| // Copyright 2026 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 "quiche/quic/core/congestion_control/bbr3_sender.h" |
| |
| #include <algorithm> |
| #include <cstddef> |
| #include <ostream> |
| #include <sstream> |
| #include <string> |
| |
| #include "quiche/quic/core/congestion_control/bandwidth_sampler.h" |
| #include "quiche/quic/core/congestion_control/bbr2_misc.h" |
| #include "quiche/quic/core/crypto/crypto_protocol.h" |
| #include "quiche/quic/core/quic_bandwidth.h" |
| #include "quiche/quic/core/quic_tag.h" |
| #include "quiche/quic/core/quic_types.h" |
| #include "quiche/quic/platform/api/quic_flag_utils.h" |
| #include "quiche/quic/platform/api/quic_flags.h" |
| #include "quiche/quic/platform/api/quic_logging.h" |
| #include "quiche/common/platform/api/quiche_logging.h" |
| #include "quiche/common/print_elements.h" |
| |
| namespace quic { |
| |
| namespace { |
| |
| const int kMaxModeChangesPerCongestionEvent = 4; |
| } // namespace |
| |
| Bbr3Sender::Bbr3Sender(QuicTime now, const RttStats* rtt_stats, |
| const QuicUnackedPacketMap* unacked_packets, |
| QuicPacketCount initial_cwnd_in_packets, |
| QuicPacketCount max_cwnd_in_packets, QuicRandom* random, |
| QuicConnectionStats* stats, BbrSender* old_sender) |
| : mode_(Bbr2Mode::STARTUP), |
| unacked_packets_(unacked_packets), |
| random_(random), |
| connection_stats_(stats), |
| params_(kDefaultMinimumCongestionWindow, |
| max_cwnd_in_packets * kDefaultTCPMSS), |
| model_(¶ms_, rtt_stats->SmoothedOrInitialRtt(), |
| rtt_stats->last_update_time(), |
| old_sender ? &old_sender->sampler_ : nullptr), |
| initial_cwnd_(params_.cwnd_limits.ApplyLimits( |
| (old_sender) ? old_sender->GetCongestionWindow() |
| : (initial_cwnd_in_packets * kDefaultTCPMSS))), |
| cwnd_(initial_cwnd_), |
| pacing_rate_(params_.startup_pacing_gain * |
| QuicBandwidth::FromBytesAndTimeDelta( |
| cwnd_, rtt_stats->SmoothedOrInitialRtt())), |
| last_sample_is_app_limited_(false) { |
| // Increment, instead of reset startup stats, so we don't lose data recorded |
| // before QuicConnection switched send algorithm to BBRv2. |
| ++connection_stats_->slowstart_count; |
| if (!connection_stats_->slowstart_duration.IsRunning()) { |
| connection_stats_->slowstart_duration.Start(now); |
| } |
| // The BBR IETF draft uses 0.5 as the drain pacing gain. |
| params_.drain_pacing_gain = 0.5f; |
| // The BBR IETF draft uses 0.9 as the PROBE_DOWN pacing gain. |
| params_.probe_bw_probe_down_pacing_gain = 0.9f; |
| // STARTUP has a shorter MaxAckHeightTracker window of 1 round. |
| params_.startup_include_extra_acked = true; |
| model_.SetMaxAckHeightTrackerWindowLength(1); |
| // Use the derived startup pacing gain in the IETF draft. |
| model_.set_pacing_gain(kDerivedStartupPacingGain); |
| |
| QUICHE_DCHECK_EQ(model_.cwnd_gain(), 2.0); |
| QUIC_DVLOG(2) << this << " Initializing Bbr3Sender. mode:" << mode_ |
| << ", PacingRate:" << pacing_rate_ << ", Cwnd:" << cwnd_ |
| << ", CwndLimits:" << params_.cwnd_limits << " @ " << now; |
| QUICHE_DCHECK_EQ(mode_, Bbr2Mode::STARTUP); |
| } |
| |
| void Bbr3Sender::SetFromConfig(const QuicConfig& config, |
| Perspective perspective) { |
| ApplyConnectionOptions(config.ClientRequestedIndependentOptions(perspective)); |
| } |
| |
| void Bbr3Sender::ApplyConnectionOptions( |
| const QuicTagVector& connection_options) { |
| if (ContainsQuicTag(connection_options, kB2NA)) { |
| params_.add_ack_height_to_queueing_threshold = false; |
| } |
| if (ContainsQuicTag(connection_options, kB2RP)) { |
| params_.avoid_unnecessary_probe_rtt = false; |
| } |
| if (ContainsQuicTag(connection_options, k1RTT)) { |
| params_.startup_full_bw_rounds = 1; |
| } |
| if (ContainsQuicTag(connection_options, k2RTT)) { |
| params_.startup_full_bw_rounds = 2; |
| } |
| if (ContainsQuicTag(connection_options, kB2HR)) { |
| params_.inflight_hi_headroom = 0.15; |
| } |
| if (ContainsQuicTag(connection_options, kICW1)) { |
| max_cwnd_when_network_parameters_adjusted_ = 100 * kDefaultTCPMSS; |
| } |
| if (ContainsQuicTag(connection_options, kBBR4)) { |
| QUICHE_DCHECK_EQ(mode_, Bbr2Mode::STARTUP); |
| max_ack_height_window_length_ = 20; |
| } |
| if (ContainsQuicTag(connection_options, kBBR5)) { |
| QUICHE_DCHECK_EQ(mode_, Bbr2Mode::STARTUP); |
| max_ack_height_window_length_ = 40; |
| } |
| if (ContainsQuicTag(connection_options, kBBQ2)) { |
| params_.startup_cwnd_gain = 2.885; |
| params_.drain_cwnd_gain = 2.885; |
| model_.set_cwnd_gain(params_.startup_cwnd_gain); |
| } |
| if (ContainsQuicTag(connection_options, kB2LO)) { |
| params_.ignore_inflight_lo = true; |
| } |
| if (ContainsQuicTag(connection_options, kB2NE)) { |
| params_.always_exit_startup_on_excess_loss = true; |
| } |
| if (ContainsQuicTag(connection_options, kB2SL)) { |
| params_.startup_loss_exit_use_max_delivered_for_inflight_hi = false; |
| } |
| if (ContainsQuicTag(connection_options, kB2H2)) { |
| params_.limit_inflight_hi_by_max_delivered = true; |
| } |
| if (ContainsQuicTag(connection_options, kB2DL)) { |
| params_.use_bytes_delivered_for_inflight_hi = true; |
| } |
| if (ContainsQuicTag(connection_options, kB2RC)) { |
| params_.enable_reno_coexistence = false; |
| } |
| if (ContainsQuicTag(connection_options, kBSAO)) { |
| model_.EnableOverestimateAvoidance(); |
| } |
| if (ContainsQuicTag(connection_options, kBBQ6)) { |
| params_.decrease_startup_pacing_at_end_of_round = true; |
| } |
| if (ContainsQuicTag(connection_options, kBBQ7)) { |
| params_.bw_lo_mode_ = Bbr2Params::QuicBandwidthLoMode::MIN_RTT_REDUCTION; |
| } |
| if (ContainsQuicTag(connection_options, kBBQ8)) { |
| params_.bw_lo_mode_ = Bbr2Params::QuicBandwidthLoMode::INFLIGHT_REDUCTION; |
| } |
| if (ContainsQuicTag(connection_options, kBBQ9)) { |
| params_.bw_lo_mode_ = Bbr2Params::QuicBandwidthLoMode::CWND_REDUCTION; |
| } |
| if (ContainsQuicTag(connection_options, kB202)) { |
