Create a new QUIC BBR ack aggregation patch which allows extra CWND only when bytes in flight has g…

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 71 matching lines @@
       random_(random),
       mode_(STARTUP),
       sampler_(),
       round_trip_count_(0),
       last_sent_packet_(0),
       current_round_trip_end_(0),
       max_bandwidth_(kBandwidthWindowSize, QuicBandwidth::Zero(), 0),
       max_ack_height_(kBandwidthWindowSize, 0, 0),
       aggregation_epoch_start_time_(QuicTime::Zero()),
       aggregation_epoch_bytes_(0),
+      bytes_acked_since_queue_drained_(0),
       min_rtt_(QuicTime::Delta::Zero()),
       min_rtt_timestamp_(QuicTime::Zero()),
       congestion_window_(initial_tcp_congestion_window * kDefaultTCPMSS),
       initial_congestion_window_(initial_tcp_congestion_window *
                                  kDefaultTCPMSS),
       max_congestion_window_(max_tcp_congestion_window * kDefaultTCPMSS),
       pacing_rate_(QuicBandwidth::Zero()),
       pacing_gain_(1),
       congestion_window_gain_(1),
       congestion_window_gain_constant_(
@@ skipping 167 matching lines @@
   DiscardLostPackets(lost_packets);
 
   // Input the new data into the BBR model of the connection.
   if (!acked_packets.empty()) {
     QuicPacketNumber last_acked_packet = acked_packets.rbegin()->first;
     is_round_start = UpdateRoundTripCounter(last_acked_packet);
     min_rtt_expired = UpdateBandwidthAndMinRtt(event_time, acked_packets);
     UpdateRecoveryState(last_acked_packet, !lost_packets.empty(),
                         is_round_start);
 
+    const QuicByteCount bytes_acked =
+        sampler_.total_bytes_acked() - total_bytes_acked_before;
     if (FLAGS_quic_reloadable_flag_quic_bbr_slow_recent_delivery) {
       QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_slow_recent_delivery, 1,
                         2);
-      UpdateRecentlyAcked(
-          event_time, sampler_.total_bytes_acked() - total_bytes_acked_before);
+      UpdateRecentlyAcked(event_time, bytes_acked);
     }
 
     if (FLAGS_quic_reloadable_flag_quic_bbr_ack_aggregation_bytes) {
       QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_ack_aggregation_bytes, 1,
                         2);
-      UpdateAckAggregationBytes(
-          event_time, sampler_.total_bytes_acked() - total_bytes_acked_before);
+      UpdateAckAggregationBytes(event_time, bytes_acked);
+    }
+    if (FLAGS_quic_reloadable_flag_quic_bbr_ack_aggregation_bytes2) {
+      QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_ack_aggregation_bytes2, 1,
+                        2);
+      UpdateAckAggregationBytes(event_time, bytes_acked);
+      if (unacked_packets_->bytes_in_flight() <=
+          1.25 * GetTargetCongestionWindow(pacing_gain_)) {
+        bytes_acked_since_queue_drained_ = 0;
+      } else {
+        bytes_acked_since_queue_drained_ += bytes_acked;
+      }
     }
   }
 
   // Handle logic specific to PROBE_BW mode.
   if (mode_ == PROBE_BW) {
     UpdateGainCyclePhase(event_time, prior_in_flight, !lost_packets.empty());
   }
 
   // Handle logic specific to STARTUP and DRAIN modes.
   if (is_round_start && !is_at_full_bandwidth_) {
@@ skipping 344 matching lines @@
       GetTargetCongestionWindow(congestion_window_gain_);
 
   if (rtt_variance_weight_ > 0.f && !BandwidthEstimate().IsZero()) {
     target_window += rtt_variance_weight_ * rtt_stats_->mean_deviation() *
                      BandwidthEstimate();
   } else if (FLAGS_quic_reloadable_flag_quic_bbr_ack_aggregation_bytes &&
              is_at_full_bandwidth_) {
     QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_ack_aggregation_bytes, 2,
                       2);
     target_window += max_ack_height_.GetBest();
+  } else if (FLAGS_quic_reloadable_flag_quic_bbr_ack_aggregation_bytes2 &&
+             is_at_full_bandwidth_) {
+    QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_ack_aggregation_bytes2, 2,
+                      2);
+    if (2 * max_ack_height_.GetBest() > bytes_acked_since_queue_drained_) {
+      target_window +=
+          2 * max_ack_height_.GetBest() - bytes_acked_since_queue_drained_;
+    }
   }
   if (FLAGS_quic_reloadable_flag_quic_bbr_add_tso_cwnd) {
     // QUIC doesn't have TSO, but it does have similarly quantized pacing, so
     // allow extra CWND to make QUIC's BBR CWND identical to TCP's.
     QuicByteCount tso_segs_goal = 0;
     if (pacing_rate_ < QuicBandwidth::FromKBitsPerSecond(1200)) {
       tso_segs_goal = kDefaultTCPMSS;
     } else if (pacing_rate_ < QuicBandwidth::FromKBitsPerSecond(24000)) {
       tso_segs_goal = 2 * kDefaultTCPMSS;
     } else {
@@ skipping 134 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