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Re: Using markers

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.

> 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 = 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
(<>).  I've tested the latest cvs systemtap with
The current version appears to be:

In the version I'm using, markers look like the trace mark example you
listed above.

David Smith
Red Hat
256.217.0141 (direct)
256.837.0057 (fax)

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