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    SubjectRe: fadvise syscall?
    At 18:35 17/03/02, Ken Hirsch wrote:
    >Anton Altaparmakov writes
    > > Posix or not I still don't see why one would want that. You know what you
    > > are going to be using a file for at open time and you are not going to be
    > > changing your mind later. If you can show me a single _real_world_ example
    > > where one would genuinely want to change from one access pattern to
    >another
    > > without closing/reopening a particular file I would agree that fadvise is
    >a
    > > good idea but otherwise I think open(2) is the superior approach.
    > >
    >
    >Sure, a database manager can change the access pattern on every query. If
    >there's an index and not too many records are expected to match, it will use
    >a random pattern, otherwise it will use sequential access.

    Last time I heard serious databases use their own memmory
    management/caching in combination with O_DIRECT, i.e. they bypass the
    kernel's buffering system completely. Hence I would deem them irrelevant to
    the problem at hand...

    If a database were not to use O_DIRECT I would think it would be using mmap
    so it would have madvise already... but I am not a database expert so take
    this with a pinch of salt...

    Best regards,

    Anton


    --
    "I've not lost my mind. It's backed up on tape somewhere." - Unknown
    --
    Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
    Linux NTFS Maintainer / WWW: http://linux-ntfs.sf.net/
    ICQ: 8561279 / WWW: http://www-stu.christs.cam.ac.uk/~aia21/

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