Self-suspension and Context Switches

• Self-suspension

– A job may invoke an external operation (e.g. request an I/O operation),
during which time it is suspended

– This means the task is no longer strictly periodic… again need to take into
account self-suspension time when calculating a schedule

• Context Switches

– Assume maximum number of context switches Ki for a job in Ti is known;
each takes tCS time units

– Compensate by setting execution time of each job, eactual = e + 2tCS


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