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
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.
Which replacement algorithm is the most efficient?
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.
Why is LRU not used?
LRU algorithm cannot be directly implemented in the critical path of computer systems, such as operating systems, due to its high overhead. An approximation of LRU, called CLOCK is commonly used for the implementation. Similarly, CLOCK-Pro is an approximation of LIRS for an low cost implementation in systems.
Does random replacement works better than FIFO replacement strategy?
Random replacement policy randomly replaces the page in memory when it needed. This eliminates the overhead cost to tracking the page references. Usually it is better than FIFO policy and for looking memory reference it is better than LRU but generally LRU perform better result in practice.
Can LRU be worse than FIFO?
LRU keeps the things that were most recently used in memory. FIFO keeps the things that were most recently added. 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.
What is the difference between FIFO and LRU page replacement algorithms?
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).
What is least frequently used algorithm in OS?
Least Frequently Used (LFU) is a type of cache algorithm used to manage memory within a computer. The standard characteristics of this method involve the system keeping track of the number of times a block is referenced in memory.
What is least recently used in OS?
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 the reason that least recently used LRU usually not used as a page replacement algorithm?
LRU is too inefficient to implement in practice.
Why is LRU better than FIFO random?
First, it's a good approximation to optimal scheduling when locality is assumed (this turns out to be a good assumption). Random scheduling cannot benefit from locality. Second, it doesn't suffer from Belady's anomaly (like FIFO); that is, bigger caches mean better performance, which isn't necessarily true with FIFO.
Why is LRU better than random?
If you have a tight loop, LRU is going to be perfect as long as the loop fits in cache, but it's going to cause a miss every time if the loop doesn't fit. A random eviction policy degrades gracefully as the loop gets too big. In practice, on real workloads, random tends to do worse than other algorithms.
What are advantages of first in first out FIFO last recently used LRU optimal?
Page Scheduling, involves many different algorithms which have their Advantages and Disadvantages.First In First Out (FIFO): Advantages – It is simple and easy to understand & implement. ... Least Recently Used (LRU): Advantages – It is open for full analysis. ... Optimal Page Replacement (OPR):
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
Abstract
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Footnotes
Research carried out while the author was visiting Cornell University, Ithaca, NY, and partly supported by the US Army Research Office.
