Re: TCP Segmentation Offloading (TSO)

From: Andi Kleen (ak@suse.de)
Date: Tue Sep 03 2002 - 04:05:30 EST


"David S. Miller" <davem@redhat.com> writes:

> From: Hirokazu Takahashi <taka@valinux.co.jp>
> Date: Tue, 03 Sep 2002 16:42:43 +0900 (JST)
>
> I guess it may also depend on bad implementations of csum_partial().
> It's wrong that some architecture assume every data in a skbuff are
> aligned on a 2byte boundary so that it would access a byte next to
> the the last byte where no pages might be there.
>
> It is real requirement, x86 works because unaligned
> access is handled transparently by cpu.
>
> But on every non-x86 csum_partial I have examined, worse than
> 2-byte aligned data start is totally not handled. It is not difficult
> to figure out why this is the case, everyone has copied by example. :-)

x86-64 handles it (also in csum-copy). I think at least Alpha does it
too (that is where I stole the C csum-partial base from) But it's ugly.
See the odd hack.

-Andi
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