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 preallocation, What is preallocation? Why do it? Allocating spa...

What is preallocation? Why do it? Allocating space for a file before making the file to allow for expansion. This reserves space for a certain file so that other files can't gr

Define input - output operations, Q. Define Input - Output operations? ...

Q. Define Input - Output operations? Serial lines, Disks, tapes and other devices should be communicated with at a very low level. The user require only specify the device and

Interpreters, Use and overview? Pure and impure interpreter?

Use and overview? Pure and impure interpreter?

Define seek time and latency time, Define seek time and latency time. T...

Define seek time and latency time. The time taken by the head to move to the appropriate cylinder or track is known as seek time. Once the head is at right track, it must wait

How virtual memory is implemented, How Virtual memory is implemented Vi...

How Virtual memory is implemented Virtual memory can be implemented along with Segmentation and Paging

Explain logical file system architecture, Logical File System Responsi...

Logical File System Responsible for providing the before discussed interface to the user including: File access. Directory operations. Security and protection.

How file record length should be chosen, How File record length should be c...

How File record length should be chosen File record length should be selected to match the data characteristics

Explain the benefits of thread over process?, BENEFITS OF THREADS OVER PROC...

BENEFITS OF THREADS OVER PROCESS If implemented correctly after those threads have some advantages of (multi) processes, they take: 1. Less time to create a new thread tha

Fork system call in unix, Forking is an important phase of Unix, critical t...

Forking is an important phase of Unix, critical to the support of its design strategies, which encourages the implementation of filters. In Unix, a filter is a process that reads i

Explain relative file organization, Relative file organization A rela...

Relative file organization A relative file is an array of fixed-length slots and the records can be inserted in the first free slot found from the beginning of the file and

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