fix: Message sending GC allocations

com.unity.netcode.gameobjects/Runtime/Messaging/Messages/NetworkVariableDeltaMessage.cs

@@ -47,7 +47,7 @@ internal struct NetworkVariableDeltaMessage : INetworkMessage
 
         private Dictionary<ulong, List<int>> m_ForwardUpdates;
 
-        private List<int> m_UpdatedNetworkVariables;
+        private NativeList<int> m_UpdatedNetworkVariables;
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private void WriteNetworkVariable(ref FastBufferWriter writer, ref NetworkVariableBase networkVariable, bool ensureNetworkVariableLengthSafety, int nonfragmentedSize, int fragmentedSize)
@@ -217,7 +217,7 @@ public void Handle(ref NetworkContext context)
             var networkBehaviour = networkObject.GetNetworkBehaviourAtOrderIndex(NetworkBehaviourIndex);
             var isServerAndDeltaForwarding = m_ReceivedMessageVersion >= k_ServerDeltaForwardingAndNetworkDelivery && networkManager.IsServer;
             var markNetworkVariableDirty = m_ReceivedMessageVersion >= k_ServerDeltaForwardingAndNetworkDelivery ? false : networkManager.IsServer;
-            m_UpdatedNetworkVariables = new List<int>();
+            m_UpdatedNetworkVariables = new NativeList<int>(Allocator.Temp);
 
             if (networkBehaviour == null)
             {
@@ -396,9 +396,9 @@ public void Handle(ref NetworkContext context)
             // When a server forwards delta updates to connected clients, it needs to preserve the previous value
             // until it is done serializing all valid NetworkVariable field deltas (relative to each client). This
             // is invoked after it is done forwarding the deltas.
-            foreach (var fieldIndex in m_UpdatedNetworkVariables)
+            for (int i = 0; i < m_UpdatedNetworkVariables.Length; i++)
             {
-                networkBehaviour.NetworkVariableFields[fieldIndex].PostDeltaRead();
+                networkBehaviour.NetworkVariableFields[m_UpdatedNetworkVariables[i]].PostDeltaRead();
             }
         }
     }

com.unity.netcode.gameobjects/Runtime/Messaging/Messages/RpcMessages.cs

@@ -83,12 +83,8 @@
             {
                 networkManager.Log.Exception(ex, new Context(LogLevel.Error, "Unhandled RPC exception!").AddNetworkBehaviour(networkBehaviour));
 
-                var methodId = metadata.NetworkRpcMethodId;
-                networkManager.Log.Info(new Context(LogLevel.Developer, "RPC Table Contents").AddCollection(rpcsForBehaviour, entry =>
-                {
-                    var invokePermission = NetworkBehaviour.__rpc_permission_table[networkBehaviour.GetType()][methodId];
-                    return $"{entry.Key} | {entry.Value.Method.Name} | {invokePermission}";
-                }));
+                var invokePermission = permission;
+                networkManager.Log.Info(new Context(LogLevel.Developer, "RPC Table Contents").AddCollection(rpcsForBehaviour, entry => $"{entry.Key} | {entry.Value.Method.Name} | {invokePermission}"));
             }
         }
     }

com.unity.netcode.gameobjects/Runtime/Messaging/NetworkMessageManager.cs

@@ -503,9 +503,9 @@ internal void CleanupDisconnectedClients()
             m_DisconnectedClients.Clear();
         }
 
-        public static int CreateMessageAndGetVersion<T>() where T : INetworkMessage, new()
+        public static int CreateMessageAndGetVersion<T>() where T : struct, INetworkMessage
         {
-            return new T().Version;
+            return default(T).Version;
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -538,10 +538,10 @@ internal int GetMessageVersion(Type type, ulong clientId, bool forReceive = fals
 
 
 
-        public static void ReceiveMessage<T>(FastBufferReader reader, ref NetworkContext context, NetworkMessageManager manager) where T : INetworkMessage, new()
+        public static void ReceiveMessage<T>(FastBufferReader reader, ref NetworkContext context, NetworkMessageManager manager) where T : struct, INetworkMessage
         {
             var messageType = typeof(T);
-            var message = new T();
+            var message = default(T);
             var messageVersion = 0;
 
             // Special cases because these are the messages that carry the version info - thus the version info isn't
@@ -633,8 +633,9 @@ internal int SendMessage<TMessageType, TClientIdListType>(ref TMessageType messa
             return largestSerializedSize;
         }
 
