By assuming sysfs events are either upper or lower case, the case
insensitive event parsing can probe for the existence of files rather
then loading all events in a directory. When the event is a json event
like inst_retired.any on Intel, this reduces the number of openat
calls on a Tigerlake laptop from 325 down to 255.

v1 sent as an RFC:
    https://lore.kernel.org/lkml/20240413040812.4042051-1-irogers@google.com/

v2: addresses review feedback from Kan Liang, by updating
    documentation and adding tests.

v3: incorporate feedback from Thomas Richter <tmricht@linux.ibm.com>
    that s390 event names are all upper case. Do a lower case probe
    then an upper case probe, make documentation and tests also agree.

Ian Rogers (6):
  perf test pmu-events: Make it clearer that pmu-events tests json
    events
  perf Document: Sysfs event names must be lower or upper case
  perf test pmu: Refactor format test and exposed test APIs
  perf test pmu: Add an eagerly loaded event test
  perf test pmu: Test all sysfs PMU event names are the same case
  perf pmu: Assume sysfs events are always the same case

 .../sysfs-bus-event_source-devices-events     |   6 +
 tools/perf/tests/pmu-events.c                 |   2 +-
 tools/perf/tests/pmu.c                        | 457 ++++++++++++------
 tools/perf/util/parse-events.c                |   2 +-
 tools/perf/util/parse-events.h                |   2 +-
 tools/perf/util/pmu.c                         | 111 +++--
 tools/perf/util/pmu.h                         |   4 +-
 tools/perf/util/pmus.c                        |  16 +-
 tools/perf/util/pmus.h                        |   2 +
 9 files changed, 405 insertions(+), 197 deletions(-)

-- 
2.44.0.769.g3c40516874-goog