Using markers

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

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.

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!

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