Re: [PATCH v3 3/8] perf arm-spe/cs-etm: Directly iterate CPU maps

[Ian Rogers]

On Fri, Feb 16, 2024 at 5:02 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> On Fri, Feb 2, 2024 at 3:41 PM Ian Rogers <irogers@xxxxxxxxxx> 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
> > taking care for when "any" CPU is specified. 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    | 114 ++++++++++++---------------
> >  tools/perf/arch/arm64/util/arm-spe.c |   4 +-
> >  2 files changed, 51 insertions(+), 67 deletions(-)
> >
> > diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
> > index 77e6663c1703..07be32d99805 100644
> > --- a/tools/perf/arch/arm/util/cs-etm.c
> > +++ b/tools/perf/arch/arm/util/cs-etm.c
> > @@ -197,38 +197,37 @@ 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 = 0;
> >         struct perf_cpu_map *event_cpus = evsel->evlist->core.user_requested_cpus;
> > -       struct perf_cpu_map *online_cpus = perf_cpu_map__new_online_cpus();
> > -
> > -       /* Set option of each CPU we have */
> > -       for (i = 0; i < cpu__max_cpu().cpu; i++) {
> > -               struct perf_cpu cpu = { .cpu = i, };
> > +       struct perf_cpu_map *intersect_cpus;
> > +       struct perf_cpu cpu;
> >
> > -               /*
> > -                * 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;
> > +       /*
> > +        * 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 has the "any"
> > +        * CPU value. Since the traced program can run on any CPUs in this case,
> > +        * thus don't skip validation.
> > +        */
> > +       if (!perf_cpu_map__has_any_cpu(event_cpus)) {
> > +               struct perf_cpu_map *online_cpus = perf_cpu_map__new_online_cpus();
> >
> > -               if (!perf_cpu_map__has(online_cpus, cpu))
> > -                       continue;
> > +               intersect_cpus = perf_cpu_map__intersect(event_cpus, online_cpus);
> > +               perf_cpu_map__put(online_cpus);
> > +       } else {
> > +               intersect_cpus = perf_cpu_map__new_online_cpus();
> > +       }
>
> Would it be ok if any of these operations fail?  I believe the
> cpu map functions work well with NULL already.

If the allocation fails then the loop below won't iterate (the map
will be empty). The map is released and not used elsewhere in the
code. An allocation failure here won't cause the code to crash, but
there are other places where the code assumes what the properties of
having done this function are and they won't be working as intended.
It's not uncommon to see ENOMEM to just be abort for this reason.

Thanks,
Ian

> Thanks,
> Namhyung
>
> >
> > -               err = cs_etm_validate_context_id(itr, evsel, i);
> > +       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);
> > +                       break;
> > +
> > +               err = cs_etm_validate_timestamp(itr, evsel, cpu.cpu);
> >                 if (err)
> > -                       goto out;
> > +                       break;
> >         }
> >
> > -       err = 0;
> > -out:
> > -       perf_cpu_map__put(online_cpus);
> > +       perf_cpu_map__put(intersect_cpus);
> >         return err;
> >  }
> >
> > @@ -435,7 +434,7 @@ 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 +460,7 @@ 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);
> > @@ -533,45 +532,31 @@ 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();
> > -
> > -       /* 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, };
> > +       struct perf_cpu_map *intersect_cpus;
> > +       struct perf_cpu cpu;
> >
> > -                       if (!perf_cpu_map__has(event_cpus, cpu) ||
> > -                           !perf_cpu_map__has(online_cpus, cpu))
> > -                               continue;
> > +       if (!perf_cpu_map__has_any_cpu(event_cpus)) {
> > +               /* cpu map is not "any" CPU , we have specific CPUs to work with */
> > +               struct perf_cpu_map *online_cpus = perf_cpu_map__new_online_cpus();
> >
> > -                       if (cs_etm_is_ete(itr, i))
> > -                               ete++;
> > -                       else if (cs_etm_is_etmv4(itr, i))
> > -                               etmv4++;
> > -                       else
> > -                               etmv3++;
> > -               }
> > +               intersect_cpus = perf_cpu_map__intersect(event_cpus, online_cpus);
> > +               perf_cpu_map__put(online_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))
> > -                               ete++;
> > -                       else if (cs_etm_is_etmv4(itr, i))
> > -                               etmv4++;
> > -                       else
> > -                               etmv3++;
> > -               }
> > +               /* Event can be "any" CPU so count all online CPUs. */
> > +               intersect_cpus = perf_cpu_map__new_online_cpus();
> >         }
> > -
> > -       perf_cpu_map__put(online_cpus);
> > +       perf_cpu_map__for_each_cpu_skip_any(cpu, idx, intersect_cpus) {
> > +               if (cs_etm_is_ete(itr, cpu.cpu))
> > +                       ete++;
> > +               else if (cs_etm_is_etmv4(itr, cpu.cpu))
> > +                       etmv4++;
> > +               else
> > +                       etmv3++;
> > +       }
> > +       perf_cpu_map__put(intersect_cpus);
> >
> >         return (CS_ETM_HEADER_SIZE +
> >                (ete   * CS_ETE_PRIV_SIZE) +
> > @@ -813,16 +798,15 @@ static int cs_etm_info_fill(struct auxtrace_record *itr,
> >         if (!session->evlist->core.nr_mmaps)
> >                 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 the cpu_map has the "any" CPU all online CPUs are involved */
> > +       if (perf_cpu_map__has_any_cpu(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);
> >
> > --
> > 2.43.0.594.gd9cf4e227d-goog
> >