Paging

Keywords and Synonyms

Caching      

Problem Definition

Computers generally have a small amount of fast memory to keep important data readily available. This is known as the cache. The question which is considered in this chapter is which pages should be kept in the cache when a new page is requested.

Formally, a two-level store of memory is considered. The cache can contain k pages, and the slow memory can contain n pages, where typically n is much larger than k. The input is a sequence of requests to pages. Whenever a requested page is not in the cache, the algorithm incurs a fault. The goal is to minimize the total number of page faults.

It is easy to give an optimal algorithm if the whole request sequence is known: on each fault, evict that page from the cache which is next requested the furthest in the future [2]. However, in practice, paging decisions need to be made without knowledge of the future. Thus an onlinealgorithm is needed, which makes its decisions for each request based...