Experimental change to use an immutable array for iterating ScenePresences, avoiding locking and copying the list each time it is accessed

1 files changed, 84 insertions, 76 deletions

diff --git a/OpenSim/Region/Framework/Scenes/SceneGraph.cs b/OpenSim/Region/Framework/Scenes/SceneGraph.cs
index deee6c3..db055f9 100644
--- a/OpenSim/Region/Framework/Scenes/SceneGraph.cs
+++ b/OpenSim/Region/Framework/Scenes/SceneGraph.cs
@@ -66,7 +66,9 @@ namespace OpenSim.Region.Framework.Scenes
 
         #region Fields
 
-        protected internal Dictionary<UUID, ScenePresence> ScenePresences = new Dictionary<UUID, ScenePresence>();
+        protected Dictionary<UUID, ScenePresence> m_scenePresences = new Dictionary<UUID, ScenePresence>();
+        protected ScenePresence[] m_scenePresenceArray = new ScenePresence[0];
+
         // SceneObjects is not currently populated or used.
         //public Dictionary<UUID, SceneObjectGroup> SceneObjects;
         protected internal EntityManager Entities = new EntityManager();
@@ -126,10 +128,12 @@ namespace OpenSim.Region.Framework.Scenes
 
         protected internal void Close()
         {
-            lock (ScenePresences)
+            lock (m_scenePresences)
             {
-                ScenePresences.Clear();
+                m_scenePresences.Clear();
+                m_scenePresenceArray = new ScenePresence[0];
             }
+
             lock (m_dictionary_lock)
             {
                 SceneObjectGroupsByFullID.Clear();
@@ -157,11 +161,9 @@ namespace OpenSim.Region.Framework.Scenes
 
         protected internal void UpdatePresences()
         {
-            List<ScenePresence> updateScenePresences = GetScenePresences();
-            foreach (ScenePresence pres in updateScenePresences)
-            {
-                pres.Update();
-            }
+            ScenePresence[] updateScenePresences = GetScenePresences();
+            for (int i = 0; i < updateScenePresences.Length; i++)
+                updateScenePresences[i].Update();
         }
 
         protected internal float UpdatePhysics(double elapsed)
@@ -190,15 +192,9 @@ namespace OpenSim.Region.Framework.Scenes
 
         protected internal void UpdateScenePresenceMovement()
         {
-            List<ScenePresence> moveEntities = GetScenePresences();
-
-            foreach (EntityBase entity in moveEntities)
-            {
-                //cfk. This throws occaisional exceptions on a heavily used region
-                //and I added this null check to try to preclude the exception.
-                if (entity != null)
-                    entity.UpdateMovement();
-            }
+            ScenePresence[] moveEntities = GetScenePresences();
+            for (int i = 0; i < moveEntities.Length; i++)
+                moveEntities[i].UpdateMovement();
         }
 
         #endregion
@@ -645,9 +641,34 @@ namespace OpenSim.Region.Framework.Scenes
 
             Entities[presence.UUID] = presence;
 
-            lock (ScenePresences)
+            lock (m_scenePresences)
             {
-                ScenePresences[presence.UUID] = presence;
+                if (!m_scenePresences.ContainsKey(presence.UUID))
+                {
+                    m_scenePresences.Add(presence.UUID, presence);
+
+                    // Create a new array of ScenePresence references
+                    int oldLength = m_scenePresenceArray.Length;
+                    ScenePresence[] newArray = new ScenePresence[oldLength + 1];
+                    Array.Copy(m_scenePresenceArray, newArray, oldLength);
+                    newArray[oldLength] = presence;
+                    m_scenePresenceArray = newArray;
+                }
+                else
+                {
+                    m_scenePresences[presence.UUID] = presence;
+                    
+                    // Do a linear search through the array of ScenePresence references
+                    // and update the modified entry
+                    for (int i = 0; i < m_scenePresenceArray.Length; i++)
+                    {
+                        if (m_scenePresenceArray[i].UUID == presence.UUID)
+                        {
+                            m_scenePresenceArray[i] = presence;
+                            break;
+                        }
+                    }
+                }
             }
         }
 
@@ -663,16 +684,30 @@ namespace OpenSim.Region.Framework.Scenes
                     agentID);
             }
 
