[ltt-dev] UST - Problems in recording trace on a current process

[Pierre-Marc Fournier]

----- Original message -----
> Hi Pierre,
>
> > > You could load in lttv both a userspace trace and a kernel trace that was
> > > recorded at the same time. You would then get appropriate events for
> drawing
> > > the CFV as well as userspace events. For that you would need to make sure
> the
> > > TSC clock is used in ust (see kernelcompat.h).
>
> I verified the clock source in kernelcompat.h. It uses gettimeofday from
> sys/time.h. As you suggested, its imperative that a tsc clock source is used
> when userspace and kernel tracing are combined.
>
> I went through the timesource patch of lttng,x86-trace-clock.patch, a patch
> dealing with switching clocksource of x86 architecture, to tsc.
>
> Can you suggest as to how we can change the clocksource to tsc in ust?

Just replace the time source function in kernelcompat.h with the one that is commented and that contains asm code to read the tsc.

>
> Regards,
> Naren