> -----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.
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
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