[Beowulf] itanium vs. x86-64

Peter Kjellstrom cap at nsc.liu.se
Wed Feb 11 00:39:02 PST 2009

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).

> 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.


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.

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