Recent from talks
Process management (computing)
Knowledge base stats:
Talk channels stats:
Members stats:
Process management (computing)
A process is a program in execution, and 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 synchronization 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 operating system to exert control over each process.
In any modern operating system, there can be more than one instance of a program loaded in memory at the same time. For example, more than one user can be executing the same program, with 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 can each execute the same program-code. Such a program is called re-entrant.[relevant?] At a given instant, the processor 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. The execution of multiple processes over a period of time, rather than simultaneously, is known as concurrent execution.
A multiprogramming or multitasking O.S. is a Operating System that can execute many processes concurrently. Multiprogramming requires that the processor be allocated to each process for a period of time and de-allocated or issued at an appropriate moment. If the processor is de-allocated during the execution of a process, it must be done in a way that the process can restart later as efficiently as possible.
There are two ways for an OS to regain control of the processor during a program's execution in order for the OS to perform de-allocation or allocation:
The stopping of one process and starting (or restarting) of another process is called a context switch or context change. In many modern operating systems, processes can consist of many sub-processes. This introduces the concept of a thread. A thread may be viewed as a sub-process; that is, a separate, independent sequence of execution within the code of one process. Threads are becoming increasingly important in the design of distributed and client–server systems and in software run on multi-processor systems.
A common trait observed among processes associated with most computer programs is that they alternate between CPU cycles and I/O cycles. For the portion of the time required for CPU cycles, the process is being executed and is occupying the CPU. During the time required for I/O cycles, the process is not using the processor. Instead, it is either waiting to perform Input/Output, or is actually performing Input/Output. An example of this is reading from or writing to a file on disk. Prior to the advent of multiprogramming, computers operated as single-user systems. Users of such systems quickly become aware that for much of the time that a computer was allocated to a single user – for example, when a user was entering information or debugging programs – the processor was idle. Computer scientists observed that the overall performance of the machine could be improved by letting a different process use the processor whenever one process was waiting for input/output. In a uni-programming system, if N users were to execute programs with individual execution times of t1, t2, ..., tN, then the total time, tuni, to service the N processes (consecutively) of all N users would be:
However, because each process consumes both CPU cycles and I/O cycles, the time which each process actually uses the CPU is a very small fraction of the total execution time for the process. So, for process i:
where
Hub AI
Process management (computing) AI simulator
(@Process management (computing)_simulator)
Process management (computing)
A process is a program in execution, and 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 synchronization 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 operating system to exert control over each process.
In any modern operating system, there can be more than one instance of a program loaded in memory at the same time. For example, more than one user can be executing the same program, with 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 can each execute the same program-code. Such a program is called re-entrant.[relevant?] At a given instant, the processor 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. The execution of multiple processes over a period of time, rather than simultaneously, is known as concurrent execution.
A multiprogramming or multitasking O.S. is a Operating System that can execute many processes concurrently. Multiprogramming requires that the processor be allocated to each process for a period of time and de-allocated or issued at an appropriate moment. If the processor is de-allocated during the execution of a process, it must be done in a way that the process can restart later as efficiently as possible.
There are two ways for an OS to regain control of the processor during a program's execution in order for the OS to perform de-allocation or allocation:
The stopping of one process and starting (or restarting) of another process is called a context switch or context change. In many modern operating systems, processes can consist of many sub-processes. This introduces the concept of a thread. A thread may be viewed as a sub-process; that is, a separate, independent sequence of execution within the code of one process. Threads are becoming increasingly important in the design of distributed and client–server systems and in software run on multi-processor systems.
A common trait observed among processes associated with most computer programs is that they alternate between CPU cycles and I/O cycles. For the portion of the time required for CPU cycles, the process is being executed and is occupying the CPU. During the time required for I/O cycles, the process is not using the processor. Instead, it is either waiting to perform Input/Output, or is actually performing Input/Output. An example of this is reading from or writing to a file on disk. Prior to the advent of multiprogramming, computers operated as single-user systems. Users of such systems quickly become aware that for much of the time that a computer was allocated to a single user – for example, when a user was entering information or debugging programs – the processor was idle. Computer scientists observed that the overall performance of the machine could be improved by letting a different process use the processor whenever one process was waiting for input/output. In a uni-programming system, if N users were to execute programs with individual execution times of t1, t2, ..., tN, then the total time, tuni, to service the N processes (consecutively) of all N users would be:
However, because each process consumes both CPU cycles and I/O cycles, the time which each process actually uses the CPU is a very small fraction of the total execution time for the process. So, for process i:
where
Recent media