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  <title>Linux Trace Toolkit Next Generation User Documentation</title>
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<h1>Linux Trace Toolkit Next Generation User Documentation</h1>

Author : Mathieu Desnoyers, September 2005<br>
Last update : January 21st, 2009<br>
(originally known as the LTTng QUICKSTART guide)

<h2>Table of Contents</h2>

<ul>
<li><a href="#intro" name="TOCintro">Introduction</a></li>
<ul>
<li><a href="#arch" name="TOCarch">Supported architectures</a></li>
</ul>

<li><a href="#section1" name="TOCsection1">Installing LTTng and LTTV from
sources</a></li>
<ul>
<li><a href="#prerequisites" name="TOCprerequisites">Prerequisistes</li>
<li><a href="#getlttng" name="TOCgetlttng">Getting the LTTng packages</li>
<li><a href="#getlttngsrc" name="TOCgetlttngsrc">Getting the LTTng kernel sources</li>
<li><a href="#installlttng" name="TOCinstalllttng">Installing a LTTng kernel</li>
<li><a href="#editconfig" name="TOCeditconfig">Editing the system wide
configuration</a>
<li><a href="#getlttctl" name="TOCgetlttctl">Getting and installing the
ltt-control package</li>
<li><a href="#userspacetracing" name="TOCuserspacetracing">Userspace Tracing</li>
<li><a href="#getlttv" name="TOCgetlttv">Getting and installing the LTTV package</ul>

<li><a href="#section2" name="TOCsection2">Using LTTng and LTTV</a></li>
<ul>
<li><a href="#uselttvgui" name="TOCuselttvgui">Use graphical LTTV to control
tracing and analyse traces</a></li>
<li><a href="#uselttngtext" name="TOCuselttngtext">Use text mode LTTng to
control tracing</a></li>
<li><a href="#uselttvtext" name="TOCuselttvtext">Use text mode LTTV</a></li>
<li><a href="#hybrid" name="TOChybrid">Tracing in "Hybrid" mode</a></li>
<li><a href="#flight" name="TOCflight">Tracing in flight recorder mode</a></li>
</ul>

<li><a href="#section3" name="TOCsection3">Adding kernel and user-space
instrumentation</a>
<ul>
<li><a href="#kerneltp" name="TOCkerneltp">Adding kernel instrumentation</a></li>
<li><a href="#usertp" name="TOCusertp">Adding userspace instrumentation</a></li>
</ul>

<li><a href="#section4" name="TOCsection4">Creating Debian and RPM packages
from LTTV</a></li>
<ul>
<li><a href="#pkgdebian" name="TOCpkgdebian">Create custom LTTV Debian
<li><a href="#pkglttng" name="TOCpkglttng">Create custom LTTng packages</a></li>
</ul>

<li><a href="#section5" name="TOCsection5">Examples of LTTng use in the
field</a></li>

</ul>

<hr />

<h2><a href="#TOCintro" name="intro">Introduction</a></h2>
<p>
This document is made of five parts : the first one explains how
to install LTTng and LTTV from sources, the second one describes the steps
to follow to trace a system and view it. The third part explains
briefly how to add a new trace point to the kernel and to user space
applications. The fourth part explains how to create Debian or RPM
packages from the LTTng and LTTV sources. The fifth and last part describes use
of LTTng in the field.
<p>
These operations are made for installing the LTTng 0.86 tracer on a linux 2.6.X
kernel. You will also find instructions for installation of LTTV 0.12.x : the
Linux Trace Toolkit Viewer. 
To see the list of compatibilities between LTTng, ltt-control, LTTV, please
refer to :
<a
href="http://ltt.polymtl.ca/svn/trunk/lttv/doc/developer/lttng-lttv-compatibility.html">LTTng+LTTV versions compatibility</a>
The lttng patch is necessary to have the tracing hooks in the kernel.

<br>
<br>
<h3><a href="#TOCarch" name="arch">Supported architectures</a></h3>
<br>
LTTng :<br>
<br>
<li> x86 32/64 bits
<li> PowerPC 32 and 64 bits
<li> ARM (with limited timestamping precision, e.g. 1HZ. Need
architecture-specific support for better precision)
<li> MIPS
<br>
<br>
LTTV :<br>
<br>
<li> Intel 32/64 bits
<li> PowerPC 32 and 64 bits
<li> Possibly others. Takes care of endianness and type size difference between
the LTTng traces and the LTTV analysis tool.

