Re: Using markers

["Julio M. Merino Vidal" <jmerino at ac dot upc dot edu>]

On 03/12/2007, at 17:28, David Smith wrote:

> Julio M. Merino Vidal wrote:
> > Hello,
> >
> > I am interested in getting traces of the SPU scheduler in the Cell
> > platform.  SystemTap seems like an excellent candidate to take those
> > traces but I'm having some trouble getting it to work as I need.   
> > Using
> > probes at function entry/exit points works in most cases, which is
> > great, but some of the functions I'm interested in tracing are  
> > declared
> > as static and therefore the debugging information lacks some  
> > details to
> > access such as, for example, their parameters.
> >
> > So I've considered using markers as the documentation explains, but I
> > cannot get them to work.  Based on bug 4446, I understand that the
> > CONFIG_MARKERS support that is in Linux 2.6.23 is not yet  
> > supported by
> > SystemTap (even though I did try them), so I tried to use the macros
> > defined in stapmark.h as shipped by SystemTap's Git repository.  But
> > those don't seem to work either.
>
> We should probably remove stapmark.h since we don't support it.

fche already did it.

> > Here is what I added in the probe's point:
> >
> > trace_mark(spufs_bind_context_new, "spu %d ctx %p", spu->number,  
> > ctx);
> > STAP_MARK_NN(spufs_bind_context_old, (int64_t)spu->number,  
> > (int64_t)ctx);
> >
> > And here is my test stp file:
> >
> > probe test.new = kernel.mark("spufs_bind_context_new") { name =  
> > "new" }
> > probe test.old = kernel.mark("spufs_bind_context_old") { name =  
> > "old" }
> > probe test.* { log("marker ".name." hit") }
> >
> > But then, when running stap on this script, none of the two  
> > markers can
> > be found.
> >
> > Am I doing something incorrectly?  Do I have to apply some kind of
> > unofficial patch to either the kernel or systemtap?
> >
> > Thanks, and kudos for this great tool!
>
> Systemtap supports the latest markers patches from the lttng project
> (<http://ltt.polymtl.ca/>).  I've tested the latest cvs systemtap with
> <http://ltt.polymtl.ca/lttng/patch-2.6.24-rc2-lttng-0.10- 
> pre23.tar.bz2>
> and
> <http://ltt.polymtl.ca/lttng/patch-2.6.24-rc3-git1-lttng-0.10- 
> pre33.tar.bz2>
> The current version appears to be:
> <http://ltt.polymtl.ca/lttng/patch-2.6.24-rc3-git3-lttng-0.10- 
> pre36.tar.bz2>
>
> In the version I'm using, markers look like the trace mark example you
> listed above.

Aha!  So all the "fixes" I posted to bug 4446 are useless ;-)

Thanks for the info!

--
Julio M. Merino Vidal <jmerino@ac.upc.edu>