Question

IN OS:

Chapter 6 CPU Scheduling

• Basic Concepts

• Scheduling Criteria – five criteria be able to discuss and apply with evidence.

• Scheduling Algorithms – FCFS, SJF (optimal), RR (be able to set and justify quantum size), SRTF, Priority - be able to apply each to a set of processes to find the sequence and calculate average wait time (we did a workshop on this). Be able to discuss related to Short Term Scheduler, medium term, long term. Be able to discuss and apply optimization criteria. Be able to determine the best algorithm for different queues in a multilevel queue system and justify selection.

• Real-Time CPU Scheduling – be able to discuss requirements of RT and how scheduling needs to address those needs. Be able to use examples or do problems. Be able to discuss how the requirements can be met for hard and soft RT.

• Algorithm Evaluation – using criteria or formulas

Chapter 7 Deadlock

• System Model

• Deadlock Characterization – what is a deadlock, deadlock identification

• Methods for Handling Deadlocks

• Deadlock Prevention

Chapter 8 Main Memory

• Basic concepts

• Segmentation

• Paging – be able to do problems like the workshop and homework

• Structure of the Page Table – various enhancements (validity bits).

• Modern OS implementations

Chapter 9 Virtual Memory:

• Basic Concepts

• Demand Paging

• Copy-on-Write - dirty bit

• Page Replacement

• Thrashing

• Memory-Mapped Files

• Allocating Kernel Memory

• Other Considerations

• Operating-System implementations.

Answer 1

• Basic concepts:

They include the overall concpets which comes in the process of schedlung i.e. the various scheduling algorithms, thr waiting time, turnaround time, completion time etc.

• Scheduling Criteria:

Scheduling criteria is basically based on the concept that the scheduling of various processes is done in such a way that the overall throughput of the CPU is maximum. The scheduling criteria are set in a way that the overall performance of the system increases and the CPU is utilised in the best possible and efficient way.

• Scheduling Algorithms:

Scheduling algorithm is just the ways of deciding the way CPU is allocated to the various processes.

The various scheduling algorithm includes:

1. First Come First Serve: In this type of scheduling, the process which comes first according to their arrival time, the CPU is allocated to that process.
2. Shortest Job First: In this type of scheduling, amongst the available processes at a particular time, the process with the minimum burst time is selected for the CPU to get allocated.
3. Round Robin: In this type of scheduling type, a particular time quanta is provided for which the CPU is allocated to all the processes. for example: if the time quanta is 2ms than the CPU is allocated to a process for only 2ms than it gets shifted to another process, and this phenomenon goes on.
4. Priority Scheduling: In this type of scheduling, CPU is allocated to the processes on the basis of the priorities of the process, the process with the highest priority gets the CPU allocation first.

Some Numerical Examples Using various algorithm techniques:

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Tune--(TA-6) 6-4-2 19-8 = 11 21-ID 11 122 flug.LOotin, 2t llt llte.소 32 Tume Ly 8

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