perf parse-events: Specially handle uncore event alias in small groups

From: Kan Liang <[email protected]>

Perf stat doesn't count the uncore event aliases from the same uncore block in a group, for example:

perf stat -e '{unc_m_cas_count.all,unc_m_clockticks}' -a -I 1000
# time counts unit events

       1.000447342      <not counted>      unc_m_cas_count.all
       1.000447342      <not counted>      unc_m_clockticks
       2.000740654      <not counted>      unc_m_cas_count.all
       2.000740654      <not counted>      unc_m_clockticks

The output is very misleading. It gives a wrong impression that the uncore event doesn't work.

An uncore block could be composed by several PMUs. An uncore event alias is a joint name which means the same event runs on all PMUs of a block. Perf doesn't support mixed events from different PMUs in the same group. It is wrong to put uncore event aliases in a big group.

The right way is to split the big group into multiple small groups which only include the events from the same PMU.
Only uncore event aliases from the same uncore block should be specially handled here. It doesn't make sense to mix the uncore events with other uncore events from different blocks or even core events in a group.

With the patch:
# time counts unit events

     1.001557653            140,833      unc_m_cas_count.all
     1.001557653      1,330,231,332      unc_m_clockticks
     2.002709483             85,007      unc_m_cas_count.all
     2.002709483      1,429,494,563      unc_m_clockticks

Reported-by Andi Kleen <[email protected]>

Signed-off-by Kan Liang <[email protected]>

---

Changes since V3
- Add more comments in parse_events__set_leader_for_uncore_aliase
- Using list_first_entry and list_last_entry to replace list_entry
- Change the ret to 0 in alloc failed path
- Move "i = 0" closer to where it is used

 tools/perf/util/evsel.h        |   1 +
 tools/perf/util/parse-events.c | 125 ++++++++++++++++++++++++++++++++++++++++-
 tools/perf/util/parse-events.h |   7 ++-
 tools/perf/util/parse-events.y |   8 +--
 4 files changed, 132 insertions(+), 9 deletions(-)

tools/perf/util/evsel.h +1 -0

index 92ec009..b13f5f2 100644
@@ -127,6 +127,7 @@ struct perf_evsel {
 	bool			precise_max;
 	bool			ignore_missing_thread;
 	bool			forced_leader;
+	bool			use_uncore_alias;
 	/* parse modifier helper */
 	int			exclude_GH;
 	int			nr_members;

tools/perf/util/parse-events.c +36 -3

index 2fb0272..0f5c1ab 100644
@@ -1219,13 +1219,16 @@ int parse_events_add_numeric(struct parse_events_state *parse_state,
 
 int parse_events_add_pmu(struct parse_events_state *parse_state,
 			 struct list_head *list, char *name,
-			 struct list_head *head_config, bool auto_merge_stats)
+			 struct list_head *head_config,
+			 bool auto_merge_stats,
+			 bool use_alias)
 {
 	struct perf_event_attr attr;
 	struct perf_pmu_info info;
 	struct perf_pmu *pmu;
 	struct perf_evsel *evsel;
 	struct parse_events_error *err = parse_state->error;
+	bool use_uncore_alias;
 	LIST_HEAD(config_terms);
 
 	pmu = perf_pmu__find(name);

@@ -1244,11 +1247,14 @@ int parse_events_add_pmu(struct parse_events_state *parse_state,
 		memset(&attr, 0, sizeof(attr));
 	}
 
+	use_uncore_alias = (pmu->is_uncore && use_alias);
+
 	if (!head_config) {
 		attr.type = pmu->type;
 		evsel = __add_event(list, &parse_state->idx, &attr, NULL, pmu, NULL, auto_merge_stats);
 		if (evsel) {
 			evsel->pmu_name = name;
+			evsel->use_uncore_alias = use_uncore_alias;
 			return 0;
 		} else {
 			return -ENOMEM;

@@ -1282,6 +1288,7 @@ int parse_events_add_pmu(struct parse_events_state *parse_state,
 		evsel->metric_expr = info.metric_expr;
 		evsel->metric_name = info.metric_name;
 		evsel->pmu_name = name;
+		evsel->use_uncore_alias = use_uncore_alias;
 	}
 
 	return evsel ? 0 : -ENOMEM;

