Re: [PATCH v1 07/14] perf arm-spe/cs-etm: Directly iterate CPU maps

[Ian Rogers]

On Tue, Dec 12, 2023 at 6:36 AM James Clark <james.clark@xxxxxxx> wrote:
>
>
>
> On 12/12/2023 14:17, James Clark wrote:
> >
> >
> > On 29/11/2023 06:02, Ian Rogers wrote:
> >> Rather than iterate all CPUs and see if they are in CPU maps, directly
> >> iterate the CPU map. Similarly make use of the intersect
> >> function. Switch perf_cpu_map__has_any_cpu_or_is_empty to more
> >> appropriate alternatives.
> >>
> >> Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
> >> ---
> >>  tools/perf/arch/arm/util/cs-etm.c    | 77 ++++++++++++----------------
> >>  tools/perf/arch/arm64/util/arm-spe.c |  4 +-
> >>  2 files changed, 34 insertions(+), 47 deletions(-)
> >>
> >> diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
> >> index 77e6663c1703..a68a72f2f668 100644
> >> --- a/tools/perf/arch/arm/util/cs-etm.c
> >> +++ b/tools/perf/arch/arm/util/cs-etm.c
> >> @@ -197,38 +197,32 @@ static int cs_etm_validate_timestamp(struct auxtrace_record *itr,
> >>  static int cs_etm_validate_config(struct auxtrace_record *itr,
> >>                                struct evsel *evsel)
> >>  {
> >> -    int i, err = -EINVAL;
> >> +    int idx, err = -EINVAL;
> >>      struct perf_cpu_map *event_cpus = evsel->evlist->core.user_requested_cpus;
> >>      struct perf_cpu_map *online_cpus = perf_cpu_map__new_online_cpus();
> >> +    struct perf_cpu_map *intersect_cpus = perf_cpu_map__intersect(event_cpus, online_cpus);
> >> +    struct perf_cpu cpu;
> >>
> >> -    /* Set option of each CPU we have */
> >> -    for (i = 0; i < cpu__max_cpu().cpu; i++) {
> >> -            struct perf_cpu cpu = { .cpu = i, };
> >> -
> >> -            /*
> >> -             * In per-cpu case, do the validation for CPUs to work with.
> >> -             * In per-thread case, the CPU map is empty.  Since the traced
> >> -             * program can run on any CPUs in this case, thus don't skip
> >> -             * validation.
> >> -             */
> >> -            if (!perf_cpu_map__has_any_cpu_or_is_empty(event_cpus) &&
> >> -                !perf_cpu_map__has(event_cpus, cpu))
> >> -                    continue;
> >
> > This has broken validation for per-thread sessions.
> > perf_cpu_map__intersect() doesn't seem to be able to handle the case
> > where an 'any' map intersected with an online map should return the
> > online map. Or at least it should for this to work, and it seems to make
> > sense for it to work that way.
> >
> > At least that was my initial impression, but I only debugged it and saw
> > that the loop is now skipped entirely.
> >
> >> -
> >> -            if (!perf_cpu_map__has(online_cpus, cpu))
> >> -                    continue;
> >> +    perf_cpu_map__put(online_cpus);
> >>
> >> -            err = cs_etm_validate_context_id(itr, evsel, i);
> >> +    /*
> >> +     * Set option of each CPU we have. In per-cpu case, do the validation
> >> +     * for CPUs to work with.  In per-thread case, the CPU map is empty.
> >> +     * Since the traced program can run on any CPUs in this case, thus don't
> >> +     * skip validation.
> >> +     */
> >> +    perf_cpu_map__for_each_cpu_skip_any(cpu, idx, intersect_cpus) {
> >> +            err = cs_etm_validate_context_id(itr, evsel, cpu.cpu);
> >>              if (err)
> >>                      goto out;
> >> -            err = cs_etm_validate_timestamp(itr, evsel, i);
> >> +            err = cs_etm_validate_timestamp(itr, evsel, idx);

I think this is an error, idx shouldn't be used here, cpu.cpu should.

