subprojects/parseq/src/main/java/com/linkedin/parseq/internal/ExecutionMonitor.java
private void checkForStall(long currentTime) {
    long delta = currentTime - _lastMonitoringStep;
    if (delta < _shortestObservedDelta) {
      _shortestObservedDelta = delta;
    }
    long stall = Math.max(0, delta - _shortestObservedDelta);
    if (stall > _minStallNano) {
      _stalls.put(_lastMonitoringStep, stall);
      if (_stalls.size() > _stallsHistorySize) {
        _stalls.pollFirstEntry();
      }
    }
  }
private void checkForStall(long currentTime) {
    long delta = currentTime - _lastMonitoringStep;
    if (delta < _shortestObservedDelta) {
      _shortestObservedDelta = delta;
    }
    long stall = Math.max(0, delta - _shortestObservedDelta);
    if (stall > _minStallNano) {
      _stalls.put(_lastMonitoringStep, stall);
      if (_stalls.size() > _stallsHistorySize) {
        _stalls.pollFirstEntry();
      }
    }
  }
Check how much we missed scheduled wake up and if it is larger than _minStallNano
then consider it a stall and remember it.