Checksum/copy (was: Re: cvs commit: src/sys/netinet ip_output.c)

Nate Lawson nate at
Wed Mar 26 21:50:28 PST 2003

On Tue, 25 Mar 2003, Mike Silbersack wrote:
> On Tue, 25 Mar 2003, Doug Ambrisko wrote:
> > Maybe an extent count could be used that said how long the chain is.
> >
> > As Sam mentioned having little things scattered around is not good thing.
> > Memory and CPU can be a lot faster then the I/O bus.
> >
> > Doug A.
> I think we could inexpensively walk the mbuf chain at the end of ip_output
> and do the counting there.  Realistically, the same chain will be rewalked
> very soon afterword when the network card tries to set up the DMA
> transfers / etc.

I don't want to hijack the thread too much, but has thought gone into a
combined checksum and copy function?  The first mention I can remember of
this is in RFC 817 p. 19-20.


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