-        internal unsafe int SendPreSerializedMessage<TMessageType>(in FastBufferWriter tmpSerializer, int maxSize, ref TMessageType message, NetworkDelivery delivery, in IReadOnlyList<ulong> clientIds, int messageVersionFilter)
+        internal unsafe int SendPreSerializedMessage<TMessageType, TClientIdListType>(in FastBufferWriter tmpSerializer, int maxSize, ref TMessageType message, NetworkDelivery delivery, in TClientIdListType clientIds, int messageVersionFilter)
             where TMessageType : INetworkMessage
+            where TClientIdListType : IReadOnlyList<ulong>
         {
             using var headerSerializer = new FastBufferWriter(FastBufferWriter.GetWriteSize<NetworkMessageHeader>(), Allocator.Temp);
 

com.unity.netcode.gameobjects/Runtime/Metrics/MetricHooks.cs

@@ -1,10 +1,12 @@
 using System;
+using System.Collections.Generic;
 
 namespace Unity.Netcode
 {
     internal class MetricHooks : INetworkHooks
     {
         private readonly NetworkManager m_NetworkManager;
+        private readonly Dictionary<Type, string> m_CachedTypeNames = new();
 
         public MetricHooks(NetworkManager networkManager)
         {
@@ -17,12 +19,12 @@ public void OnBeforeSendMessage<T>(ulong clientId, ref T message, NetworkDeliver
 
         public void OnAfterSendMessage<T>(ulong clientId, ref T message, NetworkDelivery delivery, int messageSizeBytes) where T : INetworkMessage
         {
-            m_NetworkManager.NetworkMetrics.TrackNetworkMessageSent(clientId, typeof(T).Name, messageSizeBytes);
+            m_NetworkManager.NetworkMetrics.TrackNetworkMessageSent(clientId, GetNameForType(typeof(T)), messageSizeBytes);
         }
 
         public void OnBeforeReceiveMessage(ulong senderId, Type messageType, int messageSizeBytes)
         {
-            m_NetworkManager.NetworkMetrics.TrackNetworkMessageReceived(senderId, messageType.Name, messageSizeBytes);
+            m_NetworkManager.NetworkMetrics.TrackNetworkMessageReceived(senderId, GetNameForType(messageType), messageSizeBytes);
         }
 
         public void OnAfterReceiveMessage(ulong senderId, Type messageType, int messageSizeBytes)
@@ -66,5 +68,22 @@ public void OnAfterHandleMessage<T>(ref T message, ref NetworkContext context) w
         {
             // TODO: Per-message metrics recording moved here
         }
+
+        /// <summary>
+        /// Gets the Name from a given type.
+        /// </summary>
+        private string GetNameForType(Type type)
+        {
+            if (m_CachedTypeNames.TryGetValue(type, out var cachedName))
+            {
+                return cachedName;
+            }
+
+            // type.Name does a reflection lookup that does a GC allocation
+            // Grab the name once and save to a cache.
+            var name = type.Name;
+            m_CachedTypeNames.Add(type, name);
+            return name;
+        }
     }
 }

com.unity.netcode.gameobjects/Runtime/NetworkVariable/Collections/NetworkList.cs

@@ -137,6 +137,15 @@ public override void WriteDelta(FastBufferWriter writer)
             }
         }
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private T ReadValue(FastBufferReader reader)
+        {
+            // T is constrained to unmanaged, use default rather than new() to avoid an allocation.
+            var value = default(T);
+            NetworkVariableSerialization<T>.Serializer.Read(reader, ref value);
+            return value;
+        }
+
         /// <inheritdoc cref="NetworkVariable{T}.WriteField"/>
         public override void WriteField(FastBufferWriter writer)
         {
@@ -154,9 +163,7 @@ public override void ReadField(FastBufferReader reader)
             reader.ReadValueSafe(out ushort count);
             for (int i = 0; i < count; i++)
             {
-                var value = new T();
-                NetworkVariableSerialization<T>.Serializer.Read(reader, ref value);
-                m_List.Add(value);
+                m_List.Add(ReadValue(reader));
             }
         }
 
@@ -178,8 +185,7 @@ public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
                 {
                     case NetworkListEvent<T>.EventType.Add:
                         {
-                            var value = new T();
-                            NetworkVariableSerialization<T>.Serializer.Read(reader, ref value);
+                            var value = ReadValue(reader);
                             m_List.Add(value);
 
                             if (OnListChanged != null)
@@ -188,7 +194,7 @@ public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
                                 {
                                     Type = eventType,
                                     Index = m_List.Length - 1,
-                                    Value = m_List[m_List.Length - 1]
+                                    Value = value
                                 });
                             }
 
@@ -198,7 +204,7 @@ public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
                                 {
                                     Type = eventType,
                                     Index = m_List.Length - 1,
-                                    Value = m_List[m_List.Length - 1]
+                                    Value = value
                                 });
                                 // Preserve the legacy way of handling this
                                 if (keepDirtyDelta)
@@ -211,8 +217,7 @@ public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
                     case NetworkListEvent<T>.EventType.Insert:
                         {
                             ByteUnpacker.ReadValueBitPacked(reader, out int index);
-                            var value = new T();
-                            NetworkVariableSerialization<T>.Serializer.Read(reader, ref value);
+                            var value = ReadValue(reader);
 