> >>              if (err)
> >>                      goto out;
> >>      }
> >>
> >>      err = 0;
> >>  out:
> >> -    perf_cpu_map__put(online_cpus);
> >> +    perf_cpu_map__put(intersect_cpus);
> >>      return err;
> >>  }
> >>
> >> @@ -435,7 +429,7 @@ static int cs_etm_recording_options(struct auxtrace_record *itr,
> >>       * Also the case of per-cpu mmaps, need the contextID in order to be notified
> >>       * when a context switch happened.
> >>       */
> >> -    if (!perf_cpu_map__has_any_cpu_or_is_empty(cpus)) {
> >> +    if (!perf_cpu_map__is_any_cpu_or_is_empty(cpus)) {
> >>              evsel__set_config_if_unset(cs_etm_pmu, cs_etm_evsel,
> >>                                         "timestamp", 1);
> >>              evsel__set_config_if_unset(cs_etm_pmu, cs_etm_evsel,
> >> @@ -461,7 +455,7 @@ static int cs_etm_recording_options(struct auxtrace_record *itr,
> >>      evsel->core.attr.sample_period = 1;
> >>
> >>      /* In per-cpu case, always need the time of mmap events etc */
> >> -    if (!perf_cpu_map__has_any_cpu_or_is_empty(cpus))
> >> +    if (!perf_cpu_map__is_any_cpu_or_is_empty(cpus))
> >>              evsel__set_sample_bit(evsel, TIME);
> >>
> >>      err = cs_etm_validate_config(itr, cs_etm_evsel);
> >> @@ -533,38 +527,32 @@ static size_t
> >>  cs_etm_info_priv_size(struct auxtrace_record *itr __maybe_unused,
> >>                    struct evlist *evlist __maybe_unused)
> >>  {
> >> -    int i;
> >> +    int idx;
> >>      int etmv3 = 0, etmv4 = 0, ete = 0;
> >>      struct perf_cpu_map *event_cpus = evlist->core.user_requested_cpus;
> >>      struct perf_cpu_map *online_cpus = perf_cpu_map__new_online_cpus();
> >> +    struct perf_cpu cpu;
> >>
> >>      /* cpu map is not empty, we have specific CPUs to work with */
> >> -    if (!perf_cpu_map__has_any_cpu_or_is_empty(event_cpus)) {
> >> -            for (i = 0; i < cpu__max_cpu().cpu; i++) {
> >> -                    struct perf_cpu cpu = { .cpu = i, };
> >> -
> >> -                    if (!perf_cpu_map__has(event_cpus, cpu) ||
> >> -                        !perf_cpu_map__has(online_cpus, cpu))
> >> -                            continue;
> >> +    if (!perf_cpu_map__is_empty(event_cpus)) {
> >> +            struct perf_cpu_map *intersect_cpus =
> >> +                    perf_cpu_map__intersect(event_cpus, online_cpus);
> >>
> >> -                    if (cs_etm_is_ete(itr, i))
> >> +            perf_cpu_map__for_each_cpu_skip_any(cpu, idx, intersect_cpus) {
> >> +                    if (cs_etm_is_ete(itr, cpu.cpu))
>
> Similar problem here. For a per-thread session, the CPU map is not empty
> (it's an 'any' map, presumably length 1), so it comes into this first
> if, rather than the else below which is for the 'any' scenario.
>
> Then the intersect with online CPUs results in an empty map, so no CPU
> metadata is recorded, then the session fails.
>
> If you made the intersect work in the way I mentioned above we could
> also delete the else below, because that's just another way to convert
> from 'any' to 'all online'.

I don't think intersect of "all online" with an "any CPU" should
return "all online" as these would be quite different options to
perf_event_open. Let's see if the issue above fixes this change
otherwise I can revert it to a more mechanical translation of the
existing code into the new APIs.

