From 2703867eb28417d35c2128066f9312cea53b9d3d Mon Sep 17 00:00:00 2001
From: Paul Adenot <paul@paul.cx>
Date: Fri, 19 Jul 2013 16:40:57 +0200
Subject: [PATCH] Bug 882543 - Don't spam the main thread when rendering an
 offline graph.  r=ehsan,roc

---
 content/media/MediaStreamGraph.cpp   | 53 ++++++++++++++++++++++++------------
 content/media/MediaStreamGraphImpl.h | 10 +++++++
 2 files changed, 46 insertions(+), 17 deletions(-)

diff --git a/content/media/MediaStreamGraph.cpp b/content/media/MediaStreamGraph.cpp
index a750f714b862..eed493eedc15 100644
--- a/content/media/MediaStreamGraph.cpp
+++ b/content/media/MediaStreamGraph.cpp
@@ -898,28 +898,47 @@ MediaStreamGraphImpl::PlayVideo(MediaStream* aStream)
   }
 }
 
+bool
+MediaStreamGraphImpl::ShouldUpdateMainThread()
+{
+  if (mRealtime) {
+    return true;
+  }
+
+  TimeStamp now = TimeStamp::Now();
+  if ((now - mLastMainThreadUpdate).ToMilliseconds() > MEDIA_GRAPH_TARGET_PERIOD_MS) {
+    mLastMainThreadUpdate = now;
+    return true;
+  }
+  return false;
+}
+
 void
 MediaStreamGraphImpl::PrepareUpdatesToMainThreadState(bool aFinalUpdate)
 {
   mMonitor.AssertCurrentThreadOwns();
 
-  mStreamUpdates.SetCapacity(mStreamUpdates.Length() + mStreams.Length());
-  for (uint32_t i = 0; i < mStreams.Length(); ++i) {
-    MediaStream* stream = mStreams[i];
-    if (!stream->MainThreadNeedsUpdates()) {
-      continue;
+  // We don't want to update the main thread about timing update when we are not
+  // running in realtime.
+  if (ShouldUpdateMainThread()) {
+    mStreamUpdates.SetCapacity(mStreamUpdates.Length() + mStreams.Length());
+    for (uint32_t i = 0; i < mStreams.Length(); ++i) {
+      MediaStream* stream = mStreams[i];
+      if (!stream->MainThreadNeedsUpdates()) {
+        continue;
+      }
+      StreamUpdate* update = mStreamUpdates.AppendElement();
+      update->mGraphUpdateIndex = stream->mGraphUpdateIndices.GetAt(mCurrentTime);
+      update->mStream = stream;
+      update->mNextMainThreadCurrentTime =
+        GraphTimeToStreamTime(stream, mCurrentTime);
+      update->mNextMainThreadFinished =
+        stream->mFinished &&
+        StreamTimeToGraphTime(stream, stream->GetBufferEnd()) <= mCurrentTime;
+    }
+    if (!mPendingUpdateRunnables.IsEmpty()) {
+      mUpdateRunnables.MoveElementsFrom(mPendingUpdateRunnables);
     }
-    StreamUpdate* update = mStreamUpdates.AppendElement();
-    update->mGraphUpdateIndex = stream->mGraphUpdateIndices.GetAt(mCurrentTime);
-    update->mStream = stream;
-    update->mNextMainThreadCurrentTime =
-      GraphTimeToStreamTime(stream, mCurrentTime);
-    update->mNextMainThreadFinished =
-      stream->mFinished &&
-      StreamTimeToGraphTime(stream, stream->GetBufferEnd()) <= mCurrentTime;
-  }
-  if (!mPendingUpdateRunnables.IsEmpty()) {
-    mUpdateRunnables.MoveElementsFrom(mPendingUpdateRunnables);
   }
 
   // Don't send the message to the main thread if it's not going to have
@@ -2178,7 +2197,7 @@ MediaStreamGraphImpl::MediaStreamGraphImpl(bool aRealtime)
   }
 #endif
 
-  mCurrentTimeStamp = mInitialTimeStamp = TimeStamp::Now();
+  mCurrentTimeStamp = mInitialTimeStamp = mLastMainThreadUpdate = TimeStamp::Now();
 }
 
 NS_IMPL_ISUPPORTS1(MediaStreamGraphShutdownObserver, nsIObserver)
diff --git a/content/media/MediaStreamGraphImpl.h b/content/media/MediaStreamGraphImpl.h
index 4a1f4c8ed475..dcc9ba719aa9 100644
--- a/content/media/MediaStreamGraphImpl.h
+++ b/content/media/MediaStreamGraphImpl.h
@@ -190,6 +190,12 @@ public:
    * mMonitor must be held.
    */
   void PrepareUpdatesToMainThreadState(bool aFinalUpdate);
+  /**
+   * If we are rendering in non-realtime mode, we don't want to send messages to
+   * the main thread at each iteration for performance reasons. We instead
+   * notify the main thread at the same rate
+   */
+  bool ShouldUpdateMainThread();
   // The following methods are the various stages of RunThread processing.
   /**
    * Compute a new current time for the graph and advance all on-graph-thread
@@ -395,6 +401,10 @@ public:
    */
   TimeStamp mCurrentTimeStamp;
   /**
+   * Date of the last time we updated the main thread with the graph state.
+   */
+  TimeStamp mLastMainThreadUpdate;
+  /**
    * Which update batch we are currently processing.
    */
   int64_t mProcessingGraphUpdateIndex;
-- 
2.11.4.GIT