UNIX Kernel--Process Management
The UNIX system kernel is the master organizer of UNIX. The kernel schedules processes, allocates memory and disk storage, supervises the transmissions of data between the main storage and the peripheral devices, and honors the processes' requests for service. The traditional UNIX system kernel addresses three major tasks: process management; device management; and file management. These three areas remain central, but dramatic advances in hardware and software have expanded the role of the kernel. Today's kernels usually provide these additional services: virtual memory, networking, and network file systems. Additional kernel features that exist in some versions of UNIX, but that are not universally available include multiprocessor support and lightweight process support. This paper will focus on process management. This includes starting processes, scheduling processes, swapping processes to disk, allocating resources such as memory and honoring processes' requests for service.A process is a program that is being executed. For a given program, there may be any number of processes running at a particular time. When we speak of a process, we are talking about something that is active,
I/O intensive processes tend to execute until they have to wait for the result of an I/O operation. System calls that perform I/O operations often lead to a suspension of the calling process while the data is being transferred. A signal is a message from one process to another. The two processes have two process ID numbers and different parent process ID numbers. The process table is referenced during all of the life stages of processes. Paging is a similar process found on some UNIX systems, where infrequently used parts of processes are temporarily stored on disk. The transfer completion interrupt usually updates various status elements in certain tables and then possibly initiates another transfer. Several users are often executing many programs, such as the shell, simultaneously. After a fork, there are two nearly identical processes, the parent and the child. The service requirements of the I/O peripherals are the third mechanism that causes a switch from user mode to kernel mode. If the entry contains a one, the signal will be ignored. The process is the fundamental unit of organization in the UNIX system. When a system call occurs, the kernel takes over. The lowest priority process would be selected for execution.
Common topics in this essay:
I/O I/O,
Management UNIX,
process table,
system call,
unix system,
user table,
child process,
demise child,
kernel mode,
user mode kernel,
unix system kernel,
wait demise child,
wait system call,
demise child process,
processes process,
program text,
wait system,
|
Acceptance Essays