| params_.max_probe_up_queue_rounds = 1; |
| } |
| if (ContainsQuicTag(connection_options, kB203)) { |
| params_.probe_up_ignore_inflight_hi = false; |
| } |
| if (ContainsQuicTag(connection_options, kB204)) { |
| model_.SetReduceExtraAckedOnBandwidthIncrease(true); |
| } |
| if (ContainsQuicTag(connection_options, kB205)) { |
| params_.startup_include_extra_acked = true; |
| } |
| if (ContainsQuicTag(connection_options, kBBRA)) { |
| model_.SetStartNewAggregationEpochAfterFullRound(true); |
| } |
| if (ContainsQuicTag(connection_options, kBBRB)) { |
| model_.SetLimitMaxAckHeightTrackerBySendRate(true); |
| } |
| if (ContainsQuicTag(connection_options, kADP0)) { |
| model_.SetEnableAppDrivenPacing(true); |
| } |
| if (ContainsQuicTag(connection_options, kB206)) { |
| params_.startup_full_loss_count = params_.probe_bw_full_loss_count; |
| } |
| if (ContainsQuicTag(connection_options, kBBHI)) { |
| params_.probe_up_simplify_inflight_hi = true; |
| // Simplify inflight_hi is intended as an alternative to ignoring it, |
| // so ensure we're not ignoring it. |
| params_.probe_up_ignore_inflight_hi = false; |
| } |
| if (ContainsQuicTag(connection_options, kBB2U)) { |
| params_.max_probe_up_queue_rounds = 2; |
| } |
| } |
| |
| Limits<QuicByteCount> Bbr3Sender::GetCwndLimitsByMode() const { |
| switch (mode_) { |
| case Bbr2Mode::STARTUP: |
| // Inflight_lo is never set in STARTUP. |
| QUICHE_DCHECK_EQ(Bbr2NetworkModel::inflight_lo_default(), |
| model_.inflight_lo()); |
| return NoGreaterThan(model_.inflight_lo()); |
| case Bbr2Mode::PROBE_BW: { |
| if (probe_bw_.phase == ProbePhase::PROBE_CRUISE) { |
| return NoGreaterThan( |
| std::min(model_.inflight_lo(), model_.inflight_hi_with_headroom())); |
| } |
| if (params_.probe_up_ignore_inflight_hi && |
| probe_bw_.phase == ProbePhase::PROBE_UP) { |
| // Similar to STARTUP. |
| return NoGreaterThan(model_.inflight_lo()); |
| } |
| return NoGreaterThan( |
| std::min(model_.inflight_lo(), model_.inflight_hi())); |
| } |
| case Bbr2Mode::DRAIN: |
| return NoGreaterThan(model_.inflight_lo()); |
| case Bbr2Mode::PROBE_RTT: { |
| QuicByteCount inflight_upper_bound = |
| std::min(model_.inflight_lo(), model_.inflight_hi_with_headroom()); |
| return NoGreaterThan(std::min(inflight_upper_bound, InflightTarget())); |
| } |
| default: |
| QUICHE_NOTREACHED(); |
| return Unlimited<QuicByteCount>(); |
| } |
| } |
| |
| void Bbr3Sender::AdjustNetworkParameters(const NetworkParams& params) { |
| model_.UpdateNetworkParameters(params.rtt); |
| |
| if (mode_ == Bbr2Mode::STARTUP) { |
| const QuicByteCount prior_cwnd = cwnd_; |
| |
| QuicBandwidth effective_bandwidth = |
| std::max(params.bandwidth, model_.BandwidthEstimate()); |
| connection_stats_->cwnd_bootstrapping_rtt_us = |
| model_.MinRtt().ToMicroseconds(); |
| |
| if (params.max_initial_congestion_window > 0) { |
| max_cwnd_when_network_parameters_adjusted_ = |
| params.max_initial_congestion_window * kDefaultTCPMSS; |
| } |
| cwnd_ = params_.cwnd_limits.ApplyLimits( |
| std::min(max_cwnd_when_network_parameters_adjusted_, |
| model_.BDP(effective_bandwidth))); |
| |
| if (!params.allow_cwnd_to_decrease) { |
| cwnd_ = std::max(cwnd_, prior_cwnd); |
| } |
| |
| pacing_rate_ = std::max(pacing_rate_, QuicBandwidth::FromBytesAndTimeDelta( |
| cwnd_, model_.MinRtt())); |
| } |
| } |
| |
| void Bbr3Sender::SetInitialCongestionWindowInPackets( |
| QuicPacketCount congestion_window) { |
| if (mode_ == Bbr2Mode::STARTUP) { |
| // The cwnd limits is unchanged and still applies to the new cwnd. |
| cwnd_ = params_.cwnd_limits.ApplyLimits(congestion_window * kDefaultTCPMSS); |
| } |
| } |
| |
| void Bbr3Sender::SetApplicationDrivenPacingRate( |
| QuicBandwidth application_bandwidth_target) { |
| QUIC_CODE_COUNT(quic_bbr2_set_app_driven_pacing_rate); |
| model_.SetApplicationBandwidthTarget(application_bandwidth_target); |
| } |
| |
| void Bbr3Sender::OnCongestionEvent(bool /*rtt_updated*/, |
| QuicByteCount prior_in_flight, |
| QuicTime event_time, |
| const AckedPacketVector& acked_packets, |
| const LostPacketVector& lost_packets, |
| QuicPacketCount /*num_ect*/, |
| QuicPacketCount /*num_ce*/) { |
| QUIC_DVLOG(3) << this |
| << " OnCongestionEvent. prior_in_flight:" << prior_in_flight |
| << " prior_cwnd:" << cwnd_ << " @ " << event_time; |
| Bbr2CongestionEvent congestion_event; |
| congestion_event.prior_cwnd = cwnd_; |
| congestion_event.prior_bytes_in_flight = prior_in_flight; |
| bool is_probing_for_bandwidth = false; |
| if (mode_ == Bbr2Mode::STARTUP) { |
| is_probing_for_bandwidth = true; |
| } else if (mode_ == Bbr2Mode::PROBE_BW) { |
| is_probing_for_bandwidth = probe_bw_.phase == ProbePhase::PROBE_REFILL || |
| probe_bw_.phase == ProbePhase::PROBE_UP; |
| } |
| congestion_event.is_probing_for_bandwidth = is_probing_for_bandwidth; |
| |
| model_.OnCongestionEventStart(event_time, acked_packets, lost_packets, |
| &congestion_event); |
| |
| if (InSlowStart()) { |
| if (!lost_packets.empty()) { |
| connection_stats_->slowstart_packets_lost += lost_packets.size(); |
| connection_stats_->slowstart_bytes_lost += congestion_event.bytes_lost; |
| } |
| if (congestion_event.end_of_round_trip) { |
| ++connection_stats_->slowstart_num_rtts; |
| } |
| } |
| |
| // Number of mode changes allowed for this congestion event. |
| int mode_changes_allowed = kMaxModeChangesPerCongestionEvent; |
| while (true) { |
| Bbr2Mode prev_mode = mode_; |
| switch (mode_) { |
| case Bbr2Mode::STARTUP: |
| mode_ = OnCongestionEventStartup(congestion_event); |
| break; |
| case Bbr2Mode::DRAIN: |
| mode_ = OnCongestionEventDrain(congestion_event); |
| break; |
| case Bbr2Mode::PROBE_BW: |
| mode_ = OnCongestionEventProbeBw(prior_in_flight, event_time, |
| congestion_event); |
| break; |
| case Bbr2Mode::PROBE_RTT: |
| mode_ = OnCongestionEventProbeRtt(congestion_event); |
| break; |
| } |
| |
