* [PATCH v2] perf stat: Include PMU name and split uncore events per PMU in metric-only JSON output
@ 2026-07-15 20:30 Chun-Tse Shao
2026-07-16 3:15 ` Ian Rogers
0 siblings, 1 reply; 3+ messages in thread
From: Chun-Tse Shao @ 2026-07-15 20:30 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim
Cc: Mark Rutland, Alexander Shishkin, Jiri Olsa, Ian Rogers,
Adrian Hunter, James Clark, linux-perf-users, linux-kernel,
Chun-Tse Shao
When running `perf stat` with `-A` (--no-aggr) and `--metric-only` in
JSON output mode (`-j`), `perf stat` evaluates metric expressions
across all matching PMUs (including uncore PMUs like `uncore_iio_0`,
`uncore_iio_1`, etc.).
However, `perf stat` previously formatted JSON output by printing only
"cpu" : "<id>" and grouping all metric values on a single line per CPU
without identifying which PMU instance evaluated each metric. As a
result, when an uncore event spans multiple PMU boxes, `perf stat`
printed repeated, ambiguous metric keys without PMU names.
Fix this by:
1. Including "pmu" : "<pmu_name>" in print_aggr_id_json when evsel->pmu
is a non-core or hybrid PMU in AGGR_NONE mode (-A).
2. Starting a new JSON metric line in AGGR_NONE mode (-A) whenever the
underlying PMU instance changes across PMU events.
3. Updating perf_json_output_lint.py to recognize the new "pmu" key in
the JSON test suite.
Example output:
$ perf stat -M iio_bandwidth_read -a -A --metric-only -j -I 1000
{"interval" : 1.000314908, "cpu" : "0", "pmu" : "uncore_iio_0", "MB/s iio_bandwidth_read" : "0.0"}
{"interval" : 1.000314908, "cpu" : "0", "pmu" : "uncore_iio_1", "MB/s iio_bandwidth_read" : "0.1"}
{"interval" : 1.000314908, "cpu" : "0", "pmu" : "uncore_iio_11", "MB/s iio_bandwidth_read" : "0.0"}
...
{"interval" : 1.000314908, "cpu" : "56", "pmu" : "uncore_iio_0", "MB/s iio_bandwidth_read" : "0.0"}
{"interval" : 1.000314908, "cpu" : "56", "pmu" : "uncore_iio_1", "MB/s iio_bandwidth_read" : "0.0"}
{"interval" : 1.000314908, "cpu" : "56", "pmu" : "uncore_iio_11", "MB/s iio_bandwidth_read" : "0.0"}
Signed-off-by: Chun-Tse Shao <ctshao@google.com>
Assisted-by: Gemini:gemini-3.1-pro-preview
---
v2:
- Fix print_metric_begin() initialization in print_no_aggr_metric()
to ensure tool events always open lines cleanly.
- Simplify and fix PMU line-split transition tracking when switching
between different PMU instances or transitioning from tool events.
- Add bounds check on aggr_map index in print_no_aggr_metric() to
prevent out-of-bounds array reads if sysfs CPU topology is incomplete.
