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Date:      Sat, 6 Mar 2010 12:21:31 -0800
From:      Jeremy Chadwick <freebsd@jdc.parodius.com>
To:        Nick Rogers <ncrogers@gmail.com>
Cc:        stable@freebsd.org, Jack Vogel <jfvogel@gmail.com>
Subject:   Re: em(4) interface hangs under 8.0-RELEASE
Message-ID:  <20100306202131.GA23232@icarus.home.lan>
In-Reply-To: <147432021003061208n64ebd9c9lb168cdfa520e94a3@mail.gmail.com>
References:  <147432021003051648x1a1417dfp3c778922ea2c571f@mail.gmail.com> <2a41acea1003051718r241ac3e9w6ceb37bde0128b43@mail.gmail.com> <20100306180029.GA99452@voi.aagh.net> <2a41acea1003061039s41dda598v563edf76d609c4f0@mail.gmail.com> <147432021003061208n64ebd9c9lb168cdfa520e94a3@mail.gmail.com>

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On Sat, Mar 06, 2010 at 12:08:22PM -0800, Nick Rogers wrote:
> Yes, this was the first em(4) problem I ran into when upgrading from
> 7.2-RELEASE to 8.0-RELEASE. Yourself and others on another thread eventually
> recommended turning off TSO and what not. I never had a chance to thoroughly
> test this solution on this particular hardware because we had already
> switched to a different set of interfaces (on-motherboard bge(4)). We also
> had that ALTQ problem popup on em which I'm sure you remember, which
> prevented me from going back to the em interfaces for a while.

I've re-read your ALTQ post (Subject "em(4) + ALTQ broken") and I
noticed you didn't provide any details regarding *how* you're using ALTQ
on your systems (specifically, no pf.conf directives provided).

We use pf and ALTQ on all our RELENG_7 and RELENG_8 systems, exclusively
using em(4), without any problems.  I should note that we only utilise
the ALTQ pieces of pf.conf on RELENG_7, but ALTQ is included in our
RELENG_8 systems' kernels.  The ALTQ feature we use is "bandwidth" for
rate-limiting certain IPs bound to em(4) interfaces.  We've used this
successfully at both 100mbit and 1000mbit interface rates.

I can provide specific details of the systems (pciconf -lvc from them,
including OS release + etc.) if you'd like to compare.

I'm almost certain the NIC model you use differs from ours, including
the fact that our NICs are PCIe-bound, and do use MSI + TSO + all forms
of checksum offloading.

Why I care: upgrading our RELENG_7 machine which uses ALTQ directives is
on my to-do list, and if this feature is somehow broken under RELENG_8,
I need to know in advance so I can use ipfw + dummynet instead.

-- 
| Jeremy Chadwick                                   jdc@parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |




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