Explain lru approximation page replacement, Operating System

Assignment Help:

LRU approximation page replacement

In this we are able to use the reference bit associated with the page entry to choose a page to be removed. The various algorithms used for the implementation is discussed below.

a. Second chance Algorithm

When a page is selected the reference bit is checked to see whether it has been referenced before. If that is the case afterward it is given a second chance. The page is moved as of head to tail and its reference bit is made 0. If it hasn't been referenced then it is removed.

Example Consider 1,2,3,4,3,5,6. Now 1, 2, 3 are entered in to memory and when 4 comes 1 is removed. While 5 come 2 is removed. While 6 come 4 is removed instead of 3 as 3 has been referenced in between.

b. Enhanced Second chance algorithm

In this a modify bit is as well used. Now if the ordered pair of reference and modify is

(0,0) neither recently used nor modified - the best page to replace.

(1,1) both referenced and modified- the worst to  replace

(1,0) referenced but not modified

(0,1) not recently used but modified.

This algorithm is utilized in the Macintosh virtual memory management scheme.

c. Additional Reference bits algorithm

Here we keep an 8-bit byte for every page in memory. At standard intervals the reference bit is shifted by the OS. If a shift register contains 00000000 then the page hasn't been used for the last 8 time periods. A page with a history 11000000 is more recently used than 01000000. The no of bits are able to be varied accordingly to the needs of the OS.


Related Discussions:- Explain lru approximation page replacement

Capability lists are typically kept within the address space, Q. Capabilit...

Q. Capability lists are typically kept within the address space of the user. How does the system make sure that the user cannot modify the contents of the list? Answer: An ap

Implementing group policies in a windows environment, Question: (a) As...

Question: (a) As a System administrator, elaborate on how you can manage computer accounts in Active Directory of Windows Server 2008? (b) Explain the following user p

Explain types of file allocation-contiguous allocation, Contiguous allocati...

Contiguous allocation: Every file will be allocated contiguous space in the memory. Allow the block size be 1K If a 50K files desires to be allocated space after t

What are the requirements for a swapper to work, The swapper work s on t...

The swapper work s on the biggest scheduling priority. Initially it will look for any sleeping process, if not get then it will see for the ready-to-run process for swapping. Bu

Operational management, explain the link between operations management and ...

explain the link between operations management and strategic planning of daily goods shop

Bounded and unbounded buffer, Ask question #Minimum 100 difference between ...

Ask question #Minimum 100 difference between bounded and unbounded buffer words accepted#

Explain lru page replacement in detail, LRU page replacement In least ...

LRU page replacement In least lately used page replacement algorithm we will replace that page that hasn't been used for the longest period of time. This is similar as an opti

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