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    SubjectRe: [PATCH -mm] vmscan: protect a fraction of file backed mapped pages from reclaim
    Christoph Lameter wrote:
    > On Tue, 12 May 2009, Rik van Riel wrote:
    >
    >> The patch that only allows active file pages to be deactivated
    >> if the active file LRU is larger than the inactive file LRU should
    >> protect the working set from being evicted due to streaming IO.
    >
    > Streaming I/O means access once?

    Yeah, "used-once pages" would be a better criteria, since
    you could go through a gigantic set of used-once pages without
    doing linear IO.

    I expect that some databases might do that.

    > What exactly are the criteria for a page
    > to be part of streaming I/O? AFAICT the definition is more dependent on
    > the software running than on a certain usage pattern discernible to the
    > VM. Software may after all perform multiple scans over a stream of data or
    > go back to prior locations in the file.


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