An algorithm with constant execution time for dynamic storage allocation

The predictability of the computation t ime of program modules is very important f o r estimating an accurate worst-case execution t ime ( W C E T ) of a task in real-time systems. Dynamic storage allocation ( D S A ) is a common programming technique. Although many DSA algorithms have been developed, they focus o n the average execution t ime rather than the W C E T , making it is very dif icult t o calculate their WCET accurately. In this paper, we propose a new algorithm called HalfFi t [ I ] whose WCET can be calculated accurately. The algorithm finds a free block without searching o n a free list or tree, allowing extra unusable memory called incomplete memory use. In a simulation following a queueing model of M f G l m , Half-Fit has the advantage over the binary buddy system [2] of more ef ic ient storage utilization. The binary buddy system is a conventional algorithm whose WCET can be calculated.