perf top broken on ppc64

perf top broken on ppc64

[Alexander Graf]

Hi,

While trying to find out performance bottlenecks in KVM for PowerPC I figured I'd try and use "perf top" to see what's going on in the system. This works great on my G4, but doesn't on the Powerstation (970MP).

The only weird thing I can imagine about this setup is that I'm running 32 bit userland on a 64 bit kernel. So I went ahead and compiled perf for ppc64 - without any change:

# file `which perf`
/root/bin/perf: ELF 64-bit MSB executable, 64-bit PowerPC or cisco 7500, version 1 (SYSV), for GNU/Linux 2.6.4, dynamically linked (uses shared libs), not stripped

Whenever I call 'perf top' I get the following output:


-------------------------------------------------------------------------------------------------------
   PerfTop:   57159 irqs/sec  kernel:100.0% [1000Hz cycles],  (all, 4 CPUs)
-------------------------------------------------------------------------------------------------------

             samples  pcnt  DSO
             _______ _____  


Where there would usually be functions being listed I don't get anything.
The interesting part is that 'perf record -g' and 'perf report -g' work just fine. I get reasonable output. I also had 'perf top' with the exact same binaries working by accident too once. But then I rebooted and not it's all moot again.

So the question is: why doesn't the top function work for me?


Thanks,

Alex

Re: perf top broken on ppc64

[Ian Munsie]

Excerpts from Alexander Graf's message of Wed Apr 21 09:21:36 +1000 2010:
> Hi,
> 
> While trying to find out performance bottlenecks in KVM for PowerPC I
> figured I'd try and use "perf top" to see what's going on in the
> system. This works great on my G4, but doesn't on the Powerstation
> (970MP).
> 
> The only weird thing I can imagine about this setup is that I'm
> running 32 bit userland on a 64 bit kernel. So I went ahead and
> compiled perf for ppc64 - without any change:

I'm using 32 bit userland and 64 bit kernel on a PowerPC box and it's working for me.
Are you building perf from the tip tree?

Cheers,
-Ian

Re: perf top broken on ppc64

[Alexander Graf]

On 21.04.2010, at 07:29, Ian Munsie wrote:

> Excerpts from Alexander Graf's message of Wed Apr 21 09:21:36 +1000 2010:
>> Hi,
>> 
>> While trying to find out performance bottlenecks in KVM for PowerPC I
>> figured I'd try and use "perf top" to see what's going on in the
>> system. This works great on my G4, but doesn't on the Powerstation
>> (970MP).
>> 
>> The only weird thing I can imagine about this setup is that I'm
>> running 32 bit userland on a 64 bit kernel. So I went ahead and
>> compiled perf for ppc64 - without any change:
> 
> I'm using 32 bit userland and 64 bit kernel on a PowerPC box and it's working for me.
> Are you building perf from the tip tree?

I'm using kvm.git which is pretty close to tip. The version says something 2.6.34-rc3'ish. Has anything significantly changed since then?

Either way - I'll give it a try.


Alex

Re: perf top broken on ppc64

[Ian Munsie]

> > I'm using 32 bit userland and 64 bit kernel on a PowerPC box and it's working for me.
> > Are you building perf from the tip tree?
> 
> I'm using kvm.git which is pretty close to tip. The version says something 2.6.34-rc3'ish. Has anything significantly changed since then?
> 
> Either way - I'll give it a try.


Hey Alex,

Did perf from the tip tree work for you?

Cheers,
-Ian

Re: perf top broken on ppc64

[Alexander Graf]

Am 27.04.2010 um 02:30 schrieb Ian Munsie <imunsie@au1.ibm.com>:

>>> I'm using 32 bit userland and 64 bit kernel on a PowerPC box and  
>>> it's working for me.
>>> Are you building perf from the tip tree?
>>
>> I'm using kvm.git which is pretty close to tip. The version says  
>> something 2.6.34-rc3'ish. Has anything significantly changed since  
>> then?
>>
>> Either way - I'll give it a try.
>
>
> Hey Alex,
>
> Did perf from the tip tree work for you?

Howdy,

Sorry - I left for vacation without replying :).

I tried perf from tip with kvm.git kernel and that did show the same  
effects. I didn't get around to also try to run the tip kernel, and  
won't be within this week :o


Greetings from Gran Canaria,

Alex

>