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    SubjectRe: DVD blockdevice buffers
    On Fri, May 18 2001, Eduard Hasenleithner wrote:
    > I have a problem with the buffering mechanism of my blockdevice,
    > namely a ide_scsi DVD-ROM drive. After inserting a DVD and reading
    > data linearly from the DVD, an excessive amount of buffer memory gets
    > allocated.
    >
    > This can easily be reproduced with
    > cat /dev/sr0 > /dev/null
    >
    > Remember, nearly the same task is carried out when playing a DVD.
    >
    > As a result the system performance goes down. I'm still able to use
    > my applications, but es every single piece of unused memory is swapped
    > out, and swapping in costs a certain amount of time.

    That's why streaming media applications like a dvd player should use raw
    I/O -- to bypass system cache. See /dev/raw*

    --
    Jens Axboe

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