Subject: Re: freebsd em driver
To: Jason R Thorpe <>
From: Jonathan Stone <jonathan@DSG.Stanford.EDU>
List: tech-net
Date: 06/17/2002 14:43:07
In message <>Jason R Thorpe writes
>On Mon, Jun 17, 2002 at 01:58:03PM -0700, Jonathan Stone wrote:

>The "boards" in "in most boards" refers to "motherboards".

Once more, then: Motherboards with 32/33 PCI are not a sensible test
environment for gigabit ethernet. Taking performance numbers limited
by such a 32/33 PCI host environment, and treating those numbers as a
suitable performance target, is a *very* bad idea.

Or to put it another way, s/most boards/most boards you'd put a
high-end gigabit card into/. With the exception of using my own
desktop machine for driver debugging, and the cards we built in the
lab at Stanford, I've *never* used less than double-speed or double-width
(and usually both).

I suppose it depends on whether your target is a significant (3x or
more) performance increment over 100Mbit; or to deliver as close to
line-rate as possible.  I've always been in the latter camp.  Taking
the former case as the ``good enough'' point to stop tuning, when all
the competition is delivering (or focused on) the latter, is ... not a
good place to be.