Re: [PATCH] perf evlist: Print hint for group

[Ian Rogers]

On Sun, Sep 8, 2024 at 1:28 PM <kan.liang@xxxxxxxxxxxxxxx> wrote:
>
> From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
>
> An event group is a critical relationship. There is a -g option that can
> display the relationship. But it's hard for a user to know when should
> this option be applied.
>
> If there is an event group in the perf record, print a hint to suggest
> the user apply the -g to display the group information.
>
> With the patch,
>
>  $perf record -e "{cycles,instructions},instructions" sleep 1
>  [ perf record: Woken up 1 times to write data ]
>  [ perf record: Captured and wrote 0.024 MB perf.data (4 samples) ]
>
>  $perf evlist
>  cycles
>  instructions
>  instructions
>  # Tip: use 'perf evlist -g' to show group information
>
>  $perf evlist -g
>  {cycles,instructions}
>  instructions
>
> Suggested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> Closes: https://lore.kernel.org/lkml/ZttgvduaKsVn1r4p@x1/
> Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>

Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks,
Ian

> ---
>  tools/perf/builtin-evlist.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/builtin-evlist.c b/tools/perf/builtin-evlist.c
> index 818ab21c3f73..a9bd7bbef5a9 100644
> --- a/tools/perf/builtin-evlist.c
> +++ b/tools/perf/builtin-evlist.c
> @@ -36,7 +36,7 @@ static int __cmd_evlist(const char *file_name, struct perf_attr_details *details
>                 .force     = details->force,
>         };
>         struct perf_tool tool;
> -       bool has_tracepoint = false;
> +       bool has_tracepoint = false, has_group = false;
>
>         perf_tool__init(&tool, /*ordered_events=*/false);
>         /* only needed for pipe mode */
> @@ -54,11 +54,17 @@ static int __cmd_evlist(const char *file_name, struct perf_attr_details *details
>
>                 if (pos->core.attr.type == PERF_TYPE_TRACEPOINT)
>                         has_tracepoint = true;
> +
> +               if (!evsel__is_group_leader(pos))
> +                       has_group = true;
>         }
>
>         if (has_tracepoint && !details->trace_fields)
>                 printf("# Tip: use 'perf evlist --trace-fields' to show fields for tracepoint events\n");
>
> +       if (has_group && !details->event_group)
> +               printf("# Tip: use 'perf evlist -g' to show group information\n");
> +
>         perf_session__delete(session);
>         return 0;
>  }
> --
> 2.38.1
>