oprofile and ARM A9 hardware counter

[Will Deacon]

Hi Stephane,

On Tue, Feb 07, 2012 at 11:59:21AM +0000, stephane eranian wrote:
> An easier way to verify we're getting the right number of samples is
> to use perf top:
> 
> $ taskset -c 1 noploop 1000 &
> $ sudo perf top
> 
> You'll see around 850 irqs/sec, should be closer to 1000.
> But if I drop the rate to 100Hz, then it works:
> 
> $ sudo perf top -F 100
> 
> That leads me to believe there is too much overhead somewhere.
> Could be in perf_event itself.
> 
> Will, do you get 1000 irsq/sec running the same test on your systems?

I'm away from my dev boards at the moment, but I'll give this a go next week
and get back to you.

Will