Merge 3051f013f2 into 7b3c9e94e6

transport/tuic/congestion_v2/bbr_sender.go

@@ -62,7 +62,7 @@ const (
 	// Flag.
 	defaultStartupFullLossCount  = 8
 	quicBbr2DefaultLossThreshold = 0.02
-	maxBbrBurstPackets           = 10
+	maxBbrBurstPackets           = 3
 )
 
 type bbrMode int
@@ -334,8 +334,6 @@ func (b *bbrSender) OnPacketSent(
 	}
 
 	b.sampler.OnPacketSent(sentTime, packetNumber, bytes, bytesInFlight, isRetransmittable)
-
-	b.maybeAppLimited(bytesInFlight)
 }
 
 // CanSend implements the SendAlgorithm interface.
@@ -415,6 +413,8 @@ func (b *bbrSender) OnCongestionEventEx(priorInFlight congestion.ByteCount, even
 	// packet in lost_packets.
 	var lastPacketSendState sendTimeState
 
+	b.maybeApplimited(priorInFlight)
+
 	// Update bytesInFlight
 	b.bytesInFlight = priorInFlight
 	for _, p := range ackedPackets {
@@ -541,7 +541,7 @@ func (b *bbrSender) setDrainGain(drainGain float64) {
 	b.drainGain = drainGain
 }
 
-// Get the current bandwidth estimate. Note that Bandwidth is in bits per second.
+// What's the current estimated bandwidth in bytes per second.
 func (b *bbrSender) bandwidthEstimate() Bandwidth {
 	return b.maxBandwidth.GetBest()
 }
@@ -700,13 +700,14 @@ func (b *bbrSender) checkIfFullBandwidthReached(lastPacketSendState *sendTimeSta
 	}
 }
 
-func (b *bbrSender) maybeAppLimited(bytesInFlight congestion.ByteCount) {
+func (b *bbrSender) maybeApplimited(bytesInFlight congestion.ByteCount) {
 	congestionWindow := b.GetCongestionWindow()
 	if bytesInFlight >= congestionWindow {
 		return
 	}
 	availableBytes := congestionWindow - bytesInFlight
-	if availableBytes > maxBbrBurstPackets*b.maxDatagramSize {
+	drainLimited := b.mode == bbrModeDrain && bytesInFlight > congestionWindow/2
+	if !drainLimited || availableBytes > maxBbrBurstPackets*b.maxDatagramSize {
 		b.sampler.OnAppLimited()
 	}
 }