Re: [PATCH v2] perf record: add dummy event during system wide synthesis
From: Jiri Olsa
Date: Wed Apr 22 2020 - 04:46:47 EST
On Mon, Apr 20, 2020 at 11:11:03PM -0700, Ian Rogers wrote:
> During the processing of /proc during event synthesis new processes may
> start. Add a dummy event if /proc is to be processed, to capture mmaps
> for starting processes. This reuses the existing logic for
> initial-delay.
>
> v2 fixes the dummy event configuration and a branch stack issue.
heya,
it's breaking attr tests for me:
[jolsa@krava perf]$ sudo ./perf test -v 17
17: Setup struct perf_event_attr :
--- start ---
test child forked, pid 1046560
running './tests/attr/test-record-graph-default'
running './tests/attr/test-record-raw'
running './tests/attr/test-record-branch-filter-any'
running './tests/attr/test-record-freq'
running './tests/attr/test-record-branch-any'
running './tests/attr/test-stat-group1'
running './tests/attr/test-record-no-samples'
running './tests/attr/test-record-graph-dwarf'
running './tests/attr/test-stat-C0'
running './tests/attr/test-stat-basic'
running './tests/attr/test-record-group'
running './tests/attr/test-record-branch-filter-k'
running './tests/attr/test-stat-group'
running './tests/attr/test-record-C0'
expected config=0, got 9
expected sample_type=391, got 455
expected disabled=1, got 0
FAILED './tests/attr/test-record-C0' - match failure
test child finished with -1
---- end ----
Setup struct perf_event_attr: FAILED!
jirka
>
> Suggested-by: Stephane Eranian <eranian@xxxxxxxxxx>
> Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> ---
> tools/perf/builtin-record.c | 19 ++++++++++++++-----
> tools/perf/util/evsel.c | 5 ++++-
> 2 files changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 1ab349abe904..8d1e93351298 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -805,19 +805,28 @@ static int record__open(struct record *rec)
> int rc = 0;
>
> /*
> - * For initial_delay we need to add a dummy event so that we can track
> - * PERF_RECORD_MMAP while we wait for the initial delay to enable the
> - * real events, the ones asked by the user.
> + * For initial_delay or system wide, we need to add a dummy event so
> + * that we can track PERF_RECORD_MMAP to cover the delay of waiting or
> + * event synthesis.
> */
> - if (opts->initial_delay) {
> + if (opts->initial_delay || target__has_cpu(&opts->target)) {
> if (perf_evlist__add_dummy(evlist))
> return -ENOMEM;
>
> + /* Disable tracking of mmaps on lead event. */
> pos = evlist__first(evlist);
> pos->tracking = 0;
> + /* Set up dummy event. */
> pos = evlist__last(evlist);
> pos->tracking = 1;
> - pos->core.attr.enable_on_exec = 1;
> + /*
> + * Enable the dummy event when the process is forked for
> + * initial_delay, immediately for system wide.
> + */
> + if (opts->initial_delay)
> + pos->core.attr.enable_on_exec = 1;
> + else
> + pos->immediate = 1;
> }
>
> perf_evlist__config(evlist, opts, &callchain_param);
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 6a571d322bb2..ca8f9533d8f9 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -1163,11 +1163,14 @@ void perf_evsel__config(struct evsel *evsel, struct record_opts *opts,
> }
>
> /*
> + * A dummy event never triggers any actual counter and therefore
> + * cannot be used with branch_stack.
> + *
> * 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))
> + if (is_dummy_event(evsel))
> perf_evsel__reset_sample_bit(evsel, BRANCH_STACK);
> }
>
> --
> 2.26.1.301.g55bc3eb7cb9-goog
>