event: add a benchmark with namespace capturing turned on

Change-Id: Id4a759362bbfb2d61654d4f97cd31943a6887cfd
Reviewed-on: https://go-review.googlesource.com/c/exp/+/328789
Trust: Ian Cottrell <iancottrell@google.com>
Run-TryBot: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
diff --git a/event/bench_test.go b/event/bench_test.go
index 9dc3af6..0a07dea 100644
--- a/event/bench_test.go
+++ b/event/bench_test.go
@@ -97,6 +97,12 @@
 	return event.WithExporter(context.Background(), event.NewExporter(logfmt.NewHandler(w), eventtest.ExporterOptions()))
 }
 
+func eventPrintSource(w io.Writer) context.Context {
+	opts := eventtest.ExporterOptions()
+	opts.EnableNamespaces = true
+	return event.WithExporter(context.Background(), event.NewExporter(logfmt.NewHandler(w), opts))
+}
+
 func BenchmarkEventLogNoExporter(b *testing.B) {
 	eventtest.RunBenchmark(b, eventNoExporter(), eventLog)
 }
@@ -109,6 +115,10 @@
 	eventtest.RunBenchmark(b, eventPrint(io.Discard), eventLog)
 }
 
+func BenchmarkEventLogSourceDiscard(b *testing.B) {
+	eventtest.RunBenchmark(b, eventPrintSource(io.Discard), eventLog)
+}
+
 func BenchmarkEventLogfDiscard(b *testing.B) {
 	eventtest.RunBenchmark(b, eventPrint(io.Discard), eventLogf)
 }