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Crit Job WCET off WCET on C R DHard τ 1 12 9 8 0 16Soft τ 2 8 6 5 0 10a)b)τ 1τ 2τ 1τ 20 2 4 6 8 10 12 14 160 2 4 6 8 10 12 14 16Fig. 1. Scheduling can be improved for this mixed criticality job set ifWCET on is used, enabeling the schedule in b). Using only WCET offforces the schedule in a) where τ 2 misses its deadline.III. POTENTIAL UTILIZATION AREAS OF ONLINE WCETDATA.The following points envision some possible applicationareas for the online WCET:• Some schedulability or timeliness properties of a systemcould be refined using the WCET on .• Algorithms for reclaiming the CPU capacity allocatedto a job but not used, might be improved by gettingbetter information on the real job load at the job releasetime. Similarly, strategies for overload handling, jitterreduction, power optimization etc. could potentially beimproved.• Figure 1 shows a simple mixed criticality job set whereaccess to the tighter WCET on improves schedulability.• In a quality of service perspective, programs might offermore modes of operation. Comparing the online WCETof each mode with the available CPU for the next periodmight be useful for selecting the mode.• Algorithms for dynamic deployment of jobs onto processorsand for load balancing can be improved using theonline execution time estimates.IV. PRINCIPLES FOR ONLINE ESTIMATION OF WCET.The following points suggest how the estimation challengecan be approached for increasing algorithm complexity:• The trivial case is when the estimation metric is directlyavailable. This can be the “message size”, “frame type”,“length of the linked list”, etc. The estimation algorithmwould just look up the information and translate it intothe online WCET.• A slightly worse class of programs would be whena subset of the calculations must be carried out bythe estimation algorithm - like calculating the boundsof the significant loops or the outcomes of the majorconditionals. Figure 2 gives an example of a type ofprogram where this would be successful. A frameworkfor automatically generating such estimation algorithmsis under development.for (m=1;m