mirror of
https://github.com/woodpecker-ci/woodpecker.git
synced 2024-12-18 08:26:45 +02:00
299 lines
10 KiB
Go
299 lines
10 KiB
Go
|
package congestion
|
||
|
|
||
|
import (
|
||
|
"time"
|
||
|
|
||
|
"github.com/lucas-clemente/quic-go/internal/utils"
|
||
|
"github.com/lucas-clemente/quic-go/protocol"
|
||
|
)
|
||
|
|
||
|
const (
|
||
|
maxBurstBytes = 3 * protocol.DefaultTCPMSS
|
||
|
defaultMinimumCongestionWindow protocol.PacketNumber = 2
|
||
|
renoBeta float32 = 0.7 // Reno backoff factor.
|
||
|
)
|
||
|
|
||
|
type cubicSender struct {
|
||
|
hybridSlowStart HybridSlowStart
|
||
|
prr PrrSender
|
||
|
rttStats *RTTStats
|
||
|
stats connectionStats
|
||
|
cubic *Cubic
|
||
|
|
||
|
reno bool
|
||
|
|
||
|
// Track the largest packet that has been sent.
|
||
|
largestSentPacketNumber protocol.PacketNumber
|
||
|
|
||
|
// Track the largest packet that has been acked.
|
||
|
largestAckedPacketNumber protocol.PacketNumber
|
||
|
|
||
|
// Track the largest packet number outstanding when a CWND cutback occurs.
|
||
|
largestSentAtLastCutback protocol.PacketNumber
|
||
|
|
||
|
// Congestion window in packets.
|
||
|
congestionWindow protocol.PacketNumber
|
||
|
|
||
|
// Slow start congestion window in packets, aka ssthresh.
|
||
|
slowstartThreshold protocol.PacketNumber
|
||
|
|
||
|
// Whether the last loss event caused us to exit slowstart.
|
||
|
// Used for stats collection of slowstartPacketsLost
|
||
|
lastCutbackExitedSlowstart bool
|
||
|
|
||
|
// When true, exit slow start with large cutback of congestion window.
|
||
|
slowStartLargeReduction bool
|
||
|
|
||
|
// Minimum congestion window in packets.
|
||
|
minCongestionWindow protocol.PacketNumber
|
||
|
|
||
|
// Maximum number of outstanding packets for tcp.
|
||
|
maxTCPCongestionWindow protocol.PacketNumber
|
||
|
|
||
|
// Number of connections to simulate.
|
||
|
numConnections int
|
||
|
|
||
|
// ACK counter for the Reno implementation.
|
||
|
congestionWindowCount protocol.ByteCount
|
||
|
|
||
|
initialCongestionWindow protocol.PacketNumber
|
||
|
initialMaxCongestionWindow protocol.PacketNumber
|
||
|
}
|
||
|
|
||
|
// NewCubicSender makes a new cubic sender
|
||
|
func NewCubicSender(clock Clock, rttStats *RTTStats, reno bool, initialCongestionWindow, initialMaxCongestionWindow protocol.PacketNumber) SendAlgorithmWithDebugInfo {
|
||
|
return &cubicSender{
|
||
|
rttStats: rttStats,
|
||
|
initialCongestionWindow: initialCongestionWindow,
|
||
|
initialMaxCongestionWindow: initialMaxCongestionWindow,
|
||
|
congestionWindow: initialCongestionWindow,
|
||
|
minCongestionWindow: defaultMinimumCongestionWindow,
|
||
|
slowstartThreshold: initialMaxCongestionWindow,
|
||
|
maxTCPCongestionWindow: initialMaxCongestionWindow,
|
||
|
numConnections: defaultNumConnections,
|
||
|
cubic: NewCubic(clock),
|
||
|
reno: reno,
|
||
|
}
|
||
|
}
|
||
|
|
||
|
func (c *cubicSender) TimeUntilSend(now time.Time, bytesInFlight protocol.ByteCount) time.Duration {
|
||
|
if c.InRecovery() {
|
||
|
// PRR is used when in recovery.
