What is page fault explain different page replacement algorithm?
Table of Contents
What is page fault explain different page replacement algorithm?
A page fault occurs when a page referenced by the CPU is not found in the main memory. The required page has to be brought from the secondary memory into the main memory. A page has to be replaced if all the frames of main memory are already occupied.
What is the page fault and page hit?
The page fault is also called page miss. For example, in the diagram page fault is on 2nd, 3rd, 4th and 6th columns. What is Page Hit? When we want to load the page on the memory, and the page is already available on memory, then it is called page hit.
What is the difference between LRU and NRU page replacement algorithms?
The least recently used (LRU) page replacement algorithm, though similar in name to NRU, differs in the fact that LRU keeps track of page usage over a short period of time, while NRU just looks at the usage in the last clock interval.
What is meant by page hit?
A page-hit access is defined as any read or write operation to an open page. That is, the bank containing the open page is already active and is immediately ready to service requests.
Which is the best page replacement algorithm and explain?
Optimal Page Replacement algorithm is the best page replacement algorithm as it gives the least number of page faults. It is also known as OPT, clairvoyant replacement algorithm, or Belady’s optimal page replacement policy.
What is a page fault and thrashing?
In computer science, thrashing occurs when a computer’s virtual memory resources are overused, leading to a constant state of paging and page faults, inhibiting most application-level processing. This causes the performance of the computer to degrade or collapse. This condition is referred to as thrashing.
Why is page replacement needed?
Whenever a process refers to a page that is not present in memory, a page fault occurs. Page replacement algorithms are an important part of virtual memory management and it helps the OS to decide which memory page can be moved out, making space for the currently needed page.
How do you fix a page fault?
5.4. 3. Page Faults
- Check the location of the referenced page in the PMT.
- If a page fault occured, call on the operating system to fix it.
- Using the frame replacement algorithm, find the frame location.
- Read the data from disk to memory.
- Update the page map table for the process.
Which page will NRU replace?
Out of above 4 categories, NRU will replace a Not Referenced, Not Modified page, if such page exists. Note that this algorithm implies that a Modified but Not Referenced is less important than a Not Modified and Referenced.
What is page fault Why does it happen explain?
A page fault occurs when a program attempts to access a block of memory that is not stored in the physical memory, or RAM. The fault notifies the operating system that it must locate the data in virtual memory, then transfer it from the storage device, such as an HDD or SSD, to the system RAM.