Os Process Management Questions Medium
In operating systems, device scheduling algorithms are used to manage the allocation of resources to different processes or threads. These algorithms ensure efficient utilization of devices and minimize the waiting time for processes. There are several device scheduling algorithms used in operating systems, including:
1. First-Come, First-Served (FCFS): This algorithm allocates devices to processes in the order they request them. It follows a queue-based approach, where the process that requests the device first is served first. However, FCFS may lead to poor performance if a long-running process occupies a device, causing other processes to wait for an extended period.
2. Shortest Job Next (SJN): SJN algorithm prioritizes processes based on their burst time, i.e., the time required to complete their execution. The process with the shortest burst time is given priority and allocated the device first. SJN aims to minimize the average waiting time for processes, but it requires knowledge of the burst time in advance, which may not always be available.
3. Round Robin (RR): RR is a preemptive scheduling algorithm that allocates devices to processes in a cyclic manner. Each process is given a fixed time quantum to use the device, and if it does not complete its task within the quantum, it is preempted and moved to the end of the queue. RR ensures fair allocation of devices among processes and prevents starvation, but it may lead to higher overhead due to frequent context switches.
4. Priority Scheduling: This algorithm assigns a priority value to each process based on factors such as importance, deadline, or resource requirements. The process with the highest priority is allocated the device first. Priority scheduling can be either preemptive or non-preemptive. Preemptive priority scheduling allows higher priority processes to interrupt lower priority ones, while non-preemptive priority scheduling completes the execution of the current process before considering the next one.
5. Shortest Remaining Time (SRT): SRT is a preemptive version of SJN algorithm. It dynamically adjusts the priorities of processes based on their remaining burst time. The process with the shortest remaining time is given the highest priority and allocated the device. SRT aims to minimize the waiting time and provides better response time for interactive processes.
6. Lottery Scheduling: This algorithm assigns a certain number of lottery tickets to each process. The more tickets a process has, the higher its chances of winning the device allocation. The lottery tickets are randomly drawn, and the process whose ticket is drawn gets the device. Lottery scheduling provides a fair allocation of devices and allows processes with fewer tickets to have a chance of winning.
These are some of the commonly used device scheduling algorithms in operating systems. The choice of algorithm depends on factors such as the nature of processes, resource requirements, and desired system performance.