Process Management in Operating Systems

12 Key excerpts on "Process Management in Operating Systems"

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  eBook - PDF

  Operating System Concepts

  • Abraham Silberschatz, Peter B. Galvin, Greg Gagne(Authors)
  • 2014(Publication Date)
  • Wiley

    (Publisher)

  Part Two Process Management A process can be thought of as a program in execution. A process will need certain resources — such as CPU time, memory, files, and I/O devices — to accomplish its task. These resources are allocated to the process either when it is created or while it is executing. A process is the unit of work in most systems. Systems consist of a collection of processes: operating-system processes execute system code, and user processes execute user code. All these processes may execute concurrently. Although traditionally a process contained only a single thread of control as it ran, most modern operating systems now support processes that have multiple threads. The operating system is responsible for several important aspects of process and thread management: the creation and deletion of both user and system processes; the scheduling of processes; and the provision of mechanisms for synchronization, communication, and deadlock handling for processes. 3 C H A P T E R Process Concept Early computers allowed only one program to be executed at a time. This program had complete control of the system and had access to all the sys- tem’s resources. In contrast, contemporary computer systems allow multiple programs to be loaded into memory and executed concurrently. This evolution required firmer control and more compartmentalization of the various pro- grams; and these needs resulted in the notion of a process, which is a program in execution. A process is the unit of work in a modern time-sharing system. The more complex the operating system is, the more it is expected to do on behalf of its users. Although its main concern is the execution of user programs, it also needs to take care of various system tasks that are better left outside the kernel itself. A system therefore consists of a collection of processes: operating- system processes executing system code and user processes executing user code.

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  eBook - PDF

  Operating System Concepts Essentials

  • Abraham Silberschatz, Peter B. Galvin, Greg Gagne(Authors)
  • 2013(Publication Date)
  • Wiley

    (Publisher)

  Part Two Process Management A process can be thought of as a program in execution. A process will need certain resources — such as CPU time, memory, files, and I/O devices —to accomplish its task. These resources are allocated to the process either when it is created or while it is executing. A process is the unit of work in most systems. Systems consist of a collection of processes: operating-system processes execute system code, and user processes execute user code. All these processes may execute concurrently. Although traditionally a process contained only a single thread of control as it ran, most modern operating systems now support processes that have multiple threads. The operating system is responsible for several important aspects of process and thread management: the creation and deletion of both user and system processes; the scheduling of processes; and the provision of mechanisms for synchronization, communication, and deadlock handling for processes. This page is intentionally left blank 3 C H A P T E R Processes Early computers allowed only one program to be executed at a time. This program had complete control of the system and had access to all the system’s resources. In contrast, contemporary computer systems allow multiple pro- grams to be loaded into memory and executed concurrently. This evolution required firmer control and more compartmentalization of the various pro- grams; and these needs resulted in the notion of a process, which is a program in execution. A process is the unit of work in a modern time-sharing system. The more complex the operating system is, the more it is expected to do on behalf of its users. Although its main concern is the execution of user programs, it also needs to take care of various system tasks that are better left outside the kernel itself. A system therefore consists of a collection of processes: operating- system processes executing system code and user processes executing user code.

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  Operating Systems

  • (Author)
  • 2014(Publication Date)
  • Learning Press

    (Publisher)

  ___________________________ WORLD TECHNOLOGIES ___________________________ Chapter- 3 Features and Components of Operating Systems Process management Process management is an integral part of any modern day operating system (OS). The OS must allocate resources to processes, enable processes to share and exchange information, protect the resources of each process from other processes and enable synchronisation among processes. To meet these requirements, the OS must maintain a data structure for each process, which describes the state and resource ownership of that process, and which enables the OS to exert control over each process. Multiprogramming In many modern operating systems, there can be more than one instance of a program loaded in memory at the same time; for example, more than one user could be executing the same program, each user having separate copies of the program loaded into memory. With some programs, it is possible to have one copy loaded into memory, while several users have shared access to it so that they each can execute the same program-code. Such a program is said to be re-entrant. The processor at any instant can only be executing one instruction from one program but several processes can be sustained over a period of time by assigning each process to the processor at intervals while the remainder become temporarily inactive. A number of processes being executed over a period of time instead of at the same time is called [concurrent execution] . A multiprogramming or multitasking OS is a system executing many processes concurrently. Multiprogramming requires that the processor be allocated to each process for a period of time and de-allocated at an appropriate moment. If the processor is de-allocated during the execution of a process, it must be done in such a way that it can be restarted later as easily as possible.

