Process (Linux)

A process is just a program in execution.

I had a really solid introduction through Hemal Shah, but formally learned through SE350.

A process consists of 3 components:

1. An executable program
2. Associated data needed by the program (variables, work space, buffers, etc.)
3. Execution context of the program

• All information the OS needs to manage the process

A process can be uniquely characterized by a number of elements, including the following:

• Identier (PID)
• State (see 5 State Process Model)
• Priority (relative to other processes)
• Memory pointers (Pointers + shared memory blocks)
• Context data (Registers, PSW, program counter)
• I/O status information (Outstanding I/O requests, used I/O devices)
• Accounting information
  • Amount of processor time, time limits, threads
  • Use top and ulimit

The above information is stored in a Process Control Block.

Concepts

• Process Interaction
• Mutual Exclusion
• Process Switch
• Process Creation
• Process Termination
• Process Switch
• Process Suspension

Implementing Processes in an OS

The simplest way is to design a single queue with a Two-State Process Model (see page). However, there are many limitations. This is why we move on to a Five-State Process Model, with the addition of Process Suspension.

Related

• Thread
• Scheduling