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, 164 insertions, 0 deletions

diff --git a/patches/server/0438-incremental-chunk-and-player-saving.patch b/patches/server/0438-incremental-chunk-and-player-saving.patch
new file mode 100644
index 0000000000..b53d082bfa
--- /dev/null
+++ b/patches/server/0438-incremental-chunk-and-player-saving.patch
@@ -0,0 +1,164 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Shane Freeder <[email protected]>
+Date: Sun, 9 Jun 2019 03:53:22 +0100
+Subject: [PATCH] incremental chunk and player saving
+
+
+diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
+index 1c39e141a392d96548f5ac62fb279ed1f105677d..922475997902dcc85ae42f351ace15e82b5aa638 100644
+--- a/src/main/java/net/minecraft/server/MinecraftServer.java
++++ b/src/main/java/net/minecraft/server/MinecraftServer.java
+@@ -864,7 +864,7 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
+ 
+         try {
+             this.isSaving = true;
+-            this.getPlayerList().saveAll();
++            this.getPlayerList().saveAll(); // Diff on change
+             flag3 = this.saveAllChunks(suppressLogs, flush, force);
+         } finally {
+             this.isSaving = false;
+@@ -1394,13 +1394,28 @@ public abstract class MinecraftServer extends ReentrantBlockableEventLoop<TickTa
+             }
+         }
+ 
+-        if (this.autosavePeriod > 0 && this.tickCount % this.autosavePeriod == 0) { // CraftBukkit
+-            MinecraftServer.LOGGER.debug("Autosave started");
+-            this.profiler.push("save");
+-            this.saveEverything(true, false, false);
+-            this.profiler.pop();
+-            MinecraftServer.LOGGER.debug("Autosave finished");
++        // Paper start - incremental chunk and player saving
++        int playerSaveInterval = io.papermc.paper.configuration.GlobalConfiguration.get().playerAutoSave.rate;
++        if (playerSaveInterval < 0) {
++            playerSaveInterval = autosavePeriod;
+         }
++        this.profiler.push("save");
++        final boolean fullSave = autosavePeriod > 0 && this.tickCount % autosavePeriod == 0;
++        try {
++            this.isSaving = true;
++            if (playerSaveInterval > 0) {
++                this.playerList.saveAll(playerSaveInterval);
++            }
++            for (ServerLevel level : this.getAllLevels()) {
++                if (level.paperConfig().chunks.autoSaveInterval.value() > 0) {
++                    level.saveIncrementally(fullSave);
++                }
++            }
++        } finally {
++            this.isSaving = false;
++        }
++        this.profiler.pop();
++        // Paper end
+         io.papermc.paper.util.CachedLists.reset(); // Paper
+         // Paper start - move executeAll() into full server tick timing
+         try (co.aikar.timings.Timing ignored = MinecraftTimings.processTasksTimer.startTiming()) {
+diff --git a/src/main/java/net/minecraft/server/level/ServerChunkCache.java b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
+index 44766ea7e5dd8f8411b52cf259187d7557cc0c23..fa7801158b68eaa12d6322c9c0def9de37f03814 100644
+--- a/src/main/java/net/minecraft/server/level/ServerChunkCache.java
++++ b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
+@@ -601,6 +601,15 @@ public class ServerChunkCache extends ChunkSource {
+         } // Paper - Timings
+     }
+ 
++    // Paper start - duplicate save, but call incremental
++    public void saveIncrementally() {
++        this.runDistanceManagerUpdates();
++        try (co.aikar.timings.Timing timed = level.timings.chunkSaveData.startTiming()) { // Paper - Timings
++            this.chunkMap.saveIncrementally();
++        } // Paper - Timings
++    }
++    // Paper end
++
+     @Override
+     public void close() throws IOException {
+         // CraftBukkit start
+diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
+index c0e17bbf04723da76ea6952d9558dd4d34b00f6c..fc3e5068473e1586024e87fee3eeeb6cf5124923 100644
+--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
++++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
+@@ -1120,6 +1120,37 @@ public class ServerLevel extends Level implements WorldGenLevel {
+         return !this.server.isUnderSpawnProtection(this, pos, player) && this.getWorldBorder().isWithinBounds(pos);
+     }
+ 
++    // Paper start - derived from below
++    public void saveIncrementally(boolean doFull) {
