From 246c2ce89c556bf47cb5e17ecd81d9e109246e99 Mon Sep 17 00:00:00 2001
From: Toby <tobyxdd@gmail.com>
Date: Fri, 10 Apr 2020 13:57:28 -0700
Subject: [PATCH] Throughput optimizations

---
 go.mod                   |  2 +-
 go.sum                   |  4 ++--
 pkg/congestion/brutal.go | 44 +++++++++++++++++++++++++++++++++++++++-
 3 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/go.mod b/go.mod
index ca0d4ef..da9de56 100644
--- a/go.mod
+++ b/go.mod
@@ -6,4 +6,4 @@ require github.com/golang/protobuf v1.3.1
 
 require github.com/lucas-clemente/quic-go v0.15.2
 
-replace github.com/lucas-clemente/quic-go => github.com/tobyxdd/quic-go v0.1.1-tquic-1
+replace github.com/lucas-clemente/quic-go => github.com/tobyxdd/quic-go v0.1.2-tquic-1
diff --git a/go.sum b/go.sum
index 9a5c0c4..69ed689 100644
--- a/go.sum
+++ b/go.sum
@@ -115,8 +115,8 @@ github.com/sourcegraph/syntaxhighlight v0.0.0-20170531221838-bd320f5d308e/go.mod
 github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/tarm/serial v0.0.0-20180830185346-98f6abe2eb07/go.mod h1:kDXzergiv9cbyO7IOYJZWg1U88JhDg3PB6klq9Hg2pA=
-github.com/tobyxdd/quic-go v0.1.1-tquic-1 h1:KDhDFNe+IlI+ZOvEG6wA5JcNq8OUO029OYi8bq7XnSU=
-github.com/tobyxdd/quic-go v0.1.1-tquic-1/go.mod h1:qxmO5Y4ZMhdNkunGfxuZnZXnJwYpW9vjQkyrZ7BsgUI=
+github.com/tobyxdd/quic-go v0.1.2-tquic-1 h1:PPbkQyNNlI2ZXFWDspBGvOTXAWTX/y82mVy+kDzKtgY=
+github.com/tobyxdd/quic-go v0.1.2-tquic-1/go.mod h1:qxmO5Y4ZMhdNkunGfxuZnZXnJwYpW9vjQkyrZ7BsgUI=
 github.com/viant/assertly v0.4.8/go.mod h1:aGifi++jvCrUaklKEKT0BU95igDNaqkvz+49uaYMPRU=
 github.com/viant/toolbox v0.24.0/go.mod h1:OxMCG57V0PXuIP2HNQrtJf2CjqdmbrOx5EkMILuUhzM=
 go.opencensus.io v0.18.0/go.mod h1:vKdFvxhtzZ9onBp9VKHK8z/sRpBMnKAsufL7wlDrCOA=
diff --git a/pkg/congestion/brutal.go b/pkg/congestion/brutal.go
index ae22e35..491bdd8 100644
--- a/pkg/congestion/brutal.go
+++ b/pkg/congestion/brutal.go
@@ -5,11 +5,22 @@ import (
 	"time"
 )
 
+const (
+	ackRateMinSampleInterval = 4 * time.Second
+	ackRateMaxSampleInterval = 20 * time.Second
+	ackRateMinACKSampleCount = 200
+)
+
 // BrutalSender sends packets at a constant rate and does not react to any changes in the network environment,
 // hence the name.
 type BrutalSender struct {
 	rttStats *congestion.RTTStats
 	bps      congestion.ByteCount
+
+	ackCount, lossCount  uint64
+	ackRate              float64
+	ackRateNextUpdateMin time.Time
+	ackRateNextUpdateMax time.Time
 }
 
 func NewBrutalSender(bps congestion.ByteCount) *BrutalSender {
@@ -27,7 +38,13 @@ func (b *BrutalSender) TimeUntilSend(bytesInFlight congestion.ByteCount) time.Du
 }
 
 func (b *BrutalSender) CanSend(bytesInFlight congestion.ByteCount) bool {
-	return bytesInFlight < b.GetCongestionWindow()
+	if b.ackRate == 0 {
+		return bytesInFlight < b.GetCongestionWindow()
+	} else if b.ackRate > 0.5 {
+		return bytesInFlight < congestion.ByteCount(float64(b.GetCongestionWindow())/b.ackRate)
+	} else {
+		return bytesInFlight < b.GetCongestionWindow()*2
+	}
 }
 
 func (b *BrutalSender) GetCongestionWindow() congestion.ByteCount {
@@ -44,10 +61,35 @@ func (b *BrutalSender) OnPacketSent(sentTime time.Time, bytesInFlight congestion
 
 func (b *BrutalSender) OnPacketAcked(number congestion.PacketNumber, ackedBytes congestion.ByteCount,
 	priorInFlight congestion.ByteCount, eventTime time.Time) {
+	b.ackCount += 1
+	b.maybeUpdateACKRate()
 }
 
 func (b *BrutalSender) OnPacketLost(number congestion.PacketNumber, lostBytes congestion.ByteCount,
 	priorInFlight congestion.ByteCount) {
+	b.lossCount += 1
+	b.maybeUpdateACKRate()
+}
+
+func (b *BrutalSender) maybeUpdateACKRate() {
+	now := time.Now()
+	if !now.After(b.ackRateNextUpdateMin) {
+		return
+	}
+	// Min interval reached
+	if b.ackCount >= ackRateMinACKSampleCount {
+		b.ackRate = float64(b.ackCount) / float64(b.ackCount+b.lossCount)
+		b.ackCount, b.lossCount = 0, 0
+		b.ackRateNextUpdateMin = now.Add(ackRateMinSampleInterval)
+		b.ackRateNextUpdateMax = now.Add(ackRateMaxSampleInterval)
+	} else {
+		if now.After(b.ackRateNextUpdateMax) {
+			// Max interval reached, still not enough samples, reset
+			b.ackCount, b.lossCount = 0, 0
+			b.ackRateNextUpdateMin = now.Add(ackRateMinSampleInterval)
+			b.ackRateNextUpdateMax = now.Add(ackRateMaxSampleInterval)
+		}
+	}
 }
 
 func (b *BrutalSender) InSlowStart() bool {