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SubjectRe: PATCH: Raw device IO for 2.1.131
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>>>>> "Richard" == Richard Gooch <rgooch@atnf.csiro.au> writes:

Richard> Jes Sorensen writes:
>> SGI managed to get zero copy right for write() on a socket and it
>> works great, I'd love having Linux do the same.

Richard> To get you what you want without resorting to sendfile(),
Richard> we'd have to be able to be able to pin down user pages and
Richard> then initiate DMA. Linus has said he doesn't like that idea
Richard> and has also pointed out he feels that the copy operation
Richard> would not be a significant overhead. Other have mentioned
Richard> other applications (video capture and processing) where they
Richard> feel an extra copy *is* significant. But is this the case
Richard> with your application? It seems to me that if you have a
Richard> bunch of user pages you want to DMA out, you have already
Richard> spent a considerable amount of time generating the data, so
Richard> an extra copy is not significant. Is that so?

No most of our applications do read(filefd), write(sockfd) and as
such it could probably be done with sendfile, the main issue is that
it requires rewriting the code as a special case for Linux.

Jes

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