| if (mode_ == prev_mode) { |
| break; |
| } |
| |
| QUIC_DVLOG(2) << this << " Mode change: " << prev_mode << " ==> " << mode_ |
| << " @ " << event_time; |
| |
| if (prev_mode == Bbr2Mode::STARTUP) { |
| LeaveStartup(event_time); |
| } |
| |
| if (mode_ == Bbr2Mode::PROBE_BW) { |
| if (probe_bw_.phase == ProbePhase::PROBE_NOT_STARTED) { |
| EnterProbeDown(/*probed_too_high=*/false, /*stopped_risky_probe=*/false, |
| event_time); |
| } else { |
| QUICHE_DCHECK(probe_bw_.phase == ProbePhase::PROBE_CRUISE || |
| probe_bw_.phase == ProbePhase::PROBE_REFILL); |
| probe_bw_.cycle_start_time = event_time; |
| if (probe_bw_.phase == ProbePhase::PROBE_CRUISE) { |
| EnterProbeCruise(event_time); |
| } else if (probe_bw_.phase == ProbePhase::PROBE_REFILL) { |
| EnterProbeRefill(probe_bw_.probe_up_rounds, event_time); |
| } |
| } |
| } else if (mode_ == Bbr2Mode::PROBE_RTT) { |
| EnterProbeRtt(); |
| } |
| |
| --mode_changes_allowed; |
| if (mode_changes_allowed < 0) { |
| QUIC_BUG(quic_bug_10443_1) |
| << "Exceeded max number of mode changes per congestion event."; |
| break; |
| } |
| } |
| |
| UpdatePacingRate(congestion_event.bytes_acked); |
| QUIC_BUG_IF(quic_bug_10443_2, pacing_rate_.IsZero()) |
| << "Pacing rate must not be zero!"; |
| |
| UpdateCongestionWindow(congestion_event.bytes_acked); |
| QUIC_BUG_IF(quic_bug_10443_3, cwnd_ == 0u) |
| << "Congestion window must not be zero!"; |
| |
| model_.OnCongestionEventFinish(unacked_packets_->GetLeastUnacked(), |
| congestion_event); |
| last_sample_is_app_limited_ = |
| congestion_event.last_packet_send_state.is_app_limited; |
| if (!last_sample_is_app_limited_) { |
| has_non_app_limited_sample_ = true; |
| } |
| if (congestion_event.bytes_in_flight == 0 && |
| params_.avoid_unnecessary_probe_rtt) { |
| last_quiescence_start_ = event_time; |
| } |
| |
| QUIC_DVLOG(3) |
| << this |
| << " END CongestionEvent(acked:" << quiche::PrintElements(acked_packets) |
| << ", lost:" << lost_packets.size() << ") " |
| << ", Mode:" << mode_ << ", RttCount:" << model_.RoundTripCount() |
| << ", BytesInFlight:" << congestion_event.bytes_in_flight |
| << ", PacingRate:" << PacingRate(0) << ", CWND:" << GetCongestionWindow() |
| << ", PacingGain:" << model_.pacing_gain() |
| << ", CwndGain:" << model_.cwnd_gain() |
| << ", BandwidthEstimate(kbps):" << BandwidthEstimate().ToKBitsPerSecond() |
| << ", MinRTT(us):" << model_.MinRtt().ToMicroseconds() |
| << ", BDP:" << model_.BDP(BandwidthEstimate()) |
| << ", BandwidthLatest(kbps):" |
| << model_.bandwidth_latest().ToKBitsPerSecond() |
| << ", BandwidthLow(kbps):" << model_.bandwidth_lo().ToKBitsPerSecond() |
| << ", BandwidthHigh(kbps):" << model_.MaxBandwidth().ToKBitsPerSecond() |
| << ", InflightLatest:" << model_.inflight_latest() |
| << ", InflightLow:" << model_.inflight_lo() |
| << ", InflightHigh:" << model_.inflight_hi() |
| << ", TotalAcked:" << model_.total_bytes_acked() |
| << ", TotalLost:" << model_.total_bytes_lost() |
| << ", TotalSent:" << model_.total_bytes_sent() << " @ " << event_time; |
| } |
| |
| void Bbr3Sender::UpdatePacingRate(QuicByteCount bytes_acked) { |
| if (BandwidthEstimate().IsZero()) { |
| return; |
| } |
| |
| if (model_.total_bytes_acked() == bytes_acked) { |
| // After the first ACK, cwnd_ is still the initial congestion window. |
| pacing_rate_ = QuicBandwidth::FromBytesAndTimeDelta(cwnd_, model_.MinRtt()); |
| return; |
| } |
| |
| QuicBandwidth target_rate = model_.pacing_gain() * model_.BandwidthEstimate(); |
| if (model_.full_bandwidth_reached()) { |
| pacing_rate_ = target_rate; |
| return; |
| } |
| if (params_.decrease_startup_pacing_at_end_of_round && |
| model_.pacing_gain() < Params().startup_pacing_gain) { |
| pacing_rate_ = target_rate; |
| return; |
| } |
| if (params_.bw_lo_mode_ != Bbr2Params::DEFAULT && |
| model_.loss_events_in_round() > 0) { |
| pacing_rate_ = target_rate; |
| return; |
| } |
| |
| // By default, the pacing rate never decreases in STARTUP. |
| if (target_rate > pacing_rate_) { |
| pacing_rate_ = target_rate; |
| } |
| } |
| |
| void Bbr3Sender::UpdateCongestionWindow(QuicByteCount bytes_acked) { |
| QuicByteCount target_cwnd = GetTargetCongestionWindow(model_.cwnd_gain()); |
| |
| const QuicByteCount prior_cwnd = cwnd_; |
| if (model_.full_bandwidth_reached() || Params().startup_include_extra_acked) { |
| target_cwnd += model_.MaxAckHeight(); |
| cwnd_ = std::min(prior_cwnd + bytes_acked, target_cwnd); |
| } else if (prior_cwnd < target_cwnd || prior_cwnd < 2 * initial_cwnd_) { |
| cwnd_ = prior_cwnd + bytes_acked; |
| } |
| |
| const QuicByteCount desired_cwnd = cwnd_; |
| |
| cwnd_ = GetCwndLimitsByMode().ApplyLimits(cwnd_); |
| const QuicByteCount model_limited_cwnd = cwnd_; |
| |
| cwnd_ = params_.cwnd_limits.ApplyLimits(cwnd_); |
| |
| QUIC_DVLOG(3) << this << " Updating CWND. target_cwnd:" << target_cwnd |
| << ", max_ack_height:" << model_.MaxAckHeight() |
| << ", full_bw:" << model_.full_bandwidth_reached() |
| << ", bytes_acked:" << bytes_acked |
| << ", inflight_lo:" << model_.inflight_lo() |
| << ", inflight_hi:" << model_.inflight_hi() << ". (prior_cwnd) " |
| << prior_cwnd << " => (desired_cwnd) " << desired_cwnd |
| << " => (model_limited_cwnd) " << model_limited_cwnd |
| << " => (final_cwnd) " << cwnd_; |
| } |
| |
| QuicByteCount Bbr3Sender::GetTargetCongestionWindow(float gain) const { |
| return std::max(model_.BDP(model_.BandwidthEstimate(), gain), |
| params_.cwnd_limits.Min()); |
| } |
| |
| void Bbr3Sender::OnPacketSent(QuicTime sent_time, QuicByteCount bytes_in_flight, |
| QuicPacketNumber packet_number, |
| QuicByteCount bytes, |
| HasRetransmittableData is_retransmittable) { |
| QUIC_DVLOG(3) << this << " OnPacketSent: pkn:" << packet_number |
| << ", bytes:" << bytes << ", cwnd:" << cwnd_ |
| << ", inflight:" << bytes_in_flight + bytes |
| << ", total_sent:" << model_.total_bytes_sent() + bytes |