Thanks,
Ian

> >>                              ete++;
> >> -                    else if (cs_etm_is_etmv4(itr, i))
> >> +                    else if (cs_etm_is_etmv4(itr, cpu.cpu))
> >>                              etmv4++;
> >>                      else
> >>                              etmv3++;
> >>              }
> >> +            perf_cpu_map__put(intersect_cpus);
> >>      } else {
> >>              /* get configuration for all CPUs in the system */
> >> -            for (i = 0; i < cpu__max_cpu().cpu; i++) {
> >> -                    struct perf_cpu cpu = { .cpu = i, };
> >> -
> >> -                    if (!perf_cpu_map__has(online_cpus, cpu))
> >> -                            continue;
> >> -
> >> -                    if (cs_etm_is_ete(itr, i))
> >> +            perf_cpu_map__for_each_cpu(cpu, idx, online_cpus) {
> >> +                    if (cs_etm_is_ete(itr, cpu.cpu))
> >>                              ete++;
> >> -                    else if (cs_etm_is_etmv4(itr, i))
> >> +                    else if (cs_etm_is_etmv4(itr, cpu.cpu))
> >>                              etmv4++;
> >>                      else
> >>                              etmv3++;
> >> @@ -814,15 +802,14 @@ static int cs_etm_info_fill(struct auxtrace_record *itr,
> >>              return -EINVAL;
> >>
> >>      /* If the cpu_map is empty all online CPUs are involved */
> >> -    if (perf_cpu_map__has_any_cpu_or_is_empty(event_cpus)) {
> >> +    if (perf_cpu_map__is_empty(event_cpus)) {
> >>              cpu_map = online_cpus;
> >>      } else {
> >>              /* Make sure all specified CPUs are online */
> >> -            for (i = 0; i < perf_cpu_map__nr(event_cpus); i++) {
> >> -                    struct perf_cpu cpu = { .cpu = i, };
> >> +            struct perf_cpu cpu;
> >>
> >> -                    if (perf_cpu_map__has(event_cpus, cpu) &&
> >> -                        !perf_cpu_map__has(online_cpus, cpu))
> >> +            perf_cpu_map__for_each_cpu(cpu, i, event_cpus) {
> >> +                    if (!perf_cpu_map__has(online_cpus, cpu))
> >>                              return -EINVAL;
> >>              }
> >>
> >> diff --git a/tools/perf/arch/arm64/util/arm-spe.c b/tools/perf/arch/arm64/util/arm-spe.c
> >> index 51ccbfd3d246..0b52e67edb3b 100644
> >> --- a/tools/perf/arch/arm64/util/arm-spe.c
> >> +++ b/tools/perf/arch/arm64/util/arm-spe.c
> >> @@ -232,7 +232,7 @@ static int arm_spe_recording_options(struct auxtrace_record *itr,
> >>       * In the case of per-cpu mmaps, sample CPU for AUX event;
> >>       * also enable the timestamp tracing for samples correlation.
> >>       */
> >> -    if (!perf_cpu_map__has_any_cpu_or_is_empty(cpus)) {
> >> +    if (!perf_cpu_map__is_any_cpu_or_is_empty(cpus)) {
> >>              evsel__set_sample_bit(arm_spe_evsel, CPU);
> >>              evsel__set_config_if_unset(arm_spe_pmu, arm_spe_evsel,
> >>                                         "ts_enable", 1);
> >> @@ -265,7 +265,7 @@ static int arm_spe_recording_options(struct auxtrace_record *itr,
> >>      tracking_evsel->core.attr.sample_period = 1;
> >>
> >>      /* In per-cpu case, always need the time of mmap events etc */
> >> -    if (!perf_cpu_map__has_any_cpu_or_is_empty(cpus)) {
> >> +    if (!perf_cpu_map__is_any_cpu_or_is_empty(cpus)) {
> >>              evsel__set_sample_bit(tracking_evsel, TIME);
> >>              evsel__set_sample_bit(tracking_evsel, CPU);
> >>