Interrupts 'top-like' utility for Linux

initial idea: http://et.redhat.com/~jmh/tools/xen/itop

Forked it to make it support more CPUs (up to 24 tested)

Modified by Mitch Williams to enable filtering, user-specified timing interval, and to print the full interrupt name (instead of the interrupt type and a tiny bit of the name).

itop [-a|-t|-T|-f <string>|-i <interval>|-c <string>]

 -a : force display ALL CPUs (caution if you have many CPUs and a narrow screen) + TOTAL
 -t : DON'T display ALL CPUs, just the TOTAL
 -m : display MAX interrupts per IRQ based on TOTAL
 -T : transpose the output (suitable for running "itop -a" on computers having many CPUs)

Default: display ALL CPUs + TOTAL (unless CPUs > 8, then just display the TOTAL)

-f <string>: only show interrupts that match on the specified string

Default: display all interrupts

-i <interval>: sample every <interval> seconds. Can be fractional.

-c <string> : display only specifed CPUs (e.g. "0,1,4-6") + TOTAL

Default: sample and display every second. Note: specifying very short intervals without filters may cause display flickering.

• Display all interrupts, updating once per second:

$ itop

• Display all interrupts, only show TOTAL count per IRQ, don't display per CPU stats, updating once per second:

$ itop -t

• Display all interrupts, only show TOTAL count and MAX interrupts per IRQ, updating once per second:

$ itop -t -m

• Only display interrupts related to eth0, once per second:

$ itop -f eth0

• Only display interrupts owned by the ahci driver, every five seconds:

$ itop -f ahci -i 5

• Only display interrups owned by the ixgbe driver, ten times per second:

$ itop -f ixgbe -i 0.1

• Only display cpus 0 and 6:

$ itop -c 0,6

• Only display cpus from 4 to 8:

$ itop -c 4-8