The following is a demonstration of the inttimes.d script, Here we run it for a few seconds then hit Ctrl-C, # inttimes.d Tracing... Hit Ctrl-C to end. ^C DEVICE TIME (ns) ata0 22324 uhci1 45893 ata1 138559 uhci0 229226 i80420 1305617 rtls0 2540175 In the above output, we can see that the rtls0 driver spent 2540 us on the CPU servicing interrupts, while ata0 spent only 22 us.