> Speaking of shortcuts, what is the status of some sort of direct
> page -> skb TCP sending ?
>
> What I mean is, when tcp does a sendmsg, it shouldn't need to copy the
> actual data into the skbuf, but merely the headers, and remember a ptr to
> the data area (which would have to be locked down until the fragment is
> acked or the connection breaks, of course). Then the network driver could
> (if it supports s/g DMA) send the headers + data directly from memory.
This simple zero-copy isn't really a win on most PC hardware as it takes
about the same amount of time to do a checksum as it does to do a checksum
and copy.
A more powerful scheme is being investigated by sct and a couple others. A
related scheme worked out on FreeBSD and presented at a recent Usenix
could cache checksums, for example.
-- "Love the dolphins," she advised him. "Write by W.A.S.T.E.."
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