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 internal fragmentation, Explain internal fragmentation The Inter...

Explain internal fragmentation The Internal fragmentation signifies to the result of reserving a piece of space without ever intending to use it. This space is wasted that this

What are the major differences between operating systems, Q. What are the m...

Q. What are the major differences between operating systems for mainframe computers and personal computers? Answer: In general operating systems for batch systems have simpler

What are a safe state and an unsafe state, What are a safe state and an uns...

What are a safe state and an unsafe state? Answer:  A state is safe if the system can allocate resources to every process in some order and still avoid a deadlock. A system is

What is super block, What is super block A partition control block have...

What is super block A partition control block have partitions details, such as the number of blocks in the partition, size of the blocks, free-blocks and free-block pointers an

Essential properties of operating system, Essential Properties of Operating...

Essential Properties of Operating System 1. Batch: Jobs with similar needs are batched together and run through the computer as a group by an operator or automatic job sequen

necessary conditions for a deadlock , Q) a. Given that the first three nec...

Q) a. Given that the first three necessary conditions for a deadlock are in place, comment on the feasibility of the following strategy. All processes are given  unique priorities.

Create a gantt chart for scheduling algorithms, Question: (a) The follo...

Question: (a) The following table (table 1.0) gives the length of the CPU burst time in milliseconds of processes P 1 to P 4 . Assume the processes arrived in the order P 1 ,

Vehicle tasks using semaphores, Gopher Gallery consists of a shopping mall ...

Gopher Gallery consists of a shopping mall and a cart ride that covers  the 150 acre habitat. There are m visitors and n single-person vehicles. Visitors  stroll around the mall at

MICROKERNEL, ADVANTAGES OF MICROFERNEL IN YSTEM DESIGN?

ADVANTAGES OF MICROFERNEL IN YSTEM DESIGN?

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