From b9894ab0140548807b44a0b1701df7cfbb00a3a1 Mon Sep 17 00:00:00 2001
From: Raja Subramanian <raja.gobi@tutanota.com>
Date: Thu, 20 Oct 2022 14:31:19 +0530
Subject: [PATCH] Allocate packetMeta up front to reduce number of allocations.
 (#1108)

---
 pkg/sfu/forwarder.go      |  2 +-
 pkg/sfu/sequencer.go      | 40 +++++++++++++++++++++++++--------------
 pkg/sfu/sequencer_test.go |  2 +-
 3 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/pkg/sfu/forwarder.go b/pkg/sfu/forwarder.go
index 5c5d2a396..2118d2594 100644
--- a/pkg/sfu/forwarder.go
+++ b/pkg/sfu/forwarder.go
@@ -102,7 +102,7 @@ type VideoAllocation struct {
 }
 
 func (v VideoAllocation) String() string {
-	return fmt.Sprintf("VideoAllocation{state: %s, change: %s, bw: %d, del: %d, avail: %+v, exmpt: %+v, rates: %+v, target: %s, dist: %d}",
+	return fmt.Sprintf("VideoAllocation{state: %s, change: %s, bw: %d, del: %d, avail: %+v, exempt: %+v, rates: %+v, target: %s, dist: %d}",
 		v.state, v.change, v.bandwidthRequested, v.bandwidthDelta, v.availableLayers, v.exemptedLayers, v.bitrates, v.targetLayers, v.distanceToDesired)
 }
 
diff --git a/pkg/sfu/sequencer.go b/pkg/sfu/sequencer.go
index 52ee2f54f..0fb7693af 100644
--- a/pkg/sfu/sequencer.go
+++ b/pkg/sfu/sequencer.go
@@ -93,23 +93,27 @@ func (p *packetMeta) unpackVP8() *buffer.VP8 {
 // Sequencer stores the packet sequence received by the down track
 type sequencer struct {
 	sync.Mutex
-	init      bool
-	max       int
-	seq       []*packetMeta
-	step      int
-	headSN    uint16
-	startTime int64
-	rtt       uint32
-	logger    logger.Logger
+	init         bool
+	max          int
+	seq          []*packetMeta
+	meta         []packetMeta
+	metaWritePtr int
+	step         int
+	headSN       uint16
+	startTime    int64
+	rtt          uint32
+	logger       logger.Logger
 }
 
 func newSequencer(maxTrack int, maxPadding int, logger logger.Logger) *sequencer {
 	return &sequencer{
-		startTime: time.Now().UnixNano() / 1e6,
-		max:       maxTrack + maxPadding,
-		seq:       make([]*packetMeta, maxTrack+maxPadding),
-		rtt:       defaultRtt,
-		logger:    logger,
+		startTime:    time.Now().UnixNano() / 1e6,
+		max:          maxTrack + maxPadding,
+		seq:          make([]*packetMeta, maxTrack+maxPadding),
+		meta:         make([]packetMeta, maxTrack),
+		metaWritePtr: 0,
+		rtt:          defaultRtt,
+		logger:       logger,
 	}
 }
 
@@ -133,12 +137,20 @@ func (s *sequencer) push(sn, offSn uint16, timeStamp uint32, layer int8) *packet
 		return nil
 	}
 
-	s.seq[slot] = &packetMeta{
+	s.meta[s.metaWritePtr] = packetMeta{
 		sourceSeqNo: sn,
 		targetSeqNo: offSn,
 		timestamp:   timeStamp,
 		layer:       layer,
 	}
+
+	s.seq[slot] = &s.meta[s.metaWritePtr]
+
+	s.metaWritePtr++
+	if s.metaWritePtr >= len(s.meta) {
+		s.metaWritePtr -= len(s.meta)
+	}
+
 	return s.seq[slot]
 }
 
diff --git a/pkg/sfu/sequencer_test.go b/pkg/sfu/sequencer_test.go
index 8a3eb0644..f0fb9a54c 100644
--- a/pkg/sfu/sequencer_test.go
+++ b/pkg/sfu/sequencer_test.go
@@ -84,7 +84,7 @@ func Test_sequencer_getNACKSeqNo(t *testing.T) {
 	for _, tt := range tests {
 		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
-			n := newSequencer(500, 0, logger.GetDefaultLogger())
+			n := newSequencer(5, 10, logger.GetDefaultLogger())
 
 			for _, i := range tt.fields.input {
 				n.push(i, i+tt.fields.offset, 123, 3)