Scheduling Algorithm in Operating System.pptx

Algorithm is Operating System

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2. Title: Scheduling Algorithms in Operating Systems Subtitle: Optimizing Resource Management 9/10/2023 Sample Footer Text 2

3. who can do the scheduling? ChatGPT Scheduling in an operating system is a critical task that requires the involvement of various components and entities within the system. Different entities contribute to the scheduling process, and these include: The Operating System Kernel: The core component of the operating system, known as the kernel, is responsible for managing the scheduling of processes. The kernel contains the scheduler, which is a part of the operating system responsible for deciding which processes get CPU time and in what order. The scheduler uses algorithms and policies to make these decisions. Schedulers: Schedulers are software modules or components within the operating system that implement scheduling algorithms and policies. There can be multiple schedulers within an operating system, each responsible for a specific aspect of scheduling. For example, there may be a CPU scheduler responsible for selecting which process to run on the CPU, an I/O scheduler for managing I/O operations, and a memory scheduler for memory management. System Administrators: In some cases, system administrators or users with administrative privileges may have the ability to influence or configure scheduling policies. They can set process priorities, resource limits, and scheduling parameters to optimize system performance for specific workloads. Hardware: Modern computer hardware often includes features that can influence scheduling. For example, multi-core processors and hardware-level support for virtualization can affect how processes are scheduled across CPU cores or virtual machines. Programs and Applications: Some programs and applications can have a degree of control over their own scheduling. They can request certain scheduling priorities or specify their resource requirements to the operating system. User Requests: User-initiated actions, such as keyboard and mouse input or requests for background tasks, can trigger scheduling events. For example, an interactive user interface may generate events that cause the operating system to prioritize user-facing tasks for CPU time. External Events: Events external to the system, such as hardware interrupts or signals from external devices, can also influence scheduling decisions. The operating system must respond to these events promptly and efficiently. In summary, scheduling is a collaborative effort involving various components within the operating system, as well as external factors like system administrators, hardware capabilities, user interactions, and application requirements. The ultimate goal is to allocate system resources effectively to meet the objectives of fairness, efficiency, and responsiveness while optimizing overall system performance. The specific roles and responsibilities of these entities can vary depending on the design and configuration of the operating system.

4. Agenda Introduction to Scheduling Algorithms Types of Scheduling Algorithms Common Scheduling Algorithms Comparison and Evaluation Real-World Applications Conclusion and Future Developments 9/10/2023 Sample Footer Text 4

5. Introduction to Scheduling Algorithms Definition of Scheduling Importance in Operating Systems Objectives: Fairness, Efficiency, Responsiveness Challenges in Process Scheduling 9/10/2023 Sample Footer Text 5

6. Definition of Scheduling Scheduling, in the context of operating systems, refers to the process of managing and controlling the allocation of a computer's central processing unit (CPU) and other system resources to various tasks or processes in a way that optimizes system performance and user experience. It is a fundamental aspect of modern operating systems that ensures efficient and fair utilization of resources among multiple processes or applications competing for access to the CPU. To understand this definition more comprehensively, let's break it down: Resource Allocation: Scheduling primarily deals with allocating system resources, with the CPU being the most critical resource. In a multitasking environment where multiple processes are running simultaneously, the operating system must decide which process should execute on the CPU at any given time. Optimizing System Performance: The primary goal of scheduling is to optimize system performance. This means achieving objectives like maximizing CPU utilization, minimizing response time, and ensuring fairness among competing processes. User Experience: Effective scheduling ensures a responsive and smooth user experience. It aims to minimize delays and prevent situations where a single resource-intensive process monopolizes the CPU, causing other processes to become unresponsive. Fairness: Scheduling algorithms should provide fair access to CPU time for all processes, regardless of their priority or resource requirements. Unfair scheduling can lead to dissatisfaction among users and poor system performance. Dynamic and Real-time: Scheduling is a dynamic process that continuously adapts to changing conditions. New processes can be created, existing ones may terminate, and the priority of processes can change, necessitating constant reevaluation and adjustment of scheduling decisions. Coordination with Other Resources: In addition to the CPU, scheduling also interacts with other system resources like memory, I/O devices, and network interfaces. Effective scheduling must consider the availability of these resources to avoid bottlenecks and resource contention. Complexity: Scheduling can be a complex task because it involves making decisions based on various factors, including process priorities, execution times, resource constraints, and system policies. Different scheduling algorithms are designed to address different aspects of these complexities. In summary, scheduling in operating systems is a crucial mechanism that plays a pivotal role in ensuring that the computer's resources are utilized efficiently, fairly, and in a manner that delivers a responsive and satisfactory user experience. Operating systems employ various scheduling algorithms to achieve these objectives, and the choice of algorithm can significantly impact system performance and user satisfaction.

