Re: Using user-defined traces

* Daniel Zinn ([email protected]) wrote:
> Hello,
> 
> I would like to use the 3rd option to trace userspace programs as described in 
> the README of the userspace package. This is the option in which a sparate 
> tracefile is written to /tmp, the sample is sample-highspeed.c.
> 
> Following the README file (compiling everything, running, and copying the 
> separate trace to the trace folder), I get the following error message when I 
> want to display the data:
> 
> ** ERROR **: Kernel/LTTV event size differs for event core.facility_load: 
> kernel 16, LTTV 44
> 
> lttv does terminate then (this error is generated when the userspace trace 
> file is read). If I do not copy the userspace-trace file into the trace 
> directory I can view the trace, however I still do get warnings like 
> 
> ** (lttv.real:4901): WARNING **: Facility checksum mismatch for facility 
> core : kernel 0xB96B8A8D vs XML 0x1212DF53
> 
> I did go through the source files (with some ddd) and noticed that there is a 
> FIXME in ltt/facility.c:
>       // FIXME if(checksum == f->checksum) {
>         generateFacility(f, fac, checksum);
>         generated = TRUE;
>       //}
> 
> How is the checksum for the "kernel" computed? Why does it not match the 
> checksum that is computed based on the XML file that was written by 
> the ?same? kernel?
> 
> What else might be an issue that I overlook? I am running the tracer from a 
> different machine than I do the tracing - this might have something to do 
> with my problems, but I cannot change the production system where the tracing 
> is happening.
> 

Hi Daniel,

I see that you use very recent LTTng versions. Which ones are you using
exactly?

About the checksums: the whole facilities and mandatory XML descriptions
are about to be obsoleted. This warning is just due to this transition
period.

Mathieu

> Thank you,
>       Daniel
> -- 
> "The acquisition of wealth is no longer the driving force in our
>  lives ... we work to better ourselves and the rest of humanity."
> 
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-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68