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

Determine the syntax of the assembler directive equ, Determine the syntax o...

Determine the syntax of the assembler directive EQU The following is syntax of the assembler directive EQU: EQU

Typical virtual memory layout, Using pages makes it easier to manage the wh...

Using pages makes it easier to manage the whole memory, avoiding excessive fragmentation and waste. As an analogy, think of Tetris, but with only square blocks: it is relatively ea

Unix operating system, A working Ubuntu Linux operating system.  You can us...

A working Ubuntu Linux operating system.  You can use a Live-CD to complete this assignment. Create an empty text file named assignment6.txt in your home directory. Edit this

Explain the purpose of command-line application, Question: a) The follo...

Question: a) The following questions refers to Windows XP networking: i) Briefly, explain how a host joins a network using DHCP? ii) Which IP address could be assigned to a

How file record length should be chosen, How File record length should be c...

How File record length should be chosen File record length should be selected to match the data characteristics

How is memory management done using bit maps?, How is memory management don...

How is memory management done using bit maps? A bit map is here in this we signify the bit value as 0 or 1. 1-hole 0-process In this we are able to represent the proce

What is paging? , What is paging? Paging is a memory management schem...

What is paging? Paging is a memory management scheme that authorizes the physical-address space of a process to be noncontiguous. Paging evades the considerable problem of fi

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