7. Importance of Scheduling OS The importance of scheduling in operating systems cannot be overstated. It plays a crucial role in ensuring the efficient and effective operation of computer systems. Here's an explanation of its importance in operating systems: Resource Management: Operating systems are responsible for managing the finite hardware resources of a computer, including the CPU, memory, and I/O devices. Scheduling helps allocate these resources to multiple processes or tasks, ensuring that they share resources fairly and efficiently. Without scheduling, processes might compete for resources in an uncontrolled manner, leading to resource contention and system instability. Multiprogramming and Multitasking: Modern operating systems support the execution of multiple processes or tasks concurrently. Scheduling allows the CPU to switch between these processes rapidly, giving the illusion of parallel execution to users. Without scheduling, a computer would be limited to running one program at a time, severely limiting its usefulness and efficiency. Fairness: Scheduling ensures fairness among processes, preventing any one process from monopolizing system resources indefinitely. Fairness is vital to maintain a responsive and equitable computing environment. Without scheduling, certain processes could dominate the CPU's time, leaving other processes neglected and causing dissatisfaction among users. Efficiency: Efficient scheduling maximizes the utilization of system resources. It aims to keep the CPU and other resources busy, thereby improving the overall throughput and performance of the system. Efficient scheduling ensures that tasks are completed in a timely manner, optimizing the use of expensive hardware. Responsiveness: Scheduling helps maintain system responsiveness by promptly attending to user requests and system interrupts. Interactive tasks, such as user input or real-time processes, receive timely CPU attention, preventing delays and ensuring a smooth user experience. Without scheduling, a single long-running process could block user interactions, leading to an unresponsive system. Prioritization: Operating systems often support processes with varying priorities. Scheduling allows high-priority tasks to be executed preferentially, ensuring that critical operations are completed promptly. Without scheduling, all processes would be treated equally, which might lead to critical tasks being delayed or neglected. Resource Arbitration: Scheduling plays a role in resource arbitration, deciding which process gets access to shared resources like printers, disks, or network interfaces. It helps prevent resource conflicts and ensures that processes access shared resources in an orderly and coordinated manner. Predictability: Some real-time systems require predictable and deterministic scheduling to meet strict timing requirements. Scheduling algorithms can be designed to ensure that critical tasks meet their deadlines consistently. This is essential in applications like aviation, medical devices, and industrial control systems. In summary, scheduling is at the core of operating system functionality. It allows for efficient, fair, and responsive resource allocation, making it possible to run multiple processes simultaneously, meet user expectations, and maximize the utilization of hardware resources. Effective scheduling is critical for the overall performance, stability, and usability of modern computer systems.

8. The objectives of fairness, efficiency, and responsiveness are key goals that operating system schedulers aim to achieve when managing and allocating resources to processes. Let's delve into each of these objectives in detail: Fairness: Definition: Fairness in scheduling refers to the equitable distribution of CPU time and other system resources among competing processes. It ensures that no process is unfairly starved or monopolizes system resources, regardless of its priority or resource requirements. Importance: Fairness is essential to prevent situations where one process hogs the CPU, causing other processes to become unresponsive or unable to make progress. Fair scheduling ensures that all processes, regardless of their importance or resource needs, get a reasonable share of system resources. Achieving Fairness: Schedulers achieve fairness by implementing algorithms that consider process priorities, allocate CPU time proportionally, and prevent any single process from dominating resource utilization for extended periods. Efficiency: Definition: Efficiency in scheduling focuses on maximizing the utilization of system resources, particularly the CPU. It aims to keep the CPU busy executing processes as much as possible, minimizing idle time. Importance: Efficient scheduling improves overall system throughput and ensures that resources are not wasted. It maximizes the number of tasks completed within a given time frame. Achieving Efficiency: Schedulers employ algorithms that prioritize processes based on various factors such as execution time, priority levels, and resource requirements. Techniques like preemption (where a running process can be interrupted) are used to ensure efficient utilization of the CPU. Responsiveness: Definition: Responsiveness in scheduling is related to how quickly the operating system can respond to user or system requests. It ensures that interactive tasks, such as user input or system interrupts, receive prompt attention from the CPU. Importance: Responsiveness is critical for providing a smooth and interactive user experience. Without responsiveness, the system may appear sluggish and unresponsive to user commands. Achieving Responsiveness: Schedulers often use techniques like time slicing and priority-based scheduling to give preference to interactive processes. By allocating CPU time to interactive tasks promptly, the system maintains a responsive feel, even when there are background tasks or resource-intensive processes running. In summary, the objectives of fairness, efficiency, and responsiveness are interconnected and essential for effective scheduling in operating systems. A well-designed scheduler strives to balance these objectives to provide a fair and efficient allocation of resources while ensuring that interactive tasks receive the responsiveness they require. Different scheduling algorithms and policies are designed to optimize these objectives based on the specific requirements of the operating system and the types of processes it needs to manage.

