Memory Management in Operating Systems
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What is the primary role of a dispatcher in process scheduling?

  • To schedule jobs for long-term execution
  • To manage external fragmentation
  • To allocate memory for different processes
  • To switch processes from ready state to running state (correct)

    • Which statement accurately describes internal fragmentation?

  • It occurs when memory is allocated but not fully used by a process (correct)
  • It occurs when processes are queued in the job scheduler
  • It is the result of multiple processes competing for the same memory space
  • It arises from inadequate memory being assigned to a process

    • What technique is used to manage external fragmentation?

  • Swapping
  • Compaction (correct)
  • Segmentation
  • Paging

    • How does paging influence memory management?

    <p>By splitting processes into manageable pages</p> Signup and view all the answers

    In process scheduling, which component makes high-frequency decisions?

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

    What type of fragmentation is primarily caused when there's leftover space after memory allocation?

    <p>Internal fragmentation</p> Signup and view all the answers

    What does the term ‘ready state’ refer to in process scheduling?

    <p>The state where a process is prepared to execute but is not yet running</p> Signup and view all the answers

    What is the function of a job scheduler in an operating system?

    <p>To manage long-term process execution</p> Signup and view all the answers

    What is the primary characteristic of main memory?

    <p>It is a volatile memory with fast access at a relatively high cost.</p> Signup and view all the answers

    Which statement correctly describes secondary memory?

    <p>It is non-volatile and suitable for long-term storage.</p> Signup and view all the answers

    What is a disadvantage of simple segmentation?

    <p>It results in external fragmentation.</p> Signup and view all the answers

    What is one of the key benefits of virtual memory?

    <p>It enables processes and the kernel to seemingly use more memory than is physically available.</p> Signup and view all the answers

    Which memory partitioning technique is uncommon in the industry today?

    <p>Fixed partitioning</p> Signup and view all the answers

    Why is external fragmentation a concern in memory partitioning techniques?

    <p>It causes gaps between allocated memory segments.</p> Signup and view all the answers

    Which of the following accurately describes fixed partitioning?

    <p>It divides memory into static partitions determined at system generation time.</p> Signup and view all the answers

    What is one major overhead associated with virtual memory?

    <p>Increased memory requirements for OS management.</p> Signup and view all the answers

    What leads to external fragmentation in memory management?

    <p>Varying sizes of allotted memory blocks.</p> Signup and view all the answers

    Which type of address is primarily used in source code?

    <p>Symbolic address</p> Signup and view all the answers

    What is internal fragmentation primarily caused by?

    <p>Processes needing more space than allocated blocks.</p> Signup and view all the answers

    What is one of the key functions of memory management in an OS?

    <p>Tracking memory locations for process allocation.</p> Signup and view all the answers

    Which addresses are converted from symbolic addresses at compilation?

    <p>Relative addresses</p> Signup and view all the answers

    What must be ensured to protect each process during execution?

    <p>Processes should not reference each other's memory.</p> Signup and view all the answers

    What aspect of memory management allows programs to be relocated?

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

    Which address is generated when a program is loaded into the main memory?

    <p>Physical address</p> Signup and view all the answers

    What characteristic describes a non-preemptive scheduling algorithm?

    <p>It treats all processes the same.</p> Signup and view all the answers

    What is a major drawback of the First-Come, First-Served (FCFS) scheduling algorithm?

    <p>It can lead to a high average waiting time.</p> Signup and view all the answers

    In what scenario would an algorithm prioritize processes that underutilize stressed resources?

    <p>To maintain resource balancing.</p> Signup and view all the answers

    Which type of workloads are involved in I/O-bound processes?

    <p>Applications requiring low-latency responses.</p> Signup and view all the answers

    What is the recommended approach for process treatment in a fairness-based scheduling algorithm?

    <p>Processes should be treated equally without user guidance.</p> Signup and view all the answers

    What is a key advantage of using the First-Come, First-Served (FCFS) scheduling algorithm?

    <p>It is simple to understand and implement.</p> Signup and view all the answers

    The concept of 'turnaround time' in scheduling refers to what?

    <p>Total time from submission to completion of a process.</p> Signup and view all the answers

    In scheduling, what is the implication of favoring CPU-bound processes over I/O-bound ones?

    <p>It addresses long runtimes efficiently.</p> Signup and view all the answers

    What is the main principle of the Shortest Remaining Time First (SRTF) algorithm?

    <p>It selects and executes the process with the shortest expected processing time.</p> Signup and view all the answers

    In the context of SJF scheduling, which of the following is true about the turnaround time?

    <p>It includes both waiting time and burst time.</p> Signup and view all the answers

    What is the average waiting time for the processes in the SJF example provided?

    <p>3.20</p> Signup and view all the answers

    Which process has the longest turnaround time in the SJF scheduling example?

