[ltt-dev] tracepoint layer and marker layer

[Jiaying Zhang]

On Thu, Sep 18, 2008 at 5:06 AM, Jan Blunck <jblunck at suse.de> wrote:

> On Wed, Sep 17, Jiaying Zhang wrote:
>
> > Hi Folks,
> >
> > I have a general question about LTTng kernel code. As I understand, LTTng
> > adds an extra tracepoint layer between the traced subsystems and the
> > marker layer. The extra code added by the tracepoint layer seems to
> > introduce
> > noticeable overhead according to my measurements. I wonder whether it
> will
> > be more efficient and simpler if we let subsystems call the marker layer
> > directly?
>
> I guess that was how it worked before the tracepoints. Although I don't
> fully understand why the redirection is necessary.
>
> > Any thought?
>
> You could try to disable the
> lttng-instrumentation-*-tracepoints-probes.patch
> patches. These patches register tracepoint probes just to setup a marker. I
> guess this is where the overhead is coming from.
>
> Anyway, do you have numbers that you can share with us? Mathieu still has
> the
> performance numbers with the marker patches in the tracepoints.patch. I
> guess
> he would be glad if he could update them.

Yes. I posted some performance results I measured with the latest 2.6.26
LTTng patches.
Here is my email
http://lists.casi.polymtl.ca/pipermail/ltt-dev/2008-September/000153.html

Jiaying


>
> Regards,
>        Jan
>
> --
> Jan Blunck <jblunck at suse.de>
>
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