Author: Zen and the Art of Computer Programming
In today's society, queuing is an important activity, such as making a phone call, going to work, studying, etc. In daily life, we often see various queues, such as ticket booths, parking spots, student grade test queues , waiting room waiting, vehicle queuing, etc. However, for everyone in the queue, the order in which they choose to enter the queue, the time for taking a number and queuing, what position to choose, etc. all have a crucial impact, which involves the study of queuing theory. In the field of computer networks, queuing behavior also plays a pivotal role. For example, scheduling algorithms process requests according to priority, time interval, server utilization, etc. Therefore, as a computer science-related professional, master queuing theory and Algorithms are very important. In this article, I will systematically study "queuing theory" and explain some of its basic concepts and models.
2. Explanation of basic concepts and terms
2.1 Queue
A queue (queue) is a special data structure that only allows elements to be inserted at the end of the list and elements to be deleted at the head. A queue can only be accessed from the beginning to the end of the queue, elements are added to the end of the queue (rear), and can only be removed from the end of the queue (front). For simplicity, we can think of a queue as a linear list that is limited to insertion and deletion under certain conditions.
2.2 Service Request Queue
In general, before the request enters the queue, it first needs to process some preparatory work, such as login verification, permission check, etc. A service request queue usually consists of two parts, the request queue and the service queue. The request queue stores all pending requests; the service queue stores requests that have been assigned to the server. When a request is moved from the request queue to the service queue, it is first come, first served, that is, after the first request leaves the request queue, the first server can receive the request.
2.3 Request Classification
According to the requested processor