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

What is real time system, What is real time system? A real time system ...

What is real time system? A real time system has well explained, fixed time constraints. Processing must be done within the explained constraints, or the system will fail. It i

Direct communicatio., Consider a scenario of post mailbox, there are two pr...

Consider a scenario of post mailbox, there are two processes named sender S and receiver R. Both processes can communicate with each other by name along with message. You need to I

GIS, 1. The City of Boston needs to be about 2 acres of green space per 1,0...

1. The City of Boston needs to be about 2 acres of green space per 1,000 persons. You have been hired as the GIS expert by an independent consulting company to determine where the

Explain about deadlock prevention, Explain about deadlock prevention? I...

Explain about deadlock prevention? In order for the occurrence of deadlock, the four conditions like mutual exclusion, hold and wait, no pre-emption and  circular wait must hap

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

Explain process states in the unix system, Process States A total of n...

Process States A total of nine states are acknowledged by the UNIX system. They are like as follow: User running                                                   Executing

Define a program that is in execution is known as, Define a program in exec...

Define a program in execution is known as A program in execution is known as a process

Explain about paging, Explain about paging? Answer: Paging is a memory-...

Explain about paging? Answer: Paging is a memory-management scheme that permits the physical-address space of process to be noncontiguous. Paging avoids the considerable proble

What are turnaround time and response time, What are turnaround time and re...

What are turnaround time and response time? Turnaround time is the interval among the submission of a job and its completion. Response time is the interval among submission

Discuss various services provided by the operating system, List and discuss...

List and discuss the various services provided by the operating system. Program execution - system capability to load a program into memory and to run it. I/O operatio

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