<hr />


<h2><a href="#TOCsection1" name="section1">Installation from sources</a></h2>
<p>

<h3><a href="#TOCprerequisites" name="prerequisites">Prerequisites</a></h3>
<ul>
<p>
Tools needed to follow the package download steps :

<li>wget
<li>bzip2
<li>gzip
<li>tar

<p>
You have to install the standard development libraries and programs necessary
to compile a kernel :

<PRE>
(from Documentation/Changes in the Linux kernel tree)
Gnu C                2.95.3                # gcc --version
Gnu make             3.79.1                # make --version
binutils             2.12                  # ld -v
util-linux           2.10o                 # fdformat --version
module-init-tools    0.9.10                # depmod -V
</PRE>

<p>
You might also want to have libncurses5 to have the text mode kernel
configuration menu, but there are alternatives.

<p>
Prerequisites for LTTV 0.x.x installation are :

<PRE>
gcc 3.2 or better
gtk 2.4 or better development libraries
  (Debian : libgtk2.0, libgtk2.0-dev)
  (Fedora : gtk2, gtk2-devel)
  note : For Fedora users : this might require at least core 3 from Fedora,
  or you might have to compile your own GTK2 library.
glib 2.4 or better development libraries
  (Debian : libglib2.0-0, libglib2.0-dev)
  (Fedora : glib2, glib2-devel)
libpopt development libraries
  (Debian : libpopt0, libpopt-dev)
  (Fedora : popt)
libpango development libraries
  (Debian : libpango1.0, libpango1.0-dev)
  (Fedora : pango, pango-devel)
libc6 development librairies 
  (Debian : libc6, libc6-dev)
  (Fedora : glibc, glibc)
</PRE>
</ul>

<li>Reminder</li>

<p>
See the list of compatibilities between LTTng, ltt-control and LTTV at :
<a
href="http://ltt.polymtl.ca/svn/trunk/lttv/doc/developer/lttng-lttv-compatibility.html">LTTng+LTTV
versions compatibility</a>.


<h3><a href="#TOCgetlttng" name="getlttng">Getting the LTTng packages</a></h3>

<PRE>
su -
mkdir /usr/src/lttng
cd /usr/src/lttng
(see http://ltt.polymtl.ca/lttng for package listing)
wget http://ltt.polymtl.ca/lttng/patch-2.6.X-lttng-0.x.xx.tar.bz2
bzip2 -cd patch-2.6.X-lttng-0.x.xx.tar.bz2 | tar xvof -
</PRE>


<h3><a href="#TOCgetlttngsrc" name="getlttngsrc">Getting LTTng kernel sources</a></h3>

<PRE>
su -
cd /usr/src
wget http://kernel.org/pub/linux/kernel/v2.6/linux-2.6.X.tar.bz2
bzip2 -cd linux-2.6.X.tar.bz2 | tar xvof -
cd linux-2.6.X
- For LTTng 0.9.4- cat /usr/src/lttng/patch*-2.6.X-lttng-0.x.xx* | patch -p1
- For LTTng 0.9.5+ apply the patches in the order specified in the series file,
  or use quilt
cd ..
mv linux-2.6.X linux-2.6.X-lttng-0.x.xx
</PRE>


<h3><a href="#TOCinstalllttng" name="installlttng">Installing a LTTng kernel</a></h3>

<PRE>
su -
cd /usr/src/linux-2.6.X-lttng-0.x.xx
make menuconfig (or make xconfig or make config)
    Select the < Help > button if you are not familiar with kernel
    configuration.
    Items preceded by [*] means they has to be built into the kernel.
    Items preceded by [M] means they has to be built as modules.
    Items preceded by [ ] means they should be removed.
  go to the "General setup" section
    Select the following options :
    [*] Prompt for development and/or incomplete code/drivers
    [*] Activate markers
    [*] Activate userspace markers ABI (experimental, optional)
    [*] Immediate value optimization (optional)
    [*] Linux Trace Toolkit Next Generation (LTTng) --->
    <M> or <*> Compile lttng tracing probes
    <M> or <*> Linux Trace Toolkit High-speed Lockless Data Relay
    <M> or <*> Linux Trace Toolkit Lock-Protected Data Relay
    <M> or <*> Linux Trace Toolkit Serializer
    <M> or <*>   Linux Trace Toolkit Marker Control
    <M> or <*>     Linux Trace Toolkit Tracer
    [*] Align Linux Trace Toolkit Traces
    <M> or <*> Support logging events from userspace
    [*] Support trace extraction from crash dump
    <M> or <*> Linux Trace Toolkit Trace Controller
    <M> or <*> Linux Trace Toolkit State Dump
  Select <Exit>
  Select <Exit>
  Select <Yes>
make
make modules_install
(if necessary, create a initrd with mkinitrd or your preferate alternative)
(mkinitrd -o /boot/initrd.img-2.6.X-lttng-0.x.xx 2.6.X-lttng-0.x.xx)

-- on X86, X86_64
make install
reboot
Select the Linux 2.6.X-lttng-0.x.xx kernel in your boot loader.