|
||
|
return c.prr.TimeUntilSend(c.GetCongestionWindow(), bytesInFlight, c.GetSlowStartThreshold())
|
||
|
}
|
||
|
if c.GetCongestionWindow() > bytesInFlight {
|
||
|
return 0
|
||
|
}
|
||
|
return utils.InfDuration
|
||
|
}
|
||
|
|
||
|
func (c *cubicSender) OnPacketSent(sentTime time.Time, bytesInFlight protocol.ByteCount, packetNumber protocol.PacketNumber, bytes protocol.ByteCount, isRetransmittable bool) bool {
|
||
|
// Only update bytesInFlight for data packets.
|
||
|
if !isRetransmittable {
|
||
|
return false
|
||
|
}
|
||
|
if c.InRecovery() {
|
||
|
// PRR is used when in recovery.
|
||
|
c.prr.OnPacketSent(bytes)
|
||
|
}
|
||
|
c.largestSentPacketNumber = packetNumber
|
||
|
c.hybridSlowStart.OnPacketSent(packetNumber)
|
||
|
return true
|
||
|
}
|
||
|
|
||
|
func (c *cubicSender) InRecovery() bool {
|
||
|
return c.largestAckedPacketNumber <= c.largestSentAtLastCutback && c.largestAckedPacketNumber != 0
|
||
|
}
|
||
|
|
||
|
func (c *cubicSender) InSlowStart() bool {
|
||
|
return c.GetCongestionWindow() < c.GetSlowStartThreshold()
|
||
|
}
|
||
|
|
||
|
func (c *cubicSender) GetCongestionWindow() protocol.ByteCount {
|
||
|
return protocol.ByteCount(c.congestionWindow) * protocol.DefaultTCPMSS
|
||
|
}
|
||
|
|
||
|
func (c *cubicSender) GetSlowStartThreshold() protocol.ByteCount {
|
||
|
return protocol.ByteCount(c.slowstartThreshold) * protocol.DefaultTCPMSS
|
||
|
}
|
||
|
|
||
|
func (c *cubicSender) ExitSlowstart() {
|
||
|
c.slowstartThreshold = c.congestionWindow
|
||
|
}
|
||
|
|
||
|
func (c *cubicSender) SlowstartThreshold() protocol.PacketNumber {
|
||
|
return c.slowstartThreshold
|
||
|
}
|
||
|
|
||
|
func (c *cubicSender) MaybeExitSlowStart() {
|
||
|
if c.InSlowStart() && c.hybridSlowStart.ShouldExitSlowStart(c.rttStats.LatestRTT(), c.rttStats.MinRTT(), c.GetCongestionWindow()/protocol.DefaultTCPMSS) {
|
||
|
c.ExitSlowstart()
|
||
|
}
|
||
|
}
|
||
|
|
||
|
func (c *cubicSender) OnPacketAcked(ackedPacketNumber protocol.PacketNumber, ackedBytes protocol.ByteCount, bytesInFlight protocol.ByteCount) {
|
||
|
c.largestAckedPacketNumber = utils.MaxPacketNumber(ackedPacketNumber, c.largestAckedPacketNumber)
|
||
|
if c.InRecovery() {
|
||
|
// PRR is used when in recovery.
|
||
|
c.prr.OnPacketAcked(ackedBytes)
|
||
|
return
|
||
|
}
|
||
|
c.maybeIncreaseCwnd(ackedPacketNumber, ackedBytes, bytesInFlight)
|
||
|
if c.InSlowStart() {
|
||
|
c.hybridSlowStart.OnPacketAcked(ackedPacketNumber)
|
||
|
}
|
||
|
}
|
||
|
|
||
|
func (c *cubicSender) OnPacketLost(packetNumber protocol.PacketNumber, lostBytes protocol.ByteCount, bytesInFlight protocol.ByteCount) {
|
||
|
// TCP NewReno (RFC6582) says that once a loss occurs, any losses in packets
|
||
|
// already sent should be treated as a single loss event, since it's expected.