                             if (index < m_List.Length)
                             {
@@ -230,7 +235,7 @@ public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
                                 {
                                     Type = eventType,
                                     Index = index,
-                                    Value = m_List[index]
+                                    Value = value
                                 });
                             }
 
@@ -240,7 +245,7 @@ public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
                                 {
                                     Type = eventType,
                                     Index = index,
-                                    Value = m_List[index]
+                                    Value = value
                                 });
                                 // Preserve the legacy way of handling this
                                 if (keepDirtyDelta)
@@ -252,8 +257,7 @@ public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
                         break;
                     case NetworkListEvent<T>.EventType.Remove:
                         {
-                            var value = new T();
-                            NetworkVariableSerialization<T>.Serializer.Read(reader, ref value);
+                            var value = ReadValue(reader);
                             int index = m_List.IndexOf(value);
                             if (index == -1)
                             {
@@ -323,8 +327,7 @@ public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
                     case NetworkListEvent<T>.EventType.Value:
                         {
                             ByteUnpacker.ReadValueBitPacked(reader, out int index);
-                            var value = new T();
-                            NetworkVariableSerialization<T>.Serializer.Read(reader, ref value);
+                            var value = ReadValue(reader);
                             if (index >= m_List.Length)
                             {
                                 throw new Exception("Shouldn't be here, index is higher than list length");

com.unity.netcode.gameobjects/Runtime/Serialization/BitReader.cs

@@ -170,7 +170,7 @@ public unsafe void ReadBit(out bool bit)
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private unsafe void ReadPartialValue<T>(out T value, int bytesToRead, int offsetBytes = 0) where T : unmanaged
         {
-            var val = new T();
+            var val = default(T);
             byte* ptr = ((byte*)&val) + offsetBytes;
             byte* bufferPointer = m_BufferPointer + BytePosition;
             UnsafeUtility.MemCpy(ptr, bufferPointer, bytesToRead);

com.unity.netcode.gameobjects/Runtime/Serialization/FastBufferReader.cs

@@ -707,7 +707,7 @@ public unsafe void ReadPartialValue<T>(out T value, int bytesToRead, int offsetB
             }
 #endif
 
-            var val = new T();
+            var val = default(T);
             byte* ptr = ((byte*)&val) + offsetBytes;
             byte* bufferPointer = Handle->BufferPointer + Handle->Position;
             UnsafeUtility.MemCpy(ptr, bufferPointer, bytesToRead);

com.unity.netcode.gameobjects/Tests/Editor/Messaging/MessageReceivingTests.cs

@@ -1,9 +1,10 @@
 using System;
 using System.Collections.Generic;
 using NUnit.Framework;
-using NUnit.Framework.Internal;
 using Unity.Collections;
 using Unity.Collections.LowLevel.Unsafe;
+using UnityEngine.TestTools.Constraints;
+using Is = NUnit.Framework.Is;
 
 namespace Unity.Netcode.EditorTests
 {
@@ -95,22 +96,23 @@ public void WhenHandlingAMessage_ReceiveMethodIsCalled()
             };
             var message = GetMessage();
 
-            var writer = new FastBufferWriter(1300, Allocator.Temp);
-            using (writer)
-            {
-                writer.TryBeginWrite(FastBufferWriter.GetWriteSize(message));
-                writer.WriteValue(message);
+            using var writer = new FastBufferWriter(1300, Allocator.Temp);
+            writer.TryBeginWrite(FastBufferWriter.GetWriteSize(message));
+            writer.WriteValue(message);
 
-                var reader = new FastBufferReader(writer, Allocator.Temp);
-                using (reader)
-                {
-                    m_MessageManager.HandleMessage(messageHeader, reader, 0, 0, 0);
-                    Assert.IsTrue(TestMessage.Deserialized);
-                    Assert.IsTrue(TestMessage.Handled);
-                    Assert.AreEqual(1, TestMessage.DeserializedValues.Count);
-                    Assert.AreEqual(message, TestMessage.DeserializedValues[0]);
-                }
-            }
+            using var reader = new FastBufferReader(writer, Allocator.Temp);
+            m_MessageManager.HandleMessage(messageHeader, reader, 0, 0, 0);
+            Assert.IsTrue(TestMessage.Deserialized);
+            Assert.IsTrue(TestMessage.Handled);
+            Assert.AreEqual(1, TestMessage.DeserializedValues.Count);
+            Assert.AreEqual(message, TestMessage.DeserializedValues[0]);
+
+            // Check for GC Allocations
+            Assert.That(() =>
+            {
+                reader.Seek(0);
+                m_MessageManager.HandleMessage(messageHeader, reader, 0, 0, 0);
+            }, Is.Not.AllocatingGCMemory());
         }
 
