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limit the pacing duration to the minimum pacing delay

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This commit is contained in:
Marten Seemann 2020-06-16 11:12:42 +07:00
parent 4163c255e8
commit 467e553f2b
2 changed files with 32 additions and 9 deletions
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24
internal/congestion/pacer.go
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@ -18,10 +18,9 @@ type pacer struct {
}
func newPacer(bw uint64) *pacer {
return &pacer{
bandwidth: bw,
budgetAtLastSent: maxBurstSize,
}
p := &pacer{bandwidth: bw}
p.budgetAtLastSent = p.maxBurstSize()
return p
}
func (p *pacer) SentPacket(sendTime time.Time, size protocol.ByteCount) {
@ -43,11 +42,16 @@ func (p *pacer) SetBandwidth(bw uint64) {
func (p *pacer) Budget(now time.Time) protocol.ByteCount {
if p.lastSentTime.IsZero() {
return p.budgetAtLastSent
return p.maxBurstSize()
}
return utils.MinByteCount(
budget := p.budgetAtLastSent + (protocol.ByteCount(p.bandwidth)*protocol.ByteCount(now.Sub(p.lastSentTime).Nanoseconds()))/1e9
return utils.MinByteCount(p.maxBurstSize(), budget)
}
func (p *pacer) maxBurstSize() protocol.ByteCount {
return utils.MaxByteCount(
protocol.ByteCount(uint64((protocol.MinPacingDelay+protocol.TimerGranularity).Nanoseconds())*p.bandwidth)/1e9,
maxBurstSize,
p.budgetAtLastSent+(protocol.ByteCount(p.bandwidth)*protocol.ByteCount(now.Sub(p.lastSentTime).Nanoseconds()))/1e9,
)
}
@ -56,6 +60,8 @@ func (p *pacer) TimeUntilSend() time.Time {
if p.budgetAtLastSent >= maxDatagramSize {
return time.Time{}
}
// TODO: don't allow pacing faster than MinPacingDelay
return p.lastSentTime.Add(time.Duration(math.Ceil(float64(maxDatagramSize-p.budgetAtLastSent)*1e9/float64(p.bandwidth))) * time.Nanosecond)
return p.lastSentTime.Add(utils.MaxDuration(
protocol.MinPacingDelay,
time.Duration(math.Ceil(float64(maxDatagramSize-p.budgetAtLastSent)*1e9/float64(p.bandwidth)))*time.Nanosecond,
))
}

17
internal/congestion/pacer_test.go
View file

@ -3,6 +3,8 @@ package congestion
import (
"time"
"github.com/lucas-clemente/quic-go/internal/protocol"
. "github.com/onsi/ginkgo"
. "github.com/onsi/gomega"
)
@ -22,6 +24,13 @@ var _ = Describe("Pacer", func() {
Expect(p.Budget(t)).To(BeEquivalentTo(maxBurstSize))
})
It("allows a big burst for high pacing rates", func() {
t := time.Now()
p.SetBandwidth(10000 * packetsPerSecond * uint64(maxDatagramSize))
Expect(p.TimeUntilSend()).To(BeZero())
Expect(p.Budget(t)).To(BeNumerically(">", maxBurstSize))
})
It("reduces the budget when sending packets", func() {
t := time.Now()
budget := p.Budget(t)
@ -88,4 +97,12 @@ var _ = Describe("Pacer", func() {
p.SetBandwidth(uint64(maxDatagramSize)) // reduce the bandwidth to 1 packet per second
Expect(p.TimeUntilSend()).To(Equal(t.Add(time.Second)))
})
It("doesn't pace faster than the minimum pacing duration", func() {
t := time.Now()
sendBurst(t)
p.SetBandwidth(1e6 * uint64(maxDatagramSize))
Expect(p.TimeUntilSend()).To(Equal(t.Add(protocol.MinPacingDelay)))
Expect(p.Budget(t.Add(protocol.MinPacingDelay))).To(Equal(protocol.ByteCount(protocol.MinPacingDelay) * maxDatagramSize * 1e6 / 1e9))
})
})