Components of LRU queue

Each LRU queue is composed of a pair of linked lists.

The linked list pairs are as follows:
  • FLRU (free least-recently used) list, which tracks free or unmodified pages in the queue
  • MLRU (modified least-recently used) list, which tracks modified pages in the queue
The free or unmodified page list is called the FLRU queue of the queue pair, and the modified page list is called the MLRU queue. The two separate lists eliminate the task of searching a queue for a free or unmodified page. The following figure illustrates the structure of the LRU queues.
Figure 1. LRU queue
This figure shows an LRU queue that is composed of two queues, FLRU 1 and MLRU 1. FLRU 1 contains a pointer to an unmodified page and a pointer to an empty page. MLRU 1 contains a pointer to a modified page.

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