[lttng-dev] [RELEASE] LTTng modules 2.5.0

Mathieu Desnoyers mathieu.desnoyers at efficios.com
Wed Jul 16 18:30:23 EDT 2014

The LTTng modules provide Linux kernel tracing capability to the LTTng
2.x tracer toolset.

New and noteworthy:

- State dump of block devices,
- State dump of file descriptor flags and modes,
- 3.15 Linux kernel support,
- v4lv2 instrumentation support,
- MIPS32 system call tracing,
- New /proc/lttng-logger ABI.

How to use the new /proc/lttng-logger ABI:

>From the command line (for instance):

Start lttng-sessiond as root,

# lttng-sessiond

Start tracing from root or from a user belonging to the
"tracing" group:

% lttng create
% lttng enable-event -k lttng-logger

Write event payload data to /proc/lttng-logger (from any user,
does not need to be in any group):

% echo -n "Some message" > /proc/lttng-logger

% Stop tracing, view trace

% lttng stop
% lttng view

You should see:

[10:44:24.810273367] (+?.?????????) thinkos lttng_logger: { cpu_id = 3 }, { _msg_length = 12, msg = "Some message" }

It is a quick and easy way to trace some events from user-space through
the kernel tracer. It is much more basic than UST: lttng-logger is slower
(involves system call round-trip to the kernel) and only supports
logging strings. But it's very quick and easy to use, especially from

2014-07-16 (Take Your Poet to Work Day) LTTng modules 2.5.0
        * (no change)

Project website: http://lttng.org
Download link: http://lttng.org/download
(please refer to the README files for installation instructions and
lttng-tools doc/quickstart.txt for usage information)

Mathieu Desnoyers
EfficiOS Inc.

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