paper - chunk leak
 
                 ChunkStatus chunkstatus = (ChunkStatus) intfunction.apply(j1);
                 CompletableFuture<Either<IChunkAccess, PlayerChunk.Failure>> completablefuture = playerchunk.a(chunkstatus, this);
@@ -871,6 +872,8 @@ public class PlayerChunkMap extends IChunkLoader implements PlayerChunk.d {
         while (longiterator.hasNext()) { // Spigot
             long j = longiterator.nextLong();
             longiterator.remove(); // Spigot
+            ArraySetSorted<Ticket<?>> tickets = chunkDistanceManager.tickets.get(j); // Paper - chunk leak
+            if (tickets != null && !tickets.isEmpty()) continue; // Paper - ticket got added, don't remove
             PlayerChunk playerchunk = (PlayerChunk) this.updatingChunks.remove(j);
 
             if (playerchunk != null) {