fw: remove heap allocations in incoming interest pipeline

fw/core/logger.go

@@ -137,3 +137,11 @@ func LogTrace(module interface{}, components ...interface{}) {
 		log.Debug(generateLogMessage(module, components...))
 	}
 }
+
+func HasTraceLogs() bool {
+	return shouldPrintTraceLogs
+}
+
+func HasDebugLogs() bool {
+	return logLevel <= log.DebugLevel
+}

fw/fw/bestroute.go

@@ -8,7 +8,6 @@
 package fw
 
 import (
-	"sort"
 	"time"
 
 	"github.com/named-data/ndnd/fw/core"
@@ -63,10 +62,13 @@ func (s *BestRoute) AfterReceiveInterest(
 	packet *defn.Pkt,
 	pitEntry table.PitEntry,
 	inFace uint64,
-	nexthops []*table.FibNextHopEntry,
+	nexthops [MaxNextHops]*table.FibNextHopEntry,
+	nexthopsCount int,
 ) {
-	if len(nexthops) == 0 {
-		core.LogDebug(s, "AfterReceiveInterest: No nexthop for Interest=", packet.Name, " - DROP")
+	if nexthopsCount == 0 {
+		if core.HasDebugLogs() {
+			core.LogDebug(s, "AfterReceiveInterest: No nexthop for Interest=", packet.Name, " - DROP")
+		}
 		return
 	}
 
@@ -75,21 +77,48 @@ func (s *BestRoute) AfterReceiveInterest(
 	for _, outRecord := range pitEntry.OutRecords() {
 		if outRecord.LatestNonce != *packet.L3.Interest.Nonce() &&
 			outRecord.LatestTimestamp.Add(BestRouteSuppressionTime).After(time.Now()) {
-			core.LogDebug(s, "AfterReceiveInterest: Suppressed Interest=", packet.Name, " - DROP")
+			if core.HasDebugLogs() {
+				core.LogDebug(s, "AfterReceiveInterest: Suppressed Interest=", packet.Name, " - DROP")
+			}
 			return
 		}
 	}
 
 	// Sort nexthops by cost and send to best-possible nexthop
-	sort.Slice(nexthops, func(i, j int) bool { return nexthops[i].Cost < nexthops[j].Cost })
-	for _, nh := range nexthops {
-		core.LogTrace(s, "AfterReceiveInterest: Forwarding Interest=", packet.Name, " to FaceID=", nh.Nexthop)
+	lowesthops := nexthops
+	getLowest := func() *table.FibNextHopEntry {
+		cost := uint64(1 << 63)
+		index := -1
+		for i := 0; i < nexthopsCount; i++ {
+			nh := nexthops[i]
+			if nh == nil {
+				continue
+			}
+			if nh.Cost < cost {
+				cost = nh.Cost
+				index = i
+			}
+		}
+		if index == -1 {
+			return nil
+		}
+		hop := nexthops[index]
+		lowesthops[index] = nil
+		return hop
+	}
+
+	for nh := getLowest(); nh != nil; nh = getLowest() {
+		if core.HasTraceLogs() {
+			core.LogTrace(s, "AfterReceiveInterest: Forwarding Interest=", packet.Name, " to FaceID=", nh.Nexthop)
+		}
 		if sent := s.SendInterest(packet, pitEntry, nh.Nexthop, inFace); sent {
 			return
 		}
 	}
 
-	core.LogDebug(s, "AfterReceiveInterest: No usable nexthop for Interest=", packet.Name, " - DROP")
+	if core.HasDebugLogs() {
+		core.LogDebug(s, "AfterReceiveInterest: No usable nexthop for Interest=", packet.Name, " - DROP")
+	}
 }
 
 func (s *BestRoute) BeforeSatisfyInterest(pitEntry table.PitEntry, inFace uint64) {

fw/fw/multicast.go

@@ -61,10 +61,13 @@ func (s *Multicast) AfterReceiveInterest(
 	packet *defn.Pkt,
 	pitEntry table.PitEntry,
 	inFace uint64,
-	nexthops []*table.FibNextHopEntry,
+	nexthops [MaxNextHops]*table.FibNextHopEntry,
+	nexthopsCount int,
 ) {
-	if len(nexthops) == 0 {
-		core.LogDebug(s, "AfterReceiveInterest: No nexthop for Interest=", packet.Name, " - DROP")
+	if nexthopsCount == 0 {
+		if core.HasDebugLogs() {
+			core.LogDebug(s, "AfterReceiveInterest: No nexthop for Interest=", packet.Name, " - DROP")
+		}
 		return
 	}
 
@@ -73,14 +76,22 @@ func (s *Multicast) AfterReceiveInterest(
 	for _, outRecord := range pitEntry.OutRecords() {
 		if outRecord.LatestNonce != *packet.L3.Interest.Nonce() &&
 			outRecord.LatestTimestamp.Add(MulticastSuppressionTime).After(time.Now()) {
-			core.LogDebug(s, "AfterReceiveInterest: Suppressed Interest=", packet.Name, " - DROP")
+			if core.HasDebugLogs() {
+				core.LogDebug(s, "AfterReceiveInterest: Suppressed Interest=", packet.Name, " - DROP")
+			}
 			return
 		}
 	}
 
 	// Send interest to all nexthops
-	for _, nexthop := range nexthops {
-		core.LogTrace(s, "AfterReceiveInterest: Forwarding Interest=", packet.Name, " to FaceID=", nexthop.Nexthop)
+	for i := 0; i < nexthopsCount; i++ {
+		nexthop := nexthops[i]
+		if nexthop == nil {
+			continue
+		}
+		if core.HasTraceLogs() {
+			core.LogTrace(s, "AfterReceiveInterest: Forwarding Interest=", packet.Name, " to FaceID=", nexthop.Nexthop)
+		}
 		s.SendInterest(packet, pitEntry, nexthop.Nexthop, inFace)
 	}
 }

fw/fw/strategy.go

@@ -18,6 +18,9 @@ import (
 // StrategyPrefix is the prefix of all strategy names for YaNFD
 const StrategyPrefix = "/localhost/nfd/strategy"
 