v1: lore.kernel.org/20260714174052.1826692-1-ctshao@google.com
.../tests/shell/lib/perf_json_output_lint.py | 1 +
tools/perf/util/stat-display.c | 48 ++++++++++++++-----
2 files changed, 37 insertions(+), 12 deletions(-)
diff --git a/tools/perf/tests/shell/lib/perf_json_output_lint.py b/tools/perf/tests/shell/lib/perf_json_output_lint.py
index dafbde56cc76..36767905fcdb 100644
--- a/tools/perf/tests/shell/lib/perf_json_output_lint.py
+++ b/tools/perf/tests/shell/lib/perf_json_output_lint.py
@@ -64,6 +64,7 @@ def check_json_output(expected_items):
'metric-threshold': lambda x: x in ['unknown', 'good', 'less good', 'nearly bad', 'bad'],
'metricgroup': lambda x: True,
'node': lambda x: True,
+ 'pmu': lambda x: True,
'pcnt-running': lambda x: isfloat(x),
'socket': lambda x: True,
'thread': lambda x: True,
diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
index f94f1324d24a..61d634f8be2e 100644
--- a/tools/perf/util/stat-display.c
+++ b/tools/perf/util/stat-display.c
@@ -397,6 +397,8 @@ static void print_aggr_id_json(struct perf_stat_config *config, struct outstate
json_out(os, "\"cpu\" : \"%d\"",
id.cpu.cpu);
}
+ if (evsel && evsel->pmu && (!evsel->pmu->is_core || evsel__is_hybrid(evsel)))
+ json_out(os, "\"pmu\" : \"%s\"", evsel->pmu->name);
break;
case AGGR_THREAD:
json_out(os, "\"thread\" : \"%s-%d\"",
@@ -1009,11 +1011,12 @@ static void print_counter_aggrdata(struct perf_stat_config *config,
static void print_metric_begin(struct perf_stat_config *config,
struct evlist *evlist,
- struct outstate *os, int aggr_idx)
+ struct outstate *os, int aggr_idx,
+ struct evsel *counter)
{
struct perf_stat_aggr *aggr;
struct aggr_cpu_id id;
- struct evsel *evsel;
+ struct evsel *evsel = counter ?: evlist__first(evlist);
os->first = true;
if (!config->metric_only)
@@ -1028,7 +1031,6 @@ static void print_metric_begin(struct perf_stat_config *config,
else
fprintf(config->output, "%s", os->timestamp);
}
- evsel = evlist__first(evlist);
id = config->aggr_map->map[aggr_idx];
aggr = &evsel->stats->aggr[aggr_idx];
aggr_printout(config, os, evsel, id, aggr->nr);
@@ -1066,7 +1068,7 @@ static void print_aggr(struct perf_stat_config *config,
* Without each counter has its own line.
*/
cpu_aggr_map__for_each_idx(aggr_idx, config->aggr_map) {
- print_metric_begin(config, evlist, os, aggr_idx);
+ print_metric_begin(config, evlist, os, aggr_idx, NULL);
evlist__for_each_entry(evlist, counter) {
print_counter_aggrdata(config, counter, aggr_idx, os);
@@ -1092,7 +1094,7 @@ static void print_aggr_cgroup(struct perf_stat_config *config,
os->cgrp = evsel->cgrp;
cpu_aggr_map__for_each_idx(aggr_idx, config->aggr_map) {
- print_metric_begin(config, evlist, os, aggr_idx);
+ print_metric_begin(config, evlist, os, aggr_idx, NULL);
evlist__for_each_entry(evlist, counter) {
if (counter->cgrp != os->cgrp)
@@ -1128,7 +1130,8 @@ static void print_no_aggr_metric(struct perf_stat_config *config,
perf_cpu_map__for_each_cpu(cpu, all_idx, evlist__core(evlist)->user_requested_cpus) {
struct evsel *counter;
- bool first = true;
+ struct perf_pmu *last_pmu = NULL;
+ bool line_open = false;
evlist__for_each_entry(evlist, counter) {
u64 ena, run, val;
@@ -1143,13 +1146,34 @@ static void print_no_aggr_metric(struct perf_stat_config *config,
if (config->aggr_map->map[aggr_idx].cpu.cpu == cpu.cpu)
break;
}
+ if (aggr_idx >= config->aggr_map->nr)
+ continue;
os->evsel = counter;
os->id = aggr_cpu_id__cpu(cpu, /*data=*/NULL);
- if (first) {
- print_metric_begin(config, evlist, os, aggr_idx);
- first = false;
+
+ if (config->metric_only) {
