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

Describe the three levels of data abstraction, There are three kinds of D...

There are three kinds of Data Abstraction: Physical level: The minimum level of abstraction defines how data are saved. Logical level: The next bigger level of a

What is a pure demand paging, What is a pure demand paging? When starti...

What is a pure demand paging? When starting implementation of a process with no pages in memory, the operating system sets the instruction pointer to the first instruction of t

What is busy waiting, What is busy waiting? The repeated implementation...

What is busy waiting? The repeated implementation of a loop of code while waiting for an event to happen is known as busy-waiting. The CPU is not engaged in any actual producti

What is single-level directory, What is Single-level Directory All file...

What is Single-level Directory All files are constrained in the similar directory, which is simple to support and understood. One limitation is when the number of files enhance

Split the hexadecimal format, The following is a dump of a TCP header in h...

The following is a dump of a TCP header in hexadecimal format: 00CD0018 00000EF1 00000D5D 502200D1 01BF0010 We need to first split the above hex as such 00 CD 00 18 00 00

Basic synchronization, (Add synchronization to your solutions to HW 3 to el...

(Add synchronization to your solutions to HW 3 to eliminate all of the race conditions.  You should not remove any of the sleep() commands that you used to produce the race conditi

Mark-sweep, The objects that a program can access directly are those object...

The objects that a program can access directly are those objects which are referenced by local vari-ables on the processor stack, or by any global/static variables that refer to ob

Hashed page table, Hashed page tables A common approach for handling ad...

Hashed page tables A common approach for handling address spaces larger than 32 bits is to use a hashed page table. Every entry in the hash table having a linked list of elemen

Explain busy waiting semaphores, Explain Busy Waiting Semaphores Weak, ...

Explain Busy Waiting Semaphores Weak, Busy-wait Semaphores a) The simplest way to implement semaphores. b) Useful while critical sections last for a short time, or we com

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