perf jevents: Ignore sys when determining a model directory

Existing sys directories aren't placed under a model directory like
skylake.

Placing a sys directory there causes the `is_leaf_dir` test to fail and
consequently no events or metrics are generated for the model.

Ignore sys directories in this case and update the comments to
reflect why.

This change has no affect, but when testing with a sys directory for a
model people have reported running into the no event/metric issue.
Reported-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jing Zhang <renyu.zj@linux.alibaba.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Xu Yang <xu.yang_2@nxp.com>
Link: https://lore.kernel.org/r/20240904211705.915101-1-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/pmu-events/jevents.py

@@ -635,14 +635,17 @@ def preprocess_one_file(parents: Sequence[str], item: os.DirEntry) -> None:
 
 def process_one_file(parents: Sequence[str], item: os.DirEntry) -> None:
   """Process a JSON file during the main walk."""
-  def is_leaf_dir(path: str) -> bool:
+  def is_leaf_dir_ignoring_sys(path: str) -> bool:
     for item in os.scandir(path):
-      if item.is_dir():
+      if item.is_dir() and item.name != 'sys':
         return False
     return True
 
-  # model directory, reset topic
-  if item.is_dir() and is_leaf_dir(item.path):
+  # Model directories are leaves (ignoring possible sys
+  # directories). The FTW will walk into the directory next. Flush
+  # pending events and metrics and update the table names for the new
+  # model directory.
+  if item.is_dir() and is_leaf_dir_ignoring_sys(item.path):
     print_pending_events()
     print_pending_metrics()