how to fix "interrupt storm"

[perryh at pluto.rain.com]

Nicolais <got2get.net!ns at agora.rdrop.com> wrote:
> PerryH-2 wrote:
> > There are no USB devices connected.  I think those must actually
> > be atapci1 interrupts, since irq9 is where dmesg reported it.
>
> I think this could be related to previous issues on same topic.
> I don't recall the thread titles, but the solution is located here:
>
> http://confighell.com/FreeBSD#How_to_get_rid_of_interrupt_storm_atapci0_and_others_
>
> I hope it can solve things out for you as well.

It does not seem to be the solution in this case.

(Apologies for the delay; this machine turned out to be a bit
under-resourced for kernel building, and meanwhile life got
in the way.)

So, I am back to asking what changes or additions to make in
/boot/device.hints.  I suppose I need to move either uhci0 or
atapci1 off of the (currently shared) irq9 to an unused irq,
but I'm not finding it immediately evident how to do that.

For the archives, in case the referenced page goes away in the
future, it suggests adding

  options         KDB
  options         KDB_UNATTENDED
  options         DDB

to the kernel.  This is reported to have caused an interrupt
storm, involving an atapci controller on an amd64 system, to
go away.