Maximum NIC interrupts

[Jack Vogel]

On Dec 25, 2007 4:21 AM, Jordi Espasa Clofent <jordi.espasa at opengea.org> wrote:
> Hi all,
>
> I know how to monitoring the NIC IRQ's consume, with tools as vmstat (-i
> flag), systat (-vm 1) or netstat (-m, -i), but I don't know how to
> determine the maximum interrupts that these NICs can give.
>
> I've several SuperMicro servers with Intel Pro 1000 PT NICs, which are
> controlled by em(4) driver. I've done some performance tests (with tools
> as iperf or netperf) with great results, but I don't know exactly the
> hardware limits, because I don't know the maximum IRQ rate.
>
> Obviously, before post this present message I've read a lot of
> documentation provided by vendor (Intel in this case) but I've not found it.

I'm not sure of the purpose of the question, and I don't know that there
is a specific number documented anywhere, the interrupt rate will depend
on the rate at which they are serviced.

For instance, with our new 10G card you must set the interrupt storm
threshold up to 8000 just so the kernel doesnt throttle you down :)

With a 1G interface doing line rate I don't think its necessary that it get
that high, so again, why the question?

Happy Holidays,

Jack