[PATCH] perf evlist: Print hint for group

[PATCH] perf evlist: Print hint for group

[kan.liang]

From: Kan Liang <kan.liang@linux.intel.com>

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@kernel.org>
Closes: https://lore.kernel.org/lkml/ZttgvduaKsVn1r4p@x1/
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
---
 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

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

[Ian Rogers]

On Sun, Sep 8, 2024 at 1:28 PM <kan.liang@linux.intel.com> wrote:
>
> From: Kan Liang <kan.liang@linux.intel.com>
>
> 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@kernel.org>
> Closes: https://lore.kernel.org/lkml/ZttgvduaKsVn1r4p@x1/
> Signed-off-by: Kan Liang <kan.liang@linux.intel.com>

Reviewed-by: Ian Rogers <irogers@google.com>

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
>

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

[Arnaldo Carvalho de Melo]

On Mon, Sep 09, 2024 at 09:54:57AM -0700, Ian Rogers wrote:
> On Sun, Sep 8, 2024 at 1:28 PM <kan.liang@linux.intel.com> wrote:
> >
> > From: Kan Liang <kan.liang@linux.intel.com>
> >
> > 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@kernel.org>
> > Closes: https://lore.kernel.org/lkml/ZttgvduaKsVn1r4p@x1/
> > Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
> 
> Reviewed-by: Ian Rogers <irogers@google.com>

Thanks, tested:

    Committer testing:
    
    So for a perf.data file _with_ a group:
    
      root@number:~# perf evlist -g
      {cpu_core/branch-instructions/pp,cpu_core/branches/}
      dummy:u
      root@number:~# perf evlist
      cpu_core/branch-instructions/pp
      cpu_core/branches/
      dummy:u
      # Tip: use 'perf evlist -g' to show group information
      root@number:~#
    
    Then for something _without_ a group, no hint:
    
      root@number:~# perf record ls
      <SNIP>
      [ perf record: Woken up 1 times to write data ]
      [ perf record: Captured and wrote 0.035 MB perf.data (7 samples) ]
      root@number:~# perf evlist
      cpu_atom/cycles/P
      cpu_core/cycles/P
      dummy:u
      root@number:~#
    
    No suggestion, good.
    
    Suggested-by: Arnaldo Carvalho de Melo <acme@kernel.org>
    Reviewed-by: Ian Rogers <irogers@google.com>
    Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
    Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>


Applied.

- Arnaldo