Skip to main content

ENTERPROCESS COMMUNICATION AND SYNCHRONIZATION

     

ENTERPROCESS COMMUNICATION AND SYNCHRONIZATION

·         In multi programming environment multiple process co-exit . a single  program may be broken into number of processes.

·         The process are classified into two categories : independent processes and cooperating processes.

·         An independent process is a standalone process that does not share any data with any other process. It cannot affect or be affected by the other processes executing  in the system. In other words, the modification made to an independent process does not affect the functioning of other process.

·         A cooperating processes is a process that shares data with other processes in a system it can affect or be affectedly the other processes executing in the system

·         Cooperating processes can communicate in a shred memory environment .

·         The various reasons for using cooperating processes are:

1.       Information sharing : when several  users want to access to these type of reasourses

2.       Computational speed up: a task can be broken into various subtak so that each of them can run in parallel and this gives faster computation results.

3.       To support modularity: when a system is to be created in module fashion by dividing in into small functional units, co-operating processes are required. Cooperation processes establishes communication between the different modulus.

 

INTERPROCESSES COMMUNICATION

·         Inter-process communication (IPC) is a facility provided by an operating system via which cooperating processes can communicate with each other.

·         IPC facility allows the processes to cooperate and synchronize their action without sharing the sme addresses space

·         IPC is particularly useful in a distributed environment where the communication processes may reside on different computers connected with a network. An example is chat program used in the world wide web

·         There several different methods for establishing interprocess communication. Some of these methods are:

Ø Message Passing

Ø Shared Memory

Ø Signals

Ø Shared Files ,I.E. Pipes

Ø Dynamic Data Exchange (DDE)

Ø Object Linking And Embedding(OLE)

MESSAGE PASSING MODEL

·         A message is a collection of information that may be exchanged between a sending and receiving processes.

·         A message may contain data, execution commands, or even some code to be transmitted between two or more process.

·         A message format is flexible and negotiable by each sender- reciver pair.

·         A message Is characterized by its type , length ,sender and receiver IDS and a data field.

MESSAGE FORMAT

·         The format of a message depends upon two factors:

1.       The objective of the message facilty.

2.       Whether the facility runs on a single computer or on a distributed system

·         In some operating system short, fixed length messages are preferred in order to minimize processing and storage overhead.

·         In case , a large amount of data is to be sent , the data is placed in a file and the message then simply reference that file

       

·         The header has a fixed format within a given operating system and contains the information about the message.

·         The message body is optional and contains the actual content of the message.

·         The header may contain an identification of the message a length field , and a type field to discriminate among various types of messages.

·         There may also be additional control information such as pointer field so that a linked list of message can be created ,  a sequence number , to keep track of the number and order of messages passed between source and destination and a priority field.

·         Processes generally send and receive message by using send and receive primitives:

                          Send(receiver process, message)

                          Receive (sender process, message)

·         The send and receive calls are normally implemented as operating system calls.

·         The send call sends a message to a give receiver process. The receiver call receives a message from a given sender process.

·         The following four system calls are used for message transfer among processes:

Ø  msgget(): it returns (and possibly creates ) message descriptors to designate a message from queue for in other system calls.

Ø  msgetl(): it has options to set and return parameters associated with a message descriptor. It also has an option to remove descriptors.

Ø  msgsnd(): it senda a message using a message queue.

Ø  msgrev(): it receives using a message queue.


Implementing Issues In Messages

The various implementation issues that arise in interprocess communication using messages are:

1.       naming of the sender and receiver processes : naming conventions used in the send and receive calls provide answer to some key questions:.

·         How does the sender process know the name of the receiver?

·         How does the receiver process know the name of sebder ?

2.       Message delivery protocol : protocol are the set of rules that determines the message data format and actions of processes while sending and receiving messages

3.       Operating system responsibilities : buffering of message, bloicking and waking of processes etc.

 

 

Naming

·         Processes that want to communicate must have a way to refer tro each other processes can name each other directly or indirectly.

·         If the processes use indirect naming , it is know as indirect communication.

 

 

 

Comments

Post a Comment

Popular posts from this blog

Change the priority of a process

  Change the priority of a process You can tell the computer that certain processes should have a higher priority than others, and so should be given a bigger share of the available computing time. This can make them run faster, but only in certain cases. You can also give a process a  lower  priority if you think it is taking up too much processing power. Go to the  Processes  tab and click on the process you want to have a different priority. Right-click the process, and use the  Change Priority  menu to assign the process a higher or lower priority. There is typically little need to change process priorities manually. The computer will usually do a good job of managing them itself. (The system for managing the priority of processes is called  nice .) Does higher priority make a process run faster? The computer shares its processing time between all of the running processes. This is normally shared intelligently, so programs that are doing more ...
Post a Comment
Read more

Defination of OS(operating system) and its concepts

    What do you mean by operating system?     Definition :  An operating system is a program that act as an interface between the user of a computer and the                                      Computer hardware. Operating system is a first program that gets loaded into the memory through a process called booting. Concepts of operating system : ·                       The purpose of operating system is to provide an environment in which a user can execute program in a convenient and efficient manner. ·                       Operating system is an integrated set of program that ma...
3 comments
Read more

Monolithic Architecture

  Monolithic Architecture Monolith means composed all in one piece. The  Monolithic  application describes a single-tiered  software  application in which different components combined into a single program from a single platform. Components can be: Authorization — responsible for authorizing a user Presentation — responsible for handling HTTP requests and responding with either HTML or JSON/XML (for web services APIs). Business logic — the application’s business logic. Database layer — data access objects responsible for accessing the database. Application integration — integration with other services (e.g. via messaging or REST API). Or integration with any other Data sources. Notification module — responsible for sending email notifications whenever needed. Example for Monolithic Approach Consider an example of Ecommerce application, that authorizes customer, takes an order, check products inventory, authorize payment and ships ordered products. This applicat...
Post a Comment
Read more

System structure operating architecture

  System structure operating  architecture An operating system is a construct that allows the user application programs to interact with the system hardware. Since the operating system is such a complex structure, it should be created with utmost care so it can be used and modified easily. An easy way to do this is to create the operating system in parts. Each of these parts should be well defined with clear inputs, outputs and functions. Simple Structure There are many operating systems that have a rather simple structure. These started as small systems and rapidly expanded much further than their scope. A common example of this is MS-DOS. It was designed simply for a niche amount for people. There was no indication that it would become so popular. An image to illustrate the structure of MS-DOS is as follows − It is better that operating systems have a modular structure, unlike MS-DOS. That would lead to greater control over the computer system and its various applications. T...
Post a Comment
Read more

Multilevel Feedback queue scheduling (MFQ)

  Multilevel Feedback queue scheduling (MFQ) ·          Multilevel feedback queue scheduling is an enhancement of multi-levelqueue scheduling. In this scheme, processes can move between the different queue ·          The various processes are separates in different queue on the basis of their CPU Burst Char characteristics ·          If a process consumes a lot of CPU time , it is placed into a lower priority queue. Thus I/O bound and interactive process are placed in the higher priority queue and CPU bound pricesses are in lower priority ·          If a processes waits too long in a lower priority queue it is moved higher priority queue. Such an aging prevents starvation. ·          The top priority queue is given smallest CPU time Quantum ·      ...
Post a Comment
Read more