[vortex] Why so many IRQ/sec with 3c905c (Tornado) card?

[Richard Ellis]

--- Donald Becker <becker@scyld.com> wrote:
> On Fri, 21 Jun 2002, Richard Ellis wrote:
> 
> > On my setup, the Tornado card maxes out at about 11.8 MB/sec of
> > receive data, and while receiving at this rate, it's generating
> > about 60000 irq's/second.  That works out to about 206 bytes per 
> > interrupt.
> 
> What is the interrupt count per (Tx+Rx) packet?
> There should be about one interrupt per packet, less under heavy load or
> with short packets.
> 
> If you are sharing the IRQ line with other device the interrupt rate
> is unpredictable, but should be less than the sum of the individual
> interrupt rates due to coincidental sharing.
> 
> You can reduce the interrupt rate, at the cost of increased latency.

I ran a test this morning to determine what the IRQ/packet rate was.

The results came out close enough to 1 IRQ per packet TX/RX to basically
be one IRQ per packet.  The number of IRQ's was actually about 23,000
lower than the number of packets transmitted and received, so for some
situations, one IRQ handled more than one packet.

For curiosity's sake, what settings would be adjusted to reduce the
interrupt rate?

Thanks

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