Date: Thu, 27 Feb 2003 16:03:09 -0300 From: "Daniel C. Sobral" <dcs@tcoip.com.br> To: Bill Paul <wpaul@FreeBSD.ORG> Cc: jlemon@FreeBSD.ORG, ru@FreeBSD.ORG, src-committers@FreeBSD.ORG, cvs-src@FreeBSD.ORG, cvs-all@FreeBSD.ORG Subject: Re: cvs commit: src/sys/dev/fxp if_fxp.c if_fxpreg.h if_fxpvar.h Message-ID: <3E5E60ED.70406@tcoip.com.br> In-Reply-To: <20030227183346.657C937B401@hub.freebsd.org> References: <20030227183346.657C937B401@hub.freebsd.org>
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Bill Paul wrote:
> Er... look. The checksum offload capabilities are turned on by default,
> if your chip supports them, which it appears it does. Also, please try
> and remember just how bent I can get at someone who says "it doesn't
> work" without defining in precise detail just what "it" is and what
> "doesn't work" implies.
>
> Do you mean that using ifconfig to twiddle the capabilities doesn't
> seem to make any difference?
> Do you mean that the cards aren't working with the updated driver (i.e.
> you can't talk to the network)?
> Do you mean they work but you don't notice any significant performance
> difference?
> Do you mean the machine halts and catches fire?
Well, whenever I use that txcsum/rxcsum thingy, the machine acquires a
kind of life-like appearance, and sends some strange pulses through the
TP cables and start gobbling all other switches it is connected to in a
similar fashion, in a manner very much like the BOOMERs of BubbleGum
Crisis and AD Police. I'm still wondering if that's an advanced feature
added by the .jp crew or not, though. :-)
What I mean by "doesn't work" was what I cut&pasted. If the messages
didn't show it, sorry, I must have made a mistake when preparing them.
I asked how I could see if the thing was in use or not. Someone told me
to look in the "options" field displayed by ifconfig. Well:
root@piratinga:/root# ifconfig fxp2 | grep options
options=8<VLAN_MTU>
dcs@pajeus:/home/dcs$ ifconfig xl0 | grep options
options=3<RXCSUM,TXCSUM>
From where I concluded the option was not active. So I asked how I
activated it, and was told to use the undocumented options rxcsum and
txcsum. I did that and:
root@piratinga:/root# ifconfig fxp2 rxcsum txcsum
root@piratinga:/root# ifconfig fxp2 | grep options
options=8<VLAN_MTU>
Nothing happened wrt to what ifconfig displayed.
Now, someone, maybe on irc, also told me -m would show the available
options. The result of this was:
root@piratinga:/root# ifconfig -m fxp2
fxp2: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=8<VLAN_MTU>
capability list:
=b<RXCSUM,TXCSUM,VLAN_MTU>
[...]
So, -m in fact shows rxcsum and txcsum being supported capabilities, but
they are never listed in options, no matter what I do.
> Like I said, you don't have to do anything to use the checksum offload
> capabilities: they're just on, and that's that. In terms of peformance,
> the fact that the chip doesn't do checksums over fragmented packets
> means that the biggest improvement will be with packets that fit into
> a single frame.
I suspect not even that, as all traffic going through these interfaces
is 802.1q, and you mentioned IP checksum not being on for now.
So, ignoring all that, my questions are:
1) How do I know if an interface has actually been identified as
supporting the feature?
2) How do I know if the feature is in use?
3) If it can be turned on/off, how do I do it?
4) If the answer to any of these questions is the stuff I did above, why
didn't it result in, well, the expected results?
--
Daniel C. Sobral (8-DCS)
Gerencia de Operacoes
Divisao de Comunicacao de Dados
Coordenacao de Seguranca
TCO
Fones: 55-61-313-7654/Cel: 55-61-9618-0904
E-mail: Daniel.Capo@tco.net.br
Daniel.Sobral@tcoip.com.br
dcs@tcoip.com.br
Outros:
dcs@newsguy.com
dcs@freebsd.org
capo@notorious.bsdconspiracy.net
"Don't tell me I'm burning the candle at both ends -- tell me where to
get more wax!!"
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