diff --git a/cereal/messaging/__init__.py b/cereal/messaging/__init__.py
index 9646047de3..6e97318824 100644
--- a/cereal/messaging/__init__.py
+++ b/cereal/messaging/__init__.py
@@ -92,6 +92,45 @@ def recv_one_retry(sock: SubSocket) -> capnp.lib.capnp._DynamicStructReader:
       return log_from_bytes(dat)
 
 
+class FrequencyTracker:
+  def __init__(self, service_freq: float, update_freq: float, is_poll: bool):
+    freq = max(min(service_freq, update_freq), 1.)
+    if is_poll:
+      min_freq = max_freq = freq
+    else:
+      max_freq = min(freq, update_freq)
+      if service_freq >= 2 * update_freq:
+        min_freq = update_freq
+      elif update_freq >= 2* service_freq:
+        min_freq = freq
+      else:
+        min_freq = min(freq, freq / 2.)
+
+    self.min_freq = min_freq * 0.8
+    self.max_freq = max_freq * 1.2
+    self.recv_dts: Deque[float] = deque(maxlen=int(10 * freq))
+    self.prev_time = 0.0
+
+  def record_recv_time(self, cur_time: float) -> None:
+    # TODO: Handle case where cur_time is less than prev_time
+    if self.prev_time > 1e-5:
+      self.recv_dts.append(cur_time - self.prev_time)
+    self.prev_time = cur_time
+
+  @property
+  def valid(self) -> bool:
+    if not self.recv_dts:
+      return False
+
+    avg_freq = len(self.recv_dts) / sum(self.recv_dts)
+    if self.min_freq <= avg_freq <= self.max_freq:
+      return True
+
+    recent_dts = list(self.recv_dts)[-int(self.recv_dts.maxlen / 10):]
+    avg_freq_recent = len(recent_dts) / sum(recent_dts)
+    return self.min_freq <= avg_freq_recent <= self.max_freq
+
+
 class SubMaster:
   def __init__(self, services: List[str], poll: Optional[str] = None,
                ignore_alive: Optional[List[str]] = None, ignore_avg_freq: Optional[List[str]] = None,
@@ -103,15 +142,12 @@ class SubMaster:
     self.recv_frame = {s: 0 for s in services}
     self.alive = {s: False for s in services}
     self.freq_ok = {s: False for s in services}
-    self.recv_dts: Dict[str, Deque[float]] = {}
     self.sock = {}
     self.data = {}
     self.valid = {}
     self.logMonoTime = {}
 
-    self.max_freq = {}
-    self.min_freq = {}
-
+    self.freq_tracker: Dict[str, FrequencyTracker] = {}
     self.poller = Poller()
     polled_services = set([poll, ] if poll is not None else services)
     self.non_polled_services = set(services) - polled_services
@@ -138,22 +174,7 @@ class SubMaster:
       self.data[s] = getattr(data.as_reader(), s)
       self.logMonoTime[s] = 0
       self.valid[s] = True  # FIXME: this should default to False
-
-      freq = max(min([SERVICE_LIST[s].frequency, self.update_freq]), 1.)
-      if s == poll:
-        max_freq = freq
-        min_freq = freq
-      else:
-        max_freq = min(freq, self.update_freq)
-        if SERVICE_LIST[s].frequency >= 2*self.update_freq:
-          min_freq = self.update_freq
-        elif self.update_freq >= 2*SERVICE_LIST[s].frequency:
-          min_freq = freq
-        else:
-          min_freq = min(freq, freq / 2.)
-      self.max_freq[s] = max_freq*1.2
-      self.min_freq[s] = min_freq*0.8
-      self.recv_dts[s] = deque(maxlen=int(10*freq))
+      self.freq_tracker[s] = FrequencyTracker(SERVICE_LIST[s].frequency, self.update_freq, s == poll)
 
   def __getitem__(self, s: str) -> capnp.lib.capnp._DynamicStructReader:
     return self.data[s]
@@ -182,8 +203,7 @@ class SubMaster:
       self.seen[s] = True
       self.updated[s] = True
 