+// Maximum number of possible next hops (i.e. router links) for optimization
+const MaxNextHops = 64
+
 // Strategy represents a forwarding strategy.
 type Strategy interface {
 	Instantiate(fwThread *Thread)
@@ -36,7 +39,9 @@ type Strategy interface {
 		packet *defn.Pkt,
 		pitEntry table.PitEntry,
 		inFace uint64,
-		nexthops []*table.FibNextHopEntry)
+		nexthops [MaxNextHops]*table.FibNextHopEntry,
+		nexthopsCount int,
+	)
 	BeforeSatisfyInterest(
 		pitEntry table.PitEntry,
 		inFace uint64)

fw/fw/thread.go

@@ -188,7 +188,9 @@ func (t *Thread) processIncomingInterest(packet *defn.Pkt) {
 	}
 
 	// Log PIT token (if any)
-	core.LogTrace(t, "OnIncomingInterest: ", packet.Name, ", FaceID=", incomingFace.FaceID(), ", PitTokenL=", len(packet.PitToken))
+	if core.HasTraceLogs() {
+		core.LogTrace(t, "OnIncomingInterest: ", packet.Name, ", FaceID=", incomingFace.FaceID(), ", PitTokenL=", len(packet.PitToken))
+	}
 
 	// Check if violates /localhost
 	if incomingFace.Scope() == defn.NonLocal &&
@@ -223,13 +225,17 @@ func (t *Thread) processIncomingInterest(packet *defn.Pkt) {
 
 	// Drop packet if no nonce is found
 	if interest.Nonce() == nil {
-		core.LogDebug(t, "Interest ", packet.Name, " is missing Nonce - DROP")
+		if core.HasDebugLogs() {
+			core.LogDebug(t, "Interest ", packet.Name, " is missing Nonce - DROP")
+		}
 		return
 	}
 
 	// Check if packet is in dead nonce list
 	if exists := t.deadNonceList.Find(interest.Name(), *interest.Nonce()); exists {
-		core.LogDebug(t, "Interest ", packet.Name, " is dropped by DeadNonce: ", *interest.Nonce())
+		if core.HasDebugLogs() {
+			core.LogDebug(t, "Interest ", packet.Name, " is dropped by DeadNonce: ", *interest.Nonce())
+		}
 		return
 	}
 
@@ -238,7 +244,9 @@ func (t *Thread) processIncomingInterest(packet *defn.Pkt) {
 	pitEntry, isDuplicate := t.pitCS.InsertInterest(interest, fhName, incomingFace.FaceID())
 	if isDuplicate {
 		// Interest loop - since we don't use Nacks, just drop
-		core.LogDebug(t, "Interest ", packet.Name, " is looping - DROP")
+		if core.HasDebugLogs() {
+			core.LogDebug(t, "Interest ", packet.Name, " is looping - DROP")
+		}
 		return
 	}
 
@@ -278,7 +286,9 @@ func (t *Thread) processIncomingInterest(packet *defn.Pkt) {
 			}
 		}
 	} else {
-		core.LogTrace(t, "Interest ", packet.Name, " is already pending")
+		if core.HasTraceLogs() {
+			core.LogTrace(t, "Interest ", packet.Name, " is already pending")
+		}
 
 		// Add the previous nonce to the dead nonce list to prevent further looping
 		// TODO: review this design, not specified in NFD dev guide
@@ -291,7 +301,10 @@ func (t *Thread) processIncomingInterest(packet *defn.Pkt) {
 	// If NextHopFaceId set, forward to that face (if it exists) or drop
 	if packet.NextHopFaceID != nil {
 		if dispatch.GetFace(*packet.NextHopFaceID) != nil {
-			core.LogTrace(t, "NextHopFaceId is set for Interest ", packet.Name, " - dispatching directly to face")
+			if core.HasTraceLogs() {
+				core.LogTrace(t, "NextHopFaceId is set for Interest ", packet.Name, " - dispatching directly to face")
+			}
+
 			dispatch.GetFace(*packet.NextHopFaceID).SendPacket(dispatch.OutPkt{
 				Pkt:      packet,
 				PitToken: packet.PitToken, // TODO: ??
@@ -314,16 +327,20 @@ func (t *Thread) processIncomingInterest(packet *defn.Pkt) {
 
 	// Exclude faces that have an in-record for this interest
 	// TODO: unclear where NFD dev guide specifies such behavior (if any)
-	allowedNexthops := make([]*table.FibNextHopEntry, 0, len(nexthops))
+	allowedNexthops := [MaxNextHops]*table.FibNextHopEntry{}
+	allowedNexthopsCount := 0
 	for _, nexthop := range nexthops {
 		record := pitEntry.InRecords()[nexthop.Nexthop]
 		if record == nil || nexthop.Nexthop == incomingFace.FaceID() {
-			allowedNexthops = append(allowedNexthops, nexthop)
+			allowedNexthops[allowedNexthopsCount] = nexthop
+			allowedNexthopsCount++
 		}
 	}
 
 	// Pass to strategy AfterReceiveInterest pipeline
-	strategy.AfterReceiveInterest(packet, pitEntry, incomingFace.FaceID(), allowedNexthops)
+	strategy.AfterReceiveInterest(
+		packet, pitEntry, incomingFace.FaceID(),
+		allowedNexthops, allowedNexthopsCount)
 }
 
 func (t *Thread) processOutgoingInterest(