Process table
stackoverflow What is the linux process table ? What does it consist of?
This term keeps appearing in my Operating System notes, and I'm not entirely sure what it is/where it's stored and how or why.
A
The process table in Linux (such as in nearly every other operating system) is simply a data structure in the RAM of a computer. It holds information about the processes that are currently handled by the OS.
This information includes general information about each process
- process id
- process owner
- process priority
- environment variables for each process
- the parent process
- pointers to the executable machine code of a process.
A very important information in the process table is the state in that each process currently is. This information is essential for the OS, because it enables the so called multiprocessing, i.e. the possibility to virtually run several processes on only one processing unit (CPU).
The information whether a process is currently ACTIVE, SLEEPING, RUNNING, etc. is used by the OS in order to handle the execution of processes.
Furthermore there is statistical information such as when was the process RUNNING the last time in order to enable the schedulr of the OS to decide which process should be running next.
So in summary the process table is the central organizational element for the OS to handle all the started processes.
A short introduction can be found in this thread:
http://www.linuxforums.org/forum/kernel/42062-use-process-table.html
And wikipedia also has nice information about processes:
http://en.wikipedia.org/wiki/Process_management_(computing)#Process_description_and_control
http://en.wikipedia.org/wiki/Process_table
opensourceforu The Life of a Process
在这篇文章中，从内核源码的角度描述了process table，在本地的process-lifetime/Unix-process-lifetime.md中收录了这篇文章；
cs.unc.edu Process Table
The process table is a data structure maintained by the operating system to facilitate context switching and scheduling, and other activities discussed later. Each entry in the table, often called a context block, contains information about a process such as process name and state (discussed below), priority (discussed below), registers, and a semaphore it may be waiting on (discussed later). The exact contents of a context block depends on the operating system. For instance, if the OS supports paging, then the context block contains an entry to the page table.
In Xinu, the index of a process table entry associated with a process serves to identify the process, and is known as the process id of the process.