Yes, it's possible for FIFO to beat LRU. The smallest example I can think of, Cache size: 2 pages. Access pattern: A, B, A, C After that, the LRU cache contains "A, C", whereas the FIFO cache contains "B, C". They have each missed 3 times so far. So if the next page access is "B", then FIFO beats LRU.
Can FIFO have less page faults than LRU?
For anyone visiting this thread in the future, FIFO can have less page faults in some scenarios. In this one ( <2, 6, 5, 7, ..., ..., ...> ), it can be completed with 2, 8, 6. The access of 2 means that the least recently used page is 6, but the first page in is still 2. The access of 8 replaces 2 in FIFO, but 6 in LRU.
Is 6 a hit with FIFO or LRU?
The access of 6, therefore, is a hit with FIFO, but a miss with LRU. Thanks for contributing an answer to Computer Science Stack Exchange! Please be sure to answer the question.
How well does LRU actually work?
Given real workloads, LRU works pretty well a very large fraction of the time. However, it isn't very hard to construct a reference string for which FIFO would have superior performance over LRU. Consider a linear sweep through a large address space much larger than the available pageable real memory.
Why is LRU so popular in VM cache design?
The dominance of LRU in VM cache design is the result of a long history of measuring system behavior. Given real workloads, LRU works pretty well a very large fraction of the time. However, it isn't very hard to construct a reference string for which FIFO would have superior performance over LRU.
Can FIFO be better than LRU?
Sleator and Tarjan proved that the competitive ratio of LRU and FIFO is k. In practice, however, LRU is known to perform much better than FIFO. It is believed that the superiority of LRU can be attributed to locality of reference exhibited in request sequences.
Can LRU have more page faults than FIFO?
Perplexingly, it appears that FIFO produced fewer page faults than LRU. Is this possible, or have I made a mistake? Of course it's possible. There's no single algorithm that's the best in page-replacement.
Which page replacement technique is best?
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 the difference between FIFO and LRU page replacement algorithms?
FIFO is First In First Out. It is little overhead as there is no need to keep line of the pages. This is not necessarily skilled as because more used pages can still be removed because that was the first in. LRU is Least Recently Used.
Is LRU and FIFO the same?
FIFO means First In, First Out, i.e., consider (in this case delete) elements strictly in arrival order. LRU is Least Recently Used, the cache element that hasn't been used the longest time is evicted (on the hunch that it won't be needed soon).
Which is most efficient page replacement algorithm?
LRU resulted to be the best algorithm for page replacement to implement, but it has some disadvantages. In the used algorithm, LRU maintains a linked list of all pages in the memory, in which, the most recently used page is placed at the front, and the least recently used page is placed at the rear.
What is FIFO page replacement?
First In First Out (FIFO) – This is the simplest page replacement algorithm. In this algorithm, the operating system keeps track of all pages in the memory in a queue, the oldest page is in the front of the queue. When a page needs to be replaced page in the front of the queue is selected for removal.
What is the relationship between FIFO and clock page replacement algorithms?
What is the relationship between FIFO and clock page replacement algorithms? The clock policy is similar to FIFO, except that in the clock policy, any frame with a use bit of 1 is passed over by the algorithm.
Which replacement algorithm is least recently used?
Least Recently Used (LRU) algorithm is a page replacement technique used for memory management. According to this method, the page which is least recently used is replaced. Therefore, in memory, any page that has been unused for a longer period of time than the others is replaced.
Which of the following is a replacement algorithm used for page replacement least recently used least recently utilized least recurrently used last recently used?
LRU: LRU stands for Least Recently Used. In this algorithm, we replacement the page frame that is not used recently in the given reference string out of those three frames that are currently in page frames.
What is most recent page replacement algorithm?
Thus, Optimal page replacement algorithm acts as Most Recently Used (MRU) page replacement algorithm.
What is the count of page faults using FIFO?
So, total number of page faults = 9. Given memory capacity (as number of pages it can hold) and a string representing pages to be referred, write a function to find number of page faults.
Why is LRU more efficient?
LRU is, in general, more efficient, because there are generally memory items that are added once and never used again, and there are items that are added and used frequently. LRU is much more likely to keep the frequently-used items in memory. Share. answered Jan 13 '10 at 16:39.
Is LRU good for real workloads?
The net of all this is that LRU is the standard answer because it's usually pretty good for real workloads on systems that aren't hideously overloaded (VM many times the real memory available), and that is supported by years of careful measurements.
Abstract
In the paging problem we have to manage a two-level memory system, in which the first level has short access time but can hold only up to k pages, while the second level is very large but slow. We use competitive analysis to study the relative performance of the two best known algorithms for paging, LRU and FIFO.
Author information
Department of Computer Science, University of California, Riverside, CA 92521, USA. [email protected]., US
What is LRU Page Replacement Algorithm?
The LRU stands for the Least Recently Used. It keeps track of page usage in the memory over a short period of time. It works on the concept that pages that have been highly used in the past are likely to be significantly used again in the future. It removes the page that has not been utilized in the memory for the longest time.
What is LFU Page Replacement Algorithm?
The LFU page replacement algorithm stands for the Least Frequently Used. In the LFU page replacement algorithm, the page with the least visits in a given period of time is removed. It replaces the least frequently used pages. If the frequency of pages remains constant, the page that comes first is replaced first.
Main Differences between the LRU and LFU Page Replacement Algorithm
Here, you will learn the main differences between the LRU and LFU Page Replacement Algorithm. Various differences between the LRU and LFU Page Replacement Algorithm are as follows:
Head-to-head Comparison between the LRU and LFU Page Replacement Algorithm
Here, you will learn the head-to-head comparison between the LRU and LFU Page Replacement Algorithm. The main differences between the LRU and LFU Page Replacement Algorithm are as follows: