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 concept of synchronization, Synchronization In communication am...

Synchronization In communication among processes messages passed may be blocking or nonblocking - also called as synchronous and asynchronous. Blocking send : The sending pr

Assignment, Ask question #Minimum 100 words accDefine Hashing System. Descr...

Ask question #Minimum 100 words accDefine Hashing System. Describe the Hashed page table with example and mapping figure.

What is the use of fork and exec system calls, What is the use of fork and ...

What is the use of fork and exec system calls? Fork is a system call by which a latest process is created. Exec is also a system call, which is used after a fork by one of the

What is time-stamping, time-stamping It is a method proposed by Lampor...

time-stamping It is a method proposed by Lamport, used to sequencing events in a distributed machine without the use of clocks. This process is intended to order events consis

Rule a magnetic hard disk, Q. If magnetic hard disks eventually have the s...

Q. If magnetic hard disks eventually have the same cost per gigabyte as do tapes will tapes turn into obsolete or will they still be needed? Describe your answer. Answer: Tap

Packets and time division multiplexing (tdm), Broken data into small packet...

Broken data into small packets allow time division multiplexing. In TDM every packet leaves the sender and is switched on the shared interaction channel through a multiplexer. At t

Determine what the blocking factor of a file is, Determine what the “blocki...

Determine what the “blocking factor” of a file is Blocking factor is the number of logical records in one physical record

Is anti virus a system utility, Problem: a) Explain physically what occ...

Problem: a) Explain physically what occurs when a disk is fragmented. What is the purpose of "defragmenting" a disk? b) What is the idea behind backing up data on a secondar

Action taken by the operating system when a page fault occur, Q. Under what...

Q. Under what conditions do page faults occur? Explain the actions taken by the operating system when a page fault occurs. Answer: A page fault take places when an access to

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