// returns (timer, estimated firing time) or null
static Pair<O, Long> nextFiringTimerInVM() {
  L timers = allTimersInVM();
  long time = now();
  new Lowest best;
  for (O timer : timers) pcall {
    for (O entry : unnull((Collection) getOpt(timer, 'entries))) {
      Long firstTime = cast getOpt(entry, 'firstTime);
      Long period = cast getOpt(entry, 'period);
      if (firstTime != null && period != null)
        if (time >= firstTime)
          best.put(period-((time - firstTime) % period), timer);
    }
  }
  ret best.has() ? pair(best!, time+best.getScore()) : null;
}