Committing Jim's optimization to replace the 20ms sleep in outgoing packet handling with an interruptible wait handle

4 files changed, 121 insertions, 50 deletions

diff --git a/OpenSim/Region/ClientStack/LindenUDP/LLClientView.cs b/OpenSim/Region/ClientStack/LindenUDP/LLClientView.cs
index dce9469..38bbce0 100644
--- a/OpenSim/Region/ClientStack/LindenUDP/LLClientView.cs
+++ b/OpenSim/Region/ClientStack/LindenUDP/LLClientView.cs
@@ -3320,6 +3320,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             // If we received an update about our own avatar, process the avatar update priority queue immediately
             if (data.AgentID == m_agentId)
                 ProcessAvatarTerseUpdates();
+            else
+                m_udpServer.SignalOutgoingPacketHandler();
         }
 
         private void ProcessAvatarTerseUpdates()
@@ -3407,6 +3409,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 
             lock (m_primFullUpdates.SyncRoot)
                 m_primFullUpdates.Enqueue(data.priority, objectData, data.localID);
+
+            m_udpServer.SignalOutgoingPacketHandler();
         }
 
         void ProcessPrimFullUpdates()
@@ -3450,6 +3454,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 
             lock (m_primTerseUpdates.SyncRoot)
                 m_primTerseUpdates.Enqueue(data.Priority, objectData, data.LocalID);
+
+            m_udpServer.SignalOutgoingPacketHandler();
         }
 
         void ProcessPrimTerseUpdates()
diff --git a/OpenSim/Region/ClientStack/LindenUDP/LLUDPClient.cs b/OpenSim/Region/ClientStack/LindenUDP/LLUDPClient.cs
index 134cfe5..b9d2c15 100644
--- a/OpenSim/Region/ClientStack/LindenUDP/LLUDPClient.cs
+++ b/OpenSim/Region/ClientStack/LindenUDP/LLUDPClient.cs
@@ -105,9 +105,13 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         public int TickLastPacketReceived;
         /// <summary>Environment.TickCount of the last time the outgoing packet handler executed for this client</summary>
         public int TickLastOutgoingPacketHandler;
+        /// <summary>Keeps track of the number of elapsed milliseconds since the last time the outgoing packet handler executed for this client</summary>
+        public int ElapsedMSOutgoingPacketHandler;
+        /// <summary>Keeps track of the number of 100 millisecond periods elapsed in the outgoing packet handler executed for this client</summary>
+        public int Elapsed100MSOutgoingPacketHandler;
+        /// <summary>Keeps track of the number of 500 millisecond periods elapsed in the outgoing packet handler executed for this client</summary>
+        public int Elapsed500MSOutgoingPacketHandler;
 
-        /// <summary>Timer granularity. This is set to the measured resolution of Environment.TickCount</summary>
-        public readonly float G;
         /// <summary>Smoothed round-trip time. A smoothed average of the round-trip time for sending a
         /// reliable packet to the client and receiving an ACK</summary>
         public float SRTT;
@@ -182,15 +186,14 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                 m_throttleCategories[i] = new TokenBucket(m_throttle, rates.GetLimit(type), rates.GetRate(type));
             }
 
-            // Set the granularity variable used for retransmission calculations to
-            // the measured resolution of Environment.TickCount
-            G = server.TickCountResolution;
-
             // Default the retransmission timeout to three seconds
             RTO = 3000;
 
             // Initialize this to a sane value to prevent early disconnects
-            TickLastPacketReceived = Environment.TickCount;
+            TickLastPacketReceived = Environment.TickCount & Int32.MaxValue;
+            ElapsedMSOutgoingPacketHandler = 0;
+            Elapsed100MSOutgoingPacketHandler = 0;
+            Elapsed500MSOutgoingPacketHandler = 0;
         }
 
         /// <summary>
@@ -391,6 +394,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                 {
                     // Not enough tokens in the bucket, queue this packet
                     queue.Enqueue(packet);
+                    m_udpServer.SignalOutgoingPacketHandler();
                     return true;
                 }
             }
@@ -407,13 +411,15 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         /// </summary>
         /// <remarks>This function is only called from a synchronous loop in the
         /// UDPServer so we don't need to bother making this thread safe</remarks>
-        /// <returns>True if any packets were sent, otherwise false</returns>
-        public bool DequeueOutgoing()
+        /// <returns>The minimum amount of time before the next packet
+        /// can be sent to this client</returns>
+        public int DequeueOutgoing()
         {
             OutgoingPacket packet;
             OpenSim.Framework.LocklessQueue<OutgoingPacket> queue;
             TokenBucket bucket;
-            bool packetSent = false;
+            int dataLength;
+            int minTimeout = Int32.MaxValue;
 