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  eBook - ePub

  Computer Fundamentals - 8th Edition

  Concepts, Systems & Applications

  • Pradeep K.Sinha, Pradeep K.Sinha, Priti Sinha(Authors)
  • 2004(Publication Date)
  • BPB Publications

    (Publisher)

  job ) is a program in execution. The main objective of process management module of an operating system is to manage the processes submitted to a system in a manner to minimize the idle time of processors (CPUs, I/O processors, etc.) of the system. In this section, we will learn about some of the mechanisms that modern operating systems use to achieve this objective. We will also see how these mechanisms have evolved gradually from the early days of computers.

  Process Management in Early Systems

  In early computer systems, the process of executing a job was as follows:

  1. A programmer first wrote a program on paper.
  2. The programmer or a data entry operator then punched the program and its data on cards or paper tape.
  3. The programmer then submitted the deck of cards or the paper tape containing the program and data at the reception counter of a computer centre.
  4. An operator then loaded the cards deck or paper tape manually into the system from card reader or paper tape reader. The operator also loaded any other software resource (such as a language compiler), or carried out required settings of hardware devices for execution of the job. Before loading the job, the operator used front panel switches of the system to clear any data remaining in main memory from previous job.
  5. The operator then carried out required settings of the appropriate switches in the front panel to run the job.
  6. Finally, the operator printed and submitted the result of execution of the job at the reception counter for the programmer to collect it later.

  Every job went through the same process. The method was known as manual loading mechanism because the operator loaded the jobs one after another in the system manually. Notice that in this method, job-to-job transition was not automatic. Hence, a computer remained idle while an operator loaded and unloaded jobs and prepared the system for a new job. This caused enormous wastage of valuable computer time. To reduce this idle time, researchers later devised a mechanism (called batch processing

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  eBook - PDF

  Operating System Concepts

  • Abraham Silberschatz, Peter B. Galvin, Greg Gagne(Authors)
  • 2018(Publication Date)
  • Wiley

    (Publisher)

  Part Two Process Management A process is a program in execution. A process will need certain resources — such as CPU time, memory, files, and I/O devices — to accomplish its task. These resources are typically allocated to the process while it is executing. A process is the unit of work in most systems. Systems consist of a collection of processes: operating-system processes execute system code, and user processes execute user code. All these processes may execute concurrently. Modern operating systems support processes having multiple threads of control. On systems with multiple hardware processing cores, these threads can run in parallel. One of the most important aspects of an operating system is how it schedules threads onto available processing cores. Several choices for designing CPU schedulers are available to programmers. 3 C H A P T E R Processes Early computers allowed only one program to be executed at a time. This pro- gram had complete control of the system and had access to all the system’s resources. In contrast, contemporary computer systems allow multiple pro- grams to be loaded into memory and executed concurrently. This evolution required firmer control and more compartmentalization of the various pro- grams; and these needs resulted in the notion of a process, which is a program in execution. A process is the unit of work in a modern computing system. The more complex the operating system is, the more it is expected to do on behalf of its users. Although its main concern is the execution of user programs, it also needs to take care of various system tasks that are best done in user space, rather than within the kernel. A system therefore consists of a collection of processes, some executing user code, others executing operating system code. Potentially, all these processes can execute concurrently, with the CPU (or CPUs) multiplexed among them.

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  eBook - PDF

  Introductory guide to operating systems

  • Jocelyn O. Padallan(Author)
  • 2023(Publication Date)
  • Arcler Press

    (Publisher)

  103 5.16. Priority Scheduling ....................................................................... 104 5.17. Shortest Remaining Time First ....................................................... 106 5.18. Fixed Priority Pre-Emptive Scheduling........................................... 107 5.19. Round-Robin Scheduling .............................................................. 108 5.20. Inter-Process Communication ....................................................... 110 Introductory Guide to Operating Systems 86 A program is useless until the instructions it contains are executed by a CPU. A process is a program that is currently running. Processes require computer resources to do their tasks. There could be multiple processes in the system that need the same resource at the same time. As a result, the operating system (OS) must efficiently and effectively handle all processes and resources (Giorgetti et al., 2020). To preserve consistency, some resources might have to be executed by one process at a time or else, the system may become incompatible and a deadlock may develop. In terms of Process Management, the OS is in charge of the following tasks. 5.1. PROCESS A process is basically what one would think as a running software. The execution of a has to be carried out in a particular order. A process is an entity that represents the very basic unit of work that must be implemented in the system. In other words, we write our computer programs in a text file, and when they are run, they turn into a process that completes all of the duties specified in the program. A program can be separated into four pieces when it is put into memory turns into a process: stack, heap, text, and data. The diagram in Figure 5.1 depicts a basic representation of a process in main memory. • Stack: This contains the temporary data such as method/function parameters, return address and local variables. • Heap: This is dynamically allocated memory to a process during its run time.

