Change QUIC's pacing sender to send at 1.25x the estimated bandwidth

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"
 
 namespace net {
 
 PacingSender::PacingSender(SendAlgorithmInterface* sender,
                            QuicTime::Delta alarm_granularity,
@@ skipping 49 matching lines @@
   }
   if (burst_tokens_ > 0) {
     --burst_tokens_;
     was_last_send_delayed_ = false;
     last_delayed_packet_sent_time_ = QuicTime::Zero();
     next_packet_send_time_ = QuicTime::Zero();
     return in_flight;
   }
   // The next packet should be sent as soon as the current packets has
   // been transferred.  We pace at twice the rate of the underlying
-  // sender's bandwidth estimate to help ensure that pacing doesn't become
-  // a bottleneck.
-  const float kPacingAggression = 2;
+  // sender's bandwidth estimate during slow start and 1.25x during congestion
+  // avoidance to ensure pacing doesn't prevent us from filling the window.
+  const float kPacingAggression = sender_->InSlowStart() ? 2 : 1.25;
   QuicTime::Delta delay =
       BandwidthEstimate().Scale(kPacingAggression).TransferTime(bytes);
   // If the last send was delayed, and the alarm took a long time to get
   // invoked, allow the connection to make up for lost time.
   if (was_last_send_delayed_) {
     next_packet_send_time_ = next_packet_send_time_.Add(delay);
     // The send was application limited if it takes longer than the
     // pacing delay between sent packets.
     const bool application_limited =
         last_delayed_packet_sent_time_.IsInitialized() &&
@@ skipping 76 matching lines @@
 }
 
 QuicTime::Delta PacingSender::RetransmissionDelay() const {
   return sender_->RetransmissionDelay();
 }
 
 QuicByteCount PacingSender::GetCongestionWindow() const {
   return sender_->GetCongestionWindow();
 }
 
+bool PacingSender::InSlowStart() const {
+  return sender_->InSlowStart();
+}
+
 QuicByteCount PacingSender::GetSlowStartThreshold() const {
   return sender_->GetSlowStartThreshold();
 }
 
 }  // namespace net