linux-kernel - Re: [PATCH] perf: Fix "Track with sched_switch" test by not printing warnings in quiet mode

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Date:   Wed, 12 Oct 2022 09:50:39 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     James Clark <james.clark@....com>
Cc:     linux-perf-users <linux-perf-users@...r.kernel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        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>
Subject: Re: [PATCH] perf: Fix "Track with sched_switch" test by not printing
 warnings in quiet mode

On Wed, Oct 12, 2022 at 4:13 AM James Clark <james.clark@....com> wrote:
>
>
>
> On 12/10/2022 12:10, James Clark wrote:
> > Especially when CONFIG_LOCKDEP and other debug configs are enabled,
> > Perf can print the following warning when running the "Track with
> > sched_switch" test:
>
> Oops got the wrong test name here and in the title. Should be "kernel
> lock contention analysis test"

Could you please resend?

>
> >
> >   Warning:
> >   Processed 1378918 events and lost 4 chunks!
> >
> >   Check IO/CPU overload!
> >
> >   Warning:
> >   Processed 4593325 samples and lost 70.00%!
> >
> > The test already supplies -q to run in quiet mode, so extend quiet mode
> > to perf_stdio__warning() and also ui__warning() for consistency.

I'm not sure if suppressing the warnings with -q is a good thing.
Maybe we need to separate warning/debug messages from the output.

Thanks,
Namhyung


> >
> > This fixes the following failure due to the extra lines counted:
> >
> >   perf test "lock cont" -vvv
> >
> >   82: kernel lock contention analysis test                            :
> >   --- start ---
> >   test child forked, pid 3125
> >   Testing perf lock record and perf lock contention
> >   [Fail] Recorded result count is not 1: 9
> >   test child finished with -1
> >   ---- end ----
> >   kernel lock contention analysis test: FAILED!
> >
> > Fixes: ec685de25b67 ("perf test: Add kernel lock contention test")
> > Cc: Namhyung Kim <namhyung@...nel.org>
> > Signed-off-by: James Clark <james.clark@....com>
> > ---
> >  tools/perf/ui/util.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/tools/perf/ui/util.c b/tools/perf/ui/util.c
> > index 689b27c34246..1d38ddf01b60 100644
> > --- a/tools/perf/ui/util.c
> > +++ b/tools/perf/ui/util.c
> > @@ -15,6 +15,9 @@ static int perf_stdio__error(const char *format, va_list args)
> >
> >  static int perf_stdio__warning(const char *format, va_list args)
> >  {
> > +     if (quiet)
> > +             return 0;
> > +
> >       fprintf(stderr, "Warning:\n");
> >       vfprintf(stderr, format, args);
> >       return 0;
> > @@ -45,6 +48,8 @@ int ui__warning(const char *format, ...)
> >  {
> >       int ret;
> >       va_list args;
> > +     if (quiet)
> > +             return 0;
> >
> >       va_start(args, format);
> >       ret = perf_eops->warning(format, args);