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    SubjectRe: [RFC] Limit the size of the pagecache


    Rik van Riel wrote:
    > Vaidyanathan Srinivasan wrote:
    >
    >> In my opinion, once a
    >> file page is mapped by the process, then it should be treated at par
    >> with anon pages. Application programs generally do not mmap a file
    >> page if the reuse for the content is very low.
    >
    > Why not have the VM measure this, instead of making wild
    > assumptions about every possible workload out there?

    Yes, VM page aging and page replacement algorithm should decide on the
    relevance of anon or mmap page. However we may still need to limit
    total pages in memory for a given set of process.

    > There are a few databases out there that mmap the whole
    > thing. Sleepycat for one...
    >

    That is why my suggestion would be not to touch mmapped pagecache
    pages in the current pagecache limit code. The limit should concern
    only unmapped pagecache pages.

    When the application unmaps the pages, then instantly we would go over
    limit and 'now' unmapped pages can be reclaimed. This behavior has
    been verified with my fix on top of Christoph's patch.

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