n. The maximum achievable processor utilization, W, as a percentage, for a set of n threads prioritized by applying the rate monotonic algorithm.
Wn = n (21 ⁄ n – 1)
If there’s only one thread to be run, the schedulable bound is 100%. If there are two threads, the worst-case schedulable bound drops to 82.8%. The formula approaches a limit of 69.3% (ln 2, to be precise) as the number of threads grows larger. It is important to realize, however, that a particular set of n threads with their combination of specific periods, deadlines, and worst-case execution times might be able to achieve a higher overall utilization with RMA. The formula above gives only the schedulable bound for the worst possible combination of any n threads.