I just started working with oprofile (actually working on PowerPC performance counter support for Power4 variants including GP/UL) and was wondering if there was ever any discussion of extending oprofile to sample hardware performance counters on context switches? (first step towards recording performance counters per process more accurately).

On a separate note, the architectures I'm targeting only use performance counter group  (you select all 8 counters as a group instead of individually).  I was wondering if there was any sort of existing methodology about how to configure events as groups instead of as individual counters.