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

Explain contiguous allocation, Contiguous allocation The contiguous-all...

Contiguous allocation The contiguous-allocation method needs each file to occupy a set of contiguous blocks of the disk. Disk addresses explain a linear ordering on the disk. T

Define an imperative statement, Determine an imperative statement Imper...

Determine an imperative statement Imperative statement points out an action to be carried out during execution of assembled program

What are the advantages of contiguous allocation, What are the advantages o...

What are the advantages of Contiguous allocation? The advantages are a. Supports direct access b. Supports sequential access c. Number of disk seeks is minimal.

What is the use of fork and exec system calls, What is the use of fork and ...

What is the use of fork and exec system calls? Fork is a system call by which a latest process is created. Exec is also a system call, which is used after a fork by one of the

Requirements memory management intended to satisfy?, Normal 0 f...

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4

Problem of unbalanced loads, Present your own fully documented and tested p...

Present your own fully documented and tested programming example illustrating the problem of unbalanced loads. Describe the use of OpenMP's scheduler as a means of mitigating this

Sector sparing, What is sector sparing is proper definition

What is sector sparing is proper definition

Determine a processing that is not a part of synthesis phase, Determine a p...

Determine a processing that is not a part of Synthesis phase  Perform LC processing is not a part of Synthesis phase

What is a file path name, What is a file path name? A list of the subdi...

What is a file path name? A list of the subdirectories, directories, and files we must traverse to reach a file from the root directory.

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