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

Explain interrupts, Interrupts The hardware mechanism that enables a de...

Interrupts The hardware mechanism that enables a device to inform the CPU is called an interrupt. The basic interrupt mechanism works as follows. The CPU hardware has a wire kn

Memory management unit, When a program issues a memory load or store operat...

When a program issues a memory load or store operation, the virtual addresses (VAs) used in those operations have to be translated into "real" physical memory addresses (PAs). This

What is the drawbacks of contiguous allocation of disk space, What are the ...

What are the drawbacks of contiguous allocation of disk space? The disadvantages are a. Suffers from internal fragmentation b. Suffers from external fragmentation c. F

Explain deadlock prevention, Deadlock Prevention Prevention is the name...

Deadlock Prevention Prevention is the name given to method that guarantee that deadlocks can never happen for the reason that the way the system is structured. Since 4 conditio

Programable clock modes in computer systems, Ask question #Minimuexplain th...

Ask question #Minimuexplain the programable clock modes in a computer system m 100 words accepted#

Batch system, what is a batch system give me answer in simple words so that...

what is a batch system give me answer in simple words so that i can understand

Define system call, Define System Call A system call is a request that ...

Define System Call A system call is a request that is made by any program to the operating system for carrying out tasks - picked from a predefined set - which the said program

Briefly discuss on real-time scheduling, Briefly discuss on real-time sched...

Briefly discuss on real-time scheduling? It is divided into two types.  Hard real-time systems are needed to complete a critical task within a guaranteed amount of time. T

Explain how a domain user account is authenticated, Question: a) The fo...

Question: a) The following questions pertain to User and Group accounts in Windows XP: i) Give four differences between a Power User and a Guest User account. ii) Explain h

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