Too many devices using IRQ10?

[Steffen Kluge]

Hi all,
I've got this niggling problem that I revisit every time a new kernel is
released for FC4, however, it doesn't appear to change:

On my notebook it seems that by default most devices are sharing IRQ10,
including the ones I would normally associate with performance (disk,
net):

$ cat /proc/interrupts
           CPU0
  0:      34756          XT-PIC  timer
  1:         91          XT-PIC  i8042
  2:          0          XT-PIC  cascade
  8:          1          XT-PIC  rtc
  9:       1138          XT-PIC  acpi
 10:      10853          XT-PIC  libata, ipw2200, Intel ICH6, ehci_hcd:usb1,
uhci_hcd:usb2, uhci_hcd:usb3, uhci_hcd:usb4, uhci_hcd:usb5, yenta, ohci1394, eth0
 12:        814          XT-PIC  i8042
 14:        454          XT-PIC  ide0
NMI:          0
ERR:          0

The interrupts are assigned by ACPI. Since I need ACPI for cpuspeed I
don't want to disable it altogether, but instead fiddled with boot
parameters to keep it from doing the IRQ assignment. For example, my
current boot command line contains "pci=noacpi,routeirq", which seems to
improve the situation:

$ cat /proc/interrupts
           CPU0
  0:      54122          XT-PIC  timer
  1:         73          XT-PIC  i8042
  2:          0          XT-PIC  cascade
  5:        399          XT-PIC  uhci_hcd:usb3, ohci1394, eth0
  7:          2          XT-PIC  ehci_hcd:usb1, uhci_hcd:usb2
  8:          1          XT-PIC  rtc
  9:       1727          XT-PIC  acpi
 10:         41          XT-PIC  ipw2200, Intel ICH6, uhci_hcd:usb4, yenta
 11:      10615          XT-PIC  libata, uhci_hcd:usb5
 12:        118          XT-PIC  i8042
 14:        610          XT-PIC  ide0
NMI:          0
ERR:          0

With this, the interrupts are much more evenly used.

Now, I guess my question is, does this even matter? Is sharing a single
IRQ among many devices a potential performance issue? Am I losing
anything by stopping ACPI from messing with IRQ's?

Cheers
Steffen.

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