Multi Level Feedback Queue Scheduling

Duration: 4 min

This video lesson is available to enrolled students.

Return to /learn/CDAC-C-CAT-COMPLETE-PREPARATION/section-b-os/cpu-scheduling/multilevel-queues/asset-multi-level-feedback-queue-scheduling after enrolling

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 detailed lecture on the Multi-level Feedback Queue Scheduling algorithm used in operating systems. The instructor begins by distinguishing this flexible approach from the rigid multilevel queue scheduling, where processes are permanently assigned to specific queues. He explains that the feedback mechanism allows processes to migrate between priority levels based on their CPU burst characteristics, ensuring that interactive and I/O-bound processes receive higher priority while CPU-bound processes are demoted. The lecture concludes with a specific numerical example illustrating time quanta and queue transitions.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor introduces the topic using a slide titled Multi-level Feedback Queue Scheduling. He contrasts this with standard multilevel queues, noting on-screen text that says: Normally, when the multilevel queue scheduling algorithm is used, processes are permanently assigned to a queue when they enter the system. He explains that unlike this inflexible setup, the feedback queue allows processes to move between queues. The slide text further clarifies: The multilevel feedback queue scheduling algorithm, in contrast, allows a process to move between queues. He details that processes using too much CPU time are moved to lower-priority queues, whereas I/O-bound and interactive processes remain in higher-priority queues. He also mentions that a process waiting too long in a lower-priority queue may be moved to a higher-priority queue to prevent starvation, a concept known as aging.

  2. 2:00 – 3:48 02:00-03:48

    The lecture shifts to a concrete example with a diagram on the right side of the slide. The text reads: A process entering the ready queue is put in queue 0. A process in queue 0 is given a time quantum of 8 milliseconds. The instructor points to the diagram, which shows three stacked boxes labeled quantum = 8, quantum = 16, and FCFS. He explains that if a process does not finish within 8 milliseconds, it is moved to the tail of queue 1. If it still isn't complete after 16 milliseconds in queue 1, it is preempted and put into queue 2. He draws arrows on the screen to visualize this flow, emphasizing that processes needing more than 8 but less than 24 milliseconds are served quickly with lower priority, while long processes automatically sink to queue 2 and are served in FCFS order.

The video effectively bridges theory and practice. It starts by defining the core advantage of feedback queues—flexibility and starvation prevention—before grounding the concept in a specific algorithm with defined time quanta. This progression helps students understand both the why and the how of the scheduling mechanism.

Loading lesson…