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

    What is the average turnaround time calculated for Round Robin (RR) scheduling mentioned?

    <p>7.60</p> Signup and view all the answers

    How is the average Tr/Ts ratio calculated for the SJF scheduling example?

    <p>By averaging the individual Tr/Ts values for each process.</p> Signup and view all the answers

    What does the Round Robin (RR) algorithm specifically involve?

    <p>It generates a clock interrupt at periodic intervals.</p> Signup and view all the answers

    How is the average waiting time computed based on the provided processes?

    <p>It is the summation of all individual waiting times divided by their count.</p> Signup and view all the answers

    What is the average turnaround time calculated from the given data?

    <p>10.00</p> Signup and view all the answers

    Which scheduling algorithm is a preemptive version of the shortest job first?

    <p>Shortest Remaining Time First</p> Signup and view all the answers

    What calculation represents the ratio of turnaround time to burst time for process A?

    <p>1.00</p> Signup and view all the answers

    What is the risk involved in using the Shortest Remaining Time First scheduling method?

    <p>Starvation of long processes</p> Signup and view all the answers

    What does the quantum represent in Round Robin scheduling?

    <p>The allocated time slice for each process</p> Signup and view all the answers

    Calculate the average waiting time based on the provided finish and arrival times.

    <p>2.40</p> Signup and view all the answers

    If a new process with a shorter remaining time arrives, what happens to the currently running process in SRTF?

    <p>It is preempted and the new process takes over.</p> Signup and view all the answers

    Which process had the longest waiting time in the provided example?

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

    What does the finish time represent in the context of scheduling?

    <p>The point at which a process completes its execution</p> Signup and view all the answers

    Which of the following processes had the shortest burst time?

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

    Study Notes

    Memory Management

    • Memory management is a function of the operating system (OS)
    • Manages the movement of processes between primary and secondary memory during execution
    • Tracks allocated and free memory locations
    • Facilitates process allocation and updates memory status

    Types of Addresses

    • Symbolic addresses: Used in source code (variable names, constants, instruction labels)
    • Relative addresses: Generated during compilation
    • Physical addresses: Generated by the loader when a program is loaded into main memory

    Memory Management Terms

    • Frame: A fixed-length block of main memory
    • Page: A fixed-length block of data in secondary memory, potentially copied to a frame in main memory
    • Segment: A variable-length block of data in secondary memory, potentially divided into pages and copied to main memory
    • Swapping: Temporarily moving a process from main memory to secondary memory to free up space
    • Fragmentation: Break-down of free memory spaces into smaller fragments due to continuous loading and removal of processes

    Memory Management Requirements

    • Relocation: Programs can be moved within main memory during execution
    • Protection: Processes cannot access each other's memory without permission, especially OS sections. Processes cannot access each other's data without special arrangement
    • Sharing: Processes can access the same memory locations. Sharing improves data structure management.
    • Logical organization: Modules in programs-some read-only, some modifiable.
    • Physical organization: Operating system handles the movement of information between primary and secondary memory.

    Memory Partitioning Techniques

    • Fixed Partitioning: Main memory is divided into static partitions at the time of system generation. Processes fit into matching size partitions. Simpler to implement, but inefficient when partitions are unequal or non-optimal
    • Dynamic Partitioning: Partitions are created dynamically based on process requirements. More memory efficient but can lead to external fragmentation. Uses a placement algorithm (best fit, first fit, next fit)
    • Simple Paging: Divides memory into equal sized frames and process into equal sized pages.
    • Simple Segmentation: Divides memory into segments, loaded into dynamic partitions. Reduces internal fragmentation.
    • Virtual Memory: Abstraction of main memory. Processes and kernel see a larger memory space.

    Process Scheduling

    • Scheduling: Selection of a job or task to be dispatched
    • Job Queue: All processes in the system
    • Ready Queue: Processes in main memory, waiting to execute
    • Device Queue: Processes waiting for I/O devices
    • Scheduling Objectives: Improving response time and throughput

    Process Scheduling Algorithms

    • Long-term scheduling: Controls the degree of multiprogramming by deciding which programs to admit into the system for processing (job scheduler).
    • Short-term scheduling: Decides which process to run next, when a process blocks (dispatcher)
    • Medium-term scheduling: Manage the degree of multiprogramming by swapping processes in and out

    Scheduling Criteria

    • Turnaround time: Time between submission and completion of a process
    • Response time: Time from submission to receiving a response
    • Burst time: Time a process takes to run
    • Waiting time: Time a process spends waiting in the ready queue

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    Description

    This quiz covers key concepts related to memory management, an essential function of the operating system. It includes various types of addresses, memory management terms like frames and pages, and the implications of process allocation and memory status tracking.

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