Subject: Re: BCM5704 performance questions.

From: Ben Greear <[email-masked]>
Date: Fri, 10 Jun 2005 14:09:00 -0700

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 <[email-masked]>
Candela Technologies Inc  http://www.candelatech.com