-- on PowerPC
cp vmlinux.strip /boot/vmlinux-2.6.X-lttng-0.x.xx
cp System.map /boot/System.map-2.6.X-lttng-0.x.xx
cp .config /boot/config-2.6.X-lttng-0.x.xx
depmod -ae -F /boot/System.map-2.6.X-lttng-0.x.xx 2.6.X-lttng-0.x.xx
mkinitrd /boot/initrd.img-2.6.X-lttng-0.x.xx 2.6.X-lttng-0.x.xx
(edit /etc/yaboot.conf to add a new entry pointing to your kernel : the entry
that comes first is the default kernel)
ybin
select the right entry at the yaboot prompt (see choices : tab, select : type
the kernel name followed by enter)
Select the Linux 2.6.X-lttng-0.x.xx kernel in your boot loader.
--
</PRE>

<h3><a href="#TOCeditconfig" name="editconfig">Editing the system wide
configuration</a></h3>

<p>
You must activate debugfs and specify a mount point. This is typically done in
fstab such that it happens at boot time.  If you have never used DebugFS before,
these operation would do this for you :

<PRE>
mkdir /mnt/debugfs
cp /etc/fstab /etc/fstab.lttng.bkp
echo "debugfs         /mnt/debugfs    debugfs rw              0       0"  >> /etc/fstab
</PRE>

<p>
then, rebooting or issuing the following command will activate debugfs :
<PRE>
mount /mnt/debugfs
</PRE>

<p>
You need to load the LTT modules to be able to control tracing from user
space. This is done by issuing the following commands. Note however
these commands load all LTT modules. Depending on what options you chose to
compile statically, you may not need to issue all these commands. 

<PRE>
modprobe ltt-trace-control
modprobe ltt-marker-control
modprobe ltt-tracer
modprobe ltt-serialize
modprobe ltt-relay
modprobe ipc-trace
modprobe kernel-trace
modprobe mm-trace
modprobe net-trace
modprobe fs-trace
modprobe jbd2-trace
modprobe ext4-trace
modprobe syscall-trace
modprobe trap-trace
#if locking tracing is wanted, uncomment the following
#modprobe lockdep-trace
</PRE>

<p>
If you want to have complete information about the kernel state (including all
the process names), you need to load the ltt-statedump module. This is done by
issuing the command :

<PRE>
modprobe ltt-statedump
</PRE>
<p>
You can automate at boot time loading the ltt-control module by :

<PRE>
cp /etc/modules /etc/modules.bkp
echo ltt-trace-control >> /etc/modules
echo ltt-marker-control >> /etc/modules
echo ltt-tracer >> /etc/modules
echo ltt-serialize >> /etc/modules
echo ltt-relay >> /etc/modules
echo ipc-trace >> /etc/modules
echo kernel-trace >> /etc/modules
echo mm-trace >> /etc/modules
echo net-trace >> /etc/modules
echo fs-trace >> /etc/modules
echo jbd2-trace >> /etc/modules
echo ext4-trace >> /etc/modules
echo syscall-trace >> /etc/modules
echo trap-trace >> /etc/modules
#if locking tracing is wanted, uncomment the following
#echo lockdep-trace >> /etc/modules
</PRE>


<h3><a href="#TOCgetlttctl" name="getlttctl">Getting and installing the
ltt-control package (on the traced machine)</a></h3>
<p>
(note : the ltt-control package contains lttd and lttctl. Although it has the
same name as the ltt-control kernel module, they are *not* the same thing.)

<PRE>
su -
cd /usr/src
wget http://ltt.polymtl.ca/lttng/ltt-control-0.x-xxxx2006.tar.gz
gzip -cd ltt-control-0.x-xxxx2008.tar.gz | tar xvof -
cd ltt-control-0.x-xxxx2006
(refer to README to see the development libraries that must be installed on you
system)
./configure
make
make install
</PRE>

<h3><a href="#TOCuserspacetracing" name="userspacetracing">Userspace tracing</a></h3>

<PRE>
Make sure you selected the kernel menuconfig option :
    <M> or <*> Support logging events from userspace
And that the ltt-userspace-event kernel module is loaded if selected as a
module.

