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remove ACK decimation

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The benefits of this are unclear when using Reno / Cubic.
This commit is contained in:
Marten Seemann
2020-06-11 18:49:01 +07:00
parent a854a4ace9
commit 260356140f
4 changed files with 94 additions and 143 deletions
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57
internal/ackhandler/received_packet_tracker.go
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@@ -8,6 +8,9 @@ import (
"github.com/lucas-clemente/quic-go/internal/wire"
)
// number of ack-eliciting packets received before sending an ack.
const packetsBeforeAck = 2
type receivedPacketTracker struct {
largestObserved protocol.PacketNumber
ignoreBelow protocol.PacketNumber
@@ -61,7 +64,7 @@ func (h *receivedPacketTracker) ReceivedPacket(packetNumber protocol.PacketNumbe
h.maybeQueueAck(packetNumber, rcvTime, shouldInstigateAck, isMissing)
}
// IgnoreBelow sets a lower limit for acking packets.
// IgnoreBelow sets a lower limit for acknowledging packets.
// Packets with packet numbers smaller than p will not be acked.
func (h *receivedPacketTracker) IgnoreBelow(p protocol.PacketNumber) {
if p <= h.ignoreBelow {
@@ -87,12 +90,10 @@ func (h *receivedPacketTracker) hasNewMissingPackets() bool {
return false
}
highestRange := h.packetHistory.GetHighestAckRange()
return highestRange.Smallest >= h.lastAck.LargestAcked() && highestRange.Len() <= maxPacketsAfterNewMissing
return highestRange.Smallest > h.lastAck.LargestAcked()+1 && highestRange.Len() == 1
}
// maybeQueueAck queues an ACK, if necessary.
// It is implemented analogously to Chrome's QuicConnection::MaybeQueueAck()
// in ACK_DECIMATION_WITH_REORDERING mode.
func (h *receivedPacketTracker) maybeQueueAck(packetNumber protocol.PacketNumber, rcvTime time.Time, shouldInstigateAck, wasMissing bool) {
// always ack the first packet
if h.lastAck == nil {
@@ -116,46 +117,22 @@ func (h *receivedPacketTracker) maybeQueueAck(packetNumber protocol.PacketNumber
if !h.ackQueued && shouldInstigateAck {
h.ackElicitingPacketsReceivedSinceLastAck++
if packetNumber > minReceivedBeforeAckDecimation {
// ack up to 10 packets at once
if h.ackElicitingPacketsReceivedSinceLastAck >= ackElicitingPacketsBeforeAck {
h.ackQueued = true
if h.logger.Debug() {
h.logger.Debugf("\tQueueing ACK because packet %d packets were received after the last ACK (using threshold: %d).", h.ackElicitingPacketsReceivedSinceLastAck, ackElicitingPacketsBeforeAck)
}
} else if h.ackAlarm.IsZero() {
// wait for the minimum of the ack decimation delay or the delayed ack time before sending an ack
ackDelay := utils.MinDuration(h.maxAckDelay, time.Duration(float64(h.rttStats.MinRTT())*float64(ackDecimationDelay)))
h.ackAlarm = rcvTime.Add(ackDelay)
if h.logger.Debug() {
h.logger.Debugf("\tSetting ACK timer to min(1/4 min-RTT, max ack delay): %s (%s from now)", ackDelay, time.Until(h.ackAlarm))
}
// send an ACK every 2 ack-eliciting packets
if h.ackElicitingPacketsReceivedSinceLastAck >= packetsBeforeAck {
if h.logger.Debug() {
h.logger.Debugf("\tQueueing ACK because packet %d packets were received after the last ACK (using initial threshold: %d).", h.ackElicitingPacketsReceivedSinceLastAck, packetsBeforeAck)
}
} else {
// send an ACK every 2 ack-eliciting packets
if h.ackElicitingPacketsReceivedSinceLastAck >= initialAckElicitingPacketsBeforeAck {
if h.logger.Debug() {
h.logger.Debugf("\tQueueing ACK because packet %d packets were received after the last ACK (using initial threshold: %d).", h.ackElicitingPacketsReceivedSinceLastAck, initialAckElicitingPacketsBeforeAck)
}
h.ackQueued = true
} else if h.ackAlarm.IsZero() {
if h.logger.Debug() {
h.logger.Debugf("\tSetting ACK timer to max ack delay: %s", h.maxAckDelay)
}
h.ackAlarm = rcvTime.Add(h.maxAckDelay)
h.ackQueued = true
} else if h.ackAlarm.IsZero() {
if h.logger.Debug() {
h.logger.Debugf("\tSetting ACK timer to max ack delay: %s", h.maxAckDelay)
}
h.ackAlarm = rcvTime.Add(h.maxAckDelay)
}
// If there are new missing packets to report, set a short timer to send an ACK.
// Queue an ACK if there are new missing packets to report.
if h.hasNewMissingPackets() {
// wait the minimum of 1/8 min RTT and the existing ack time
ackDelay := time.Duration(float64(h.rttStats.MinRTT()) * float64(shortAckDecimationDelay))
ackTime := rcvTime.Add(ackDelay)
if h.ackAlarm.IsZero() || h.ackAlarm.After(ackTime) {
h.ackAlarm = ackTime
if h.logger.Debug() {
h.logger.Debugf("\tSetting ACK timer to 1/8 min-RTT: %s (%s from now)", ackDelay, time.Until(h.ackAlarm))
}
}
h.ackQueued = true
}
}