-      if self.recv_time[s] > 1e-5:
-        self.recv_dts[s].append(cur_time - self.recv_time[s])
+      self.freq_tracker[s].record_recv_time(cur_time)
       self.recv_time[s] = cur_time
       self.recv_frame[s] = self.frame
       self.data[s] = getattr(msg, s)
@@ -194,27 +214,10 @@ class SubMaster:
       if SERVICE_LIST[s].frequency > 1e-5 and not self.simulation:
         # alive if delay is within 10x the expected frequency
         self.alive[s] = (cur_time - self.recv_time[s]) < (10. / SERVICE_LIST[s].frequency)
-
-        # check average frequency; slow to fall, quick to recover
-        dts = self.recv_dts[s]
-        assert dts.maxlen is not None
-        recent_dts = list(dts)[-int(dts.maxlen / 10):]
-        try:
-          avg_freq = 1 / (sum(dts) / len(dts))
-          avg_freq_recent = 1 / (sum(recent_dts) / len(recent_dts))
-        except ZeroDivisionError:
-          avg_freq = 0
-          avg_freq_recent = 0
-
-        avg_freq_ok = self.min_freq[s] <= avg_freq <= self.max_freq[s]
-        recent_freq_ok = self.min_freq[s] <= avg_freq_recent <= self.max_freq[s]
-        self.freq_ok[s] = avg_freq_ok or recent_freq_ok
+        self.freq_ok[s] = self.freq_tracker[s].valid
       else:
         self.freq_ok[s] = True
-        if self.simulation:
-          self.alive[s] = self.seen[s] # alive is defined as seen when simulation flag set
-        else:
-          self.alive[s] = True
+        self.alive[s] = self.seen[s] if self.simulation else True
 
   def all_alive(self, service_list: Optional[List[str]] = None) -> bool:
     if service_list is None:
diff --git a/cereal/messaging/tests/test_pub_sub_master.py b/cereal/messaging/tests/test_pub_sub_master.py
index ba5b397aad..99965319eb 100644
--- a/cereal/messaging/tests/test_pub_sub_master.py
+++ b/cereal/messaging/tests/test_pub_sub_master.py
@@ -89,8 +89,8 @@ class TestSubMaster:
       for service, (max_freq, min_freq) in checks.items():
         if max_freq is not None:
           assert sm._check_avg_freq(service)
-          assert sm.max_freq[service] == max_freq*1.2
-          assert sm.min_freq[service] == min_freq*0.8
+          assert sm.freq_tracker[service].max_freq == max_freq*1.2
+          assert sm.freq_tracker[service].min_freq == min_freq*0.8
         else:
           assert not sm._check_avg_freq(service)
 
diff --git a/selfdrive/test/profiling/lib.py b/selfdrive/test/profiling/lib.py
index 93ba215386..62bb305ca8 100644
--- a/selfdrive/test/profiling/lib.py
+++ b/selfdrive/test/profiling/lib.py
@@ -1,4 +1,4 @@
-from collections import defaultdict, deque
+from collections import defaultdict
 from cereal.services import SERVICE_LIST
 import cereal.messaging as messaging
 import capnp
@@ -45,7 +45,7 @@ class SubMaster(messaging.SubMaster):
     self.rcv_frame = {s: 0 for s in services}
     self.valid = {s: True for s in services}
     self.freq_ok = {s: True for s in services}
-    self.recv_dts = {s: deque([0.0] * messaging.AVG_FREQ_HISTORY, maxlen=messaging.AVG_FREQ_HISTORY) for s in services}
+    self.freq_tracker = {s: messaging.FrequencyTracker(SERVICE_LIST[s].frequency, SERVICE_LIST[s].frequency, False) for s in services}
     self.logMonoTime = {}
     self.sock = {}
     self.freq = {}