The operating system manages the limited resources of the system. When multiple processes (or requests issued by multiple processes) want to use these resources, because of the limited resources, the process (request) must be selected according to certain principles to occupy the resources. This is scheduling. The purpose is to control the number of resource users, and select the resource users to allow the resource occupation or occupation of resources. At this time, the process can be processed according to different scheduling methods.
FCFS(First-Come，First-Served)
First-come, first-served scheduling algorithm: In process scheduling, FCFS selects the first progress to the ready queue from the head of the ready queue, and allocates CPU to the process. To put it simply, which team arrives first, the CPU will be allocated to which pair first. If there are external constraints, the impact of external conditions needs to be considered.
SPF(Shortest-Process-First)
Short process priority scheduling algorithm: It selects the process with the shortest estimated running time from the ready queue, and assigns the processor to it, so that it executes immediately and has been executed all the time, or when an event occurs and the processor is blocked and the processor is abandoned, then reschedule . To put it simply, which team is ready first and has the shortest running time, the CPU will be allocated to which pair first. If there are external constraints, the impact of external conditions needs to be considered.
PSL(Priority-Scheduling Lgorithm)
Priority scheduling algorithm: In a system using priority scheduling, each process has a priority associated with it, and the priority value is usually a fixed number. The system may design the higher the priority value, the higher the priority; it may also design the smaller the priority value, the lower the priority month. Simply put, it is to look at the priority of the design in the topic, and allocate the CPU to the ready queue according to the priority given in the topic. If there are external constraints, you also need to consider the impact of external conditions.
RR(Round-Robin)
Time slice round-robin scheduling algorithm: It is a schedule scheduling algorithm widely used in modern time-sharing systems. UNIX, Linux and Windows operating systems all adopt a hybrid process scheduling algorithm based on time slice runners, supporting priority and preemptive scheduling.