Interactive processes have priority over longer ones, because long process migrate to lower priority queues. Give larger quanta to lower-priority. Many additional policies exist. Evaluating Policies Mathematical Analysis involves a mathematical formulation of the policy and a derivation of its behavior. The primary drawback of mathematical analysis is that the model is only an approximation to the actual system, and complex systems are often impossible to solve.
Simulation involves tracking a large number of processes through a model and collecting statistics.
Unfortunately, because the system tested must be built, experimentation is usually expensive. Always run real-time processes above normal. It uses priorities with either a FIFO or round-robin policy. On each timer interrupt one credit is deducted until zero is reached at which time the process is preempted. Windows NT Scheduling Windows NT uses threads as the basic scheduling unit.