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Unified Diff: net/quic/congestion_control/cubic_bytes.cc

Issue 2193073003: Move shared files in net/quic/ into net/quic/core/ (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: io_thread_unittest.cc Created 4 years, 5 months ago
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Index: net/quic/congestion_control/cubic_bytes.cc
diff --git a/net/quic/congestion_control/cubic_bytes.cc b/net/quic/congestion_control/cubic_bytes.cc
deleted file mode 100644
index cae49226ab4ba43162b9c81e74a1d66850eca46d..0000000000000000000000000000000000000000
--- a/net/quic/congestion_control/cubic_bytes.cc
+++ /dev/null
@@ -1,175 +0,0 @@
-// Copyright (c) 2015 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_bytes.h"
-
-#include <stdint.h>
-#include <algorithm>
-#include <cmath>
-
-#include "base/logging.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;
-// The cube factor for packets in bytes.
-const uint64_t kCubeFactor =
- (UINT64_C(1) << kCubeScale) / kCubeCongestionWindowScale / kDefaultTCPMSS;
-
-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
-
-CubicBytes::CubicBytes(const QuicClock* clock)
- : clock_(clock),
- num_connections_(kDefaultNumConnections),
- epoch_(QuicTime::Zero()),
- last_update_time_(QuicTime::Zero()) {
- Reset();
-}
-
-void CubicBytes::SetNumConnections(int num_connections) {
- num_connections_ = num_connections;
-}
-
-float CubicBytes::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 CubicBytes::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 CubicBytes::Reset() {
- epoch_ = QuicTime::Zero(); // Reset time.
- last_update_time_ = QuicTime::Zero(); // Reset time.
- last_congestion_window_ = 0;
- last_max_congestion_window_ = 0;
- acked_bytes_count_ = 0;
- estimated_tcp_congestion_window_ = 0;
- origin_point_congestion_window_ = 0;
- time_to_origin_point_ = 0;
- last_target_congestion_window_ = 0;
-}
-
-void CubicBytes::OnApplicationLimited() {
- // When sender is not using the available congestion window, the window does
- // not grow. But to be RTT-independent, Cubic assumes that the sender has been
- // using the entire window during the time since the beginning of the current
- // "epoch" (the end of the last loss recovery period). Since
- // application-limited periods break this assumption, we reset the epoch when
- // in such a period. This reset effectively freezes congestion window growth
- // through application-limited periods and allows Cubic growth to continue
- // when the entire window is being used.
- epoch_ = QuicTime::Zero();
-}
-
-QuicByteCount CubicBytes::CongestionWindowAfterPacketLoss(
- QuicByteCount 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());
-}
-
-QuicByteCount CubicBytes::CongestionWindowAfterAck(
- QuicByteCount acked_bytes,
- QuicByteCount current_congestion_window,
- QuicTime::Delta delay_min) {
- acked_bytes_count_ += acked_bytes;
- 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.
- DVLOG(1) << "Start of epoch";
- epoch_ = current_time; // Start of epoch.
- acked_bytes_count_ = acked_bytes; // 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_;
- }
- }
- // 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;
- QuicByteCount delta_congestion_window =
- ((kCubeCongestionWindowScale * offset * offset * offset) >> kCubeScale) *
- kDefaultTCPMSS;
-
- QuicByteCount target_congestion_window =
- origin_point_congestion_window_ - delta_congestion_window;
-
- DCHECK_LT(0u, estimated_tcp_congestion_window_);
- // Increase the window by Alpha * 1 MSS of bytes every time we ack an
- // estimated tcp window of bytes.
- estimated_tcp_congestion_window_ += acked_bytes_count_ *
- (Alpha() * kDefaultTCPMSS) /
- estimated_tcp_congestion_window_;
- acked_bytes_count_ = 0;
-
- // 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
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