Lecture 2. Process Concepts, Performance Measures and Evaluation Techniques. Lecture Highlights. What is a process Process Control Block Process states and process life cycle Performance Measures Evaluation Techniques. What is a process.
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
Process Concepts, Performance Measures and Evaluation Techniques
When a new process is created, the operating system typically does the following:
A PCB is a data structure which stores certain information about each process. A typical PCB looks as follows:
The system assigns each process a unique identifier which is used by other processes for scheduling, communication and any other purpose.
The system keeps track of the time a process enters the process queue for scheduling purposes.
This parameter is used by scheduling algorithms which order processes by the amount of time they need to complete execution. Mathematical formulae are used to calculate the estimated execution time of a process.
Some processes, such as system processes, have a higher priority than others and the operating system uses this priority during scheduling and memory management.
It is the size of the process in bytes. This parameter indicates the memory location of a process also.
The program counter value stores the address of the next instruction to be executed.
This PCB parameter saves the state of different registers used by that particular process.
This PCB parameter indicates the quantities of system resources needed by that particular process.
The state of a process is defined in part by its current activity. As it executes, it changes state. Each process may be in one of the following states:
It is important to quantify performance so that it can be measured. Commonly used performance measures:
Before we discuss the individual performance measures, we need to understand the related concepts of context switching and starvation.
When developing an operating system or the modules thereof, evaluation of its performance is needed before it is installed for real usage. Evaluation provides useful clues to which algorithms would best serve the cases of application.
All evaluation techniques can be classified into the following three types:
In the analytic method, a mathematical formula is developed to represent a computing system. This method provides clear and intuitive evaluation of system performance, and is most useful to a specific algorithm. However, it is too simple to examine a complex and near-real system.
The simulation method entails development of a model of a real system which contains a number of algorithms, variables and parameters. Changing these factors in simulation enables one to know its affect on system performance. This method, thus, is best suited for our purpose of studying the operating systems design.
The following topics shall be covered in the next lecture: