perf python: Add parse_metrics function

Add parse_metrics function that takes a string of metrics and/or
metric groups and returns the evlist containing the events and
metrics.

For example:
```
>>> import perf
>>> perf.parse_metrics("TopdownL1")
evlist([cpu/TOPDOWN.SLOTS/,cpu/topdown-retiring/,cpu/topdown-fe-bound/,
cpu/topdown-be-bound/,cpu/topdown-bad-spec/,cpu/INT_MISC.CLEARS_COUNT/,
cpu/INT_MISC.UOP_DROPPING/])
```

Reviewed-by: Howard Chu <[email protected]>
Signed-off-by: Ian Rogers <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Chun-Tse Shao <[email protected]>
Cc: Collin Funk <[email protected]>
Cc: Dr. David Alan Gilbert <[email protected]>
Cc: Gautam Menghani <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Clark <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Falcon <[email protected]>
Cc: Thomas Richter <[email protected]>
Cc: Tiezhu Yang <[email protected]>
Cc: Weilin Wang <[email protected]>
Cc: Xu Yang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

tools/perf/util/python.c

@@ -1891,6 +1891,40 @@ static PyObject *pyrf__parse_events(PyObject *self, PyObject *args)
 	return result;
 }
 
+static PyObject *pyrf__parse_metrics(PyObject *self, PyObject *args)
+{
+	const char *input;
+	struct evlist evlist = {};
+	PyObject *result;
+	PyObject *pcpus = NULL, *pthreads = NULL;
+	struct perf_cpu_map *cpus;
+	struct perf_thread_map *threads;
+	int ret;
+
+	if (!PyArg_ParseTuple(args, "s|OO", &input, &pcpus, &pthreads))
+		return NULL;
+
+	threads = pthreads ? ((struct pyrf_thread_map *)pthreads)->threads : NULL;
+	cpus = pcpus ? ((struct pyrf_cpu_map *)pcpus)->cpus : NULL;
+
+	evlist__init(&evlist, cpus, threads);
+	ret = metricgroup__parse_groups(&evlist, /*pmu=*/"all", input,
+					/*metric_no_group=*/ false,
+					/*metric_no_merge=*/ false,
+					/*metric_no_threshold=*/ true,
+					/*user_requested_cpu_list=*/ NULL,
+					/*system_wide=*/true,
+					/*hardware_aware_grouping=*/ false);
+	if (ret) {
+		errno = -ret;
+		PyErr_SetFromErrno(PyExc_OSError);
+		return NULL;
+	}
+	result = pyrf_evlist__from_evlist(&evlist);
+	evlist__exit(&evlist);
+	return result;
+}
+
 static PyMethodDef perf__methods[] = {
 	{
 		.ml_name  = "tracepoint",
@@ -1904,6 +1938,13 @@ static PyMethodDef perf__methods[] = {
 		.ml_flags = METH_VARARGS,
 		.ml_doc	  = PyDoc_STR("Parse a string of events and return an evlist.")
 	},
+	{
+		.ml_name  = "parse_metrics",
+		.ml_meth  = (PyCFunction) pyrf__parse_metrics,
+		.ml_flags = METH_VARARGS,
+		.ml_doc	  = PyDoc_STR(
+			"Parse a string of metics or metric groups and return an evlist.")
+	},
 	{
 		.ml_name  = "pmus",
 		.ml_meth  = (PyCFunction) pyrf__pmus,