Messages in this thread | | | From | Ian Rogers <> | Date | Sun, 5 Jul 2020 17:47:42 -0700 | Subject | Re: [PATCH] perf evsel: Don't set sample_regs_intr/sample_regs_user for dummy event |
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On Fri, Jul 3, 2020 at 5:31 PM Jin, Yao <yao.jin@linux.intel.com> wrote: > > Hi Jiri, > > On 7/3/2020 7:00 PM, Jiri Olsa wrote: > > On Fri, Jul 03, 2020 at 08:42:15AM +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' > >>
Sorry for the breakage caused by modifying the dummy event. Could we add a test to cover the issue? Perhaps in tools/perf/tests/shell/. Trying to reproduce with a register on my skylakex on a 5.6.14 kernel with:
$ perf record -e cycles:p -IAX -a -- sleep 1
succeeds.
Thanks, Ian
> >> 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 pieces. > >> > >> /* 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 be not set with > >> PERF_PMU_CAP_EXTENDED_REGS. But unfortunately in current code, 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. > >> > >> 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) ] > > > > LGTM, Adrian (cc-ed) just added another check to the same place, > > but it looks like both of them should be there: > > > > https://lore.kernel.org/lkml/20200630133935.11150-2-adrian.hunter@intel.com/ > > > > jirka > > > > Thanks Jiri! Yes, it looks like both of checks should be added here. > > So do I post v2 (just rebase) once Adrian's patch gets merged? > > Thanks > Jin Yao > > >> > >> 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 | 4 ++-- > >> 1 file changed, 2 insertions(+), 2 deletions(-) > >> > >> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c > >> index 96e5171dce41..df3315543e86 100644 > >> --- a/tools/perf/util/evsel.c > >> +++ b/tools/perf/util/evsel.c > >> @@ -1020,12 +1020,12 @@ 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) { > >> + if (opts->sample_intr_regs && !is_dummy_event(evsel)) { > >> attr->sample_regs_intr = opts->sample_intr_regs; > >> evsel__set_sample_bit(evsel, REGS_INTR); > >> } > >> > >> - if (opts->sample_user_regs) { > >> + if (opts->sample_user_regs && !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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