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Date:      Fri, 6 Sep 2002 13:52:30 -0600
From:      "Kenneth D. Merry" <ken@kdm.org>
To:        Terry Lambert <tlambert2@mindspring.com>
Cc:        Dan Ellard <ellard@eecs.harvard.edu>, hackers@FreeBSD.ORG
Subject:   Re: gigabit NIC of choice?
Message-ID:  <20020906135229.A18971@panzer.kdm.org>
In-Reply-To: <3D78E69C.4152CC8@mindspring.com>; from tlambert2@mindspring.com on Fri, Sep 06, 2002 at 10:32:12AM -0700
References:  <Pine.BSF.4.44.0209061151560.35790-100000@bowser.eecs.harvard.edu> <3D78E69C.4152CC8@mindspring.com>

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On Fri, Sep 06, 2002 at 10:32:12 -0700, Terry Lambert wrote:
> Dan Ellard wrote:
> > What's the gigabit ethernet NIC of choice these days?  (I've had good
> > experiences with the NetGear G620T, but apparently this card is no
> > longer being sold.)
> > 
> > I'm looking for:
> > 
> >         - Easy FreeBSD integration.
> >         - Reliability.
> >         - High performance.
> 
> The Tigon II has the best performances, but that's because
> software people rewrote the firmware, instead of hardware
> engineers moonlighting as programmers.  8-) 8-).

You'll get good performance with the Tigon II with jumbo frames under
-current with ZERO_COPY_SOCKETS and TI_JUMBO_HDRSPLIT turned on.

Note that "good performance" == "lower CPU utilization" here, although it
is difficult to see any improvement in -current with SMP enabled, and the
improvement isn't as large in UP mode as it used to be.

You can easily get wire rates with jumbo frames with a Tigon II without
zero copy, given a reasonably fast machine.  (At least on -stable.
Reasonably fast == 1GHz Pentium III, 64 bit PCI.)

With 1500 byte frames, though, the Tigon II won't perform as well as some
other controllers.  For most folks, performance with 1500 byte frames is
what matters, since you usually need a jumbo-capable gigabit switch to take
advantage of jumbo frames in anything more than a point to point
environment.

The modifications I made to the Tigon firmware (the ones that are in
FreeBSD) are actually relatively minor.  The main "trick" is to make sure
that the header is in its own scatter/gather element, so the payload will
be page aligned.  (Assuming the second and subsequent scatter/gather
elements are page aligned.)

So if your workload consists of jumbo frames for the most part, and receive
performance is important, I would suggest a Tigon II-based board, like the
GA620T, if you can find one.  (Obviously that's getting more and more
difficult nowadays.)  Otherwise, I would suggest another card with better
performance with 1500 byte frames.  (I haven't done any tests with other
boards, so I can't make specific recommendations.)

Ken
-- 
Kenneth Merry
ken@kdm.org

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