linux-kernel - Re: [PATCH 3/4] perf python: Add evlist close and next methods

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Message-ID: <CAP-5=fX1qodprWrwK7yq2WYZNnLtiEe_rjvw0aJ7gXY2ma+Hzw@mail.gmail.com>
Date: Thu, 1 May 2025 08:49:08 -0700
From: Ian Rogers <irogers@...gle.com>
To: Gautam Menghani <gautam@...ux.ibm.com>
Cc: peterz@...radead.org, mingo@...hat.com, acme@...nel.org, 
	namhyung@...nel.org, mark.rutland@....com, alexander.shishkin@...ux.intel.com, 
	jolsa@...nel.org, adrian.hunter@...el.com, kan.liang@...ux.intel.com, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	maddy@...ux.ibm.com
Subject: Re: [PATCH 3/4] perf python: Add evlist close and next methods

On Thu, May 1, 2025 at 2:37 AM Gautam Menghani <gautam@...ux.ibm.com> wrote:
>
> Add support for the evlist close and next methods. The next method
> enables iterating over the evsels in an evlist.
>
> Signed-off-by: Gautam Menghani <gautam@...ux.ibm.com>
> ---
>  tools/perf/util/python.c | 47 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 47 insertions(+)
>
> diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c
> index 5a4d2c9aaabd..599cb37600f1 100644
> --- a/tools/perf/util/python.c
> +++ b/tools/perf/util/python.c
> @@ -1163,6 +1163,16 @@ static PyObject *pyrf_evlist__open(struct pyrf_evlist *pevlist,
>         return Py_None;
>  }
>
> +static PyObject *pyrf_evlist__close(struct pyrf_evlist *pevlist)
> +{
> +       struct evlist *evlist = &pevlist->evlist;
> +
> +       evlist__close(evlist);
> +
> +       Py_INCREF(Py_None);
> +       return Py_None;
> +}
> +
>  static PyObject *pyrf_evlist__config(struct pyrf_evlist *pevlist)
>  {
>         struct record_opts opts = {
> @@ -1202,6 +1212,31 @@ static PyObject *pyrf_evlist__enable(struct pyrf_evlist *pevlist)
>         return Py_None;
>  }
>
> +static PyObject *pyrf_evlist__next(struct pyrf_evlist *pevlist,
> +                                  PyObject *args, PyObject *kwargs)
> +{
> +       struct evlist *evlist = &pevlist->evlist;
> +       PyObject *py_evsel;
> +       struct perf_evsel *pevsel;
> +       struct evsel *evsel;
> +       struct pyrf_evsel *next_evsel = PyObject_New(struct pyrf_evsel, &pyrf_evsel__type);
> +       static char *kwlist[] = { "evsel", NULL };
> +
> +       if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O", kwlist,
> +                                        &py_evsel))
> +               return NULL;
> +
> +       pevsel = (py_evsel == Py_None) ? NULL : &(((struct pyrf_evsel *)py_evsel)->evsel.core);
> +       pevsel = perf_evlist__next(&(evlist->core), pevsel);
> +       if (pevsel != NULL) {
> +               evsel = container_of(pevsel, struct evsel, core);
> +               next_evsel = container_of(evsel, struct pyrf_evsel, evsel);
> +               return (PyObject *) next_evsel;
> +       }
> +
> +       return Py_None;
> +}
> +

Thanks for this! Have you looked at the existing iteration support?
There's an example here:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/python/tracepoint.py?h=perf-tools-next#n26
```
    for ev in evlist:
        ev.sample_type = ev.sample_type & ~perf.SAMPLE_IP
        ev.read_format = 0
```
In the next patch you have:
```
        evsel = evlist.next(None)
        while evsel != None:
            counts = evsel.read(0, 0)
            print(counts.val, counts.ena, counts.run)
            evsel = evlist.next(evsel)
```
I believe the former looks better. It also isn't clear to me if next
belongs on evlist or evsel.

Thanks,
Ian


>  static PyMethodDef pyrf_evlist__methods[] = {
>         {
>                 .ml_name  = "all_cpus",
> @@ -1221,6 +1256,12 @@ static PyMethodDef pyrf_evlist__methods[] = {
>                 .ml_flags = METH_VARARGS | METH_KEYWORDS,
>                 .ml_doc   = PyDoc_STR("open the file descriptors.")
>         },
> +       {
> +               .ml_name  = "close",
> +               .ml_meth  = (PyCFunction)pyrf_evlist__close,
> +               .ml_flags = METH_NOARGS,
> +               .ml_doc   = PyDoc_STR("close the file descriptors.")
> +       },
>         {
>                 .ml_name  = "poll",
>                 .ml_meth  = (PyCFunction)pyrf_evlist__poll,
> @@ -1263,6 +1304,12 @@ static PyMethodDef pyrf_evlist__methods[] = {
>                 .ml_flags = METH_NOARGS,
>                 .ml_doc   = PyDoc_STR("Enable the evsels in the evlist.")
>         },
> +       {
> +               .ml_name  = "next",
> +               .ml_meth  = (PyCFunction)pyrf_evlist__next,
> +               .ml_flags = METH_VARARGS | METH_KEYWORDS,
> +               .ml_doc   = PyDoc_STR("Return next evsel")
> +       },
>         { .ml_name = NULL, }
>  };
>
> --
> 2.49.0
>