The basic assumptions behind LRU have been invalidated by streaming media, garbage collection and other things possible in large address spaces, but until 2002 there weren't many replacements available that are suitable to be implemented in a general purpose OS. However, with the advent of LIRS, ARC, Clock-pro and CAR/CART algorithms, it looks like there could be a benefit to Linux in implementing something better than LRU or the unbalanced use-once that is in use currently.

The only problem is, the advanced page replacement algorithms need to keep a history of recently evicted pages, and we don't want to spend too much memory or cpu on that. This page is a template for brainstorming on how we can implement such a framework, and on which of the advanced page replacement algorithms we should experiment with.

Please feel free to edit this page.


The replacement algorithms

Linux implementations


NetBSD folks are also discussing better page replacement policies.

Advanced Replacement in other systems

Operating systems are not the only place where advanced cache replacement algorithms have been studied and implemented. Databases and web proxies also tend to have fancy replacement algorithms.

Recently ARC was implemented in the postgresql DB. However, after it was discovered that ARC is patented (by IBM) it was removed again. You can see a patch that was sent to the pgsql-patches mail-list proposing that ARC be reverted back to LRU here.

More details about ARC removal from PostgreSQL.

It looks like ARC has finally been replaced by the 2Q algorithm, which is a cache replacement algorithm designed for databases.


Testing is an essential part of implementing one of the above page replacement algorithms on Linux.

The PageReplacementTesting page points out problems with LRU worst cases and is used to collect benchmarks to demonstrate LRU deficiencies.

For other pages in this category, see CategoryAdvancedPageReplacement

LinuxMM: AdvancedPageReplacement (last edited 2017-12-30 01:05:10 by localhost)