| << ", total_acked:" << model_.total_bytes_acked() |
| << ", total_lost:" << model_.total_bytes_lost() << " @ " |
| << sent_time; |
| if (InSlowStart()) { |
| ++connection_stats_->slowstart_packets_sent; |
| connection_stats_->slowstart_bytes_sent += bytes; |
| } |
| if (bytes_in_flight == 0 && params_.avoid_unnecessary_probe_rtt) { |
| OnExitQuiescence(sent_time); |
| } |
| model_.OnPacketSent(sent_time, bytes_in_flight, packet_number, bytes, |
| is_retransmittable); |
| } |
| |
| void Bbr3Sender::OnPacketNeutered(QuicPacketNumber packet_number) { |
| model_.OnPacketNeutered(packet_number); |
| } |
| |
| bool Bbr3Sender::CanSend(QuicByteCount bytes_in_flight) { |
| return bytes_in_flight < GetCongestionWindow(); |
| } |
| |
| QuicByteCount Bbr3Sender::GetCongestionWindow() const { |
| return cwnd_; |
| } |
| |
| QuicBandwidth Bbr3Sender::PacingRate(QuicByteCount /*bytes_in_flight*/) const { |
| return pacing_rate_; |
| } |
| |
| void Bbr3Sender::OnApplicationLimited(QuicByteCount bytes_in_flight) { |
| if (bytes_in_flight >= GetCongestionWindow()) { |
| return; |
| } |
| |
| model_.OnApplicationLimited(); |
| QUIC_DVLOG(2) << this << " Becoming application limited. Last sent packet: " |
| << model_.last_sent_packet() |
| << ", CWND: " << GetCongestionWindow(); |
| } |
| |
| QuicByteCount Bbr3Sender::GetTargetBytesInflight() const { |
| QuicByteCount bdp = model_.BDP(model_.BandwidthEstimate()); |
| return std::min(bdp, GetCongestionWindow()); |
| } |
| |
| void Bbr3Sender::PopulateConnectionStats(QuicConnectionStats* stats) const { |
| stats->num_ack_aggregation_epochs = model_.num_ack_aggregation_epochs(); |
| } |
| |
| void Bbr3Sender::LeaveStartup(QuicTime now) { |
| connection_stats_->slowstart_duration.Stop(now); |
| // Clear bandwidth_lo if it's set during STARTUP. |
| model_.clear_bandwidth_lo(); |
| // Increase the max_ack_height_tracker window when exiting STARTUP from 1. |
| model_.SetMaxAckHeightTrackerWindowLength(max_ack_height_window_length_); |
| drain_rounds_ = 0; |
| } |
| |
| void Bbr3Sender::OnExitQuiescence(QuicTime now) { |
| if (last_quiescence_start_ == QuicTime::Zero()) { |
| return; |
| } |
| |
| Bbr2Mode prev_mode = mode_; |
| switch (mode_) { |
| case Bbr2Mode::STARTUP: |
| case Bbr2Mode::DRAIN: |
| break; |
| case Bbr2Mode::PROBE_BW: |
| QUIC_DVLOG(3) << this << " Postponing min_rtt_timestamp(" |
| << model_.MinRttTimestamp() << ") by " |
| << now - last_quiescence_start_; |
| model_.PostponeMinRttTimestamp(now - last_quiescence_start_); |
| break; |
| case Bbr2Mode::PROBE_RTT: |
| if (now > probe_rtt_.exit_time) { |
| mode_ = Bbr2Mode::PROBE_BW; |
| } |
| break; |
| } |
| |
| if (mode_ != prev_mode) { |
| QUICHE_DCHECK_EQ(mode_, Bbr2Mode::PROBE_BW); |
| if (probe_bw_.phase == ProbePhase::PROBE_NOT_STARTED) { |
| EnterProbeDown(/*probed_too_high=*/false, /*stopped_risky_probe=*/false, |
| now); |
| } else { |
| QUICHE_DCHECK(probe_bw_.phase == ProbePhase::PROBE_CRUISE || |
| probe_bw_.phase == ProbePhase::PROBE_REFILL); |
| probe_bw_.cycle_start_time = now; |
| if (probe_bw_.phase == ProbePhase::PROBE_CRUISE) { |
| EnterProbeCruise(now); |
| } else if (probe_bw_.phase == ProbePhase::PROBE_REFILL) { |
| EnterProbeRefill(probe_bw_.probe_up_rounds, now); |
| } |
| } |
| } |
| last_quiescence_start_ = QuicTime::Zero(); |
| } |
| |
| std::string Bbr3Sender::GetDebugState() const { |
| std::ostringstream stream; |
| stream << ExportDebugState(); |
| return stream.str(); |
| } |
| |
| Bbr2DebugState Bbr3Sender::ExportDebugState() const { |
| Bbr2DebugState s; |
| s.mode = mode_; |
| s.round_trip_count = model_.RoundTripCount(); |
| s.bandwidth_hi = model_.MaxBandwidth(); |
| s.bandwidth_lo = model_.bandwidth_lo(); |
| s.bandwidth_est = BandwidthEstimate(); |
| s.inflight_hi = model_.inflight_hi(); |
| s.inflight_lo = model_.inflight_lo(); |
| s.max_ack_height = model_.MaxAckHeight(); |
| s.min_rtt = model_.MinRtt(); |
| s.min_rtt_timestamp = model_.MinRttTimestamp(); |
| s.congestion_window = cwnd_; |
| s.pacing_rate = pacing_rate_; |
| s.last_sample_is_app_limited = last_sample_is_app_limited_; |
| s.end_of_app_limited_phase = model_.end_of_app_limited_phase(); |
| |
| s.startup.full_bandwidth_reached = model_.full_bandwidth_reached(); |
| s.startup.full_bandwidth_baseline = model_.full_bandwidth_baseline(); |
| s.startup.round_trips_without_bandwidth_growth = |
| model_.rounds_without_bandwidth_growth(); |
| |
| s.drain.drain_target = DrainTarget(); |
| |
| s.probe_bw.phase = probe_bw_.phase; |
| s.probe_bw.cycle_start_time = probe_bw_.cycle_start_time; |
| s.probe_bw.phase_start_time = probe_bw_.phase_start_time; |
| |
| s.probe_rtt.inflight_target = InflightTarget(); |
| s.probe_rtt.exit_time = probe_rtt_.exit_time; |
| |
| return s; |
| } |
| |
| Bbr2Mode Bbr3Sender::OnCongestionEventStartup( |
| const Bbr2CongestionEvent& congestion_event) { |
| if (model_.full_bandwidth_reached()) { |
| QUIC_BUG(quic_bug_10463_2) |
| << "In STARTUP, but full_bandwidth_reached is true."; |
| return Bbr2Mode::DRAIN; |
| } |
| if (!congestion_event.end_of_round_trip) { |
| return Bbr2Mode::STARTUP; |
| } |
| bool has_bandwidth_growth = model_.HasBandwidthGrowth(congestion_event); |
| // By default, don't exit STARTUP if there was bandwidth growth. |
| if (params_.always_exit_startup_on_excess_loss || !has_bandwidth_growth) { |
| CheckExcessiveLosses(congestion_event); |
| } |
| |
| if (params_.decrease_startup_pacing_at_end_of_round) { |
| QUICHE_DCHECK_GT(model_.pacing_gain(), 0); |
| if (!congestion_event.last_packet_send_state.is_app_limited) { |
| // Multiply by startup_pacing_gain, so if the bandwidth doubles, |
| // the pacing gain will be the full startup_pacing_gain. |
| if (startup_max_bw_at_round_beginning_ > QuicBandwidth::Zero()) { |
| const float bandwidth_ratio = std::max( |
| 1., model_.MaxBandwidth().ToBitsPerSecond() / |
