On Tue, May 19, 2020 at 6:54 PM Arnaldo Carvalho de Melo <arnaldo.m...@gmail.com> wrote: > > Em Wed, Apr 22, 2020 at 10:36:15AM -0700, Ian Rogers escreveu: > > 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. > > > > v3 fixes the attr test of test-record-C0 > > v2 fixes the dummy event configuration and a branch stack issue. > > Something I noticed only now is that this ends up in the perf.data file, > and we don't need it at all there, i.e. > > # perf record -I > > I.e. system wide, asking for registers now ends up with: > > [root@quaco ~]# perf record -I > ^C[ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 2.855 MB perf.data (4902 samples) ] > [root@quaco ~]# perf evlist > cycles > dummy:HG > [root@quaco ~]# perf evlist -v > cycles: size: 120, { sample_period, sample_freq }: 4000, sample_type: > IP|TID|TIME|ID|CPU|PERIOD|REGS_INTR, read_format: ID, disabled: 1, inherit: > 1, freq: 1, precise_ip: 3, sample_id_all: 1, exclude_guest: 1, > sample_regs_intr: 0xff0fff > dummy:HG: type: 1, size: 120, config: 0x9, { sample_period, sample_freq }: > 4000, sample_type: IP|TID|TIME|ID|CPU|PERIOD|REGS_INTR, read_format: ID, > inherit: 1, mmap: 1, comm: 1, freq: 1, task: 1, sample_id_all: 1, mmap2: 1, > comm_exec: 1, ksymbol: 1, bpf_event: 1, sample_regs_intr: 0xff0fff > [root@quaco ~]# > > For perf top is ok to reuse the main evlist, as those are not going to > hit the disk, but for 'perf record' it pollutes the perf.data file with > that dummy event. > > This was a problem introduced with initial-delay, that IIRC predates the > side band thread tho, I'll have to think about it, just writing this > down to revisit this, as may raise some eyebrows by now being more > exposed.
Agreed. We've had to adjust some tooling like the protobuf convertor because of this: https://github.com/google/perf_data_converter/pull/88 Thanks, Ian > - Arnaldo > > > Suggested-by: Stephane Eranian <eran...@google.com> > > Signed-off-by: Ian Rogers <irog...@google.com> > > --- > > tools/perf/builtin-record.c | 19 +++++++--- > > tools/perf/tests/attr/system-wide-dummy | 50 +++++++++++++++++++++++++ > > tools/perf/tests/attr/test-record-C0 | 12 +++++- > > tools/perf/util/evsel.c | 5 ++- > > 4 files changed, 78 insertions(+), 8 deletions(-) > > create mode 100644 tools/perf/tests/attr/system-wide-dummy > > > > 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/tests/attr/system-wide-dummy > > b/tools/perf/tests/attr/system-wide-dummy > > new file mode 100644 > > index 000000000000..eba723cc0d38 > > --- /dev/null > > +++ b/tools/perf/tests/attr/system-wide-dummy > > @@ -0,0 +1,50 @@ > > +# Event added by system-wide or CPU perf-record to handle the race of > > +# processes starting while /proc is processed. > > +[event] > > +fd=1 > > +group_fd=-1 > > +cpu=* > > +pid=-1 > > +flags=8 > > +type=1 > > +size=120 > > +config=9 > > +sample_period=4000 > > +sample_type=455 > > +read_format=4 > > +# Event will be enabled right away. > > +disabled=0 > > +inherit=1 > > +pinned=0 > > +exclusive=0 > > +exclude_user=0 > > +exclude_kernel=0 > > +exclude_hv=0 > > +exclude_idle=0 > > +mmap=1 > > +comm=1 > > +freq=1 > > +inherit_stat=0 > > +enable_on_exec=0 > > +task=1 > > +watermark=0 > > +precise_ip=0 > > +mmap_data=0 > > +sample_id_all=1 > > +exclude_host=0 > > +exclude_guest=0 > > +exclude_callchain_kernel=0 > > +exclude_callchain_user=0 > > +mmap2=1 > > +comm_exec=1 > > +context_switch=0 > > +write_backward=0 > > +namespaces=0 > > +use_clockid=0 > > +wakeup_events=0 > > +bp_type=0 > > +config1=0 > > +config2=0 > > +branch_sample_type=0 > > +sample_regs_user=0 > > +sample_stack_user=0 > > diff --git a/tools/perf/tests/attr/test-record-C0 > > b/tools/perf/tests/attr/test-record-C0 > > index 93818054ae20..317730b906dd 100644 > > --- a/tools/perf/tests/attr/test-record-C0 > > +++ b/tools/perf/tests/attr/test-record-C0 > > @@ -9,6 +9,14 @@ cpu=0 > > # no enable on exec for CPU attached > > enable_on_exec=0 > > > > -# PERF_SAMPLE_IP | PERF_SAMPLE_TID PERF_SAMPLE_TIME | # PERF_SAMPLE_PERIOD > > +# PERF_SAMPLE_IP | PERF_SAMPLE_TID | PERF_SAMPLE_TIME | > > +# PERF_SAMPLE_ID | PERF_SAMPLE_PERIOD > > # + PERF_SAMPLE_CPU added by -C 0 > > -sample_type=391 > > +sample_type=455 > > + > > +# Dummy event handles mmaps, comm and task. > > +mmap=0 > > +comm=0 > > +task=0 > > + > > +[event:system-wide-dummy] > > 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); > > } > > > > -- > > 2.26.2.303.gf8c07b1a785-goog > > > > -- > > - Arnaldo