diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
index bac63524d12f..dba19de2f9ea 100644
--- a/tools/perf/util/metricgroup.c
+++ b/tools/perf/util/metricgroup.c
@@ -93,36 +93,72 @@ struct egroup {
 	bool has_constraint;
 };
 
+/**
+ * Find a group of events in perf_evlist that correpond to those from a parsed
+ * metric expression.
+ * @perf_evlist: a list of events something like: {metric1 leader, metric1
+ * sibling, metric1 sibling}:W,duration_time,{metric2 leader, metric2 sibling,
+ * metric2 sibling}:W,duration_time
+ * @pctx: the parse context for the metric expression.
+ * @has_constraint: is there a contraint on the group of events? In which case
+ * the events won't be grouped.
+ * @metric_events: out argument, null terminated array of evsel's associated
+ * with the metric.
+ * @evlist_used: in/out argument, bitmap tracking which evlist events are used.
+ * @return the first metric event or NULL on failure.
+ */
 static struct evsel *find_evsel_group(struct evlist *perf_evlist,
 				      struct expr_parse_ctx *pctx,
+				      bool has_constraint,
 				      struct evsel **metric_events,
 				      unsigned long *evlist_used)
 {
-	struct evsel *ev;
-	bool leader_found;
-	const size_t idnum = hashmap__size(&pctx->ids);
-	size_t i = 0;
-	int j = 0;
+	struct evsel *ev, *current_leader = NULL;
 	double *val_ptr;
+	int i = 0, matched_events = 0, events_to_match;
+	const int idnum = (int)hashmap__size(&pctx->ids);
+
+	/* duration_time is grouped separately. */
+	if (!has_constraint &&
+	    hashmap__find(&pctx->ids, "duration_time", (void **)&val_ptr))
+		events_to_match = idnum - 1;
+	else
+		events_to_match = idnum;
 
 	evlist__for_each_entry (perf_evlist, ev) {
-		if (test_bit(j++, evlist_used))
+		/*
+		 * Events with a constraint aren't grouped and match the first
+		 * events available.
+		 */
+		if (has_constraint && ev->weak_group)
 			continue;
-		if (hashmap__find(&pctx->ids, ev->name, (void **)&val_ptr)) {
-			if (!metric_events[i])
-				metric_events[i] = ev;
-			i++;
-			if (i == idnum)
-				break;
-		} else {
-			/* Discard the whole match and start again */
-			i = 0;
+		if (!has_constraint && ev->leader != current_leader) {
+			/*
+			 * Start of a new group, discard the whole match and
+			 * start again.
+			 */
+			matched_events = 0;
 			memset(metric_events, 0,
 				sizeof(struct evsel *) * idnum);
+			current_leader = ev->leader;
 		}
+		if (hashmap__find(&pctx->ids, ev->name, (void **)&val_ptr))
+			metric_events[matched_events++] = ev;
+		if (matched_events == events_to_match)
+			break;
 	}
 
-	if (i != idnum) {
+	if (events_to_match != idnum) {
+		/* Add the first duration_time. */
+		evlist__for_each_entry(perf_evlist, ev) {
+			if (!strcmp(ev->name, "duration_time")) {
+				metric_events[matched_events++] = ev;
+				break;
+			}
+		}
+	}
+
+	if (matched_events != idnum) {
 		/* Not whole match */
 		return NULL;
 	}
@@ -130,18 +166,8 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
 	metric_events[idnum] = NULL;
 
 	for (i = 0; i < idnum; i++) {
-		leader_found = false;
-		evlist__for_each_entry(perf_evlist, ev) {
-			if (!leader_found && (ev == metric_events[i]))
-				leader_found = true;
-
-			if (leader_found &&
-			    !strcmp(ev->name, metric_events[i]->name)) {
-				ev->metric_leader = metric_events[i];
-			}
-			j++;
-		}
 		ev = metric_events[i];
+		ev->metric_leader = ev;
 		set_bit(ev->idx, evlist_used);
 	}
 
@@ -157,7 +183,7 @@ static int metricgroup__setup_events(struct list_head *groups,
 	int i = 0;
 	int ret = 0;
 	struct egroup *eg;
-	struct evsel *evsel;
+	struct evsel *evsel, *tmp;
 	unsigned long *evlist_used;
 
 	evlist_used = bitmap_alloc(perf_evlist->core.nr_entries);
@@ -173,7 +199,8 @@ static int metricgroup__setup_events(struct list_head *groups,
 			ret = -ENOMEM;
 			break;
 		}
-		evsel = find_evsel_group(perf_evlist, &eg->pctx, metric_events,
+		evsel = find_evsel_group(perf_evlist, &eg->pctx,
+					eg->has_constraint, metric_events,
 					evlist_used);
 		if (!evsel) {
 			pr_debug("Cannot resolve %s: %s\n",
@@ -200,6 +227,12 @@ static int metricgroup__setup_events(struct list_head *groups,
 		list_add(&expr->nd, &me->head);
 	}
 
+	evlist__for_each_entry_safe(perf_evlist, tmp, evsel) {
+		if (!test_bit(evsel->idx, evlist_used)) {
+			evlist__remove(perf_evlist, evsel);
+			evsel__delete(evsel);
+		}
+	}
 	bitmap_free(evlist_used);
 
 	return ret;
