Using systemtap on MPI applications

[Olausson, Bjoern]

On Wed, Mar 16, 2016 at 3:07 PM, Frank Ch. Eigler <fche@redhat.com> wrote:
> Hi -
>
>> > "Olausson, Bjoern"  wrote:
>
>> Indeed it would be great if stap would be MPI aware in some way.
>
> "patches welcome" :-)  we'd be glad to advise, but aren't planning
> to undertake the work ourselves very soon.
>

Understood :-)

>
>> Still there is the issue on how to filter what stap is tracing. How
>> would I tell stap to only focus on one particular executable or PID
>> when using the --remote  switch so target() can be used.
>> Any ideas on that?
>
> I believe the "stap -c CMD" and "stap -x PID" options both travel
> through "stap --remote ..." ssh, though of course the former makes a
> lot more sense.  The "-c CMD" may be good enough for MPI purposes.
> And there's always filtering from first principles:
>
>   if (execname() =~ ".*foo.*" && uid() == 44) { }
>
> - FChE


Excuse that stupid question, but I thought using "-c CMD" will always
instantly execute the CMD, so that would not play will with MPI
executed applications :)

But is there a way to pass a string to stap on which I can apply e.g.
your above filter instead of hardcoding the exec name I want to filter
on?

Cheers and thanks a lot for all your quick answers,
Bjoern