Re: Is sendfile all that sexy?

[Russell Leighton <leighton@imake.com>]

"copy this fd to that one, and optimize that if you can"

... isn't this Larry M's "splice" (http://www.bitmover.com/lm/papers/splice.ps)?

Andreas Dilger wrote:

> 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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