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 a file path name, What is a file path name? A list of the subdi...

What is a file path name? A list of the subdirectories, directories, and files we must traverse to reach a file from the root directory.

What is a file, What is a file? A file is a named collection of related...

What is a file? A file is a named collection of related information that is recorded on secondary storage. A file having either programs or data. A file has particular "structu

Paging, Paging full question

Paging full question

What is an i/o subsystem?, What is an I/O subsystem? The control of dev...

What is an I/O subsystem? The control of devices connected to the computer is a main issue while designing operating systems. Since I/O devices differ widely in their function

Determine the requiring variables on the scope of a thread, Determine the R...

Determine the Requiring Variables on the Scope of a Thread It is very common in server application programs to require variables on the scope of a thread. To provide such a sco

What advantages are there to this two-level directory, What advantages are ...

What advantages are there to this two-level directory? Users are isolated from each other. Users have more freedom in choosing file names.

Difference between threads and processes, Difference between threads and pr...

Difference between threads and processes 1. Thread is flow of implementation. Process is group of instruction which is alike to that of a program except which may be stopped an

Management Information Systems, Select any business process within this fir...

Select any business process within this firm, describe it as a set of steps then fill the following table (flow, information, sender and receivern #Minimum 100 words accepted#

What is a client server system, What is a client server system? Central...

What is a client server system? Centralized systems proceed as server systems to satisfy request generated by client systems Server system is able to be broadly div

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