| static_cast<double>( |
| startup_max_bw_at_round_beginning_.ToBitsPerSecond())); |
| // Even when bandwidth isn't increasing, use a gain large enough to |
| // cause a full_bw_threshold increase. |
| const float new_gain = |
| ((bandwidth_ratio - 1) * |
| (params_.startup_pacing_gain - params_.full_bw_threshold)) + |
| params_.full_bw_threshold; |
| // Allow the pacing gain to decrease. |
| model_.set_pacing_gain(std::min(params_.startup_pacing_gain, new_gain)); |
| // Clear bandwidth_lo if it's less than the pacing rate. |
| // This avoids a constantly app-limited flow from having it's pacing |
| // gain effectively decreased below 1.25. |
| if (model_.bandwidth_lo() < |
| model_.MaxBandwidth() * model_.pacing_gain()) { |
| model_.clear_bandwidth_lo(); |
| } |
| } |
| startup_max_bw_at_round_beginning_ = model_.MaxBandwidth(); |
| } |
| } |
| |
| // TODO(wub): Maybe implement STARTUP => PROBE_RTT. |
| return model_.full_bandwidth_reached() ? Bbr2Mode::DRAIN : Bbr2Mode::STARTUP; |
| } |
| |
| void Bbr3Sender::CheckExcessiveLosses( |
| const Bbr2CongestionEvent& congestion_event) { |
| QUICHE_DCHECK(congestion_event.end_of_round_trip); |
| |
| if (model_.full_bandwidth_reached()) { |
| return; |
| } |
| |
| // At the end of a round trip. Check if loss is too high in this round. |
| if (model_.IsInflightTooHigh(congestion_event, |
| params_.startup_full_loss_count)) { |
| QuicByteCount new_inflight_hi = model_.BDP(); |
| if (params_.startup_loss_exit_use_max_delivered_for_inflight_hi) { |
| if (new_inflight_hi < model_.max_bytes_delivered_in_round()) { |
| new_inflight_hi = model_.max_bytes_delivered_in_round(); |
| } |
| } |
| QUIC_DVLOG(3) << this << " Exiting STARTUP due to loss at round " |
| << model_.RoundTripCount() |
| << ". inflight_hi:" << new_inflight_hi; |
| // TODO(ianswett): Add a shared method to set inflight_hi in the model. |
| model_.set_inflight_hi(new_inflight_hi); |
| model_.set_full_bandwidth_reached(); |
| connection_stats_->bbr_exit_startup_due_to_loss = true; |
| } |
| } |
| |
| Bbr2Mode Bbr3Sender::OnCongestionEventDrain( |
| const Bbr2CongestionEvent& congestion_event) { |
| model_.set_pacing_gain(params_.drain_pacing_gain); |
| |
| // Only STARTUP can transition to DRAIN, both of them use the same cwnd gain. |
| QUICHE_DCHECK_EQ(model_.cwnd_gain(), params_.drain_cwnd_gain); |
| model_.set_cwnd_gain(params_.drain_cwnd_gain); |
| |
| if (congestion_event.end_of_round_trip) { |
| ++drain_rounds_; |
| } |
| |
| QuicByteCount drain_target = DrainTarget(); |
| if (congestion_event.bytes_in_flight <= drain_target || drain_rounds_ > 3) { |
| QUIC_DVLOG(3) << this << " Exiting DRAIN. bytes_in_flight:" |
| << congestion_event.bytes_in_flight |
| << ", bdp:" << model_.BDP() |
| << ", drain_target:" << drain_target |
| << ", drain_rounds:" << drain_rounds_ << " @ " |
| << congestion_event.event_time; |
| return Bbr2Mode::PROBE_BW; |
| } |
| |
| QUIC_DVLOG(3) << this << " Staying in DRAIN. bytes_in_flight:" |
| << congestion_event.bytes_in_flight << ", bdp:" << model_.BDP() |
| << ", drain_target:" << drain_target << " @ " |
| << congestion_event.event_time; |
| return Bbr2Mode::DRAIN; |
| } |
| |
| QuicByteCount Bbr3Sender::DrainTarget() const { |
| QuicByteCount bdp = model_.BDP(); |
| return std::max<QuicByteCount>(bdp, GetMinimumCongestionWindow()); |
| } |
| |
| Bbr2Mode Bbr3Sender::OnCongestionEventProbeBw( |
| QuicByteCount prior_in_flight, QuicTime event_time, |
| const Bbr2CongestionEvent& congestion_event) { |
| QUICHE_DCHECK_NE(probe_bw_.phase, ProbePhase::PROBE_NOT_STARTED); |
| |
| if (congestion_event.end_of_round_trip) { |
| if (probe_bw_.cycle_start_time != event_time) { |
| ++probe_bw_.rounds_since_probe; |
| } |
| if (probe_bw_.phase_start_time != event_time) { |
| ++probe_bw_.rounds_in_phase; |
| } |
| } |
| |
| bool switch_to_probe_rtt = false; |
| |
| if (probe_bw_.phase == ProbePhase::PROBE_UP) { |
| UpdateProbeUp(congestion_event); |
| } else if (probe_bw_.phase == ProbePhase::PROBE_DOWN) { |
| UpdateProbeDown(prior_in_flight, congestion_event); |
| // Maybe transition to PROBE_RTT at the end of this cycle. |
| if (probe_bw_.phase != ProbePhase::PROBE_DOWN && |
| model_.MaybeExpireMinRtt(congestion_event)) { |
| switch_to_probe_rtt = true; |
| } |
| } else if (probe_bw_.phase == ProbePhase::PROBE_CRUISE) { |
| UpdateProbeCruise(congestion_event); |
| } else if (probe_bw_.phase == ProbePhase::PROBE_REFILL) { |
| UpdateProbeRefill(congestion_event); |
| } |
| |
| // Do not need to set the gains if switching to PROBE_RTT, they will be set |
| // when Bbr2ProbeRttMode::Enter is called. |
| if (switch_to_probe_rtt) { |
| return Bbr2Mode::PROBE_RTT; |
| } |
| model_.set_pacing_gain(PacingGainForPhase(probe_bw_.phase)); |
| if (probe_bw_.phase == ProbePhase::PROBE_UP) { |
| model_.set_cwnd_gain(params_.probe_up_cwnd_gain); |
| } else { |
| model_.set_cwnd_gain(params_.probe_bw_cwnd_gain); |
| } |
| |
| return Bbr2Mode::PROBE_BW; |
| } |
| |
| void Bbr3Sender::UpdateProbeDown(QuicByteCount prior_in_flight, |
| const Bbr2CongestionEvent& congestion_event) { |
| QUICHE_DCHECK_EQ(probe_bw_.phase, ProbePhase::PROBE_DOWN); |
| |
| if (probe_bw_.rounds_in_phase == 1 && congestion_event.end_of_round_trip) { |
| probe_bw_.is_sample_from_probing = false; |
| |
| if (!congestion_event.last_packet_send_state.is_app_limited) { |
| QUIC_DVLOG(2) |
| << this << " Advancing max bw filter after one round in PROBE_DOWN."; |
| model_.AdvanceMaxBandwidthFilter(); |
| probe_bw_.has_advanced_max_bw = true; |
| } |
| |
| if (probe_bw_.last_cycle_stopped_risky_probe && |
| !probe_bw_.last_cycle_probed_too_high) { |
| EnterProbeRefill(/*probe_up_rounds=*/0, congestion_event.event_time); |
| return; |
| } |
| } |
| |
| MaybeAdaptUpperBounds(congestion_event); |
| |
| if (IsTimeToProbeBandwidth(congestion_event)) { |
| EnterProbeRefill(/*probe_up_rounds=*/0, congestion_event.event_time); |