+ struct perf_pmu *pmu = counter->pmu;
+
+ if (!evsel__is_tool(counter)) {
+ if (config->json_output && line_open &&
+ (!last_pmu || pmu != last_pmu)) {
+ print_metric_end(config, os);
+ line_open = false;
+ }
+ if (!line_open) {
+ print_metric_begin(config, evlist, os,
+ aggr_idx, counter);
+ line_open = true;
+ }
+ last_pmu = pmu;
+ } else if (!line_open) {
+ print_metric_begin(config, evlist, os,
+ aggr_idx, counter);
+ line_open = true;
+ }
}
+
val = ps->aggr[aggr_idx].counts.val;
ena = ps->aggr[aggr_idx].counts.ena;
run = ps->aggr[aggr_idx].counts.run;
@@ -1157,7 +1181,7 @@ static void print_no_aggr_metric(struct perf_stat_config *config,
uval = val * counter->scale;
printout(config, os, uval, run, ena, 1.0, aggr_idx);
}
- if (!first)
+ if (line_open)
print_metric_end(config, os);
}
}
@@ -1520,7 +1544,7 @@ static void print_cgroup_counter(struct perf_stat_config *config, struct evlist
print_metric_end(config, os);
os->cgrp = counter->cgrp;
- print_metric_begin(config, evlist, os, /*aggr_idx=*/0);
+ print_metric_begin(config, evlist, os, /*aggr_idx=*/0, NULL);
}
print_counter(config, counter, os);
@@ -1570,7 +1594,7 @@ void evlist__print_counters(struct evlist *evlist, struct perf_stat_config *conf
} else if (config->cgroup_list) {
print_cgroup_counter(config, evlist, &os);
} else {
- print_metric_begin(config, evlist, &os, /*aggr_idx=*/0);
+ print_metric_begin(config, evlist, &os, /*aggr_idx=*/0, NULL);
evlist__for_each_entry(evlist, counter) {
print_counter(config, counter, &os);
}
--
2.55.0.141.g00534a21ce-goog
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] perf stat: Include PMU name and split uncore events per PMU in metric-only JSON output
2026-07-15 20:30 [PATCH v2] perf stat: Include PMU name and split uncore events per PMU in metric-only JSON output Chun-Tse Shao
@ 2026-07-16 3:15 ` Ian Rogers
2026-07-23 6:03 ` Namhyung Kim
0 siblings, 1 reply; 3+ messages in thread
From: Ian Rogers @ 2026-07-16 3:15 UTC (permalink / raw)
To: Chun-Tse Shao
Cc: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim, Mark Rutland, Alexander Shishkin, Jiri Olsa,
Adrian Hunter, James Clark, linux-perf-users, linux-kernel
On Wed, Jul 15, 2026 at 1:30 PM Chun-Tse Shao <ctshao@google.com> wrote:
>
> When running `perf stat` with `-A` (--no-aggr) and `--metric-only` in
> JSON output mode (`-j`), `perf stat` evaluates metric expressions
> across all matching PMUs (including uncore PMUs like `uncore_iio_0`,
> `uncore_iio_1`, etc.).
>
> However, `perf stat` previously formatted JSON output by printing only
> "cpu" : "<id>" and grouping all metric values on a single line per CPU
> without identifying which PMU instance evaluated each metric. As a
> result, when an uncore event spans multiple PMU boxes, `perf stat`
> printed repeated, ambiguous metric keys without PMU names.
>
> Fix this by:
> 1. Including "pmu" : "<pmu_name>" in print_aggr_id_json when evsel->pmu
> is a non-core or hybrid PMU in AGGR_NONE mode (-A).
> 2. Starting a new JSON metric line in AGGR_NONE mode (-A) whenever the
> underlying PMU instance changes across PMU events.
> 3. Updating perf_json_output_lint.py to recognize the new "pmu" key in
> the JSON test suite.
>
> Example output:
> $ perf stat -M iio_bandwidth_read -a -A --metric-only -j -I 1000
> {"interval" : 1.000314908, "cpu" : "0", "pmu" : "uncore_iio_0", "MB/s iio_bandwidth_read" : "0.0"}
> {"interval" : 1.000314908, "cpu" : "0", "pmu" : "uncore_iio_1", "MB/s iio_bandwidth_read" : "0.1"}
> {"interval" : 1.000314908, "cpu" : "0", "pmu" : "uncore_iio_11", "MB/s iio_bandwidth_read" : "0.0"}
> ...
