[lttng-dev] calibrate ?

[Thibault, Daniel]

I took note of http://lwn.net/Articles/492296/ (Mathieu Desnoyers, Julien Desfossez, David Goulet; LTTng 2.0: Tracing for power users and developers - part 2, April 18, 2012) and ran this (using the Ubuntu lttng packages this time; babeltrace is 1.0.0~rc1-0ubuntu1 and lttng is 2.0.1-0ubuntu1 [liblttng-ctl0, lttng-tools] and 2.0.2-0ubuntu1 [liblttng-ust0, lttng-modules-dkms]):

$ sudo -H lttng create calibrate-session
Session calibrate-session created.
Traces will be written in /root/lttng-traces/calibrate-session-20130213-143220
$ sudo -H lttng enable-event calibrate-event -k --function lttng_calibrate_kretprobe
kernel event calibrate-event created in channel channel0
$ sudo -H lttng add-context -k -t perf:LLC-load-misses -t perf:LLC-store-misses -t perf:LLC-prefetch-misses
Error: perf:LLC-prefetch-misses: Add kernel context failed
kernel context perf:LLC-store-misses added to all channels
kernel context perf:LLC-load-misses added to all channels
Warning: Some command(s) went wrong
$ sudo -H lttng start
Tracing started for session calibrate-session
$ for a in $(seq 1 10); do \
> sudo -H lttng calibrate -k --function; \
> done
Kernel calibration done
Kernel calibration done
Kernel calibration done
Kernel calibration done
Kernel calibration done
Kernel calibration done
Kernel calibration done
Kernel calibration done
Kernel calibration done
Kernel calibration done
$ sudo -H lttng destroy
Session calibrate-session destroyed at /root
$ sudo -H babeltrace /root/lttng-traces/calibrate-session-20130213-143220
error syntax error
[error] Error creating AST
[warning] Unable to open trace metadata for path "/root/lttng-traces/calibrate-session-20130213-143220/kernel".
[warning] [Context] Cannot open_trace of the format /root/lttng-traces/calibrate-session-20130213-143220/kernel .

[warning] [Context] opening trace "/root/lttng-traces/calibrate-session-20130213-143220/kernel" from /root/lttng-traces/calibrate-session-20130213-143220 for reading.

##########
Now, the "Error: perf:LLC-prefetch-misses: Add kernel context failed" is probably because 'dmesg | grep "generic r"' reports just two generic registers, although it seems odd the error would occur on the first context attempt and not the last.

My real problem is with the trace thus generated and babeltrace's handling of it.  It consists of five files: metadata and channel0_0 through channel0_3.  There is no kernel file.

I moved the trace to another machine and tried a more up-to-date babeltrace (babeltrace-1.0.3+-217b52c), with little difference:

error syntax error
[error] Error creating AST
[warning] Unable to open trace metadata for path "/home/daniel/lttng-traces/calibrate-session-20130213-143220/kernel".
[warning] [Context] Cannot open_trace of format ctf at path /home/daniel/lttng-traces/calibrate-session-20130213-143220/kernel.

[warning] [Context] cannot open trace "/home/daniel/lttng-traces/calibrate-session-20130213-143220/kernel" from /home/daniel/lttng-traces/calibrate-session-20130213-143220 for reading.
[error] Cannot open any trace for reading.

Daniel U. Thibault
R & D pour la défense Canada - Valcartier (RDDC Valcartier) / Defence R&D Canada - Valcartier (DRDC Valcartier)
Cyber sécurité pour les missions essentielles (CME) / Mission Critical Cyber Security (MCCS)
Protection des systèmes et contremesures (PSC) / Systems Protection & Countermeasures (SPC)
2459 route de la Bravoure
Québec, QC  G3J 1X5
CANADA
Vox : (418) 844-4000 x4245
Fax : (418) 844-4538
NAC : 918V QSDJ <http://www.travelgis.com/map.asp?addr=918V%20QSDJ>
Gouvernement du Canada / Government of Canada
<http://www.valcartier.drdc-rddc.gc.ca/>