Reduce locking when collecting receive statistics.

webrtc/modules/rtp_rtcp/source/receive_statistics_impl.cc

Index: webrtc/modules/rtp_rtcp/source/receive_statistics_impl.cc
diff --git a/webrtc/modules/rtp_rtcp/source/receive_statistics_impl.cc b/webrtc/modules/rtp_rtcp/source/receive_statistics_impl.cc
index a3e1ef12544407d555e7065d42d1c5cf28c3fb39..9c7bb2a8eca00abd771168f7f9344d13aa7f2dfb 100644
--- a/webrtc/modules/rtp_rtcp/source/receive_statistics_impl.cc
+++ b/webrtc/modules/rtp_rtcp/source/receive_statistics_impl.cc
@@ -29,13 +29,14 @@ const int64_t kStatisticsProcessIntervalMs = 1000;
 StreamStatistician::~StreamStatistician() {}
 
 StreamStatisticianImpl::StreamStatisticianImpl(
+    uint32_t ssrc,
     Clock* clock,
     RtcpStatisticsCallback* rtcp_callback,
     StreamDataCountersCallback* rtp_callback)
-    : clock_(clock),
+    : ssrc_(ssrc),
+      clock_(clock),
       incoming_bitrate_(kStatisticsProcessIntervalMs,
                         RateStatistics::kBpsScale),
-      ssrc_(0),
       max_reordering_threshold_(kDefaultMaxReorderingThreshold),
       jitter_q4_(0),
       cumulative_loss_(0),
@@ -56,16 +57,17 @@ StreamStatisticianImpl::StreamStatisticianImpl(
 void StreamStatisticianImpl::IncomingPacket(const RTPHeader& header,
                                             size_t packet_length,
                                             bool retransmitted) {
-  UpdateCounters(header, packet_length, retransmitted);
-  NotifyRtpCallback();
+  auto counters = UpdateCounters(header, packet_length, retransmitted);
+  rtp_callback_->DataCountersUpdated(counters, ssrc_);
 }
 
-void StreamStatisticianImpl::UpdateCounters(const RTPHeader& header,
-                                            size_t packet_length,
-                                            bool retransmitted) {
+StreamDataCounters StreamStatisticianImpl::UpdateCounters(
+    const RTPHeader& header,
+    size_t packet_length,
+    bool retransmitted) {
   rtc::CritScope cs(&stream_lock_);
   bool in_order = InOrderPacketInternal(header.sequenceNumber);
-  ssrc_ = header.ssrc;
+  RTC_DCHECK_EQ(ssrc_, header.ssrc);
   incoming_bitrate_.Update(packet_length, clock_->TimeInMilliseconds());
   receive_counters_.transmitted.AddPacket(packet_length, header);
   if (!in_order && retransmitted) {
@@ -109,6 +111,7 @@ void StreamStatisticianImpl::UpdateCounters(const RTPHeader& header,
   // Our measured overhead. Filter from RFC 5104 4.2.1.2:
   // avg_OH (new) = 15/16*avg_OH (old) + 1/16*pckt_OH,
   received_packet_overhead_ = (15 * received_packet_overhead_ + packet_oh) >> 4;
+  return receive_counters_;
 }
 
 void StreamStatisticianImpl::UpdateJitter(const RTPHeader& header,
@@ -150,35 +153,15 @@ void StreamStatisticianImpl::UpdateJitter(const RTPHeader& header,
   }
 }
 
-void StreamStatisticianImpl::NotifyRtpCallback() {
-  StreamDataCounters data;
-  uint32_t ssrc;
-  {
-    rtc::CritScope cs(&stream_lock_);
-    data = receive_counters_;
-    ssrc = ssrc_;
-  }
-  rtp_callback_->DataCountersUpdated(data, ssrc);
-}
-
-void StreamStatisticianImpl::NotifyRtcpCallback() {
-  RtcpStatistics data;
-  uint32_t ssrc;
-  {
-    rtc::CritScope cs(&stream_lock_);
-    data = last_reported_statistics_;
-    ssrc = ssrc_;
-  }
-  rtcp_callback_->StatisticsUpdated(data, ssrc);
-}
-
 void StreamStatisticianImpl::FecPacketReceived(const RTPHeader& header,
                                                size_t packet_length) {
+  StreamDataCounters counters;
   {
     rtc::CritScope cs(&stream_lock_);
     receive_counters_.fec.AddPacket(packet_length, header);
+    counters = receive_counters_;
   }
-  NotifyRtpCallback();
+  rtp_callback_->DataCountersUpdated(counters, ssrc_);
 }
 
 void StreamStatisticianImpl::SetMaxReorderingThreshold(
@@ -210,8 +193,7 @@ bool StreamStatisticianImpl::GetStatistics(RtcpStatistics* statistics,
     *statistics = CalculateRtcpStatistics();
   }
 
-  NotifyRtcpCallback();
-
+  rtcp_callback_->StatisticsUpdated(*statistics, ssrc_);
   return true;
 }
 
@@ -402,7 +384,7 @@ void ReceiveStatisticsImpl::IncomingPacket(const RTPHeader& header,
     if (it != statisticians_.end()) {
       impl = it->second;
     } else {
-      impl = new StreamStatisticianImpl(clock_, this, this);
+      impl = new StreamStatisticianImpl(header.ssrc, clock_, this, this);
       statisticians_[header.ssrc] = impl;
     }
   }
@@ -415,12 +397,16 @@ void ReceiveStatisticsImpl::IncomingPacket(const RTPHeader& header,
 
 void ReceiveStatisticsImpl::FecPacketReceived(const RTPHeader& header,
                                               size_t packet_length) {
-  rtc::CritScope cs(&receive_statistics_lock_);
-  StatisticianImplMap::iterator it = statisticians_.find(header.ssrc);
-  // Ignore FEC if it is the first packet.
-  if (it != statisticians_.end()) {
-    it->second->FecPacketReceived(header, packet_length);
+  StreamStatisticianImpl* impl;
+  {
+    rtc::CritScope cs(&receive_statistics_lock_);
+    StatisticianImplMap::iterator it = statisticians_.find(header.ssrc);
+    // Ignore FEC if it is the first packet.
+    if (it == statisticians_.end())
+      return;
+    impl = it->second;
   }
+  impl->FecPacketReceived(header, packet_length);
 }
 
 StatisticianMap ReceiveStatisticsImpl::GetActiveStatisticians() const {