Index: net/quic/congestion_control/cubic.cc |
diff --git a/net/quic/congestion_control/cubic.cc b/net/quic/congestion_control/cubic.cc |
deleted file mode 100644 |
index ca90d7148e32d12989bf7075ea8b82e732146411..0000000000000000000000000000000000000000 |
--- a/net/quic/congestion_control/cubic.cc |
+++ /dev/null |
@@ -1,197 +0,0 @@ |
-// Copyright (c) 2012 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/cubic.h" |
- |
-#include <stdint.h> |
-#include <algorithm> |
-#include <cmath> |
- |
-#include "base/logging.h" |
-#include "net/quic/quic_flags.h" |
-#include "net/quic/quic_protocol.h" |
-#include "net/quic/quic_time.h" |
- |
-using std::max; |
- |
-namespace net { |
- |
-namespace { |
- |
-// Constants based on TCP defaults. |
-// The following constants are in 2^10 fractions of a second instead of ms to |
-// allow a 10 shift right to divide. |
-const int kCubeScale = 40; // 1024*1024^3 (first 1024 is from 0.100^3) |
- // where 0.100 is 100 ms which is the scaling |
- // round trip time. |
-const int kCubeCongestionWindowScale = 410; |
-const uint64_t kCubeFactor = |
- (UINT64_C(1) << kCubeScale) / kCubeCongestionWindowScale; |
- |
-const uint32_t kDefaultNumConnections = 2; |
-const float kBeta = 0.7f; // Default Cubic backoff factor. |
-// Additional backoff factor when loss occurs in the concave part of the Cubic |
-// curve. This additional backoff factor is expected to give up bandwidth to |
-// new concurrent flows and speed up convergence. |
-const float kBetaLastMax = 0.85f; |
- |
-} // namespace |
- |
-Cubic::Cubic(const QuicClock* clock) |
- : clock_(clock), |
- num_connections_(kDefaultNumConnections), |
- epoch_(QuicTime::Zero()), |
- app_limited_start_time_(QuicTime::Zero()), |
- last_update_time_(QuicTime::Zero()) { |
- Reset(); |
-} |
- |
-void Cubic::SetNumConnections(int num_connections) { |
- num_connections_ = num_connections; |
-} |
- |
-float Cubic::Alpha() const { |
- // TCPFriendly alpha is described in Section 3.3 of the CUBIC paper. Note that |
- // beta here is a cwnd multiplier, and is equal to 1-beta from the paper. |
- // We derive the equivalent alpha for an N-connection emulation as: |
- const float beta = Beta(); |
- return 3 * num_connections_ * num_connections_ * (1 - beta) / (1 + beta); |
-} |
- |
-float Cubic::Beta() const { |
- // kNConnectionBeta is the backoff factor after loss for our N-connection |
- // emulation, which emulates the effective backoff of an ensemble of N |
- // TCP-Reno connections on a single loss event. The effective multiplier is |
- // computed as: |
- return (num_connections_ - 1 + kBeta) / num_connections_; |
-} |
- |
-void Cubic::Reset() { |
- epoch_ = QuicTime::Zero(); // Reset time. |
- app_limited_start_time_ = QuicTime::Zero(); |
- last_update_time_ = QuicTime::Zero(); // Reset time. |
- last_congestion_window_ = 0; |
- last_max_congestion_window_ = 0; |
- acked_packets_count_ = 0; |
- estimated_tcp_congestion_window_ = 0; |
- origin_point_congestion_window_ = 0; |
- time_to_origin_point_ = 0; |
- last_target_congestion_window_ = 0; |
-} |
- |
-void Cubic::OnApplicationLimited() { |
- if (FLAGS_shift_quic_cubic_epoch_when_app_limited) { |
- // When sender is not using the available congestion window, Cubic's epoch |
- // should not continue growing. Record the time when sender goes into an |
- // app-limited period here, to compensate later when cwnd growth happens. |
- if (app_limited_start_time_ == QuicTime::Zero()) { |
- app_limited_start_time_ = clock_->ApproximateNow(); |
- } |
- } else { |
- // When sender is not using the available congestion window, Cubic's epoch |
- // should not continue growing. Reset the epoch when in such a period. |
- epoch_ = QuicTime::Zero(); |
- } |
-} |
- |
-QuicPacketCount Cubic::CongestionWindowAfterPacketLoss( |
- QuicPacketCount current_congestion_window) { |
- if (current_congestion_window < last_max_congestion_window_) { |
- // We never reached the old max, so assume we are competing with another |