Simple userspace tracing is available through
echo "some text to record" > /mnt/debugfs/ltt/write_event

It will appear in the trace under event :
channel : userspace
event name : event
</PRE>

<h3><a href="#TOCgetlttv" name="getlttv">Getting and installing the LTTV package
(on the visualisation machine, same
or different from the visualisation machine)</a></h3>

<PRE>
su -
cd /usr/src
wget http://ltt.polymtl.ca/packages/lttv-0.x.xx-xxxx2008.tar.gz
gzip -cd lttv-0.x.xx-xxxx2008.tar.gz | tar xvof -
cd lttv-0.x.xx-xxxx2008
(refer to README to see the development libraries that must be installed on your
system)
./configure
make
make install
</PRE>

<hr />


<h2><a href="#TOCsection2" name="section2">Using LTTng and LTTV</a></h2>

<li><b>IMPORTANT : Arm Linux Kernel Markers after each boot before tracing</b></li>
<PRE>
ltt-armall
</PRE>

<h3><a href="#TOCuselttvgui" name="uselttvgui">Use graphical LTTV to control
tracing and analyse traces</a></h3>
<PRE>
lttv-gui (or /usr/local/bin/lttv-gui)
  - Spot the "Tracing Control" icon : click on it
      (it's a traffic light icon)
    - enter the root password
    - click "start"
    - click "stop"
    - Yes
      * You should now see a trace
</PRE>

<h3><a href="#TOCuselttngtext" name="uselttngtext">Use text mode LTTng to control tracing</a></h3>
<PRE>
The tracing can be controlled from a terminal by using the lttctl command (as
root).

Start tracing :

lttctl -C -w /tmp/trace1 trace1

Stop tracing and destroy trace channels :

lttctl -D trace1

see lttctl --help for details.
</PRE>
<p>
(note : to see if the buffers has been filled, look at the dmesg output after
lttctl -R or after stopping tracing from the GUI, it will show an event lost
count. If it is the case, try using larger buffers. See lttctl --help to learn 
how. lttv now also shows event lost messages in the console when loading a trace
with missing events or lost subbuffers.)

<h3><a href="#TOCuselttvtext" name="uselttvtext">Use text mode LTTV</a></h3>
<p>
Feel free to look in /usr/local/lib/lttv/plugins to see all the text and
graphical plugins available.
<p>
For example, a simple trace dump in text format is available with :
<PRE>
lttv -m textDump -t /tmp/trace
</PRE>
<p>
See lttv -m textDump --help for detailed command line options of textDump.
<p>
It is, in the current state of the project, very useful to use "grep" on the
text output to filter by specific event fields. You can later copy the timestamp
of the events to the clipboard and paste them in the GUI by clicking on the
bottom right label "Current time". Support for this type of filtering should
be added to the filter module soon.

<h3><a href="#TOChybrid" name="hybrid">Tracing in "Hybrid" mode</a></h3>
<p>
Starting from LTTng 0.5.105 and ltt-control 0.20, a new mode can be used :
hybrid. It can be especially useful when studying big workloads on a long period
of time.
<p>
When using this mode, the most important, low rate control information will be
recorded during all the trace by lttd (i.e. process creation/exit). The high
rate information (i.e. interrupt/traps/syscall entry/exit) will be kept in a
flight recorder buffer (now named flight-channelname_X).
<p>
The following lttctl commands take an hybrid trace :
<p>
Create trace channel, start lttd on normal channels, start tracing:
<PRE>
lttctl -C -w /tmp/trace2 -o channel.kernel.overwrite=1 trace2
</PRE>
<p>
Stop tracing, start lttd on flight recorder channels, destroy trace channels :
<PRE>
lttctl -D -w /tmp/trace2 trace2
</PRE>
<p>
Each "overwrite" channel is flight recorder channel.


