From: Kan Liang kan.liang@linux.intel.com
[ Upstream commit 95035c5e167ae6e740b1ddd30210ae0eaf39a5db ]
'perf record' will error out if both --delay and LBR are applied.
For example:
# perf record -D 1000 -a -e cycles -j any -- sleep 2 Error: dummy:HG: PMU Hardware doesn't support sampling/overflow-interrupts. Try 'perf stat' #
A dummy event is added implicitly for initial delay, which has the same configurations as real sampling events. The dummy event is a software event. If LBR is configured, perf must error out.
The dummy event will only be used to track PERF_RECORD_MMAP while perf waits for the initial delay to enable the real events. The BRANCH_STACK bit can be safely cleared for the dummy event.
After applying the patch:
# perf record -D 1000 -a -e cycles -j any -- sleep 2 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 1.054 MB perf.data (828 samples) ] #
Reported-by: Sunil K Pandey sunil.k.pandey@intel.com Signed-off-by: Kan Liang kan.liang@linux.intel.com Acked-by: Jiri Olsa jolsa@kernel.org Tested-by: Arnaldo Carvalho de Melo acme@redhat.com Cc: Andi Kleen ak@linux.intel.com Cc: Namhyung Kim namhyung@kernel.org Cc: Peter Zijlstra peterz@infradead.org Link: http://lkml.kernel.org/r/1531145722-16404-1-git-send-email-kan.liang@linux.i... Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- tools/perf/util/evsel.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index 226a9245d1db..2227ee92d8e2 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -824,6 +824,12 @@ static void apply_config_terms(struct perf_evsel *evsel, } }
+static bool is_dummy_event(struct perf_evsel *evsel) +{ + return (evsel->attr.type == PERF_TYPE_SOFTWARE) && + (evsel->attr.config == PERF_COUNT_SW_DUMMY); +} + /* * The enable_on_exec/disabled value strategy: * @@ -1054,6 +1060,14 @@ void perf_evsel__config(struct perf_evsel *evsel, struct record_opts *opts, else perf_evsel__reset_sample_bit(evsel, PERIOD); } + + /* + * For initial_delay, a dummy event is added implicitly. + * The software event will trigger -EOPNOTSUPP error out, + * if BRANCH_STACK bit is set. + */ + if (opts->initial_delay && is_dummy_event(evsel)) + perf_evsel__reset_sample_bit(evsel, BRANCH_STACK); }
static int perf_evsel__alloc_fd(struct perf_evsel *evsel, int ncpus, int nthreads)