Move GetOutstandingBytes() call inside field trial check to avoid taking an unneccessary lock.

webrtc/modules/congestion_controller/send_side_congestion_controller.cc

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 277 matching lines @@
 }
 
 void SendSideCongestionController::OnSentPacket(
     const rtc::SentPacket& sent_packet) {
   // We're not interested in packets without an id, which may be stun packets,
   // etc, sent on the same transport.
   if (sent_packet.packet_id == -1)
     return;
   transport_feedback_adapter_.OnSentPacket(sent_packet.packet_id,
                                            sent_packet.send_time_ms);
-  LimitOutstandingBytes(transport_feedback_adapter_.GetOutstandingBytes());
+  if (in_cwnd_experiment_)
+    LimitOutstandingBytes(transport_feedback_adapter_.GetOutstandingBytes());
 }
 
 void SendSideCongestionController::OnRttUpdate(int64_t avg_rtt_ms,
                                                int64_t max_rtt_ms) {
   rtc::CritScope cs(&bwe_lock_);
   delay_based_bwe_->OnRttUpdate(avg_rtt_ms, max_rtt_ms);
 }
 
 int64_t SendSideCongestionController::TimeUntilNextProcess() {
   return bitrate_controller_->TimeUntilNextProcess();
@@ skipping 53 matching lines @@
     result = delay_based_bwe_->IncomingPacketFeedbackVector(
         feedback_vector, acknowledged_bitrate_estimator_->bitrate_bps());
   }
   if (result.updated) {
     bitrate_controller_->OnDelayBasedBweResult(result);
     // Update the estimate in the ProbeController, in case we want to probe.
     MaybeTriggerOnNetworkChanged();
   }
   if (result.recovered_from_overuse)
     probe_controller_->RequestProbe();
-  LimitOutstandingBytes(transport_feedback_adapter_.GetOutstandingBytes());
+  if (in_cwnd_experiment_)
+    LimitOutstandingBytes(transport_feedback_adapter_.GetOutstandingBytes());
 }
 
 void SendSideCongestionController::LimitOutstandingBytes(
     size_t num_outstanding_bytes) {
-  if (!in_cwnd_experiment_)
+  RTC_DCHECK(in_cwnd_experiment_);
+  rtc::CritScope lock(&network_state_lock_);
+  rtc::Optional<int64_t> min_rtt_ms =
+      transport_feedback_adapter_.GetMinFeedbackLoopRtt();
+  // No valid RTT. Could be because send-side BWE isn't used, in which case
+  // we don't try to limit the outstanding packets.
+  if (!min_rtt_ms)
     return;
-  {
-    rtc::CritScope lock(&network_state_lock_);
-    rtc::Optional<int64_t> min_rtt_ms =
-        transport_feedback_adapter_.GetMinFeedbackLoopRtt();
-    // No valid RTT. Could be because send-side BWE isn't used, in which case
-    // we don't try to limit the outstanding packets.
-    if (!min_rtt_ms)
-      return;
-    const size_t kMinCwndBytes = 2 * 1500;
-    size_t max_outstanding_bytes =
-        std::max<size_t>((*min_rtt_ms + accepted_queue_ms_) *
-                             last_reported_bitrate_bps_ / 1000 / 8,
-                         kMinCwndBytes);
-    LOG(LS_INFO) << clock_->TimeInMilliseconds()
-                 << " Outstanding bytes: " << num_outstanding_bytes
-                 << " pacer queue: " << pacer_->QueueInMs()
-                 << " max outstanding: " << max_outstanding_bytes;
-    LOG(LS_INFO) << "Feedback rtt: " << *min_rtt_ms
-                 << " Bitrate: " << last_reported_bitrate_bps_;
-    pause_pacer_ = num_outstanding_bytes > max_outstanding_bytes;
-  }
+  const size_t kMinCwndBytes = 2 * 1500;
+  size_t max_outstanding_bytes =
+      std::max<size_t>((*min_rtt_ms + accepted_queue_ms_) *
+                           last_reported_bitrate_bps_ / 1000 / 8,
+                       kMinCwndBytes);
+  LOG(LS_INFO) << clock_->TimeInMilliseconds()
+               << " Outstanding bytes: " << num_outstanding_bytes
+               << " pacer queue: " << pacer_->QueueInMs()
+               << " max outstanding: " << max_outstanding_bytes;
+  LOG(LS_INFO) << "Feedback rtt: " << *min_rtt_ms
+               << " Bitrate: " << last_reported_bitrate_bps_;
+  pause_pacer_ = num_outstanding_bytes > max_outstanding_bytes;
 }
 
 std::vector<PacketFeedback>
 SendSideCongestionController::GetTransportFeedbackVector() const {
   RTC_DCHECK_RUNS_SERIALIZED(&worker_race_);
   return transport_feedback_adapter_.GetTransportFeedbackVector();
 }
 
 void SendSideCongestionController::MaybeTriggerOnNetworkChanged() {
   uint32_t bitrate_bps;
@@ skipping 47 matching lines @@
 bool SendSideCongestionController::IsSendQueueFull() const {
   return pacer_->ExpectedQueueTimeMs() > PacedSender::kMaxQueueLengthMs;
 }
 
 bool SendSideCongestionController::IsNetworkDown() const {
   rtc::CritScope cs(&network_state_lock_);
   return network_state_ == kNetworkDown;
 }
 
 }  // namespace webrtc