04 – The Abstraction – The Process

CPU virtualization

the OS can promote the illusion that many virtual CPUs exists

Time Sharing

running one process, then stopping it and running another

Performance

time sharing, the potential cost is _

Context Switch

time sharing, the potential cost is performance via a mechanism called _ _

Mechanism

low-level methods or protocols that implement a functionality

Context switch

example of mechanism

Policy

algorithms for making some kinds of decision within the OS

Scheduling policy

example of policy

Process

a running program

Program Image

a program is lifeless, just sits on the disk as bunch of instructions (and some data)

Memory, Register, I/O Information

machine state is composed of _ _ _ _

Memory

the address space, range of address that a process can access

Registers

high speed storage for small data items

I/O Information

list of open files

Create

create a new process to run a program, process API (1)

Destroy

halt a runaway process, process API (2)

Wait

wait for a process to stop running, process API (3)

Miscellaneous Control

some kind of method to suspend a process and then resume it, process API (4)

Status

get some status info about a process, process API (5)

Load, Memory

_ a program code into _ , into the address space of the process, process creation (1)

Disk, Executable format

programs initially reside on _ in _ _

Run time, Stack

the program’s _ _ _ is allocated, process creation (2)

Heap

the program’s _ is created, process creation (3)

Heap

used for explicitly requested dynamically allocated data

Initialization tasks

the OS does some other _ _, process creation (4)

Standard input, output, error

each process by default has three open file descriptors

Start, main

_ the program running at the entry point, namely _

Running

a process is _ on a processor, instructions are being executed

Ready

a process is _ to run but for some reason the OS has chosen not to run it at this given moment

Blocked

a process has performed some kind of operation and is waiting for the result

Initial and Final

2 additional states may be present depending on the OS

Process Lists

ready processes, blocked processes, currently running processes

Register context

will hold the values of the registers when a process is stopped or paused

Register context

will be copied back to the actual register during a context switch to resume the stopped or paused process

Process Control Block

a C-structure that contains information about a process