[PATCH] perf stat: Ensure metrics are displayed even with failed events
From: Chun-Tse Shao
Date: Tue Feb 03 2026 - 18:08:06 EST
Currently, `perf stat` skips or hides metrics when the underlying
hardware events cannot be counted (e.g., due to insufficient permissions
or unsupported events). In `--metric-only` mode, this often results in
missing columns or blank spaces, making the output difficult to parse.
Modify the logic to ensure metrics are consistently displayed by
propagating NAN (Not a Number) through the expression evaluator.
Specifically:
1. Update `prepare_metric()` in stat-shadow.c to treat uncounted events
(where `run == 0`) as NAN. This leverages the existing math in expr.y
to propagate NAN through metric expressions.
2. Remove the early return in the display logic's `printout()` function
that was previously skipping metrics in `--metric-only` mode for
failed events.
3. Simplify `perf_stat__skip_metric_event()` to no longer depend on
event runtime.
Tested:
1. `perf all metrics test` did not crash while paranoid is 2.
2. Multiple combinations with `CPUs_utilized` while paranoid is 2.
$ ./perf stat -M CPUs_utilized -a -- sleep 1
Performance counter stats for 'system wide':
<not supported> msec cpu-clock:u # nan CPUs CPUs_utilized
1,006,356,120 duration_time
1.004375550 seconds time elapsed
$ ./perf stat -M CPUs_utilized -a -j -- sleep 1
{"counter-value" : "<not supported>", "unit" : "msec", "event" : "cpu-clock:u", "event-runtime" : 0, "pcnt-running" : 100.00, "metric-value" : "nan", "metric-unit" : "CPUs CPUs_utilized"}
{"counter-value" : "1006642462.000000", "unit" : "", "event" : "duration_time", "event-runtime" : 1, "pcnt-running" : 100.00}
$ ./perf stat -M CPUs_utilized -a --metric-only -- sleep 1
Performance counter stats for 'system wide':
CPUs CPUs_utilized
nan
1.004424652 seconds time elapsed
$ ./perf stat -M CPUs_utilized -a --metric-only -j -- sleep 1
{"CPUs CPUs_utilized" : "none"}
Signed-off-by: ctshao@xxxxxxxxxx
---
tools/perf/util/stat-display.c | 59 +++++++++++++++-------------------
tools/perf/util/stat-shadow.c | 8 ++---
tools/perf/util/stat.h | 2 +-
3 files changed, 29 insertions(+), 40 deletions(-)
diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
index 2ce0602974a1..dc2b66855f6c 100644
--- a/tools/perf/util/stat-display.c
+++ b/tools/perf/util/stat-display.c
@@ -820,12 +820,6 @@ static void printout(struct perf_stat_config *config, struct outstate *os,
}
if (run == 0 || ena == 0 || counter->counts->scaled == -1) {
- if (config->metric_only) {
- pm(config, os, METRIC_THRESHOLD_UNKNOWN, /*format=*/NULL,
- /*unit=*/NULL, /*val=*/0);
- return;
- }
-
ok = false;
if (counter->supported) {
@@ -848,33 +842,32 @@ static void printout(struct perf_stat_config *config, struct outstate *os,
print_running(config, os, run, ena, /*before_metric=*/true);
}
- if (ok) {
- if (!config->metric_only && counter->default_metricgroup && !counter->default_show_events) {
- void *from = NULL;
-
- aggr_printout(config, os, os->evsel, os->id, os->aggr_nr);
- /* Print out all the metricgroup with the same metric event. */
- do {
- int num = 0;
-
- /* Print out the new line for the next new metricgroup. */
- if (from) {
- if (config->json_output)
- new_line_json(config, (void *)os);
- else
- __new_line_std_csv(config, os);
