I was taking a look at the proposed performance monitoring and kerneltop.c. I 
noticed that  http://redhat.com/~mingo/perfcounters/kerneltop.c doesn't work 
with the v3 version. I didn't see a more recent version available, so I made 
some modifications to make allow it to work with the v3 kernel (with the 
attached). However, I assume some where there is an updated version of kerneltop.c

The Documentation/perf-counters.txt doesn't describe how the group_fd is used. 
Found that -1 used to indicate not connected to any other fd.

-Will