             //string queueDebugOutput = String.Empty; // Serious debug business
 
@@ -428,12 +434,18 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                     // leaving a dequeued packet still waiting to be sent out. Try to
                     // send it again
                     OutgoingPacket nextPacket = m_nextPackets[i];
-                    if (bucket.RemoveTokens(nextPacket.Buffer.DataLength))
+                    dataLength = nextPacket.Buffer.DataLength;
+                    if (bucket.RemoveTokens(dataLength))
                     {
                         // Send the packet
                         m_udpServer.SendPacketFinal(nextPacket);
                         m_nextPackets[i] = null;
-                        packetSent = true;
+                        minTimeout = 0;
+                    }
+                    else if (minTimeout != 0)
+                    {
+                        // Check the minimum amount of time we would have to wait before this packet can be sent out
+                        minTimeout = Math.Min(minTimeout, ((dataLength - bucket.Content) / bucket.DripPerMS) + 1);
                     }
                 }
                 else
@@ -445,16 +457,23 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                     {
                         // A packet was pulled off the queue. See if we have
                         // enough tokens in the bucket to send it out
-                        if (bucket.RemoveTokens(packet.Buffer.DataLength))
+                        dataLength = packet.Buffer.DataLength;
+                        if (bucket.RemoveTokens(dataLength))
                         {
                             // Send the packet
                             m_udpServer.SendPacketFinal(packet);
-                            packetSent = true;
+                            minTimeout = 0;
                         }
                         else
                         {
                             // Save the dequeued packet for the next iteration
                             m_nextPackets[i] = packet;
+
+                            if (minTimeout != 0)
+                            {
+                                // Check the minimum amount of time we would have to wait before this packet can be sent out
+                                minTimeout = Math.Min(minTimeout, ((dataLength - bucket.Content) / bucket.DripPerMS) + 1);
+                            }
                         }
 
                         // If the queue is empty after this dequeue, fire the queue
@@ -473,7 +492,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             }
 
             //m_log.Info("[LLUDPCLIENT]: Queues: " + queueDebugOutput); // Serious debug business
-            return packetSent;
+            return minTimeout;
         }
 
         /// <summary>
@@ -504,7 +523,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             }
 
             // Always round retransmission timeout up to two seconds
-            RTO = Math.Max(2000, (int)(SRTT + Math.Max(G, K * RTTVAR)));
+            RTO = Math.Max(2000, (int)(SRTT + Math.Max(m_udpServer.TickCountResolution, K * RTTVAR)));
             //m_log.Debug("[LLUDPCLIENT]: Setting agent " + this.Agent.FullName + "'s RTO to " + RTO + "ms with an RTTVAR of " +
             //    RTTVAR + " based on new RTT of " + r + "ms");
         }
diff --git a/OpenSim/Region/ClientStack/LindenUDP/LLUDPServer.cs b/OpenSim/Region/ClientStack/LindenUDP/LLUDPServer.cs
index 952d147..7d5c11e 100644
--- a/OpenSim/Region/ClientStack/LindenUDP/LLUDPServer.cs
+++ b/OpenSim/Region/ClientStack/LindenUDP/LLUDPServer.cs
@@ -96,6 +96,9 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 
         private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
 
