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westworld.go
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westworld.go
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package dilithium
import (
"github.com/sirupsen/logrus"
"sync"
"time"
)
// WestworldAlgorithm implements the latest iteration of "westworld"-style flow control.
//
type WestworldAlgorithm struct {
capacity int
txPortalSize int
rxPortalSize int
successCount int
successAccumulator int
dupAckCount int
retxCount int
lastRttProbe time.Time
rttAvg []uint16
retxMs int
ii InstrumentInstance
wpf *WestworldProfile
pf *TxProfile
lock *sync.Mutex
ready *sync.Cond
}
func NewWestworldAlgorithm(pf *WestworldProfile, ii InstrumentInstance) TxAlgorithm {
wa := &WestworldAlgorithm{
capacity: pf.StartSize,
txPortalSize: 0,
rxPortalSize: 0,
successCount: 0,
successAccumulator: 0,
dupAckCount: 0,
retxCount: 0,
lastRttProbe: time.Time{},
retxMs: pf.RetxStartMs,
wpf: pf,
pf: pf.Txpf,
ii: ii,
}
wa.ii.TxPortalCapacityChanged(wa.capacity)
wa.ii.NewRetxMs(wa.retxMs)
return wa
}
func (wa *WestworldAlgorithm) SetLock(lock *sync.Mutex) {
wa.lock = lock
wa.ready = sync.NewCond(wa.lock)
go wa.debug()
}
func (wa *WestworldAlgorithm) Tx(segmentSize int) {
for !wa.availableCapacity(segmentSize) {
wa.ready.Wait()
}
wa.txPortalSize += segmentSize
wa.ii.TxPortalSzChanged(wa.txPortalSize)
}
func (wa *WestworldAlgorithm) Success(segmentSize int) {
wa.txPortalSize -= segmentSize
wa.successCount++
wa.successAccumulator += segmentSize
if wa.successCount == wa.wpf.SuccessThresh {
wa.updateCapacity(wa.capacity + int(float64(wa.successAccumulator)*wa.wpf.SuccessScale))
wa.successCount = 0
wa.successAccumulator = 0
}
wa.ready.Broadcast()
wa.ii.TxPortalSzChanged(wa.txPortalSize)
}
func (wa *WestworldAlgorithm) DuplicateAck() {
wa.dupAckCount++
wa.successCount = 0
if wa.dupAckCount >= wa.wpf.DupAckThresh {
wa.updateCapacity(int(float64(wa.capacity) * wa.wpf.DupAckCapacityScale))
wa.dupAckCount = 0
wa.successAccumulator = int(float64(wa.successAccumulator) * wa.wpf.DupAckSuccessScale)
}
}
func (wa *WestworldAlgorithm) Retransmission(_ int) {
wa.retxCount++
wa.successCount = 0
if wa.retxCount >= wa.wpf.RetxThresh {
wa.updateCapacity(int(float64(wa.capacity) * wa.wpf.RetxCapacityScale))
wa.retxCount = 0
wa.successAccumulator = int(float64(wa.successAccumulator) * wa.wpf.RetxSuccessScale)
}
}
func (wa *WestworldAlgorithm) ProbeRTT() bool {
if time.Since(wa.lastRttProbe).Milliseconds() >= int64(wa.wpf.RttProbeMs) {
wa.lastRttProbe = time.Now()
return true
}
return false
}
func (wa *WestworldAlgorithm) UpdateRTT(rttMs int) {
wa.rttAvg = append(wa.rttAvg, uint16(rttMs))
if len(wa.rttAvg) > wa.wpf.RttProbeAvg {
wa.rttAvg = wa.rttAvg[1:]
}
if len(wa.rttAvg) == wa.wpf.RttProbeAvg {
accum := 0
for _, rttMs := range wa.rttAvg {
accum += int(rttMs)
}
accum /= len(wa.rttAvg)
wa.retxMs = accum + wa.wpf.RetxAddMs
wa.ii.NewRetxMs(wa.retxMs)
}
}
func (wa *WestworldAlgorithm) RetxMs() int {
// TODO: This needs to consider RTT. This is just hard-coded for the sake of plumbing development.
return wa.retxMs
}
func (wa *WestworldAlgorithm) RxPortalSize() int {
return wa.rxPortalSize
}
func (wa *WestworldAlgorithm) UpdateRxPortalSize(rxPortalSize int) {
wa.rxPortalSize = rxPortalSize
wa.ii.TxPortalRxSzChanged(rxPortalSize)
wa.ready.Broadcast()
}
func (wa *WestworldAlgorithm) RxPortalPacing(oldSize, newSize int) bool {
sendKeepalive := oldSize > 4*1024 && newSize < oldSize/2
return sendKeepalive
}
func (wa *WestworldAlgorithm) Profile() *TxProfile {
return wa.pf
}
func (wa *WestworldAlgorithm) availableCapacity(segmentSize int) bool {
txPortalCapacity := wa.capacity - int(float64(wa.rxPortalSize)*wa.wpf.RxSizePressureScale) - (wa.txPortalSize + segmentSize)
return txPortalCapacity > 0
}
func (wa *WestworldAlgorithm) updateCapacity(capacity int) {
wa.capacity = capacity
if wa.capacity < wa.wpf.MinSize {
wa.capacity = wa.wpf.MinSize
}
if wa.capacity > wa.wpf.MaxSize {
wa.capacity = wa.wpf.MaxSize
}
wa.ii.TxPortalCapacityChanged(wa.capacity)
}
func (wa *WestworldAlgorithm) debug() {
logrus.Info("started")
defer logrus.Info("exited")
for {
time.Sleep(1 * time.Second)
wa.lock.Lock()
logrus.Infof("WestworldAlgorithm = {\n\tcapacity: %d\n\ttxPortalSize: %d\n\trxPortalSize: %d\n}", wa.capacity, wa.txPortalSize, wa.rxPortalSize)
wa.lock.Unlock()
}
}
type WestworldProfile struct {
StartSize int
MinSize int
MaxSize int
SuccessThresh int
SuccessScale float64
DupAckThresh int
DupAckCapacityScale float64
DupAckSuccessScale float64
RetxStartMs int
RetxAddMs int
RetxThresh int
RetxCapacityScale float64
RetxSuccessScale float64
RxSizePressureScale float64
RttProbeMs int
RttProbeAvg int
Txpf *TxProfile
}
func NewBaselineWestworldProfile() *WestworldProfile {
return &WestworldProfile{
StartSize: 96 * 1024,
MinSize: 16 * 1024,
MaxSize: 4 * 1024 * 1024,
SuccessThresh: 16,
SuccessScale: 1.0,
DupAckThresh: 64,
DupAckCapacityScale: 0.9,
DupAckSuccessScale: 0.75,
RetxStartMs: 200,
RetxAddMs: 50,
RetxThresh: 24,
RetxCapacityScale: 0.75,
RetxSuccessScale: 0.825,
RxSizePressureScale: 2.8911,
RttProbeMs: 50,
RttProbeAvg: 8,
Txpf: DefaultTxProfile(),
}
}
func (wp *WestworldProfile) Create(ii InstrumentInstance) (TxAlgorithm, error) {
return NewWestworldAlgorithm(wp, ii), nil
}