Paper/patches/server/0729-Separate-lookup-locking-from-state-access-in-UserCac.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <spottedleaf@spottedleaf.dev>
Date: Sat, 11 Jul 2020 05:09:28 -0700
Subject: [PATCH] Separate lookup locking from state access in UserCache

Prevent lookups from stalling simple state access/write calls

diff --git a/src/main/java/net/minecraft/server/players/GameProfileCache.java b/src/main/java/net/minecraft/server/players/GameProfileCache.java
index d7eba4190110b92641664c827c6bc50f62d2ae15..534373a1e305942d63ffb0fc97ea3f165eca76b5 100644
--- a/src/main/java/net/minecraft/server/players/GameProfileCache.java
+++ b/src/main/java/net/minecraft/server/players/GameProfileCache.java
@@ -62,6 +62,11 @@ public class GameProfileCache {
     @Nullable
     private Executor executor;
 
+    // Paper start
+    protected final java.util.concurrent.locks.ReentrantLock stateLock = new java.util.concurrent.locks.ReentrantLock();
+    protected final java.util.concurrent.locks.ReentrantLock lookupLock = new java.util.concurrent.locks.ReentrantLock();
+    // Paper end
+
     public GameProfileCache(GameProfileRepository profileRepository, File cacheFile) {
         this.profileRepository = profileRepository;
         this.file = cacheFile;
@@ -69,6 +74,7 @@ public class GameProfileCache {
     }
 
     private void safeAdd(GameProfileCache.GameProfileInfo entry) {
+        try { this.stateLock.lock(); // Paper - allow better concurrency
         GameProfile gameprofile = entry.getProfile();
 
         entry.setLastAccess(this.getNextOperation());
@@ -83,6 +89,7 @@ public class GameProfileCache {
         if (uuid != null) {
             this.profilesByUUID.put(uuid, entry);
         }
+        } finally { this.stateLock.unlock(); } // Paper - allow better concurrency
 
     }
 
@@ -119,7 +126,7 @@ public class GameProfileCache {
         return com.destroystokyo.paper.PaperConfig.isProxyOnlineMode(); // Paper
     }
 
-    public synchronized void add(GameProfile profile) { // Paper - synchronize
+    public void add(GameProfile profile) { // Paper - synchronize // Paper - allow better concurrency
         Calendar calendar = Calendar.getInstance();
 
         calendar.setTime(new Date());
@@ -137,17 +144,20 @@ public class GameProfileCache {
 
     // Paper start
     @Nullable public GameProfile getProfileIfCached(String name) {
+        try { this.stateLock.lock(); // Paper - allow better concurrency
         GameProfileCache.GameProfileInfo entry = this.profilesByName.get(name.toLowerCase(Locale.ROOT));
         if (entry == null) {
             return null;
         }
         entry.setLastAccess(this.getNextOperation());
         return entry.getProfile();
+        } finally { this.stateLock.unlock(); } // Paper - allow better concurrency
     }
     // Paper end
 
-    public synchronized Optional<GameProfile> get(String name) { // Paper - synchronize
+    public Optional<GameProfile> get(String name) { // Paper - synchronize // Paper start - allow better concurrency
         String s1 = name.toLowerCase(Locale.ROOT);
+        boolean stateLocked = true; try { this.stateLock.lock(); // Paper - allow better concurrency
         GameProfileCache.GameProfileInfo usercache_usercacheentry = (GameProfileCache.GameProfileInfo) this.profilesByName.get(s1);
         boolean flag = false;
 
@@ -163,8 +173,12 @@ public class GameProfileCache {
         if (usercache_usercacheentry != null) {
             usercache_usercacheentry.setLastAccess(this.getNextOperation());
             optional = Optional.of(usercache_usercacheentry.getProfile());
+            stateLocked = false; this.stateLock.unlock(); // Paper - allow better concurrency
         } else {
+            stateLocked = false; this.stateLock.unlock(); // Paper - allow better concurrency
+            try { this.lookupLock.lock(); // Paper - allow better concurrency
             optional = GameProfileCache.lookupGameProfile(this.profileRepository, name); // Spigot - use correct case for offline players
+            } finally { this.lookupLock.unlock(); } // Paper - allow better concurrency
             if (optional.isPresent()) {
                 this.add((GameProfile) optional.get());
                 flag = false;
@@ -176,6 +190,7 @@ public class GameProfileCache {
         }
 
         return optional;
+        } finally { if (stateLocked) {  this.stateLock.unlock(); } } // Paper - allow better concurrency
     }
 
     public void getAsync(String username, Consumer<Optional<GameProfile>> consumer) {
@@ -202,6 +217,7 @@ public class GameProfileCache {
     }
 
     public Optional<GameProfile> get(UUID uuid) {
+        try { this.stateLock.lock(); // Paper - allow better concurrency
         GameProfileCache.GameProfileInfo usercache_usercacheentry = (GameProfileCache.GameProfileInfo) this.profilesByUUID.get(uuid);
 
         if (usercache_usercacheentry == null) {
@@ -210,6 +226,7 @@ public class GameProfileCache {
             usercache_usercacheentry.setLastAccess(this.getNextOperation());
             return Optional.of(usercache_usercacheentry.getProfile());
         }
+        } finally { this.stateLock.unlock(); } // Paper - allow better concurrency
     }
 
     public void setExecutor(Executor executor) {
@@ -290,7 +307,7 @@ public class GameProfileCache {
         JsonArray jsonarray = new JsonArray();
         DateFormat dateformat = GameProfileCache.createDateFormat();
 
-        this.getTopMRUProfiles(org.spigotmc.SpigotConfig.userCacheCap).forEach((usercache_usercacheentry) -> { // Spigot
+        this.listTopMRUProfiles(org.spigotmc.SpigotConfig.userCacheCap).forEach((usercache_usercacheentry) -> { // Spigot // Paper - allow better concurrency
             jsonarray.add(GameProfileCache.writeGameProfile(usercache_usercacheentry, dateformat));
         });
         String s = this.gson.toJson(jsonarray);
@@ -330,8 +347,19 @@ public class GameProfileCache {
     }
 
     private Stream<GameProfileCache.GameProfileInfo> getTopMRUProfiles(int limit) {
-        return ImmutableList.copyOf(this.profilesByUUID.values()).stream().sorted(Comparator.comparing(GameProfileCache.GameProfileInfo::getLastAccess).reversed()).limit((long) limit);
+        // Paper start - allow better concurrency
+        return this.listTopMRUProfiles(limit).stream();
+    }
+
+    private List<GameProfileCache.GameProfileInfo> listTopMRUProfiles(int limit) {
+        try {
+            this.stateLock.lock();
+            return this.profilesByUUID.values().stream().sorted(Comparator.comparing(GameProfileCache.GameProfileInfo::getLastAccess).reversed()).limit(limit).toList();
+        } finally {
+            this.stateLock.unlock();
+        }
     }
+    // Paper end
 
     private static JsonElement writeGameProfile(GameProfileCache.GameProfileInfo entry, DateFormat dateFormat) {
         JsonObject jsonobject = new JsonObject();