gfe-relnote: In QUIC, use 2 burst tokens in bootstrapping experiment, protected by gfe2_reloadable_flag_quic_conservative_bursts.
Also decrease cwnd gain and pacing gain.
PiperOrigin-RevId: 247919205
Change-Id: Ic3a205e6f0ec8e23d3f17db9f8b252fd9638d08c
diff --git a/quic/core/congestion_control/bbr_sender.cc b/quic/core/congestion_control/bbr_sender.cc
index 004ec91..7d7258f 100644
--- a/quic/core/congestion_control/bbr_sender.cc
+++ b/quic/core/congestion_control/bbr_sender.cc
@@ -355,12 +355,14 @@
if (new_cwnd > congestion_window_) {
QUIC_RELOADABLE_FLAG_COUNT_N(quic_fix_bbr_cwnd_in_bandwidth_resumption, 1,
2);
- // Decrease cwnd gain when cwnd increases.
- set_high_cwnd_gain(kDerivedHighCWNDGain);
} else {
QUIC_RELOADABLE_FLAG_COUNT_N(quic_fix_bbr_cwnd_in_bandwidth_resumption, 2,
2);
}
+ // Decreases cwnd gain and pacing gain. Please note, if pacing_rate_ has
+ // been calculated, it cannot decrease in STARTUP phase.
+ set_high_gain(kDerivedHighCWNDGain);
+ set_high_cwnd_gain(kDerivedHighCWNDGain);
congestion_window_ = std::max(new_cwnd, congestion_window_);
}
}
diff --git a/quic/core/congestion_control/pacing_sender.cc b/quic/core/congestion_control/pacing_sender.cc
index 53d5096..0968935 100644
--- a/quic/core/congestion_control/pacing_sender.cc
+++ b/quic/core/congestion_control/pacing_sender.cc
@@ -122,6 +122,13 @@
pacing_limited_ = false;
}
+void PacingSender::SetBurstTokens(uint32_t burst_tokens) {
+ initial_burst_size_ = burst_tokens;
+ burst_tokens_ = std::min(
+ initial_burst_size_,
+ static_cast<uint32_t>(sender_->GetCongestionWindow() / kDefaultTCPMSS));
+}
+
QuicTime::Delta PacingSender::TimeUntilSend(
QuicTime now,
QuicByteCount bytes_in_flight) const {
diff --git a/quic/core/congestion_control/pacing_sender.h b/quic/core/congestion_control/pacing_sender.h
index 8420c7f..781a921 100644
--- a/quic/core/congestion_control/pacing_sender.h
+++ b/quic/core/congestion_control/pacing_sender.h
@@ -66,6 +66,9 @@
// making up for lost time.
void OnApplicationLimited();
+ // Set burst_tokens_ and initial_burst_size_.
+ void SetBurstTokens(uint32_t burst_tokens);
+
QuicTime::Delta TimeUntilSend(QuicTime now,
QuicByteCount bytes_in_flight) const;
diff --git a/quic/core/quic_sent_packet_manager.cc b/quic/core/quic_sent_packet_manager.cc
index 865cf3f..061ebac 100644
--- a/quic/core/quic_sent_packet_manager.cc
+++ b/quic/core/quic_sent_packet_manager.cc
@@ -66,6 +66,11 @@
transmission_type == RTO_RETRANSMISSION;
}
+// If pacing rate is accurate, > 2 burst token is not likely to help first ACK
+// to arrive earlier, and overly large burst token could cause incast packet
+// losses.
+static const uint32_t kConservativeUnpacedBurst = 2;
+
} // namespace
#define ENDPOINT \
@@ -268,6 +273,10 @@
SetInitialRtt(rtt);
}
const QuicByteCount old_cwnd = send_algorithm_->GetCongestionWindow();
+ if (GetQuicReloadableFlag(quic_conservative_bursts) && using_pacing_) {
+ QUIC_RELOADABLE_FLAG_COUNT(quic_conservative_bursts);
+ pacing_sender_.SetBurstTokens(kConservativeUnpacedBurst);
+ }
send_algorithm_->AdjustNetworkParameters(bandwidth, rtt);
if (debug_delegate_ != nullptr) {
debug_delegate_->OnAdjustNetworkParameters(
