-----Original Message-----
From: Andi Kleen [mailto:ak@suse.de] 
Sent: Wednesday, September 15, 2004 11:21 PM
To: David S. Miller
Cc: John Heffner; netdev@oss.sgi.com; leonid.grossman@s2io.com
Subject: Re: The ultimate TOE design

On Wed, Sep 15, 2004 at 02:46:24PM -0700, David S. Miller wrote:

quoted

On Wed, 15 Sep 2004 17:36:18 -0400 (EDT) John Heffner 
[off-list ref] wrote:

quoted

The other (much nicer) solution to case (b) is to just 

USE A BIGGER MTU.

quoted

quoted

1500 bytes is ridiculously small.  Even with a 9k MTU, 

the benefits 

quoted

quoted

of TOE or TSO are nearly vanishing.  Those who say they 

require high 

quoted

quoted

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