From 9a1d62e382309ac3fcbfd62911b954974b2f00f3 Mon Sep 17 00:00:00 2001
From: John L <johlafo@microsoft.com>
Date: Tue, 22 Aug 2017 17:27:19 -0700
Subject: [PATCH] Fix per frame memory allocation in stats manager and social
 manager (#113)

---
 .../api/Social/Manager/MockSocialManager.cs       | 15 ++++++++++++---
 .../Source/api/Social/Manager/SocialManager.cs    | 15 +++++++++++----
 .../Source/api/Stats/Manager/MockStatsManager.cs  | 11 ++++++++++-
 .../Source/api/Stats/Manager/StatsManager.cs      | 12 +++++++++++-
 4 files changed, 44 insertions(+), 9 deletions(-)

diff --git a/CSharpSource/Source/api/Social/Manager/MockSocialManager.cs b/CSharpSource/Source/api/Social/Manager/MockSocialManager.cs
index ff25a02d..42da1659 100644
--- a/CSharpSource/Source/api/Social/Manager/MockSocialManager.cs
+++ b/CSharpSource/Source/api/Social/Manager/MockSocialManager.cs
@@ -15,6 +15,7 @@ public class MockSocialManager : ISocialManager
     {
         private static Random rng = new Random();
         private List<SocialEvent> events;
+        private static readonly List<SocialEvent> emptyEventsList = new List<SocialEvent>();
 
         internal MockSocialManager()
         {
@@ -132,9 +133,17 @@ private void InitUserForOnlinePresence(ref XboxSocialUser groupUser)
 
         public IList<SocialEvent> DoWork()
         {
-            List<SocialEvent> currentEvents = this.events;
-            this.events = new List<SocialEvent>();
-            return currentEvents;
+            List<SocialEvent> returnList = null;
+            if (this.events.Count > 0)
+            {
+                returnList = this.events;
+                this.events = new List<SocialEvent>();
+            }
+            else
+            {
+                returnList = emptyEventsList;
+            }
+            return returnList;
         }
 
         private static XboxSocialUser CreateUser(ulong id = 0)
diff --git a/CSharpSource/Source/api/Social/Manager/SocialManager.cs b/CSharpSource/Source/api/Social/Manager/SocialManager.cs
index 5016bdfd..2c3218d1 100644
--- a/CSharpSource/Source/api/Social/Manager/SocialManager.cs
+++ b/CSharpSource/Source/api/Social/Manager/SocialManager.cs
@@ -22,6 +22,7 @@ public class SocialManager : ISocialManager
         private readonly Dictionary<XboxLiveUser, HashSet<WeakReference>> userGroupsMap = new Dictionary<XboxLiveUser, HashSet<WeakReference>>(new XboxUserIdEqualityComparer());
 
         private Queue<SocialEvent> eventQueue = new Queue<SocialEvent>();
+        private static readonly List<SocialEvent> emptyEventList = new List<SocialEvent>();
 
         private SocialManager()
         {
@@ -180,13 +181,19 @@ public void UpdateUserGroup(XboxLiveUser user, XboxSocialUserGroup group, List<u
 
         public IList<SocialEvent> DoWork()
         {
-            Queue<SocialEvent> eventQueueSnapshot = this.eventQueue;
-            this.eventQueue = new Queue<SocialEvent>();
-
             List<SocialEvent> events;
             lock (this.syncRoot)
             {
-                events = eventQueueSnapshot.ToList();
+                if (this.eventQueue.Count > 0)
+                {
+                    events = this.eventQueue.ToList();
+                    this.eventQueue.Clear();
+                }
+                else
+                {
+                    events = emptyEventList;
+                }
+
                 foreach (SocialGraph graph in this.userGraphs.Values)
                 {
                     graph.DoWork(events);
diff --git a/CSharpSource/Source/api/Stats/Manager/MockStatsManager.cs b/CSharpSource/Source/api/Stats/Manager/MockStatsManager.cs
index 4245c65f..eefc165c 100644
--- a/CSharpSource/Source/api/Stats/Manager/MockStatsManager.cs
+++ b/CSharpSource/Source/api/Stats/Manager/MockStatsManager.cs
@@ -13,6 +13,7 @@ class MockStatsManager : IStatsManager
     {
         private StatsValueDocument statValueDocument;
         private List<StatEvent> statEventList;
+        private static readonly List<StatEvent> emptyStatEventList = new List<StatEvent>();
         private MockLeaderboardService leaderboardService;
 
         internal MockStatsManager()
@@ -97,7 +98,15 @@ public void RequestFlushToService(XboxLiveUser user, bool isHighPriority = false
 
         public List<StatEvent> DoWork()
         {
-            var copyList = this.statEventList.ToList();
+            List<StatEvent> copyList = null;
+            if (this.statEventList.Count > 0)
+            {
+                copyList = this.statEventList.ToList();
+            }
+            else
+            {
+                copyList = emptyStatEventList;
+            }
 
             this.statValueDocument.DoWork();
             this.statEventList.Clear();
diff --git a/CSharpSource/Source/api/Stats/Manager/StatsManager.cs b/CSharpSource/Source/api/Stats/Manager/StatsManager.cs
index cb32788c..f3245781 100644
--- a/CSharpSource/Source/api/Stats/Manager/StatsManager.cs
+++ b/CSharpSource/Source/api/Stats/Manager/StatsManager.cs
@@ -20,6 +20,7 @@ public class StatsManager : IStatsManager
 
         private readonly Dictionary<string, StatsValueDocument> userDocumentMap;
         private readonly List<StatEvent> eventList;
+        private static readonly List<StatEvent> emptyEventList = new List<StatEvent>();
         private readonly CallBufferTimer<XboxLiveUser> statTimer;
         private readonly CallBufferTimer<XboxLiveUser> statPriorityTimer;
 
@@ -241,7 +242,16 @@ public List<StatEvent> DoWork()
         {
             lock (this.userDocumentMap)
             {
-                var copyList = this.eventList.ToList();
+                List<StatEvent> copyList = null;
+                if (this.eventList.Count > 0)
+                {
+                    copyList = this.eventList.ToList();
+                }
+                else
+                {
+                    copyList = emptyEventList;
+                }
+
                 foreach (var userContextPair in this.userDocumentMap)
                 {
                     userContextPair.Value.DoWork();