Os Process Management Questions Medium
There are several thread scheduling algorithms used in operating systems to efficiently manage and schedule threads. Some of the commonly used algorithms are:
1. First-Come, First-Served (FCFS): In this algorithm, threads are scheduled in the order they arrive. The first thread that arrives is the first to be executed. However, this algorithm may lead to poor performance if a long-running thread arrives first, as it can block subsequent threads.
2. Shortest Job Next (SJN): This algorithm schedules threads based on their burst time, where the thread with the shortest burst time is executed first. It aims to minimize the average waiting time and turnaround time. However, it requires knowledge of the burst time in advance, which may not always be available.
3. Round Robin (RR): This algorithm assigns a fixed time slice (quantum) to each thread in a cyclic manner. Threads are executed for a predefined time quantum, and if they are not completed, they are moved to the end of the queue. RR ensures fairness and prevents starvation, but it may result in higher overhead due to frequent context switching.
4. Priority Scheduling: This algorithm assigns a priority value to each thread, and the thread with the highest priority is executed first. It can be either preemptive or non-preemptive. Preemptive priority scheduling allows higher priority threads to interrupt lower priority threads, while non-preemptive priority scheduling allows a thread to run until it voluntarily releases the CPU.
5. Multilevel Queue Scheduling: This algorithm divides threads into multiple queues based on their priority or characteristics. Each queue can have its own scheduling algorithm, such as FCFS, SJN, or RR. Threads are initially assigned to a specific queue based on their priority, and then scheduling is performed within each queue.
6. Multilevel Feedback Queue Scheduling: This algorithm is an extension of multilevel queue scheduling. It allows threads to move between different queues based on their behavior. Threads that use excessive CPU time are moved to lower priority queues, while threads that are I/O bound are moved to higher priority queues. This algorithm provides better responsiveness and adaptability to varying workloads.
These are some of the commonly used thread scheduling algorithms in operating systems. The choice of algorithm depends on factors such as system requirements, workload characteristics, and performance goals.