Re: zero-copy TCP

From: Ingo Molnar (
Date: Sun Sep 03 2000 - 12:34:18 EST

On 3 Sep 2000, Jes Sorensen 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.


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