performance counters

[Matthew Fluet]

Thanks for the links.  I'll see about installing the perfctr kernel patch
this weekend.  It seems to be the most maintained of the various projects
out there.

> Matthew, if you're looking into performance counters, here are a couple of links
> I had stashed from when I looked into them ages ago.
> 
> http://www.scl.ameslab.gov/Projects/Rabbit/
> http://icl.cs.utk.edu/projects/papi/

> And the one I saved away was
>         http://www.fz-juelich.de/zam/PCL/