@@ -1317,7 +1324,8 @@ int parse_events_multi_pmu_add(struct parse_events_state *parse_state,
 				list_add_tail(&term->list, head);
 
 				if (!parse_events_add_pmu(parse_state, list,
-							  pmu->name, head, true)) {
+							  pmu->name, head,
+							  true, true)) {
 					pr_debug("%s -> %s/%s/\n", str,
 						 pmu->name, alias->str);
 					ok++;

@@ -1339,7 +1347,115 @@ int parse_events__modifier_group(struct list_head *list,
 	return parse_events__modifier_event(list, event_mod, true);
 }
 
-void parse_events__set_leader(char *name, struct list_head *list)
+/*
+ * Check if the two uncore PMUs are from the same uncore block
+ * The format of the uncore PMU name is uncore_#blockname_#pmuidx
+ */
+static bool is_same_uncore_block(const char *pmu_name_a, const char *pmu_name_b)
+{
+	char *end_a, *end_b;
+
+	end_a = strrchr(pmu_name_a, '_');
+	end_b = strrchr(pmu_name_b, '_');
+
+	if (!end_a || !end_b)
+		return false;
+
+	if ((end_a - pmu_name_a) != (end_b - pmu_name_b))
+		return false;
+
+	return (strncmp(pmu_name_a, pmu_name_b, end_a - pmu_name_a) == 0);
+}
+
+static int
+parse_events__set_leader_for_uncore_aliase(char *name, struct list_head *list,
+					   struct parse_events_state *parse_state)
+{
+	struct perf_evsel *evsel, *leader;
+	uintptr_t *leaders;

tools/perf/util/parse-events.c +12 -0

+
+	 __evlist__for_each_entry(list, evsel) {
+
+		/* Only split the uncore group which members use alias */
+		if (!evsel->use_uncore_alias)
+			goto out;
+
+		/* The events must be from the same uncore block */
+		if (!is_same_uncore_block(leader->pmu_name, evsel->pmu_name))
+			goto out;
+
+		if (!is_leader)

tools/perf/util/parse-events.c +54 -0

+		/* The name is always alias name */
+		WARN_ON(strcmp(leader->name, evsel->name));
+
+		/* Store the leader event for each PMU */
+		leaders[nr_pmu++] = (uintptr_t) evsel;
+	}
+
+	/* only one event alias */
+	if (nr_pmu == total_members) {
+		parse_state->nr_groups--;
+		goto handled;
+	}
+
+	/*
+	 * An uncore event alias is a joint name which means the same event
+	 * runs on all PMUs of a block.
+	 * Perf doesn't support mixed events from different PMUs in the same
+	 * group. The big group has to be split into multiple small groups
+	 * which only include the events from the same PMU.
+	 *
+	 * Here the uncore event aliases must be from the same uncore block.
+	 * The number of PMUs must be same for each alias. The number of new
+	 * small groups equals to the number of PMUs.
+	 * Setting the leader event for corresponding members in each group.
+	 */
+	i = 0;
+	__evlist__for_each_entry(list, evsel) {
+		if (i >= nr_pmu)
+			i = 0;
+		evsel->leader = (struct perf_evsel *) leaders[i++];
+	}
+
+	/* The number of members and group name are same for each group */
+	for (i = 0; i < nr_pmu; i++) {
+		evsel = (struct perf_evsel *) leaders[i];
+		evsel->nr_members = total_members / nr_pmu;
+		evsel->group_name = name ? strdup(name) : NULL;
+	}
+
+	/* Take the new small groups into account */
+	parse_state->nr_groups += nr_pmu - 1;
+
+handled:
+	ret = 1;
+out:
+	free(leaders);
+	return ret;
+}
+
+void parse_events__set_leader(char *name, struct list_head *list,
+			      struct parse_events_state *parse_state)
 {
 	struct perf_evsel *leader;
 

@@ -1348,6 +1464,9 @@ void parse_events__set_leader(char *name, struct list_head *list)
 		return;
 	}
 
+	if (parse_events__set_leader_for_uncore_aliase(name, list, parse_state))
+		return;
+
 	__perf_evlist__set_leader(list);
 	leader = list_entry(list->next, struct perf_evsel, node);
 	leader->group_name = name ? strdup(name) : NULL;

tools/perf/util/parse-events.h +5 -2

index 5015cfd..4473dac 100644
@@ -167,7 +167,9 @@ int parse_events_add_breakpoint(struct list_head *list, int *idx,
 				void *ptr, char *type, u64 len);
 int parse_events_add_pmu(struct parse_events_state *parse_state,
 			 struct list_head *list, char *name,
-			 struct list_head *head_config, bool auto_merge_stats);
+			 struct list_head *head_config,
+			 bool auto_merge_stats,
+			 bool use_alias);
 
 int parse_events_multi_pmu_add(struct parse_events_state *parse_state,
 			       char *str,