<h3><a href="#TOCflight" name="flight">Tracing in flight recorder mode</a></h3>
<li>Flight recorder mode</li>
<p>
The flight recorder mode writes data into overwritten buffers for all channels,
including control channels, except for the facilities tracefiles. It consists of
setting all channels to "overwrite".
<p>
The following lttctl commands take a flight recorder trace :
<PRE>
lttctl -C -w /tmp/trace3 -o channel.all.overwrite=1 trace3
...
lttctl -D -w /tmp/trace3 trace3
</PRE>

<hr />


<h2><a href="#TOCsection3" name="section3">Adding new instrumentations with the
markers</a></h2>
<p>

<h3><a href="#TOCkerneltp" name="kerneltp">Adding kernel
instrumentation</a></h3>

<p>
See <a
href="http://git.kernel.org/?p=linux/kernel/git/compudj/linux-2.6-lttng.git;a=blob;f=Documentation/markers.txt">Documentation/markers.txt</a>
and <a
href="http://git.kernel.org/?p=linux/kernel/git/compudj/linux-2.6-lttng.git;a=blob;f=Documentation/tracepoints.txt">Documentation/tracepoints.txt</a> in your kernel
tree.
<p>
Also see <a
href="http://git.kernel.org/?p=linux/kernel/git/compudj/linux-2.6-lttng.git;a=tree;f=ltt/probes">ltt/probes/</a>
for LTTng probe examples.

<h3><a href="#TOCusertp" name="usertp">Adding userspace instrumentation</a></h3>

Add new events to userspace programs with
<a href="http://ltt.polymtl.ca/packages/">userspace markers packages</a>.
Get the latest markers-userspace-*.tar.bz2 and see the Makefile and examples. It
allows inserting markers in executables and libraries, currently only on x86_32
and x86_64.
See <a
href="http://ltt.polymtl.ca/packages/markers-userspace-0.5.tar.bz2">markers-userspace-0.5.tar.bz2</a> or more recent.

<p>
Note that a new design document for a 3rd generation of tracepoint/marker-based
userspace tracing is available at <a
href="http://ltt.polymtl.ca/svn/trunk/lttv/doc/developer/ust.html">LTTng User-space Tracing
Design</a>. This new infrastructure is not yet implemented.

<p>
The easy quick-and-dirty way to perform userspace tracing is currently to write
an string to /mnt/debugfs/ltt/write_event. See <a
href="#userspacetracing">Userspace tracing</a> in the
installation for sources section of this document.

<hr />

<h2><a href="#TOCsection4" name="section4">Creating Debian or RPM packages</a></h2>
<p>

<h3><a href="#TOCpkgdebian" name="pkgdebian">Create custom LTTV Debian packages</a></h3>

<PRE>
Use : dpkg-buildpackage -rfakeroot
</PRE>
<p>
You should then have your LTTV .deb files created for your architecture.

<h3><a href="#TOCpkglttng" name="pkglttng">Create custom LTTng packages</a></h3>
<p>
For building LTTng Debian packages :
get the build tree with patches applies as explained in section 2.

<PRE>
make menuconfig (or xconfig or config) (customize your configuration)
make-kpkg kernel_image
</PRE>
<p>
You will then see your freshly created .deb in /usr/src. Install it with
<PRE>
dpkg -i /usr/src/(image-name).deb
</PRE>
<p>
Then, follow the section "Editing the system wide configuration" in section 2.

<hr />

<h2><a href="#TOCsection5" name="section5">Examples of LTTng use in the field</a></h2>
<p>
A few examples of successful LTTng users :

<ul>
<li> Google are deploying LTTng on their servers. They want to use it to
  monitor their production servers (with flight recorder mode tracing)
  and to help them solve hard to reproduce problems. They have had
  success with such tracing approach to fix "rare disk delay" issues and
  VM-related issues presented in this article :
<ul>
  <li> <a href="http://ltt.polymtl.ca/papers/bligh-Reprint.pdf">Linux Kernel
Debugging on Google-sized clusters at Ottawa Linux
    Symposium 2007</a>
</ul>
<li> IBM Research have had problems with Commercial Scale-out applications,
  which are being an increasing trend to split large server workloads.
  They used LTTng successfully to solve a distributed filesystem-related
  issue. It's presented in the same paper above.

<li> Autodesk, in the development of their next-generation of Linux
  audio/video edition applications, used LTTng extensively to solve
  soft real-time issues they had. Also presented in the same paper.

<li> Wind River included LTTng in their Linux distribution so their
  clients, already familiar to Wind River own tracing solution in
  VxWorks, car have the same kind of feature they have relied on for a
  long time.

<li> Montavista have integrated LTTng in their distribution for the same
  reasons. It's used by Sony amongst others.

<li> SuSE are currently integrating LTTng in their next SLES distribution,
  because their clients asking for solutions which supports a kernel
  closer to real-time need such tools to debug their problems.

<li> A project between Ericsson, the Canadian Defense, NSERC and various
  universities is just starting. It aims at monitoring and debugging
  multi-core systems and provide automated and help user system behavior
  analysis.

<li> Siemens have been using LTTng internally for quite some time now.
</ul>
  </body>
</html>