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| 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #include "net/quic/congestion_control/tcp_cubic_sender_packets.h" | |
| 6 | |
| 7 #include <algorithm> | |
| 8 | |
| 9 #include "base/metrics/histogram_macros.h" | |
| 10 #include "net/quic/congestion_control/prr_sender.h" | |
| 11 #include "net/quic/congestion_control/rtt_stats.h" | |
| 12 #include "net/quic/crypto/crypto_protocol.h" | |
| 13 #include "net/quic/proto/cached_network_parameters.pb.h" | |
| 14 #include "net/quic/quic_bug_tracker.h" | |
| 15 #include "net/quic/quic_flags.h" | |
| 16 | |
| 17 using std::max; | |
| 18 using std::min; | |
| 19 | |
| 20 namespace net { | |
| 21 | |
| 22 namespace { | |
| 23 // Constants based on TCP defaults. | |
| 24 // The minimum cwnd based on RFC 3782 (TCP NewReno) for cwnd reductions on a | |
| 25 // fast retransmission. The cwnd after a timeout is still 1. | |
| 26 const QuicPacketCount kDefaultMinimumCongestionWindow = 2; | |
| 27 } // namespace | |
| 28 | |
| 29 TcpCubicSenderPackets::TcpCubicSenderPackets( | |
| 30 const QuicClock* clock, | |
| 31 const RttStats* rtt_stats, | |
| 32 bool reno, | |
| 33 QuicPacketCount initial_tcp_congestion_window, | |
| 34 QuicPacketCount max_tcp_congestion_window, | |
| 35 QuicConnectionStats* stats) | |
| 36 : TcpCubicSenderBase(clock, rtt_stats, reno, stats), | |
| 37 cubic_(clock), | |
| 38 congestion_window_count_(0), | |
| 39 congestion_window_(initial_tcp_congestion_window), | |
| 40 min_congestion_window_(kDefaultMinimumCongestionWindow), | |
| 41 slowstart_threshold_(max_tcp_congestion_window), | |
| 42 max_tcp_congestion_window_(max_tcp_congestion_window), | |
| 43 initial_tcp_congestion_window_(initial_tcp_congestion_window), | |
| 44 initial_max_tcp_congestion_window_(max_tcp_congestion_window), | |
| 45 min_slow_start_exit_window_(min_congestion_window_) {} | |
| 46 | |
| 47 TcpCubicSenderPackets::~TcpCubicSenderPackets() {} | |
| 48 | |
| 49 void TcpCubicSenderPackets::SetCongestionWindowFromBandwidthAndRtt( | |
| 50 QuicBandwidth bandwidth, | |
| 51 QuicTime::Delta rtt) { | |
| 52 QuicPacketCount new_congestion_window = | |
| 53 bandwidth.ToBytesPerPeriod(rtt) / kDefaultTCPMSS; | |
| 54 if (FLAGS_quic_no_lower_bw_resumption_limit) { | |
| 55 // Limit new CWND to be in the range [1, kMaxCongestionWindow]. | |
| 56 congestion_window_ = | |
| 57 max(min_congestion_window_, | |
| 58 min(new_congestion_window, kMaxResumptionCongestionWindow)); | |
| 59 } else { | |
| 60 congestion_window_ = | |
| 61 max(min(new_congestion_window, kMaxResumptionCongestionWindow), | |
| 62 kMinCongestionWindowForBandwidthResumption); | |
| 63 } | |
| 64 } | |
| 65 | |
| 66 void TcpCubicSenderPackets::SetCongestionWindowInPackets( | |
| 67 QuicPacketCount congestion_window) { | |
| 68 congestion_window_ = congestion_window; | |
| 69 } | |
| 70 | |
| 71 void TcpCubicSenderPackets::SetMinCongestionWindowInPackets( | |
| 72 QuicPacketCount congestion_window) { | |
| 73 min_congestion_window_ = congestion_window; | |
| 74 } | |
| 75 | |
| 76 void TcpCubicSenderPackets::SetNumEmulatedConnections(int num_connections) { | |
| 77 TcpCubicSenderBase::SetNumEmulatedConnections(num_connections); | |
| 78 cubic_.SetNumConnections(num_connections_); | |
| 79 } | |
| 80 | |
| 81 void TcpCubicSenderPackets::ExitSlowstart() { | |
| 82 slowstart_threshold_ = congestion_window_; | |
| 83 } | |
| 84 | |
| 85 void TcpCubicSenderPackets::OnPacketLost(QuicPacketNumber packet_number, | |
| 86 QuicByteCount lost_bytes, | |
| 87 QuicByteCount bytes_in_flight) { | |
| 88 // TCP NewReno (RFC6582) says that once a loss occurs, any losses in packets | |
| 89 // already sent should be treated as a single loss event, since it's expected. | |
| 90 if (packet_number <= largest_sent_at_last_cutback_) { | |
| 91 if (last_cutback_exited_slowstart_) { | |
| 92 ++stats_->slowstart_packets_lost; | |
| 93 stats_->slowstart_bytes_lost += lost_bytes; | |
| 94 if (slow_start_large_reduction_) { | |
| 95 if (stats_->slowstart_packets_lost == 1 || | |
| 96 (stats_->slowstart_bytes_lost / kDefaultTCPMSS) > | |
| 97 (stats_->slowstart_bytes_lost - lost_bytes) / kDefaultTCPMSS) { | |
| 98 // Reduce congestion window by 1 for every mss of bytes lost. | |
| 99 congestion_window_ = | |
| 100 max(congestion_window_ - 1, min_slow_start_exit_window_); | |
| 101 } | |
| 102 slowstart_threshold_ = congestion_window_; | |
| 103 } | |
| 104 } | |
| 105 DVLOG(1) << "Ignoring loss for largest_missing:" << packet_number | |
| 106 << " because it was sent prior to the last CWND cutback."; | |
| 107 return; | |
| 108 } | |
| 109 ++stats_->tcp_loss_events; | |
| 110 last_cutback_exited_slowstart_ = InSlowStart(); | |
| 111 if (InSlowStart()) { | |
| 112 ++stats_->slowstart_packets_lost; | |
| 113 } | |
| 114 | |
| 115 if (!no_prr_) { | |
| 116 prr_.OnPacketLost(bytes_in_flight); | |
| 117 } | |
| 118 | |
| 119 // TODO(jri): Separate out all of slow start into a separate class. | |
| 120 if (slow_start_large_reduction_ && InSlowStart()) { | |
| 121 DCHECK_LT(1u, congestion_window_); | |
| 122 if (congestion_window_ >= 2 * initial_tcp_congestion_window_) { | |
| 123 min_slow_start_exit_window_ = congestion_window_ / 2; | |
| 124 } | |
| 125 congestion_window_ = congestion_window_ - 1; | |
| 126 } else if (reno_) { | |
| 127 congestion_window_ = congestion_window_ * RenoBeta(); | |
| 128 } else { | |
| 129 congestion_window_ = | |
| 130 cubic_.CongestionWindowAfterPacketLoss(congestion_window_); | |
| 131 } | |
| 132 // Enforce a minimum congestion window. | |
| 133 if (congestion_window_ < min_congestion_window_) { | |
| 134 congestion_window_ = min_congestion_window_; | |
| 135 } | |
| 136 slowstart_threshold_ = congestion_window_; | |
| 137 largest_sent_at_last_cutback_ = largest_sent_packet_number_; | |
| 138 // reset packet count from congestion avoidance mode. We start | |
| 139 // counting again when we're out of recovery. | |
| 140 congestion_window_count_ = 0; | |
| 141 DVLOG(1) << "Incoming loss; congestion window: " << congestion_window_ | |
| 142 << " slowstart threshold: " << slowstart_threshold_; | |
| 143 } | |
| 144 | |
| 145 QuicByteCount TcpCubicSenderPackets::GetCongestionWindow() const { | |
| 146 return congestion_window_ * kDefaultTCPMSS; | |
| 147 } | |
| 148 | |
| 149 QuicByteCount TcpCubicSenderPackets::GetSlowStartThreshold() const { | |