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  No longer available |Learn more

  CentOS Quick Start Guide

  Get up and running with CentOS server administration

  • Shiwang Kalkhanda(Author)
  • 2018(Publication Date)
  • Packt Publishing

    (Publisher)

  Process Management

  Processes access multiple resources in a running system. Process management is essential to manage these resources effectively and keep your system up and running smoothly. In this chapter, you will learn how to view processes running on a Linux system and how to employ interactive management from the command line. Then, you will learn how to control different programs running on a Linux system using the command line. You will also learn how to communicate with different processes using signals and how to modify their priority level on a running system.

  In this chapter, we will cover the following topics:

  • Understanding processes
  • Viewing current processes
  • Communicating with processes using signals
  • Monitoring processes and load averages
  • Managing a processes' priority levels with nice and renice
  • Controlling jobs on the command line

  Passage contains an image

  Understanding processes

  This section deals with various concepts related to processes, such as their types, states, attributes, and so on. Process management is an essential skill that all types of users of Linux systems should master.

  Passage contains an image

  Defining a process

  A process is an instance of a program in execution. It differs from a program or command in the sense that a single program can start several processes simultaneously. Each process uses several resources, as mentioned in the following list:

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  eBook - ePub

  UNIX Programming

  UNIX Processes, Memory Management, Process Communication, Networking, and Shell Scripting

  • Dr. Vineeta Khemchandani, Dr. Sandeep Harit, Dr. Sandeep Harit, Dr. Darpan Anand, Dr. Vineeta Khemchandani, Dr. Sandeep Harit, Dr. Sandeep Harit, Dr. Darpan Anand(Authors)
  • 2022(Publication Date)
  • BPB Publications

    (Publisher)

  HAPTER 3

  Process Management

  Introduction

  The Kernel performs various primitive operations on behalf of user processes. These operations include controlling the execution of processes by allowing their creation, termination, or suspension and communication. Scheduling processes fairly for execution on the CPU. Allocating main and secondary memory for executing processes. Protecting processes’ address spaces. The Kernel also controls access to peripheral devices such as terminals and other devices. UNIX maintains a parent–child relationship among different processes executed in the system. The UNIX Kernel maintains this process tree through different process IDs to keep control of process creation, execution, and termination. This chapter discusses all these primitive operations to perform effective process management.

  Structure

  We will cover the following topics in this chapter:

  • Processes and their relationships
  • Processes related operations
  • Process control and execution
  • Memory allocation to the executing process.
  • Process communication

  Objectives

  After going through this chapter, you will be able to:

  • Understand fundamental concepts of process management
  • Learn how processes are identified in the UNIX system
  • Get to know the process related operations such as creation, execution, termination, and suspension
  • Understand how processes communicate with each other
  • Understand how UNIX controls process execution and switching

  UNIX process

  A program in execution is a process. In UNIX, a process is a unit of work. The system consists of a collection of processes: operating system processes executing system code and user processes executing user code. All the processes execute concurrently with the CPU switching between the processes.

  A process executes by following a strict sequence of instructions that is self-contained and does not jump to that of another process.

  Process IDs

  Each process has an identification number called process id that identifies it uniquely. The getpid()

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  eBook - ePub

  C++ Programming for Linux Systems

  Create robust enterprise software for Linux and Unix-based operating systems

  • Desislav Andreev, Stanimir Lukanov(Authors)
  • 2023(Publication Date)
  • Packt Publishing

    (Publisher)

  2

  Learning More about Process Management

  You became familiar with the concept of processes in the previous chapter. Now, it’s time to get into details. It is important to understand how process management is related to the system’s overall behavior. In this chapter, we will emphasize fundamental OS mechanisms that are used specifically for process control and resource access management. We will use this opportunity to show you how to use some C++ features too.

  Once we’ve investigated the program and its corresponding process as system entities, we are going to discuss the states that one process goes through during its lifetime. You are going to learn about spawning new processes and threads. You are also going to see the underlying problems of such activities. Later we are going to check out some examples while slowly introducing the multithreaded code. By doing so, you will have the opportunity to learn the basics of some POSIX and C++ techniques that are related to asynchronous execution.

  Regardless of your C++ experience, this chapter will help you to understand some of the traps that you could end up in at the system level. You can use your knowledge of various language features to enhance your execution control and process predictability.

