Messages in this thread | | | Date | Mon, 20 Jul 2020 11:17:48 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH v2] perf evsel: Don't set sample_regs_intr/sample_regs_user for dummy event |
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On Mon, Jul 20, 2020 at 09:00:13AM +0800, Jin Yao wrote: > Since commit 0a892c1c9472 ("perf record: Add dummy event during system wide synthesis"), > a dummy event is added to capture mmaps. > > But if we run perf-record as, > > # perf record -e cycles:p -IXMM0 -a -- sleep 1 > Error: > dummy:HG: PMU Hardware doesn't support sampling/overflow-interrupts. Try 'perf stat' > > The issue is, if we enable the extended regs (-IXMM0), but the > pmu->capabilities is not set with PERF_PMU_CAP_EXTENDED_REGS, the kernel > will return -EOPNOTSUPP error. > > See following code: > > /* in kernel/events/core.c */ > static int perf_try_init_event(struct pmu *pmu, struct perf_event *event) > > { > .... > if (!(pmu->capabilities & PERF_PMU_CAP_EXTENDED_REGS) && > has_extended_regs(event)) > ret = -EOPNOTSUPP; > .... > } > > For software dummy event, the PMU should not be set with > PERF_PMU_CAP_EXTENDED_REGS. But unfortunately now, the dummy > event has possibility to be set with PERF_REG_EXTENDED_MASK bit. > > In evsel__config, /* tools/perf/util/evsel.c */ > > if (opts->sample_intr_regs) { > attr->sample_regs_intr = opts->sample_intr_regs; > } > > If we use -IXMM0, the attr>sample_regs_intr will be set with > PERF_REG_EXTENDED_MASK bit. > > It doesn't make sense to set attr->sample_regs_intr for a > software dummy event. > > This patch adds dummy event checking before setting > attr->sample_regs_intr and attr->sample_regs_user. > > After: > # ./perf record -e cycles:p -IXMM0 -a -- sleep 1 > [ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.413 MB perf.data (45 samples) ] > > v2: > --- > Rebase to perf/core > > Fixes: 0a892c1c9472 ("perf record: Add dummy event during system wide synthesis") > Signed-off-by: Jin Yao <yao.jin@linux.intel.com> > --- > tools/perf/util/evsel.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c > index 9aa51a65593d..11794d3b7879 100644 > --- a/tools/perf/util/evsel.c > +++ b/tools/perf/util/evsel.c > @@ -1014,12 +1014,14 @@ void evsel__config(struct evsel *evsel, struct record_opts *opts, > if (callchain && callchain->enabled && !evsel->no_aux_samples) > evsel__config_callchain(evsel, opts, callchain); > > - if (opts->sample_intr_regs && !evsel->no_aux_samples) { > + if (opts->sample_intr_regs && !evsel->no_aux_samples && > + !evsel__is_dummy_event(evsel)) {
hum, I thought it'd look something like this:
if (opts->sample_intr_regs && (!evsel->no_aux_samples || !evsel__is_dummy_event(evsel))
but I'm not sure how no_aux_samples flag works exactly.. so it might be correct.. just making sure ;-)
cc-ing Adrian
jirka
> attr->sample_regs_intr = opts->sample_intr_regs; > evsel__set_sample_bit(evsel, REGS_INTR); > } > > - if (opts->sample_user_regs && !evsel->no_aux_samples) { > + if (opts->sample_user_regs && !evsel->no_aux_samples && > + !evsel__is_dummy_event(evsel)) { > attr->sample_regs_user |= opts->sample_user_regs; > evsel__set_sample_bit(evsel, REGS_USER); > } > -- > 2.17.1 >
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