Re: excessive interrupts on network cards

Benjamin LaHaise (
Tue, 25 Sep 2001 17:42:04 -0400

On Tue, Sep 25, 2001 at 06:38:31PM -0300, Chris Newton wrote:
> Yea, it is a single port card... I had meant to mention that in the email I
> sent out... ie: that it wasn't reporting correctly... but, I didnt really
> think it was related, since the eepro was doing the same thing.
> As for comparing with ifconfig, I ran 'watch 1 ifconfig -a', and sure
> enough, I have about ~7000-7500 packets coming in right now. And, the
> 'procinfo -D', reports ~21000-22000 interrupts per second.

This is heavily dependant on the interrupt mitigation features that a card
has. At least for the ns83820 driver, I'm testing a technique where the
driver essentially switches to polled mode once the interrupt load goes
above a certain threshold, thereby limiting the load to ~2500 irq/sec.
Combined with carefully placed data prefetching, I'm seeing a huge increase
in performance. Of course, this comes at the expense of latency.

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