2.1 Process Management

2.1 Process Management

It involves various tasks like creation, scheduling, termination of processes, and a dead lock.

Process management

It is a program that is under execution

Process

It is the unit of work in a modern computing system.

process

TRUE OR FALSE

The more complex the operating system is, the more it is expected to do on behalf of its users.

TRUE

TRUE OR FALSE

An operating system executes a variety of programs that run as a process.

TRUE

TRUE OR FALSE

Process execution must progress in a sequential fashion. No parallel execution of instructions of a single process.

TRUE

ENUMERATE: An operating system executes a variety of programs:

• Batch Systems (Jobs)

• Time-shared systems (user programs or tasks)

The unit of execution within a process.

Threads

TRUE OR FALSE

A process can have one or more threads.

TRUE

TRUE OR FALSE

A process with a single thread executes only one task at a time, while a multithreaded process can execute a task per thread.

TRUE

ENUMERATE: Parts of a Process

• Text Section

• Current activity including program counter, processor registers

• Stack

• Data Section

• Heap

The program code of process is callled?

Text Section

In process, it contains temporary data

• Function parameters, return addresses, local variables

Stack

In process, it contain the global variables

Data section

In process, it contains memory dynamically allocated during run time

Heap

TRUE OR FALSE

• The program becomes process when an executable file is loaded into memory

TRUE

TRUE OR FALSE

• One program can be several processes

  • Consider multiple users executing the same program

TRUE

TRUE OR FALSE

As a process executes, it changes state

TRUE

ENUMERATE: Process State

• New

• Running

• Waiting

• Ready

• Terminated

The state where the process is being created

New

The state where instructions of process are being executed

Running

The state where the process is waiting for some event to occur

Waiting

The state where the process is waiting to be assigned to a processor

Ready

The state where the process has finished execution

Terminated

Each process is represented in the operating system by a ?

process control block (PCB)

Other term for process control block

Task Control Block

ENUMERATE: Information associated with each process

• Process Number

• Process State

• Program Counter

• I/O Status Information

• CPU Registers

• CPU Scheduling Information

• Memory-management Information

• Accounting Information

is the unique number representing a process

Process Number/Process ID

location of instruction to next execute

Program Counter

contents of all process-centric registers

CPU registers

memory allocated to the process

Memory-manage information

CPU used, clock time elapsed since start, time limits

Accounting Information

I/O devices allocated to process, list of open files

I/O Status Information

TRUE OR FALSE

• The goal -- the objective of multiprogramming is to have some process running at all times to maximize CPU utilization.

TRUE

The goal -- the objective of ______ is to have some process running at all times to maximize CPU utilization.

multiprogramming

The objective of _______ is to switch the CPU among processes so frequently that users can interact with each program while it is running. 

time sharing

This selects among available processes for the next execution on the CPU core

Process scheduler

ENUMERATE: Process Scheduler maintains scheduling queues of processes, what are these?

• Job queues

• Ready queue

• Wait queue

As processes enter the system, they are put into a _____ queue, which consists of all processes in the system

job

set of all processes residing in main memory, ready and waiting to execute

Ready Queue

set of processes waiting for an event (i.e., I/O)

Wait Queue

TRUE OR FALSE

• Interrupts cause the OS to change a CPU from its current task and to run a kernel routine. Such operations happen frequently on a general-purpose system. 

TRUE

When CPU switches to another process, the system must save the state of the old process and load the saved state for the new process via a __________

context switch

Context of a process represented in the ____-

PCB (Process Control Block)

TRUE OR FALSE

• Context-switch time is pure overhead; the system does no useful work while switching

  • The more complex the OS and the PCB - the longer the context switch

TRUE

A process may create several new processes via ________ during the course of execution.

create- process system call

selects which process should be executed next and allocates CPU

Short-Term Scheduler / CPU Scheduler

TRUE OR FALSE

Short-term scheduler is invoked frequently (milliseconds)  (must be fast)

TRUE

selects which processes should be brought into the ready queue

Long-term scheduler / Job Scheduler

TRUE OR FALSE

Long-term scheduler is invoked infrequently (seconds, minutes)  (may be slow)

ENUMERATE: Process can be describe as either

• I/O Bound Process

• CPU-bound process

This process spends more time doing I/O than computations, many short CPU bursts

I/O Bound Process

This process spends more time doing computations; few very long CPU bursts

CPU-bound processes

The creating process is called the _____-, and the new processes are called the _______ of that process. 

parent process

children

TRUE OR FALSE

• Parent process creates children processes, which, in turn, create other processes, forming a tree of processes structure

TRUE

Generally, the process identified and managed via a _____-

process identifier (PID)

ENUMERATE: In process creation, the resource sharing options are:

• Parent and children share all resources

• Children share a subset of parent’s resources

• Parent and child share no resources

ENUMERATE: In process creation, the execution options are:

