Re: [PATCH] perf topdown: Don't require config1==0 for a slots event

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Wed, Sep 16, 2026 at 02:22:45PM -0700, Ian Rogers wrote:
> On Wed, Sep 16, 2026 at 1:37 PM Zide Chen <zide.chen@intel.com> wrote:
> >
> > arch_is_topdown_slots() requires config1 == 0, so it misidentified
> > "cpu/slots,metrics_clear=1/" as not being the slots event, and an
> > additional slots event gets inserted, which fails event scheduling
> > since the group now needs two fixed counter 3.
> >
> >   $ perf stat -e "{cpu/slots,metrics_clear=1/,cpu/topdown-retiring/}" -- sleep 1
> >   WARNING: events were regrouped to match PMUs
> >        <not counted>      slots
> >      <not supported>      cpu/slots,metrics_clear=1/
> >        <not counted>      cpu/topdown-retiring/
> >
> > Drop the config1 == 0 check from arch_is_topdown_slots(). This is
> > safe: config1 has no bearing on the event's identifying config value
> > (TOPDOWN_SLOTS, 0x0400).
> >
> > The attr.type == PERF_TYPE_RAW check is what actually matters: only the
> > core PMU is registered with PERF_TYPE_RAW, and on x86, 0x400 is
> > guaranteed to be slots event on core CPU.
> >
> > arch_is_topdown_metrics() keeps its own config1 == 0 check, since
> > genuine metrics events have no "metrics_clear" and config1 remains 0.
> >
> > Add a test verifying that an explicit "slots,metrics_clear=1" event in
> > a group does not trigger an extra slots event injection.
> >
> > Fixes: 5b546de9cc17 ("perf topdown: Use attribute to see an event is a topdown metic or slots")
> > Signed-off-by: Zide Chen <zide.chen@intel.com>
> 
> Reviewed-by: Ian Rogers <irogers@google.com>
> 
> Note, there's a Sashiko warning about a potentially missing #include
> for musl compatibility that maybe you or Arnaldo could address.

Merging, will look add address that comment,

Thanks,

- Arnaldo
 
> Thanks,
> Ian
> 
> > ---
> >  tools/perf/arch/x86/tests/topdown.c | 28 ++++++++++++++++++++++++++++
> >  tools/perf/arch/x86/util/topdown.c  |  3 +--
> >  2 files changed, 29 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/perf/arch/x86/tests/topdown.c b/tools/perf/arch/x86/tests/topdown.c
> > index 2b6f47ce4932..b1ce9f83db00 100644
> > --- a/tools/perf/arch/x86/tests/topdown.c
> > +++ b/tools/perf/arch/x86/tests/topdown.c
> > @@ -229,10 +229,38 @@ static int test__x86_topdown_slots_injection(struct test_suite *test __maybe_unu
> >         return TEST_OK;
> >  }
> >
> > +/*
> > + * An explicit "slots,metrics_clear=1" event is still the slots event and
> > + * must not cause an extra slots event to be injected into the group.
> > + */
> > +static int test__x86_topdown_metrics_clear(struct test_suite *test __maybe_unused,
> > +                                          int subtest __maybe_unused)
> > +{
> > +       struct perf_pmu *pmu;
> > +       char event_str[128];
> > +       int ret;
> > +
> > +       if (!topdown_sys_has_perf_metrics())
> > +               return TEST_OK;
> > +
> > +       pmu = perf_pmus__find_by_type(PERF_TYPE_RAW);
> > +       if (!pmu || !perf_pmu__has_format(pmu, "metrics_clear"))
> > +               return TEST_OK;
> > +
> > +       snprintf(event_str, sizeof(event_str),
> > +                "{%s/slots,metrics_clear=1/,%s/topdown-retiring/}",
> > +                pmu->name, pmu->name);
> > +       ret = test_sort(event_str, 2, 1);
> > +       TEST_ASSERT_EQUAL("explicit metrics_clear slots event isn't duplicated", ret, TEST_OK);
> > +
> > +       return TEST_OK;
> > +}
> > +
> >  static struct test_case x86_topdown_tests[] = {
> >         TEST_CASE("topdown events", x86_topdown),
> >         TEST_CASE("topdown sorting", x86_topdown_sorting),
> >         TEST_CASE("topdown slots injection", x86_topdown_slots_injection),
> > +       TEST_CASE("topdown metrics_clear no extra slots", x86_topdown_metrics_clear),
> >         { .name = NULL, }
> >  };
> >
> > diff --git a/tools/perf/arch/x86/util/topdown.c b/tools/perf/arch/x86/util/topdown.c
> > index bafd285119d7..64bc64e335a2 100644
> > --- a/tools/perf/arch/x86/util/topdown.c
> > +++ b/tools/perf/arch/x86/util/topdown.c
> > @@ -37,8 +37,7 @@ bool topdown_sys_has_perf_metrics(void)
> >  bool arch_is_topdown_slots(const struct evsel *evsel)
> >  {
> >         return evsel->core.attr.type == PERF_TYPE_RAW &&
> > -              evsel->core.attr.config == TOPDOWN_SLOTS &&
> > -              evsel->core.attr.config1 == 0;
> > +              evsel->core.attr.config == TOPDOWN_SLOTS;
> >  }
> >
> >  bool arch_is_topdown_metrics(const struct evsel *evsel)
> > --
> > 2.55.0
> >