Remain in packet conservation mode if BBR is in PROBE_BW and not in high-gain mode. Protected by F…

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 497 matching lines @@
 
     case CONSERVATION:
       if (is_round_start) {
         recovery_state_ = GROWTH;
       }
 
     case GROWTH:
       // Exit recovery if appropriate.
       if (!has_losses && last_acked_packet > end_recovery_at_) {
         recovery_state_ = NOT_IN_RECOVERY;
+        return;
+      }
+
+      if (!FLAGS_quic_reloadable_flag_quic_bbr_extra_conservation) {
+        return;
+      }
+
+      // Use "single round in conservation" approach outside of PROBE_BW.
+      if (mode_ != PROBE_BW) {
+        return;
+      }
+
+      // Switch between conservation and growth depending on position in the
+      // gain cycle.
+      if (cycle_current_offset_ == 0 ||
+          cycle_current_offset_ == kGainCycleLength - 1) {
+        recovery_state_ = GROWTH;
+      } else {
+        recovery_state_ = CONSERVATION;
       }
       break;
   }
 }
 
 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 =
@@ skipping 161 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