[ltt-dev] lockdep trace

[Mathieu Desnoyers]

* Alexandre Montplaisir (alexandre.montplaisir at polymtl.ca) wrote:
> On 11-03-16 10:34 AM, Mathieu Desnoyers wrote:
> > * Harald Gustafsson (hgu1972 at gmail.com) wrote:
> >>> Sounds good. Which version of lttng are you using ?
> >> I have tried this both on my x86 machine using the ubuntu ppa package
> >> which uses kernel 2.6.35-24 and to me unknown lttng version. But I
> >> also tried this on a ARM development board with kernel 2.6.34 and
> >> lttng version 0.221 without success.
> >>
> >>> In your kernel config, under the "Kernel Hacking" menu, did you enable
> >>> the options related to lock dependency debug, and lock proving and so
> >>> on ? You should ensure that CONFIG_LOCKDEP is selected in your kernel
> >>> config file.
> >> In the ubuntu-ppa lttng package only LOCKDEP_SUPPORT is enabled, not
> >> LOCKDEP and not LOCKDEP_DEBUG, neither DEBUG_LOCK_ALLOC,
> >> PROVE_LOCKING, LOCK_STAT or any of the
> >> INLINE_{READ|WRITE|SPIN}_LOCK_*. The same configuration have been used
> >> on the ARM board.
> >>
> >> Hence, I should enable LOCKDEP, LOCKDEP_DEBUG, DEBUG_LOCK_ALLOC and
> >> PROVE_LOCKING.
> > PROVE_LOCKING might not be needed (and is quite heavyweight), but yes,
> > enabling at the very least LOCKDEP is needed.
> >
> > Thanks,
> >
> > Mathieu
> >
> 
> Indeed, the packaged kernel is built using all the default LTTng options.
> 
> Mathieu, is there a big overhead in enabling CONFIG_LOCKDEP? If not,
> should it (or any other non-default options) be enabled in the package?

Yes, there is a big overhead to it.

What I should do is to do not build the lockdep tracing module if
CONFIG_LOCKDEP is not enabled.

Mathieu

> 
> -- 
> 
> Alexandre Montplaisir
> DORSAL lab,
> École Polytechnique de Montréal
> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com