diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 7a811eb61f75..9bf582750561 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -14,8 +14,8 @@
 
 struct perf_pmu_alias {
 	char *name;
-	struct list_head terms;
-	struct list_head list;
+	struct list_head terms; /* HEAD struct parse_events_term -> list */
+	struct list_head list;  /* ELEM */
 	char unit[UNIT_MAX_LEN+1];
 	double scale;
 };
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index c14a543ce1f3..1c1e2eecbe1f 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -17,9 +17,9 @@ struct perf_pmu {
 	char *name;
 	__u32 type;
 	struct cpu_map *cpus;
-	struct list_head format;
-	struct list_head aliases;
-	struct list_head list;
+	struct list_head format;  /* HEAD struct perf_pmu_format -> list */
+	struct list_head aliases; /* HEAD struct perf_pmu_alias -> list */
+	struct list_head list;    /* ELEM */
 };
 
 struct perf_pmu *perf_pmu__find(const char *name);