> -----Original Message-----
> From: Andi Kleen [mailto:ak@xxxxxxx]
> Sent: Wednesday, September 15, 2004 11:21 PM
> To: David S. Miller
> Cc: John Heffner; netdev@xxxxxxxxxxx; leonid.grossman@xxxxxxxx
> Subject: Re: The ultimate TOE design
>
> On Wed, Sep 15, 2004 at 02:46:24PM -0700, David S. Miller wrote:
> > On Wed, 15 Sep 2004 17:36:18 -0400 (EDT) John Heffner
> > <jheffner@xxxxxxx> wrote:
> >
> > > The other (much nicer) solution to case (b) is to just
> USE A BIGGER MTU.
> > > 1500 bytes is ridiculously small. Even with a 9k MTU,
> the benefits
> > > of TOE or TSO are nearly vanishing. Those who say they
> require high
> > > performance, but are unwilling to buy or produce networking gear
> > > with an MTU larger than 1500 bytes probably deserve what they get.
> >
> > TSO gives a kind of virtual 64K MTU, FWIW. But I do see your point.
>
> We still need to solve the same problem for RX though.
>
> -Andi
Ditto.
We can dream about benefits of huge MTUs, but the reality is that moving
beyond 9k MTU is years away. Reasons - mainly infrastructure, plus MTU above
~10k may loose checksum protection (granted, this depends whether the errors
are simple or complex, and also this may not be a showstopper for some
people).
Even 9k MTU is very far from being universally accepted, eight years after
our Alteon spec went out :-).
TSO works great for the transmit side (even for 9k MTU, the impact is not
insignificant), but RX problem that Andi is talking about is a major issue
for a lot of users.
I don't have hard data yet, but the expectations are that the effect of
doing "RX side TSO" will be close to having 64k RX MTU - I'll publish some
numbers once we bring up first Unix drivers with this feature and do some
measurements.
Leonid
>
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