[Beowulf] itanium vs. x86-64

Eric Thibodeau kyron at neuralbs.com
Wed Feb 11 07:12:43 EST 2009


Peter Kjellstrom wrote:
> On Wednesday 11 February 2009, Eric Thibodeau wrote:
>   
>> Tom Elken wrote:
>>     
>>>> Which profilers can
>>>> benefit from all this info?
>>>>         
>>> We have found Oprofile to be a useful text-oriented tool:
>>> http://oprofile.sourceforge.net/about/
>>> From the Overview on this page:
>>> "OProfile is a system-wide profiler for Linux systems, capable of
>>> profiling all running code at low overhead. OProfile is released under
>>> the GNU GPL.
>>>
>>> It consists of a kernel driver and a daemon for collecting sample data,
>>> and several post-profiling tools for turning data into information.
>>>
>>> OProfile leverages the hardware performance counters of the CPU to enable
>>> profiling of a wide variety of interesting statistics, which can also be
>>> used for basic time-spent profiling. All code is profiled: hardware and
>>> software interrupt handlers, kernel modules, the kernel, shared
>>> libraries, and applications."
>>>
>>> -Tom
>>>       
>> Yes, Oprofile is a fantastic switch to turn on for profiling the entire
>> system.
>>     
>
> Compared to Tau it is _very_ simplistic and won't take long to learn (that 
> scores points for both Oprofile and Tau depending on what you want).
>   
Well, I was assuming this was the Beowulf ML and that people are usually 
interested in parallel stuff ;) I'll agree that, TAU is a beast, mostly 
due to its versatility which requires attention when setting up. But, 
IMHO, using it is quite simple and it provides intuitive and powerful 
viewing tools. The only issue I have for the moment is one of the 
interfaces being very slow to generate graphs...can't pinpoint 
why...guess I'll have to profile TAU :P

>> Now, last time I tried to use it it totally crashed my system.
>>     
>
> I've used Oprofile many times over the last few years and on many different 
> systems and have yet to see one crash.
>   
Yeah, like I said, _my_ single use crashed the system and I had to move 
forward.
> ...
>
> Worth noting here is that Oprofile uses its own kernel module (which ships 
> with current kernels from both CentOS-5/RHEL5 and kernel.org) while Tau 
> depends on PAPI.
>
> PAPI typically uses the perfctr kernel module/patch which you'll have to patch 
> into your kernel on your own and it conflicts (run time) with Oprofile. 
> Alternatively you can build PAPI on top of perfmon2 (also probably a kernel 
> patch) but this I havn't tried.
>   
Yes in both cases. I just recently patched a 2.6.28 gentoo-sources with 
no problems but only using the perfctr patch set from it's homepage (the 
one packaged with PAPI lags too much)
> /Peter
>   
Eric

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