|
||
|
if packetNumber <= c.largestSentAtLastCutback {
|
||
|
if c.lastCutbackExitedSlowstart {
|
||
|
c.stats.slowstartPacketsLost++
|
||
|
c.stats.slowstartBytesLost += lostBytes
|
||
|
if c.slowStartLargeReduction {
|
||
|
if c.stats.slowstartPacketsLost == 1 || (c.stats.slowstartBytesLost/protocol.DefaultTCPMSS) > (c.stats.slowstartBytesLost-lostBytes)/protocol.DefaultTCPMSS {
|
||
|
// Reduce congestion window by 1 for every mss of bytes lost.
|
||
|
c.congestionWindow = utils.MaxPacketNumber(c.congestionWindow-1, c.minCongestionWindow)
|
||
|
}
|
||
|
c.slowstartThreshold = c.congestionWindow
|
||
|
}
|
||
|
}
|
||
|
return
|
||
|
}
|
||
|
c.lastCutbackExitedSlowstart = c.InSlowStart()
|
||
|
if c.InSlowStart() {
|
||
|
c.stats.slowstartPacketsLost++
|
||
|
}
|
||
|
|
||
|
c.prr.OnPacketLost(bytesInFlight)
|
||
|
|
||
|
// TODO(chromium): Separate out all of slow start into a separate class.
|
||
|
if c.slowStartLargeReduction && c.InSlowStart() {
|
||
|
c.congestionWindow = c.congestionWindow - 1
|
||
|
} else if c.reno {
|
||
|
c.congestionWindow = protocol.PacketNumber(float32(c.congestionWindow) * c.RenoBeta())
|
||
|
} else {
|
||
|
c.congestionWindow = c.cubic.CongestionWindowAfterPacketLoss(c.congestionWindow)
|
||
|
}
|
||
|
// Enforce a minimum congestion window.
|
||
|
if c.congestionWindow < c.minCongestionWindow {
|
||
|
c.congestionWindow = c.minCongestionWindow
|
||
|
}
|
||
|
c.slowstartThreshold = c.congestionWindow
|
||
|
c.largestSentAtLastCutback = c.largestSentPacketNumber
|
||
|
// reset packet count from congestion avoidance mode. We start
|
||
|
// counting again when we're out of recovery.
|
||
|
c.congestionWindowCount = 0
|
||
|
}
|
||
|
|
||
|
func (c *cubicSender) RenoBeta() float32 {
|
||
|
// kNConnectionBeta is the backoff factor after loss for our N-connection
|
||
|
// emulation, which emulates the effective backoff of an ensemble of N
|
||
|
// TCP-Reno connections on a single loss event. The effective multiplier is
|
||
|
// computed as:
|
||
|
return (float32(c.numConnections) - 1. + renoBeta) / float32(c.numConnections)
|
||
|
}
|
||
|
|
||
|
// Called when we receive an ack. Normal TCP tracks how many packets one ack
|
||
|
// represents, but quic has a separate ack for each packet.
|
||
|
func (c *cubicSender) maybeIncreaseCwnd(ackedPacketNumber protocol.PacketNumber, ackedBytes protocol.ByteCount, bytesInFlight protocol.ByteCount) {
|
||
|
// Do not increase the congestion window unless the sender is close to using
|
||
|
// the current window.
|
||
|
if !c.isCwndLimited(bytesInFlight) {
|
||
|
c.cubic.OnApplicationLimited()
|
||
|
return
|
||
|
}
|
||
|
if c.congestionWindow >= c.maxTCPCongestionWindow {
|
||
|
return
|
||
|
}
|
||
|
if c.InSlowStart() {
|
||
|
// TCP slow start, exponential growth, increase by one for each ACK.
|
||
|
c.congestionWindow++
|
||
|
return
|
||
|
}
|
||
|
if c.reno {
|
||
|
// Classic Reno congestion avoidance.
|
||
|
c.congestionWindowCount++
|
||
|
// Divide by num_connections to smoothly increase the CWND at a faster
|
||
|
// rate than conventional Reno.
