Remove //net (except for Android test stuff) and sdch

net/quic/congestion_control/cubic.cc

-// 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),
-      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,
-                                         QuicPacketCount new_reno_mode_cwnd) {
-  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.
-    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.
-      stats_->cwnd_increase_cubic_mode +=
-          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,
-    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.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