[PATCH v4 0/7] Event parsing fixes

[Ian Rogers]

On Thu, Aug 22, 2024 at 7:32 AM Liang, Kan <kan.liang at linux.intel.com> wrote:
>
>
>
> On 2024-08-22 9:24 a.m., James Clark wrote:
> > I rebased this one and made some other fixes so that I could test it,
> > so I thought I'd repost it here in case it's helpful. I also added a
> > new test.
> >
> > But for the testing it all looks ok.
> >
> > There is one small difference where it now shows "stalled-cycles-..."
> > as <not supported> events, when before it just didn't show them at all when
> > they weren't supported:
> >
> >   $ perf stat -- true
> >
> >   Performance counter stats for 'true':
> >
> >               0.66 msec task-clock                       #    0.384 CPUs utilized
> >                  0      context-switches                 #    0.000 /sec
> >                  0      cpu-migrations                   #    0.000 /sec
> >                 52      page-faults                      #   78.999 K/sec
> >      <not counted>      cpu_atom/instructions/                                                  (0.00%)
> >            978,399      cpu_core/instructions/           #    1.02  insn per cycle
> >      <not counted>      cpu_atom/cycles/                                                        (0.00%)
> >            959,722      cpu_core/cycles/                 #    1.458 GHz
> >    <not supported>      cpu_atom/stalled-cycles-frontend/
> >    <not supported>      cpu_core/stalled-cycles-frontend/
> >
>
> Intel didn't support the events for a very long time. It would impact
> many existing generations and all future generations.
> The current method is to hide the non-exist events. The TopdownL1 is an
> example. If it doesn't exist in the json file, perf stat will not
> display it.
> I don't think it's a good idea to disclose non-exist events in the perf
> stat default.
>
> The <not supported> doesn't help here, since there could be many reasons
> that the perf tool fails to open a counter. It just provides a
> misleading message for an event that never existed.

The list of "default" events, not metrics, similarly has "<not
supported>" in many configurations with "-dd" or "-ddd" on AMD. I'm
not sure the set of default events, at different detail levels, is
necessarily the best. The default events can also be a source of
multiplexing, for example, showing branch miss rate alongside topdown
metrics. Anyway, for the "<not supported>" we should probably be able
to tweak should_skip_zero_counter that is in stat-display.c and tag
these default events as "skippable".

Thanks,
Ian

> Thanks,
> Kan
> > I don't think that's a big deal though and could probably be fixed up
> > later if we really want to.
> >
> > Tested on Raptor Lake, Juno, N1, Ampere (with the DSU cycles PMU) and
> > I also faked an Apple M on Juno.
> >
> > Changes since v3:
> >
> >   * Rebase onto perf-tools-next 6236ebe07
> >   * Fix Intel TPEBS counting mode test
> >   * Fix arm-spe build
> >   * Add support for DT devices in stat test
> >   * Add a new test for hybrid perf stat default arguments
> >
> > Ian Rogers (5):
> >   perf evsel: Add alternate_hw_config and use in evsel__match
> >   perf stat: Uniquify event name improvements
> >   perf stat: Remove evlist__add_default_attrs use strings
> >   perf evsel x86: Make evsel__has_perf_metrics work for legacy events
> >   perf evsel: Remove pmu_name
> >
> > James Clark (2):
> >   perf test: Make stat test work on DT devices
> >   perf test: Add a test for default perf stat command
> >
> >  tools/perf/arch/arm64/util/arm-spe.c          |   4 +-
> >  tools/perf/arch/x86/util/evlist.c             |  74 +----
> >  tools/perf/arch/x86/util/evsel.c              |  35 ++-
> >  tools/perf/builtin-diff.c                     |   6 +-
> >  tools/perf/builtin-stat.c                     | 291 +++++++-----------
> >  tools/perf/tests/parse-events.c               |   2 +-
> >  tools/perf/tests/shell/stat.sh                |  33 +-
> >  .../perf/tests/shell/test_stat_intel_tpebs.sh |  11 +-
> >  tools/perf/util/evlist.c                      |  46 +--
> >  tools/perf/util/evlist.h                      |  12 -
> >  tools/perf/util/evsel.c                       |  28 +-
> >  tools/perf/util/evsel.h                       |  22 +-
> >  tools/perf/util/metricgroup.c                 |   4 +-
> >  tools/perf/util/parse-events.c                |  58 ++--
> >  tools/perf/util/parse-events.h                |   8 +-
> >  tools/perf/util/parse-events.y                |   2 +-
> >  tools/perf/util/pmu.c                         |   6 +-
> >  tools/perf/util/pmu.h                         |   2 +-
> >  tools/perf/util/stat-display.c                | 101 ++++--
> >  tools/perf/util/stat-shadow.c                 |  14 +-
> >  tools/perf/util/stat.c                        |   2 +-
> >  21 files changed, 348 insertions(+), 413 deletions(-)
> >