[lttng-dev] [RFC Patch Tools 0/4] Configurable lttng-probe modules

David Goulet dgoulet at efficios.com
Thu Apr 10 15:45:51 EDT 2014

On 03 Apr (12:57:43), Jan Glauber wrote:
> Hi LTTng'ers,
> I've asked briefly for the configurable probes feature at the Tracing summit,
> here is an RFC how we could implement it.
> Why I want to have this feature:
> Currently the LTTng probes that are loaded when a session is created are defined
> in a static list. If the user wants to change the loaded probes (for instance
> disable the very noisy rcu) then lttng-tools must be recompiled or the modules must
> be blacklisted or deleted. I also found that in our embedded environment the default
> busybox configuration is to disable the blacklist feature, so blacklisting is not an
> option.
> Therefore I want to have a more flexible way of defining which probes to load
> on session start. We could use an environment variable that (if present)
> overrides the default and only loads the probes named in the variable.
> Patch 1 is a cleanup and patch 2 & 3 are preparation for the feature in patch 4.
> Please review and give feedback if this approach is feasible.

Hi Jan,

First of all, thanks for this! Except some syntax issue, this looks
great! Sorry took a while to respond, busy busy improving lttng :P.

Before we go further in mergin this, I see you took the approach of
adding an env. variable to provide the list of probes you want to load.
Right now in the upstream master (for 2.5), we have the support for a
configuration file for lttng-sessiond. Could it be a way you would
prefer (or use) instead of env. var? I understand that embedded stuff, a
conf file might not be preferable.

Anyhow, I'm comfortable merging this and adding this env. var but an
option in the configuration file could also be awesome! :)

One thing that would be great if you have a minute, is to send me a
patch for the man page update of that new variable.


> thanks,
> Jan
> ---
> Harman Becker Automotive GmbH
> System Profiling & Optimizing Team
> Jan Glauber (4):
>   Use common functions for module loading and unloading
>   Seperate probe modules from control modules
>   Remove required parameter from module parameters
>   Dynamic probe list support
>  src/bin/lttng-sessiond/kern-modules.h |    3 +-
>  src/bin/lttng-sessiond/modprobe.c     |  292 ++++++++++++++++++---------------
>  src/common/defaults.h                 |    3 +
>  src/common/utils.c                    |   10 ++
>  src/common/utils.h                    |    1 +
>  5 files changed, 172 insertions(+), 137 deletions(-)
> -- 
> _______________________________________________
> lttng-dev mailing list
> lttng-dev at lists.lttng.org
> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
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