Interrupts question

[Alex Zbyslaw]

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.

 Interrupts
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,

--Alex