Operating System Tutorial

Operating System Tutorial Types of Operating System Evolution of Operating System Functions of Operating System Operating System Properties Operating System Services Components of Operating System Needs of the Operating System

Operating Systems

Linux Operating System Unix Operating System Ubuntu Operating System Chrome Operating Systems Fedora Operating System MAC Operating System MS Windows Operating System Solaris Operating System Cooperative Operating System CorelDRAW Operating System CentOS FreeBSD Operating Systems Batch Operating System MS-DOS Operating System Commercial Mobile Operating Systems


Difference Between Multi-programming and Multitasking Difference between C-LOOK and C-SCAN Difference between Rotational Latency and Disk Assess Time Trap vs Interrupt Difference between C-SCAN and SSTF Difference between SCAN and FCFS Difference between Seek Time and Disk Access Time Difference between SSTF and LOOK Difference between Process and Program in the Operating System Difference between Protection and Security in Operating System

How To

How to implement Monitors using Semaphores How to Install a Different Operating System on a PC


What is Kernel and Types of Kernel What is DOS Operating System What is Thread and Types of Thread What is Process Scheduler and Process Queue What is Context Switching What is CPU Scheduling What is Producer-Consumer Problem What is Semaphore in Operating System Monitors in Operating System What is Deadlock What is Paging and Segmentation What is Demand Paging What is Virtual Memory What is a Long term Scheduler What is Page Replacement in Operating System What is BSR Mode What is Convoy Effect What is Job Sequencing in Operating System Why is it critical for the Scheduler to distinguish between I/O-bound and CPU-bound programs Why is there a Need for an Operating System


Process Management Process State Scheduling Algorithm FCFS (First-come-First-Serve) Scheduling SJF (Shortest Job First) Scheduling Round-Robin CPU Scheduling Priority Based Scheduling HRRN (Highest Response Ratio Next) Scheduling Process Synchronization Lock Variable Mechanism TSL Mechanism Turn Variable Mechanism Interested Variable Mechanism Deadlock Avoidance Strategies for Handling Deadlock Deadlock Prevention Deadlock Detection and Recovery Resource Allocation Graph Banker’s Algorithm in Operating System Fixed Partitioning and Dynamic Partitioning Partitioning Algorithms Disk Scheduling Algorithms FCFS and SSTF Disk Scheduling Algorithm SCAN and C-SCAN Disk Scheduling Algorithm Look and C-Look Disk Scheduling Algorithm File in Operating System File Access Methods in Operating System File Allocation Method Directory Structure in Operating System N-Step-SCAN Disk Scheduling Feedback Queue in Operating System Contiguous Memory Allocation in Operating System Real-time Operating System Starvation in Operating System Thrashing in Operating System 5 Goals of Operating System Advantages of Operating System Advantages of UNIX Operating System Bit Vector in Operating System Booting Process in Operating System Can a Computer Run Without the Operating System Dining Philosophers Problem in Operating System Free Space Management in Operating System Inter Process Communication in Operating System Swapping in Operating System Memory Management in Operating System Multiprogramming Operating System Multitasking Operating Systems Multi-user Operating Systems Non-Contiguous Memory Allocation in Operating System Page Table in Operating System Process Scheduling in Operating System Segmentation in Operating System Simple Structure in Operating System Single-User Operating System Two Phase Locking Protocol Advantages and Disadvantages of Operating System Arithmetic operations in binary number system Assemblers in the operating system Bakery Algorithm in Operating System Benefits of Ubuntu Operating System CPU Scheduling Criteria in Operating System Critical Section in Operating System Device Management in Operating System Linux Scheduler in Operating System Long Term Scheduler in Operating System Mutex in Operating System Operating System Failure Peterson's Solution in Operating System Privileged and Non-Privileged Instructions in Operating System Swapping in Operating System Types of Operating System Zombie and Orphan Process in Operating System 62-bit operating system Advantages and Disadvantages of Batch Operating System Boot Block and Bad Block in Operating System Contiguous and Non - Contiguous Memory Allocation in Operating System Control and Distribution Systems in Operations Management Control Program in Operating System Convergent Technologies in Operating System Convoy Effect in Operating System Copy Operating Systems to SSD Core Components of Operating System Core of UNIX Operating System Correct Value to return to the Operating System Corrupted Operating System Cos is Smart Card Operating System Cosmos Operating Systems Examples Generation of Operating System Hardware Solution in Operating System Process Control Block in Operating System Function of Kernel in Operating System Operating System Layers History of Debian Operating Systems Branches and Architecture of Debian Operating Systems Features and Packages of Debian Operating Systems Installation of Operating System on a New PC Organizational Structure and Development in Debian Operating Systems User Interface in Operating System Types Of Memory in OS Operating System in Nokia Multilevel Paging in OS Memory Mapping Techniques in OS Memory Layout of a Process in Operating System Hardware Protection in Operating System Functions of File Management in Operating System Core of Linux Operating System Cache Replacement Policy in Operating System Cache Line and Cache Size in Operating System What is Memory Mapping? Difference Between Network Operating System And Distributed Operating System What is the difference between a Hard link and a Soft Link? Principles of Preemptive Scheduling Process Scheduling Algorithms What is NOS? What is the Interrupt I/O Process? What is Time Sharing OS What is process termination? What is Time-Sharing Operating System

