Re: PEBS availability

["Pádraig Brady" <P@draigBrady.com>]

On 24/05/11 21:37, Arun Sharma wrote:
> On Tue, May 24, 2011 at 04:49:27PM +0100, Pádraig Brady wrote:
>>
>> So am I out of look with my new i3 sandy bridge CPU?
>> Are PEBS restricted to i7 versions only?
>> Is this documented anywhere?
> 
> i3 and i7 are marketing terms that don't mean much.
> Engineers care more about the output of:
> 
> #!/usr/bin/env python
> 
> import struct
> 
> def cpuid(eax):
>     f = open("/dev/cpu/0/cpuid", "rb")
>     f.seek(eax)
>     data = f.read(16)
>     f.close()
>     return struct.unpack('IIII', data)
> 
> print "%x" % cpuid(1)[0]
> 
>>
>> 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
> 
> Your kernel probably has support for most of PEBS. What's missing is
> support in user space for all the events in manuals.
> 
> http://thread.gmane.org/gmane.comp.linux.perfmon2.devel/2912

Well that was easy.
My Fedora 15 kernel was missing support for sandy bridge PEBS,
and creating a new bzImage with the patch I referenced makes
the counters available:

old-kern:$ perf stat -e L1-dcache-loads true
  Error: L1-dcache-loads event is not supported.
  Fatal: Not all events could be opened.

new-kern:$ perf stat -e L1-dcache-loads true
  98,331 L1-dcache-loads

cheers,
Pádraig.