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KernelTrap: Page Replacement Design

Jan 25, 2007, 07:00 (0 Talkback[s])

"A university student studying operating systems asked about why the Linux kernel uses two chained lists in its LRU (least recently used) page replacement algorithm. Andrea Arcangeli, whose virtual memory subsystem was merged into the 2.4.10 kernel, explained, 'back then I designed it with two lru lists because by splitting the active from the inactive cache allows to detect the cache pollution before it starts discarding the working set.' He went on to add, 'a page in the inactive list will be collected much more quickly than a page in the active list, so the pollution will be collected more quickly than the working set. Then the VM while freeing cache tries to keep a balance between the size of the two lists to avoid being too unfair, obviously at some point the active list have to be de-activated too...'"

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