CPU Scheduling Algorithms Quiz
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Questions and Answers

What is the short definition of a process?

  • A process is a 'set of global variables.'
  • A process is a 'program code in a file.'
  • A process is a 'program in execution.' (correct)
  • A process is a 'collection of function parameters.'

    • What does the data section of a process contain?

  • Temporary data
  • Global variables (correct)
  • Local variables
  • Return addresses

    • What is the key concept underlying modern operating system design?

  • A process (correct)
  • Heap memory management
  • Multithreading
  • Asynchronous activities

    • What type of activities does an operating system involve?

    <p>Asynchronous and sometimes parallel/concurrent</p> Signup and view all the answers

    What is the address space of a process typically?

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

    In Round Robin scheduling, if there are 4 processes in the ready queue and the time quantum is 10 milliseconds, what is the maximum time any process has to wait to get CPU time?

    <p>40 milliseconds</p> Signup and view all the answers

    If the burst times for processes P1, P2, P3, and P4 in Round Robin scheduling with time quantum 20 are 25, 15, 30, and 20 respectively, what is the completion time of process P3?

    <p>80 milliseconds</p> Signup and view all the answers

    What is the purpose of Round Robin scheduling in interactive systems?

    <p>Minimize response time</p> Signup and view all the answers

    In Round Robin scheduling, if the time quantum is very large, what effect does this have on short CPU burst processes?

    <p>They experience longer waiting times</p> Signup and view all the answers

    How does the turnaround time of long CPU burst processes change in Round Robin scheduling?

    <p>It increases</p> Signup and view all the answers

    Which event does not cause process creation?

    <p>Process termination</p> Signup and view all the answers

    What is the purpose of the fork() system call in UNIX?

    <p>To create a new process as a clone of the parent process</p> Signup and view all the answers

    What are the possible process states in an operating system?

    <p>Ready, running, blocked/waiting, new, terminated</p> Signup and view all the answers

    How are processes created and deleted in an operating system?

    <p>Processes are created and deleted dynamically</p> Signup and view all the answers

    What does the process control block (PCB) contain information about?

    <p>Computation, memory management, and file management</p> Signup and view all the answers

    What are the benefits of using threads?

    <p>Low overhead context switching, resource sharing, economy, and utilization of multiprocessor architectures</p> Signup and view all the answers

    What are the states that threads go through?

    <p>Ready, blocked, running, and terminated</p> Signup and view all the answers

    What are the disadvantages of user-level threads?

    <p>Potential for any user-level thread to block the entire task if the kernel is single threaded</p> Signup and view all the answers

    What are the types of thread implementations mentioned in the text?

    <p>Kernel-supported threads, user-level threads, and hybrid approaches</p> Signup and view all the answers

    What is the role of kernel threads?

    <p>Supported and managed by the kernel, allowing explicit scheduling and parallel processing</p> Signup and view all the answers

    What are some of the performance terms associated with scheduling?

    <p>Fairness, CPU and resource utilization, throughput</p> Signup and view all the answers

    What are the scheduling objectives mentioned in the text?

    <p>Enforcing fairness, priorities, equipment utilization</p> Signup and view all the answers

    What are some of the threading issues mentioned in the text?

    <p>Semantics of fork() and exec() system calls, handling of global variables</p> Signup and view all the answers

    What does low-level scheduling involve?

    <p>Assigning a CPU to a ready process and selection from the ready queue</p> Signup and view all the answers

    What is a characteristic of program behavior mentioned in the text?

    <p>CPU-I/O burst cycles</p> Signup and view all the answers

    What is the main performance metric for FCFS scheduling?

    <p>Average waiting time</p> Signup and view all the answers

    What is the preemptive version of Shortest-Job-First (SJF) scheduling known as?

    <p>Shortest-Remaining-Time-First (SRTF)</p> Signup and view all the answers

    What technique can be used to solve the problem of starvation in priority scheduling?

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

    In FCFS scheduling, what occurs when short processes wait behind long processes?

