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SubjectRe: zero-copy TCP fileserving
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>Latency? zero-copy TCP is not going to do anything to the latency,
>since a NIC that does TCP checksumming on TX will have to do it as
>'store and forward' since the checksum is in the header. The world is
>about bulk data transfers ;-)

True enough. But if you are transmitting bulk data (ie back to back packets),
which is where zero copy is likely to be especially appealing, you can hide
the latency by loading (and checksumming) one packet as the previous one is
still going out on the wire.

>I am still looking forward to the day when we will have zero-copy TX
>support, it should give us even more performance on the Linux boxes
>running our tape silos.

Yeah. I have some half-done patches somewhere to add iovec support to skb's
for transmit purposes, which I cooked up a while ago with this sort of thing
in mind. As it happens one of the projects I am working on at the moment is
one where zero copy networking in general (though not TCP specifically) would
be a bonus; I'll try to dig them out again.

p.



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