- // flow. Use our extra back off factor to allow the other flow to go up. |
- last_max_congestion_window_ = |
- static_cast<int>(kBetaLastMax * current_congestion_window); |
- } else { |
- last_max_congestion_window_ = current_congestion_window; |
- } |
- epoch_ = QuicTime::Zero(); // Reset time. |
- return static_cast<int>(current_congestion_window * Beta()); |
-} |
- |
-QuicPacketCount Cubic::CongestionWindowAfterAck( |
- QuicPacketCount current_congestion_window, |
- QuicTime::Delta delay_min) { |
- acked_packets_count_ += 1; // Packets acked. |
- QuicTime current_time = clock_->ApproximateNow(); |
- |
- // Cubic is "independent" of RTT, the update is limited by the time elapsed. |
- if (last_congestion_window_ == current_congestion_window && |
- (current_time - last_update_time_ <= MaxCubicTimeInterval())) { |
- return max(last_target_congestion_window_, |
- estimated_tcp_congestion_window_); |
- } |
- last_congestion_window_ = current_congestion_window; |
- last_update_time_ = current_time; |
- |
- if (!epoch_.IsInitialized()) { |
- // First ACK after a loss event. |
- epoch_ = current_time; // Start of epoch. |
- acked_packets_count_ = 1; // Reset count. |
- // Reset estimated_tcp_congestion_window_ to be in sync with cubic. |
- estimated_tcp_congestion_window_ = current_congestion_window; |
- if (last_max_congestion_window_ <= current_congestion_window) { |
- time_to_origin_point_ = 0; |
- origin_point_congestion_window_ = current_congestion_window; |
- } else { |
- time_to_origin_point_ = static_cast<uint32_t>( |
- cbrt(kCubeFactor * |
- (last_max_congestion_window_ - current_congestion_window))); |
- origin_point_congestion_window_ = last_max_congestion_window_; |
- } |
- } else { |
- // If sender was app-limited, then freeze congestion window growth during |
- // app-limited period. Continue growth now by shifting the epoch-start |
- // through the app-limited period. |
- if (FLAGS_shift_quic_cubic_epoch_when_app_limited && |
- app_limited_start_time_ != QuicTime::Zero()) { |
- QuicTime::Delta shift = current_time - app_limited_start_time_; |
- DVLOG(1) << "Shifting epoch for quiescence by " << shift.ToMicroseconds(); |
- epoch_ = epoch_ + shift; |
- app_limited_start_time_ = QuicTime::Zero(); |
- } |
- } |
- |
- // Change the time unit from microseconds to 2^10 fractions per second. Take |
- // the round trip time in account. This is done to allow us to use shift as a |
- // divide operator. |
- int64_t elapsed_time = |
- ((current_time + delay_min - epoch_).ToMicroseconds() << 10) / |
- kNumMicrosPerSecond; |
- |
- int64_t offset = time_to_origin_point_ - elapsed_time; |
- QuicPacketCount delta_congestion_window = |
- (kCubeCongestionWindowScale * offset * offset * offset) >> kCubeScale; |
- |
- QuicPacketCount target_congestion_window = |
- origin_point_congestion_window_ - delta_congestion_window; |
- |
- DCHECK_LT(0u, estimated_tcp_congestion_window_); |
- // With dynamic beta/alpha based on number of active streams, it is possible |
- // for the required_ack_count to become much lower than acked_packets_count_ |
- // suddenly, leading to more than one iteration through the following loop. |
- while (true) { |
- // Update estimated TCP congestion_window. |
- QuicPacketCount required_ack_count = static_cast<QuicPacketCount>( |
- estimated_tcp_congestion_window_ / Alpha()); |
- if (acked_packets_count_ < required_ack_count) { |
- break; |
- } |
- acked_packets_count_ -= required_ack_count; |
- estimated_tcp_congestion_window_++; |
- } |
- |
- // We have a new cubic congestion window. |
- last_target_congestion_window_ = target_congestion_window; |
- |
- // Compute target congestion_window based on cubic target and estimated TCP |
- // congestion_window, use highest (fastest). |
- if (target_congestion_window < estimated_tcp_congestion_window_) { |
- target_congestion_window = estimated_tcp_congestion_window_; |
- } |
- |
- DVLOG(1) << "Final target congestion_window: " << target_congestion_window; |
- return target_congestion_window; |
-} |
- |
-} // namespace net |