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

Data transfer between two processes, Q. Data transfer between two processes...

Q. Data transfer between two processes? Communication: Data transfer between two processes is essential for some time. Both processes are on the one computer or on different

Explain load balancing client server components, Explain Load Balancing Cli...

Explain Load Balancing Client Server Components When migration functionality from the client - only model to the client - server model, care must be taken not over-or underutil

How is a process chosen for being swapped either in or out?, How is a proce...

How is a process chosen for being swapped either in or out? Swap out: a.         If the process is idle. b.         If process has been in main memory for a long time.

Operating system, What criteria are important in choosing a file organisati...

What criteria are important in choosing a file organisation?

Changing the runlevel of system from 5 to 3 on startup, Front page We n...

Front page We need to continue or customization and documentation of our system. Currently our system boots into runlevel 5 and we need it to boot into runlevel 3. For future r

Beladys anomaly algorithm, Q.  You have devised a fresh page-replacement a...

Q.  You have devised a fresh page-replacement algorithm that you think may be optimal. In a few contorted test cases Belady's anomaly occurs. Is the fresh algorithm optimal? Descr

Major advantage of the layered approach to system design, Q. What is the ma...

Q. What is the major advantage of the layered approach to system design? What are the de-merits of using the layered approach? Answer: As in all cases of modular design as well

Program that will input an interger target value, When you turn in an assig...

When you turn in an assignment to be graded in this class, you are making the claim that you neither gave nor received assistance on the work you turned in (except, of course, assi

Explain the worker model, Explain the Worker Model The Worker Model of ...

Explain the Worker Model The Worker Model of client-server application architecture provides a very good understanding of threads and their power to the developer. This exercis

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