Context Switching in CPU Scheduling
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What is the main purpose of scheduling in a system?

  • To manage the memory allocation of a process
  • To prioritize the execution of a specific process
  • To handle the I/O operations of a process
  • To ensure efficient execution of processes and optimal CPU utilization (correct)

    • Which type of scheduling allows the OS to assign resources to a process for a predetermined period?

  • Preemptive scheduling (correct)
  • Medium-term scheduling
  • Non-preemptive scheduling
  • Long-term scheduling

    • What is the function of the Job Queue in a system?

  • It schedules the processes to be executed next
  • It contains all the processes in the system (correct)
  • It manages the swapping of processes in and out of memory
  • It handles the I/O operations of a process

    • What type of scheduler determines which processes are to be admitted into the system?

    <p>Long-term Scheduler (Job Scheduler)</p> Signup and view all the answers

    Which type of scheduling is used when a process terminates?

    <p>Non-Preemptive scheduling</p> Signup and view all the answers

    What is the function of the Short-term Scheduler (CPU Scheduler)?

    <p>It schedules the processes to be executed next</p> Signup and view all the answers

    What is the primary advantage of the First-Come, First-Served scheduling algorithm?

    <p>Simple and easy to implement</p> Signup and view all the answers

    What is the function of the Medium-term Scheduler?

    <p>It manages the swapping of processes in and out of memory</p> Signup and view all the answers

    What type of scheduling is used when a process switches from running state to ready state?

    <p>Preemptive scheduling</p> Signup and view all the answers

    What is the formula to calculate the Turnaround Time of a process?

    <p>Turnaround Time = Completion Time - Arrival Time</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the Shortest Job Next (SJN) scheduling algorithm?

    <p>Executes processes in the order of arrival</p> Signup and view all the answers

    What is the Response Time of a process?

    <p>Time between process arrival and first execution</p> Signup and view all the answers

    What is the term for the moment when a process enters the ready queue and awaits execution by the CPU?

    <p>Arrival Time</p> Signup and view all the answers

    What is the formula to calculate the Waiting Time of a process?

    <p>Waiting Time = Turnaround Time - Burst Time</p> Signup and view all the answers

    In the FCFS scheduling algorithm, which process will be executed first?

    <p>P1</p> Signup and view all the answers

    What is the waiting time for P3?

    <p>5</p> Signup and view all the answers

    What is the primary purpose of context switching in operating systems?

    <p>To switch the CPU from one process to another for smooth execution</p> Signup and view all the answers

    Which of the following statements is true about FCFS?

    <p>It is a non-preemptive scheduling algorithm</p> Signup and view all the answers

    When does context switching happen?

    <p>When a high-priority process comes to a ready state</p> Signup and view all the answers

    What is the definition of a thread in operating systems?

    <p>The smallest unit of a process that can be scheduled and executed by the CPU</p> Signup and view all the answers

    What is the burst time for P5?

    <p>2</p> Signup and view all the answers

    What is an advantage of using threads in operating systems?

    <p>Responsiveness and resource sharing</p> Signup and view all the answers

    What is the average waiting time for the given processes?

    <p>4.8</p> Signup and view all the answers

    What type of thread is managed by the operating system kernel?

    <p>Kernel-Level Thread (KLT)</p> Signup and view all the answers

    In FCFS, which process will be executed last?

    <p>P5</p> Signup and view all the answers

    What is the state of a thread when it is waiting for resources?

    <p>Blocked</p> Signup and view all the answers

    What is the arrival time for P4?

    <p>6</p> Signup and view all the answers

    What is the purpose of calculating the average waiting time?

    <p>To evaluate the performance of the scheduling algorithm</p> Signup and view all the answers

    What is process scheduling in operating systems?

    <p>The method by which the operating system decides which process runs at any given time</p> Signup and view all the answers

    Why is creating and managing threads less costly than processes?

    <p>Because threads share memory and resources</p> Signup and view all the answers

    What is the main characteristic of Non-preemptive SJF scheduling?

    <p>Once a process starts, it cannot be interrupted until it finishes.</p> Signup and view all the answers

    What is the main advantage of Priority Scheduling?

    <p>It minimizes average waiting time.</p> Signup and view all the answers

    What is the solution to Starvation in Priority Scheduling?

    <p>Aging, which is a technique of gradually increasing the priority of processes that wait in the system for a long time.</p> Signup and view all the answers

    What is the main characteristic of Preemptive SJF scheduling?

