linux-kernel - Re: [PATCH v1 3/8] perf stat: Display "none" for NaN with metric only json

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Message-ID: <CAP-5=fW0QQSwEAxK11bt8a8uPA+M=PyOUb=Y2+se+15peDqwPQ@mail.gmail.com>
Date: Tue, 8 Oct 2024 16:38:35 -0700
From: Ian Rogers <irogers@...gle.com>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Kan Liang <kan.liang@...ux.intel.com>, 
	John Garry <john.g.garry@...cle.com>, Will Deacon <will@...nel.org>, 
	James Clark <james.clark@...aro.org>, Mike Leach <mike.leach@...aro.org>, 
	Leo Yan <leo.yan@...ux.dev>, Yicong Yang <yangyicong@...ilicon.com>, 
	Weilin Wang <weilin.wang@...el.com>, Tim Chen <tim.c.chen@...ux.intel.com>, 
	Thomas Richter <tmricht@...ux.ibm.com>, Sumanth Korikkar <sumanthk@...ux.ibm.com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 3/8] perf stat: Display "none" for NaN with metric only json

On Tue, Oct 8, 2024 at 3:38 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> On Fri, Oct 04, 2024 at 04:41:15PM -0700, Ian Rogers wrote:
> > Return earlier for an empty unit case. If snprintf of the fmt doesn't
> > produce digits between vals and ends, as happens with NaN, make the
> > value "none" as happens in print_metric_end.
>
> Then it could be "NaN" or is there any other case?  But probably "none"
> would be more generic.

We use "none" here in print_metric_end as mentioned in the commit message:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/stat-display.c?h=perf-tools-next#n1090
If we used NaN then it'd be another case for users to parse, hence
trying to be consistent and using "none".

Thanks,
Ian

> >
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > ---
> >  tools/perf/util/stat-display.c | 11 +++++++----
> >  1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/perf/util/stat-display.c b/tools/perf/util/stat-display.c
> > index 5402998881c4..e392ee5efb45 100644
> > --- a/tools/perf/util/stat-display.c
> > +++ b/tools/perf/util/stat-display.c
> > @@ -609,19 +609,22 @@ static void print_metric_only_json(struct perf_stat_config *config __maybe_unuse
> >  {
> >       struct outstate *os = ctx;
> >       FILE *out = os->fh;
> > -     char buf[64], *vals, *ends;
> > +     char buf[64], *ends;
> >       char tbuf[1024];
> > +     const char *vals;
> >
> >       if (!valid_only_metric(unit))
> >               return;
> >       unit = fixunit(tbuf, os->evsel, unit);
> > +     if (!unit[0])
> > +             return;
> >       snprintf(buf, sizeof(buf), fmt ?: "", val);
> > -     ends = vals = skip_spaces(buf);
> > +     vals = ends = skip_spaces(buf);
> >       while (isdigit(*ends) || *ends == '.')
> >               ends++;
> >       *ends = 0;
> > -     if (!unit[0] || !vals[0])
> > -             return;
> > +     if (!vals[0])
> > +             vals = "none";
> >       fprintf(out, "%s\"%s\" : \"%s\"", os->first ? "" : ", ", unit, vals);
> >       os->first = false;
> >  }
> > --
> > 2.47.0.rc0.187.ge670bccf7e-goog
> >