Real Time Operating Systems

4,539 views

Published on

Published in: Technology
0 Comments
6 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
4,539
On SlideShare
0
From Embeds
0
Number of Embeds
838
Actions
Shares
0
Downloads
0
Comments
0
Likes
6
Embeds 0
No embeds

No notes for slide

Real Time Operating Systems

  1. 1. -Training Presentation by Rohit Joshi
  2. 2.  Real-Time Systems.  A few Concepts.  Real-Time OS.  Case Study Nucleus – Introduction will cover in detail in next presentation.
  3. 3. Decreasing order of Familiarity Applications OS Hardware System Mostly RTOS
  4. 4.  A system where correctness of computation depends on logical correctness and the time upon which the results are produced.  Guaranteeing timing means predictability.  A high degree of utilization while timing constraints are met.  A bounded latency rather than high average performance.
  5. 5.  Hard Real-Time Systems  If timing constraints are not met causes a catastrophic system failure.  Soft Real-Time Systems  If timing constraints are not met causes a degradation in the system performance.
  6. 6.  Multiple “Task” are scheduled to run.  Each task maintains its Own state  CPU Register  Execution Stack  Not always beneficial.
  7. 7.  With more than one task, some means is required to choose among them  FIFO Scheduling  Each task is run in sequence until it blocks or is finished  (cooperative multitasking)  Shortest Job First  The task requiring the least CPU time goes first  Round Robin  Scheduled tasks are periodically interrupted and another task is given the opportunity to execute  None of these algorithms are suitable for an embedded system!
  8. 8.  Task may have an inherent precedence.  Precedence must be observed when allocating CPU.  Highest priority task ready to run (not pended or delayed) is allocated to the CPU  Reschedule can occur anytime, due to:  Kernel calls.  System clock tick
  9. 9. t3 completes t3 preempts t2 t2 completes Task t3 t2 preempts t1 Task t2 Task t2 Task t1 Task t1 TIME
  10. 10. t4 completes t4 preempts t2 Task t4 t1 t2 t3 t1 t2 t2 t3 TIME
  11. 11.  Ability to provide the required level of service with a bounded response time.  Multithreaded and preemptible.  Static priorities.  Predictable thread synchronization mechanism.  Priority inheritance.
  12. 12.  Documented OS behavior  Interrupt latency  Interrupt masking times  System service latency  System interrupt levels  Device IRQ levels
  13. 13.  Task Switches  Number of tasks shouldn’t effect switching time.  IPC and Synchronization  Message sizes should not influence time.  Memory Allocation.  Fragmentation should be avoided.  Can’t rely on garbage collectors.
  14. 14.  Multitasking real-time kernel  Priority, pre-emptive scheduler  Inter-task Communication (mailboxes,queues, pipes)  Inter-task synchronization (semaphores, signals, events)  Dynamic creation and deletion of all objects
  15. 15.  Proven  Complete product line  No royalties  Source code  Vast CPU support

×