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 are privileged instructions, What are privileged instructions? Som...

What are privileged instructions? Some of the machine instructions that may cause harm to a system are designated as privileged instructions. The hardware permits the privilege

Necessary conditions for deadlock, Here are the conditions necessary for a ...

Here are the conditions necessary for a deadlock to occur; note that all of them are necessary, and none is suf?cient: 1. ?nite resources: the resources are held in a mutually-e

Relationship among the capabilities of domain level j and i, Q. In a ring-...

Q. In a ring-protection system the level 0 has the greatest access to objects and level n (greater than zero) has fewer access rights. The access rights of a program at a partic

DMA block diagram, I need help,i want a brief and easy explanation to under...

I need help,i want a brief and easy explanation to understand and write in exams and easy to understand topic of DMA block diagram which Is of I/O management and scheduling? can u

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 ?

Why do organisations need a structure, Problem 1: (a) The grouping of o...

Problem 1: (a) The grouping of organisational activities (usually into ‘departments' or larger ‘divisions') can be done in different ways. Outline 7 criteria which can be used

Explain inverted page table, Inverted page table In page table the page...

Inverted page table In page table the page table has one entry for every page that the process is using. The operating system must translate this reference into a physical memo

Unix operating system, A working Ubuntu Linux operating system.  You can us...

A working Ubuntu Linux operating system.  You can use a Live-CD to complete this assignment. Create an empty text file named assignment6.txt in your home directory. Edit this

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