comp229-slide-6 - Concordia university Department of...

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Lesson 6 - Process management 1 Concordia university Department of computer science System software – COMP229 Lesson 6 : Process management © Author : Kerly Titus
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Lesson 6 - Process management 2 Process management Contents 1. The process concept 3 2. Resources 13 3. Process relationship 18 4. Threads 22 5. Unix 27 6. Key points 45 7. References 47
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Lesson 6 - Process management 3 1. The process concept Introduction Process states Process description Process address space
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Lesson 6 - Process management 4 The process concept Introduction Definition of a process. A process represents an abstract environment that is created by the OS to manage the execution of a program. The process environment. Includes code, data, descriptor, stack, and resources. Each environment is separate. Protection and sharing of resources among processes. Program vs process. A program is a passive entity. A process is an active entity. Many processes can execute a same program. Program Program Process Abstract Computing Environment File Manager Memory Manager Device Manager Protection Protection Deadlock Deadlock Synchronization Synchronization Process Description Process Description Scheduler Scheduler Resource Manager Resource Manager Resource Manager Resource Manager Resource Manager Resource Manager CPU CPU Other H/W Other H/W Memory Memory Devices Devices • Abstract computing environment
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Lesson 6 - Process management 5 The process concept Process states • The state indicates the current activity of a process. • The state changes when the activity changes. • The states are represented by a state diagram. – Nodes represent states. – Edges represent events that cause a transition to a new state. Ready Running Blocked Exit Interrupt Request Terminated New Allocation Select Admit Request •Process state diagram
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Lesson 6 - Process management 6 The process concept Process states •T h e n e w s t a t e . – Occurs at the beginning of the execution of a program. – The OS allocates the resources to create the new process. – Every process is created by another process, except for the first OS process. – Causes of process creation. • Execution of a system call by a program to create a new process. • Submission of batch jobs. • User connection at a terminal. • Execution of a program by a user. • Execution of an OS service. • Parallelism of an application.
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Lesson 6 - Process management 7 The process concept Process states • The terminated state. – Occurs at the end of the execution of a process. – Resources used by the terminating process are deallocated. – Process accounting information are preserved. – Causes of process termination. • Execution of an exit system call by a program.
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comp229-slide-6 - Concordia university Department of...

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