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

NETWORK OPERATING SYSTEM, explain about design issues of network operating ...

explain about design issues of network operating system

Search and print between two words/patterns, what if we need the portion fr...

what if we need the portion from a text based on some keyword. For eg. My file is like below, ------------------------------------------------ Order=[ 1 2 3 4 5 Order=[ 6 7 8 9

Explain memory management using bit maps, MEMORY MANAGEMENT USING BIT MAPS ...

MEMORY MANAGEMENT USING BIT MAPS   In this memory is separated into different allocation units each of some particular size(a few bites).consider every space of size 4k. A

How can the deadlock be prevented-bankers algorithm, How can the deadlock b...

How can the deadlock be prevented Bankers algorithm : The Resource allocation graph algorithm isn't applicable to a resource allocation system with multiple instances of every

We can view an operating system as a resource allocator, We can view an ope...

We can view an operating system as a resource allocator. Explain. We can outlook an operating system as a resource allocator. A computer system has Many resources (software and

Explain structure, Explain Structure The Grammar for programming langua...

Explain Structure The Grammar for programming language is a formal description of Structure

What is critical section problem, What is critical section problem? Con...

What is critical section problem? Consider a system consists of 'n' processes. Every process has segment of code called a critical section, in which the process might be changi

Garbage collection, The dynamic memory allocator is a layer between the app...

The dynamic memory allocator is a layer between the application and the OS, managing heap objects. When a program requests memory from the allocator (via malloc(), for instance), t

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