Do some simple queue empty checks in the main outgoing udp loop instead of always performing these on a separate fired thread.

This appears to improve cpu usage since launching a new thread is more expensive than performing a small amount of inline logic.
However, needs testing at scale.

OpenSim/Region/ClientStack/Linden/UDP/LLClientView.cs

@@ -485,6 +485,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             m_udpServer = udpServer;
             m_udpClient = udpClient;
             m_udpClient.OnQueueEmpty += HandleQueueEmpty;
+            m_udpClient.HasUpdates += HandleHasUpdates;
             m_udpClient.OnPacketStats += PopulateStats;
 
             m_prioritizer = new Prioritizer(m_scene);
@@ -4133,8 +4134,14 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 
         void HandleQueueEmpty(ThrottleOutPacketTypeFlags categories)
         {
+//            if (!m_udpServer.IsRunningOutbound)
+//                return;
+
             if ((categories & ThrottleOutPacketTypeFlags.Task) != 0)
             {
+//                if (!m_udpServer.IsRunningOutbound)
+//                    return;
+
                 if (m_maxUpdates == 0 || m_LastQueueFill == 0)
                 {
                     m_maxUpdates = m_udpServer.PrimUpdatesPerCallback;
@@ -4160,6 +4167,27 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                 ImageManager.ProcessImageQueue(m_udpServer.TextureSendLimit);
         }
 
+        internal bool HandleHasUpdates(ThrottleOutPacketTypeFlags categories)
+        {
+            bool hasUpdates = false;
+
+            if ((categories & ThrottleOutPacketTypeFlags.Task) != 0)
+            {
+                if (m_entityUpdates.Count > 0)
+                    hasUpdates = true;
+                else if (m_entityProps.Count > 0)
+                    hasUpdates = true;                   
+            }
+
+            if ((categories & ThrottleOutPacketTypeFlags.Texture) != 0)
+            {
+                if (ImageManager.HasUpdates())
+                    hasUpdates = true;
+            }
+
+            return hasUpdates;
+        }
+
         public void SendAssetUploadCompleteMessage(sbyte AssetType, bool Success, UUID AssetFullID)
         {
             AssetUploadCompletePacket newPack = new AssetUploadCompletePacket();

OpenSim/Region/ClientStack/Linden/UDP/LLImageManager.cs

@@ -206,6 +206,13 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             }
         }
 
+        public bool HasUpdates()
+        {
+            J2KImage image = GetHighestPriorityImage();
+
+            return image != null && image.IsDecoded;
+        }
+
         public bool ProcessImageQueue(int packetsToSend)
         {
             int packetsSent = 0;

OpenSim/Region/ClientStack/Linden/UDP/LLUDPClient.cs

@@ -31,6 +31,7 @@ using System.Net;
 using System.Threading;
 using log4net;
 using OpenSim.Framework;
+using OpenSim.Framework.Monitoring;
 using OpenMetaverse;
 using OpenMetaverse.Packets;
 
@@ -81,6 +82,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         /// hooked to put more data on the empty queue</summary>
         public event QueueEmpty OnQueueEmpty;
 
+        public event Func<ThrottleOutPacketTypeFlags, bool> HasUpdates;
+
         /// <summary>AgentID for this client</summary>
         public readonly UUID AgentID;
         /// <summary>The remote address of the connected client</summary>
@@ -613,14 +616,37 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         /// <param name="categories">Throttle categories to fire the callback for</param>
         private void BeginFireQueueEmpty(ThrottleOutPacketTypeFlags categories)
         {
-            if (m_nextOnQueueEmpty != 0 && (Environment.TickCount & Int32.MaxValue) >= m_nextOnQueueEmpty)
+//            if (m_nextOnQueueEmpty != 0 && (Environment.TickCount & Int32.MaxValue) >= m_nextOnQueueEmpty)
+            if (!m_isQueueEmptyRunning && (Environment.TickCount & Int32.MaxValue) >= m_nextOnQueueEmpty)
             {
+                m_isQueueEmptyRunning = true;
+
+                int start = Environment.TickCount & Int32.MaxValue;
+                const int MIN_CALLBACK_MS = 30;
+
+                m_nextOnQueueEmpty = start + MIN_CALLBACK_MS;
+                if (m_nextOnQueueEmpty == 0)
+                    m_nextOnQueueEmpty = 1;
+
                 // Use a value of 0 to signal that FireQueueEmpty is running
-                m_nextOnQueueEmpty = 0;
+//                m_nextOnQueueEmpty = 0;
+
+                m_categories = categories;
+
+                if (HasUpdates(m_categories))
+                {
                     // Asynchronously run the callback
                     Util.FireAndForget(FireQueueEmpty, categories);
                 }
+                else
+                {
+                    m_isQueueEmptyRunning = false;
                 }
+            }
+        }
+
+        private bool m_isQueueEmptyRunning;
+        private ThrottleOutPacketTypeFlags m_categories = 0;
 
         /// <summary>
         /// Fires the OnQueueEmpty callback and sets the minimum time that it
@@ -631,22 +657,31 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         /// signature</param>
         private void FireQueueEmpty(object o)
         {
-            const int MIN_CALLBACK_MS = 30;
+//            int start = Environment.TickCount & Int32.MaxValue;
+//            const int MIN_CALLBACK_MS = 30;
 
+//            if (m_udpServer.IsRunningOutbound)
+//            {        
                 ThrottleOutPacketTypeFlags categories = (ThrottleOutPacketTypeFlags)o;
                 QueueEmpty callback = OnQueueEmpty;                      
 
-            int start = Environment.TickCount & Int32.MaxValue;
-
                 if (callback != null)
                 {
+//                    if (m_udpServer.IsRunningOutbound)
+//                    {                
                         try { callback(categories); }
                         catch (Exception e) { m_log.Error("[LLUDPCLIENT]: OnQueueEmpty(" + categories + ") threw an exception: " + e.Message, e); }
+//                    }
                 }
+//            }
 
-            m_nextOnQueueEmpty = start + MIN_CALLBACK_MS;
+//            m_nextOnQueueEmpty = start + MIN_CALLBACK_MS;
-            if (m_nextOnQueueEmpty == 0)
+//            if (m_nextOnQueueEmpty == 0)
-                m_nextOnQueueEmpty = 1;
+//                m_nextOnQueueEmpty = 1;
+
+//            }
+
+            m_isQueueEmptyRunning = false;
         }
 
         /// <summary>

OpenSim/Region/ClientStack/Linden/UDP/LLUDPServer.cs

@@ -1662,8 +1662,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             // Action generic every round
             Action<IClientAPI> clientPacketHandler = ClientOutgoingPacketHandler;
 
-//            while (true)
+            while (true)
-            while (base.IsRunningOutbound)
+//            while (base.IsRunningOutbound)
             {
                 try
                 {

OpenSim/Region/ClientStack/Linden/UDP/OpenSimUDPBase.cs

@@ -308,8 +308,8 @@ namespace OpenMetaverse
 
         public void AsyncBeginSend(UDPPacketBuffer buf)
         {
-            if (IsRunningOutbound)
+//            if (IsRunningOutbound)
-            {
+//            {
                 try
                 {
                     m_udpSocket.BeginSendTo(
@@ -323,7 +323,7 @@ namespace OpenMetaverse
                 }
                 catch (SocketException) { }
                 catch (ObjectDisposedException) { }
-            }
+//            }
         }
 
         void AsyncEndSend(IAsyncResult result)