Networking: Still waiting for mbuf cluster.

Torsten Landschoff torsten.landschoff at
Wed Sep 26 07:14:35 UTC 2007

Hi Chris,

Chris Johns wrote:
> Torsten Landschoff wrote:
>> Okay, so much seems clear to me. It's just that an ping -f works fine,
>> therefore I would expect the driver to correctly transmit and receive
>> packets. It also creates a hell lot of interrupts - there is a lot of
>> room for improvements of the xiltemac driver.
> The continuous stream of packets and therefore interrupts can be
> keeping the driver working. I have seen cases like this on other
> hardware and it tended to be the way the interrupt acknowledge
> sequence worked.
I can't really follow what you are trying to say. Either
a) "Creating a lot of interrupts is normal and it should be that way." or
b) "No wonder your system breaks down with that many interrupts."

About (a): I was referring to the fact that the Xilinx tri-mode MAC
supports interrupt coalescing. However, as I just noticed, this is only
supported when scatter-gather DMA is enable. Currently neither my FPGA
configuration nor the RTEMS driver support that.

About (b): Interestingly, the working configuration generates as many
interrupts and works flawless (what ttcp is concerned at least).

Greetings, Torsten

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