Re: Questing regarding KVM Guest PMU

[Gleb Natapov <gleb@redhat.com>]

On Sun, Mar 18, 2012 at 06:27:53PM +0530, shashank rachamalla wrote:
> 2012/3/18 Gleb Natapov <gleb@redhat.com>:
> > On Sun, Mar 18, 2012 at 03:48:53PM +0530, shashank rachamalla wrote:
> >>
> >> CPU: Core 2, speed 2200.19 MHz (estimated)
> >> Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a
> >> unit mask of 0x00 (Unhalted core cycles) count 100000
> >> CPU_CLK_UNHALT...|
> >>  samples|      %|
> >> ------------------
> >>        1 100.000 /no-vmlinux
> >>
> >>
> > What happens if you run "perf stat -e cycles a.out"?
> 
> This is what i get when I run "perf stat ./a.out" ( with --cpu host
> passed in qemu-kvm )
> 
> Performance counter stats for './a.out':
> 
>      954.925996  task-clock-msecs         #      0.955 CPUs
>              23  context-switches         #      0.000 M/sec
>               0  CPU-migrations           #      0.000 M/sec
>              93  page-faults              #      0.000 M/sec
>      2110635735  cycles                   #   2210.261 M/sec
>       901816391  instructions             #      0.427 IPC
>          247677  cache-references         #      0.259 M/sec
>           15044  cache-misses             #      0.016 M/sec
> 
>     0.999846560  seconds time elapsed
> 
> This is without --cpu host  ( Note that only software events get monitored )
> 
> Performance counter stats for './a.out':
> 
>      913.826372  task-clock-msecs         #      0.990 CPUs
>              13  context-switches         #      0.000 M/sec
>               0  CPU-migrations           #      0.000 M/sec
>              93  page-faults              #      0.000 M/sec
>   <not counted>  cycles
>   <not counted>  instructions
>   <not counted>  cache-references
>   <not counted>  cache-misses
> 
>     0.923182044  seconds time elapsed
> 
> I guess things are working fine with perf. But why not with oprofile ?
> 
Looks like it. I never tried oprofile. Will try to reproduce your
problem and see what oprofile is doing.

--
			Gleb.