Round Robin Advantage Vs Disadvantage

Duration: 9 min

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Inside: a video lesson and guided study material.

Module outline

  1. Section A | English: Vocabulary, Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Preposition, Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Articles, Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Verbal Analogy (Word Based Analogy)
  2. Section A | Quant Aptitude: Ratio and Proportion (Ratios), Mixture and Alligation, Permutation and Combination, Number System, HCF LCM, Sequence and Series (Series), Speed Time and Distance, Arithmetic, Algebra, Powers and Exponents (Surds and Indices), Average, Age Problems, Percentage, Profit and Loss, Partnership, Time and Work, Simple Interest and Compound Interest, Mensuration and Geometry, Probability, Pipe and Cistern
  3. Section A | Reasoning: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Data Sufficiency, Calendar, Clock, Blood Relations, Directions (Direction Test), Seating Arrangements, Ranking, Order and Sequence, Puzzle Solving (Puzzles)
  4. Section B | C Programming: C Programming by Yash Sir, Coding Questions by Yash Sir
  5. Section B | Data Structures: Algorithm Analysis, Greedy Algorithms, Time Complexity Analysis, Sorting Algorithms, Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs
  6. Section B | OOP (C++): Object Oriented Programming (OOPS), Programming in C++
  7. Section B | OS: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management, Windows OS
  8. Section B | Networking: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, DLL: Framing, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Net Layer:Routing Protocol, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware basics
  9. Section B | AI & Big Data Basics: AI & ML by Arun Sir, Big Data Systems
  10. Section C | Digital Electronics: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation, Analog-Digital Conversion
  11. Section A, C | Comp. Fundamentals, COA: Basics of COA, Floating Point Rep, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design, Register Transfer and Microoperations, Multiprocessors, Programming the Basic Computer
  12. MOCK TEST:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This educational video provides a comprehensive lecture on the Round Robin (RR) CPU scheduling algorithm. The instructor begins by explaining the core principles of RR, including the concept of a time quantum (q) and how it ensures fairness by giving each of the n processes in the ready queue a turn to execute for at most q time units. A key point is that the maximum waiting time for a process before its next quantum is (n-1)q. The lecture then transitions to the impact of the time quantum's size, explaining that a very large quantum makes RR behave like First-Come, First-Served (FCFS), while a very small quantum creates the illusion of multiple processors, a concept known as processor sharing. The video concludes with a detailed analysis of RR's advantages and disadvantages. Advantages include excellent average response time, making it ideal for time-sharing and interactive systems, and its nature as a preemptive SJF implementation. Disadvantages include the potential for longer processes to starve and the fact that performance is highly sensitive to the time quantum's value, as it affects both average response time and CPU utilization. A table of process metrics is used to illustrate the calculation of completion time, turn around time, and waiting time.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video opens with a slide defining the Round Robin (RR) scheduling algorithm. The instructor explains that if there are n processes in the ready queue and the time quantum is q, each process gets 1/n of the CPU time in chunks of at most q time units. He emphasizes that each process must wait no longer than (n-1)q time units for its next quantum. To illustrate this, he draws a timeline on the whiteboard, labeling processes P1, P2, and P3, and shows how they would be scheduled in a round-robin fashion, with each getting a slice of time q. He also writes the formula for the maximum waiting time as (n-1)q.

  2. 2:00 – 5:00 02:00-05:00

    The instructor discusses the effect of the time quantum's size. He states that if the time quantum is extremely large, RR behaves like the FCFS policy. Conversely, if the time quantum is extremely small (e.g., 1 millisecond), the RR approach is called processor sharing, where it creates the illusion that each of the n processes has its own processor running at 1/n the speed of the real processor. He draws a diagram to show the transition from a large quantum (max) leading to FCFS to a small quantum (min) leading to processor sharing. He also mentions that the effect of context switching on performance must be considered.

  3. 5:00 – 8:37 05:00-08:37

    The video presents a slide on the advantages and disadvantages of RR. Advantages include performing best in terms of average response time, making it suitable for time-sharing, client-server, and interactive systems, and being a kind of SJF implementation. The instructor then moves to the disadvantages: longer processes may starve, and performance is heavily dependent on the time quantum. He explains that a very small quantum gives a good average response time but causes many context switches, while a very large quantum results in poor average response time but fewer context switches and better CPU utilization. The video concludes with a table showing process metrics (P0 to P5) and a Gantt chart, which the instructor uses to calculate completion time, turn around time (TAT = CT - AT), and waiting time (WT = TAT - BT).

The lecture systematically builds an understanding of the Round Robin scheduling algorithm. It starts with the fundamental definition and fairness guarantee, using a timeline diagram to visualize the process. It then explores the critical parameter of the time quantum, showing how its size dictates the algorithm's behavior, from FCFS to processor sharing. Finally, it provides a balanced view by outlining the key advantages, such as excellent response time for interactive systems, and the main disadvantages, including starvation and the trade-off between response time and CPU utilization. The use of a process table and Gantt chart provides a practical example of how to calculate key performance metrics, reinforcing the theoretical concepts.

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