diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
index f1eb73957765..cfdbb5f7fb77 100644
--- a/tools/perf/util/metricgroup.c
+++ b/tools/perf/util/metricgroup.c
@@ -1896,9 +1896,10 @@ static int find_and_set_counters(struct metricgroup__event_info *e,
 {
 	int ret;
 	unsigned long find_bit = 0;
-
-	if (e->taken_alone && current_group->taken_alone)
+	if (e->taken_alone && current_group->taken_alone) {
+		pr_debug("current group with taken alone event already\n");
 		return -ENOSPC;
+	}
 	if (e->free_counter)
 		return 0;
 	if (e->fixed_counter) {
@@ -2017,7 +2018,8 @@ static int assign_event_grouping(struct metricgroup__event_info *e,
 
 	list_for_each_entry(g, groups, nd) {
 		if (!strcasecmp(g->pmu_name, e->pmu_name)) {
-			pr_debug("found group for event %s in pmu %s\n", e->name, g->pmu_name);
+			pr_debug("found group header for event %s in pmu %s\n",
+				e->name, g->pmu_name);
 			pmu_group_head = g;
 			break;
 		}
@@ -2146,26 +2148,22 @@ static int hw_aware_metricgroup__build_event_string(struct list_head *group_strs
  */
 static int create_grouping(struct list_head *pmu_info_list,
 			  struct list_head *event_info_list,
-			  struct list_head *groupings,
-			  const char *modifier)
+			  struct list_head *grouping)
 {
 	int ret = 0;
 	struct metricgroup__event_info *e;
-	LIST_HEAD(groups);
 	char *bit_buf = malloc(NR_COUNTERS);
 
-	//TODO: for each new core group, we should consider to add events that uses fixed counters
+	//TODO: for each new core group, we could consider to add events that
+	//uses fixed counters
 	list_for_each_entry(e, event_info_list, nd) {
 		bitmap_scnprintf(e->counters, NR_COUNTERS, bit_buf, NR_COUNTERS);
 		pr_debug("Event name %s, [pmu]=%s, [counters]=%s, [taken_alone]=%d\n",
 			e->name, e->pmu_name, bit_buf, e->taken_alone);
-		ret = assign_event_grouping(e, pmu_info_list, &groups);
+		ret = assign_event_grouping(e, pmu_info_list, grouping);
 		if (ret)
-			goto out;
+			return ret;
 	}
-	ret = hw_aware_metricgroup__build_event_string(groupings, modifier, &groups);
-out:
-	metricgroup__free_group_list(&groups);
 	return ret;
 };
 
@@ -2186,9 +2184,8 @@ static bool is_special_event(const char *id)
  * @groupings: header to the list of final event grouping.
  * @modifier: any modifiers added to the events.
  */
-static int hw_aware_build_grouping(struct expr_parse_ctx *ctx __maybe_unused,
-				  struct list_head *groupings __maybe_unused,
-				  const char *modifier __maybe_unused)
+static int hw_aware_build_grouping(struct expr_parse_ctx *ctx,
+				   struct list_head *grouping)
 {
 	int ret = 0;
 	struct hashmap_entry *cur;
@@ -2220,8 +2217,7 @@ static int hw_aware_build_grouping(struct expr_parse_ctx *ctx __maybe_unused,
 	ret = get_pmu_counter_layouts(&pmu_info_list, ltable);
 	if (ret)
 		goto err_out;
-	ret = create_grouping(&pmu_info_list, &event_info_list, groupings,
-			     modifier);
+	ret = create_grouping(&pmu_info_list, &event_info_list, grouping);
 
 err_out:
 	metricgroup__free_event_info(&event_info_list);
@@ -2267,23 +2263,25 @@ static int hw_aware_parse_ids(struct perf_pmu *fake_pmu,
 {
 	struct parse_events_error parse_error;
 	struct evlist *parsed_evlist;
-	LIST_HEAD(groupings);
+	LIST_HEAD(grouping_str);
+	LIST_HEAD(grouping);
 	struct metricgroup__group_strs *group;
 	int ret;
 
 	*out_evlist = NULL;
-	ret = hw_aware_build_grouping(ids, &groupings, modifier);
-	if (ret) {
-		metricgroup__free_grouping_strs(&groupings);
-		return ret;
-	}
+	ret = hw_aware_build_grouping(ids, &grouping);
+	if (ret)
+		goto out;
+	ret = hw_aware_metricgroup__build_event_string(&grouping_str, modifier, &grouping);
+	if (ret)
+		goto out;
 
 	parsed_evlist = evlist__new();
 	if (!parsed_evlist) {
 		ret = -ENOMEM;
 		goto err_out;
 	}
-	list_for_each_entry(group, &groupings, nd) {
+	list_for_each_entry(group, &grouping_str, nd) {
 		struct strbuf *events = &group->grouping_str;
 
 		pr_debug("Parsing metric events '%s'\n", events->buf);
@@ -2303,7 +2301,9 @@ static int hw_aware_parse_ids(struct perf_pmu *fake_pmu,
 err_out:
 	parse_events_error__exit(&parse_error);
 	evlist__delete(parsed_evlist);
-	metricgroup__free_grouping_strs(&groupings);
+out:
+	metricgroup__free_group_list(&grouping);
+	metricgroup__free_grouping_strs(&grouping_str);
 	return ret;
 }
 
