Re: Help adding trace events to xHCI

Re: Help adding trace events to xHCI

[Mathieu Desnoyers]

* Sarah Sharp (sarah.a.sharp@linux.intel.com) wrote:
> On Fri, Jul 12, 2013 at 07:25:59AM +0300, Kalle Valo wrote:
> > Sarah Sharp <sarah.a.sharp@linux.intel.com> writes:
> > 
> > > My initial list of specific trace points was something like:
> > >
> > > 1. xHCI host initialization and shutdown
> > >
> > > 2. xHCI memory allocation (dynamic ring resizing, structure alloc, etc)
> > >
> > > 3. A few individual xHCI host controller command tracepoints:
> > >    * status only for all completed commands
> > >    * Address Device command status and output
> > >    * Configure Endpoint and Evaluate Context output
> > >    * individual trace points for other xHCI commands
> > >
> > > 4. Tracepoints for all USB transfer types:
> > >    * Control TX output (only for non-successful transfers)
> > >    * Bulk TX
> > >    * Interrupt TX
> > >    * Isoc TX
> > >
> > > 5. URB cancellation
> > >
> > > And probably more.  Basically, I want to be able to control what gets
> > > printed, based on where I think the xHCI bug might be.  Does that sound
> > > reasonable?
> > 
> > Instead of individual trace points for command I would recommend to
> > consider just pushing the whole command buffer to the trace point and
> > parse the command in trace-cmd plugin in user space. Kernel code would
> > be simpler that way.
> 
> 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?

(CCing lttng-dev)

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
- http://lttng.org

Thanks,

Mathieu

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

Re: Help adding trace events to xHCI

[Mark Wielaard]

Hi Mathieu,

On Fri, Jul 12, 2013 at 01:08:28PM -0400, Mathieu Desnoyers wrote:
> * Sarah Sharp (sarah.a.sharp@linux.intel.com) wrote:
> > 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? Can tools use lttng-ust and <sys/sdt.h> tracepoints
interchangeably by parsing the ELF notes described in
http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation

Thanks,

Mark

Re: Help adding trace events to xHCI

[Mark Wielaard]

Hi Mathieu,

On Fri, Jul 12, 2013 at 01:08:28PM -0400, Mathieu Desnoyers wrote:
> * Sarah Sharp (sarah.a.sharp@linux.intel.com) wrote:
> > 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? Can tools use lttng-ust and <sys/sdt.h> tracepoints
interchangeably by parsing the ELF notes described in
http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation

Thanks,

Mark

Re: Help adding trace events to xHCI

[Mathieu Desnoyers]

* Mark Wielaard (mjw@redhat.com) wrote:
> Hi Mathieu,
> 
> On Fri, Jul 12, 2013 at 01:08:28PM -0400, Mathieu Desnoyers wrote:
> > * Sarah Sharp (sarah.a.sharp@linux.intel.com) wrote:
> > > 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