[PATCH v2 17/18] perf jevents: Sort strings in the big C string to reduce faults

[Ian Rogers]

Sort the strings within the big C string based on whether they were
for a metric and then by when they were added. This helps group
related strings and reduce minor faults by approximately 10 in 1740,
about 0.57%.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/pmu-events/jevents.py | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/tools/perf/pmu-events/jevents.py b/tools/perf/pmu-events/jevents.py
index 01335a452e70..e5bce57f5688 100755
--- a/tools/perf/pmu-events/jevents.py
+++ b/tools/perf/pmu-events/jevents.py
@@ -113,13 +113,24 @@ class BigCString:
   strings: Set[str]
   big_string: Sequence[str]
   offsets: Dict[str, int]
+  insert_number: int
+  insert_point: Dict[str, int]
+  metrics: Set[str]
 
   def __init__(self):
     self.strings = set()
+    self.insert_number = 0;
+    self.insert_point = {}
+    self.metrics = set()
 
-  def add(self, s: str) -> None:
+  def add(self, s: str, metric: bool) -> None:
     """Called to add to the big string."""
-    self.strings.add(s)
+    if s not in self.strings:
+      self.strings.add(s)
+      self.insert_point[s] = self.insert_number
+      self.insert_number += 1
+      if metric:
+        self.metrics.add(s)
 
   def compute(self) -> None:
     """Called once all strings are added to compute the string and offsets."""
@@ -160,8 +171,11 @@ class BigCString:
     self.big_string = []
     self.offsets = {}
 
+    def string_cmp_key(s: str) -> Tuple[bool, int, str]:
+      return (s in self.metrics, self.insert_point[s], s)
+
     # Emit all strings that aren't folded in a sorted manner.
-    for s in sorted(self.strings):
+    for s in sorted(self.strings, key=string_cmp_key):
       if s not in folded_strings:
         self.offsets[s] = big_string_offset
         self.big_string.append(f'/* offset={big_string_offset} */ "')
@@ -574,19 +588,20 @@ def preprocess_one_file(parents: Sequence[str], item: os.DirEntry) -> None:
       assert len(mgroup) > 1, parents
       description = f"{metricgroup_descriptions[mgroup]}\\000"
       mgroup = f"{mgroup}\\000"
-      _bcs.add(mgroup)
-      _bcs.add(description)
+      _bcs.add(mgroup, metric=True)
+      _bcs.add(description, metric=True)
       _metricgroups[mgroup] = description
     return
 
   topic = get_topic(item.name)
   for event in read_json_events(item.path, topic):
     pmu_name = f"{event.pmu}\\000"
-    _bcs.add(pmu_name)
     if event.name:
-      _bcs.add(event.build_c_string(metric=False))
+      _bcs.add(pmu_name, metric=False)
+      _bcs.add(event.build_c_string(metric=False), metric=False)
     if event.metric_name:
-      _bcs.add(event.build_c_string(metric=True))
+      _bcs.add(pmu_name, metric=True)
+      _bcs.add(event.build_c_string(metric=True), metric=True)
 
 def process_one_file(parents: Sequence[str], item: os.DirEntry) -> None:
   """Process a JSON file during the main walk."""
-- 
2.42.0.rc1.204.g551eb34607-goog