| return; |
| } |
| |
| if (HasPhaseLasted(model_.MinRtt(), congestion_event)) { |
| QUIC_DVLOG(3) << this << " Proportional time based PROBE_DOWN exit"; |
| EnterProbeCruise(congestion_event.event_time); |
| return; |
| } |
| |
| const QuicByteCount inflight_with_headroom = |
| model_.inflight_hi_with_headroom(); |
| QUIC_DVLOG(3) |
| << this << " Checking if have enough inflight headroom. prior_in_flight:" |
| << prior_in_flight << " congestion_event.bytes_in_flight:" |
| << congestion_event.bytes_in_flight |
| << ", inflight_with_headroom:" << inflight_with_headroom; |
| QuicByteCount bytes_in_flight = congestion_event.bytes_in_flight; |
| |
| if (bytes_in_flight > inflight_with_headroom) { |
| // Stay in PROBE_DOWN. |
| return; |
| } |
| |
| // Transition to PROBE_CRUISE iff we've drained to target. |
| QuicByteCount bdp = model_.BDP(); |
| QUIC_DVLOG(3) << this << " Checking if drained to target. bytes_in_flight:" |
| << bytes_in_flight << ", bdp:" << bdp; |
| if (bytes_in_flight < bdp) { |
| EnterProbeCruise(congestion_event.event_time); |
| } |
| } |
| |
| Bbr3Sender::AdaptUpperBoundsResult Bbr3Sender::MaybeAdaptUpperBounds( |
| const Bbr2CongestionEvent& congestion_event) { |
| const SendTimeState& send_state = congestion_event.last_packet_send_state; |
| if (!send_state.is_valid) { |
| QUIC_DVLOG(3) << this << " " << ProbePhaseToString(probe_bw_.phase) |
| << ": NOT_ADAPTED_INVALID_SAMPLE"; |
| return NOT_ADAPTED_INVALID_SAMPLE; |
| } |
| |
| QuicByteCount inflight_at_send = BytesInFlight(send_state); |
| if (params_.use_bytes_delivered_for_inflight_hi) { |
| if (congestion_event.last_packet_send_state.total_bytes_acked <= |
| model_.total_bytes_acked()) { |
| inflight_at_send = |
| model_.total_bytes_acked() - |
| congestion_event.last_packet_send_state.total_bytes_acked; |
| } else { |
| QUIC_BUG(quic_bug_10463_3) |
| << "Total_bytes_acked(" << model_.total_bytes_acked() |
| << ") < send_state.total_bytes_acked(" |
| << congestion_event.last_packet_send_state.total_bytes_acked << ")"; |
| } |
| } |
| if (model_.IsInflightTooHigh(congestion_event, |
| params_.probe_bw_full_loss_count)) { |
| if (probe_bw_.is_sample_from_probing) { |
| probe_bw_.is_sample_from_probing = false; |
| if (!send_state.is_app_limited || params_.max_probe_up_queue_rounds > 0) { |
| const QuicByteCount inflight_target = |
| GetTargetBytesInflight() * (1.0 - params_.beta); |
| if (params_.limit_inflight_hi_by_max_delivered) { |
| QuicByteCount new_inflight_hi = |
| std::max(inflight_at_send, inflight_target); |
| if (new_inflight_hi < model_.max_bytes_delivered_in_round()) { |
| new_inflight_hi = model_.max_bytes_delivered_in_round(); |
| } |
| QUIC_DVLOG(3) << this |
| << " Setting inflight_hi due to loss. new_inflight_hi:" |
| << new_inflight_hi |
| << ", inflight_at_send:" << inflight_at_send |
| << ", inflight_target:" << inflight_target |
| << ", max_bytes_delivered_in_round:" |
| << model_.max_bytes_delivered_in_round() << " @ " |
| << congestion_event.event_time; |
| model_.set_inflight_hi(new_inflight_hi); |
| } else { |
| model_.set_inflight_hi(std::max(inflight_at_send, inflight_target)); |
| } |
| } |
| |
| QUIC_DVLOG(3) << this << " " << ProbePhaseToString(probe_bw_.phase) |
| << ": ADAPTED_PROBED_TOO_HIGH"; |
| return ADAPTED_PROBED_TOO_HIGH; |
| } |
| return ADAPTED_OK; |
| } |
| |
| if (model_.inflight_hi() == model_.inflight_hi_default()) { |
| QUIC_DVLOG(3) << this << " " << ProbePhaseToString(probe_bw_.phase) |
| << ": NOT_ADAPTED_INFLIGHT_HIGH_NOT_SET"; |
| return NOT_ADAPTED_INFLIGHT_HIGH_NOT_SET; |
| } |
| |
| // Raise the upper bound for inflight. |
| if (inflight_at_send > model_.inflight_hi()) { |
| QUIC_DVLOG(3) |
| << this << " " << ProbePhaseToString(probe_bw_.phase) |
| << ": Adapting inflight_hi from inflight_at_send. inflight_at_send:" |
| << inflight_at_send << ", old inflight_hi:" << model_.inflight_hi(); |
| model_.set_inflight_hi(inflight_at_send); |
| } |
| |
| return ADAPTED_OK; |
| } |
| |
| bool Bbr3Sender::IsTimeToProbeBandwidth( |
| const Bbr2CongestionEvent& congestion_event) const { |
| if (HasCycleLasted(probe_bw_.probe_wait_time, congestion_event)) { |
| return true; |
| } |
| |
| if (IsTimeToProbeForRenoCoexistence(1.0, congestion_event)) { |
| ++connection_stats_->bbr_num_short_cycles_for_reno_coexistence; |
| return true; |
| } |
| return false; |
| } |
| |
| bool Bbr3Sender::HasCycleLasted( |
| QuicTime::Delta duration, |
| const Bbr2CongestionEvent& congestion_event) const { |
| bool result = |
| (congestion_event.event_time - probe_bw_.cycle_start_time) > duration; |
| QUIC_DVLOG(3) << this << " " << ProbePhaseToString(probe_bw_.phase) |
| << ": HasCycleLasted=" << result << ". elapsed:" |
| << (congestion_event.event_time - probe_bw_.cycle_start_time) |
| << ", duration:" << duration; |
| return result; |
| } |
| |
| bool Bbr3Sender::HasPhaseLasted( |
| QuicTime::Delta duration, |
| const Bbr2CongestionEvent& congestion_event) const { |
| bool result = |
| (congestion_event.event_time - probe_bw_.phase_start_time) > duration; |
| QUIC_DVLOG(3) << this << " " << ProbePhaseToString(probe_bw_.phase) |
| << ": HasPhaseLasted=" << result << ". elapsed:" |
| << (congestion_event.event_time - probe_bw_.phase_start_time) |
| << ", duration:" << duration; |
| return result; |
| } |
| |
| bool Bbr3Sender::IsTimeToProbeForRenoCoexistence( |
| double probe_wait_fraction, |
| const Bbr2CongestionEvent& /*congestion_event*/) const { |
| if (!params_.enable_reno_coexistence) { |
| return false; |
| } |
| |
| uint64_t rounds = params_.probe_bw_probe_max_rounds; |
| if (params_.probe_bw_probe_reno_gain > 0.0) { |
| QuicByteCount target_bytes_inflight = GetTargetBytesInflight(); |
| uint64_t reno_rounds = params_.probe_bw_probe_reno_gain * |
| target_bytes_inflight / kDefaultTCPMSS; |
| rounds = std::min(rounds, reno_rounds); |
