LTTng 2.0 modules

Mathieu Desnoyers
July 19, 2011

LTTng 2.0 kernel modules build against a vanilla or distribution kernel, without
need for additional patches. Other features:

- Produces CTF (Common Trace Format) natively,
  (http://www.efficios.com/ctf)
- Function tracer, perf counters and kprobes support,
- Integrated interface for both kernel and userspace tracing,
- Have the ability to attach "context" information to events in the
  trace (e.g. any perf counter, pid, ppid, tid, comm name, etc).
  basically, all the extra information fields to be collected with
  events are optional, specified on a per-tracing-session basis
  (except for timestamp and event id, which are mandatory).

To build and install, you will need to have your kernel headers available (or
access to your full kernel source tree), and use:

make
make modules_install

If you need to specify the target directory to the kernel you want to build
against, use:

KERNELDIR=path_to_kernel_dir make
KERNELDIR=path_to_kernel_dir make modules_install

Use lttng-tools (git://git.lttng.org/lttng-tools.git) to control the tracer.
LTTng tools should automatically load the kernel modules when needed.

Use Babeltrace (git://git.efficios.com/babeltrace.git) to print traces as a
human-readable text log.

Please note that the LTTng-UST 2.0 (user-space tracing counterpart of LTTng 2.0)
is still in active development and not released yet.

So far, it has been tested on vanilla kernels 2.6.38 and 2.6.39 (on x86 at the
moment). It should work fine with newer kernels and other architectures, but
expect build issues with kernels older than 2.6.36. The clock source currently
used is the standard gettimeofday (slower, less scalable and less precise than
the LTTng 0.x clocks). Support for LTTng 0.x clocks will be added back soon into
LTTng 2.0.