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

["Liang, Kan" <kan.liang@linux.intel.com>]

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.

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(-)
>