@@ -178,7 +180,8 @@ int parse_events_copy_term_list(struct list_head *old,
 
 enum perf_pmu_event_symbol_type
 perf_pmu__parse_check(const char *name);
-void parse_events__set_leader(char *name, struct list_head *list);
+void parse_events__set_leader(char *name, struct list_head *list,
+			      struct parse_events_state *parse_state);
 void parse_events_update_lists(struct list_head *list_event,
 			       struct list_head *list_all);
 void parse_events_evlist_error(struct parse_events_state *parse_state,

tools/perf/util/parse-events.y +4 -4

index d14464c..47f6399 100644
@@ -161,7 +161,7 @@ PE_NAME '{' events '}'
 	struct list_head *list = $3;
 
 	inc_group_count(list, _parse_state);
-	parse_events__set_leader($1, list);
+	parse_events__set_leader($1, list, _parse_state);
 	$$ = list;
 }
 |

@@ -170,7 +170,7 @@ PE_NAME '{' events '}'
 	struct list_head *list = $2;
 
 	inc_group_count(list, _parse_state);
-	parse_events__set_leader(NULL, list);
+	parse_events__set_leader(NULL, list, _parse_state);
 	$$ = list;
 }
 

@@ -232,7 +232,7 @@ PE_NAME '/' event_config '/'
 		YYABORT;
 
 	ALLOC_LIST(list);
-	if (parse_events_add_pmu(_parse_state, list, $1, $3, false)) {
+	if (parse_events_add_pmu(_parse_state, list, $1, $3, false, false)) {
 		struct perf_pmu *pmu = NULL;
 		int ok = 0;
 		char *pattern;

@@ -251,7 +251,7 @@ PE_NAME '/' event_config '/'
 					free(pattern);
 					YYABORT;
 				}
-				if (!parse_events_add_pmu(_parse_state, list, pmu->name, terms, true))
+				if (!parse_events_add_pmu(_parse_state, list, pmu->name, terms, true, false))
 					ok++;
 				parse_events_terms__delete(terms);
 			}

Signature · 1 line

2.7.4

Quoted 7 lines

tools/perf/util/parse-events.c +6 -0

+static int
+parse_events__set_leader_for_uncore_aliase(char *name, struct list_head *list,
+					   struct parse_events_state *parse_state)
+{
+	struct perf_evsel *evsel, *leader;
+	uintptr_t *leaders;

tools/perf/util/parse-events.c int parse_events__modifier_group(struct list_head *list, · line 1385

Quoted 10 lines

tools/perf/util/parse-events.c +10 -0

+	bool is_leader = true;
+	int i, nr_pmu = 0, total_members, ret = 0;
+
+	leader = list_first_entry(list, struct perf_evsel, node);
+	evsel = list_last_entry(list, struct perf_evsel, node);
+	total_members = evsel->idx - leader->idx + 1;
+
+	leaders = calloc(total_members, sizeof(uintptr_t));
+	if (!leaders)
+		return 0;

I see.. I meant we should return -ENOMEM in here, but we don't check it in the called anyway.. so perhaps

	if (WARN_ON(!leaders))
		return 0;

Quoted 18 lines

tools/perf/util/parse-events.c +17 -0

+
+	 __evlist__for_each_entry(list, evsel) {
+
+		/* Only split the uncore group which members use alias */
+		if (!evsel->use_uncore_alias)
+			goto out;
+
+		/* The events must be from the same uncore block */
+		if (!is_same_uncore_block(leader->pmu_name, evsel->pmu_name))
+			goto out;
+
+		if (!is_leader)
+			continue;
+		/*
+		 * If the event's PMU name starts to repeat, it must be a new
+		 * event. That can be used to distinguish the leader from
+		 * other members, even they have the same event name.

tools/perf/util/parse-events.c int parse_events__modifier_group(struct list_head *list, · line 1407

Quoted 5 lines

tools/perf/util/parse-events.c +5 -0

+		 */
+		if ((leader != evsel) && (leader->pmu_name == evsel->pmu_name)) {
+			is_leader = false;
+			continue;
+		}

I still don't get why you don't 'break' in here.. you set is_leader to false, then the loop will never get pass the !is_leader condition above