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    SubjectRe: PATCH: Raw device IO for 2.1.131
    Jes Sorensen writes:
    > >>>>> "Richard" == Richard Gooch <> 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.

    How about mmap(filefd); write (sockfd, mmap_addr); ?



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