perf metrics: Ensure at least 1 id per metric

We may have no events for a metric evaluated to a constant. In such a
case ensure a tool event is at least evaluated for metric parsing and
displaying.

Fixes: 0e33350534a4823e ("perf metrics: Don't add all tool events for sharing")
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Link: https://lore.kernel.org/r/20220618013957.999321-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
index ee8fcfa115e50347845e28a873b68c9f150ca65b..8f7baeabc5cf600035e3d93db35f5a23aed7b120 100644 (file)
--- a/tools/perf/util/metricgroup.c
+++ b/tools/perf/util/metricgroup.c
@@ -1372,6 +1372,7 @@ static int parse_ids(bool metric_no_merge, struct perf_pmu *fake_pmu,
 
        *out_evlist = NULL;
        if (!metric_no_merge || hashmap__size(ids->ids) == 0) {
+               bool added_event = false;
                int i;
                /*
                 * We may fail to share events between metrics because a tool
@@ -1393,8 +1394,16 @@ static int parse_ids(bool metric_no_merge, struct perf_pmu *fake_pmu,
                                if (!tmp)
                                        return -ENOMEM;
                                ids__insert(ids->ids, tmp);
+                               added_event = true;
                        }
                }
+               if (!added_event && hashmap__size(ids->ids) == 0) {
+                       char *tmp = strdup("duration_time");
+
+                       if (!tmp)
+                               return -ENOMEM;
+                       ids__insert(ids->ids, tmp);
+               }
        }
        ret = metricgroup__build_event_string(&events, ids, modifier,
                                              has_constraint);