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

[James Clark <james.clark@arm.com>]

On 17/02/2024 01:33, Ian Rogers wrote:
> On Fri, Feb 16, 2024 at 5:02 PM Namhyung Kim <namhyung@kernel.org> wrote:
>>
>> On Fri, Feb 2, 2024 at 3:41 PM Ian Rogers <irogers@google.com> 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@google.com>
>>> ---
>>>  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
>>

Reviewed-by: James Clark <james.clark@arm.com>

About the out of memory case, I don't really have much preference about
that. I doubt much of the code is tested or resiliant to it and the
behaviour is probably already unpredictable.

>>>
>>> -               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
>>>