[ltt-dev] Problems on usage of markers in combination with tracepoint probes

[Mathieu Desnoyers]

* jerome zh (jeromezhr at gmail.com) wrote:
> Hi Mathieu,
> 
> I did some read on the paper of lttng project, especially your Ph.D thesis.
> I have got some questions:
> 
> 1. Why and when should the marker be used in combination with tracepoint probes?

LTTng is not aware of tracepoints at the moment. So a marker
"declaration" is required to declare the event type and fields. A
tracepoint probe needs to be connected on the tracepoint to write the
event data into the trace stream. See ltt/ltt-type-serializer.c for
details.

> 2. If I want to insert tracepoints in kernel files, such as
> net/ipv4/ip_input.c, can I implement the tracepoints as module?
> Since samples given in samples/tracepoint do NOT show this.

The tracepoint itself must be inserted into the kernel code.

The tracepoint probes, alongside with marker type declaration, must go
into ltt/probes/, which are basically kernel modules.

Thanks,

Mathieu


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