A 64bit counter can overflow within the time of a query
so lets take it that the measurement is the small value
rather than an order 1e12 millisecond query.

tested with:

int main()
{
  ulonglong start = ULONGLONG_MAX - 30;
  ulonglong end = 600;
  ulonglong cycles = 10000;

  cycles += end - start;
  if (unlikely(end < start))
     cycles += ULONGLONG_MAX;

  printf("cycles %llu\n", cycles);
}