[PATCH v3 00/18] Switch the default perf stat metrics to json

Ian Rogers
2025-11-11T04:04:26Z

Prior to this series stat-shadow would produce hard coded metrics if
certain events appeared in the evlist. This series produces equivalent
json metrics and cleans up the consequences in tests and display
output. A before and after of the default display output on a
tigerlake is:

Before:
```
$ perf stat -a sleep 1

Performance counter stats for 'system wide':

16,041,816,418 cpu-clock # 15.995 CPUs utilized
5,749 context-switches # 358.376 /sec
121 cpu-migrations # 7.543 /sec
1,806 page-faults # 112.581 /sec
825,965,204 instructions # 0.70 insn per cycle
1,180,799,101 cycles # 0.074 GHz
168,945,109 branches # 10.532 M/sec
4,629,567 branch-misses # 2.74% of all branches
# 30.2 % tma_backend_bound
# 7.8 % tma_bad_speculation
# 47.1 % tma_frontend_bound
# 14.9 % tma_retiring
```

After:
```
$ perf stat -a sleep 1

Performance counter stats for 'system wide':

2,890 context-switches # 179.9 cs/sec cs_per_second
16,061,923,339 cpu-clock # 16.0 CPUs CPUs_utilized
43 cpu-migrations # 2.7 migrations/sec migrations_per_second
5,645 page-faults # 351.5 faults/sec page_faults_per_second
5,708,413 branch-misses # 1.4 % branch_miss_rate (88.83%)
429,978,120 branches # 26.8 K/sec branch_frequency (88.85%)
1,626,915,897 cpu-cycles # 0.1 GHz cycles_frequency (88.84%)
2,556,805,534 instructions # 1.5 instructions insn_per_cycle (88.86%)
TopdownL1 # 20.1 % tma_backend_bound
# 40.5 % tma_bad_speculation (88.90%)
# 17.2 % tma_frontend_bound (78.05%)
# 22.2 % tma_retiring (88.89%)

1.002994394 seconds time elapsed
```

Having the metrics in json brings greater uniformity, allows events to
be shared by metrics, and it also allows descriptions like:
```
$ perf list cs_per_second
...
cs_per_second
[Context switches per CPU second]
```

A thorn in the side of doing this work was that the hard coded metrics
were used by perf script with '-F metric'. This functionality didn't
work for me (I was testing `perf record -e instructions,cycles`
with/without leader sampling and then `perf script -F metric` but saw
nothing but empty lines) but anyway I decided to fix it to the best of
my ability in this series. So the script side counters were removed
and the regular ones associated with the evsel used. The json metrics
were all searched looking for ones that have a subset of events
matching those in the perf script session, and all metrics are
printed. This is kind of weird as the counters are being set by the
period of samples, but I carried the behavior forward. I suspect there
needs to be follow up work to make this better, but what is in the
series is superior to what is currently in the tree. Follow up work
could include finding metrics for the machine in the perf.data rather
than using the host, allowing multiple metrics even if the metric ids
of the events differ, fixing pre-existing `perf stat record/report`
issues, etc.

There is a lot of stat tests that, for example, assume '-e
instructions,cycles' will produce an IPC metric. These things needed
tidying as now the metric must be explicitly asked for and when doing
this ones using software events were preferred to increase
compatibility. As the test updates were numerous they are distinct to
the patches updating the functionality causing periods in the series
where not all tests are passing. If this is undesirable the test fixes
can be squashed into the functionality updates, but this will be kind
of messy, especially as at some points in the series both the old
metrics and the new metrics will be displayed.

v3: Rebase resolving merge conflicts in
tools/perf/pmu-events/empty-pmu-events.c by just regenerating it
(Dapeng Mi).

v2: Drop merged patches, add json to document target_cpu/core_wide and
example to "Add care to picking the evsel for displaying a metric"
commit message (Namhyung).
https://lore.kernel.org/lkml/20251106231508.448793-1-irogers@google.com/

v1: https://lore.kernel.org/lkml/20251024175857.808401-1-irogers@google.com/

Ian Rogers (18):
perf metricgroup: Add care to picking the evsel for displaying a
metric
perf expr: Add #target_cpu literal
perf jevents: Add set of common metrics based on default ones
perf jevents: Add metric DefaultShowEvents
perf stat: Add detail -d,-dd,-ddd metrics
perf script: Change metric format to use json metrics
perf stat: Remove hard coded shadow metrics
perf stat: Fix default metricgroup display on hybrid
perf stat: Sort default events/metrics
perf stat: Remove "unit" workarounds for metric-only
perf test stat+json: Improve metric-only testing
perf test stat: Ignore failures in Default[234] metricgroups
perf test stat: Update std_output testing metric expectations
perf test metrics: Update all metrics for possibly failing default
metrics
perf test stat: Update shadow test to use metrics
perf test stat: Update test expectations and events
perf test stat csv: Update test expectations and events
perf tool_pmu: Make core_wide and target_cpu json events

tools/perf/builtin-script.c | 238 ++++++++++-
tools/perf/builtin-stat.c | 154 ++-----
.../arch/common/common/metrics.json | 151 +++++++
.../pmu-events/arch/common/common/tool.json | 12 +
tools/perf/pmu-events/empty-pmu-events.c | 229 ++++++----
tools/perf/pmu-events/jevents.py | 28 +-
tools/perf/pmu-events/pmu-events.h | 2 +
.../tests/shell/lib/perf_json_output_lint.py | 4 +-
tools/perf/tests/shell/lib/stat_output.sh | 2 +-
tools/perf/tests/shell/stat+csv_output.sh | 2 +-
tools/perf/tests/shell/stat+json_output.sh | 2 +-
tools/perf/tests/shell/stat+shadow_stat.sh | 4 +-
tools/perf/tests/shell/stat+std_output.sh | 4 +-
tools/perf/tests/shell/stat.sh | 6 +-
.../perf/tests/shell/stat_all_metricgroups.sh | 3 +
tools/perf/tests/shell/stat_all_metrics.sh | 7 +-
tools/perf/util/evsel.h | 1 +
tools/perf/util/expr.c | 8 +-
tools/perf/util/metricgroup.c | 92 +++-
tools/perf/util/stat-display.c | 55 +--
tools/perf/util/stat-shadow.c | 404 +-----------------
tools/perf/util/stat.h | 2 +-
tools/perf/util/tool_pmu.c | 24 +-
tools/perf/util/tool_pmu.h | 9 +-
24 files changed, 756 insertions(+), 687 deletions(-)
create mode 100644 tools/perf/pmu-events/arch/common/common/metrics.json

--
2.51.2.1041.gc1ab5b90ca-goog