    <p>Convoy effect</p> Signup and view all the answers

    What is the main goal of Shortest-Job-First (SJF) scheduling?

    <p>To schedule the process with the shortest next CPU burst</p> Signup and view all the answers

    What does the data section of a process contain?

    <p>Global variables</p> Signup and view all the answers

    What is the key concept underlying modern operating system design?

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

    What is the main goal of Shortest-Job-First (SJF) scheduling?

    <p>Minimize turnaround time</p> Signup and view all the answers

    What are some of the threading issues mentioned in the text?

    <p>Thread safety</p> Signup and view all the answers

    What type of activities does an operating system involve?

    <p>Asynchronous and parallel activities</p> Signup and view all the answers

    In Round Robin (RR) scheduling, if there are 4 processes in the ready queue and the time quantum is 20 milliseconds, what is the maximum time any process has to wait to get CPU time?

    <p>80 milliseconds</p> Signup and view all the answers

    What is the completion time of process P3 in Round Robin (RR) scheduling with time quantum 20, if the burst times for processes P1, P2, P3, and P4 are 25, 15, 30, and 20 respectively?

    <p>95 milliseconds</p> Signup and view all the answers

    What is the main goal of Round Robin (RR) scheduling?

    <p>Minimize response time</p> Signup and view all the answers

    What happens to the turnaround time of long CPU burst processes in Round Robin (RR) scheduling?

    <p>It usually becomes longer</p> Signup and view all the answers

    What is the formula to calculate the maximum waiting time for any process in Round Robin (RR) scheduling?

    <p>$ (n-1) \times q $</p> Signup and view all the answers

    What are the advantages of user-level threads?

    <p>Reduced context switch times and elimination of kernel overhead</p> Signup and view all the answers

    What is a disadvantage of kernel threads compared to user-level threads?

    <p>Less control over scheduling and higher overhead</p> Signup and view all the answers

    What is a characteristic of thread operations?

    <p>Creation, blocking, unblocking, and termination</p> Signup and view all the answers

    What type of thread implementation reduces context switch times and eliminates kernel overhead?

    <p>User-level threads</p> Signup and view all the answers

    How do multiple threaded processes enhance throughput and performance?

    <p>By allowing one thread to run while another is blocked and waiting</p> Signup and view all the answers

    What is the purpose of the fork() system call in UNIX?

    <p>To create a new process as a clone of the parent process</p> Signup and view all the answers

    What are the possible process states in an operating system?

    <p>New, running, blocked/waiting, ready, terminated</p> Signup and view all the answers

    What is the main goal of Shortest-Job-First (SJF) scheduling?

    <p>To minimize the average waiting time for processes</p> Signup and view all the answers

    What does the process control block (PCB) contain information about?

    <p>Computation, memory management, and file management</p> Signup and view all the answers

    What are some of the threading issues mentioned in the text?

    <p>Concurrency, synchronization, and communication</p> Signup and view all the answers

    What is the main performance metric for First Come First Serve (FCFS) scheduling?

    <p>Average waiting time</p> Signup and view all the answers

    What is the preemptive version of Shortest-Job-First (SJF) scheduling known as?

    <p>Shortest-Remaining-Time-First (SRTF)</p> Signup and view all the answers

    What problem may occur in priority scheduling and can be solved using aging?

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

    What is the term for the effect in FCFS scheduling when short processes wait behind long processes?

    <p>Convoy effect</p> Signup and view all the answers

    What is the main goal of Shortest-Job-First (SJF) scheduling?

    <p>Minimize average waiting time</p> Signup and view all the answers

    In Round Robin scheduling, how does an increase in the time quantum affect the waiting time of processes with long CPU burst times?

    <p>The waiting time decreases significantly</p> Signup and view all the answers

    What is the main goal of high-level scheduling in batch systems?

    <p>Selecting a mix of CPU-bound and I/O-bound jobs</p> Signup and view all the answers

    What is a critical issue related to threading and signal handling in threads?

