Re: [PATCH v8 15/16] perf python: Add metrics function

[Xu Yang]

Hi Ian,

On Wed, Jul 23, 2025 at 04:22:16PM -0700, Ian Rogers wrote:
> The metrics function returns a list dictionaries describing metrics as
> strings mapping to strings, except for metric groups that are a string
> mapping to a list of strings. For example:
> ```
> >>> import perf
> >>> perf.metrics()[0]
> {'MetricGroup': ['Power'], 'MetricName': 'C10_Pkg_Residency',
>  'PMU': 'default_core', 'MetricExpr': 'cstate_pkg@c10\\-residency@ / TSC',
>  'ScaleUnit': '100%', 'BriefDescription': 'C10 residency percent per package'}
> ```
> 
> Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> ---
>  tools/perf/util/python.c | 83 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 83 insertions(+)
> 
> diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c
> index bee7c8a69bad..a8ba1379cf21 100644
> --- a/tools/perf/util/python.c
> +++ b/tools/perf/util/python.c
> @@ -2073,7 +2073,90 @@ static PyObject *pyrf__parse_metrics(PyObject *self, PyObject *args)
>  	return result;
>  }
>  
> +static PyObject *pyrf__metrics_groups(const struct pmu_metric *pm)
> +{
> +	PyObject *groups = PyList_New(/*len=*/0);
> +	const char *mg = pm->metric_group;
> +
> +	if (!groups)
> +		return NULL;
> +
> +	while (mg) {
> +		PyObject *val = NULL;
> +		const char *sep = strchr(mg, ';');
> +		size_t len = sep ? (size_t)(sep - mg) : strlen(mg);
> +
> +		if (len > 0) {
> +			val = PyUnicode_FromStringAndSize(mg, len);
> +			if (val)
> +				PyList_Append(groups, val);
> +
> +			Py_XDECREF(val);
> +		}
> +		mg = sep ? sep + 1 : NULL;
> +	}
> +	return groups;
> +}
> +
> +static int pyrf__metrics_cb(const struct pmu_metric *pm,
> +			    const struct pmu_metrics_table *table __maybe_unused,
> +			    void *vdata)
> +{
> +	PyObject *py_list = vdata;
> +	PyObject *dict = PyDict_New();
> +	PyObject *key = dict ? PyUnicode_FromString("MetricGroup") : NULL;
> +	PyObject *value = key ? pyrf__metrics_groups(pm) : NULL;
> +
> +	if (!value || PyDict_SetItem(dict, key, value) != 0) {
> +		Py_XDECREF(key);
> +		Py_XDECREF(value);
> +		Py_XDECREF(dict);
> +		return -ENOMEM;
> +	}
> +
> +	if (!add_to_dict(dict, "MetricName", pm->metric_name) ||
> +	    !add_to_dict(dict, "PMU", pm->pmu) ||
> +	    !add_to_dict(dict, "MetricExpr", pm->metric_expr) ||
> +	    !add_to_dict(dict, "MetricThreshold", pm->metric_threshold) ||
> +	    !add_to_dict(dict, "ScaleUnit", pm->unit) ||
> +	    !add_to_dict(dict, "Compat", pm->compat) ||
> +	    !add_to_dict(dict, "BriefDescription", pm->desc) ||
> +	    !add_to_dict(dict, "PublicDescription", pm->long_desc) ||
> +	    PyList_Append(py_list, dict) != 0) {
> +		Py_DECREF(dict);
> +		return -ENOMEM;
> +	}
> +	Py_DECREF(dict);
> +	return 0;
> +}
> +
> +static PyObject *pyrf__metrics(PyObject *self, PyObject *args)
> +{
> +	const struct pmu_metrics_table *table = pmu_metrics_table__find();
> +	PyObject *list = PyList_New(/*len=*/0);
> +	int ret;
> +
> +	if (!list)
> +		return NULL;
> +
> +	ret = pmu_metrics_table__for_each_metric(table, pyrf__metrics_cb, list);
> +	if (ret) {
> +		Py_DECREF(list);
> +		errno = -ret;
> +		PyErr_SetFromErrno(PyExc_OSError);
> +		return NULL;
> +	}

Could the system metric be supported?

I notice that "perf list metric" shows some system metrics, but this python
binding doesn't show these metrics:

root@imx93evk:~/python# perf list metric

List of pre-defined events (to be used in -e or -M):

Metrics:

  imx93_bandwidth_usage.lpddr4x
       [bandwidth usage for lpddr4x evk board]
  imx93_ddr_read.all
       [bytes all masters read from ddr]
  imx93_ddr_write.all
       [bytes all masters write to ddr]

root@imx93evk:~/python# python3
>>> import perf
>>> perf.metrics()
[]
>>>

If I add below code here, it can be shown too.

pmu_for_each_sys_metric(pyrf__metrics_cb, list);

Thanks,
Xu Yang

> +	return list;
> +}
> +
>  static PyMethodDef perf__methods[] = {
> +	{
> +		.ml_name  = "metrics",
> +		.ml_meth  = (PyCFunction) pyrf__metrics,
> +		.ml_flags = METH_NOARGS,
> +		.ml_doc	  = PyDoc_STR(
> +			"Returns a list of metrics represented as string values in dictionaries.")
> +	},
>  	{
>  		.ml_name  = "tracepoint",
>  		.ml_meth  = (PyCFunction) pyrf__tracepoint,
> -- 
> 2.50.0.727.gbf7dc18ff4-goog
>