CPU Scheduling in OS
CPU scheduling is a process that allows one process to use the CPU while the execution of another process is on hold(in waiting state) due to unavailability of any resource like I/O etc, thereby making full use of CPU. The aim of CPU scheduling is to make the system efficient, fast, and fair. This website explained the basic concept very well.
Preemptive vs Non-preemptive
Preemptive scheduling is used when a process switches from running state to ready state or from waiting state to ready state. Non-preemptive Scheduling is used when a process terminates, or a process switches from running to waiting state. There’s also a difference in the resources process.
Scheduling algorithm%20Multilevel%20Queue%20Scheduling) CPU Scheduling can run in different ways, so there’s a variation of algorithm of it. There are SJF (Shortest Job First), RR (Round-Robin), and others.
What is Dispatcher?
Dispatcher is a special program which comes into play after the scheduler. When the scheduler completes its job of selecting a process, it is the dispatcher which takes that process to the desired state/queue. The dispatcher is the module that gives a process control over the CPU after it has been selected by the short-term scheduler.
Scheduling Criteria
There are different options to choose scheduling algorithms. To choose it, the criteria are CPU utilization, Throughput, Turnaround time, Waiting time, and Response time.
Priority Scheduling Implementation
This website shows me how to implement priority scheduling algorithm in C program. The algorithm used is FCFS.
Multilevel Queue
Multilevel Queue Scheduling is used when processes in the ready queue can be divided into different classes where each class has its own scheduling needs. For example, a common division is a foreground (interactive) process and background (batch) processes.
Multilevel Feedback Queue
This Scheduling is like Multilevel Queue Scheduling but in this process can move between the queues. Multilevel Feedback Queue Scheduling (MLFQ) keep analyzing the behavior (time of execution) of processes and according to which it changes its priority.
Thread Scheduling
Execution of multiple threads on a single CPU in some order is called scheduling. This article explains the thread scheduling in a simple way!
Rate Monotonic Scheduling
Rate monotonic scheduling is a priority algorithm that belongs to the static priority scheduling category of Real Time Operating Systems. This is is a preemptive algorithm. The priority is decided according to the cycle time of the processes that are involved.