improve benchmarks

contrib/segmentio/kafka.go.v0/kafka_test.go

@@ -23,6 +23,7 @@ import (
  "gopkg.in/DataDog/dd-trace-go.v1/contrib/internal/namingschematest"
  "gopkg.in/DataDog/dd-trace-go.v1/contrib/segmentio/kafka.go.v0/internal/tracing"
  "gopkg.in/DataDog/dd-trace-go.v1/datastreams"
+ "gopkg.in/DataDog/dd-trace-go.v1/ddtrace"
  "gopkg.in/DataDog/dd-trace-go.v1/ddtrace/ext"
  "gopkg.in/DataDog/dd-trace-go.v1/ddtrace/mocktracer"
  "gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
@@ -446,6 +447,9 @@ func TestNamingSchema(t *testing.T) {
  namingschematest.NewKafkaTest(genSpans)(t)
 }
 
+// benchSpan is a package-level variable used to prevent compiler optimisations in the benchmarks below.
+var benchSpan ddtrace.Span
+
 func BenchmarkReaderStartSpan(b *testing.B) {
  ctx := context.Background()
  kafkaCfg := tracing.KafkaConfig{
@@ -457,11 +461,13 @@ func BenchmarkReaderStartSpan(b *testing.B) {
  Key: []byte("key1"),
  Value: []byte("value1"),
  }
+ var result ddtrace.Span
 
  b.ResetTimer()
  for n := 0; n < b.N; n++ {
- tr.StartConsumeSpan(ctx, wrapMessage(&msg))
+ result = tr.StartConsumeSpan(ctx, wrapMessage(&msg))
  }
+ benchSpan = result
 }
 
 func BenchmarkWriterStartSpan(b *testing.B) {
@@ -480,9 +486,11 @@ func BenchmarkWriterStartSpan(b *testing.B) {
  Key: []byte("key1"),
  Value: []byte("value1"),
  }
+ var result ddtrace.Span
 
  b.ResetTimer()
  for n := 0; n < b.N; n++ {
- tr.StartProduceSpan(ctx, wrapTracingWriter(kw), wrapMessage(&msg))
+ result = tr.StartProduceSpan(ctx, wrapTracingWriter(kw), wrapMessage(&msg))
  }
+ benchSpan = result
 }