em driver - issue #2

[Joerg Sonnenberger]

On Sun, Feb 06, 2005 at 03:04:38PM -0500, EM1897 at xxxxxxx wrote:
> I think there are a couple of things wrong with that solution.
> First, controllers know what to do with empty descriptors, in that they fall 
> into a RNR condition. Thats part of the basic design. Its the drivers 
> responsibility to clear up such conditions. At 145Kpps, you're not going to achieve 
> much by trying to fool the driver into thinking that it has memory, except 
> losing a lot of packets. The point of the RNR condition is to get the other end to 
> stop sending until you can handle it. The driver is doing something wrong in 
> this case, and it needs to be cleaned up properly.

With 145 Kpps, the interrupt load is too high for the system to do anything
else. You can try DEVICE_POLLING, which allows the card to use the normal
dropping mechanism for RX overflow. I don't think this is a fault of DragonFly,
You could get the same situation with multiple network cards at the same
package rate in other systems.

Joerg