optimal page replacement algorithm in java

Page Replacement technique uses the following approach. Page Fault – It is basically a memory error, and it occurs when the current programs attempt to access the memory page for mapping into virtual address space, but it is unable to load into the physical memory then this is referred to as Page fault. The main objective of all the Page replacement policies is to decrease the maximum number of page faults. In Virtual Memory Management, Page Replacement Algorithms play an important role. This technique provides complete separation between logical memory and physical memory. To reduce the overhead of page replacement a modify bit (dirty bit) is used in order to indicate whether each page is modified. Page replacement prevents the over-allocation of the memory by modifying the page-fault service routine. And all these require double the disk access time. The Operating system must then write the victim frame to the disk then read the desired page into the frame and then update the page tables. The operating system must use any page replacement algorithm in order to select the victim frame. In this case, if a process requests a new page and supposes there are no free frames, then the Operating system needs to decide which page to replace. This technique is called Page replacement and is most commonly used. Or, find some pages that are not being used right now, move them to the disk to get free frames. Or, remove some other process completely from the memory to free frames. Put the process in the wait queue, until any other process finishes its execution thereby freeing frames. Following steps can be taken to deal with this problem : but what happens when a process requests for more pages and no free memory is available to bring them in. This allows us to get more processes into memory at the same time. In this tutorial, we will be covering the concept of Page replacement and its algorithms in the Operating system.Īs studied in Demand Paging, only certain pages of a process are loaded initially into the memory. Longest Remaining Time First Scheduling.('ENTER NUMBER OF REFERENCES') įloat hr=(float)hit/((float)hit+(float)miss) In Least Recently Used (LRU) page replacement algorithm is associated with the each page the time of that page's last use.When a page must be replaced,In Least Recently Used (LRU) page replacement algorithm chooses that page has not been used for longest period of time.The In Least Recently Used (LRU) page replacement algorithm Policy is often used as page replacement algorithm and is consider to be good.The major problem is how to implement In Least Recently Used (LRU) page replacement algorithm.An In Least Recently Used (LRU) page replacement algorithm may require substantial hardware assistance. In Least Recently Used (LRU) page replacement algorithm we use the recent past as an approximation of the near future,then we will replace the pagethat has not been used for the longest period of time.

Optimal page replacement algorithm in java