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

Ubuntu shell script - linux, Task 1 description: Design and implement the ...

Task 1 description: Design and implement the disableuser.sh script. Required script functionality: disableuser.sh -v : prints the script version number and exits dis

GIS, 1. The City of Boston needs to be about 2 acres of green space per 1,0...

1. The City of Boston needs to be about 2 acres of green space per 1,000 persons. You have been hired as the GIS expert by an independent consulting company to determine where the

Explain how protection is provided for the hardware resource, Explain how p...

Explain how protection is provided for the hardware resources by the operating system. Dual mode operation Sharing system resources needs operating system to make sure

Blocking locks, We have talked about blocking locks, which voluntarily yiel...

We have talked about blocking locks, which voluntarily yield, and spinlocks, which just spin until they acquire the lock. At ?rst, it seems like spinlocks are verywasteful, and tha

Unix, UNIX Shell and History feature. 1.Creating a child process. 2.Creatin...

UNIX Shell and History feature. 1.Creating a child process. 2.Creating a history feature. Its exactly "programming project 1 - Unix Shell and History Feature (p.157-159)" in the Si

Find the optimal solution and optimal value, Find the optimal solution and ...

Find the optimal solution and optimal value of the following linear program. Use both (a) the enumerating the corner points method and (b) the iso-profit line method. Also identify

What is co-operative process, What is co-operative process? A process i...

What is co-operative process? A process is co-operating if it can influence or be affected by the other processes implementing in the system. Any process that share data with o

Determine what a locality of reference entails, Locality of reference entai...

Locality of reference entails that the page reference being made by a process  Locality of reference entails that the page reference being made by a process is similarly to be

Briefly describe the producer-consumer problem, Question: a) Each proc...

Question: a) Each process is represented in the operating system by a process control block (PCB). The PCB contains many pieces of information associated with a specific proce

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