Problem 12: Large Distributed Systems ECU1 BUS CC1 ECU2CC2 ECU3CC3 S1 S2 S3 S4 S5 5 Real-Time Input Streams - with jitter - with bursts - deadline > period 3 ECU’s with own CC’s 12 Tasks & 7 Messages -with different WCED -fully preemptive & independent 2 Scheduling Policies - Earliest Deadline First (ECU’s) - Fixed Priority (ECU’s & CC’s) Hierarchical Scheduling - Static & Dynamic Polling Servers Bus with TDMA - 4 time slots with different lengths (#1,#3 for CC1, #2 for CC3, #4 for CC3) Total Utilization: - ECU159 % - ECU287 % - ECU367 % - BUS56 %

Specification Data

ECU1BUS (TDMA) C1.1 C1.2 C2.1 C3.1 C4.1 C5.1 C3.2 T1.1 T1.3 T2.1 T3.1 T3.3 PS FP CC1 ECU2 T4.1 T5.1 FP CC2 ECU3 T1.2 FP CC3 T3.2 FP EDF T2.2 PS T4.2 PS T5.2 S1 S2 S3 S4 S5 S1 S3 Within FP-blocks priorities are assigned from top (highest) to bottom (lowest). Communication tasks that share a TDMA slot use FP-scheduling.

Questions Is it schedulable? Minimum reqiured buffers? End-to-end delays of all streams?

Periodic Server A polling server can be thought of as a periodic task T (p, e). When the server-task T is selected to run by the scheduler, the server-task checks whether workload is waiting to be processed by the server. If yes, the server will provide e resources to process the waiting workload. If no work is available for the server, the task will immediately be finished, i.e. the server will not check for arriving work anymore until the next period starts. While the server is processing, it is preemptable. When it is preempted, it is put back into the ready-queue. If the server could not provide e resources during a time interval T, even though there was always enough work available, then this is treated the same as a deadline-miss. I.e. the system is considered to be not schedulable.