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SubjectRe: zero-copy TCP
Ingo Molnar wrote:
> > At CERN we had a bunch of applications where this would be a win, data
> > aquisition servers taking data in from on some custom hardware and
> > sending out data over the wire on another card. You never really want
> > to touch data in memory with the CPU but because of the lack of
> > write() zero copy you end up having to do so.
> yep i agree - in this case a receivefile() implementation would be handy
> (we are 100% ready in 2.4 to introduce it - from the pagecache and VFS
> point of view, it's just not there yet), thus you could receivefile() your
> data into a temporary file, and sendfile() it to the other card, without
> ever touching data. This is faster than any zero-copy read()/write(),
> because it can do things straight in the pagecache, without having to deal
> with user-space page mappings.

It's not faster than card->card DMA, which falls out naturally from my
zero-copy proposal :-)

-- Jamie
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