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 disadvantages of the two-level directory, How do we overcome the di...

How do we overcome the disadvantages of the two-level directory? Give links from one user directory to another, creating path names; system files become available by letting th

Explain multithreading operating system, Multithreading - Operating system...

Multithreading - Operating systems that permit different parts of a software program to run concurrently. Operating systems that would come into this category are: Linux UNI

Define the properties of batch operating systems, Define the properties ope...

Define the properties operating systems: Batch :- Jobs with similar needs are batched together and  run through the computer as a group by an operator or automatic job sequenc

Explain banker''s algorithm, Banker's Algorithm In this analogy ...

Banker's Algorithm In this analogy Customers ≡ processes Units ≡ resources, say, tape drive Ba

Hashed page table, W hat is hashed page table & method of hashed page tabl...

W hat is hashed page table & method of hashed page table with details

Define a daemon process , A daemon is a process that removes itself from t...

A daemon is a process that removes itself from the terminal and disconnected, executes, in the background, waiting for requests and responding to them. It may also be described as

Memory pages, Applications allocate memory in terms of the number of bytes ...

Applications allocate memory in terms of the number of bytes that they need, but this level of granularity is too ?ne-grained for the operating system to manage the system memory i

Os structures, #question.explain varios types of system calls..

#question.explain varios types of system calls..

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