Page Replacement Algorithm in OS

-

Page Fault-


  • When a page referenced by the CPU is not found in the main memory, it is called as a page fault.
  • When a page fault occurs, the required page has to be fetched from the secondary memory into the main memory.

Reference String

The string of memory references is called reference string. Reference strings are generated artificially or by tracing a given system and recording the address of each memory reference. The latter choice produces a large number of data, where we note two things.
  • For a given page size, we need to consider only the page number, not the entire address.
  • If we have a reference to a page p, then any immediately following references to page p will never cause a page fault. Page p will be in memory after the first reference; the immediately following references will not fault.
  • For example, consider the following sequence of addresses − 123,215,600,1234,76,96
  • If page size is 100, then the reference string is 1,2,6,12,0,0
---> page Replacement Algorithm is used to  reduced page fault.
Various page Replacement Algorithm we are discussing in next topic..

Thank you viewers..
This is contributed by soumy Sinha..

Comments

Post a Comment

Popular posts from this blog

Introduction of Digital computer

-
Image
INTRODUCTION Digital computer concept:- 1. Digital computers are designed to store, process and communicate information in digital form. 2. Digital computer is any of a class of digital devices capable of solving problems by processing information in discrete form. 3. It is used for processing data represented by discrete, localized physica signals, as the presence or electic current. 4.The main three components of digital computer:- >input:- The user gives a set of input data through input devices. >Processing :- The input data is processed with the help of CPU by well defined and finite sequence of step. >Output : - Some data available from the processing step are output to the user. TYPE OF DIGITAL COMPUTER :- 1.Microcomputer/Desktop computer 2.Minicomputer 3.Mainframe computer 4.Supercomputers Microcomputer :- 1.Microcomputer is also called a personal computer or desktop computer. 2.It includes a microprocessor, memory, and
Read more

INTRODUCTION OF DBMS

-
What is Database :- The database is a collection of inter-related data which is used to retrieve, insert and delete the data efficiently. It is also used to organize the data in the form of a table, schema, views, and reports, etc. For example: The college Database organizes the data about the admin, staff, students and faculty etc. Using the database, you can easily retrieve, insert, and delete the information. DBMS (Database Management System):- Database management system is a software which is used to manage the database. For example: MySQL, Oracle, etc are a very popular commercial database which is used in different applications.DBMS provides an interface to perform various operations like database creation, storing data in it, updating data, creating a table in the database and a lot more.It provides protection and security to the database. In the case of multiple users, it also maintains data consistency. DBMS allows users the following tasks:- Data Definition: I
Read more

Introduction to cache memory

-
Image
Cache Memory in Computer Organization Cache Memory  is a special very high-speed memory. It is used to speed up and synchronizing with high-speed CPU. Cache memory is costlier than main memory or disk memory but economical than CPU registers. Cache memory is an extremely fast memory type that acts as a buffer between RAM and the CPU. It holds frequently requested data and instructions so that they are immediately available to the CPU when needed. Cache memory is used to reduce the average time to access data from the Main memory. The cache is a smaller and faster memory which stores copies of the data from frequently used main memory locations. There are various different independent caches in a CPU, which stored instruction and data. Levels of memory: Level 1 or Register – It is a type of memory in which data is stored and accepted that are immediately stored in CPU. Most commonly used register is accumulator, Program counter, address register etc. Level 2 or Cac
Read more