|
||
|
if protocol.PacketNumber(c.congestionWindowCount*protocol.ByteCount(c.numConnections)) >= c.congestionWindow {
|
||
|
c.congestionWindow++
|
||
|
c.congestionWindowCount = 0
|
||
|
}
|
||
|
} else {
|
||
|
c.congestionWindow = utils.MinPacketNumber(c.maxTCPCongestionWindow, c.cubic.CongestionWindowAfterAck(c.congestionWindow, c.rttStats.MinRTT()))
|
||
|
}
|
||
|
}
|
||
|
|
||
|
func (c *cubicSender) isCwndLimited(bytesInFlight protocol.ByteCount) bool {
|
||
|
congestionWindow := c.GetCongestionWindow()
|
||
|
if bytesInFlight >= congestionWindow {
|
||
|
return true
|
||
|
}
|
||
|
availableBytes := congestionWindow - bytesInFlight
|
||
|
slowStartLimited := c.InSlowStart() && bytesInFlight > congestionWindow/2
|
||
|
return slowStartLimited || availableBytes <= maxBurstBytes
|
||
|
}
|
||
|
|
||
|
// BandwidthEstimate returns the current bandwidth estimate
|
||
|
func (c *cubicSender) BandwidthEstimate() Bandwidth {
|
||
|
srtt := c.rttStats.SmoothedRTT()
|
||
|
if srtt == 0 {
|
||
|
// If we haven't measured an rtt, the bandwidth estimate is unknown.
|
||
|
return 0
|
||
|
}
|
||
|
return BandwidthFromDelta(c.GetCongestionWindow(), srtt)
|
||
|
}
|
||
|
|
||
|
// HybridSlowStart returns the hybrid slow start instance for testing
|
||
|
func (c *cubicSender) HybridSlowStart() *HybridSlowStart {
|
||
|
return &c.hybridSlowStart
|
||
|
}
|
||
|
|
||
|
// SetNumEmulatedConnections sets the number of emulated connections
|
||
|
func (c *cubicSender) SetNumEmulatedConnections(n int) {
|
||
|
c.numConnections = utils.Max(n, 1)
|
||
|
c.cubic.SetNumConnections(c.numConnections)
|
||
|
}
|
||
|
|
||
|
// OnRetransmissionTimeout is called on an retransmission timeout
|
||
|
func (c *cubicSender) OnRetransmissionTimeout(packetsRetransmitted bool) {
|
||
|
c.largestSentAtLastCutback = 0
|
||
|
if !packetsRetransmitted {
|
||
|
return
|
||
|
}
|
||
|
c.hybridSlowStart.Restart()
|
||
|
c.cubic.Reset()
|
||
|
c.slowstartThreshold = c.congestionWindow / 2
|
||
|
c.congestionWindow = c.minCongestionWindow
|
||
|
}
|
||
|
|
||
|
// OnConnectionMigration is called when the connection is migrated (?)
|
||
|
func (c *cubicSender) OnConnectionMigration() {
|
||
|
c.hybridSlowStart.Restart()
|
||
|
c.prr = PrrSender{}
|
||
|
c.largestSentPacketNumber = 0
|
||
|
c.largestAckedPacketNumber = 0
|
||
|
c.largestSentAtLastCutback = 0
|
||
|
c.lastCutbackExitedSlowstart = false
|
||
|
c.cubic.Reset()
|
||
|
c.congestionWindowCount = 0
|
||
|
c.congestionWindow = c.initialCongestionWindow
|
||
|
c.slowstartThreshold = c.initialMaxCongestionWindow
|
||
|
c.maxTCPCongestionWindow = c.initialMaxCongestionWindow
|
||
|
}
|
||
|
|
||
|
// SetSlowStartLargeReduction allows enabling the SSLR experiment
|
||
|
func (c *cubicSender) SetSlowStartLargeReduction(enabled bool) {
|
||
|
c.slowStartLargeReduction = enabled
|
||
|
}
|
||
|
|
||
|
// RetransmissionDelay gives the time to retransmission
|
||
|
func (c *cubicSender) RetransmissionDelay() time.Duration {
|
||
|
if c.rttStats.SmoothedRTT() == 0 {
|
||
|
return 0
|
||
|
}
|
||
|
return c.rttStats.SmoothedRTT() + c.rttStats.MeanDeviation()*4
|
||
|
}
|