[PATCH v1] perf stat: Don't display metric header for non-leader uncore events

[Ian Rogers]

On an Intel tigerlake laptop a metric like:
```
    {
        "BriefDescription": "Test",
        "MetricExpr": "imc_free_running@data_read@ + imc_free_running@data_write@",
        "MetricGroup": "Test",
        "MetricName": "Test",
        "ScaleUnit": "6.103515625e-5MiB"
    },
```
Will have 4 events:
uncore_imc_free_running_0/data_read/
uncore_imc_free_running_0/data_write/
uncore_imc_free_running_1/data_read/
uncore_imc_free_running_1/data_write/

If aggregration is disabled with metric-only 2 column headers are
needed:
```
$ perf stat -M test --metric-only -A -a sleep 1

 Performance counter stats for 'system wide':

                  MiB  Test            MiB  Test
CPU0                 1821.0               1820.5
```
But when not, the counts aggregated in the metric leader and only 1
column should be shown:
```
$ perf stat -M test --metric-only -a sleep 1
 Performance counter stats for 'system wide':

            MiB  Test
              5909.4

       1.001258915 seconds time elapsed
```
Achieve this by skipping events that aren't metric leaders when
printing column headers and aggregation isn't disabled.

The bug is long standing, the fixes tag is set to a refactor as that
is as far back as is reasonable to backport.

Fixes: 088519f318be ("perf stat: Move the display functions to stat-display.c")
Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/util/stat-display.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
index ea11e3437444..bb6bbb821b5a 100644
--- a/tools/perf/util/stat-display.c
+++ b/tools/perf/util/stat-display.c
@@ -1251,6 +1251,9 @@ static void print_metric_headers(struct perf_stat_config *config,
 
 	/* Print metrics headers only */
 	evlist__for_each_entry(evlist, counter) {
+		if (config->aggr_mode != AGGR_NONE && counter->metric_leader != counter)
+			continue;
+
 		os.evsel = counter;
 
 		perf_stat__print_shadow_stats(config, counter, 0,
-- 
2.45.0.118.g7fe29c98d7-goog