| } |
| bool result = probe_bw_.rounds_since_probe >= (rounds * probe_wait_fraction); |
| QUIC_DVLOG(3) << this << " " << ProbePhaseToString(probe_bw_.phase) |
| << ": IsTimeToProbeForRenoCoexistence=" << result |
| << ". rounds_since_probe:" << probe_bw_.rounds_since_probe |
| << ", rounds:" << rounds |
| << ", probe_wait_fraction:" << probe_wait_fraction; |
| return result; |
| } |
| |
| void Bbr3Sender::RaiseInflightHighSlope() { |
| QUICHE_DCHECK_EQ(probe_bw_.phase, ProbePhase::PROBE_UP); |
| uint64_t growth_this_round = 1 << probe_bw_.probe_up_rounds; |
| // The number 30 below means |growth_this_round| is capped at 1G and the lower |
| // bound of |probe_up_bytes| is (practically) 1 mss, at this speed inflight_hi |
| // grows by approximately 1 packet per packet acked. |
| probe_bw_.probe_up_rounds = |
| std::min<uint64_t>(probe_bw_.probe_up_rounds + 1, 30); |
| uint64_t probe_up_bytes = GetCongestionWindow() / growth_this_round; |
| probe_bw_.probe_up_bytes = |
| std::max<QuicByteCount>(probe_up_bytes, kDefaultTCPMSS); |
| QUIC_DVLOG(3) << this << " Rasing inflight_hi slope. probe_up_rounds:" |
| << probe_bw_.probe_up_rounds |
| << ", probe_up_bytes:" << probe_bw_.probe_up_bytes; |
| } |
| |
| void Bbr3Sender::ProbeInflightHighUpward( |
| const Bbr2CongestionEvent& congestion_event) { |
| QUICHE_DCHECK_EQ(probe_bw_.phase, ProbePhase::PROBE_UP); |
| if (params_.probe_up_ignore_inflight_hi) { |
| return; |
| } |
| if (params_.probe_up_simplify_inflight_hi) { |
| // Raise inflight_hi exponentially if it was utilized this round. |
| probe_bw_.probe_up_acked += congestion_event.bytes_acked; |
| if (!congestion_event.end_of_round_trip) { |
| return; |
| } |
| if (!model_.inflight_hi_limited_in_round() || |
| model_.loss_events_in_round() > 0) { |
| probe_bw_.probe_up_acked = 0; |
| return; |
| } |
| } else { |
| if (congestion_event.prior_bytes_in_flight < congestion_event.prior_cwnd) { |
| QUIC_DVLOG(3) << this |
| << " Raising inflight_hi early return: Not cwnd limited."; |
| // Not fully utilizing cwnd, so can't safely grow. |
| return; |
| } |
| |
| if (congestion_event.prior_cwnd < model_.inflight_hi()) { |
| QUIC_DVLOG(3) |
| << this |
| << " Raising inflight_hi early return: inflight_hi not fully used."; |
| // Not fully using inflight_hi, so don't grow it. |
| return; |
| } |
| |
| // Increase inflight_hi by the number of probe_up_bytes within |
| // probe_up_acked. |
| probe_bw_.probe_up_acked += congestion_event.bytes_acked; |
| } |
| |
| if (probe_bw_.probe_up_acked >= probe_bw_.probe_up_bytes) { |
| uint64_t delta = probe_bw_.probe_up_acked / probe_bw_.probe_up_bytes; |
| probe_bw_.probe_up_acked -= delta * probe_bw_.probe_up_bytes; |
| QuicByteCount new_inflight_hi = |
| model_.inflight_hi() + delta * kDefaultTCPMSS; |
| if (new_inflight_hi > model_.inflight_hi()) { |
| QUIC_DVLOG(3) << this << " Raising inflight_hi from " |
| << model_.inflight_hi() << " to " << new_inflight_hi |
| << ". probe_up_bytes:" << probe_bw_.probe_up_bytes |
| << ", delta:" << delta |
| << ", (new)probe_up_acked:" << probe_bw_.probe_up_acked; |
| |
| model_.set_inflight_hi(new_inflight_hi); |
| } else { |
| QUIC_BUG(quic_bug_10463_4) |
| << "Not growing inflight_hi due to wrap around. Old value:" |
| << model_.inflight_hi() << ", new value:" << new_inflight_hi; |
| } |
| } |
| |
| if (congestion_event.end_of_round_trip) { |
| RaiseInflightHighSlope(); |
| } |
| } |
| |
| void Bbr3Sender::UpdateProbeCruise( |
| const Bbr2CongestionEvent& congestion_event) { |
| QUICHE_DCHECK_EQ(probe_bw_.phase, ProbePhase::PROBE_CRUISE); |
| MaybeAdaptUpperBounds(congestion_event); |
| QUICHE_DCHECK(!probe_bw_.is_sample_from_probing); |
| |
| if (IsTimeToProbeBandwidth(congestion_event)) { |
| EnterProbeRefill(/*probe_up_rounds=*/0, congestion_event.event_time); |
| return; |
| } |
| } |
| |
| void Bbr3Sender::UpdateProbeRefill( |
| const Bbr2CongestionEvent& congestion_event) { |
| QUICHE_DCHECK_EQ(probe_bw_.phase, ProbePhase::PROBE_REFILL); |
| MaybeAdaptUpperBounds(congestion_event); |
| QUICHE_DCHECK(!probe_bw_.is_sample_from_probing); |
| |
| if (probe_bw_.rounds_in_phase > 0 && congestion_event.end_of_round_trip) { |
| EnterProbeUp(congestion_event.event_time); |
| return; |
| } |
| } |
| |
| void Bbr3Sender::UpdateProbeUp(const Bbr2CongestionEvent& congestion_event) { |
| QUICHE_DCHECK_EQ(probe_bw_.phase, ProbePhase::PROBE_UP); |
| if (MaybeAdaptUpperBounds(congestion_event) == ADAPTED_PROBED_TOO_HIGH) { |
| EnterProbeDown(/*probed_too_high=*/true, /*stopped_risky_probe=*/false, |
| congestion_event.event_time); |
| return; |
| } |
| |
| ProbeInflightHighUpward(congestion_event); |
| |
| bool is_risky = false; |
| bool is_queuing = false; |
| if (probe_bw_.last_cycle_probed_too_high && |
| congestion_event.prior_bytes_in_flight >= model_.inflight_hi()) { |
| is_risky = true; |
| QUIC_DVLOG(3) << this << " Probe is too risky. last_cycle_probed_too_high:" |
| << probe_bw_.last_cycle_probed_too_high |
| << ", prior_in_flight:" |
| << congestion_event.prior_bytes_in_flight |
| << ", inflight_hi:" << model_.inflight_hi(); |
| } else if (probe_bw_.rounds_in_phase > 0) { |
| if (params_.max_probe_up_queue_rounds > 0) { |
| if (congestion_event.end_of_round_trip) { |
| model_.CheckPersistentQueue(congestion_event, |
| params_.full_bw_threshold); |
| if (model_.rounds_with_queueing() >= |
| params_.max_probe_up_queue_rounds) { |
| is_queuing = true; |
| } |
| } |
| } else { |
| QuicByteCount queuing_threshold_extra_bytes = |
| model_.QueueingThresholdExtraBytes(); |
| if (params_.add_ack_height_to_queueing_threshold) { |
| queuing_threshold_extra_bytes += model_.MaxAckHeight(); |
| } |
| QuicByteCount queuing_threshold = |
| (params_.full_bw_threshold * model_.BDP()) + |
| queuing_threshold_extra_bytes; |
| |
| is_queuing = congestion_event.bytes_in_flight >= queuing_threshold; |
