ACPI floods CPUs with interrupts

[John Baldwin]

On Tuesday 20 April 2004 09:31 am, Artem Koutchine wrote:
> I have installed FreeBSd 5.2-RC2 on ASUS P2B-DS
> with 3ware raid controller and DUAL PIII (slot2) 550Mhz.
> Updated motherboard bios to
> the latest bios and after patching the twe driver, so it does not
> show the "PCI parity erro" several times a second. (I think
> it is related to the fact that 3ware 7506 controller is pci 2.2
> while p2b is pci 2.1). After that i did top and saw that
> 50% of cpu power is wasted on interrupts. I did
> sysstat and :vmstat. It showed that 46700 interrupts per
> second were generated by acpi on irq 20. So, i booted without
> acpi and got 100% cpu idle. The question is:
> How ACPI can generate IRQs? I thought it is just some kind
> of interface and protocol standard, not > a real hardware part which 
> can rise irq. Why does it generate so many irqs? May it be related
> to the PCI parity error on twe?

It is because the ACPI interrupt is programmed incorrectly (due to a buggy 
BIOS) and is treated as edge triggered when it is actually level triggered.
You can try updating to -current to see if that fixes it.

-- 
John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org