Affiliations: School of Electrical Engineering and Computer Science,
Seoul National University, Seoul 151-742, Korea | College of Information and Communications, Hanyang
University, Seoul 133-791, Korea
Abstract: This paper presents two classes of admission control schemes for
embedded system applications that have real-time constraints but with composite
characteristics in request arrivals and resource requirements. First, we
present admission control tests using utilization demands to handle a mix
of periodic and aperiodic tasks with deterministic execution times. The
utilization demand is defined as the processor utilization required for a task
to meet its deadline with certainty, thus for deterministic deadline
guarantees. We show that the use of utilization demands eliminates the need for
complicated schedulability analysis and enables on-line admission control.
Second, we present statistical admission control schemes using effective
execution times to handle stochastic execution times. Effective execution
times are determined from the specified probability demanded by the application
and stochastic properties of task execution times. Every task is associated
with an effective execution time and is restricted to using processor time not
exceeding its effective execution time. This scheme allows every task to meet
its deadline with the specified probability without being interfered with, and
greatly simplifies the admission control when combined with utilization
demands. Our experimental results confirm the correctness of the proposed
approaches. They also show that our admission tests are very accurate to
achieve high-level processor utilization.