9. Challanges of Scheduling Process scheduling in operating systems is a complex task that comes with several challenges due to the dynamic nature of computing environments and the diverse requirements of different processes. Some of the key challenges in process scheduling include: Optimizing Multiple Objectives: Schedulers need to strike a balance between various conflicting objectives, such as fairness, efficiency, and responsiveness. Designing a scheduling algorithm that optimizes all these objectives simultaneously can be challenging. Real-time Requirements: Real-time systems have stringent timing requirements. Meeting deadlines for critical tasks is essential in applications like aviation, medical devices, and industrial control systems. Scheduling processes with hard real-time constraints is challenging and requires careful design. Resource Contention: Schedulers must handle resource contention when multiple processes compete for shared resources like the CPU, memory, or I/O devices. Balancing resource access and preventing resource starvation can be difficult. Process Prioritization: Assigning priorities to processes is challenging, as it requires a fair and effective way to determine which processes should receive preferential treatment. The priority scheme must reflect the importance and urgency of tasks accurately. Load Balancing: In multiprocessor systems, distributing processes efficiently across multiple CPUs is a challenge. Load balancing aims to ensure that CPUs are utilized evenly to maximize system performance. Dynamic Workloads: Operating systems must adapt to changing workloads and process behavior. Some processes may be CPU-bound, while others are I/O-bound. The scheduler needs to adjust priorities and resource allocation dynamically. Synchronization and Deadlocks: Ensuring proper synchronization among processes to avoid data corruption or deadlock situations is challenging. Process scheduling must account for the need to lock and unlock resources safely. Starvation: The scheduler should prevent processes from experiencing starvation, where a process is consistently denied access to resources. Fairness mechanisms must be in place to ensure that all processes eventually get their share. Complexity of Scheduling Algorithms: There are numerous scheduling algorithms available, each with its own complexity and performance characteristics. Choosing the right algorithm for a specific environment and workload can be challenging. User and System Expectations: Meeting user expectations for responsiveness and system performance is challenging, as users typically demand fast response times, even when the system is under heavy load. Balancing user experience with system efficiency is crucial. Resource Overhead: Scheduling itself consumes system resources (e.g., CPU cycles and memory) to make scheduling decisions. Minimizing this overhead while making effective scheduling decisions is a challenge. Security Concerns: Some scheduling decisions can have security implications. For example, scheduling high-priority processes can be exploited for privilege escalation or denial-of-service attacks. Security-aware scheduling is necessary to mitigate these risks. Energy Efficiency: In mobile and battery-powered devices, power consumption is a critical concern. Schedulers must consider energy-efficient scheduling to prolong battery life while maintaining performance. Addressing these challenges requires careful design, evaluation, and refinement of scheduling algorithms. Operating systems often employ a combination of strategies and heuristics to tackle these issues, with different scheduling algorithms and policies tailored to specific use cases and environments.

