Re: EXPLAIN ANALYZE printing logical and hardware I/O per-node

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