| 150 return slowstart_threshold_ * kDefaultTCPMSS; | |
| 151 } | |
| 152 | |
| 153 // Called when we receive an ack. Normal TCP tracks how many packets one ack | |
| 154 // represents, but quic has a separate ack for each packet. | |
| 155 void TcpCubicSenderPackets::MaybeIncreaseCwnd( | |
| 156 QuicPacketNumber acked_packet_number, | |
| 157 QuicByteCount /*acked_bytes*/, | |
| 158 QuicByteCount bytes_in_flight) { | |
| 159 QUIC_BUG_IF(InRecovery()) << "Never increase the CWND during recovery."; | |
| 160 // Do not increase the congestion window unless the sender is close to using | |
| 161 // the current window. | |
| 162 if (!IsCwndLimited(bytes_in_flight)) { | |
| 163 cubic_.OnApplicationLimited(); | |
| 164 return; | |
| 165 } | |
| 166 if (congestion_window_ >= max_tcp_congestion_window_) { | |
| 167 return; | |
| 168 } | |
| 169 if (InSlowStart()) { | |
| 170 // TCP slow start, exponential growth, increase by one for each ACK. | |
| 171 ++congestion_window_; | |
| 172 DVLOG(1) << "Slow start; congestion window: " << congestion_window_ | |
| 173 << " slowstart threshold: " << slowstart_threshold_; | |
| 174 return; | |
| 175 } | |
| 176 // Congestion avoidance | |
| 177 if (reno_) { | |
| 178 // Classic Reno congestion avoidance. | |
| 179 ++congestion_window_count_; | |
| 180 // Divide by num_connections to smoothly increase the CWND at a faster | |
| 181 // rate than conventional Reno. | |
| 182 if (congestion_window_count_ * num_connections_ >= congestion_window_) { | |
| 183 ++congestion_window_; | |
| 184 congestion_window_count_ = 0; | |
| 185 } | |
| 186 | |
| 187 DVLOG(1) << "Reno; congestion window: " << congestion_window_ | |
| 188 << " slowstart threshold: " << slowstart_threshold_ | |
| 189 << " congestion window count: " << congestion_window_count_; | |
| 190 } else { | |
| 191 congestion_window_ = min(max_tcp_congestion_window_, | |
| 192 cubic_.CongestionWindowAfterAck( | |
| 193 congestion_window_, rtt_stats_->min_rtt())); | |
| 194 DVLOG(1) << "Cubic; congestion window: " << congestion_window_ | |
| 195 << " slowstart threshold: " << slowstart_threshold_; | |
| 196 } | |
| 197 } | |
| 198 | |
| 199 void TcpCubicSenderPackets::HandleRetransmissionTimeout() { | |
| 200 cubic_.Reset(); | |
| 201 slowstart_threshold_ = congestion_window_ / 2; | |
| 202 congestion_window_ = min_congestion_window_; | |
| 203 } | |
| 204 | |
| 205 void TcpCubicSenderPackets::OnConnectionMigration() { | |
| 206 TcpCubicSenderBase::OnConnectionMigration(); | |
| 207 cubic_.Reset(); | |
| 208 congestion_window_count_ = 0; | |
| 209 congestion_window_ = initial_tcp_congestion_window_; | |
| 210 slowstart_threshold_ = initial_max_tcp_congestion_window_; | |
| 211 max_tcp_congestion_window_ = initial_max_tcp_congestion_window_; | |
| 212 } | |
| 213 | |
| 214 CongestionControlType TcpCubicSenderPackets::GetCongestionControlType() const { | |
| 215 return reno_ ? kReno : kCubic; | |
| 216 } | |
| 217 | |
| 218 } // namespace net | |
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Chromium Code Reviews
Issue 2193073003:
Move shared files in net/quic/ into net/quic/core/ (Closed)
Base URL: https://chromium.googlesource.com/chromium/src.git@master