[PATCH 1/5] perf metricgroup: Support printing metrics for arm64

[John Garry]

Calling perf_pmu__find_map(NULL) returns the cpumap for the common CPU
PMU. However arm64 supports heterogeneous-CPU based systems, and so there
may be no common CPU PMU. As such, perf_pmu__find_map(NULL) returns NULL
for arm64.

To support printing metrics for arm64, iterate through all PMUs, looking
for a CPU PMU, and use the cpumap there for determining supported metrics.

For heterogeneous systems (like arm big.LITTLE), supporting metrics has
potential challenges, like not all CPUs in a system not supporting a
specific metric event. So just don't support it for now.

Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
---
 tools/perf/util/metricgroup.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
index 26c990e32378..9a2a23093961 100644
--- a/tools/perf/util/metricgroup.c
+++ b/tools/perf/util/metricgroup.c
@@ -6,6 +6,7 @@
 /* Manage metrics and groups of metrics from JSON files */
 
 #include "metricgroup.h"
+#include "cpumap.h"
 #include "debug.h"
 #include "evlist.h"
 #include "evsel.h"
@@ -615,10 +616,31 @@ static int metricgroup__print_sys_event_iter(struct pmu_event *pe, void *data)
 				     d->details, d->groups, d->metriclist);
 }
 
+static struct pmu_events_map *find_cpumap(void)
+{
+	struct perf_pmu *pmu = NULL;
+
+	while ((pmu = perf_pmu__scan(pmu))) {
+		if (!is_pmu_core(pmu->name))
+			continue;
+
+		/*
+		 * The cpumap should cover all CPUs. Otherwise, some CPUs may
+		 * not support some events or have different event IDs.
+		 */
+		if (pmu->cpus && pmu->cpus->nr != cpu__max_cpu())
+			return NULL;
+
+		return perf_pmu__find_map(pmu);
+	}
+
+	return NULL;
+}
+
 void metricgroup__print(bool metrics, bool metricgroups, char *filter,
 			bool raw, bool details)
 {
-	struct pmu_events_map *map = perf_pmu__find_map(NULL);
+	struct pmu_events_map *map = find_cpumap();
 	struct pmu_event *pe;
 	int i;
 	struct rblist groups;
-- 
2.26.2