    <p>A running process can be interrupted if a new process with a high priority number arrives.</p> Signup and view all the answers

    What is the main disadvantage of Priority Scheduling?

    <p>It can lead to starvation of lower priority processes.</p> Signup and view all the answers

    What is the main characteristic of Round Robin scheduling?

    <p>A process is allocated a fixed time slot and is preempted if it does not finish execution within that time.</p> Signup and view all the answers

    What is the main difference between Preemptive SJF and Non-preemptive SJF?

    <p>The ability to interrupt a running process.</p> Signup and view all the answers

    What is the term for a process running out of resources because other processes are using it?

    <p>Starvation</p> Signup and view all the answers

    Study Notes

    Context Switching

    • Involves switching the CPU from one process to another, ensuring smooth execution of multiple processes.
    • Happens when a high-priority process comes to a ready state, an interrupt occurs, user and kernel-mode switch, or preemptive CPU scheduling is used.

    Threads in Operating Systems

    • Definition: The smallest unit of a process that can be scheduled and executed by the CPU.
    • Importance: Allows parallelism within a process, leading to more efficient and faster execution.
    • Types of Threads:
      • User-Level Threads (ULTs): Managed by user-level libraries, with fast context switch and no OS modification required.
      • Kernel-Level Threads (KLTs): Managed by the operating system kernel, with the OS managing and scheduling threads independently.

    Advantages of Using Threads

    • Responsiveness: Allows a program to continue running even if part of it is blocked.
    • Resource Sharing: Threads of the same process share memory and resources.
    • Economy: Creating and managing threads is less costly than processes.
    • Scalability: Threads can run on different processors in a multiprocessor system.

    Thread Lifecycle

    • New: Thread is created.
    • Runnable: Thread is ready to run.
    • Running: CPU is executing the thread.
    • Blocked: Thread is waiting for resources.
    • Terminated: Thread has finished execution.

    Process Scheduling in Operating Systems

    • Definition: The method by which the operating system decides which process runs at any given time.
    • Importance: Ensures efficient execution of processes, optimal CPU utilization, and overall system performance.

    Categories of Scheduling

    • Non-preemptive: A process's resource cannot be taken before the process has finished running.
    • Preemptive: The OS assigns resources to a process for a predetermined period, and the process switches from running state to ready state or from waiting state to ready state during resource allocation.

    Types of Schedulers

    • Long-term Scheduler (Job Scheduler): Determines which processes are to be admitted into the system and brings the new process to the 'Ready State'.
    • Short-term Scheduler (CPU Scheduler): Selects which process should be executed next and brings process from the ready state for scheduling it on the running state.
    • Medium-term Scheduler: Manages swapping of processes in and out of memory to balance load.

    Scheduling Queues

    • Job Queue: All processes in the system.
    • Ready Queue: Processes that are ready to run.
    • Device Queue: Processes waiting for devices (I/O).

    Scheduling Algorithms Overview

    • Two types of scheduling methods:
      • Preemptive Scheduling: Used when a process switches from running state to ready state or from waiting state to ready state.
      • Non-Preemptive Scheduling: Used when a process terminates, or when a process switches from running state to waiting state.

    CPU Scheduling Algorithms

    • First-Come, First-Served (FCFS): Processes are executed in the order they arrive.
    • Shortest Job Next (SJN): Processes are executed in the order of their burst time.
    • Priority Scheduling: Processes are assigned priority numbers, and the highest priority process is selected next.
    • Round Robin (RR): Each process is allocated a fixed time slot (time quantum), and if a process does not finish execution within its time quantum, it is preempted and placed at the end of the ready queue.

    Key Concepts in CPU Scheduling

    • Arrival Time: The moment in time when a process enters the ready queue and is awaiting execution by the CPU.
    • Burst Time: The amount of CPU time the process requires to complete its execution.
    • Completion Time: The summation of the arrival, waiting, and burst times.
    • Turnaround Time: The time elapsed between the arrival of a process and its completion.
    • Waiting Time: A process's duration in the ready queue before it begins executing.
    • Response Time: The duration between the arrival of a process and the first time it runs.

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    CH3 Process Management.pptx

    Description

    This quiz covers the concept of context switching, which involves switching the CPU from one process to another, ensuring smooth execution of multiple processes.

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