[lttng-dev] calibrate ?

[Mathieu Desnoyers]

The calibrate function is just a rough sketch really. It could use some
more work, but it's very low priority for now.

If you feel like it, please open a feature request for this against
lttng-tools.

Thanks,

Mathieu

* Thibault, Daniel (Daniel.Thibault at drdc-rddc.gc.ca) wrote:
> 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)
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> 
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-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com