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    SubjectRe: Is sendfile all that sexy?
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    Roger Wolff writes:
    > I'd prefer an interface that says "copy this fd to that one, and
    > optimize that if you can".
    >
    > For example, copying a file from one disk to another. I'm pretty sure
    > that some efficiency can be gained if you don't need to handle the
    > possibility of the userspace program accessing the data in between the
    > read and the write. Sure this may not qualify as a "trivial
    > optimization, that can be done with the existing infrastructure" right
    > now, but programs that want to indicate "kernel, please optimize this
    > if you can" can say so.

    Actually, this is a great example, because at one point I was working
    on a device interface which would offload all of the disk-disk copying
    overhead to the disks themselves, and not involve the CPU/RAM at all.

    I seem to recall that I2O promised something along these lines as well
    (i.e. direct device-device communication).

    Cheers, Andreas
    --
    Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto,
    \ would they cancel out, leaving him still hungry?"
    http://www-mddsp.enel.ucalgary.ca/People/adilger/ -- Dogbert
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