Continue sending at the max bandwidth measured in the last two rounds for another SRTT. Protected …

net/quic/core/congestion_control/bbr_sender.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/core/congestion_control/bbr_sender.h"
 
 #include <algorithm>
 #include <sstream>
 
 #include "net/quic/core/congestion_control/rtt_stats.h"
@@ skipping 127 matching lines @@
 }
 
 QuicTime::Delta BbrSender::TimeUntilSend(QuicTime /* now */,
                                          QuicByteCount bytes_in_flight) const {
   if (bytes_in_flight < GetCongestionWindow()) {
     return QuicTime::Delta::Zero();
   }
   return QuicTime::Delta::Infinite();
 }
 
-QuicBandwidth BbrSender::PacingRate(QuicByteCount /*bytes_in_flight*/) const {
+QuicBandwidth BbrSender::PacingRate(QuicByteCount bytes_in_flight) const {
   if (pacing_rate_.IsZero()) {
     return kHighGain * QuicBandwidth::FromBytesAndTimeDelta(
                            initial_congestion_window_, GetMinRtt());
   }
+  if (FLAGS_quic_reloadable_flag_quic_bbr_keep_sending_at_recent_rate &&
+      mode_ == PROBE_BW && bytes_in_flight > congestion_window_) {
+    QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_keep_sending_at_recent_rate,
+                      1, 2);
+    return max_bandwidth_.GetThirdBest();
+  }
   return pacing_rate_;
 }
 
 QuicBandwidth BbrSender::BandwidthEstimate() const {
   return max_bandwidth_.GetBest();
 }
 
 QuicByteCount BbrSender::GetCongestionWindow() const {
   if (mode_ == PROBE_RTT) {
     return kMinimumCongestionWindow;
   }
 
   if (InRecovery()) {
     return std::min(congestion_window_, recovery_window_);
   }
 
+  if (FLAGS_quic_reloadable_flag_quic_bbr_keep_sending_at_recent_rate &&
+      mode_ == PROBE_BW) {
+    QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_keep_sending_at_recent_rate,
+                      2, 2);
+    // Send for another SRTT at a more recently measured bandwidth.
+    return congestion_window_ +
+           max_bandwidth_.GetThirdBest() * rtt_stats_->smoothed_rtt();
+  }
+
   return congestion_window_;
 }
 
 QuicByteCount BbrSender::GetSlowStartThreshold() const {
   return 0;
 }
 
 bool BbrSender::InRecovery() const {
   return recovery_state_ != NOT_IN_RECOVERY;
 }
@@ skipping 533 matching lines @@
   os << "Minimum RTT timestamp: " << state.min_rtt_timestamp.ToDebuggingValue()
      << std::endl;
 
   os << "Last sample is app-limited: "
      << (state.last_sample_is_app_limited ? "yes" : "no");
 
   return os;
 }
 
 }  // namespace net