1 /*
2 * Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 #include "modules/pacing/bitrate_prober.h"
12
13 #include <algorithm>
14
15 #include "absl/memory/memory.h"
16 #include "api/rtc_event_log/rtc_event.h"
17 #include "api/rtc_event_log/rtc_event_log.h"
18 #include "logging/rtc_event_log/events/rtc_event_probe_cluster_created.h"
19 #include "rtc_base/checks.h"
20 #include "rtc_base/logging.h"
21 #include "system_wrappers/include/metrics.h"
22
23 namespace webrtc {
24
25 namespace {
26 constexpr TimeDelta kProbeClusterTimeout = TimeDelta::Seconds(5);
27 constexpr size_t kMaxPendingProbeClusters = 5;
28
29 } // namespace
30
BitrateProberConfig(const FieldTrialsView * key_value_config)31 BitrateProberConfig::BitrateProberConfig(
32 const FieldTrialsView* key_value_config)
33 : min_probe_delta("min_probe_delta", TimeDelta::Millis(2)),
34 max_probe_delay("max_probe_delay", TimeDelta::Millis(10)),
35 min_packet_size("min_packet_size", DataSize::Bytes(200)) {
36 ParseFieldTrial({&min_probe_delta, &max_probe_delay, &min_packet_size},
37 key_value_config->Lookup("WebRTC-Bwe-ProbingBehavior"));
38 }
39
~BitrateProber()40 BitrateProber::~BitrateProber() {
41 RTC_HISTOGRAM_COUNTS_1000("WebRTC.BWE.Probing.TotalProbeClustersRequested",
42 total_probe_count_);
43 RTC_HISTOGRAM_COUNTS_1000("WebRTC.BWE.Probing.TotalFailedProbeClusters",
44 total_failed_probe_count_);
45 }
46
BitrateProber(const FieldTrialsView & field_trials)47 BitrateProber::BitrateProber(const FieldTrialsView& field_trials)
48 : probing_state_(ProbingState::kDisabled),
49 next_probe_time_(Timestamp::PlusInfinity()),
50 total_probe_count_(0),
51 total_failed_probe_count_(0),
52 config_(&field_trials) {
53 SetEnabled(true);
54 }
55
SetEnabled(bool enable)56 void BitrateProber::SetEnabled(bool enable) {
57 if (enable) {
58 if (probing_state_ == ProbingState::kDisabled) {
59 probing_state_ = ProbingState::kInactive;
60 RTC_LOG(LS_INFO) << "Bandwidth probing enabled, set to inactive";
61 }
62 } else {
63 probing_state_ = ProbingState::kDisabled;
64 RTC_LOG(LS_INFO) << "Bandwidth probing disabled";
65 }
66 }
67
OnIncomingPacket(DataSize packet_size)68 void BitrateProber::OnIncomingPacket(DataSize packet_size) {
69 // Don't initialize probing unless we have something large enough to start
70 // probing.
71 // Note that the pacer can send several packets at once when sending a probe,
72 // and thus, packets can be smaller than needed for a probe.
73 if (probing_state_ == ProbingState::kInactive && !clusters_.empty() &&
74 packet_size >=
75 std::min(RecommendedMinProbeSize(), config_.min_packet_size.Get())) {
76 // Send next probe right away.
77 next_probe_time_ = Timestamp::MinusInfinity();
78 probing_state_ = ProbingState::kActive;
79 }
80 }
81
CreateProbeCluster(const ProbeClusterConfig & cluster_config)82 void BitrateProber::CreateProbeCluster(
83 const ProbeClusterConfig& cluster_config) {
84 RTC_DCHECK(probing_state_ != ProbingState::kDisabled);
85
86 total_probe_count_++;
87 while (!clusters_.empty() &&
88 (cluster_config.at_time - clusters_.front().requested_at >
89 kProbeClusterTimeout ||
90 clusters_.size() > kMaxPendingProbeClusters)) {
91 clusters_.pop();
92 total_failed_probe_count_++;
93 }
94
95 ProbeCluster cluster;
96 cluster.requested_at = cluster_config.at_time;
97 cluster.pace_info.probe_cluster_min_probes =
98 cluster_config.target_probe_count;
99 cluster.pace_info.probe_cluster_min_bytes =
100 (cluster_config.target_data_rate * cluster_config.target_duration)
101 .bytes();
102 RTC_DCHECK_GE(cluster.pace_info.probe_cluster_min_bytes, 0);
103 cluster.pace_info.send_bitrate_bps = cluster_config.target_data_rate.bps();
104 cluster.pace_info.probe_cluster_id = cluster_config.id;
105 clusters_.push(cluster);
106
107 RTC_LOG(LS_INFO) << "Probe cluster (bitrate:min bytes:min packets): ("
108 << cluster.pace_info.send_bitrate_bps << ":"
109 << cluster.pace_info.probe_cluster_min_bytes << ":"
110 << cluster.pace_info.probe_cluster_min_probes << ")";
111
112 // If we are already probing, continue to do so. Otherwise set it to
113 // kInactive and wait for OnIncomingPacket to start the probing.
