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SubjectRe: NETIF_F_SG question
Date
> On Mon, 3 Feb 2003, Joakim Tjernlund wrote:
>
> > > You get zerocopy, yes. :-) No HW cksum, no zerocopy.
> >
> > OK, but it should be easy to remove HW cksum as a condition to do zerocopy?
>
> Nope. You're looking at this the wrong way: the goal is not zero copy, but
> zero data access by CPU. Once you realize that, it's clear that SG alone
> is no good.
>
> This is not necessarily the only approach, but it is the current approach
> in the Linux IPv4 stack. It's not worth the effort to re-engineer the code
> in order to support the fast-disappearing hardware which supports SG but
> not cksums.

Agreed.
>
> > zerocopy without requiring HW cksums only OR could for instance the forwarding
> > procdure also benefit from SG without requiring HW cksums?
>
> The forwarding procedure is already dealing with linear buffers because
> 99.99% of the network cards on the market receive packets into one linear
> buffer. So again SG is useless for that.

I see, thanks for your patience with me.

Joakim
>
> Ion

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