         [Test]
@@ -220,44 +222,45 @@ public unsafe void WhenReceivingMultipleMessagesAndProcessingMessageQueue_Receiv
             var message = GetMessage();
             var message2 = GetMessage();
 
-            var writer = new FastBufferWriter(1300, Allocator.Temp);
-            using (writer)
+            using var writer = new FastBufferWriter(1300, Allocator.Temp);
+            writer.WriteValueSafe(batchHeader);
+            BytePacker.WriteValueBitPacked(writer, messageHeader.MessageType);
+            BytePacker.WriteValueBitPacked(writer, messageHeader.MessageSize);
+            writer.WriteValueSafe(message);
+            BytePacker.WriteValueBitPacked(writer, messageHeader.MessageType);
+            BytePacker.WriteValueBitPacked(writer, messageHeader.MessageSize);
+            writer.WriteValueSafe(message2);
+
+            // Fill out the rest of the batch header
+            writer.Seek(0);
+            batchHeader = new NetworkBatchHeader
             {
-                writer.WriteValueSafe(batchHeader);
-                BytePacker.WriteValueBitPacked(writer, messageHeader.MessageType);
-                BytePacker.WriteValueBitPacked(writer, messageHeader.MessageSize);
-                writer.WriteValueSafe(message);
-                BytePacker.WriteValueBitPacked(writer, messageHeader.MessageType);
-                BytePacker.WriteValueBitPacked(writer, messageHeader.MessageSize);
-                writer.WriteValueSafe(message2);
+                Magic = NetworkBatchHeader.MagicValue,
+                BatchSize = writer.Length,
+                BatchHash = XXHash.Hash64(writer.GetUnsafePtr() + sizeof(NetworkBatchHeader), writer.Length - sizeof(NetworkBatchHeader)),
+                BatchCount = 2
+            };
+            writer.WriteValue(batchHeader);
 
-                // Fill out the rest of the batch header
-                writer.Seek(0);
-                batchHeader = new NetworkBatchHeader
-                {
-                    Magic = NetworkBatchHeader.MagicValue,
-                    BatchSize = writer.Length,
-                    BatchHash = XXHash.Hash64(writer.GetUnsafePtr() + sizeof(NetworkBatchHeader), writer.Length - sizeof(NetworkBatchHeader)),
-                    BatchCount = 2
-                };
-                writer.WriteValue(batchHeader);
+            var data = new ArraySegment<byte>(writer.ToArray());
+            m_MessageManager.HandleIncomingData(0, data, 0);
+            Assert.IsFalse(TestMessage.Deserialized);
+            Assert.IsFalse(TestMessage.Handled);
+            Assert.IsEmpty(TestMessage.DeserializedValues);
 
-                var reader = new FastBufferReader(writer, Allocator.Temp);
-                using (reader)
-                {
-                    m_MessageManager.HandleIncomingData(0, new ArraySegment<byte>(writer.ToArray()), 0);
-                    Assert.IsFalse(TestMessage.Deserialized);
-                    Assert.IsFalse(TestMessage.Handled);
-                    Assert.IsEmpty(TestMessage.DeserializedValues);
+            m_MessageManager.ProcessIncomingMessageQueue();
+            Assert.IsTrue(TestMessage.Deserialized);
+            Assert.IsTrue(TestMessage.Handled);
+            Assert.AreEqual(2, TestMessage.DeserializedValues.Count);
+            Assert.AreEqual(message, TestMessage.DeserializedValues[0]);
+            Assert.AreEqual(message2, TestMessage.DeserializedValues[1]);
 
-                    m_MessageManager.ProcessIncomingMessageQueue();
-                    Assert.IsTrue(TestMessage.Deserialized);
-                    Assert.IsTrue(TestMessage.Handled);
-                    Assert.AreEqual(2, TestMessage.DeserializedValues.Count);
-                    Assert.AreEqual(message, TestMessage.DeserializedValues[0]);
-                    Assert.AreEqual(message2, TestMessage.DeserializedValues[1]);
-                }
-            }
+            // Check for GC Allocations
+            Assert.That(() =>
+            {
+                m_MessageManager.HandleIncomingData(0, data, 0);
+                m_MessageManager.ProcessIncomingMessageQueue();
+            }, Is.Not.AllocatingGCMemory());
         }
     }
 }

com.unity.netcode.gameobjects/Tests/Editor/Serialization/BytePackerTests.cs

@@ -92,7 +92,7 @@ private unsafe void RunTypeTest<T>(T value) where T : unmanaged
                 using (reader)
                 {
 
-                    var outVal = new T();
+                    var outVal = default(T);
                     MethodInfo method;
                     if (value is Enum)
                     {