Apply suggestions from code review

Co-authored-by: Robert Pająk <pellared@hotmail.com>
Co-authored-by: Damien Mathieu <42@dmathieu.com>

sdk/trace/span.go

@@ -208,9 +208,10 @@ func (s *recordingSpan) SetStatus(code codes.Code, description string) {
 	s.status = status
 }
 
-// ensureAttributesCapacity inlines functionality from golang.org/x/exp/slices.Grow
+// ensureAttributesCapacity inlines functionality from slices.Grow
 // so that we can avoid needing to import golang.org/x/exp for go1.20.
-// Once support for go1.20 is dropped, we can use slices.Grow in 1.21+ instead.
+// Once support for go1.20 is dropped, we can use slices.Grow available since go1.21 instead.
+// Tracking issue: https://github.com/open-telemetry/opentelemetry-go/issues/4819.
 func (s *recordingSpan) ensureAttributesCapacity(minCapacity int) {
 	if n := minCapacity - cap(s.attributes); n > 0 {
 		s.attributes = append(s.attributes[:cap(s.attributes)], make([]attribute.KeyValue, n)...)[:len(s.attributes)]
@@ -287,7 +288,7 @@ func (s *recordingSpan) addOverCapAttrs(limit int, attrs []attribute.KeyValue) {
 
 	// Now that s.attributes is deduplicated, adding unique attributes up to
 	// the capacity of s will not over allocate s.attributes.
-	if limit-len(s.attributes) > 0 {
+	if len(s.attributes) > limit {
 		s.ensureAttributesCapacity(limit)
 	}
 	for _, a := range attrs {

sdk/trace/span_test.go

@@ -255,6 +255,7 @@ func BenchmarkRecordingSpanSetAttributes(b *testing.B) {
 	}
 
 	ctx := context.Background()
+	b.ResetTimer()
 	for n := 0; n < b.N; n++ {
 		_, span := tracer.Start(ctx, "span")
 		span.SetAttributes(attrs...)