+        /// <summary>The measured resolution of Environment.TickCount</summary>
+        public readonly float TickCountResolution;
+
         /// <summary>Handlers for incoming packets</summary>
         //PacketEventDictionary packetEvents = new PacketEventDictionary();
         /// <summary>Incoming packets that are awaiting handling</summary>
@@ -112,20 +115,19 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         private Scene m_scene;
         /// <summary>The X/Y coordinates of the scene this UDP server is attached to</summary>
         private Location m_location;
-        /// <summary>The measured resolution of Environment.TickCount</summary>
-        private float m_tickCountResolution;
         /// <summary>The size of the receive buffer for the UDP socket. This value
         /// is passed up to the operating system and used in the system networking
         /// stack. Use zero to leave this value as the default</summary>
         private int m_recvBufferSize;
         /// <summary>Flag to process packets asynchronously or synchronously</summary>
         private bool m_asyncPacketHandling;
-        /// <summary>Track whether or not a packet was sent in the
+        /// <summary>Track the minimum amount of time needed to send the next packet in the
         /// OutgoingPacketHandler loop so we know when to sleep</summary>
-        private bool m_packetSentLastLoop;
+        private int m_minTimeout = Int32.MaxValue;
+        /// <summary>EventWaitHandle to signify the outgoing packet handler thread that
+        /// there is more work to do</summary>
+        private EventWaitHandle m_outgoingWaitHandle;
 
-        /// <summary>The measured resolution of Environment.TickCount</summary>
-        public float TickCountResolution { get { return m_tickCountResolution; } }
         public Socket Server { get { return null; } }
 
         public LLUDPServer(IPAddress listenIP, ref uint port, int proxyPortOffsetParm, bool allow_alternate_port, IConfigSource configSource, AgentCircuitManager circuitManager)
@@ -134,16 +136,17 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             #region Environment.TickCount Measurement
 
             // Measure the resolution of Environment.TickCount
-            m_tickCountResolution = 0f;
+            TickCountResolution = 0f;
             for (int i = 0; i < 5; i++)
             {
                 int start = Environment.TickCount;
                 int now = start;
                 while (now == start)
                     now = Environment.TickCount;
-                m_tickCountResolution += (float)(now - start) * 0.2f;
+                TickCountResolution += (float)(now - start) * 0.2f;
             }
             m_log.Info("[LLUDPSERVER]: Average Environment.TickCount resolution: " + TickCountResolution + "ms");
+            TickCountResolution = (float)Math.Ceiling(TickCountResolution);
 
             #endregion Environment.TickCount Measurement
 
@@ -171,6 +174,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 
             base.Start(m_recvBufferSize, m_asyncPacketHandling);
 
+            m_outgoingWaitHandle = new EventWaitHandle(false, EventResetMode.AutoReset);
+
             // Start the incoming packet processing thread
             Thread incomingThread = new Thread(IncomingPacketHandler);
             incomingThread.Name = "Incoming Packets (" + m_scene.RegionInfo.RegionName + ")";
@@ -185,6 +190,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         {
             m_log.Info("[LLUDPSERVER]: Shutting down the LLUDP server for " + m_scene.RegionInfo.RegionName);
             base.Stop();
+
+            m_outgoingWaitHandle.Close();
         }
 
         public void AddScene(IScene scene)
@@ -768,6 +775,11 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             packetInbox.Clear();
         }
 
+        public bool SignalOutgoingPacketHandler()
+        {
+            return m_outgoingWaitHandle.Set();
+        }
+
         private void OutgoingPacketHandler()
         {
             // Set this culture for the thread that outgoing packets are sent
@@ -778,14 +790,28 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             {
                 try
                 {
-                    m_packetSentLastLoop = false;
+                    m_minTimeout = Int32.MaxValue;
 
+                    // Handle outgoing packets, resends, acknowledgements, and pings for each
+                    // client. m_minTimeout will be set to 0 if more packets are waiting in the
+                    // queues with bandwidth to spare, or the number of milliseconds we need to
+                    // wait before at least one packet can be sent to a client
                     m_scene.ClientManager.ForEachSync(ClientOutgoingPacketHandler);
 
-                    // If no packets at all were sent, sleep to avoid chewing up CPU cycles
-                    // when there is nothing to do
-                    if (!m_packetSentLastLoop)
-                        Thread.Sleep(20);
+                    // Can't wait for a negative amount of time, and put a 100ms ceiling on our
+                    // maximum wait time
+                    m_minTimeout = Utils.Clamp(m_minTimeout, 0, 100);
+
+                    if (m_minTimeout > 0)
+                    {
+                        // Don't bother waiting for a shorter interval than our TickCountResolution
+                        // since the token buckets wouldn't update anyways
+                        m_minTimeout = Math.Max(m_minTimeout, (int)TickCountResolution);
+
+                        // Wait for someone to signal that packets are ready to be sent, or for our
+                        // sleep interval to expire
+                        m_outgoingWaitHandle.WaitOne(m_minTimeout);
+                    }
                 }
                 catch (Exception ex)
                 {
@@ -802,32 +828,48 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                 {
                     LLUDPClient udpClient = ((LLClientView)client).UDPClient;
 
