Jes.Sorensen@cern.ch said:
> >>>>> "Alexey" == kuznet <kuznet@ms2.inr.ac.ru> writes:
>
> >> There is no point in using it for transmit since the Linux TCP
> >> stack currently doesn't support this.
>
> Alexey> Hmm... Are you sure? Until now I thought exaclty the same with
> Alexey> opposite sign. 8) Namely: there are no reasons to awake the
> Alexey> feature in TCP, because no drivers support this.
>
> Well in order to use it and really gain on it for transmit, you want
> scatter/gather skbuffs, something which I really want to look at
> (provided I can find the time). If you are doing the data copy anyway,
> there checksum is almost free.
Agreed. Back in the early 2.2 days I changed the kernel in a generic
way not to checksum outgoing TCP/UDP packets if it knew the card could
handle it, and experimented using a Packet Engines Hamachi gigE. The
changes to the stack are fairly small, and the gains are near
negligible (max 5% faster) since a checksum while copying is indeed
free.
The curious might see http://dancer.ca.sandia.gov/~pw, but I'd much
rather see the card DMA the unchecksummed payload directly from
userspace.
-- Pete
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This archive was generated by hypermail 2b29 : Tue Feb 15 2000 - 21:00:19 EST