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On Thu, 14 Sep 2000, jamal wrote:

> If i remember correctly some of the 3coms still give this 'mid-interupt',
> no? It could useful to just say quickly read the header and make routing
> decisions as in fast routing but not under heavy load.

The 3Com cards can generate this interrupt, however this is not used in
current 3c59x.c. I suggested this to Andrew, but he is already worried
about the current interrupt rate and unhappy that 3Com cards do not
provide hardware support for Rx mitigation.

An ideea might be to combine Rx early interrupts with some kind of
software timer-based mitigation. IMHO this has 2 advantages:
- because of the overhead that Andrew pointed out, by the time the CPU
reaches the ISR code and the skbuff allocation is done, the entire packet
might already be transferred; however, a check has to be done to assure
that the packet was not dropped by the hardware and you try to fit a
packet in a skbuff sized for the previous packet (in case several packets
can be transferred during the "overhead" time)
- under load, because interrupts occur anyway (the Rx early ones), you
don't loose anything in terms of latency.


Bogdan Costescu

IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
E-mail: Bogdan.Costescu@IWR.Uni-Heidelberg.De

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