Re: PEBS availability

[David Ahern <dsahern@gmail.com>]

On 05/24/11 09:49, Pádraig Brady wrote:
> Hi,
> 
> I've just got a shiny new i3-2310M and am a
> bit surprised that `perf` isn't listing
> detailed stats like L1 cache misses etc.

'perf list | grep Hardware' will show you counters recognized by perf
(perhaps with F15, "perf list hw"  works). You can add more counters
using the -e option.

You might also want to try 2.6.39 kernel and upstream version of perf.
Ingo added a number of default counters to perf stat.

David

> 
> $ perf stat true
> 
>  Performance counter stats for 'true':
> 
>              1,239 cache-misses             #      1.555 M/sec
>              9,314 cache-references         #     11.693 M/sec
>              3,940 branch-misses            #      4.871 %
>             80,885 branches                 #    101.546 M/sec
>            403,808 instructions             #      0.000 IPC
>      <not counted> cycles
>                 81 page-faults              #      0.102 M/sec
>                  0 CPU-migrations           #      0.000 M/sec
>                  1 context-switches         #      0.001 M/sec
>           0.796537 task-clock-msecs         #      0.032 CPUs
> 
>         0.024654938  seconds time elapsed
> 
> I searched for a while but found it _very_ difficult
> to find info on what was available on particular intel CPUs.
> 
> I did see in the "Nehalem Core PMU programming guide":
> http://software.intel.com/file/30320
> that the above stats are core features and that the other
> counters I mentioned are PEBS (Precise Event Based Sampling)
> and are not available on all systems.
> 
> So am I out of look with my new i3 sandy bridge CPU?
> Are PEBS restricted to i7 versions only?
> Is this documented anywhere?
> 
> Maybe I need some kernel support as hinted at by:
> http://lwn.net/Articles/430100/
> My kernel is 2.6.38.6-27.fc15.x86_64
> 
> cheers.
> Pádraig.
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