> {"interval" : 1.000314908, "cpu" : "56", "pmu" : "uncore_iio_0", "MB/s iio_bandwidth_read" : "0.0"}
> {"interval" : 1.000314908, "cpu" : "56", "pmu" : "uncore_iio_1", "MB/s iio_bandwidth_read" : "0.0"}
> {"interval" : 1.000314908, "cpu" : "56", "pmu" : "uncore_iio_11", "MB/s iio_bandwidth_read" : "0.0"}
>
> Signed-off-by: Chun-Tse Shao <ctshao@google.com>
> Assisted-by: Gemini:gemini-3.1-pro-preview
Reviewed-by: Ian Rogers <irogers@google.com>
Nit: It may be nice to include the before output (i.e., without the
PMU showing that differentiation isn't possible) in the commit
message.
Thanks,
Ian
> ---
>
> v2:
> - Fix print_metric_begin() initialization in print_no_aggr_metric()
> to ensure tool events always open lines cleanly.
> - Simplify and fix PMU line-split transition tracking when switching
> between different PMU instances or transitioning from tool events.
> - Add bounds check on aggr_map index in print_no_aggr_metric() to
> prevent out-of-bounds array reads if sysfs CPU topology is incomplete.
>
> v1: lore.kernel.org/20260714174052.1826692-1-ctshao@google.com
>
> .../tests/shell/lib/perf_json_output_lint.py | 1 +
> tools/perf/util/stat-display.c | 48 ++++++++++++++-----
> 2 files changed, 37 insertions(+), 12 deletions(-)
>
> diff --git a/tools/perf/tests/shell/lib/perf_json_output_lint.py b/tools/perf/tests/shell/lib/perf_json_output_lint.py
> index dafbde56cc76..36767905fcdb 100644
> --- a/tools/perf/tests/shell/lib/perf_json_output_lint.py
> +++ b/tools/perf/tests/shell/lib/perf_json_output_lint.py
> @@ -64,6 +64,7 @@ def check_json_output(expected_items):
> 'metric-threshold': lambda x: x in ['unknown', 'good', 'less good', 'nearly bad', 'bad'],
> 'metricgroup': lambda x: True,
> 'node': lambda x: True,
> + 'pmu': lambda x: True,
> 'pcnt-running': lambda x: isfloat(x),
> 'socket': lambda x: True,
> 'thread': lambda x: True,
> diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
> index f94f1324d24a..61d634f8be2e 100644
> --- a/tools/perf/util/stat-display.c
> +++ b/tools/perf/util/stat-display.c
> @@ -397,6 +397,8 @@ static void print_aggr_id_json(struct perf_stat_config *config, struct outstate
> json_out(os, "\"cpu\" : \"%d\"",
> id.cpu.cpu);
> }
> + if (evsel && evsel->pmu && (!evsel->pmu->is_core || evsel__is_hybrid(evsel)))
> + json_out(os, "\"pmu\" : \"%s\"", evsel->pmu->name);
> break;
> case AGGR_THREAD:
> json_out(os, "\"thread\" : \"%s-%d\"",
> @@ -1009,11 +1011,12 @@ static void print_counter_aggrdata(struct perf_stat_config *config,
>
> static void print_metric_begin(struct perf_stat_config *config,
> struct evlist *evlist,
> - struct outstate *os, int aggr_idx)
> + struct outstate *os, int aggr_idx,
> + struct evsel *counter)
> {
> struct perf_stat_aggr *aggr;
> struct aggr_cpu_id id;
> - struct evsel *evsel;
> + struct evsel *evsel = counter ?: evlist__first(evlist);
>
> os->first = true;
> if (!config->metric_only)
> @@ -1028,7 +1031,6 @@ static void print_metric_begin(struct perf_stat_config *config,
> else
> fprintf(config->output, "%s", os->timestamp);
> }
> - evsel = evlist__first(evlist);
> id = config->aggr_map->map[aggr_idx];
> aggr = &evsel->stats->aggr[aggr_idx];
> aggr_printout(config, os, evsel, id, aggr->nr);
> @@ -1066,7 +1068,7 @@ static void print_aggr(struct perf_stat_config *config,
> * Without each counter has its own line.
