linux-kernel - Re: [PATCH v1] perf metrics: Remove the "No

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Date: Wed, 3 Apr 2024 13:26:35 -0700
From: Ian Rogers <irogers@...gle.com>
To: "Liang, Kan" <kan.liang@...ux.intel.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v1] perf metrics: Remove the "No_group" metric group

On Wed, Apr 3, 2024 at 11:57 AM Liang, Kan <kan.liang@...ux.intel.com> wrote:
>
>
>
> On 2024-04-03 2:31 p.m., Ian Rogers wrote:
> > On Wed, Apr 3, 2024 at 10:59 AM Liang, Kan <kan.liang@...ux.intel.com> wrote:
> >>
> >>
> >>
> >> On 2024-04-03 12:46 p.m., Ian Rogers wrote:
> >>> Rather than place metrics without a metric group in "No_group" place
> >>> them in a a metric group that is their name. Still allow such metrics
> >>> to be selected if "No_group" is passed, this change just impacts perf
> >>> list.
> >>
> >> So it looks like the "No_group" is not completely removed.
> >> They are just not seen in the perf list, but users can still use it via
> >> perf stat -M No_group, right?
> >>
> >> If so, why we want to remove it from perf list? Where can the end user
> >> know which metrics are included in the No_group?
> >>
> >> If the No_group is useless, why not completely remove it?
> >
> > Agreed. For command line argument deprecation we usually keep the
> > option but hide it from help with PARSE_OPT_HIDDEN, so I was trying to
> > follow that pattern albeit that a metric group isn't a command line
> > option it's an option to an option.
> >
>
> Perf list has a deprecated option to show the deprecated events.
> The "No_group" should be a deprecated metrics group.
>
> If so, to follow the same pattern, I think perf list should still
> display the "No_group" with the --deprecated option at least.

Such metrics would be shown twice, once under No_group and once under
a metric group of their name. With deprecated events this isn't the
case, you can only see them with --deprecated. Given we can see the
metric without the No_group grouping, what is being added by having a
No_group grouping? It feels entirely redundant and something we don't
need to advertise.

Thanks,
Ian

> Thanks,
> Kan
>
> > Thanks,
> > Ian
> >
> >> Thanks,
> >> Kan
> >>
> >>>
> >>> Signed-off-by: Ian Rogers <irogers@...gle.com>
> >>> ---
> >>>  tools/perf/util/metricgroup.c | 4 ++--
> >>>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
> >>> index 79ef6095ab28..6ec083af14a1 100644
> >>> --- a/tools/perf/util/metricgroup.c
> >>> +++ b/tools/perf/util/metricgroup.c
> >>> @@ -455,7 +455,7 @@ static int metricgroup__add_to_mep_groups(const struct pmu_metric *pm,
> >>>       const char *g;
> >>>       char *omg, *mg;
> >>>
> >>> -     mg = strdup(pm->metric_group ?: "No_group");
> >>> +     mg = strdup(pm->metric_group ?: pm->metric_name);
> >>>       if (!mg)
> >>>               return -ENOMEM;
> >>>       omg = mg;
> >>> @@ -466,7 +466,7 @@ static int metricgroup__add_to_mep_groups(const struct pmu_metric *pm,
> >>>               if (strlen(g))
> >>>                       me = mep_lookup(groups, g, pm->metric_name);
> >>>               else
> >>> -                     me = mep_lookup(groups, "No_group", pm->metric_name);
> >>> +                     me = mep_lookup(groups, pm->metric_name, pm->metric_name);
> >>>
> >>>               if (me) {
> >>>                       me->metric_desc = pm->desc;