| 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 dc6b89bf9d01fb5e7e0307000a7bb80509a45761..0000000000000000000000000000000000000000
|
| --- a/net/quic/congestion_control/cubic.cc
|
| +++ /dev/null
|
| @@ -1,191 +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 <algorithm>
|
| -#include <cmath>
|
| -
|
| -#include "base/basictypes.h"
|
| -#include "base/logging.h"
|
| -#include "base/time/time.h"
|
| -#include "net/quic/quic_flags.h"
|
| -#include "net/quic/quic_protocol.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 kCubeFactor = (GG_UINT64_C(1) << kCubeScale) /
|
| - kCubeCongestionWindowScale;
|
| -
|
| -const uint32 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, QuicConnectionStats* stats)
|
| - : clock_(clock),
|
| - num_connections_(kDefaultNumConnections),
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| - epoch_(QuicTime::Zero()),
|
| - last_update_time_(QuicTime::Zero()),
|
| - stats_(stats) {
|
| - 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.
|
| - 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::UpdateCongestionControlStats(QuicPacketCount new_cubic_mode_cwnd,
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| - QuicPacketCount new_reno_mode_cwnd) {
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| - QuicPacketCount highest_new_cwnd = max(new_cubic_mode_cwnd,
|
| - new_reno_mode_cwnd);
|
| - if (last_congestion_window_ < highest_new_cwnd) {
|
| - // cwnd will increase to highest_new_cwnd.
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| - stats_->cwnd_increase_congestion_avoidance +=
|
| - highest_new_cwnd - last_congestion_window_;
|
| - if (new_cubic_mode_cwnd > new_reno_mode_cwnd) {
|
| - // This cwnd increase is due to cubic mode.
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| - stats_->cwnd_increase_cubic_mode +=
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| - new_cubic_mode_cwnd - last_congestion_window_;
|
| - }
|
| - }
|
| -}
|
| -
|
| -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,
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| - 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.
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| - if (last_congestion_window_ == current_congestion_window &&
|
| - (current_time.Subtract(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.
|
| - DVLOG(1) << "Start of epoch";
|
| - 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>(cbrt(kCubeFactor * (last_max_congestion_window_ -
|
| - current_congestion_window)));
|
| - origin_point_congestion_window_ =
|
| - last_max_congestion_window_;
|
| - }
|
| - }
|
| - // 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 elapsed_time =
|
| - (current_time.Add(delay_min).Subtract(epoch_).ToMicroseconds() << 10) /
|
| - base::Time::kMicrosecondsPerSecond;
|
| -
|
| - int64 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_++;
|
| - }
|
| -
|
| - // Update cubic mode and reno mode stats in QuicConnectionStats.
|
| - UpdateCongestionControlStats(target_congestion_window,
|
| - 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) << "Target congestion_window: " << target_congestion_window;
|
| - return target_congestion_window;
|
| -}
|
| -
|
| -} // namespace net
|
|
|