On Mon, 17 Dec 2007, Decibel! wrote:
> Someone want to throw together some code that actually measures this? Maybe
> something that keeps a histogram of how many instructions take place per I/O
> request? If it turns out that counters do vary too much between CPUs, there
> might be ways that we can account for that.
I'd expect the easiest way to do a proof of concept here would be to use
the Linux oprofile tool. That's already abstracted away the differences
in hardware counters and provides a relatively simple interface to collect
the data without getting bogged down with implementation there. Starting
from scratch, going right to the hardware counters and building from
there, is a big project--they've been hacking on oprofile for almost six
years now and still aren't suggesting it's release quality yet.
--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD