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    SubjectRe: [PATCH] properly account readahead file major faults

    On Mon, Nov 21, 2005 at 12:00:38PM -0200, Marcelo Tosatti wrote:
    > Hi,
    > The fault accounting of filemap_dopage() is currently unable to account
    > for readahead pages as major faults.

    Sorry, I don't know much about the definition of major/minor page faults.
    So I googled one that explains the old behavior:

    --> Page Faults <--
    These come in two varieties. Minor and Major faults. A Major fault results
    when an application tries to access a memory page that has been swapped out to
    disk. The page must be swapped back in. A Minor fault results when an
    application tries to access a memory page that is still in memory, but the
    physical location of which is not immediately known. The address must be
    looked up.

    With the current accounting logic:
    - major faults reflect the times one has to wait for real I/O.
    - the more success read-ahead, the less major faults.
    - anyway, major+minor faults remain the same for the same benchmark.

    With your patch:
    - major faults are expected to remain the same with whatever read-ahead.
    - but what's the new meaning of minor faults?

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