Re: backtrace using LTTng in Kernel

  Hi Mathieu,

Thanks for the pointers. 
I will keep you posted with my implementation.
Thanks indeed
Sagar





On Mon, 18 Jun 2007 Mathieu Desnoyers wrote :
>* Sagar Borikar ([email protected]) wrote:
> >
> > Hello,
> >
> > I am consistently using LTTng for tracing the MIPS system. While adding the events, I was bit stuck in finding out which of the kernel memcpy function is consuming lot of CPU. I need to search a kernel call which is having highest probability of stalling the cpu. So in short, I would like to see backtrace in LTTng. Can anyone point me out about using backtracking feature in LTTng if at all it is present?
> >
> > Thanks in advance,
> >
>
>Hi Sagar,
>
>You would have to port part of ltt/probes/ltt-probe-stack_arch_i386.c
>(there is also a x86_64 implementation) to MIPS. You take the standard
>kernel stack trace (see arch/mips/kernel/stacktrace.c) and, instead of
>sending the output well formatted to printk, you follow what is done in
>LTTng to 1 - calculate the size of the sequence in the first pass and 2
>- copy the data into the sequence in the 2nd pass.
>
>Note that the way function calls are put is very important: I use an
>address that is on the current thread's stack as a start value; it must
>not change between the 1st and the 2nd pass.
>
>If you can do that on recent kernels (2.6.22-rc4-mm2), I could integrate
>that to LTTng, that would be great :)
>
>Mathieu
>
> > Sagar
> >
>
> > _______________________________________________
> > Ltt-dev mailing list
> > [email protected]
> > http://listserv.shafik.org/mailman/listinfo/ltt-dev
>
>
>--
>Mathieu Desnoyers
>Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
>OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68

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