CPU Scheduling Criteria in Operating System

CPU scheduling is the process by which the operating system manages the allocation of CPU time to different processes or threads. When multiple processes are competing for the CPU, the operating system must decide which process to execute next, and for how long.  

  • CPU scheduling is a critical component of modern operating systems because it allows multiple processes to share a single CPU, maximizing the utilization of computing resources. By switching between processes quickly and efficiently, CPU scheduling enables the operating system to provide the illusion of parallelism, allowing multiple programs to run seemingly simultaneously.
  • The choice of scheduling algorithm depends on various factors such as the type of workload, system requirements, and performance goals.
  • CPU scheduling is a process that allows the operating system to manage the allocation of CPU time to different processes or threads.

Following are the commonly used criteria for CPU scheduling in an operating system:

  • CPU Utilization: The primary objective of a CPU scheduler is to maximize the CPU utilization. The CPU should be busy executing processes as much as possible to achieve maximum efficiency.
  • Throughput: The throughput is defined as the number of processes that are completed per unit of time. The CPU scheduler must ensure that the maximum numbers of processes are completed in the shortest possible time.
  • Turnaround Time: The turnaround time is the time taken from the submission of a process to its completion. The CPU scheduler must ensure that the turnaround time for each process is minimized.
  • Waiting Time: The waiting time is the time that a process spends waiting in the ready queue before it is assigned to the CPU. The CPU scheduler must ensure that the waiting time for each process is minimized.
  • Response Time: The response time is the time taken from the submission of a request until the first response is produced. The CPU scheduler must ensure that the response time for each process is minimized, especially for interactive processes that require quick responses.
  • Fairness: The CPU scheduler should provide fair allocation of CPU time to all processes. No process should be starved for CPU time, and all processes should get a fair share of the CPU time.

Here's an example of how CPU scheduling works in an operating system:

Suppose there are three processes P1, P2, and P3, and they all request CPU time at the same time. Each process has a different CPU burst time, which is the time required to execute the process on the CPU.

Process P1 has a CPU burst time of 5 milliseconds, process P2 has a burst time of 7 milliseconds, and process P3 has a burst time of 3 milliseconds.

The CPU scheduling algorithm decides which process to execute first and how long to allocate the CPU time to each process.

For example, if we use the Shortest Job First (SJF) scheduling algorithm, the operating system will select the process with the shortest burst time first. In this case, the operating system will select P3 first because it has the shortest burst time of 3 milliseconds. After P3 finishes executing, the operating system will select the next shortest job, which is P1. Finally, P2 will be executed.

The actual order of execution may vary depending on the scheduling algorithm and the characteristics of the workload. The objective of CPU scheduling is to allocate CPU time efficiently while minimizing turnaround time, waiting time, and other performance metrics.

Here's an example of CPU scheduling using the First-Come-First-Serve (FCFS) algorithm:

Suppose we have three processes, P1, P2, and P3, that need to be executed on a single CPU, and their arrival times and burst times are as follows:

ProcessArrival TimeBurst Time

Using the FCFS algorithm, the operating system will execute the processes in the order in which they arrive, starting with P1.

The Gantt chart for the execution of the processes would look like this:


In this example, P1 arrives first, so it is executed first. P1 has a burst time of 10, so it runs for 10 units of time until it completes. Next, P2 arrives and is executed, running for 4 units of time until completion. Finally, P3 arrives and is executed, running for 6 units of time until completion.

Note: You must note that this is just one example of CPU scheduling, and different scheduling algorithms would produce different execution orders and completion times for the same set of processes.