Lru implementation details, Operating System

Assignment Help:

Now, let us discuss two related algorithms for deciding which pages to evict. The clock algorithm is one of the most popular choices. It works by keeping frames in a circular structure. (Note that this circle may be very large: a 32-bit machine with 4k pages can have up to 220  1 million frames.) When a page fault occurs, it checks the reference bit of the next frame. If that bit is zero, it evicts that page and sets its bit to 1; if the reference bit is 1, the algorithm sets the bit to 0 and advances the pointer to next frame. 

An implementation which is often used in real operating systems is a segmented queue. This type of algorithm divides all existing pages into two sets of pages. The most-active one-third of all pages use a clock algorithm. After that, pages that are evicted out of the clock are moved to a "uncommon" linked list, in which we use exact LRU. This way, we approximate LRU for the frequently-referenced pages (1/3 of the page frames - fast clock algorithm), and at the same time use exact LRU on the infrequently accessed pages (2/3 of all page frames). Since the pages in the uncommon list are not accessed very frequently, it is okay if their accesses are a little slower due to some pointer manipulation.


Related Discussions:- Lru implementation details

What is the sequence in which resources may be utilized, What is the sequen...

What is the sequence in which resources may be utilized? Under normal mode of operation, a process may utilize a resource in the following sequence: Request: If the requ

SYSTEM PROGRAMMING, advantages and disadvantages of monolithic and layered ...

advantages and disadvantages of monolithic and layered approach

Operating system strectures, with the aid of diagrams describe the followin...

with the aid of diagrams describe the following os structures monolithic , layered, client server

Define action that implementing meaning of instruction, Determine how Actio...

Determine how Action implementing instruction’s meaning are a actually carried out   Action implementing meaning of instruction are a actually carried out Instruction executio

Rf, whta is an operating system ? what sorts services are provided by an op...

whta is an operating system ? what sorts services are provided by an operating system ?

What is an operating system, What is an operating system? An operating ...

What is an operating system? An operating system is a program that manages the computer hardware. It acts as an intermediate among users of a computer and the computer hardware

Define throughput, Define throughput? Throughput in CPU scheduling is t...

Define throughput? Throughput in CPU scheduling is the number of processes that are completed per unit time. For long processes, this rate might be one process per hour; for sh

Major differences between capability lists and access lists, Q. What are th...

Q. What are the major differences between capability lists and access lists? Answer: An access list is a list for each object consisting of the domains with a nonempty set of

Perl script, Write a Perl script assignGrades.pl to assign letter grades to...

Write a Perl script assignGrades.pl to assign letter grades to the students.

What do you mean by best fit, What do you mean by best fit? Best fit al...

What do you mean by best fit? Best fit allocates the smallest hole that is big sufficient. The entire list has to be searched, until it is sorted by size. This strategy creates

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd