Add functionality which limits the number of bytes on the network.

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.
  */
 
 #include "webrtc/modules/congestion_controller/include/send_side_congestion_controller.h"
 
 #include <algorithm>
 #include <memory>
 #include <vector>
 
 #include "webrtc/modules/bitrate_controller/include/bitrate_controller.h"
 #include "webrtc/modules/congestion_controller/acknowledged_bitrate_estimator.h"
 #include "webrtc/modules/congestion_controller/probe_controller.h"
 #include "webrtc/modules/pacing/alr_detector.h"
 #include "webrtc/modules/remote_bitrate_estimator/include/bwe_defines.h"
 #include "webrtc/rtc_base/checks.h"
 #include "webrtc/rtc_base/logging.h"
 #include "webrtc/rtc_base/ptr_util.h"
 #include "webrtc/rtc_base/rate_limiter.h"
 #include "webrtc/rtc_base/socket.h"
 #include "webrtc/rtc_base/timeutils.h"
+#include "webrtc/system_wrappers/include/field_trial.h"
 
 namespace webrtc {
 namespace {
 
+const char kCwndExperiment[] = "WebRTC-CwndExperiment";
+
+bool CwndExperimentEnabled() {
+  std::string experiment_string =
+      webrtc::field_trial::FindFullName(kCwndExperiment);
+  // The experiment is enabled iff the field trial string begins with "Enabled".
+  return experiment_string.find("Enabled") == 0;
+}
+
 static const int64_t kRetransmitWindowSizeMs = 500;
 
 // Makes sure that the bitrate and the min, max values are in valid range.
 static void ClampBitrates(int* bitrate_bps,
                           int* min_bitrate_bps,
                           int* max_bitrate_bps) {
   // TODO(holmer): We should make sure the default bitrates are set to 10 kbps,
   // and that we don't try to set the min bitrate to 0 from any applications.
   // The congestion controller should allow a min bitrate of 0.
   if (*min_bitrate_bps < congestion_controller::GetMinBitrateBps())
@@ skipping 51 matching lines @@
       acknowledged_bitrate_estimator_(
           rtc::MakeUnique<AcknowledgedBitrateEstimator>()),
       probe_controller_(new ProbeController(pacer_.get(), clock_)),
       retransmission_rate_limiter_(
           new RateLimiter(clock, kRetransmitWindowSizeMs)),
       transport_feedback_adapter_(clock_),
       last_reported_bitrate_bps_(0),
       last_reported_fraction_loss_(0),
       last_reported_rtt_(0),
       network_state_(kNetworkUp),
+      pause_pacer_(false),
+      pacer_paused_(false),
       min_bitrate_bps_(congestion_controller::GetMinBitrateBps()),
       delay_based_bwe_(new DelayBasedBwe(event_log_, clock_)),
+      in_cwnd_experiment_(CwndExperimentEnabled()),
       was_in_alr_(0) {
   delay_based_bwe_->SetMinBitrate(min_bitrate_bps_);
 }
 
 SendSideCongestionController::~SendSideCongestionController() {}
 
 void SendSideCongestionController::RegisterPacketFeedbackObserver(
     PacketFeedbackObserver* observer) {
   transport_feedback_adapter_.RegisterPacketFeedbackObserver(observer);
 }
@@ skipping 97 matching lines @@
 }
 
 TransportFeedbackObserver*
 SendSideCongestionController::GetTransportFeedbackObserver() {
   return this;
 }
 
 void SendSideCongestionController::SignalNetworkState(NetworkState state) {
   LOG(LS_INFO) << "SignalNetworkState "
                << (state == kNetworkUp ? "Up" : "Down");
-  if (state == kNetworkUp) {
-    pacer_->Resume();
-  } else {
-    pacer_->Pause();
-  }
   {
     rtc::CritScope cs(&network_state_lock_);
+    pause_pacer_ = state == kNetworkDown;
     network_state_ = state;
   }
   probe_controller_->OnNetworkStateChanged(state);
   MaybeTriggerOnNetworkChanged();
 }
 
 void SendSideCongestionController::SetTransportOverhead(
     size_t transport_overhead_bytes_per_packet) {
   transport_feedback_adapter_.SetTransportOverhead(
       transport_overhead_bytes_per_packet);
 }
 
 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());
 }
 
 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();
 }
 
 void SendSideCongestionController::Process() {
+  bool pause_pacer;
+  // TODO(holmer): Once this class is running on a task queue we should
+  // replace this with a task instead.
+  {
+    rtc::CritScope lock(&network_state_lock_);
+    pause_pacer = pause_pacer_;
+  }
+  if (pause_pacer && !pacer_paused_) {
+    pacer_->Pause();
+    pacer_paused_ = true;
+  } else if (!pause_pacer && pacer_paused_) {
+    pacer_->Resume();
+    pacer_paused_ = false;
+  }
   bitrate_controller_->Process();
   probe_controller_->Process();
   MaybeTriggerOnNetworkChanged();
 }
 
 void SendSideCongestionController::AddPacket(
     uint32_t ssrc,
     uint16_t sequence_number,
     size_t length,
     const PacedPacketInfo& pacing_info) {
@@ skipping 26 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());
+}
+
+void SendSideCongestionController::LimitOutstandingBytes(
+    size_t num_outstanding_bytes) {
+  if (!in_cwnd_experiment_)
+    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 int64_t kAcceptedQueueMs = 250;
+    const size_t kMinCwndBytes = 2 * 1500;
+    size_t max_outstanding_bytes =
+        std::max<size_t>((*min_rtt_ms + kAcceptedQueueMs) *
+                             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