Re: [PATCH v4 0/7] Event parsing fixes

On 2024-08-22 11:10 a.m., Ian Rogers wrote:

On Thu, Aug 22, 2024 at 7:32 AM Liang, Kan [off-list ref] wrote:

quoted

On 2024-08-22 9:24 a.m., James Clark wrote:

quoted

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".

The "skippable" should be fine as long as it's completely hidden.

BTW: The stalled-cycles-backend should be similar to the
stalled-cycles-frontend, but it isn't shown in the example. Is the
stalled-cycles-backend event missed?

Thanks,
Kan

Thanks,
Ian

quoted

Thanks,
Kan

quoted

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(-)