proclag

system/proclogd.py

@@ -128,7 +128,8 @@ _SMAPS_KEYS = {b'Pss:', b'Pss_Anon:', b'Pss_Shmem:'}
 _smaps_path: str | None = None  # auto-detected on first call
 
 # per-VMA smaps is expensive (kernel walks page tables for every VMA).
-# cache results and only refresh every N cycles to keep CPU low.
+# Cache results and stagger refreshes across N cycles so all large processes
+# aren't scanned in the same cycle.
 _smaps_cache: dict[int, SmapsData] = {}
 _smaps_cycle = 0
 _SMAPS_EVERY = 20  # refresh every 20th cycle (40s at 0.5Hz)
@@ -158,8 +159,8 @@ def _read_smaps(pid: int) -> SmapsData:
 
 
 def _get_smaps_cached(pid: int) -> SmapsData:
-  """Return cached smaps data, refreshing every _SMAPS_EVERY cycles."""
-  if _smaps_cycle == 0 or pid not in _smaps_cache:
+  """Return cached smaps data, refreshing each PID in its assigned cycle."""
+  if pid % _SMAPS_EVERY == _smaps_cycle:
     _smaps_cache[pid] = _read_smaps(pid)
   return _smaps_cache.get(pid, {'pss': 0, 'pss_anon': 0, 'pss_shmem': 0})
 

system/tests/test_proclogd.py

@@ -0,0 +1,20 @@
+from openpilot.system import proclogd
+
+
+def test_smaps_refreshes_are_staggered(monkeypatch):
+  monkeypatch.setattr(proclogd, "_smaps_cycle", 3)
+  monkeypatch.setattr(proclogd, "_smaps_cache", {24: {"pss": 1, "pss_anon": 2, "pss_shmem": 3}})
+
+  refreshed = {"pss": 4, "pss_anon": 5, "pss_shmem": 6}
+  reads = []
+
+  def read_smaps(pid):
+    reads.append(pid)
+    return refreshed
+
+  monkeypatch.setattr(proclogd, "_read_smaps", read_smaps)
+
+  assert proclogd._get_smaps_cached(23) == refreshed
+  assert proclogd._get_smaps_cached(24) == {"pss": 1, "pss_anon": 2, "pss_shmem": 3}
+  assert proclogd._get_smaps_cached(25) == {"pss": 0, "pss_anon": 0, "pss_shmem": 0}
+  assert reads == [23]