Re: Help adding trace events to xHCI

* Mark Wielaard (mjw@redhat.com) wrote:

Hi Mathieu,

On Fri, Jul 12, 2013 at 01:08:28PM -0400, Mathieu Desnoyers wrote:

quoted

* Sarah Sharp (sarah.a.sharp@linux.intel.com) wrote:

quoted

Thanks for the suggestion.  I'm not familiar with all the userspace
tools for trace events, so I didn't know about the command parser.  Is
there documentation or a list of resources for all the userspace trace
event plugins?  If so, can you give us a pointer to it?

You might want to try out LTTng-UST. It provides TRACEPOINT_EVENT() and
tracepoint() for user-space instrumentation. See:

- https://lttng.org/files/doc/man-pages/man3/lttng-ust.3.html

Is that build on the <sys/sdt.h> ust probe points as embedded in glibc
for example that gdb and systemtap use to access user space trace
points?

LTTng-UST tracepoints are not built on sdt.h, but they can optionally
emit sdt.h instrumentation. All you need to do is run:

./configure --with-sdt

when configuring lttng-ust, and after a make install, sdt.h
STAP_PROBEV() will be emitted whenever a lttng-ust tracepoint() macro is
used in the system.

Can tools use lttng-ust and <sys/sdt.h> tracepoints
interchangeably by parsing the ELF notes described in
http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation

Since lttng-ust tracepoints emit sdt.h instrumentation, yes. However,
please note that the reverse is not possible: sdt.h instrumentation does
not allow tracing with LTTng-UST.

Thanks,

Mathieu

Thanks,

Mark

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com