[ltt-dev] LTTng kernel tracing with -a (append) feature

[srikanth krishnakar]

Hello Mathieu,

Thanks a lot for your quick response !!

If i interpret your pointers correctly, then I understand,
destroying+Appending trace result to previously destroyed trace session will
not write matching meta-data to old channels, right ? which further results
in difference in event sizes !

So correcting my execution script :

###################################
#!/bin/bash

mount -t debugfs debugfs /mnt/debug

ltt-armall

lttctl -C -w /home/root/trace1 trace1

lttctl -s trace1
sleep 2

lttctl -p trace1

#lttctl -D trace1  # Pause and destroy a trace named trace1 and
*<<<<< Eliminated
the Destroy operation *
sleep 10

lttctl -C trace1 -w  /home/root/trace1 *-a*    *<<< Retain append option for
continuation with existing data*

lttctl -s trace1
sleep 2

lttctl -p trace1

lttctl -D trace1

ltt-disarmall

lttv -m textDump -t /home/root/trace1
###################################

Does it looks OK ? Or still needs correction ?

And also one more small doubt regarding difference among '-c' && '-C'
options, any significant changes that result after swapping these ?

Thanks & Regards
-Srikant
----------

On Tue, Dec 21, 2010 at 12:57 AM, Mathieu Desnoyers <
mathieu.desnoyers at polymtl.ca> wrote:

> * srikanth krishnakar (skrishnakar at gmail.com) wrote:
> > Hello Mathieu,
> >
> > I am trying to test the append functionality of the ltt-control :
> >
> > ltt-control : 0.79
> > lttv-0.12.31
> > Linux-2.6.32.9
> >
> > #############################################
> >
> > #!/bin/sh
> > mount -t debugfs debugfs /mnt/debug
> > *ltt-armall*
> > *
> > *
> > *lttctl -C -w  /home/root/trace1 trace1*
> > *
> > *
> > *lttctl -s trace1*
> > sleep 2
> >
> > *lttctl -p trace1*
> > *
> > *
> > # Pause and destroy a trace named trace1 and
>
> "-a" will not work if you stop+destroy a trace session and try appending
> to the saved trace from a new trace session. The typical use-case is to
> stop tracing (keeping the trace session alive), and then later on start
> tracing again (within the same trace session), and there use the -a
> switch to append to the existing trace files.
>
> The problem is that the metadata (event IDs, event sizes, etc) are
> supposed to be invariant across a whole trace session, but by appending
> to the old trace files, you are combining two trace sessions together
> with conflicting metadata.
>
> Thanks,
>
> Mathieu
>
>
> > *lttctl -D trace1*
> >
> > *lttctl -C trace1 -w  /home/root/trace1 -a                <<<<< Appending
> > trace to existing one*
> > *
> > *
> > *lttctl -s trace1*
> > sleep 2
> >
> > *lttctl -p trace1*
> > *
> > *
> > *lttctl -D trace1*
> > *
> > *
> > *ltt-disarmall*
> >
> > *lttv -m textDump -t /home/root/trace1*
> > *
> > *
> > *###########################################*
> >
> >
> > Executing the above steps without  *'-a'* (append) options works
> perfectly
> > and i am able to get the trace output after dumping. But the problem lies
> in
> > when I try to execute with '-a' (append) feature, then the error
> displayed
> > is difference in kernel event sizes and unable to dump the ouput
> >
> >
> --------------------------------------------------------------------------------
> > ** ERROR **: Kernel/LTTV event size differs for event timer_set: kernel
> 11,
> > LTTV 12
> > aborting...
> > /usr/bin/lttv: line 15:  1516 Aborted                 $0.real $*
> >
> --------------------------------------------------------------------------------
> >
> > Is there anything missing or am i running out of process that needs to be
> > followed to obtain the appended trace result ??
> >
> > Is there any info in LTTng user manual that shows the steps to follow for
> > using append feature of LTT-CONTROL in kernel tracing ?
> >
> > Thanks in advance !!!
> > -S
> >
> >
> > --
> > "The Good You Do, The Best You GET"
> >
> > Regards
> > Srikanth Krishnakar
> > **********************
>
> --
> Mathieu Desnoyers
> Operating System Efficiency R&D Consultant
> EfficiOS Inc.
> http://www.efficios.com
>



-- 
"The Good You Do, The Best You GET"

Regards
Srikanth Krishnakar
**********************
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