On 11/29/2013 04:10 PM, Carsten Emde wrote:
BTW: Power saving and real-time do not necessarily exclude each other. If a - still deterministic - but a little longer latency is acceptable, some light sleep states and a somewhat lower clock frequency may be allowed which still may result in considerable energy saving. If, however, the fastest possible real-time response is required, C states and P states must be disabled (or set to polling and maximum speed, repsectively) and the power bill must be payed.
Well, I do not fully agree. To be sure that you can clock down the processor for executing a task which has sufficient time to meet its deadline, your system must be "time triggered", all the timer events must be known in advance. Because on a fully dynamic system, you may make that decision, but a new timer may be scheduled which causes the system to miss its deadline whereas it would not have missed it if it had run at full speed.
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