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

BC0056, Write a C program that illustrates the creation of child process us...

Write a C program that illustrates the creation of child process using fork system call. One process finds sum of even series and other process finds sum of odd series.

What is starvation?, What is starvation? A main problem related to dead...

What is starvation? A main problem related to deadlock is starvation. Starvation is the circumstances where process waits indefinitely within the semaphore. Indefinite blocking

Interpreters, Use and overview? Pure and impure interpreter?

Use and overview? Pure and impure interpreter?

What is sector sparing, What is sector sparing? Low-level formatting al...

What is sector sparing? Low-level formatting also sets aside extra sectors not visible to the operating system. The controller can be told to change each bad sector logically w

Give an overview of unix based file systems, Give an overview of UNIX based...

Give an overview of UNIX based file systems. UNIX and UNIX-like operating systems allocate a device name to each device, other than this isn't how the files on that device are

Virtual memory and paging, A- Consider a computer system that provides a vi...

A- Consider a computer system that provides a virtual memory space that consists of 8  pages. The physical memory contains 4 pages where the page size is 4Kbytes. Assume that at sp

Independent process, what is independent process? distinguished between ind...

what is independent process? distinguished between independent process and co-operating process

Gang scheduling , Gang Scheduling : A set of related process is scheduled ...

Gang Scheduling : A set of related process is scheduled to execute on a set of processors at the similar time, on a 1-to-1 basis. Closely related processes or threads may be sched

What is real time system, What is real time system? A real time system ...

What is real time system? A real time system has well explained, fixed time constraints. Processing must be done within the explained constraints, or the system will fail. It i

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