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

How does an operating system make multiprogramming possible, How does an op...

How does an operating system make multiprogramming possible by using single processor?

Define thrashing, Define thrashing. Thrashing is the accident of high p...

Define thrashing. Thrashing is the accident of high page traffic and low CPU utilization. It is observed that the cause of thrashing is an under-commitment of memory to program

FUNDAMENTAL OF OS, WHAT IS OPERATING SYSTEM ?ENLIST AND EXPLAIN BASIC SERVI...

WHAT IS OPERATING SYSTEM ?ENLIST AND EXPLAIN BASIC SERVICES PROVIDE BY OS

Activities of an operating system, Q. What are the five main activities of ...

Q. What are the five main activities of an operating system in regard to process management? Answer: a. The creation as well as deletion of both user and system processes

Benefits and drawbacks of batch system, Q. Benefits and Drawbacks of Batch ...

Q. Benefits and Drawbacks of Batch System? Benefits of Batch System: Move much of the work of operator to computer. Increased performance as it was possible for j

Explain the beginthread function used in the netware, Explain the BeginThre...

Explain the BeginThread Function used in the NetWare example code BeginThread(MyThread Function, stack,size, arg) BeginThread creates a thread and places it on the NetWar

Multilevel queue scheduling algorithm suffer from starvation, 1. Suggest so...

1. Suggest some mechanism(s) to lower the dispatch latency while scheduling for a real-time system. Also, discuss any trade-off or consequent constraint associated with it, if a

What is micro-kernel?, Question 1 What is Micro-kernel? What are the benef...

Question 1 What is Micro-kernel? What are the benefits of Micro-kernel? Question 2 Explain seven state process models used for OS with necessary diagram. Differentiate betwee

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