> */
> cpu_aggr_map__for_each_idx(aggr_idx, config->aggr_map) {
> - print_metric_begin(config, evlist, os, aggr_idx);
> + print_metric_begin(config, evlist, os, aggr_idx, NULL);
>
> evlist__for_each_entry(evlist, counter) {
> print_counter_aggrdata(config, counter, aggr_idx, os);
> @@ -1092,7 +1094,7 @@ static void print_aggr_cgroup(struct perf_stat_config *config,
> os->cgrp = evsel->cgrp;
>
> cpu_aggr_map__for_each_idx(aggr_idx, config->aggr_map) {
> - print_metric_begin(config, evlist, os, aggr_idx);
> + print_metric_begin(config, evlist, os, aggr_idx, NULL);
>
> evlist__for_each_entry(evlist, counter) {
> if (counter->cgrp != os->cgrp)
> @@ -1128,7 +1130,8 @@ static void print_no_aggr_metric(struct perf_stat_config *config,
>
> perf_cpu_map__for_each_cpu(cpu, all_idx, evlist__core(evlist)->user_requested_cpus) {
> struct evsel *counter;
> - bool first = true;
> + struct perf_pmu *last_pmu = NULL;
> + bool line_open = false;
>
> evlist__for_each_entry(evlist, counter) {
> u64 ena, run, val;
> @@ -1143,13 +1146,34 @@ static void print_no_aggr_metric(struct perf_stat_config *config,
> if (config->aggr_map->map[aggr_idx].cpu.cpu == cpu.cpu)
> break;
> }
> + if (aggr_idx >= config->aggr_map->nr)
> + continue;
>
> os->evsel = counter;
> os->id = aggr_cpu_id__cpu(cpu, /*data=*/NULL);
> - if (first) {
> - print_metric_begin(config, evlist, os, aggr_idx);
> - first = false;
> +
> + if (config->metric_only) {
> + struct perf_pmu *pmu = counter->pmu;
> +
> + if (!evsel__is_tool(counter)) {
> + if (config->json_output && line_open &&
> + (!last_pmu || pmu != last_pmu)) {
> + print_metric_end(config, os);
> + line_open = false;
> + }
> + if (!line_open) {
> + print_metric_begin(config, evlist, os,
> + aggr_idx, counter);
> + line_open = true;
> + }
> + last_pmu = pmu;
> + } else if (!line_open) {
> + print_metric_begin(config, evlist, os,
> + aggr_idx, counter);
> + line_open = true;
> + }
> }
> +
> val = ps->aggr[aggr_idx].counts.val;
> ena = ps->aggr[aggr_idx].counts.ena;
> run = ps->aggr[aggr_idx].counts.run;
> @@ -1157,7 +1181,7 @@ static void print_no_aggr_metric(struct perf_stat_config *config,
> uval = val * counter->scale;
> printout(config, os, uval, run, ena, 1.0, aggr_idx);
> }
> - if (!first)
> + if (line_open)
> print_metric_end(config, os);
> }
> }
> @@ -1520,7 +1544,7 @@ static void print_cgroup_counter(struct perf_stat_config *config, struct evlist
> print_metric_end(config, os);
>
> os->cgrp = counter->cgrp;
> - print_metric_begin(config, evlist, os, /*aggr_idx=*/0);
> + print_metric_begin(config, evlist, os, /*aggr_idx=*/0, NULL);
> }
>
> print_counter(config, counter, os);
> @@ -1570,7 +1594,7 @@ void evlist__print_counters(struct evlist *evlist, struct perf_stat_config *conf
> } else if (config->cgroup_list) {
> print_cgroup_counter(config, evlist, &os);
> } else {
> - print_metric_begin(config, evlist, &os, /*aggr_idx=*/0);
> + print_metric_begin(config, evlist, &os, /*aggr_idx=*/0, NULL);
> evlist__for_each_entry(evlist, counter) {
> print_counter(config, counter, &os);
> }
> --
> 2.55.0.141.g00534a21ce-goog
