relnote: Limit the number of burst tokens in QUIC's pacing sender to the

net/quic/congestion_control/pacing_sender.cc

 // Copyright (c) 2013 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/congestion_control/pacing_sender.h"
 
+#include "net/quic/quic_flags.h"
+
+using std::min;
+
 namespace net {
 
 PacingSender::PacingSender(SendAlgorithmInterface* sender,
                            QuicTime::Delta alarm_granularity,
                            uint32 initial_packet_burst)
     : sender_(sender),
       alarm_granularity_(alarm_granularity),
       initial_packet_burst_(initial_packet_burst),
       burst_tokens_(initial_packet_burst),
       last_delayed_packet_sent_time_(QuicTime::Zero()),
@@ skipping 37 matching lines @@
     QuicPacketSequenceNumber sequence_number,
     QuicByteCount bytes,
     HasRetransmittableData has_retransmittable_data) {
   const bool in_flight =
       sender_->OnPacketSent(sent_time, bytes_in_flight, sequence_number,
                             bytes, has_retransmittable_data);
   if (has_retransmittable_data != HAS_RETRANSMITTABLE_DATA) {
     return in_flight;
   }
   if (bytes_in_flight == 0) {
-    // Add more burst tokens anytime the connection is leaving quiescence.
-    burst_tokens_ = initial_packet_burst_;
+    // Add more burst tokens anytime the connection is leaving quiescence, but
+    // limit it to the equivalent of a single bulk write, not exceeding the
+    // current CWND in packets.
+    if (FLAGS_quic_limit_pacing_burst) {
+      burst_tokens_ = min(
+          initial_packet_burst_,
+          static_cast<uint32>(sender_->GetCongestionWindow() / kDefaultTCPMSS));
+    } else {
+      burst_tokens_ = initial_packet_burst_;
+    }
   }
   if (burst_tokens_ > 0) {
     --burst_tokens_;
     was_last_send_delayed_ = false;
     last_delayed_packet_sent_time_ = QuicTime::Zero();
     ideal_next_packet_send_time_ = QuicTime::Zero();
     return in_flight;
   }
   // The next packet should be sent as soon as the current packets has been
   // transferred.
@@ skipping 90 matching lines @@
 
 QuicByteCount PacingSender::GetSlowStartThreshold() const {
   return sender_->GetSlowStartThreshold();
 }
 
 CongestionControlType PacingSender::GetCongestionControlType() const {
   return sender_->GetCongestionControlType();
 }
 
 }  // namespace net