> pmc is used on arm (xscale) and i386.  the pmc stuff has not yet been
> defined for powerpc yet.  We really do need it for powerpc 
> and we should figure which of the PMC counter we should support.

I really like Linux's implementation of using /proc filesystem to get/set
PMC. Anyhow, the set of PMC counters to support can always be refined with
time. If we start supporting some of the basic ones, e.g. 

for MPC750:

PMC1:
   6 - # of cycles spent in table search for ITLB accesses
   7 - # of L2 hits

PMC2:
   5 - # of L1 instruction cache misses
   6 - # of ITLB misses
   7 - # of L2 instruction misses

PMC3:
   5 - # of L1 data cache misses
   6 - # of DTLB misses
   7 - # of L2 data misses

PMC4:
   5 - # of L2 castouts
   6 - # of cycles spent in table search for DTLB accesses
   8 - # of mispredicted branches

Once we have s'thing working, we can always add onto it.

Dheeraj