[Fwd: Interrupts question]

Alex Zbyslaw xfb52 at dial.pipex.com
Mon Jul 17 14:22:28 UTC 2006

No responses from questions at .  Anyone here understand what's going on?  
I was monitoring a machine with "systat -vmstat" and noticed something
about the interrupts and I don't know if it's a problem or not. If it
is a problem, is there anything I can do about it?

The interrupts for the network interface (em0) on irq 64 exactly match
those for a uhc device on irq 16.

And the interrupts for the hardware raid (amr) on irq 46 exactly match
those for a uhc device on irq 18.

The machine is a Dell 2850 running 5.4. Relevant bits from the dmesg are:

ioapic0: Changing APIC ID to 2
ioapic1: Changing APIC ID to 3
ioapic1: WARNING: intbase 32 != expected base 24
ioapic2: Changing APIC ID to 4
ioapic2: WARNING: intbase 64 != expected base 56
ioapic3: Changing APIC ID to 5
ioapic3: WARNING: intbase 96 != expected base 88
ioapic0 <Version 2.0> irqs 0-23 on motherboard
ioapic1 <Version 2.0> irqs 32-55 on motherboard
ioapic2 <Version 2.0> irqs 64-87 on motherboard
ioapic3 <Version 2.0> irqs 96-119 on motherboard
amr0: <LSILogic MegaRAID 1.51> mem
  0xdfdc0000-0xdfdfffff,0xd80f0000-0xd80fffff irq 46 at device 14.0 on pci2
em0: <Intel(R) PRO/1000 Network Connection, Version - 1.7.35> port
  0xecc0-0xecff mem 0xdfae0000-0xdfafffff irq 64 at device 7.0 on pci6
uhci0: <Intel 82801EB (ICH5) USB controller USB-A> port 0xace0-0xacff
  irq 16 at device 29.0 on pci0

uhci2: <Intel 82801EB (ICH5) USB controller USB-C> port 0xaca0-0xacbf
  irq 18 at device 29.2 on pci0

Turning off USB isn't an option as it's required for the
pseudo-keyboard/mouse used by the DRAC.

Here a sample of the interrupt section. The number of interrupts for
em0 at 64/uhc at 16 can easily be in the thousands rather than hundreds.

1950 total
6: fdc0
128 8: rtc
13: npx
14: ata
450 16: uhc
409 18: uhc
19: uhc
23: ata
409 46: amr
450 64: em0
4 65: em1
106: ah
107: ah

Any insight appreciated,


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