| |
| QUIC_DVLOG(3) << this |
| << " Checking if building up a queue. prior_in_flight:" |
| << congestion_event.prior_bytes_in_flight |
| << ", post_in_flight:" << congestion_event.bytes_in_flight |
| << ", threshold:" << queuing_threshold |
| << ", is_queuing:" << is_queuing |
| << ", max_bw:" << model_.MaxBandwidth() |
| << ", min_rtt:" << model_.MinRtt(); |
| } |
| } |
| |
| if (is_risky || is_queuing) { |
| EnterProbeDown(/*probed_too_high=*/false, /*stopped_risky_probe=*/is_risky, |
| congestion_event.event_time); |
| } |
| } |
| |
| void Bbr3Sender::EnterProbeDown(bool probed_too_high, bool stopped_risky_probe, |
| QuicTime now) { |
| QUIC_DVLOG(2) << this |
| << " Phase change: " << ProbePhaseToString(probe_bw_.phase) |
| << " ==> " |
| << "PROBE_DOWN" << " after " << now - probe_bw_.phase_start_time |
| << ", or " << probe_bw_.rounds_in_phase |
| << " rounds. probed_too_high:" << probed_too_high |
| << ", stopped_risky_probe:" << stopped_risky_probe << " @ " |
| << now; |
| probe_bw_.last_cycle_probed_too_high = probed_too_high; |
| probe_bw_.last_cycle_stopped_risky_probe = stopped_risky_probe; |
| |
| probe_bw_.cycle_start_time = now; |
| probe_bw_.phase = ProbePhase::PROBE_DOWN; |
| probe_bw_.rounds_in_phase = 0; |
| probe_bw_.phase_start_time = now; |
| ++connection_stats_->bbr_num_cycles; |
| if (params_.bw_lo_mode_ != Bbr2Params::QuicBandwidthLoMode::DEFAULT) { |
| model_.clear_bandwidth_lo(); |
| } |
| |
| // Pick probe wait time. |
| probe_bw_.rounds_since_probe = |
| RandomUint64(params_.probe_bw_max_probe_rand_rounds); |
| probe_bw_.probe_wait_time = |
| params_.probe_bw_probe_base_duration + |
| QuicTime::Delta::FromMicroseconds(RandomUint64( |
| params_.probe_bw_probe_max_rand_duration.ToMicroseconds())); |
| |
| probe_bw_.probe_up_bytes = std::numeric_limits<QuicByteCount>::max(); |
| probe_bw_.has_advanced_max_bw = false; |
| model_.RestartRoundEarly(); |
| } |
| |
| void Bbr3Sender::EnterProbeCruise(QuicTime now) { |
| if (probe_bw_.phase == ProbePhase::PROBE_DOWN) { |
| ExitProbeDown(); |
| } |
| QUIC_DVLOG(2) << this |
| << " Phase change: " << ProbePhaseToString(probe_bw_.phase) |
| << " ==> " |
| << "PROBE_CRUISE" << " after " |
| << now - probe_bw_.phase_start_time << ", or " |
| << probe_bw_.rounds_in_phase << " rounds. @ " << now; |
| |
| model_.cap_inflight_lo(model_.inflight_hi()); |
| probe_bw_.phase = ProbePhase::PROBE_CRUISE; |
| probe_bw_.rounds_in_phase = 0; |
| probe_bw_.phase_start_time = now; |
| probe_bw_.is_sample_from_probing = false; |
| } |
| |
| void Bbr3Sender::EnterProbeRefill(uint64_t probe_up_rounds, QuicTime now) { |
| if (probe_bw_.phase == ProbePhase::PROBE_DOWN) { |
| ExitProbeDown(); |
| } |
| QUIC_DVLOG(2) << this |
| << " Phase change: " << ProbePhaseToString(probe_bw_.phase) |
| << " ==> " |
| << "PROBE_REFILL" << " after " |
| << now - probe_bw_.phase_start_time << ", or " |
| << probe_bw_.rounds_in_phase |
| << " rounds. probe_up_rounds:" << probe_up_rounds << " @ " |
| << now; |
| probe_bw_.phase = ProbePhase::PROBE_REFILL; |
| probe_bw_.rounds_in_phase = 0; |
| probe_bw_.phase_start_time = now; |
| probe_bw_.is_sample_from_probing = false; |
| probe_bw_.last_cycle_stopped_risky_probe = false; |
| |
| model_.clear_bandwidth_lo(); |
| model_.clear_inflight_lo(); |
| probe_bw_.probe_up_rounds = probe_up_rounds; |
| probe_bw_.probe_up_acked = 0; |
| model_.RestartRoundEarly(); |
| } |
| |
| void Bbr3Sender::EnterProbeUp(QuicTime now) { |
| QUICHE_DCHECK_EQ(probe_bw_.phase, ProbePhase::PROBE_REFILL); |
| QUIC_DVLOG(2) << this |
| << " Phase change: " << ProbePhaseToString(probe_bw_.phase) |
| << " ==> " |
| << "PROBE_UP" << " after " << now - probe_bw_.phase_start_time |
| << ", or " << probe_bw_.rounds_in_phase << " rounds. @ " |
| << now; |
| probe_bw_.phase = ProbePhase::PROBE_UP; |
| probe_bw_.rounds_in_phase = 0; |
| probe_bw_.phase_start_time = now; |
| probe_bw_.is_sample_from_probing = true; |
| RaiseInflightHighSlope(); |
| |
| model_.RestartRoundEarly(); |
| } |
| |
| void Bbr3Sender::ExitProbeDown() { |
| QUICHE_DCHECK_EQ(probe_bw_.phase, ProbePhase::PROBE_DOWN); |
| if (!probe_bw_.has_advanced_max_bw) { |
| QUIC_DVLOG(2) << this << " Advancing max bw filter at end of cycle."; |
| model_.AdvanceMaxBandwidthFilter(); |
| probe_bw_.has_advanced_max_bw = true; |
| } |
| } |
| |
| void Bbr3Sender::EnterProbeRtt() { |
| model_.set_pacing_gain(1.0); |
| model_.set_cwnd_gain(1.0); |
| probe_rtt_.exit_time = QuicTime::Zero(); |
| } |
| |
| Bbr2Mode Bbr3Sender::OnCongestionEventProbeRtt( |
| const Bbr2CongestionEvent& congestion_event) { |
| if (probe_rtt_.exit_time == QuicTime::Zero()) { |
| if (congestion_event.bytes_in_flight <= InflightTarget() || |
| congestion_event.bytes_in_flight <= GetMinimumCongestionWindow()) { |
| probe_rtt_.exit_time = |
| congestion_event.event_time + params_.probe_rtt_duration; |
| QUIC_DVLOG(2) << this << " PROBE_RTT exit time set to " |
| << probe_rtt_.exit_time |
| << ". bytes_inflight:" << congestion_event.bytes_in_flight |
| << ", inflight_target:" << InflightTarget() |
| << ", min_congestion_window:" |
| << GetMinimumCongestionWindow() << " @ " |
| << congestion_event.event_time; |
| } |
| return Bbr2Mode::PROBE_RTT; |
| } |
| |
| return congestion_event.event_time > probe_rtt_.exit_time |
| ? Bbr2Mode::PROBE_BW |
| : Bbr2Mode::PROBE_RTT; |
| } |
| |
| QuicByteCount Bbr3Sender::InflightTarget() const { |
| return model_.BDP(model_.MaxBandwidth(), |
| params_.probe_rtt_inflight_target_bdp_fraction); |
| } |
| |
| float Bbr3Sender::PacingGainForPhase(ProbePhase phase) const { |
| if (phase == ProbePhase::PROBE_UP) { |
| return params_.probe_bw_probe_up_pacing_gain; |
| } |
| if (phase == ProbePhase::PROBE_DOWN) { |
| return params_.probe_bw_probe_down_pacing_gain; |
| } |
| return params_.probe_bw_default_pacing_gain; |
| } |
| |
| } // namespace quic |
