How can I know which IRQ is responsible of high CPU usage
Well, since you're specifically asking how to know which IRQ is responsible for the number in mpstat, you can assume it's not the local interrupt timer (LOC), since those numbers are fairly equal, and yet mpstat shows some of those cpus at 0 %irq.
That leaves IRQ 0, which is the system timer, and which you can't do anything about, and IRQ 177, which is tied to your b4xxp driver.
My guess is that IRQ 177 would be your culprit.
If this is causing a problem, and you would like to change the behavior your see, try:
disabling the software that uses that card, and see if the interrupts decrease.
removing that card from the system, and unloading the driver, and see if there's improvement.
move that card to another slot and see if that helps.
check for updated drivers or patches for the software.
If it's not a problem, and you were just curious, then carry on. :)
watch -n1 -d cat /proc/interrupts
BP410P is a ISDN card with 4 BRI Lines, if all four lines are connected you should be getting four sync packets at a time and when calls are being made you can have 8 voices channels active all sending packets, etc
If you get a high IRQ count without any calls being made this could be a symptom of 2 bad things:
- There's a sync problem with the operator, you should also get bad voice quality.
- IRQ lines are conflicting, in this case your
ata_piix(ide/sata) is using the same line has the BP410P card, the drivers might not like that very much, in this case do has the previous answer suggested try and change the card to another slot.
To debug you can also try removing the BRI cables and see if it makes a difference.