[linux-cirrus] Re: EP93xx networking performance
- From: Harald Krammer <Harald.Krammer@xxxxxx>
- To: linux-cirrus@xxxxxxxxxxxxx
- Date: Thu, 28 Jun 2007 23:08:32 +0200
Andy Henson schrieb:
> Does anyone have any figures for network performance which the EP93xx
> family can achieve?
>
> I am considering it for a project where the application would need to
> stream a lot of data out of the ethernet port. (The goal is around
> 6MB/sec).
>
> Andy Henson
>
Hello Andy,
don't forget to look into the errata sheet.
I switched to 10 MBIT half duplex to prevent a network failure with our
custom board. :-/ BTW, I have a high load, bad network irq latency and
that seems be the reason.
Currently I use the implementation from cirrus - I could be that the
mainline kernel version works better, but I am not sure. I think for
tests you should evaluate both versions (mainline and cirrus).
Br,
Harald
Errata vom Cirrus:
http://www.cirrus.com/en/pubs/errata/ER653E2B.pdf
When there is inadequate AHB bus bandwidth for data to be transferred
from the Ethernet controller FIFO to the receive descriptor, the
Ethernet FIFO will overflow and cause the Ethernet controller to fail to
receive any more packets.
This problem will also occur if the processor is too busy to service
incoming packets in a timely manner. By the time that new receive
descriptors are available, the data in the FIFO will contain frames that
are corrupted.
It is the job of the system designer to ensure that there is adequate
bandwidth for the applications being run.
Workaround
This is a rare occurrence, however at a system level it is important to
reserve adequate bandwidth for the Ethernet controller. This can be
accomplished by some of the following:
- Reducing the bandwidth use of other bus masters in the system.
- Lowering Ethernet rate to half duplex or 10Mbit if higher
bandwidth is not required.
- Ensuring that the Ethernet controller receive descriptor
processing is given a high enough priority to ensure that the controller
never runs out of receive descriptors.
--
Harald Krammer
Brucknerstrasse 33
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Mail: Harald.Krammer (at) hkr.at
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