10. Types of Scheduling Algorithms Preemptive vs. Non-Preemptive CPU-bound vs. I/O-bound Long-term, Short-term, and Medium-term scheduling Global vs. Local Scheduling 9/10/2023 Sample Footer Text 10

11. Preemptive vs. Non-Preemptive Preemptive and non-preemptive scheduling algorithms are two fundamental approaches to process scheduling in operating systems. These approaches determine how the operating system manages and prioritizes the execution of processes. Here's an explanation of each: 1. Preemptive Scheduling Algorithm: Definition: In preemptive scheduling, the operating system has the capability to interrupt or preempt a currently running process and switch to another process based on a certain event or condition. This means that a process can be forcibly taken off the CPU before it has completed its execution, allowing other processes to execute in a time-sliced or priority-based manner. Characteristics: Processes can be interrupted during their execution. The scheduler has control over process execution, allowing it to make dynamic decisions based on process priorities, time quantum, or external events. Well-suited for multitasking and real-time systems where responsiveness and fairness are crucial. Examples of preemptive scheduling algorithms include Round Robin (RR) and Priority Scheduling. Advantages: Provides better responsiveness as high-priority tasks can be scheduled promptly. Fairly allocates CPU time among competing processes. Suitable for environments with dynamic workloads. Disadvantages: May introduce some overhead due to frequent context switches. More complex to implement and manage than non-preemptive scheduling. 2. Non-Preemptive (or Cooperative) Scheduling Algorithm: Definition: In non-preemptive scheduling, a running process is not forcibly interrupted by the operating system. Instead, the process voluntarily relinquishes control of the CPU, typically through system calls or explicit yield statements. The scheduler selects the next process to run only when the currently running process gives up control. Characteristics: Processes run until they voluntarily yield or block (e.g., I/O operation). The scheduler's decisions are limited to when processes explicitly release the CPU. Common in older and simpler operating systems, as well as some embedded systems. Advantages: Simpler to implement and manage, as there are fewer context switches. Lower overhead compared to preemptive scheduling due to fewer interrupts. Disadvantages: Lacks responsiveness in situations where processes do not voluntarily yield. Can lead to inefficiency if a process hogs the CPU and does not yield, causing delays for other processes. Unsuitable for environments with real-time or time-sharing requirements where fairness and responsiveness are essential. Choosing Between Preemptive and Non-Preemptive Scheduling: The choice between preemptive and non-preemptive scheduling depends on the specific requirements of the operating system and the nature of the tasks it needs to manage. Preemptive scheduling is often preferred in multitasking and real-time systems, where responsiveness and fairness are critical. Non-preemptive scheduling may be suitable for simpler or embedded systems with less demanding scheduling requirements but may be less suitable for general-purpose operating systems where responsiveness and multitasking are essential. Many modern operating systems use a combination of both approaches, depending on the context and priorities of processes.

12. Long-term, Short-term, and Medium-term scheduling Long-term, short-term, and medium-term scheduling are three distinct phases or types of process scheduling that occur in an operating system. Each serves a specific purpose in managing processes and system resources effectively. Here's an explanation of each type: Long-term Scheduling (Job Scheduling): Purpose: Long-term scheduling is responsible for selecting processes from the pool of all available processes in the system and deciding which processes to admit into the ready queue for execution. It determines which programs or tasks are allowed to enter the execution phase from the "job pool." Characteristics: Typically, long-term scheduling is not as frequent as other types of scheduling. It involves deciding when to initiate a new process or job, such as when a user starts a new application or submits a batch job for processing. The goal is to maintain a balance between system load and resource availability by controlling the number of processes in the system at any given time. Considerations: Long-term scheduling decisions may be based on factors like available memory, CPU utilization, and the desired degree of multitasking. It aims to prevent overloading the system with too many processes. Short-term Scheduling (CPU Scheduling): Purpose: Short-term scheduling, also known as CPU scheduling, is responsible for deciding which process from the ready queue (i.e., the pool of processes ready to execute) will be allocated the CPU next. It focuses on managing CPU resources efficiently. Characteristics: Short-term scheduling decisions occur frequently and rapidly, often in the order of milliseconds. The goal is to maximize CPU utilization, minimize response time, and ensure fair access to CPU resources among competing processes. Common CPU scheduling algorithms include First-Come-First-Serve (FCFS), Shortest Job Next (SJN)/Shortest Job First (SJF), Round Robin (RR), and Priority Scheduling. Considerations: The choice of scheduling algorithm impacts factors like process turnaround time, waiting time, and system responsiveness. Different algorithms prioritize different aspects, such as fairness or throughput. Medium-term Scheduling (Swapping): Purpose: Medium-term scheduling is responsible for managing processes that are partially in memory (i.e., partially loaded) and partially on secondary storage (e.g., disk). It is primarily concerned with memory management and the movement of processes between main memory (RAM) and secondary storage. Characteristics: Medium-term scheduling is less frequent than short-term scheduling but more frequent than long-term scheduling. When memory becomes scarce due to a large number of processes in the system, medium-term scheduling can help free up memory by swapping out less active processes to secondary storage. Swapping involves moving portions of a process (or entire processes) between RAM and disk as needed to manage memory efficiently. Considerations: The goal of medium-term scheduling is to avoid excessive paging (swapping smaller chunks of memory between RAM and disk) by moving whole processes, which can be more efficient. It plays a crucial role in maintaining system performance and preventing excessive memory usage. In summary, long-term, short-term, and medium-term scheduling are integral parts of process management in operating systems. They work together to control the admission of processes into the system, efficiently allocate CPU time, and manage memory resources effectively. These scheduling types are crucial for achieving system responsiveness, fairness, and efficient resource utilization.