• Parent and children execute concurrently

• Parent waits until children terminate

ENUMERATE: In process creation, the address spaces are:

• Child duplicate of the parent (same data and program as the parent)

• The child has a program loaded into it

In UNIX operating systems, this system call creates a new process

fork()

In UNIX operating systems, this system call used after a fork() to replace the process’ memory space with a new program

exec()

In UNIX operating system, parent process calls ___ waiting for the child to terminate

wait()

The process executes the last statement and then asks the operating system to delete it using the _____ system call.

exit()

In process termination, this system call returns status data from child to parent

wait()

The parent may terminate the execution of children processes using the ____ system call.

abort()

ENUMERATE: The parent may terminate the execution of children processes using the abort() system call. Some reasons for doing so:

• The child has exceeded allocated resources

• The task assigned to the child is no longer required

• The parent is exiting, and the operating systems do not allow a child to continue if its parent terminates

Some operating systems do not allow a child to exists if its parent has terminated. If a process terminates, then all its children must also be terminated. This is called?

Cascading Termination

The parent process may wait for the termination of a child process by using the ___ system call.

wait()

In process termination, if no parent waiting (did not invoke wait()) process is a ____

zombie

In process termination, if parent terminated without invoking wait(), the process is an ___

orphan

ENUMERATE: Android Process Importance Hierarchy (Most to Least)

• Foreground Process

• Visible Process

• Service Process

• Background Process

• Empty Process

The current process visible on the screen, representing the application the user is currently interacting with

Foreground Process

A process that is not directly visible on the foreground but that is performing an activity that the foreground process is referring to (that is, a process performing an activity whose status is displayed on the foreground process)

Visible Process

A process that is similar to a background process but is performing an activity that is apparent to the user (such as streaming music)

Service Process

A process that may be performing an activity but is not apparent to the user.

Background Process

A process that holds no active components associated
with any application

Empty Process

TRUE OR FALSE

• Android will begin terminating processes that are most important.

• Android will begin terminating processes that are least important.

ENUMERATE: Processes executing concurrently in the operating system may be either ?

• independent processes

• cooperating processes.

A process is ______- if it does not share data with any other processes executing in the system.

independent

A process is _____ if it can affect or be affected by the other processes executing in the system.

cooperating

Clearly, any process that shares data with other processes is a ________ process.

cooperating

ENUMERATE: There are several reasons for providing an environment that allows process cooperation:

• Information sharing. Since several applications may be interested in the same piece of information (for instance, copying and pasting), we must provide an environment to allow concurrent access to such information.

• Computation speedup. If we want a particular task to run faster, we must break it into subtasks, each of which will be executing in parallel with the others. Notice that such a speedup can be achieved only if the computer has multiple processing cores.

• Modularity. We may want to construct the system in a modular fashion, dividing the system functions into separate processes or threads

Cooperating processes require an ________ mechanism that will allow them to exchange data— that is, send data to and receive data from each other.

interprocess communication (IPC)

ENUMERATE: There are two fundamental models of interprocess communication:

• Shared Memory

• Message Passing

ENUMERATE: Google Chrome Browser is multiprocess with 3 different types of processes:

• Browser process manages user interface, disk, and network I/O

• Renderer process renders web pages, deals with HTML, Javascript. A new renderer created for each website opened

  • Runs in sandbox restricting disk and network I/O, minimizing the effect of security exploits

• Plug-in process for each type of plug-in

In Google Chrome Browser, this process manages user interface, disk, and network I/O

Browser process

In Google Chrome Browser, this process renders web pages, deals with HTML, Javascript. A new renderer created for each website opened

Renderer process

In Google Chrome Browser, this process for each type of plug-in

Plug-in process

An area of memory shared among the processes that wish to communicate

IPC - Shared Memory

TRUE OR FALSE

In shared memory, the communication is under the control of the users' processes, not the operating system. Major issues are to provide a mechanism that will allow the user processes to synchronize their actions when they access shared memory.

TRUE

Communication between processes takes place through calls to _____ primitives.

send() and receive()

ENUMERATE: Message passing may be either?

blocking or nonblocking —also known as synchronous and asynchronous.

The sending process is blocked until the message is received by the receiving process or by the mailbox.

Blocking Send

The sending process sends the message and resumes operation.

Nonblocking Send

The receiver blocks until a message is available.

Blocking Receive

The receiver retrieves either a valid message or a null.

Nonblocking Receive

If both send and receive are blocking, we have a _____

rendezvous

ENUMERATE: Whether the communication is direct or indirect, messages exchanged by communicating processes reside in a temporary queue. Basically, such queues can be implemented in three ways:

• Zero Capacity

• Bounded Capacity

• Unbounded Capacity

The queue has a maximum length of zero; thus, the link cannot have any messages waiting in it. In this case, the sender must block until the recipient receives the message.

Zero Capacity