-            lock (ScenePresences)
+            lock (m_scenePresences)
             {
-                if (!ScenePresences.Remove(agentID))
+                if (m_scenePresences.Remove(agentID))
+                {
+                    // Copy all of the elements from the previous array
+                    // into the new array except the removed element
+                    int oldLength = m_scenePresenceArray.Length;
+                    ScenePresence[] newArray = new ScenePresence[oldLength - 1];
+                    int j = 0;
+                    for (int i = 0; i < m_scenePresenceArray.Length; i++)
+                    {
+                        ScenePresence presence = m_scenePresenceArray[i];
+                        if (presence.UUID != agentID)
+                        {
+                            newArray[j] = presence;
+                            ++j;
+                        }
+                    }
+                    m_scenePresenceArray = newArray;
+                }
+                else
                 {
                     m_log.WarnFormat("[SCENE] Tried to remove non-existent scene presence with agent ID {0} from scene ScenePresences list", agentID);
                 }
-//                else
-//                {
-//                    m_log.InfoFormat("[SCENE] Removed scene presence {0} from scene presences list", agentID);
-//                }
             }
         }
 
@@ -704,20 +739,21 @@ namespace OpenSim.Region.Framework.Scenes
 
         public void RecalculateStats()
         {
-            List<ScenePresence> SPList = GetScenePresences();
+            ScenePresence[] presences = GetScenePresences();
             int rootcount = 0;
             int childcount = 0;
 
-            foreach (ScenePresence user in SPList)
+            for (int i = 0; i < presences.Length; i++)
             {
+                ScenePresence user = presences[i];
                 if (user.IsChildAgent)
-                    childcount++;
+                    ++childcount;
                 else
-                    rootcount++;
+                    ++rootcount;
             }
+
             m_numRootAgents = rootcount;
             m_numChildAgents = childcount;
-            
         }
 
         public int GetChildAgentCount()
@@ -767,12 +803,9 @@ namespace OpenSim.Region.Framework.Scenes
         /// locking is required to iterate over it.
         /// </summary>
         /// <returns></returns>
-        protected internal List<ScenePresence> GetScenePresences()
+        protected internal ScenePresence[] GetScenePresences()
         {
-            lock (ScenePresences)
-            {
-                return new List<ScenePresence>(ScenePresences.Values);
-            }
+            return m_scenePresenceArray;
         }
 
         protected internal List<ScenePresence> GetAvatars()
@@ -817,14 +850,13 @@ namespace OpenSim.Region.Framework.Scenes
             // No locking of scene presences here since we're passing back a list...
 
             List<ScenePresence> result = new List<ScenePresence>();
-            List<ScenePresence> ScenePresencesList = GetScenePresences();
+            ScenePresence[] scenePresences = GetScenePresences();
 
-            foreach (ScenePresence avatar in ScenePresencesList)
+            for (int i = 0; i < scenePresences.Length; i++)
             {
+                ScenePresence avatar = scenePresences[i];
                 if (filter(avatar))
-                {
                     result.Add(avatar);
-                }
             }
 
             return result;
@@ -839,9 +871,9 @@ namespace OpenSim.Region.Framework.Scenes
         {
             ScenePresence sp;
             
-            lock (ScenePresences)
+            lock (m_scenePresences)
             {
-                ScenePresences.TryGetValue(agentID, out sp);
+                m_scenePresences.TryGetValue(agentID, out sp);
             }
 
             return sp;
@@ -1000,48 +1032,24 @@ namespace OpenSim.Region.Framework.Scenes
 
         protected internal bool TryGetAvatar(UUID avatarId, out ScenePresence avatar)
         {
-            ScenePresence presence;
-            
-            lock (ScenePresences)
-            {
-                if (ScenePresences.TryGetValue(avatarId, out presence))
-                {
-                    avatar = presence;
-                    return true;
-
-                    //if (!presence.IsChildAgent)
-                    //{
-                    //    avatar = presence;
-                    //    return true;
-                    //}
-                    //else
-                    //{
-                    //    m_log.WarnFormat(
-                    //        "[INNER SCENE]: Requested avatar {0} could not be found in scene {1} since it is only registered as a child agent!",
-                    //        avatarId, m_parentScene.RegionInfo.RegionName);
-                    //}
-                }
-            }
-
-            avatar = null;
-            return false;
+            lock (m_scenePresences)
+                return m_scenePresences.TryGetValue(avatarId, out avatar);
         }
 
         protected internal bool TryGetAvatarByName(string avatarName, out ScenePresence avatar)
         {
-            lock (ScenePresences)
+            ScenePresence[] presences = GetScenePresences();
+
+            for (int i = 0; i < presences.Length; i++)
             {
-                foreach (ScenePresence presence in ScenePresences.Values)
+                ScenePresence presence = presences[i];
+
+                if (!presence.IsChildAgent)
                 {
-                    if (!presence.IsChildAgent)
+                    if (String.Compare(avatarName, presence.ControllingClient.Name, true) == 0)
                     {
-                        string name = presence.ControllingClient.Name;
-
-                        if (String.Compare(avatarName, name, true) == 0)
-                        {
-                            avatar = presence;
-                            return true;
-                        }
+                        avatar = presence;
+                        return true;
                     }
                 }
             }