13. Global vs. Local Scheduling Global and local scheduling are two distinct approaches to process scheduling in operating systems. They determine how processes are managed and allocated to system resources like CPUs. Here's an explanation of each: 1. Global Scheduling: Definition: Global scheduling, also known as system-level scheduling, involves making scheduling decisions for all processes in the entire system. In other words, it considers all processes running on all CPUs in the system when making scheduling decisions. Characteristics: Global scheduling algorithms typically aim to optimize system-wide performance and resource utilization. These algorithms often take into account factors like process priorities, fairness, and overall system load. The scheduler may move processes between different CPUs to achieve load balancing and ensure efficient use of all available CPU cores. Global scheduling is commonly used in multiprocessor or multi-core systems to distribute processes across CPUs for parallel execution. Advantages: Efficient utilization of all available CPU resources. Effective load balancing across multiple CPUs, which can improve system performance. Disadvantages: Increased complexity due to the need to coordinate scheduling decisions across multiple CPUs. Potential overhead from process migrations between CPUs. 2. Local Scheduling: Definition: Local scheduling, also known as processor-level scheduling, focuses on making scheduling decisions within the context of an individual CPU or processor core. Each CPU manages its own ready queue and selects processes to run on that CPU independently. Characteristics: Local scheduling algorithms consider the state of the CPU they are responsible for, including the ready queue of processes specific to that CPU. These algorithms are typically simpler and more localized in their decision-making compared to global scheduling. Local scheduling is often used in single-processor systems or in systems where each CPU core operates independently without shared memory. Advantages: Lower complexity because each CPU manages its own scheduling independently. Minimal overhead from process migrations between CPUs. Disadvantages: Limited scope for optimizing system-wide performance or load balancing in multi-CPU systems. May not be as effective at managing system resources in complex, multi-CPU environments. Choosing Between Global and Local Scheduling: The choice between global and local scheduling depends on the system architecture and the specific requirements of the operating system. Here are some considerations: Single-Processor Systems: In single-processor systems, local scheduling is the natural choice, as there is only one CPU to manage. Multiprocessor/Multi-Core Systems: In systems with multiple CPUs or CPU cores, global scheduling is often preferred to efficiently utilize all available resources, balance workloads, and optimize system performance. However, the complexity of global scheduling algorithms and the potential for process migrations should be carefully managed. Hybrid Approaches: Some systems employ a combination of global and local scheduling. For example, within a multi-core CPU, each core may use local scheduling, while a global scheduler manages the allocation of processes to different CPU cores. Ultimately, the choice of scheduling approach depends on the specific goals and requirements of the operating system and the hardware it runs on.

14. Common Scheduling Algorithms First-Come-First-Serve (Non-preemptive) Shortest Job Next / Shortest Job First Priority Scheduling Round Robin Multilevel Queue Scheduling Multilevel Feedback Queue Scheduling 9/10/2023 Sample Footer Text 14

