SYSC-3303-12-ProcessScheduler-Part2

SYSC-3303-12-ProcessScheduler-Part2 - Fixed versus Dynamic...

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Fixed versus Dynamic Priority Scheduling Cyclic Executives and RMA uses FPS Priority may be temporarily altered (e.g. priority inheritance or ceiling) but … priority is assigned atically as part of the system design statically as part of the system design Changes are under program control Priority assignments largely centred on process eriod/rate (e g RMA) period/rate (e.g. RMA) Dynamic Priority Scheduling “Priority” is calculated at runtime, based on the response rate required of the process Response time deadline PS Deadline Scheduling DPS 3/25/2009 SYSC 3303 Winter 2009 C. Schramm 18
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PS or Deadline Scheduling DPS or Deadline Scheduling http://www.embedded.com/story/OEG20010304S0004 Hard real time tasks must finish at a particular time. Something ll bd ill h if th d' t really bad will happen if they don't. Soft real time tasks have a preferred completion time, but the consequences of not completing on time are not totally tastrophic. catastrophic. The target completion time for a task is called its deadline . A dynamic priority scheduler may never deal with priority. It arranges scheduling queues by execution eligibility, and if tasks g g q y gy ,
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SYSC-3303-12-ProcessScheduler-Part2 - Fixed versus Dynamic...

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