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

Explainoptimal page replacement in detail, Optimal page replacement An...

Optimal page replacement An optimal page replacement algorithm has the least page fault rate of all algorithms. The algorithm states that put back the page that will not be us

Write note on process, Write note on process, process state? A process ...

Write note on process, process state? A process is in excess of the program code which is sometimes known as text section. It as well includes the current activity as represent

System protection, what is the need-to-know principle? why is it important ...

what is the need-to-know principle? why is it important for a protection system to adhere to this principle?

Architects applications by making use of multitasking, Architects Applicati...

Architects Applications by Making Use of Multitasking As the capability of computer hardware keeps increasing, operating systems are presented with overwhelming opportunities.

Explain the alphabet and string, Explain the Alphabet and String A fini...

Explain the Alphabet and String A finite set of symbols is known as alphabet. An alphabet is frequently denoted by sigma, yet can be given any name. B = {0, 1} says B is an

Explain process scheduling in multiprogramming, Normal 0 false ...

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

What is the purpose of the virtual memory in windows xp, Question: a) T...

Question: a) The following refers to optimization under Windows XP: i) Give five steps which could undertake to enhance overall system performance in a default Windows XP in

Difference among pre-emptive and non pre-emptive scheduling, Q. Define the ...

Q. Define the difference among pre-emptive and non pre-emptive scheduling. Answer: Pre-emptive scheduling permits a process to be interrupted in the midst of its execution ta

Why page sizes always powers of 2, Q. Why page sizes always powers of 2? ...

Q. Why page sizes always powers of 2? Answer: Recall that paging is executed by breaking up an address into a page and offset number. It is most competent to break the address

Describe services of operating systems, (a) Describe services of operating ...

(a) Describe services of operating systems. (b) Differentiate among the short term, medium term and long term scheduling that are given by multi-tasking operating systems.

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