15. First-Come-First-Serve Description Pros and Cons Visual Representation Example 9/10/2023 Sample Footer Text 15

16. First-Come-First-Serve First-Come-First-Serve (FCFS) is one of the simplest and most intuitive CPU scheduling algorithms used in operating systems. As the name suggests, it schedules processes in the order they arrive in the ready queue, with the first process to arrive being the first to be executed. FCFS operates on the principle of "first in, first out" (FIFO). Here's an explanation of FCFS scheduling: How FCFS Scheduling Works: Arrival of Processes: When processes arrive and are ready to run, they are placed in a queue known as the ready queue. The ready queue contains all the processes that are waiting for CPU time. Execution Order: FCFS selects the process at the front of the ready queue for execution. The process is allowed to run until it completes or voluntarily gives up the CPU by entering a blocked or waiting state (e.g., for I/O operations). Process Completion: When the currently running process finishes its execution, the next process in the queue becomes the new running process. This process continues until all processes are executed in the order they arrived. Characteristics of FCFS Scheduling: Non-Preemptive: FCFS is a non-preemptive scheduling algorithm, meaning that once a process starts executing, it cannot be interrupted or preempted by another process until it completes its execution or voluntarily yields the CPU. Simple and Fair: FCFS is straightforward to implement and understand, and it provides a fair allocation of CPU time because processes are executed in the order they are received. Convoy Effect: FCFS may suffer from the "convoy effect" when a long process is followed by many short processes. In this case, short processes are forced to wait behind the long process, leading to increased average waiting times for the short processes. Low Overhead: FCFS has low overhead because it does not require complex priority calculations or context switches (process switches). It simply executes processes in the order they are queued. Lack of Responsiveness: FCFS can be unresponsive to interactive processes. If a long-running CPU-bound process is at the front of the queue, interactive tasks may experience significant delays, making the system seem unresponsive.

17. Advantages and Disadvantages of FCFS Scheduling: Advantages: Simple to implement and understand. The absence of low or high-priority preferences makes it fairer n terms of allocating CPU time to processes based on their arrival order. Useful when the processes have a large burst time since it is low overhead and minimal context switching. Disadvantages: Inefficient in terms of average waiting time, especially if there is a mix of long and short processes. Not suitable for real-time or time-critical applications. Lack of responsiveness to interactive tasks can result in a poor user experience. In summary, FCFS scheduling is a straightforward algorithm that operates on the principle of "first come, first served." While it is easy to implement, it may not always provide optimal performance, particularly in scenarios with a mix of short and long processes or when responsiveness is a critical requirement. More advanced scheduling algorithms, such as Shortest Job Next (SJN) or Round Robin (RR), are often used in practice to address some of the limitations of FCFS.

18. First-Come-First-Serve  Visual Representation Here's a simple example of a Gantt chart for FCFS scheduling with three processes: P1, P2, and P3. Each process arrives at a specific time and executes one after the other: |----------------------- Gantt Chart ------------------------| |  P1  |  P2  |  P3  |             |             |             | In this Gantt chart: Process P1 arrives first and starts executing. Once P1 completes, P2 begins execution. After P2 completes, P3 starts executing. The empty space represents idle time when no process is running. FCFS executes processes strictly in the order they arrived, so there is no preemption or rearrangement of process execution order. The Gantt chart provides a visual representation of how processes are scheduled in FCFS, following the "first come, first served" principle. Each bar represents the execution time of a specific process, and the order of bars corresponds to the order of process arrivals.

19. First-Come-First-Serve  Example Let's consider an example of First-Come-First-Serve (FCFS) scheduling with four processes and their respective burst times (the time it takes for each process to complete its execution): Process P1: Arrival Time: 0 ms Burst Time: 10 ms Process P2: Arrival Time: 2 ms Burst Time: 5 ms Process P3: Arrival Time: 3 ms Burst Time: 2 ms Process P4: Arrival Time: 5 ms Burst Time: 8 ms We'll use a Gantt chart to visually represent how these processes are scheduled using FCFS: |----------------------- Gantt Chart ------------------------|
|  P1  |       P2      |       P3      |       P4      | In this Gantt chart: Process P1 arrives first at time 0 ms and starts executing. It runs for 10 ms. Process P2 arrives at time 2 ms but waits until P1 completes its execution. After P1 finishes, P2 starts executing and runs for 5 ms. Process P3 arrives at time 3 ms and waits for both P1 and P2 to complete. After P2 finishes, P3 starts executing and runs for 2 ms. Process P4 arrives at time 5 ms and waits for P1, P2, and P3 to complete. After P3 finishes, P4 starts executing and runs for 8 ms. The empty spaces in the Gantt chart represent idle time when no process is running. FCFS schedules processes based on their arrival times, ensuring that they execute in the order they arrived. The total completion time for all processes can be calculated by adding their respective burst times: Total Completion Time = 10 ms (P1) + 15 ms (P2) + 17 ms (P3) + 25 ms (P4) = 67 ms In this example, the total completion time is 67 ms , and this is how FCFS schedules the processes based on their arrival times and burst times.