++        ServerChunkCache chunkproviderserver = this.getChunkSource();
++
++        if (doFull) {
++            org.bukkit.Bukkit.getPluginManager().callEvent(new org.bukkit.event.world.WorldSaveEvent(getWorld()));
++        }
++
++        try (co.aikar.timings.Timing ignored = this.timings.worldSave.startTiming()) {
++            if (doFull) {
++                this.saveLevelData();
++            }
++
++            this.timings.worldSaveChunks.startTiming(); // Paper
++            if (!this.noSave()) chunkproviderserver.saveIncrementally();
++            this.timings.worldSaveChunks.stopTiming(); // Paper
++
++            // Copied from save()
++            // CraftBukkit start - moved from MinecraftServer.saveChunks
++            if (doFull) { // Paper
++                ServerLevel worldserver1 = this;
++
++                this.serverLevelData.setWorldBorder(worldserver1.getWorldBorder().createSettings());
++                this.serverLevelData.setCustomBossEvents(this.server.getCustomBossEvents().save());
++                this.convertable.saveDataTag(this.server.registryHolder, this.serverLevelData, this.server.getPlayerList().getSingleplayerData());
++            }
++            // CraftBukkit end
++        }
++    }
++    // Paper end
++
+     public void save(@Nullable ProgressListener progressListener, boolean flush, boolean savingDisabled) {
+         // Paper start - rewrite chunk system - add close param
+         this.save(progressListener, flush, savingDisabled, false);
+diff --git a/src/main/java/net/minecraft/server/level/ServerPlayer.java b/src/main/java/net/minecraft/server/level/ServerPlayer.java
+index 582b9595aa06dd6787fd84c0ea0058c890f84c33..02bb4ecdc6797d1c5bccc64cc235fe63bdc7ccd4 100644
+--- a/src/main/java/net/minecraft/server/level/ServerPlayer.java
++++ b/src/main/java/net/minecraft/server/level/ServerPlayer.java
+@@ -179,6 +179,7 @@ import org.bukkit.inventory.MainHand;
+ public class ServerPlayer extends Player {
+ 
+     private static final Logger LOGGER = LogUtils.getLogger();
++    public long lastSave = MinecraftServer.currentTick; // Paper
+     private static final int NEUTRAL_MOB_DEATH_NOTIFICATION_RADII_XZ = 32;
+     private static final int NEUTRAL_MOB_DEATH_NOTIFICATION_RADII_Y = 10;
+     public ServerGamePacketListenerImpl connection;
+diff --git a/src/main/java/net/minecraft/server/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
+index f37787b9d018a624b509612729f18ca077b55f55..b0120df807a61db21da04324644fbd71a285f461 100644
+--- a/src/main/java/net/minecraft/server/players/PlayerList.java
++++ b/src/main/java/net/minecraft/server/players/PlayerList.java
+@@ -569,6 +569,7 @@ public abstract class PlayerList {
+     protected void save(ServerPlayer player) {
+         if (!player.getBukkitEntity().isPersistent()) return; // CraftBukkit
+         if (!player.didPlayerJoinEvent) return; // Paper - If we never fired PJE, we disconnected during login. Data has not changed, and additionally, our saved vehicle is not loaded! If we save now, we will lose our vehicle (CraftBukkit bug)
++        player.lastSave = MinecraftServer.currentTick; // Paper
+         this.playerIo.save(player);
+         ServerStatsCounter serverstatisticmanager = (ServerStatsCounter) player.getStats(); // CraftBukkit
+ 
+@@ -1171,10 +1172,22 @@ public abstract class PlayerList {
+     }
+ 
+     public void saveAll() {
++        // Paper start - incremental player saving
++        this.saveAll(-1);
++    }
++
++    public void saveAll(int interval) {
+         net.minecraft.server.MCUtil.ensureMain("Save Players" , () -> { // Paper - Ensure main
+         MinecraftTimings.savePlayers.startTiming(); // Paper
++        int numSaved = 0;
++        long now = MinecraftServer.currentTick;
+         for (int i = 0; i < this.players.size(); ++i) {
+-            this.save(this.players.get(i));
++            ServerPlayer entityplayer = this.players.get(i);
++            if (interval == -1 || now - entityplayer.lastSave >= interval) {
++                this.save(entityplayer);
++                if (interval != -1 && ++numSaved <= io.papermc.paper.configuration.GlobalConfiguration.get().playerAutoSave.maxPerTick()) { break; }
++            }
++            // Paper end
+         }
+         MinecraftTimings.savePlayers.stopTiming(); // Paper
+         return null; }); // Paper - ensure main