Using exact feasibility tests for allocating real-time tasks in multiprocessor systems

This paper introduces improvements in partitioning schemes for multiprocessor real-time systems which allow higher processor utilization and enhanced schedulability by using exact feasibility tests to evaluate the schedulability limit of a processor: The paper analyzes how to combine these tests with existing bin-packing algorithms for processor allocation and provides new variants which are exhaustively evaluated using two assumptions: variable and fired number of processors. The problem of evaluating this algorithms is complex, since metrics are usually based on comparing the performance of a given algorithm to an optimal one, but determining optimals is often NP-hard on multiprocessors. This problem has been overcome by defining lower or upper bounds on the performance of an optimal algorithm and then defining metrics with respect this bounds. The evaluation has shown that the algorithms exhibit extremely good behaviors and they can be considered very close to the maximum achievable utilization. It is also shown that dynamic priority policies produces significantly better results than fired priorities policies when task sets require high processor utilizations.