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SubjectRe: Is sendfile all that sexy?
Date
In article <200101192018.XAA25263@ms2.inr.ac.ru>,
<kuznet@ms2.inr.ac.ru> wrote:
>Hello!
>
>> It's about direct i/o from/to pages,
>
>Yes. Formally, there are no problems to send to tcp directly from io space.

Actually, as long as there is no "struct page" there _are_ problems.
This is why the NUMA stuff was brought up - it would require that there
be a mem_map for the PCI pages.. (to do ref-counting etc).

>But could someone explain me one thing. Does bus-mastering
>from io really work? And if it does, is it enough fast?
>At least, looking at my book on pci, I do not understand
>how such transfers are able to use bursts. MRM is banned for them...

It does work at least on some hardware. But no, I don't think you can
depend on bursting (but I don't see why it couldn't work in theory).

Linus
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