Page Faults in LFU

The Least Frequently Use aka LFU is a concept of page memory management, can also be used as a replacement algorithm. This process take a lead we the particular page needs a replacement when a new page is on the way by the process. LFU is one of the page replacement policy where an user can replace the least frequency of a particular operation page. If the page frequency is same in a process, then it will come first on the replacement list.

Here we will take a page sequence of an array of pages denoted as pages[], whose length is N with a memory capacity of C. We need to evaluate the number of occurrence as page faults by imposing the algorithm mentioned below.

Input for the LFU algorithm −

The pages taken for the process = { 1, 2, 3, 4, 2, 1, 5 }

Output For The Process Is −

Faults Occurrence In This Process = 6

Hits Needed For This Process = 1

Here the total capability of this particular process is here 3, which can save the max to max 3 pages in that allotted time in a memory location.

Page 1 - It is required to run the process.

As page 1 is not exist in the list,

So, we can consider it as a page fault occurence: The value of page fault is = 1

Page 2 - It is needed for to run the process.

Since page 2 is not exist in the list,

So, we can consider it as a page fault occurence: The value of page fault is = 1 + 1 = 2

Page 3 - It is required to run the process.

Since page 3 is not exist in the list,

So, we can consider it as a page fault occurence: The value of page fault is =2 + 1 = 3

Page 4 - It is required to run the process.

Since page 4 is not exist in the list,

it replaces LFU page 1 : page fault = 3 + 1 = 4

Page 2 - It is required to run the process.

Since page 2 is not exist in the list,

So, we can not consider it as a page fault occurence: The value of page fault is = = 4 + 0 = 4

Continue the process....

The LFU algorithm is a replacement process mentioned here in the field of operating system. This process always least frequently used pages present in the process.

Step 1 − Initialize the process of LFU operation.

Step 2 − Declare and mention the total count as 0.

Step 3 − Create a vector class.

Step 4 − Construct and declare an array with the desired array size.

Step 5 − Start the process with the size of memory capacity.

Step 6 − Create a map.

Step 7 − Store the frequency value to the map of the pages.

Step 8 − Traverse page elements.

Step 9 − If; the desired element is available in that particular location in the memory, then erase and push it for next level.

Step 10 − Step 9 increase the process frequency.

Step 11 − Else; the main memory totally occupied; remove the initial element and decrease the possible frequency of the data.

Step 12 − Count increase.

Step 13 − Compare the frequency result.

Step 14 − Sort the pages as per their frequency and time based result.

Step 15 − If we get the same frequency, then the page will arrive at first.

Step 16 − Repeat the process.

Step 17 − Return the result.

Step 18 − Terminate the process