Interrupt statistics?

Does anyone have recent statistics for interrupt latency and arrival
timings?  I am very interested in our idle load characteristics.  It seems
most systems I've analyzed have an average idle interrupt rate of about
225 per second, dominated by the clk and rtc interrupts as shown below.

clk irq0            99/sec
rtc irq8           127/sec

Since these are both clocks, I assume the arrival of their interrupts are
equally spaced and not correlated to each other.  How much latency do the
handlers for these have?  Are there any system processes which generate
repetitive bursts of very short tasks?  If so, how long do those tasks
take?

The reason why I ask is I'm coming up with a default policy for CPU sleep
states which can have as high a latency as a few hundred microseconds.  On
an idle system, this should be fine although it does add to the latency
for the above clock handlers.  But I also need to be able to demote
quickly to short sleep states (e.g., HLT) if the system is becoming active
to decrease response times.

Thanks for any info,
Nate