Integrating LTTng in Ubuntu

[Julien Desfossez]

Hello,

LTTng, the Linux Trace Toolkit Next Generation, is a project that aims
at producing a highly efficient full system tracing solution. It is
composed of several components to allow tracing of the kernel, of
userspace, trace viewing and analysis and trace streaming.

Ubuntu is more and more popular as a server-grade distribution and
having a comprehensive tracing infrastructure built into the kernel
would allow system administrators to investigate problems as they appear
without patching the kernel and rebooting the server.

For example, with LTTng you know really quickly what is the I/O
bandwidth (network or disk) associated with a particular process, and in
this process which file is the culprit for slowing down your whole
system. LTTng can also be used as a highly efficient userspace tracer
with UST. When the user-space and kernel-space traces are combined,
application developpers and sysadmins have a very detailed overview of
what is happening on their system.

Over the last months, the size of the LTTng kernel patchset has been
considerably shrinked for Linux distributions by removing all
LTTng-specific instrumentation from the tree.

You can find the latest patchset here [1].

Please note that the patches within this patchset are elected as the
first items from the LTTng project to eventually get into the mainline
Linux kernel. This includes TRACE_EVENT() changes, the LTTng trace
clocks and the Generic Ring Buffer Library. Please take into account
that most of those patches are really small patches that have been split
to facilitate mainlining by addressing them to the appropriate maintainers.

Also, you will notice that most of the bigger patches are actually new
functionalities that won't conflict with existing code base, because
they create files in new directories of the kernel tree.

The upcoming UDS would be a good timing to discuss the integration of
the new LTTng as an efficient tracer especially for the server flavour
of the Ubuntu kernel.

I submitted a blueprint [2] and following the discussion with Leann
Ogasawara I'm asking the Ubuntu Kernel-team their feedbacks and opinions
about making a full fledged blueprint/spec. I will be in Budapest next week.

The Linaro project already ships with LTTng. For the next Ubuntu
release, it would be really interesting to have a LTTng-ready kernel in
archive to see if it could become the default kernel in the next LTS.
Our mainlining expectations for the biggest patches are around september
2011.

Thanks,

Julien

[1]
http://lttng.org/files/lttng/patch-2.6.38.4-lttng-dev-snapshot-20110430.tar.bz2
[2] https://blueprints.launchpad.net/ubuntu/+spec/kernel-o-lttng