    <p>Conflicts over the use of global variables</p> Signup and view all the answers

    What are the program behavior characteristics mentioned in the text?

    <p>CPU-I/O burst cycles and histogram of CPU burst times</p> Signup and view all the answers

    What is the primary concern regarding the semantics of fork() and exec() system calls in threading?

    <p>Proper creation and execution of new processes</p> Signup and view all the answers

    ______ issues include semantics of fork() and exec() system calls and handling of global variables like errno and malloc().

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

    Conflicts between threads over the use of global variables can occur, potentially leading to errors and ______.

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

    Scheduling algorithm goals include high, intermediate, and ______ scheduling for batch systems.

    <p>low-level</p> Signup and view all the answers

    Low-level scheduling, also called CPU scheduling, involves assigning a CPU to a ready process and selection from the ______ queue.

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

    Program behavior characteristics include CPU-I/O burst cycles, CPU/IO cycles, and histogram of CPU burst ______.

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

    FCFS scheduling is ________ and uses FIFO queues

    <p>non-preemptive</p> Signup and view all the answers

    Shortest-Job-First (SJF) scheduling aims to schedule the process with the ________ next CPU burst

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

    Priority scheduling may lead to ________, and aging can be used as a solution to the problem

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

    Determining the length of the next CPU burst involves guessing based on history using ________ averaging

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

    Priority scheduling can be used in both ________ and interactive systems, with each job assigned a priority

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

    Multiple processes are executed concurrently with CPU ______ among them

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

    Principal events causing process creation include system initialization, process creation system execution, user request, and ______ job initiation

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

    In UNIX, the fork() system call creates a new process as a clone of the parent process, while execve() system call replaces the process’ memory space with a new ______

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

    Processes exist in a hierarchy forming a process group or process tree in many operating ______

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

    Processes are implemented through a process table or process control block (PCB) containing information about computation, memory management, and ______ management

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

    An operating system executes a variety of programs: – Batch system – jobs – Time-shared systems – user programs or tasks Short definition: A process is a ______.

    <p>program in execution</p> Signup and view all the answers

    A program is the code sitting in a file in this terminology. 3 Process Concept Multiple parts – The program code, also called text section – Current activity including program counter register and processor registers – Stack containing temporary data Function parameters, return addresses, local variables – Data section containing global variables – Heap containing memory dynamically allocated during run time (through new and malloc()). 4 Process in Memory Address space of a process (typically ______).

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

    The notion of a software process is used in operating systems to express the management and control of such activities. A process is the key concept underlying modern operating system ______.

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

    An operating system involves asynchronous, and sometimes parallel/concurrent, activities. The notion of a software process is used in operating systems to express the management and control of such activities. A process is the key concept underlying modern operating system ______.

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

    Multithreading involves creating a new ______ for each HTTP request

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

    Threads offer benefits such as low overhead context switching, resource sharing, economy, and utilization of ______ architectures

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

    In a single process, a thread shares its code section, data section, and OS resources with other ______

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

    Thread operations include creation, blocking, unblocking, and ______, similar to processes

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

    Multiple threaded processes enhance throughput and performance by allowing one thread to run while another is ______ and waiting

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

    Each process in Round Robin scheduling gets 1/n of the CPU time in chunks of at most ______ time units at once.

    <p>$q$</p> Signup and view all the answers

    Short CPU burst processes in Round Robin scheduling get their chance and exit the queue quickly when they are done, such as ______ tasks.

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

    If the burst times for processes P1, P2, P3, and P4 in Round Robin scheduling with time quantum 20 are 25, 15, 30, and 20 respectively, the completion time of process P3 is ______.

    <p>77</p> Signup and view all the answers

    In Round Robin scheduling, an increase in the time quantum ______ the waiting time of processes with long CPU burst times.

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

    In Round Robin scheduling, if there are 4 processes in the ready queue and the time quantum is 10 milliseconds, the maximum time any process has to wait to get CPU time is ______.

