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' 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/[email protected]/ 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 <[email protected]> --- 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
