MULTIPROCESSOR AND REAL TIME SCHEDULING.ppt
- 1. MULTIPROCESSOR AND REAL TIME SCHEDULING Presentation & Delivery VEERANAN VEERANAN I M.Sc. Computer Science Roll No. P22PCS123 GOVERNMENT ARTS COLLEGE, MELUR PG. Department of Computer Science
- 2. Operating System Multiprocessor Real Time Scheduling Granularity Design Issues Process Scheduling Thread Scheduling Characteristics of Real Time OS Real Time Scheduling Deadline Scheduling
- 3. Multiprocessor Loosely coupled or distributed multiprocessor, or cluster Functionally Specialized Processors Tightly Coupled Multiprocessor
- 4. Multiprocessor Granularity Independent Parallelism Coarse and Very Coarse Grained Parallelism Medium Grained Parallelism Fine Grained Parallelism
- 5. Multiprocessor Design Issues Assignment of Processes to processors The use of multiprogramming on Indirected Processors Process Dispatching
- 6. Multiprocessor Process Scheduling Assignment of Processes to processors The use of multiprogramming on Indirected Processors Process Dispatching
- 7. Multiprocessor Thread Scheduling Load Sharing Gang Scheduling Dedicated Processor Assignment Dynamic Scheduling
- 8. Operating System Real Time Scheduling Characteristics of Real Time OS Real Time Scheduling
- 10. Real Time Scheduling Real time computing is becoming an increasingly important discipline. The OS and in particular the scheduler, is perhaps the most important component of real time system. Examples Current applications of real time systems include control of laboratory experiments, process control in industrial plants, robotics, air traffic control, telecommunications, and military commands and control systems. Benefits Real-time systems are designed to perform tasks that must be executed within precise cycle deadlines (down to microseconds).
- 11. Real Time Scheduling A Hard real time task is one that must meet its deadline; otherwise it will cause unacceptable damage or a fatal error to the system. A Soft real time task has an associated deadline that is desirable but not mandatory; it still makes sense to schedule and complete the task even if it has passed its deadline.
- 12. Real – Time Operating Systems Characteristics of Real Time OS Determinism Responsiveness User Control Reliability Fail – Soft Operation
- 13. Real time OS features: Fast process or thread switch Small size (with its associated minimal functionality) Ability to respond to external Interrupts quickly Multitasking with inter process communication tools such as semaphores, signals and events. Use of special sequential files that can accumulate data at a fast rate. Pre-emptive scheduling based on priority Minimization of intervals during which Interrupts are disabled. Primitives to delay tasks for a amount of time and to pause/resume tasks Special alarms and timeout.
- 14. Real Time Scheduling: Real time scheduling is one of the most active areas of research in computer Science. Whether a system performs schedule a ability analysis If it does, whether it is done statistically or dynamically Whether the result of the analysis itself produces a schedule or plan according to which tasks are dispatched at run time
- 15. Real – Time Operating Systems Real Time Scheduling Static Table – Driven Approaches Static Priority Driven Preemptive Approaches Dynamic planning based approaches Dynamic Best Effort Approaches
- 17. Static Table – Driven Approaches These perform a static analysis of feasible schedules of dispatching. The result of the analysis is a schedule that determines, at run time, when a task must begin execution.
- 18. Static Table – Driven Approaches Again, a static analysis is performed, but no schedule is drawn back. Rather, the analysis is used to assign priorities to task, so that a traditional priority driven pre-emptive scheduler can be used.
- 19. Dynamic planning based approaches Feasibility is determined at run time rather than offline prior to the start of execution (statically). An arriving task is accepted for execution only of it is feasible to meet it’s time constraints. One of the results of the feasibility analysis is a schedule or plan that is used to decide when to dispatch this task.
- 20. Dynamic Best Effort Approaches No feasibility analysis is performed. The system tries to meet all deadlines and aborts any stated process whose deadline is missed.