Re: [Valgrind-users] Bogus cycles from pthread context switches in callgrind?

[<stu...@nu...>]

Hi Josef,

Thanks very much for the reply.  Comments below...

> > I am running valgrind 3.4.1 on a ppc32 system, using uClibc.  I am 
using 
> > 3.4.1 because 3.5.0 won't compile for ppc32.
> 
> Oh, what is the reason?

http://osdir.com/ml/kde-bugs-dist/2009-08/msg13796.html

I have since tried using 3.6 from the TRUNK however, and I got the same 
problem.

> Yes, it is known that Callgrind sometimes is completely wrong regarding 
calls
> and returns on PPC{32/64}, as well as on the newly introduced ARM 
support in
> the upcoming 3.6.0 (see bug 252091 for the ARM bug report,
>  https://bugs.kde.org/show_bug.cgi?id=252091).
> 
> The reason are some hardcoded assumptions which only are true on 
x86/amd64.
> 
> Can you open a similar bug report for PPC32 for this, describing the 
problems
> you see?

I will get a small sample program to behave badly, and then post it in a 
bug report.

This sucks quite a bit, since callgrind is the only profiling solution 
available on my platform (gprof and orprofile won't work for various 
reasons).

As I said however, the output from callgrind looks relatively sane.  Am I 
a fool to rely on it as some sort of guide for optimisation work?

In the meantime, I will work with the developers to get this fixed.  Am 
happy to do dev work.  It's very important to me that this be resolved.

Thanks again,

Stuart

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