![]() Number of heavily used Web pages in its memory cache. That cache block misses are satisfied from main memory, which has no seek timeĪ second example is in a Web server. ![]() This problem is precisely the same as page replacementĮxcept on a shorter time scale (it has to be done in a few nanoseconds, not When the cache is full, some block has toīe chosen for removal. ForĮxample, most computers have one or more memory caches consisting of recently Replacement" occurs in other areas of computer design as well. It is worth noting that the problem of "page The subject of page replacement algorithms, both theoretical and experimental.īelow we will describe some of the most important algorithms. If a heavily used page is removed, it will probably have to beīrought back in quickly, resulting in extra overhead. Page fault, system performance is much better if a page that is not heavily used While it would be possible to pick a random page to evict at each The page to be read in just overwrites the page If, however, the page has notīeen changed (e.g., it contains program text), the disk copy is already up toĭate, so no rewrite is needed. To the disk to bring the disk copy up to date. The page to be removed has been modified while in memory, it must be rewritten ![]() To remove from memory to make room for the page that has to be brought in. When a page fault occurs, the operating system has to choose a page
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