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    SubjectRe: fadvise syscall?
    At 19:20 17/03/02, Joel Becker wrote:
    >On Sun, Mar 17, 2002 at 01:41:37PM +0000, Anton Altaparmakov wrote:
    > > When you want large data streaming, i.e. you start getting worried about
    > > memory pressure, then you want open(2) + O_DIRECT. No caching done.
    > Perfect
    > > for large data streams and we have that already. I agree that you may want
    > > some form of asynchronous read ahead with passed pages being dropped from
    > > the cache but that could be just a open(2) + O_SEQUENTIAL (doesn't
    > exist yet).
    >
    > O_DIRECT isn't the right thing for large streaming. You want
    >readahead and dropbehind. O_DIRECT takes substantial penalties for its
    >lack of copy/cacheing. This works fine in certain circumstances
    >(applications that keep their own caching), but for something like a
    >video or mp3, you'll win with working dropbehind easily.

    Oh absolutely. For mp3s, dvds, etc. Note I wrote O_SEQUENTIAL... Perhaps I
    didn't emphasize it enough. In multimedia applications you very well know
    in advance what you want so you can specify it at open(2) time.

    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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