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

Multi Level Queue Scheduling (MLQ)

  Multi Level Queue Scheduling (MLQ) ·          Multilevel queue scheduling classifies the processes according to their types for example, a multilevel queue scheduling algorithm makes a common. ·          In this scheduling ready queue is divided into various queue that are called sub queues. A subqueue is a distinct operational queue ·          The process are permanently assigned to subqueues, generally based on some property of the process such as memory size,priority or process type ·          Each subqueue has its process sucheduling algorithm. For example interactive process at the foreground may use round robin scheduling while batch jobs at the background may use the FCFS method ·          For example, consider a system with four different queues 1.   ...
Post a Comment
Read more

Micro kernel architecture

  Micro kernel  architecture What is Kernel? A kernel is an important part of an OS that manages system resources. It also acts as a bridge between the software and hardware of the computer. It is one of the first program which is loaded on start-up after the bootloader. The Kernel is also responsible for offering secure access to the machine's hardware for various programs. It also decides when and how long a certain application uses specific hardware. What is Microkernel? Microkernel  is a software or code which contains the required minimum amount of functions, data, and features to implement an operating system. It provides a minimal number of mechanisms, which is good enough to run the most basic functions of an operating system. It allows other parts of the operating system to be implemented as it does not impose a lot of policies. Microkernels and their user environments are usually implemented in the C++ or C programming languages with a little bit of assembly. Ho...
Post a Comment
Read more

Exokernel architecture

Exokernel architecture Most of us know what kernels are and how do they work to make programmers’ lives easier. But, how many of us know what exokernels are? I hope you will be able to get a brief introduction on this terminology through this blog. Let’s start with a brief introduction on kernel. What is a kernel? A kernel is the foundational layer of an operating system that functions at a basic level, communicating with hardware and managing resources, such as CPU and the memory. It works as an interface between the user application and the hardware. There   are two main types of kernel 1. Micro kernel 2. Monolithic Kernel 1.  Monolithic architecture 2.      Layerd archtecture . 3.       Virtual machine architecture 4.       Exokernel architecture 5.      Client server architecture   6.       Micro kernel architecture Now let’s head into our main focus. What is an Exokern...
Post a Comment
Read more

Shortest Job First Scheduling (SJF)

  Shortest Job First Scheduling (SJF) ·          SJF ia also known as shortest-job-next(SJN) algorithm and is faster than FCFS. ·          In SJF, the process with the least estimated execution time is selected from the ready queue for   execution. ·          For this, SJF algorithm associates with each process, the length of its next CPU burst. When the CPU is available, it is assigned to the process that has the smallest next CPU burst. ·          If tow processes have the same length of next CPU burst ,FCFS scheduling algorithm is used to break the tie. ·          SJF algorithm can be preemptive or non-preemptive.     Non-preeptive SJF ·          In non-preemptive SJF, scheduling, CPU is always assigned to the ...
Post a Comment
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