Summary

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We have seen the introduction of a number of page-replacement (and other) policies, which are part of the VM subsystem of all modern operating systems. Modern systems add some tweaks to straightforward LRU approximations like clock; for example, scan resistance is an important part of many modern algorithms, such as ARCARC: A Self-Tuning, Low Overhead Replacement Cache” by Nimrod Megiddo and Dharmendra S. Modha. FAST 2003, February 2003, San Jose, California. An excellent modern paper about replacement algorithms, which includes a new policy, ARC, that is now used in some systems. Recognized in 2014 as a “Test of Time” award winner by the storage systems community at the FAST ’14 conference.. Scan-resistant algorithms are usually LRU-like but also try to avoid the worst-case behavior of LRU, which we saw with the looping-sequential workload. Thus, the evolution of page-replacement algorithms continues.

However, in many cases, the importance of said algorithms has decreased, as the discrepancy between memory-access and disk-access times has increased. Because paging to disk is so expensive, the cost of frequent paging is prohibitive. Thus, the best solution to excessive paging is often a simple (if intellectually unsatisfying) one: buy more memory.

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