114 if (probing_state_ != ProbingState::kActive)
115 probing_state_ = ProbingState::kInactive;
116 }
117
NextProbeTime(Timestamp now) const118 Timestamp BitrateProber::NextProbeTime(Timestamp now) const {
119 // Probing is not active or probing is already complete.
120 if (probing_state_ != ProbingState::kActive || clusters_.empty()) {
121 return Timestamp::PlusInfinity();
122 }
123
124 return next_probe_time_;
125 }
126
CurrentCluster(Timestamp now)127 absl::optional<PacedPacketInfo> BitrateProber::CurrentCluster(Timestamp now) {
128 if (clusters_.empty() || probing_state_ != ProbingState::kActive) {
129 return absl::nullopt;
130 }
131
132 if (next_probe_time_.IsFinite() &&
133 now - next_probe_time_ > config_.max_probe_delay.Get()) {
134 RTC_DLOG(LS_WARNING) << "Probe delay too high"
135 " (next_ms:"
136 << next_probe_time_.ms() << ", now_ms: " << now.ms()
137 << "), discarding probe cluster.";
138 clusters_.pop();
139 if (clusters_.empty()) {
140 probing_state_ = ProbingState::kSuspended;
141 return absl::nullopt;
142 }
143 }
144
145 PacedPacketInfo info = clusters_.front().pace_info;
146 info.probe_cluster_bytes_sent = clusters_.front().sent_bytes;
147 return info;
148 }
149
RecommendedMinProbeSize() const150 DataSize BitrateProber::RecommendedMinProbeSize() const {
151 if (clusters_.empty()) {
152 return DataSize::Zero();
153 }
154 DataRate send_rate =
155 DataRate::BitsPerSec(clusters_.front().pace_info.send_bitrate_bps);
156 return send_rate * config_.min_probe_delta;
157 }
158
ProbeSent(Timestamp now,DataSize size)159 void BitrateProber::ProbeSent(Timestamp now, DataSize size) {
160 RTC_DCHECK(probing_state_ == ProbingState::kActive);
161 RTC_DCHECK(!size.IsZero());
162
163 if (!clusters_.empty()) {
164 ProbeCluster* cluster = &clusters_.front();
165 if (cluster->sent_probes == 0) {
166 RTC_DCHECK(cluster->started_at.IsInfinite());
167 cluster->started_at = now;
168 }
169 cluster->sent_bytes += size.bytes<int>();
170 cluster->sent_probes += 1;
171 next_probe_time_ = CalculateNextProbeTime(*cluster);
172 if (cluster->sent_bytes >= cluster->pace_info.probe_cluster_min_bytes &&
173 cluster->sent_probes >= cluster->pace_info.probe_cluster_min_probes) {
174 RTC_HISTOGRAM_COUNTS_100000("WebRTC.BWE.Probing.ProbeClusterSizeInBytes",
175 cluster->sent_bytes);
176 RTC_HISTOGRAM_COUNTS_100("WebRTC.BWE.Probing.ProbesPerCluster",
177 cluster->sent_probes);
178 RTC_HISTOGRAM_COUNTS_10000("WebRTC.BWE.Probing.TimePerProbeCluster",
179 (now - cluster->started_at).ms());
180
181 clusters_.pop();
182 }
183 if (clusters_.empty()) {
184 probing_state_ = ProbingState::kSuspended;
185 }
186 }
187 }
188
CalculateNextProbeTime(const ProbeCluster & cluster) const189 Timestamp BitrateProber::CalculateNextProbeTime(
190 const ProbeCluster& cluster) const {
191 RTC_CHECK_GT(cluster.pace_info.send_bitrate_bps, 0);
192 RTC_CHECK(cluster.started_at.IsFinite());
193
194 // Compute the time delta from the cluster start to ensure probe bitrate stays
195 // close to the target bitrate. Result is in milliseconds.
196 DataSize sent_bytes = DataSize::Bytes(cluster.sent_bytes);
197 DataRate send_bitrate =
198 DataRate::BitsPerSec(cluster.pace_info.send_bitrate_bps);
199
200 TimeDelta delta = sent_bytes / send_bitrate;
201 return cluster.started_at + delta;
202 }
203
204 } // namespace webrtc
205