Re: [PATCH] perf jevents: return potentially empty metrics table

[Namhyung Kim <namhyung@kernel.org>]

Hello,

On Mon, Jul 01, 2024 at 07:19:55PM +0200, Lucas Stach wrote:
> Hi,
> 
> has this patch fallen through the cracks? It fixes a functional
> regression where the DDR controller metrics are completely unavailable
> on all i.MX8M* systems and thus would be nice if someone could have a
> look.
> 
> Regards,
> Lucas
> 
> Am Freitag, dem 31.05.2024 um 21:44 +0200 schrieb Lucas Stach:
> > Don't return NULL when a empty (num_pmus = 0) metrics table is encountered,
> > as this causes many of the users to bail out, which will skip matching any
> > potentially existing sys metrics later on. Instead return the empty table
> > which will be handled properly by the iterators and allows matching to
> > continue.
> > 
> > This fixes metrics reporting on systems where only the sys, but not the
> > core PMUs have metrics defined.
> > 
> > Fixes: f20c15d13f01 ("perf pmu-events: Remember the perf_events_map for a PMU")
> > Signed-off-by: Lucas Stach <l.stach@pengutronix.de>

Looks ok to me.  Ian?

Thanks,
Namhyung


> > ---
> >  tools/perf/pmu-events/jevents.py | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/pmu-events/jevents.py b/tools/perf/pmu-events/jevents.py
> > index e42efc16723e..0a1ed9ee1429 100755
> > --- a/tools/perf/pmu-events/jevents.py
> > +++ b/tools/perf/pmu-events/jevents.py
> > @@ -1081,7 +1081,7 @@ const struct pmu_metrics_table *perf_pmu__find_metrics_table(struct perf_pmu *pm
> >          if (!map)
> >                  return NULL;
> >  
> > -        if (!pmu)
> > +        if (!pmu || !map->metric_table.num_pmus)
> >                  return &map->metric_table;
> >  
> >          for (size_t i = 0; i < map->metric_table.num_pmus; i++) {
>