[Bridge] maximum throughput for linux bridge

[Bridge] maximum throughput for linux bridge

[Paul P. Pongco]

Hi,

Apologies if I am not suscribed to this list.

I have setup a linux bridge using 3c905C-TX/TX-M [Tornado] cards. Im
running it on RH 7.3 2.4.19 kernel.
Lately, I have seen the following errors on the bridge

Feb 10 07:40:24 safe kernel: eth2: Too much work in interrupt, status e401.
Feb 10 07:40:52 safe last message repeated 3 times
Feb 10 08:12:16 safe kernel: br0: received tcn bpdu on port 1(eth2)
Feb 10 08:12:16 safe kernel: br0: topology change detected, sending tcn bpdu
Feb 10 08:13:09 safe kernel: br0: received tcn bpdu on port 1(eth2)
Feb 10 08:13:09 safe kernel: br0: topology change detected, sending tcn bpdu

Im currently pushing around 45Mbs/20Mbs (down/up)  of traffic on the
bridge (doing some bandwidth management) and Im concerned about its
performance and how it would scale.
Thanks in advance for your advice. 

-- 
Cheers,

Paul P. Pongco
Mosaic Communications Inc.

Re: [Bridge] maximum throughput for linux bridge

[Stephen Hemminger]

Paul P. Pongco wrote:

>Hi,
>
>Apologies if I am not suscribed to this list.
>
>I have setup a linux bridge using 3c905C-TX/TX-M [Tornado] cards. Im
>running it on RH 7.3 2.4.19 kernel.
>Lately, I have seen the following errors on the bridge
>
>Feb 10 07:40:24 safe kernel: eth2: Too much work in interrupt, status e401.
>Feb 10 07:40:52 safe last message repeated 3 times
>Feb 10 08:12:16 safe kernel: br0: received tcn bpdu on port 1(eth2)
>Feb 10 08:12:16 safe kernel: br0: topology change detected, sending tcn bpdu
>Feb 10 08:13:09 safe kernel: br0: received tcn bpdu on port 1(eth2)
>Feb 10 08:13:09 safe kernel: br0: topology change detected, sending tcn bpdu
>
>Im currently pushing around 45Mbs/20Mbs (down/up)  of traffic on the
>bridge (doing some bandwidth management) and Im concerned about its
>performance and how it would scale.
>Thanks in advance for your advice. 
>  
>
It is not a bridge problem, just that bridging puts more stress on the 
network driver.

The problem is that the 3c905 cards don't support interrupt mitigation, 
so when lots
of network traffic hits, they drop data.  The 3c59x driver allocates and 
copies every
received frame in the interrupt routine.  What is needed is a new driver 
that does NAPI
(any volunteers)? 

Or you could get different hardware that doesn't copy every packet 
within the interrupt
routine.  Either a card that can receive direct into the socket buffer, 
or has a driver that
supports NAPI to do it in the IRQ.

I have added the linux-net list to see if anyone else has ideas.

Re: [Bridge] maximum throughput for linux bridge

[Steffen Klassert]

On Fri, Feb 13, 2004 at 10:01:54AM -0800 or thereabouts, Stephen Hemminger wrote:
> 
> The problem is that the 3c905 cards don't support interrupt mitigation, 
> so when lots
> of network traffic hits, they drop data.  The 3c59x driver allocates and 
> copies every
> received frame in the interrupt routine.  What is needed is a new driver 
> that does NAPI
> (any volunteers)? 
> 

Is seems that it is not possible to get the technical reference
for the 3c905 cards from the 3com webpage any more.
Filling out the cgi form at 
http://support.3com.com/partners/developer/developer_form.html
will leed to a server error.

Re: [Bridge] maximum throughput for linux bridge

[Paul P. Pongco]

Thanks for your reply.

> >
> It is not a bridge problem, just that bridging puts more stress on the 
> network driver.
Yep, i really suspected it was something with the 3com card. Found
something on the bridge FAQ regarding 3com cards (setting
interrupt_work=10000). If you have additional options such as indicated
on the bridge FAQ available that you know or links that discuss this
please let me know. 

> 
> The problem is that the 3c905 cards don't support interrupt mitigation, 
> so when lots
> of network traffic hits, they drop data.  The 3c59x driver allocates and 
> copies every
> received frame in the interrupt routine.  What is needed is a new driver 
> that does NAPI
> (any volunteers)? 
would you know of any network card that can work as a bridge and at the
same time has NAPI drivers?


-- 
Cheers,

Paul P. Pongco
Mosaic Communications Inc.