Explain the different types of CPU scheduling algorithms in Operating System.
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First Come First Serve
First Come First Serve is the full form of FCFS. It is the easiest and most simple CPU scheduling algorithm. In this type of algorithm, the process which requests the CPU gets the CPU allocation first. This scheduling method can be managed with a FIFO queue.
Shortest Remaining Time
The full form of SRT is Shortest remaining time. It is also known as SJF preemptive scheduling. In this method, the process will be allocated to the task, which is closest to its completion. This method prevents a newer ready state process from holding the completion of an older process.
Priority Based Scheduling
priority scheduling is a method of scheduling processes based on priority. In this method, the scheduler selects the tasks to work as per the priority.
Priority scheduling also helps OS to involve priority assignments. The processes with higher priority should be carried out first, whereas jobs with equal priorities are carried out on a round-robin or FCFS basis. Priority can be decided based on memory requirements, time requirements, etc.
As the process enters the ready queue, its PCB (Process Control Block) is linked with the tail of the queue. So, when CPU becomes free, it should be assigned to the process at the beginning of the queue.
Round-Robin Scheduling
Round robin is the oldest, simplest scheduling algorithm. The name of this algorithm comes from the round-robin principle, where each person gets an equal share of something in turn. It is mostly used for scheduling algorithms in multitasking. This algorithm method helps for starvation free execution of processes.
Shortest Job First
SJF is a full form of (Shortest job first) is a scheduling algorithm in which the process with the shortest execution time should be selected for execution next. This scheduling method can be preemptive or non-preemptive. It significantly reduces the average waiting time for other processes awaiting execution.
Shortest Job First
SJF is a full form of (Shortest job first) is a scheduling algorithm in which the process with the shortest execution time should be selected for execution next. This scheduling method can be preemptive or non-preemptive. It significantly reduces the average waiting time for other processes awaiting execution.
CPU scheduling algorithms are essential for determining which processes run at any given time in an operating system. Here are the main types:
1. First-Come, First-Served (FCFS): Processes are scheduled in the order they arrive in the ready queue. It’s simple but can lead to the convoy effect, where short processes wait for long ones.
2. Shortest Job Next (SJN): Also known as Shortest Job First (SJF), this non-preemptive algorithm selects the process with the smallest execution time. It minimizes average waiting time but requires accurate predictions of process durations.
3. Priority Scheduling: Processes are assigned priorities, and the CPU is allocated to the process with the highest priority. This can be preemptive or non-preemptive. Low-priority processes may suffer from starvation, which can be mitigated with aging (gradually increasing the priority of waiting processes).
4. Round Robin (RR): Each process is assigned a fixed time slice (quantum) in a cyclic order. It is preemptive and designed for time-sharing systems, ensuring fair CPU time distribution but can lead to high context switching overhead.
5. Multilevel Queue Scheduling: Processes are classified into multiple queues based on priority or type (e.g., system, interactive, batch). Each queue can use a different scheduling algorithm. This is useful for separating different types of workloads.
6. Multilevel Feedback Queue Scheduling: An extension of multilevel queue scheduling where processes can move between queues based on their behavior and aging. It dynamically adjusts priorities to optimize performance and reduce starvation.
Each algorithm has its advantages and trade-offs, making them suitable for different types of operating system environments.
Different types of CPU scheduling
CPU scheduling is a crucial aspect of operating systems, and there are several types of CPU scheduling algorithms. Here are some of the most common ones:
1. First-Come-First-Served (FCFS):
In FCFS scheduling, the process that arrives first in the ready queue is executed first. This algorithm is simple and easy to implement, but it can lead to poor performance and starvation of other processes.
2. Shortest Job First (SJF):
In SJF scheduling, the process with the shortest burst time is executed first. This algorithm is optimal in terms of average waiting time, but it requires knowledge of the burst time of each process, which is not always possible.
3. Priority Scheduling:
In priority scheduling, each process is assigned a priority, and the process with the highest priority is executed first. This algorithm is useful in systems where certain processes require more urgent attention than others.
4. Round Robin (RR) Scheduling:
In RR scheduling, each process is given a fixed time slice (called a time quantum) to execute before the next process is scheduled. This algorithm is fair and provides good response time, but it can lead to overhead due to context switching.
5. Preemptive Scheduling:
In preemptive scheduling, the operating system can interrupt a running process and schedule another process. This algorithm is used in most modern operating systems and provides better responsiveness and fairness
6. Non-Preemptive Scheduling:
In non-preemptive scheduling, once a process is scheduled, it runs until it completes or blocks. This algorithm is simpler to implement but can lead to poor performance and starvation of other processes.