Deprecate FLAGS_quic_reloadable_flag_quic_bbr_ack_spacing2 in the disabled position because it neve…

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 62 matching lines @@
                      QuicRandom* random)
     : rtt_stats_(rtt_stats),
       unacked_packets_(unacked_packets),
       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_spacing_(kBandwidthWindowSize, QuicTime::Delta::Zero(), 0),
-      largest_acked_time_(QuicTime::Zero()),
-      largest_acked_sent_time_(QuicTime::Zero()),
       max_ack_height_(kBandwidthWindowSize, 0, 0),
       aggregation_epoch_start_time_(QuicTime::Zero()),
       aggregation_epoch_bytes_(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()),
@@ skipping 147 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);
-    if (FLAGS_quic_reloadable_flag_quic_bbr_ack_spacing2) {
-      QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_ack_spacing2, 1, 2);
-      UpdateAckSpacing(event_time, last_acked_packet, acked_packets);
-    }
     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);
     }
   }
 
   // Handle logic specific to PROBE_BW mode.
   if (mode_ == PROBE_BW) {
@@ skipping 253 matching lines @@
 
     case GROWTH:
       // Exit recovery if appropriate.
       if (!has_losses && last_acked_packet > end_recovery_at_) {
         recovery_state_ = NOT_IN_RECOVERY;
       }
       break;
   }
 }
 
-// TODO(ianswett): Move this logic into BandwidthSampler.
-void BbrSender::UpdateAckSpacing(QuicTime ack_time,
-                                 QuicPacketNumber largest_newly_acked,
-                                 const CongestionVector& acked_packets) {
-  // Ignore acks of reordered packets.
-  if (largest_newly_acked < unacked_packets_->largest_observed()) {
-    return;
-  }
-  // Ignore acks of only one packet to filter out delayed acks.
-  if (acked_packets.size() == 1) {
-    return;
-  }
-  QuicTime largest_newly_acked_sent_time =
-      unacked_packets_->GetTransmissionInfo(largest_newly_acked).sent_time;
-  // Initialize on the first ack.
-  if (!largest_acked_time_.IsInitialized()) {
-    largest_acked_time_ = ack_time;
-    largest_acked_sent_time_ = largest_newly_acked_sent_time;
-    return;
-  }
-  QuicTime::Delta ack_delta = ack_time - largest_acked_time_;
-  QuicTime::Delta send_delta =
-      largest_newly_acked_sent_time - largest_acked_sent_time_;
-  largest_acked_time_ = ack_time;
-  largest_acked_sent_time_ = largest_newly_acked_sent_time;
-  if (ack_delta <= send_delta) {
-    return;
-  }
-
-  // Limit the ack spacing to SRTT to filter outliers.
-  QuicTime::Delta ack_spacing =
-      std::min(ack_delta - send_delta, rtt_stats_->smoothed_rtt());
-  max_ack_spacing_.Update(ack_spacing, round_trip_count_);
-}
-
-// TODO(ianswett): Move this logic into BandwidthSampler.
 void BbrSender::UpdateAckAggregationBytes(QuicTime ack_time,
                                           QuicByteCount newly_acked_bytes) {
   // Compute how many bytes are expected to be delivered, assuming max bandwidth
   // is correct.
   QuicByteCount expected_bytes_acked =
       max_bandwidth_.GetBest() * (ack_time - aggregation_epoch_start_time_);
   // Reset the current aggregation epoch as soon as the ack arrival rate is less
   // than or equal to the max bandwidth.
   if (aggregation_epoch_bytes_ <= expected_bytes_acked) {
     // Reset to start measuring a new aggregation epoch.
@@ skipping 36 matching lines @@
   if (mode_ == PROBE_RTT) {
     return;
   }
 
   QuicByteCount target_window =
       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_spacing2 &&
-             is_at_full_bandwidth_) {
-    QUIC_FLAG_COUNT_N(quic_reloadable_flag_quic_bbr_ack_spacing2, 2, 2);
-    // Add CWND for inter-ack spacing once STARTUP has been exited.
-    target_window += max_ack_spacing_.GetBest() * 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();
   }
   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;
@@ skipping 100 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