20. Shortest Job Next / Shortest Job First Description Pros and Cons Visual Representation Example 9/10/2023 Sample Footer Text 20

21. Priority Scheduling Description Pros and Cons Visual Representation Example 9/10/2023 Sample Footer Text 21

22. Round Robin Description Pros and Cons Visual Representation Example 9/10/2023 Sample Footer Text 22

23. Multilevel Queue Scheduling Description Pros and Cons Visual Representation Example 9/10/2023 Sample Footer Text 23

24. Multilevel Feedback Queue Scheduling Multilevel Feedback Queue Scheduling is an extension of the Multilevel Queue Scheduling but in this, the process can move between the queues based on their behavior. This dynamic approach provides a flexible way to handle a wide range of workloads efficiently. Here's a detailed explanation: Multiple Queues with Different Priorities:  Similar to multilevel queue scheduling, processes are categorized into different queues based on their characteristics or priority levels. Each queue has a different priority. Process Behavior Monitoring:  The scheduler monitors the behavior of processes, specifically how they utilize CPU time. This could include metrics like the number of CPU bursts a process requires. Priority Adjustment:  Based on their behavior, processes can be moved between queues. For example, a process that uses minimal CPU time may be moved to a higher-priority queue, while a process that uses a lot of CPU time may be moved to a lower-priority queue. 4. Aging: To prevent starvation, aging is used. If a process remains in a lower-priority queue for too long, it may be promoted to a higher-priority queue. 5. Queue Selection: The scheduler selects a process from the highest-priority non-empty queue for execution. If there are no processes in the highest-priority queue, it moves down to the next highest-priority queue. 6. Feedback Mechanism: The feedback mechanism is used to move processes between queues. This is typically based on observed behavior, such as the number of CPU bursts a process requires. 7. Process Movement Between Queues: Processes can move between queues based on their observed behavior. For example, a process that is consistently using a lot of CPU time may be demoted to a lower-priority queue.

25. Multilevel Queue Scheduling - Explain the Multilevel Queue Scheduling algorithm - Describe how processes are divided into different priority queues - Discuss how each queue can have its own scheduling algorithm, suited to its priorities Operating Systems: Most modern operating systems, including Windows, macOS, and Linux, use multilevel queue scheduling to manage processes. They typically have different priority levels and scheduling algorithms for system-level tasks, interactive user tasks, and background processes. Real-Time Systems: In real-time systems, tasks are often categorized based on their criticality or timing requirements. For example, a flight control system may have separate queues for critical flight control tasks and non-critical background tasks. Web Servers: Web servers use multilevel queues to handle different types of requests. For example, requests for static content may be placed in a high-priority queue, while requests requiring database access may be placed in a lower-priority queue. Multimedia Applications: Video editing software may use multilevel queue scheduling to prioritize real-time video rendering over background rendering tasks. Industrial Automation: Manufacturing systems may use multilevel queues to prioritize control tasks for critical machinery over monitoring and reporting tasks. Database Management Systems: Database systems may use multilevel queues to handle different types of queries, with high-priority queues for time-sensitive transactions and lower-priority queues for background maintenance tasks. Networking Devices: Routers and switches use multilevel queues to handle different types of network traffic. For example, voice-over-IP (VoIP) packets may be placed in a high-priority queue for low latency.

26. Multilevel Feedback Queue Scheduling Description Pros and Cons Visual Representation Example 9/10/2023 Sample Footer Text 26

27. Comparison and Evaluation Comparative Analysis of Scheduling Algorithms Factors for Evaluation Real-World Use Cases 9/10/2023 Sample Footer Text 27

28. Real-World Applications How Scheduling Algorithms are used in Operating Systems Case Study: Windows, Linux, macOS 9/10/2023 Sample Footer Text 28

29. Conclusion and Future Developments Recap of Key Points Emerging Trends in Scheduling Algorithms Future Challenges and Directions 9/10/2023 Sample Footer Text 29

30. Questions and Discussion Open the floor for questions and discussions 9/10/2023 Sample Footer Text 30

31. Thank You Express gratitude to the audience Provide contact information for further inquiries 9/10/2023 Sample Footer Text 31

32. Additional Resources List of recommended books, articles, and websites for further reading 9/10/2023 Sample Footer Text 32 Scheduling Algorithm Selection : The OS chooses a scheduling algorithm based on the system's requirements, characteristics, and workload.