Oprofile usage with performance counters events

[Sabra G. <sab...@ya...>]

Hi,
I'am using Oprofile (for Cortex-A9) to experiment profiling with some performance counters.
Following are commands that I run with the error message I got when trying to display results  :

#opcontrol --init
#opcontrol --event=CPU_CYCLES:100000:0:1:1  
#opcontrol --event=DCACHE_ACCESS:10000:0:1:1 
#opcontrol --start
# opcontrol --stop
# opreport -l
WARNING! The OProfile kernel driver reports sample buffer overflows.
Such overflows can result in incorrect sample attribution, invalid sample
files and other symptoms.  See the oprofiled.log for details.
You should adjust your sampling frequency to eliminate (or at least minimize)
these overflows.
opreport error: Already displaying results for parameter event with values:
CPU_CYCLES:100000,DCACHE_ACCESS:10000,
which conflicts with parameter cpu.
Suggestion: specify event:, count: or unitmask: (see also --merge=unitmask)

What's wrong ? Could you help me to understand these messages? Could I specify several events in the same profiling session?

Thanx