linux-kernel - Re: [PATCH v2 2/7] perf evlist: Add evlist__findnew_tracking

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Date:   Wed, 19 Jul 2023 19:59:17 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Ian Rogers <irogers@...gle.com>,
        Yang Jihong <yangjihong1@...wei.com>
Cc:     peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...nel.org, namhyung@...nel.org, kan.liang@...ux.intel.com,
        james.clark@....com, tmricht@...ux.ibm.com, ak@...ux.intel.com,
        anshuman.khandual@....com, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2 2/7] perf evlist: Add evlist__findnew_tracking_event()
 helper

On 19/07/23 19:44, Ian Rogers wrote:
> On Fri, Jul 14, 2023 at 8:31 PM Yang Jihong <yangjihong1@...wei.com> wrote:
>>
>> Currently, intel-bts, intel-pt, and arm-spe may add a dummy event for
>> tracking to the evlist. We may need to search for the dummy event for
>> some settings. Therefore, add evlist__findnew_tracking_event() helper.
>>
>> evlist__findnew_tracking_event() also deal with system_wide maps if
>> system_wide is true.
> 
> I'm wondering if we can simplify the naming in the API, we have "dummy
> event" which makes sense as we literally call the event "dummy",
> "sideband" which refers to the kind of samples/events the dummy event
> will record but "tracking" I think tends to get used as a verb rather
> than a noun. So I think evlist__findnew_tracking_event should be
> evlist__findnew_dummy_event.

Except the tracking event has "tracking" set but there can be other dummy
events that do not.

> 
> Thanks,
> Ian
> 
>> Signed-off-by: Yang Jihong <yangjihong1@...wei.com>
>> ---
>>  tools/perf/builtin-record.c | 11 +++--------
>>  tools/perf/util/evlist.c    | 18 ++++++++++++++++++
>>  tools/perf/util/evlist.h    |  1 +
>>  3 files changed, 22 insertions(+), 8 deletions(-)
>>
>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
>> index aec18db7ff23..ca83599cc50c 100644
>> --- a/tools/perf/builtin-record.c
>> +++ b/tools/perf/builtin-record.c
>> @@ -1295,14 +1295,9 @@ static int record__open(struct record *rec)
>>          */
>>         if (opts->target.initial_delay || target__has_cpu(&opts->target) ||
>>             perf_pmus__num_core_pmus() > 1) {
>> -               pos = evlist__get_tracking_event(evlist);
>> -               if (!evsel__is_dummy_event(pos)) {
>> -                       /* Set up dummy event. */
>> -                       if (evlist__add_dummy(evlist))
>> -                               return -ENOMEM;
>> -                       pos = evlist__last(evlist);
>> -                       evlist__set_tracking_event(evlist, pos);
>> -               }
>> +               pos = evlist__findnew_tracking_event(evlist, false);
>> +               if (!pos)
>> +                       return -ENOMEM;
>>
>>                 /*
>>                  * Enable the dummy event when the process is forked for
>> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
>> index 7ef43f72098e..25c3ebe2c2f5 100644
>> --- a/tools/perf/util/evlist.c
>> +++ b/tools/perf/util/evlist.c
>> @@ -1694,6 +1694,24 @@ void evlist__set_tracking_event(struct evlist *evlist, struct evsel *tracking_ev
>>         tracking_evsel->tracking = true;
>>  }
>>
>> +struct evsel *evlist__findnew_tracking_event(struct evlist *evlist, bool system_wide)
>> +{
>> +       struct evsel *evsel;
>> +
>> +       evsel = evlist__get_tracking_event(evlist);
>> +       if (!evsel__is_dummy_event(evsel)) {
>> +               evsel = evlist__add_aux_dummy(evlist, system_wide);
>> +               if (!evsel)
>> +                       return NULL;
>> +
>> +               evlist__set_tracking_event(evlist, evsel);
>> +       } else if (system_wide) {
>> +               perf_evlist__go_system_wide(&evlist->core, &evsel->core);
>> +       }
>> +
>> +       return evsel;
>> +}
>> +
>>  struct evsel *evlist__find_evsel_by_str(struct evlist *evlist, const char *str)
>>  {
>>         struct evsel *evsel;
>> diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
>> index 664c6bf7b3e0..98e7ddb2bd30 100644
>> --- a/tools/perf/util/evlist.h
>> +++ b/tools/perf/util/evlist.h
>> @@ -387,6 +387,7 @@ bool evlist_cpu_iterator__end(const struct evlist_cpu_iterator *evlist_cpu_itr);
>>
>>  struct evsel *evlist__get_tracking_event(struct evlist *evlist);
>>  void evlist__set_tracking_event(struct evlist *evlist, struct evsel *tracking_evsel);
>> +struct evsel *evlist__findnew_tracking_event(struct evlist *evlist, bool system_wide);
>>
>>  struct evsel *evlist__find_evsel_by_str(struct evlist *evlist, const char *str);
>>
>> --
>> 2.30.GIT
>>