NON-PREEMPTIVE_SCHEDULING operating system

Os

1. NON PRE-EMPTIVE SCHEDULING ALGORITHM SUBJECT : OPERATING SYSTEM(SEMINAR) GROUP MEMBERS CLASS : 4IT1 KETAN CHUNARA(53 ) KEVAL PARMAR(54) KHUSHAL PRAJAPATI(55)

2. OUTLINES SCHEDULING NON PRE EMPTIVE SCHEDULING ADVANTAGES & DISADVANTAGES FIRST COME FIRST SERVE SHORTEST JOB FIRST NON PRE EMPTIVE PRIORITY PREEMPTIVE VS NON PREEMPTIVE CONCLUSION

3. 3 SCHEDULING Scheduling is the process of selecting a process from a ready queue. And allotting cpu to this process for execution. Scheduler is a part of operating system that allots computer resources to the processes. Scheduler uses scheduling algorithms to decide which processes it must allot to the cpu .

4. 4 CONT... Scheduling provides 1) better efficiency 2) reduce any kind of delay 3) even waiting time

5. 5

6. 6 NON PRE-EMPTIVE SCHEDULING In non pre-emptive scheduling, once a process is selected, it runs to completion until is blocked for an i/o devices or other events. This scheduling does not interrupt a process running CPU in the middle of the execution. It wait till the process completes its CPU burst time, and it can allocate the CPU to another process.

7. 7 ADVANTAGES OF NON PRE-EMPTIVE SCHEDULING It has a minimal scheduling burden. It is a very easy procedure. Less computational resources are used. It has a high throughput rate. It is a very simple method.

8. 8 DISADVANTAGES OF NON PRE-EMPTIVE SCHEDULING It has poor response time for process. A machine can freeze up due to bugs. Waiting time is high.

9. 9

10. 10 FIRST COME FIRST SERVE 1) s election area As the name suggests, the FCFS assign the CPU to the process that arrive first in the ready queue. This means that the process that requests the CPU for its execution first will get the CPU allocated first. 2) decision m ode Once a process is selected, it run until either it is blocked for an i \o or some event or it is terminated

11. 11 CONT... 3) implementation This method can be easily implemented by fifo . When CPU becomes free, a process from the first position in a queue is selected to run.

12. 12 EXAMPLE OF FCFS

13. 13 CONT .. Advantages of FCFS 1) it is a simplest form of scheduling algorithm. 2) its implementations is easy Disadvantages of FCFS 1) not efficient because average waiting time is high.

14. 14 SHORTEST JOB FIRST selection area • The process, that requires shortest time to complete execution, is served first. 2) decision mode • Once a process is selected, it run until either it is blocked for i \o some other event or it is terminated.

15. 15 3) implementation This method can be easily implemented by FIFO. All processes in queue are sorted in ascending order based on their required CPU bursts. When CPU becomes free, a process from the first position in a queue is selected to run. CONT...

16. 16 EXAMPLE OF SJF

17. 17 CONT.. Advantages 1) less waiting time. 2) good response for short process. Disadvantages 1) it is difficult to estimate time required to complete execution. 2) starvation is possible for long process. Long process may wait forever.

18. 18 NON-PRE-EMPTIVE PRIORITY 1) s election area The process, that has highest priority is served first. 2) decision mode Once a process is selected, it runs until it blocks for an i \o or some event or it terminates.

19. 19 CONT... 3) implementation This method can be implemented by using sorted fifo queue. All process in queue an sorted based on their priority with highest priority process at front end. When cpu becomes free, a process from the first position in a queue is selected to run.

20. 20 EXAMPLE OF NON PRE-EMPTIVE

21. 21 CONT... Advantages 1) priority is considered so critical process can get even better response time. Disadvantages 1) starvation is possible for low priority process. It can be overcome by using technique called “aging”. Aging : gradually increases the priority of process that wait in the system for a long time.

22. 22 DIFFERENCE PRE-EMPTIVE In this resources are allocated to a process for a limited time. Process can be interrupted in between. NON-PRE-EMPTIVE Once resources are allocated to a process the process holds it till it completes its burst time or switches to waiting state. Process can not be interrupted until it terminates itself or its time is up.

23. 23 CONT... It has overheads of scheduling the process. Flexible Cost associated Cpu utilization is high. Waiting time is less. Response time is less. It does not have overheads. Rigid No cost associated Cpu utilization is low. Waiting time is high. Response time is high.

24. 24 CONCLUSION Non-pre emptive scheduling algorithms offer efficiency, predictability, fairness, lower overhead, and simplicity, making them suitable for various computing environments, especially those with stringent timing requirements or resource limitations.