linux-kernel - Re: [PATCH 1/1] perf lock info: Display both map and thread by default

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Date: Sun, 12 May 2024 18:41:36 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Nick Forrington <nick.forrington@....com>
Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	"Liang, Kan" <kan.liang@...ux.intel.com>
Subject: Re: [PATCH 1/1] perf lock info: Display both map and thread by default

On Thu, May 9, 2024 at 3:01 AM Nick Forrington <nick.forrington@...com> wrote:
>
> Hello,
>
> On 08/05/2024 22:18, Namhyung Kim wrote:
> > Hello,
> >
> > On Wed, May 8, 2024 at 6:46 AM Nick Forrington <nick.forrington@....com> wrote:
> >> Change "perf lock info" argument handling to:
> >>
> >> Display both map and thread info (rather than an error) when neither are
> >> specified.
> >>
> >> Display both map and thread info (rather than just thread info) when
> >> both are requested.
> >>
> >> Signed-off-by: Nick Forrington <nick.forrington@....com>
> >> ---
> >>   tools/perf/Documentation/perf-lock.txt |  4 ++--
> >>   tools/perf/builtin-lock.c              | 22 +++++++++++++++++-----
> >>   2 files changed, 19 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/tools/perf/Documentation/perf-lock.txt b/tools/perf/Documentation/perf-lock.txt
> >> index f5938d616d75..57a940399de0 100644
> >> --- a/tools/perf/Documentation/perf-lock.txt
> >> +++ b/tools/perf/Documentation/perf-lock.txt
> >> @@ -111,11 +111,11 @@ INFO OPTIONS
> >>
> >>   -t::
> >>   --threads::
> >> -       dump thread list in perf.data
> >> +       dump only the thread list in perf.data
> >>
> >>   -m::
> >>   --map::
> >> -       dump map of lock instances (address:name table)
> >> +       dump only the map of lock instances (address:name table)
> >>
> >>
> >>   CONTENTION OPTIONS
> >> diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
> >> index 230461280e45..d0b8645487ad 100644
> >> --- a/tools/perf/builtin-lock.c
> >> +++ b/tools/perf/builtin-lock.c
> >> @@ -1483,11 +1483,16 @@ static int dump_info(void)
> >>
> >>          if (info_threads)
> >>                  dump_threads();
> >> -       else if (info_map)
> >> +
> >> +       if (info_map) {
> >> +               if (info_threads)
> >> +                       fputc('\n', lock_output);
> > it seems you need pr_info("\n").  Where does lock_output come from?
>
>
> It's a static FILE* that defaults to stderr.

Oh, right.  I somehow confused this with perf sched. ;-p

>
>
> It's used by dump_threads and dump_map (via fprintf), so I think it
> makes sense to use it for the output spacing between them?
>
> >
> >
> >>                  dump_map();
> >> -       else {
> >> +       }
> >> +
> >> +       if (!info_threads && !info_map) {
> >>                  rc = -1;
> >> -               pr_err("Unknown type of information\n");
> >> +               pr_err("No lock info specified\n");
> >>          }
> > I think we can remove this block now.
>
>
> The original error looked like a function input sanity check (rather
> than for handling user input), so I kept it (even if it should no longer
> be possible for a user to trigger it).
>
>
> Although I can remove it (or move it to the start of the function) if
> you prefer.

Yep, I think we can just remove it.

Thanks,
Namhyung