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Re: BCM5704 performance questions.

To: Michael Chan <mchan@xxxxxxxxxxxx>
Subject: Re: BCM5704 performance questions.
From: Ben Greear <greearb@xxxxxxxxxxxxxxx>
Date: Fri, 10 Jun 2005 14:09:00 -0700
Cc: "'netdev@xxxxxxxxxxx'" <netdev@xxxxxxxxxxx>
In-reply-to: <1118363861.5838.29.camel@rh4>
Organization: Candela Technologies
References: <42A8E0FE.3020708@xxxxxxxxxxxxxxx> <1118361376.5838.20.camel@rh4> <42A8EBDA.6010306@xxxxxxxxxxxxxxx> <1118363861.5838.29.camel@rh4>
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Michael Chan wrote:
On Thu, 2005-06-09 at 18:24 -0700, Ben Greear wrote:

Michael Chan wrote:

Unfortunately, the 5704 requires the "ONE_DMA" workaround which will
limit throughput in a PCIX 100/133 bus. If you comment out the line that
sets the DMA_RWCTRL_ONE_DMA flag in tg3.c, you should see improved
performance. However, you may run into some DMA issues on certain
systems.

Is there any way I can tell which systems are affected?  It won't be
an option for me to purposefully ship possibly busted drivers/hardware,
but if I can be certain that my systems are immune, I will try this
modification.


I mentioned this so that you could verify that the slow performance was
indeed caused by ONE_DMA. Even if your system is affected, it's a very
subtle problem that won't show up right away and should allow you to get
some performance numbers.

I commented out the code and ran the pktgen test again.  It may be a small
bit better, but not much:  770Mbps in one direction, 750Mbps in the other.

Have you done any tests with 2 tg3 NICs in a single machine to see if they
can run at or near line speed (full duplex)?

Thanks,
Ben

--
Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc  http://www.candelatech.com


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