    <p>30</p> Signup and view all the answers

    Study Notes

    CPU Scheduling Algorithms Overview

    • First Come First Serve (FCFS) policy allocates CPU to the first arriving process
    • FCFS scheduling is non-preemptive and uses FIFO queues
    • FCFS performance metric is the average waiting time
    • FCFS scheduling example demonstrates Gantt chart visualization and average waiting time calculation
    • Convoy effect in FCFS occurs when short processes wait behind long processes
    • Shortest-Job-First (SJF) scheduling aims to schedule the process with the shortest next CPU burst
    • SJF has non-preemptive and preemptive versions, with preemptive being known as Shortest-Remaining-Time-First (SRTF)
    • Non-preemptive SJF example shows Gantt chart visualization and average waiting time calculation
    • Preemptive SJF example demonstrates Gantt chart visualization and average waiting time calculation
    • Determining the length of the next CPU burst involves guessing based on history using exponential averaging
    • Priority scheduling can be used in both batch and interactive systems, with each job assigned a priority
    • Priority scheduling may lead to starvation, and aging can be used as a solution to the problem.

    Operating System Scheduling and Threading

    • Solaris 2 and Windows NT/2000 with ThreadFiber package allow the operating system to create a sufficient number of kernel threads.
    • Threading issues include semantics of fork() and exec() system calls and handling of global variables like errno and malloc().
    • Signal handling in threads raises the question of which thread should catch the signals, especially in user-threads.
    • Conflicts between threads over the use of global variables can occur, potentially leading to errors and suspensions.
    • Processes and thread scheduling involves scheduling objectives for batch, interactive, and real-time systems.
    • Scheduling objectives include enforcing fairness, priorities, equipment utilization, and preference to processes exhibiting good behavior.
    • Performance terms associated with scheduling include fairness, CPU and resource utilization, throughput, turnaround time, waiting time, and response time.
    • Program behavior characteristics include CPU-I/O burst cycles, CPU/IO cycles, and histogram of CPU burst times.
    • Scheduling algorithm goals include high, intermediate, and low-level scheduling for batch systems.
    • High-level scheduling involves selecting a mix of CPU-bound and I/O-bound jobs and alternate selection criteria.
    • Intermediate scheduling involves temporarily suspending or resuming jobs to smooth fluctuations in system load.
    • Low-level scheduling, also called CPU scheduling, involves assigning a CPU to a ready process and selection from the ready queue.

    Multithreading: Types, Models, and Usage

    • Multithreading involves creating a new process for each HTTP request, but this can lead to high overhead.
    • Threads offer benefits such as low overhead context switching, resource sharing, economy, and utilization of multiprocessor architectures.
    • In a single process, a thread shares its code section, data section, and OS resources with other threads.
    • Thread usage examples include a word processor with three threads for input, reformat, and save, as well as graphics applications like augmented reality.
    • Thread operations include creation, blocking, unblocking, and termination, similar to processes.
    • Threads go through states like ready, blocked, running, and terminated, and they are considered cooperating with no protection among threads.
    • Multiple threaded processes enhance throughput and performance by allowing one thread to run while another is blocked and waiting.
    • Extensive sharing in threads makes CPU switching and thread creation inexpensive compared to heavyweight processes.
    • There are different types of thread implementations including kernel-supported threads, user-level threads, and hybrid approaches.
    • User-level threads are managed by a user-level threads library, reducing context switch times and eliminating kernel overhead.
    • Disadvantages of user-level threads include the potential for any user-level thread to block the entire task if the kernel is single threaded.
    • Kernel threads are supported and managed by the kernel, allowing explicit scheduling and parallel processing, but with less control over scheduling and higher overhead compared to user-level threads.

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    Related Documents

    Chapter_02_Slides Processes and Threads.pdf

    Description

    Test your knowledge of CPU scheduling algorithms with this quiz. Explore First Come First Serve (FCFS), Shortest-Job-First (SJF), and Priority scheduling, and learn about their features, performance metrics, and potential issues. Dive into examples with Gantt chart visualizations and average waiting time calculations to deepen your understanding of these essential algorithms.

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