perf: skip QuestionHistory expire sweep when nothing can be reclaimed

bluetoothbot · bluetoothbot · commit ad93f34665a4 · 2026-05-19T23:40:38.000Z
diff --git a/src/zeroconf/_history.py b/src/zeroconf/_history.py
@@ -41,13 +41,16 @@ def __init__(self) -> None:
     def add_question_at_time(self, question: DNSQuestion, now: _float, known_answers: set[DNSRecord]) -> None:
         """Remember a question with known answers."""
         # Bound history size between the periodic 10s cleanup ticks. When at
-        # cap, first drop entries past the duplicate-suppression window; if
-        # still at cap, evict the oldest insertion (dict is ordered).
+        # cap, peek at the oldest insertion (dict is ordered) — only run the
+        # full O(n) async_expire sweep if it could actually reclaim something,
+        # else a sustained flood at cap turns each insert into a wasted scan.
         if question not in self._history and len(self._history) >= _MAX_QUESTION_HISTORY_ENTRIES:
-            self.async_expire(now)
+            oldest = next(iter(self._history))
+            oldest_than, _ = self._history[oldest]
+            if now - oldest_than > _DUPLICATE_QUESTION_INTERVAL:
+                self.async_expire(now)
             while len(self._history) >= _MAX_QUESTION_HISTORY_ENTRIES:
-                oldest = next(iter(self._history))
-                del self._history[oldest]
+                del self._history[next(iter(self._history))]
         self._history[question] = (now, known_answers)
 
     def suppresses(self, question: DNSQuestion, now: _float, known_answers: set[DNSRecord]) -> bool:
