Re: [PATCH] select appropriate skb size in tcp_sendmsg when TSO is used

[Jeff Garzik <jgarzik@xxxxxxxxx>]

David S. Miller wrote:
> On Wed, 27 Oct 2004 10:22:09 +1000
> Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote:
>
>
> > On Tue, Oct 26, 2004 at 08:15:31PM -0400, Jeff Garzik wrote:
> >
> > > > IMHO it is valid to disable SG without disabling checksums, no?
> > >
> > > It's useless:  The packet header is always in a separate memory
> > > location from the packet data, when using zerocopy sendfile(2).
> > >
> > > When not using zerocopy sendfile, you are copying the data _anyway_.
> >
> > I'm fine with adding this check.  However I think that belongs in
> > another patch since we don't check that in register_netdev currently.
> >
> > Dave, what do you think?
>
>
> I believe that allowing TX csum support without SG _is_
> useful even though it is not _effective_.
>
> It is quite desirable for a driver author to be able to
> test out his TX csum offload support first, then add
> SG support next.  Similarly, if a driver author suspects
> some issues with either SG or TX csum support, he can
> better isolate the problem if we allow this.
>
> Jeff do you agree?


<shrug>  it's never used that way in practice AFAIK, only used by 
confused sysadmins :)

I won't object if you preserve the behavior, but I still don't see much 
value in allowing it.

        Jeff