Change the pacing sender to always pacing the initial burst, even when

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,
                            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()),
       next_packet_send_time_(QuicTime::Zero()),
-      was_last_send_delayed_(false),
-      has_valid_rtt_(false) {
+      was_last_send_delayed_(false) {
 }
 
 PacingSender::~PacingSender() {}
 
 void PacingSender::SetFromConfig(const QuicConfig& config, bool is_server) {
-  // TODO(ianswett): Consider using the suggested RTT for pacing an initial
-  // response.
   sender_->SetFromConfig(config, is_server);
 }
 
 void PacingSender::SetNumEmulatedConnections(int num_connections) {
   sender_->SetNumEmulatedConnections(num_connections);
 }
 
 void PacingSender::OnIncomingQuicCongestionFeedbackFrame(
       const QuicCongestionFeedbackFrame& feedback,
       QuicTime feedback_receive_time) {
   sender_->OnIncomingQuicCongestionFeedbackFrame(
       feedback, feedback_receive_time);
 }
 
 void PacingSender::OnCongestionEvent(bool rtt_updated,
                                      QuicByteCount bytes_in_flight,
                                      const CongestionVector& acked_packets,
                                      const CongestionVector& lost_packets) {
-  if (rtt_updated) {
-    has_valid_rtt_ = true;
-  }
   sender_->OnCongestionEvent(
       rtt_updated, bytes_in_flight, acked_packets, lost_packets);
 }
 
 bool PacingSender::OnPacketSent(
     QuicTime sent_time,
     QuicByteCount bytes_in_flight,
     QuicPacketSequenceNumber sequence_number,
     QuicByteCount bytes,
     HasRetransmittableData has_retransmittable_data) {
-  // Only pace data packets once we have an updated RTT.
   const bool in_flight =
       sender_->OnPacketSent(sent_time, bytes_in_flight, sequence_number,
                             bytes, has_retransmittable_data);
-  if (has_retransmittable_data != HAS_RETRANSMITTABLE_DATA || !has_valid_rtt_) {
+  if (has_retransmittable_data != HAS_RETRANSMITTABLE_DATA) {
     return in_flight;
   }
   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
@@ skipping 37 matching lines @@
 void PacingSender::RevertRetransmissionTimeout() {
   sender_->RevertRetransmissionTimeout();
 }
 
 QuicTime::Delta PacingSender::TimeUntilSend(
       QuicTime now,
       QuicByteCount bytes_in_flight,
       HasRetransmittableData has_retransmittable_data) const {
   QuicTime::Delta time_until_send =
       sender_->TimeUntilSend(now, bytes_in_flight, has_retransmittable_data);
-  if (!has_valid_rtt_) {
-    // Don't pace if we don't have an updated RTT estimate.
-    return time_until_send;
-  }
   if (bytes_in_flight == 0) {
     // Add more burst tokens anytime the connection is entering quiescence.
     burst_tokens_ = initial_packet_burst_;
   }
   if (burst_tokens_ > 0) {
     // Don't pace if we have burst tokens available.
     return time_until_send;
   }
 
   if (!time_until_send.IsZero()) {
     DCHECK(time_until_send.IsInfinite());
     // The underlying sender prevents sending.
     return time_until_send;
   }
 
   if (has_retransmittable_data == NO_RETRANSMITTABLE_DATA) {
     // Don't pace ACK packets, since they do not count against CWND and do not
     // cause CWND to grow.
     return QuicTime::Delta::Zero();
   }
 
   // If the next send time is within the alarm granularity, send immediately.
+  // TODO(ianswett): This granularity logic ends up sending more packets than
+  // intended in an effort to make up for lost time that wasn't lost.
   if (next_packet_send_time_ > now.Add(alarm_granularity_)) {
     DVLOG(1) << "Delaying packet: "
              << next_packet_send_time_.Subtract(now).ToMicroseconds();
     was_last_send_delayed_ = true;
     return next_packet_send_time_.Subtract(now);
   }
 
   DVLOG(1) << "Sending packet now";
   return QuicTime::Delta::Zero();
 }
@@ skipping 24 matching lines @@
 
 QuicByteCount PacingSender::GetSlowStartThreshold() const {
   return sender_->GetSlowStartThreshold();
 }
 
 CongestionControlType PacingSender::GetCongestionControlType() const {
   return sender_->GetCongestionControlType();
 }
 
 }  // namespace net