Favor passing small value copy over pointer

cmd/trace-agent/concentrator.go

@@ -101,12 +101,8 @@ func (c *Concentrator) Add(t processedTrace) {
 			c.buckets[btime] = b
 		}
 
-		sublayers, ok := t.Sublayers[s.Span]
-		if ok {
-			b.HandleSpan(s, t.Env, c.aggregators, &sublayers)
-		} else {
-			b.HandleSpan(s, t.Env, c.aggregators, nil)
-		}
+		sublayers, _ := t.Sublayers[s.Span]
+		b.HandleSpan(s, t.Env, c.aggregators, sublayers)
 	}
 
 	c.mu.Unlock()

model/stats_test.go

@@ -317,7 +317,7 @@ func TestStatsBucketSublayers(t *testing.T) {
 	// No custom aggregators only the defaults
 	aggr := []string{}
 	for _, s := range wt {
-		srb.HandleSpan(s, defaultEnv, aggr, &sublayers)
+		srb.HandleSpan(s, defaultEnv, aggr, sublayers)
 	}
 	sb := srb.Export()
 
@@ -415,7 +415,7 @@ func TestStatsBucketSublayersTopLevel(t *testing.T) {
 	// No custom aggregators only the defaults
 	aggr := []string{}
 	for _, s := range wt {
-		srb.HandleSpan(s, defaultEnv, aggr, &sublayers)
+		srb.HandleSpan(s, defaultEnv, aggr, sublayers)
 	}
 	sb := srb.Export()
 
@@ -545,7 +545,7 @@ func BenchmarkHandleSpanSublayers(b *testing.B) {
 	b.ReportAllocs()
 	for i := 0; i < b.N; i++ {
 		for _, s := range wt {
-			srb.HandleSpan(s, defaultEnv, aggr, &sublayers)
+			srb.HandleSpan(s, defaultEnv, aggr, sublayers)
 		}
 	}
 }

model/statsraw.go

@@ -184,7 +184,7 @@ func assembleGrain(b *bytes.Buffer, env, resource, service string, m map[string]
 }
 
 // HandleSpan adds the span to this bucket stats, aggregated with the finest grain matching given aggregators
-func (sb *StatsRawBucket) HandleSpan(s *WeightedSpan, env string, aggregators []string, sublayers *[]SublayerValue) {
+func (sb *StatsRawBucket) HandleSpan(s *WeightedSpan, env string, aggregators []string, sublayers []SublayerValue) {
 	if env == "" {
 		panic("env should never be empty")
 	}
@@ -202,11 +202,8 @@ func (sb *StatsRawBucket) HandleSpan(s *WeightedSpan, env string, aggregators []
 	grain, tags := assembleGrain(&sb.keyBuf, env, s.Resource, s.Service, m)
 	sb.add(s, grain, tags)
 
-	// sublayers - special case
-	if sublayers != nil {
-		for _, sub := range *sublayers {
-			sb.addSublayer(s, grain, tags, sub)
-		}
+	for _, sub := range sublayers {
+		sb.addSublayer(s, grain, tags, sub)
 	}
 }