Re: [PATCH 2/3] perf stat: Merge event counts from all hybrid PMUs

[Ian Rogers]

On Thu, Apr 21, 2022 at 11:57 PM <zhengjun.xing@xxxxxxxxxxxxxxx> wrote:
>
> From: Zhengjun Xing <zhengjun.xing@xxxxxxxxxxxxxxx>
>
> For hybrid events, by default stat aggregates and reports the event counts
> per pmu.
>
>   # ./perf stat -e cycles -a  sleep 1
>
>    Performance counter stats for 'system wide':
>
>       14,066,877,268      cpu_core/cycles/
>        6,814,443,147      cpu_atom/cycles/
>
>          1.002760625 seconds time elapsed
>
> Sometimes, it's also useful to aggregate event counts from all PMUs.
> Create a new option '--hybrid-merge' to enable that behavior and report
> the counts without PMUs.
>
>   # ./perf stat -e cycles -a --hybrid-merge  sleep 1
>
>    Performance counter stats for 'system wide':
>
>       20,732,982,512      cycles
>
>          1.002776793 seconds time elapsed
>
> Signed-off-by: Zhengjun Xing <zhengjun.xing@xxxxxxxxxxxxxxx>
> Reviewed-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>

This feels related to aggregation, but aggregation is for a single
evsel on a single PMU. What happens if you have both instructions and
cycles with --hybrid-merge? Normally we aggregate all counts for each
CPU into a the two evsels and then compute a metric:
```
$ perf stat -e instructions,cycles /bin/true

 Performance counter stats for '/bin/true':

         1,830,554      instructions              #    1.17  insn per
cycle
         1,561,415      cycles
```
This kind of aggregation behavior may be needed more widely for metrics.

Thanks,
Ian

> ---
>  tools/perf/Documentation/perf-stat.txt | 10 ++++++++++
>  tools/perf/builtin-stat.c              |  2 ++
>  tools/perf/util/stat-display.c         | 17 +++++++++++++++--
>  tools/perf/util/stat.h                 |  1 +
>  4 files changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
> index c06c341e72b9..8d1cde00b8d6 100644
> --- a/tools/perf/Documentation/perf-stat.txt
> +++ b/tools/perf/Documentation/perf-stat.txt
> @@ -454,6 +454,16 @@ Multiple events are created from a single event specification when:
>  2. Aliases, which are listed immediately after the Kernel PMU events
>     by perf list, are used.
>
> +--hybrid-merge::
> +Merge the hybrid event counts from all PMUs.
> +
> +For hybrid events, by default, the stat aggregates and reports the event
> +counts per PMU. But sometimes, it's also useful to aggregate event counts
> +from all PMUs. This option enables that behavior and reports the counts
> +without PMUs.
> +
> +For non-hybrid events, it should be no effect.
> +
>  --smi-cost::
>  Measure SMI cost if msr/aperf/ and msr/smi/ events are supported.
>
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index a96f106dc93a..ea88ac5bed2d 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -1235,6 +1235,8 @@ static struct option stat_options[] = {
>         OPT_SET_UINT('A', "no-aggr", &stat_config.aggr_mode,
>                     "disable CPU count aggregation", AGGR_NONE),
>         OPT_BOOLEAN(0, "no-merge", &stat_config.no_merge, "Do not merge identical named events"),
> +       OPT_BOOLEAN(0, "hybrid-merge", &stat_config.hybrid_merge,
> +                   "Merge identical named hybrid events"),
>         OPT_STRING('x', "field-separator", &stat_config.csv_sep, "separator",
>                    "print counts with custom separator"),
>         OPT_CALLBACK('G', "cgroup", &evsel_list, "name",
> diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
> index 46b3dd134656..d9629a83aa78 100644
> --- a/tools/perf/util/stat-display.c
> +++ b/tools/perf/util/stat-display.c
> @@ -612,6 +612,19 @@ static bool hybrid_uniquify(struct evsel *evsel)
>         return perf_pmu__has_hybrid() && !is_uncore(evsel);
>  }
>
> +static bool hybrid_merge(struct evsel *counter, struct perf_stat_config *config,
> +                        bool check)
> +{
> +       if (hybrid_uniquify(counter)) {
> +               if (check)
> +                       return config && config->hybrid_merge;
> +               else
> +                       return config && !config->hybrid_merge;
> +       }
> +
> +       return false;
> +}
> +
>  static bool collect_data(struct perf_stat_config *config, struct evsel *counter,
>                             void (*cb)(struct perf_stat_config *config, struct evsel *counter, void *data,
>                                        bool first),
> @@ -620,9 +633,9 @@ static bool collect_data(struct perf_stat_config *config, struct evsel *counter,
>         if (counter->merged_stat)
>                 return false;
>         cb(config, counter, data, true);
> -       if (config->no_merge || hybrid_uniquify(counter))
> +       if (config->no_merge || hybrid_merge(counter, config, false))
>                 uniquify_event_name(counter, config);
> -       else if (counter->auto_merge_stats)
> +       else if (counter->auto_merge_stats || hybrid_merge(counter, config, true))
>                 collect_all_aliases(config, counter, cb, data);
>         return true;
>  }
> diff --git a/tools/perf/util/stat.h b/tools/perf/util/stat.h
> index 335d19cc3063..91d989dfeca4 100644
> --- a/tools/perf/util/stat.h
> +++ b/tools/perf/util/stat.h
> @@ -122,6 +122,7 @@ struct perf_stat_config {
>         bool                     ru_display;
>         bool                     big_num;
>         bool                     no_merge;
> +       bool                     hybrid_merge;
>         bool                     walltime_run_table;
>         bool                     all_kernel;
>         bool                     all_user;
> --
> 2.25.1
>