+                    // Update ElapsedMSOutgoingPacketHandler
                     int thisTick = Environment.TickCount & Int32.MaxValue;
-                    int elapsedMS = thisTick - udpClient.TickLastOutgoingPacketHandler;
+                    if (udpClient.TickLastOutgoingPacketHandler > thisTick)
+                        udpClient.ElapsedMSOutgoingPacketHandler += ((Int32.MaxValue - udpClient.TickLastOutgoingPacketHandler) + thisTick);
+                    else
+                        udpClient.ElapsedMSOutgoingPacketHandler += (thisTick - udpClient.TickLastOutgoingPacketHandler);
 
                     if (udpClient.IsConnected)
                     {
                         // Check for pending outgoing resends every 100ms
-                        if (elapsedMS >= 100)
+                        if (udpClient.ElapsedMSOutgoingPacketHandler >= 100)
                         {
                             ResendUnacked(udpClient);
+                            udpClient.ElapsedMSOutgoingPacketHandler -= 100;
+                            udpClient.Elapsed100MSOutgoingPacketHandler += 1;
+                        }
 
-                            // Check for pending outgoing ACKs every 500ms
-                            if (elapsedMS >= 500)
-                            {
-                                SendAcks(udpClient);
-
-                                // Send pings to clients every 5000ms
-                                if (elapsedMS >= 5000)
-                                {
-                                    SendPing(udpClient);
-                                }
-                            }
+                        // Check for pending outgoing ACKs every 500ms
+                        if (udpClient.Elapsed100MSOutgoingPacketHandler >= 5)
+                        {
+                            SendAcks(udpClient);
+                            udpClient.Elapsed100MSOutgoingPacketHandler -= 5;
+                            udpClient.Elapsed500MSOutgoingPacketHandler += 1;
+                        }
+
+                        // Send pings to clients every 5000ms
+                        if (udpClient.Elapsed500MSOutgoingPacketHandler >= 10)
+                        {
+                            SendPing(udpClient);
+                            udpClient.Elapsed500MSOutgoingPacketHandler -= 10;
                         }
 
                         // Dequeue any outgoing packets that are within the throttle limits
-                        if (udpClient.DequeueOutgoing())
-                            m_packetSentLastLoop = true;
+                        // and get the minimum time we would have to sleep before this client
+                        // could send a packet out
+                        int minTimeoutThisLoop = udpClient.DequeueOutgoing();
+                        
+                        // Although this is not thread safe, it is cheaper than locking and the
+                        // worst that will happen is we sleep for slightly longer than the
+                        // minimum necessary interval
+                        if (minTimeoutThisLoop < m_minTimeout)
+                            m_minTimeout = minTimeoutThisLoop;
                     }
 
                     udpClient.TickLastOutgoingPacketHandler = thisTick;
diff --git a/OpenSim/Region/ClientStack/LindenUDP/TokenBucket.cs b/OpenSim/Region/ClientStack/LindenUDP/TokenBucket.cs
index 0a64095..bdbd284 100644
--- a/OpenSim/Region/ClientStack/LindenUDP/TokenBucket.cs
+++ b/OpenSim/Region/ClientStack/LindenUDP/TokenBucket.cs
@@ -98,6 +98,14 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         }
 
         /// <summary>
+        /// The speed limit of this bucket in bytes per millisecond
+        /// </summary>
+        public int DripPerMS
+        {
+            get { return tokensPerMS; }
+        }
+
+        /// <summary>
         /// The number of bytes that can be sent at this moment. This is the
         /// current number of tokens in the bucket
         /// <remarks>If this bucket has a parent bucket that does not have
@@ -106,11 +114,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         /// </summary>
         public int Content
         {
-            get
-            {
-                Drip();
-                return content;
-            }
+            get { return content; }
         }
 
         #endregion Properties
@@ -182,7 +186,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         /// call to Drip
         /// </summary>
         /// <returns>True if tokens were added to the bucket, otherwise false</returns>
-        private bool Drip()
+        public bool Drip()
         {
             if (tokensPerMS == 0)
             {