Subject: Re: high interrupt cpu usage on Athlon-64?
To: Stephen Degler <>
From: Jonathan Kay <>
List: port-amd64
Date: 08/21/2007 12:17:23
On Mon, 20 Aug, 2007 at 10:37:47PM -0400, it was scribed by that:
> Jonathan Kay wrote:
> >Hi all
> >  I'm having a problem on a new dedicated box (so I'm not sure what the
> >exact motherboard brand is)
> >It's an Athlon-64, with 1gb of ram, on what looks like an ATI-based
> >motherboard.
> >
> >It has extremely high number of interrupt requests though; running
> >sysstat vm 1 shows that it has around 64,000 interrupts/second, and
> >spends more than 80% of it's CPU handling interrupt requests.
> >
> Nothing leaps out to me but I have some general recommendations:
> 1) Take a bios update and call me in the morning.  Seriously, a bios 
> update may fix irq routing and help to resolve your issues.
> 2) Check that you have PNP OS set to off in the bios.  This will allow 
> the bios to perform initial programming and configuration of many 
> devices.  It may do it wrong, but it helps me more often than it hurts.
> 3) Disable usb legacy support.
> 4) Configure PCI_INTR_FIXUP on your kernel.
> 5) If everything else fails, try to go into the bios and disable devices 
> until things start to work.
> I have a very similar setup with an ATI/AMD motherboard, and sb400/sb600 
> based southbridge, and everything is
> working well.

Hi again,

  I had already set the PCI_INTR_FIXUP in a different kernel & it
hadn't worked, but, I asked the hosting company to
1) disable PNP OS in the bios
2) disable legacy USB
and that seems to have done it!
I'm down to about 300 or so interrupts/sec!
Now I just have to track down a really slow 2ndary sata drive.

Thank you!