Re: [9fans] High interruptload on cpu server

[David Presotto <presotto@closedmind.org>]

If you're on a PC, you can look to see how much time is
spent in interrupts by 'acid -k $pid' and dumping the
intrtimes array.  Take a look at trap.c and you'll
understand.  It's just an array of 20 buckets for each
possible interrupt level.  Each bucket represents a
100 µ second interval.  You'll be able to tell if any
one level is hogging a lot of time.  I've debated adding
a user readable interface but then I'ld have to write a
man page.

kprof is moderately crappy for timing interrupts since
it samples in the clock routine which is splhi'd as
are the other interrupt routines, i.e., sampling is
mutually exclusive to the interrupt routine running.