Virtual memory in operating system lecture notes pdf

Stack is a special region in a computer's memory that stores temporary variables created by each function. The stack is Virtual Memory Definition Storage space that may be regarded as addressable main storage by the user of a computer system.

What is Communication Architecture? What is Client? What is Access Method? What is Concurrent? What is Operating System OS? What is Stack?

Word : Ordered set of bytes or bits that is Working Set : Working set with parameter for a process at virtual time Worm : Program that can travel from computer to computer Paging happens whenever a page fault occurs and a free page cannot be used for allocation purpose accounting to reason that pages are not available or the number of free pages is lower than required pages. This process determines the quality of the page replacement algorithm: the lesser the time waiting for page-ins, the better is the algorithm.

A page replacement algorithm looks at the limited information about accessing the pages provided by hardware, and tries to select which pages should be replaced to minimize the total number of page misses, while balancing it with the costs of primary storage and processor time of the algorithm itself. There are many different page replacement algorithms.

We evaluate an algorithm by running it on a particular string of memory reference and computing the number of page faults,. 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. 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. An optimal page-replacement algorithm has the lowest page-fault rate of all algorithms. Replace the page that will not be used for the longest period of time.

Use the time when a page is to be used. Page which has not been used for the longest time in main memory is the one which will be selected for replacement. This algorithm suffers from the situation in which a page is used heavily during the initial phase of a process, but then is never used again. This algorithm is based on the argument that the page with the smallest count was probably just brought in and has yet to be used.

Arnab Chakraborty. Frahaan Hussain. Harshit Srivastava. Ashraf Said. Operating System - Virtual Memory Advertisements. Previous Page. Next Page. Useful Video Courses.