- }
-
- print_noise(config, os, counter, noise, /*before_metric=*/true);
- print_running(config, os, run, ena, /*before_metric=*/true);
- from = perf_stat__print_shadow_stats_metricgroup(config, counter, aggr_idx,
- &num, from, &out);
- } while (from != NULL);
- } else {
- perf_stat__print_shadow_stats(config, counter, aggr_idx, &out);
- }
+ if (!config->metric_only && counter->default_metricgroup &&
+ !counter->default_show_events) {
+ void *from = NULL;
+
+ aggr_printout(config, os, os->evsel, os->id, os->aggr_nr);
+ /* Print out all the metricgroup with the same metric event. */
+ do {
+ int num = 0;
+
+ /* Print out the new line for the next new metricgroup. */
+ if (from) {
+ if (config->json_output)
+ new_line_json(config, (void *)os);
+ else
+ __new_line_std_csv(config, os);
+ }
+
+ print_noise(config, os, counter, noise,
+ /*before_metric=*/true);
+ print_running(config, os, run, ena,
+ /*before_metric=*/true);
+ from = perf_stat__print_shadow_stats_metricgroup(
+ config, counter, aggr_idx, &num, from, &out);
+ } while (from != NULL);
} else {
- pm(config, os, METRIC_THRESHOLD_UNKNOWN, /*format=*/NULL, /*unit=*/NULL, /*val=*/0);
+ perf_stat__print_shadow_stats(config, counter, aggr_idx, &out);
}
if (!config->metric_only) {
@@ -987,7 +980,7 @@ static void print_counter_aggrdata(struct perf_stat_config *config,
ena = aggr->counts.ena;
run = aggr->counts.run;
- if (perf_stat__skip_metric_event(counter, ena, run))
+ if (perf_stat__skip_metric_event(counter))
return;
if (val == 0 && should_skip_zero_counter(config, counter, &id))
diff --git a/tools/perf/util/stat-shadow.c b/tools/perf/util/stat-shadow.c
index 9c83f7d96caa..5d8d09e0e6ae 100644
--- a/tools/perf/util/stat-shadow.c
+++ b/tools/perf/util/stat-shadow.c
@@ -83,7 +83,7 @@ static int prepare_metric(struct perf_stat_config *config,
}
/* Time events are always on CPU0, the first aggregation index. */
aggr = &ps->aggr[is_tool_time ? tool_aggr_idx : aggr_idx];
- if (!aggr || !metric_events[i]->supported) {
+ if (!aggr || !metric_events[i]->supported || aggr->counts.run == 0) {
/*
* Not supported events will have a count of 0, which
* can be confusing in a metric. Explicitly set the
@@ -335,14 +335,10 @@ void perf_stat__print_shadow_stats(struct perf_stat_config *config,
* perf_stat__skip_metric_event - Skip the evsel in the Default metricgroup,
* if it's not running or not the metric event.
*/
-bool perf_stat__skip_metric_event(struct evsel *evsel,
- u64 ena, u64 run)
+bool perf_stat__skip_metric_event(struct evsel *evsel)
{
if (!evsel->default_metricgroup)
return false;
- if (!ena || !run)
- return true;
-
return !metricgroup__lookup(&evsel->evlist->metric_events, evsel, false);
}
diff --git a/tools/perf/util/stat.h b/tools/perf/util/stat.h
index f986911c9296..4bced233d2fc 100644
--- a/tools/perf/util/stat.h
+++ b/tools/perf/util/stat.h
@@ -163,7 +163,7 @@ void perf_stat__print_shadow_stats(struct perf_stat_config *config,
struct evsel *evsel,
int aggr_idx,
struct perf_stat_output_ctx *out);
-bool perf_stat__skip_metric_event(struct evsel *evsel, u64 ena, u64 run);
+bool perf_stat__skip_metric_event(struct evsel *evsel);
void *perf_stat__print_shadow_stats_metricgroup(struct perf_stat_config *config,
struct evsel *evsel,
int aggr_idx,
--
2.53.0.rc2.204.g2597b5adb4-goog