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] perf stat: Include PMU name and split uncore events per PMU in metric-only JSON output
2026-07-16 3:15 ` Ian Rogers
@ 2026-07-23 6:03 ` Namhyung Kim
0 siblings, 0 replies; 3+ messages in thread
From: Namhyung Kim @ 2026-07-23 6:03 UTC (permalink / raw)
To: Ian Rogers, Chun-Tse Shao
Cc: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Mark Rutland, Alexander Shishkin, Jiri Olsa, Adrian Hunter,
James Clark, linux-perf-users, linux-kernel
On Wed, Jul 15, 2026 at 08:15:46PM -0700, Ian Rogers wrote:
> On Wed, Jul 15, 2026 at 1:30 PM Chun-Tse Shao <ctshao@google.com> wrote:
> >
> > When running `perf stat` with `-A` (--no-aggr) and `--metric-only` in
> > JSON output mode (`-j`), `perf stat` evaluates metric expressions
> > across all matching PMUs (including uncore PMUs like `uncore_iio_0`,
> > `uncore_iio_1`, etc.).
> >
> > However, `perf stat` previously formatted JSON output by printing only
> > "cpu" : "<id>" and grouping all metric values on a single line per CPU
> > without identifying which PMU instance evaluated each metric. As a
> > result, when an uncore event spans multiple PMU boxes, `perf stat`
> > printed repeated, ambiguous metric keys without PMU names.
> >
> > Fix this by:
> > 1. Including "pmu" : "<pmu_name>" in print_aggr_id_json when evsel->pmu
> > is a non-core or hybrid PMU in AGGR_NONE mode (-A).
> > 2. Starting a new JSON metric line in AGGR_NONE mode (-A) whenever the
> > underlying PMU instance changes across PMU events.
> > 3. Updating perf_json_output_lint.py to recognize the new "pmu" key in
> > the JSON test suite.
> >
> > Example output:
> > $ perf stat -M iio_bandwidth_read -a -A --metric-only -j -I 1000
> > {"interval" : 1.000314908, "cpu" : "0", "pmu" : "uncore_iio_0", "MB/s iio_bandwidth_read" : "0.0"}
> > {"interval" : 1.000314908, "cpu" : "0", "pmu" : "uncore_iio_1", "MB/s iio_bandwidth_read" : "0.1"}
> > {"interval" : 1.000314908, "cpu" : "0", "pmu" : "uncore_iio_11", "MB/s iio_bandwidth_read" : "0.0"}
> > ...
> > {"interval" : 1.000314908, "cpu" : "56", "pmu" : "uncore_iio_0", "MB/s iio_bandwidth_read" : "0.0"}
> > {"interval" : 1.000314908, "cpu" : "56", "pmu" : "uncore_iio_1", "MB/s iio_bandwidth_read" : "0.0"}
> > {"interval" : 1.000314908, "cpu" : "56", "pmu" : "uncore_iio_11", "MB/s iio_bandwidth_read" : "0.0"}
> >
> > Signed-off-by: Chun-Tse Shao <ctshao@google.com>
> > Assisted-by: Gemini:gemini-3.1-pro-preview
>
> Reviewed-by: Ian Rogers <irogers@google.com>
>
> Nit: It may be nice to include the before output (i.e., without the
> PMU showing that differentiation isn't possible) in the commit
> message.
Hi CT, can you please update the commit message? It'd be very helpful
for others to understand the problem.
Thanks,
Namhyung
^ permalink raw reply [flat|nested] 3+ messages in thread
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2026-07-15 20:30 [PATCH v2] perf stat: Include PMU name and split uncore events per PMU in metric-only JSON output Chun-Tse Shao
2026-07-16 3:15 ` Ian Rogers
2026-07-23 6:03 ` Namhyung Kim
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