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 demand paging, What is Demand paging? Virtual memory is commonl...

What is Demand paging? Virtual memory is commonly executed by demand paging. In demand paging, the pager brings only those essential pages into memory instead of swapping in a

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

What are batch systems, What are batch systems? Batch systems are quite...

What are batch systems? Batch systems are quite appropriate for implementing large jobs that need little interaction. The user can submit jobs and return later for the results.

Timers could be utilized to compute the current time, Q. Timers could be ut...

Q. Timers could be utilized to compute the current time. Provide a little description of how this could be accomplished. Answer: A program could utilize the following ap

Explain load balancing client server components, Explain Load Balancing Cli...

Explain Load Balancing Client Server Components When migration functionality from the client - only model to the client - server model, care must be taken not over-or underutil

Explain long term scheduling, Long term scheduling Scheduling explicitl...

Long term scheduling Scheduling explicitly performed when a new process is created and it determines which programs are admitted to the system for processing. Therefore it cont

Illustrate the handshaking protocol, Q. The instance of handshaking used 2...

Q. The instance of handshaking used 2 bits: a busy bit as well as a command-ready bit. Is it probable to implement this handshaking with only 1 bit? If it is illustrate the protoc

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

Unix, what is difference between file descriptor and file pointer?

what is difference between file descriptor and file pointer?

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