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  eBook - ePub

  Real-Time Embedded Systems

  Open-Source Operating Systems Perspective

  • Ivan Cibrario Bertolotti, Gabriele Manduchi(Authors)
  • 2017(Publication Date)
  • CRC Press

    (Publisher)

  If it is not, the operating system still supports multiple threads, which share the same address space and can freely read and write each other’s data. 3.6 Summary In this chapter, the concept of process has been introduced. A process is an abstraction of an executing program and encompasses not only the program itself, which is a static entity, but also the state information that fully characterizes execution. The notion of process as well as the distinction between programs and processes become more and more important when going from sequential to concurrent programming because it is essential to describe, in a sound and formal way, all the activities going on in parallel within a concurrent system. This is especially important for real-time applications since the vast majority of them are indeed concurrent. The second main concept presented in this chapter is the PSD. Its main purpose is to define and represent the different states a process may be in during its lifetime. Moreover, it also formalizes the rules that govern the transition of a process from one state to another. As it will be better explained in the next chapters, the correct definition of process states and transitions plays a central role in understanding how processes are scheduled for execution, when they outnumber the processors available in the systems, how they exchange information among themselves, and how they interact with the outside world in a meaningful way. Last, the idea of having more than one execution flow within the same process, called multithreading, has been discussed. Besides being popular in modern, general-purpose systems, multithreading is of interest for real-time systems, too. This is because hardware limitations may sometimes prevent real-time operating systems from supporting multiple processes in an effective way. In that case, typical of small embedded systems, multithreading is the only option left to support concurrency anyway.

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  eBook - ePub

  Basic Principles of an Operating System

  Learn the Internals and Design Principles

  • Dr. Priyanka Rathee, Priyanka Rathee(Authors)
  • 2019(Publication Date)
  • BPB Publications

    (Publisher)

  HAPTER 3

  Process Management

  In this chapter, we are going to learn the process, different stages of a process, process scheduling, and scheduling algorithms.

  3.1 Introduction

  A process is a program in execution. The process is an entity i.e. every process has its own address space which consists of:

  1. Stack region: Instructions and local variables for active procedure calls are stored in the stack region.
  2. Text region: The text region contains the code of the executing process.
  3. Data region: The dynamically allocated memory and variables used by a process during execution are stored in a data region.

  The local variables and instructions for active procedure call are stored in the stack region, a data region and text region. The stack contents expand as the process issues nested procedure calls and shrink as the called procedures return. The program is a passive entity and process is an active entity.

  3.1.1 Process Control Blocks/Process Descriptors

  When a process is created, the operating system should be able to identify the process. Therefore, the Process Identification numbers (PID) are given to the processes. Operating systems also create a Process Control Block (PCB)/Process Descriptors that contain the information required by the operating system to manage the processes. The information contained by PCBs is PID, process state, program counter, scheduling, priority, address space, parent process, child process, flags, and execution content. The operating system maintains pointers to each PCB corresponding to the particular process ID.

  (figure 3.1 )

  Figure 3.1 Process descriptors

  3.1.2 Process Operations

  There are various process operations performed by the operating system.

  (figure 3.2 )

  These are:

  • Creating process: The new process may be created by the operating system or the process itself. If the process creates a new process, then the process which is producing a sub process is called a parent process and the produced process is known as a child process.

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  eBook - PDF

  Systems Architecture

  • Stephen D. Burd(Author)
  • 2015(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  As a result, total hardware resource requirements are reduced, compared with installing each server on a separate computer. Sharing a single hardware platform across multiple virtual servers can also simplify administrative tasks, such as installation, backup, and recovery, although it might complicate other tasks, such as hardware maintenance and upgrades. ( continued ) Virtual server 1 CPUs Memory Hardware resources Hypervisor Disks I/O devices Virtual server 2 Virtual server 3 Virtual server 4 FIGURE 11.6 Virtual servers sharing a single computer system with a hypervisor Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Process Management 401 PROCESS MANAGEMENT A process is a unit of executing software that’s managed independently by the OS and can request and receive hardware resources and OS services. It can be a stand-alone entity or part of a group of processes cooperating to achieve a common purpose. Processes can communicate with other processes executing on the same computer or with processes executing on other computers. Process Control Data Structures The OS keeps track of each process by creating and updating a data structure called a process control block (PCB) for each active process. It creates a PCB when a process is created, updates the PCB as process status changes, and deletes the PCB when the process terminates. Using information stored in the PCB, the OS can perform a number of functions, including allocating resources, securing resource access, and protecting active processes from interference by other active processes.

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